In this embodiment of this application, the two ends of the secondary-side winding of the transformer 105 are connected to the two alternating current ports of the two-phase two-bridge-arm converter 103, and the primary-side winding of the transformer 105 is connected to the alternating current charging port 106, to isolate an alternating current that is input from the alternating current charging port 106 and then transmit the alternating current to the two-phase two-bridge-arm converter 103. Then, the two-phase two-bridge-arm converter 103 may convert the alternating current into a direct current and transmit the direct current to the battery 101, to charge the battery 101.