Research And Design Of Triac Dimming Circuit To LED Drive Chip

LED lighting is called fourth-generation lighting technology and is a leap lighting calendar of the human. It is one important way to solve the energy shortage and excessive consumption. LED lighting has been widely used in various electronic devices, especially mobile phones, pad and other small portable devices. With the rapid development of LED, LED dimming industry has been accelerating development.Dimming technology can not only save energy and prolong the life of LED, but also enhance the visual effects and improve quality of life. TRIAC dimming began to appear since the 1960 s. it has ruled the entire lighting dimming fields for nearly half a century. It beats consumers by high compatibility, low cost, small size,etc.The paper mainly discusses TRIAC dimming, and designes the related dimming circuit. Then it elaborates the significance of developing LED dimming industry,analyzes and compares with the currently popular dimming technology, and their advantages and disadvantages, and focuses on analyzing the TRIAC dimming technology, and ultimately determines adopting it as the scheme of the chip dimming.To solve the dimming flicker trouble, the paper designs discharge path and joins the active damping network. In order to achieve the brightness control, the paper designs to the phase control circuit which controls the average current of LED by measuring the phase angle of the thyristor. The chip meets a wide input voltage range and it is self-powered. The design adopts Buck flyback converter as the peripheral structure of the LED driver chip; By using a novel control algorithm, it achieves accurate constant current, eliminats the need for the complex control loop compensation, reduces the use of external devices, and improves efficiency.In this paper, it analyzes in detail and verifies the function of several key modules in the chip, including the power supply circuit, the bandgap reference circuit,zero-crossing detection, phase control module,etc. By using TSMC 0.5um BCD process and cadence、hspice software to simulate, the results show that the chip which has a TRIAC dimming function meets the design requirements, it has the range of flicker dimming reaching from 4% to 100%.