Design Of LED Constant-current Driver Control Chip With3-Channel

In recent years, LED decorative lighting is finding wider and wider applicationfrom monochrome static decorative to colorful dynamic decorative. The rapiddevelopment of LED decorative lighting owns to the diversity of its own color and thecorresponding development of the driver. As the market continues to expand in LEDdecorative lighting, general driver is unable to meet a wide range of needs. Therefore,the research of a constant current driver which is used in LED decorative lighting isvery useful.In this paper, a3-channel constant current LED driver which uses the topologicalstructure of linear constant current is designed. With three resistances, each channelcurrent can be set independently. This chip built SPWM pulse density adjustmentmechanism, so that it is able to output the16gray-scale data of grade65536. As theconstant current output range of this chip is very wide, it can easily realize all kinds’adjustment of brightness.The analog portion of the chip uses a stable PTAT current bias circuit to bias. Withchopper modulation technique, voltage offset caused by process disorder in the Bandgapcan be effectively eliminated. The oscillator with low power sensitivity can ensure thestability of the digital clock under various working conditions. The use of powerMOSEFT broadens the output range of the channel current. The speed of the channelopen and shut can effectively improve with the unique rapid start-up circuit. The designof POR and OTP can improve the reliability of the system.Based on TSMC0.25μm BCD process, EDA simulation tools such as Cadence andHspice is used to design and simulate the sub-modules, then the whole analog circuit ofthe chip is verified through simulation. Besides the current matching precision betweenchips and channels, major performance and indexes are all analyzed with the simulation.Theoretical analysis and simulation results show that the functions of the chip arenormal, meet the design expectations.