| 摘要 |
<p>An electrical control system controls an electrical load device, particularly an inductive load such as the ballast of a gas discharge lamp which generates a back EMF when power is removed therefrom. The control system includes a first electronic switch for controlling the application of power to and withdrawal of power from the load and a second electronic switch which controls the first electronic switch. The second switch is responsive to a command signal preferably occurring between 90 DEG and 180 DEG of the AC power half wave to turn on and thus switch off the first switch which in turn withdraws power from the load. The circuit remains in this state until a predetermined circuit condition occurs at which point the potentials on the load and the AC power supply are at predetermined levels. The equal potential turns the second switch off, whereupon power is reapplied to the load by the first electronic switch. In an inductive load, the back EMF generated when the first switch withdraws power from the load serves as a feedback signal which is referenced against the AC power supply to determine an equal potential circuit condition.</p> |
