Active miller clamp circuit and servo driver

Abstract

The application discloses an active Miller clamp circuit and a servo driver, and relates to the technical field of semiconductors.The circuit comprises a driving circuit, a clamp circuit and a power switching device.The input end of the driving circuit is used for receiving a PWM signal to amplify the PWM signal;the first end of a first clamp branch is connected with the reference voltage end of the driving circuit; the control end of the first clamp branch is connected with the output end of the driving circuit; and the second end of the first clamp branch is connected with the reference ground end of the driving circuit; the control end of a second clamp branch is connected with the reference voltage end of the driving circuit; the control end of the second clamp branch is also connected with the first end of the first clamp branch; the second end of the second clamp branch is connected with the reference ground end of the driving circuit; the control end of the power switching device is connected with the first end of the second clamp branch; the clamp circuit is responsive to the amplified PWM signal, and the first clamp branch is turned off and the second clamp branch is turned on to limit the Miller voltage of the power switching device.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, specifically to an active Miller clamping circuit and a servo driver. Background Technology

[0002] In power-type devices such as medium-power or high-power servo drives, the drive circuit typically employs a bridge inverter circuit composed of insulated-gate bipolar transistors (IGBTs), and modulates the voltage required by the load using methods such as space vector pulse width modulation (SVPWM) or sinusoidal pulse width modulation (SPWM). However, due to the parasitic Miller capacitance inherent in IGBT devices, the Miller effect is easily generated during switching, leading to undesirable conduction behavior. If this effect is not effectively suppressed, it can easily cause brief shoot-through of the upper and lower bridge arm IGBT devices, thereby increasing the device's power consumption and heat generation. Prolonged operation may lead to thermal runaway of the device, affecting the lifespan of the servo drive, and in severe cases, even causing device damage or the entire device to fail. Summary of the Invention

[0003] This application provides an active Miller clamping circuit for clamping the Miller effect and a servo driver equipped with the circuit.

[0004] According to one aspect of this application, one embodiment provides an active Miller clamping circuit, comprising: A driving circuit, comprising an input terminal, an output terminal, a reference voltage terminal, and a reference ground terminal; the input terminal of the driving circuit is used to receive a PWM signal and amplify the PWM signal. A clamping circuit includes a first clamping branch and a second clamping branch. A first terminal of the first clamping branch is connected to the reference voltage terminal of the drive circuit, a control terminal of the first clamping branch is connected to the output terminal of the drive circuit, and a second terminal of the first clamping branch is connected to the reference ground terminal of the drive circuit. The control terminal of the second clamping branch is connected to the reference voltage terminal of the drive circuit, and the control terminal of the second clamping branch is also connected to the first terminal of the first clamping branch. The second terminal of the second clamping branch is connected to the reference ground terminal of the drive circuit. A power switching device, wherein the control terminal of the power switching device is connected to the first terminal of the second clamping branch; The clamping circuit responds to the amplified PWM signal by disconnecting the first clamping branch and turning on the second clamping branch to limit the Miller voltage of the power switching device.

[0005] In one embodiment, the first clamping branch includes a switching transistor Q1, a first end of the switching transistor Q1 is connected to a first end of the first clamping branch, a second end of the switching transistor Q1 is connected to a second end of the first clamping branch, and a control end of the switching transistor Q1 is connected to a control end of the first clamping branch.

[0006] In one embodiment, the first clamping branch further includes a resistor R4, and the control terminal of the first clamping branch is connected to the output terminal of the drive circuit through the resistor R4.

[0007] In one embodiment, the second clamping circuit includes a switching transistor Q2, the first end of which is connected to the first end of the second clamping branch, the second end of which is connected to the second end of the second clamping branch, and the control end of which is connected to the control end of the second clamping branch.

[0008] In one embodiment, the second clamping branch further includes a resistor R1, and the control terminal of the second clamping branch is connected to the reference voltage terminal of the driving circuit through the resistor R1.

[0009] In one embodiment, the active Miller clamping circuit further includes a turn-off auxiliary circuit for releasing charge when the power switching device is turned off; The first end of the shutdown auxiliary circuit is connected to the output end of the drive circuit, and the second end of the shutdown auxiliary circuit is connected to the control end of the power switching device.

[0010] In one embodiment, the shutdown auxiliary circuit includes a resistor R2 and a diode D2. The first end of the resistor R2 is connected to the first end of the shutdown auxiliary circuit, the second end of the resistor R2 is connected to the output end of the diode D2, and the input end of the diode D2 is connected to the second end of the shutdown auxiliary circuit.

[0011] In one embodiment, the active Miller clamping circuit further includes an overvoltage protection circuit for providing overvoltage protection when the power switching device is turned on; The overvoltage protection circuit includes a diode D1, the output terminal of which is connected to the output terminal of the drive circuit, and the input terminal of which is connected to the reference voltage terminal of the power switching device.

[0012] In one embodiment, the driving circuit further includes a resistor R3, and the output terminal of the driving circuit outputs the turn-off voltage through the resistor R3.

[0013] According to another aspect of this application, one embodiment provides a servo driver including an active Miller clamping circuit as described in any of the above embodiments.

[0014] According to the above embodiments, the active Miller clamping circuit and servo driver include a driving circuit, a clamping circuit, and a power switching device. The driving circuit includes an input terminal, an output terminal, a reference voltage terminal, and a reference ground terminal, capable of receiving and amplifying a PWM signal. The clamping circuit includes a first clamping branch and a second clamping branch. The first clamping branch has a first terminal connected to the reference voltage terminal, a second terminal connected to the reference ground terminal, and a control terminal connected to the output terminal of the driving circuit. The control terminal of the second clamping branch is connected to the reference voltage terminal and to the first terminal of the first clamping branch, and its second terminal is connected to the reference ground terminal. The control terminal of the power switching device is connected to the first terminal of the second clamping branch. This structure controls the state of the clamping branch through the amplified PWM signal. By disconnecting the first clamping branch and turning on the second clamping branch, Miller voltage suppression is achieved. This application can effectively clamp the control terminal voltage of the power switching device when it is turned off, preventing the gate voltage rise caused by Miller current, thereby suppressing device mis-turn-on. Furthermore, by dynamically switching between two clamping branches, stable control of the power devices can be maintained under different operating conditions, thereby improving the reliability of circuit operation. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of an active Miller clamp circuit in one embodiment. Figure 1 ; Figure 2 This is a circuit diagram of an active Miller clamp circuit in one embodiment; Figure 3 This is a schematic diagram of the structure of an active Miller clamp circuit in one embodiment. Figure 2 ; Figure 4 This is a schematic diagram of the structure of an active Miller clamp circuit in one embodiment. Figure 3 ; Figure 5 This is a driving waveform diagram of an active Miller clamp circuit in one embodiment; Figure 6 This is a schematic diagram of the servo driver in another embodiment. Detailed Implementation

[0016] The present application will now be described in further detail with reference to specific embodiments and accompanying drawings. Similar elements in different embodiments are referred to by related similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the present application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to the present application are not shown or described in the specification. This is to avoid obscuring the core parts of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0017] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments, and the operational steps involved in each embodiment can also be rearranged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the specification and drawings are only for clearly describing a particular embodiment and do not imply that they represent the necessary components and / or order.

[0018] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).

[0019] Please refer to Figure 1 This application provides an active Miller clamping circuit 100, including a drive circuit 110, a clamping circuit 120, and a power switching device 130.

[0020] In one embodiment, the drive circuit 110 converts the PWM signal from the controller into a voltage capable of driving the power switching device 130, thereby achieving on / off control of the power switching device 130. The drive circuit 110 includes an input terminal, an output terminal, a reference voltage terminal, and a reference ground terminal. The input terminal of the drive circuit 110 receives the PWM signal output from the controller and amplifies it. The output terminal of the drive circuit 110 is connected to a clamping circuit 120 and outputs the amplified PWM signal. Since the amplified PWM signal includes both high and low levels, the output terminal of the drive circuit 110 actually outputs either a turn-on voltage or a turn-off voltage based on the amplified PWM signal. The reference voltage terminal of the drive circuit 110 provides a high-level voltage (e.g., 16V) for driving. The reference ground terminal of the drive circuit 110 is a ground terminal. The drive circuit 110 controls the voltage at its output terminal according to the amplified PWM signal to achieve effective control of the power switching device 130. Specifically, when the amplified PWM signal is at a high level, the output terminal of the drive circuit 110 outputs a turn-on voltage according to the amplified PWM signal; when the amplified PWM signal is at a low level, the output terminal of the drive circuit 110 outputs a turn-off voltage according to the amplified PWM signal.

[0021] It should be noted that the driving circuit 110 of this application converts a weak electrical signal (e.g., 3.3V or 5V) into a voltage (e.g., 0V~16V) that can drive the power switching device 130. Through the voltage conversion and isolation function of the driving circuit 110, the driving circuit 110 can provide sufficient voltage amplitude and current driving capability to ensure that the power switching device 130 maintains a stable working state during high-speed switching operation.

[0022] In one embodiment, to prevent the power switching device 130 from experiencing false turn-on or transient current due to the Miller effect during high-frequency driving, the active Miller clamping circuit 100 further includes a clamping circuit 120. The clamping circuit 120 is disposed between the driving circuit 110 and the power switching device 130, and is used to limit and regulate the voltage changes at the control terminal of the power switching device 130, thereby suppressing the Miller voltage formed during the switching of the upper and lower bridge arms of the power switching device 130.

[0023] Specifically, the clamping circuit 120 includes a first clamping branch 121 and a second clamping branch 122. The first end of the first clamping branch 121 is connected to the reference voltage terminal of the drive circuit 110, the second end of the first clamping branch 121 is connected to the reference ground terminal of the drive circuit 110, and the control terminal of the first clamping branch 121 is connected to the output terminal of the drive circuit 110. The first end of the second clamping branch 122 is connected to the reference voltage terminal of the drive circuit 110, the second end of the second clamping branch 122 is connected to the reference ground terminal, and the control terminal of the second clamping branch 122 is connected to both the first end of the first clamping branch 121 and the reference voltage terminal of the drive circuit 110.

[0024] In one embodiment, upon entering the turn-off phase, the drive circuit 110 controls the output terminal to a low level according to the amplified PWM signal. The output terminal of the drive circuit 110 outputs a turn-off voltage, and the clamping circuit 120 responds accordingly: the first clamping branch 121 is disconnected, while the second clamping branch 122 is turned on. Through this process, the clamping circuit 120 quickly pulls the control terminal of the power switching device 130 down to a low potential, thereby effectively clamping the control terminal voltage rise that may be caused by the Miller effect, preventing the power switching device 130 from briefly turning on, further avoiding shoot-through, reducing device losses, and improving circuit stability and the service life of the power switching device 130.

[0025] In one embodiment, the power switching device 130 is composed of IGBTs. When the IGBT is in the upper bridge position in a set of drive bridge circuits, its collector is connected to the positive terminal of the power supply, and its emitter is connected to the collector of the lower bridge IGBT. When the IGBT is in the lower bridge position in a set of drive bridge circuits, its collector is connected to the emitter of the upper bridge IGBT, and its emitter is connected to the negative terminal of the power supply.

[0026] Please refer to Figure 2 In one embodiment, the driving circuit 110 includes a driving chip U1 and a resistor R3. The driving chip U1 is an isolated driving chip; its primary input terminal receives the PWM signal output by the control circuit, and its secondary side is connected to the output terminal, reference voltage terminal, and reference ground terminal of the driving circuit 110 (the output terminal is...). Figure 2 In this context, VO is the reference voltage terminal. Figure 2 VCC in the reference ground is... Figure 2The GND in the output is used to provide the turn-on or turn-off voltage for driving the power switching device 130. The driver chip U1 converts low-voltage control signals (e.g., 3.3V or 5V) from the control circuit into high-voltage signals (e.g., 0V to 16V) suitable for driving the power switching device 130, enabling reliable driving of the power switching device 130. Furthermore, the driver chip U1 integrates an isolation structure, providing effective electrical isolation between the control side and the power side. This effectively prevents interference signals in the power circuit from coupling to the control circuit, improving the system's anti-interference performance and protecting low-voltage components in the control circuit from high-voltage damage.

[0027] In one embodiment, to further control the drive current and prevent excessive surge current from impacting the power switching device 130 and the driver chip U1, a resistor R3 is connected in series between the output terminal of the driver chip U1 and the power switching device 130. That is, the output terminal of the drive circuit 110 outputs the turn-on voltage or turn-off voltage through resistor R3. The value of resistor R3 has a significant impact on circuit performance: when the resistance of resistor R3 is too large, it will slow down the turn-on speed of the power switching device 130, increasing conduction losses during the turn-on process; while when the resistance of resistor R3 is too small, although it can improve the turn-on speed, it may lead to excessive drive current, thereby shortening the device lifespan and potentially affecting the dead time setting between the upper and lower bridges, thus causing faults such as bridge arm short circuits. Therefore, the resistance value of resistor R3 needs to be selected reasonably by comprehensively considering factors such as the switching frequency of the circuit, the characteristics of the IGBT in the power switching device 130, and electromagnetic compatibility, to balance the efficiency and reliability of the circuit.

[0028] It should be noted that the driver chip U1 can be a commercial IGBT driver chip with functions such as high voltage isolation, wide driving voltage range and short circuit protection, such as 1ED020I12-F2, 1ED3122MU12H, UCC21750, UCC5350, ACPL-333J and ACPL-W346.

[0029] Please refer to Figure 2 In one embodiment, the first clamping branch 121 includes a switching transistor Q1, which is used to selectively turn the first clamping branch 121 on or off under the action of a PWM signal, thereby clamping the voltage at the control terminal of the power switching device 130. Specifically, the first terminal of the switching transistor Q1 is connected to the first terminal of the first clamping branch 121, i.e., the reference voltage terminal of the drive circuit 110; the second terminal of the switching transistor Q1 is connected to the second terminal of the first clamping branch 121, i.e., the reference ground terminal of the drive circuit 110; and the control terminal of the switching transistor Q1 is connected to the control terminal of the first clamping branch 121, i.e., the output terminal of the drive circuit 110.

[0030] In one embodiment, the first clamping branch 121 further includes a resistor R4, which is disposed between the control terminal of the first clamping branch 121 and the output terminal of the drive circuit 110, and is used to provide current limiting protection for the control terminal of the first clamping branch 121, so that the turn-on voltage and turn-off voltage generated by the PWM signal can stably drive the switching transistor Q1 to turn on or off.

[0031] In one embodiment, the second clamping branch 122 includes a switching transistor Q2. The first terminal of the switching transistor Q2 is connected to the first terminal of the second clamping branch 122, i.e., the reference voltage terminal of the drive circuit 110. The second terminal of the switching transistor Q2 is connected to the second terminal of the second clamping branch 122, i.e., the reference ground terminal of the drive circuit 110. The control terminal of the switching transistor Q2 is connected to the control terminal of the second clamping branch 122, i.e., the first terminal of the first clamping branch 121 and the reference voltage terminal of the drive circuit 110. By controlling the conduction state of the switching transistor Q2, the voltage at its control terminal can be effectively clamped during the turn-off process of the power switching device 130, suppressing the undesirable conduction phenomenon caused by Miller voltage, thereby improving the turn-off reliability of the power switching device 130 and the anti-interference capability of the entire circuit.

[0032] In one embodiment, the second clamping branch 122 further includes a resistor R1. The control terminal of the second clamping branch 122 is connected to the reference voltage terminal of the drive circuit 110 through the resistor R1 to achieve current limiting protection and level adaptation for the switching transistor Q2.

[0033] It is worth noting that the switching transistors Q1 and Q2 in the clamping circuit 120 are not limited to being constructed using bipolar transistors (BJTs). Their clamping function can also be achieved by other controllable semiconductor devices, such as metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), or silicon controlled rectifiers (SCRs). As long as they can achieve controlled conduction to establish a gate discharge path, they can all be used to realize the clamping function of the present invention.

[0034] It should also be emphasized that when the drive circuit 110 controls the output terminal to be at a high level (e.g., 10V~16V) according to the received PWM signal, the output terminal of the drive circuit 110 outputs a conduction voltage. A loop is formed between the output terminal of the drive circuit 110, resistor R4, and the base and emitter of the switching transistor Q1. The voltage between the base and emitter of the switching transistor Q1 is equal to the conduction voltage Vbe1 of the switching transistor Q1, and the current flowing through it is sufficiently large (e.g., 1mA~3mA), thus the switching transistor Q1 is in a saturated conduction state. The base of the switching transistor Q2 is pulled low, and at this time, the switching transistor Q2 is in a turn-off state. This has no effect on the drive voltage Vge of the IGBT in the power switching device 130, and the IGBT in the power switching device 130 can be driven to conduct normally. Since the IGBT in the power switching device 130 needs to be turned on at this time, Miller clamping protection for the drive voltage Vge is not required in this state.

[0035] When the drive circuit 110 controls the output level to be low (e.g., 0V~0.7V) according to the received PWM signal, the output of the drive circuit 110 is the turn-off voltage. At this time, the voltage between the base and emitter of the switch Q1 is less than the turn-on voltage Vbe1 of the switch Q1, and the switch Q1 is in the turn-off state. The reference voltage VCC output from the reference voltage terminal of the drive circuit 110 forms a loop through the resistor R1, the base and emitter of the switch Q2, and the voltage between the base and emitter of the switch Q2 is equal to the turn-on voltage Vbe2 of the switch Q2. The current flowing through it is large enough, so the switch Q2 is in the saturation conduction state, and the drive voltage Vge is pulled low. In this state, it is necessary to keep the IGBT in the power switching device 130 in the turn-off state. When the drive voltage Vge forms a Miller voltage due to the switching characteristics of the IGBT in the power switching device 130, it will be clamped to 0V through the switch Q2, effectively preventing the occurrence of IGBT brief conduction.

[0036] Please refer to Figure 3 In one embodiment, the active Miller circuit provided in this application further includes a turn-off auxiliary circuit 140, which is used to effectively release the charge in the internal capacitor of the control terminal when the power switching device 130 is turned off, so as to accelerate the turn-off process of the power switching device 130, reduce turn-off losses, and improve the overall dynamic performance of the circuit.

[0037] In one embodiment, the first terminal of the turn-off auxiliary circuit 140 is connected to the output terminal of the drive circuit 110, and the second terminal of the turn-off auxiliary circuit 140 is connected to the control terminal of the power switching device 130. When the IGBT of the power switching device 130 is in the on state, there is a drive voltage Vge between its gate and emitter, which is usually output by the drive circuit 110. When the drive circuit 110 outputs the turn-off voltage, the IGBT of the power switching device 130 turns off. However, since there is a parasitic capacitance between the gate and emitter of the IGBT of the power switching device 130, the charge in the parasitic capacitance needs to be released through a path during the process of the drive voltage Vge being pulled down. If there is no effective release path, the charge is slowly released through the internal structure of the drive circuit 110, resulting in a slow voltage drop rate of the drive voltage Vge, which manifests as a "tailing effect" during turn-off. This causes a delay in the turn-off of the IGBT of the power switching device 130, increases switching losses, and may even lead to the risk of a bridge arm short circuit.

[0038] Please refer to Figure 2 In one embodiment, an auxiliary release path is constructed using resistor R2 and diode D2 in the turn-off auxiliary circuit 140. The first end of resistor R2 is connected to the first terminal of the turn-off auxiliary circuit 140, the second end of resistor R2 is connected to the output terminal of diode D2, and the input terminal of diode D2 is connected to the second terminal of the turn-off auxiliary circuit 140. When the drive voltage Vge is pulled low, diode D2 conducts due to its single-phase conduction characteristic, allowing gate charge to flow through resistor R2 to the output terminal of the drive circuit 110, thereby rapidly releasing the charge on the gate. The resistance value of resistor R2 affects the release rate, i.e., the IGBT turn-off speed of the power switching device 130. Diode D2 is preferably a high-speed switching diode with a short reverse recovery time to ensure a fast response to the turn-off signal, maintain a steep edge of the gate signal, and further improve the anti-interference capability and dynamic performance of the drive circuit 110.

[0039] Please refer to Figure 4 In one embodiment, the active Miller circuit further includes an overvoltage protection circuit 150 for voltage limiting of the power switching device 130 during its conduction period to prevent damage to the device due to excessive voltage. A first terminal of the overvoltage protection circuit 150 is connected to a reference voltage terminal of the drive circuit 110, and a second terminal of the overvoltage protection circuit 150 is connected to a control terminal of the power switching device 130.

[0040] For details, please refer to Figure 2The overvoltage protection circuit 150 includes diode D1, which is a high-speed switching diode with a forward conduction voltage of Vf. The input terminal of diode D1 is connected to the control terminal of the power switching device 130, and the output terminal of diode D1 is connected to the reference voltage terminal of the drive circuit 110. In actual operation, during the conduction period of the IGBT in the power switching device 130, the drive voltage Vge at its control terminal should theoretically remain near the reference voltage VCC output from the reference voltage terminal of the drive circuit 110. However, due to factors such as parasitic inductance and capacitance in the circuit, the drive voltage Vge may momentarily rise, exceeding the reference voltage and forming an overvoltage state. At this time, diode D1 enters the conducting state, forming a current path, which quickly clamps the drive voltage Vge within VCC+Vf, thereby effectively limiting the voltage rise of the IGBT in the power switching device 130 and preventing device breakdown caused by overvoltage.

[0041] Please refer to Figure 2 In one embodiment, the active Miller clamping circuit 100 further includes capacitors C1 and C2. The first end of capacitor C1 is connected to the reference voltage terminal of the driving circuit 110, and the second end of capacitor C1 is connected to the reference ground terminal of the driving circuit 110. The first end of capacitor C2 is connected to the reference voltage terminal of the driving circuit 110, and the second end of capacitor C2 is connected to the reference ground terminal of the driving circuit 110.

[0042] Please refer to Figure 5 In one embodiment, Figure 5 H-PWM and L-PWM are the upper-bridge PWM (i.e., the turn-on voltage) and lower-bridge PWM (i.e., the turn-off voltage) sent by the control circuit to the drive circuit 110, respectively. After isolation and amplification by the drive circuit 110, they become the upper-bridge drive and lower-bridge drive, respectively. Without the clamping circuit 120, at the alternation point of the upper-bridge drive and lower-bridge drive ( Figure 5 The Miller voltage with an amplitude of Vov will be generated at times t1, t2, t3, and t4. At times t2 and t4, +Vov will be generated (t2 and t4 are the turn-off times of the IGBT in the power switching device 130), and at times t1 and t3, -Vov will be generated (t1 and t3 are the turn-on times of the IGBT in the power switching device 130). -Vov has no effect on the turn-on of the IGBT in the power switching device 130, but if the amplitude of +Vov is too high, when it exceeds the threshold voltage for the IGBT to turn on in the power switching device 130, the IGBT in the power switching device 130 will have a brief turn-on phenomenon, at which time the IGBT in the power switching device 130 will be at risk of shoot-through. After adding the clamping circuit 120 in this application, such as... Figure 5At times t1', t2', t3', and t4', corresponding to t2' and t4' respectively, +Vov will be eliminated, causing the drive voltage Vge to be clamped to 0V, effectively preventing the IGBT in the power switching device 130 from being mis-turned on due to Miller voltage.

[0043] Please refer to Figure 6 Another embodiment of this application provides a servo driver 10, which includes an active Miller clamp circuit 100. The active Miller clamp circuit 100 adopts the active Miller clamp circuit 100 in any of the above embodiments. Since the active Miller clamp circuit 100 has been clearly described in the above embodiments, it will not be described again here.

[0044] The above-described specific examples are for illustrative purposes only and are not intended to limit the scope of this invention. Those skilled in the art to which this invention pertains can make various simple deductions, modifications, or substitutions based on the concept of this invention.

Claims

1. An active Miller clamping circuit, characterized in that, include: The driving circuit includes an input terminal, an output terminal, a reference voltage terminal, and a reference ground terminal; The input terminal of the driving circuit is used to receive PWM signals and amplify the PWM signals; A clamping circuit, comprising a first clamping branch and a second clamping branch, wherein a first end of the first clamping branch is connected to the reference voltage terminal of the drive circuit, a control terminal of the first clamping branch is connected to the output terminal of the drive circuit, and a second end of the first clamping branch is connected to the reference ground terminal of the drive circuit. The control terminal of the second clamping branch is connected to the reference voltage terminal of the drive circuit, and the control terminal of the second clamping branch is also connected to the first terminal of the first clamping branch. The second terminal of the second clamping branch is connected to the reference ground terminal of the drive circuit. A power switching device, wherein the control terminal of the power switching device is connected to the first terminal of the second clamping branch; The clamping circuit responds to the amplified PWM signal by disconnecting the first clamping branch and turning on the second clamping branch to limit the Miller voltage of the power switching device.

2. The active Miller clamp circuit as described in claim 1, characterized in that, The first clamping branch includes a switching transistor Q1, the first end of which is connected to the first end of the first clamping branch, the second end of which is connected to the second end of the first clamping branch, and the control end of which is connected to the control end of the first clamping branch.

3. The active Miller clamping circuit as described in claim 2, characterized in that, The first clamping branch also includes a resistor R4, and the control terminal of the first clamping branch is connected to the output terminal of the drive circuit through the resistor R4.

4. The active Miller clamp circuit as described in claim 1, characterized in that, The second clamping branch includes a switching transistor Q2. The first end of the switching transistor Q2 is connected to the first end of the second clamping branch, the second end of the switching transistor Q2 is connected to the second end of the second clamping branch, and the control end of the switching transistor Q2 is connected to the control end of the second clamping branch.

5. The active Miller clamping circuit as described in claim 4, characterized in that, The second clamping branch also includes a resistor R1, and the control terminal of the second clamping branch is connected to the reference voltage terminal of the drive circuit through the resistor R1.

6. The active Miller clamp circuit as described in claim 1, characterized in that, The active Miller clamping circuit also includes a turn-off auxiliary circuit for releasing charge when the power switching device is turned off; The first end of the shutdown auxiliary circuit is connected to the output end of the drive circuit, and the second end of the shutdown auxiliary circuit is connected to the control end of the power switching device.

7. The active Miller clamp circuit as described in claim 6, characterized in that, The shutdown auxiliary circuit includes a resistor R2 and a diode D2. The first end of the resistor R2 is connected to the first end of the shutdown auxiliary circuit, the second end of the resistor R2 is connected to the output end of the diode D2, and the input end of the diode D2 is connected to the second end of the shutdown auxiliary circuit.

8. The active Miller clamp circuit as described in claim 1, characterized in that, The active Miller clamping circuit also includes an overvoltage protection circuit for overvoltage protection when the power switching device is turned on. The overvoltage protection circuit includes a diode D1, the output terminal of which is connected to the output terminal of the drive circuit, and the input terminal of which is connected to the reference voltage terminal of the power switching device.

9. The active Miller clamping circuit as described in claim 1, characterized in that, The driving circuit also includes a resistor R3, and the output terminal of the driving circuit outputs a turn-off voltage through the resistor R3.

10. A servo driver, characterized in that, Includes the active Miller clamping circuit as described in any one of claims 1-9.

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