Battery charger.

摘要

A battery charger includes a transformer having a primary coil and a secondary coil, a switch for duty control of a current flowing through the primary coil of the transformer, a detector for detecting a value of a current flowing through the secondary coil of the transformer, and a secondary controller for receiving the detected value from the detector and for outputting a charge control signal. The pulse of the charge control signal is modulated in accordance with the detected value by the detector. The battery charger further includes a light emitter controlled by the charge control signal for flickering, a phototransistor turning on and off according to the flickering of the light emitter, and a primary controller for converting the ratio of the time during on of the phototransistor to the time during off of the same into an analog value, and for outputting to the switch a pulse signal which is modulated to have a duty cycle corresponding to the analog value so as to control a duty cycle of the switch. <IMAGE>