A hybrid lamp power control scheme for dimmable electronic ballast to minimize ambient temperature effect

A hybrid lamp power control scheme for dimmable electronic ballast is proposed. Apart from adjusting the brightness of the lamp, the proposed method can also minimize the ambient temperature effect on affecting the light output. Instead of regulating the lamp current, the proposed method is based on regulating the power supplying to the lamp. First dimming operation is achieved by regulating the DC voltage at the ballast inverter input. Second variation of the lamp power (due to the temperature effect) is regulated by sensing the inverter average input current to adjust the switching frequency of the inverter. An 18 W prototype has been built and tested. The lamp power and luminous output of the prototype at the ambient temperature from 5 °C to 35 °C have been studied.