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 DCM is presented in this work, besides an equivalent circuit from a control point of view. Small signal ac model is obtained and feedback control loop designed based upon frequency response. HID dynamics is inserted into converter model, with feedback directly implemented. For design conformity, experimental and simulation results from Matlab and PSIM are presented, as well as discussions about its feasibility.