Design And Implementation Of High Efficiency Driving Circuits For High Power LED Lighting

As the new generation of lighting source,LED is known for its energy saving,high efficiency,long life,and safety and environmental friendly.With the gradual maturity of technology in recent years,the cost of LED lamps has been greatly reduced,thus LED lighting has gradually replaced traditional lighting sources,result in a fast increasing in market share.Unlike traditional light sources,LED light strings are driven by constant current sources.Therefore,designing a driver with high efficiency and high reliability become core technical issues in LED lighting system design.In order to overcome the flaw of low efficiency and large size of power module in conventional LED driver,this thesis presents a quasi-resonant soft-switching driving circuit based on the application requirements of high output voltage and high power LED lighting.The driver operates under Boundary Conduction Mode(BCM).Based on the LC oscillation modeling theory,when the inductor current crosses zero,once valley voltage at the drain of power switch is detected during resonance,the power switch turns on,thus soft-switching process of zero-voltage switching(ZVS)and zero-current switching(ZCS)is achieved to solve the serious switching loss caused by hard-switching of traditional high-voltage LED drivers,enables the power supply to operate at a higher frequency.The proposed LED driver has designed a self-powered system to store the dV/dt current generated by the drain of power switch at the moment of turning off as charge on a capacitor,taking advantage of the collected energy to power the system.The built-in power supply voltage is stabilized by the power supply regulation circuit and the active clamp circuit,thereby further improving system efficiency.The LED driver was simulated in Huahong 0.35μm BCD process.The simulation results suggest that under the condition of the input voltage of 200 V,a LED power source with stable output of 98.4V and 468.6mA can be obtained at the switching frequency of 100 kHz.The theoretical efficiency of the LED system is up to 97.3%.