ICL8001G / ICLS8082G
Design Guidelines
Design Optimizations
Application Note
17
Version 2.0, 2011-04-14
The lower curve corresponds closely to the lumen flux of the LED array supplied by the driver and illustrates a
continuous increase for the switching angle variation at the wall dimmer.
5.1.2
Dimmer Compatibility
The driver operation with TRIAC dimmers makes it necessary to observe the requirements regarding their hold-
up currents. In addition, the steep rising voltage slopes can excitate disturbing interactions with the parasitics of
the EMI filter of the driver. To dampen these interactions it is useful to implement a low-pass filter close to the EMI
filter. As placement of the filter in front of the input rectifier would decrease the EMI filter performance it is
recommendable to choose a position parallel to the input voltage divider. In the circuit diagram further below, an
R-C circuit is implemented. Dimensioning of R8 = 220 Ω and C8 = 68 nF (not integrated in the standard demo
board layout) provides stabilization for leading-edge dimmer operation. The non-dimming driver efficiency is
reduced by only typically 1 %.
Figure 12
Extended application circuit for dimming
Especially for applications with low input voltage and resulting higher input currents, shaping of the input current
waveforms has been shown to be effective in achieving dimming stability. For this, an increase in the ratio
R17 / (R17+ R19) and increase in R4 for keeping the LED power constant is suggested. The principal modification
of the modification on the different waveforms is indicated in
Figure 13
below.
C1
C11
R1
C12
D5
C15
D6
R4
D21
C25
L1
R2
VCC
GND
T1
np
na
ns
R6
R3
ZCV
ICL8001G
VLED
Vac
BR1
C18
VR
PWM-Control
Protection
Gate Driver
Start-Up
Cell
Continuous Mode
DIM Control
PFC
C5
CS
R19
R17
NC
HV
GD
D7
Q1
C17
R5
L2
R7
Vin
C8
R8
5
3
1
2
6
8
