New type of ballast for HID lamps using distributed constant line

This paper presents a new type of solid-state ballast, which operates in the MHz frequency range. A circuit composed of a voltage-fed half-bridge inverter, a distributed constant line and a parallel LC resonant circuit has been developed for this purpose. An HID (high-intensity discharge) lamp is connected to the output terminal of the inverter through the distributed constant line. Here, since the length of the line is adjusted to 1/4 of the propagation wavelength λ, the output voltage of the voltage-fed inverter can be converted to a current source at the load side. From the experimental results, the following issues are considered. The ballast can supply not only high voltage to the HID lamp for igniting for discharge but also constant current to it during discharge condition. The proposed ballast also has the capability of dimming control