A lithium battery charging protection circuit, protection board and lithium battery system

Abstract

The present invention discloses a lithium battery charging protection circuit, a protection board and a lithium battery system. The protection circuit includes a first rectifier module, a second rectifier module and a charging detection module; the first rectifier module is connected to an AC power supply through a power relay, and is used to provide charging input for the lithium battery, and to power an optocoupler control module, an optocoupler and a relay drive module; the optocoupler control module receives a control signal from the charging detection module, controls the internal light-emitting unit of the optocoupler to be turned on, and the transistor of the optocoupler controls the relay drive module, and the relay drive module is used to control the power relay; the charging detection module monitors the charging voltage of the lithium battery, and determines whether the lithium battery has reached a full state through a voltage-dividing resistor and a comparison circuit, and sends a control signal to the optocoupler control module when the lithium battery has reached a full state. The present invention can realize overcharge protection of the lithium battery through a simple circuit, and realize electrical isolation of the high and low voltage parts.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium battery protection, and in particular relates to a lithium battery charging protection circuit, a protection board and a lithium battery system. Background Art

[0002] As a high energy density and long life energy storage device, lithium battery is widely used in consumer electronics, electric vehicles and energy storage systems. However, if lithium battery is overcharged during charging, it may cause battery overheating, expansion or even fire, seriously affecting the safety and service life of the battery. The safety of lithium battery during charging has always been an important concern in related technical fields. Therefore, designing a reliable charging protection circuit for lithium battery is a key link in battery application. This function is mainly realized by the lithium battery management system (Battery Management System, BMS), which aims to prevent battery overcharge and ensure safe use through precise control.

[0003] The Chinese invention patent application with publication number CN109962509A discloses a self-power-off charger circuit for electric vehicles, which includes a rectifier circuit, a conversion circuit, a detection control circuit and a delay protection circuit. When the indication is that the battery is fully charged, the charger is controlled to enter a trickle charging stage (floating charge) of 200-300mA. By changing the resistance value of the potentiometer RP2, the charger can be adjusted from a constant current charging state to a trickle charging state. The capacitor C14 is charged for about 3 hours. At this time, the battery is fully charged, the normally closed switch of the relay KA is disconnected, and the 220V power supply is cut off. At this time, the charger has no output voltage and stops working. At the same time, the battery pack continues to charge the capacitor C14 through the resistor R35 and the potentiometer RP3, and the field effect transistor VT5 remains on and the relay KA is disconnected.

[0004] However, the above solution requires the use of complex microcontrollers and program algorithms, resulting in high circuit design costs and low reliability. In addition, since the charging circuit is prone to electromagnetic interference and there is a lack of effective electrical isolation between the input and output signals, it may affect the stability of the circuit and user safety. Summary of the invention

[0005] The present invention provides a lithium battery charging protection circuit, a protection board and a lithium battery system, aiming to solve the problems of complex circuits, electromagnetic interference affecting stability and safety in the prior art when protecting lithium batteries from overcharging.

[0006] In order to solve the above technical problems, the first aspect of the present invention provides a lithium battery charging protection circuit, comprising a first rectifier module, a second rectifier module and a charging detection module, wherein the second rectifier module is connected to an AC power supply to provide a working power supply for the charging detection module;

[0007] The first rectifier module is connected to the AC power supply through a power relay to provide charging input for the lithium battery and power the optocoupler control module, the photoelectric coupler and the relay drive module;

[0008] The optical coupling control module receives the control signal of the charging detection module, controls the internal light-emitting unit of the photoelectric coupler to turn on, and the output transistor of the photoelectric coupler controls the on-off of the relay driving module, and the relay driving module is used to control the on-off of the power relay;

[0009] The charging detection module monitors the charging voltage of the lithium battery through the signal interface and the external connection unit, and determines whether the lithium battery has reached a full state through a voltage divider resistor and a comparison circuit. When the lithium battery has reached a full state, a control signal is sent to the optical coupler control module.

[0010] Preferably, the models of the first rectifier module and the second rectifier module are both KBP310.

[0011] Preferably, an energy storage resistor is connected between the positive output end of the first rectifier module and the negative output end after passing through a plurality of voltage-dividing resistors, and the specification of the energy storage resistor is 4.7 μF / 200V.

[0012] Preferably, the power relay is a set of normally open 24V double-coil magnetic latching power relays.

[0013] Preferably, the power relay is HFE60 / 24-1HST-L2.

[0014] Preferably, the photoelectric coupler is PC817C-SOP4, pins 1 and 2 are connected to the output of the photocoupler control module, and pins 3 and 4 are output ends connected to the relay drive module.

[0015] Preferably, the charging detection module further includes a battery voltage sampling unit, a reference voltage sampling unit, a signal interface and an external connection unit, and a control signal output unit. The battery voltage sampling unit collects the real-time voltage of the lithium battery through the signal interface and the external connection unit, and determines whether the lithium battery is full after comparing it with the reference voltage. If the lithium battery is full, a control signal is sent to the optocoupler control module through the control signal output unit.

[0016] Preferably, output ends of the first rectifier module and the second rectifier module are both connected to filter capacitors.

[0017] The second aspect of the present invention further provides a lithium battery charging protection board, which includes the lithium battery charging protection circuit as described in the first aspect of the present invention.

[0018] A third aspect of the present invention further provides a lithium battery system, comprising:

[0019] Lithium batteries; and

[0020] As described in the second aspect of the present invention, the lithium battery charging protection board is used to disconnect the charging circuit after the lithium battery is fully charged.

[0021] Compared with the prior art, the present invention has the following technical effects:

[0022] 1. Compared with the intelligent charging solution based on microcontroller, the lithium battery charging protection circuit proposed in the present invention adopts analog circuit design, and the core control unit is mainly based on relays and optocouplers, which saves complicated program design and expensive microcontroller chips. The circuit design is simple, and the components are easy to obtain, which greatly reduces the overall cost.

[0023] 2. The lithium battery charging protection circuit proposed in the present invention uses an optical coupling isolation module, which effectively isolates the input and output signals, prevents the input high voltage or high current from damaging the battery and subsequent circuits, and enhances the anti-interference ability and reliability of the system. At the same time, the use of optical coupling also further improves the safety of the circuit and ensures the safety of users and equipment.

[0024] 3. The lithium battery charging protection circuit proposed in the present invention adopts a modular design, including a rectifier module, a charging control module, a voltage detection module and a protection module, etc. The parameters or functions of each module can be flexibly adjusted according to specific needs, and is suitable for different types of lithium battery charging scenarios, such as consumer electronics, electric vehicles, energy storage equipment and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the charging protection circuit of the present invention;

[0026] Figure 2 4 is a circuit diagram of the charging protection circuit according to an embodiment of the present invention.

[0027] Figure numerals: 1. first rectifier module; 2. second rectifier module; 3. charging detection module; 4. power relay; 5. optocoupler control module; 6. photoelectric coupler; 7. relay drive module. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in combination with specific embodiments of the present application and with reference to the accompanying drawings.

[0029] Embodiment 1

[0030] like Figure 1As shown, this embodiment is a lithium battery charging protection circuit, comprising a first rectifier module 1, a second rectifier module 2 and a charging detection module 3. The second rectifier module 2 is connected to an AC power source, rectifies the AC input into a DC output, and provides a DC working voltage to subsequent circuits, such as providing a working power supply for the charging detection module 3.

[0031] The first rectifier module 1 is connected to an AC power source through a power relay 4 to provide charging input for the lithium battery and to supply power to the optocoupler control module 5 , the photoelectric coupler 6 and the relay drive module 7 .

[0032] The optical coupling control module 5 receives the control signal of the charging detection module 3 to control the internal light-emitting unit of the photoelectric coupler 6 to turn on. The output transistor of the photoelectric coupler 6 controls the on-off of the relay driving module 7, and the relay driving module 7 is used to control the on-off of the power relay 4.

[0033] The charging detection module 3 monitors the charging voltage of the lithium battery through the signal interface and the external connection unit, and determines whether the lithium battery has reached a full state through a voltage divider resistor and a comparison circuit. When the lithium battery has reached a full state, a control signal is sent to the optical coupler control module 5.

[0034] The specific circuit diagram is as follows Figure 2 As shown, the first rectifier module 1 and the second rectifier module 2 are both of the model KBP310. The first rectifier module 1 is BR2 in the figure, and its access end is directly connected to the neutral line N of the AC power supply, and the connection with the phase line L of the AC power supply is indirectly connected to the phase line L through the power relay 4. The second rectifier module 2 is BR1 in the figure, and its access end is directly connected to the phase line L and the neutral line N of the AC power supply.

[0035] After the positive output end of the first rectifier module 1 passes through a number of voltage-dividing resistors, an energy storage resistor is connected to the negative output end, and the specification of the energy storage resistor is 4.7μF / 200V. Specifically, the positive output (V+) of the first rectifier module 1 first passes through the first voltage-dividing resistor string and is connected to the input side of the optocoupler control module 5, and the rectified high-voltage direct current is reduced to the voltage range required by the optocoupler input end through voltage division. From the positive output of BR2 to the optocoupler input side, after the current passes through the voltage-dividing network, the internal light-emitting diode of the optocoupler is driven by appropriate current.

[0036] In this embodiment, the first voltage-dividing resistor string is six 5KΩ resistors connected in series, as shown in the figure, including resistors R11, R13, R14, R12, R8 and R9. A filter capacitor C2 is arranged in parallel at both ends of the first voltage-dividing resistor string.

[0037] In addition, the positive output of the first rectifier module 1 first passes through the first voltage-dividing resistor string and then passes through the second voltage-dividing resistor string. The second voltage-dividing resistor string is also six 5KΩ resistors connected in series, as shown in the figure, including resistors R15, R17, R16, R18, R19 and R20. It is used to provide an independent voltage sampling signal for another input channel of the optocoupler to achieve more accurate detection. The second voltage-dividing resistor string is an auxiliary sampling path, providing another set of sampling signals for distinguishing different states (such as charging completion or overvoltage, etc.).

[0038] The photocoupler 6 is PC817C-SOP4, pins 1 and 2 are connected to the output of the photocoupler control module 5, and pins 3 and 4 are output terminals connected to the relay drive module 7. The photocoupler 6 is used to achieve electrical isolation of the high and low voltage parts, and to transmit the charging status signal to avoid interference of the high voltage on the control circuit. When the lithium battery voltage is close to the full charge cut-off voltage, the circuit is connected to the photocoupler 6 ( Figure 2 U1) transmits the signal. Figure 2 As shown, when the photocoupler 6 receives the trigger signal, its output transistor is turned on (pins 3 and 4 are turned on), the circuit activates the gate of the switch tube Q1, and then turns on the source and gate of the switch tube Q1, turns on the coil of the power relay 4, and finally switches the contacts of the power relay 4, cutting off the AC input of the first rectifier module 1, and then stops the charging input.

[0039] The power relay 4 is a normally open 24V double-coil magnetic latching power relay. Specifically, the power relay 4 in this embodiment adopts HFE60 / 24-1HST-L2.

[0040] The charging detection module 3 further includes a battery voltage sampling unit, a reference voltage sampling unit, a signal interface and an external connection unit, and a control signal output unit. The battery voltage sampling unit collects the real-time voltage of the lithium battery through the signal interface and the external connection unit, and determines whether the lithium battery is full after comparing it with the reference voltage. If the lithium battery is full, a control signal is sent to the optical coupler control module 5 through the control signal output unit.

[0041] Specifically, in Figure 2 In the figure, the positive output (V+) of the second rectifier module 2 is led out and connected to the battery voltage sampling unit and the filter capacitor C1 respectively. The other end of the filter capacitor is connected to the reference voltage sampling unit. The battery voltage sampling unit forms a voltage divider circuit through voltage divider resistors R1, R2, R3, R5, R6, and R7. The voltage divider circuit is connected to an external signal or an external unit through a high-speed switching diode D2 to sample the voltage of the lithium battery. The reference voltage sampling unit is composed of two high-speed switching diodes D1 and D4 and two resistors R4 and R52. D1 and D4 are in series, and D1, R4, and R52 are in parallel. The signal interface and the external connection unit are as follows: Figure 2 As shown in P3, P5, P21 and P22 in FIG, external signals such as lithium batteries and temperature sensors are connected.

[0042] The high-speed switching diode used in this embodiment is 1N4148.

[0043] The output ends of the first rectifier module 1 and the second rectifier module 2 are both connected with filter capacitors, namely the filter capacitors C1 and C2 mentioned above.

[0044] The working principle of this embodiment is as follows:

[0045] When the 220V AC power supply is connected, the closed coil of the power relay 4 receives a 24V short-time pulse, the contacts are closed, the input end of the first rectifier module 1 is connected to the AC power supply, and the charging circuit is activated. The charger starts to charge the lithium battery, and the LED on the photocoupler 6 is off. When the lithium battery is fully charged, the charging detection module 3 compares the detected lithium battery voltage with the reference voltage, detects that the lithium battery voltage reaches the preset cut-off voltage, and the charger lights up the green light diode and outputs a control signal to the optocoupler control module 5. The optocoupler control module 5 provides a 2V level signal to the photocoupler 6, controls the internal LED of the photocoupler 6 to turn on, causes the output end transistor to turn on, the output end of the photocoupler 6 to turn on, the coil of the power relay 4 is energized, the contacts switch state, and the charging circuit is cut off, that is, the input phase line L connected to the first rectifier module 1 is cut off. Once the contacts of the power relay 4 are switched, the charging circuit stops charging the battery because the output of the AC power supply is cut off, thereby preventing overcharging.

[0046] In some other embodiments of the present invention, in addition to the lithium battery voltage reaching a preset cut-off voltage, the full state determination condition also includes collecting the temperature data of the lithium battery. The battery is determined to be fully charged only when the lithium battery voltage reaches the preset cut-off voltage and the temperature is normal.

[0047] Embodiment 2

[0048] This embodiment is a lithium battery charging protection board, and the lithium battery charging protection board includes the lithium battery charging protection circuit as described in the first embodiment.

[0049] Embodiment 3

[0050] This embodiment is a lithium battery system, comprising:

[0051] Lithium batteries; and

[0052] As described in the second embodiment of the lithium battery charging protection board, the lithium battery charging protection board is used to disconnect the charging circuit after the lithium battery is fully charged.

[0053] The above is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A lithium battery charging protection circuit, comprising a first rectifier module (1), a second rectifier module (2) and a charging detection module (3), wherein the second rectifier module (2) is connected to an AC power supply to provide a working power supply for the charging detection module (3); It is characterized in that The first rectifier module (1) is connected to an AC power source via a power relay (4) to provide charging input for the lithium battery and to supply power to the optical coupling control module (5), the photoelectric coupler (6) and the relay drive module (7); The optical coupling control module (5) receives a control signal from the charging detection module (3), controls the internal light-emitting unit of the photoelectric coupler (6) to be turned on, and the output transistor of the photoelectric coupler (6) controls the on and off of the relay driving module (7), and the relay driving module (7) is used to control the on and off of the power relay (4); The charging detection module (3) monitors the charging voltage of the lithium battery through a signal interface and an external connection unit, determines whether the lithium battery has reached a fully charged state through a voltage-dividing resistor and a comparison circuit, and sends a control signal to the optical coupling control module (5) when the lithium battery has reached a fully charged state.

2. A lithium battery charging protection circuit according to claim 1, characterized in that: The models of the first rectifier module (1) and the second rectifier module (2) are both KBP310.

3. A lithium battery charging protection circuit according to claim 1, characterized in that: After passing through a plurality of voltage-dividing resistors, an energy storage resistor is connected between the positive output end of the first rectifier module (1) and the negative output end, and the specification of the energy storage resistor is 4.7 μF / 200V.

4. A lithium battery charging protection circuit according to claim 1, characterized in that: The power relay (4) is a set of normally open 24V double-coil magnetic latching power relays.

5. A lithium battery charging protection circuit according to claim 4, characterized in that: The power relay (4) is HFE60 / 24-1HST-L2.

6. A lithium battery charging protection circuit according to claim 1, characterized in that: The photoelectric coupler (6) is PC817C-SOP4, pins 1 and 2 are connected to the output of the photocoupler control module (5), and pins 3 and 4 are output ends connected to the relay drive module (7).

7. A lithium battery charging protection circuit according to claim 1, characterized in that: The charging detection module (3) further comprises a battery voltage sampling unit, a reference voltage sampling unit, a signal interface and an external connection unit, and a control signal output unit. The battery voltage sampling unit collects the real-time voltage of the lithium battery through the signal interface and the external connection unit, and determines whether the lithium battery is fully charged after comparing it with the reference voltage. If the lithium battery is fully charged, a control signal is sent to the optical coupling control module (5) through the control signal output unit.

8. A lithium battery charging protection circuit according to claim 1, characterized in that: The output ends of the first rectifier module (1) and the second rectifier module (2) are both connected to filter capacitors.

9. A lithium battery charging protection board, characterized in that: The lithium battery charging protection board includes the lithium battery charging protection circuit as described in any one of claims 1-8.

10. A lithium battery system, characterized in that: include: Lithium batteries; as well as According to the lithium battery charging protection board described in claim 9, the lithium battery charging protection board is used to disconnect the charging circuit after the lithium battery is fully charged.

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