Automotive HID headlamps producing compact electronic ballasts using power ICs

Incandescent halogen lamps have been the standard for automotive headlamps; however, metal halide high-intensity discharge (HID) lamps have slowly begun to be commercially used since the mid-1990s. The lighting system of the metal halide HID headlamp makes a great contribution to energy savings, longer lamp life and better visibility in traffic zones compared with halogen lamps. (Lamp life is lengthened because it prevents the loss of sodium metal as plus ions through the quartz of the lamp bulb.) This article describes power ICs consisting of full bridge inverters and their drivers in detail. Market requirements for electronic ballasts include more compact size, lighter weight, and lower cost. On the other hand, lamp manufacturers recommend that automotive metal halide HID lamps should be operated at negative voltage potential to the body of automotive headlight fixture in order to lengthen lamp life. In order to meet these requirements, a new multichip power integrated circuit (IC) for electronic ballast of automotive HID headlamps has been developed. Discrete power metal-oxide-semiconductor field-effect transistors (MOSFETs) are used for the inverter of the HID electronic ballast. It contains a high-voltage driver IC including a P-channel lateral double diffused MOSFET (LDMOS) to control the full bridge power MOSFETs.