Self-sustained oscillating resonant converters operating above the resonant frequency

This paper presents a new control techniqne for resonant converters. Unlike conventional variable frequency control which externally imposes the switc hing frequency, the proposed scheme is based on controlling the displacemen t angle between one of the resonant circuit variables, typically the curren t through the resonant inductor, and the voltage at the output of the inver ter, As a result, zero-voltage switching (ZVS) can be ensured over a wide o perating range. The proposed control technique can be applied for series, p arallel, and series-parallel resonant converters. As an example, the static characteristics and dynamic model of a series-parallel resonant converter with the proposed controller are derived and the system behavior is investi gated in detail, Experimental results are given to demonstrate the operatio n of resonant converters with the proposed controller and to validate the a nalysis.