Sticking and differential pressure detection circuit for a relay

Abstract

The application discloses a kind of sticking and pressure difference detection circuit of relay, including with the vehicle high-voltage charging package of charging port connection, be located at the anode of the anode relay of the charging port, and be located at the cathode of the cathode relay of the charging port, further include being located between the differential detection circuit of the charging port and the vehicle high-voltage charging package, switching circuit that the differential detection circuit detection state is switched, and control the main control unit of the switching circuit operating state, the output end of the main control unit is connected with the differential detection circuit, and can be according to the output signal of the differential detection circuit judging the state of the anode relay and the cathode relay.Compared with prior art, the sticking state of the relay can be effectively identified, and the sticking detection of the relay is not affected by external voltage, and the state of the relay can be effectively judged.

Description

Technical Field

[0001] This invention relates to the field of relays for new energy vehicles, and in particular to a relay adhesion and differential pressure detection circuit. Background Technology

[0002] New energy vehicles possess unparalleled advantages over traditional gasoline-powered vehicles, such as low energy consumption and low pollution, and can alleviate problems like energy shortages and environmental pollution. In recent years, new energy vehicles have achieved remarkable results under the strong and continuous support and guidance of the government. The rapid development and popularization of new energy vehicles have also led to increasingly higher, more comprehensive, and systematic requirements for the charging and battery swapping process and the safety of the entire vehicle.

[0003] The main function of relays in new energy vehicles is to control the opening and closing of the main power line to protect the safety of the controller and motor. However, due to excessive external load current, unstable pull-in voltage, and large load interruption, relays are prone to sticking together. Existing relay sticking detection technologies and methods have problems such as complex circuits, low detection efficiency, poor accuracy, and susceptibility to external voltage influences leading to false detections. This results in high-voltage relay sticking being undetectable or false alarms, which in turn prevents new energy vehicles from charging or damages components.

[0004] Therefore, how to design a relay adhesion and differential pressure detection circuit that can overcome the shortcomings of existing technologies is a technical problem that the industry urgently needs to solve. Summary of the Invention

[0005] To address the issues of low detection efficiency and poor accuracy in existing relay adhesion detection technologies, this invention proposes a relay adhesion and differential pressure detection circuit.

[0006] The technical solution of this invention is to propose a relay adhesion and differential pressure detection circuit, including an on-board high-voltage charging pack connected to a charging port, a positive relay disposed at the positive terminal of the charging port, and a negative relay disposed at the negative terminal of the charging port. It also includes a differential detection circuit disposed between the charging port and the on-board high-voltage charging pack, a switching circuit for switching the detection state of the differential detection circuit, and a main control unit for controlling the operating state of the switching circuit. The main control unit is connected to the output terminal of the differential detection circuit and can determine the state of the positive and negative relays based on the output signal of the differential detection circuit.

[0007] Furthermore, the differential detection circuit includes: resistors R1A, R2A, R3A, R4A, R5A, R6A, R1B, R2B, R3B, R4B, R5B, R6B, and differential amplifier U1.

[0008] One end of resistor R3A is connected between the positive relay and the positive terminal of the vehicle high-voltage battery pack, and the other end is connected in series with resistor R4A and then grounded. One end of resistor R3B is connected between the positive relay and the positive terminal of the vehicle high-voltage battery pack, and the other end is connected in series with resistor R4B and then grounded. One end of resistor R5A is connected between the positive terminal of the charging port and the positive relay, and the other end is connected to the first input terminal of the switching circuit. One end of resistor R6A is connected between the negative terminal of the charging port and the negative relay, and the other end is connected to the second input terminal of the switching circuit. One end of resistor R1A is connected to the first output terminal of the switching circuit, and the other end is connected in series with resistor R4A. The resistor R2A is connected to ground. One end of the resistor R5B is connected between the positive relay and the positive terminal of the vehicle high-voltage battery pack, and the other end is connected to the third input terminal of the switching circuit. One end of the resistor R6B is connected between the negative relay and the negative terminal of the vehicle high-voltage battery pack, and the other end is connected to the fourth input terminal of the switching circuit. One end of the resistor R1B is connected to the second output terminal of the switching circuit, and the other end is connected to ground after being connected in series with the resistor R2B. The non-inverting input terminal of the differential amplifier U1 is connected between the resistors R1B and R2B, the inverting input terminal is connected between the resistors R1A and R2A, and the output terminal is connected to the main control unit.

[0009] Furthermore, it also includes a bias voltage setting circuit connected to the differential detection circuit, the bias voltage setting circuit including resistor R7A and resistor R7B;

[0010] One end of resistor R7A is connected to a bias power supply, and the other end is connected in series with resistor R7B and then grounded. The voltage between resistor R7A and resistor R7B is used as the bias voltage. The non-inverting input terminal of differential amplifier U1 is also connected between resistor R7A and resistor R7B to obtain the bias voltage.

[0011] Furthermore, the resistance values ​​of resistor R7A and resistor R7B are the same.

[0012] Furthermore, the switching circuit includes relays RLY1, RLY2A, and RLY2B;

[0013] The first moving end of relay RLY2A is connected to the differential detection circuit as the first input end of the switching circuit, the second moving end is connected to the differential detection circuit as the second input end of the switching circuit, and the stationary end is connected to the first end of relay RLY1. The second end of relay RLY1 is connected to the differential detection circuit as the first output end of the switching circuit. The first moving end of relay RLY2B is connected to the differential detection circuit as the third input end of the switching circuit, the second moving end is connected to the differential detection circuit as the fourth input end of the switching circuit, and the stationary end is connected to the differential detection circuit as the second output end of the switching circuit.

[0014] Furthermore, it also includes a power supply circuit connected to the differential detection circuit and the main control unit. The power supply circuit includes an auxiliary source conversion circuit and a voltage conversion circuit. When the power supply circuit receives a wake-up signal from the main control unit, it supplies power to the differential amplifier U1 in the differential detection circuit.

[0015] Furthermore, the main control unit is also connected to the battery management system of the vehicle system, and can adjust the conduction state of the positive relay, the negative relay, and the switching circuit according to the control commands issued by the battery management system.

[0016] Furthermore, when the relay RLY1 is disconnected, the main control unit controls the power supply circuit to be in a sleep state, and the differential detection circuit operates in the default state;

[0017] When relay RLY1 is closed, and the stationary terminal of relay RLY2A is connected to its first moving terminal, and the stationary terminal of relay RLY2B is connected to its first moving terminal, the main control unit controls the power supply circuit to be in a wake-up state, and the differential detection circuit operates in a positive relay sticking detection state.

[0018] When relay RLY1 is closed, and the stationary terminal of relay RLY2A is connected to its second moving terminal, and the stationary terminal of relay RLY2B is connected to its second moving terminal, the main control unit controls the power supply circuit to be in a wake-up state, and the differential detection circuit operates in a negative relay adhesion detection state.

[0019] Furthermore, when the relay RLY1 and the negative relay are closed, the positive relay is open, and the stationary terminal of the relay RLY2A is connected to its first moving terminal, and the stationary terminal of the relay RLY2B is connected to its first moving terminal, the main control unit controls the power supply circuit to be in a wake-up state, and the differential detection circuit operates in a differential pressure detection state.

[0020] Furthermore, when the differential detection circuit operates in the positive relay sticking detection state, and the voltage of the output signal of the differential detection circuit is equal to the bias given voltage, the positive relay is sticking.

[0021] When the differential detection circuit operates in the negative relay sticking detection state, and the voltage of the output signal of the differential detection circuit is equal to the bias given voltage, the negative relay is sticking.

[0022] When the differential detection circuit operates in differential pressure detection mode, the difference between the voltage of the output signal of the differential detection circuit and the bias given voltage is converted into the differential pressure between the charging port and the vehicle high-voltage battery pack through a certain numerical conversion.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] 1. The present invention uses a Wheatstone bridge circuit consisting of a set of associated action relays, related sampling resistors and operational amplifiers, which increases the circuit detection accuracy and efficiency, and can identify and judge even small voltage difference changes.

[0025] 2. When relay adhesion and differential pressure detection are not performed, the present invention is in a default non-detection state. At this time, the differential pressure detection circuit is in a dormant state, which can effectively reduce the static current loss of new energy vehicles.

[0026] 3. When performing relay adhesion and differential pressure detection, this invention is not affected by the residual voltage of the charging pile or the voltage on the vehicle's high-voltage charging pack. It can effectively avoid the influence of external voltage on the relay status judgment and can effectively identify the relay status under various voltage adjustments, effectively protecting the relay and motor from damage.

[0027] 4. The differential pressure detection circuit of the present invention uses a set of associated action relays. When one relay fails, it will not affect the judgment of the other relay. The state judgments of the two relays are independent of each other and are not affected.

[0028] 5. This invention detects the voltage difference across the relay before closing the relay. When the voltage difference across the relay is lower than a certain threshold, the high-voltage relay is closed. This can effectively reduce the inrush current generated at the moment the high-voltage relay closes, protecting the controller and motor from damage. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram illustrating the working principle of the present invention;

[0031] Figure 2 This is a connection diagram of the present invention in its default operating state;

[0032] Figure 3 This is a connection diagram of the present invention operating in the negative electrode relay adhesion detection state;

[0033] Figure 4 This is a connection diagram of the present invention operating in the positive electrode relay adhesion detection state;

[0034] Figure 5 This is a connection diagram of the present invention operating in differential pressure detection mode;

[0035] Figure 6 This is the output result of the present invention when simulating different impedances of a negative relay;

[0036] Figure 7 This is the output result of the present invention when simulating different impedances of a positive relay;

[0037] Figure 8 This invention simulates the output results when there are different voltage differences between the charging port and the vehicle high-voltage battery.

[0038] Figure 9 This is the overall control flowchart of the present invention. Detailed Implementation

[0039] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present 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 present invention and are not intended to limit the present invention.

[0040] Therefore, a feature pointed out in this specification is used to describe one feature of one embodiment of the invention, and does not imply that every embodiment of the invention must have the described feature. Furthermore, it should be noted that this specification describes many features. Although certain features may be combined to illustrate possible system designs, these features may also be used in other combinations not explicitly stated. Therefore, unless otherwise stated, the described combinations are not intended to be limiting.

[0041] The principles and structure of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0042] Existing relay sticking detection technologies suffer from problems such as complex circuitry, low detection efficiency, poor accuracy, and susceptibility to external voltage fluctuations leading to false detections. These issues result in relay sticking being undetectable or triggering false alarms, causing new energy vehicles to fail to charge or damaging components. The present invention aims to design a relay sticking and differential voltage detection circuit. This circuit employs a Wheatstone bridge configuration consisting of a set of associated relays, a related sampling circuit, and operational amplifiers, increasing detection accuracy and efficiency while reducing the occurrence of false detections.

[0043] The relay adhesion and differential pressure detection circuit proposed in this invention includes an on-board high-voltage charging pack connected to the charging port, a positive relay set at the positive terminal of the charging port, and a negative relay set at the negative terminal of the charging port. When the on-board high-voltage charging pack is charged through the charging port, closing the positive relay and the negative relay can make the charging port and the on-board high-voltage battery pack form a circuit, thereby performing the charging action.

[0044] To detect whether the positive and negative relays are stuck together, this invention includes a differential detection circuit, a switching circuit for switching the detection state of the differential detection circuit, and a main control unit for controlling the working state of the switching circuit between the charging port and the vehicle high-voltage charging pack.

[0045] The differential detection circuit can output different voltage signals to the main control unit under different states of the positive and negative relays. The main control unit can determine whether the positive and negative relays are stuck based on the voltage signals. In addition, according to the usage requirements under different conditions, the differential detection circuit of this invention can also have a default state, in which no detection is performed, so that the differential detection circuit is in a dormant state, reducing static current loss.

[0046] The positive relay sticking detection status is determined by the output voltage of the differential detection circuit to determine whether the positive relay has a sticking problem;

[0047] The negative relay sticking detection status is determined by the output voltage of the differential detection circuit to determine whether the negative relay has a sticking problem;

[0048] In differential pressure detection mode, the output voltage of the differential detection circuit is used to determine the voltage difference across the positive or negative relay, thus avoiding the inrush current generated when the relay closes and protecting the controller and motor from damage.

[0049] The switching between its various states is achieved through a switching circuit, which is controlled by the main control unit. That is, the present invention can switch the working state of the differential detection circuit under the control of the main control unit, thereby meeting various detection requirements.

[0050] Please see Figure 1 The differential detection circuit includes: resistors R1A, R2A, R3A, R4A, R5A, R6A, R1B, R2B, R3B, R4B, R5B, R6B, and differential amplifier U1.

[0051] Among them, one end of resistor R3A is connected between the positive relay and the positive terminal of the vehicle high-voltage battery pack, and the other end is connected to ground in series with resistor R4A. One end of resistor R3B is connected between the positive relay and the positive terminal of the vehicle high-voltage battery pack, and the other end is connected to ground in series with resistor R4B. One end of resistor R5A is connected between the positive terminal of the charging port and the positive relay, and the other end is connected to the first input terminal of the switching circuit. One end of resistor R6A is connected between the negative terminal of the charging port and the negative relay, and the other end is connected to the second input terminal of the switching circuit. One end of resistor R1A is connected to the first output terminal of the switching circuit, and the other end... The resistor R2A is connected in series and then grounded. One end of resistor R5B is connected between the positive relay and the positive terminal of the vehicle high-voltage battery pack, and the other end is connected to the third input terminal of the switching circuit. One end of resistor R6B is connected between the negative relay and the negative terminal of the vehicle high-voltage battery pack, and the other end is connected to the fourth input terminal of the switching circuit. One end of resistor R1B is connected to the second output terminal of the switching circuit, and the other end is connected in series with resistor R2B and then grounded. The non-inverting input terminal of differential amplifier U1 is connected between resistors R1B and R2B, the inverting input terminal is connected between resistors R1A and R2A, and the output terminal is connected to the main control unit.

[0052] The switching circuit includes relays RLY1, RLY2A, and RLY2B;

[0053] In this circuit, the first moving end of relay RLY2A is connected to the differential detection circuit as the first input terminal of the switching circuit, the second moving end is connected to the differential detection circuit as the second input terminal of the switching circuit, and the stationary end is connected to the first terminal of relay RLY1. The second terminal of relay RLY1 is connected to the differential detection circuit as the first output terminal of the switching circuit. In this circuit, the first moving end of relay RLY2B is connected to the differential detection circuit as the third input terminal of the switching circuit, the second moving end is connected to the differential detection circuit as the fourth input terminal of the switching circuit, and the stationary end is connected to the differential detection circuit as the second output terminal of the switching circuit.

[0054] Please see Figure 1The vehicle-mounted high-voltage charging pack is called Battery, the positive relay is relay RLY_QC+, and the negative relay is relay RLY_QC-. QC+ serves as the positive terminal of the charging port, and QC- serves as the negative terminal of the charging port. In this invention, by adjusting the conduction states of relays RLY1, RLY2A, and RLY2B, the input voltages of the non-inverting and inverting input terminals of the differential amplifier can be switched, thereby determining whether relays RLY_QC+ and RLY_QC- are stuck together.

[0055] like Figure 3 In this configuration, when relay RLY1 is closed and the stationary terminals of relays RLY2A and RLY2B are connected to their second moving terminals, the inverting input terminal of differential amplifier U1 is powered through resistors R1A and R2A, and is connected to the voltage of the negative terminal of the charging port. The non-inverting input terminal is powered through resistors R1B and R2B, and is connected to the voltage of the negative relay facing the negative terminal of the vehicle's high-voltage battery pack. If the negative relay has a sticking problem, the voltages at both ends of the negative relay will be the same. In this case, by detecting the output voltage of differential amplifier U1, it can be determined whether the negative relay has a sticking problem.

[0056] like Figure 4 In this configuration, when relay RLY1 is closed and the stationary terminals of relays RLY2A and RLY2B are connected to their first moving terminals, the inverting input terminal of differential amplifier U1 is powered through resistors R1A and R2A, and is connected to the voltage of the positive terminal of the charging port. The non-inverting input terminal is powered through resistors R1B and R2B, and is connected to the voltage of the positive relay facing the positive terminal of the vehicle's high-voltage battery pack. If the positive relay is stuck, the voltages across its two terminals will be the same. In this case, by detecting the output voltage of differential amplifier U1, it is possible to determine whether the negative relay is stuck.

[0057] like Figure 5 When relays RY1 and RLY_QC- are closed, and the stationary terminals of relays RLY2A and RLY2B are connected to their first moving terminals, the inverting input terminal of differential amplifier U1 is powered through resistors R1A and R2A, and the voltage connected is the positive voltage of the positive relay facing the charging port. The non-inverting input terminal is powered through resistors R1B and R2B, and the voltage connected is the positive voltage of the positive relay facing the positive side of the vehicle high-voltage battery pack. That is, the voltages connected to the non-inverting and inverting input terminals of differential amplifier U1 are the voltages across the positive relay, respectively. In this case, the voltage difference across the positive relay can be determined by detecting the output voltage of differential amplifier U1.

[0058] In other words, by setting up the differential detection circuit and switching circuit described above, the adhesion and differential pressure detection of the positive and negative relays can be realized in this invention.

[0059] To facilitate the determination of the status of the positive and negative relays, the present invention also includes a bias voltage setting circuit, which consists of resistors R7A and R7B. One end of resistor R7A is connected to the bias power supply, and the other end is connected in series with resistor R7B and then grounded. The voltage between resistors R7A and R7B is used as the bias voltage. The non-inverting input of differential amplifier U1 is connected between resistors R7A and R7B to obtain the bias voltage.

[0060] This configuration allows a bias voltage to be applied to the non-inverting input of the differential amplifier U1. If the positive or negative relay becomes stuck during detection, the voltages obtained by the differential detection circuit from the non-inverting and inverting inputs of the differential amplifier U1 will be the same. Without an additional bias voltage, no voltage output can be detected after passing through the differential amplifier U1. However, this invention, through the bias voltage application circuit, adds an extra bias voltage to the non-inverting input of the differential amplifier U1. Therefore, whether the positive or negative relay has become stuck can be determined by whether the final output voltage of the differential amplifier U1 equals this bias voltage, making the overall detection more intuitive and convenient.

[0061] Furthermore, to more accurately determine the magnitude of the bias voltage, the resistance values ​​of resistor R7A and resistor R7B are set to be the same in this invention. In this case, the magnitude of the bias voltage can be determined as half of the bias power supply, which is easier to determine.

[0062] Since resistors R7A and R7B are in series, according to the series voltage division, the voltage between resistors R7A and R7B should be (VREF*R7B) / (R7A+R7B). In other embodiments of the present invention, the ratio of resistors R7A to R7B can also be adjusted to adjust different bias voltages to the differential amplifier U1.

[0063] The present invention provides a power supply circuit between the differential detection circuit and the main control circuit. The power supply circuit includes an auxiliary source conversion circuit and a voltage conversion circuit. The power supply circuit will only be triggered and supply power to the differential amplifier U1 when it receives a wake-up signal from the main control unit.

[0064] like Figure 1In this circuit, the auxiliary source conversion circuit is the auxiliary source (U3), the voltage conversion circuit is the LDO (U4), and the main control unit is the MCU. The auxiliary source conversion circuit is woken up by the signal S1 sent by the main control unit. After the auxiliary source conversion circuit is woken up, it will control the voltage conversion circuit to work and supply power to the voltage conversion circuit to ensure the normal operation of the differential detection circuit.

[0065] The main control unit is also connected to the battery management system of the vehicle system. The battery management system will issue corresponding control commands according to its own needs, so that the differential detection circuit can work in sleep mode, positive relay sticking detection mode, negative relay sticking detection mode and differential pressure detection mode. The main control unit is also connected to relays RLY1, RLY2A and RLY2B respectively to control the state of relays RLY1, RLY2A and RLY2B.

[0066] like Figure 1 The battery management system (BMS) can issue control command K1 to the main control unit as needed. The main control unit will then issue control signals to each relay according to the control command K1. Signal S2 serves as the RLY1 control signal, used to control the on / off state of relay RLY1. Signal S3 serves as the RLY2 control signal, used to control the connection of the stationary terminals of relays RLY2A and RLY2B to the first or second moving terminals respectively. Signal S4 serves as the RLY_QC- control signal, used to control the on / off state of relay RLY_QC-. Signal S5 serves as the RLY_QC+ control signal, used to control the on / off state of relay RLY_QC-. The main control unit issues different control signals according to the control command K1 issued by the battery management system, which can be used to realize the adhesion of positive or negative relays and differential pressure detection functions.

[0067] Among them, relay RLY1 can be set as a normally open relay. When the main control unit receives the control command K1 issued by the battery management system, the main control unit sends a high-level signal to relay RLY1, thereby closing relay RLY1. Relays RLY2A and RLY2B can be set as normally closed relays, and in the normally closed state, the stationary terminal is connected to the second moving terminal. When the main control unit receives the control command issued by the battery management system, the main control unit sends a high-level signal to relays RLY2A and RLY2B, so that the stationary terminals of relays RLY2A and RLY2B are connected to the first moving terminal, thereby realizing the control of the above detection states.

[0068] Please see Figure 2 When relay RLY1 is disconnected, the main control unit controls the power supply circuit to be in sleep mode, and the differential detection circuit operates in the default state.

[0069] In this state, the main control unit does not receive the control command K1 issued by the battery management system. Signals S2, S3, S4, and S5 issued by the main control unit are all at a low level. At this time, relays RLY1, RLY_QC-, and RLY_QC+ are disconnected, and relays RLY2A and RLY2B are in the default state. The main control unit controls the auxiliary source conversion circuit to go into sleep mode through the S1 signal. At this time, the voltage conversion circuit stops supplying power, and the entire detection system is in sleep mode to minimize the static current loss of the system.

[0070] Please see Figure 3 When relay RLY1 is closed, and the stationary terminal of relay RLY2A is connected to its second moving terminal, and the stationary terminal of relay RLY2B is connected to its second moving terminal, the main control unit controls the power supply circuit to be in the wake-up state, and the differential detection circuit operates in the negative relay sticking detection state.

[0071] In this state, the main control unit receives the control command K1 from the vehicle's battery management system to detect the RLY_QC-adhesion relay. The main control unit first wakes up the auxiliary power conversion circuit through the S1 signal, thereby enabling the voltage conversion circuit to start supplying power. At the same time, it closes the relay RLY1 through the signals S2 and S3. The stationary terminals of the relays RLY2A and RLY2B are connected to their second moving terminals, and the system enters the relay RLY_QC-adhesion detection state.

[0072] If relay RLY_QC- is in a stuck state, the impedance of relay RLY_QC- is very small. At this time, relay RLY_QC- is approximately short-circuited, and the voltages across relay RLY_QC- are the same. The voltage obtained by the non-inverting input of differential amplifier U1 from resistors R1A and R2A is equal to the voltage obtained by its inverting input from resistors R1B and R2B. Since a bias voltage is also connected to the non-inverting input of differential amplifier U1, the bias power supply in this invention is 5V, and the resistances of resistors R7A and R7B are the same, with a bias voltage of 2.5V. Therefore, in the stuck state of relay RLY_QC-, differential amplifier U1 will output a voltage of 2.5V, which is the bias given voltage.

[0073] Conversely, when relay RLY_QC- is in a non-adhesive state, the impedance of relay RLY_QC- is very large. At this time, relay RLY_QC- is approximately open-circuit. The voltage obtained by the inverting input terminal of differential amplifier U1 through resistors R1A and R2A has a certain difference from the voltage obtained by the non-inverting input terminal through resistors R1B and R2B. At this time, the output voltage of the differential amplifier circuit is equal to the bias given voltage plus the differential amplification voltage. Therefore, in this case, the output voltage of the differential amplifier will be higher than the bias voltage by 2.5V.

[0074] In the negative relay sticking detection state, if the voltage of the output signal of the differential amplifier U1 is equal to the bias given voltage, it is determined that the relay RLY_QC-sticking; if the voltage of the output signal of the differential amplifier U1 is greater than the bias given voltage, it is determined that the relay RLY_QC-not sticking.

[0075] Please see Figure 6 The on-board high-voltage charging pack is typically 250V, 300V, and 500V. When the relay RLY_QC- is in a stuck state, the voltage of the output signal of the differential amplifier U1 is the bias voltage of 2.5V. When the relay RLY_QC- is in a non-sticky state, the voltage of the output signal of the differential amplifier U1 is much greater than the bias voltage of 2.5V. The results show that the voltage of the on-board high-voltage charging pack does not affect the sticking detection of the relay RLY_QC-.

[0076] Please see Figure 4 When relay RLY1 is closed, and the stationary terminal of relay RLY2A is connected to its first moving terminal, and the stationary terminal of relay RLY2B is connected to its first moving terminal, the main control unit controls the power supply circuit to be in the wake-up state, and the differential detection circuit operates in the positive relay sticking detection state.

[0077] In this state, the main control unit receives the control command K1 from the vehicle's battery management system to detect the RLY_QC+ sticking of the relay. The main control unit first wakes up the auxiliary power conversion circuit through the S1 signal, thereby enabling the voltage conversion circuit to start supplying power. At the same time, it closes the relay RLY1 through the signals S2 and S3. The stationary terminals of the relays RLY2A and RLY2B are connected to their first moving terminals, and the system enters the relay RLY_QC+ sticking detection state.

[0078] If relay RLY_QC+ is in a stuck state, the impedance of relay RLY_QC+ is very small. At this time, relay RLY_QC+ is approximately short-circuited, and the voltages across relay RLY_QC+ are the same. The voltage obtained by the non-inverting input of differential amplifier U1 from resistors R1A and R2A is equal to the voltage obtained by its inverting input from resistors R1B and R2B. Since the non-inverting input of differential amplifier U1 is also connected to an additional bias voltage, the bias power supply in this invention is 5V, and the resistances of resistors R7A and R7B are the same, the bias voltage is 2.5V. Therefore, in the stuck state of relay RLY_QC+, the differential amplifier will output a voltage of 2.5V, which is the bias given voltage.

[0079] Conversely, when the relay RLY_QC+ is in a non-adhesive state, the impedance of the relay RLY_QC+ is very large. At this time, the relay RLY_QC+ is approximately open-circuit. The voltage obtained by the inverting input terminal of the differential amplifier U1 through resistors R1A and R2A has a certain difference from the voltage obtained by the non-inverting input terminal through resistors R1B and R2B. At this time, the output voltage of the differential amplifier circuit is equal to the bias given voltage minus the differential amplifier voltage. Therefore, in this case, the output voltage of the differential amplifier U1 will be lower than the bias voltage of 2.5V.

[0080] In the positive relay sticking detection state, if the voltage of the output signal of the differential amplifier U1 is equal to the bias given voltage, it is determined that the relay RLY_QC+ is sticking; if the voltage of the output signal of the differential amplifier U1 is less than the bias given voltage, it is determined that the relay RLY_QC+ is not sticking.

[0081] Please see Figure 7 The on-board high-voltage charging pack is typically 250V, 300V, and 500V. When the relay RLY_QC+ is in a stuck state, the voltage of the output signal of the differential amplifier U1 is the bias voltage of 2.5V. When the relay RLY_QC+ is in a non-sticky state, the voltage of the output signal of the differential amplifier U1 is much smaller than the bias voltage of 2.5V. The results show that the voltage of the on-board high-voltage charging pack does not affect the sticking detection of the relay RLY_QC+.

[0082] Please see Figure 5 When relays RLY1 and RLY_QC- are closed, relay RLY_QC+ is open, and the stationary terminal of relay RLY2A is connected to its first moving terminal, and the stationary terminal of relay RLY2B is connected to its first moving terminal, the main control unit controls the power supply circuit to be in the wake-up state, and the differential detection circuit operates in the differential pressure detection state.

[0083] In this state, the entire circuit forms two power supply loops. The non-inverting input of differential amplifier U1 obtains the voltage of the positive terminal of the vehicle high-voltage charging pack through resistors R1B and R2B, and the inverting input obtains the voltage of the positive terminal of the vehicle high-voltage charging pack through resistors R1A and R2A. Therefore, the voltage of the output signal of differential amplifier U1 in this case can represent the voltage difference between the charging port and the vehicle high-voltage battery pack, that is, the voltage difference across relay RLY_QC+. Since the non-inverting input of differential amplifier U1 is connected to a bias voltage, the difference between the voltage of the output signal of differential amplifier U1 and the bias voltage, after a certain numerical conversion, becomes the voltage difference between the charging port and the vehicle high-voltage battery pack.

[0084] Please see Figure 8When there is a certain voltage difference between the charging port and the vehicle's high-voltage battery pack, the output voltage of the differential amplifier changes linearly, and the voltage signal read by the main control unit also changes. Therefore, by reading the real-time voltage sampling signal, the voltage difference across the relay can be determined. By setting a certain judgment range and setting the relay closing conditions according to different relay parameters, the inrush current generated at the moment of relay closing can be effectively reduced.

[0085] In this invention, based on the specifications of the relay, when the voltage difference across the relay is greater than 5V, a voltage difference fault is reported and the relay RLY_QC+ is not closed; when the voltage difference across the relay RLY_QC+ is less than 5V, the relay RLY_QC+ is closed normally.

[0086] Since the inrush current is emitted through the positive terminal of the charging port, the differential pressure is determined by closing the relay RLY_QC-. If the inrush current is not considered, the differential pressure across the relay RLY_QC- can also be obtained by closing the relays RLY_QC+ and RLY1, and connecting the stationary terminals of the relays RLY2A and RLY2B to the second moving terminal. The working principle is the same as that of obtaining the differential pressure across the relay RLY_QC+, so it will not be described again.

[0087] Please see Figure 9 The overall control process of this invention is mainly divided into four stages: triggering stage, control and adhesion detection stage, differential pressure detection stage, and status reporting stage.

[0088] Triggering phase: Used to judge the control command of the relay and determine whether to enter the adhesion detection state;

[0089] Control and adhesion detection stage: Based on the control command of the relay, the corresponding adhesion detection judgment is performed. If the received command is the closing command of the relay, the adhesion state detection is directly entered; if the received command is the opening command of the relay, the relay is opened first and then the adhesion state detection of the relay is performed.

[0090] Differential pressure detection stage: After the relay needs to be closed and the adhesion test has been completed without fault, differential pressure detection is performed. The decision on whether to close the relay RLY_QC+ is based on the status of the differential pressure detection.

[0091] Status reporting phase: Report the relay status (open, closed, fault) based on the requested status and the detected status, and report the relay status (open, closed) based on the control status.

[0092] Compared with the prior art, the present invention has at least the following beneficial effects:

[0093] 1. The present invention uses a Wheatstone bridge circuit consisting of a set of associated action relays, related sampling resistors and operational amplifiers, which increases the circuit detection accuracy and efficiency, and can identify and judge even small voltage difference changes.

[0094] 2. When relay adhesion and differential pressure detection are not performed, the present invention is in a default non-detection state. At this time, the differential pressure detection circuit is in a dormant state, which can effectively reduce the static current loss of new energy vehicles.

[0095] 3. When performing relay adhesion and differential pressure detection, this invention is not affected by the residual voltage of the charging pile or the voltage on the vehicle's high-voltage charging pack. It can effectively avoid the influence of external voltage on the relay status judgment and can effectively identify the relay status under various voltage adjustments, effectively protecting the relay motor from damage.

[0096] 4. The differential pressure detection circuit of the present invention uses a set of associated action relays. When one relay fails, it will not affect the judgment of the other relay. The state judgments of the two relays are independent of each other and are not affected.

[0097] 5. This invention detects the voltage difference across the relay before closing the relay. When the voltage difference across the relay is lower than a certain threshold, the high-voltage relay is closed. This can effectively reduce the inrush current generated at the moment the high-voltage relay closes, protecting the controller and motor from damage.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A sticking and differential pressure detection circuit of a relay, comprising a vehicle-mounted high-voltage charging pack connected with a charging port, a positive relay provided at a positive electrode of the charging port, and a negative relay provided at a negative electrode of the charging port, characterized in that, It also includes a differential detection circuit disposed between the charging port and the vehicle high-voltage charging pack, a switching circuit for switching the detection state of the differential detection circuit, and a main control unit for controlling the working state of the switching circuit. The main control unit is connected to the output terminal of the differential detection circuit and can determine the state of the positive relay and the negative relay based on the output signal of the differential detection circuit. The switching circuit includes relays RLY1, RLY2A, and RLY2B; The first moving terminal of relay RLY2A is connected to the differential detection circuit as the first input terminal of the switching circuit, the second moving terminal is connected to the differential detection circuit as the second input terminal of the switching circuit, and the stationary terminal is connected to the first terminal of relay RLY1. The second terminal of relay RLY1 is connected to the differential detection circuit as the first output terminal of the switching circuit. The first moving terminal of relay RLY2B is connected to the differential detection circuit as the third input terminal of the switching circuit, the second moving terminal is connected to the differential detection circuit as the fourth input terminal of the switching circuit, and the stationary terminal is connected to the differential detection circuit as the second output terminal of the switching circuit. When the relay RLY1 is disconnected, the main control unit controls the power supply circuit to be in a sleep state, and the differential detection circuit operates in the default state; When relay RLY1 is closed, and the stationary terminal of relay RLY2A is connected to its first moving terminal, and the stationary terminal of relay RLY2B is connected to its first moving terminal, the main control unit controls the power supply circuit to be in a wake-up state, and the differential detection circuit operates in a positive relay sticking detection state. When relay RLY1 is closed, and the stationary terminal of relay RLY2A is connected to its second moving terminal, and the stationary terminal of relay RLY2B is connected to its second moving terminal, the main control unit controls the power supply circuit to be in a wake-up state, and the differential detection circuit operates in a negative relay adhesion detection state. When the relay RLY1 and the negative relay are closed, the positive relay is open, and the stationary terminal of the relay RLY2A is connected to its first moving terminal, and the stationary terminal of the relay RLY2B is connected to its first moving terminal, the main control unit controls the power supply circuit to be in the wake-up state, and the differential detection circuit operates in the differential pressure detection state.

2. The stick and differential pressure detection circuit of claim 1, wherein, The differential detection circuit includes: resistors R1A, R2A, R3A, R4A, R5A, R6A, R1B, R2B, R3B, R4B, R5B, R6B, and differential amplifier U1. One end of resistor R3A is connected between the positive relay and the positive terminal of the vehicle high-voltage battery pack, and the other end is connected in series with resistor R4A and then grounded. One end of resistor R3B is connected between the positive relay and the positive terminal of the vehicle high-voltage battery pack, and the other end is connected in series with resistor R4B and then grounded. One end of resistor R5A is connected between the positive terminal of the charging port and the positive relay, and the other end is connected to the first input terminal of the switching circuit. One end of resistor R6A is connected between the negative terminal of the charging port and the negative relay, and the other end is connected to the second input terminal of the switching circuit. One end of resistor R1A is connected to the first output terminal of the switching circuit, and the other end is connected in series with... Resistor R2A is grounded. One end of resistor R5B is connected between the positive relay and the positive terminal of the vehicle high-voltage battery pack, and the other end is connected to the third input terminal of the switching circuit. One end of resistor R6B is connected between the negative relay and the negative terminal of the vehicle high-voltage battery pack, and the other end is connected to the fourth input terminal of the switching circuit. One end of resistor R1B is connected to the second output terminal of the switching circuit, and the other end is connected to ground after being connected in series with resistor R2B. The non-inverting input terminal of the differential amplifier U1 is connected between resistors R1B and R2B, the inverting input terminal is connected between resistors R1A and R2A, and the output terminal is connected to the main control unit.

3. The stick and differential pressure detection circuit of claim 2, wherein, It also includes a bias voltage setting circuit connected to the differential detection circuit, the bias voltage setting circuit including resistor R7A and resistor R7B; One end of resistor R7A is connected to a bias power supply, and the other end is connected in series with resistor R7B and then grounded. The voltage between resistor R7A and resistor R7B is used as the bias voltage. The non-inverting input terminal of differential amplifier U1 is also connected between resistor R7A and resistor R7B to obtain the bias voltage.

4. The adhesion and differential pressure detection circuit according to claim 3, characterized in that, The resistor R7A has the same resistance value as the resistor R7B.

5. The adhesion and differential pressure detection circuit according to claim 1, characterized in that, It also includes a power supply circuit connected to the differential detection circuit and the main control unit. The power supply circuit includes an auxiliary source conversion circuit and a voltage conversion circuit. When the power supply circuit receives a wake-up signal from the main control unit, it supplies power to the differential amplifier U1 in the differential detection circuit.

6. The adhesion and differential pressure detection circuit according to claim 2, characterized in that, The main control unit is also connected to the battery management system of the vehicle system, and can adjust the conduction state of the positive relay, the negative relay, and the switching circuit according to the control commands issued by the battery management system.

7. The adhesion and differential pressure detection circuit according to claim 6, characterized in that, When the differential detection circuit operates in the positive relay sticking detection state, and the voltage of the output signal of the differential detection circuit is equal to the bias given voltage, the positive relay is sticking. When the differential detection circuit operates in the negative relay sticking detection state, and the voltage of the output signal of the differential detection circuit is equal to the bias given voltage, the negative relay is sticking. When the differential detection circuit operates in differential pressure detection mode, the difference between the voltage of the output signal of the differential detection circuit and the bias given voltage is converted into the differential pressure between the charging port and the vehicle high-voltage battery pack.

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