Balanced switching control circuit for battery management system

Abstract

The invention discloses a balanced switching control circuit for a battery management system. The balanced switching control circuit is characterized by comprising a backward stage switching switch group, a preceding stage lower half switching switch group, a preceding stage upper half switching switch group, and a CPU (Central Processing Unit), wherein the backward stage switching switch group is formed by a backward stage lower switching switch and a backward stage upper switching switch; the number of switches of the preceding stage lower half switching switch group is one more than units of battery cells forming a lower half series battery group; and the number of switches of the preceding stage upper half switching switch group is one more than units of battery cells forming an upper half series battery group. The backward stage switching switch group is a bipolar on-off switching switch, static contacts of the backward stage lower switching switch and the backward stage upper switching switch are respectively connected with balanced BUS- and balanced BUS+, controlled terminals of all the switching switches are connected with the CPU, the CPU sends a command to control the switching, and one battery cell needs to be balanced is switched to be connected onto the balanced BUS+ and BUS- so as to be connected with a discharging and charging module. According to the circuit, the withstand voltage requirement of the switching switches is reduced by half, and low-voltage switching switches are beneficial for being popularized and applied in battery balanced circuits with multiple strings.

Description

technical field [0001] The invention relates to a battery management system, in particular to a balanced switching control circuit for the battery management system. Background technique [0002] The battery pack composed of new batteries including lithium-ion batteries connected in series, due to the inconsistency of the battery cells, will lead to a decrease in the available capacity of the entire battery pack when used; charging a battery cell with a high voltage will cause the charging process to advance Termination, so that the charging capacity becomes smaller; when the battery cell with low voltage is discharged, it will cause the discharge process to terminate early, so that the discharge capacity is reduced. An equalizer or equalization circuit module is set in the battery management system (Battery management system, abbreviated as BMS) to balance the battery cells, discharge the cells with high voltage, and charge the cells with low voltage, which can Effectively...

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Problems solved by technology

[0003] The changeover switch is one of a solid-state relay and a mechanical relay including a Metal Oxide Semiconductor Field Effect Transistor (Metal Oxide Semiconductor Field Effect Transistor, abbreviated as MOSFET), and its cost varies with the on-resistance / withstand voltage of the device. The geometric progression rises, the on-resistance is small, and the switch cost of the equalizer with high withstand voltage is relatively high. Choosing a switch with low withstand voltage can effectively reduce the cost, but there is a risk of breakdown, especially for those connected to the last battery cell. The MOSFET in the solid-state relay of the MOSFET needs to withstand a withstand voltage equal to the multiple of the number of battery cells. For example, a series battery pack composed of 12 battery cells BT1~BT12 in series is turned off when the battery cell BT1 needs to be balanced. The MOSFET in the solid state relay connected to the last battery cell BT12 corresponding to the state needs to withstand the high voltage of 12 battery cells. If the voltage of the battery cell is 3.8V, the high voltage is as high as 3.8×12=45.6V, and the withstand voltage is required to be 60V MOSFET, the cost of such a switch is very high, and it is not conducive to the popularization and application of low-voltage switching switches in multi-string battery balancing circuits

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