The following file is an application note from st.com describing the two stages of electronic ballast for a 250 W HID metal halide lamp. The components include a PFC driver, half-bridge drivers, a microcontroller, an auxiliary power supply, a voltage reference, logic parts, an amplifier, comparators, power devices as Power MOSFETs, IGBTs, and fast diodes. Get detail information about Circuit Diagram for 250 W HID Metal Halide Electronic Ballast here – free download PDF file.