Design of a Novel Low-Frequency Square-Wave Digital Electronic Ballast for HID Lamps

This paper presents a low-cost low-frequency square-wave digital electronic ballast for high density discharge (HID) lamps. A highly efficient and reliable topology-dual buck half-bridge inverter (DBI) is adopted to supply the lamp with low-frequency square-wave positive and negative current avoiding acoustic resonances. The constant bus voltage is provided by the front end PFC stage. The DBI is controlled to operate under ZVS condition and the problem of excessive inductor current during low-frequency reversal transient is solved by single cycle control. The AVR special microcontroller for HID ballast is used to raise control performance and simplify the control circuit. The presented circuit was verified with experimental results. A prototype of 70 W digital HID ballast has been built with the whole efficiency of 93%.