Improved averaged model and stability analysis of voltage-mode controlled positive output super-lift Luo converter

Abstract

Positive output super-lift (POSL) Luo converter, which has some particular good features: such as its power switch being grounded, high voltage gain and positive polarity output, is a good topology for overcoming the drawbacks of the conventional Buck and Boost converters to obtain high output voltage and power for satisfying the requirements in practical engineering. In this paper, based on the averaging method and taking into account the abrupt changing of the voltage across the energy-transferring capacitor, the improved reduced order averaged model and the corresponding small signal model of the POSL Luo converter are established, and its transfer function from the duty cycle to the output voltage is derived and analyzed. By combining the derived transfer function from the duty cycle to the output voltage of the POSL Luo converter, with that for the voltage compensator and that for the pulse width modalation (PWM) generator, the transfer function from the reference voltage to the output voltage of the voltage-mode controlled POSL Luo converter is also derived. And then, the stability of the voltage-mode controlled POSL Luo converter is identified by calculating the poles of its transfer function from the reference voltage to the output voltage, so the corresponding stability boundaries are obtained. The power electronic simulator (PSIM) software is applied to simulate the POSL Luo converter in time domain and frequency domain to preliminarily confirm the effectiveness of the established transfer function from the duty cycle to the output voltage of the POSL Luo converter, and to simulate the voltage-mode controlled POSL Luo converter to preliminarily verify the theoretical analysis about its stability. Finally, the hardware circuits for the POSL Luo converter and the voltage-mode controlled POSL Luo converter are designed, and the circuit experimental results in time domain from the digital oscilloscope and in frequency domain from the impedance/gain-phase analyzer are presented for further validation. Theoretical analysis, PSIM simulations and circuit experiments are in basic agreement with one other, and all of them demonstrate that it is effective to use the improved average model to analyze the performance of the POSL Luo converter and the stability of the voltage-mode controlled POSL Luo converter.