Study And Design Of LED Lighting Power Supply With Dimming

The light-emitting diode(LED) characterized by high efficiency, energy saving and long life cycle is expected to be the fourth generation of green lighting sources. LED driving power directly determines the reliability and life of LED lights, promoting the development of LED lighting. Through PWM dimming, the energy-saving and environmental protection of LED lights is better reflected, the life of driving power is extended. LED driving power with dimming function becomes the focus of the research content at the field of LED lighting now. This paper researches LED constant current driver and PWM dimming technology, accomplishing a 40V/0.90 A LED constant current driving power based on single-stage flyback converter. The main work and results are summarized as follows:(1)The key technologies of LED driving power is researched. LED driving power with dimming includes current driver and PWM dimmer. Its topology construction, dimming mode, power factor correction technology and other key technologies is analyzed. For the critical conduction mode of single-stage PFC flyback converter is researched, its qualitative analysis and in-depth research is carried out. This converter achieves higher power factor than 0.92 with simply circuit and low cost.(2)The improved PWM dimmer is researched. Several key points of PWM dimmer is analyzed. Through the dimmer switch in parallel with LED lamp, the way to achieve PWM dimming circuit is improved, achieving LED dimming without effecting constant current LED driver and no use a dedicated chip. The high frequency PWM wave and adding pulse is produced by microcontroller MSP430F4152, effectively reducing the dimming time delay and achieving a wide range of dimming. The most appropriate PWM dimming frequency is determined by the optimization of the software and a large number of experiments, solving the flicker and noise problems in the dimming process.(3)The whole circuit of LED dimming power supply is achieved. According to the parameters of the power supply, LED dimming power supply is designed in detail, including the main circuit of single-stage PFC flyback transformer, flyback transformer, clamp circuit, constant current and limited voltage circuit, PWM dimming circuit and electromagnetic compatibility, the calculation method of the parameters was presented.(4)The prototype was manufactured and the system is tested. On the basis of theoretical analysis, a 36 W prototype is tested, combined with the specific parameter calculation. The performance of the power supply is as follows: the power factor is higher than 0.92,the efficiency is more than 0.87, this power supply reach 0 ~ 100% flicker-free dimming. The power supply meet the design requirements.Based on the good performance of LED constant current driving power, the PWM dimming function is achieved. The improved way of PWM dimming circuit is proposed, and this paper raise effective solution for PWM dimming delay, flicker and noise problems, achieving a wide dimming range and no flicker dimming. The whole power supply has high power efficiency, high power factor, low cost. It has good practical performance and application prospect.