| 摘要 |
A control system includes a zero crossing detecting circuit for detecting a zero crossing of an AC signal. The circuit includes a transformer having a primary portion and a secondary portion. The primary portion receives the AC signal. The secondary portion comprises first and second terminals. The first terminal is biased at a first DC voltage level. An output switch is operatively connected to the second terminal and has an on state and an off state. The output switch selectively activates an output signal of the zero crossing detecting circuit according to an activation voltage level sensed by the output switch and corresponding to the zero crossing. While in the off state, the output switch is biased at a second DC voltage level. A voltage difference between the first and second DC voltage levels substantially equals the activation voltage level. A controller monitors the output signal and controls an operation based on the output signal.
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