An integrated circuit provides a complete electronic ballast control with power
factor correction for fluorescent lamps. The integrated circuit contains a simplified
power factor correction (PFC) circuit to reduce component count and supply voltage
requirements to reduce manufacturing costs while providing a robust control. The
PFC circuit has a variable gain for fast response at high gain and optimized power
factor control at low gain. An increased on time for the PFC switch when the input
line voltage approaches zero dynamically reduces crossover distortion, thereby
reducing total harmonic distortion. The integrated circuit incorporates a number
of fault protections.