Research On A High Power Density LCC Resonant Converter For LED Driver Without Electrolytic Capacitors

LED has many advantages,such as energy saving,environmental protection,small size,long lifetime,which is recognized as a 'new green light' and its advantages of energy conservation is particularly important in todays.The LEDs are light emitting diodes,which need specialized DC constant current source as power supply.In order to balance the difference between input power and output power,usually,there is a high-capacity electrolytic capacitor in traditional LED drivers.However,the lifetime of electrolytic capacitor only about a tenth ofthe lifetime of LED lamp bead,which can't take full advantage of the lifetime of LED lamp bead.High power density resonant converter has the advantages of low cost and efficient.Consequently,it is very useful to research the high power density resonant converter for LED driver without electrolytic capacitors.The existing works of LED driver without electrolytic capacitors are summaried in this paper.Considering the factors such as PF,efficiency,reliability,the article chooses Boost circuit as APFC topology.According to the function of storage capacitor in Boost circuit,the detailed relationships between the capacity of the storage capacitor and the key parameters of capacitor voltage are analysed.Then,the minimum capacity of storage capacitor is calculated which guarantees the Boost circuit normally working.We use film capacitance in place of electrolytic capacitors of the traditional LED driver.In order to guarantee a high PF in the stable state of LED driver without electrolytic capacitors,a new control method based on the Boost PFC circuit is proposed that the voltage control loop of a LED driver could be selected from fast to slow response in starting-up.In addition,based on LCC DC-DC circuit,the working principle and working characteristics of LCC circuit are analysed in detailed.Then,the full process of the LCC circuit parameter design for LED is given.In order to increase the power density and efficiency of LED driver,a new large leakage inductance transformer is proposed,which can use the leakage inductance as resonant component.Then,this article detailed analysis and compares the characteristic of integrated magnetic circuit and independent magnetic circuit,and related experiments are conducted.A 150W and 3.85A constant-current LED driver without electrolytic capacitor is built.When input voltage ranges from 90Vac-rms to 305Vac-rms,THD are less than 20%,PF is greater than 0.9 under full load,which meet the criteria of IEC1000-3-2 Class C.When input voltage is 220Vac,full load output,THD is under 5%,PF is higher than 0.985,the efficiency of the whole machinery is over 91%.The experimental results further validate the effectiveness of the proposed method.