| 摘要 |
<p>POWER SUPPLY AND CONTROL CIRCUIT FOR SERIES CONNECTED CONTROLLER A control circuit for a power switch like a triac to be connected in series with a load device, at a situs where only one AC power conductor and a conductor extending to the load device is available, is energized from a DC power supply energized from these conductors. The power supply includes at least one rectifier connected in series with a capacitor, the terminals of which constitute the DC output terminal of the DC power supply, an impedance of much greater resistance than that of the load device and through which the capacitor is charged when the triac is in its non-con-ductive mode, and a normally non-conductive triggerable low impedance threshold device shunting the high impedance and triggered momentarily into conduction as the applied AC voltage goes through zero when the triac is to be in its conductive mode. Current flow through this threshold device triggers the power switch into conduction a short interval after passage of this voltage through zero. The capacitor charges only during each such short interval it takes to initiate. conduction of the power switch.</p> |
