PWM Controller Simplifies High Power LED Designs

  
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High brightness (HB) and super HB LEDs are found in LCD TFT backlighting in highend TVs, industrial lighting, and projectors. One popular area is for instrument panel backlighting, interior lighting, and the brake lights of many cars and trucks. Luxury automobile manufacturers are increasingly taking advantage of the latest technologies in solid-s
PWM Controller Simplifies High Power LED Designs - schematic

tate LED lighting to enhance the aesthetics of their 2007-2008 model vehicles by relying on these lighter, smaller, and more durable devices for interior and exterior illumination. LEDs promise lower long-term cost and longer life which are among many advantages over incandescent light bulbs for interior lighting, for example, and HID (high-intensity discharge) and halogen lamps for headlights. Driving LEDs at high current requires a DC/DC converter to accurately regulate the current to ensure uniform light intensity and color integrity as well as to protect the LEDs. Furthermore, a significant challenge is to power one or several strings of LEDs from a battery voltage that can be less than, equal to, or higher than its load voltage. Yet another concern is to efficiently dim the LEDs over a large dimming ratio while preserving their chromatic characteristics at both low and high brightness levels. Furthermore, efficient operation of the DC/DC driver is a crucial requirement, especially in driving HB (high brightness) LEDs, since all the power not emitted as light is dissipated as heat. The new LTC3783 from Linear Technology is a current-mode multitopology converter with constant-current PWM dimming for driving high-power LED strings and clusters. Proprietary techniques provide extremely fast, true PWM load switching with no transient undervoltage or overvoltage issues: dimming ratios of 3000:1 (at 100Hz) can be achieved...



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