Electric vehicle on-board charger and dc power converter comprehensive tester

Abstract

The electric vehicle on-board charger and DC power converter comprehensive detector is characterized in that it comprises a main control unit U101; a sampling circuit, which is in communication connection with the main control unit U101 and is used for collecting power supply voltage and power supply current; a voltage and current adjusting circuit, which is connected with the main control unit U101 and is used for adjusting the voltage and current output by the debugging high-voltage power supply; an output control circuit, which is connected with the main control unit U101 and is used for controlling the output and shutdown of the voltage; an alternating current control circuit, which is connected with the main control unit U101 and is used for controlling the output and shutdown of the alternating current; a discharge control circuit, which is connected with the main control unit U101 and is used for controlling the high-voltage DC contactor to discharge; and a charge-discharge conversion control circuit, which inputs DC high-voltage power on one side, outputs on the other side, and is connected with the main control unit U101 for control, and is used for switching the charge and discharge.

Description

Technical Field

[0001] This invention relates to the field of electric vehicle testing, and more particularly to a comprehensive testing instrument for electric vehicle on-board chargers and DC power converters. Background Technology

[0002] With the increasing number of electric vehicles on the road in recent years, the demand for repairs of electric vehicle components has also risen. Among these, on-board chargers and DC-DC power converters are two of the most frequently used components in electric vehicles. When these parts are no longer covered by the manufacturer's service, and malfunctions occur, repair shops often lack the technical expertise to diagnose and repair them, forcing owners to purchase new parts at high prices, resulting in financial losses. Furthermore, due to issues with the manufacturer, some parts are simply unavailable as replacements.

[0003] Vehicles manufactured by different companies use on-board chargers and DC power converters with varying operating parameters and starting methods, which increases the technical difficulty of testing and repair. Summary of the Invention

[0004] To address the aforementioned issues, this technical solution provides a comprehensive testing instrument for electric vehicle on-board chargers and DC-DC power converters. This invention is designed for on-board chargers and DC-DC power converters used in vehicles from different manufacturers, and can be tested with minimal training. It offers excellent manufacturer compatibility, rapid off-vehicle testing of on-board chargers and DC-DC power converters, and high performance at a competitive cost. It can be used as professional equipment for batch repairs. Vehicle owners no longer need to purchase expensive new parts, reducing unnecessary losses.

[0005] To achieve the above objectives, the technical solution is as follows:

[0006] A comprehensive tester for electric vehicle on-board chargers and DC power converters, including a first main control unit U101;

[0007] The sampling circuit is communicatively connected to the first main control unit U101 and is used to collect power supply voltage and power supply current.

[0008] A voltage and current regulating circuit, connected to the first main control unit U101, is used to adjust the voltage and current output of the debugging high-voltage power supply;

[0009] An output control circuit, connected to the first main control unit U101, is used to control the voltage output and shut it down.

[0010] An AC control circuit, connected to the first main control unit U101, is used to control the output and shutdown of AC power;

[0011] The discharge control circuit is connected to the first main control unit U101 and is used to control the high-voltage DC contactor to discharge.

[0012] The charge / discharge conversion control circuit has a DC high-voltage input on one side and an output on the other side. It is connected to the first main control unit U101 for control and is used to switch between charge and discharge.

[0013] In some embodiments, a fourth main control unit U10 is also included;

[0014] The low-voltage output and charge / discharge switching circuit is connected to the fourth main control unit U10. It receives two different voltage values ​​and outputs the corresponding voltage according to the requirements.

[0015] The CP amplifier circuit, connected to the fourth main control unit U10, is used to monitor the corresponding CP signal status and adjust the equipment control status.

[0016] In some embodiments, a third main control unit U3 is also included;

[0017] Load control is connected to the third main control unit U3 to enable different load control loops.

[0018] In some embodiments, the charge / discharge conversion control circuit includes;

[0019] Optocoupler PC2 has pin 1 connected to the first main control unit U101 via resistor R124, pin 2 grounded, pin 4 grounded, and pin 3 connected to the base of transistor Q105 via resistor R125. The emitter of transistor Q105 is connected to -15V, and the collector is connected to pin 5 of chip U105. The collector is also connected to +15V via resistors R116 and R114. Pin 6 of chip U105 is grounded.

[0020] The chip U105 has a DC high voltage input HV+ on pins 2 and 3, pin 1 connected to +15V, pin 7 connected to +15V through resistor R115, and also connected to the base of transistors Q102 and Q103 through resistor R120. The collector of transistor Q102 is connected to +15V, and the emitter is connected to the driver circuit Q104 through resistor R118.

[0021] The collector of the transistor Q103 is connected to -15V, and the emitter is connected to the drive circuit Q104 through resistor R121.

[0022] In some embodiments, the voltage and current regulating circuit includes;

[0023] A voltage regulating isolation unit U111 is connected to the first main control unit U101;

[0024] The voltage regulating unit U109 is connected to the voltage regulating isolation unit U111 and is used to adjust the DC high voltage HV+.

[0025] The current regulating unit U110 is connected to the voltage regulating isolation unit U111 and is used to adjust the DC high voltage HV+.

[0026] In some embodiments, the output control circuit includes;

[0027] Transistor Q106, the base of transistor Q106 is connected to the first main control unit U101 through resistor R126, the emitter is grounded, the collector is connected to the coil terminal of relay K101, and a voltage is input to the other end of the coil terminal;

[0028] The relay K101 receives a DC high voltage HV+ at its conducting terminal and outputs it.

[0029] In some embodiments, the low-voltage output and charge / discharge switching circuit includes:

[0030] Transistors Q2 and Q3, the bases of both transistors are connected to the fourth main control unit U10, and the emitters of both transistors are grounded. The collectors of both transistors are connected to relays K1 and K2 respectively.

[0031] The coil terminals of relays K1 and K2 are respectively connected to two different voltage values, and the other end is connected to a diode D3. The diode D3 is connected to a resistor RX1 and grounded through a MOSFET Q1.

[0032] The common connection is also connected to pin 2 of chip U5 through resistors R5 and R7. The diode D3 is connected to pin 3 of chip U5 through resistors R9 and R11. Pin 7 is connected to the MOS transistor Q1 through resistor R10.

[0033] In some embodiments, the CP amplifier circuit includes;

[0034] The second main control unit U7 receives PWM control signals from the fourth main control unit U10. Its pin 6 is connected to the CP drive power supply P+12V and is also connected to pin 3 of chip U8 through resistor R24. The CP drive power supply P+12V is connected to pin 2 of chip U8 through resistor R18. Pin 7 of chip U8 is connected to the base of transistors Q4 and Q5. The collector of transistor Q4 is connected to the positive terminal of the CP drive power supply P+12V, and the collector of transistor Q5 is connected to the negative terminal of the CP drive power supply P+12V. The emitters of both transistors are connected to a diode D6, and the diode D6 is connected to the fourth main control unit U10 through resistor R17.

[0035] The beneficial effects of this application are:

[0036] This application's electric vehicle on-board charger and DC power converter tester collects operating parameters of electric vehicle on-board chargers and DC power converters from different manufacturers, such as operating voltage and CAN communication start commands, and stores or sends the data to the electric vehicle air conditioning compressor test bench. This allows operators to test electric vehicle on-board chargers and DC power converters from different manufacturers with just a few simple operations, without needing to master too many professional skills.

[0037] This electric vehicle on-board charger and DC power converter tester allows for vehicle-less testing, determining the condition of the on-board charger or DC power converter even when no vehicle is present. Therefore, using this tester can save after-sales maintenance personnel the hassle of vehicle testing.

[0038] This application's electric vehicle on-board charger and DC power converter tester replaces the high-voltage battery pack, low-voltage battery, and charging gun of an electric vehicle, enabling battery-free repair of electric vehicle on-board chargers and DC power converters. This saves repair shops significant costs and eliminates safety accidents caused by improper battery use. It also achieves automatic load resistor matching, has good compatibility, and is applicable to most on-board charger and DC power converter models currently on the market. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0040] Figure 1 This is a schematic diagram of the operation flow structure of an embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of the test interface according to an embodiment of the present invention;

[0042] Figure 3 This is a schematic diagram of the low-voltage control circuit structure according to an embodiment of the present invention;

[0043] Figure 4 This is a schematic diagram of the load control circuit structure according to an embodiment of the present invention;

[0044] Figure 5 This is a schematic diagram of the high-voltage control circuit structure according to an embodiment of the present invention. Detailed Implementation

[0045] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0046] Please refer to Figure 1-5 As shown, the comprehensive tester for electric vehicle on-board chargers and DC power converters includes a first main control unit U101;

[0047] The power supply circuit comprises three independent, isolated DC power supplies. One power module outputs power to the internal circuitry of the high-voltage DC control module and load switching module, and converts the voltage according to the different circuit requirements. Another power module outputs power to the main control module via the CON101 interface, supplying power to the main control module and then to the touchscreen display. The final power module outputs power to the low-voltage control and low-voltage load module via the CON102 interface, providing the necessary power to the low-voltage lines.

[0048] The sampling circuit, which is communicatively connected to the first main control unit U101, is used to collect power supply voltage and current. The sampling circuit uses the HT7017 chip to collect the high-voltage power supply voltage and high-voltage power supply operating current. The collected voltage and current data are then transmitted to the main control chip STM32F103C8TX via serial communication through the communication isolation chip U104 (SI8622).

[0049] A voltage and current regulating circuit, connected to the first main control unit U101, is used to adjust the voltage and current output of the debugging high-voltage power supply;

[0050] An output control circuit, connected to the first main control unit U101, is used to control the voltage output and shut it down.

[0051] An AC control circuit, connected to the first main control unit U101, is used to control the output and shutdown of AC power;

[0052] The discharge control circuit, connected to the first main control unit U101, controls the high-voltage DC contactor to discharge. The high-voltage discharge circuit consists of R107, Q110, D111, and CON109, where CON is connected to the high-voltage DC contactor coil, controlling the high voltage to discharge through the load resistor. After the discharge circuit stabilizes, the main control chip issues a command to have the high-voltage DC contactor take over the long-term operation of Q104 (IGBT) to protect Q104. After the test is completed, this circuit also controls the release of the high-voltage electricity stored inside the equipment to prevent injury to personnel.

[0053] The charge / discharge conversion control circuit has a DC high voltage input on one side and an output on the other side, and is connected to the first main control unit U101 for control, used to switch between charge and discharge.

[0054] The main control chip has two temperature acquisition circuits, which collect ambient temperature and heat sink temperature respectively. When the temperature is too high, the main control chip will trigger the protection mechanism and execute the corresponding protection action.

[0055] When the temperature is too high, the main control chip will issue a control command to close the K103 relay, and the cooling fan will be powered on and start working.

[0056] The CAN communication circuit serves as a bridge connecting the high-voltage DC control module, load switching module, and other modules. It facilitates communication between the main control modules via the device's CAN bus. It primarily consists of an isolated power supply (DC101) and a communication isolation chip (ISO1050) to ensure electrical and physical isolation between modules and reduce mutual interference.

[0057] Electric vehicle on-board chargers and DC power converters are both dual-power devices that supply both high and low voltage simultaneously.

[0058] This patent simulates the functions of a high-voltage battery pack for electric vehicles (primarily charging and discharging) under the operating conditions of an on-board charger and DC-DC converter by using a high-voltage DC control module, a load switching module, an adjustable high-voltage power supply, and a load resistor. This avoids a series of safety accidents such as explosions and fires caused by improper use of high-voltage battery packs for electric vehicles, and also avoids the inconveniences associated with transportation and storage.

[0059] This patent simulates the low-voltage battery function (primarily charging and discharging) of an electric vehicle under the operating conditions of an on-board charger and DC-DC converter through a low-voltage control and low-voltage load module. This avoids safety issues caused by short circuits during battery use.

[0060] This patent, through low-voltage control and low-voltage load modules, also simulates the function of an AC charging gun that conforms to the national standard GB / T20234. This is equivalent to the device having a built-in charging gun. Compared with the standard slow charging interface of electric vehicles, it can be more conveniently connected to the vehicle charging interface, improving the convenience of actual testing.

[0061] This patent uses a load switching module to convert different load resistance values ​​and power to meet the voltage requirements of on-board chargers for different vehicle models, ranging from 72V to 700V, thus improving product compatibility.

[0062] This patented electrical circuit is divided into four parts: AC mains power, high-voltage DC power, low-voltage DC power, and the internal power supply for the equipment. Physical isolation is implemented between these four parts to ensure the safety of each module. The main control module issues commands via a communication bus to coordinate the operation of the other modules. It simulates the various operating conditions required by the on-board charger and DC power converter to meet the needs of off-vehicle testing, avoiding the hassle of repeated on-vehicle testing during maintenance and greatly improving maintenance efficiency.

[0063] This patented technology uses a discharge resistor to completely release the high-voltage energy from the equipment and the tested components after each test, thus avoiding the risk of electric shock to personnel.

[0064] In this embodiment, a fourth main control unit U10 is also included;

[0065] The low-voltage output and charge / discharge switching circuit is connected to the fourth main control unit U10. It receives two different voltage values ​​and outputs the corresponding voltage according to the requirements.

[0066] The CP amplifier circuit, connected to the fourth main control unit U10, is used to monitor the corresponding CP signal status and adjust the equipment control status.

[0067] In this embodiment, a third main control unit U3 is also included;

[0068] Load control is connected to the third main control unit U3 to enable different load control loops.

[0069] In this embodiment, the charge / discharge conversion control circuit includes:

[0070] Optocoupler PC2 has pin 1 connected to the first main control unit U101 via resistor R124, pin 2 grounded, pin 4 grounded, and pin 3 connected to the base of transistor Q105 via resistor R125. The emitter of transistor Q105 is connected to -15V, and the collector is connected to pin 5 of chip U105. The collector is also connected to +15V via resistors R116 and R114. Pin 6 of chip U105 is grounded.

[0071] The chip U105 has a DC high voltage input HV+ on pins 2 and 3, pin 1 connected to +15V, pin 7 connected to +15V through resistor R115, and also connected to the base of transistors Q102 and Q103 through resistor R120. The collector of transistor Q102 is connected to +15V, and the emitter is connected to the driver circuit Q104 through resistor R118.

[0072] The collector of the transistor Q103 is connected to -15V, and the emitter is connected to the drive circuit Q104 through resistor R121.

[0073] The charge / discharge conversion control circuit is a circuit that automatically switches between charge and discharge states. It features a fast response speed to ensure that the electric vehicle on-board charger can switch to the discharge state (which is the charging state for the on-board charger) immediately upon startup, and to ensure that the on-board charger can detect the charging state and maintain continuous operation.

[0074] Before starting, the car charger checks if the high-voltage battery pack is connected. It first checks if there is power at the output terminal (by detecting the voltage). If there is voltage and it is within the range, and other conditions of the car charger are met, it will start outputting. However, after the car charger starts outputting, it will quickly perform current detection. Only if the current is large enough will it determine that a real battery is connected and continue charging. Otherwise, the car charger will immediately stop outputting.

[0075] While a battery pack can be connected for testing, it is bulky and contains internal control and detection circuits. This makes it costly, inconvenient, and unsafe, thus unsuitable for widespread adoption. Alternatively, a high-voltage DC power supply can be used to provide a high voltage to start the vehicle charger, but once started, it lacks sufficient current to sustain continuous operation. Another option is to provide both high-voltage DC power and a load to meet current detection requirements, but this introduces another problem: the high-voltage DC power supply will directly discharge to the load. This necessitates a sufficiently high power output from the high-voltage DC power supply, significantly increasing its cost. Furthermore, it consumes energy during startup, making it unsuitable for widespread adoption.

[0076] The key feature of this circuit is that it uses voltage difference to switch between charging and discharging. This means that the power of the high-voltage DC power supply does not need to be very large. At startup, only one voltage needs to be provided for detection. When the vehicle is charging, the high-voltage DC power supply will be disconnected and the circuit will switch to load discharge mode.

[0077] This circuit mainly consists of comparator U105 (LM393), D101, IGBT driver circuit, Q102, Q103, and Q104. HV+ and HV- are connected to the DC high-voltage power supply, and HV+ and GND are connected to the positive and negative terminals of the on-board charger output. The load resistor is connected across HV+ and LOAD. When the on-board charger starts, the high-voltage DC power supply current returns to the negative terminal through D101. At this time, the voltage at pin 2 (IN-) of U105 will be greater than the voltage at pin 3 (IN+). U105 will then output a negative voltage to the Q104 driver circuit. Q104 is currently off, and the high voltage will not discharge to GND through the load resistor. The voltage from the high-voltage DC power supply can be directly supplied to the on-board charger for detection. After the on-board charger starts, a voltage greater than the output voltage of the high-voltage DC power supply will be generated across HV+ and GND. Since HV+ is the common terminal, the voltage at pin 2 (IN-) of U105 will be lower than the voltage at pin 3 (IN+). U105 will quickly switch to positive voltage output, and the Q104 drive circuit will receive positive voltage, causing Q104 to conduct. The power output from the car charger will form a loop from HV+ -> load -> Q104 -> GND. The car charger can detect the presence of charging current and maintain subsequent operation. At the same time, because the voltage difference across D101 is in reverse, the high-voltage DC power supply does not discharge externally.

[0078] In this embodiment, the voltage and current regulating circuit includes:

[0079] A voltage regulating isolation unit U111 is connected to the first main control unit U101;

[0080] The voltage regulating unit U109 is connected to the voltage regulating isolation unit U111 and is used to adjust the DC high voltage HV+.

[0081] The current regulating unit U110, connected to the voltage regulating isolation unit U111, is used to adjust the DC high voltage HV+.

[0082] The high-voltage voltage and current regulation is achieved by the main control chip using SPI communication via the isolated communication chip U111 (IS3740HW) to send commands to U109 (DAC7512N, voltage regulator) and U110 (DAC7512N, current regulator). These two chips then output the corresponding voltages, which are connected to the voltage and current regulation interfaces of the adjustable high-voltage power supply via CON104 and CON105, respectively, to adjust the output voltage and current of the adjustable high-voltage power supply. This circuit converts digital voltage and current information into analog quantities that actually control the power supply.

[0083] In this embodiment, the output control circuit includes:

[0084] Transistor Q106, the base of transistor Q106 is connected to the first main control unit U101 through resistor R126, the emitter is grounded, the collector is connected to the coil terminal of relay K101, and a voltage is input to the other end of the coil terminal;

[0085] The relay K101 receives a DC high voltage HV+ at its conducting terminal and outputs it.

[0086] In this embodiment, the low-voltage output and charge / discharge switching circuit includes:

[0087] Transistors Q2 and Q3, the bases of both transistors are connected to the fourth main control unit U10, and the emitters of both transistors are grounded. The collectors of both transistors are connected to relays K1 and K2 respectively.

[0088] The coil terminals of relays K1 and K2 are respectively connected to two different voltage values, and the other end is connected to a diode D3. The diode D3 is connected to a resistor RX1 and grounded through a MOSFET Q1.

[0089] The common connection is also connected to pin 2 of chip U5 through resistors R5 and R7. The diode D3 is connected to pin 3 of chip U5 through resistors R9 and R11. Pin 7 is connected to the MOS transistor Q1 through resistor R10.

[0090] The low-voltage control and low-voltage load module mainly consists of various power conversion circuits, low-voltage output and charge / discharge switching circuits, CP amplification circuits, sampling circuits, main control chips, and CAN communication circuits.

[0091] The low-voltage control and low-voltage load module can output two voltages: 12V and 24V, to meet the low-voltage power supply requirements of most new energy vehicles. The 12V power supply is obtained by stepping down the 24V power supply. Figure 3 As shown, the selection circuit then selects the corresponding voltage output. The load circuit mainly consists of U5 (OPA2604), Q1 (discharge switch), and RX1 (discharge resistor). The low-voltage charging method is similar to the high-voltage charging principle. In the low-voltage circuit, the two ends of D3 are connected to the internal power supply of the device and the DC power converter, respectively. When the DC power converter has no output, there is a positive voltage across D3, U5 outputs a negative voltage, Q1 is off, and no current flows through RX1 for discharge. Therefore, the device discharges internally, equivalent to a DC regulated power supply outputting externally. When the DC power converter has an output, there is a reverse voltage across D3, U5 outputs a positive voltage, and Q1 conducts. At this time, the power supply of the DC power converter discharges through RX1 and Q1. Simultaneously, because the voltage of D3 is reversed, the internal power supply of the device cannot output.

[0092] In this embodiment, the CP amplifier circuit includes:

[0093] The second main control unit U7 receives the PWM control signal from the fourth main control unit U10. Its pin 6 is connected to the CP drive power supply P+12V and is also connected to pin 3 of chip U8 through resistor R24. The CP drive power supply P+12V is connected to pin 2 of chip U8 through resistor R18. Pin 7 of chip U8 is connected to the base of transistors Q4 and Q5. The collector of transistor Q4 is connected to the positive terminal of the CP drive power supply P+12V, and the collector of transistor Q5 is connected to the negative terminal of the CP drive power supply P+12V. The emitters of both transistors are connected to a diode D6, and the diode D6 is connected to the fourth main control unit U10 through resistor R17.

[0094] The CP amplifier circuit converts the PWM signal generated by the main control chip into a ±12V PWM signal via isolation chip U7 and operational amplifier U8 to meet the characteristics of the CP signal for vehicle charging. It also includes a sampling circuit composed of D6, R17, R21, C7, and C8, which is collected by the main control chip. This monitors the corresponding CP signal status and adjusts the equipment control state accordingly.

[0095] The load control includes;

[0096] Several load control relays, one end of the coil of each load control relay is connected to +24V, and the other end is grounded through a corresponding load control transistor. The control terminal of each load control transistor is connected to the third main control unit U3.

[0097] Each of the load control relays has a corresponding current-limiting resistor at its on-state, and they are connected in series. One end of the load control relay on one side is used for input voltage, and the other end of the load control relay on the other side outputs different voltages depending on the resistance value.

[0098] The load switching circuit mainly consists of six relays (K1-6) and three high-power discharge resistors (RX1-3). The main control chip controls the relays, changing the series and parallel connection of the three resistors to obtain corresponding resistance values ​​and power. This satisfies the requirements of different voltage levels between 72V and 700V, thus simulating the operating current required by different on-board chargers.

[0099] Operating Instructions: This instrument is a two-in-one device that can test both electric vehicle on-board chargers and DC power converters. After turning on the instrument, you can select the type of product to be tested on the interface.

[0100] Then you can select the model to be tested by vehicle type or manufacturer. After selecting the model, the system will retrieve the corresponding test parameters and enter the test interface (e.g., Figure 2 (As shown).

[0101] The device's real-time operating parameters will be displayed in the leftmost column. The middle section displays the status of the product under test, and the test information shows the test progress and fault information.

[0102] After startup, the program will select the appropriate test procedure based on the product model to meet the startup conditions of the product under test. Once all conditions are met, if the device starts normally, it will maintain product operation for 60 seconds. Then it will shut down and provide the test results.

[0103] Once started, if any step fails or conditions are not met, the test will stop and report an error.

[0104] The above description is only a preferred embodiment of this application and is not intended to limit the scope of implementation of this application. Any other embodiments whose principles and basic structures are the same as or similar to those of this application are within the protection scope of this application.

Claims

1. A comprehensive testing instrument for electric vehicle on-board chargers and DC power converters, characterized in that, Including the first main control unit U101; The sampling circuit is communicatively connected to the first main control unit U101 and is used to collect power supply voltage and power supply current. A voltage and current regulating circuit, connected to the first main control unit U101, is used to adjust the voltage and current output of the debugging high-voltage power supply; An output control circuit, connected to the first main control unit U101, is used to control the voltage output and shut it down. An AC control circuit, connected to the first main control unit U101, is used to control the output and shutdown of AC power; The discharge control circuit is connected to the first main control unit U101 and is used to control the high-voltage DC contactor to discharge. The charge / discharge conversion control circuit has a DC high voltage input on one side and an output on the other side, and is connected to the first main control unit U101 for control, used to switch between charge and discharge. It also includes the fourth main control unit U10; The low-voltage output and charge / discharge switching circuit is connected to the fourth main control unit U10. It receives two different voltage values ​​and outputs the corresponding voltage according to the requirements. The CP amplifier circuit is connected to the fourth main control unit U10 and is used to monitor the corresponding CP signal status and adjust the equipment control status. The CP signal is the control pilot function signal. The low-voltage output and charge / discharge switching circuit includes: Transistors Q2 and Q3, the bases of both transistors are connected to the fourth main control unit U10, and the emitters of both transistors are grounded. The collectors of both transistors are connected to relays K1 and K2 respectively. The coil terminals of relays K1 and K2 are respectively connected to two different voltage values, and the other end is connected to a diode D3. The diode D3 is connected to a resistor RX1 and grounded through a MOSFET Q1. The common connection is also connected to pin 2 of chip U5 through resistors R5 and R7. The diode D3 is connected to pin 3 of chip U5 through resistors R9 and R11. Pin 7 is connected to the MOS transistor Q1 through resistor R10.

2. The comprehensive testing instrument for electric vehicle on-board chargers and DC power converters according to claim 1, characterized in that: It also includes the third main control unit U3; Load control is connected to the third main control unit U3 to enable different load control loops.

3. The comprehensive testing instrument for electric vehicle on-board chargers and DC power converters according to claim 1, characterized in that: The charge / discharge conversion control circuit includes: Optocoupler PC2 has pin 1 connected to the first main control unit U101 via resistor R124, pin 2 grounded, pin 4 grounded, and pin 3 connected to the base of transistor Q105 via resistor R125. The emitter of transistor Q105 is connected to -15V, and the collector is connected to pin 5 of chip U105. The collector is also connected to +15V via resistors R116 and R114. Pin 6 of chip U105 is grounded. The chip U105 has a DC high voltage input HV+ on pins 2 and 3, pin 1 connected to +15V, pin 7 connected to +15V through resistor R115, and also connected to the base of transistors Q102 and Q103 through resistor R120. The collector of transistor Q102 is connected to +15V, and the emitter is connected to the driver circuit Q104 through resistor R118. The collector of the transistor Q103 is connected to -15V, and the emitter is connected to the drive circuit Q104 through resistor R121.

4. The comprehensive testing instrument for electric vehicle on-board chargers and DC power converters according to claim 3, characterized in that: The voltage and current regulating circuit includes: A voltage regulating isolation unit U111 is connected to the first main control unit U101; The voltage regulating unit U109 is connected to the voltage regulating isolation unit U111 and is used to adjust the DC high voltage HV+. The current regulating unit U110 is connected to the voltage regulating isolation unit U111 and is used to adjust the DC high voltage HV+.

5. The comprehensive testing instrument for electric vehicle on-board chargers and DC power converters according to claim 1, characterized in that: The output control circuit includes: Transistor Q106, the base of transistor Q106 is connected to the first main control unit U101 through resistor R126, the emitter is grounded, the collector is connected to the coil terminal of relay K101, and a voltage is input to the other end of the coil terminal; The relay K101 receives a DC high voltage HV+ at its conducting terminal and outputs it.

6. The comprehensive testing instrument for electric vehicle on-board chargers and DC power converters according to claim 5, characterized in that: The CP amplifier circuit includes: The second main control unit U7 receives PWM control signals from the fourth main control unit U10. Its pin 6 is connected to the CP drive power supply P+12V and is also connected to pin 3 of chip U8 through resistor R24. The CP drive power supply P+12V is connected to pin 2 of chip U8 through resistor R18. Pin 7 of chip U8 is connected to the base of transistors Q4 and Q5. The collector of transistor Q4 is connected to the positive terminal of the CP drive power supply P+12V, and the collector of transistor Q5 is connected to the negative terminal of the CP drive power supply P+12V. The emitters of both transistors are connected to a diode D6, and the diode D6 is connected to the fourth main control unit U10 through resistor R17.

7. The comprehensive testing instrument for electric vehicle on-board chargers and DC power converters according to claim 2, characterized in that: The load control includes; Several load control relays, one end of the coil of each load control relay is connected to +24V, and the other end is grounded through a corresponding load control transistor. The control terminal of each load control transistor is connected to the third main control unit U3. Each of the conducting terminals of the load control relays corresponds to a current-limiting resistor, and they are connected in series. One end of the load control relay on one side is used for input voltage, and the other end of the load control relay on the other side outputs different voltages depending on the resistance value.

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