ICL5101_16 Datasheet, PDF (20/44 Pages) Infineon Technologies AG – Resonant controller IC with PFC for LED driver

2.3
PFC Preconverter
ICL5101
Functional Description
2.3.1
Operation Modes of the PFC Converter
The digitally controlled PFC pre-converter starts with an internally fixed ON time of typically t_ON = 4.0µs and
variable frequency. The ON time is increased every 280 µs (typical) up to a maximum ON time of 24 µs. The
control switches quite immediately from discontinuous conduction mode (DCM) to critical conduction mode
(CrCM) as soon as a sufficient ZCD signal becomes available. The frequency range in CrCM is 22 kHz up to
500 kHz, depending on the power (Figure 14) with a variation in the ON time of 24 µs > t_ON > 0.5µs.
1000,00
Discontinuous Conduction Mode (DCM) <> Critical Condution Mode (CritCM)
100,00
100,00
10,00
10,00
1,00
1,00
0,10
0,01
0,01
0,10
1,00
Normalized Output Power [% ]
Frequency DCM Frequency CritCM Ton DCM
Figure 14 PFC DCM / CrCM vs Power and ON Time
10,00
Ton CritCM
0,10
100,00
For lower loads (P_OUTNorm < 8 % of the normalized load¹) the controller operates in discontinuous conduction
mode (DCM) with an ON time of 4.0 µs and increasing OFF time. The frequency during DCM is variable in a
range from 144 kHz down to typically 22 kHz @ 0.1 % load. With this control method, the PFC converter
enables stable operation from a 100 % load down to 0.1 %. Figure 14 shows the ON time range in DCM and
CrCM (Critical Conduction Mode) operation. In the overlapping area of CrCM and DCM there is a hysteresis of
the ON time, which causes a negligible frequency change.
1 _{Normalized Power @ Low Line Input Voltage and maximum Lload}
Datasheet
20
Rev. 1.3, 2016-01-15