The Design And Implementation Of LLC120W LED Driver

Under today’s condition of environmentally friendly and energy saving, because of its highefficiency, long life, non-polluting, energy-saving advantages,LED lighting become flourishing inthe lighting market. LED’s advantage of long life and energy saving are relying on the power driver,unlike traditional lighting directly connected to the mains, LED belongs to the low-voltage DCpower supply device, therefore, LED requires to matched the corresponding power driver. Thepower driver of using general topology have problems of severe circuit losses at light loads, lowefficiency and serious fever, so for high-power LED driver general topologies are not suitable. Inresponse to this situation, this article will use the LLC resonant converter scheme to develop anhigh-power LED driver which works efficient and stable in the whole load range.Based on the comparison and analysis of existing structure on power driver, choose athree-stage driver circuit structure. First of all, brief introduce the power factor correction and softswitch technology, the development status and requirements of power driver is discussed. Secondly,propose definition of power factor correction, compare the pros and cons of passive power factorcorrection and active power factor correction，select the design scheme of active power factorcorrection, PFC circuit was designed in detail. The second stage of power driver is a design schemeof half-bridge resonant converter, the inadequacies of traditional resonant converter was pointedout. The converter’s operating principle of different frequency bands is described, the equivalentcircuit model is established using fundamental approximation, the performance influence ofconverter’s network of different parameters is discussed, the parameter of resonant network maincircuit and control circuit is completed. Due to the output of resonant converter is constant voltage,constant current is needed for output of LED driver, the third stage uses Boost constant current anddual op amp control scheme, the main circuit and control circuit of constant current section is done.Finally, adopting the proposed scheme, a120W LED power driver prototype with constantcurrent output is built and studied by experiment, the effectiveness and feasibility is verified by theanalysis of the result.