ICL8001G / ICLS8082G
Design Guidelines
Design Optimizations
Application Note
20
Version 2.0, 2011-04-14
Figure 14
LED current behavior according to power factor using foldback correction
The table below shows the relevant design parameters. Consideration of EMI and driver efficiency designs with
PF > 90 % are recommended.
The LED driver should be designed for operation at the maximum voltage arising in the input voltage range.
5.2.2
Discrete Power Stabilization Circuit for ICL8001G
For especially high requirements regarding input power or LED current stability for line voltage variations, such as
∆ILED ≤ +/- 2 % at ∆Vac = +/- 10 %, and for low harmonic distortion, a solution using a discrete differential amplifier
can be proposed. Here the Vin signal is sensed by means of a voltage divider consisting of R21 and R22, and
smoothed by C21. The Zener diode D21 is used for the reference voltage. When the smoothed voltage is much
smaller than the reference voltage, the current though R23 will flow only through R24 and there is no influence on
the output power of the demo board. When the value of the smoothed voltage is near the reference voltage, part
of the current flowing through R23 will begin flowing through R25, R26 and R4 to GND to generate an additional
voltage drop. Subsequently, its waveform shows the same slope at pin CS as the rectified input voltage Vin(t).
Table 4
Design parameters for stabilization using foldback correction
R17
R19
R6
R4
Pin, rel
[%]
ILEDrel, dec
[%]
ILEDrel, inc
[%]
10k
560k
10k
3R3
4.9
3.8
4
10k
560k
6k8
3R3
6
5
5
3k9
560k
10k
2R7
12
11.6
10
