Circuit and method for monitoring switching state of power switching device and motor controller thereof

Abstract

The invention discloses a monitoring circuit and method for the switching state of a power switching device and a motor controller thereof, and relates to the technical field of power switching devices, and the monitoring circuit comprises a driving chip which is used for driving the switching-on and switching-off of the power switching device; the state detection module is connected between the collector electrode or the drain electrode of the power switch device and the ground, and is used for sampling the conduction voltage drop of the power switch device and generating a state detection signal; the input end of the signal isolation and transmission module is connected with the output end of the state detection module, and the signal isolation and transmission module is used for isolating the state detection signal and transmitting the signal to a low-voltage side; and the low-voltage side is configured to judge the turn-on or turn-off state of the power switch device according to the signal output by the signal isolation and transmission module. The on-off state of the power switch device is monitored; dependence on a specific diagnosis function integrated in the driving chip is abandoned, so that the driving chip can be matched with any universal driving chip for use, the system cost is reduced, and the flexibility and universality of circuit design are enhanced.

Description

Technical Field

[0001] This invention relates to the field of power switching device technology, and in particular to a monitoring circuit, method, and motor controller for the switching state of a power switching device. Background Technology

[0002] Insulated-gate bipolar transistors (IGBTs) and silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) are core switching elements in power electronic devices such as motor controllers and frequency converters. Their operational reliability and health directly affect the safety and lifespan of the entire system. Real-time and accurate monitoring of the switching status of power devices is crucial for achieving overcurrent protection, fault diagnosis, and health management.

[0003] In existing technologies, a common approach to monitoring switch states relies on the diagnostic functions built into the power driver chip. For example, Chinese utility model patent CN219609128U discloses a turn-off path testing device covering the entire actuator, which diagnoses whether the power device is experiencing abnormal states such as jamming by using a comparator, constant current source, and signal isolation feedback channel integrated within the driver chip. However, this approach has a limitation: it is highly dependent on the hardware functions of a specific driver chip. This means that to obtain state monitoring capabilities, the system must use a dedicated driver chip that integrates these complex functions, which undoubtedly increases hardware costs, limits the range of driver chip selection, and lacks design flexibility.

[0004] Furthermore, existing technologies also include solutions for precisely measuring the on-state voltage drop of power devices for junction temperature monitoring or health status assessment. For example, Chinese invention patent CN117031227B discloses a non-destructive online monitoring circuit for the on-state voltage drop of power semiconductor devices. This solution utilizes normally-on switching devices and clamping voltage sources as basic units, enabling it to withstand high voltage when the power device is off and extract its low on-state voltage drop non-destructively when it is on. While this technology can achieve high-precision voltage drop measurement, and even extend to converter-level monitoring, its circuit structure is relatively complex, especially when monitoring multiple devices or bridge circuits, requiring specific combinations of multiple basic units. Its core purpose is to accurately measure the analog value of the on-state voltage drop, rather than simply and cost-effectively determining the digital state of the switch (i.e., "on" or "off").

[0005] Therefore, there is an urgent need for a power device switching state monitoring scheme that can break free from the dependence on expensive, function-specific dedicated driver chips, while also possessing the characteristics of simple circuit structure, low cost, and ease of implementation. Summary of the Invention

[0006] In a first aspect, to solve the above-mentioned technical problems, a monitoring circuit for the switching state of a power switching device is provided, comprising: Driver chip, used to drive the power switching devices to turn on and off; A status detection module, connected between the collector or drain of the power switching device and ground, is used to sample the on-state voltage drop of the power switching device and generate a status detection signal; and A signal isolation and transmission module, the input of which is connected to the output of the status detection module, is used to isolate the status detection signal and transmit it to the low-voltage side; wherein, the low-voltage side is configured to determine the on or off state of the power switching device based on the signal output by the signal isolation and transmission module.

[0007] Furthermore, the state detection module includes a voltage divider unit and a voltage offset unit, wherein: The first end of the voltage divider unit is connected to a high-voltage power supply, and the second end is grounded through the voltage offset unit. The voltage divider node of the voltage divider unit serves as the output terminal of the status detection module and is connected to the input terminal of the signal isolation and transmission module.

[0008] Further: The voltage divider unit includes a first resistor and a second resistor connected in series, wherein the node between the first resistor and the second resistor serves as the voltage divider node; The voltage offset unit includes a high-voltage reverse-biased diode and a Zener diode connected in series. The cathode of the high-voltage reverse-biased diode is connected to the collector or drain of the power switching device, and the anode is connected to the cathode of the Zener diode. The anode of the Zener diode is grounded.

[0009] Furthermore, the signal isolation and transmission module is a digital isolator, wherein: When the power switching device is turned on, the input voltage of the digital isolator is lower than its logic threshold, and the output level is low. When the power switching device is turned off, the input voltage of the digital isolator is higher than its logic threshold, and the output level is high.

[0010] Furthermore, the signal isolation and transmission module is an analog isolator, wherein: The low-voltage side is configured to compare the output voltage of the analog isolator with a preset threshold to determine the on or off state of the power switching device.

[0011] Furthermore, the power switching device is an IGBT or a SiC MOSFET.

[0012] A second aspect of the present invention provides a method for monitoring the switching state of a power switching device, applied to the monitoring circuit, the method comprising: A state detection module connected between the collector or drain of the power switching device and ground is used to sample the on-state voltage drop of the power switching device and generate a state detection signal. The status detection signal is isolated and transmitted to the low-voltage side via a signal isolation and transmission module; On the low-voltage side, the on or off state of the power switching device is determined based on the received signal.

[0013] Furthermore, the state detection module includes a voltage divider unit composed of a first resistor and a second resistor, and a voltage offset unit composed of a high-voltage reverse-biased diode and a Zener diode; wherein, the step of generating the state detection signal includes: When the power switching device is turned off, the level of the state detection signal is generated based on the voltage division value of the voltage divider unit; When the power switching device is turned on, the level of the state detection signal is generated based on the on-state voltage drop of the power switching device, the on-state voltage drop of the high-voltage reverse-biased diode, and the voltage regulation value of the Zener diode.

[0014] Furthermore, the signal isolation and transmission module is a digital isolator; the power switching device switching state determination step includes: The power switching device can be determined to be in the off or on state directly based on whether the output of the digital isolator is high or low.

[0015] Further: When the power switching device is turned on, the voltage at the input terminal of the digital isolator satisfies the following relationship:

[0016] When the power switching device is turned off, the voltage at the input of the digital isolator satisfies the following relationship:

[0017] In the formula, , These represent the levels of the state detection signals, respectively. This represents the forward voltage drop of the high-voltage reverse-biased diode; This indicates the on-state voltage drop of a power switching device; This indicates the voltage regulation value of the Zener diode; This indicates the voltage value of the high-voltage power supply; , These represent the resistance values ​​of the first resistor and the second resistor, respectively.

[0018] Furthermore, the signal isolation and transmission module is an analog isolator; the power switching device switching state determination step includes: The output voltage of the analog isolator is compared with a preset threshold, and the on or off state of the power switching device is determined based on the comparison result.

[0019] Further: When the power switching device is turned on, the voltage at the input terminal of the analog isolator satisfies the expression:

[0020] When the power switching device is turned off, the voltage at the input of the analog isolator satisfies the expression:

[0021] In the formula, , These represent the levels of the state detection signals, respectively. This represents the forward voltage drop of the high-voltage reverse-biased diode; This indicates the on-state voltage drop of a power switching device; This indicates the voltage value of the high-voltage power supply; , These represent the resistance values ​​of the first resistor and the second resistor, respectively.

[0022] A third aspect of the present invention provides a motor controller, including a monitoring circuit for the switching state of the power switching device.

[0023] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: This invention achieves the monitoring of the switching state of power switching devices by designing an external state detection circuit independent of the driver chip and cooperating with a general signal isolation and transmission circuit. It eliminates the traditional reliance on the driver chip to integrate specific diagnostic functions (such as comparators and constant current sources), enabling it to be used with any general-purpose driver chip, thereby reducing system costs, enhancing the flexibility and versatility of circuit design, and ensuring the reliability of state monitoring. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1This is a circuit schematic diagram of the digital isolation scheme disclosed in an embodiment of the present invention; Figure 2 This is a circuit schematic diagram of the analog isolation scheme disclosed in an embodiment of the present invention. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The present invention aims to provide a power switching device switching state monitoring circuit that is simple in structure, low in cost, and highly versatile. It detects the change in the on-state voltage drop of the power switching device through an external circuit independent of the driver chip, and uses a general isolation device to transmit the signal characterizing the switching state to the low-voltage side for processing, thereby completely eliminating the dependence on specific diagnostic functions inside the driver chip.

[0028] Please see Figure 1-2 The power switching device switching state monitoring circuit provided by this invention mainly includes a driver chip U2, a state detection module, and a signal isolation and transmission module. The driver chip U2 is used to drive the power switching device Q1 to turn on and off. The state detection module is connected between the collector or drain of the power switching device Q1 and ground, and is used to sample the on-state voltage drop of the power switching device Q1 and generate a state detection signal. The input terminal of the signal isolation and transmission module is connected to the output terminal of the state detection module, and is used to isolate the state detection signal and transmit it to the low-voltage side. The low-voltage side is configured to determine the on or off state of the power switching device Q1 based on the signal output by the signal isolation and transmission module.

[0029] In this scheme, the power switching device Q1 is the object being monitored, which is either an IGBT or a SiC MOSFET. The collector (or drain) of the power switching device Q1 is connected to the high-voltage power supply VCCH, the emitter (or source) is grounded, and the gate is controlled by the driver chip U2.

[0030] The driver chip U2 is a general-purpose driver chip, requiring no built-in specific diagnostic comparator or constant current source. Its core function is simply to provide sufficient drive voltage and current to reliably control the turn-on and turn-off of the power switching device Q1. This is one of the key prerequisites for the cost reduction and versatility of this invention.

[0031] In a further embodiment, a state detection module is connected between the collector (or drain) of the power switching device Q1 and ground to sample the on-state voltage drop Vce of the power switching device Q1. The state detection module includes a voltage divider unit and a voltage offset unit; wherein, the first terminal of the voltage divider unit is connected to the high-voltage power supply VCCH, and the second terminal is grounded through the voltage offset unit; the voltage divider node of the voltage divider unit serves as the output terminal of the state detection module and is connected to the input terminal of the signal isolation and transmission module.

[0032] Specific; The voltage divider unit includes a first resistor R1 and a second resistor R2 connected in series. The node between the first resistor R1 and the second resistor R2 serves as the voltage divider node.

[0033] The voltage offset unit includes a high-voltage reverse-biased diode D1 and a Zener diode D2 connected in series. The cathode of the high-voltage reverse-biased diode D1 is connected to the collector or drain of the power switching device Q1, and the anode is connected to the cathode of the Zener diode D2. The anode of the Zener diode D2 is grounded. When the power switching device Q1 is off and subjected to a high voltage, the high-voltage reverse-biased diode D1 is in a reverse-biased state. Its high reverse breakdown voltage characteristic prevents high voltage from entering the subsequent low-voltage detection circuit, playing a crucial role in isolation and protection. In the digital isolation scheme, the Zener diode D2 is used to generate a fixed voltage offset with a regulated voltage Vz, which is key to achieving logic level conversion.

[0034] In a further embodiment, the input of the signal isolation and transmission module is connected to the output of the status detection module, specifically the voltage divider node of the first resistor R1 and the second resistor R2. The signal isolation and transmission module can be either a digital isolator or an analog isolator. The low-voltage side is configured to receive the isolated signal and perform status determination, wherein: exist Figure 1 In the digital isolation scheme shown, the signal isolation and transmission module is a digital isolator. The high and low levels of the U1-OUT pin of the digital isolator can be directly read from the low-voltage side. Specifically, when the power switch Q1 is turned on, the input voltage of the digital isolator is lower than its logic threshold, and the output is low; when the power switch Q1 is turned off, the input voltage of the digital isolator is higher than its logic threshold, and the output is high.

[0035] exist Figure 2 In the analog isolation scheme shown, the signal isolation and transmission module is an analog isolator, whose output signal Vout has a linear relationship with the input signal Vin, i.e., Vout = k*Vin. Specifically, on the low-voltage side, a comparator is used to compare the output voltage Vout of the analog isolator with a preset threshold voltage Vth to determine the on or off state of the power switching device Q1.

[0036] The present invention also provides a method for monitoring the switching state of a power switching device applied to the above-mentioned circuit, comprising the following steps: S1. By connecting the state detection module between the collector or drain of the power switching device Q1 and ground, the on-state voltage drop of the power switching device Q1 is sampled to generate a state detection signal.

[0037] In a further embodiment, the state detection module includes a voltage divider unit consisting of a first resistor R1 and a second resistor R2, and a voltage offset unit consisting of a high-voltage reverse-biased diode D1 and a Zener diode D2.

[0038] The steps for generating state detection signals include: When the power switch Q1 is turned off, the level of the status detection signal is generated based on the voltage division value of the voltage divider unit.

[0039] When the power switch Q1 is turned on, the level of the status detection signal is generated based on the forward voltage drop of the power switch Q1, the forward voltage drop of the high voltage reverse bias diode D1, and the voltage regulation value of the Zener diode D2.

[0040] S2. The status detection signal is isolated and transmitted to the low-voltage side through the signal isolation and transmission module.

[0041] S21. The signal isolation and transmission module is a digital isolator; the power switching device switching state determination steps include: The power switch Q1 can be determined to be in the off or on state by directly judging whether the output of the digital isolator is high or low.

[0042] S22, The signal isolation and transmission module is an analog isolator; the power switching device switching state determination steps include: The output voltage of the analog isolator is compared with a preset threshold, and the on or off state of the power switching device Q1 is determined based on the comparison result.

[0043] S3. On the low-voltage side, determine the on or off state of the power switching device Q1 based on the received signal.

[0044] S31. When the signal isolation and transmission module is a digital isolator: When power switching device Q1 is turned on, the voltage at the input of the digital isolator satisfies the following relationship:

[0045] When power switching device Q1 is turned off, the voltage at the input of the digital isolator satisfies the following relationship:

[0046] In the formula, , These represent the levels of the state detection signal, respectively. This represents the forward voltage drop of the high-voltage reverse-biased diode D1; This indicates the on-state voltage drop of a power switching device; This indicates the Zener voltage of the Zener diode D2; This indicates the voltage value of the high-voltage power supply; , These represent the resistance values ​​of the first resistor R1 and the second resistor R2, respectively.

[0047] Specifically: When power switching device Q1 is turned on, its collector voltage is its on-state voltage drop Vce, which is typically 2-5V. Because Vce is very low, the high-voltage reverse-biased diode D1 is forward-biased, and its voltage drop is VF. Since both VF and Vce are very small, subtracting Vz... The value will be lower than the logic low-level threshold of digital isolator U1. At this time, U1-OUT outputs a low level, indicating that power switching device Q1 is in the on state.

[0048] When power switch Q1 is turned off, its collector voltage is close to the high-voltage power supply VCCH. By properly configuring the values ​​of the first resistor R1 and the second resistor R2, and the Zener diode D2's Zener voltage Vz, it is possible to design a system that... The value is higher than the logic high-level threshold of digital isolator U1. At this time, U1-OUT outputs a high level, indicating that power switching device Q1 is in the off state.

[0049] S32. When the signal isolation and transmission module is an analog isolator: When power switching device Q1 is turned on, the voltage at the input of the analog isolator satisfies the expression:

[0050] Analog isolator output:

[0051] When power switching device Q1 is turned off, the voltage at the input of the analog isolator satisfies the expression:

[0052] In the formula, , These represent the levels of the state detection signal; This represents the forward voltage drop of the high-voltage reverse-biased diode D1; This indicates the on-state voltage drop of a power switching device; This indicates the voltage value of the high-voltage power supply; , These represent the resistance values ​​of the first resistor R1 and the second resistor R2, respectively.

[0053] Specifically: On the low-pressure side, a point between... f and Threshold voltage between threshold It can be flexibly set or adjusted on the low-voltage side without modifying the high-voltage side hardware, and can adapt to different models of power devices or temperature changes.

[0054] when > When the power switching device Q1 is in the off state, it is determined that the power switching device Q1 is in the off state.

[0055] when < When the power switching device Q1 is in the on state, it is determined that the power switching device Q1 is in the on state.

[0056] It should be noted that motor controllers that include the power switching device switching status monitoring circuit described above are also within the scope of protection of this invention.

[0057] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A monitoring circuit for a switching state of a power switching device, characterized by The method comprises: a driving chip for driving the turn-on and turn-off of the power switching device; a state detection module connected between the collector or drain of the power switching device and the ground for sampling the conduction voltage drop of the power switching device and generating a state detection signal; and a signal isolation and transmission module having an input end connected to the output end of the state detection module for isolating and transmitting the state detection signal to a low-voltage side; wherein the low-voltage side is configured to determine the turn-on or turn-off state of the power switching device according to the signal output by the signal isolation and transmission module.

2. The monitoring circuit of a power switching device switching state according to claim 1, characterized in that, The state detection module comprises a voltage dividing unit and a voltage offset unit, wherein: the first end of the voltage dividing unit is connected to a high-voltage power supply, and the second end is connected to the ground through the voltage offset unit; the voltage dividing node of the voltage dividing unit serves as the output end of the state detection module and is connected to the input end of the signal isolation and transmission module.

3. The monitoring circuit for the switching state of the power switching device according to claim 2, wherein: the voltage dividing unit comprises a first resistor and a second resistor connected in series, and the node between the first resistor and the second resistor serves as the voltage dividing node; the voltage offset unit comprises a high-voltage reverse-biased diode and a stabilized diode connected in series, the cathode of the high-voltage reverse-biased diode is connected to the collector or drain of the power switching device, the anode of the high-voltage reverse-biased diode is connected to the cathode of the stabilized diode, and the anode of the stabilized diode is connected to the ground.

4. The monitoring circuit of a power switching device switching state according to claim 1, characterized in that, The signal isolation and transmission module is a digital isolator, wherein: when the power switching device is turned on, the input end voltage of the digital isolator is lower than its logic threshold, and the output is low; when the power switching device is turned off, the input end voltage of the digital isolator is higher than its logic threshold, and the output is high.

5. The monitoring circuit of a power switching device switching state according to claim 1, characterized in that, The signal isolation and transmission module is an analog isolator, wherein: the low-voltage side is configured to compare the output voltage of the analog isolator with a preset threshold to determine the turn-on or turn-off state of the power switching device.

6. The monitoring circuit of the switching state of a power switching device according to any one of claims 1 to 5, characterized in that, The power switching device is an IGBT or a SIC MOSFET.

7. A method of monitoring the switching state of a power switching device, characterized in that The method is applied to the monitoring circuit according to any one of claims 1-6, and the method comprises: sampling the conduction voltage drop of the power switching device by a state detection module connected between the collector or drain of the power switching device and the ground to generate a state detection signal; isolating and transmitting the state detection signal to a low-voltage side by a signal isolation and transmission module; determining the turn-on or turn-off state of the power switching device according to the received signal at the low-voltage side.

8. The method of claim 7, wherein, The state detection module comprises a voltage dividing unit composed of a first resistor and a second resistor, and a voltage offset unit composed of a high-voltage reverse-biased diode and a stabilized diode; wherein the step of generating the state detection signal comprises: when the power switching device is turned off, the level of the state detection signal is generated based on the voltage dividing value of the voltage dividing unit; when the power switching device is turned on, the level of the state detection signal is generated based on the conduction voltage drop of the power switching device, the conduction voltage drop of the high-voltage reverse-biased diode, and the stabilized voltage of the stabilized diode.

9. The method of claim 8, wherein, The signal isolation and transmission module is a digital isolator; the power switch device switch state judging step comprises: directly judging the power switch device as being in an off state or an on state according to the digital isolator output end being a high level or a low level.

10. The power switch device switch state monitoring method according to claim 9, characterized in that: when the power switch device is on, the voltage of the digital isolator input end satisfies the relationship: when the power switch device is off, the voltage of the digital isolator input end satisfies the relationship: wherein, , respectively represent the level of the state detection signal; represents the forward conduction voltage drop of the high-voltage reverse biased diode; represents the conduction voltage drop of the power switching device; represents the voltage stabilization value of the voltage stabilization diode; represents the voltage value of the high-voltage power supply; , respectively represent the resistance value of the first resistor and the second resistor.

11. The method of claim 8, wherein the method further comprises: The signal isolation and transmission module is an analog isolator; the power switch device switch state judging step comprises: comparing the output voltage of the analog isolator with a preset threshold value, and judging the on or off state of the power switch device according to the comparison result.

12. The power switch device switch state monitoring method according to claim 11, characterized in that: when the power switch device is on, the voltage of the analog isolator input end satisfies the expression: when the power switch device is off, the voltage of the analog isolator input end satisfies the expression: wherein, , respectively represent the level of the state detection signal; represents the forward conduction voltage drop of the high-voltage reverse biased diode; represents the conduction voltage drop of the power switching device; represents the voltage value of the high-voltage power supply; , respectively represent the resistance value of the first resistor and the second resistor.

13. An electric machine controller characterized by The power switch device switch state monitoring circuit comprises the power switch device switch state monitoring circuit according to any one of claims 1-6.

Images