PWM White LED Driver Circuit

Following Simple PWM White LED Driver circuit designed by using IC LT3491 and IC LTC6992 from Analog devices. Here LT3491 is fixed frequency Step up DC-DC Converter specifically designed to drive up to six white LEDs in series from a Li-Ion battery. LTC 6992 is a silicon Oscillator with an easy to use analog voltage controlled pulse width modulation (PWM) Capability.




LT3491 can drive white LEDs from 3 Volt supply an it has internal Schottky diode and also has one pin dimming and shutdown feature. Internal Switching frequency of this IC is 2.3MHz. It can operate with side range of Input supply from 2.5V to 12V. It Requires 1 µF Output Capacitor only. This IC comes in 6-lead DFN package and 8 lead plastic SC70 package.

Circuit Diagram

Components Required (BOM)

1C2, C31µFC_0805_2012Metric2
2C10.1µFC_0805_2012Metric1
3R11KΩR_0805_2012Metric1
4R250KΩR_0805_2012Metric1
5R3100KΩR_0805_2012Metric1
6R410ΩR_0805_2012Metric1
7L110µHL_0805_2012Metric1
8D1, D2, D3, D4LEDLED_0805_2012Metric4
9U2LT3491DFN-6-1EP_2x2mm_P0.5mm_EP0.6×1.37mm1
10U1LTC6992SOT-23-61
11RV12KΩPotentiometer_Bourns_3214G_Horizontal1
12Q1Si2302SOT-231
13J1Screw_Terminal_01x02JWT_A3963_1x02_P3.96mm_Vertical1

Construction & Working

This Circuit Constructed to drive four small white LEDs from Li-Ion battery power supply, we can dimming the LED Brightness by varying the PWM from IC LTC6992 or by changing the value of R3 Resistor. Four white LEDs are connected with the LED pin5 and to the Q1 MOSFET drain pin, Gate terminal of Si2302 is connected with CTRL Pin of LT3491 and PWM out Pin of LTC6992.

IC LTC6992 Oscillates the PWM from Simple 0V to 1V Analog input, Here the MOD pin is connected to the power supply through R1 and RV1 Resistors in order to change the analog voltage input at MOD pin. This IC can oscillate from 3.81Hz to 1MHz Output frequency. This IC Comes in DFN and SOT packages Refer datasheet for more information.

Printed Circuit Board

PWM White LED Driver Circuit PCB Gerber files.

Interactive Board Viewer

     




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