Phase-controlled parallel-series (LCpCs) resonant converter to drive high-brightness power LEDs

This paper presents the analysis and design of a resonant converter suitable to drive high-brightness power LED lamps for outdoor lighting applications. The inverter stage arises from the parallel connection of two class D LC_pC_s resonant inverters. The output stage is based on a central tap rectifier without electrolytic capacitor. The output current can be precisely adjusted, at constant switching frequency, trough the phase displacement, Ψ, of the control signals of each class D section. The dimming control follows a PWM pattern whose on-state is set by the nominal phase displacement Ψ and the off-state by setting Ψ at 180° where the output current is cancelled out. Therefore, the average lamp current is modified without necessity of extra switches. The fast dynamics of the resonant stage ensures an operation free of instabilities and flicker effect. A 120W prototype has been built to validate the design proposal.