Philips Electronics North America Corporation

Tom Mg Mobers

Naveed Majid

Erwin G Seinen

A switched-mode power supply circuit having an operating mode and a stand-by mode, includes a functional ON/OFF switch. The switched-mode power supply circuit includes a transformer and a controllable switch connected to a primary winding of the transformer for switchably connecting the primary winding to a source of d.c. voltage. In the stand-by mode, based on a detected voltage level at an input of a controller IC, the switched-mode power supply circuit is arranged to switchable connect the primary winding to the d.c. voltage source in bursts which occur at a low frequency. By switchably connecting this input to a power source for the switched-mode power supply circuit, the controller IC detects the absence of this power source, and turns off the switched-mode power supply circuit allowing a minimum current consumption by the switched-mode power supply circuit.

Functional on/off switch for switched-mode power supply circuit with

A switched-mode power supply circuit includes a first controller for controlling power to a main power output through a first transformer, and a second controller for controlling power to a control output through a second transformer. In order to effect a very low power stand-by mode, the second controller turns off the first controller, the second controller only operating. When a load is selectively coupled across the control output, the second controller detects this load and turns on the first controller thereby effecting the operating mode.

Switched-mode power supply circuit having a very low power stand-by mode

A switched-mode power supply circuit having an operating mode and a stand-by mode. The switched-mode power supply circuit includes a transformer and a controllable switch connected to a primary winding of the transformer for switchably connecting the primary winding to a source of d.c. voltage. In the stand-by mode, the switched-mode power supply circuit is arranged to switchable connect the primary winding to the d.c. voltage source in bursts which occur at a low frequency. Between each of the bursts, an auxiliary capacitor, which is ordinarily charged by an auxiliary winding during switching of the controllable switch, is now charged by a start-up current source contained in a controller for controlling the controllable switch.

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Tom Mg Mobers