Resonance Parameters Optimization Research Of Wide Voltage Output LLC Resonant Converter

For the past few years,with the popularity of energy conservation,emissions reduction and low carbon life LED lighting is quickly developing as a new generation of green lighting devices,because of its high efficiency,no polluting,long life,low power consumption and so on.The LED driver as a key part of the LED lighting has ushered in a huge development opportunities.Additionally,switching power supply technology has also developed quickly.The switching power supply is mainly made up of the DC-DC converter,which is the core part of the converter.The LLC resonant converter has became the focus of attention in DC-DC converter as which has excellent properties of high efficiency,high power density,the ability of operating in high frequency condition,simple constructure and natural soft switch.Therefore,LLC resonant converter rapidly and widely apply to the LED driver.Facing to the actual application of LED,its voltage level are various.Different customers need the LED driver output of current that are not the same,which requires the LED driver to have the ability of wide voltage output so that the complexity of the actual production can be reduced.The best working region of LLC resonant transform is close to the resonant working point.With the load range of LLC resonant transform becomeing wide,the operating frequency range of resonant circuit are also increasing. That the resonant circuit parameters selection is not reasonable will also cause the output oscillation and abnormalities of the power supply.Therefore,under the background of application of LED power supply,we put forward the resonant parameters optimization research of wide voltage output LLC resonant transform,which has practical application value and the reference value on the further research about LLC resonant transform.Firstly,the paper detailed the operating characteristics of LLC resonant converter and the working process in the exceed resonance region.We also analyse the characteristics of each work area of the LLC resonant converter.Secondly,we will be modeling for LLC resonant converter by first harmonic analysis(FHA) and analyze its model in detail.We deduce transformer dc gain formula and portray its curve graph in Mathcad software so that we can study the characteristics more intuitively.Based on the FHA method for resonant circuit,we study the zero voltage switch tube opening conditions. What#s more,we study the characteristics of wide range of output LLC resonant transform and preliminary determine the resonant circuit parameters through the known conditions.Through these analysis,we find out that the essence of resonance parameters optimization is the optimization of inductance coefficient(K) and quality factor(Q).We study the effect of resonance parameters on circuit performance through comparing different inductance coefficient(K) and the quality factor(Q) that generate changes on its dc gain curve.We design resonant parameters of LLC resonant converter applying to LED driver and create the corresponding Simplis closed-loop simulation model.We verified the actual design parameters by model simulation and experimental method and compared the two results so that we can verify the rationality of the design parameters and the mode.We analyse that the region of the operating frequency of the resonant circuit impact on the efficiency of the power supply through experiment test and analysis methods.At last,we put forward the K value selection principle of wide range output of resonant circuit.When the converter realized wide range output,we studied the resonant circuit operating frequency range and comparative analysis under different inductance coefficient K output load conditions in the simulation model,which verified the method of K value under the condition of wide range output.Finally,we studied the two magnetic devices that decided LLC resonant inductance coefficient design method.We explained the magnetic device parameters so that we can have a more clear understanding for practical design and derived the AP design method process.We introduced the over-current protection method of resonant circuit and gived the over-current protection circuit commonly used and design principles.