ICL8001G / ICLS8082G
Design Guidelines
Explicit Questions and Answers
Application Note
24
Version 2.0, 2011-04-14
7
Explicit Questions and Answers
7.1
Application
What are the main applications of ICL8001G / ICLS8082G Control?
ICL8001G / ICLS8082G is optimized for offline LED lighting like dimmable LED bulbs for incandescent lamp
replacement, LED downlights and LED tubes. The PFC function enables a power range of typically 5 W to 50 W
to be applied.
Should LED drivers for universal input voltage be designed?
Universal input designs lead to essential efficiency reduction in the LED driver and are therefore not supported by
special IC features.
Is it possible to supply different LED modules with strong variations in total forward voltages?
The LED driver requirements under strongly varying conditions of phase-cut dimming are tough. The VCC concept
compatible with these requirements and proposed here does not allow for strong variations in the DC output
voltage but only for limited output voltage variation. Only in this case is a constant transformer winding ratio or a
design with single transformer connecting points at the auxiliary winding sufficient.
How can driver efficiencies exceeding 90 % be realized?
Generally at higher power applications with pin ≈ 15 W, driver efficiencies > 90% can be realized using optimized
QR control with ICL8001G / ICLS8082G.
Can we disable the dimming function and use it as a constant current LED driver with a good power
factor?
TDA 4863-2 is recommended for this kind of application. For details, see the Application Note AN186.
What will happen under no-load conditions?
The application circuits based on ICL8001G / ICLS8082G are designed to work with LEDs only. Under no-load
conditions it will go to either the auto restart mode due to Vcc OVP or latched off mode due to output OVP.
7.2
Control Principle
How does ICL8001G / ICLS8082G realize dimming control and power factor correction?
Both dimming control and PFC are achieved with the input mains voltage sensing at the VR pin. This signal is used
to set the peak current of the primary winding and consequently allows both PFC and phase-cut dimming
functionality by regulating the cycle energy.
What are the effects of constant power control compared to constant current?
Under constant power control, variations in the LED forward voltage may cause certain variations in the lumen
output while, in contrast, the output remains approximately unchanged under constant LED current control.
However, the power control concept also enables the LEDs to be operated thermally under stable conditions.
Combination of output power control with power stabilization under input voltage variation as proposed above
makes it possible to optimize the heat sink design of an LED bulb or LED lighting fixture and hence minimize
system costs.
How does the ICL8001G / ICLS8082G achieve the regulation of the current through the LEDs?
ICL8001G / ICLS8082G controls the cycle energy stored in the primary inductance of the flyback transformer.
When also considering the frequency behavior, the resulting LED power depends on quite a few parameters. The
influence of input voltage variation can be reduced with the design means described above. The tolerances of the
