Application Note
21 of 28
V 1.0
2019-01-23
ILD8150 80 V high side buck LED driver IC with hybrid dimming
Measurement results with reference design
Figure 23
Thermal image
4.7
Output current ripple
Figure 24 shows output current waveforms with capacitors of 10 nF and 4.7 µF accordingly. It can be seen that
placing a 4.7 µF capacitor in parallel with the LED reduces output ripple current from 21.6 percent to 5.6
percent.
Iout
Vsw
Iout
Vsw
Figure 24
Output current ripple with C
OUT
= 10 nF (left) and with C
OUT
= 4.7 µF (right)
Some applications, such as machine vision, are not allowed to use PWM dimming. In this case an output
electrolytic capacitor, which filters output PWM, is recommended. Figure 25 shows output current waveform
with input voltage 70 V, 17 LEDs or 51 V, dimming level 6.25 percent, output capacitor 100 µF. An electrolytic
capacitor reduces output ripple to 12.5 percent peak-to-peak.
