Two-stage low-frequency square-wave electronic ballast with analog and digital control

This paper investigates a two-stage low-frequency square-wave (LFSW) electronic ballast with a combined analogue and digital control. The first stage of the ballast is a power factor correction (PFC) converter and the second is a half-bridge (HB) converter with an igniter. The advantage of the proposed scheme compared to conventional LFSW ballasts, is including an improved modified HB circuit. This approach contributes to two benefits regarding the body-diode ruggedness and its reverse recovery charge process. The combined analogue and digital control additionally provides a high operating frequency range. Further, an improved methodology is proposed for the design of the inductors, including eddy current loss estimation and core type selection. Finally, design application considerations are derived concerning the proposed electronic ballast.