Getting started

AN2809

16/22

In this condition, the power provided to the LEDs is simply calculated as:

current delivered to the load (the sum of the current of the six channels). Since all the

channels are in parallel (120 mA total current), a single string of 150 mA-rated LEDs is

required as load (

Figure 10).

Figure 10.

Efficiency measurement setup

Figure 11 and Figure 12 show two efficiency measurements against the duty-cycle of the

dimming signal at two different input voltages.

P

LOAD

V

STRING

I

STRING

⋅

=

PWM Generator

4.5V – 32V @ 2A

Power Supply

10 WLEDs 150mA array

VBOOST

VIN+

VIN-

GND

DIM

+

A-Meter

V-Meter

ROW1

V-Meter

A-Meter

PWM Generator

4.5V – 32V @ 2A

Power Supply

10 WLEDs 150mA array

VBOOST

VIN+

VIN-

GND

DIM

+

A-Meter

V-Meter

ROW1

V-Meter

A-Meter