Suppression of switching frequency variation for current sensor-less hysteretic current mode switching supply

This paper presents a suppression method of the switching frequency variation for a hysteretic current mode converter without detecting the inductor current. The renewable energy is difficult to keep the constant output because it is influenced climate change etc. It is need to add the charging system in order to keep the power supply and demand balance. The ac-dc converter is used in the wind power plants which generate the ac output in order to charge the energy to the charging system. The continuous current mode PFC (power factor correction) is controlled in the average current mode, peak current mode and hysteretic current mode. In the hysteretic current mode PFC the switching frequency variates if the circuit conditions are changed. It makes hard to design EMI filter. The continuous current mode PFC is necessary to detect the inductor current. The current detection resistor is a cause of loss. In the proposed method, the ripple of the inductor current is changed by detecting the circuit condition using the digital control. The inductor current is predicted by solving the equations derived from the circuit analysis of main circuit. The converter is operated in the hysteretic current mode using the predicted inductor current. This prediction needs to detect only the input and output voltage. It is able to eliminate current detection and reduce the power loss by current detection resistor. As a result, the proposed method is able to suppress the variation of the switching frequency respect to change in the circuit conditions and kept to operate in the hysteretic current mode without current detection.