Current-fed isolated PFC pre-regulator for multiple LED lamps with extended lifetime

Xiaohui Qu, Siu Chung Wong, Chi Kong Tse

Research output: Journal article publicationJournal articleAcademic researchpeer-review

7 Citations (Scopus)


To emit high-quality LED light, one or a bin of LED lamp(s) is normally driven by a PWM-controlled constant current source to minimize device variation and achieve accurate brightness control. Powered from offline AC mains, the front-end power converters should provide a relatively low DC voltage bus for the inputs of post-end LED current regulators. To match the long lifetime of LEDs, the whole LED driver (ballast) should work as durably as the LEDs. However, the lifetime of the driver is usually limited by the high-voltage electrolytic charge storage capacitors used in conventional PFC pre-regulators. In this paper, our previously proposed resonant current-fed isolated PFC pre-regulator is extended to operate in discontinuous conduction mode (DCM). It allows the use of the low-voltage storage capacitors on the transformer secondary, and therefore extends the overall lifetime of the LED lighting system. A detailed procedure for finding the expected lifetime of the low-voltage electrolytic capacitor is given. As before, the high-voltage stress on the main switches, which is typical in current-fed isolated converters, is reduced substantially by taking advantage of the transformer leakage inductance necessary for resonance. Additionally, high efficiency is ensured by the use of dual non-cascading structures. Steady-state state-space averaging analysis is performed for designing the converter in DCM operation. A prototype converter is built to verify performance of the proposed PFC LED pre-regulator. Copyright To extend the system lifetime of an offline LED driver due to the low-lifetime high-voltage electrolytic capacitors, a current-fed isolated PFC pre-regulator shown in Figure 2 is proposed. The regulator topologically moves the main charge storage capacitor C0to the transformer secondary and utilizes leakage inductance LPof the transformer to reduce stresses of switches, ensuring system reliability and long lifetime. Experimental results confirm the effectiveness of the circuit topology and the analytical calculations.
Original languageEnglish
Pages (from-to)759-775
Number of pages17
JournalInternational Journal of Circuit Theory and Applications
Issue number8
Publication statusPublished - 1 Aug 2012


  • capacitor lifetime
  • LED lighting
  • offline LED driver
  • PFC pre-regulator

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Computer Science Applications
  • Electrical and Electronic Engineering
  • Applied Mathematics


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