Conversion circuit, voltage conversion device and electric automobile

文档序号：395783 发布日期：2021-12-14 浏览：5次中文

阅读说明：本技术 一种转换电路、电压转换装置及电动汽车 (Conversion circuit, voltage conversion device and electric automobile ) 是由李小秋于 2021-01-29 设计创作，主要内容包括：本申请公开了一种转换电路、电压转换装置及电动汽车,该转换电路包括buck-boost单元和开关电容单元。buck-boost单元可以对接收到的第一输入电压进行buck转换或boost转换,并将buck转换或boost转换后的第一输入电压作为正向电压提供给开关电容单元。开关电容单元可以对正向电压进行升压转换,并将升压转换后的正向电压作为第一输出电压输出。该转换电路不仅可以支持变比连续可调,且转换电路的最大变比不再受限于开关电容单元的变比,转换电路的第一输出电压可以是不小于第一输入电压的任一电压。(The application discloses converting circuit, voltage conversion device and electric automobile, this converting circuit includes buck-boost unit and switched capacitor unit. The buck-boost unit may perform buck conversion or boost conversion on the received first input voltage, and provide the buck-converted or boost-converted first input voltage as a forward voltage to the switched capacitor unit. The switched capacitor unit may perform boost conversion on the forward voltage, and output the boost-converted forward voltage as the first output voltage. The conversion circuit can support that the transformation ratio is continuously adjustable, the maximum transformation ratio of the conversion circuit is not limited by the transformation ratio of the switched capacitor unit any more, and the first output voltage of the conversion circuit can be any voltage not less than the first input voltage.)

1. A conversion circuit comprising a buck-boost unit and a switched capacitor unit, wherein:

the high-potential end of the buck-boost unit and the high-potential end of the switched capacitor unit are both connected with the high-potential output end of the conversion circuit, the first middle end of the buck-boost unit is connected with the second middle end of the switched capacitor unit, and the low-potential end of the buck-boost unit and the low-potential end of the switched capacitor unit are both connected with the low-potential output end of the conversion circuit;

the buck-boost unit is used for receiving a first input voltage, performing buck-boost conversion on the first input voltage, taking the first input voltage after buck-boost conversion as a forward voltage, and providing the forward voltage to the switched capacitor unit through the first middle end;

the switch capacitor unit is used for performing boost conversion on the forward voltage;

the high potential output end and the low potential output end of the conversion circuit are used for outputting a first output voltage, and the first output voltage is the forward voltage subjected to boost conversion.

2. The conversion circuit according to claim 1, wherein the buck-boost unit comprises a first diode, a second diode, a first switch tube, a second switch tube and a first inductor;

one end of the first inductor is connected with a high-potential input end of the conversion circuit, and the other end of the first inductor is respectively connected with an anode of the first diode, a first electrode of the first switch tube and a first electrode of the second switch tube;

the cathode of the first diode is connected with the high-potential output end of the conversion circuit, the second electrode of the first switching tube is connected with the anode of the second diode, and the cathode of the second diode is connected with the second middle end of the switched capacitor unit;

the second electrode of the second switching tube is respectively connected with the low potential input end and the low potential output end of the conversion circuit, and the high potential input end and the low potential input end of the conversion circuit are used for receiving the first input voltage.

3. The conversion circuit according to claim 2, wherein the first output voltage is not less than the first input voltage, and the first output voltage is not greater than N times the first input voltage, N being a transformation ratio of the switched capacitor unit, N being an integer greater than or equal to 1;

the first switching tube is used for keeping off in a period time;

the second switch tube is used for:

keeping conducting in a first time period of the cycle time to charge the first inductor;

remain off for a second period of the cycle time to discharge the first inductor.

4. The conversion circuit according to claim 2, wherein the first output voltage is not less than N times the first input voltage, N is a transformation ratio of the switched capacitor unit, and N is an integer greater than or equal to 1;

the second switch tube is used for keeping conduction in the period time;

the first switch tube is used for:

keeping on for a first time period of the cycle time to charge the inductor;

remains off for a second period of the cycle time to discharge the inductor.

5. The conversion circuit according to any one of claims 2 to 4, wherein the high potential output terminal and the low potential output terminal of the conversion circuit are further configured to receive a second input voltage, and the high potential input terminal and the low potential input terminal of the conversion circuit are further configured to output a second output voltage;

the switched capacitor unit is further configured to perform voltage reduction conversion on the second input voltage, use the voltage-reduced and converted second input voltage as a reverse voltage, and provide the reverse voltage to the buck-boost unit through the second middle end;

and the buck-boost unit is used for performing buck-boost conversion on the reverse voltage, taking the reverse voltage after buck-boost conversion as a second output voltage, and outputting the second output voltage through a high potential input end and a low potential input end of the conversion circuit.

6. The conversion circuit of claim 5, wherein the buck-boost unit further comprises a third switching tube and a fourth switching tube, the third switching tube comprising the first diode, the fourth switching tube comprising the second diode;

a first electrode of the third switching tube is connected with a high-potential output end of the conversion circuit, and a second electrode of the third switching tube is connected with the other end of the first inductor;

and a first electrode of the fourth switching tube is connected with a second electrode of the second switching tube, and a second electrode of the fourth switching tube is connected with a second middle end of the switched capacitor unit.

7. The switching circuit according to claim 6, wherein the first switching tube comprises a third diode, an anode of the third diode is connected to the first electrode of the fourth switching tube, and a cathode of the third diode is connected to the other end of the first inductor;

the second switch tube comprises a fourth diode, the anode of the fourth diode is respectively connected with the low potential input end and the low potential output end of the conversion circuit, and the cathode of the fourth diode is connected with the other end of the first inductor.

8. The conversion circuit according to claim 7, wherein the second output voltage is not less than 0 and is not greater than 1/N of the second input voltage, N is a transformation ratio of the switched capacitor unit, and N is an integer greater than or equal to 1;

the first switching tube, the second switching tube and the third switching tube are used for keeping off in a period time;

the fourth switching tube is used for:

keeping conducting in a first time period of the cycle time to charge the first inductor;

remain off for a second period of the cycle time to discharge the first inductor.

9. The conversion circuit according to claim 7, wherein the second output voltage is not less than 1/N of a second input voltage, and the second output voltage is not greater than the second input voltage, N is a transformation ratio of the switched capacitor unit, and N is an integer greater than or equal to 1;

the first switching tube and the second switching tube are used for keeping off in a period time;

the fourth switching tube is used for keeping conduction in the period time;

the third switch tube is used for:

keeping conducting in a first time period of the cycle time to charge the first inductor;

remain off for a second period of the cycle time to discharge the first inductor.

10. A voltage conversion apparatus comprising a conversion circuit and a control circuit, the conversion circuit comprising a buck-boost unit and a switched capacitor unit, wherein:

the control circuit is configured to:

controlling the buck-boost unit to perform buck-boost conversion on the received first input voltage, taking the first input voltage subjected to buck-boost conversion as a forward voltage, and providing the forward voltage to the switched capacitor unit through the first middle end;

controlling the switched capacitor unit to perform boost conversion on the forward voltage;

11. The voltage conversion device according to claim 10, wherein the buck-boost unit comprises a first diode, a second diode, a first switch tube, a second switch tube and a first inductor;

12. The voltage conversion apparatus according to claim 11, wherein the first output voltage is not less than the first input voltage, and the first output voltage is not greater than N times the first input voltage, N being a transformation ratio of the switched capacitor unit, N being an integer greater than or equal to 1;

the control circuit is specifically configured to:

controlling the first switching tube to be kept off within a period time;

controlling the second switch tube to be kept conducted in a first time period of the cycle time so as to charge the first inductor;

and controlling the second switching tube to be kept off in a second time period of the cycle time so as to discharge the first inductor.

13. The voltage conversion device of claim 12, wherein the control circuit is further configured to:

keeping the first switching tube turned off, and adjusting the duty ratio of the second switching tube, wherein the duty ratio of the second switching tube is the ratio of the first time period in which the second switching tube is turned on to the cycle time;

when the first output voltage reaches a first target voltage, the control circuit keeps the current duty ratio of the second switching tube.

14. The voltage conversion apparatus according to claim 11, wherein the first output voltage is not less than N times the first input voltage, N being a transformation ratio of the switched capacitor unit, N being an integer greater than or equal to 1;

the control circuit is specifically configured to:

controlling the second switch tube to be kept conducted in the period time;

controlling the first switch tube to be kept conducted in a third time period of the cycle time so as to charge the inductor;

and controlling the first switching tube to be kept off in a fourth period of the cycle time so as to discharge the inductor.

15. The voltage conversion device of claim 14, wherein the control circuit is further configured to:

keeping the second switching tube conducted, and adjusting the duty ratio of the first switching tube, wherein the duty ratio of the first switching tube is the ratio of the third time period in which the first switching tube is conducted to the cycle time;

when the first output voltage reaches a first target voltage, the control circuit keeps the current duty ratio of the first switching tube.

16. The voltage conversion apparatus according to any one of claims 11 to 15, wherein the high potential output terminal and the low potential output terminal of the conversion circuit are further configured to receive a second input voltage, and the high potential input terminal and the low potential input terminal of the conversion circuit are further configured to output a second output voltage;

the control circuit is further configured to:

controlling the switched capacitor unit to perform voltage reduction conversion on the second input voltage, taking the voltage-reduced and converted second input voltage as a reverse voltage, and providing the reverse voltage to the buck-boost unit through the second middle end;

and controlling the buck-boost unit to perform buck-boost conversion on the reverse voltage, taking the reverse voltage after buck-boost conversion as a second output voltage, and outputting the second output voltage through a high potential input end and a low potential input end of the conversion circuit.

17. The voltage conversion device according to claim 16, wherein the buck-boost unit further comprises a third switching tube and a fourth switching tube, the third switching tube comprising the first diode, the fourth switching tube comprising the second diode;

18. The voltage conversion device according to claim 17, wherein the first switch tube comprises a third diode, an anode of the third diode is connected to the first electrode of the fourth switch tube, and a cathode of the third diode is connected to the other end of the first inductor;

19. The voltage conversion device according to claim 18, wherein the second output voltage is not less than 0, and the second output voltage is not greater than 1/N of the second input voltage, N being a transformation ratio of the switched capacitor unit, N being an integer greater than or equal to 1;

the control circuit is specifically configured to:

controlling the first switching tube, the second switching tube and the third switching tube to be kept off in a period time;

controlling the fourth switching tube to be kept conducted in a fifth time period of the cycle time so as to charge the first inductor;

and controlling the fourth switching tube to be kept off in a sixth time period of the cycle time so as to discharge the first inductor.

20. The voltage conversion device of claim 19, wherein the control circuit is further configured to:

keeping the first switching tube, the second switching tube and the third switching tube turned off within a period time, and adjusting the duty ratio of the fourth switching tube, wherein the duty ratio of the fourth switching tube is the ratio of a fifth time period in which the fourth switching tube is turned on to the period time;

when the second output voltage reaches a second target voltage, the control circuit keeps the current duty ratio of the fourth switching tube.

21. The voltage conversion device according to claim 18, wherein the second output voltage is not less than 1/N of a second input voltage, and the second output voltage is not greater than the second input voltage, N is a transformation ratio of the switched capacitor unit, and N is an integer greater than or equal to 1;

the control circuit is specifically configured to:

controlling the first switching tube and the second switching tube to be kept off within a period time;

controlling the fourth switching tube to be kept conducted in the period time;

controlling the third switching tube to be kept conducted in a seventh time period of the cycle time so as to charge the first inductor;

and controlling the third switching tube to be kept off in an eighth time period of the cycle time so as to discharge the first inductor.

22. The voltage conversion device of claim 21, wherein the control circuit is further configured to:

keeping the first switching tube and the second switching tube turned off, keeping the fourth switching tube turned on, and adjusting the duty ratio of the third switching tube, wherein the duty ratio of the third switching tube is the ratio of the seventh period of time during which the third switching tube is turned on in the cycle time;

when the second output voltage reaches a second target voltage, the control circuit keeps the current duty ratio of the third switching tube.

23. An electric vehicle comprising a power battery and a voltage conversion device according to any one of claims 10 to 22 for charging the power battery.

Technical Field

The application relates to the technical field of new energy vehicles, in particular to a conversion circuit, a voltage conversion device and an electric vehicle.

Background

The switched capacitor circuit, which may also be referred to as a switched capacitor boost topology, has the advantages of high efficiency, small size, etc., and thus is widely used in various types of electronic devices. The switch capacitor circuit mainly comprises a plurality of conversion switch tubes and a plurality of conversion capacitors, and the plurality of conversion capacitors can be controlled to be periodically charged and discharged through the plurality of conversion switch tubes, so that the boost conversion is realized.

The ratio of the output voltage to the input voltage of the switched capacitor circuit may be referred to as a transformation ratio of the switched capacitor circuit. Generally, the transformation ratio realized by the switched capacitor circuit is an integer, although in some current conversion circuits, the buck circuit and the switched capacitor circuit can be integrated at the same time, so that the conversion circuit can realize continuous transformation ratio. However, the maximum transformation ratio that can be realized by such a conversion circuit is also limited by the transformation ratio of the switched capacitor circuit.

Therefore, the switching circuit integrated with the switched capacitor circuit is still under further study.

Disclosure of Invention

The application provides a converting circuit, voltage conversion device and electric automobile, this converting circuit can support continuous regulation transformation ratio, and compare in switched capacitor circuit, this converting circuit can realize higher transformation ratio.

In a first aspect, the present application provides a conversion circuit, which mainly includes a buck-boost unit and a switched capacitor unit. The high-potential end of the buck-boost unit and the high-potential end of the switched capacitor unit are both connected with the high-potential output end of the conversion circuit, the first middle end of the buck-boost unit is connected with the second middle end of the switched capacitor unit, and the low-potential end of the buck-boost unit and the low-potential end of the switched capacitor unit are both connected with the low-potential output end of the conversion circuit. The buck-boost unit may receive the first input voltage, perform buck conversion or boost conversion on the first input voltage, and provide the forward voltage to the switched capacitor unit through the first intermediate terminal by using the first input voltage after the buck conversion or the boost conversion as the forward voltage. The switched capacitor unit may perform a boost conversion on the forward voltage. The high potential output end and the low potential output end of the conversion circuit can output a first output voltage which is the forward voltage after the voltage boosting conversion.

Specifically, the buck-boost unit can perform buck conversion and boost conversion on the first input voltage. In the case where the buck-boost unit performs buck conversion on the first input voltage, the forward voltage may be any voltage not less than 1/N of the first input voltage and not greater than the first input voltage. Wherein N represents the transformation ratio of the switched capacitor unit, and is an integer greater than or equal to 1. In this case, the switched capacitor unit performs boost conversion on the forward voltage, so that the boost-converted forward voltage (i.e., the first output voltage) can reach any voltage between the first input voltage and N times the first input voltage.

In the case where the buck-boost unit performs boost conversion on the first input voltage, the forward voltage may be any voltage not less than the first input voltage. In this case, the switched capacitor unit performs boost conversion on the forward voltage, so that the boost-converted forward voltage (i.e., the first output voltage) can reach any voltage of the first input voltage that is not less than N times.

Therefore, the conversion circuit provided by the application can support that the transformation ratio is continuously adjustable, the maximum transformation ratio of the conversion circuit is not limited by the transformation ratio of the switched capacitor unit, the first output voltage of the conversion circuit can be any voltage which is not less than the first input voltage, and the universality of the conversion circuit is favorably improved.

Illustratively, the buck-boost unit comprises a first diode, a second diode, a first switch tube, a second switch tube and a first inductor. One end of the first inductor is connected with the high-potential input end of the conversion circuit, and the other end of the first inductor is respectively connected with the anode of the first diode, the first electrode of the first switch tube and the first electrode of the second switch tube. The cathode of the first diode is connected with the high-potential output end of the conversion circuit, the second electrode of the first switching tube is connected with the anode of the second diode, and the cathode of the second diode is connected with the second middle end of the switched capacitor unit. The second electrode of the second switching tube is respectively connected with the low potential input end and the low potential output end of the conversion circuit, and the high potential input end and the low potential input end of the conversion circuit are used for receiving the first input voltage.

As described above, the buck-boost unit may perform buck conversion on the first input voltage. Specifically, the first switch tube can be kept off in the cycle time; the second switch tube can be kept conducted in the first time period of the cycle time so as to charge the first inductor. The second switch tube is kept off in a second time period of the cycle time so as to discharge the first inductor. In this case, the buck-boost unit may perform buck conversion on the first input voltage, and the obtained first output voltage may be any voltage that is not less than the first input voltage and not more than N times the first input voltage.

As described above, the buck-boost unit may boost convert the first input voltage. Specifically, the second switch tube may be kept conductive during the cycle time. The first switch tube can be kept conductive in the first period of the cycle time so as to charge the inductor. The second switching tube is kept off in a second time period of the cycle time so as to discharge the inductor. In this case, the buck-boost unit may perform boost conversion on the first input voltage, and the resulting first output voltage may be any voltage not less than N times the first input voltage.

In one possible implementation, the conversion circuit provided by the present application also supports bidirectional voltage conversion, that is, the conversion circuit can not only receive a first input voltage through a high potential input terminal and a low potential input terminal and output a first output voltage through a high potential output terminal and a low potential output terminal, but also receive a second input voltage, and the high potential input terminal and the low potential input terminal of the conversion circuit can also output the second output voltage. In this case, the switched capacitor unit may further perform voltage-down conversion on the second input voltage, and provide the buck-boost unit with the voltage-down converted second input voltage as a reverse voltage through the second intermediate terminal. The buck-boost unit can perform buck conversion or boost conversion on the reverse voltage, and output the second output voltage through a high potential input end and a low potential input end of the conversion circuit by taking the buck-converted or boost-converted reverse voltage as the second output voltage.

Specifically, the reverse voltage provided by the switched-capacitor unit to the buck-boost unit may be 1/N of the second input voltage. The buck-boost unit can not only carry out buck conversion on reverse voltage, but also carry out boost conversion on the reverse voltage. When the buck-boost unit performs buck conversion on the reverse voltage, the second output voltage can be any voltage not greater than the reverse voltage, namely the second output voltage can be any voltage not greater than 1/N of the second input voltage. When the buck-boost unit performs boost conversion on the reverse voltage, the second output voltage may be any voltage which is not less than the reverse voltage and is not greater than N times the reverse voltage, that is, the second output voltage may be any voltage which is not less than 1/N of the second input voltage and is not greater than the second input voltage.

Illustratively, the buck-boost unit may further include a third switching tube and a fourth switching tube, the third switching tube includes the first diode, and the fourth switching tube includes the second diode. The first electrode of the third switching tube is connected with the high-potential output end of the conversion circuit, and the second electrode of the third switching tube is connected with the other end of the first inductor. And a first electrode of the fourth switching tube is connected with a second electrode of the second switching tube, and a second electrode of the fourth switching tube is connected with the second middle end of the switched capacitor unit.

In order to enable the first switch tube and the second switch tube not to affect the conversion of the buck-boost unit to the reverse voltage, in a possible implementation manner, the first switch tube includes a third diode, an anode of the third diode is connected with a first electrode of the fourth switch tube, and a cathode of the third diode is connected with the other end of the first inductor. The second switch tube comprises a fourth diode, the anode of the fourth diode is respectively connected with the low potential input end and the low potential output end of the conversion circuit, and the cathode of the fourth diode is connected with the other end of the first inductor. In this case, when the buck-boost unit converts the reverse voltage, the first switching tube and the second switching tube may be turned off, and the diodes in the first switching tube and the second switching tube may keep the charging loop and the discharging loop of the first inductor in the buck-boost unit turned on, so that the influence of the first switching tube and the second switching tube on the conversion process of the reverse voltage may be reduced.

As mentioned above, the buck-boost unit can perform buck conversion on the reverse voltage. Specifically, the first switch tube, the second switch tube and the third switch tube can be kept off in the period time. The fourth switch tube can be kept conducted in the first period of the cycle time so as to charge the first inductor. The fourth switching tube can be kept switched off in the second time period of the cycle time so as to discharge the first inductor. In this case, the buck-boost unit may buck convert the reverse voltage, and the resulting second output voltage may be any voltage not greater than 1/N of the second input voltage.

As mentioned above, the buck-boost unit can boost convert the reverse voltage. Specifically, the first switching tube and the second switching tube may be kept off during the period time. The fourth switching tube can be kept conductive in the period time. The third switch tube can be kept conductive in the first period of the cycle time so as to charge the first inductor. The third switching tube may remain off during a second period of the cycle time to discharge the first inductor. In this case, the buck-boost unit can boost-convert the reverse voltage, and the obtained second output voltage can be any voltage which is not less than 1/N of the second input voltage and not more than the second input voltage.

In a second aspect, the present application provides a voltage conversion apparatus that mainly includes a conversion circuit and a control circuit. The conversion circuit may be any one of the conversion circuits provided in the first aspect, and the technical effects of the corresponding solutions in the second aspect may refer to the technical effects that can be obtained by the corresponding solutions in the first aspect, and repeated parts are not described in detail.

Illustratively, the conversion circuit may include a buck-boost unit and a switched capacitor unit. The high-potential end of the buck-boost unit and the high-potential end of the switched capacitor unit are both connected with the high-potential output end of the conversion circuit, the first middle end of the buck-boost unit is connected with the second middle end of the switched capacitor unit, and the low-potential end of the buck-boost unit and the low-potential end of the switched capacitor unit are both connected with the low-potential output end of the conversion circuit. The control circuit can control the buck-boost unit to perform buck conversion or boost conversion on the received first input voltage, and the first input voltage after buck conversion or boost conversion is used as a forward voltage which is provided for the switched capacitor unit through the first middle end. The control circuit controls the switched capacitor unit to perform boost conversion on the forward voltage, wherein the high potential output end and the low potential output end of the conversion circuit can output a first output voltage, and the first output voltage can be the forward voltage after the boost conversion.

Illustratively, the buck-boost unit may include a first diode, a second diode, a first switch tube, a second switch tube, and a first inductor. One end of the first inductor is connected with the high-potential input end of the conversion circuit, and the other end of the first inductor is respectively connected with the anode of the first diode, the first electrode of the first switch tube and the first electrode of the second switch tube. The cathode of the first diode is connected with the high-potential output end of the conversion circuit, the second electrode of the first switching tube is connected with the anode of the second diode, and the cathode of the second diode is connected with the second middle end of the switched capacitor unit. The second electrode of the second switching tube is respectively connected with the low potential input end and the low potential output end of the conversion circuit, and the high potential input end and the low potential input end of the conversion circuit are used for receiving the first input voltage.

As mentioned above, the control circuit can control the buck-boost unit to perform buck conversion on the first input voltage. Specifically, the control circuit may control the first switching tube to remain off during a cycle time, control the second switching tube to remain on during a first period of the cycle time, so as to charge the first inductor, and control the second switching tube to remain off during a second period of the cycle time, so as to discharge the first inductor. In this case, the buck-boost unit may perform buck conversion on the first input voltage, and the obtained first output voltage may be any voltage that is not less than the first input voltage and not more than N times the first input voltage.

In this application, the control circuit may first keep the first switching tube turned off, and adjust a duty ratio of the second switching tube, where the duty ratio of the second switching tube is a ratio of the first time period during which the second switching tube is turned on to the cycle time. When the first output voltage reaches the first target voltage, the control circuit keeps the current duty ratio of the second switching tube. By adopting the implementation mode, the control circuit can determine the duty ratio of the second switching tube, so that the first output voltage can reach the first target voltage.

As mentioned above, the control circuit can control the buck-boost unit to boost-convert the first input voltage. Specifically, the control circuit may control the second switching tube to be kept on during the cycle time, control the first switching tube to be kept on during a third period of the cycle time to charge the inductor, and control the first switching tube to be kept off during a fourth period of the cycle time to discharge the inductor. In this case, the buck-boost unit may perform boost conversion on the first input voltage, and the resulting first output voltage may be any voltage not less than N times the first input voltage.

In this application, the control circuit may first keep the second switching tube turned on, and adjust a duty ratio of the first switching tube, where the duty ratio of the first switching tube is a ratio of a third time period in which the first switching tube is turned on to a cycle time. When the first output voltage reaches the first target voltage, the control circuit keeps the current duty ratio of the first switching tube. By adopting the implementation mode, the control circuit can determine the duty ratio of the first switching tube, so that the first output voltage can reach the first target voltage.

In one possible implementation, the voltage conversion apparatus provided by the present application further supports bidirectional voltage conversion, that is, the high potential output terminal and the low potential output terminal of the conversion circuit may further receive the second input voltage, and the high potential input terminal and the low potential input terminal of the conversion circuit may further output the second output voltage. The control circuit can also control the switched capacitor unit to perform voltage reduction conversion on the second input voltage, the second input voltage subjected to voltage reduction conversion is used as reverse voltage, and the reverse voltage is supplied to the buck-boost unit through the second middle end; the control circuit controls the buck-boost unit to carry out buck conversion or boost conversion on the reverse voltage, the reverse voltage after buck conversion or boost conversion is used as a second output voltage, and the second output voltage is output through the high-potential input end and the low-potential input end of the conversion circuit.

The buck-boost unit may further include a third switching tube and a fourth switching tube, where the third switching tube includes the first diode and the fourth switching tube includes the second diode. The first electrode of the third switching tube is connected with the high-potential output end of the conversion circuit, and the second electrode of the third switching tube is connected with the other end of the first inductor. And a first electrode of the fourth switching tube is connected with a second electrode of the second switching tube, and a second electrode of the fourth switching tube is connected with the second middle end of the switched capacitor unit.

As mentioned above, the control circuit can control the buck-boost unit to perform buck conversion on the reverse voltage. Specifically, the control circuit may control the first switching tube, the second switching tube and the third switching tube to be kept off during the cycle time, control the fourth switching tube to be kept on during a fifth period of the cycle time to charge the first inductor, and control the fourth switching tube to be kept off during a sixth period of the cycle time to discharge the first inductor. In this case, the buck-boost unit may buck convert the reverse voltage, and the resulting second output voltage may be any voltage not greater than 1/N of the second input voltage.

In the application, the control circuit may first keep the first switching tube, the second switching tube and the third switching tube turned off within a period time, and adjust a duty cycle of the fourth switching tube, where the duty cycle of the fourth switching tube is a ratio of a fifth time period in which the fourth switching tube is turned on to the period time; when the second output voltage reaches the second target voltage, the control circuit keeps the current duty ratio of the fourth switching tube. By adopting the implementation mode, the control circuit can determine the duty ratio of the fourth switching tube, so that the second output voltage can reach the second target voltage.

As mentioned above, the control circuit can control the buck-boost unit to boost convert the reverse voltage. Specifically, the control circuit may control the first switching tube and the second switching tube to remain off during a cycle time, control the fourth switching tube to remain on during the cycle time, control the third switching tube to remain on during a seventh period of the cycle time to charge the first inductor, and control the third switching tube to remain off during an eighth period of the cycle time to discharge the first inductor. In this case, the buck-boost unit can boost-convert the reverse voltage, and the obtained second output voltage can be any voltage which is not less than 1/N of the second input voltage and not more than the second input voltage.

In the application, the control circuit may first keep the first switching tube and the second switching tube turned off, keep the fourth switching tube turned on, and adjust a duty cycle of the third switching tube, where the duty cycle of the third switching tube is a ratio of a seventh period of time during which the third switching tube is turned on to the cycle time; when the second output voltage reaches the second target voltage, the control circuit keeps the current duty ratio of the third switching tube. By adopting the implementation mode, the control circuit can determine the duty ratio of the third switching tube, so that the second output voltage can reach the second target voltage.

In a third aspect, the present application provides an electric vehicle, which mainly comprises a power battery and any one of the voltage conversion devices as described in the second aspect above, wherein the voltage conversion device can charge the power battery.

These and other aspects of the present application will be more readily apparent from the following description of the embodiments.

Drawings

FIG. 1 is a schematic diagram of an electric vehicle charging system;

FIG. 2 is a schematic diagram of a conversion circuit;

FIG. 3 is a schematic diagram of a control signal;

fig. 4a and 4b are schematic diagrams of equivalent circuit structures of the conversion circuit;

FIG. 5 is a schematic diagram of a conversion circuit;

FIG. 6 is a schematic diagram of a conversion circuit;

FIGS. 7a and 7b are schematic diagrams of equivalent circuit structures of the conversion circuit;

FIG. 8 is a schematic diagram of a conversion circuit;

fig. 9 is a schematic structural diagram of a conversion circuit according to an embodiment of the present application;

FIG. 10 is a schematic diagram of a control signal provided in an embodiment of the present application;

fig. 11a and fig. 11b are schematic equivalent circuit structures of a conversion circuit provided in an embodiment of the present application;

FIG. 12 is a schematic diagram of a control signal provided in an embodiment of the present application;

fig. 13a and 13b are schematic equivalent circuit structures of a conversion circuit provided in an embodiment of the present application;

fig. 14 is a schematic structural diagram of a conversion circuit according to an embodiment of the present application;

FIG. 15 is a schematic diagram of a control signal provided in an embodiment of the present application;

fig. 16a and 16b are schematic equivalent circuit structures of a conversion circuit provided in an embodiment of the present application;

FIG. 17 is a schematic diagram of a control signal provided in an embodiment of the present application;

fig. 18a and 18b are schematic equivalent circuit structures of a conversion circuit provided in an embodiment of the present application;

fig. 19 is a flowchart illustrating a method for determining a duty cycle of a switching tube according to an embodiment of the present disclosure;

FIG. 20 is a schematic diagram of a conventional boost circuit;

FIG. 21 is one of comparative graphs of the effects provided by the examples of the present application;

FIG. 22 is a second comparison graph of the effect provided by the embodiment of the present application;

fig. 23 is a third comparison graph of the effects provided by the embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more clear, the present application will be further described in detail with reference to the accompanying drawings. The particular methods of operation in the method embodiments may also be applied to apparatus embodiments or system embodiments. It is to be noted that "at least one" in the description of the present application means one or more, where a plurality means two or more. In view of this, the "plurality" may also be understood as "at least two" in the embodiments of the present invention. "and/or" describes the association relationship of the associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" generally indicates that the preceding and following related objects are in an "or" relationship, unless otherwise specified. In addition, it is to be understood that the terms first, second, etc. in the description of the present application are used for distinguishing between the descriptions and not necessarily for describing a sequential or chronological order.

It is to be noted that "connected" in the embodiments of the present application may be understood as an electrical connection, and the connection of two electrical components may be a direct or indirect connection between the two electrical components. For example, a and B may be connected directly, or a and B may be connected indirectly through one or more other electrical elements, for example, a and B may be connected, or a and C may be connected directly, or C and B may be connected directly, and a and B are connected through C.

It should be noted that the switch tube in the embodiment of the present application may be integrated with a diode, and the switch tube in the embodiment of the present application may be one or more of various switch tubes such as a relay, a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), a Bipolar Junction Transistor (BJT), an Insulated Gate Bipolar Transistor (IGBT), and a silicon carbide (SiC) transistor, which are not listed in the embodiment of the present application. The packaging form of each switch tube may be a single-tube package or a multi-tube package, which is not limited in this application. Each of the switching tubes may include a first electrode, a second electrode, and a control electrode, wherein the control electrode is used for controlling the switching tubes to be turned on or off. When the switching tube is switched on, current can be transmitted between the first electrode and the second electrode of the switching tube, and when the switching tube is switched off, current cannot be transmitted between the first electrode and the second electrode of the switching tube. Taking the IGBT as an example, the control electrode of the switching tube is a gate electrode, and the first electrode of the switching tube may be a collector electrode of the switching tube, and the second electrode may be an emitter electrode of the switching tube, or the first electrode may be an emitter electrode of the switching tube, and the second electrode may be a collector electrode of the switching tube. The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

The switched capacitor circuit, which may also be referred to as a switched capacitor boost topology, has the advantages of high efficiency, small size, etc., and thus is widely used in various types of electronic devices. For example, in an on-board charger of an electric vehicle, a switched capacitor circuit is often provided, and DC/DC conversion can be realized by the switched capacitor circuit.

Taking an electric vehicle as an example, fig. 1 schematically illustrates an electric vehicle charging system. As shown in fig. 1, the charging post 20 may provide a charging voltage to the electric vehicle 10, and in some scenarios, the charging voltage may be a direct current voltage (mostly no greater than 500V). The electric vehicle 10 can charge the power battery 12 by using the charging voltage provided by the charging pile 20.

At present, more and more electric vehicles 10 adopt a high-voltage power battery pack, that is, the charging voltage value required by the power battery 12 is higher (more than or equal to 800V), and part of the charging voltage provided by the charging pile 20 cannot directly charge the power battery 12.

In view of this, the electric vehicle 10 may further include a direct current booster (DCDC boost) 11, and the DCDC boost 11 may boost and convert the charging voltage, so that the voltage-converted charging voltage may be adapted to the power battery 12, thereby charging the power battery 12.

Specifically, the DCDC boost 11 includes an interface P1 and an interface P2, and the DCDC boost 11 may be connected to the charging post 20 through the interface P1 and to the power battery 12 through the interface P2, respectively. The DCDC boost 11 may further include fast charging contactors K1 and K2, a bypass contactor K3, Electromagnetic Compatibility (EMC) filter circuits 111 and 113, and a converter circuit 112.

One end of the quick-charging contactor K1 is connected with the high-potential input end of the interface P1, and the other end of the quick-charging contactor K1 is connected with the high-potential input end of the EMC filter circuit 111. One end of the quick-charging contactor K2 is connected with the low-potential input end of the interface P1, and the other end of the quick-charging contactor K2 is connected with the low-potential input end of the EMC filter circuit 111.

When the electric vehicle 10 is charged, the quick charging contactors K1 and K2 are turned on, and a path is formed between the charger 20 and the DCDC boost 11. When the electric automobile 10 stops charging, the quick charging contactors K1 and K2 are turned off, the interface P1 is prevented from being electrified, and the safety of users is protected.

A high potential output terminal of the EMC filter circuit 111 is connected to a high potential input terminal of the conversion circuit 112, and a low potential output terminal of the EMC filter circuit 111 is connected to a low potential input terminal of the conversion circuit 112. The EMC filter circuit 111 may filter the received charging voltage and provide the filtered charging voltage to the conversion circuit 112.

The converter circuit 112 may be a DC/DC converter circuit, and may boost-convert the charging voltage. For example, the charging voltage provided by the charging post 20 is 500V, and the charging voltage adapted by the power battery 12 is 800V, the converting circuit 112 may boost-convert the charging voltage of 500V to 800V.

A high potential output terminal of the conversion circuit 112 is connected to a high potential input terminal of the EMC filter circuit 113, and a low potential output terminal of the conversion circuit 112 is connected to a low potential input terminal of the EMC filter circuit 113. The conversion circuit 112 may output the boost-converted charging voltage to the EMC filter circuit 113, so that the EMC filter circuit 113 may further filter the boost-converted charging voltage.

In the electric vehicle 10, the high potential output terminal of the EMC filter circuit 113 is connected to the high potential terminal of the interface P2, and the high potential terminal of the interface P2 may be connected to the positive electrode of the power battery 12. The low potential output terminal of the EMC filter circuit 113 is connected to the low potential terminal of the interface P2, and the low potential terminal of the interface P2 can be connected to the negative terminal of the power battery 12. Therefore, the EMC filter circuit 113 can supply the filtered and boost-converted charging voltage to the power battery 12 through the interface P2, so that the power battery 12 can be charged.

As shown in fig. 1, a bypass contactor K3 may also be included in DCDC boost 11. One end of the bypass contactor K3 is connected to the high potential input terminal of the conversion circuit 112, and the other end of the bypass contactor K3 is connected to the low potential input terminal of the conversion circuit 112. The bypass contactor K3 can be kept conductive when the charging voltage provided by the charging post 20 can be adapted to the power battery 12. In this case, the charging voltage provided by the charging post 20 is filtered by the EMC filter circuit 111 and the EMC filter circuit 113, and then can be transmitted to the power battery 12, so as to directly charge the power battery 12. When the charging voltage provided by the charging post 20 cannot be adapted to the power battery 12, the bypass contactor K3 can be switched off. In this case, the charging voltage provided by the charging post 20 needs to be converted by the converting circuit 112 to fit the power battery 12.

As shown in fig. 1, the DCDC boost 11 may further include a control circuit 114, and the control circuit 114 is connected to the converting circuit 112 and may control the converting circuit 112 to perform voltage conversion. For example, the receiving control module 102 may be a processor, a microprocessor, a controller, etc. of the electric vehicle 10, and may be, for example, a general-purpose Central Processing Unit (CPU), a general-purpose processor, a Digital Signal Processing (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, a transistor logic device, a hardware component, or any combination thereof.

As can be seen from the above, the conversion circuit 112 is the basis for implementing the boost conversion function of the DCDC boost 11. Next, the conversion circuit 112 will be further explained.

Fig. 2 schematically shows a structure of a conversion circuit. The conversion circuit 112 shown in fig. 2 mainly includes an inductor Lr1, switching transistors Q1 to Q4, a capacitor C1, and a capacitor C2. The first electrode of the switching tube Q1 is used for connecting the high-potential output terminal o + of the conversion circuit 112, and the second electrode of the switching tube Q1 is connected with the first electrode of the switching tube Q2. The second electrode of the switching tube Q2 is connected to the first electrode of the switching tube Q3, the second electrode of the switching tube Q3 is connected to the first electrode of the switching tube Q4, and the second electrodes of the switching tube Q4 are connected to the low-potential input terminal i-and the low-potential output terminal o-of the converting circuit 112, respectively.

One end of the capacitor C1 is connected to the first electrode of the switching tube Q2, and the other end of the capacitor C1 is connected to the second electrode of the switching tube Q3. One end of the capacitor C2 is connected to the high potential output terminal o + of the conversion circuit 112, and the other end of the capacitor C2 is connected to the low potential output terminal o-of the conversion circuit 112.

For example, each capacitor in the embodiments of the present application may be a capacitor type such as a thin film capacitor, an electrolytic capacitor, a ceramic capacitor, and the like, which is not limited in the embodiments of the present application.

One end of the inductor Lr1 is connected to the high potential input terminal i + of the conversion circuit 112, and the other end of the inductor Lr1 is connected to the second electrode of the switching transistor Q2. The voltage between one end of the inductor Lr1 and the second electrode of the switching tube Q4 can be understood as the input voltage Vin of the conversion circuit 112.

In the embodiment of the present application, the control electrodes of the switching tubes Q1 to Q4 may be connected to the control circuit 114, so that the control circuit 114 may control the on and off of the switching tubes Q1 to Q4, respectively, and it should be understood that, for the sake of simplifying the illustration, the connection relationship is not shown in the drawings of the embodiment of the present application.

Based on the converting circuit 112 shown in fig. 2, the control circuit 114 can provide the control signals S1 to S4 shown in fig. 3 for the switching tube Q1 to the switching tube Q4, respectively. Specifically, the control circuit 114 may provide the control signal S1 for the switching transistor Q1, the control signal S2 for the switching transistor Q2, the control signal S3 for the switching transistor Q3, and the control signal S4 for the switching transistor Q4.

Assuming that the transistors Q1 to Q4 are all high-level on and low-level off transistors, the control signals S1 to S4 can be as shown in fig. 3. As can be seen from FIG. 3, the control signals S1-S4 are all periodic signals with a period T. The period T includes the period T1 and the period T2, and next, the equivalent circuits of the conversion circuit 112 in the period T1 and the period T2 are explained, respectively.

Time period t1

During the time period t1, the control signals S1 and S3 are at a high level, and the control signals S2 and S4 are at a low level, so that the switching tubes Q1 and Q3 are turned on, and the switching tubes Q2 and Q4 are turned off. In this case, the equivalent circuit of the conversion circuit 112 may be as shown in fig. 4 a.

As shown in fig. 4a, a current is input from the high potential input terminal i + of the conversion circuit 112, and is output from the low potential input terminal i-of the conversion circuit 112 after being sequentially transmitted through the inductor Lr1, the switching tube Q2, the capacitor C1 and the switching tube Q4. The capacitor C1 is charged by the input voltage Vin, so that the voltage of the capacitor C1 gradually reaches the input voltage Vin.

Time period t2

During the time period t1, the control signals S1 and S3 are low level, and the control signals S2 and S4 are high level, so the switching tubes Q1 and Q3 are turned off, and the switching tubes Q2 and Q4 are turned on. In this case, the equivalent circuit of the conversion circuit 112 may be as shown in fig. 4 b.

As shown in fig. 4b, the current is input from the high potential input terminal i + of the conversion circuit 112, and is sequentially transmitted through the inductor Lr1, the switching transistor Q3, the capacitor C1, the switching transistor Q1, and the capacitor C2, and then the current is output from the low potential input terminal i-of the conversion circuit 112. The input voltage Vin is connected in series with the capacitor C1 to charge the capacitor C2. The output voltage Vout of the converting circuit 112, i.e., the voltage of the capacitor C2, is the sum of the input voltage Vin and the voltage of the capacitor C1. Since the voltage of the capacitor C1 reaches the input voltage Vin in the period t1, the output voltage Vout of the conversion circuit 112 may reach 2Vin in the period t 2.

It should be noted that the inductor Lr1 may resonate with the capacitor C1. When the switching frequency Fsw of the switching tubes Q1 to Q4 satisfies the following formula one, the inductor Lr1 may implement Zero Current Switching (ZCS) when the switching tube Q2 and the switching tube Q4 are turned on.

In formula one, Lr1 represents the inductance of inductor Lr1, and C1 represents the capacitance of capacitor C1. When the switch tube Q2 and the switch tube Q4 realize zero-current switching, the conduction loss of the switch tube Q2 and the switch tube Q4 can be effectively reduced, which is beneficial to improving the efficiency of the conversion circuit 112.

It is understood that the conversion ratio of the conversion circuit 112 shown in fig. 2 is 2, i.e., Vout — 2 Vin. On the basis of the conversion circuit 112 shown in fig. 2, by increasing the number of switching tubes and capacitors, a higher conversion ratio can be achieved. For example, in fig. 5, by adding a pair of switching tubes (switching tubes Q5 and Q6) and a capacitor C3, the transformation ratio of the conversion circuit 112 can be increased to 3, that is, Vout is 3 Vin.

In summary, the converting circuit 112 shown in fig. 2 controls the charging and discharging of the capacitor through the switch tube to realize the voltage conversion, so the converting circuit 112 shown in fig. 2 can also be referred to as a switched capacitor circuit. It should be noted that the inductor Lr1 is mainly used to make the switching tubes Q2 and Q4 realize ZCS, and the inductance of the inductor Lr1 is small and has negligible influence on voltage conversion.

At present, the transformation ratio of the switched capacitor circuit is an integer, and the output voltage of the switched capacitor circuit cannot be continuously adjusted. For example, the conversion ratio of the conversion circuit 112 shown in fig. 2 is 2, and the output voltage Vout is 2 Vin. For another example, the conversion ratio of the conversion circuit 112 shown in fig. 5 is 3, and the output voltage Vout is 3Vin, which limits the application of the switched capacitor circuit to the conversion circuit 112. In addition, during the time period t2, since the inductor Lr1 resonates with the capacitor C1 and the capacitor C2 at the same time, if ZCS of the switching tube Q1 and the switching tube Q3 is to be realized, the switching frequency Fsw of the switching tubes Q1 to Q4 satisfies the following formula two:

wherein C2 in the formula two represents the capacitance of the capacitor C2.

Comparing the formula I with the formula II, the Fsw obtained by calculation according to the formula II is larger than the Fsw obtained by calculation according to the formula I. That is, in the case where the switching tube Q2 and the switching tube Q4 realize ZCS, the switching tube Q1 and the switching tube Q3 cannot realize ZCS. Accordingly, in the case where the switching tube Q1 and the switching tube Q3 realize ZCS, the switching tube Q2 and the switching tube Q4 cannot realize ZCS. Therefore, the efficiency of the conversion circuit shown in fig. 2 still needs to be further improved.

In view of this, the conversion circuit 112 can also be as shown in fig. 6. The conversion circuit 112 includes switching tubes Q1 to Q4, a capacitor C2, a capacitor C3, an inductor Lr1, and a capacitor Cr 1. The connection relationship between the switching tubes Q1 to Q4 is similar to that in fig. 2, and is not described again.

One end of the capacitor C2 is connected to the high potential output terminal o + of the conversion circuit 112, and the other end of the capacitor C2 is connected to one end of the capacitor C3. One end of the capacitor C3 is connected to the first electrode of the switching tube Q3 and the high potential input terminal i + of the converting circuit 112, respectively, and the other end of the capacitor C3 is connected to the second electrode of the switching tube Q4 and the low potential input terminal i-of the converting circuit 112, respectively. One end of the inductor Lr1 is connected to the first electrode of the switching tube Q2, the other end of the inductor Lr1 is connected to one end of the capacitor Cr1, and the other end of the capacitor Cr1 is connected to the second electrode of the switching tube Q3.

In the switching circuit 112 shown in fig. 6, the switching transistors Q1 to Q4 can still be applied to the control signals shown in fig. 3. Based on the conversion circuit 112 shown in fig. 6, next, description will be made of equivalent circuits of the conversion circuit 112 in the period t1 and the period t2, respectively.

Time period t1

The current is input from the high potential input terminal i + of the conversion circuit 112, transmitted through the switching tube Q2, the inductor Lr1, the capacitor Cr1 and the switching tube Q4, and then output from the low potential input terminal i-of the conversion circuit 112. In the process, the capacitor Cr1 and the inductor Lr1 are charged. It is considered that the sum of the voltage of the capacitor Cr1 and the voltage of the inductor Lr1 may reach the input voltage Vin.

It can be seen that the inductor Lr1 and the capacitor Cr1 resonate during the time period t 1. That is, when the switching frequencies Fsw of the switching tubes Q1 to Q4 satisfy the following formula three, ZCS can be realized by the switching tubes Q2 and Q4:

in formula three, Cr1 represents the capacitance of the capacitor Cr 1.

Time period 2

During the time period t2, the control signals S1 and S3 are at a high level, and the control signals S2 and S4 are at a low level, so that the switching tubes Q1 and Q3 are turned on, and the switching tubes Q2 and Q4 are turned off. In this case, the equivalent circuit of the conversion circuit 112 may be as shown in fig. 7 b.

The current is output from one end of the capacitor Cr1 close to the inductor Lr1, transmitted through the inductor Lr1, the switching tube Q1, the capacitor C2 and the switching tube Q3, and then flows back to one end of the capacitor Cr1 close to the switching tube Q3. In the process, the capacitor Cr1 and the inductor Lr1 are discharged, so that the capacitor C2 can be charged. Since the sum of the voltages of the capacitor Cr1 and the inductor Lr1 may reach the input voltage Vin in the period t1, the voltage of the capacitor C2 may reach the input voltage Vin in the period t 2.

As can be seen from fig. 7b, the capacitor C2 and the capacitor C3 are connected in series between the high potential output terminal o + and the low potential output terminal o-of the conversion circuit 112, and thus the output voltage Vout is equal to the sum of the voltages of the capacitor C2 and the capacitor C3. The voltage across the capacitor C3 is the input voltage Vin. In the case where the voltage of the capacitor C2 is also the input voltage Vin, the output voltage Vout of the conversion circuit 112 shown in fig. 6 may reach 2 Vin. That is, the conversion ratio of the conversion circuit shown in fig. 6 is 2.

It can be seen that the inductor Lr1, the capacitor Cr1 and the capacitor C2 resonate in the time period t 1. That is, when the switching frequencies Fsw of the switching tubes Q1 to Q4 satisfy the following formula four, ZCS can be realized by the switching tubes Q1 and Q3:

generally, the capacitance of the capacitor C2 is much larger than that of the capacitor Cr1, for example, the capacitance of the capacitor C2 may be 100 times that of the capacitor Cr 1. Then four Fsw may be approximately equal toApproaching to Fsw shown in equation three. Therefore, when the switching frequency Fsw shown in formula three is adopted, the switching tubes Q1 to Q4 in the switched capacitor shown in fig. 6 can all realize ZCS, which is beneficial to further improving the efficiency of the converter circuit 112.

Although the conversion circuit 112 shown in fig. 2 and fig. 6 has high efficiency, it is a switched capacitor circuit in nature, and only integer conversion ratio can be realized, and the conversion ratio of the conversion circuit 112 cannot be continuously adjusted. In view of this, a step-down (buck) circuit may also be integrated in the conversion circuit 112, as shown in fig. 8. The conversion circuit 112 shown in fig. 8 mainly includes a buck unit and a switched capacitor unit, where the buck unit adopts a buck circuit topology and the switched capacitor unit adopts a switched capacitor circuit topology.

For specific implementation of the switched capacitor unit, reference may be made to fig. 6, which is not described in detail again. For ease of understanding, the present embodiment will be described below with a scenario in which the conversion ratio of the switched capacitor unit is 2.

For convenience of explanation, the embodiment of the present application represents the output voltage of the buck unit as a forward voltage. The buck unit may perform a step-down conversion on the input voltage Vin to obtain the forward voltage. Specifically, as shown in fig. 8, the buck unit includes a capacitor C1, an inductor L1, a switching tube Q7, and a switching tube Q8. One end of the inductor L1 is connected to the high potential input terminal i + of the switching circuit 112, and the other end of the inductor L1 is connected to the second electrode of the switching tube Q7 and the first electrode of the switching tube Q8, respectively. A first electrode of the switching tube Q7 is connected to the high potential output o + of the switching circuit 112. A second electrode of the switching tube Q8 is connected to one end of the capacitor C3 in the switched capacitor unit. One end of the capacitor C1 is connected to the high potential input terminal i + of the conversion circuit 112, and the other end of the capacitor C1 is connected to the low potential input terminal i-of the conversion circuit 112 and the low potential output terminal o-of the conversion circuit 112, respectively.

Illustratively, the inductor L1 may be an inductor with a strong energy storage capability that includes a coil and a magnetic core. The magnetic core of the inductor L1 may be ferrite, iron powder core, etc., and the coil may be a flat wire, litz wire, etc., which is not limited in this embodiment.

During each cycle, there are mainly two switch states of the switching circuit 112 shown in fig. 8:

the first state: the switch tube Q7 is turned on, and the switch tube Q8 is turned off.

In this case, a current is input from the high potential input terminal i + of the inverter circuit 112, transmitted through the inductor L1 and the switching tube Q7, and then output from the high potential output terminal o + of the inverter circuit 112. The returned current is input from the low potential output terminal o-of the inverter circuit 112 and returned to the low potential input terminal i-of the inverter circuit 112, thereby constituting a charging loop of the inductor L1. In this case, the inductor L1 is charged, and the output voltage Vout is the difference between the input voltage Vin and the voltage of the inductor L1. That is, the voltage VL1 of the inductor L1 at this time satisfies the following formula five:

VL1 is Vin-Vout (formula five)

It should be noted that in the embodiment of the present application, the voltage of the inductor L1 is a potential difference obtained by subtracting the potential of the other end of the inductor L1 from the potential of the end connected to the high potential input end i + in the inductor L1, and further description of subsequent embodiments is omitted.

And a second state: the switch tube Q7 is turned off, and the switch tube Q8 is turned on.

In this case, the current is input from the high potential input terminal i + of the converting circuit 112, and after being transmitted through the inductor L1, the switching tube Q8 and the capacitor C3, the current flows back to the low potential input terminal i-of the converting circuit 112, thereby forming a discharging loop of the inductor L1. In this case, the inductor L1 discharges, and the voltage of the capacitor C3 is the difference between the input voltage Vin and the voltage of the inductor L1. Namely VC 3-Vin-VL 1. Since the conversion ratio of the switched capacitor unit is 2, that is, Vout is 2VC3, the following equation six can be obtained:

VL1 is Vin-Vout/2 (formula six)

Assuming that the duty cycle of the switching tube Q7 is D, the on-time of the switching tube Q7 in each cycle is proportional to the cycle. Then, according to the volt-second balance principle, (Vin-Vout) D + (Vin-Vout/2) (1-D) is 0, and the following formula seven is obtained:

in formula seven, the duty ratio D of the switching tube Q7 may be any value of [0,1 ]. By adjusting the duty ratio D of the switching tube Q7, the output voltage Vout can be continuously varied from Vin to 2 Vin. When the value of D is 0, that is, the switching tube Q7 keeps off in a period, and the switching tube Q8 keeps on in a period, at this time, the output voltage Vout can reach 2 Vin. When the value of D is 1, that is, the switching tube Q7 keeps on in a period, and the switching tube Q8 keeps off in a period, at this time, the output voltage Vout can reach Vin.

However, the output voltage Vout of the conversion circuit 112 shown in fig. 8 still has a limit, and the maximum output voltage Vout can only reach 2Vout, that is, the maximum transformation ratio of the conversion circuit 112 can only reach the transformation ratio of the switched capacitor unit. In view of the above, the present embodiment provides a conversion circuit, which can be used as the conversion circuit 112 shown in fig. 1. The maximum transformation ratio of the conversion circuit is not limited by the transformation ratio of the switched capacitor unit, and continuous adjustment of the transformation ratio of the conversion circuit is supported.

Illustratively, as shown in fig. 9, the conversion circuit 90 provided in the embodiment of the present application mainly includes a buck-boost (buck-boost) unit 91 and a switched capacitor unit 92. The high potential end of the buck-boost unit 91 and the high potential end of the switched capacitor unit 92 are both connected to the high potential output end o + of the conversion circuit 90, the first middle end of the buck-boost unit 91 is connected to the second middle end of the switched capacitor unit 92, and the low potential end of the buck-boost unit 91 and the low potential end of the switched capacitor unit 92 are both connected to the low potential output end o-of the conversion circuit 90.

The buck-boost unit 91 may receive the first input voltage Vin1, perform buck conversion or boost conversion on the first input voltage Vin1 to obtain a forward voltage, and provide the forward voltage to the switched capacitor unit. Specifically, the buck-boost unit 91 can perform buck conversion on the first input voltage Vin1, in which case the forward voltage is not less than 1/N of the first input voltage Vin1 and not greater than the first input voltage Vin 1. N is a transformation ratio of the switched capacitor unit 92, and N is an integer greater than or equal to 1. The buck-boost unit 91 may also boost convert the first input voltage Vin1, in which case the forward voltage is not less than the first input voltage Vin 1. The switched-capacitor unit 92 may boost-convert the forward voltage and output the boost-converted forward voltage as the first output voltage Vout 1. Assuming that the forward voltage is V1, the first output voltage Vout1 is NV 1.

Since the buck-boost unit 91 in the embodiment of the present application can perform buck conversion on the first input voltage, in the case that the buck-boost unit 91 performs buck conversion on the first input voltage, according to the seventh formula, the first output voltage Vout1 can reach any voltage between Vin1 and 2Vin 1. Since the buck-boost unit 91 can also perform boost conversion on the first input voltage, the forward voltage can reach a value not less than Vin when the buck-boost unit 91 performs boost conversion on the first input voltage. After the switched capacitor unit 32 performs the boost conversion on the forward voltage, the first output voltage Vout1 may reach a value not less than 2Vin 1.

Therefore, the conversion circuit 90 provided in the embodiment of the present application can support that the transformation ratio is continuously adjustable, and the maximum transformation ratio of the conversion circuit 90 is no longer limited by the transformation ratio of the switched capacitor unit 92. Therefore, the conversion circuit 90 provided by the embodiment of the present application has higher universality.

It is to be understood that the embodiment of the present application is not limited to the specific implementation of the switched capacitor unit 92, and the second middle terminal and the low potential terminal of the switched capacitor unit 92 may be understood as two terminals of the switched capacitor unit 92 for receiving the forward voltage. As an example, the circuit topology of the switched capacitor unit 92 may be the switched capacitor circuit topology shown in fig. 2 and 6. In the conversion circuit 90 shown in fig. 9, the second intermediate terminal of the switched capacitor unit 92 can be understood as any one of connection points in the electrical connection between the capacitor C2 and the capacitor C3.

Next, the buck-boost unit 91 in the embodiment of the present application is further exemplified by the following embodiments.

Example one

As shown in fig. 9, the buck-boost unit 91 includes an inductor L1, a diode D1, a diode D2, a switching tube Q8, and a switching tube Q9. One end of the inductor L1 is connected to the high-potential input terminal i + of the switching circuit 90, and the other end of the inductor L1 is connected to the anode of the diode D1, the first electrode of the switching tube Q9, and the first electrode of the switching tube Q8, respectively. The cathode of the diode D1 is connected to the high potential output terminal o + of the switching circuit 90, and the second electrode of the switching tube Q8 is connected to the low potential input terminal i-and the low potential output terminal o-of the switching circuit 90, respectively. A second electrode of the switching tube Q9 is connected to an anode of the diode D2, and a cathode of the diode D2 may be connected to a second intermediate terminal of the switched capacitor unit 92 as a first intermediate terminal of the buck-boost unit 91.

The buck-boost unit 91 in fig. 9 can perform buck conversion on the first input voltage V1 and boost conversion on the first input voltage V1, specifically:

1. when the buck-boost unit 91 performs buck conversion on the first input voltage Vin1, the first output voltage Vout1 of the conversion circuit 90 may be any value between Vin1 and 2Vin 1.

Based on the switching circuit 90 shown in fig. 9, it is assumed that the switching tube Q8 and the switching tube Q9 are both switching tubes that are turned on at a high level and turned off at a low level. Then, using the control signals shown in fig. 10, the buck-boost unit 91 may be caused to buck convert the first input voltage Vin 1. The control signal S8 is used to control the on/off of the switching tube Q8, and the control signal S9 is used to control the on/off of the switching tube Q9.

As shown in fig. 10, the control signal S8 is low during the period T, so the switch Q8 remains off during the period T. In the period ta of the period T, the control signal S9 is at a high level, so the switching tube Q9 remains on in the period ta. During the period tb of the period T, the control signal S9 is at low level, so the switching tube Q9 remains off during the period tb. Next, taking a scene in which the conversion ratio of the switched capacitor unit 92 is 2 as an example, the equivalent circuit of the buck-boost unit 91 in the time period ta and the time period tb will be described. It should be noted that, the switching state of the buck-boost unit 91 is not necessarily related to the switching state of the switched capacitor unit 92. Therefore, the embodiments of the present application do not limit the switching state of the switched capacitor unit 92 in the following.

Time period ta

As shown in fig. 10, the control signal S8 is at low level during the time period ta, and therefore the switching tube Q8 is turned off. The control signal S9 is high, so that the switch Q9 is turned on, and the equivalent circuit of the converting circuit 90 can be as shown in fig. 11 a. The current is input from the high potential input terminal i + of the conversion circuit 90, transmitted through the inductor L1, the switching tube Q9, the diode D2 and the capacitor C3, and then flows back to the low potential input terminal i-of the conversion circuit 90, thereby forming a charging loop of the inductor L1.

At this time, the buck-boost unit 91 supplies the forward voltage of the switched capacitor unit 92, that is, the voltage of the capacitor C3. As can be seen from fig. 11a, the forward voltage at this time is the difference between the first input voltage Vin1 and the voltage of the inductor L1, i.e., VC3 is equal to Vin1-VL 1. Further, the first output voltage Vout1 becomes 2VC3, so that VL1 becomes Vin1-Vout 1/2.

Time period tb

As shown in fig. 10, the control signal S8 is low during the time period tb, so the switching tube Q8 is turned off. The control signal S9 is low, so the switch Q9 is turned off, and the equivalent circuit of the converting circuit 90 can be as shown in fig. 11 b. A current is input from the high potential input terminal i + of the inverter circuit 90, transmitted through the inductor L1 and the diode D1, and output from the high potential output terminal o + of the inverter circuit 90. The returned current is input from the low potential output terminal o-of the inverter circuit 90 and returned to the low potential input terminal i-of the inverter circuit 90, thereby constituting a discharge loop of the inductor L1. At this time, Vin1-VL1-Vout1 is equal to 0, and VL1 is equal to Vin1-Vout 1.

When the voltage of the inductor L1 in the time period ta and the time period tb is combined, the voltage can be obtained according to the volt-second balance principle: (Vin1-Vout1/2) ta + (Vin1-Vout1) tb equals 0. Assuming that the duty ratio of the switching tube Q9 is D1, i.e., D1 is ta/T is ta/(ta + tb), the following equation eight can be obtained:

in the eighth formula, the duty ratio D1 of the switching tube Q9 may be any value of [0,1 ]. By adjusting the duty ratio D1 of the switching tube Q9, the first output voltage Vout1 can be continuously varied between Vin1 and 2Vin 1. When the value of D1 is 0, that is, the switching tube Q9 is kept off in a period, at this time, the first output voltage Vout1 may reach Vin 1. When D1 is equal to 1, i.e. the switch Q9 remains on during the period, the first output voltage Vout1 can reach 2Vin 1.

2. When the buck-boost unit 91 performs boost conversion on the first input voltage Vin1, the first output voltage Vout1 of the conversion circuit 90 may be any value not less than 2Vin 1.

Based on the switching circuit 90 shown in fig. 9, it is assumed that the switching tube Q8 and the switching tube Q9 are both switching tubes that are turned on at a high level and turned off at a low level. Then, using the control signals shown in fig. 12, the buck-boost unit 91 may be caused to boost convert the first input voltage Vin 1. The control signal S8 is used to control the on/off of the switching tube Q8, and the control signal S9 is used to control the on/off of the switching tube Q9.

As shown in fig. 10, the control signal S9 is high during the period T, so the switch Q9 remains on during the period T. In the period ta of the period T, the control signal S8 is at a high level, so the switching tube Q8 remains on in the period ta. During the period tb of the period T, the control signal S8 is at low level, so the switching tube Q8 remains off during the period tb. Next, taking a scene in which the conversion ratio of the switched capacitor unit 92 is 2 as an example, the equivalent circuit of the buck-boost unit 91 in the time period ta and the time period tb will be described. It should be noted that, the switching state of the buck-boost unit 91 is not necessarily related to the switching state of the switched capacitor unit 92. Therefore, the embodiments of the present application do not limit the switching state of the switched capacitor unit 92 in the following.

Time period ta

As shown in fig. 12, the control signal S9 is at a high level during the time period ta, and therefore the switching tube Q9 is turned on. The control signal S8 is high, so that the switch Q8 is turned on, and the equivalent circuit of the converting circuit 90 can be as shown in fig. 13 a. The current is input from the high potential input terminal i + of the conversion circuit 90, transmitted through the inductor L1 and the switching tube Q8, and then flows back to the low potential input terminal i-of the conversion circuit 90, thereby forming a charging loop of the inductor L1. At this time, Vin1-VL1 become 0, and VL1 becomes Vin 1.

Time period tb

As shown in fig. 12, the control signal S8 is low during the time period tb, so the switching tube Q8 is turned off. The control signal S9 is high, so that the switch Q9 is turned on, and the equivalent circuit of the converting circuit 90 can be as shown in fig. 13 b.

The current is input from the high potential input terminal i + of the conversion circuit 90, transmitted through the inductor L1, the switching tube Q9, the diode D2 and the capacitor C3, and then flows back to the low potential input terminal i-of the conversion circuit 90, thereby forming a discharge loop of the inductor L1. At this time, Vin1-VL1-VC3 is equal to 0, and the voltage VC3 of the capacitor C3 is the forward voltage provided by the buck-boost unit 91 to the switched capacitor unit 92. Further, Vout1 becomes 2VC3, and VL1 becomes Vin1-Vout 1/2.

When the voltage of the inductor L1 in the time period ta and the time period tb is combined, the voltage can be obtained according to the volt-second balance principle: (Vin1) ta + (Vin1-Vout1/2) tb. Assuming that the duty ratio of the switching tube Q8 is D2, i.e., D2 is ta/T is ta/(ta + tb), the following formula nine is obtained:

in the formula nine, the duty ratio D2 of the switching tube Q8 can be any value of [0,1 ]. By adjusting the duty ratio D2 of the switching tube Q8, the first output voltage Vout1 can be continuously varied within a range of 2Vin to ∞. When the value of D2 is 0, that is, the switching tube Q8 is kept off in a period, at this time, the first output voltage Vout1 may reach 2Vin 1. When D2 is equal to 1, i.e., the switch Q8 remains on during the period, the first output voltage Vout1 can reach infinity.

It should be noted that the embodiment of the present application considers that the first output voltage can reach infinity without considering the limitation of the energy storage capability of the inductor L1. In practical applications, the maximum value that the first output voltage Vout1 can actually reach is also limited by factors such as the inductance of the inductor L1.

Example two

In one possible implementation, the conversion circuit 90 provided in the embodiment of the present application may further receive the second input voltage Vin2 through the high-potential output terminal o + and the low-potential output terminal o-. The switched-capacitor unit 92 may down-convert the second input voltage Vin2 to obtain a reverse voltage. Assuming that the transformation ratio of the switched capacitor unit 92 is N, the reverse voltage may be Vin 2/N.

The switched-capacitor unit 92 may transmit the reverse voltage to the buck-boost unit 91 through the second intermediate terminal and the low potential terminal. The buck-boost unit 91 performs buck-boost conversion on the reverse voltage, and outputs the buck-boost converted reverse voltage as a second output voltage Vout2 through a high potential input terminal i + and a low potential input terminal i-of the conversion circuit 90, which is the second output voltage Vout 2.

Illustratively, as shown in fig. 14, the buck-boost unit 91 may further include a switch tube Q7 and a switch tube Q10. The switch Q7 includes the diode D1, and the switch Q10 includes the diode D2. A first electrode of the switching tube Q7 is connected to the high potential output o + of the switching circuit 90, and a second electrode of the switching tube Q7 is connected to the other end of the inductor L1. A first electrode of the switching tube Q10 is connected to the switched capacitor unit 92 as a first middle end of the buck-boost unit 91, and a second electrode of the switching tube Q10 is connected to a second electrode of the switching tube Q9.

And the switching tube Q8 comprises a diode D3, the anode of the diode D3 is connected with the low potential input terminal i-of the conversion circuit, and the cathode of the diode D3 is connected with the other end of the inductor L1 close to the switching tube Q9. The switching tube Q9 includes a diode D4, an anode of the diode D4 is connected to the switching tube Q10, and a cathode of the diode D4 is connected to the inductor L1.

It can be understood that, in order to make the switching tube Q7 and the switching tube Q10 not affect the transition of the first input voltage Vin1 to the first output voltage Vout1, the switching tube Q7 and the switching tube Q10 may be kept turned off during the transition of the first input voltage Vin1 to the first output voltage Vout 1.

For example, as shown in fig. 10, the control signal S7 is a control signal for controlling the switch Q7, and the control signal S10 is a control signal for controlling the switch Q10. As can be seen from fig. 10, when the buck-boost unit performs buck conversion on the first input voltage Vin1, the control signals S7 and S10 are both low, and the switching transistors Q7 and Q10 are kept off. For example, as shown in fig. 12, when the buck-boost unit performs boost conversion on the first input voltage Vin1, the control signals S7 and S10 are both low, and the switching transistors Q7 and Q10 are kept off.

The conversion circuit 90 shown in fig. 14 may down-convert the second input voltage Vin 2. The buck-boost unit 91 can perform buck conversion on the reverse voltage and also perform boost conversion on the reverse voltage. Specifically, the method comprises the following steps:

1. when the buck-boost unit 91 performs buck conversion on the reverse voltage, the second output voltage Vout2 of the conversion circuit 90 may be any value between 0 and Vin 2/2.

Based on the switching circuit 90 shown in fig. 14, it is assumed that the switching transistors Q7 to Q10 are all high-level conducting switching transistors and low-level conducting switching transistors. Then, using the control signal shown in fig. 15, the buck-boost unit 91 can be caused to buck convert the reverse voltage.

As shown in fig. 15, the control signals S7, S8, and S9 are low during the period T, so the switching tubes Q7 to Q9 are kept off during the period T. In the period ta of the period T, the control signal S10 is at a high level, so the switching tube Q10 remains on in the period ta. During the period tb of the period T, the control signal S10 is at low level, so the switching tube Q10 remains off during the period tb.

Next, taking a scene in which the conversion ratio of the switched capacitor unit 92 is 2 as an example, the equivalent circuit of the buck-boost unit 91 in the time period ta and the time period tb will be described. It should be noted that, the switching state of the buck-boost unit 91 is not necessarily related to the switching state of the switched capacitor unit 92. Therefore, the embodiments of the present application do not limit the switching state of the switched capacitor unit 92 in the following.

Time period ta

As shown in fig. 15, during the time period ta, the switching tubes Q7, Q8 and Q9 are turned off, the switching tube Q10 is turned on, and the equivalent circuit of the converting circuit 90 can be as shown in fig. 16 a.

The current is output from one end of the capacitor C3 close to the switch tube Q10, transmitted through the switch tube Q10, the diode D4 in the switch tube Q9 and the inductor L1, and then output from the high potential input terminal i + of the conversion circuit 90. The returned current is input from the low potential input terminal i-of the inverter circuit 90 and returned to the end of the capacitor C3 near the low potential input terminal i-of the inverter circuit 90, thereby constituting a charging loop of the inductor L1.

At this time, the switched capacitor unit 92 supplies the reverse voltage to the buck-boost unit 91, that is, the voltage of the capacitor C3. As can be seen from fig. 16a, at this time, VC3+ VL1-Vout2 is equal to 0, that is, VL1 is equal to Vout2-VC3 is equal to Vout2-Vin 2/2.

Time period tb

As shown in fig. 15, the control signals S7 to S10 are all low during the time period tb, so that the switching tubes Q7 to Q10 are all turned off, and the equivalent circuit of the converting circuit 90 can be as shown in fig. 16 b. The current is output from the high potential input terminal i + of the conversion circuit 90, and the returned current is input from the low potential input terminal i-of the conversion circuit 90 and is returned to the end of the inductor L1 close to the switching tube Q8 through the diode D3, so that a discharge loop of the inductor L1 is formed. At this time, Vout2-VL1 is 0, that is, VL1 is Vout 2.

When the voltage of the inductor L1 in the time period ta and the time period tb is combined, the voltage can be obtained according to the volt-second balance principle: (Vout2-Vin2/2) ta + (Vout2) tb equal to 0. Assuming that the duty ratio of the switching tube Q10 is D3, i.e., D3 is ta/T is ta/(ta + tb), the following equation ten can be obtained:

in the formula ten, the duty ratio D3 of the switching tube Q10 may be any value of [0,1 ]. The second output voltage Vout2 can be continuously varied between 0 and Vin2/2 by adjusting the duty cycle D3 of the switching transistor Q10. When the value of D3 is 0, that is, the switching tube Q10 is kept off in a cycle, at this time, the second output voltage Vout2 may reach 0. When D3 is equal to 1, i.e. the switch Q10 remains on during the period, the second output voltage Vout2 can reach Vin 2/2.

2. When the buck-boost unit 91 performs boost conversion on the reverse voltage, the second output voltage Vout2 of the conversion circuit 90 may be any value from Vin2/2 to Vin 2.

Based on the switching circuit 90 shown in fig. 14, it is assumed that the switching transistors Q7 to Q10 are all high-level conducting switching transistors and low-level conducting switching transistors. Then, using the control signals shown in fig. 17, the buck-boost unit 91 can be caused to boost-convert the reverse voltage.

As shown in fig. 17, the control signals S8 and S9 are low during the period T, so the switching transistors Q8 and Q9 remain off during the period T. The control signal S10 is high during the period T, so the switch Q10 remains on during the period T. In the period ta of the period T, the control signal S7 is at a high level, so the switching tube Q7 remains on in the period ta. During the period tb of the period T, the control signal S7 is at low level, so the switching tube Q7 remains off during the period tb.

Time period ta

As shown in fig. 17, during the time period ta, the switching tubes Q8 and Q9 are turned off, the switching tubes Q7 and Q10 are turned on, and the equivalent circuit of the converting circuit 90 may be as shown in fig. 18 a. The current is input from the high potential output terminal o + of the conversion circuit 90, transmitted through the switching tube Q7 and the inductor L1, and output from the high potential input terminal i + of the conversion circuit 90. The returned current is input from the low potential input terminal i-of the inverter circuit 90 and returned to the low potential output terminal o-of the inverter circuit 90, thereby constituting a charging loop of the inductor L1. In this case, Vin2+ VL1-Vout2 is 0, i.e., VL1 is Vout2-Vin 2.

Time period tb

As shown in fig. 17, the control signals S7 to S9 are all at low level during the time period tb, so the switching tubes Q7 to Q9 are all off, and the control signal S10 is at high level, so the switching tube Q10 is turned on, and the equivalent circuit of the converting circuit 90 can be as shown in fig. 18 b. The current is output from one end of the capacitor C3 close to the switching tube Q10, is transmitted through the inductor L1 and is output from the high potential input end i + of the conversion circuit 90, and the returned current is input from the low potential input end i-of the conversion circuit 90 and is returned to one end of the capacitor C3 close to the low potential input end i-of the conversion circuit 90, so that a discharge loop of the inductor L1 is formed. At this time, Vout2-VL1-VC3 is 0. The voltage VC3 of the capacitor C3, i.e., the reverse voltage provided by the switched capacitor unit 92 to the buck-boost unit 91, can be further derived from VL1 being Vout2-VC3 being Vout2-Vin 2/2.

When the voltage of the inductor L1 in the time period ta and the time period tb is combined, the voltage can be obtained according to the volt-second balance principle: (Vout2-Vin2) ta + (Vout2-Vin2/2) tb ═ 0. Assuming that the duty ratio of the switching tube Q7 is D4, i.e., D4 is ta/T is ta/(ta + tb), the following formula eleven is obtained:

in the formula eleven, the duty ratio D4 of the switching tube Q7 may be any value of [0,1 ]. By adjusting the duty ratio D4 of the switching tube Q7, the second output voltage Vout2 can be continuously varied from Vin2/2 to Vin 2. When the value of D4 is 0, that is, the switching tube Q7 is kept off in a period, at this time, the second output voltage Vout2 may reach Vin 2/2. When D4 is equal to 1, i.e. the switch Q7 remains on during the period, the second output voltage Vout2 can reach Vin 2.

As can be seen from the above embodiment, the conversion circuit 90 provided in the embodiment of the present application can convert the first input voltage Vin1 to Vin1 to infinity. For example, the control circuit 114 may determine the duty ratio of the switching tube Q8 or the switching tube Q9 by using the method shown in fig. 19, so that the first output voltage Vin1 may reach the first target voltage output by the conversion circuit 90. Specifically, the method mainly comprises the following steps:

s1901: the voltage conversion device is powered on. The voltage conversion means may be, for example, the DCDC booster11 shown in fig. 1. After the voltage conversion device is powered on, the high potential input terminal i + and the low potential input terminal i-of the conversion circuit 90 may receive the first input voltage Vin 1.

S1902: the control circuit 114 controls the switching tubes Q1 to Q4 in the switched capacitor unit 92 to turn on and off, so that the voltages of the capacitor C2 and the capacitor C3 are balanced, that is, the voltages of the two are equal.

S1903: the control circuit 114 keeps the switching tubes Q7, Q8 and Q10 off and adjusts the duty cycle D1 of the switching tube Q9. For example, the control circuit 114 may adjust the duty ratio D1 of the switching tube Q9 in such a manner that the duty ratio D1 of the switching tube Q9 gradually increases from 0 to 1.

S1904: in the process of adjusting the duty ratio D1 in the range of [0,1], if the first output voltage Vout1 reaches the first target voltage, the control circuit 114 continues to perform S1905. If the duty ratio D1 is adjusted within the range of [0,1] and the first output voltage Vout1 cannot reach the first target voltage, the control circuit 114 continues to execute S1906.

S1905: the control circuit 114 maintains the current duty cycle D1 of the switching tube Q9.

S1906: if the duty ratio D1 is adjusted within the range of [0,1], the first output voltage Vout1 cannot reach the first target voltage, which indicates that the first target output voltage may exceed 2Vin 1. Therefore, the control circuit 114 may keep the switching tubes Q7 and Q10 turned off, the switching tube Q9 turned on, and adjust the duty ratio D2 of the switching tube Q8.

S1907: in the process of adjusting the duty ratio D2 in the range of [0,1], if the first output voltage Vout1 reaches the first target voltage, the control circuit 114 continues to perform S1908. If the duty ratio D2 is adjusted within the range of [0,1] and the first output voltage Vout1 cannot reach the first target voltage, the control circuit 114 continues to execute S1909.

S1908: the control circuit 114 maintains the current duty cycle D2 of the switching tube Q8.

S1909: the switching circuit 90 is out of order. The control circuit 114 may report the error. For example, if the first target voltage is less than Vin1, the conversion circuit 90 cannot output the first output voltage meeting the first target voltage, and a status error may occur.

Similar to fig. 19, the control circuit 114 may also first keep the switching transistors Q7 to Q9 turned off, and adjust the duty ratio D3 of the switching transistor Q10. In this process, if the second output voltage Vin2 can reach the second target voltage, the control circuit 114 can maintain the current duty ratio D3 of the switching tube Q10. If the duty ratio D3 is adjusted within [0,1] and the second output voltage cannot reach the second target voltage, the control circuit 114 may keep the switching tubes Q8 and Q9 turned off, keep the switching tube Q10 turned on, and adjust the duty ratio D4 of the switching tube Q7. In this process, if the second output voltage Vin2 can reach the second target voltage, the control circuit 114 can maintain the current duty ratio D4 of the switching tube Q7. If the duty ratio D4 is adjusted within [0,1] and the second output voltage cannot reach the second target voltage, it means that the state of the switching circuit 90 is incorrect. The control circuit 114 may report the error.

In summary, the present embodiment provides a conversion circuit 90, the conversion circuit 90 includes a buck-boost unit 91 and a switched capacitor unit, and the transformation ratio of the conversion circuit 90 is not limited by the switched capacitor unit. It should be noted that, since the switched capacitor unit 92 has a boosting function in the embodiment of the present application, the requirement on the boosting capability of the buck-boost unit 91 is low, and the inductor L1 may be implemented by an inductor with a small inductance. Generally, the larger the inductance of the inductor, the larger the loss and the size, so that the conversion circuit 90 provided by the embodiment of the present invention is beneficial to improving the efficiency and reducing the size compared with the conventional boost circuit.

Taking the conventional boost circuit shown in fig. 20 as an example, the conventional boost circuit mainly includes an inductor and two switching tubes. Assume that the first input voltage Vin1 of the conversion circuit 90 and the input voltage of the conventional boost circuit are both 300-500V; the first output voltage Vout1 of the conversion circuit 90 and the output voltage of the conventional boost circuit are both 600-850V; the power of the switching circuit 90, as well as the power of the conventional boost circuit, is 12.5 kw. The design parameters of the conversion circuit 90 and the conventional boost circuit are shown in the following table one:

watch 1

Specifically, an IGBT with a withstand voltage of 650V and a maximum current of 75A is used for each switching tube in the switching circuit 90, the inductance of the inductor L1 is 100uH, and the switching frequency is 20 kHz. Each switching tube in the traditional boost circuit adopts an IGBT with 1200V withstand voltage and 75A maximum current, the inductance of an inductor is 500uH, and the switching frequency is 15 kHz.

By contrast, as can be seen from fig. 21, the volume of the conventional boost circuit is close to that of the conversion circuit 90 provided in the embodiment of the present application. However, as can be seen from fig. 22, the weight of the conversion circuit 90 provided in the embodiment of the present application is much smaller than that of the conventional boost circuit, which is mainly because the present application can use a smaller inductor in the buck-boost unit 91, so that the weight of the inductor can be reduced. As can be seen from fig. 23, the efficiency of the conventional boost circuit is about 97.5%, whereas the efficiency of the conversion circuit 90 provided in the embodiment of the present application can be as high as 98.5%, and the efficiency of the conversion circuit 90 is significantly improved.

Based on the same technical concept, the embodiment of the present application further provides a voltage conversion apparatus, which may include the conversion circuit 90 provided in any of the above embodiments of the present application. For example, the voltage conversion device may be used as the DCDC booster11 in the electric vehicle 10. The switching circuit 90 can be used as the switching circuit 112 in the DCDC booster11, and the control circuit 114 is connected to the control electrodes of the switching tubes in the buck-boost unit 91 and the switched capacitor unit 92, respectively, so as to control the switching circuit 90 to implement voltage conversion.

Based on the same technical concept, the embodiment of the application also provides an electric automobile, and the electric automobile can be shown as fig. 1. The electric vehicle 10 includes a DCDC booster11 therein, and the DCDC booster11 is connected with the power battery and can charge the power battery 12. In the DCDC booster11, the conversion circuit 112 may be implemented by using the conversion circuit 90 provided in the embodiment of the present application.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.

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