Supply controls LED light levels
By Richard A Quinnell, Contributing Editor -- EDN, January 5, 2006
The LTC3783 current-mode multitopology converter drives high-power-LED strings and clusters. The device provides constant-current PWM (pulse-width-modulated) power to control the brightness level of the LEDs. It can achieve a dimming ratio of 3000-to-1 using digital methods and 100-to-1 using analog control. The device also offers a dimming mode that guarantees the color integrity of white and RGB LEDs.
This versatile controller can operate in several modes, including boost, buck, buck-boost, SEPIC (single-ended primary-inductance converter), and flyback converter. It can also operate as a constant-current/constant-voltage regulator without the need for a current-sense resistor.
The LTC3783 can accept input voltages of 3 to 36V and provides overvoltage protection. It has integrated drivers for power and load MOSFET switches and 20-kHz to 1-MHz switches based on a single frequency-setting resistor. To reduce noise, designers can also synchronize it to an external clock. Price is $2.85 (1000).
Linear Technology Corp, www.linear.com.
