| 摘要 |
A pulse-width modulator controls a switching transistor. The switching transistor is coupled to a primary winding of a chopper transformer. The switching transistor and the primary winding are referenced to a nonisolated ground conductor. To initiate a standby mode of operation, a first on/off control signal that is referenced to an isolated ground conductor disables a horizontal oscillator that is energized from a secondary winding of the chopper transformer and that is also referenced to the isolated ground conductor. As a result, a decrease loading of circuit elements that are referenced to the isolated ground occurs. In the standby mode, current pulses in the primary winding are produced at a substantially higher frequency than in normal operation. A frequency detector referenced to the nonisolated ground generates a second on/off control signal that is referenced to the nonisolated ground in accordance with the frequency of the current pulses in the chopper transformer. In this way, the second on/off control signal is generated without the need for an additional isolation element other than the chopper transformer.
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