Research On Topology And Control Technologies Of Single-stage Single-switch LED Driver

LED has been widely used in automotive lighting,indoor lighting and backlighting,owing to its high efficacy,long working life and fast response and so on.The performance of LED lighting is determined by LED driver.Therefore,LED driver should own these characteristics of low cost,high reliability,high efficiency.To improve the input and output performance of LED driver,the detailed research contents are shown as follows:Firstly,a single-stage single-switch structure is presented by integrating active power switch in PFC cell and DC-DC converter cell to improve the input chatacterisitic and decrease the cost of system.Therefore,integration rules of singlestage single-switch structure are analyzed and summaried.In medium-low power lighting application,Flyback converter is usually adopted as mian DC-DC converter cell.Based on Flyback converter,summarizing integration rules are summarized to solve the problem of source-electrode pole connected-to-ground to reduce the complexity of drive circuit design.A reasonable and cost-effective scheme can be provided for different lighting applications as theoretical support.Secondly,an optimized quasi-resonant and primary-side control scheme are adopted applied in single-stage single-switch topology,in order to improve the efficiency and reliability based on Flyback converter.Quasi-resonant control method with limited resonant working period is proposed to improve the performance on light load condition and extend the soft-switching working period.Switching loss of system decreases sharply and efficency is increased.Meanwhile,primary-side control method can improve the reliability,compared to traditional control technique,further to improve the accuracy of primary-side control method.Integration capacitor,signal phase shift recognition circuit and sample and hold circuit with mirror capacitor are adopted to improve the accuracy of secondary-side diode turn-on time and peak current,solve the inaccuracy of traditional primary-side control.Based on BuckBoost and Flyback single-stage single-switch topology,experimental results verify the validity of analysis.Thirdly,a high-efficiency scheme of LED drive system based on Class E resonant converter is presented.Because Flyback converter can not simply realize zero-voltage-switching soft-switching characteristics to achieve low-cost highefficiency high-power lighting application demanding.The Class E resonant converter can realize ZVS soft-switching characterisitic,which has only one switch with simple control and low cost.But unsuitable PFC cell and modulation control technique makes system operating in hard-switching condition.Therefore,a research and analysis on integration rules of soft-switching structure is done.This paper proposes a ZVS type single-stage LED driving system based on Flyback-Class E,compared to Buck-Boost-Class E,the proposed ZVS type topology can achieve a higher system efficiency.Meanwhile,an optimized PWM control method is proposed for the proposed structure,and the working scope of soft switching is extended.Lastly,an optimized primary-side control method is presented for single-stage single-switch topology based on Class E resonant converter,further to improve reliability.By measuring the peak value of resonant current and phase-shift of voltage,the output current can be tested.Different from the traditional primary-side constant output voltage control,the proposed primary-side control method can achieve constant output current control.Meanwhile,to improve the accuracy of the proposed primary-side control method,Kalman Filter iterative algorithm is adopted,which can optimize the sinusoidal shape of resonant current and improve control precision.The system dynamic characteristic is analyzed based on Extended Describing Functions(EDFs)small signal model method.Based on Flyback and Class E single-switch single-stage converter,the feasibility of proposed primary-side control method is verified.The improvement of the topology and control technology in single-stage singleswitch LED driver ensures the efficient and reliable operation for lighting system,and promotes the wide application area of LED solid-state lighting source,and is of great significance to the realization of green lighting.