Research Of Off-line LED Driver Based On A Novel Forward-flyback Converter

With the development of semiconductor lighting technology, LED as next genera-tion light source, possesses a good shock resistance, no flicker, long life, high lightefficiency, no pollution, no radiation, and energy saving features, being widely usedin telecommunications, Postal, financial, transportation and other industries.The goodLED driver need to make LED lighting system more reliability and security to meetpeople’s needs.The status of the topology of LED driver is summarized,Some disadvantage of thevarious topology in the application is analysised detailed, a novel forward-flybackconverter based on the traditional forward-flyback converter is proposed in this article.The principle of the novel forward-flyback converter is analysised and steady stateperformance is theoretical analysised using the state space averaging method. Thetheoretical analysis results verified through SABER software simulation methods.Meanwhile, the various components loss model is established,and the formulas andmethods of devices loss calculation is given. The validity of theoretical calculation isverified by experimental methods.A medium-low power LED driver prototype is designed and set up, a power factorcorrection circuit based on Boost converter and a DC-DC circuit based on novelforward-flyback converter is included. Boost circuit is controlled by current-PFMcontrol method and forward-flyback circuit is controlled by voltage-PFM controlmethod, two-level converter circuits are operating in boundary mode. In this paper themain components parameters and control circuit parameters of the prototype in thedetailed is designed, including the BOOST main circuit inductance, switch and diode,the transformer of the forward-flyback main circuit, resonant inductor and capacitanceand so on.Through detailed analysis the experimental waveforms,what conclusions isderived is that energy can be transtered into the load through the transformer double-end, high utilization of the transformer, converter power density and large capacitymachine can be obtained under the conditions of using the same components,and theconverter can operate in resonant mode, the machine efficiency increases, and the main circuit and control circuit structure is relatively simple, overall cost of converteris relatively low.Experimental results of the steady-state performance of the prototypeis consistent with the theoretical analysis. This prototype the maximum efficiency atfull load is up to94%.