Datasheet

CCM-PFC
ICE2PCS02/G
Functional Description
Version 2.4 8 22 Mar 2010
.
Figure 5 Startup with controlled maximum current
3.4 System Protection
The IC provides several protection features in order to
ensure the PFC system in safe operating range:
• VCC Undervoltage Lockout (UVLO)
• Input Brown-out Detection (IBOP)
• Soft Over Current Control (SOC)
• Peak Current Limit (PCL)
• Open-Loop Detection (OLP)
• Output Over-Voltage Protection (OVP)
After the system is supplied with the correct level of
VCC and V
IN
, the system will enter into its normal mode
of operation. Figure 6 shows situation when these
protections features are active, as a function of the
output voltage V
OUT
.
An activation of the UVLO, IBOP and OLP results in the
internal fault signal going high and brings the IC into the
standby mode.
As the function of UVLO has already described in the
earlier “Power Supply” section, the following sections
continue to describe the functionality of these
protection features.
Figure 6 Protection Features
3.4.1 Input Brown-Out Protection (IBOP)
Brown-out occurs when the input voltage V
IN
falls below
the minimum input voltage of the design (i.e. 85V for
universal input voltage range) and the VCC has not
entered into the V
CCUVLO
level yet. For a system without
IBOP, the boost converter will increasingly draw a
higher current from the mains at a given output power
which may exceed the maximum design values of the
input current.
ICE2PCS02/G provides a new IBOP feature whereby it
senses directly the input voltage for Input Brown-Out
condition via an external resistor/capacitor/diode
network as shown in Figure 7. This network provides a
filtered value of V
IN
which turns the IC on when the
voltage at pin 4 (VINS) is more than 1.5V. The IC enters
into the standby mode when VINS goes below 0.71V.
The hysteresis prevents the system to oscillate
between normal and standby mode. Note also that V
IN
needs to at least 20% of the rated V
OUT
in order to
overcome OLP and powerup the system.
Figure 7 Input Brown-Out Protection (IBOP)
av(I
IN
)
V
OUT
t
V
OUT
=rated
95%rated
Window Detect
Normal Control
t
Max Vcomp current
83%rated
VCOMP
Level-shifted VCOMP
t
V
OUT
PCL / SOC
20%
100%
OLP OLP
108%
OVP
V
OUT,Rated
UVLO / IBOP
Supply
related
Current
related
Output
related
ICE2PCS02/G
85 ... 265 VAC
Vin
C1
D2 ... D5
VINS
C4
C5
R
S
1.5V
0.71V
Brown-Out Detection
R8
R9C6
D7
brown-out
3.5V