Study On A Novel Electrolytic-Capacitor-Free Buck-Boost Forward-Flyback LED Drive Circuit

Traditional lighting generally adopts lighting such as incandescent lamp, fluorescent lamp, however, incandescent lamp has low efficiency、high energy consumption and Fluorescent lamp life has short service life and problems such as environmental pollution. In recent years, the LED lighting technology has been rapid developed, in service life, energy conservation, environmental protection and application conditions the LED lighting are much better than traditional lighting. Single stage without the application of electrolytic capacitor PFC technology not only keep the LED driver small volume, high power factor, but also make it easy control, and greatly prolong the service life of the LED driver. Power factor correction technology of single stage without electrolytic capacitor in the application of LED power supply has natural advantage, has gradually become a research hotspot in recent years.This article firstly analysises several common single stage PFC converter without electrolytic capacitor in detail, compares the characteristics of several kinds of converter,and single stage without electrolytic capacitor Buck - Boost flyback type PFC converter has high power factor, easy control, low intermediate level capacitance and leakage inductance of the current feedback, advantage above makes it broad application prospects. This paper analysis working principle and characteristics of the traditional single-stage PFC converter without electrolytic capacitor in theory, and the correctness of the theoretical analysis is verified by the simulation analysis. In order to solve the shortcoming of small power and large voltage and current ripple of traditional converter, the paper introduces forward and fly-back circuit into the DC/DC converter, then constructs a new type of non-electrolytic capacitor forward and flyback circuit PFC converter.New non-electrolytic capacitor Buck-Boost forward and flyback circuit type PFC converter inherits high power factor and simple control and feedback circuit of leakage inductance, at the same time the transformer primary side and the vice side both have capacitance as intermediate grade energy storage component, transformer work in forward and fly-back mode, improves the power density of the transformer and the transformer vice side stream inductance, reduces the rate of the output voltage ripple current under the condition of increasing power output. In this paper, the working mode of converter is divided into MDCM (Magnetizing Current Discontinuous Mode) and MCCM (Magnetizing Current Continuous Mode) based on whether the magnetizing current is continuous or not, and make detailed analysis of different working mode of converter, the MCCM mode converter can realize zero voltage switch on conduction, in low voltage large current condition, this mode has better performance, in these two kinds of working Mode, voltage of middle capacitor is lower than traditional LED driver. According to whether the output filter inductance is continuous or not, the working mode is divided into filtering inductance intermittent mode and filtering inductance continuous model, and analyzes theoretically the better output filter inductance characteristic in continuous mode, finally, the new type LED drive circuit has been carried on by simulation analysis and design.At last, a 30 W prototype is designed, in the experiment, the prototype works separately in MCCM modal and MDCM mode under 110Vac and 220Vac input, and the prototype can work normally in these two mode. The experiment results verify the validity of the theoretical analysis and the feasibility of the experiment scheme, show that the converter has high power factor and low output voltage and current ripple, etc.