A constant power control strategy of electronic ballast for HID lamp

A novel and efficacious constant power control strategy of electronic ballast for HID lamp is proposed in this paper. The constant power control gear mainly consists of an 8-bit micro-controller and a PWM control IC. The micro-controller samples the lamp voltage, and calculates an appropriate value of lamp current. The PWM IC controls the lamp current equal to the calculated current value. Thus constant power can be approached. The digital-analog mixed control circuit is low cost, reliable and adaptive. A novel hysteresis algorithm provides an excellent performance of the constant power control gear, the variation of the lamp power is less than 1%