Patent ID: 8222867

Claim:
A charging and discharging module coupled to a direct-current power source and a battery, the charging and discharging module comprising: a current-limiting transistor; a current-limiting resistor connected with the current-limiting transistor in series; a charging controlling unit coupled to the power source, the current-limiting transistor and the current-limiting resistor, when the charging and discharging module charges the battery, the voltage across two ends of the current-limiting transistor and the current-limiting resistor connected in series is limited to a first fixed value by the charging controlling unit; and a discharging controlling unit coupled to the power source, the current-limiting transistor and the current-limiting resistor, when the charging and discharging module discharges the battery, the voltage across two ends of the current-limiting transistor and the current-limiting resistor connected in series is limited to a second fixed value by the discharging controlling unit, and the discharging controlling unit feedbacks the discharging energy from the battery to the power source in a direct current.