Discharge protection circuit and its control method
A discharge protection circuit has a cell combination with more than one cell, a power supply circuit, an output circuit, a MCU chip, a voltage detection circuit, a NTC circuit, a current detection circuit, a drive circuit and a drive switch. The power supply circuit, the output circuit and the cell combination form a series connection and the MCU chip forms an electrical connection with the voltage detection circuit, the drive circuit and the current detection circuit, respectively, with the voltage detection module being electrically connected with the cell combination and the NTC circuit respectively. A control method includes enabling a discharge procedure of the discharge protection circuit to discharge with a power quantity 0.2 times nominal power quantity each hour. In this procedure, the MCU chip is cyclically dormant to reduce the control power dissipation and improve discharge quantity while achieving discharge protection of the battery pack.
1. A discharge protection circuit of a battery pack and an electrical tool, the battery pack having a cell combination comprising a plurality of battery cells, the discharge protection circuit comprising:
a power supply circuit, an output circuit, a MCU chip, a voltage detection circuit, a NTC circuit, a current detection circuit, a drive circuit and a drive switch;
the power supply circuit, the output circuit and the cell combination forming a series connection, the MCU chip forming an electrical connection with the voltage detection circuit, the drive circuit and the current detection circuit respectively, and the voltage detection module being electrically connected with the cell combination and the NTC circuit respectively, the drive switch comprising two switch ends and a control end, the two switch ends of the drive switch being connected in series between the output circuit and the cell combination, the current detection circuit being electrically connected to a circuit between the output circuit and the switch ends of the drive switch, and the drive circuit being electrically connected to the control end of the drive switch to control turn-on and turn-off operations of the two switch ends,
wherein the MCU chip comprises a cycle time,
wherein within the cycle time, the MCU chip comprises at least an operation time period and a dormant time period, and
wherein the length of the cycle time of the dormant time period is 5 to 20 times the length of the cycle time of the operation time period, so as to enable the discharge protection circuit to discharge with a power quantity 0.2 times nominal power quantity each hour.
2. The discharge protection circuit according to claim 1 , wherein the power supply circuit is located on a high-voltage side of the output circuit and the drive switch is located on a low-voltage side of the output circuit.
3. The discharge protection circuit according to claim 1 , wherein the cell combination comprises more than one series-connected unit, each of the series-connected units forming a series connection there between, each of the series-connected unit comprising more than one cell, and the cells in a common same series-connected unit being connected in parallel; a plurality of voltage sampling circuits being disposed between the voltage detection circuit and the cell combination, each voltage sampling circuit being provided with a sampling control switch, and the voltage sampling circuit being electrically connected to a high-voltage end of the series-connected unit.
4. The discharge protection circuit according to claim 3 , wherein, that when one sampling control switch is turned on, the remaining sampling control circuits are all turned off.
5. The discharge protection circuit according to claim 1 , wherein the drive switch is a MOSFET switch.