Wide voltage input charging method for lithium battery with same charging and discharging port

Abstract

The invention relates to the technical field of a lithium battery BMS (Battery Management System), in particular to a wide voltage input charging method of a lithium battery with the same charging and discharging port. A wide voltage input charging method for a lithium battery with the same charging and discharging port is characterized in that the positive electrode end of the battery is connected with one end of a charging MOS and one end of a wide voltage input constant-current constant-voltage source module, the other end of the charging MOS is connected with one end of a discharging MOS, and the other end of the discharging MOS and the other end of the wide voltage input constant-current constant-voltage source module are combined and connected with a charger; one end of the battery is connected with one end of the current sampling unit, and the other end of the current sampling unit is connected with the charger; the battery is connected with the AFE through a battery cell voltage sampling circuit, the current sampling unit is connected with the AFE through a current sampling circuit, and the AFE is respectively connected with the charging MOS and the discharging MOS through a control signal circuit. Compared with the prior art, wide-voltage charging can be realized under the condition that discharging and large-current charging are not influenced.

Description

Technical Field

[0001] This invention relates to the technical field of lithium battery BMS, specifically a wide voltage input charging method for lithium batteries with the same charging and discharging port. Background Technology

[0002] Lithium batteries are becoming increasingly common, and lithium batteries with different series ratios and different chemical compositions have different voltages. Therefore, the corresponding charger voltages also differ. If a circuit could be provided that allows a single battery to be compatible with chargers on multiple voltage platforms, it would greatly facilitate battery replacement, allowing customers to replace the battery directly without changing the charger. Batteries are further divided into those with separate charge / discharge ports and those with a single charge / discharge port. For applications with separate charge / discharge ports, since the charging port is independent, achieving a wide voltage input can be achieved simply by adding a wide voltage input regulated power supply to the charging port, which is not difficult. However, for applications with a single charge / discharge port, since the same port needs to both discharge and charge, and for some electric vehicle applications, it also needs to absorb the charging current induced by braking, a single regulated power supply is insufficient.

[0003] Therefore, for applications that use the same charging and discharging port, a method needs to be designed to achieve wide-voltage charging while ensuring that discharging and high-current charging are not affected. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a wide voltage input charging method for lithium batteries with the same charging and discharging port, which can achieve wide voltage charging without affecting discharge and high current charging.

[0005] To achieve the above objectives, a wide-voltage input charging method for lithium batteries with simultaneous charging and discharging is designed, comprising a battery, a battery management system (BMS), and a charger. The BMS is characterized by: a charging MOS, a discharging MOS, a wide-voltage input constant current / constant voltage source module, an amplifier front-end (AFE), an MCU, a charger voltage detection circuit, and a current sampling unit. The positive terminal of the battery is connected to one end of the charging MOS and one end of the wide-voltage input constant current / constant voltage source module, respectively. The other end of the charging MOS is connected to one end of the discharging MOS, and the other end of the discharging MOS and the other end of the wide-voltage input constant current / constant voltage source module are combined and connected to the charger. One end of the battery is connected to one end of the current sampling unit, and the other end of the current sampling unit is connected to the charger. The battery is connected to the AFE via a cell voltage sampling line, and the current sampling unit is connected to the AFE via a current sampling line. The AFE is connected to the charging MOS and the discharging MOS via control signal lines, respectively. The AFE is connected to the MCU via an I2C communication line, and the charger voltage detection circuit is connected to the MCU via the charger voltage sampling line. The wide voltage input charging method includes the following steps: S1, set a total voltage threshold, which is the full charge voltage of the battery, and is also equal to the output voltage of the constant current and constant voltage source built into the BMS. S2, AFE detects the current voltage of the battery. When the battery voltage is lower than the total voltage threshold, AFE controls the charging MOS and discharging MOS to be turned on, so that the battery can be charged and discharged normally. S3, AFE detects the current voltage of the battery. When the battery voltage is greater than or equal to the total voltage threshold and there is charging current, the MCU controls the AFE to turn off the charging MOS and discharging MOS, and turn on the wide voltage input constant current constant voltage source module. S4. After the trickle charging is complete, the MCU determines whether the charger is in place by detecting the voltage of the charger voltage detection circuit. If it is in place, the charging MOS and discharging MOS remain in the off state. If it has been removed, the charging MOS and discharging MOS are turned on.

[0006] In step S1, the total voltage threshold includes the voltage threshold of the ternary lithium battery cell and the voltage threshold of the iron phosphate battery cell. The voltage threshold of the ternary lithium battery cell is the number of series * 4.2V, and the voltage threshold of the iron phosphate battery cell is the transmission * 3.65V.

[0007] In step S3, whether there is a charging current is determined by the current sampling unit sending the current signal to the AFE, and the MCU reading the current collected by the AFE through the I2C communication line.

[0008] In step S3, before and after turning off the charging MOS and discharging MOS, the power supply for charging the battery changes from an external constant current and constant voltage source to an internal constant current and constant voltage source. There are two possible scenarios: (1) When the current of the external constant current and constant voltage source is greater than that of the internal one, the battery voltage will drop when switching. At this time, when the internal constant current and constant voltage source is charging, it will first maintain constant current and then constant voltage. (2) When the current of the external constant current and constant voltage source is less than or equal to that of the internal source, the battery voltage remains unchanged during the switching process, and the internal constant current and constant voltage source directly enters the constant voltage stage.

[0009] Since the voltage will drop when switching in situation (1), in order to prevent the battery voltage from falling below the total voltage and causing the charging MOS and discharging MOS to turn on again, the charging MOS and discharging MOS will not be turned on during the charging switching process.

[0010] The BMS mentioned is a lithium battery management system.

[0011] The AFE mentioned is a digital front-end chip for lithium battery BMS, and the model of the AFE is Zhongying SH367309.

[0012] The MCU mentioned is a microcontroller chip for lithium battery BMS, and the MCU model is STM32F072.

[0013] The wide voltage input constant current and constant voltage source is a DC-DC module with wide voltage input and constant current and constant voltage functions.

[0014] Compared with the prior art, the present invention provides a wide voltage input charging method for lithium batteries with the same charging and discharging port, which can achieve wide voltage charging without affecting discharge and high current charging.

[0015] The onboard constant current and constant voltage source only operates in the trickle or near-trickek stage, so the power can be made smaller, which does not affect the total charging time and can also effectively reduce heat generation and cost. Attached Figure Description

[0016] Figure 1 This is a structural connection diagram of the present invention. Detailed Implementation

[0017] The present invention will now be further described with reference to the accompanying drawings.

[0018] like Figure 1 As shown, a wide-voltage input charging method for a lithium battery with a single charging and discharging port includes a battery, a battery management system (BMS), and a charger. The BMS includes a charging MOS, a discharging MOS, a wide-voltage input constant current / constant voltage source module, an amplifier front-end (AFE), an MCU, a charger voltage detection circuit, and a current sampling unit. The positive terminal of the battery is connected to one end of the charging MOS and one end of the wide-voltage input constant current / constant voltage source module, respectively. The other end of the charging MOS is connected to one end of the discharging MOS, and the other end of the discharging MOS and the other end of the wide-voltage input constant current / constant voltage source module are connected together to the charger. One end of the battery is connected to one end of the current sampling unit, and the other end of the current sampling unit is connected to the charger. The battery is connected to the AFE through a cell voltage sampling line, and the current sampling unit is connected to the AFE through a current sampling line. The AFE is connected to the charging MOS and the discharging MOS through control signal lines, respectively. The AFE is connected to the MCU through an I2C communication line, and the charger voltage detection circuit is connected to the MCU through the charger voltage sampling line.

[0019] BMS: Lithium Battery Management System.

[0020] AFE: Digital front-end chip used in lithium battery BMS. The AFE model is Zhongying SH367309. It mainly monitors battery voltage, temperature and current, and controls the opening and closing of charging MOS and discharging MOS.

[0021] MCU: Microcontroller chip used in lithium battery BMS. The MCU model is STM32F072. The MCU communicates with AFE via I2C to obtain parameters such as current, voltage, and temperature, and can send commands to control AFE to turn off the charging MOS or discharging MOS.

[0022] Wide-input constant-current constant-voltage source: This is a DC-DC module with wide-input constant-current and constant-voltage functions. It can convert the charger voltage into the voltage required by the battery pack. It is connected to the main circuit containing the charging MOS and discharging MOS (i.e., Figure 1 The circuit 1) is connected in parallel as the second path for charging, and this circuit can only charge and cannot discharge.

[0023] Charging MOS: When turned on, current can flow through the main circuit to charge the battery; when turned off, current cannot flow through the main circuit to charge the battery.

[0024] Discharge MOS: When turned on, current can discharge through the main circuit; when turned off, current cannot discharge through the main circuit.

[0025] Current sampling unit: The AFE collects current through this module.

[0026] Charger voltage detection circuit: The MCU uses an ADC to detect the voltage at the charging and discharging port.

[0027] The wide voltage input charging method includes the following steps: S1, set a total voltage threshold, which is the full charge voltage of the battery, and is also equal to the output voltage of the constant current and constant voltage source built into the BMS.

[0028] The total voltage threshold includes the voltage threshold of ternary lithium batteries and the voltage threshold of iron phosphate batteries. The voltage threshold of ternary lithium batteries is the number of series * 4.2V, and the voltage threshold of iron phosphate batteries is the transmission * 3.65V.

[0029] S2, AFE detects the current voltage of the battery. When the battery voltage is lower than the total voltage threshold, AFE controls the charging MOS and discharging MOS to be turned on, so that the battery can be charged and discharged normally.

[0030] S3, AFE detects the current battery voltage. When the battery voltage is greater than or equal to the total voltage threshold and there is charging current, the MCU controls the AFE to turn off the charging MOS and discharging MOS, and turn on the wide voltage input constant current constant voltage source module.

[0031] Whether there is charging current is determined by the current sampling unit sending the current signal to the AFE, and the MCU reading the current collected by the AFE through the I2C communication line.

[0032] S4. After the trickle charging is complete, the MCU determines whether the charger is in place by detecting the voltage of the charger voltage detection circuit. If it is in place, the charging MOS and discharging MOS remain in the off state. If it has been removed, the charging MOS and discharging MOS are turned on.

[0033] Before and after turning off the charging MOS and discharging MOS, the power supply for charging the battery changes from an external constant current and constant voltage source to an internal constant current and constant voltage source. There are two possible scenarios: The first scenario: When the current of the external constant current and constant voltage source is greater than that of the internal one, the battery voltage will drop when switching. At this time, when the internal constant current and constant voltage source is charging, it will first maintain constant current and then constant voltage. The second scenario: When the current of the external constant current and constant voltage source is less than or equal to that of the internal source, the battery voltage remains unchanged during switching, and the internal constant current and constant voltage source directly enters the constant voltage stage.

[0034] Since the voltage drops during the first scenario, in order to prevent the battery voltage from falling below the total voltage and causing the charging MOS and discharging MOS to turn on again, the charging MOS and discharging MOS are not turned on during the charging switching process.

[0035] like Figure 1 As shown, loop 1 (main loop) and loop 2 are connected in parallel. The charging MOSFET and discharging MOSFET on loop 1 can be considered as switches. When the switches are open, the impedance of loop 1 is very small, while loop 2 is a power supply with a very large impedance. Therefore, when the charging MOSFET and discharging MOSFET on loop 1 are open, the current only flows through loop 1 and not through loop 2. When the charging MOSFET and discharging MOSFET on loop 1 are closed, the impedance of loop 1 becomes very large, and the current can only flow through loop 2.

[0036] In addition, the wide voltage input constant current and constant voltage source module has an enable switch controlled by the MCU. When loop 1 is working, loop 1 is open and loop 2 is closed; when loop 2 is working, loop 1 is closed and loop 2 is open.

[0037] The battery cell has an internal resistance, which is denoted as Ri. The cell open-circuit voltage (the voltage when there is no current) is denoted as V0. The external constant current is denoted as I1, and the internal constant current is denoted as I2.

[0038] In the first scenario, where I1 > I2, let the actual cell voltage under constant external voltage be V1, and the actual cell voltage under internal voltage be V2. Then, V1 = V0 + I1 * Ri, and V2 = V0 + I2 * Ri. Since I1 > I2, V1 > V2. The switching occurs when V1 equals the constant voltage. Since V2 is less than the constant voltage at this point, constant current is applied first, and then constant voltage is applied once V2 equals the constant voltage.

[0039] The characteristic of a constant current and constant voltage source is that it operates with constant current first and then constant voltage. No operation is required. When the voltage is lower than the constant voltage point, it outputs the maximum current. When the voltage is higher than the constant voltage point, the voltage remains constant and the current decreases.

[0040] To prevent the battery voltage from falling below the total voltage, which could cause the charge / discharge MOSFET to re-turn on. If: currently in loop 2 and the charger is present, then do not switch to loop 2. If: currently in loop 2 and the charger is not present, then switch back to loop 2.

Claims

1. A wide-voltage input charging method for a lithium battery with a single charging and discharging port, comprising a battery, a BMS, and a charger, characterized in that: The BMS includes a charging MOS, a discharging MOS, a wide-voltage input constant current and constant voltage source module, an AFE, an MCU, a charger voltage detection circuit, and a current sampling unit. The positive terminal of the battery is connected to one end of the charging MOS and one end of the wide-voltage input constant current and constant voltage source module, respectively. The other end of the charging MOS is connected to one end of the discharging MOS, and the other end of the discharging MOS and the other end of the wide-voltage input constant current and constant voltage source module are connected together to the charger. One end of the battery is connected to one end of the current sampling unit, and the other end of the current sampling unit is connected to the charger. The battery is connected to the AFE through a cell voltage sampling line, and the current sampling unit is connected to the AFE through a current sampling line. The AFE is connected to the charging MOS and the discharging MOS through control signal lines, respectively. The AFE is connected to the MCU via an I2C communication line, and the charger voltage detection circuit is connected to the MCU via a charger voltage sampling line. The wide voltage input charging method includes the following steps: S1, set a total voltage threshold, which is the full charge voltage of the battery, and is also equal to the output voltage of the constant current and constant voltage source built into the BMS. S2, AFE detects the current voltage of the battery. When the battery voltage is lower than the total voltage threshold, AFE controls the charging MOS and discharging MOS to be turned on, so that the battery can be charged and discharged normally. S3, AFE detects the current voltage of the battery. When the battery voltage is greater than or equal to the total voltage threshold and there is charging current, the MCU controls the AFE to turn off the charging MOS and discharging MOS, and turn on the wide voltage input constant current constant voltage source module. S4. After the trickle charging is complete, the MCU determines whether the charger is in place by detecting the voltage of the charger voltage detection circuit. If it is in place, the charging MOS and discharging MOS remain in the off state. If it has been removed, the charging MOS and discharging MOS are turned on.

2. The wide voltage input charging method for a lithium battery with a simultaneous charge and discharge port according to claim 1, characterized in that: In step S1, the total voltage threshold includes the voltage threshold of the ternary lithium battery cell and the voltage threshold of the iron phosphate battery cell. The voltage threshold of the ternary lithium battery cell is the number of series * 4.2V, and the voltage threshold of the iron phosphate battery cell is the transmission * 3.65V.

3. The wide voltage input charging method for a lithium battery with a simultaneous charge and discharge port according to claim 1, characterized in that: In step S3, whether there is a charging current is determined by the current sampling unit sending the current signal to the AFE, and the MCU reading the current collected by the AFE through the I2C communication line.

4. The wide voltage input charging method for a lithium battery with a simultaneous charge and discharge port according to claim 1, characterized in that: In step S3, before and after turning off the charging MOS and discharging MOS, the power supply for charging the battery changes from an external constant current and constant voltage source to an internal constant current and constant voltage source. There are two possible scenarios: (1) When the current of the external constant current and constant voltage source is greater than that of the internal one, the battery voltage will drop when switching. At this time, when the internal constant current and constant voltage source is charging, it will first maintain constant current and then constant voltage. (2) When the current of the external constant current and constant voltage source is less than or equal to that of the internal source, the battery voltage remains unchanged during the switching process, and the internal constant current and constant voltage source directly enters the constant voltage stage.

5. The wide voltage input charging method for a lithium battery with a simultaneous charge and discharge port according to claim 4, characterized in that: Since the voltage will drop when switching in situation (1), in order to prevent the battery voltage from falling below the total voltage and causing the charging MOS and discharging MOS to turn on again, the charging MOS and discharging MOS will not be turned on during the charging switching process.

6. The wide voltage input charging method for a lithium battery with a simultaneous charge and discharge port according to claim 1, characterized in that: The BMS mentioned is a lithium battery management system.

7. The wide voltage input charging method for a lithium battery with a simultaneous charge and discharge port according to claim 1, characterized in that: The AFE mentioned is a digital front-end chip for lithium battery BMS, and the model of the AFE is Zhongying SH367309.

8. The wide voltage input charging method for a lithium battery with a simultaneous charge and discharge port according to claim 1, characterized in that: The MCU mentioned is a microcontroller chip for lithium battery BMS, and the MCU model is STM32F072.

9. A wide-voltage input charging method for a lithium battery with a simultaneous charge and discharge port according to claim 1, characterized in that: The wide voltage input constant current and constant voltage source is a DC-DC module with wide voltage input and constant current and constant voltage functions.

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