The Integrated Coupled-inductor Boost-fiyback Converter

The technology of power electronics is being used in a variety of fields and it is closely related to our social activities. From the exploration of the universe caused by human beings to the differing areas of national economy, power electronics devices always play a pivotal role in our society. The load could acquire AC and DC power source of varying voltage levels resulting from power electronics devices, which could make the load work normally. And in the domain of power source, due to the switching power source’s small size and high efficiency, it is gradually taking place of the linear power source to be the mainstream of power source applications. At present, in order to satisfy the different application requirements, the switching power source has been developing by leaps and bounds. The novel power electronics circuits and power electronics devices adapting to the needs of higher frequency are designed continuously.In this paper, after analyzing the drawbacks of traditional DC-DC converter, the integrated coupled-inductor boost-flyback converter(ICBFC) is proposed based on the integrated boost-flyback converter. This circuit could fulfill higher step-up ratio and higher efficiency by using the coupled inductor under low duty cycle. The circuit demonstrates several advantages: the disappearance of ultimate duty cycle when the circuit is working to achieve comparatively large voltage gain; the decline of the voltage stress on the switch and the reduction of conduction losses and switching losses; the effective suppression of the reverse recovery of the output diode and thereby decreasing reverse recovery losses and improving the reliability of power devices.The operating principle of the circuit in continuous-conduction mode(CCM) is analyzed in detail in this paper. Besides, the relationships among the voltage gain, efficiency, parasitic parameters and duty cycle are derived in the paper by using the principles of inductor volt-second balance and capacitor ampere-second balance. A new design of the circuit is mainly introduced in this paper, including the transformer core selection, the devices selection, the RCD clamp circuit and the driving circuit of the switch. A small-signal model of this converter is established by using the state-space averaging method and the closed-loop control is realized by using the lead-lag compensation, then introduces the feedback control circuit. The simulation and setting of the control model and circuit parameters are completed by the Saber simulation software and ensure constant output voltage of 50 V. Finally, a 30 W prototype has been made in the laboratory to verify the validation of the proposed converter. The experimental results are consistent with simulation results, which indicate the validity of the proposed circuit.