Protection circuit and protection method of starting type lithium battery

Abstract

The invention belongs to the technical field of lithium batteries, and discloses a starting type lithium battery protection circuit and a protection method.The starting type lithium battery protection circuit comprises a main power supply circuit, a charging circuit and a management system.The main power supply circuit comprises an original vehicle generator and an electric appliance, and the original vehicle generator is connected with the electric appliance in series; the charging circuit comprises an original vehicle generator, a relay and a lithium battery power pack, the original vehicle generator is connected with the relay and the lithium battery power pack in series, and the original vehicle generator is used for supplying power to electric appliances and charging the lithium battery power pack at the same time when working; the lithium battery charging device is simple in overall structure, can charge the lithium battery, ensures that the lithium battery does not output superimposed current to other electric appliances, and achieves the effect of protecting the electric appliances.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and in particular relates to a protection circuit and a protection method for a starter-type lithium battery. Background Art

[0002] When the car is driving, the generator not only supplies power to the electrical appliances in the car, but also charges the starting lithium battery to replenish the power consumption during startup and ensure that the starting lithium battery always maintains sufficient power.

[0003] When the vehicle is stopped, starting lithium batteries primarily power a portion of the vehicle's electrical loads. This power supply covers key loads such as the instrument panel (including the full LCD display and sensor network), lighting system (LED headlights and ambient lighting), and air conditioning system (electric compressor and blower). Therefore, starting lithium batteries frequently undergo charge and discharge cycles during use.

[0004] In the prior art, starting lithium batteries are often protected by connecting a charging MOS tube and a discharging MOS tube in series in the circuit. When the charging protection condition is reached, the charging MOS tube is disconnected, and only discharging is possible but not charging. When the discharging protection condition is reached, the discharging MOS tube is disconnected, and only charging is possible but not discharging.

[0005] like Figure 1-2 As shown, a schematic diagram of a lithium battery protection circuit in the prior art and a schematic diagram of a circuit when the charging MOS tube in the prior art lithium battery protection circuit is disconnected are shown. The lithium battery power pack 7 is used in parallel with the electrical appliance 2 and the original vehicle generator 1, while the charging MOS tube 5 (Metal-Oxide-Semiconductor Field-Effect Transistor, i.e., a metal oxide semiconductor field effect transistor. It is a semiconductor device that uses the electric field effect to control the current size. The core structure consists of a metal gate, an oxide insulating layer, and a semiconductor channel) and the discharging MOS tube 4 are used in series with the lithium battery power pack 7. When the vehicle is started, part of the electricity generated by the original vehicle generator 1 is used by the electrical appliance 2, and part is used to charge the lithium battery power pack 7. During this period, the original vehicle generator 1 adjusts the power generation through the voltage regulator 3.

[0006] When the lithium battery power pack 7 reaches the charging protection condition, the charging MOS tube 5 is disconnected, and the lithium battery power pack 7 is no longer charged, causing the voltage of the original vehicle generator 1 to rise instantaneously. In this circuit, the original vehicle generator 1 adopts a generator with a voltage regulator 3, which can adjust the generator power generation by setting a threshold value, that is, the voltage of the original vehicle generator 1 rises instantaneously and reaches the threshold value of the voltage regulator 3, thereby controlling the original vehicle generator 1 to reduce or stop power generation. At this time, the voltage of the original vehicle generator 1 drops instantaneously again, and then the voltage regulator 3 controls the power generation of the original vehicle generator 1 to restore it. During this period, the discharge MOS tube 4 is always connected. When the voltage of the original vehicle generator 1 drops, the lithium battery power pack 7 is triggered to start discharging. At this moment, current superposition will be instantly formed in the power supply circuit of the electrical appliance 2, generating a surge, thereby burning part of the electrical appliance 2.

[0007] In the car's starting circuit, surge is a phenomenon in which voltage or current fluctuates violently and instantaneously in the circuit. It occurs in an extremely short time and the amplitude exceeds the standard: the voltage or current peak value can reach several to dozens of times the normal value. In the battery management system (BMS), if the CAN bus communication chip in the BMS is hit by a surge, it may cause data transmission errors or system paralysis, and even lead to the risk of battery thermal runaway, which is extremely harmful.

[0008] Therefore, although the use of MOS tubes can protect the lithium battery, it is easy to cause damage to the electrical appliance 2.

[0009] A Chinese patent application, CN2015108475770, discloses a lithium battery pack charge and discharge protection circuit. The positive and negative electrodes of the lithium battery pack are respectively connected to the positive and negative electrodes of an external power supply or external device. The protection circuit includes a battery management module and a control unit MCU. One output port of the MCU is connected to the input port of a discharge control signal amplifier U2, and the other output port is connected to the input port of a charge control signal amplifier U1. The output port of the discharge control signal amplifier U2 is connected to the gate of a discharge MOSFET, and the output port of the charge control signal amplifier U1 is connected to the gate of a charge MOSFET. The sources of both the discharge MOSFET and the charge MOSFET are grounded. This invention solves the problem in existing charge protection circuits where the source of the MOSFET is not grounded, requiring the addition of an isolation circuit to drive it. However, the application uses a discharge MOSFET and a charge MOSFET. Although this can protect the lithium battery pack from charging and discharging, if the circuit is connected to other electrical appliances, it will inevitably cause current superposition to other electrical appliances and damage them. Summary of the Invention

[0010] The main technical problem to be solved by the present invention is to provide a protection circuit and protection method for a starting type lithium battery with a simple overall structure, which can realize charging of a lithium battery power pack and at the same time ensure that the lithium battery power pack does not output superimposed current to other electrical appliances when a sudden voltage change occurs, thereby achieving the effect of protecting the electrical appliances.

[0011] In order to solve the above technical problems, the present invention provides the following technical solutions: A protection circuit for a starting lithium battery includes a main power supply circuit, a charging circuit, and a management system. The main power supply circuit includes an original vehicle generator and electrical appliances, which are connected in series. The charging circuit includes an original vehicle generator, a relay, and a lithium battery power pack, which are connected in series. When the original vehicle generator is working, it is used to power the electrical appliances and charge the lithium battery power pack at the same time.

[0012] The following is a further optimization of the above technical solution by the present invention: The management system includes a battery management module and a processing system.

[0013] Further optimization: the positive pole of the output end of the original vehicle generator is connected in series with the voltage regulator and then connected to the positive pole of the lithium battery power pack through the contact switch of the relay, and the negative pole of the output end of the original vehicle generator is connected to the negative pole of the lithium battery power pack.

[0014] Further optimization: the positive pole of the output end of the original vehicle generator is connected to the positive pole of the electrical appliance, and the negative pole of the output end of the original vehicle generator is electrically connected to the negative pole of the electrical appliance.

[0015] Further optimization: The battery management module detects the current voltage value of the lithium battery power pack.

[0016] Further optimization: the control coil of the relay is simultaneously connected to the processing system of the management system.

[0017] Further optimization: The battery management module transmits the detected current voltage value to the processing system, and the processing system then compares the current voltage value with the safe voltage value to control the disconnection or connection of the relay contacts.

[0018] The present invention also provides a protection method for a starter-type lithium battery, based on the above-mentioned protection circuit for a starter-type lithium battery, comprising the following steps: S1. Start the car, energize the relay, and start the original car generator at the same time, so that the original car generator can supply power to the electrical appliances; S2, the processing system is preset with a safe voltage range of V1 to V2, and the battery management module feeds back the detected voltage V to the processing system for comparison; S3. When the V compared by the processing system is smaller than V1, the contacts of the control relay are closed, connecting the circuit between the original vehicle generator and the lithium battery power pack, and then the original vehicle generator charges the lithium battery power pack; When V is within the range of V1~V2, the contacts of the relay are kept closed, the circuit between the original vehicle generator and the lithium battery power pack is connected, and the lithium battery power pack is charged; When V is greater than V2, the contacts of the processing system control relay are disconnected, cutting off the charging circuit between the original vehicle generator and the lithium battery power pack, to prevent the lithium battery power pack from outputting superimposed current to the electrical appliances when the voltage fluctuates, causing damage; S4. When the charging circuit of the lithium battery power pack is cut off, the output current of the original vehicle generator will all flow to the electrical appliances, causing the voltage at both ends of the electrical appliances to rise instantly. At this time, the voltage regulator detects the voltage rise and immediately reduces the excitation current of the original vehicle generator, thereby reducing its power generation and restoring the system voltage to a stable value to protect the electrical appliances; S5. When the car stops, the relay keeps the contacts disconnected due to power outage, the original car generator stops working, and the lithium battery power pack directly supplies power to the electrical equipment on the car that needs to maintain basic functions. At this time, the lithium battery power pack discharges to ensure the basic functions of these electrical equipment.

[0019] The present invention adopts the above technical solution and has the following beneficial effects: 1. The present invention adopts the above technical solution, which is ingenious in conception and reasonable in structure. It can detect the voltage of the lithium battery power pack on the vehicle while the vehicle is moving, automatically charge the lithium battery power pack, and after charging is completed, it automatically stops charging the lithium battery power pack by controlling the relay to disconnect the contacts. This ensures that when the charging circuit is disconnected and the system voltage changes instantaneously, the lithium battery power pack will not superimpose discharge current on the electrical appliances through the circuit, thereby protecting the electrical appliances and preventing damage to the electrical appliances due to surge current. 2. The device of the present application can further protect electrical appliances through the regulation of the voltage regulator, avoiding additional voltage mutations that may cause electrical appliances to be subjected to overvoltage surge impacts, thereby further ensuring the use effect and life of the electrical appliances.

[0020] The present invention will be further described below with reference to the accompanying drawings and examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of a lithium battery protection circuit in the prior art; Figure 2 This is a circuit diagram of a lithium battery protection circuit in the prior art when the charging MOS tube is disconnected; Figure 3 A schematic diagram of a protection circuit for charging according to an embodiment of the present invention; Figure 4Schematic diagram of a protection circuit for a disconnected relay in an embodiment of the present invention.

[0022] In the picture: 1. Original vehicle generator; 2. Electrical appliances; 3. Voltage regulator; 4. Discharge MOS tube; 5. Charging MOS tube; 6. Management system; 61. Relay; 7. Lithium battery power pack. DETAILED DESCRIPTION

[0023] like Figure 3-4 As shown: A protection circuit for a starting type lithium battery, including a main power supply circuit, a charging circuit and a management system 6. The main power supply circuit includes an original vehicle generator 1 and an electrical appliance 2, which are connected in series. The charging circuit includes the original vehicle generator 1, a relay 61 and a lithium battery power pack 7, which are connected in series with the original vehicle generator 1, the relay 61 and the lithium battery power pack 7. When the original vehicle generator 1 is working, it is used to power the electrical appliance 2 and charge the lithium battery power pack 7 at the same time.

[0024] The management system 6 includes a battery management module and a processing system; The battery management module detects the current voltage value of the lithium battery power pack 7.

[0025] The positive output terminal of the original vehicle generator 1 is connected in series with the voltage regulator 3 and then connected to the positive electrode of the lithium battery power pack 7 through the contact switch of the relay 61. The negative output terminal of the original vehicle generator 1 is electrically connected to the negative electrode of the lithium battery power pack 7.

[0026] The positive pole of the output end of the original vehicle generator 1 is connected to the positive pole of the electrical appliance 2 , and the negative pole of the output end of the original vehicle generator 1 is connected to the negative pole of the electrical appliance 2 .

[0027] The control coil of the relay 61 is also electrically connected to the processing system of the management system 6. That is, the processing system switches the contacts between two states by controlling the on and off of the relay 61 coil: Closed state: the processing system controls the relay 61 contacts to close, thus connecting the charging circuit from the original vehicle generator 1 to the lithium battery power pack 7; Disconnected state: The processing system controls the contacts of the relay 61 to be disconnected, cutting off the charging circuit from the original vehicle generator 1 to the lithium battery power pack 7, thereby preventing the lithium battery power pack 7 from superimposing a discharge current on the electrical appliance 2 due to voltage fluctuations when the charging circuit is disconnected.

[0028] In this embodiment, the relay 61 is a solid-state relay, which can eliminate contact bounce and avoid the harm of new surges caused by contact bounce.

[0029] The processing system is the MCU unit of the car, which can preset a safe voltage value. The battery management module transmits the detected current voltage value to the processing system, and the processing system then compares the current voltage value with the safe voltage value to control the contact of relay 61 to open or close.

[0030] When the contacts of the relay 61 are closed, the connection circuit between the original vehicle generator 1 and the lithium battery power pack 7 is connected, and the original vehicle generator 1 can charge the lithium battery power pack 7.

[0031] When the contacts of the relay 61 are disconnected, the connection circuit between the original vehicle generator 1 and the lithium battery power pack 7 is disconnected, and the original vehicle generator 1 cannot charge the lithium battery power pack 7. At the same time, it prevents the lithium battery power pack 7 from superimposing a discharge current on the electrical appliance 2 when the voltage fluctuates.

[0032] The voltage regulator 3 can identify the real-time voltage of the original vehicle generator 1 and adjust the power generation of the original vehicle generator 1 in real time to ensure a stable output voltage. The specific identification and adjustment principles are well known in the prior art and will not be repeated here.

[0033] Exemplarily, the safety voltage value is preset to a minimum of V1 and a maximum of V2. V1 and V2 are the safety voltages of the lithium battery power pack 7. The detected voltage is V. When it is detected that the voltage V is less than V1, the lithium battery power pack 7 is controlled to be charged. When it is detected that the voltage V is greater than V2, the charging of the lithium battery power pack 7 is stopped.

[0034] When the voltage V is detected to be between V1 and V2, the lithium battery power pack 7 is also kept charged.

[0035] The MCU, also known as a single-chip microcomputer or single-chip microcomputer, is a chip-level computer that reduces the frequency and specifications of the central processing unit (CPU) and integrates memory, timers, USB, A / D conversion, UART, PLC, DMA and other peripheral interfaces, and even LCD driver circuits on a single chip. It can provide different combination controls for different applications. Its specific principles and connection methods are well known and will not be repeated here.

[0036] The protection method of the protection circuit of the present application includes the following steps: S1, start the car and energize the relay 61, and at the same time start the original vehicle generator 1, which then supplies power to the electrical appliance 2; S2, the processing system is preset with a safe voltage range of V1 to V2, and the battery management module feeds back the detected voltage V to the processing system for comparison; S3. When the value V compared by the processing system is smaller than V1, the contact of the control relay 61 is closed, connecting the circuit between the original vehicle generator 1 and the lithium battery power pack 7. Then, the original vehicle generator 1 charges the lithium battery power pack 7. When V is within the range of V1 to V2, the contacts of the relay 61 are kept closed, the circuit between the original vehicle generator 1 and the lithium battery power pack 7 is connected, and the lithium battery power pack 7 is charged; When V is greater than V2, the processing system controls the contacts of the relay 61 to be disconnected, cutting off the charging circuit between the original vehicle generator 1 and the lithium battery power pack 7, thereby preventing the lithium battery power pack 7 from outputting superimposed current to the electrical appliance 2 when the voltage fluctuates, thereby preventing damage. That is, this operation simultaneously disconnects the potential path for the lithium battery power pack 7 to discharge to the electrical appliance 2 through the contacts of the relay 61. More importantly, it avoids the superimposed discharge current that may be generated by the lithium battery power pack 7 due to the voltage fluctuation of the original vehicle generator 1 at the moment the charging circuit is disconnected, thereby protecting the electrical appliance 2 from surge damage.

[0037] During S4, when the charging circuit of the lithium battery power pack 7 is cut off (i.e., the contacts of the relay 61 are disconnected), the output current of the original vehicle generator 1 will all flow to the electrical appliance 2, which may cause the voltage across it to increase instantaneously. At this time, the voltage regulator 3 detects the voltage increase and immediately reduces the excitation current (or equivalent control signal) of the original vehicle generator 1, thereby reducing its power generation and restoring the system voltage to a stable value, thereby protecting the electrical appliance 2; S5. When the car stops, the relay 61 remains in the disconnected state due to power failure, the original vehicle generator 1 stops working, and the lithium battery power pack 7 directly supplies power to the electrical devices on the car that need to maintain basic functions (such as the alarm system). At this time, the lithium battery power pack 7 discharges to ensure the basic functions of these electrical devices.

[0038] This design ensures that the service life of the electrical appliances 2 that require direct power supply from the original vehicle generator 1 is extended when the electrical appliances 2 are used to start the vehicle, without generating surges and improving the service life.

[0039] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A protection circuit for a starter-type lithium battery, comprising a main power supply circuit, a charging circuit, and a management system (6), characterized in that: The main power supply circuit includes an original vehicle generator (1) and an electrical appliance (2), the original vehicle generator (1) and the electrical appliance (2) are connected in series, and the charging circuit includes the original vehicle generator (1), a relay (61) and a lithium battery power pack (7), the original vehicle generator (1) and the relay (61) and the lithium battery power pack (7) are connected in series. When the original vehicle generator (1) is in operation, it is used to supply power to the electrical appliance (2) and charge the lithium battery power pack (7) at the same time.

2. The protection circuit of a starter type lithium battery according to claim 1, characterized in that: The management system (6) comprises a battery management module and a processing system.

3. The protection circuit of a starter type lithium battery according to claim 2, characterized in that: The positive electrode of the output end of the original vehicle generator (1) is connected in series with the voltage regulator (3) and then connected to the positive electrode of the lithium battery power pack (7) through the contact switch of the relay (61), and the negative electrode of the output end of the original vehicle generator (1) is connected to the negative electrode of the lithium battery power pack (7).

4. The protection circuit for a starter-type lithium battery according to claim 3, characterized in that: The positive pole of the output end of the original vehicle generator (1) is connected to the positive pole of the electrical appliance (2), and the negative pole of the output end of the original vehicle generator (1) is electrically connected to the negative pole of the electrical appliance (2).

5. The protection circuit of a starter type lithium battery according to claim 4, characterized in that: The battery management module detects the current voltage value of the lithium battery power pack (7).

6. The protection circuit of a starter type lithium battery according to claim 5, characterized in that: The control coil of the relay (61) is simultaneously connected to the processing system of the management system (6).

7. The protection circuit of a startup type lithium battery according to claim 6, characterized in that: The battery management module transmits the detected current voltage value to the processing system, and the processing system then compares the current voltage value with the safe voltage value to control the disconnection and connection of the contacts of the relay (61).

8. A method for protecting a starter-type lithium battery, based on the protection circuit of the starter-type lithium battery according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1, start the car and energize the relay (61), and at the same time start the original car generator (1), so that the original car generator (1) supplies power to the electrical appliance (2); S2, the processing system is preset with a safe voltage range of V1 to V2, and the battery management module feeds back the detected voltage V to the processing system for comparison; S3, when the V compared by the processing system is smaller than V1, the contact of the control relay (61) is closed, and the circuit between the original vehicle generator (1) and the lithium battery power pack (7) is connected, and then the original vehicle generator (1) charges the lithium battery power pack (7); When V is within the range of V1 to V2, the contacts of the relay (61) are kept closed, the circuit between the original vehicle generator (1) and the lithium battery power pack (7) is connected, and the lithium battery power pack (7) is charged; When V is greater than V2, the contacts of the processing system control relay (61) are disconnected, cutting off the charging circuit between the original vehicle generator (1) and the lithium battery power pack (7), thereby preventing the lithium battery power pack (7) from outputting superimposed current to the electrical appliance (2) when the voltage fluctuates, thereby preventing damage; S4. When the charging circuit of the lithium battery power pack (7) is cut off, the output current of the original vehicle generator (1) will all flow to the electrical appliance (2), causing the voltage at both ends of the electrical appliance to increase instantly. At this time, the voltage regulator (3) detects the voltage increase and immediately reduces the excitation current of the original vehicle generator (1), thereby reducing its power generation and restoring the system voltage to a stable value, thereby protecting the electrical appliance (2); S5. When the car stops, the relay (61) maintains the contact disconnected state due to power failure, the original vehicle generator (1) stops working, and the lithium battery power pack (7) directly supplies power to the electrical equipment on the car that needs to maintain basic functions. At this time, the lithium battery power pack (7) discharges to ensure the basic functions of these electrical equipment.

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