Research of passive PFC circuits in LED driver circuit

Aiming at LED driver circuit for low-power filed,due to size and cost constraints,the driver circuit can not use the active power factor correction(PFC) circuit,leading to the problem of poor factor.It was first analyzed why the factor needs to be corrected.Then,the research was done in passive power factor correction circuit designing and the model of capacity with 20 W LED driver circuit.Based on the research,there were four circuits which were compared with others,so that one valley-fill passive power factor correction circuit was found.Reseach results indicate that it is with low cost and high power factor and the circuit can meet Energy Star standards and there is no crest factor and other issues.