A power unit state monitoring circuit and an inverter circuit

Abstract

The utility model provides a kind of power unit state monitoring circuit and inverter circuit, power switch device body operating state and the driving power supply operating state of power drive circuit can be monitored, overcurrent event protection and driving abnormal protection can be preferably realized, power unit state monitoring circuit is set to a power switch device of corresponding inverter circuit, and it include: first monitoring unit, first detection unit includes first voltage division resistance module, the voltage of first voltage division resistance module is used to detect the state of the driving power supply of power switch device;Second detection unit includes monitoring diode, one end of monitoring diode is connected to the drain of power switch device, the gate of power switch device is connected drive signal input end, the source of power switch device is grounded, the other end of monitoring diode is connected with second voltage division resistance module after grounding, the voltage of second voltage division resistance module is used to detect the operating state of power switch device.

Description

Technical Field

[0001] This utility model relates to the field of state monitoring technology for power switching devices in inverter circuits, specifically to a power unit state monitoring circuit and an inverter circuit. Background Technology

[0002] like Figure 1 As shown, common inverter circuits in the prior art mainly have three types of short circuits: 1. Inverter breakdown may be caused by the simultaneous conduction of the high-side and low-side power switches in one of the inverter's bridge arms, or by electromagnetic interference, controller or gate driver failure, or damage or failure of a power switch in one of the bridge arms.

[0003] 2. Phase-to-phase short circuit, which may be caused by insulation breakdown between motor windings due to degradation, overheating or overvoltage events.

[0004] 3. Relative short circuit. This may be caused by insulation breakdown between the motor windings and the motor housing, usually due to degradation, overheating, or overvoltage events. A low-side shunt resistor is typically used to detect overcurrent in the negative DC bus, thereby protecting the power switching devices.

[0005] Three implementation methods for monitoring overcurrent in the power loop in a bridge circuit are as follows: Figure 2 As shown, in Figure 2 Position ① allows for vector or trapezoidal control at a relatively low cost by monitoring the negative bus current. However, this requires two measurements synchronized with the PWM mode in each PWM cycle, and the measurement accuracy is low. Monitoring of phase-to-phase short circuits in the three short-circuit conditions is not feasible. Figure 2 Position ② uses a three-phase low-side shunt to synchronously sample the three-phase current signal, which improves measurement accuracy compared to position ①. However, it can only perform indirect and discontinuous reverse phase current sampling, and can only measure when the low-side switch is open, making it unable to monitor short circuits between the phase and ground. Figure 2 Position ③ allows for direct, continuous sampling of phase current, enabling the phase current to be distributed across a PWM cycle for higher accuracy and / or allowing the driver to run twice in each PWM. This implementation can monitor phase-to-phase short circuits and phase-to-ground short circuits. However, it cannot be implemented for bridge arm breakdown short circuits.

[0006] Based on the above description of the three overcurrent monitoring implementation methods, it can be seen that positions ① and ② cannot protect against overcurrent of high-side power switching devices, and position ③ cannot protect against overcurrent of low-side power switching devices. Based on these reasons, this invention proposes a power unit status monitoring circuit. Utility Model Content

[0007] To address the aforementioned issues, this invention provides a power unit status monitoring circuit and an inverter circuit, which can monitor the operating status of the power switching device and the power supply of the power drive circuit, and can effectively achieve overcurrent event protection and drive anomaly protection.

[0008] The technical solution is as follows: a power unit status monitoring circuit, characterized in that the power unit status monitoring circuit is configured with a power switching device corresponding to the inverter circuit, including: The first monitoring unit includes a first voltage divider resistor module. One end of the first voltage divider resistor module is connected to the driving power supply, and the other end of the first voltage divider resistor module is grounded. The voltage of the first voltage divider resistor module is used to detect the state of the driving power supply of the power switching device. The second detection unit includes a monitoring diode. One end of the monitoring diode is connected to the drain of the power switching device, the gate of the power switching device is connected to the drive signal input terminal, and the source of the power switching device is grounded. The other end of the monitoring diode is connected to a second voltage divider resistor module and then grounded. The voltage of the second voltage divider resistor module is used to detect the operating state of the power switching device. The signal processing unit is connected to the first monitoring unit and the second detection unit, and receives and processes voltage signals from the first monitoring unit and the second detection unit.

[0009] Furthermore, the signal processing unit includes at least two comparators. The voltage of the second voltage divider resistor module and the voltage of the first voltage divider resistor module are respectively input to one input terminal of different comparators. The other input terminal of the comparator is input to a reference voltage, and the output terminal of the comparator outputs a comparison signal.

[0010] Furthermore, the second voltage divider resistor module and the first voltage divider resistor module each include at least one voltage divider resistor.

[0011] Furthermore, the second voltage divider resistor module includes a voltage divider resistor R2 and a voltage divider resistor R3 connected in series. One end of the voltage divider resistor R3 is grounded, and a filter capacitor C1 is connected in parallel across the two ends of the voltage divider resistor R3. The input terminal of the signal processing unit is connected between the voltage divider resistor R2 and the voltage divider resistor R3.

[0012] Furthermore, the second detection unit also includes a current-limiting resistor R1 connected in parallel with the power switching device and the monitoring diode.

[0013] Furthermore, a gate drive resistor Rg is provided between the gate of the power switching device and the drive signal input terminal.

[0014] Furthermore, the first voltage divider resistor module includes a voltage divider resistor R4 and a voltage divider resistor R5 connected in series, with one end of the voltage divider resistor R5 grounded, and the input terminal of the signal processing unit connected between the voltage divider resistor R4 and the voltage divider resistor R5.

[0015] Furthermore, it also includes an MCU unit, which is connected to the signal processing unit. The MCU unit receives the comparison signal output by the signal processing unit and processes the power switching device and the driving power supply of the power switching device.

[0016] An inverter circuit, characterized in that it includes at least one of the above-described power unit status monitoring circuits.

[0017] The power unit status monitoring circuit of this utility model monitors the voltage status of the drive power supply through the first monitoring unit, realizing protection against abnormal drive voltage. The second detection unit directly monitors the drain-source voltage status of the power switching device, realizing rapid detection of overcurrent or short-circuit events. The combination of the first monitoring unit and the second detection unit can provide comprehensive and low-cost overcurrent protection and drive abnormality protection, eliminate the protection blind spots of the prior art, and improve the reliability and safety of the entire system. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of three common short-circuit conditions in inverter circuits; Figure 2 This is a schematic diagram of existing technology for monitoring overcurrent in a three-phase inverter; Figure 3 This is a block diagram of a power unit status monitoring circuit in one embodiment; Figure 4 This is a circuit diagram of a power unit status monitoring circuit in one embodiment; Figure 5 A schematic diagram illustrating the working principle of the drive power supply for the power switching device detected by the first monitoring unit; Figure 6 A schematic diagram illustrating the working principle of the second monitoring unit for detecting the operating status of power switching devices; Figure 7 This is a block diagram of a power unit status monitoring circuit in another embodiment. Detailed Implementation

[0019] See Figure 3 and Figure 4 This utility model embodiment proposes a power unit status monitoring circuit, which can monitor the status of a single power switching device Q1 in the inverter circuit.

[0020] See Figure 4The driving circuit provides a driving signal to the power switching device Q1. Here, VCC represents the driving power supply, Vo represents the driving signal output terminal, and VSS represents the reference ground. In this embodiment, the power switching device Q1 is a MOSFET, but it can also be other types of power switching devices such as IGBTs.

[0021] In this embodiment, the power unit status monitoring circuit includes: The first monitoring unit 100 includes a first voltage divider resistor module. One end of the first voltage divider resistor module is connected to the drive power supply VCC, and the other end of the first voltage divider resistor module is grounded VSS. The voltage Vi1 of the first voltage divider resistor module is used to detect the state of the drive power supply of the power switching device. The second detection unit 200 includes a monitoring diode D1. One end of the monitoring diode D1 is connected to the drain of the power switching device Q1. The gate of the power switching device Q1 is connected to the drive signal input terminal Vo. The source of the power switching device Q1 is grounded to VSS. The other end of the monitoring diode D1 is connected to a second voltage divider resistor module and then grounded. The voltage Vi2 of the second voltage divider resistor module is used to detect the operating state of the power switching device and determine whether an overcurrent event has occurred. To facilitate the determination of the voltage Vi1 of the first voltage divider resistor module and the voltage Vi2 of the second voltage divider resistor module, a signal processing unit 300 is also provided. The signal processing unit includes at least two comparators. The voltages of the second voltage divider resistor module and the first voltage divider resistor module are respectively input to one input terminal of different comparators. The other input terminal of the comparator is input to a reference voltage, and the output terminal of the comparator outputs a comparison signal.

[0022] In this embodiment, the first voltage divider resistor module includes a voltage divider resistor R4 and a voltage divider resistor R5 connected in series. One end of the voltage divider resistor R5 is grounded. The input terminal of the signal processing unit is connected between the voltage divider resistor R4 and the voltage divider resistor R5. The signal Vi1 is obtained at the connection point of the voltage divider resistor R4 and the voltage divider resistor R5. In other embodiments of this utility model, the voltage divider resistor of the first voltage divider resistor module can be composed of multiple resistors, and a filter capacitor can also be added to improve the stability of the Vi1 signal and prevent false alarms caused by power supply noise. The second voltage divider resistor module includes voltage divider resistors R2 and R3 connected in series. One end of voltage divider resistor R3 is grounded, and a filter capacitor C1 is connected in parallel across the two ends of voltage divider resistor R3. The input terminal of the signal processing unit is connected between voltage divider resistors R2 and R3, and signal Vi2 is obtained at the connection point of voltage divider resistors R2 and R3, i.e., node b. Similarly, in other embodiments of the present utility model, the voltage dividing resistors of the second voltage dividing resistor module are not limited to two resistors, and may be a series-parallel network of multiple resistors to achieve a more accurate voltage division ratio or obtain a specific power rating. The filter capacitor C1 is also not limited to a single capacitor, and may be formed by parallel connection of a plurality of capacitors with different capacitance values to achieve a better filtering effect in a wider frequency band.

[0023] In an embodiment, the second detection unit further comprises a current-limiting resistor R1 connected in parallel with the power switching device and the monitoring diode, which can isolate the driving circuit from the monitoring circuit and limit inrush current.

[0024] In an embodiment, a gate driving resistor Rg is arranged between the gate of the power switching device and the driving signal input terminal, for adjusting the switching characteristics of the power switching device Q1.

[0025] The working principle of the first monitoring unit 100 is described in combination with Figure 5 as follows: one comparator of the signal processing unit 300 compares and monitors the state of the driving power supply VCC, and its reference voltage Vref1 is set as a lower threshold representing the normal range of VCC. When VCC is within the normal value range, a stable level signal is generated through the resistor R4 and the resistor R5, Vi1>Vref1, and the comparator outputs a low level; when VCC drops, Vi1<Vref1, the output of the comparator jumps to a high level, and an alarm is issued.

[0026] The working principle of the second monitoring unit 200 is described in combination with Figure 6 as follows: In an embodiment, the voltage at node b between the voltage dividing resistor R2 and the voltage dividing resistor R3 is input to one of the comparators of the signal processing unit 300, for monitoring the overcurrent state of the power switching device Q1, and its reference voltage Vref2 is set as a threshold that distinguishes the normal on-state voltage drop and the overcurrent voltage drop of Q1. When the power switching device Q1 performs a turn-on action, Vo will output a high level. At this time, if the state of Q1 is normal, that is, no overcurrent event occurs, the potential of node a will be a level of "VDSsat(Q1)+VD1", where VDSsat(Q1) is the saturated drain-source voltage of the power switching device Q1 in the normal conduction state, VD1 is the forward conduction voltage of the diode D1, node b will also be lower than the level flip threshold of Vi2, Vi2<Vref2, the comparator outputs a low level, and the circuit does not actually operate; when an overcurrent event occurs to Q1, the potential of node a will be "VDS+VD1", where VDS is the drain-source voltage of the power switching device Q1 in an abnormal state. At this time, VDS is no longer the minimum on-state voltage drop due to the occurrence of a short circuit event, the potential of node a will continue to rise, and finally the potential of node b rises beyond the level flip threshold of Vi2, Vi2>Vref2, the circuit generates a jump signal and issues an alarm.

[0027] The power unit status monitoring circuit in this embodiment monitors the voltage status of the drive power supply through a first monitoring unit to protect against abnormal drive voltage. It directly monitors the drain-source voltage status of the power switching device body through a second detection unit to achieve rapid detection of overcurrent or short-circuit events. The first monitoring unit and the second detection unit complement each other, which can prevent device damage due to overcurrent caused by external short circuit or internal failure, and also avoid overheating damage caused by insufficient drive voltage leading to the device operating in the non-saturation region. This achieves comprehensive monitoring of the health status of a single power device. The second detection unit in this embodiment directly monitors the drain-source voltage of the power device. When an overcurrent occurs, the device will quickly exit the saturation region and VDS will rise sharply. This change can be captured by this circuit instantly. The detection method of the second detection unit is faster and more direct than the indirect method of detecting the current and then making a judgment. It can perform protection actions at the microsecond level before the device is damaged. The power unit status monitoring circuit in this embodiment has extremely low hardware cost and is easy to integrate. By simply adjusting the resistance values ​​of the resistors in the first and second voltage divider resistor modules, the protection threshold can be set very flexibly to adapt to different specifications of power devices and system voltage levels.

[0028] See Figure 7 In one embodiment, the system further includes an MCU unit 400 connected to the signal processing unit 300. The MCU unit 400 receives a comparison signal output by the signal processing unit 300 and processes the power switching device and its drive power supply, including: When VCC is below the normal range, after the signal processing unit 300 receives the Vi1 signal below the threshold, the signal processing circuit will generate a switching signal. When the MCU receives the signal, it will immediately turn off the output of Vo to realize the abnormal protection of the Q1 power switching device. When an overcurrent event occurs in Q1, the voltage Vi2 at node b between voltage divider resistors R2 and R3 rises above the threshold. The signal processing unit generates a jump signal, and the MCU receives this jump signal and immediately shuts off the output of Vo, thereby achieving overcurrent protection for the Q1 power switching device.

[0029] In other embodiments, the monitoring diode D1 is not limited to a conventional diode; it can be a Schottky diode with a faster response speed to improve detection speed; it can also be a Zener diode to provide more stable voltage clamping; or it can be a combination of other semiconductor devices with unidirectional conduction characteristics.

[0030] In embodiments of this utility model, an inverter circuit is also provided. Each arm of the inverter circuit includes two power switching devices, one on the high side and one on the low side. In practice, at least one, preferably each power switching device, is equipped with the aforementioned power unit status monitoring circuit. By equipping each switching device with an independent monitoring circuit, comprehensive protection for the entire inverter circuit can be achieved. Whether it is an overcurrent in a single device caused by a bridge arm short circuit, a phase-to-phase short circuit, or a phase-to-ground short circuit, or a drive power supply failure, it can be detected and protected in a timely manner, greatly improving the reliability of the inverter circuit.

[0031] The power unit status monitoring circuit in the above embodiments can be configured for each power switching device in the inverter circuit, whether on the high side or the low side. When the monitored object is the high-side power switching device Q1, its reference ground VSS needs to be a set of reference grounds isolated from the system main ground. In this case, the driving circuit can be an isolated driving architecture, such as a gate driver using a pulse transformer or capacitor isolation. The output signal of the signal processing circuit can also be transmitted to the MCU through isolation devices, such as high-speed optocouplers or digital isolators. For low-side power switching device applications, a simple non-isolated architecture can be used.

[0032] The power unit status monitoring circuit of this invention can be flexibly applied to high-side or low-side power switching devices in bridge circuits, and has strong applicability.

[0033] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention.

[0034] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A power unit status monitoring circuit, characterized in that, The power unit status monitoring circuit is configured with a power switching device corresponding to the inverter circuit, including: The first monitoring unit includes a first voltage divider resistor module. One end of the first voltage divider resistor module is connected to the driving power supply, and the other end of the first voltage divider resistor module is grounded. The voltage signal of the first voltage divider resistor module is used to detect the state of the driving power supply of the power switching device. The second detection unit includes a monitoring diode. One end of the monitoring diode is connected to the drain of the power switching device, the gate of the power switching device is connected to the drive signal input terminal, and the source of the power switching device is grounded. The other end of the monitoring diode is connected to a second voltage divider resistor module and then grounded. The voltage signal of the second voltage divider resistor module is used to detect the operating state of the power switching device. The signal processing unit is connected to the first monitoring unit and the second detection unit, and receives and processes voltage signals from the first monitoring unit and the second detection unit.

2. The power unit status monitoring circuit according to claim 1, characterized in that: The signal processing unit includes at least two comparators. The voltage of the second voltage divider resistor module and the voltage of the first voltage divider resistor module are respectively input to one input terminal of different comparators. The other input terminal of the comparator is input to a reference voltage. The output terminal of the comparator outputs a comparison signal.

3. The power unit status monitoring circuit according to claim 2, characterized in that: The second voltage divider resistor module and the first voltage divider resistor module each include at least one voltage divider resistor.

4. The power unit status monitoring circuit according to claim 3, characterized in that: The second voltage divider resistor module includes a voltage divider resistor R2 and a voltage divider resistor R3 connected in series. One end of the voltage divider resistor R3 is grounded, and a filter capacitor C1 is connected in parallel across the two ends of the voltage divider resistor R3. The input terminal of the signal processing unit is connected between the voltage divider resistor R2 and the voltage divider resistor R3.

5. The power unit status monitoring circuit according to claim 1, characterized in that: The second detection unit also includes a current-limiting resistor R1 connected in parallel with the power switching device and the monitoring diode.

6. The power unit status monitoring circuit according to claim 1, characterized in that: A gate drive resistor Rg is provided between the gate of the power switching device and the drive signal input terminal.

7. The power unit status monitoring circuit according to claim 1, characterized in that: The first voltage divider resistor module includes a voltage divider resistor R4 and a voltage divider resistor R5 connected in series. One end of the voltage divider resistor R5 is grounded, and the input terminal of the signal processing unit is connected between the voltage divider resistor R4 and the voltage divider resistor R5.

8. The power unit status monitoring circuit according to claim 1, characterized in that: It also includes an MCU unit, which is connected to the signal processing unit. The MCU unit receives the comparison signal output by the signal processing unit and processes the power switching device and the drive power supply of the power switching device.

9. An inverter circuit, characterized in that, It includes at least one power unit status monitoring circuit as described in any one of claims 1 to 8.

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