Modified flyback for HID lamp supply: Concept and design

This paper presents a ballast for driving high intensity discharge (HID) lamps with low frequency square waveform from a dc supply, with expansion for integrated PFC (buck-boost converter). From the dc source (battery or PFC rail), a flyback arrangement is inserted into a switching structure whose output provides low frequency voltage yet avoiding instability issues. Proposal´s main advantage is the need for reduced chokes count and two active switches only. Converter design for discontinuous conduction mode (DCM) is presented in this work, highlighting its principle and design. For proposal validation, experimental results from a built prototype are presented, as well as discussions about its feasibility and general aspects.