Power supply with standby mode, e.g. for TV set, has two switched-mode supplies one of which is disabled when in standby mode

摘要

The current supply has two switched-mode stages (I,II) each provided with a transformer (TR1,TR2), both networks being employed in a normal equipment operating mode. In a standby mode a control voltage (US) is used to disable the first switched mode supply and to reduce the switching frequency of the second supply. Preferably the control voltage is transferred over an opto coupler (OK1) and the two supplies are synchronized by a series circuit (C3,D3,R3) between the output of the first driver stage (IC1) and the oscillator input of the second driver stage.