A reverse connection protection circuit for suppressing common-mode circulating current in the DC auxiliary power supply of an inverter

Abstract

This invention provides a reverse connection protection circuit for suppressing common-mode circulating current in the DC auxiliary power supply of an inverter. The circuit includes diodes D5, D6, D7, and D8, a Zener diode D9, an NMOS transistor Q3, an optocoupler U1, resistors R11, R12, R13, and R14, capacitors C6, C7, and C8. The power supply terminals are the battery positive terminal (BAT+) and the battery negative terminal (BAT-), and the power supply output terminals are the DC auxiliary power supply positive terminal (DC+) and the DC auxiliary power supply negative terminal (DC-). This invention addresses the problem of unstable DC auxiliary power supply in photovoltaic and energy storage inverters due to common-mode interference, improves the reliability of energy storage systems, and enables DC reverse connection detection, facilitating rapid on-site assembly by construction personnel.

Description

Technical Field

[0001] This invention relates to the field of inverter reverse connection protection, and more particularly to a reverse connection protection circuit that can suppress common-mode circulating current of the inverter's DC auxiliary power source. Background Technology

[0002] With the global energy transition and the construction of an energy system dominated by renewable energy, the energy storage and photovoltaic industries are developing rapidly. High voltage and large capacity are the development trends. High voltage and large capacity bring high dU / dt and dI / dt, which makes the common mode problem of inverter systems more prominent. Large common mode voltage will interfere with the supporting equipment or inverter control and auxiliary power supply systems. In practical applications of DC auxiliary power supplies for energy storage and photovoltaic inverters, there are many failure problems caused by high common mode voltage, which affects the reliability of inverters. DC auxiliary power supply systems can avoid failure problems caused by high common mode voltage by optimizing the reverse connection protection circuit.

[0003] Currently, photovoltaic and energy storage inverters are developing towards high voltage and large capacity. The high dU / dt and dI / dt lead to prominent common-mode problems in the system. The DC auxiliary power supply system uses a rectifier bridge anti-reverse connection circuit, and the DC auxiliary power supply bus cannot clamp to the battery voltage. The high common-mode voltage of the inverter will charge the DC auxiliary power supply bus voltage to a level far higher than the battery voltage, resulting in overvoltage damage to the DC auxiliary power supply system.

[0004] See the attached diagram in the instruction manual for details. Figure 3 The red path represents the common-mode voltage VCM+ between the positive bus and PE of the energy storage inverter, which charges the parasitic capacitor of PE or Y capacitor Y1 on the positive bus of the DC auxiliary power supply. The yellow path represents the common-mode voltage VCM- between the negative bus and PE of the inverter, which charges the parasitic capacitor of PE or Y capacitor Y2 on the negative bus of the DC auxiliary power supply. The sum of VCM+ and VCM- equals the inverter bus voltage, but the sum of the peak values ​​of VCM+ and VCM- is much higher than the energy storage inverter bus voltage. When the DC auxiliary power supply is under light load, the energy demand of the auxiliary power supply is small, and Y2 and Y1 will charge the DC auxiliary power supply bus capacitors according to the blue path. The energy of the DC auxiliary power supply bus capacitors cannot be consumed by the downstream load, causing the DC auxiliary power supply bus voltage to gradually increase. When the sum of the peak values ​​of VCM+ and VCM- exceeds the capacitor voltage stress specification or MOSFET specification, it will cause the auxiliary power supply to fail due to overvoltage. When all the anti-reverse diodes are removed, or only the anti-reverse diodes in the positive or negative circuit are removed, the DC auxiliary power bus capacitor will be clamped to the battery voltage, and the common-mode overcharge problem will not occur. After removing the anti-reverse diodes, the DC auxiliary power supply will not have the battery reverse connection protection function.

[0005] Therefore, it is necessary to provide a reverse connection protection circuit that can suppress the common-mode circulating current of the inverter's DC auxiliary power supply to solve the above-mentioned technical problems. Summary of the Invention

[0006] This invention provides a reverse connection protection circuit that can suppress common-mode circulating current of inverter DC auxiliary power supply, solving the problem that the existing technology cannot simultaneously achieve protection against common-mode overcharging and battery reverse connection.

[0007] To solve the above-mentioned technical problems, the present invention provides a reverse connection protection circuit for suppressing common-mode circulating current of the inverter's DC auxiliary power supply, comprising diodes D5, D6, D7, and D8, a Zener diode D9, an NMOS transistor Q3, an optocoupler U1, resistors R11, R12, R13, and R14, capacitors C6, C7, and C8. The power supply terminals are the positive terminal BAT+ and negative terminal BAT- of the battery, and the power supply output terminals are the positive terminal DC+ and negative terminal DC- of the DC auxiliary power supply. The positive terminal of diode D7 is connected to the positive terminal BAT+ of the battery, and the negative terminal of diode D7 is connected to the positive terminal DC+ of the DC auxiliary power supply, thereby supplying power to the DC auxiliary power supply. The positive terminal of diode D8 is connected to the negative terminal BAT- of the battery, and the negative terminal of diode D8 is connected to the positive terminal DC+ of the DC auxiliary power source to supply power to the DC auxiliary power source. The positive terminal of diode D6 is connected to the negative terminal DC- of the DC auxiliary power source, and the negative terminal of diode D6 is connected to the positive terminal BAT+ of the battery. The positive terminal of the body diode of the NMOS transistor Q3 is connected to the negative terminal of the DC auxiliary power source DC-, and the negative terminal of the body diode of the NMOS transistor Q3 is connected to the negative terminal of the battery BAT-. The positive terminal of diode D5 is connected to the positive terminal BAT+ of the battery, and the negative terminal of diode D5 is connected to pin 1 of resistor R11. The capacitor C6, the resistor R12, and pins 1 and 2 of the optocoupler U1 are all connected in parallel with the diode D5; Pin 2 of resistor R11 is connected to the negative terminal BAT- of the battery, and pin 1 of resistor R11 is simultaneously connected to the negative terminal of diode D5, pin 2 of capacitor C6, pin 1 of resistor R12, and pin 1 of optocoupler U1. The secondary side pin 4 of the optocoupler U1 is simultaneously connected to pin 1 of the resistor R13, pin 2 of the capacitor C7, pin 1 of the NMOS transistor Q3, pin 3 of the Zener diode D9, and pin 2 of the capacitor C8. The secondary side pin 3 of the optocoupler U1 is simultaneously connected to pin 2 of the diode D6, pin 2 of the resistor R13, pin 1 of the capacitor C7, pin 3 of the NMOS transistor Q3, pin 1 of the Zener diode D9, and pin 1 of the capacitor C8, and these connection terminals are all connected to the negative terminal DC- of the DC auxiliary power source. One end of the resistor R14 is connected to the positive terminal of the DC auxiliary power source DC+, and the other end is connected to the connection terminal of the capacitor C8 and the Zener diode D9, so as to store energy for the capacitor C8 and supply power to the Zener diode D9.

[0008] Preferably, the charging time constant of capacitor C6 is less than that of capacitor C8, so that the primary diode of optocoupler U1 reaches the conduction condition first, avoiding the NMOS transistor Q3 from being mis-conducted due to the gate-source voltage reaching the conduction threshold in advance.

[0009] Preferably, the Zener diode D9 is used to clamp the voltage across the capacitor C8 to a set value, providing a stable gate drive voltage for the NMOS transistor Q3 to conduct.

[0010] Preferably, pin 1 of the NMOS transistor Q3 is the gate and pin 3 is the source. The voltage between the gate and the source is controlled by the on / off state of the secondary side of the optocoupler U1, thereby realizing the on / off control of the NMOS transistor Q3 body MOS transistor.

[0011] Preferably, the resistor R13 and the capacitor C7 are connected in parallel between the gate and source of the NMOS transistor Q3 to form an RC buffer circuit, which is used to suppress the spike fluctuations of the gate voltage of the NMOS transistor Q3 and stabilize the gate drive signal.

[0012] Preferably, the resistor R12 is a current-limiting resistor on the primary side of the optocoupler U1, used to limit the current flowing through the diode on the primary side of the optocoupler U1, so as to prevent the optocoupler U1 from being damaged due to overcurrent.

[0013] Preferably, the diode D5 is a reverse clamping diode. When the battery is connected with normal polarity, the diode D5 is turned on, clamping the voltage across the primary side of the optocoupler U1, so that the optocoupler U1 is in a cut-off and non-working state.

[0014] Preferably, the circuit is further configured with a battery voltage sampling circuit, which detects the voltage between the positive terminal BAT+ and the negative terminal BAT- of the battery to realize fault detection of reverse polarity of the battery.

[0015] Preferably, the positive terminal DC+ and the negative terminal DC- of the auxiliary DC power supply are the power take-off terminals of the auxiliary DC power supply, and the auxiliary DC power supply outputs positive Power and ground GND to provide working power for the inverter control system.

[0016] Preferably, after the NMOS transistor Q3 is turned on, the negative terminal BAT- of the battery is directly connected to the negative terminal DC- of the DC auxiliary power source.

[0017] Compared with related technologies, the reverse connection protection circuit for suppressing common-mode circulating current of inverter DC auxiliary power supply provided by the present invention has the following beneficial effects: This invention provides a reverse connection protection circuit that can suppress common-mode circulating current of inverter DC auxiliary power supply, solving the problem of DC auxiliary power supply in photovoltaic and energy storage inverters being susceptible to failure and instability due to inverter common-mode interference, improving the operational reliability of energy storage systems. The reverse connection protection circuit of DC auxiliary power supply system can realize DC reverse connection detection of inverter and help construction personnel to quickly locate on-site assembly. Attached Figure Description

[0018] Figure 1 A schematic diagram of a preferred embodiment of the reverse connection protection circuit for suppressing common-mode circulating current of inverter DC auxiliary power supply provided by the present invention; Figure 2 for Figure 1 The diagram shows the waveforms of the inverter bus common-mode voltage VCM+ facing the PE and the bus negative common-mode voltage VCM- facing the PE. Figure 3 The circuit diagram for the common-mode overcharge circuit of the DC auxiliary power bus in the prior art; Figure 4 for Figure 1 The diagram shows a DC auxiliary power supply reverse connection protection circuit. Figure 5 for Figure 1 The diagram shown is a structural block diagram of the battery reverse connection protection. Figure 6 for Figure 1 The diagram shows the structure of the inverter bus and the DC auxiliary power supply bus negative terminal connected in series with the anti-reverse diode. Figure 7 for Figure 1 The diagram shows the structure of the inverter bus and the DC auxiliary power supply bus with anti-reverse diodes connected in series. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] First Embodiment Please refer to the following: Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 ,in, Figure 1 A schematic diagram of a preferred embodiment of the reverse connection protection circuit for suppressing common-mode circulating current of inverter DC auxiliary power supply provided by the invention; Figure 2 for Figure 1 The diagram shows the waveforms of the inverter bus common-mode voltage VCM+ facing the PE and the bus negative common-mode voltage VCM- facing the PE. Figure 3 The circuit diagram for the common-mode overcharge circuit of the DC auxiliary power bus in the prior art; Figure 4 for Figure 1 The diagram shows a DC auxiliary power supply reverse connection protection circuit. Figure 5 for Figure 1 The diagram shown is a structural block diagram of the battery reverse connection protection. Figure 6 for Figure 1 The diagram shows the structure of the inverter bus and the DC auxiliary power supply bus negative terminal connected in series with the anti-reverse diode. Figure 7 for Figure 1 The diagram shows a block diagram of a reverse connection protection diode connected in series with the positive terminal of the inverter bus and the DC auxiliary power supply bus. The reverse connection protection circuit, which suppresses common-mode circulating current in the inverter's DC auxiliary power supply, includes diodes D5, D6, D7, and D8, a Zener diode D9, an NMOS transistor Q3, an optocoupler U1, resistors R11, R12, R13, and R14, capacitors C6, C7, and C8. The power supply terminals are the battery positive terminal BAT+ and the battery negative terminal BAT-, and the power supply output terminals are the DC auxiliary power supply positive terminal DC+ and the DC auxiliary power supply negative terminal DC-. The positive terminal of diode D7 is connected to the positive terminal BAT+ of the battery, and the negative terminal of diode D7 is connected to the positive terminal DC+ of the DC auxiliary power source to supply power to the DC auxiliary power source. The positive terminal of diode D8 is connected to the negative terminal BAT- of the battery, and the negative terminal of diode D8 is connected to the positive terminal DC+ of the DC auxiliary power source to supply power to the DC auxiliary power source. The positive terminal of diode D6 is connected to the negative terminal of the DC auxiliary power source DC-, and the negative terminal of diode D6 is connected to the positive terminal of the battery BAT+. The positive terminal of the body diode of NMOS transistor Q3 is connected to the negative terminal of DC auxiliary power supply DC-, and the negative terminal of the body diode of NMOS transistor Q3 is connected to the negative terminal of battery BAT-. The positive terminal of diode D5 is connected to the positive terminal BAT+ of the battery, and the negative terminal of diode D5 is connected to pin 1 of resistor R11. Capacitor C6, resistor R12, and pins 1 and 2 of optocoupler U1 are all connected in parallel with diode D5, that is, one end is connected to the negative terminal of diode D5 / pin 1 of resistor R11, and the other end is connected to the positive terminal BAT+ of battery. Pin 2 of resistor R11 is connected to the negative terminal BAT- of the battery, and pin 1 of resistor R11 is simultaneously connected to the negative terminal of diode D5, pin 2 of capacitor C6, pin 1 of resistor R12, and pin 1 of optocoupler U1. Pin 4 of the secondary side of optocoupler U1 is connected to pin 1 of resistor R13, pin 2 of capacitor C7, pin 1 of NMOS transistor Q3, pin 3 of Zener diode D9, and pin 2 of capacitor C8. Pin 3 of the secondary side of optocoupler U1 is connected to pin 2 of diode D6, pin 2 of resistor R13, pin 1 of capacitor C7, pin 3 of NMOS transistor Q3, pin 1 of Zener diode D9, and pin 1 of capacitor C8. All of these connections are connected to the negative terminal of the DC auxiliary power source DC-. One end of resistor R14 is connected to the positive terminal of the DC auxiliary power source DC+, and the other end is connected to the connection terminal of capacitor C8 and Zener diode D9, so that capacitor C8 stores energy and Zener diode D9 is powered.

[0021] The DC auxiliary power input reverse connection protection circuit, based on single-phase full-bridge rectification, replaces the lower transistor of the rear bridge arm with an N-MOSFET. When the polarity connection between the energy storage inverter and the battery side is correct, diode D5 conducts, and optocoupler U1 is reverse-clamped by diode D5, so optocoupler U1 does not work. Due to the presence of the body diode of NMOS transistor Q3, when NMOS transistor Q3 is not working, the battery voltage is rectified through diode D7 and the body diode of NMOS transistor Q3 to supply power to the DC auxiliary power bus. The DC auxiliary power bus voltage stores energy for capacitor C8 through resistor R14. The voltage of capacitor C8 is clamped to the set voltage by Zener diode D9. At this time, NMOS transistor Q3 conducts, connecting the negative terminal BAT- of the battery and the negative terminal of the DC auxiliary power bus, avoiding the problem of over-voltage damage to the DC auxiliary power bus caused by the inverter common-mode voltage.

[0022] When the battery voltage polarity is reversed, the battery voltage will pass through resistor R11 and the primary diode of optocoupler U1, causing the secondary transistor of optocoupler U1 to conduct. The gate voltage of NMOS transistor Q3 is pulled low by the secondary transistor of optocoupler U1, and the main MOS transistor of NMOS transistor Q3 will not conduct.

[0023] Please see Figure 4 and Figure 5 To prevent the NMOS transistor Q3 from being mistakenly turned on by the main MOS transistor, the charging time constant of capacitor C6 needs to be much smaller than that of capacitor C8. This way, the primary diode of optocoupler U1 will reach the conduction condition first, and the gate-source voltage of NMOS transistor Q3 will not reach the conduction threshold. The secondary transistor of optocoupler U1 will already be turned on, clamping the gate-source voltage of NMOS transistor Q3 below the threshold voltage. NMOS transistor Q3 will not be turned on at this time. Meanwhile, the battery voltage will supply power to the DC auxiliary power supply through the diode D8 and diode D6 circuit (reverse connection protection circuit). After the DC auxiliary power supply starts, the inverter control system will work, and the battery voltage sampling circuit can detect the reverse connection of the battery, upload the fault to the monitoring module, and prompt the staff to check the reverse polarity of the battery.

[0024] DC auxiliary power supply reverse connection circuit connection relationship: The positive terminal of diode D7 is connected to the positive terminal of the battery BAT+, and the negative terminal of diode D7 is connected to the positive terminal of the DC auxiliary power supply DC+ to supply power to the DC auxiliary power supply; the positive terminal of diode D8 is connected to the negative terminal of the battery BAT+, and the negative terminal of diode D8 is connected to the positive terminal of the DC auxiliary power supply DC+ to supply power to the DC auxiliary power supply; the positive terminal of diode D6 is connected to the negative terminal of the DC auxiliary power supply DC-, and the negative terminal of diode D6 is connected to the positive terminal of the battery BAT+; the positive terminal of the body diode of NMOS transistor Q3 is connected to the negative terminal of the DC auxiliary power supply DC-, and the negative terminal of the body diode of NMOS transistor Q3 is connected to the negative terminal of the battery BAT-. The positive terminal of diode D5 is connected to the positive terminal BAT+ of the battery, and the negative terminal of diode D5 is connected to pin 1 of resistor R11; the pins 1 and 2 of capacitor C6, resistor R12, and optocoupler U1 are connected in parallel with diode D5; pin 2 of resistor R11 is connected to the negative terminal BAT- of the battery, and pin 1 of resistor R11 is connected to pin 1 of diode D5, pin 2 of capacitor C6, pin 1 of resistor R12, and pin 1 of optocoupler U1. The secondary side of optocoupler U1, that is, pin 4, is simultaneously connected to pin 1 of resistor R13, pin 2 of capacitor C7, pin 1 of NMOS transistor Q3, pin 3 of Zener diode D9, and pin 2 of capacitor C8; pin 3 of optocoupler U1 is simultaneously connected to pin 2 of diode D6, pin 2 of resistor R13, pin 1 of capacitor C7, pin 3 of NMOS transistor Q3, pin 1 of Zener diode D9, and pin 1 of capacitor C8, and then connected together to the negative terminal DC- of the DC auxiliary power supply; DC power supply is the battery, which supplies power to the reverse connection protection circuit from the positive terminal BAT+ and the negative terminal BAT- of the battery. Battery voltage sampling: Detect the voltage between the positive terminal BAT+ and the negative terminal BAT- of the battery; The DC auxiliary power supply draws power from the positive terminal DC+ and the negative terminal DC- of the DC auxiliary power source; the DC auxiliary power supply outputs positive Power and ground GND to supply power to the inverter control system.

[0025] The charging time constant of capacitor C6 is less than that of capacitor C8, which allows the primary diode of optocoupler U1 to reach the conduction condition first, thus preventing the NMOS transistor Q3 from being mis-turned due to the gate-source voltage reaching the conduction threshold in advance.

[0026] Zener diode D9 is used to clamp the voltage across capacitor C8 to a set value, providing a stable gate drive voltage for the NMOS transistor Q3 to turn on.

[0027] Pin 1 of NMOS transistor Q3 is the gate and pin 3 is the source. The voltage between its gate and source is controlled by the on / off state of the secondary side of optocoupler U1, thereby realizing the on / off control of the NMOS transistor Q3 itself.

[0028] Resistor R13 and capacitor C7 are connected in parallel between the gate and source of NMOS transistor Q3 to form an RC buffer circuit, which is used to suppress the spike fluctuations of the gate voltage of NMOS transistor Q3 and stabilize the gate drive signal.

[0029] Resistor R12 is a current-limiting resistor on the primary side of optocoupler U1, used to limit the current flowing through the diode on the primary side of optocoupler U1, and to prevent optocoupler U1 from being damaged due to overcurrent.

[0030] Diode D5 is a reverse clamping diode. When the battery is connected with the correct polarity, diode D5 conducts, clamping the voltage across the primary side of optocoupler U1, thus keeping optocoupler U1 in a cut-off and non-working state.

[0031] The circuit is also equipped with a battery voltage sampling circuit, which detects the voltage between the positive terminal BAT+ and the negative terminal BAT- of the battery to realize fault detection of reverse polarity of the battery.

[0032] The positive terminal DC+ and the negative terminal DC- of the DC auxiliary power supply are the power take-off terminals of the DC auxiliary power supply. The DC auxiliary power supply outputs positive Power and ground GND to provide working power for the inverter control system.

[0033] After NMOS transistor Q3 is turned on, the negative terminal of the battery BAT- is directly connected to the negative terminal of the DC auxiliary power supply DC-, thereby achieving short-circuit clamping between the negative terminal of the DC auxiliary power supply bus and the negative terminal of the battery, and preventing the inverter common-mode voltage from overcharging the DC auxiliary power supply bus.

[0034] Second Embodiment Please refer to Figure 6 The first embodiment differs in that an anti-reverse diode is connected in series between the negative terminals of the inverter bus and the DC auxiliary power supply bus. The DC auxiliary power supply bus is clamped by the positive bus of the inverter to prevent common-mode overcharging. However, the DC auxiliary power supply does not have a reverse connection function, and the inverter cannot realize DC reverse connection detection.

[0035] Third Embodiment Please refer to Figure 7 The first embodiment differs in that an anti-reverse diode is connected in series between the positive terminals of the inverter bus and the DC auxiliary power supply bus. This clamps the DC auxiliary power supply bus via the inverter's positive bus, preventing common-mode overcharging. Similar to Scheme 2, the inverter cannot perform DC reverse connection detection.

[0036] The working principle of the reverse connection protection circuit for suppressing common-mode circulating current of the inverter's DC auxiliary power supply provided by this invention is as follows: The anode of diode D7 is connected to the positive terminal BAT+ of the battery, and the cathode of diode D7 is connected to the positive terminal DC+ of the DC auxiliary power supply, supplying power to the DC auxiliary power supply; the anode of diode D8 is connected to the negative terminal BAT- of the battery, and the cathode of diode D8 is connected to the positive terminal DC+ of the DC auxiliary power supply, supplying power to the DC auxiliary power supply; the anode of diode D6 is connected to the negative terminal DC- of the DC auxiliary power supply, and the cathode of diode D6 is connected to the positive terminal BAT+ of the battery; the anode of the body diode of NMOS transistor Q3 is connected to the negative terminal DC- of the DC auxiliary power supply, and the cathode of the body diode of NMOS transistor Q3 is connected to the negative terminal BAT- of the battery; the anode of diode D5 is connected to the positive terminal BAT+ of the battery, and the cathode of diode D5 is connected to pin 1 of resistor R11; the capacitor C6, resistor R12, and pins 1 and 2 of optocoupler U1 are all connected in parallel with diode D5, i.e., one end is connected to both terminals. The negative terminal of diode D5 and pin 1 of resistor R11 are connected together to the positive terminal BAT+ of the battery. Pin 2 of resistor R11 is connected to the negative terminal BAT- of the battery. Pin 1 of resistor R11 is also connected to the negative terminal of diode D5, pin 2 of capacitor C6, pin 1 of resistor R12, and pin 1 of optocoupler U1. Pin 4 of the secondary side of optocoupler U1 is connected to pin 1 of resistor R13, pin 2 of capacitor C7, pin 1 of NMOS transistor Q3, pin 3 of Zener diode D9, and capacitor C8. Pin 2 of the optocoupler is connected; pin 3 of the secondary side of optocoupler U1 is connected to pin 2 of diode D6, pin 2 of resistor R13, pin 1 of capacitor C7, pin 3 of NMOS transistor Q3, pin 1 of Zener diode D9, and pin 1 of capacitor C8. These connection terminals are all connected to the negative terminal DC- of the DC auxiliary power supply; one end of resistor R14 is connected to the positive terminal DC+ of the DC auxiliary power supply, and the other end is connected to the connection terminal of capacitor C8 and Zener diode D9, storing energy for capacitor C8 and supplying power to Zener diode D9.

[0037] Compared with related technologies, the reverse connection protection circuit for suppressing common-mode circulating current of inverter DC auxiliary power supply provided by the present invention has the following beneficial effects: To address the issue of DC auxiliary power supply failure and instability in photovoltaic and energy storage inverters due to common-mode interference, and to improve the operational reliability of energy storage systems, the DC auxiliary power supply system reverse connection protection circuit can realize DC reverse connection detection of inverters and help construction personnel quickly locate and assemble on-site.

[0038] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A reverse connection protection circuit for suppressing common-mode circulating current of an inverter's DC auxiliary power supply, comprising diodes D5, D6, D7, and D8, a Zener diode D9, an NMOS transistor Q3, an optocoupler U1, resistors R11, R12, R13, and R14, capacitors C6, C7, and C8, with the power supply terminals being the positive terminal BAT+ and negative terminal BAT- of the battery, and the power supply output terminals being the positive terminal DC+ and negative terminal DC- of the DC auxiliary power supply, characterized in that... The positive terminal of diode D7 is connected to the positive terminal BAT+ of the battery, and the negative terminal of diode D7 is connected to the positive terminal DC+ of the DC auxiliary power source to supply power to the DC auxiliary power source. The positive terminal of diode D8 is connected to the negative terminal BAT- of the battery, and the negative terminal of diode D8 is connected to the positive terminal DC+ of the DC auxiliary power source to supply power to the DC auxiliary power source. The positive terminal of diode D6 is connected to the negative terminal DC- of the DC auxiliary power source, and the negative terminal of diode D6 is connected to the positive terminal BAT+ of the battery. The positive terminal of the body diode of the NMOS transistor Q3 is connected to the negative terminal of the DC auxiliary power source DC-, and the negative terminal of the body diode of the NMOS transistor Q3 is connected to the negative terminal of the battery BAT-. The positive terminal of diode D5 is connected to the positive terminal BAT+ of the battery, and the negative terminal of diode D5 is connected to pin 1 of resistor R11. The capacitor C6, the resistor R12, and pins 1 and 2 of the optocoupler U1 are all connected in parallel with the diode D5; Pin 2 of resistor R11 is connected to the negative terminal BAT- of the battery, and pin 1 of resistor R11 is simultaneously connected to the negative terminal of diode D5, pin 2 of capacitor C6, pin 1 of resistor R12, and pin 1 of optocoupler U1. The secondary side pin 4 of the optocoupler U1 is simultaneously connected to pin 1 of the resistor R13, pin 2 of the capacitor C7, pin 1 of the NMOS transistor Q3, pin 3 of the Zener diode D9, and pin 2 of the capacitor C8. The secondary side pin 3 of the optocoupler U1 is simultaneously connected to pin 2 of the diode D6, pin 2 of the resistor R13, pin 1 of the capacitor C7, pin 3 of the NMOS transistor Q3, pin 1 of the Zener diode D9, and pin 1 of the capacitor C8, and these connection terminals are all connected to the negative terminal DC- of the DC auxiliary power source. One end of the resistor R14 is connected to the positive terminal of the DC auxiliary power source DC+, and the other end is connected to the connection terminal of the capacitor C8 and the Zener diode D9, so as to store energy for the capacitor C8 and supply power to the Zener diode D9.

2. The reverse connection protection circuit for suppressing common-mode circulating current of the inverter's DC auxiliary power supply according to claim 1, characterized in that, The charging time constant of capacitor C6 is less than that of capacitor C8, which allows the primary diode of optocoupler U1 to reach the conduction condition first, thus preventing the NMOS transistor Q3 from being mis-conducted due to the gate-source voltage reaching the conduction threshold in advance.

3. The reverse connection protection circuit for suppressing common-mode circulating current of the inverter's DC auxiliary power supply according to claim 1, characterized in that, The Zener diode D9 is used to clamp the voltage across the capacitor C8 to a set value, providing a stable gate drive voltage for the NMOS transistor Q3 to conduct.

4. The reverse connection protection circuit for suppressing common-mode circulating current of the inverter's DC auxiliary power supply according to claim 1, characterized in that, The NMOS transistor Q3 has a gate at pin 1 and a source at pin 3. The voltage between its gate and source is controlled by the on / off state of the secondary side of the optocoupler U1, thereby controlling the on / off state of the NMOS transistor Q3.

5. The reverse connection protection circuit for suppressing common-mode circulating current of inverter DC auxiliary power supply according to claim 1, characterized in that, The resistor R13 and the capacitor C7 are connected in parallel between the gate and source of the NMOS transistor Q3 to form an RC buffer circuit, which is used to suppress the spike fluctuations of the gate voltage of the NMOS transistor Q3 and stabilize the gate drive signal.

6. The reverse connection protection circuit for suppressing common-mode circulating current of the inverter's DC auxiliary power supply according to claim 1, characterized in that, The resistor R12 is a current-limiting resistor on the primary side of the optocoupler U1, used to limit the current flowing through the diode on the primary side of the optocoupler U1, so as to prevent the optocoupler U1 from being damaged due to overcurrent.

7. The reverse connection protection circuit for suppressing common-mode circulating current of inverter DC auxiliary power supply according to claim 1, characterized in that, The diode D5 is a reverse clamping diode. When the battery is connected with normal polarity, the diode D5 is turned on, clamping the voltage across the primary side of the optocoupler U1, so that the optocoupler U1 is in a cut-off and non-working state.

8. The reverse connection protection circuit for suppressing common-mode circulating current of the inverter's DC auxiliary power supply according to claim 1, characterized in that, The circuit is also equipped with a battery voltage sampling circuit, which detects the voltage between the positive terminal BAT+ and the negative terminal BAT- of the battery to realize fault detection of reverse polarity connection of the battery.

9. The reverse connection protection circuit for suppressing common-mode circulating current of inverter DC auxiliary power supply according to claim 1, characterized in that, The positive terminal DC+ and the negative terminal DC- of the auxiliary DC power supply are the power take-off terminals of the auxiliary DC power supply. The auxiliary DC power supply outputs positive Power and ground GND to provide working power for the inverter control system.

10. The reverse connection protection circuit for suppressing common-mode circulating current of inverter DC auxiliary power supply according to claim 1, characterized in that, After the NMOS transistor Q3 is turned on, the negative terminal BAT- of the battery is directly connected to the negative terminal DC- of the DC auxiliary power source.

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