| 摘要 |
<p>A power control circuit for controlling the power drawn by a load such as a lamp control ballast from a source of rectified A.C. voltage source provided on a voltage supply line. The power control circuit includes a keep-alive portion having a capacitor which receives and stores charge during intervals when the rectified A.C. voltage exceeds a threshold level, and discharges to support operation of the ballast during intervals when the rectified A.C. voltage is below the threshold level. The capacitor receives charge from the current flowing through the primary winding of the ballast transformer. The power control circuit also includes a feedback capacitor connected between the primary winding of the ballast transformer and the active line of the power supply to store a feedback charge when the current through the primary winding of the ballast transformer flows in a first direction and to discharge the feedback charge to the voltage supply line when the current through the primary winding of the ballast transformer flows in a second direction.</p> |
