Low-cost power factor correction circuit and method for electronic ballasts

摘要

The present invention provides a low-cost power factor corrected electronic ballast circuit. A preferred embodiment includes a discontinuous conduction mode boost power factor correction circuit that is controlled with a simple pulse-width modulator (PWM) circuit comprising a few discrete components instead of an integrated circuit. The PWM circuit utilizes a reference waveform signal derived from the ballast inverter. The reference waveform is combined with a feedback signal to create a composite signal that is compared with a reference voltage to create a pulse-width-modulated signal. The feedback signal is used to regulate the bulk DC voltage. In an alternative embodiment, a feedforward signal that is proportional to the time-varying level of the rectified line voltage is added to the reference waveform and the feedback signal, and serves to modulate the pulse width of the boost circuit in a manner that reduces the harmonic distortion of the input current. In addition to the boost circuit, the power factor correction circuit can be realized with flyback and buck-boost topologies. The invention can also utilize several different types of inverter circuits.