阅读说明：本技术 基于斜波复位的斜波注入电路和开关电源中误差补偿方法 (Ramp wave injection circuit based on ramp wave reset and error compensation method in switching power supply ) 是由 向本才 于 2021-04-13 设计创作，主要内容包括：基于斜波复位的斜波注入电路和开关电源中误差补偿方法,斜波注入电路中利用斜波电压产生模块在第一控制信号的控制下产生电压值线性上升的斜波电压,仅当第一控制信号从第一状态转变为第二状态时控制斜波电压的电压值复位至零；利用误差补偿模块产生与参考电压成比例的补偿电压,斜波注入电路将斜波电压减去补偿电压后作为最终斜波电压输出。将本发明应用于开关电源时,由于斜波电压与开关电源中开关器件的工作占空比无关,从而解决了传统内部集成斜波注入电路的开关电源中由于斜波电压与开关电源中开关器件的工作占空比有关而引入的输出误差问题,实现不同占空比情况下开关电源的输出电压保持恒定,消除了开关电源的输出误差。(The ramp injection circuit generates a ramp voltage with a linearly rising voltage value under the control of a first control signal by using a ramp voltage generation module, and the voltage value of the ramp voltage is controlled to be reset to zero only when the first control signal is changed from a first state to a second state; and generating a compensation voltage proportional to the reference voltage by using the error compensation module, and outputting the ramp voltage subtracted by the ramp injection circuit as a final ramp voltage. When the method is applied to the switching power supply, the ramp voltage is irrelevant to the working duty ratio of the switching device in the switching power supply, so that the problem of output error introduced by the fact that the ramp voltage is relevant to the working duty ratio of the switching device in the switching power supply in the traditional switching power supply with the ramp injection circuit integrated inside is solved, the output voltage of the switching power supply is kept constant under the conditions of different duty ratios, and the output error of the switching power supply is eliminated.)

1. A ramp wave injection circuit based on ramp wave reset is characterized by comprising a ramp wave voltage generation module and an error compensation module; the ramp voltage generation module is used for generating ramp voltage with a linearly rising voltage value under the control of the first control signal, and controlling the voltage value of the ramp voltage to be reset to zero only when the first control signal is changed from a first state to a second state; the error compensation module is used for generating a compensation voltage proportional to the reference voltage; and the ramp injection circuit subtracts the compensation voltage from the ramp voltage to output the final ramp voltage.

2. The ramp-reset-based ramp injection circuit according to claim 1, wherein the ramp voltage generation module comprises a timing control unit and a ramp generation unit;

the time sequence control unit is used for generating a pulse signal according to the first control signal, the pulse signal is effective only when the first control signal is changed from a first state to a second state, and otherwise, the pulse signal is ineffective;

the ramp wave generating unit comprises a first capacitor, a first switch, a second switch and a current source, wherein a first connecting end of the first capacitor is grounded, and a second connecting end of the first capacitor is connected with the current source after passing through the first switch on one hand and is grounded after passing through the second switch on the other hand; the first switch and the second switch are controlled by the pulse signal, the first switch is controlled to be switched off and the second switch is controlled to be switched on when the pulse signal is effective, and the first switch is controlled to be switched on and the second switch is controlled to be switched off when the pulse signal is ineffective; and the second connecting end of the first capacitor outputs the ramp voltage.

3. The ramp reset-based ramp injection circuit according to claim 2, wherein the timing control unit comprises a not gate and an and gate, wherein the input terminal of the not gate is connected to the first input terminal of the and gate and the first control signal, and the output terminal of the not gate is connected to the second input terminal of the and gate; the output end of the AND gate generates the pulse signal.

4. The ramp-reset based ramp injection circuit according to any of claims 1 to 3, wherein the error compensation module comprises an amplifier, a first resistor, a second resistor, a third resistor and a fourth resistor, the first resistor and the second resistor are connected in series and in parallel between the reference voltage and ground, and the series point is connected to the positive input terminal of the amplifier; the third resistor and the fourth resistor are connected in series and in parallel between the output end of the amplifier and the ground, and the series point of the third resistor and the fourth resistor is connected with the negative input end of the amplifier; the output of the amplifier generates the compensation voltage.

5. The error compensation method in the switching power supply comprises the steps that a signal obtained by superposing a reference voltage with a ramp voltage is used as a comparison reference by the switching power supply and is compared with a feedback voltage of an output voltage of the switching power supply, and a pulse width modulation signal is generated according to a comparison result to control the working duty ratio of a switching device in the switching power supply;

the error compensation method in the switching power supply is characterized by comprising the following steps:

firstly, a switching device in the switching power supply comprises an upper power tube and a lower power tube which are connected in series and in parallel between a power supply and the ground, and a signal of a series point of the upper power tube and the lower power tube is taken as a first control signal;

step two, enabling the voltage value of the ramp voltage to rise linearly, and resetting the voltage value of the ramp voltage to zero only when the first control signal changes from a low level to a high level, so that the ramp voltage is independent of the working duty ratio of a switching device in the switching power supply;

and thirdly, taking a signal obtained by superposing the reference voltage on the ramp voltage and subtracting a compensation voltage proportional to the reference voltage as a final comparison reference for comparison with a feedback voltage of the output voltage of the switching power supply, so that the comparison reference is constant, and the error caused by the ramp voltage is eliminated.

6. The method of claim 5, wherein the structure for generating the ramp voltage in the second step comprises a timing control unit and a ramp generating unit;

the time sequence control unit is used for generating a pulse signal according to the first control signal, the pulse signal is effective only when the first control signal is changed from a low level to a high level, and otherwise, the pulse signal is ineffective;

the ramp wave generating unit comprises a first capacitor, a first switch, a second switch and a current source, wherein a first connecting end of the first capacitor is grounded, and a second connecting end of the first capacitor is connected with the current source after passing through the first switch on one hand and is grounded after passing through the second switch on the other hand; the first switch and the second switch are controlled by the pulse signal, the first switch is controlled to be switched off and the second switch is controlled to be switched on when the pulse signal is effective, the first switch is controlled to be switched on and the second switch is controlled to be switched off when the pulse signal is ineffective, and the second connecting end of the first capacitor outputs the ramp voltage.

7. The method of claim 6, wherein the error compensation is performed in a switching power supplyDirectly using the reference voltage as the compensation voltage, wherein I is the current value of the current source, and T is the current value of the current source_swIs the duty cycle of the switching power supply, C is the capacitance of the first capacitor, V_refIs the voltage value of the reference voltage.

Technical Field

The invention belongs to the technical field of power electronics, and relates to a ramp injection circuit, in particular to a ramp injection circuit based on a ramp reset technology and having an error compensation function, and a method for performing error compensation in a switching power supply by using the ramp injection circuit.

Background

With the development of technology, in order to meet market demands, the requirements on the switching power supply are higher and higher, and the switching power supply is generally required to have the advantages of high response speed and the like. The switching power supply with fixed on-time can integrate a ramp wave injection circuit in order to simplify peripheral devices and reduce output ripples. As shown in fig. 1, in a conventional fixed on-time switching power supply with an internally integrated ramp injection circuit, the ramp injection circuit generates a ramp voltage Vripple, which is superimposed on a reference voltage Vref, and then the ramp voltage Vripple is compared with a feedback voltage Vfb of an output voltage Vout of the switching power supply, and PWM is performed according to the comparison result.

However, in this structure, the injected ramp waves are different under different duty ratios, as shown in fig. 3, (b), (c), and (d) in fig. 3 are respectively the case where the ramp wave voltage Vripple corresponding to three different duty ratios is superposed with the reference voltage Vref and then compared with the feedback voltage Vfb, and (a) in fig. 3 is a schematic drawing of (b), (c), and (d) in fig. 3, and it can be seen that the ramp wave voltages Vripple corresponding to three different duty ratios are different, resulting in different superposed values of Vripple and Vref, and thus causing a change in the feedback voltage Vfb.

Since the switching power supply output voltage Vout is (Vfb) ((R1 + R2)/R1) ((Vref + Vripple) ((R1 + R2)/R1, the feedback voltage Vfb differs and the switching power supply output voltage Vout also differs for different duty ratios. It is obvious that the conventional ramp injection circuit causes the switching power supply to introduce an output error, and a ramp injection circuit capable of compensating the output error is required.

Disclosure of Invention

Aiming at the problem of output error introduced by the fact that the ramp voltage is related to the working duty ratio of a switching device in a switching power supply of an internal integrated ramp injection circuit, the invention provides a ramp injection circuit based on ramp reset. In addition, the invention also provides a scheme for applying the ramp injection circuit in the switching power supply, and the output error of the switching power supply is eliminated.

The technical scheme of the ramp wave injection circuit provided by the invention is as follows:

a ramp wave injection circuit based on ramp wave reset comprises a ramp wave voltage generation module and an error compensation module; the ramp voltage generation module is used for generating ramp voltage with a linearly rising voltage value under the control of the first control signal, and controlling the voltage value of the ramp voltage to be reset to zero only when the first control signal is changed from a first state to a second state; the error compensation module is used for generating a compensation voltage proportional to the reference voltage; and the ramp injection circuit subtracts the compensation voltage from the ramp voltage to output the final ramp voltage.

Specifically, the ramp voltage generation module comprises a time sequence control unit and a ramp generation unit;

the time sequence control unit is used for generating a pulse signal according to the first control signal, the pulse signal is effective only when the first control signal is changed from a first state to a second state, and otherwise, the pulse signal is ineffective;

the ramp wave generating unit comprises a first capacitor, a first switch, a second switch and a current source, wherein a first connecting end of the first capacitor is grounded, and a second connecting end of the first capacitor is connected with the current source after passing through the first switch on one hand and is grounded after passing through the second switch on the other hand; the first switch and the second switch are controlled by the pulse signal, the first switch is controlled to be switched off and the second switch is controlled to be switched on when the pulse signal is effective, and the first switch is controlled to be switched on and the second switch is controlled to be switched off when the pulse signal is ineffective; and the second connecting end of the first capacitor outputs the ramp voltage.

Specifically, the time sequence control unit comprises a not gate and an and gate, wherein the input end of the not gate is connected with the first input end of the and gate and the first control signal, and the output end of the not gate is connected with the second input end of the and gate; the output end of the AND gate generates the pulse signal.

Specifically, the error compensation module comprises an amplifier, a first resistor, a second resistor, a third resistor and a fourth resistor, wherein the first resistor and the second resistor are connected in series and in parallel between the reference voltage and the ground, and the series point of the first resistor and the second resistor is connected with the positive input end of the amplifier; the third resistor and the fourth resistor are connected in series and in parallel between the output end of the amplifier and the ground, and the series point of the third resistor and the fourth resistor is connected with the negative input end of the amplifier; the output of the amplifier generates the compensation voltage.

The ramp injection circuit provided by the invention is applied to a switching power supply to eliminate output errors, and the technical scheme is as follows:

the error compensation method in the switching power supply comprises the steps that the switching power supply takes a signal obtained by superposing a reference voltage with a ramp wave voltage as a comparison reference to be compared with a feedback voltage of an output voltage of the switching power supply, and generates a pulse width modulation signal according to a comparison result to control the working duty ratio of a switching device in the switching power supply;

the error compensation method in the switching power supply comprises the following steps:

firstly, a switching device in the switching power supply comprises an upper power tube and a lower power tube which are connected in series and in parallel between a power supply and the ground, and a signal of a series point of the upper power tube and the lower power tube is taken as a first control signal;

step two, enabling the voltage value of the ramp voltage to rise linearly, and resetting the voltage value of the ramp voltage to zero only when the first control signal changes from a low level to a high level, so that the ramp voltage is independent of the working duty ratio of a switching device in the switching power supply;

and thirdly, taking a signal obtained by superposing the reference voltage on the ramp voltage and subtracting a compensation voltage proportional to the reference voltage as a final comparison reference for comparison with a feedback voltage of the output voltage of the switching power supply, so that the comparison reference is constant, and the error caused by the ramp voltage is eliminated.

Specifically, the structure for generating the ramp voltage in the second step includes a timing control unit and a ramp generating unit;

the time sequence control unit is used for generating a pulse signal according to the first control signal, the pulse signal is effective only when the first control signal is changed from a low level to a high level, and otherwise, the pulse signal is ineffective;

the ramp wave generating unit comprises a first capacitor, a first switch, a second switch and a current source, wherein a first connecting end of the first capacitor is grounded, and a second connecting end of the first capacitor is connected with the current source after passing through the first switch on one hand and is grounded after passing through the second switch on the other hand; the first switch and the second switch are controlled by the pulse signal, the first switch is controlled to be switched off and the second switch is controlled to be switched on when the pulse signal is effective, the first switch is controlled to be switched on and the second switch is controlled to be switched off when the pulse signal is ineffective, and the second connecting end of the first capacitor outputs the ramp voltage.

In particular, whenDirectly using the reference voltage as the compensation voltage, wherein I is the current value of the current source, and T is the current value of the current source_swIs the duty cycle of the switching power supply, C is the capacitance of the first capacitor, V_refIs the voltage value of the reference voltage.

The invention has the beneficial effects that: the ramp wave injection circuit provided by the invention utilizes a ramp wave reset technology to generate a ramp wave voltage irrelevant to the working duty ratio of a switching device in a switching power supply, and utilizes a voltage proportional to a reference voltage to compensate, so that the compensation of the error generated on a system by the traditional ramp wave voltage is realized; the invention is applied to the switching power supply, can solve the problem of output error introduced by the correlation between the ramp voltage and the working duty ratio of a switching device in the switching power supply in the traditional switching power supply with an internally integrated ramp injection circuit, realizes the constant output voltage of the switching power supply under the condition of different duty ratios, and eliminates the output error of the switching power supply.

Drawings

The following description of various embodiments of the invention may be better understood with reference to the following drawings, which schematically illustrate major features of some embodiments of the invention. These figures and examples provide some embodiments of the invention in a non-limiting, non-exhaustive manner. For purposes of clarity, the same reference numbers will be used in different drawings to identify the same or similar elements or structures having the same function.

Fig. 1 is a schematic diagram of a switching power supply of a conventional integrated ramp injection circuit.

Fig. 2 is a schematic diagram of a conventional circuit for generating a ramp voltage.

Fig. 3 is a waveform diagram of a key signal under different duty cycles in a switching power supply of a conventional integrated ramp injection circuit, where (b) (c) (d) are a waveform diagram of a signal Vref + Vripple generated by controlling a control signal Vsw under three duty cycles and superimposed with a reference voltage Vref, and a waveform diagram of a corresponding feedback voltage Vfb, and the diagram (a) is a comparison diagram integrating the three cases.

Fig. 4 is a circuit block diagram of a ramp injection circuit based on ramp reset according to the present invention applied to a switching power supply.

Fig. 5 is a waveform diagram of a key node when the ramp wave injection circuit based on ramp wave reset according to the present invention is applied to a switching power supply, where (b) (c) (d) are waveform diagrams obtained by respectively comparing a reference voltage Vref with a ramp wave voltage Vripple generated by control of a first control signal Vsw and subtracting a compensation voltage Vec with a feedback voltage Vfb of an output voltage of the switching power supply under three duty ratios, and the diagram (a) is a comparison diagram integrating the three conditions.

Fig. 6 is a specific circuit diagram of a ramp injection circuit according to an embodiment of the present invention.

Fig. 7 is a waveform diagram of key signals at different duty ratios in a ramp wave injection circuit based on ramp wave reset proposed by the present invention, where (b) (c) (d) are waveforms of a ramp wave voltage Vripple generated by the control of the control signal Vsw and a compensation voltage Vec generated at three duty ratios, respectively, and (a) is a comparison graph integrating the three cases, it can be seen that the peak value of the ramp wave voltage Vripple is kept the same as the compensation voltage Vec at different duty ratios to compensate for errors introduced by the ramp wave voltage.

Fig. 8 is a circuit diagram of a first implementation of a ramp injection circuit based on ramp reset according to an embodiment of the present invention to implement an error compensation module.

Fig. 9 is a circuit diagram of a second implementation of the ramp injection circuit based on ramp reset according to the present invention, in which the error compensation module is implemented in an embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It is to be noted that, in the present invention, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. For example, the first state and the second state of the control signal may be interchanged, and the first state may represent a high level, and the second state may represent a low level, or the first state may represent a low level, and the second state may represent a high level, which does not affect the implementation of the technical solution of the present invention.

The invention provides a ramp wave injection circuit based on ramp wave reset, which comprises a ramp wave voltage generation module and an error compensation module, wherein the ramp wave voltage generation module is used for generating a ramp wave voltage Vriple with a linearly rising voltage value under the control of a first control signal Vsw, and the control logic is that the voltage value of the ramp wave voltage Vriple is reset to zero only when the first control signal Vsw is changed from a first state to a second state, and then the ramp wave voltage Vriple rises linearly from zero. As shown in fig. 6, an implementation structure of the ramp voltage generating module is provided, in this embodiment, the ramp voltage generating module includes a timing control unit and a ramp generating unit, the timing control unit is configured to generate a pulse signal according to a first control signal Vsw, the voltage value of the ramp voltage Vripple is effectively controlled to be reset to zero only when the first control signal Vsw transitions from a first state to a second state, otherwise, the voltage value of the ramp voltage Vripple is not effectively controlled by the pulse signal to linearly increase. As shown in fig. 6, in the present embodiment, a not gate 210 and an and gate 211 are used to generate the pulse signal, the input terminal of the not gate 210 is connected to the first input terminal of the and gate 211 and the first control signal Vsw, and the output terminal thereof is connected to the second input terminal of the and gate 211; the output of the and gate 211 generates a pulse signal.

As shown in fig. 6, the ramp wave generating unit in this embodiment includes a first capacitor 201, a first switch 202, a second switch 203, and a current source 204, a first connection end of the first capacitor 201 is grounded, and a second connection end of the first capacitor 201 is connected to the current source 204 through the first switch 202 and is grounded through the second switch 203; the first switch 202 and the second switch 203 are controlled by pulse signals, when the pulse signals are effective, the first switch 202 is controlled to be switched off, the second switch 203 is controlled to be switched on, and when the pulse signals are ineffective, the first switch 202 is controlled to be switched on, and the second switch 203 is controlled to be switched off; a second connection of the first capacitor 201 outputs a ramp voltage Vripple.

The invention can be applied to the switching power supply, and is particularly suitable for the switching power supply with fixed on-time because the switching power supply with fixed on-time (including fixed off-time) often has the requirement of ramp wave injection in order to reduce output ripple waves. When the present invention is applied to a switching power supply with a fixed on-time, the control signal may be generated according to the voltage Vsw at the connection point of the upper power transistor 106 and the lower power transistor 107 in the switching power supply, for example, the voltage Vsw at the connection point of the upper power transistor 106 and the lower power transistor 107 in the switching power supply is directly taken as the first control signal Vsw in the embodiment shown in fig. 4, so that the first state of the first control signal Vsw in this embodiment is a low level, the second state is a high level, and the pulse signal generates an effective pulse when the first control signal Vsw is turned from low to high.

In the switching power supply, an upper power tube 106 and a lower power tube 107 are connected in series and in parallel between a power supply and the ground, a gate drive signal of the upper power tube 106 and the lower power tube 107 is controlled by a PWM pulse width modulation module 101, the conventional switching power supply integrated with a ramp wave circuit uses a reference voltage Vref superposed with a ramp wave voltage Vripple as a comparison reference, and then the reference voltage is compared with a feedback voltage Vfb of an output voltage of the switching power supply, the PWM pulse width modulation module 101 is adjusted according to a comparison result, because the ramp wave voltage Vripple is generated according to a voltage Vsw at a connection part of the upper power tube 106 and the lower power tube 107, the ramp wave voltage Vripple is related to a working duty ratio of a switching device in the switching power supply, and when the working duty ratios of the switching device in the switching power supply are different, the superposed ramp wave voltage vrip.

In the present embodiment, the timing control unit is utilized to generate a control signal V and a first control signal V_SWThe ramp wave is always aligned with the working period Tsw of the switching power supply, and the working period does not change along with the duty ratio, so that the ramp wave voltage Vripple generated by the embodiment is not changed when the duty ratio is changed, and therefore, an error introduced by the ramp wave voltage Vripple can be compensated by generating a proper direct current voltage Vec by the error compensation module.

The invention utilizes an error compensation module to generate a compensation voltage Vec proportional to a reference voltage Vref, and as shown in FIG. 8, a first implementation structure of the embodiment of the error compensation module is provided, which comprises an amplifier 400, a first resistor 403, a second resistor 404, a third resistor 401 and a fourth resistor 402, wherein the first resistor 403 and the second resistor 404 are connected in series and in parallel between the reference voltage Vref and the ground, and the series point is connected with the positive input end of the amplifier 400; the third resistor 401 and the fourth resistor 402 are connected in series and in parallel between the output terminal of the amplifier 400 and the ground, and the series point is connected with the negative input terminal of the amplifier 400; the output of amplifier 400 produces the compensation voltage Vec. A second implementation of the error compensation module in the embodiment shown in fig. 9 is provided, and compared with the structure shown in fig. 8, the error compensation module in the structure shown in fig. 9 removes the voltage dividing resistor from the structure shown in fig. 8, and implements a different ratio between the compensation voltage Vec and the reference voltage Vref.

In practice, when the capacitance value of the first capacitor 201 and the current value of the current source 204 are suitable (i.e. the circuit is suitable)) The reference voltage Vref can be directly outputted as the compensation voltage Vec, where I is the current value of the current source, T_swIs the duty cycle of the switching power supply, C is the capacitance of the first capacitor, V_refIs the voltage value of the reference voltage.

When the invention is applied to a switching power supply, the ramp voltage Vripple can be connected to one positive input end of the comparator 102, and the compensation voltage Vec can be connected to one negative input end of the comparator 102, as shown in fig. 4, the other positive input end of the comparator 102 is connected to the reference voltage Vref, and the other negative input end of the comparator 102 is connected to the feedback voltage Vfb after the output voltage is divided by the resistor, so that the reference voltage Vref is superposed with the initial ramp voltage Vripple, and the signal obtained by subtracting the compensation voltage Vec is used as a new comparison reference to be compared with the feedback voltage Vfb.

As shown in fig. 5, the waveform diagram is obtained by comparing the new comparison reference Vref + Vripple-Vec with the feedback voltage Vfb, and (b), (c) and (d) in fig. 5 are the comparison conditions of the new comparison reference Vref + Vripple-Vec and the feedback voltage Vfb corresponding to three different duty ratios, respectively, and (a) in fig. 5 is a schematic diagram obtained by drawing (b), (c) and (d) in fig. 5 together.

In summary, the present invention is based on a ramp reset technique to generate a ramp voltage independent of the duty cycle of a switching device in a switching power supply, and an error compensation module is used to generate a dc voltage as a compensation voltage, and subtract the compensation voltage from the ramp voltage to obtain a final ramp voltage.