An electronic ballast with a novel low-cost power factor correction circuit

A discontinuous-mode boost power factor correction (PFC) circuit using a novel pulse-width-modulation (PWM) circuit comprising only a few discrete components is proposed as an alternative to commercially available integrated circuits. The PWM circuit combines a reference waveform signal derived from a ballast inverter together with feedback and feedforward signals to create a composite signal that is applied to the base of a Darlington transistor, which is used to drive the gate of a power MOSFET. This paper presents an optimal linear approximation to the ideal control law for discontinuous-mode boost PFC circuits. An experimental electronic ballast is described in which the proposed low-cost PWM circuit implements the optimum linear control law. The experimental ballast has an input current with a total harmonic distortion (THD) of only 6.2%, and an overall efficiency of 90%.