Alternating current insulation detection circuit, bidirectional vehicle-mounted charger and vehicle

Abstract

The utility model relates to a kind of AC insulation detection circuit, two-way vehicle charger and vehicle, comprising: AC filter module, with inverter AC output end connection;Voltage division and direct current separation module, with AC filter module connection, for AC voltage division and prevent high-voltage direct current damage insulation detection circuit when withstand voltage test;LC filter module, with voltage division and direct current separation module connection;Bias module, with LC filter module connection;Matching module, with bias module connection, for the output voltage potential is limited in pre-set low voltage range, and according to the sinusoidal wave that bias voltage and AC output two-pole voltage division voltage output peak voltage changes with insulation resistance value changes;Digital control module, with matching module connection, for according to the peak voltage of the sinusoidal wave obtained by sampling to output the insulation resistance value of two-way vehicle charger unilateral failure, and make two-way vehicle charger stop working when unilateral insulation failure.The utility model significantly improves the reliability of insulation detection circuit.

Description

Technical Field

[0001] This utility model relates to the field of detection circuit technology, specifically to an AC insulation detection circuit, a bidirectional on-board charger, and a vehicle. Background Technology

[0002] With the development of electric vehicle technology, energy storage technology, and semiconductor technology, and the increasing environmental awareness of low-carbon travel, the development of new energy vehicles is steadily improving, and the demand for electric vehicles is further increasing. As an indispensable part of new energy electric vehicles, the reliability and safety of the on-board power supply are important standards for evaluating the quality of electric vehicles. In inverter mode, a bidirectional on-board charging power supply can detect the insulation resistance on the AC side, promptly preventing device failure or leakage accidents caused by AC side insulation failure, thus significantly improving vehicle safety and reliability.

[0003] Insulation testing circuits can be divided into DC insulation testing circuits and AC insulation testing circuits. In the field of electric vehicles, DC insulation testing circuits are mostly used for insulation testing of the DC side of DC charging piles, and these DC insulation testing circuits are widely used. However, AC insulation testing circuits are mostly used for insulation testing of the AC side during bidirectional vehicle power inverter operation, and most of them are tested by external instruments and equipment under static conditions. At the same time, they are complex to operate and have high circuit costs.

[0004] Therefore, it is necessary to develop a new AC insulation detection circuit, a bidirectional on-board charger, and a vehicle. Utility Model Content

[0005] The purpose of this invention is to provide an AC insulation detection circuit, a bidirectional on-board charger, and a vehicle, which can significantly improve the reliability of the insulation detection circuit.

[0006] In a first aspect, the present invention provides an AC insulation detection circuit for a bidirectional on-board charger, comprising: The AC filter module is connected to the AC output terminal of the inverter and is used to filter the output power supply to reduce noise interference. The voltage divider and DC blocking module is connected to the AC filter module and is used for AC voltage division and to prevent high voltage DC from damaging the insulation detection circuit during withstand voltage tests. The LC filter module, connected to the voltage divider and DC blocking module, is used to filter out high-frequency noise in the circuit. The bias module is connected to the LC filter module and connected to the bias power supply to provide bias voltage for the AC insulation detection circuit. The matching module, connected to the bias module, is used to limit the output voltage potential within a preset low voltage range and output a sine wave whose peak voltage varies with the insulation resistance based on the bias voltage and the AC output voltage divider. The digital control module, connected to the matching module, is used to output the insulation resistance value of the bidirectional on-board charger when one side fails, based on the peak voltage of the sampled sine wave, and to enable the bidirectional on-board charger to work normally when the insulation is normal, and to stop the bidirectional on-board charger when the insulation fails on one side.

[0007] Optionally, the voltage divider and DC blocking module includes a resistor R3, a Y capacitor C3, a resistor R4, and a Y capacitor C4; The first end of the resistor R3 is connected to the output live wire L, and the second end of the resistor R3 is connected to the first end of the Y capacitor C3. The first end of the resistor R4 is connected to the output neutral line N, and the second end of the resistor R4 is connected to the first end of the Y capacitor C4. The second terminals of both Y capacitors C3 and C4 are connected to the LC filter module. Resistors R3 and R4 form a voltage divider circuit, which divides the AC voltage of the output live wire L and the output neutral wire N, converting the high voltage into a lower voltage suitable for subsequent circuit processing, facilitating detection and analysis by the subsequent modules. Capacitors C3 and C4 act as DC blockers, preventing high-voltage DC from entering the AC insulation detection circuit during withstand voltage tests, avoiding damage to components in the circuit, and improving the reliability and safety of the circuit.

[0008] Optionally, the LC filter module adopts a two-stage LC filter circuit, including ferrite bead FB1, ferrite bead FB2, capacitor C5 and capacitor C6; The first end of the magnetic bead FB1 is connected to the output end of the voltage divider and DC blocking module, and the second end of the magnetic bead FB1 is connected to the first end of the magnetic bead FB2 and the first end of the capacitor C5. The second terminal of the ferrite bead FB2 is connected to the first terminal of capacitor C6, and the second terminals of capacitors C5 and C6 are both grounded. A two-stage LC filter circuit is used, consisting of ferrite beads FB1 and FB2, capacitors C5 and C6. Compared with single-stage filtering, this two-stage filtering structure can more effectively filter out high-frequency noise and spurious waves in the circuit, making the output voltage smoother and more stable, improving signal quality, and providing a cleaner input signal for subsequent bias and matching modules. The ferrite beads have the function of suppressing electromagnetic interference, absorbing and dissipating high-frequency interference energy in the circuit, further reducing the impact of high-frequency noise on the circuit, and improving the anti-interference capability of the entire AC insulation detection circuit.

[0009] Optionally, the bias module includes a magnetic bead FB3, a resistor R6, a chip U2, a capacitor C8, a capacitor C7, and a resistor R5; The first ends of resistor R5 and capacitor C7 are both connected to the output end of the LC filter module, and the second ends of resistor R5 and capacitor C7 are both connected to the first and second pins of chip U2, the first end of resistor R6 and the first end of capacitor C8. The third pin of chip U2 is grounded, and the second end of resistor R6 is connected to the first end of ferrite bead FB3. The second end of ferrite bead FB3 is connected to power supply VS2. Power supply VS2 is supplied through ferrite bead FB3 and resistor R6, and chip U2 outputs a bias voltage. Resistor R5 and capacitor C7 form a filter circuit to filter the bias voltage output by chip U2, making the output bias voltage more stable and providing a stable reference voltage for the subsequent matching module, ensuring that the matching module can accurately process the input signal. Ferrite bead FB3 plays a role in isolation and anti-interference, preventing noise and interference signals from the power supply from entering chip U2 and subsequent circuits, ensuring the purity and stability of the bias voltage.

[0010] Optionally, the matching module includes a voltage clamping unit, a voltage following unit, and a filtering unit; The input terminal of the voltage clamping unit is connected to the output terminal of the bias module, and the output terminal of the voltage clamping unit is connected to the input terminal of the voltage follower unit. The output of the voltage follower unit is connected to the input of the filter unit, and the output of the filter unit is connected to the digital control module. The voltage clamping unit limits the input voltage to a preset low-voltage range, preventing damage to the voltage follower unit, filter unit, and digital control module caused by excessively high voltage from the preceding stage during AC insulation testing of the bidirectional on-board charger. The voltage follower unit achieves signal buffering and isolation with high input and low output impedance, reducing interference to the preceding load and ensuring stable drive for the following stage. Its precise following characteristics allow the signal to be compatible with the digital control module. The filter unit removes high-frequency noise and interference from the output signal of the voltage follower unit.

[0011] Optionally, the voltage clamping unit in the matching module includes clamping diode D1 and clamping diode D2; The cathode of clamping diode D1 is connected to the VS1 power supply. The anodes of clamping diode D1 and the cathode of clamping diode D2 are voltage clamping points, connected between the output of the bias module and the voltage follower unit of the matching module. Clamping diodes D1 and D2 form a voltage clamping circuit, which can clamp the input voltage within a specific voltage range. When the input voltage exceeds the set clamping voltage, the diodes conduct, limiting the voltage within a safe range, preventing overvoltage from damaging subsequent circuits, and ensuring that the circuit operates within the normal operating voltage range.

[0012] Optionally, the voltage follower unit in the matching module includes a follower U1 and a capacitor C9; The non-inverting input terminal of the follower U1 is connected to the voltage clamping unit, and the inverting input terminal and output terminal of the follower U1 are respectively connected to the filtering unit. The first terminal of capacitor C9 is connected to the power supply pin of follower U1, the first terminal of ferrite bead FB3, and the second terminal of resistor R6, while the second terminal of capacitor C9 is grounded.

[0013] Optionally, the filtering unit in the matching module includes a resistor R7 and a capacitor C10; The first end of the resistor R7 is connected to the output end of the follower U1, and the second end of the resistor R7 is connected to the first end of the capacitor C10 and the digital control module, respectively. The second terminal of capacitor C10 is grounded. Resistor R7 and capacitor C10 form a filter circuit to further filter the signal output by operational amplifier U1, removing high-frequency noise and spurious waves from the signal, making the output signal smoother and more stable, and improving the sampling accuracy and judgment accuracy of the digital control module.

[0014] Secondly, the bidirectional vehicle charger described in this utility model adopts the AC insulation detection circuit described in this utility model.

[0015] Thirdly, the vehicle described in this utility model uses the bidirectional on-board charger as described in this utility model.

[0016] This utility model has the following unexpected technical effects: 1. Significantly improves the reliability of insulation detection circuits, addressing the reliability pain points of existing detection methods. In this invention, Y capacitors C3 and C4 are added to the output live wire L and output neutral wire N, respectively. When the vehicle power supply undergoes withstand voltage and surge tests, high-voltage DC current is applied to the AC side. Traditional circuits are easily damaged under such conditions, leading to invalid test results or even circuit failure. The Y capacitors C3 and C4 in this invention effectively prevent the influence of AC-side DC current on the AC insulation detection circuit, providing a reliable protective barrier for the circuit. Whether in daily use or under special experimental environments, the insulation detection circuit can be ensured to operate stably, greatly enhancing its reliability. This fundamentally solves the problem of insufficient reliability of existing detection methods in complex electrical environments, guarantees the validity of insulation test results, and provides a solid guarantee for the safe operation of the bidirectional vehicle charger.

[0017] 2. Significantly enhances anti-interference capabilities, overcoming the problem of weak anti-interference in existing detection methods. The sampling voltage of this invention first passes through a two-stage LC filter circuit. Ferrite beads FB1 and FB2 suppress electromagnetic interference, absorbing and dissipating high-frequency interference energy in the circuit, while capacitors C5 and C6 further filter out high-frequency noise. After these two stages of filtering, high-frequency interference is significantly reduced. The filtered voltage is then superimposed with the bias voltage obtained from the bias module. Ferrite bead FB3 in the bias module also provides isolation and anti-interference, preventing noise and interference signals from the power supply from entering subsequent circuits. Through this series of designs, this circuit can significantly reduce high-frequency interference, effectively overcoming the problem of weak anti-interference capability in existing detection circuits. This makes the sampling results of the insulation detection circuit more accurate and stable, providing reliable data support for the digital control module and ensuring the accuracy of insulation detection.

[0018] 3. Effectively reduces costs and enables real-time detection, overcoming the shortcomings of existing detection methods that are expensive and cannot provide real-time detection. The insulation detection circuit in this invention is mainly composed of common resistive and capacitive components, which are inexpensive and readily available, significantly reducing the overall cost of the circuit. Simultaneously, the digital control module reads the peak voltage of the I / O port in real time and converts it into the corresponding insulation resistance value, achieving real-time detection of the insulation status on the AC side. Compared with traditional insulation detection circuits, this circuit has a simple structure, requires no complex external instruments or cumbersome operating procedures, not only reducing costs but also improving the versatility and convenience of the detection. This real-time detection function can promptly detect insulation faults, preventing safety accidents caused by insulation problems, providing strong protection for the safe operation of new energy vehicles, and effectively compensating for the shortcomings of existing detection methods in terms of cost and real-time performance. Attached Figure Description

[0019] Figure 1 This is a structural block diagram of the AC insulation detection circuit described in the embodiments of this application; Figure 2 This is a circuit diagram of the AC insulation detection circuit in an embodiment of this application; Figure 3 When the AC side of the on-board charger is properly insulated, the voltage VL of the live wire to ground, the voltage VN of the neutral wire to ground, and... Figure 2 Waveform of voltage VA in the middle; Figure 4 When the AC side of the on-board charger experiences a single-sided insulation fault, the voltage VL of the live wire to ground, the voltage VN of the neutral wire to ground, and... Figure 2 Waveform of voltage VA in the middle. Detailed Implementation

[0020] The embodiments of this utility model will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. It should be understood that the preferred embodiments are only for illustrating this utility model and not for limiting the scope of protection of this utility model.

[0021] like Figure 1 As shown in the embodiment of this application, an AC insulation detection circuit for a bidirectional on-board charger includes an AC filter module, a voltage divider and DC blocking module, an LC filter module, a bias module, a matching module, and a digital control module. The AC filter module is connected to the AC output terminal of the inverter and is used to filter the output power supply. The voltage divider and DC blocking module is connected to the AC filter module and is used for AC voltage division and to prevent high-voltage DC from damaging the insulation detection circuit during withstand voltage tests. The LC filter module is connected to the voltage divider and DC blocking module and is used to filter out high-frequency noise in the circuit. The bias module is connected to the LC filter module and is connected to a bias power supply to provide a bias voltage for the AC insulation detection circuit. The matching module is connected to the bias module and is used to limit the output voltage potential within a preset low-voltage range, and output a sine wave whose peak voltage varies with the insulation resistance based on the bias voltage and the AC output voltage divider. The digital control module is connected to the matching module and is used to output the insulation resistance value of the bidirectional on-board charger when one side fails, based on the peak voltage of the sine wave obtained by sampling. When the insulation is normal, the bidirectional on-board charger works normally, and when the insulation fails on one side, the bidirectional on-board charger stops working.

[0022] When the bidirectional on-board charger operates under inverter conditions, the output AC voltage terminals are L and N, where L represents the live wire and N represents the neutral wire. The voltages of the output live wire L and the output neutral wire N relative to ground are VL and VN, respectively. The AC voltage is filtered by an AC filter module, and then passed through a voltage divider and DC blocking module to obtain a superimposed voltage VC. Under normal insulation conditions, the amplitude of voltage VC is the bias voltage; under abnormal insulation conditions, the amplitude varies with the voltage division of VL and VN. Voltage VC is filtered by an LC filter module to reduce high-frequency interference, resulting in a more stable voltage VB. Simultaneously, voltage VB is superimposed with the bias voltage output from the bias module, and then passed through a matching module to provide a sine wave whose peak value varies with the insulation resistance. This sine wave is then fed to the sampling port of the digital control module. The peak voltage of the sine wave is obtained through software, and the insulation status is determined to control whether the bidirectional on-board charger operates.

[0023] The digital control module corresponds to different single-sided insulation resistance values ​​based on different output voltage peaks. When the single-sided insulation resistance value is detected to be less than the preset threshold, the digital control module determines that the single-sided insulation has failed and performs a shutdown operation on the bidirectional on-board charger.

[0024] The following is a detailed explanation of each module: like Figure 2 As shown, when the bidirectional on-board charger is in inverter mode, it outputs AC power. To meet the EMI requirements during forward OBC operation, there are Y capacitors (i.e., Y-capacitors) between the live wire (L) and ground wire, and between the neutral wire (N) and ground wire, at the AC output port. Figure 2 The capacitors C1 and C2 in the Y capacitor are equal in value.

[0025] like Figure 2 As shown, capacitors C1 and C2 represent the Y capacitances of the live wire L and neutral wire N to ground at the AC output port, respectively. Resistors R1 and R2 represent the insulation resistances of the live wire L to ground and the neutral wire N to ground, respectively. Under normal insulation conditions, the resistances of the output live wire L and the output neutral wire N to ground are equal and in the megaohm range. Due to the presence and equality of capacitors C1 and C2, the output live wire L and the output neutral wire N each have a voltage to ground, with equal voltage amplitudes and a 180° phase shift.

[0026] When a single-sided insulation failure occurs on the AC side, that is, the resistance of the output live wire L or the output neutral wire N to ground decreases significantly, the insulation resistance of resistors R1 and R2 is not equal, the voltage division amplitude of the output live wire L and the output neutral wire N to ground is not equal, and the phase difference is not 180°.

[0027] like Figure 2 As shown, in some instances, the voltage divider and DC blocking module includes resistor R3, Y capacitor C3, resistor R4, and Y capacitor C4. Resistors R3 and R4 represent multiple megaohm-level resistors connected in series.

[0028] Typically, to meet the insulation resistance and withstand voltage requirements of products, the insulation resistance is generally required to be tens of megohms, and the insulation withstand voltage usually needs to reach 2kV-4kV. Because the voltage divider resistance between the output live wire (L) or output neutral wire (N) and the ground wire needs to reach tens of megohms, multiple megohm resistors need to be connected in series, increasing costs. In this embodiment, the number of megohm resistors in series with resistors R3 and R4 is small (in conventional circuits, to meet the insulation resistance and withstand voltage requirements, the number of megohm resistors in series with the voltage divider is usually 10 or more; in this embodiment, by adding Y capacitors C3 and C4, the direct connection between the AC side and ground can be effectively avoided, and even a small number of series resistors can meet the insulation resistance requirements). Furthermore, the addition of Y capacitors C3 and C4 can effectively prevent damage to the insulation detection circuit due to withstand voltage testing, and at a lower cost, the product's insulation resistance requirements can be met.

[0029] like Figure 2 As shown, the specific connection relationship of the voltage divider and DC blocking module is as follows: The first end of resistor R3 is connected to the output live wire L, and the second end of resistor R3 is connected to the first end of Y capacitor C3. The first end of resistor R4 is connected to the output neutral wire N, and the second end of resistor R4 is connected to the first end of Y capacitor C4. The second ends of Y capacitors C3 and C4 are both connected to the LC filter module (i.e., the first end of ferrite bead FB1).

[0030] like Figure 2 As shown, in some examples, the LC filter module uses a two-stage LC filter circuit, which includes ferrite bead FB1, ferrite bead FB2, capacitor C5, and capacitor C6, with the specific connection relationship as follows: The first terminal of ferrite bead FB1 is connected to the output terminal of the voltage divider and DC blocking module. The second terminal of ferrite bead FB1 is connected to the first terminal of ferrite bead FB2 and the first terminal of capacitor C5. The second terminal of ferrite bead FB2 is connected to the first terminal of capacitor C6. The second terminals of capacitors C5 and C6 are both grounded. Ferrite bead FB1 and capacitor C5, and ferrite bead FB2 and capacitor C6 constitute a two-stage LC filter used to filter the voltage input from the voltage divider and DC blocking module.

[0031] like Figure 2 As shown, in some examples, the bias module includes ferrite bead FB3, resistor R6, chip U2 (e.g., TL431 three-terminal regulator), capacitor C8, capacitor C7, and resistor R5, with the specific connection relationships as follows: The first terminals of resistor R5 and capacitor C7 are both connected to the output of the LC filter module. The second terminals of resistor R5 and capacitor C7 are connected to the first and second pins of chip U2, the first terminal of resistor R6, and the first terminal of capacitor C8. The third pin of chip U2 is grounded. The second terminal of resistor R6 is connected to the first terminal of ferrite bead FB3, and the second terminal of ferrite bead FB3 is connected to power supply VS2. The power supply provides power to chip U2 through ferrite bead FB3 and resistor R6, causing the first and second pins of chip U2 to output bias voltages. After filtering by resistor R5 and capacitor C7, the output bias voltage is more stable.

[0032] like Figure 2 As shown, in some instances, the matching module includes a voltage clamping unit, a voltage follower unit, and a filtering unit, with the specific connection relationships as follows: The voltage clamping unit's input is connected to the bias module's output, its output to the voltage follower unit's input, the voltage follower unit's output to the filter unit's input, and the filter unit's output to the digital control module. The voltage clamping unit limits the preceding stage's output voltage potential to a preset low range to prevent excessive voltage from damaging components in subsequent circuits. The voltage follower unit outputs a sampled voltage based on the bias voltage and the voltage divider, which is then filtered by the filter unit before being output to the digital control module for processing.

[0033] like Figure 2 As shown, in some instances, the voltage clamping unit in the matching module includes clamping diode D1 and clamping diode D2, with the specific connection relationship as follows: The negative terminal of clamping diode D1 is connected to the VS1 power supply. The positive terminal of clamping diode D1 and the negative terminal of clamping diode D2 are voltage clamping points, which are connected between the output terminal of the bias module and the voltage follower unit of the matching module.

[0034] like Figure 2 As shown, in some instances, the voltage follower unit in the matching module includes a follower U1 and a capacitor C9, with the specific connection relationship as follows: The non-inverting input of follower U1 is connected to the voltage clamping unit, and the inverting input and output of follower U1 are connected to the filter unit, respectively. The first terminal of capacitor C9 is connected to the power supply pin of follower U1, the first terminal of ferrite bead FB3, and the second terminal of resistor R6, and the second terminal of capacitor C9 is grounded.

[0035] like Figure 2 As shown, in some instances, the filtering unit in the matching module includes resistor R7 and capacitor C10, with the specific connection relationship as follows: The first terminal of resistor R7 is connected to the output terminal of follower U1, and the second terminal of resistor R7 is connected to the first terminal of capacitor C10 and the digital control module. The second terminal of capacitor C10 is grounded.

[0036] like Figure 2 As shown, voltages VL and VN pass through an AC filter circuit and resistors R3 and R4, Y capacitors C3 and C4, and then pass through the first terminal of ferrite bead FB1 to obtain voltage VC. Voltage VC passes through an LC filter module to obtain voltage VB. Voltage VB passes through a bias module and a matching module and is then output to voltage VA of the digital control module.

[0037] When the bidirectional on-board charger operates under inverter conditions with normal insulation, the voltage VB equals the bias voltage. In the event of a single-sided insulation failure, the voltage VB becomes a sinusoidal voltage with the bias voltage as its neutral line. The greater the difference in insulation resistance between the two sides, the greater the sinusoidal fluctuation and the higher the peak value. The voltage VB is fed into the digital control module via the bias module and matching module to obtain the voltage VA. The digital control module outputs the single-sided insulation resistance value based on the peak value of the input voltage VA, thereby determining whether an insulation abnormality has occurred. If a single-sided insulation failure is detected, the bidirectional on-board charger stops operating.

[0038] like Figure 3 As shown, under normal insulation conditions of the bidirectional on-board charger, the voltages VL and VN have equal amplitudes and a phase difference of 180°, the voltage VB is close to a straight line, and the AC voltage division is 0. Figure 4 As shown, when the insulation of a bidirectional on-board charger fails on one side, the voltages VL and VN have different amplitudes and a phase difference of not 180°. The voltage VB is a sine wave, and its amplitude is determined by the magnitude of the insulation resistance on one side.

[0039] In this embodiment of the application, the AC insulation detection circuit has: Insulation withstand voltage protection: such as Figure 2 As shown, Y capacitors C3 and C4 are added to both the output live wire L and the output neutral wire N. In this embodiment, the safety characteristics of the Y capacitors are utilized to achieve real-time monitoring of insulation detection, meet the withstand voltage insulation requirements under dynamic conditions, and reduce costs.

[0040] Strong anti-interference ability: such as Figure 2 As shown, the sampling voltage VB, through the LC filter module and the bias module, can effectively filter out high-frequency interference and noise during bidirectional vehicle power supply inverter, thereby improving the purity and anti-interference capability of the sampling voltage.

[0041] Real-time monitoring, simple circuitry: such as Figure 2As shown, the AC insulation detection circuit in this embodiment mainly consists of resistors, capacitors, and voltage followers. After the digital control module acquires the superimposed AC voltage VC, it processes the data through software to read the peak voltage of the superimposed voltage VC in real time and determine the corresponding insulation resistance value, thereby achieving real-time detection of the AC side insulation status. Traditional AC side insulation detection requires a power outage and external instruments to perform insulation detection using the AC injection method. This not only requires a signal generator, multi-stage isolation circuits, injection sampling circuits, relays, and filtering circuits, but also has the problems of complex operation and inability to perform insulation detection during vehicle power inversion. Therefore, compared with traditional AC insulation detection circuits, the AC insulation detection circuit in this embodiment can not only monitor AC side insulation in real time, but is also simpler to operate, has a simpler circuit, and is lower in cost.

[0042] In this embodiment, the operation of the AC insulation detection circuit is as follows: The bidirectional on-board charger operates under inverter conditions, outputting AC voltage, which includes VL and VN. VL is the voltage between the live wire (L) and ground, and VN is the voltage between the neutral wire (N) and ground. The AC voltage is filtered by an AC filter module. The filtered voltage is then passed through a voltage divider and DC blocking module to obtain a superimposed voltage VC. Under normal insulation conditions, the amplitude of VC is the bias voltage; under abnormal insulation conditions, the amplitude varies with the voltage division of VL and VN. Voltage VC is then filtered by an LC filter module to reduce high-frequency interference, resulting in voltage VB. Voltage VB is superimposed with the bias voltage output from the bias module, and then passed through a matching module to transmit a sine wave whose peak value varies with the insulation resistance to the digital control module. The digital control module acquires the peak voltage of the sine wave and determines the insulation resistance on one side based on the different peak values. When the detected insulation resistance on one side is less than a preset threshold, a single-sided insulation failure is identified, and the bidirectional on-board charger is shut down.

[0043] When the bidirectional on-board charger operates under inverter conditions with normal insulation, the voltage VB equals the bias voltage. In the event of a single-sided insulation failure, the voltage VB becomes a sinusoidal voltage with the bias voltage as its neutral line. Furthermore, the greater the difference in insulation resistance between the two sides, the greater the sinusoidal fluctuation and the higher the peak value. The voltage VB is fed into the digital control module via the bias module and matching module to obtain the voltage VA. The digital control module outputs the single-sided insulation resistance value based on the peak value of the input voltage VA, thereby determining whether an insulation abnormality has occurred.

[0044] In this embodiment of the application, a bidirectional on-board charger employs the AC insulation detection circuit as described in this embodiment of the application.

[0045] In this embodiment of the application, a vehicle employs a bidirectional on-board charger as described in this embodiment of the application.

[0046] The above embodiments are preferred embodiments of the present utility model, but the embodiments of the present utility model are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present utility model shall be considered equivalent substitutions and shall be included within the protection scope of the present utility model.

Claims

1. An AC insulation detection circuit for a bidirectional on-board charger, characterized in that, include: The AC filter module is connected to the AC output terminal of the inverter and is used to filter the output power supply. The voltage divider and DC blocking module is connected to the AC filter module and is used for AC voltage division and to prevent high voltage DC from damaging the insulation detection circuit during withstand voltage test. The LC filter module, connected to the voltage divider and DC blocking module, is used to filter out high-frequency noise in the circuit. The bias module is connected to the LC filter module and is connected to the bias power supply to provide bias voltage for the AC insulation detection circuit. The matching module, connected to the bias module, is used to limit the output voltage potential within a preset low voltage range, and output a sine wave whose peak voltage varies with the insulation resistance based on the bias voltage and the AC output voltage divider. The digital control module, connected to the matching module, is used to output the insulation resistance value of the bidirectional on-board charger when one side fails, based on the peak voltage of the sampled sine wave, and to enable the bidirectional on-board charger to work normally when the insulation is normal, and to stop the bidirectional on-board charger when the insulation fails.

2. The AC insulation detection circuit according to claim 1, characterized in that, The voltage divider and DC blocking module includes resistor R3, Y capacitor C3, resistor R4, and Y capacitor C4; The first end of the resistor R3 is connected to the output live wire L, and the second end of the resistor R3 is connected to the first end of the Y capacitor C3. The first end of the resistor R4 is connected to the output neutral line N, and the second end of the resistor R4 is connected to the first end of the Y capacitor C4. The second terminals of both Y capacitors C3 and C4 are connected to the LC filter module.

3. The AC insulation detection circuit according to claim 1, characterized in that, The LC filter module adopts a two-stage LC filter circuit, including ferrite bead FB1, ferrite bead FB2, capacitor C5 and capacitor C6. The first end of the magnetic bead FB1 is connected to the output end of the voltage divider and DC blocking module, and the second end of the magnetic bead FB1 is connected to the first end of the magnetic bead FB2 and the first end of the capacitor C5. The second end of the magnetic bead FB2 is connected to the first end of the capacitor C6, and the second ends of both capacitors C5 and C6 are grounded.

4. The AC insulation detection circuit according to claim 1, characterized in that, The bias module includes a magnetic bead FB3, a resistor R6, a chip U2, a capacitor C8, a capacitor C7, and a resistor R5; The first ends of resistor R5 and capacitor C7 are both connected to the output end of the LC filter module, and the second ends of resistor R5 and capacitor C7 are both connected to the first and second pins of chip U2, the first end of resistor R6 and the first end of capacitor C8. The third pin of the chip U2 is grounded, the second end of the resistor R6 is connected to the first end of the ferrite bead FB3, and the second end of the ferrite bead FB3 is connected to the power supply VS2.

5. The AC insulation detection circuit according to claim 4, characterized in that, The matching module includes a voltage clamping unit, a voltage following unit, and a filtering unit; The input terminal of the voltage clamping unit is connected to the output terminal of the bias module, and the output terminal of the voltage clamping unit is connected to the input terminal of the voltage follower unit. The output of the voltage follower unit is connected to the input of the filter unit, and the output of the filter unit is connected to the digital control module.

6. The AC insulation detection circuit according to claim 5, characterized in that, The voltage clamping unit in the matching module includes clamping diode D1 and clamping diode D2; The negative terminal of the clamping diode D1 is connected to the VS1 power supply, and the positive terminal of the clamping diode D1 and the negative terminal of the clamping diode D2 are voltage clamping points, which are connected between the output terminal of the bias module and the voltage follower unit of the matching module.

7. The AC insulation detection circuit according to claim 5, characterized in that, The voltage follower unit in the matching module includes a follower U1 and a capacitor C9; The non-inverting input terminal of the follower U1 is connected to the voltage clamping unit, and the inverting input terminal and output terminal of the follower U1 are respectively connected to the filtering unit. The first terminal of capacitor C9 is connected to the power supply pin of follower U1, the first terminal of ferrite bead FB3, and the second terminal of resistor R6, while the second terminal of capacitor C9 is grounded.

8. The AC insulation detection circuit according to claim 5, characterized in that, The filtering unit in the matching module includes a resistor R7 and a capacitor C10; The first end of the resistor R7 is connected to the output end of the follower U1, and the second end of the resistor R7 is connected to the first end of the capacitor C10 and the digital control module, respectively. The second terminal of the capacitor C10 is grounded.

9. A bidirectional on-board charger, characterized in that, The AC insulation detection circuit as described in any one of claims 1 to 8 is adopted.

10. A vehicle, characterized in that, The bidirectional on-board charger as described in claim 9 is used.

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