An optocouplerless two-stage high power factor LED driver

An optocouplerless two-stage high power factor LED driver is proposed in this paper. The first stage is an optocouplerless isolated PFC converter and the second stage is a constant-current controlled non-isolated DC/DC LED driver. Optocoupler and secondary amplifier circuit of the first PFC stage can be removed. Besides, the output capacitor s of the PFC stage can be reduced due to low output ripple voltage requirement and acceptable wide input voltage range of the secondary stage in the two-stage LED driver. Hence the circuit structure of the proposed optocouplerless two-stage high power factor LED Driver is much simplified. A prototype LED driver for 12W LED fluorescent tube is built up to verify theoretical analysis and experiment results are presented.