The Design Of Serial And Parellel White LEDs Driver IC In Current-Mode

SMSP (Switch Mode Power Supply) is the leading product of steady voltage supply. The internal large power MOS in switch mode power supply operates in intermittent state, its equivalent resistance is very small, so it consumes very little energy. Its efficiency can reach nearly double that of normal linear steady voltage supply. Switch mode power supplies have the virtues of higher integration level, fewer components needed in additional circuit, higher efficiency. Because its high efficiency, it is now replacing the linear steady voltage supply, and becoming an essential common portion in ultra large integrated system.This research is about a white LED driver IC with wide range input and high current output. This chip can supply for Serial or Parellel White LEDs. This chip is a buck switch power IC based on the principle of PWM modulation mode, working under current-mode. Its frequency is 83KHz. The chip includes bandgap, oscillator circuit for sawtooth wave, circuit of sample for inductance current also for over current limiting, error amplifier, sampled signal amplifier and several digital logic units.The paper introduces switch power, white LED first, and the principle of DC/DC switch power, including the topology of DC/DC driver, modulation mode and control mode and so on. The design is finished based on the target. My work includes the analyses for the whole circuit and every sub-circuit, and simulation for the whole circuit and every sub-circuit using Cadence. The simulation result shows that the circuit satisfies my target. The end of paper is including the layout of some sub-circuits.