STEVAL-ILL013V1 Datasheet, PDF (19/43 Pages) STMicroelectronics – 80 W offline LED driver with PFC

Measurement
9
Measurement
UM0670
9.1
Output waveform measurement
Figure 13 shows the output LED current waveform. The LED current was set to 350 mA and,
as shown, the current ripple is 92 mA and the switching frequency for the modified buck
converter is 125 kHz. The input voltage was 230 VAC and 12 LEDs were used as the load
(OSTAR LED LE UW E3B; see Section 11: References and related materials 6).
The output LED current slightly varies with the output voltage, as explained in detail in
application note AN2928, (Section 11: References and related materials 2) and therefore
this design is optimal for a fixed number of LEDs. The output LED current accuracy for
different LED voltages is demonstrated in Figure 14.
Figure 13. Output LED current waveform (I_LED = 350 mA)
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