High frequency electronic ballast for HID lamps based on λ/4-long distributed constant line with buck-boost AC-DC converter suitable for half bridge inverter

A novel type of solid-state ballast, which operates in the MHz-range frequency, is presented in this paper. A circuit composed of a buck-boost type AC-DC power converter (rectifier), a voltage-source half-bridge inverter, a distributed constant line and a parallel LC resonant circuit has been developed for use in this new ballast. The 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 (λ/4 condition), the output voltage of the voltage-source inverter can be converted to a current source at the load side. Therefore, the ballast can not only supply the HID lamp with high voltage to initiate discharge, but can also supply with stable current during lamp running condition. Further, the proposed ballast enables the HID lamps to control luminous intensity with the novel buck-boost AC-DC power converter and the discharge current feedback control. The experimental results from a prototype system verify the theory underlying this research