Circuitry for charging a battery includes a switch for coupling the power source to the battery. The switch is turned on and off in accordance with a periodic control signal including a plurality of periods. Each period includes a first duration during which the control signal is in a first state and a second duration during which the control signal is in a second state. The switch is turned on when the control signal is in the first state to couple the power source to the battery, and turned off when the control signal is in the second state to decouple the power source from the battery. Since the switch is periodically turned off while the battery is being charged, the average amount of heat generated by the switch is reduced, thereby preventing excessive thermal emission from the battery charging circuitry.