Battery charging and discharging circuit, battery system

Abstract

The utility model discloses a battery charging and discharging circuit, including main circuit and control unit, main circuit includes the first series branch that constitutes by first electronic switch, second electronic switch, inductor, first electronic switch, second electronic switch reverse series connection, still including the second series branch that constitutes by controllable switch, first electronic switch anti-parallel first diode, second electronic switch anti-parallel second diode, first series branch, second series branch parallel, main circuit is equipped with current detection unit, first electronic switch, second electronic switch, controllable switch all are controlled in control unit, and current detection unit connects control unit. The utility model discloses a battery system and control method thereof. The utility model can effectively control the charging and discharging current of battery, avoid the damage of device caused by too large current, guarantee the safety of battery and service life.

Description

Technical Field

[0001] This utility model relates to the field of battery application technology, and in particular to a battery charging and discharging circuit and a battery system. Background Technology

[0002] In applications requiring high-current DC power, multiple batteries are typically connected in parallel to increase power capacity. However, under high-current operating conditions, especially during switching on and off, the resulting inrush current can affect battery safety and lifespan. Therefore, appropriate battery charging and discharging currents can effectively ensure battery safety and extend its lifespan. In particular, when batteries are connected in parallel, their voltages are not perfectly uniform; the higher-voltage battery will charge the lower-voltage battery. Direct parallel connection can result in a large current, causing battery damage or shortening battery lifespan.

[0003] When a battery is used to drive a motor, an additional pre-charging circuit is generally used to pre-charge the motor controller during battery discharge. The motor controller has many capacitors at its input. At the moment the battery discharge begins, the battery charges the capacitors through the DC bus, which is equivalent to a short circuit and generates a large instantaneous current. The existing solution is to add an additional pre-charging circuit consisting of a current-limiting resistor and a switch to charge the capacitors with a small current for a certain period of time before turning on the main circuit switch. Utility Model Content

[0004] To address the aforementioned problems, this utility model aims to provide a battery charging and discharging circuit, a battery system, and a control method thereof, which can effectively control the charging and discharging current of the battery, avoid damage to components due to excessive current, and ensure the safety and lifespan of the battery.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0006] Battery charging and discharging circuit, including main circuit and control unit;

[0007] The main circuit includes a first series branch consisting of a first electronic switch, a second electronic switch, and an inductor, wherein the first electronic switch and the second electronic switch are connected in reverse series; it also includes a second series branch consisting of a controllable switch, wherein the first electronic switch is connected in antiparallel to a first diode, the second electronic switch is connected in antiparallel to a second diode, and the first series branch and the second series branch are connected in parallel.

[0008] The main circuit is equipped with a current detection unit;

[0009] The first electronic switch, the second electronic switch, and the controllable switch are all controlled by the control unit, and the current detection unit is connected to the control unit.

[0010] Preferably, the first electronic switch and the second electronic switch are both MOSFETs or IGBTs, and the controllable switch is a relay or an anti-parallel thyristor.

[0011] Preferably, the current detection unit includes a Hall current sensor, a current transformer, or a shunt.

[0012] Furthermore, the control unit includes a control chip, a drive circuit, and a signal conditioning circuit. The control chip controls the first electronic switch, the second electronic switch, and the controllable switch through the drive circuit. The current detection unit is connected to the control chip through the signal conditioning circuit.

[0013] This utility model also discloses a battery system, which includes the above-mentioned battery charging and discharging circuit.

[0014] Preferably, the battery system includes at least two battery packs, with the main circuit connected in series on one electrode of each battery pack, and all battery packs connected in parallel.

[0015] Preferably, each battery pack is equipped with one control unit; or:

[0016] All battery packs share a single control unit.

[0017] Furthermore, the battery pack includes a plurality of associated cells, wherein the cells are lithium batteries.

[0018] This utility model also discloses a control method applicable to the above-mentioned battery system, including the following control strategies:

[0019] Discharge control: When the discharge current of the battery pack is greater than the first predetermined value, both the first electronic switch and the second electronic switch are turned off, and the controllable switch is closed; when the discharge current of the battery pack is not greater than the first predetermined value, the controllable switch is turned off, and one of the first electronic switch and the second electronic switch used for discharge is turned on, while the other is turned off.

[0020] Charging control: When the battery pack is charging, the controllable switch is turned off, one of the first electronic switch and the second electronic switch used for charging is turned on and the other is turned off, and the charging current is controlled not to exceed the second predetermined value.

[0021] Preferably, both the discharge current and the charging current are obtained through a current detection unit, and the method for controlling the charging current to be no greater than a second predetermined value is achieved by the control unit using PWM to control the duty cycle of the electronic switch used for charging.

[0022] The beneficial effects of this utility model are as follows:

[0023] 1. This utility model can effectively control the charging and discharging current of the battery, avoid damage to the device caused by excessive current, and ensure the safety and service life of the battery.

[0024] 2. This utility model uses an inductor, which can suppress sudden changes in current and further protect the device.

[0025] 3. This utility model is particularly suitable for the parallel use of batteries. When a battery with a higher voltage charges a battery with a lower voltage due to differences in battery voltage, it can effectively limit the current within a predetermined range and avoid damage to the device caused by excessive current.

[0026] 4. When the battery drives the motor, this utility model can achieve a small current output at the moment of power-on by controlling the duty cycle of the first electronic switch or the second electronic switch, thereby charging the capacitor at the input end of the motor controller with a small current. No additional pre-charging circuit is required, which reduces circuit complexity and saves costs. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the electronic switch in Example 1 when a MOSFET is used.

[0028] Figure 2 This is a schematic diagram of Example 2. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this utility model clearer, the following detailed description is provided in conjunction with the accompanying drawings.

[0030] Example 1

[0031] This embodiment discloses a battery charging and discharging circuit, including a main circuit and a control unit. The main circuit includes a first electronic switch and a second electronic switch, both of which are MOSFETs; however, IGBTs can also be used. Figure 1 In this design, NMOS transistors are used as MOSFETs, and relays are used as controllable switches. Specifically:

[0032] The source of MOSFET Q1 is connected to the source of MOSFET Q2, the cathode of diode D1, and the cathode of diode D2. The drain of MOSFET Q1 is connected to the anode of diode D1. The drain of MOSFET Q2 is connected to the anode of diode D2 and one end of inductor L1. The other end of inductor L1 is connected to one end of the normally open contact of relay K1. The other end of the normally open contact of relay K1 is connected to the drain of MOSFET Q1.

[0033] The current detection unit 1 is used to detect the current in the main circuit described above. The current detection unit 1 can be a Hall current sensor, a current transformer, or a shunt. The control unit 2 includes a control chip, a drive circuit, and a signal conditioning circuit. The control chip controls MOSFETs Q1 and Q2 and relay K1 through the drive circuit. The current detection unit 1 is connected to the control chip through the signal conditioning circuit.

[0034] The current detection unit 1, the gate of MOSFET Q1, the gate of MOSFET Q2, and the coil of relay K1 are all connected to the control unit 2.

[0035] In application, the main circuit is connected in series with the battery electrodes. The control unit 2 controls the MOSFET Q1 and MOSFET Q2 and the relay K1 according to the current detected by the current detection unit 1, so that the charging and discharging current passes through the contacts of MOSFET Q1, diode D2, inductor L1 or MOSFET Q2, diode D1, inductor L1 or relay K1.

[0036] For example, the main circuit described above can be connected in series with the negative terminal of the battery, that is, the drain of MOSFET Q1 is connected to the end closest to the battery, and the other end of inductor L1 is connected to the load or charging device. The current detection unit is used to detect the charging and discharging current through the main circuit; its specific operating state is as follows:

[0037] When the battery is discharging, the other end of inductor L1 is connected to the load, MOSFET Q1 is turned on, MOSFET Q2 is turned off, relay K1 is opened, and the current flows from the positive terminal of the battery to the load, then to inductor L1, diode D2, MOSFET Q1, and finally to the negative terminal of the battery. Alternatively, both MOSFETs Q1 and Q2 are turned off, relay K1 is closed, and the current flows from the positive terminal of the battery to the load, then to relay K1, and finally to the negative terminal of the battery.

[0038] When the battery is charging, the other end of inductor L1 is connected to the charging device. MOSFET Q1 is off, MOSFET Q2 is on, relay K1 is off, and the current flows from the negative terminal of the battery to the positive terminal of the battery. Alternatively, both MOSFETs Q1 and Q2 are off, relay K1 is closed, and the current flows from the negative terminal of the battery to the positive terminal of the battery.

[0039] When the battery is discharging through MOSFET Q1, the controller can adjust the duty cycle of MOSFET Q1 using PWM based on the current value detected by the current detection unit 1, thereby controlling the discharge current. When the battery is charging through MOSFET Q2, the controller can adjust the duty cycle of MOSFET Q2 using PWM based on the current value detected by the current detection unit 1, thereby controlling the charging current.

[0040] For cases where the first and second electronic switches use PMOS transistors or IGBTs or other suitable devices, and the controllable switch uses anti-parallel thyristors or other suitable devices, it can be determined according to... Figure 1 The electrical characteristics of the device are then used to establish the corresponding connection relationships, which will not be elaborated here.

[0041] Example 2

[0042] Based on Example 1, this example discloses a battery system, which includes the battery charging and discharging circuit as described in Example 1, specifically as follows: Figure 2 As shown, at least two battery packs are used in parallel. The negative terminal of each battery pack is connected in series with the battery charging and discharging circuit of Example 1. When the voltages of any two battery packs are unbalanced, when the battery pack with the higher voltage charges the battery pack with the lower voltage, relay K1 is disconnected. The battery pack with the higher voltage discharges through MOSFET Q1, and the battery pack with the lower voltage charges through MOSFET Q2, forming a current loop. The controller detects the current magnitude through the current measurement unit and adjusts the duty cycle of MOSFETs Q1 and Q2 using PWM to control the current within a predetermined range, preventing excessive current from damaging the devices. At the same time, the inductor can also suppress sudden current changes, further protecting the devices.

[0043] The battery pack comprises several associated battery cells, which are lithium batteries, including lithium iron phosphate cells, ternary lithium cells, lead-acid cells, and sodium-ion cells. Each battery pack is equipped with a control unit, or all battery packs share a single control unit.

[0044] Example 3

[0045] Based on Example 2, this example discloses a control method for this type of battery system, specifically including the following control strategies:

[0046] Discharge control: When the discharge current of the battery pack is greater than the first predetermined value, both the first electronic switch and the second electronic switch are turned off, and the controllable switch is closed; when the discharge current of the battery pack is not greater than the first predetermined value, the controllable switch is turned off, and one of the first electronic switch and the second electronic switch used for discharge is turned on, while the other is turned off.

[0047] Charging control: When the battery pack is charging, the controllable switch is turned off, one of the first electronic switch and the second electronic switch used for charging is turned on and the other is turned off, and the charging current is controlled not to exceed the second predetermined value.

[0048] In this embodiment, both the first predetermined value and the second predetermined value can be set to 50A. This effectively limits the charging current, especially preventing large charging and discharging currents between battery packs when they are unbalanced.

[0049] Example 4

[0050] Based on Example 3, this example discloses a control method for this type of battery system when used for motor drive, including a pre-charging method, as follows:

[0051] In the discharge control, during the initial stage of discharge, the duty cycle of the discharge electronic switch is controlled by PWM modulation to control the discharge current to not exceed the predetermined pre-charge current and maintain it for a predetermined duration, thereby achieving pre-charging of the capacitor at the input terminal of the motor controller. After the pre-charging is completed, the duty cycle of the discharge electronic switch is adjusted to switch to normal discharge.

[0052] Of course, there may be other embodiments of this utility model. Without departing from the spirit and essence of this utility model, those skilled in the art can make various corresponding changes and modifications based on this utility model, but these corresponding changes and modifications should all fall within the protection scope of the appended claims of this utility model.

Claims

1. A battery charging and discharging circuit, characterized in that, Including the main circuit and control unit; The main circuit includes a first series branch consisting of a first electronic switch, a second electronic switch, and an inductor, wherein the first electronic switch and the second electronic switch are connected in reverse series; it also includes a second series branch consisting of a controllable switch, wherein the first electronic switch is connected in antiparallel to a first diode, the second electronic switch is connected in antiparallel to a second diode, and the first series branch and the second series branch are connected in parallel. The main circuit is equipped with a current detection unit; The first electronic switch, the second electronic switch, and the controllable switch are all controlled by the control unit, and the current detection unit is connected to the control unit.

2. The battery charging and discharging circuit according to claim 1, characterized in that, Both the first electronic switch and the second electronic switch are MOSFETs or IGBTs, and the controllable switch is a relay or an anti-parallel thyristor.

3. The battery charging and discharging circuit according to claim 1, characterized in that: The current detection unit includes a Hall current sensor, a current transformer, or a shunt.

4. The battery charging and discharging circuit according to claim 1, characterized in that, The control unit includes a control chip, a drive circuit, and a signal conditioning circuit. The control chip controls a first electronic switch, a second electronic switch, and a controllable switch through the drive circuit. The current detection unit is connected to the control chip through the signal conditioning circuit.

5. A battery system, characterized in that, The battery system includes the battery charging and discharging circuit as described in any one of claims 1-4.

6. The battery system according to claim 5, characterized in that, It includes at least two battery packs, with the main circuit connected in series on one electrode of each battery pack, and all battery packs connected in parallel.

7. The battery system according to claim 6, characterized in that, Each battery pack is equipped with a control unit; or: All battery packs share a single control unit.

8. The battery system according to claim 6, characterized in that, The battery pack includes a plurality of associated cells, wherein the cells are lithium batteries.

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