Battery charging / discharging circuit system

Abstract

The present invention relates to a battery charging / discharging circuit system comprising: a battery pack; a switching MOSFET for switching the current of the battery pack; a battery management system (BMS) IC which controls discharging of the battery pack and protects the battery pack from overcharging and overdischarging; a passive balancing circuit which, when an imbalance in voltage between cells is detected by the BMS IC while the battery pack is being charged, activates a balance terminal to receive a control signal from the BMS IC and consumes the overcharge voltage of a corresponding battery cell exceeding a target voltage as heat energy; and an active balancing circuit which, when an imbalance in voltage between cells is detected by the BMS IC while the battery pack is not being charged, activates the balance terminal to receive a control signal from the BMS IC and supplies a current from a battery cell having a relatively high cell voltage to a battery cell having a relatively low cell voltage.

Description

Battery charging and discharging circuit system

[0001] The present invention relates to a battery charging / discharging circuit system that can perform passive balancing for voltage imbalance between cells during charging and separately perform active balancing when not in a charging or discharging state, depending on whether the battery pack is charged.

[0002] Typically, battery cells can be repeatedly charged and discharged through electrochemical reactions of their components, and a battery pack can be equipped with multiple such battery cells to increase the output voltage or output current.

[0003] Meanwhile, since the battery cells of the battery pack are arranged in a dense manner, it is important to release the heat generated from each battery cell. However, if the heat generated from the battery cells during the charging and discharging process is not properly released, heat accumulation occurs inside the battery pack, causing the battery cells to overheat, resulting in frequent accidents in which the battery cells ignite and explode.

[0004] For example, battery cells can be hazardous if charged significantly above their rated charge range, and battery life can be shortened if discharged below their rated charge range. The state of charge of these battery cells can become unbalanced due to a number of factors, most notably during manufacturing or during repeated charge and discharge cycles of the battery.

[0005] Accordingly, a technology is required that can effectively balance the voltage imbalance between cells by ensuring smooth flow of current during charging and discharging.

[0006] The technical problem to be achieved by the present invention is to provide a battery charging / discharging circuit system that can perform passive balancing when charging and separate active balancing when not in a charging or discharging state, depending on whether the battery pack is charged or not, for voltage imbalance between cells.

[0007] In order to achieve the above-described object, an embodiment of the present invention comprises: a battery pack having a plurality of battery cells connected in series and a balance terminal connected to each battery cell; a switching MOSFET that switches the current of the battery pack; a BMS (Battery Management System) IC that controls the switching MOSFET, monitors the cell voltages of the battery cells through the balance terminals to detect an imbalance in voltage between cells, controls to charge the battery pack until a target voltage is reached, controls cell balancing through a balance cable connected to each battery cell, controls discharge of the battery pack, and protects the battery pack from overcharge and overdischarge; a passive balancing circuit that, when charging of the battery pack is in progress and an imbalance in voltage between cells is detected by the BMS IC, activates the balance terminals, receives a control signal from the BMS IC, and consumes an overcharge voltage of a corresponding battery cell exceeding a target voltage as heat energy; And, a battery charging / discharging circuit system including an active balancing circuit that monitors the cell voltage of the battery cell through the balance terminal to detect a voltage imbalance between cells, and when charging or discharging of the battery pack is not in progress, if a voltage imbalance between cells is detected by the BMS IC, activates the balance terminal to receive a control signal from the BMS IC and supplies current from a battery cell having a relatively high cell voltage to a battery cell having a relatively low cell voltage.

[0008] Here, the passive balancing circuit can perform passive balancing by comprising N balance resistors connected in parallel for each battery cell and a balance MOSFET that switches the overcharge voltage applied to the corresponding battery cell for the balance resistor.

[0009] In addition, the active balancing circuit can perform active balancing by comprising N inductors each connected in parallel for each battery cell, and an active balance controller that switches to supply current from a battery cell having a relatively high cell voltage to a battery cell having a relatively low cell voltage through the inductors.

[0010] In addition, the BMS IC can activate the passive balancing circuit and the active balancing circuit when the cell voltage is 3.6 V or higher and the voltage difference between cells is 0.1 V or higher, and can deactivate the passive balancing circuit and the active balancing circuit when the voltage difference between cells is 0.03 V or lower.

[0011] In addition, the BMS IC can activate the switching MOSFET when there is no overvoltage, overdischarge, overcharge, or undervoltage state, and can deactivate the switching MOSFET when there is an overvoltage, overdischarge, overcharge, or undervoltage state.

[0012] In addition, the BMS IC can protect against overcurrent by deactivating the switching MOSFET when the voltage difference between the voltage of the battery pack and the voltage applied to the BMS IC is above a certain level.

[0013] According to the present invention, depending on whether the battery pack is charged, passive balancing is performed during charging for voltage imbalance between cells, and active balancing is performed separately when not in a charging or discharging state, thereby minimizing unnecessary energy consumption, resolving cell balance imbalance due to differences in natural discharge rates caused by differences in internal resistance of each cell, and detecting voltage differences due to voltage drops to protect the BMS IC from overcurrent.

[0014] Figure 1 is a schematic diagram showing a battery charging / discharging circuit system according to an embodiment of the present invention.

[0015] Fig. 2 is a separate example of a passive balancing circuit of the battery charging / discharging circuit system of Fig. 1.

[0016] Fig. 3 is a separate example of an active balancing circuit of the battery charging / discharging circuit system of Fig. 1.

[0017] Fig. 4 is a separated example of the BMS IC of the battery charging / discharging circuit system of Fig. 1.

[0018] Hereinafter, an embodiment of the present invention having the above-described features will be described in more detail with reference to the attached drawings.

[0019] The battery charge / discharge circuit system according to an embodiment of the present invention comprises a battery pack (110) having a battery cell (111) and a balance terminal (112), a switching MOSFET (120) for switching the current of the battery pack (110), a BMS (Battery Management System) IC (130) for controlling the switching MOSFET (120), monitoring the cell voltage of the battery cell (111) through the balance terminal (112) to detect a voltage imbalance between cells, and controlling to charge the battery pack (110) until the target voltage is reached, controlling cell balancing through a balance cable connected to each battery cell (111), controlling discharge of the battery pack (110), and protecting the battery pack (110) from overcharge and overdischarge, and when charging of the battery pack (110) is in progress, activating the balance terminal (112) to receive a control signal from the BMS IC (130) and controlling the corresponding voltage exceeding the target voltage. The main idea is to perform passive balancing or active balancing depending on whether the battery pack (110) is charged, including a passive balancing circuit (140) that consumes the overcharge voltage of the battery cell (111) as heat energy, and an active balancing circuit (150) that activates the balance terminal (112) to receive a control signal from the BMS IC (130) and supplies current from a battery cell (111) with a relatively high cell voltage to a battery cell (111) with a relatively low cell voltage when charging or discharging of the battery pack (110) is not in progress.

[0020] Hereinafter, with reference to the drawings, the battery charging / discharging circuit system of the above-described configuration will be described in detail as follows.

[0021] First, referring to FIG. 1, the battery pack (110) has a plurality of battery cells (111) electrically connected in series, and a balance terminal (112) electrically connected to a BMS IC (130) by wiring each individual battery cell (111), and the analog voltage value of each balance terminal (112) can be converted into a digital voltage value through an ADC (Analog to Digital Converter) (113) and input to the BMS IC (130).

[0022] Next, the switching MOSFET (120) switches the current of the battery pack (110) according to a control signal from the BMS IC (130), as shown in FIG. 1, and is composed of a plurality of n sets of parallel-connected MOSFETs, with two sets of series-connected MOSFETs, so that it can withstand a continuous current of 100 A or more and an instantaneous maximum current of 1000 A of the battery pack.

[0023] That is, the switching MOSFET (120) switches the current application to a load such as an electric motor electrically connected to the battery pack (110), and the switching MOSFET (120) can switch the electrical connection between the (-) terminal on the load side and the (-) terminal of the battery pack (110).

[0024] Next, the BMS (Battery Management System) IC (130) controls the switching MOSFET (120) to switch the current of the battery pack (110), monitors the cell voltage of the battery cell (111) through the balance terminal (112) to detect a voltage imbalance between cells, controls the charging of the battery pack (110) until the target voltage of the battery pack (110) is reached, controls cell balancing through a balance cable connected to each balance terminal (112) of the battery cell (111), controls discharge of the battery pack (110), and protects the battery pack (110) from overcharge and overdischarge.

[0025] Next, the passive balancing circuit (140), referring to FIGS. 1 and 2, when charging of the battery pack (110) is in progress from an external power source through the BMS IC (130), if an imbalance in the voltage between cells is detected by the BMS IC (130), the circuit activates the balance terminal (112) to receive a control signal from the BMS IC (130) and consumes the overcharge voltage of the corresponding battery cell (111) exceeding the target voltage as heat energy to achieve voltage balance between the cells.

[0026] For example, the passive balancing circuit (140) is composed of N balance resistors (141) connected in parallel for each battery cell (111) and a balance MOSFET (142) that switches the application of the overcharge voltage to the corresponding battery cell (111) to the balance resistor (141), so that passive balancing can be performed by turning on the balance MOSFET (142) corresponding to overcharge and applying the overcharge voltage to the balance resistor (141) to disperse it as heat energy.

[0027] Meanwhile, by further including a temperature sensor (not shown) for measuring the temperature of the balance resistor (141), when the temperature rises excessively, the BMS IC (130) can stop balancing by the passive balancing circuit (140) for a certain period of time and resume passive balancing when the temperature drops below a certain level.

[0028] For example, a temperature sensor can be added to the balance resistor (141) side to measure the temperature of the balance resistor (141), and when a temperature exceeding the set temperature is measured on the balance resistor (141) side, the BMS IC (130) can cut off the balance MOSFET (142), and when the temperature drops below the set temperature, the operation of the balance MOSFET (142) can be resumed.

[0029] Next, the active balancing circuit (150), referring to FIGS. 1 and 3, when charging or discharging of the battery pack (110) is not in progress, for example, when not in a charging or discharging state, if an imbalance in voltage between cells is detected by the BMS IC (130), the circuit activates the balance terminal (112) to receive a control signal from the BMS IC (130) and supplies current from a battery cell (111) having a relatively high cell voltage to a battery cell (111) having a relatively low cell voltage to achieve voltage balance between cells.

[0030] For example, the active balancing circuit (150) is composed of N inductors (151) connected in parallel for each battery cell (111), and an active balance controller (152) that switches to supply current from a battery cell (111) having a relatively high cell voltage to a battery cell (111) having a relatively low cell voltage through the inductor (151), so that active balancing for excess voltage can be performed by applying a balance current of 1 A or more through the inductor (151).

[0031] That is, the BMS IC (130) can activate the passive balancing circuit (140) and the active balancing circuit (150) when the cell voltage is 3.6 V or higher and the voltage difference between cells is 0.1 V or higher, and can deactivate the passive balancing circuit (140) and the active balancing circuit (150) when the voltage difference between cells is 0.03 V or lower.

[0032] Meanwhile, the BMS IC (130) can activate the switching MOSFET (120) to perform charging and discharging of the battery pack (110) if it is not in an overvoltage, overdischarge, overcharge, or low voltage state, and can deactivate the switching MOSFET (120) to stop charging and discharging of the battery pack (110) if it is in an overvoltage, overdischarge, overcharge, or low voltage state.

[0033] In addition, the BMS IC (130) can protect against overcurrent by deactivating the switching MOSFET (120) when the voltage difference between the voltage of the battery pack (110) and the voltage applied to the BMS IC (130) is above a certain level.

[0034] That is, when an excessive level of current flows, the switching MOSFET (120) enters a breakdown state and cannot perform the switching function. When a high current flows, a voltage drop occurs in which the voltage detected by the BMS IC (130) becomes lower than the voltage of the battery pack (110). Therefore, when the voltage drop is detected and the voltage difference between the voltage of the battery pack (110) and the voltage applied to the BMS IC (130) increases, it is regarded that an excessively high current is flowing to the load side, and the control signal for the switching MOSFET (120) can be blocked to protect the internal circuit of the BMS IC (130).

[0035] For example, referring to FIG. 4, if the voltage of TOC1 (Timer Output Compare 1) of the BMS IC (130) is higher than the voltage of the battery pack (110), it is considered normal operation, and if the voltage of TOC2 (Timer Output Compare 2) of the BMS IC (130) is higher than the voltage of the battery pack (110), it is considered overcurrent and the circuit can be shut off.

[0036] Accordingly, by configuring the battery charge / discharge circuit system as described above, depending on whether the battery pack is charged, passive balancing is performed during charging for cell-to-cell voltage imbalance, and active balancing is performed separately during continuous or discharge, thereby minimizing unnecessary energy consumption, resolving cell balance imbalance due to differences in natural discharge rates caused by differences in internal resistance of each cell, and detecting voltage differences due to voltage drops to protect the BMS IC from overcurrent.

[0037] The embodiments described in this specification and the configurations illustrated in the drawings are only the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention. Therefore, it should be understood that there may be various equivalents and modified examples that can replace them at the time of filing this application.

Claims

1. A battery pack having a plurality of battery cells connected in series and a balance terminal connected to each battery cell; A switching MOSFET for switching the current of the above battery pack; A BMS (Battery Management System) IC that controls the switching MOSFET, monitors the cell voltage of the battery cell through the balance terminal to detect a voltage imbalance between cells, controls charging of the battery pack until a target voltage is reached, controls cell balancing through a balance cable connected to each battery cell, controls discharge of the battery pack, and protects the battery pack from overcharge and overdischarge; When charging of the battery pack is in progress, if an imbalance in the voltage between cells is detected by the BMS IC, a passive balancing circuit that activates the balance terminal to receive a control signal from the BMS IC and consumes the overcharge voltage of the corresponding battery cell exceeding the target voltage as heat energy; and In the case where charging of the battery pack is not in progress, when an imbalance in the voltage between cells is detected by the BMS IC, the balance terminal is activated to receive a control signal from the BMS IC and supply current from a battery cell with a relatively high cell voltage to a battery cell with a relatively low cell voltage, including an active balancing circuit; Battery charging and discharging circuit system.

2. In paragraph 1, The above passive balancing circuit is characterized in that it performs passive balancing by comprising N balance resistors connected in parallel for each battery cell and a balance MOSFET that switches the overcharge voltage application of the corresponding battery cell to the balance resistor. Battery charging and discharging circuit system.

3. In paragraph 1, The above active balancing circuit is characterized in that it performs active balancing by comprising N inductors each connected in parallel for each battery cell, and an active balance controller that switches to supply current from a battery cell with a relatively high cell voltage to a battery cell with a relatively low cell voltage through the inductor. Battery charging and discharging circuit system.

4. In paragraph 2 or paragraph 3, The BMS IC is characterized in that it activates the passive balancing circuit and the active balancing circuit when the cell voltage is 3.6 V or higher and the voltage difference between cells is 0.1 V or higher, and deactivates the passive balancing circuit and the active balancing circuit when the voltage difference between cells is 0.03 V or lower. Battery charging and discharging circuit system.

5. In paragraph 1, The above BMS IC is characterized in that it activates the switching MOSFET when it is not in an overvoltage, overdischarge, overcharge, or undervoltage state, and deactivates the switching MOSFET when it is in an overvoltage, overdischarge, overcharge, or undervoltage state. Battery charging and discharging circuit system.

6. In paragraph 1, The BMS IC is characterized in that, when the voltage difference between the voltage of the battery pack and the voltage applied to the BMS IC is above a certain level, the switching MOSFET is disabled to protect against overcurrent. Battery charging and discharging circuit system.

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