Design of FAN6300 quasi-resonant LED street light power supply

Abstract: In recent years, LED has been widely used in street lighting due to energy saving and environmental protection. In order to meet the electrical characteristics of high-power LEDs, a quasi-resonant high-voltage constant-current LED street lamp driving power supply is designed based on the traditional flyback converter based on Fairchild FAN6300. The principle and advantages of quasi-resonant switching power supply are expounded, and the circuit schematic diagram and the parameters calculation and selection methods of key components are given. The experimental results demonstrate the feasibility and effectiveness of the design.

As the energy crisis and climate warming become more and more serious, energy conservation has become a topic of global concern. Lighting is an important aspect of human energy consumption, accounting for about 20% of the world's total energy consumption. Therefore, research and development of green energy-saving lighting technology has received more and more attention. High-power LED street lamps are a new type of lighting method that illuminates high-power LED groups by DC voltage. Therefore, the traditional power supply for driving incandescent lamps, fluorescent lamps, energy-saving lamps, sodium lamps, etc. is not suitable for direct driving. Power LED. Based on the operating characteristics (VI characteristics) of high-power LEDs and the driving requirements of LED street lamps, this paper uses power electronics technology and PWM integrated control chip to design a wide input voltage range (90~265 V). A quasi-resonant high-voltage constant current LED street lamp driving power source simplifies the circuit structure and improves the working efficiency of the power supply.

For a traditional hard-switched flyback converter, the parasitic capacitance will oscillate with the leakage inductance of the primary side of the transformer. The value of the voltage on the parasitic capacitor is generally large. When the MOSFET of the next clock cycle is turned on again, the parasitic capacitance will discharge through the MOSFET and generate a large current spike. Since the MOSFET drain source is subjected to a high voltage at this time, the current spike will cause switching loss, and the current spike contains a large amount of harmonic content, which in turn generates EMI. After considering the above factors, if the detection circuit can effectively identify the MOSFET The valley value of the drain-source voltage, and the MOSFET is turned on at this time. Since the voltage on the parasitic capacitor is the smallest at this time, the current spike at the time of conduction will also be minimized. This mode of operation is often called a quasi-resonant switch [3]. Therefore, the basic principle of the quasi-resonant technology is to use the capacitance between the two ends of the MOSFET (parasitic capacitance or external capacitance) and the leakage inductance of the primary side of the transformer to control the near-zero voltage turn-on of the switching tube by detecting the valley voltage at both ends of the switching device in real time. The switching loss of the MOSFET is reduced, and the efficiency of the converter is improved. In addition, softer switching characteristics reduce the EMI noise of the power supply, allowing designers to reduce the number of filters used and thus reduce costs. The whole circuit has a simple structure, high full load efficiency and low no-load loss.

1 drive power design requirements

The LED is a current-driven component whose brightness depends on its forward current [4], so driving the LED with a constant current source is the best method. The constant current source can avoid fluctuations in the output current due to fluctuations in the input voltage, so that the brightness of the LED remains constant. For the constant current drive mode, the LED is connected in series and is the best choice. Considering that the series connection will cause the output voltage to be too high, in this example, 40 1 W LEDs are connected in series, which requires the design of a power supply with a rated power of 40 W. According to the actual lighting requirements of the street lamp, it is only necessary to use the 40 W power supply as a basic module for corresponding power expansion. The specific design requirements for the 40 W power supply are as follows: (1) the input voltage is 90~265 V; (2) the rated output voltage is 132 V; (3) the rated output current is 330 mA; (4) the power efficiency η = 90%.

2 Quasi-resonant circuit design based on FAN6300

The FAN6300 is a highly integrated PWM control chip from Fairchild, and OSRAM is also considering the FAN6300 for its 12 W to 60 W LED driver products. The FAN6300's internal valley voltage detector ensures that the power system operates in near-resonant conditions over a wide range of household power and any load conditions, and reduces switching losses to minimize switching voltage on the MOSFET drain. The FAN6300 also features a variety of protection features such as pulse-by-pulse current limiting to provide short-circuit and open-circuit protection for the system, enhancing power supply reliability. Therefore, the FAN6300 can greatly improve the performance of the flyback converter. In this paper, the main circuit of the power supply adopts a single-ended flyback topology, and the circuit is shown in Figure 1.

Weiku PDF download: Design based on FAN6300 quasi-resonant LED street light power supply.rar

references:

[1]. FAN6300 datasheet http://+_1457656.html.