Design And Implementation Of LED Dimming Power Supply Based On PWM Technology

LED lighting has become one of the alternatives to traditional lighting because of its environmental protection,energy saving,long life and other advantages.The driving power supply technology of LED lighting is becoming more and more mature.In view of the shortcomings of LED lighting in the current market,such as low dimming range,flickering phenomenon in low light band,low power efficiency and so on,a kind of LED dimming power driver circuit based on PWM technology compatible with thyristor dimmer is designed in this paper.The main work and achievements of this paper are as follows:1.In order to avoid the disturbance signal of thyristor characteristic,the output voltage phase angle of thyristor dimmer is judged by the way of single chip microcomputer software filtering,so that the PWM signal with different duty ratio is output to control the follow-up circuit to follow the dimmer change accurately and make the LED lamp change continuously,so as to realize wide range non-flickering dimming.2.Because the output voltage and current phase of thyristor dimmer deviate greatly,active PFC control technology is adopted to improve power factor.Accurate input voltage phase angle is obtained by single chip microcomputer,so the current in APFC circuit is controlled to ensure the matching of PFC parameters in the dimming process and in the maximum power state.3.In order to improve the efficiency of power supply,a flyback DC converter with high conversion efficiency and low cost is adopted.The switching tube is controlled to turn on and off by PWM signals with different duty ratios output by a single chip microcomputer,and the power supply for LED is converted to a suitable DC voltage by a DC/DC converter.Pulse voltage output from auxiliary coil of transformer is used to supply power to single chip microcomputer to absorb residual energy of main power supply and improve power efficiency.On the basis of theoretical research,a LED dimming power supply system with output power of 20 W is designed,which is compatible with most of the thyristor dimmers on the market.Without changing the original lighting system circuit,the LED dimming can be realized by replacing the traditional lighting fixtures.The test results show that the power factor is 98%,the efficiency is 80%,and the constant current precision is less than 2%.The thyristor dimmer can realize continuous dimming without flicker in the conduction angle range of 22.6 to 151.1 degrees.This shows that the design of the LED output constant driving current,high power efficiency,high power factor,can achieve a wide range of continuous smooth dimming function,with good practicability.