Design And Research Of LED Driver System That Base On PWM Control

In recent years,with the development of electronic information and the popularity of related electronic products,the light source has become the main energy requirement.Incandescent,fluorescent and other traditional light source have been replaced by LED.LED with low power consumption,small size,best efficiency and low heat has been used as environmental light source.Especially with the upgrading of the technology of LED-display and LED-lighting,making the design research of LED driver more valuable.This paper bases on the principle of PWM control mode and DC-DC control system,designs a peak current controlled LED driver chip.The core circuits of LED driver chip primarily contain:bandgap reference,oscillator,slope compensation,error amplifier,PWM comparator,over-temperature and over-voltage protected circuit.The voltage fluctuate of band-gap reference circuit which has a good temperature performance is 2mV in the range of-20? to 140?.The oscillator circuit can output stable pulse waves and triangle waves.The slope compensation circuit is capable of eliminating harmonic oscillation problem.The gain of the error amplifier is more than 80dB,and the phase margin is more than 75°.The PWM comparator circuit can output a stable square waves modulation signal.The over-temperature protection which has a good temperature protection effect closes the chip at the temperature above 130? and restores the chip when the temperature drops to 95?.The hysteresis voltage of comparator in the over-voltage protection circuit is 50mV,the over-voltage protection circuit shutdowns the chip when the sampling voltage exceeds 2.55V and restores the chip when the sampling voltage down to 2.5V.The simulation results of this thesis which running by Cadence ADE show the chip meets the expectations.The work of this paper laid a good foundation for the next step in the chip layout.