TPS40200-Q1
SLUS739D –SEPTEMBER 2006–REVISED JULY 2011
www.ti.com
Application 3: Wide-Input-Voltage LED Constant-Current Driver
This application uses the TPS40200 as a buck controller that drives a string of LED diodes. The feedback point
for this circuit is a sense resistor in series with this string. The low 0.7-V reference minimizes power wasted in
this resistor and maintains the LED current at a value given by 0.7 V/RSENSE. As the input voltage is varied, the
duty cycle changes to maintain the LED current at a constant value, so that the light intensity does not change
with large input-voltage variations.
+
+
Figure 51. Wide-Input-Voltage Range LED Driver
100
90
80
70
60
50
10.0
15.0
20.0
25.0
30.0
Input Voltage - V
Figure 52. Efficiency vs Input Voltage
34
Copyright © 2006–2011, Texas Instruments Incorporated
TI [ TEXAS INSTRUMENTS ]
