Portable device with reduced power dissipation

摘要

A low power portable device includes a terminal (2) for connection of the device to a power source. A rectifier (3) is connected to the terminal and a half-bridge circuit (4) is connected to the rectifier in order to generate an a.c. switching voltage and includes a half-bridge point (5). A control circuit (6) controls the half-bridge circuit from a power supply (7) which derives a supply voltage for the control circuit from the switching AC voltage supplied by the half-bridge circuit. The power supply comprises a charging capacitor (10) connected to the half-bridge point. A load circuit (8) is connected to the half-bridge point and the charging capacitor is connected to the half-bridge point through an impedance (13, 16).