Design Of Constant-current LED Driver Based On BCD Technology

LED (light-emitting diode) has advantages of efficiency, durable and safety, so ithas been widely used recently. China’s LED industry is developing very fast, and thescale of the industry had reached about100billion yuan by2010. Yet, LED has thedisadvantages of high discretion of electric parameter, obvious temperature effect andhigh positive onset voltage. So specially power management IC is needed for LEDdrive. The LED drivers have become the hot nowadays.The article has analyzed the basic principles of commonly LED driver.Considering the demand of the market, based on BCD technology a PFM current-modeDC/DC convert for LED driver is designed. The article has given the working principleand the design method of the chip and its main sub-circuits. The circuits of the chipwere simulated by Cadence spectre. The results achieved the design requirements. Thedesign of the layout was given finally.The design and simulation of the chip and its layout based on CSMC0.5um BCDprocess. The range of the chip’s input voltage was7V~36V. It can provide up to1Aoutput current, with the efficient up to about90%. The chip contains LDNMOS, it candrive several LED with only a little external devices. LED dimming by pulse widthmodulation (PWM) or linear voltage is another feature of the chip. The chip’s workingfrequency can be set by an external resistance, and the max frequency can be up to1MHz.