ICL5101_16 Datasheet, PDF (25/44 Pages) Infineon Technologies AG – Resonant controller IC with PFC for LED driver

ICL5101
Functional Description
How to do:
To improve the THD the resistor – see R3 Figure 18 or red signed resistor in Figure 19 – at ZCD PIN 7 can be
trimmed to an optimal value (several k-ohm ~ 20 up to 100k) in order to reach best THD results.
Step one is to define the inductivity of the PFC choke and the MOSFET. After fixing PFC choke and transistor,
two scenarios are happen:
1/ operation in stable load condition e.g. lamp ON / OFF
SET nominal load condition and vary the value of the resistor until you get the best THD results. Outcome sees
Figure 20 black curve
2/ operation with load variation e.g. dimming of an LED
Choose a resistor and vary the load. Change value up or down in order to get your best result over the whole
load range – outcome sees Figure 20 red curve.
Mechanism:
The controller operates in two modes:
- Critical Conduction Mode (CrCM) in a wide load range
- Wait Cycle Mode (WCM – a kind of DCM) for low load
Switch from CrCM into WCM):
The ICL5101 has an integrated logic which can be regulated via the resistor at the ZCD PIN 7 in varying the
value of the resistor.
Limit:
The digital logic of the controller is limited. At high line input voltages, the controller reduces the ON time of the
PFC gate driver. If the minimum ON time is reached – physically given by the internal digital stage – the
controller switches over from the critical conduction mode CrCM into the wait cycle mode WCM. This switch
over can be seen in the THD measurement shown in Figure 20 black curve. Depending on the load (stable or
variable) the optimum configuration can be found as shown in Figure 20 red curve. This effect can be prevented
by trimming the resistor at the ZCD PIN 7 – lower the resistance leads to a smother cross over from CrCM into
WCM (red curve) but increases slightly the THD.
THD vs. Load @ VACIN = 230 using diff. RZCD 110W Board
45
40
35
30
RZCD = 51kΩ ideal for stable Load Conditions
25
Mode change from CritCM into WCM
20
Limit starting THD is higher
15
10
5 _{RZCD = 39kΩ ideal for vary Load Conditions}
Smooth mode change
0
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105
Load[%]
THD [%] 39kΩ
THD [%] 51kΩ
Figure 20 Mode switching in stable or vary load condition
Datasheet
25
Rev. 1.3, 2016-01-15