| 摘要 |
<p>An embodiment of the present invention is a dimmable, high power factor, high-efficiency electronic ballast comprising, on a single integrated circuit chip (300) a shunt regulator (302), a voltage reference (306), a high-temperature shutdown (316), an undervoltage lockout (304), a timer for startup and restarting (314), a variable oscillator (322), a mode control (320), an op-amp (318) for receiving a signal proportional to lamp current and for controlling the variable oscillator or the duty-cycle of pulses output in a closed-loop servo, and active power factor correction including an analog multiplier (12) for receiving an AC voltage and an AC current sample, and for multiplying these together to result in a comparison with a DC voltage. The comparison produces a control signal for a MOSFET (28) switch on a boost converter transformer (18) that actively corrects the power factor at a rate set by the oscillator.</p> |
