Study And Design Of Sectioned High-Voltage AC LED Driving Chip

With the continuous development of technology and the increasing requirement in the LED market, the LED lighting systems, which are considered as the 4th generation lighting products, are fast developing. Up to now, AC/DC switched power supply is used to drive LED by most of the LED products on the market, which can cause energy loss during AC-DC transformation. AC LED technology can solve this problem because it can be droved by AC power directly. Hence,the high- voltage AC LED driver attracts great attention for the market, and further study and improvement of AC LED driver has great significance for the development of the lighting products.Characteristics of current used in LED lighting and driving systems are analyzed in this thesis. In order to solve the problem in the respect of system efficiency and utilization rate of light lamps that exist in the current LED drive chips, a new sectional drive scheme in which variable current and constant current coexist was proposed based on our previous research results. This new drive scheme can improve system efficiency to 94%. At the same time, it can improve utilization rate of light lamps and reduce flicker effect. In order to solve the system stability problem existed in the current LED drive chips, a new sectional control method was proposed. This new sectional control method worked together with the constant current module in the high voltage range not only can control the current thro ugh LED more accurately, but also handle well with the stability problem coursed by the effect of non-ideal factors. The chip can work normally even if the mains fluctuate 20%, and the current still stay within the safe range while the noise run up to 50 V, so that there is no overshoot current flowing through LED. To solve the problem of overshoot current when starting up of the power supply, a new power supply protection circuit based on the detection of the position of valleys when starting up of the power supply at any time was proposed and designed. This new starting protect circuit can keep the current through LED within the safe range. The designed chip could operate properly under 120 ℃. It would be suspended when the temperature is excessive this temperature limit and revive to normal operation state when the temperature drops back to 80℃.The 1um SPDM 5V40V700 V monolithic was adopted in this design. C hips of the AC LED system have been designed and simulated by use of the EDA tool Cadence. After the final layout, simulation results show that the chip could achieve the intended function and meet the requirements of chip design.