Dynamic behaviour of PI controlled class-E resonant converter for step-down applications using piezoelectric transformers

The target of a power converter controller using a piezoelectric transformer (PT) designed as a resonant circuit, as in half-bridge or class-E topology is to maintain constant output voltage or current and to achieve the ZVS (zero-voltage-switching) condition over the operation range. In the presented class-E application, the design of the closed-loop feedback is achieved for 0-3 Watts at 6 V/DC output with a varied output load between 12 Omega-1.2 kOmega, at input voltage range of 85-260 V/AC using different PT samples, at switching frequency range of 145 to 180 kHz, with the concept of PI control. The transient responses of the controller are presented with the jump of load and input voltage. In addition, the transfer function of class-E from original 4th order transfer function is linearized to be 1st order linear function as a function of the output current from the switching frequency and the varied input voltage. The Laplace transformation of the class-E converter with feed back PI control is analyzed using a linear model method. The stability condition of the closed loop control is analyzed with the Routh-Hurwitz stability criterion method