AN75

Issue 1 – January 2011

10

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© Diodes Incorporated 2010

Results

The performance of the system is outlined in Figures 4, and 5.

They display a level of system efficiency higher than 87% when driving 18 LEDs. The system

efficiency reduces with decreasing number of LEDs but 83% can still be achieved when driving

14LEDs at 264Vac input.

When driving 18 LEDs, a current regulation of around 3% is achieved between the input voltages of

110Vac to 264Vac. The LED current drops to 190mA at 85Vac as the minimum bus voltage V

IN(min)

falls below the LED stack voltage (V

Figure 6 shows the power factor across the line voltage range. Power factor greater than 0.9 can be

achieved at 85Vac.

Figure 4 LED driver system efficiency

Figure 5 LED driver current regulation