A time delay circuit for a relay and an electric vehicle

Abstract

The application relates to a relay delay power-off circuit and an electric vehicle, and relates to the technical field of power electronics. The circuit comprises a first controllable switch, a switching circuit, a delay circuit and a voltage comparison circuit. The first controllable switch is connected with a first relay in series. The second end of the delay circuit is connected with the voltage comparison circuit, and the delay circuit is used for outputting a first voltage to the voltage comparison circuit. The delay circuit comprises a first capacitor. The switching circuit is used for charging the first capacitor by a power supply when the input port of the LSD is grounded, and is used for disconnecting the loop between the power supply and the first capacitor to make the first capacitor discharge when the input port of the LSD is disconnected with the ground. The voltage comparison circuit controls the opening and closing of the controllable switch when the first voltage is greater than or equal to a reference voltage, so that the first relay is attracted; and the voltage comparison circuit controls the first controllable switch to be disconnected when the first voltage is less than the reference voltage, so that the first relay is powered off. The scheme can control the relays to be disconnected in turn according to the sequence, and ensures that the high-voltage line of the electric vehicle can be normally cut off.

Description

Technical Field

[0001] This application relates to the field of electronic power technology, and in particular to a time-delayed power-off circuit for a relay and an electric vehicle. Background Technology

[0002] A relay is an electrical switching device that includes components such as a coil, an armature, and contacts. When the relay coil is energized, a magnetic field is generated inside the coil. This magnetic field can cause the armature to move, thereby changing the state of the contacts and thus connecting or disconnecting the circuit controlled by the relay.

[0003] With the booming development of the new energy vehicle industry and the vigorous promotion of charging infrastructure construction, the charging safety of electric vehicles is becoming increasingly important. Currently, to ensure safety during fast charging, a relay is added to both the positive and negative terminals of the high-voltage circuit in the power distribution unit (PDU) of an electric vehicle. When the electric vehicle is fast charging, both relays are energized, making the circuit conductive. When the electric vehicle is not fast charging, the two relays control the high-voltage circuit to disconnect, ensuring that the fast charging interface of the electric vehicle does not carry high voltage, thus guaranteeing personal safety.

[0004] However, when the control relay disconnects, due to the high charging voltage in high-power fast charging scenarios, a momentary high potential will be generated in the relay coil due to electromagnetic induction at the instant the relay de-energizes. This high potential, combined with the charging voltage, is superimposed on the relay contacts, potentially causing damage or sticking of the relay when it disconnects while energized. Relay sticking mainly refers to the fixed and / or movable contacts of the relay melting and sticking together, thus preventing the relay from properly controlling the circuit to disconnect. If relay sticking occurs, it may prevent high-voltage lines from disconnecting properly, posing a safety hazard. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems in the prior art, this application provides a time-delay power-off circuit for a relay and an electric vehicle, which can control the relays to disconnect in sequence so that two relays will not be damaged at the same time, that is, at least one relay can disconnect normally, ensuring that the high-voltage line of the electric vehicle can be disconnected normally.

[0006] In a first aspect, this application provides a time-delayed power-off circuit for a relay, the circuit comprising: a first controllable switch, a switching circuit, a delay circuit, and a voltage comparison circuit; the first controllable switch is connected in series with a first relay; a first terminal of the switching circuit is connected to the input port of a low-side drive LSD, and a second terminal of the switching circuit is connected to the first terminal of the delay circuit; the second terminal of the delay circuit is connected to the voltage comparison circuit and is used to output a first voltage to the voltage comparison circuit; the delay circuit includes a first capacitor, and the first voltage is the voltage of the first capacitor; the switching circuit is used to control the power supply to charge the first capacitor when the input port of the LSD is grounded, and to disconnect the circuit between the power supply and the first capacitor when the input port of the LSD is disconnected from ground, so as to discharge the first capacitor; when the input port of the LSD is grounded, after the first capacitor has finished charging, the first voltage is greater than a reference voltage; the voltage comparison circuit is used to control the controllable switch to close when the first voltage is greater than or equal to the reference voltage, so as to activate the first relay; and to control the first controllable switch to open when the first voltage is less than the reference voltage, so as to de-energize the first relay.

[0007] The delayed power-off circuit provided in this application, when the first relay is normally engaged, the switching circuit controls the power supply to charge the first capacitor. When the electric vehicle needs to control the first relay to de-energize, the LSD input port will first disconnect from ground. At this time, the first relay in the prior art will directly de-energize. However, in the technical solution of this application, after the LSD input port is disconnected from ground, the first capacitor will first discharge. Before the voltage of the first capacitor drops below the reference voltage, the first relay will remain engaged. Only when the voltage of the first capacitor drops below the reference voltage will the first controllable switch open, and the first relay will de-energize. Therefore, the delayed power-off of the first relay is achieved. When the controller of the electric vehicle controls multiple relays to disconnect, taking the control of the first and second relays to disconnect as an example, after adopting the solution of this application, the second relay disconnects first, and the first relay controlled by the delayed power-off circuit can disconnect with a delay. Therefore, the two relays disconnect in sequence so that the two relays will not be damaged at the same time, that is, at least one relay can disconnect normally, ensuring that the high-voltage line of the electric vehicle can be disconnected normally.

[0008] In one possible implementation, the switching circuit includes: a second controllable switch, a first voltage divider circuit, and a diode; the first voltage divider circuit includes a first resistor and a second resistor; the first end of the first resistor is connected to the power supply and the source of the second controllable switch, the second end of the first resistor is connected to the first end of the second resistor and the gate of the second controllable switch, and the second end of the second resistor is connected to the second end of the switching circuit.

[0009] The drain of the second controllable switch is connected to the anode of the diode, and the cathode of the diode is connected to the second terminal of the switching circuit.

[0010] In one possible implementation, the delay circuit includes a third resistor and a first capacitor; the first terminal of the first capacitor is connected to the second terminal of the switching circuit, and the second terminal of the first capacitor is grounded; the first terminal of the first capacitor is used to output a first voltage to the voltage comparison circuit; the third resistor is connected in parallel with the first capacitor.

[0011] In one possible implementation, the voltage comparison circuit includes a voltage comparator, a second voltage divider circuit, and a third voltage divider circuit; the first input terminal of the voltage comparator is used to connect to a first voltage; the second voltage divider circuit is used to output a reference voltage to the second input terminal of the voltage comparator; the first terminal of the third voltage divider circuit is connected to a power supply, and the second terminal of the third voltage divider circuit is grounded; the output terminal of the third voltage divider circuit is connected to the output terminal of the voltage comparator and the gate of the first controllable switch; the voltage comparator is used to connect the ground line inside the voltage comparator when the first voltage is greater than or equal to the reference voltage, and to disconnect the ground line inside the voltage comparator when the first voltage is less than the reference voltage.

[0012] In one possible implementation, the second voltage divider circuit includes a fourth resistor and a fifth resistor; the first end of the fourth resistor is connected to a power supply, the second end of the fourth resistor is connected to the first end of the fifth resistor, and the second end of the fifth resistor is grounded; the second end of the fourth resistor is used to output a reference voltage to the second input terminal of the voltage comparator.

[0013] In one possible implementation, the first voltage divider circuit further includes a second capacitor connected in parallel with the fifth resistor. The second capacitor is used for voltage regulation, filtering out transient interference voltages, preventing comparator malfunctions, and ensuring that the first voltage divider circuit outputs a stable reference voltage to the voltage comparator.

[0014] In one possible implementation, the third voltage divider circuit includes a sixth resistor and a seventh resistor; the first end of the sixth resistor is connected to a power supply, the second end of the sixth resistor is connected to the first end of the seventh resistor and the output terminal of the third voltage divider circuit; the second end of the seventh resistor is grounded.

[0015] In one possible implementation, the first controllable switch and the first relay are connected in series on the positive DC bus, and the positive DC bus is connected to the positive terminal of the power battery pack.

[0016] Secondly, this application also provides an electric vehicle, which includes a time-delayed power-off circuit for the relay described in the first aspect and any implementation thereof, and further includes a first relay, wherein the time-delayed power-off circuit for the relay is used to control the first relay to delay power-off.

[0017] In one possible implementation, the electric vehicle also includes a second relay connected in series on the negative DC bus, which is connected to the negative terminal of the battery pack. A time-delay power-off circuit for the relay is used to control the power-off time delay of the first relay and the power-off time of the second relay. Attached Figure Description

[0018] Figure 1 A schematic diagram of an electric vehicle electrical system provided for this application;

[0019] Figure 2 An example diagram illustrating the circuit principle for DC fast charging of electric vehicles provided in this application;

[0020] Figure 3 A schematic diagram of a time-delayed power-off circuit for a relay provided in an embodiment of this application;

[0021] Figure 4 A schematic diagram of another delayed power-off circuit for a relay provided in an embodiment of this application;

[0022] Figure 5 This is a schematic diagram of an electric vehicle provided in an embodiment of this application. Detailed Implementation

[0023] To enable those skilled in the art to better understand the present application, the application scenarios of the present application are described below.

[0024] See Figure 1 The figure is a schematic diagram of an electric vehicle electrical system provided in this application.

[0025] The electrical system of the electric vehicle shown in the diagram mainly includes a motor controller 10, a motor 20, a power battery pack 30, a high-voltage distribution box 40, a DC / DC converter circuit 50, a low-voltage battery 60, a DC charging circuit 70, and an on-board charger 80.

[0026] The power battery pack 30 provides high-voltage direct current (VDC) to the electric vehicle. A portion of this VDC is converted to alternating current (AC) via the high-voltage distribution box 40 and the motor controller 10, supplying the motor 20 to drive the electric vehicle. Another portion of the VDC is converted to low-voltage direct current via the high-voltage distribution box 40 and the DC / DC converter circuit 50, supplying the low-voltage battery 60 and / or the low-voltage system of the electric vehicle. The high-voltage distribution box 40 can also be referred to as a power distribution unit (PDU).

[0027] When an electric vehicle is charging, in some embodiments, the electric vehicle charges the power battery pack 30 through a DC charging circuit 70. At this time, the DC charging circuit 70 is connected to a DC charging pile. This charging method is also called "DC fast charging". DC fast charging has a larger charging power.

[0028] In other embodiments, the electric vehicle is charged via an on-board charger 80, which is connected to an AC charging station or the AC power grid. Some on-board chargers 80 can also simultaneously charge the low-voltage battery 60.

[0029] See Figure 2 The figure is an example diagram of the circuit principle for DC fast charging of electric vehicles provided in this application.

[0030] The diagram shows the connection points for the vehicle plug and the vehicle socket. The vehicle plug is used to connect to the off-board charger, also known as a charging station. The vehicle socket is typically located on the electric vehicle and is used to connect the positive bus (DC+), negative bus (DC4-), and the vehicle's ground (PE) to the battery pack.

[0031] Off-board chargers convert AC power to DC power and then charge the battery pack in electric vehicles via the vehicle interface. The fuse on the off-board charger is used to blow and protect the circuit in case of excessive current. IMD_EVSE is the insulation monitoring device (IMD) on the electric vehicle supply equipment (EVSE), used to detect the off-board charger's impedance to ground.

[0032] Relays K5 and K6, located on the vehicle's positive bus DC+ and negative bus DC4-, are the vehicle's main relays, also known as fast-charging relays. K5 and K6 are circuit devices used to connect or disconnect the electric vehicle from the charging station. Under normal driving conditions, slow charging, or other non-fast-charging conditions, relays K5 / K6 should be in the open state. If they are in the closed state, the vehicle's fast-charging port will be energized, posing a risk of electric shock to personnel.

[0033] In existing technology, when fast charging ends or when it is necessary to disconnect a high-voltage line, relays K5 and K6 are typically driven simultaneously to perform a power-off action, thus disconnecting the contacts in the line. Driving both relays simultaneously requires a large drive current, and at the moment of power-off, due to electromagnetic induction, a momentary high potential is generated in the coil. This potential, combined with the high voltage in the line, is superimposed on the contacts of the current-carrying relays, potentially causing damage or sticking of the relays when disconnecting under energized conditions. If the relays stick, the high-voltage line cannot be disconnected properly, posing a safety hazard.

[0034] To address the above issues, this application provides a delayed power-off circuit for a relay and an electric vehicle. The first relay controlled by the delayed power-off circuit experiences a delayed power-off when disconnected, ensuring that the two relays in the high-voltage line of the electric vehicle disconnect sequentially without simultaneous damage. This means that at least one relay can disconnect normally, ensuring that the high-voltage line of the electric vehicle can be properly disconnected.

[0035] Using the solution of this application, when the relay is de-energized, the relays on the positive and negative busbars can be disconnected in sequence, ensuring that under extreme operating conditions, at most one relay will be damaged when the relay is de-energized, and two relays will not be damaged at the same time. That is, at least one relay can be disconnected normally, ensuring that the high-voltage line of the electric vehicle can be disconnected normally, thus improving the safety performance of the electric vehicle.

[0036] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described below with reference to the accompanying drawings.

[0037] The terms "first" and "second" used in this application description are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0038] In this application, unless otherwise expressly specified and limited, the term "connection" shall be interpreted broadly. For example, "connection" may be a fixed connection, a detachable connection, or an integral part; it may be a direct connection or an indirect connection through an intermediate medium.

[0039] This application provides a delayed power-off circuit for a relay, which will be described in detail below with reference to the accompanying drawings.

[0040] See Figure 3 The figure is a schematic diagram of a time-delay power-off circuit for a relay provided in an embodiment of this application.

[0041] The delayed power-off circuit 300 includes: a switching circuit 10, a delay circuit 20, a voltage comparison circuit 30, and a first controllable switch Q1.

[0042] The first controllable switch Q1 is connected in series with the first relay. The first controllable switch Q1 can be an insulated-gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), or a silicon carbide metal-oxide-semiconductor field-effect transistor (SiC MOSFET), etc., and this application embodiment does not specifically limit it. This application embodiment uses an NMOS transistor as an example for illustration. The first relay in this application embodiment is used to control the on / off state of the positive DC bus, denoted as Relay+. This positive DC bus is connected to the positive terminal of the electric vehicle's power battery pack.

[0043] In this embodiment, the input port of the High Side Drive (HSD) is connected to a high level; for example, the HSD port is connected to 12V. The input port of the Low Side Drive (LSD) is connected to the vehicle's ground (PE).

[0044] The first terminal of the switching circuit 10 is connected to the input port of the low-side drive LSD, and the second terminal of the switching circuit 10 is connected to the first terminal of the delay circuit 20.

[0045] The second terminal of the delay circuit 20 is connected to the voltage comparator circuit 30, and is used to output a first voltage to the voltage comparator circuit. The delay circuit 20 includes a first capacitor, and the first voltage is the voltage across the first capacitor. The first voltage is an analog voltage signal. Since the first voltage is the voltage across the first capacitor, its magnitude changes as the first capacitor charges and discharges.

[0046] The switching circuit is used to control the power supply to charge the first capacitor when the input port of the LSD is grounded, and to disconnect the circuit between the power supply and the first capacitor when the input port of the LSD is disconnected from ground, so as to discharge the first capacitor.

[0047] The voltage comparison circuit 30 is used to control the controllable switch Q1 to close when the first voltage is greater than or equal to the reference voltage, so as to activate the first relay. When the first voltage is less than the reference voltage, it controls the first controllable switch Q1 to open, so as to de-energize the first relay.

[0048] In the embodiment of this application, when the input port of the LSD is grounded, the first capacitor is charged. After the first capacitor is fully charged, the first voltage is greater than the reference voltage. That is, when the input port of the LSD is grounded, the voltage comparison circuit 30 controls the controllable switch to close so that the relay can be normally engaged.

[0049] When an electric vehicle needs to control the first relay to de-energize, the LSD input port will first disconnect from ground. In the prior art, the first relay will directly de-energize. However, in the technical solution of this application, after the LSD input port is disconnected from ground, the first capacitor will first discharge. Before the voltage of the first capacitor drops below the reference voltage, the first relay will remain in the energized state. Only when the voltage of the first capacitor drops below the reference voltage will the first controllable switch open and the first relay de-energize. Therefore, the delayed de-energization of the first relay is achieved.

[0050] When the controller of an electric vehicle controls multiple relays to disconnect, taking the control of the first and second relays to disconnect as an example, with the solution of this application, the second relay disconnects first, and the first relay controlled by the delayed power-off circuit can disconnect after a delay. Therefore, the two relays disconnect in sequence so that the two relays will not be damaged at the same time, that is, at least one relay can disconnect normally, ensuring that the high-voltage line of the electric vehicle can be disconnected normally.

[0051] The following section will explain the specific implementation method.

[0052] See Figure 4 The figure is a schematic diagram of another time-delay power-off circuit for a relay provided in an embodiment of this application.

[0053] In this embodiment, the first relay is used to control the on / off state of the positive DC bus, denoted as Relay+. The second relay is used to control the on / off state of the negative DC bus, denoted as Relay-.

[0054] The first terminal of the second relay is connected to the input port of the LSD, and the second terminal of the second relay is connected to the input port of the HSD through the third controllable switch Q3. The gate of the third controllable switch Q3 is connected to the drive circuit 200 of the second relay. The drive circuit 200 can respond to the control command of the controller of the electric vehicle by controlling the third controllable switch Q3 to conduct so that the second relay is energized, or control the third controllable switch Q3 to open so that the second relay is de-energized.

[0055] The delayed power-off ground circuit 300 is used to achieve a delayed power-off for the first relay.

[0056] In this embodiment, the switching circuit 10 specifically includes a first voltage divider circuit, a second controllable switch Q2, and a diode D1.

[0057] The first voltage divider circuit includes a first resistor R1 and a second resistor R2. In this embodiment, a PMOS transistor is used as the second controllable switch.

[0058] The first end of the first resistor R1 is connected to the power supply VCC and the source S of the second controllable switch Q2. The second end of the first resistor R1 is connected to the first end of the second resistor R2 and the gate G of the second controllable switch. The second end of the second resistor R2 is connected to the second end of the switching circuit 10.

[0059] The drain D of the second controllable switch Q2 is connected to the anode of diode D1, and the cathode of diode D1 is connected to the second terminal of the switch circuit.

[0060] Diode D1 is used to prevent the first capacitor C1 from discharging through the body diode in the second controllable switch Q2, thereby extending the discharge time of the first capacitor C1 and ensuring that the specific delay of the first relay de-energization matches the actual needs.

[0061] When the LSD's input port is grounded, the power supply VCC is grounded through resistors R1 and R2. Taking a VCC voltage of 5V as an example, the voltage V between the gate and source of the second controllable switch Q2 is... GS =-5V*R1 / (R1+R2)=-4.55V. Since the second controllable switch Q2 is a PMOS transistor, it is turned on at this time. The power supply VCC charges C1 through Q2, D1, and R8. R8 is a current-limiting resistor used for circuit protection.

[0062] After C1 is fully charged, the voltage across its terminals will be close to the voltage of the power supply VCC.

[0063] The delay circuit 20 includes a third resistor R3 and a first capacitor C1. The first terminal of the first capacitor C1 is connected to the second terminal of the switching circuit 10, and the second terminal of the first capacitor C1 is grounded. The first terminal of the first capacitor is used to output a first voltage to the voltage comparison circuit 30. The third resistor R3 is connected in parallel with the first capacitor C1, and the third resistor R3 is the discharge resistor of C1.

[0064] The voltage comparison circuit 30 includes a voltage comparator U1, whose first input terminal is port 3, used to connect to a first voltage.

[0065] The second input terminal of voltage comparator U1 is port 2, which is used to connect to the reference voltage.

[0066] The voltage comparison circuit 30 also includes a second voltage divider circuit and a third voltage divider circuit.

[0067] The second voltage divider circuit is used to output a reference voltage to the second input terminal of the voltage comparator U1.

[0068] The second voltage divider circuit in this embodiment includes a fourth resistor R4 and a fifth resistor R5. The first terminal of the fourth resistor R4 is connected to the power supply VCC, the second terminal of the fourth resistor R4 is connected to the first terminal of the fifth resistor R5, and the second terminal of the fifth resistor R5 is grounded. The second terminal of the fourth resistor R4 is used to output a reference voltage to the second input terminal of the voltage comparator U1.

[0069] Taking VCC as 5V as an example, when the resistance values ​​of R4 and R5 are 1:1, the reference voltage is 2.5V.

[0070] The first terminal of the third voltage divider circuit is connected to the power supply VCC, and the second terminal of the third voltage divider circuit is grounded. The output terminal of the third voltage divider circuit is connected to the output terminal of the voltage comparator U1 and the gate G of the first controllable switch Q1. The third voltage divider circuit is used to drive Q1 to open or close under the control of U1.

[0071] The third voltage divider circuit in this embodiment includes a sixth resistor R6 and a seventh resistor R7. The first terminal of the sixth resistor R6 is connected to the power supply VCC, and the second terminal of the sixth resistor R6 is connected to the first terminal of the seventh resistor R7 and the output terminal of the third voltage divider circuit. The second terminal of the seventh resistor R7 is grounded.

[0072] The working principle of this delayed power-off circuit is explained in detail below.

[0073] When the LSD's input port is grounded, the power supply VCC is grounded through resistors R1 and R2. Taking a VCC voltage of 5V as an example, the voltage V between the gate and source of the second controllable switch Q2 is... GS The voltage is approximately -4.55V. Since the second controllable switch Q2 is a PMOS transistor, it is currently turned on, and the power supply VCC charges C1. After C1 is fully charged, the voltage across it is close to the voltage of the power supply VCC. Therefore, the first voltage output by C1 is greater than the reference voltage. At this time, U1 keeps its internal grounding switch open, disconnecting the output terminal 1 of U1 from ground. The voltage V between the gate and source of Q1 at this time... GS =5V*R7 / (R6+R7)=4.55V. Since Q1 is an NMOS transistor, Q1 is turned on, and current begins to flow through the coil of the first relay, allowing the first relay to engage normally.

[0074] When the first control relay is disconnected, the input port of the control LSD is first disconnected from the vehicle ground (PE), causing the voltage V between the gate and source of Q2 to decrease. GS Q2 cannot remain on and will switch to off state.

[0075] When Q2 is turned off, VCC stops charging C1, and C1 begins to discharge through R3. Because R3 has a relatively large resistance, the current in the circuit is small, and C1 discharges for a longer time. During the discharge process of C1, the initial voltage gradually decreases.

[0076] Before the first voltage is lower than the reference voltage, that is, while the first voltage is still greater than or equal to the reference voltage, U1 will maintain the disconnection between output terminal 1 and ground, so that the voltage V between the gate and source of Q1 remains constant. GS The voltage can still be maintained at 4.55V, so Q1 remains on and the first relay remains energized.

[0077] When the first voltage drops below the reference voltage hysteresis, U1 will connect output terminal 1 to ground. At this time, the gate of Q1 is grounded, and the voltage V between the gate and source of Q1... GS When the voltage drops to low, Q1 switches to the off state, de-energizing the first relay.

[0078] The time it takes for the first voltage value to drop from 4.55V to 2.5V is the delay time for the first relay to cut off power. By properly designing the parameters of the capacitor and resistor, and the magnitude of the reference voltage, the delay time for the first relay to cut off power can be adjusted according to actual needs. Figure 4 The parameters listed are for illustrative purposes only and do not constitute a limitation on the technical solution of this application. Figure 4 Taking the data as an example, the voltage on C1 drops to 2.5V after about 0.5s, meaning the first relay can delay power-off by 0.5s. The voltage on C1 can complete the discharge in about 1s, causing the first voltage to drop to almost 0.

[0079] Furthermore, the first voltage divider circuit may also include a second capacitor C2, which is connected in parallel with the fifth resistor R5. C2 can filter out transient interference voltages, enabling the first voltage divider circuit to output a stable reference voltage to the voltage comparator U1, preventing the comparator from malfunctioning and improving the reliability of the delayed power-off circuit.

[0080] In summary, the delayed power-off circuit provided in this application embodiment enables the controlled relays to disconnect after a delay. Therefore, when multiple relays in the circuit are disconnected simultaneously, the relays can be disconnected sequentially, avoiding the simultaneous sticking of all relays due to abnormally large currents. This ensures that the relays controlled by the delayed power-off circuit in the line can disconnect normally, thereby ensuring that the high-voltage lines of electric vehicles can be disconnected normally and improving the safety of electric vehicles.

[0081] Based on the time-delay power-off circuit of the relay provided in the above embodiments, this application also provides an electric vehicle, which will be described in detail below with reference to the accompanying drawings.

[0082] See Figure 5 The figure is a schematic diagram of an electric vehicle provided in an embodiment of this application.

[0083] The electric vehicle 100 includes a time-delay power-off circuit 100 for a relay, as well as a first relay 200 and a second relay (not shown in the figure).

[0084] The on / off state of the first relay 200 is controlled by the relay's delayed power-off circuit 100.

[0085] The on / off state of the second relay can be controlled using existing methods, which will not be elaborated here.

[0086] When the controller of the electric vehicle disconnects the first and second relays, the solution of this application ensures that the second relay disconnects first, allowing the first relay, controlled by the delayed power-off circuit, to disconnect after a delay. This ensures the two relays disconnect sequentially, preventing simultaneous damage and guaranteeing at least one relay can disconnect normally. This ensures the high-voltage lines of the electric vehicle are properly disconnected, improving vehicle safety. Furthermore, the component parameters of the delay circuit in the delayed power-off circuit can be adjusted according to actual conditions. For example, adjusting the parameters of the capacitor and resistor in the RC delay circuit can adjust the specific delay time, as can adjusting the reference voltage of the voltage comparator. Since the delay time is implemented using analog circuitry, this solution has low hardware cost and high practicality.

[0087] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0088] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. The device embodiments described above are merely illustrative, and the units and modules described as separate components may or may not be physically separate. Furthermore, some or all of the units and modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0089] The above description is only a specific embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A time-delayed power-off circuit for a relay, characterized in that, The circuit includes: a first controllable switch, a switching circuit, a delay circuit, and a voltage comparison circuit; The first controllable switch is connected in series with the first relay; The first terminal of the switching circuit is connected to the input port of the low-side driving LSD, and the second terminal of the switching circuit is connected to the first terminal of the delay circuit. The second terminal of the delay circuit is connected to the voltage comparison circuit and is used to output a first voltage to the voltage comparison circuit. The delay circuit includes a first capacitor, and the first voltage is the voltage of the first capacitor. The switching circuit is used to control the power supply to charge the first capacitor when the input port of the LSD is grounded, and to disconnect the circuit between the power supply and the first capacitor when the input port of the LSD is disconnected from ground, so as to discharge the first capacitor. When the input port of the LSD is grounded, after the first capacitor has been charged, the first voltage is greater than the reference voltage. The voltage comparison circuit is used to control the controllable switch to close when the first voltage is greater than or equal to the reference voltage, so as to activate the first relay; and to control the first controllable switch to open when the first voltage is less than the reference voltage, so as to de-energize the first relay.

2. The circuit according to claim 1, characterized in that, The switching circuit includes: a second controllable switch, a first voltage divider circuit, and a diode; The first voltage divider circuit includes a first resistor and a second resistor; The first end of the first resistor is connected to the power supply and the source of the second controllable switch, the second end of the first resistor is connected to the first end of the second resistor and the gate of the second controllable switch, and the second end of the second resistor is connected to the second end of the switch circuit. The drain of the second controllable switch is connected to the anode of the diode, and the cathode of the diode is connected to the second terminal of the switching circuit.

3. The circuit according to claim 1 or 2, characterized in that, The delay circuit includes a third resistor and a first capacitor; The first terminal of the first capacitor is connected to the second terminal of the switching circuit, and the second terminal of the first capacitor is grounded. The first terminal of the first capacitor is used to output the first voltage to the voltage comparison circuit; The third resistor is connected in parallel with the first capacitor.

4. The circuit according to claim 1, characterized in that, The voltage comparison circuit includes a voltage comparator, a second voltage divider circuit, and a third voltage divider circuit; The first input terminal of the voltage comparator is used to connect to the first voltage; The second voltage divider circuit is used to output the reference voltage to the second input terminal of the voltage comparator; The first terminal of the third voltage divider circuit is connected to the power supply, and the second terminal of the third voltage divider circuit is grounded. The output terminal of the third voltage divider circuit is connected to the output terminal of the voltage comparator and the gate of the first controllable switch; The voltage comparator is configured to connect the output terminal of the voltage comparator to the ground line inside the voltage comparator when the first voltage is greater than or equal to the reference voltage, and to disconnect the output terminal of the voltage comparator from the ground line inside the voltage comparator when the first voltage is less than the reference voltage.

5. The circuit according to claim 4, characterized in that, The second voltage divider circuit includes: a fourth resistor and a fifth resistor; The first end of the fourth resistor is connected to the power supply, the second end of the fourth resistor is connected to the first end of the fifth resistor, and the second end of the fifth resistor is grounded. The second terminal of the fourth resistor is used to output the reference voltage to the second input terminal of the voltage comparator.

6. The circuit according to claim 5, characterized in that, The first voltage divider circuit also includes a second capacitor; The second capacitor is connected in parallel with the fifth resistor.

7. The circuit according to claim 4, characterized in that, The third voltage divider circuit includes: a sixth resistor and a seventh resistor; The first end of the sixth resistor is connected to the power supply, and the second end of the sixth resistor is connected to the first end of the seventh resistor and the output end of the third voltage divider circuit. The second terminal of the seventh resistor is grounded.

8. The circuit according to claim 1, characterized in that, The first controllable switch and the first relay are connected in series on the positive DC bus, and the positive DC bus is connected to the positive terminal of the power battery pack.

9. An electric vehicle, characterized in that, The electric vehicle includes a time-delayed power-off circuit for the relay according to any one of claims 1-8, and further includes a first relay, wherein the time-delayed power-off circuit of the relay is used to control the first relay to delay power-off.

10. The electric vehicle according to claim 9, further comprising a second relay, wherein the time-delay power-off circuit of the relay is used to control the power-off time delay of the first relay and the power-off time of the second relay.

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