A driving circuit

Abstract

This invention discloses a driving circuit, including an edge modulation circuit, an isolation transformer, an energy storage circuit, a demodulation circuit, and a switch control circuit. The demodulation circuit includes diodes D2 and D3, Zener diodes Z3 and Z4, switching transistors S1 and S2, a resistor R1, and a voltage regulation unit. This invention can respond to modulated positive and negative voltages transmitted from the primary winding to the secondary winding of the isolation transformer. It demodulates a positive voltage of a certain amplitude on the secondary winding of the isolation transformer into an on-state signal to drive the power semiconductor device to turn on, and demodulates a negative voltage of a certain amplitude on the secondary winding of the isolation transformer into an off-state signal to drive the power semiconductor device to turn off. Furthermore, by increasing the on-state and off-state thresholds of the signal demodulation circuit, the circuit's anti-interference capability is flexibly improved, preventing false on-state and false off-state.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of isolated driving, in particular to a driving circuit. BACKGROUND

[0002] With the development of science and technology, power semiconductor devices are widely used in various industries. As we all know, each power semiconductor device needs a drive to control its conduction and turn-off. In practical applications, power semiconductors can have two forms: ground and floating ground. In ground applications, a non-isolated totem pole drive can be used, while in floating ground applications, a special driving method is needed. Traditional floating ground driving has three types: bootstrap driving, transformer isolation driving and driving power supply plus driver. These driving methods are relatively mature technologies in the industry, but each has different advantages and disadvantages. Bootstrap driving is limited by semiconductor manufacturing processes and cannot meet high isolation voltage. Traditional transformer driving has a large volume, and the driving power supply plus driver scheme has high cost.

[0003] In order to solve the problems of traditional transformer isolation driving in terms of voltage resistance, cost and volume, a driving control method and its circuit are proposed in Chinese patent CN113193735A. By modulating the input PWM signal into a pulse signal, the transformer excitation time is reduced, thereby achieving the purpose of reducing the volume of the transformer and then reducing the volume of the driving circuit. At the same time, the duty cycle and frequency of the drive are also improved. Figure 1 The working principle is briefly described as follows: when the positive pulse voltage is transmitted to the secondary winding of the transformer, the energy is stored in the capacitor C1 through the diode D1, marked as energy storage voltage a, at the same time, the diode D2 and the switch tube S1 are turned on, the voltage of the signal restoration point b rises to the voltage of the secondary winding minus the voltage drop of the diode D2, and the highest does not exceed the voltage of the voltage stabilizing tube Z2. At this time, the switch tube S3 starts to conduct, and the capacitor C1 provides a driving voltage to the driven power semiconductor device through the switch tube S3; when the negative pulse voltage is transmitted to the secondary winding of the transformer, the switch tube S2 and the diode D3 are turned on, and the voltage of the signal restoration point b is lowered to the negative value, and the lowest does not exceed the voltage of the voltage stabilizing tube Z1. At this time, the switch tube S4 is turned on, and the driving voltage of the driven power semiconductor device is pulled down to the secondary ground. Since the voltage of the signal restoration point b is negative, the switch tube S4 is a P-channel MOS tube, therefore, the switch tube S4 can be reliably turned on to prevent the influence of crosstalk.

[0004] However, the following limitations exist:

[0005] 1. The problem of false turn-on and false turn-off, as shown in Figure 2, the pulse voltage generated by the edge modulation circuit is transmitted to the modulation signal of the secondary winding through the transformer. In practical applications, the modulation signal is affected by the parasitic parameters and the demagnetizing current of the transformer, and overshoot or undershoot occurs at the end of the positive or negative pulse. The technical solution in the prior art has the problems that: Figure 1 In the technical solution, under normal circumstances, when the modulation signal is a positive pulse voltage, it is an on signal, and the driving voltage c should remain high. However, when the negative voltage generated at the end of the positive pulse voltage of the modulation signal reaches the off threshold of the secondary circuit, that is, the on threshold of the switch S2 plus the on voltage drop V th2 +V D3 of the diode D3, the switch S2 and the diode D3 are turned on, the voltage of the signal restoration point b decreases, and the driving voltage c of the driven power semiconductor device also decreases. Since the duration of the negative voltage is short, the driving voltage c will not be completely turned off, which will cause the driving voltage c to drop. Similarly, when the modulation signal is a negative pulse voltage, it is an off signal, and the driving voltage c should remain low. However, when the positive voltage generated at the end of the negative pulse voltage on the modulation signal reaches the on threshold of the secondary circuit, that is, the on threshold of the switch S1 plus the on voltage drop V th1 +V D2 of the diode D2, the driving voltage c of the driven power semiconductor device will rise, causing false turn-on.

[0006] 2. The problem of low driving voltage, as shown in the prior art, Figure 1 The scheme controls the on and off of the switch S3 to control the driving voltage c provided by the capacitor C1 to the driven power semiconductor device. The switch S3 is an N-channel MOS tube, and the driving voltage Vgs_3 is the voltage of the signal restoration point b minus the driving voltage c, that is, Vgs_3 = Vb-Vc. As shown in the prior art, Figure 3 When the supply voltage is Vcc, the pulse voltage generated by the edge modulation circuit has an amplitude of Vcc. When the turns ratio of the transformer is 1:1, the voltage amplitude of the modulation signal is also Vcc. When the first positive pulse voltage of the modulation signal arrives, it is an on signal. At this time, the energy storage voltage a and the voltage of the signal restoration point b are both approximately equal to Vcc. The switch S3 starts to conduct, and the capacitor C1 provides the driving voltage to the driven power semiconductor device through the switch S3. The driving voltage c starts to rise. Since the driving voltage Vgs_3 of the switch S3 is Vb-Vc, the voltage Vb of the signal restoration point b is constant, and the voltage Vc of the driving voltage c rises, the driving voltage Vgs_3 of the switch S3 will decrease with the rise of the driving voltage c. When the driving voltage of the switch S3 decreases to its on threshold Vth3, that is, Vgs_3 = Vth3, the switch S3 is turned off. At this time, the voltage of the driving voltage c is Vcc-Vth3. Therefore, affected by the on threshold Vth3 of the switch S3, the driving voltage c is lower than Vcc by Vth3. SUMMARY

[0007] Therefore, the present application aims to overcome at least one of the above-mentioned defects in the prior art, and provide a driving circuit which can achieve the purpose of isolating signal demodulation, and solve the problems of false turn-on and false turn-off and low driving voltage.

[0008] To solve the above technical problems, the present application adopts the technical solutions as follows:

[0009] In one aspect, the present application provides a driving circuit, comprising: an edge modulation circuit, an isolation transformer, an energy storage circuit, a demodulation circuit and a switch control circuit; a first input end of the edge modulation circuit is used for connecting a voltage Vcc, a second input end of the edge modulation circuit is used for connecting a PWM signal, a ground end of the edge modulation circuit is connected to a ground GND, a first output end of the edge modulation circuit is connected to a same name end of a primary winding of the isolation transformer, and a second output end of the edge modulation circuit is connected to an opposite name end of the primary winding of the isolation transformer; a same name end of a secondary winding of the isolation transformer is connected to an input end of the energy storage circuit and an input end of the demodulation circuit; an output end of the energy storage circuit is connected to a first input end of the switch control circuit; an output end of the demodulation circuit is connected to a second input end of the switch control circuit; an output end of the switch control circuit is used as an output port of the driving circuit and is connected to a gate of a power semiconductor device to be driven; the opposite name end of the secondary winding of the isolation transformer is connected to a ground end of the energy storage circuit, a ground end of the demodulation circuit and a ground end of the switch control circuit, and is used as an output ground SGND of the driving circuit and is connected to a source of the power semiconductor device to be driven; the demodulation circuit comprises: a diode D2, a diode D3, a voltage stabilizing tube Z3, a voltage stabilizing tube Z4, a switch tube S1, a switch tube S2, a resistor R1 and a voltage stabilizing unit; an anode of the diode D2 and a cathode of the diode D3 are commonly connected and connected to the same name end of the secondary winding of the isolation transformer; a cathode of the diode D2 is connected to a source of the switch tube S1; a gate of the switch tube S1 is connected to a cathode of the voltage stabilizing tube Z4; an anode of the diode D3 is connected to a source of the switch tube S2; a gate of the switch tube S2 is connected to an anode of the voltage stabilizing tube Z3, and a drain is connected to one end of the resistor R1; the other end of the resistor R1, a drain of the switch tube S1 and a first end of the voltage stabilizing unit are commonly connected, and are used as an output end of the demodulation circuit and connected to the second input end of the switch control circuit; a cathode of the voltage stabilizing tube Z3, an anode of the voltage stabilizing tube Z4 and a second end of the voltage stabilizing unit are commonly connected, and are used as a ground end of the demodulation circuit and connected to the opposite name end of the secondary winding of the isolation transformer and the source of the power semiconductor device to be driven.

[0010] Preferably, the demodulation circuit further comprises an adjusting unit, the adjusting unit comprising a diode D4, a Zener Z5 and a capacitor C2; the cathode of the diode D4 is connected with one end of the capacitor C2, the other end of the resistor R1 and the drain of the switch tube S1 as the first end of the adjusting unit; the anode of the diode D4 is connected with the anode of the Zener Z5; the cathode of the Zener Z5 is connected with the other end of the capacitor C2, and the first end of the voltage stabilizing unit is connected with the second end of the adjusting unit; the other end of the resistor R1 and the drain of the switch tube S1 are connected with the first end of the voltage stabilizing unit through the adjusting unit.

[0011] Preferably, the voltage stabilizing unit comprises a Zener Z1 and a Zener Z2 connected in reverse series, or a diode D5 and a Zener Z1 connected in reverse series.

[0012] Preferably, the voltage stabilizing unit comprises a Zener Z1 and a Zener Z2 connected in reverse series, the first end of the voltage stabilizing unit is the anode of the Zener Z1, the second end is the anode of the Zener Z2, the cathode of the Zener Z1 and the cathode of the Zener Z2 are connected, or the first end of the voltage stabilizing unit is the cathode of the Zener Z2, the second end is the cathode of the Zener Z1, the anode of the Zener Z1 and the anode of the Zener Z2 are connected.

[0013] Preferably, the voltage stabilizing unit comprises a diode D5 and a Zener Z1 connected in reverse series, the first end of the voltage stabilizing unit is the cathode of the diode D5, the second end is the cathode of the Zener Z1, the anode of the diode D5 and the anode of the Zener Z1 are connected.

[0014] Preferably, the energy storage circuit comprises a diode D1 and a capacitor C1; the anode of the diode D1 is connected with the same-named end of the secondary winding of the isolation transformer as the input end of the energy storage circuit, the cathode of the diode D1 and one end of the capacitor C1 are commonly connected, and the output end of the energy storage circuit is connected with the first input end of the switch control circuit, the other end of the capacitor C1 is connected with the different-named end of the secondary winding of the isolation transformer as the ground end of the energy storage circuit, and is used for being connected with the source of the driven power semiconductor device.

[0015] Preferably, the switch control circuit comprises a switch tube S3 and a switch tube S4, the drain of the switch tube S3 is connected with the output end of the energy storage circuit as the first input end of the switch control circuit; the source of the switch tube S3 is connected with the source of the switch tube S4 and is used for being connected with the gate of the driven power semiconductor device as the output end of the switch control circuit; the gate of the switch tube S3 is connected with the gate of the switch tube S4 and is connected with the output end of the demodulation circuit as the second input end of the switch control circuit; the drain of the switch tube S4 is connected with the different-named end of the secondary winding of the isolation transformer as the ground end of the switch control circuit, and is used for being connected with the source of the driven power semiconductor device.

[0016] In another aspect, a driving circuit is provided, comprising: an edge modulation circuit, an isolation transformer, a diode D1, a diode D2, a diode D3, a diode D4, a voltage stabilizing tube Z1, a voltage stabilizing tube Z2, a voltage stabilizing tube Z3, a voltage stabilizing tube Z4, a switch tube S1, a switch tube S2, a switch tube S3, a switch tube S4, a resistor R1, a capacitor C1; a first input end of the edge modulation circuit is used for connecting a voltage Vcc, a second input end of the edge modulation circuit is used for connecting a PWM signal, a ground end of the edge modulation circuit is connected to a ground GND, a first output end of the edge modulation circuit is connected to a same name end of a primary winding of the isolation transformer, a second output end of the edge modulation circuit is connected to a different name end of the primary winding of the isolation transformer; an anode of the diode D1, an anode of the diode D2, a cathode of the diode D3, and a same name end of a secondary winding of the isolation transformer are commonly connected; a cathode of the diode D2 is connected to a source of the switch tube S1; a gate of the switch tube S1 is connected to a cathode of the voltage stabilizing tube Z4; an anode of the diode D3 is connected to a source of the switch tube S2; a gate of the switch tube S2 is connected to an anode of the voltage stabilizing tube Z3, a drain is connected to one end of the resistor R1; the other end of the resistor R1, a drain of the switch tube S1, a cathode of the diode D4, and one end of the capacitor C2 are commonly connected; an anode of the diode D4 is connected to an anode of the voltage stabilizing tube Z5; a cathode of the voltage stabilizing tube Z5, the other end of the capacitor C2, a gate of the switch tube S3, a gate of the switch tube S4, and a cathode of the voltage stabilizing tube Z2 are commonly connected; a cathode of the diode D1, one end of the capacitor C1, and a drain of the switch tube S3 are commonly connected; a source of the switch tube S3 and a source of the switch tube S4 are connected as an output end of the driving circuit and are used for being connected to a gate of a power semiconductor device to be driven; a different name end of the secondary winding of the isolation transformer, a cathode of the voltage stabilizing tube Z3, an anode of the voltage stabilizing tube Z4, the other end of the capacitor C1, a cathode of the voltage stabilizing tube Z1, and a drain of the switch tube S4 are commonly connected and are used as an output ground SGND of the driving circuit and are used for being connected to a source of the power semiconductor device to be driven.

[0017] The working principle of the present application will be analyzed in detail in the specific implementation mode, and the present application has the following beneficial effects compared with the prior art:

[0018] 1) By increasing the secondary demodulation circuit opening and closing threshold, the anti-interference ability of the circuit is improved, and the false opening and false closing are prevented.

[0019] 2) By improving the voltage of the secondary demodulation circuit, the influence of the switch tube conduction threshold on the output driving voltage is eliminated, the driving output voltage reaches the set value, and the problem that the driving voltage is lower than the set voltage is solved. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a schematic diagram of the existing driving technology circuit;

[0021] Figure 2 is a schematic diagram of the anti-interference waveform of the existing driving technology;

[0022] Figure 3 is the signal voltage and the driving output voltage waveform of the prior art driving technology;

[0023] Figure 4 is the specific circuit diagram of the driving circuit according to the first embodiment of the present application;

[0024] Figure 5 is the anti-interference waveform of the first embodiment of the present application;

[0025] Figure 6 is the specific circuit diagram of the driving circuit according to the second embodiment of the present application;

[0026] Figure 7 is the signal voltage and the driving output voltage waveform of the second embodiment of the present application;

[0027] Figure 8 is the specific circuit diagram of the driving circuit according to the third embodiment of the present application.

[0028] Reference signs: 100 - edge modulation circuit, 200 - isolation transformer, 300 - energy storage circuit, 400 - demodulation circuit, 500 - switch control circuit. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described in detail below with reference to the accompanying drawings. The accompanying drawings are only used for illustrative description and should not be understood as a limitation to the present patent. Some components in the drawings may be omitted, enlarged or reduced for better illustration of the embodiments. It is understandable for those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings. The technical solutions of the present application will be further described below with reference to the accompanying drawings and embodiments. In order to better understand the driving circuit design of the present application, the specific embodiments of the present application will be described in detail with reference to the accompanying drawings.

[0030] First embodiment

[0031] Referring to the accompanying drawings, Figure 1 In the prior art, when the positive voltage on the secondary winding Vs reaches the conduction voltage drop of the diode D2, the diode D2 is turned on, and the source-gate of the switch S1 is charged. The switch S1 is a P-channel MOS tube, so when the source-gate voltage reaches the conduction threshold V th1When the switch S1 is turned on, the diode D2 and the switch S1 are turned on, and the determination is that the on signal is turned on, that is, as long as the positive voltage on the secondary winding Vs exceeds Vth1+VD2, it is turned on, and for the same reason, as long as the negative voltage on the secondary winding Vs exceeds Vth2+VD3, it is turned off. Obviously, this voltage is more susceptible to interference under some harsh application conditions, thereby causing false opening and false closing.

[0032] Reference is made to the accompanying drawings Figure 4 In order to solve the above problems, in the embodiment, a driving circuit is provided, which comprises: an edge modulation circuit 100, an isolation transformer 200, an energy storage circuit 300, a demodulation circuit 400 and a switch control circuit 500; the first input end of the edge modulation circuit 100 is used for connecting the voltage Vcc, the second input end of the edge modulation circuit 100 is used for connecting the PWM signal, the ground end of the edge modulation circuit 100 is connected to the ground GND, the first output end of the edge modulation circuit 100 is connected to the same end of the primary winding Vp of the isolation transformer 200, and the second output end of the edge modulation circuit 100 is connected to the different end of the primary winding Vp of the isolation transformer 200; the same end of the secondary winding Vs of the isolation transformer 200 is connected to the input end of the energy storage circuit 300 and the input end of the demodulation circuit 400; the output end of the energy storage circuit 300 is connected to the first input end of the switch control circuit 500; the output end of the demodulation circuit 400 is connected to the second input end of the switch control circuit 500; the output end of the switch control circuit 500 is used as the output port of the driving circuit and is connected to the gate of the power semiconductor device to be driven; the different end of the secondary winding Vs of the isolation transformer 200 is connected to the ground end of the energy storage circuit 300, the ground end of the demodulation circuit 400 and the ground end of the switch control circuit 500, and is used as the output ground SGND of the driving circuit and is connected to the source of the power semiconductor device to be driven; the demodulation circuit 400 comprises: a diode D2, a diode D3, a voltage stabilizing tube Z3, a voltage stabilizing tube Z4, a switch S1, a switch S2, a resistor R1 and a voltage stabilizing unit; the anode of the diode D2 and the cathode of the diode D3 are commonly connected as the input end of the demodulation circuit 400 and are connected to the same end of the secondary winding Vs of the isolation transformer 200; the cathode of the diode D2 is connected to the source of the switch S1; the gate of the switch S1 is connected to the cathode of the voltage stabilizing tube Z4; the anode of the diode D3 is connected to the source of the switch S2; the gate of the switch S2 is connected to the anode of the voltage stabilizing tube Z3, and the drain is connected to one end of the resistor R1; the other end of the resistor R1 and the drain of the switch S1 are commonly connected to the first end of the voltage stabilizing unit, and are connected to the second input end of the switch control circuit 500 as the output end of the demodulation circuit 400; the cathode of the voltage stabilizing tube Z3, the anode of the voltage stabilizing tube Z4 and the second end of the voltage stabilizing unit are commonly connected as the ground end of the demodulation circuit 400 and are connected to the different end of the secondary winding Vs of the isolation transformer 200 and are used for connecting the source of the power semiconductor device to be driven.

[0033] As a specific embodiment of the voltage stabilizing unit, the voltage stabilizing unit comprises voltage stabilizing tubes Z1 and Z2 connected in reverse series, the first end of the voltage stabilizing unit is the anode of the voltage stabilizing tube Z1, the second end is the anode of the voltage stabilizing tube Z2, and the cathode of the voltage stabilizing tube Z1 and the cathode of the voltage stabilizing tube Z2 are connected.

[0034] As a specific embodiment of the energy storage circuit 300, the energy storage circuit 300 comprises a diode D1 and a capacitor C1; the anode of the diode D1 is connected to the same-named end of the secondary winding Vs of the isolation transformer 200 as the input end of the energy storage circuit 300, the cathode of the diode D1 and one end of the capacitor C1 are commonly connected, and the other end of the capacitor C1 is connected to the different-named end of the secondary winding Vs of the isolation transformer 200 as the ground end of the energy storage circuit 300 and is used for being connected to the source of the power semiconductor device to be driven.

[0035] As a specific embodiment of the switch control circuit 500, the switch control circuit 500 comprises switch tubes S3 and S4; the drain of the switch tube S3 is connected to the output end of the energy storage circuit 300 as the first input end of the switch control circuit 500; the source of the switch tube S3 and the source of the switch tube S4 are connected and used as the output end of the switch control circuit 500 for being connected to the gate of the power semiconductor device to be driven; the gate of the switch tube S3 and the gate of the switch tube S4 are connected and connected to the output end of the demodulation circuit 400 as the second input end of the switch control circuit 500; and the drain of the switch tube S4 is connected to the different-named end of the secondary winding Vs of the isolation transformer 200 as the ground end of the drive circuit and is used for being connected to the source of the power semiconductor device to be driven.

[0036] Specifically, the switch tube S1 and the switch tube S4 are P-channel MOS tubes, and the switch tube S2 and the switch tube S3 are N-channel MOS tubes.

[0037] The specific working principle of the drive circuit described in the embodiment is as follows: the positive voltage modulation signal on the secondary winding Vs of the transformer is demodulated into a turn-on signal to turn on the MOS tube to be driven, and the energy is stored on the capacitor C1; the negative voltage modulation signal on the secondary winding Vs of the transformer is demodulated into a turn-off signal to turn off the MOS tube to be driven. Through the optimization of the circuit, the problems of false turn-on and false turn-off caused by parasitic parameters in the prior art can be solved. In the embodiment, the voltage threshold for turning on and turning off the circuit is improved by adding the voltage stabilizing tube Z4 at the gate of the switch tube S1 and the voltage stabilizing tube Z3 at the gate of the switch tube S2, so that the anti-interference performance of the overall circuit is improved.

[0038] The specific working process of the embodiment is described as follows: Figure 5 The specific working process of the embodiment is described as follows:

[0039] At time t0, the normal positive voltage modulation signal arrives, that is, the same-name terminal of the secondary winding Vs is at a high level. At this time, diode D3 is cut off and diode D1 is turned on, charging capacitor C1. Since the voltage amplitude of the positive modulation signal of the secondary winding Vs is greater than Vth1+VD2+VZ4, it is determined to be an on signal. Therefore, the signal restoration point b remains at a high level, that is, in the on state.

[0040] At time t1, the positive voltage modulation signal ends, and the voltage on the secondary winding Vs drops to zero. At this time, the voltage at the signal restoration point b continues to remain at a high level.

[0041] At time t2, due to the influence of parasitic parameters, after the voltage on the secondary winding Vs drops to zero, a negative interference voltage appears. When the amplitude of the interference voltage exceeds Vth2 + VD3, existing technology would interpret it as a turn-off signal, such as... Figure 5 In the waveform shown by the dashed line, the voltage at signal restoration point b drops, which in turn causes the driving voltage c to drop, resulting in false turn-off. However, this invention raises the turn-off voltage threshold to Vth2+VD3+VZ3. Therefore, the negative interference voltage generated at the end of the positive pulse voltage is within Vth2+VD3+VZ3 and will not have any impact on the driving circuit. This can enhance anti-interference capability, weaken the impact of interference voltage, and thus eliminate false turn-off.

[0042] At time t3, the normal negative voltage modulation signal arrives, that is, the opposite terminal of the secondary winding Vs is at a high level. At this time, diodes D1 and D2 are reverse cut off. Since the voltage amplitude of the negative modulation signal of the secondary winding Vs is greater than Vth2+VD3+VZ3, it is determined to be a turn-off signal. Therefore, the voltage at signal restoration point b begins to drop.

[0043] At time t4, the negative voltage modulation signal ends, and the voltage on the secondary winding Vs drops to zero. At this time, the voltage at the signal restoration point b is approximately -VZ1.

[0044] At time t5, due to the influence of parasitic parameters, after the voltage on the secondary winding Vs drops to zero, a positive interference voltage appears. When the amplitude of the interference voltage exceeds Vth1 + VD2, existing technology would determine it as a turn-on signal, such as... Figure 5 In the waveform shown by the dashed line, the voltage at signal restoration point b rises, which in turn causes the driving voltage c to rise, resulting in false turn-on. However, this invention raises the turn-off voltage threshold to Vth1+VD2+VZ4. Therefore, the positive interference voltage generated at the end of the negative pulse voltage is within Vth1+VD2+VZ4 and will not have any impact on the driving circuit. This can enhance anti-interference capability, weaken the influence of interference voltage, and thus eliminate false turn-on.

[0045] Second Embodiment

[0046] Reference is made to the accompanying drawings Figure 1 Since the voltage of the signal restoration point b and the voltage of the capacitor C1 in the prior art scheme are both from the secondary winding Vs, when the secondary winding Vs is a modulated signal of positive voltage, the voltage of the signal restoration point b starts to rise, when its voltage exceeds the turn-on threshold Vth3 of the switch tube S3, the switch tube S3 is turned on, the driving voltage C starts to rise, and the voltage of the signal restoration point b will eventually be substantially equal to the voltage a of the capacitor C1, then when the driving voltage rises, the driving voltage Vgs_3 of the switch tube S3 = V b -V c gradually decreases, when the driving voltage of the switch tube S3 decreases to the turn-on threshold Vth3, the switch tube S3 is turned off, at this time, the voltage of the driving voltage C is V a -Vth3, then due to the existence of the turn-on threshold Vth3 of the switch tube S3, the driving voltage C will always be less than the set value.

[0047] To solve the above problems, the embodiment provides a driving circuit, which is different from the first embodiment, in the embodiment, the demodulation circuit 400 further comprises an adjusting unit, the adjusting unit comprises a diode D4, a voltage stabilizing tube Z5 and a capacitor C2; the cathode of the diode D4 is connected with one end of the capacitor C2, the first end of the adjusting unit is connected with the other end of the resistor R1 and the drain of the switch tube S1; the anode of the diode D4 is connected with the anode of the voltage stabilizing tube Z5; the cathode of the voltage stabilizing tube Z5 is connected with the other end of the capacitor C2, the second end of the adjusting unit is connected with the first end of the voltage stabilizing unit; the other end of the resistor R1 and the drain of the switch tube S1 are connected with the first end of the voltage stabilizing unit through the adjusting unit.

[0048] In the embodiment, the voltage stabilizing unit comprises the voltage stabilizing tube Z1 and the voltage stabilizing tube Z2 connected in reverse series, the first end of the voltage stabilizing unit is the cathode of the voltage stabilizing tube Z2, the second end is the cathode of the voltage stabilizing tube Z1, and the anode of the voltage stabilizing tube Z1 and the anode of the voltage stabilizing tube Z2 are connected.

[0049] Specifically, reference is made to the accompanying drawings Figure 6For the specific circuit diagram of the driving circuit described in the embodiment, it comprises edge modulation circuit 100, isolation transformer 200, diode D1, diode D2, diode D3, diode D4, voltage stabilizing tube Z1, voltage stabilizing tube Z2, voltage stabilizing tube Z3, voltage stabilizing tube Z4, voltage stabilizing tube Z5, switch tube S1, switch tube S2, switch tube S3, switch tube S4, resistor R1, capacitor C1, capacitor C2. The switch tube S1 and switch tube S4 are P-channel MOS tubes, and the switch tube S2 and switch tube S3 are N-channel MOS tubes. The first input end of the edge modulation circuit 100 is connected with voltage Vcc, the second input end of the edge modulation circuit 100 is connected with PWM signal, the ground end of the edge modulation circuit 100 is connected with ground GND, the first output end of the edge modulation circuit 100 is connected with the same end of the primary winding Vp of the isolation transformer 200, and the second output end of the edge modulation circuit 100 is connected with the different end of the primary winding of the isolation transformer 200; the same end of the secondary winding Vs of the isolation transformer 200 is connected with the anode of diode D1, the anode of diode D2 and the cathode of diode D3 at the same time; the cathode of diode D1 is connected with one end of capacitor C1 and the drain of switch tube S3 at the same time, the cathode of diode D2 is connected with the source of switch tube S1, the gate of switch tube S1 is connected with the cathode of voltage stabilizing tube Z4, the anode of diode D3 is connected with the source of switch tube S2, the gate of switch tube S2 is connected with the anode of voltage stabilizing tube Z3, the drain of switch tube S2 is connected with one end of resistor R1, the other end of resistor R1 is connected with the drain of switch tube S1, one end of capacitor C2 and the cathode of diode D4 at the same time, the anode of diode D4 is connected with the anode of voltage stabilizing tube Z5, the cathode of voltage stabilizing tube Z5 is connected with the other end of capacitor C2, the cathode of voltage stabilizing tube Z2, the gate of switch tube S3 and the gate of switch tube S4 at the same time, the source of switch tube S3 is connected with the source of switch tube S4 as the output end of the driving circuit, connected with the gate of the driven power semiconductor device, the anode of voltage stabilizing tube Z2 is connected with the anode of voltage stabilizing tube Z1, the cathode of voltage stabilizing tube Z1 is connected with the drain of switch tube S4, the other end of capacitor C1, the cathode of voltage stabilizing tube Z3, the anode of voltage stabilizing tube Z4, the different end of the secondary winding Vs of the isolation transformer 200, and the source of the driven power semiconductor device connected with the ground SGND of the driving circuit.

[0050] Compared with the prior art, reference is made to the accompanying Figure 6The driving circuit of the embodiment adds a capacitor C2 in the loop of the signal restoration point b, which is used to store the voltage of the pulse modulation signal of the negative voltage of the secondary winding Vs, and a voltage stabilizing tube Z5 is used to limit the amplitude of the voltage, generally VZ5>Vth3, so that the voltage on the capacitor C2 is VZ5 when the signal is off, and the voltage of the signal restoration point b is the voltage of the capacitor C2 plus the voltage of the secondary winding Vs, that is, Vcc+VZ5 when the signal is on. In order to prevent the forward conduction of the voltage stabilizing tube Z5 when it is on, the signal passes through the voltage stabilizing tube Z5 without passing through the capacitor C2, which affects the signal restoration. A diode D4 is connected in series with the voltage stabilizing tube Z5, so that the loop of the voltage stabilizing tube Z5 can only conduct in reverse direction and be cut off in forward direction. Since the voltage of the signal restoration point b is raised by VZ5, and VZ5>Vth3, the voltage of the driving output voltage c can be equal to the voltage of the capacitor C1, that is, the set value. The embodiment contains the functions and beneficial effects realized by the first embodiment, and solves the problem that the driving voltage is lower than the set value due to the conduction threshold value Vth3 of the switch tube S3 through circuit optimization.

[0051] The specific working process of the second embodiment of the application is described as follows: Figure 7 The specific working process of the second embodiment of the application is described as follows:

[0052] At t0, the normal negative voltage modulation signal arrives, that is, the high level of the secondary winding Vs, at this time, the diode D1 and the diode D2 are reverse cut off, and since the voltage amplitude of the negative modulation signal of the secondary winding Vs is greater than Vth2+VD3+VZ3, it is determined as an off signal, the diode D3 and the switch tube S2 are turned on, and the voltage of the secondary winding Vs is charged to the gate-drain of the switch tube S4 through the loop composed of the capacitor C2, the resistor R1, the switch tube S2 and the diode D3, so that the voltage of the signal restoration point b starts to drop, and then drives the driving voltage Vgs_3 of the switch tube S3 and the driving voltage C to drop, and at this time, the voltage on the capacitor C2 starts to rise;

[0053] At t1, the negative voltage modulation signal ends, the voltage on the secondary winding Vs decreases to zero, and the voltage at the signal restoration point b drops to the lowest value. Due to the action of the voltage stabilizing tube Z1, the voltage at the signal restoration point b is ultimately about -VZ1. After the driving voltage C decreases to zero, the driving voltage of the switch tube S3 also decreases to about -VZ1. The voltage on the capacitor C2 is ultimately about VZ5 due to the action of the voltage stabilizing tube Z5. At this time, the P-channel switch tube S4 is turned on, and the N-channel switch tube S3 is turned off, thereby terminating the energy transmission to the gate of the power semiconductor device and connecting the gate of the power semiconductor device to the secondary ground SGND to turn off the driven power semiconductor device. Since the gate-drain voltage of the P-channel switch tube S4 is negative, the switch tube S4 can be kept fully open, and the driven power semiconductor device can be reliably turned off.

[0054] During the period from t1 to t2, the driving voltage Vgs_3 of the signal restoration point b and the switch tube S3 are maintained at about -VZ1 due to the continuous negative voltage modulation signal. The driving voltage C is continuously pulled down by the switch tube S4, and the voltage on the capacitor C2 is maintained at about VZ5. Since the gate-drain voltage of the P-channel switch tube S4 is a continuous negative voltage, the switch tube S4 can be kept fully open, and the driven power semiconductor device can be reliably turned off.

[0055] During the period from t2 to t3, a normal positive voltage modulation signal arrives, i.e., the same end of the secondary winding Vs is at a high level. At this time, the diode D3 is turned off, and the diode D1 is turned on to charge the capacitor C1. Since the voltage amplitude of the positive modulation signal of the secondary winding Vs is greater than Vth1+VD2+VZ4, it is determined to be an on signal. The voltage of the secondary winding is charged to the gate-drain of the switch tube S4 through the loop composed of the diode D2, the switch tube S1, and the capacitor C2. Therefore, the signal restoration point b starts to rise, and then drives the driving voltage Vgs_3 of the switch tube S3 and the driving voltage C to rise. Since the capacitor C2 is connected in series in the loop and the voltage on the capacitor C2 is limited to the voltage stabilizing value of the voltage stabilizing tube Z5 in the previous process, the voltage of the signal restoration point is the voltage of the secondary winding Vs plus the voltage on the capacitor C2, i.e., Vcc+VZ5. At this time, the P-channel switch tube S4 is turned off, and the N-channel switch tube S3 is turned on and continuously turned on, thereby transmitting the energy stored in the capacitor C1 to the driven power semiconductor device to open the driven power semiconductor device. Since the voltage of the signal restoration point b is raised by VZ5, and VZ5>Vth3, the voltage of the driving output voltage c can be equal to the voltage a of the capacitor C1, reaching the set value.

[0056] In the time period from t3 to t4, due to the continuous positive voltage modulation signal, the signal restoration point b keeps a continuous high level, the capacitor C1 keeps charging, and due to the continuous transfer of energy, the driving voltage C will also keep a continuous high level, and the driven power semiconductor device can keep a continuous and reliable opening.

[0057] Third embodiment

[0058] Different from the second embodiment, with reference to Figure 8 , Figure 8 The specific circuit diagram of the driving circuit described in this embodiment, in this embodiment, the voltage stabilizing unit includes a diode D5 and a voltage stabilizing tube Z1 connected in reverse series, the first end of the voltage stabilizing unit is the cathode of the diode D5, the second end is the cathode of the voltage stabilizing tube Z1, and the anode of the diode D5 and the anode of the voltage stabilizing tube Z1 are connected.

[0059] Specifically, the switch control circuit 500 comprises an edge modulation circuit 100, an isolation transformer 200, a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a Zener Z1, a Zener Z3, a Zener Z4, a Zener Z5, a switch S1, a switch S2, a switch S3, a switch S4, a resistor R1, a capacitor C1, a capacitor C2. The switch S1 and the switch S4 are P-channel MOSFETs, and the switch S2 and the switch S3 are N-channel MOSFETs. The first input terminal of the edge modulation circuit 100 is connected to a voltage Vcc, the second input terminal of the edge modulation circuit 100 is connected to a PWM signal, the ground terminal of the edge modulation circuit 100 is connected to a ground GND, the first output terminal of the edge modulation circuit 100 is connected to the same terminal of a primary winding Vp of the isolation transformer 200, and the second output terminal of the edge modulation circuit 100 is connected to the different terminal of the primary winding of the isolation transformer 200; the same terminal of a secondary winding Vs of the isolation transformer 200 is connected to the anode of the diode D1, the anode of the diode D2 and the cathode of the diode D3; the cathode of the diode D1 is connected to one end of the capacitor C1 and the drain of the switch S3, the cathode of the diode D2 is connected to the source of the switch S1, the gate of the switch S1 is connected to the cathode of the Zener Z4, the anode of the diode D3 is connected to the source of the switch S2, the gate of the switch S2 is connected to the anode of the Zener Z3, the drain of the switch S2 is connected to one end of the resistor R1, the other end of the resistor R1 is connected to the drain of the switch S1, one end of the capacitor C2 and the cathode of the diode D4, the anode of the diode D4 is connected to the anode of the Zener Z5, the cathode of the Zener Z5 is connected to the other end of the capacitor C2, the cathode of the diode D5, the gate of the switch S3 and the gate of the switch S4, the source of the switch S3 is connected to the source of the switch S4 as an output terminal of a driving voltage, connected to the gate of a driven power semiconductor device, the anode of the diode D5 is connected to the anode of the Zener Z1, the cathode of the Zener Z1 is connected to the drain of the switch S4, the other end of the capacitor C1, the cathode of the Zener Z3, the anode of the Zener Z4, the different terminal of the secondary winding Vs of the isolation transformer 200, and the source of the driven power semiconductor device connected to the ground SGND of the secondary winding of the transformer.

[0060] Specifically, the working principle of the embodiment is as follows: when the isolation transformer 200 transmits a negative pulse to the secondary side, that is, the non-identical end of the secondary side winding Vs is high, at this time, the diode D1 and the diode D2 are reverse cut-off, when the voltage of the non-identical end of the secondary side winding Vs exceeds the voltage of the voltage stabilizing tube Z3, for example, 3.3V, the diode D3 and the switch tube S2 are turned on, the voltage of the secondary side winding is charged reversely to the gate-drain of the switch tube S4 through the loop composed of the capacitor C2, the resistor R1, the switch tube S2 and the diode D3, the voltage on the capacitor C2 is limited to the voltage of the voltage stabilizing tube Z5, for example, 5.1V, the gate-drain voltage of the switch tube S4 is limited to the voltage of the voltage stabilizing tube Z1, for example, -3.3V, as a turn-off signal, at this time, the P-channel switch tube S4 is turned on, and the N-channel switch tube S3 is turned off, the energy transmission to the gate of the power semiconductor device is terminated, and the gate of the power semiconductor device is connected to the ground SGND of the secondary side to turn off the driven power semiconductor device, since the gate-drain voltage of the P-channel switch tube S4 is negative, the switch tube S4 can be kept fully open, and the driven power semiconductor device can be kept reliably turned off;

[0061] When the isolation transformer 200 transmits a positive pulse to the secondary side, that is, the identical end of the secondary side winding Vs is high, at this time, the diode D3 is cut off, and the diode D1 is turned on to charge the capacitor C1, when the voltage of the identical end of the secondary side winding Vs exceeds the voltage of the voltage stabilizing tube Z4, for example, 3.3V, the diode D2 and the switch tube S1 are turned on, the voltage of the secondary side winding Vs is charged to the gate-drain of the switch tube S4 through the loop composed of the diode D2, the switch tube S1 and the capacitor C2, since the capacitor C2 is connected in series in the loop and the voltage on the capacitor C2 is limited to the voltage of the voltage stabilizing tube Z5, for example, 5.1V, the gate-drain voltage of the switch tube S4 is the voltage of the secondary side winding Vs plus the voltage on the capacitor C2, as a turn-on signal, at this time, the P-channel switch tube S4 is turned off, and the N-channel switch tube S3 is turned on, and the N-channel switch tube S3 is kept on, and the energy stored in the capacitor C1 is transmitted to the driven power semiconductor device to turn on the driven power semiconductor device, since the gate-drain voltage of the switch tube S4 is higher than the voltage on the capacitor C1, that is, the drain voltage of the N-channel switch tube S3 is lower than the gate voltage, the source voltage of the N-channel switch tube S3 can be equal to the drain voltage, and the driving voltage of the driven power semiconductor device is equal to the voltage on the capacitor C1, and the set voltage can be reached.

[0062] When the modulated signal of the secondary side Vs of the isolation transformer 200 is a positive pulse voltage, at the end of the pulse, a negative undershoot voltage is generated. Only when the voltage reaches the voltage stabilizing value VZ3 of the voltage stabilizer Z3, for example, 3.3V, the voltage stabilizer Z3 is turned on, and reaches the conduction threshold VD3 of the diode D3 and the conduction threshold Vth2 of the switch S2, the switch S2 and the diode D3 are turned on. Therefore, the negative undershoot voltage generated at the end of the positive pulse voltage is within Vth2+VD3+VZ3, which does not affect the switch control circuit 500.

[0063] Similarly, when the modulated signal of the secondary side Vs of the isolation transformer 200 is a negative pulse voltage, at the end of the pulse, a positive overshoot voltage is generated. Only when the voltage reaches the voltage stabilizing value VZ4 of the voltage stabilizer Z4, for example, 3.3V, the voltage stabilizer Z4 is turned on, and reaches the conduction threshold VD2 of the diode D2 and the conduction threshold Vth1 of the switch S1, the switch S1 and the diode D2 are turned on. Therefore, the positive overshoot voltage generated at the end of the negative pulse voltage is within Vth1+VD2+VZ4, which does not affect the switch control circuit 500.

[0064] The above is only the preferred embodiment of the present application, it should be noted that the above preferred embodiment should not be considered as a limitation of the present application, for those skilled in the art, without departing from the spirit and scope of the present application, can make several improvements and refinements, the transformer structure is improved and refined should also be considered as the protection scope of the present application, hereinafter no longer use examples, the protection scope of the present application should be limited by the scope defined by the claims.

Claims

1. A drive circuit comprising: The edge modulation circuit, the isolation transformer, the energy storage circuit, the demodulation circuit and the switch control circuit; The first input end of the edge modulation circuit is used for receiving the voltage Vcc, the second input end of the edge modulation circuit is used for receiving the PWM signal, the ground end of the edge modulation circuit is connected to the ground GND, the first output end of the edge modulation circuit is connected to the same end of the primary winding of the isolation transformer, the second output end of the edge modulation circuit is connected to the different end of the primary winding of the isolation transformer; the same end of the secondary winding of the isolation transformer is connected to the input end of the energy storage circuit and the input end of the demodulation circuit; the output end of the energy storage circuit is connected to the first input end of the switch control circuit; the output end of the demodulation circuit is connected to the second input end of the switch control circuit; the output end of the switch control circuit is used as the output port of the driving circuit and is connected to the gate of the power semiconductor device to be driven; the different end of the secondary winding of the isolation transformer is connected to the ground end of the energy storage circuit, the ground end of the demodulation circuit and the ground end of the switch control circuit, and is used as the output ground SGND of the driving circuit and is connected to the source of the power semiconductor device to be driven; characterized in that: the demodulation circuit comprises a diode D2, a diode D3, a voltage stabilizing tube Z3, a voltage stabilizing tube Z4, a switch tube S1, a switch tube S2, a resistor R1 and a voltage stabilizing unit; the anode of the diode D2 and the cathode of the diode D3 are commonly connected to the input end of the demodulation circuit and are connected to the same end of the secondary winding of the isolation transformer; the cathode of the diode D2 is connected to the source of the switch tube S1; the gate of the switch tube S1 is connected to the cathode of the voltage stabilizing tube Z4; the anode of the diode D3 is connected to the source of the switch tube S2; the gate of the switch tube S2 is connected to the anode of the voltage stabilizing tube Z3, and the drain is connected to one end of the resistor R1; the other end of the resistor R1, the drain of the switch tube S1 and the first end of the voltage stabilizing unit are commonly connected to the output end of the demodulation circuit and are connected to the second input end of the switch control circuit; the cathode of the voltage stabilizing tube Z3, the anode of the voltage stabilizing tube Z4 and the second end of the voltage stabilizing unit are commonly connected to the ground end of the demodulation circuit and are connected to the different end of the secondary winding of the isolation transformer and the source of the power semiconductor device to be driven.

2. A drive circuit according to claim 1, characterised in that The demodulation circuit further comprises an adjusting unit, and the adjusting unit comprises a diode D4, a voltage stabilizing tube Z5 and a capacitor C2; the cathode of the diode D4 is connected to one end of the capacitor C2, and the first end of the adjusting unit is connected to the other end of the resistor R1 and the drain of the switch tube S1; the anode of the diode D4 is connected to the anode of the voltage stabilizing tube Z5; the cathode of the voltage stabilizing tube Z5 is connected to the other end of the capacitor C2, and the second end of the adjusting unit is connected to the first end of the voltage stabilizing unit; the other end of the resistor R1 and the drain of the switch tube S1 are connected to the first end of the voltage stabilizing unit through the adjusting unit.

3. The drive circuit of claim 1, wherein The voltage stabilizing unit comprises the voltage stabilizing tube Z1 and the voltage stabilizing tube Z2 connected in reverse series, or the diode D5 and the voltage stabilizing tube Z1 connected in reverse series.

4. A drive circuit according to claim 3, characterised in that The voltage stabilizing unit comprises a voltage stabilizing tube Z1 and a voltage stabilizing tube Z2 connected in reverse series, the first end of the voltage stabilizing unit is the anode of the voltage stabilizing tube Z1, the second end is the anode of the voltage stabilizing tube Z2, the cathode of the voltage stabilizing tube Z1 and the cathode of the voltage stabilizing tube Z2 are connected, or the first end of the voltage stabilizing unit is the cathode of the voltage stabilizing tube Z2, the second end is the cathode of the voltage stabilizing tube Z1, the anode of the voltage stabilizing tube Z1 and the anode of the voltage stabilizing tube Z2 are connected.

5. The drive circuit of claim 3, wherein The voltage stabilizing unit comprises a diode D5 and a voltage stabilizing tube Z1 connected in series, the first end of the voltage stabilizing unit is the cathode of the diode D5, the second end is the cathode of the voltage stabilizing tube Z1, the anode of the diode D5 and the anode of the voltage stabilizing tube Z1 are connected.

6. A drive circuit according to any one of claims 1 to 5, wherein The energy storage circuit comprises a diode D1 and a capacitor C1; the anode of the diode D1 is connected with the same-named end of the secondary winding of the isolation transformer as the input end of the energy storage circuit, the cathode of the diode D1 and one end of the capacitor C1 are commonly connected and connected with the first input end of the switch control circuit as the output end of the energy storage circuit, the other end of the capacitor C1 is connected with the different-named end of the secondary winding of the isolation transformer as the ground end of the energy storage circuit and used for being connected with the source of the driven power semiconductor device.

7. A drive circuit according to any one of claims 1 to 5, wherein The switch control circuit comprises a switch tube S3 and a switch tube S4, the drain of the switch tube S3 is connected with the output end of the energy storage circuit as the first input end of the switch control circuit; the source of the switch tube S3 is connected with the source of the switch tube S4 and used for being connected with the gate of the driven power semiconductor device as the output end of the switch control circuit; the gate of the switch tube S3 is connected with the gate of the switch tube S4 and connected with the output end of the demodulation circuit as the second input end of the switch control circuit; the drain of the switch tube S4 is connected with the different-named end of the secondary winding of the isolation transformer as the ground end of the switch control circuit and used for being connected with the source of the driven power semiconductor device.

8. A drive circuit, characterized by The method comprises the steps that: Edge modulation circuit, isolation transformer, diode D1, diode D2, diode D3, diode D4, Zener Z1, Zener Z2, Zener Z3, Zener Z4, switch tube S1, switch tube S2, switch tube S3, switch tube S4, resistor R1, capacitor C1;The first input end of the edge modulation circuit is used for connecting the voltage Vcc, the second input end of the edge modulation circuit is used for connecting the PWM signal, the ground of the edge modulation circuit is connected with the ground GND, the first output end of the edge modulation circuit is connected with the same end of the primary winding of the isolation transformer, and the second output end of the edge modulation circuit is connected with the different end of the primary winding of the isolation transformer;The anode of diode D1, the anode of diode D2, the cathode of diode D3 and the same end of the secondary winding of the isolation transformer are connected together;The cathode of diode D2 is connected with the source of switch tube S1;The gate of switch tube S1 is connected with the cathode of Zener Z4;The anode of diode D3 is connected with the source of switch tube S2;The gate of switch tube S2 is connected with the anode of Zener Z3, and the drain is connected with one end of resistor R1;The other end of resistor R1, the drain of switch tube S1, the cathode of diode D4 and one end of capacitor C2 are connected together;The anode of diode D4 is connected with the anode of Zener Z5;The cathode of Zener Z5, the other end of capacitor C2, the gate of switch tube S3, the gate of switch tube S4 and the cathode of Zener Z2 are connected together;The cathode of diode D1, one end of capacitor C1 and the drain of switch tube S3 are connected together;The source of switch tube S3 and the source of switch tube S4 are connected as the output end of the driving circuit and are used for being connected with the gate of the driven power semiconductor device;The different end of the secondary winding of the isolation transformer, the cathode of Zener Z3, the anode of Zener Z4, the other end of capacitor C1, the cathode of Zener Z1 and the drain of switch tube S4 are connected together and are used as the output ground SGND of the driving circuit and are used for being connected with the source of the driven power semiconductor device.

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