| 摘要 |
A power switch detection system for a power supply including an operator-accessible power switch coupled to the secondary ground of the power supply and to one side of an isolation capacitor. The other side of the isolation capacitor is coupled to a switch detection circuit referenced to primary ground for detecting the state of the power switch through the isolation capacitor. The switch detection circuit controls a control circuit on the primary side based on the state of the power switch, where the control circuit correspondingly controls the power state of the power supply and a corresponding electronic device. In this manner, the power switch remains isolated by the isolation capacitor but controls the power state of the device. The control circuit controls conversion of AC power from an AC source coupled to the primary side through a transformer. Although the primary and secondary grounds are isolated from each other, a reference ground of the AC source and the secondary ground are coupled together, typically through a conductive chassis of the electronic device. This electrically conductive connection establishes a high impedance, low current path between the AC source and the isolation capacitor when the power switch is closed. A low frequency current signal from the AC source charges the isolation capacitor when the power switch is closed, which is detected by the switch detection circuit.
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