Power IC of electronic ballast for automotive HID lamp

Abstract

Halogen lamps were mainly used for automobile headlamps, but in recent years, metal halide lamps with HID (high intensity discharge) lighting system began to be used in Europe and in Japan, they have been commercially used since 1996 in Japan. The metal halide lamp is superior to the halogen lamp at the points of lower electric loss, longer life and better visibility. We have started to market a discrete MOS transistor from 1997 to be used for inverter of HID electronic ballast. Market requirements to the electronic ballast are more compact in size, more light in weight and lower cost. On the other hand, it is recommended by lamp manufactures that automotive metal halide HID lamp should be operated on a condition of negative voltage potential to the body (mainly optical reflector) of automotive headlight fixture in order to lengthen lamp life. In order to solve these requirements, a hybrid power IC has been developed. It contains full bridge power MOSFETs and high voltage driver IC including p-channel LDMOS to control full bridge power MOSFETs. An HID headlamp can be operated on a condition of negative potential to the earth potential of automobiles by the power IC. This paper presents the newly developed hybrid power IC and the application system.