Application Note
20 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
4.5
Efficiency
Efficiency measurement results in the input range 52 V to 70 V for 17 LEDs is shown in Figure 22. The efficiency is
measured with different inductors – 860, 150 and 100 µH. It reflects the maximum switching frequency – 86, 360
and 520 kHz accordingly. As seen from the character of the curves, when the difference between input and
output voltage is quite low efficiency is quite high with a wide inductance range, because the switching
frequency is relatively low. In applications with fixed output voltage, which is close to the output voltage, and
low input voltage deviation/ripple, a small inductor may be used. In applications with wide output voltage
range and input voltage ripple, such as 100 or 120 Hz, and 10 percent of ripple, which is normal on the primary
stage, switching losses create additional power dissipation. In this case inductance should be increased or
output current limited.
Figure 22
Efficiency vs supply voltage
4.6
Thermal behavior
The maximum temperature attained by the demonstration board is 73.8°C, as shown in Figure 23. The test was
performed with input 70 V and 17 LEDs.
97,6
97,3
97,0
96,8
96,5
97,4
97,1
96,7
96,3
95,9
97,4
97,1
96,6
95,8
95,5
94,0
94,5
95,0
95,5
96,0
96,5
97,0
97,5
98,0
52
55
60
65
70
Ef
fici
en
cy
Input Voltage
Efficiency vs Input voltage
L=860uH
L=150uH
L=100uH
