Research On A Composite Single-stage LED Power Driver With Low Output Current Ripple&Without Electrolytic Capacitor

As countries policies of the elimination of incandescent lamp was introduced and im plemented,LED With advantages of environmental protection,high efficiency,and energy saving have the increasingly huge market demand.As a new generation of electric light source.LED lamps including LED driver are required to have good performance?long-1 ife and cheaper price.Composite Single-stage PFC circuit got extensive researches in recent years,its adva ntage is that:The auxiliary converter through the secondary winding involves in modulati on of' the output voltage or output current,have excellent output performance,at the sam e time,the auxiliary Converter assume only a small number of power by appropriate con trol strategy,reduced the cost,and also improve the efficiency of the LED driver.so co mposite Single-stage circuit has great application value in the fierce market competition o f LED driver.In addition,electrolytic capacitor-less LED driver eliminate electrolytic cap acitor which is LED driver life's short board,prolong the life time,The research have th eoretical value and practical significance.This article summary and analyze the composite Single-stage circuit that is based on Flyback convertor's auxiliary winding,analyze the output ripple's suppression mechanism of the circuit?the working mode and cost advantage and efficiency advantage of the c ircuit in details;Based on the work mechanism of the circuit and the circuit structure,a nalyze its key problems,including the driver's input and output performance,the key p arameters design considerations are given.Composite Single-stage circuits which can be e quivalent to two voltage source in series exist a match problem of the output voltage an d load voltage.And based on Flyback convertor in which auxiliary winding cascades Bu ck convertor.This paper proposes a control strategy with adaptivc control functions,the control strategy ensure circuit's good input characteristics?output steady state performance with low output ripple and fast dynamic performance of a small scale,meanwhile when the load voltage change it can automatically adjust PFC stage feedback loop voltage be nchmark instead of' having to resort to Buck output voltage to bear the load variation,so that solve the problem existing in the traditional solution about the small load voltage r ange.And design differential circuit applied to solve the problem of output current overs hoot when the circuit startup.Using circuit simulation software PSIM to make simulation academically,the simulation both verify the circuits feasibility.Single-stage composite can reduce the requirement of the Ooutput capacitance of the c ircuit by two equivalent output voltage source working cooperatively.And in order to furt her reduce the output capacitance to use high frequency capacitance instead of electrolyti c capacitors,a kind of load harmonic current injection solution is proposed.the function equation between output voltage ripple and load current is deduced,the effect of pulse current's phase to capacitor voltage ripple is analyzed in details,and the design basis o f the scheme of output current harmonic injection is given;Then a load current ripple in jection scheme of which the input voltage is sampled to generate harmonic signal is appl ied to this circuit,the implementation of the scheme is given;And make circuit improve ment according to the above analysis,an optimization scheme is given to realize the co mposite single-stage LED driver without electrolytic capacitor.The low output current ripple LED driver is Developed and set up with the paramet ers of AC 176-277Vrms input,150W output.The prototype has 0V-10V dimmer function and multiple output specifications with constant power.Under the full input voltage ran ge and full load range,THD less than 18.3%,meet IEC61000-3-2 Class C harmonic sta ndards,The machine efficiency is no less than 92.33%,output current ripple is less than 1%.Under the condition of 220 Vac input,full load output,THD is less than 12%,PF is greater than 0.983,The machine efficiency is more than 93.3%.The experimental res ults verify the feasibility of design scheme.Then the proposed load current ripple injection scheme is applied to this prototype,The output capacitances of two winding are decreased to 40 uF and 70 uF so that to us e CBB capacitor and patch capacitance.Through the low gain loop design,the prototype without electrolytic capacitor,THD are less than 13.6%,PF is greater than 0.912 under Under the full input voltage range and 75%-100%load range.And under the condition of 220 Vac,full load output,THD is 9.3%,PF is 0.977,The machine efficiency reaches 92.36%.Meanwhile the output ripple is always less than 38%,in the acceptable range.The experimental results verify the effectiveness of the proposed scheme.