Datasheet
50
60
70
80
90
100
10.0 15.0 20.0 25.0 30.0
InputVoltage-V
Efficiency-%
+
+
TPS40200-Q1
SLUS739E –SEPTEMBER 2006–REVISED JULY 2013
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/R
SENSE
. 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
Figure 52. Efficiency vs Input Voltage
32 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated