ICB2FL03G Datasheet, PDF (23/60 Pages) Infineon Technologies AG – 2nd Generation FL Controller for Fluorescent Lamp Ballasts

2.4
PFC Preconverter
ICB2FL03G
Controller for Fluorescent Lamp Ballasts
Functional Description
2.4.1 Discontinuous Conduction and Critical Conduction Mode Operation
The digitally controlled PFC preconverter starts with an internally fixed ON time of typically t_ON = 4.0 μs and a
variable frequency. The ON time is increased every 280 μs (typical) up to a maximum ON time of 24 μs. The
control switches practically immediately from the discontinuous conduction mode (DCM) to critical conduction
mode (CritCM) as soon as a sufficient ZCD signal becomes available. The frequency range in CritCM is 22 kHz
to 500 kHz depending on the power (Figure 14), with a variation of the ON time from 24 μs > t_ON > 0.5μs.
1000,00
100,00
10,00
1,00
0,10
Discontinuous Conduction Mode (DCM) <> Critical Condution Mode (CritCM)
100,00
Frequency @ CritCM Operation
Frequency @ DCM Operation
Nominal Load
10,00
Light Load
Increasing Power
ON Time Hysteresis
PRE HEATING
ON Time @ CritCM Operation
ON Time @ DCM Operation
1,00
Decreasing Power
ON Time Hysteresis
in RUN MODE
0,01
0,01
0,10
1,00
Normalized Output Power [% ]
Frequency DCM Frequency CritCM Ton DCM
10,00
Ton CritCM
0,10
100,00
Figure 14 Operating Frequency and ON Time versus Power in DCM and CritCM Operation
For lower loads (P_OUTNorm < 8 % from the normalized load¹⁾) the control operates in discontinuous conduction mode
(DCM) with an ON time from 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 (Figure 14). With this control method, the PFC converter
enables stable operation from 100 % load down to 0.1 %. Figure 14 shows the ON time range in DCM and CritCM
(Critical Conduction Mode) operation. In the overlapping area of CritCM and DCM there is a hysteresis of the ON
time which causes a negligible frequency change.
2.4.2 PFC Bus Voltage Sensing
Overvoltage, open loop, bus 95 % and undervoltage states (Figure 15) of the PFC bus voltage are sensed at the
PFCVS pin via the network R14, R15, R20 and C11 – Figure 3 (C11 acts as a spike suppression filter).
1) Normalized power @ low line input voltage and maximum load
Final Data Sheet
23
V1.1, 2013-08-14