WO2024041059A1

WO2024041059A1 - Adhesion detection and voltage difference measurement circuit for relay

Info

Publication number: WO2024041059A1
Application number: PCT/CN2023/096128
Authority: WO
Inventors: 冯颖盈; 姚顺; 刘骥; 高春华
Original assignee: 深圳威迈斯新能源股份有限公司
Priority date: 2022-08-25
Filing date: 2023-05-24
Publication date: 2024-02-29
Also published as: CN115308591A

Abstract

An adhesion detection and voltage difference measurement circuit for a relay. The circuit comprises a vehicle-mounted high-voltage charging pack connected to a charging port, a positive electrode relay arranged at a positive electrode of the charging port, and a negative electrode relay arranged at a negative electrode of the charging port. The circuit further comprises a differential measurement circuit arranged between the charging port and the vehicle-mounted high-voltage charging pack, a switching circuit for switching a measurement state of the differential measurement circuit, and a main control unit for controlling the working state of the switching circuit, wherein the main control unit is connected to an output end of the differential measurement circuit, and can determine the state of the positive electrode relay and the state of the negative electrode relay according to an output signal of the differential measurement circuit. The circuit can effectively identify the adhesion state of the relay, and relay adhesion detection is not affected by an external voltage, such that the state of the relay can be effectively determined.

Description

A relay adhesion and pressure difference detection circuit

Technical field

The invention relates to the field of new energy vehicle relays, in particular to a relay adhesion and pressure difference detection circuit.

Background technique

New energy vehicles have incomparable advantages such as low energy consumption and light pollution that traditional fuel vehicles cannot match, and can improve problems such as energy shortage and environmental pollution. Since the "Tenth Five-Year Plan", the Chinese government has attached great importance to the research and development of the new energy vehicle industry, and as China As a strategic emerging industry and a key area of "Made in China 2025", new energy vehicles have achieved outstanding results in recent years under the leadership of the government's strong and sustained support. With the rapid development and popularization of new energy vehicles, the safety requirements for the charging and swapping process and the entire vehicle are getting higher and higher, becoming more comprehensive and systematic;

The main function of relays on new energy vehicles is to control the closing or disconnection 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 breaking, the relay Adhesion is prone to occur, and the existing relay adhesion detection technology and methods have complex circuits, low detection efficiency, poor accuracy, and are prone to false detection due to the influence of external voltages. As a result, high-voltage relay adhesion cannot be identified or faults are falsely reported, resulting in New energy vehicles cannot be charged or their components are damaged.

Therefore, how to design a relay adhesion and voltage difference detection circuit that can solve the shortcomings of the existing technology is an urgent technical problem that needs to be solved in the industry.

Contents of the invention

In order to solve the problems of low detection efficiency and poor accuracy of relay adhesion detection technology in the prior art, the present invention proposes a relay adhesion and pressure difference detection circuit.

The technical solution of the present invention is to propose a relay adhesion and pressure difference detection circuit, which includes a vehicle-mounted high-voltage charging pack connected to a charging port, a positive relay located at the positive electrode of the charging port, and a positive relay located at the positive electrode of the charging port. The negative relay at the negative pole also includes a differential detection circuit provided between the charging port and the vehicle-mounted high-voltage charging pack, a switching circuit that switches the detection state of the differential detection circuit, and a circuit that controls the working state of the switching circuit. A main control unit, the main control unit is connected to the output end of the differential detection circuit, and can determine the status of the positive relay and the negative relay according to the output signal of the differential detection circuit.

Further, the differential detection circuit includes: resistor R1A, resistor R2A, resistor R3A, resistor R4A, resistor R5A, resistor R6A, resistor R1B, resistor R2B, resistor R3B, resistor R4B, resistor R5B, resistor R6B, and differential amplifier U1;

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

Further, it also includes a bias voltage given circuit connected to the differential detection circuit, the bias voltage given circuit includes a resistor R7A and a resistor R7B;

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

Further, the resistance value of the resistor R7A and the resistor R7B is the same.

Further, the switching circuit includes relay RLY1, relay RLY2A, and relay RLY2B;

The first moving end of the relay RLY2A serves as the first input end of the switching circuit and the differential

The detection circuit is connected, and the second moving end is connected to the differential detection circuit as the second input end of the switching circuit. The fixed end is connected to the first end of the relay RLY1, and the second end of the relay RLY1 is used as the second input end of the switching circuit. The first output end of the switching circuit is connected to the differential detection circuit, the first moving end of the relay RLY2B serves as the third input end of the switching circuit and is connected to the differential detection circuit, and the second moving end serves as the The fourth input terminal of the switching circuit is connected to the differential detection circuit, and the fixed terminal serves as the second output terminal of the switching circuit and is connected to the differential detection circuit.

Further, 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. The power supply circuit receives a wake-up signal from the main control unit. When receiving a signal, power is supplied to the differential amplifier U1 in the differential detection circuit.

Further, 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 instructions issued by the battery management system.

Further, 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 works in a default state;

When the relay RLY1 is closed, the fixed end of the relay RLY2A is connected to its first moving end, and the fixed end of the relay RLY2B is connected to its first moving end, the main control unit controls the power supply. The circuit is in a wake-up state, and the differential detection circuit works in the positive relay adhesion detection state;

When the relay RLY1 is closed, the fixed end of the relay RLY2A is connected to its second moving end, and the fixed end of the relay RLY2B is connected to its second moving end, the main control unit controls the power supply. The circuit is in the wake-up state, and the differential detection circuit works in the negative relay adhesion detection state.

Further, when the relay RLY1 and the negative relay are closed, the positive relay is disconnected, and the non-moving end of the relay RLY2A is connected to its first moving end, and the non-moving end of the relay RLY2B is connected to its first moving end. , the main control unit controls the power supply circuit to be in a wake-up state, and the differential detection circuit works in a voltage difference detection state.

Further, 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 sticks;

When the differential detection circuit works in the negative relay adhesion detection state, and the differential detection circuit

When the voltage of the output signal is equal to the bias given voltage, the negative relay sticks;

When the differential detection circuit works in the voltage difference detection state, the difference between the voltage of the output signal of the differential detection circuit and the bias given voltage, through a certain numerical conversion, is the difference between the charging port and the The voltage difference between vehicle high-voltage battery packs.

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

The invention adopts a set of associated action relays, associated sampling resistors and operational amplifiers to form a Wheatstone bridge circuit form, which increases circuit detection accuracy and efficiency, and small voltage difference changes can also be identified and judged;

When the invention does not perform relay adhesion and pressure difference detection, it is in a default non-detection state. At this time, the pressure difference detection circuit is in a dormant state, which can effectively reduce the static current loss of new energy vehicles;

When detecting the adhesion and pressure difference of the relay, the present invention will not be affected by the residual voltage of the charging pile or the voltage on the vehicle-mounted high-voltage charging pack. It can effectively avoid the influence of external voltage on the judgment of the relay status, and can operate under various voltage adjustments. It can effectively identify the status of the relay and effectively protect the relay and motor from damage;

The pressure difference 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 status judgment of the two relays is independent of each other and will not be affected;

The invention detects the voltage difference at both ends of the relay before the relay is closed. When the voltage difference at both ends of the relay is lower than a certain threshold, the high-voltage relay is closed again, which can effectively reduce the impact current generated at the moment the high-voltage relay is closed and protect the controller and motor from damage.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings in the following description are only illustrative of the present invention. For some embodiments, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is a working principle diagram of the present invention;

Figure 2 is a connection schematic diagram of the present invention working in a default state;

Figure 3 is a schematic connection diagram of the present invention working in the negative relay adhesion detection state;

Figure 4 is a schematic connection diagram of the present invention working in the positive relay adhesion detection state;

Figure 5 is a schematic connection diagram of the present invention working in a pressure difference detection state;

Figure 6 shows the output results of the present invention when simulating different impedances of the negative relay;

Figure 7 shows the output results of the present invention when simulating different impedances of the positive relay;

Figure 8 shows the output results when the pressure difference between the simulated charging port and the vehicle high-voltage battery of the present invention is different;

Figure 9 is an overall control flow chart of the present invention.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention.

Thus, a feature noted in this specification is intended to illustrate one of the features of an embodiment of the invention, but does not imply that every embodiment of the invention must have the illustrated feature. Furthermore, it should be noted that this specification describes many features. Although certain features may be combined together to illustrate possible system designs, the features may also be used in other, not expressly illustrated, combinations. Thus, unless otherwise stated, the illustrated combinations are not intended to be limiting.

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

The existing relay adhesion detection technology has problems such as complex circuits, low detection efficiency, poor accuracy, and susceptibility to misdetection due to the influence of external voltages, resulting in unrecognized relay adhesion or false alarms, resulting in new energy vehicles being unable to charge or device damage. . The idea of the present invention is to design a relay adhesion and voltage difference detection circuit, using a set of associated action relays, associated sampling circuits and operational amplifiers to form a Wheatstone bridge circuit, thereby increasing circuit detection accuracy and efficiency and reducing false detections. problems occur.

The relay adhesion and pressure difference detection circuit proposed by the present invention includes a vehicle-mounted high-voltage charging pack connected to the charging port, a positive relay arranged at the positive electrode of the charging port, and a negative relay arranged at the negative electrode of the charging port. After charging, When the port charges the vehicle-mounted high-voltage charging pack, closing the positive relay and the negative relay can form a circuit between the charging port and the vehicle-mounted high-voltage battery pack, and then the charging action can be performed.

In order to detect whether the positive relay and the negative relay are stuck, the present invention is provided with a differential detection circuit between the charging port and the vehicle-mounted high-voltage charging pack, a switching circuit that switches the detection status of the differential detection circuit, and a main control unit that controls the working status of the switching circuit. .

Among them, the differential detection circuit can output different voltage signals to the main control unit under different states of the positive relay and the negative relay. The main control unit can determine whether the positive relay and the negative relay are stuck based on the voltage signal. In addition, according to the usage requirements in different situations, the differential detection circuit of the present invention can have a default state and no detection is performed, so that the differential detection circuit is in a dormant state and reduces static current loss;

Positive relay adhesion detection status, through the output voltage of the differential detection circuit, determine whether the positive relay has adhesion problems;

Negative relay adhesion detection status, through the output voltage of the differential detection circuit, determine whether the negative relay has adhesion problems;

Pressure difference detection status, through the output voltage of the differential detection circuit, determines the voltage difference between the two ends of the positive relay or negative relay, avoiding the inrush current generated at the moment when the relay is closed, and protecting the controller and motor from damage.

Switching between various states is realized 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.

Please refer to Figure 1. The differential detection circuit includes: resistor R1A, resistor R2A, resistor R3A, resistor R4A, resistor R5A, resistor R6A, resistor R1B, resistor R2B, resistor R3B, resistor R4B, resistor R5B, resistor R6B, differential amplifier U1;

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

The switching circuit includes relay RLY1, relay RLY2A, and relay RLY2B;

Among them, the first moving end of relay RLY2A serves as the first input end of the switching circuit and the differential detection circuit.

The second moving end is connected to the differential detection circuit as the second input end of the switching circuit, the fixed end is connected to the first end of the relay RLY1, and the second end of the relay RLY1 is used as the first output end of the switching circuit and is connected to the differential detection circuit. Circuit connection, 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 non-moving end is used as the third input end of the switching circuit. The two output terminals are connected to the differential detection circuit.

Please refer to Figure 1. The vehicle-mounted high-voltage charging pack is Battery, the positive relay is relay RLY_QC+, and the negative relay is relay RLY_QC-. QC+ serves as the positive pole of the charging port, and QC- serves as the negative pole of the charging port. In the present invention, by adjusting relay RLY1 and relay The conduction state of RLY2A and relay RLY2B can switch the access voltage of the non-inverting input terminal and the inverting input terminal of the differential amplifier, and then be used to determine whether the relay RLY_QC+ and relay RLY_QC- have sticking problems.

As shown in Figure 3, when relay RLY1 is closed and the non-moving terminals of relay RLY2A and relay RLY2B are connected to their second moving terminals, the inverting input terminal of differential amplifier U1 takes power through resistor R1A and resistor R2A, and is connected to the charging terminal. The voltage of the negative terminal of the port, the non-inverting input terminal takes power through the resistor R1B and the resistor R2B, and is connected to the voltage on the negative side of the negative relay facing the vehicle-mounted high-voltage battery pack. If the negative relay has an adhesion problem, the voltages at both ends of the negative relay are the same. In this case, by detecting the output voltage of the differential amplifier U1, it can be determined whether the negative relay has a sticking problem;

As shown in Figure 4, when relay RLY1 is closed and the non-moving terminals of relay RLY2A and relay RLY2B are connected to their first moving terminals, the inverting input terminal of differential amplifier U1 takes power through resistor R1A and resistor R2A, and is connected to the charging terminal. The voltage of the positive terminal of the port, the non-phase input terminal takes power through the resistor R1B and the resistor R2B, and is connected to the voltage on the positive side of the positive relay towards the positive side of the vehicle high-voltage battery pack. If the positive relay has an adhesion problem, the voltages at both ends of the positive relay are the same. In this case, by detecting the output voltage of the differential amplifier U1, it can be determined whether the negative relay has a sticking problem.

As shown in Figure 5, when relay RY1, relay RLY_QC- are closed, and the non-moving terminals of relay RLY2A and relay RLY2B are connected to their first moving terminals, the inverting input terminal of differential amplifier U1 takes power through resistor R1A and resistor R2A. What is input is the voltage from the positive relay toward the positive side of the charging port. The non-inverting input terminal takes power through resistor R1B and resistor R2B. What is connected is the voltage from the positive relay toward the positive side of the vehicle high-voltage battery pack, that is, the non-inverting input terminal of differential amplifier U1. and the input voltage of the inverting input terminal are respectively the voltages across the positive relay. In this case, by detecting the output voltage of the differential amplifier U1, the voltage difference across the positive relay can be determined.

That is, in the present invention, through the arrangement of the above-mentioned differential detection circuit and switching circuit, the adhesion and pressure difference detection of the positive relay and the negative relay can be realized.

In order to facilitate the judgment of the status of the positive relay and the negative relay, the present invention is also provided with a bias voltage given circuit, which is composed of a resistor R7A and a resistor R7B. One end of the resistor R7A is connected to the bias power supply, and the other end is connected in series with the resistor R7B and then connected to ground. The voltage between the resistor R7A and the resistor R7B serves as the bias voltage, and the non-inverting input end of the differential amplifier U1 is connected between the resistor R7A and the resistor R7B to obtain the bias voltage.

Through this setting method, a bias voltage can be given to the non-inverting input terminal of the differential amplifier U1. If the positive relay or the negative relay has a sticking problem during detection, in this case, the non-inverting input terminal and the inverting input terminal of the differential amplifier U1 pass through the differential The voltage obtained by the detection circuit is the same. If a bias voltage is not added, the voltage output will not be detected after passing through the differential amplifier U1. In the present invention, by setting the bias voltage given circuit, an additional bias voltage will be added to the non-inverting input end of the differential amplifier U1. That is, the positive pole can be determined based on whether the final output voltage of the differential amplifier U1 is equal to the bias voltage. Whether there is adhesion problem in the relay or negative relay, the overall inspection is more intuitive and convenient.

Furthermore, in order to determine the magnitude of the bias voltage more accurately, in the present invention, the resistance value of the resistor R7A is set to be the same as the resistance value of the resistor R7B. In this case, the magnitude of the bias voltage can be determined as half of the bias power supply. , easier to determine.

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

The present invention is provided with 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 trigger and activate the wake-up signal from the main control unit when it receives the wake-up signal from the main control unit. Provide power to differential amplifier U1.

As shown in Figure 1, 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. Its auxiliary source conversion circuit is awakened by the signal S1 sent by the main control unit. After the circuit is awakened, it will control the operation of the voltage conversion circuit and provide power to the voltage conversion circuit to ensure the normal operation of the differential detection circuit.

Among them, the main control unit is also connected to the battery management system of the vehicle system. The battery management system will issue corresponding control instructions according to its own needs, so that the differential detection circuit works in sleep mode, positive relay adhesion detection mode, negative relay adhesion detection mode, And in the differential pressure detection mode, its main control unit is also connected to relay RLY1, relay RLY2A, and relay RLY2B respectively to control the status of relay RLY1, relay RLY2A, and relay RLY2B.

As shown in Figure 1, the battery management system is BMS, which can issue control instructions K1 to the main control unit according to needs. The main control unit will issue control signals for each relay according to the control instructions K1. Its signal S2 is used as the RLY1 control signal for control The on-off state of relay RLY1, signal S3 is used as the RLY2 control signal, used to control the fixed end of relay RLY2A and relay RLY2B respectively, connected to the first moving end or the second moving end, and signal S4 is used as the RLY_QC- control signal, used to control The on-off state of relay RLY_QC-, signal S5 is used as the RLY_QC+ control signal, used to control the on-off state of relay RLY_QC-. The main control unit sends different control signals according to the control command K1 issued by the battery management system, which can be used to achieve Positive relay or negative relay adhesion and pressure difference detection function.

Among them, relay RLY1 can be set as a normally open relay. When the main control unit receives the control command K1 from the battery management system, the main control unit sends a high level signal to relay RLY1, and then closes relay RLY1, relay RLY2A and relay RLY2B. It can be set as a normally closed relay, and the fixed end is connected to the second moving end in the normally closed state. When the main control unit receives the control command from the battery management system, the main control unit sends a high level to relay RLY2A and relay RLY2B. The signal connects the non-moving ends of the relays RLY2A and RLY2B to the first moving end, thereby realizing the control of each of the above detection states.

Please refer to Figure 2. When relay RLY1 is disconnected, the main control unit controls the power supply circuit to be in a dormant state, and the differential detection circuit works in the default state.

In this state, the main control unit has not received the control command K1 from the battery management system, and the signals S2, S3, S4, and S5 sent by the main control unit are all in a low level state. At this time, the relays RLY1 and RLY_QC- , relay RLY_QC+ is disconnected, relay RLY2A and relay RLY2B are in the default state, and the main control unit controls the auxiliary source conversion circuit to sleep through the S1 signal. At this time, the voltage conversion circuit stops supplying power, and the entire detection system is in a sleep state, minimizing the system's Quiescent current loss;

Please refer to Figure 3. When relay RLY1 is closed, and the non-moving end of relay RLY2A is connected to its second moving end, and the non-moving end of relay RLY2B is connected to its second moving end, the main control unit controls the power supply circuit to be in a wake-up state. And the differential detection circuit works in the negative relay adhesion detection state.

In this state, the main control unit receives the control command K1 sent by the vehicle's battery management system to detect relay RLY_QC-adhesion. The main control unit first wakes up the auxiliary source conversion circuit through the S1 signal, so that the voltage conversion circuit starts to supply power. At the same time, it Signal S2 and signal S3 make relay RLY1 in the closed state, the non-moving ends of relay RLY2A and relay RLY2B are connected to their second moving ends, and the system enters the relay RLY_QC-adhesion detection state.

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 in a short-circuit state. The voltages at both ends of relay RLY_QC- are the same. The non-inverting input terminal of differential amplifier U1 is obtained between resistor R1A and resistor R2A. The voltage of is equal to the voltage obtained by its inverting input terminal from the resistor R1B and the resistor R2B. Since the non-inverting input terminal of the differential amplifier U1 is additionally connected to a bias voltage, the bias power supply in the present invention is 5V, and the resistor R7A and the resistor R7B are The values are the same and the bias voltage is 2.5V. Therefore, when the relay RLY_QC is stuck, the differential amplifier U1 will output a voltage of 2.5V, which is the bias given voltage;

On the contrary, when the relay RLY_QC- is in the non-sticking state, the impedance of the relay RLY_QC- is very large. At this time, the relay RLY_QC- is approximately in an open circuit state. The voltage obtained by the inverting input terminal of the differential amplifier U1 through the resistor R1A and the resistor R2A passes through the non-inverting input terminal. There is a certain difference in the voltage obtained by resistor R1B and resistor 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 2.5 higher than the bias voltage. V.

That is, 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- is stuck. 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-is not adhered.

Please refer to Figure 6. The vehicle high-voltage charging package is typically 250V, 300V, 500V. When the relay RLY_QC- is in the adhesion state, the voltage of the output signal of the differential amplifier U1 is the bias voltage 2.5V. When the relay RLY_QC- is in the non-adhesion state state, the voltage of the output signal of the differential amplifier U1 is much greater than the bias voltage 2.5V. From the results, it can be seen that the voltage of the vehicle high-voltage charging pack will not affect the adhesion detection of the relay RLY_QC-.

Please refer to Figure 4. When relay RLY1 is closed, and the non-moving end of relay RLY2A is connected to its first moving end, and when the non-moving end of relay RLY2B is connected to its first moving end, the main control unit controls the power supply circuit to be in a wake-up state. And the differential detection circuit works in the positive relay adhesion detection state;

In this state, the main control unit receives the control command K1 for detecting relay RLY_QC+ adhesion from the battery management system of the vehicle. The main control unit first wakes up the auxiliary source conversion circuit through the S1 signal, so that the voltage conversion circuit starts to supply power, and at the same time passes the signal S2 and signal S3 make relay RLY1 in the closed state, the non-moving ends of relay RLY2A and relay RLY2B are connected to their first moving ends, and the system enters the relay RLY_QC+ adhesion detection state.

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 in a short-circuit state. The voltages at both ends of relay RLY_QC+ are the same. The voltage obtained by the non-inverting input terminal of differential amplifier U1 from between resistor R1A and resistor R2A is equal to its inverse. The phase input terminal obtains the voltage from the resistor R1B and the resistor R2B. Since the non-inverting input terminal of the differential amplifier U1 is additionally connected to a bias voltage, the bias power supply in the present invention is 5V. The resistor R7A and the resistor R7B have the same resistance. The voltage is 2.5V, so when the relay RLY_QC is stuck, the differential amplifier will output a voltage of 2.5V, which is the bias given voltage;

On the contrary, when relay RLY_QC+ is in a non-sticking state, the impedance of relay RLY_QC+ is very large. At this time, relay RLY_QC+ is approximately in an open circuit state. The voltage obtained by the inverting input terminal of differential amplifier U1 through resistor R1A and resistor R2A is the same as the voltage obtained by the non-inverting input terminal through resistor R1B and resistor R2A. There is a certain difference in the voltage obtained by resistor R2B. At this time, the output voltage of the differential amplifier circuit is equal to the bias given voltage minus the differential amplification voltage. Therefore, in this case, the output voltage of differential amplifier U1 will be 2.5V lower than the bias voltage.

That is, 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 stuck. 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 stuck. The relay RLY_QC+ is not stuck.

Please refer to Figure 7. The vehicle high-voltage charging package is typically 250V, 300V, or 500V. When the relay RLY_QC+ is in the adhesion state, the voltage of the output signal of the differential amplifier U1 is the bias voltage 2.5V. When the relay RLY_QC+ is in the non-adhesion state , the voltage of the output signal of the differential amplifier U1 is much smaller than the bias voltage 2.5V. From the results, it can be seen that the voltage of the vehicle high-voltage charging pack will not affect the adhesion detection of the relay RLY_QC+.

Please refer to Figure 5. When relay RLY1 and relay RLY_QC- are closed, relay RLY_QC+ is open, and the non-moving end of relay RLY2A is connected to its first moving end, and the non-moving end of relay RLY2B is connected to its first moving end, the main The control unit controls the power supply circuit to be in a wake-up state, and the differential detection circuit works in a voltage difference detection state.

In this state, the entire circuit will form two power supply loops. The non-inverting input end of the differential amplifier U1 obtains the voltage of the positive pole of the vehicle high-voltage charging pack through resistors R1B and R2B, and the inverting input end obtains the vehicle high-voltage voltage through resistors R1A and R2A. The voltage of the positive pole of the charging pack, so in this case, the voltage of the output signal of the differential amplifier U1 can represent the voltage difference between the charging port and the vehicle high-voltage battery pack, that is, the voltage difference between the two ends of the relay RLY_QC+, and due to the non-inverting input of the differential amplifier U1 The bias voltage is connected to the terminal, so the difference between the voltage of the output signal of the differential amplifier U1 and the bias voltage, through a certain numerical conversion, is the voltage difference between the charging port and the vehicle high-voltage battery pack.

Please refer to Figure 8. When there is a certain voltage difference between the charging port and the vehicle high-voltage battery pack, the output voltage of the differential amplifier changes linearly, and the voltage signal read by the corresponding main control unit also changes. Therefore, by reading By taking 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 the relay closes can be effectively reduced.

In the present invention, according to the specification parameters of the relay, when the voltage difference across the relay is greater than 5V, the 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 normally closed.

Here, since the inrush current is sent out through the positive pole of the charging port, the voltage difference is judged by closing the relay RLY_QC-. Without considering the inrush current, you can also close the relay RLY_QC+ and the relay RLY1, and the relay RLY2A and the relay RLY2B. The fixed end is connected to the second moving end to obtain the voltage difference between the two ends of the relay RLY_QC-. Its working principle is the same as the pressure difference between the two ends of the relay RLY_QC+, so it will not be described again.

Please refer to Figure 9. The overall control process of the present invention is mainly divided into four stages: trigger stage, control and adhesion detection stage, pressure difference detection stage, and status reporting stage.

Trigger stage: used to judge the control command of the relay and decide whether to enter the adhesion detection state;

Control and adhesion detection stage: Make corresponding adhesion detection judgment according to the control command of the relay. If the closing command of the relay is received, it will directly enter the adhesion state detection; if the disconnection command of the relay is received, the disconnection will be controlled first. Open the relay and then detect the adhesion status of the relay;

Pressure difference detection stage: When the relay needs to be closed and the adhesion detection has been completed without failure, the pressure difference detection is performed, and whether to close the relay RLY_QC+ is determined based on the status of the pressure difference detection;

Status reporting stage: Report the relay status (open, closed, fault) according to the requested status and detected status, and report the relay status (open, closed) according to the control status.

1. The present invention uses a set of associated action relays, associated sampling resistors and operational amplifiers to form a Wheatstone bridge circuit, which increases circuit detection accuracy and efficiency, and small voltage difference changes can also be identified and judged;

2. When the present invention does not perform relay adhesion and pressure difference detection, it is in a non-detection state by default. At this time, the voltage difference detection circuit is in a dormant state, which can effectively reduce the static current loss of new energy vehicles;

3. When detecting the adhesion and pressure difference of the relay, the present invention will not be affected by the residual voltage of the charging pile or the voltage on the vehicle-mounted high-voltage charging pack, and can effectively avoid the influence of external voltage on the judgment of the relay status. It can be used in various voltage adjustments. The status of the relay can be effectively identified under any circumstances, and the motor of the relay can be effectively protected from damage;

4. A set of associated action relays is used in the pressure difference detection circuit of the present invention. When one relay fails, it will not affect the judgment of the other relay. The status judgment of the two relays is independent of each other and will not be affected;

5. The present invention detects the voltage difference between the two ends of the relay before the relay is closed. When the voltage difference between the two ends of the relay is lower than a certain threshold, the high-voltage relay is then closed, which can effectively reduce the inrush current generated at the moment the high-voltage relay is closed and protect the controller and motor. not damaged.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims

A relay adhesion and pressure difference detection circuit includes a vehicle-mounted high-voltage charging pack connected to a charging port, a positive relay located at the positive pole of the charging port, and a negative relay located at the negative pole of the charging port, wherein It is characterized in that it also includes a differential detection circuit provided between the charging port and the vehicle-mounted high-voltage charging pack, a switching circuit that switches the detection state of the differential detection circuit, and a main control unit that controls the working state of the switching circuit. The main control unit is connected to the output end of the differential detection circuit, and can determine the status of the positive relay and the negative relay according to the output signal of the differential detection circuit.
The adhesion and pressure difference detection circuit according to claim 1, characterized in that the differential detection circuit includes: resistor R1A, resistor R2A, resistor R3A, resistor R4A, resistor R5A, resistor R6A, resistor R1B, resistor R2B, resistor R3B, resistor R4B, resistor R5B, resistor R6B, differential amplifier U1;

One end of the resistor R3A is connected between the positive relay and the positive electrode of the vehicle-mounted high-voltage battery pack, the other end is connected in series with the resistor R4A and then grounded, and one end of the resistor R3B is connected between the positive relay and the vehicle-mounted high-voltage battery. Between the positive electrodes of the package, the other end is connected in series with resistor R4B and then grounded. One end of the resistor R5A is connected between the positive electrode of the charging port and the positive relay, and the other end is connected to the first input end of the switching circuit, so One end of the resistor R6A is connected between the negative electrode of the charging port and the negative relay, the other end is connected to the second input end of the switching circuit, and one end of the resistor R1A is connected to the first output end of the switching circuit. The other end of the resistor R2A is connected in series and then connected to ground. One end of the resistor R5B is connected between the positive relay and the positive electrode of the vehicle-mounted high-voltage battery pack. The other end is connected to the third input end of the switching circuit. The resistor R6B One end is connected between the negative electrode relay and the negative electrode of the vehicle-mounted high-voltage battery pack, the other end is connected to the fourth input end of the switching circuit, one end of the resistor R1B is connected to the second output end of the switching circuit, The other end is connected in series with resistor R2B and then connected to ground. The non-inverting input end of the differential amplifier U1 is connected between the resistor R1B and the resistor R2B, the inverting input end is connected between the resistor R1A and the resistor R2A, and the output terminal is connected to the main control unit.
The adhesion and pressure difference detection circuit according to claim 2, further comprising a bias voltage given circuit connected to the differential detection circuit, the bias voltage given circuit including a resistor R7A and a resistor R7B;

One end of the resistor R7A is connected to the bias power supply, and the other end is connected in series with the resistor R7B and then connected to ground. The voltage between the resistor R7A and the resistor R7B is used as the bias voltage. The non-inverting input end of the differential amplifier U1 is also connected to between the resistor R7A and the resistor R7B to obtain the bias voltage.
The adhesion and pressure difference detection circuit according to claim 3, wherein the resistor R7A and the resistor R7B have the same resistance.
The adhesion and pressure difference detection circuit according to claim 1, characterized in that the switching circuit includes relay RLY1, relay RLY2A, and relay RLY2B;

The first moving end of the relay RLY2A is connected to the differential detection circuit as the first input end of the switching circuit, and the second moving end is connected to the differential detection circuit as the second input end of the switching circuit. The moving end is connected to the first end of the relay RLY1, the second end of the relay RLY1 is connected to the differential detection circuit as the first output end of the switching circuit, and the first moving end of the relay RLY2B is used as the first output end of the switching circuit. The third input terminal of the switching circuit is connected to the differential detection circuit, the second moving terminal serves as the fourth input terminal of the switching circuit and is connected to the differential detection circuit, and the fixed terminal serves as the second output of the switching circuit. terminal is connected to the differential detection circuit.
The adhesion and pressure difference detection circuit according to claim 5, further comprising a power supply circuit connected to the differential detection circuit and the main control unit, the power supply circuit including an auxiliary source conversion circuit and a voltage conversion circuit , when the power supply circuit receives the wake-up signal sent by the main control unit, it supplies power to the differential amplifier U1 in the differential detection circuit.
The adhesion and pressure difference detection circuit according to claim 6, wherein the main control unit is also connected to the battery management system of the vehicle system, and can adjust the positive electrode according to the control instructions issued by the battery management system. relay, negative relay, and the conduction state of the switching circuit.
The adhesion and pressure difference detection circuit according to claim 7, characterized in that when the relay RLY1 is disconnected, the main control unit controls the power supply circuit to be in a dormant state, and the differential detection circuit works in the default state. state;

When the relay RLY1 is closed, the fixed end of the relay RLY2A is connected to its first moving end, and the fixed end of the relay RLY2B is connected to its first moving end, the main control unit controls the power supply. The circuit is in a wake-up state, and the differential detection circuit works in the positive relay adhesion detection state;

When the relay RLY1 is closed, the fixed end of the relay RLY2A is connected to its second moving end, and the fixed end of the relay RLY2B is connected to its second moving end, the main control unit controls the power supply. The circuit is in the wake-up state, and the differential detection circuit works in the negative relay adhesion detection state.
The adhesion and pressure difference detection circuit according to claim 8, characterized in that when the relay RLY1 and the negative relay are closed, the positive relay is disconnected, and the non-moving end of the relay RLY2A is connected to its first moving end, When the fixed end of the relay RLY2B is connected to its first moving end, the main control unit controls the power supply circuit to be in the wake-up state, and the differential detection circuit works in the voltage difference detection state.
The adhesion and pressure difference detection circuit according to claim 9, characterized in that when the differential detection circuit works in the positive relay adhesion 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 stuck;

When the differential detection circuit works 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 sticks;

When the differential detection circuit works in the voltage difference detection state, the difference between the voltage of the output signal of the differential detection circuit and the bias given voltage, through a certain numerical conversion, is the difference between the charging port and the The voltage difference between vehicle high-voltage battery packs.