Study And Design Of Multi-channel AC LED Driving Chips

With the continuous progress of technology,LEDs with long life,high luminous efficiency,small size and fast response are replacing traditional lighting sources.LED driver is an important part of LED lighting.At present,the LED driver on the market is mainly DC driver.At the same time,the study on multi-channel LED driver is only concentrated on the DC driver.However,LED DC driver has problems such as high energy loss and unstable system,while AC driver is mostly single-channel driver,which can not fully meet the needs of market-specific lighting.Therefore,study on multi-channel AC LED driver is of great significance.In this thesis,based on the CSMC 025um_enhance₃0v₆0v_BCD₂P5M_Process,a multi-channel AC LED driving chip with simple structure,high system efficiency and adjustable driving current for each channel is designed.The chip uses full-wave rectified mains signal to directly drive multiple LED strings of different colors,generally WLED?white LED?,RLED?red LED?,GLED?green LED?and BLED?blue LED?light string.The main study contents of the thesis are as follows:In the design of the driving control circuit,the WLED light string is disposed by detecting the current in the rising phase and comparing the voltage in the falling phase,and then combined with the logic control circuit,the switchs at all levels controlling the WLED light strings are switched accordingly to achieve a stable and reliable control method.At the same time,the logic control circuit expands all levels of switching signals of the controlling the WLED light strings into the same three-way signal,and controls the switch transistors of the RLED,GLED and BLED light strings respectively,so as to realize multi-channel LED lights of different colors lightened or extinguished simultaneously and simplying the control mode of the multi-channel driving circuit;Two different spectral distribution adjustment methods are designed for different application scenarios with different spectral distribution of special lighting: when the application does not require accurate spectral requirements,the spectrum distribution can be adjusted by changing the current values of different color LED strings;when the application needs fine dimming,it can be adjusted by changing the duty ratio of the dimming signal generated inside the chip.In practical applications,two adjustment modes can also be used simultaneously to achieve more accurate spectral adjustment;In response to the problem of driving power consumption,on the one hand,the design controls the current of all LED strings to change with the driving voltage,so as to avoid the switch transistors suffering from too high voltage drop;on the other hand,except for the WLED strings,the LED strings of the remaining colors are supplied with current by a current mirror composed of MOS transistors when they are turned on but do not reached the constant current,thereby improving the efficiency of the driving system.The circuit simulation results show that the chip is powered up after 60 ms,and then enters the normal logic state.The chip has an over-temperature protection function and can work normally within ±10% of the mains fluctuation,and the system efficiency is 93.01%,which satisfies the design specifications.Finally,the layout design of the proposed driving chip is carried out.