Research on a novel circuit topology for electronic ballast of HID lamps

A novel cost-effective electronic ballast, with an asymmetric control, is proposed for high intensity discharging (HID) lamp. The ballast topology is composed of a half-bridge inverter to supply the lamp with high-frequency square-wave voltage and a serial resonant circuit to filter the lamp current into quasi-sine wave. The asymmetric control, with the fixed frequency PWM, can regulate the lamp power and make the switches of the inverter turn on softly. Constant lamp current control is achieved in the ballast by adjusting the duty cycle at fixed time range, which makes the lamp work steadily. A rated power 300 W prototype ballast demonstrates the proposed topology and the control method.