CN220475756U - Driving circuit and voltage clamping circuit of switching device - Google Patents

Abstract

The application provides a driving circuit and a voltage clamping circuit of a switching device, which comprise a first control signal input end and a driving signal output end; the circuit comprises a first Zener diode and a second Zener diode connected in parallel with the first Zener diode, wherein the first Zener diode and the second Zener diode share a cathode or a common anode. By the arrangement, the voltage difference between the peak voltage of the two zener diodes in the peak generation stage and the voltage of the two zener diodes in the positive voltage recovery stage is reduced, the zener diode with larger reverse breakdown voltage can be selected, the gate-source voltage of the switching device in the positive voltage recovery stage can be improved, and the switching speed and the switching-off of the switching device are not influenced.

Description

Driving circuit and voltage clamping circuit of switching device

Technical Field

The present application relates to, but is not limited to, a switching device driving circuit and a voltage clamping circuit.

Background

Novel switching elements such as gallium nitride (GaN) and silicon carbide (SiC) have great potential as compared with existing silicon (Si) elements, and thus, novel elements such as gallium nitride and silicon carbide have been widely used in switching circuits.

The novel switching element represented by the gallium nitride switching device has the characteristics of high switching speed and relatively small on-resistance Rdson, and is widely applied to high-power density power supplies. However, the threshold voltage Vgsth of such switching devices is low, making the switching devices susceptible to false triggering. The gate withstand voltage (which may also be referred to as gate withstand voltage) of such switching devices is lower than that of silicon switching tubes, so the gates of such switching devices cannot withstand a relatively large gate-source voltage. The gate-source voltage of the switching device needs to be relatively large to make the on-resistance Rdson sufficiently low so as to fully exert the electrical characteristics thereof.

Considering the characteristics of low on threshold voltage, low gate voltage resistance, negative correlation between on resistance and gate source voltage and the like of the switching device, a driving circuit needs to be reasonably designed so that the advantages of the switching device can be fully exerted.

Disclosure of Invention

The application provides a driving circuit of a switching device, comprising:

A first control signal input terminal and a driving signal output terminal;

the signal conversion circuit is coupled between the first control signal input end and the driving signal output end;

the protection circuit is coupled to the driving signal output end and comprises a first Zener diode and a second Zener diode connected in parallel with the first Zener diode, and the first Zener diode and the second Zener diode share a cathode or a common anode.

In some embodiments, the signal conversion circuit includes a first resistor and a first capacitor connected in parallel, a first end of the first resistor being a first end of the signal conversion circuit, a second end of the first resistor being a second end of the signal conversion circuit;

the first end of the signal conversion circuit is coupled to the first control signal input end and is used for receiving the first control signal from the control circuit, and the second end of the signal conversion circuit is coupled to the driving signal output end.

In some embodiments, the reverse breakdown voltage of the first zener diode is equal to the reverse breakdown voltage of the second zener diode.

In some embodiments, the reverse breakdown voltage of the first zener diode is less than the reverse breakdown voltage of the second zener diode.

In some embodiments, the reverse breakdown voltage of the first zener diode is determined based on the turn-on gate-source voltage of the switching device.

In some embodiments, the reverse breakdown voltage of the second zener diode is determined according to the gate-source withstand voltage of the switching device.

In some embodiments, the signal conversion circuit further includes a second resistor connected in series with the first capacitor.

In some embodiments, the first resistance is greater than the second resistance.

In some embodiments, the signal conversion circuit further includes a third resistor connected in series with the first capacitor and the first resistor in parallel.

In some embodiments, the signal conversion circuit further comprises: a second control signal input terminal;

the second control signal input end is coupled with the first end of the first capacitor and is used for receiving a second control signal from the control circuit.

Some embodiments of the present application further provide a voltage clamping circuit of a switching device, the voltage clamping circuit including: a first zener diode and a second zener diode connected in parallel with the first zener diode;

the first zener diode and the second zener diode share a cathode or a common anode, and the voltage clamping circuit has three ports.

The driving circuit of the switching device comprises a first control signal input end and a driving signal output end, a signal conversion circuit and a protection circuit, wherein the signal conversion circuit is coupled between the first control signal input end and the driving signal output end, the protection circuit is coupled between the driving signal output end, the protection circuit comprises a first zener diode and a second zener diode connected in parallel with the first zener diode, the first zener diode and the second zener diode share a cathode or share an anode, through the arrangement, the two zener diodes can shunt current of the driving signal output end of the signal conversion circuit in the peak voltage generation stage, compared with a scheme adopting one zener diode, the current flowing through each zener diode is reduced, the upper voltage of each zener diode is reduced, so that the voltage of the driving signal output end of the signal conversion circuit in the peak voltage generation stage is reduced, the peak voltage of the two zener diodes in the peak voltage generation stage and the voltage of the zener diode in the recovery stage are reduced, the voltage breakdown of the two zener diodes in the peak voltage generation stage can be selected, and the voltage of the switching device can be improved in the positive voltage reverse stage. In addition, the capacitance or resistance of the capacitor in the signal conversion circuit does not need to be adjusted, and the switching speed and the switching-off of the switching device are not affected.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application.

Fig. 1 is a gate turn-on characteristic of a gallium nitride switching device;

fig. 2 is a driving circuit of a gallium nitride switching device;

FIG. 3 is a timing diagram of the operation of the drive circuit of the GaN switching device;

FIG. 4 is a schematic diagram of a charging path of the driving circuit of the GaN switching device shown in FIG. 2 during a spike voltage generation stage;

fig. 5 is a schematic diagram of a charging path of the driving circuit of the gan switching device shown in fig. 2 in a positive voltage recovery stage;

FIG. 6 is a schematic diagram of a discharge path of the driving circuit of the GaN switching device shown in FIG. 2 during a negative voltage recovery stage;

FIG. 7 is a characteristic curve of a zener diode;

fig. 8 to 13 are diagrams illustrating a driving circuit of a switching device according to some embodiments of the present application;

FIG. 14 is a schematic diagram of a charging path of the driving circuit of the GaN switching device shown in FIG. 8 during a spike voltage generation stage;

fig. 15 is a schematic diagram of a charging path of the driving circuit of the gan switching device shown in fig. 8 in a positive voltage recovery phase;

FIG. 16 is a schematic diagram of a discharge path of the driving circuit of the GaN switching device shown in FIG. 8 during a negative voltage recovery stage;

Fig. 17 is a schematic diagram of a charging path of the driving circuit of the gan switching device shown in fig. 10 during a spike voltage generation stage;

fig. 18 is a schematic diagram of a charging path of the driving circuit of the gan switching device shown in fig. 10 in a positive voltage recovery phase;

fig. 19 is a schematic diagram of a discharge path of the driving circuit of the gan switching device shown in fig. 10 in a negative voltage recovery stage.

Reference numerals:

110. a signal conversion circuit; 120. a protection circuit; 130. a switching device; 113. a first control signal input; 114. a drive signal output terminal; 115. a second control signal input; t1, a first NPN triode; t2, a first PNP triode; 141. a PWM signal generating circuit; r1, a first resistor; r2, a second resistor; r3, a third resistor; c1, a first capacitor; 140. a control circuit; z1, a first Zener diode; z2, a second zener diode; s1, a peak voltage generation stage; s2, a positive voltage recovery stage; s3, a negative voltage generation stage; s4, a negative voltage recovery stage; k1, a first switch; k2, a second switch.

Specific embodiments thereof have been shown by way of example in the drawings and will herein be described in more detail. These drawings and the written description are not intended to limit the scope of the inventive concepts in any way, but to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments.

Detailed Description

Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numbers in different drawings refer to the same or similar elements, unless otherwise indicated. The implementations described in the following exemplary examples are not representative of all implementations consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with some aspects of the present application as detailed in the accompanying claims.

The gallium nitride switching device will be specifically described below as an example. The gate withstand voltage characteristics of the gallium nitride switching device are: the gate voltage withstand capability of the gallium nitride switching device can reach-10V. However, the forward continuous voltage withstand capability is only 6.5V, the transient voltage withstand capability is 8.5V, and the pulse application to the gate of the gallium nitride switching device cannot be repeated multiple times. The gate-on characteristics of the gallium nitride switching device are: the minimum on threshold voltage of the gate is 1V, the maximum on threshold voltage of the gate is 2.5V, and the standard on threshold voltage of the gate is typically 1.65V. The minimum on threshold voltage is relatively low, and if the gate is turned off with a low positive voltage, it is likely to be triggered erroneously, so a negative voltage is generally used to turn off the gate.

Fig. 1 is an on-resistance characteristic of a gallium nitride switching device. As shown in fig. 1, a curve 1 represents a relationship between drain current and on-resistance when gate-source voltage vgs=4v, a curve 2 represents a relationship between drain current and on-resistance when gate-source voltage vgs=5v, and a curve 3 represents a relationship between drain current and on-resistance when gate-source voltage vgs=6v. For drain current id=30a, and gate-source voltage vgs=4v, on-resistance rdson=0.22Ω of the gallium nitride switching device. For drain current id=30a, and gate-source voltage vgs=6v, on-resistance rdson=0.13Ω of the gallium nitride switching device. The magnitude of the gate-source voltage Vgs thus significantly affects the magnitude of the on-resistance, the larger the gate-source voltage Vgs, the smaller the on-resistance of the gallium nitride switching device and the higher the efficiency of the gallium nitride switching device. However, the higher the gate-source voltage, the higher the voltage exceeding 6.5V can be caused under certain working conditions, resulting in the problem of damaging the gallium nitride switching device.

Typically, the gallium nitride switching device is provided with a driving circuit for controlling the gallium nitride switching device to be turned on or off, and also protecting the gallium nitride switching device. Considering the characteristics of low on threshold voltage, low gate voltage resistance, negative correlation between on resistance and gate source voltage, and the like of the gallium nitride switching device, a driving circuit of the gallium nitride switching device needs to be reasonably designed so as to fully exert the advantages of the gallium nitride switching device.

Fig. 2 is a driving circuit of a gallium nitride switching device, and as shown in fig. 2, the driving circuit includes a signal conversion circuit 110 and a protection circuit 120.

The signal conversion circuit 110 comprises a first control signal input 113 and a drive signal output 114, and the control circuit 140 comprises an output. An output terminal of the control circuit 140 is connected to the first control signal input terminal 113 of the signal conversion circuit 110, the protection circuit 120 is connected to the driving signal output terminal 114 of the signal conversion circuit 110, and the driving signal output terminal 114 of the signal conversion circuit 110 is connected to the gate of the gallium nitride switching device 130.

The control circuit 140 is configured to output a first control signal via the output terminal, and the signal conversion circuit 110 performs signal conversion on the first control signal and outputs a driving signal. The protection circuit 120 is used to clamp the voltage of the driving signal output by the signal conversion circuit 110 when the signal conversion circuit 110 converts the first control signal. By setting the clamp voltage of the protection circuit 120, damage to the gallium nitride switching device 130 due to an excessive voltage of the driving signal can be avoided.

More specifically, the control circuit 140 outputs a pulse width modulation (PWM, pulse Width Modulation) signal, and the signal conversion circuit 110 converts the PWM signal into a waveform suitable for driving the gallium nitride switching device 130.

More specifically, the control circuit 140 includes a PWM signal generator 141, a first NPN transistor T1, and a first PNP transistor T2. The collector of the first NPN transistor T1 is connected to the first power supply terminal V1, and the emitter of the first NPN transistor T1 is connected to the emitter of the first PNP and then used as the output terminal of the control circuit 140, for connecting to the first control signal input terminal 113 of the signal conversion circuit 110, and the collector of the first PNP is connected to the ground terminal. The base of the first NPN transistor T1 is connected to the base of the first PNP transistor T2, and the base of the first NPN transistor T1 is connected to the output of the PWM signal generator 141. The PWM signal generator 141 is for outputting a PWM signal. The first NPN transistor T1 and the first PNP transistor T2 are configured to increase a voltage amplitude of the high level in the PWM signal.

The signal conversion circuit 110 includes a first resistor R1, a second resistor R2, and a first capacitor C1, where a second end of the second resistor R2 is connected to a first end of the first capacitor C1, a first end of the first resistor R1 is connected to a first end of the second resistor R2, and a second end of the first resistor R1 is connected to a second end of the first capacitor C1. The first end of the first resistor R1 serves as a first control signal input terminal 113, and the second end of the first resistor R1 serves as a driving signal output terminal 114. The first resistance R1 is greater than the second resistance R2.

The protection circuit 120 includes a first Zener diode (Zener). The cathode of the first zener diode Z1 is connected to the driving signal output 114 of the signal conversion circuit 110. The reverse breakdown voltage of the zener diode is relatively large, but the forward conduction voltage drop is relatively small, and the voltage of the zener diode increases with the increase of current on the basis of the reverse breakdown voltage after reverse breakdown. Accordingly, connecting the zener diode in reverse, i.e., the cathode of the zener diode to the drive signal output 114 of the signal conversion circuit 110, clamps the drive signal to a relatively high value.

Fig. 3 is a timing diagram of the operation of the driving circuit of the gan switching device, and as shown in fig. 3, the signal conversion circuit 110 and the protection circuit 120 include four operation stages. The first stage is a Spike (Spike) voltage generation stage S1, the second stage is a positive voltage recovery stage S2, the third stage is a negative voltage generation stage S3, and the fourth stage is a negative voltage recovery stage S4.

The PWM signal generator 141 outputs a switch from a low level to a high level, the first NPN transistor T1 is turned on, the first PNP transistor T2 is turned off, and the first control signal input terminal 113 turns on the first power supply terminal V1. Fig. 4 is a schematic diagram of a charging path of the driving circuit of the gan switching device in the peak voltage generation stage S1, as shown in fig. 4, in the peak voltage generation stage S1, the first power supply terminal V1 charges the first capacitor C1 through the second resistor R2, the second resistor R2 is generally smaller, the first charging current of the first capacitor C1 is larger, the cathode voltage of the first zener diode Z1 also rises faster, and when the cathode voltage of the first zener diode Z1 reaches the reverse breakdown voltage, the first zener diode Z1 breaks down reversely. Since the first charging current of the first capacitor C1 is relatively large when the first zener diode Z1 breaks down in the reverse direction, the breakdown current flowing through the first zener diode Z1 is relatively large, and the cathode voltage of the first zener diode Z1 rises rapidly after the reverse breakdown, so as to form the spike voltage Vsp. After the cathode voltage of the first zener diode Z1 rapidly rises to form a spike voltage, the voltage division of the first zener diode Z1 is relatively large, the first charging current of the first capacitor C1 becomes small, the breakdown current flowing through the first zener diode Z1 becomes small, and the cathode voltage of the first zener diode Z1 decreases. The gate of the gallium nitride switching device 130 is connected to the cathode of the first zener diode Z1, and the gallium nitride switching device 130 is turned on rapidly.

Fig. 5 is a schematic diagram of a charging path of the driving circuit of the gan switching device in the positive voltage recovery stage S2, and as shown in fig. 5, the driving circuit enters the positive voltage recovery stage S2 when the voltage on the first capacitor C1 is about to reach the steady-state value. At this time, the first zener diode Z1 continues to breakdown reversely, the first control signal input terminal 113 continues to turn on the first power supply terminal V1, and the first power supply charges the gate of the gallium nitride switching device 130 through the first resistor R1. The gate voltage of the gallium nitride switching device 130 is related to the voltage Vf of the first zener diode Z1 at the second charging current in the positive voltage recovery stage S2, that is, the on-resistance of the gallium nitride switching device 130 is related to the voltage of the gallium nitride switching device 130 at the second charging current.

The PWM signal generator output switches from high level to low level, the first NPN transistor T1 is turned off, the first PNP transistor T2 is turned on, and the first control signal input 113 is connected to the ground. Since the steady-state voltage on the first capacitor C1 is relatively large at the end of the positive voltage recovery stage S2, and the plate connected to the gate of the gan switching device 130 on the first capacitor C1 is negatively charged, according to the charge balance principle between the first capacitor C1 and the gate-source equivalent capacitor Cgs of the gan switching device 130, when the capacitance of the first capacitor C1 is sufficiently large, a negative voltage is generated on the gate-source equivalent capacitor Cgs, so that the gan is reliably turned off.

Fig. 6 is a schematic diagram of a discharge path of the driving circuit of the gan switching device in the negative voltage recovery stage, as shown in fig. 6, since the first control signal input terminal 113 is connected to the ground terminal, the charge on the plate connected to the second resistor R2 in the first capacitor C1 is transferred to the plate connected to the gate of the gan switching device 130 in the first capacitor C1 through the second resistor R2, the ground, and the first zener diode Z1, so as to form a discharge path of the first capacitor C1, and the gate-source voltage of the gan switching device 130 is gradually recovered to 0V.

In order to avoid damage caused by excessively high gate voltage of the gan switching device 130, a zener diode with a lower reverse breakdown voltage is generally selected to reduce the spike voltage in the spike voltage generation stage S1, but the gate-source voltage of the gan switching device 130 in the positive voltage recovery stage S2 is also reduced, and the on-resistance of the gan switching device 130 is inversely related to the gate-source voltage, which increases the on-resistance of the gan switching device 130 and increases the loss of the gan switching device 130.

Based on the above considerations, it is generally desirable that the voltage difference between the spike voltage of the first zener diode Z1 in the spike generation stage and the voltage in the positive voltage recovery stage S2 is relatively small. A zener diode with a relatively large reverse breakdown voltage can be selected, so that the gate-source voltage of the gan switching device 130 in the positive voltage recovery stage S2 can be increased, and the on-resistance of the gan switching device 130 can be reduced.

Fig. 7 is an inverse characteristic curve of the zener diode, as shown in fig. 7, the zener diode includes an undeployed phase P1, a broken down linear region P2, and a broken down nonlinear region P3. When the zener diode is in the breakdown linearity region P2, the voltage drop across the zener diode is relatively small when the current of the zener diode changes. When the zener diode is in the breakdown nonlinear region, the current of the zener diode changes and the voltage drop across the zener diode changes very much.

In general, the resistance value of the first resistor R1 is smaller, and the charging current of the first capacitor C1 is larger in the spike voltage generating stage S1, so that the zener diode is in a nonlinear region, a larger spike voltage is formed, and the turn-on speed of the gan switching device 130 is increased. The resistance value of the second resistor R2 is relatively large, and the second charging current of the gate of the gallium nitride switching device 130 is relatively small in the positive voltage recovery stage S2, so that the zener diode is in a linear region, and the gate voltage of the gallium nitride switching device 130 is clamped in the positive voltage recovery stage S2. In this way, the voltage difference between the peak voltage of the first zener diode Z1 in the peak generation stage and the voltage in the positive voltage recovery stage S2 is relatively large.

In order to reduce the voltage difference between the spike voltage of the first zener diode Z1 in the spike voltage generation stage and the voltage in the positive voltage recovery stage S2. The following three schemes are generally employed.

As a first implementation, by increasing the resistance of the second resistor R2, the current flowing through the first zener diode Z1 in the spike voltage generation stage S1 can be reduced, and the spike voltage in the spike voltage generation stage S1 can be reduced, but this reduces the turn-on speed of the gan switching device 130, and increases the turn-on time of the freewheel diode when the gan switching device 130 is applied to a zero voltage switch (Zero Voltage Switch, abbreviated as ZVS) of a half bridge topology.

As a second implementation scheme, by reducing the capacitance of the first capacitor C1, the first capacitor C1 has a certain voltage division effect, so that the current flowing through the first zener diode Z1 in the spike voltage generation stage S1 can be reduced, and the spike voltage in the spike voltage generation stage S1 can be reduced, but the turn-on speed of the gallium nitride switching device 130 is reduced, and at the same time, the capacitance of the first capacitor C1 is reduced, so that a reliable negative voltage cannot be generated, and the gallium nitride switching device 130 may be triggered and turned on by mistake.

As a third implementation scheme, a zener diode with larger current capacity is selected, so that the current variation range covered by the linear region of the zener diode is larger, the voltage difference between the peak voltage of the first zener diode Z1 in the peak voltage generation stage S1 and the voltage in the positive voltage recovery stage S2 is reduced, but the package occupation area of the zener diode is large, and the parasitic capacitance of the zener diode is larger and is close to the gate equivalent capacitance Cgs of the gallium nitride switching device 130, which affects the switching speed of the gallium nitride switching device 130 and further affects the efficiency.

Some embodiments of the present application provide solutions that involve the above considerations. Fig. 8 to 13 are schematic diagrams illustrating a driving circuit of a switching device according to some embodiments of the present application.

The driving circuit of the switching device comprises a first control signal input 113 and a driving signal output 114. The driving signal output 114 is used for connection with a control terminal of the switching device 130. The driving circuit further includes a signal conversion circuit 110 and a protection circuit 120, wherein the signal conversion circuit 110 is coupled between the first control signal input terminal 113 and the driving signal output terminal 114. The protection circuit 120 is coupled to the driving signal output 114.

The protection circuit 120 includes a first zener diode Z1 and a second zener diode Z2, wherein the first zener diode Z1 is connected in parallel with the second zener diode Z2, and the first zener diode Z1 and the second zener diode Z2 are co-cathode or co-anode.

In the driving circuits of the switching devices shown in fig. 8 to 12, the first zener diode Z1 and the second zener diode Z2 are common anodes, the port 125 is a common anode terminal when the first zener diode Z1 and the second zener diode Z2 are common anodes, the common anode terminal is connected to the ground terminal, the port 123 is the cathode of the first zener diode Z1, and the port 124 is the cathode of the second zener diode Z2. Both port 123 and port 124 are connected to the drive signal output 114 of the signal conversion circuit 110.

Fig. 13 shows a driving circuit of the switching device in which a first zener diode Z1 and a second zener diode Z2 are common cathodes. When the first zener diode Z1 and the second zener diode Z2 share the cathode, the port 126 is a common cathode terminal, the common cathode terminal is connected to the driving signal output terminal 114 of the signal conversion circuit 110, the port 121 is an anode of the first zener diode Z1, and the port 122 is an anode of the second zener diode Z2. Both port 121 and port 122 are connected to ground.

The first control signal input terminal 113 of the signal conversion circuit 110 is configured to receive the first control signal, convert the first control signal, and output a driving signal, and the protection circuit 120 is configured to clamp a voltage of the driving signal output by the signal conversion circuit 110 when the signal conversion circuit 110 converts the first control signal. Since the protection circuit 120 includes two zener diodes, the two zener diodes can shunt the current of the driving signal output terminal 114 of the signal conversion circuit 110.

In the spike voltage generating stage S1, two zener diodes may shunt the current flowing through the driving signal output 114 of the signal converting circuit 110 in the spike voltage generating stage S1, and compared with a scheme using one zener diode, the voltage on each zener diode is reduced when the current flowing through each zener diode is reduced, so that the voltage of the driving signal output 114 of the signal converting circuit 110 in the spike voltage generating stage S1 is reduced, the voltage difference between the spike voltage of the first zener diode Z1 or the second zener diode Z2 in the spike voltage generating stage and the voltage of the driving signal output 114 in the positive voltage recovering stage S2 is reduced, a zener diode with a larger reverse breakdown voltage can be selected, and the gate-source voltage of the switching device 130 in the positive voltage recovering stage S2 can be increased. In addition, the capacitance or resistance of the capacitor in the signal conversion circuit 110 does not need to be adjusted, and the switching speed and the turn-off of the switching device 130 are not affected.

In some embodiments, the reverse breakdown voltage of the first zener diode Z1 is equal to the reverse breakdown voltage of the second zener diode Z2. That is, the conduction characteristic of the first zener diode Z1 is the same as the conduction characteristic of the second zener diode Z2. Both zener diodes are reverse breakdown conductive at the same time.

In the peak voltage generation stage S1, the signal conversion circuit 110 continuously increases the cathode voltages of the two zener diodes, and when the reverse breakdown voltage of the zener diodes is reached, the two zener diodes can shunt the current of the driving signal output terminal 114 of the signal conversion circuit 110 in the peak voltage generation stage S1, the voltage of the zener diodes is related to the current flowing through the zener diodes, and compared with the scheme adopting one zener diode, the current flowing through each zener diode is reduced, the upper voltage of each zener diode is reduced, so that the voltage of the driving signal output terminal 114 of the signal conversion circuit 110 in the peak voltage generation stage S1 is reduced.

In the positive voltage recovery stage S2, the two zener diodes continue to shunt the current of the driving signal output 114 of the signal conversion circuit 110 in the positive voltage recovery stage S2, and the voltage of the zener diodes is related to the zener diode flowing current, and since the zener diodes are in the reverse breakdown linear region at the time of small current, that is, the current changes but the voltage changes are small, the voltage of the driving signal output 114 of the signal conversion circuit 110 in the positive voltage recovery stage S2 in the two zener diode scheme is slightly reduced compared with the voltage of the driving signal output 114 of the signal conversion circuit 110 in the positive voltage recovery stage S2 in the one zener diode scheme.

In some embodiments, the reverse breakdown voltage of the first zener diode Z1 is less than the reverse breakdown voltage of the second zener diode Z2. I.e. the conduction characteristics of the first zener diode Z1 and the second zener diode Z2 are different. The two zener diodes do not break down and conduct simultaneously in opposite directions.

In the spike voltage generating stage S1, the signal converting circuit 110 continuously increases the cathode voltages of the two zener diodes, and when reaching the reverse breakdown voltage of the first zener diode Z1, the first zener diode Z1 is turned on reversely. The signal conversion circuit 110 continues to increase the cathode voltages of the two zener diodes, when the reverse breakdown voltage of the second zener diode Z2 is reached, the second zener diode Z2 is turned on reversely, at this time, the first zener diode Z1 and the second zener diode Z2 are turned on, the two zener diodes shunt, and since the second zener diode Z2 operates in the reverse breakdown linear region, that is, the current changes but the voltage changes are smaller, the current on the second zener diode Z2 is more, at this time, the voltage of the driving signal output terminal 114 of the signal conversion circuit 110 is close to the reverse breakdown voltage of the second zener diode Z2, compared with the scheme adopting one zener diode, the current flowing through each zener diode is reduced, so that the voltage on each zener diode is reduced, and the voltage of the driving signal output terminal 114 of the signal conversion circuit 110 in the peak voltage generation stage S1 is reduced.

In the positive voltage recovery stage S2, the two zener diodes continue to shunt the current of the driving signal output 114 of the signal conversion circuit 110 in the positive voltage recovery stage S2, since the reverse breakdown voltage of the first zener diode Z1 is smaller than the reverse breakdown voltage of the second zener diode Z2, the current of the first zener diode Z1 may be greater than the current of the second zener diode Z2, and finally, only the first zener diode Z1 may flow, and no current flows through the second zener diode Z2, so that the voltage of the driving signal output 114 of the signal conversion circuit 110 is close to the reverse breakdown voltage of the first zener diode Z1, and the voltage of the driving signal output 114 of the signal conversion circuit 110 in the positive voltage recovery stage S2 in the two zener diode scheme is the same as the voltage of the driving signal output 114 of the signal conversion circuit 110 in the positive voltage recovery stage S2 in the one zener diode scheme.

In some embodiments, when the reverse breakdown voltage of the first zener diode Z1 is less than the reverse breakdown voltage of the second zener diode Z2. Since in the spike voltage generating stage S1, the voltage of the driving signal output 114 of the signal converting circuit 110 is close to the reverse breakdown voltage of the second zener diode Z2. Since the voltage of the driving signal output 114 of the signal conversion circuit 110 is close to the reverse breakdown voltage of the first zener diode Z1 in the positive voltage recovery stage S2. The reverse breakdown voltage of the first zener diode Z1 is determined according to the turn-on gate-source voltage of the switching device 130. The reverse breakdown voltage of the second zener diode Z2 is determined according to the gate-source withstand voltage of the switching device 130. By such arrangement, the phenomenon of damage caused by excessively high gate voltage of the switching device 130 can be avoided, and the on-resistance of the switching device 130 can be minimized, thereby reducing the on-loss of the switching device 130.

In some embodiments, as shown in fig. 8, the signal conversion circuit 110 includes a first resistor R1 and a first capacitor C1, where the first capacitor C1 is connected in parallel with the first resistor R1. The signal conversion circuit 110 has a first end 111 and a second end 112, the first end of the first resistor R1 is used as the first end 111 of the signal conversion circuit 110, and the second end of the first resistor R1 is used as the second end 112 of the signal conversion circuit 110. The first terminal 111 of the signal conversion circuit 110 is coupled to the first control signal input terminal 113 for receiving the first control signal from the control circuit 140, and the second terminal 112 of the signal conversion circuit 110 is coupled to the driving signal output terminal 114.

The control circuit 140 may be designed according to the function of the control circuit 140, and as an implementation, as shown in fig. 8, the control circuit 140 includes a PWM signal generator 141, a first PNP type transistor T2, and a first NPN type transistor T1. The collector of the first NPN transistor T1 is connected to the first power supply terminal V1, and the emitter of the first NPN transistor T1 is connected to the emitter of the first PNP and then used as the output terminal of the control circuit 140, for connecting to the first control signal input terminal 113 of the signal conversion circuit 110, and the collector of the first PNP is connected to the ground terminal. The base electrode of the first NPN triode T1 is connected with the base electrode of the first PNP triode T2, and the base electrode of the first NPN triode T1 is connected with the output end of the PWM signal generator. The PWM signal generator is configured to output a PWM signal. The first NPN transistor T1 and the first PNP transistor T2 are configured to increase a voltage amplitude of the high level in the PWM signal. The first control signal input 113 of the signal conversion circuit 110 receives the PWM signal with increased amplitude.

Fig. 14 is a schematic diagram of a charging path of the driving circuit of the gan switching device shown in fig. 8 in the spike voltage generation stage S1. As shown in fig. 14, in the peak voltage generation stage S1, the first control signal input terminal 113 is connected to the first power terminal V1, and the first power terminal V1 charges the first capacitor C1, so that the first zener diode Z1 and the second zener diode Z2 are turned on by reverse breakdown sequentially or simultaneously.

Fig. 15 is a schematic diagram of a charging path of the driving circuit of the gan switching device shown in fig. 8 in the positive voltage recovery stage S2. As shown in fig. 15, in the positive voltage recovery phase S2, the first zener diode Z1 continues to reverse breakdown, and the first control signal input terminal 113 continues to turn on the first power supply terminal V1. If the reverse breakdown voltage of the first zener diode Z1 is the same as the reverse breakdown voltage of the second zener diode Z2, the first resistor R1 and the first zener diode Z1 form a charging loop, and the first resistor R1 and the second zener diode Z2 form a charging loop. If the reverse breakdown voltage of the first zener diode Z1 is smaller than the reverse breakdown voltage of the second zener diode Z2, only the first resistor R1 and the first zener diode Z1 form a charging loop.

In the negative voltage generation stage S3, the first capacitor C1 and the gate-source equivalent capacitance of the gallium nitride switching device 130 form a negative voltage at the gate of the gallium nitride switching device 130.

Fig. 16 is a schematic diagram of a discharge path of the driving circuit of the gan switching device shown in fig. 8 in a negative voltage recovery stage. As shown in fig. 16, in the negative voltage recovery stage S4, the charges on the first capacitor C1 and the gate-source equivalent capacitance of the gallium nitride switching device 130 are discharged due to the parasitic resistance of the wiring.

Unlike the driving circuit of the switching device shown in fig. 8, in the driving circuit of the switching device shown in fig. 9, the signal conversion circuit 110 further includes a second resistor R2, and the second resistor R2 is connected in series with the first capacitor C1. That is, the second end of the second resistor R2 is connected to the first end of the first capacitor C1, the first end of the second resistor R2 is connected to the first end of the first resistor R1, and the second end of the first resistor R1 is connected to the second end of the first capacitor C1. Wherein the first resistance is greater than the second resistance.

Unlike the respective stages of the driving circuit of the switching device shown in fig. 14 to 16, for the driving circuit of the switching device shown in fig. 9, the spike voltage generating stage S1, the first power source terminal V1 charges the first capacitor C1 through the second resistor R2. In the positive voltage recovery stage S2, if the reverse breakdown voltages of the first zener diode Z1 and the second zener diode Z2 are the same, the first resistor R1 and the first zener diode Z1 form a loop, and the first resistor R1 and the second zener diode Z2 form a loop. If the reverse breakdown voltage of the first zener diode Z1 is smaller than the reverse breakdown voltage of the second zener diode Z2, the first resistor R1 and the first zener diode Z1 form a loop. In the negative voltage recovery stage S4, the charges on the first capacitor C1 and the gate-source equivalent capacitance of the gallium nitride switching device 130 are discharged due to the presence of the line parasitic resistance and the second resistance R2.

Unlike the driving circuit of the switching device shown in fig. 8, in the driving circuit of the switching device shown in fig. 10, the signal conversion circuit 110 further includes a second resistor R2, and the second resistor R2 is connected in series with the first capacitor C1. That is, the second end of the second resistor R2 is connected to the first end of the first capacitor C1, the first end of the second resistor R2 is connected to the first end of the first resistor R1, and the second end of the first resistor R1 is connected to the second end of the first capacitor C1. The signal conversion circuit 110 further includes a second control signal input terminal 115, and the second control signal input terminal 115 is coupled to the first terminal of the first capacitor C1 for receiving the second control signal from the control circuit 140.

The control circuit 140 may be designed according to the function of the control circuit 140, and as an implementation, as shown in fig. 10, the control circuit 140 includes a first switch K1 and a second switch K2. A first terminal of the first switch K1 is connected to the first power supply terminal V1, and a second terminal of the first switch K1 is connected to the first control signal input terminal 113 of the signal conversion circuit 110 as a first output terminal of the control circuit 140. The first end of the second switch K2 is used as a second output end of the control circuit 140, and is connected to the second control signal input end 115 of the signal conversion circuit 110, and the second end of the second switch K2 is connected to the ground.

Fig. 17 is a schematic diagram of a charging path of the driving circuit of the gan switching device shown in fig. 10 in the spike voltage generation stage S1. As shown in fig. 17, in the peak voltage generating stage S1, the first switch K1 is turned on, the second switch K2 is turned off, the first control signal input terminal 113 is turned on to the first power terminal V1, the second control signal input terminal 115 is turned off from the ground terminal, and the first power terminal V1 charges the first capacitor C1 through the second resistor R2, so that the first zener diode Z1 and the second zener diode Z2 are turned on in reverse breakdown order or simultaneously.

Fig. 18 is a schematic diagram of a charging path of the driving circuit of the gan switching device shown in fig. 10 in the positive voltage recovery stage S2. As shown in fig. 18, in the positive voltage recovery phase S2, the first switch K1 is closed, the second switch K2 is opened, the first control signal input terminal 113 is connected to the first power supply terminal V1, and the second control signal input terminal 115 is disconnected from the ground terminal. If the reverse breakdown voltage of the first zener diode Z1 is the same as the reverse breakdown voltage of the second zener diode Z2, the first resistor R1 and the first zener diode Z1 form a loop, and the first resistor R1 and the second zener diode Z2 form a loop. If the reverse breakdown voltage of the first zener diode Z1 is smaller than the reverse breakdown voltage of the second zener diode Z2, only the first resistor R1 and the first zener diode Z1 form a loop.

In the negative voltage generating stage S3, the first switch K1 is opened, the second switch K2 is closed, the first control signal input terminal 113 is disconnected from the first power source terminal V1, and the second control signal input terminal 115 is connected to the ground terminal. The first capacitance C1 and the gate-source equivalent capacitance of the gallium nitride switching device 130 form a negative voltage at the gate of the gallium nitride switching device 130.

Fig. 19 is a schematic diagram of a discharge path of a driving circuit of a gan switching device in a negative voltage recovery stage. As shown in fig. 19, in the negative voltage recovery stage S4, the first switch K1 is opened, the second switch K2 is closed, the first control signal input terminal 113 is disconnected from the first power supply terminal V1, and the second control signal input terminal 115 is connected to the ground terminal. The charge on the first capacitance C1 and the gate-source equivalent capacitance of the gallium nitride switching device 130 is discharged due to the presence of the second resistor R2.

Unlike the driving circuit of the switching device shown in fig. 8, in the driving circuit of the switching device shown in fig. 11, the signal conversion circuit 110 further includes a third resistor R3, and the third resistor R3 is connected in series with the first capacitor C1 and the first resistor R1. That is, two ends of the third resistor R3 are connected to the first end of the first resistor R1, the first end of the third resistor R3 is used as the first end of the signal conversion circuit 110, and the second end of the first resistor R1 is used as the second end of the signal conversion circuit 110.

Unlike the respective stages of the driving circuits of the switching devices shown in fig. 14 to 16, for the driving circuit of the switching device shown in fig. 11, the spike voltage generating stage S1, the first power source terminal V1 charges the first capacitor C1 through the third resistor R3. In the positive voltage recovery stage S2, if the reverse breakdown voltages of the first zener diode Z1 and the second zener diode Z2 are the same, the first resistor R1, the third resistor R3 and the first zener diode Z1 form a loop, and the first resistor R1, the third resistor R3 and the second zener diode Z2 form a loop. If the reverse breakdown voltage of the first zener diode Z1 is smaller than the reverse breakdown voltage of the second zener diode Z2, the first resistor R1, the third resistor R3 and the first zener diode Z1 form a loop. In the negative voltage recovery stage S4, the charge on the first capacitance C1 and the gate-source equivalent capacitance of the gallium nitride switching device 130 is discharged due to the presence of the third resistance R3 of the line.

The respective stages of the driving circuits of the switching devices shown in fig. 12 and 13 may refer to the respective stages of the driving circuits of the switching devices shown in fig. 8 to 11, and are not described again.

The following describes, in connection with a specific case, a driving circuit of the switching device shown in fig. 9 as an example.

In one case, the first power supply terminal V1 provides a voltage of 12V, the ground terminal voltage is 0V, the first resistor r1=1.2kΩ, the second resistor r2=47 Ω, the first capacitor c1=6.8nf, the reverse breakdown voltage of the first zener diode Z1 is 5.1V, and the reverse breakdown voltage of the second zener diode Z2 is 5.1V.

The current at reverse breakdown is:

Iz1＝0.5×(12V-5.1V)/R2＝0.5×147mA

when charging the gate of the gallium nitride switching device 130 through the second resistor R2, the charging current is:

Iz2＝0.5×(12V-5.1V)/R2＝0.5×5.75mA

iz1 is also the peak voltage corresponding current of the zener diode in the peak voltage generation stage S1, and Iz2 is also the voltage corresponding current of the zener diode in the positive voltage recovery stage S2. That is, the current at reverse breakdown of two zener diodes is half that of one zener diode, compared to one zener diode. The cathodes of the two zener diodes are at half the current of the positive voltage recovery stage S2 when the current of the positive voltage recovery stage S2 is one zener diode. In the spike voltage generation stage S1, the zener diode works in a reverse breakdown nonlinear region, and the current is halved, so that the tip voltage can be obviously reduced. In the positive voltage recovery stage S2, the zener diode operates in the reverse breakdown linear region, and the current halving voltage variation is not obvious.

In one case, the first power terminal V1 provides a voltage of 12V, the ground terminal voltage is 0V, the first resistor r1=1.2kΩ, the second resistor r2=47 Ω, and the first capacitor c1=6.8nf.

The reverse breakdown voltage of the first zener diode Z1 is determined to be 5.1V according to the gate-source voltage corresponding to the minimum on-resistance of the gallium nitride switching device 130. The reverse breakdown voltage of the second zener diode Z2 is determined to be 5.6V according to the gate-source withstand voltage of the gallium nitride switching device 130. When both zener diodes break down in reverse, the total breakdown current is:

Iz1＝(12-5.6)/R2＝136mA

the total current is distributed by two zener diodes, at this time, the first zener diode Z1 operates in the reverse breakdown nonlinear operation region, the second zener diode Z2 operates in the reverse breakdown linear region, the voltage in the second zener diode Z2 changes slowly, the current in the second zener diode Z2 is more, and the current in the first zener diode Z1 is relatively smaller. Compared with the zener diode with the same reverse breakdown voltage, the first zener diode Z1 in the zener diode with different reverse breakdown voltages has smaller current and lower peak voltage. In the positive voltage recovery phase S2, only the first zener diode Z1 breaks down in the reverse direction and the second zener diode Z2 does not participate. The same voltage as the positive voltage recovery stage S2 with only one zener diode.

In the above technical solution, in the spike voltage generating stage S1, two zener diodes are connected in parallel, so that the current flowing through the zener diodes becomes smaller, the two zener diodes are close to the reverse breakdown linear region in the spike voltage generating stage S1, the spike voltage is reduced, the voltage difference between the spike voltage of the zener diode in the spike voltage generating stage and the voltage in the positive voltage recovering stage S2 is reduced, the zener diode with a relatively large reverse breakdown voltage can be selected, the gate-source voltage of the gallium nitride switching device 130 in the positive voltage recovering stage S2 can be improved, and the conduction loss of the gallium nitride switching device 130 is reduced.

Some embodiments of the present application further provide a voltage clamping circuit of a switching device, where the voltage clamping circuit includes a first zener diode and a second zener diode connected in parallel with the first zener diode. The first zener diode and the second zener diode share a cathode or a common anode, and the voltage clamping circuit has three ports.

When the first zener diode and the second zener diode share the cathode, the common cathode terminal of the first zener diode and the second zener diode is used as a first port of the voltage clamping circuit, the anode of the first zener diode is used as a second port of the voltage clamping circuit, and the anode of the second zener diode is used as a third port of the voltage clamping circuit.

When the first zener diode and the second zener diode share the anode, the cathode of the first zener diode is used as the first port of the voltage clamping circuit, the cathode of the second zener diode is used as the second port of the voltage clamping circuit, and the common anode terminal of the first zener diode and the second zener diode is used as the third port of the voltage clamping circuit.

In some embodiments, the reverse breakdown voltage of the first zener diode is the same as the reverse breakdown voltage of the second zener diode. When the voltage clamping circuit works, the first zener diode and the second zener diode are simultaneously reversely broken down.

In some embodiments, the reverse breakdown voltage of the first zener diode and the reverse breakdown voltage of the second zener diode are different. When the voltage clamping circuit works, the zener diode with small reverse breakdown voltage breaks down first, and the zener diode with large reverse breakdown voltage breaks down later.

The reverse breakdown voltage of the first zener diode is the same as the reverse breakdown voltage of the second zener diode, and it can be understood that the difference between the reverse breakdown voltage of the first zener diode and the reverse breakdown voltage of the second zener diode is less than the preset threshold.

The reverse breakdown voltage of the first zener diode is different from the reverse breakdown voltage of the second zener diode, which can be understood as that the difference between the reverse breakdown voltage of the first zener diode and the reverse breakdown voltage of the second zener diode is greater than or equal to a preset threshold.

In the above technical scheme, the voltage clamping circuit includes two parallel first zener diodes and second zener diodes, the first zener diodes and the second zener diodes share cathodes or anodes, when the voltage clamping circuit works, the two zener diodes can shunt working current, after any one or both of the two zener diodes are broken down, at least one zener diode can work in a linear region of reverse breakdown, and the voltage clamping circuit can clamp the voltage in a narrower range, so that the performance of the voltage clamping circuit can be improved.

The above-described embodiments refer to the concept that both high and low levels are opposite (i.e., the voltage value of the high level is higher than the voltage value of the low level corresponding thereto), and are not limited to the specific voltage value of the high level or the specific voltage value of the low level. The high levels applied to the different signal lines in this embodiment are not limited to being equal, nor are the high levels applied to the specific signal lines at different stages. It will be appreciated by those skilled in the art that the values of the respective high and low levels may be set by themselves, depending on process nodes, speed requirements, reliability requirements, etc.

Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the application following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the application pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.

It is to be understood that the present application is not limited to the precise arrangements and instrumentalities shown in the drawings, which have been described above, and that various modifications and changes may be effected without departing from the scope thereof. The scope of the application is limited only by the appended claims.

Claims (11)

1. A driving circuit of a switching device, comprising:

a first control signal input terminal and a driving signal output terminal;

the signal conversion circuit is coupled between the first control signal input end and the driving signal output end;

the protection circuit is coupled to the driving signal output end, and comprises a first zener diode and a second zener diode connected in parallel with the first zener diode, wherein the first zener diode and the second zener diode share a cathode or a common anode.

2. The driving circuit of a switching device according to claim 1, wherein:

the signal conversion circuit comprises a first resistor and a first capacitor which are connected in parallel, wherein the first end of the first resistor is used as the first end of the signal conversion circuit, and the second end of the first resistor is used as the second end of the signal conversion circuit;

the first end of the signal conversion circuit is coupled to the first control signal input end and is used for receiving a first control signal from the control circuit, and the second end of the signal conversion circuit is coupled to the driving signal output end.

3. The driving circuit of a switching device according to claim 1, wherein:

the reverse breakdown voltage of the first zener diode is equal to the reverse breakdown voltage of the second zener diode.

4. The driving circuit of a switching device according to claim 1, wherein:

the reverse breakdown voltage of the first zener diode is less than the reverse breakdown voltage of the second zener diode.

5. The driving circuit of a switching device according to claim 4, wherein:

the reverse breakdown voltage of the first zener diode is determined according to the turn-on gate-source voltage of the switching device.

6. The driving circuit of a switching device according to claim 4, wherein:

the reverse breakdown voltage of the second zener diode is determined according to the gate-source withstand voltage of the switching device.

7. The driving circuit of a switching device according to claim 2, wherein:

the signal conversion circuit also comprises a second resistor, and the second resistor is connected in series with the first capacitor.

8. The switching device driving circuit according to claim 7, wherein the first resistance is larger than the second resistance.

9. The driving circuit of a switching device according to claim 2, wherein:

the signal conversion circuit further comprises a third resistor, and the third resistor is connected in series with the first capacitor and the first resistor which are connected in parallel.

10. The driving circuit of a switching device according to claim 2, wherein the signal conversion circuit further comprises: a second control signal input terminal;

the second control signal input terminal is coupled to the first terminal of the first capacitor for receiving a second control signal from the control circuit.

11. A voltage clamp circuit for a switching device, the voltage clamp circuit comprising: a first zener diode and a second zener diode connected in parallel with the first zener diode;

The first zener diode and the second zener diode share a cathode or a common anode, and the voltage clamping circuit has three ports.