Improvement in control stability for high-efficiency electronic ballast

The energy loss of an electronic ballast is mainly composed of switch loss and inductor loss. The entire loss decreases when setting the component values so as to reduce the phase angle of the load circuit. However, the lamp current limiting action falls and fails to stably operate the lamp. We have examined the ways to improve the control stability by using the loop transfer function; the bode plot in particular. By designing a control circuit with the experimentally measured loop transfer function and with the calculated transfer function of each functional circuit block, the tested apparatus was able to operate the lamp stably.