阅读说明：本技术 用于开关电路的功率器件驱动方法、驱动电路及开关电路 (Power device driving method for switching circuit, driving circuit and switching circuit ) 是由 徐爱民 窦训金 周逊伟 于 2019-08-21 设计创作，主要内容包括：本发明公开了一种用于开关电路的功率器件驱动方法、驱动电路及开关电路,开关电路包括主开关管、同步整流管和感性元件,当开关信号表征同步整流管从导通到关断,主开关管从关断到导通时,利用MOS管的体效应,将同步整流管的驱动极电压下拉到低于所述同步整流管阈值电压,高于零电压,并开始计时,当检测到主开关管驱动极电压上升到第一电压或者计时达到第一时间,则将同步整流管的驱动极电压下拉到零电压。本发明可以减少同步整流管关断到主开关管管开启时同步整流管体二极管的导通,降低开关损耗,提高转换效率。(The invention discloses a power device driving method, a driving circuit and a switching circuit for the switching circuit, wherein the switching circuit comprises a main switching tube, a synchronous rectifier tube and an inductive element, when a switching signal represents that the synchronous rectifier tube is switched from on to off and the main switching tube is switched from off to on, the driving voltage of the synchronous rectifier tube is pulled to be lower than the threshold voltage of the synchronous rectifier tube and higher than zero voltage by using the body effect of an MOS (metal oxide semiconductor) tube, timing is started, and when the driving voltage of the main switching tube is detected to rise to the first voltage or the timing reaches the first time, the driving voltage of the synchronous rectifier tube is pulled to be zero voltage. The invention can reduce the conduction of the diode of the synchronous rectifier tube body when the synchronous rectifier tube is switched off and the main switch tube is switched on, reduce the switching loss and improve the conversion efficiency.)

1. A power device driving method for a switch circuit comprises a main switch tube, a synchronous rectifier tube and an inductive element, when a switch signal represents that the synchronous rectifier tube is switched from on to off and the main switch tube is switched from off to on, the drive pole voltage of the synchronous rectifier tube is pulled to be lower than the threshold voltage of the synchronous rectifier tube and higher than zero voltage by using the body effect of an MOS tube, timing is started, and when the drive pole voltage of the main switch tube is detected to rise to the first voltage or the timing reaches the first time, the drive pole voltage of the synchronous rectifier tube is pulled to be zero voltage.

2. The power device driving method according to claim 1, characterized in that: when the switching signal represents that the synchronous rectifying tube is switched from on to off and the main switching tube is switched from off to on, the driving pole voltage of the synchronous rectifying tube is pulled to be close to and lower than the threshold voltage of the synchronous rectifying tube.

3. When a switching signal indicates that the synchronous rectifier is switched on and off and the main switch is switched on and off, the driving pole voltage of the synchronous rectifier is pulled to be lower than the threshold voltage of the synchronous rectifier and higher than zero voltage by using the body effect of an MOS (metal oxide semiconductor) tube, timing is started, and when the driving pole voltage of the main switch is detected to rise to the first voltage or the timing reaches the first time, the driving pole voltage of the synchronous rectifier is pulled to be zero voltage.

4. The power device driving circuit according to claim 3, wherein: when the switching signal represents that the synchronous rectifying tube is switched from on to off and the main switching tube is switched from off to on, the driving pole voltage of the synchronous rectifying tube is pulled to be close to and lower than the threshold voltage of the synchronous rectifying tube.

5. The power device driving circuit according to claim 4, wherein: the power device driving circuit comprises a synchronous rectifier tube driving circuit, wherein the synchronous rectifier tube driving circuit comprises a first switch tube, a second switch tube and a driving amplification circuit, a grid electrode, a source electrode and a body of the first switch tube are connected, and are connected to a driving electrode of the synchronous rectifier tube, a switch signal is connected to the driving electrode of the second switch tube through the driving amplification circuit, a drain electrode of the first switch tube is connected to a reference ground through the second switch tube, and when the switch signal indicates that the synchronous rectifier tube is switched from on to off and a main switch tube is switched from off to on, the driving electrode voltage of the synchronous rectifier tube is pulled to be lower than the threshold voltage of the synchronous rectifier tube through the body effect of the first switch tube.

6. The power device driving circuit according to claim 5, wherein: the first switching tube and the synchronous rectifying tube are devices of the same type.

7. The power device driving circuit according to claim 5, wherein: the synchronous rectification driving circuit further comprises a delay circuit and a pull-down circuit, wherein the delay circuit receives a switching signal, the pull-down circuit receives the output voltage of the delay circuit, and pulls down the driving electrode of the synchronous rectification tube according to the output voltage of the pull-down circuit; when the switching signal represents that the synchronous rectifying tube is switched on and off, and the main switching tube is switched off and on, the delay circuit delays the first time, and the pull-down circuit pulls down the driving electrode of the synchronous rectifying tube.

8. The power device driving circuit according to claim 5, wherein: the synchronous rectification driving circuit further comprises a comparison circuit and a pull-down circuit, wherein the comparison circuit receives a main switching tube driving signal, the pull-down circuit receives the output voltage of the comparison circuit and pulls down the driving electrode of the synchronous rectification tube according to the output voltage of the comparison circuit; when the comparison circuit detects that the driving voltage of the main switching tube is higher than a first driving voltage, the pull-down circuit pulls down the driving electrode of the synchronous rectifying tube.

9. A switching circuit, characterized by: comprising a power device driver circuit as claimed in any one of claims 3 to 8.

Technical Field

The invention relates to the technical field of power electronics, in particular to a power device driving method for a switching circuit, a driving circuit and the switching circuit.

Background

In a switching power supply, a freewheeling diode is replaced with a synchronous rectifier in order to improve system efficiency. However, when the synchronous rectifier is turned off and the main switch is turned on, a dead time is required to be added to prevent shoot-through. In the dead time, the main switch tube is not conducted, the synchronous rectifier tube is turned off, and the current passes through the body diode of the synchronous rectifier tube. When the main switch tube is conducted, reverse recovery current caused by the conduction of a body diode of the synchronous rectifier tube exists. This reverse recovery current causes large switching losses. Therefore, how to improve and optimize the switching process of the synchronous rectifier tube turning off and the main switching tube turning on is an urgent problem to be solved in the switching power supply.

Disclosure of Invention

In view of the above, an object of the present invention is to provide a power device driving method, a driving circuit and a switching circuit for a switching circuit, so as to solve the problem in the prior art that when a synchronous rectifier is turned off and a main switching transistor is turned on, a body diode of the synchronous rectifier is turned on, thereby reducing system efficiency.

The technical scheme of the invention is to provide a power device driving method for a switching circuit, wherein the switching circuit comprises a main switching tube, a synchronous rectifier tube and an inductive element, when a switching signal represents that the synchronous rectifier tube is switched from on to off and the main switching tube is switched from off to on, the driving pole voltage of the synchronous rectifier tube is pulled to be lower than the threshold voltage of the synchronous rectifier tube and higher than zero voltage by using the body effect of an MOS (metal oxide semiconductor) tube, timing is started, and when the driving pole voltage of the main switching tube is detected to rise to the first voltage or the timing reaches the first time, the driving pole voltage of the synchronous rectifier tube is pulled to be zero voltage.

Optionally, when the switching signal indicates that the synchronous rectifier is turned on to off and the main switch is turned off to on, the driving voltage of the synchronous rectifier is pulled to be close to and lower than the threshold voltage of the synchronous rectifier.

The invention also provides a power device driving circuit for a switching circuit, which comprises a main switch tube, a synchronous rectifier tube and an inductive element, when a switching signal indicates that the synchronous rectifier tube is switched from on to off and the main switch tube is switched from off to on, the driving pole voltage of the synchronous rectifier tube is pulled to be lower than the threshold voltage of the synchronous rectifier tube and higher than zero voltage by using the body effect of an MOS tube, and timing is started, and when the driving pole voltage of the main switch tube is detected to rise to the first voltage or the timing reaches the first time, the driving pole voltage of the synchronous rectifier tube is pulled to be zero voltage.

Optionally, when the switching signal indicates that the synchronous rectifier is turned on to off and the main switch is turned off to on, the driving voltage of the synchronous rectifier is pulled to be close to and lower than the threshold voltage of the synchronous rectifier.

Optionally, the power device driving circuit includes a synchronous rectifier driving circuit, the synchronous rectifier driving circuit includes a first switching tube, a second switching tube and a driving amplifier circuit, a gate, a source and a body of the first switching tube are connected to each other and to a driving electrode of the synchronous rectifier tube, the switching signal is connected to the driving electrode of the second switching tube through the driving amplifier circuit, a drain of the first switching tube is connected to a reference ground through the second switching tube, and when the switching signal indicates that the synchronous rectifier tube is turned on to off and the main switching tube is turned off to on, the driving electrode voltage of the synchronous rectifier tube is pulled to be lower than the threshold voltage of the synchronous rectifier tube through a body effect of the first switching tube.

Optionally, the first switching tube and the synchronous rectifying tube are devices of the same type.

Optionally, the synchronous rectification driving circuit further includes a delay circuit and a pull-down circuit, the delay circuit receives a switching signal, and the pull-down circuit receives an output voltage of the delay circuit and pulls down a driving electrode of the synchronous rectification tube according to the output voltage of the pull-down circuit; when the switching signal represents that the synchronous rectifying tube is switched on and off, and the main switching tube is switched off and on, the delay circuit delays the first time, and the pull-down circuit pulls down the driving electrode of the synchronous rectifying tube.

Optionally, the synchronous rectification driving circuit further includes a comparison circuit and a pull-down circuit, the comparison circuit receives a main switching tube driving signal, the pull-down circuit receives an output voltage of the comparison circuit, and pulls down a driving electrode of the synchronous rectification tube according to the output voltage of the comparison circuit; when the comparison circuit detects that the driving voltage of the main switching tube is higher than a first driving voltage, the pull-down circuit pulls down the driving electrode of the synchronous rectifying tube.

Another technical solution of the present invention is to provide a switching circuit.

Compared with the prior art, the circuit structure and the method have the following advantages that: the conduction of diodes of the synchronous rectification tube body is reduced when the synchronous rectification tube is switched off and the main switching tube is switched on, the switching loss is reduced, and the conversion efficiency is improved.

Drawings

FIG. 1 is a schematic circuit diagram of a BUCK BUCK circuit with synchronous rectifiers;

FIG. 2 is a schematic waveform diagram of a switching signal PWM, a main switching tube driving voltage TG and a synchronous rectifier tube driving voltage BG according to the present invention;

FIG. 3 is a schematic circuit diagram of a BOOST BOOST circuit with NMOS synchronous rectifier;

FIG. 4 is a schematic circuit diagram of a BOOST BOOST circuit with PMOS synchronous rectifier tubes;

FIG. 5 is a circuit diagram of a synchronous rectifier driving circuit according to an embodiment of the present invention;

FIG. 6 is a circuit diagram of a synchronous rectifier driving circuit according to another embodiment of the present invention;

FIG. 7 is a schematic circuit diagram of a synchronous rectifier driving circuit in which the synchronous rectifier is an NMOS in the BOOST circuit according to an embodiment of the present invention;

FIG. 8 is a circuit diagram of a synchronous rectifier driving circuit with PMOS synchronous rectifiers in a BOOST circuit according to an embodiment of the present invention.

Detailed Description

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to only these embodiments. The invention is intended to cover alternatives, modifications, equivalents and alternatives which may be included within the spirit and scope of the invention.

In the following description of the preferred embodiments of the present invention, specific details are set forth in order to provide a thorough understanding of the present invention, and it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

The invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the drawings are in simplified form and are not to precise scale, which is only used for convenience and clarity to assist in describing the embodiments of the present invention.

The invention provides a power device driving circuit for a switching circuit, which comprises a main switching tube, a synchronous rectifier tube and an inductive element, wherein when a switching signal represents that the synchronous rectifier tube is switched from on to off and the main switching tube is switched from off to on, the driving pole voltage of the synchronous rectifier tube is pulled to be lower than the threshold voltage of the synchronous rectifier tube and higher than zero voltage by using the body effect of an MOS (metal oxide semiconductor) tube, timing is started, and when the driving pole voltage of the main switching tube is detected to rise to the first voltage or the timing reaches the first time, the driving pole voltage of the synchronous rectifier tube is pulled to be zero voltage. The main switch tube and the synchronous rectifier tube are both power devices, but the power device driving of the invention mainly focuses on the driving of the synchronous rectifier tube. Taking a BUCK step-down circuit as an example, please refer to fig. 1, which is a BUCK circuit with synchronous rectification, a power device driving circuit receives a PWM signal generated by a control circuit and generates a main switching tube driving voltage TG and a synchronous rectification tube driving voltage BG. Referring to fig. 2, waveforms of a switching signal PWM, a driving voltage TG of a main switching tube and a driving voltage BG of a synchronous rectifier tube in a BUCK circuit are shown, at a time t01, the driving voltage BG of the synchronous rectifier tube is pulled down to V01, that is, lower than a threshold voltage of the synchronous rectifier tube and higher than a zero voltage, and when the driving voltage TG of the main switching tube is detected to rise to a first voltage, the driving voltage BG of the synchronous rectifier tube is pulled down to the zero voltage at a time t 02. In another embodiment, at time t01, the driving voltage of the synchronous rectifier is pulled to V01 and the timing is started, and at time t02, when the timing reaches the first time, the driving voltage of the synchronous rectifier is pulled to zero voltage. The body effect of the MOS transistor is the influence of the body voltage on the channel, and the threshold voltage is increased by increasing the BIAS voltage of the SOURCE body (SOURCE TO body-BIAS).

In one embodiment, when the switching signal is indicative of the synchronous rectifier going from on to off and the main switching transistor going from off to on, the drive voltage of the synchronous rectifier is pulled to near and below the synchronous rectifier threshold voltage.

The invention is not limited to the BUCK voltage-reducing circuit, and can be used for any switching circuit with synchronous rectification, for example, it can also be used for BOOST circuit, referring to fig. 3, which is a BOOST circuit with synchronous rectification transistor M03 as NMOS; referring to fig. 4, the BOOST circuit is shown in which the synchronous rectifier M03 is PMOS.

Referring to fig. 5, taking a BUCK step-down circuit as an example, the power device driving circuit includes a synchronous rectifier driving circuit 100, where the synchronous rectifier driving circuit 100 includes a first switch M120, a second switch M130, and a driving amplifier circuit 110, the first switch is an NMOS, a gate, a source, and a BODY (BODY) of the first switch are connected, and connected to a driving electrode BG of the synchronous rectifier, the switch signal is connected to a driving electrode BG of the second switch through the driving amplifier circuit, a drain of the first switch is connected to a reference ground through the second switch, and when the switch signal indicates that the synchronous rectifier is turned on to off, and the main switch is turned on from off, the driving electrode voltage of the synchronous rectifier is pulled to be lower than the synchronous rectifier threshold voltage through a BODY effect of the first switch M120. Since the voltage on M120 is the voltage between the gate and the drain, the body voltage is higher than the drain, and the threshold voltage of the switching tube is lowered. Because in the switch tube, in many cases, the drain and the source are equivalent, similar to the body effect, that is, the body voltage is lower than the source voltage, the threshold of the switch tube is raised; the body voltage is higher than the source voltage, and the threshold value of the switching tube is reduced.

In one embodiment, with continued reference to fig. 5, the synchronous rectification driver circuit further includes a non-overlap logic circuit 140 and a pull-up circuit, which is implemented with a PMOS M110 in fig. 5. The switching signal PWM generates non-overlapping driving signals of M110 and M130 through the non-overlapping logic circuit 140, respectively, so that M110 and M130 are not simultaneously turned on, preventing shoot-through. The pull-up circuit M110 turns on the synchronous rectifier by pulling up BG, and when the synchronous rectifier is turned off, M110 is turned off.

In one embodiment, the first switch M120 and the synchronous rectifier M01 are of the same type. The turn-on threshold of the first switch M120 and the turn-on threshold of the synchronous rectifier M01 are made to approach each other, so that the turn-on threshold of the first switch M120 is adjusted by changing the BODY (BODY) voltage of the first switch M.

In an embodiment, please refer to fig. 5 again, the synchronous rectification driving circuit 100 further includes a delay circuit 120 and a pull-down circuit 130, wherein the delay circuit 120 receives a switching signal PWM, and the pull-down circuit 130 receives an output voltage of the delay circuit 120 and pulls down the driving electrode BG of the synchronous rectification transistor according to the output voltage of the pull-down circuit 130; when the switching signal indicates that the synchronous rectifying tube is turned on to turned off, and the main switching tube is turned off to turned on, the delay circuit 120 delays the first time, and the pull-down circuit 130 pulls down the driving electrode BG of the synchronous rectifying tube.

In another embodiment, referring to fig. 6, the synchronous rectification driving circuit further includes a comparing circuit 160 and a pull-down circuit 130, the comparing circuit 160 receives a main switching tube driving signal TG, the pull-down circuit 130 receives an output voltage of the comparing circuit 160, and pulls down a driving electrode BG of the synchronous rectification tube according to the output voltage of the comparing circuit 160; when the comparison circuit detects that the driving voltage of the main switching tube is higher than the first driving voltage, the pull-down circuit 130 pulls down the driving electrode BG of the synchronous rectifying tube.

Referring to fig. 7, an embodiment of a synchronous rectifier driving circuit 200 of the BOOST circuit of fig. 3 is shown. The difference between fig. 5 and fig. 6 is that the power supply of the synchronous rectification drive circuit is between the BST voltage and the SW voltage, rather than between VD and the reference ground. BST and SW are relatively stable voltage maintained by a capacitor, and then the capacitor is supplemented by VD when the lower tube is opened, so that relatively stable power supply voltage is between BST voltage and SW voltage.

Referring to fig. 8, an embodiment of a synchronous rectifier driving circuit 200 of the BOOST circuit of fig. 4 is shown. The power device driving circuit comprises a synchronous rectifier tube driving circuit 200, wherein the synchronous rectifier tube driving circuit 200 comprises a switching tube M220, a switching tube M210 and a driving amplifying circuit 210, the switching tube M220 is PMOS, the grid electrode, the source electrode and the BODY (BODY) of the M220 are connected and connected to the driving electrode BG of the synchronous rectifier tube, the switching signal is connected to the driving electrode of the M210 through the driving amplifying circuit 210, the drain electrode of the M220 is connected to a power supply end VD through the M210, and when the switching signal represents that the synchronous rectifier tube is switched on to switched off and the main switching tube is switched off to on, the driving electrode voltage of the synchronous rectifier tube is pulled up to be higher than the threshold voltage of the synchronous rectifier tube through the BODY effect of the switching tube M220. Since M220 is PMOS, the synchronous rectifier is made non-conductive by pulling the threshold voltage higher than the threshold voltage of the synchronous rectifier.

In one embodiment, with continued reference to fig. 8, the synchronous rectification driving circuit further includes a non-overlap logic circuit 240 and a pull-down circuit, and in fig. 8, the pull-down circuit is implemented by an NMOS M230. The switching signal PWM generates non-overlapping driving signals of M210 and M230 through the non-overlapping logic circuit 240, respectively, so that M210 and M230 are not simultaneously turned on, preventing shoot-through. The pull-down circuit M230 turns on the synchronous rectifier through pull-down BG, and when the synchronous rectifier is turned off, M230 is turned off.

The invention provides a driving method of a switching circuit, which comprises a main switching tube, a synchronous rectifier tube and an inductive element, wherein when a switching signal represents that the synchronous rectifier tube is switched from on to off and the main switching tube is switched from off to on, the driving pole voltage of the synchronous rectifier tube is pulled to be lower than the threshold voltage of the synchronous rectifier tube and higher than zero voltage by using the body effect of an MOS (metal oxide semiconductor) tube, timing is started, and when the driving pole voltage of the main switching tube is detected to rise to the first voltage or the timing reaches the first time, the driving pole voltage of the synchronous rectifier tube is pulled to be zero voltage.

In one embodiment, when the switching signal is indicative of the synchronous rectifier going from on to off and the main switching transistor going from off to on, the drive voltage of the synchronous rectifier is pulled to near and below the synchronous rectifier threshold voltage.

Although the embodiments have been described and illustrated separately, it will be apparent to those skilled in the art that some common techniques may be substituted and integrated between the embodiments, and reference may be made to one of the embodiments not explicitly described, or to another embodiment described.

The above-described embodiments do not limit the scope of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the above-described embodiments should be included in the protection scope of the technical solution.