Adaptive preheat and strike of microcontroller based ballast

Analog controlled parallel loaded series resonant and LCC circuits are widely used in electronic ballasts. Using microcontroller technology, an adaptive preheat and strike technique has been developed. By changing frequency of the inverter and detecting the response of the tank, the characteristic of the resonant tank and the parasitic elements can be measured before and during preheat and ignition. The microcontroller can then select the optimum frequency to preheat and strike the lamp with minimum component stress. This approach helps to minimize the value of the parallel resonant capacitor and improve the efficiency due to reduced circulation current and core size of the resonant inductor.