Research And Design On High Efficient LED Driver Based On LLC Series Resonant

With the characteristics of energy-saving and environmental protection,LED will lead us into a new time of lighting. It is of great significance to designa high-quality LED driver, which should be high efficient under variable loads,meanwhile, with short response time. This thesis focuses on this. It first analyzesdifferent driving techniques, then proposes a driving topology consisting ofAPFC, DC/DC converter and synchronous rectifier. At last, the thesis givespersuasive experimental results of the designed topology on two kinds of load,LED light bar and LED monitor, both of which are widely used in practice.In order to rise the PF of the converter, boost active power factor correctioncircuit is selected as the previous stage. Small-signal model analysis and Sabersimulations are implemented on this.LLC series resonant circuit is used to improve efficiency of DC/DCconverter. Its parameters are selected to make the converter operate at zerovoltage switch state. Moreover, some practical specifics (e.g. overvoltageprotection, overcurrent protection, undervoltage lockout) are taken intoconsideration.At the circuit of synchronous rectifier, small on-resistance MOSFET insteadof rectifier diode is used to avoid loss on diode caused by high current. Besides,EMC is considered to meet GB.The designed LED driver is tested under variable conditions. Results showthat the driver works well. When the input is220V/50Hz, the highest efficiencyand the maximum PF reaches90.6%and0.975respectively. When the input is110V/50Hz, the two parameters get88.9%and0.996correspondingly. Underthe condition of no load and light load，the efficiency is high too.