| 摘要 |
An electrical load power control device is described that reduces the power consumption of inductive and inductive-dissipative loads, including for example fluorescent lighting. The power circuit of the invention interrupts AC power supply to the load during a plurality of intervals within each half cycle of the AC mains signal frequency whilst providing an alternate path for current flow during the interruption to maintain a sinusoidal-like current to the load. During a crossover lag zone encompassing zero crossing points of the voltage and current and during which the voltage and current have opposite polarities, both elements of the power switch are switched to the "on" condition, one element of the circulating switch is switched to the "on" condition when a positive current is flowing in the load and the other element of the circulating switch is switched to the "on" condition when a negative current is flowing in the load. The power factor presented by the load and other current parameters of the load such as form factor and total harmonic distortion may be desirably modified. In the preferred embodiment an oscillator has a duty cycle control circuit which deactivates the power switch during a predetermined portion of the oscillator duty cycle. The duty cycle establishes the amount of power reduction. |
