Datasheet

CCM-PFC
ICE2PCS01/G
Functional Description
Version 2.3 9 22 March 2010
Figure 8 SOC and PCL Protection as function of
V
ISENSE
The rated output power with a minimum V
IN
(V
INMIN
) is
Due to the internal parameter tolerance, the maximum
power with V
INMIN
is
3.4.2 Peak Current Limit (PCL)
The IC provides a cycle by cycle peak current limitation
(PCL). It is active when the voltage at pin 3 (ISENSE)
reaches -1.04V. This voltage is amplified by OP1 by a
factor of -1.43 and connected to comparator C2 with a
reference voltage of 1.5V as shown in Figure 9. A
deglitcher with 300ns after the comparator improves
noise immunity to the activation of this protection.
Figure 9 Peak Current Limit (PCL)
3.4.3 Open Loop Protection / Input Under
Voltage Protect (OLP)
Whenever VSENSE voltage falls below 0.6V, or
equivalently V
OUT
falls below 20% of its rated value, it
indicates an open loop condition (i.e. VSENSE pin not
connected) or an insufficient input voltage V
IN
for
normal operation. In this case, most of the blocks within
the IC will be shutdown. It is implemented using
comparator C3 with a threshold of 0.6V as shown in the
IC block diagram in Figure 2.
3.4.4 Over-Voltage Protection (OVP)
Whenever V
OUT
exceeds the rated value by 5%, the
over-voltage protection OVP is active as shown in
Figure 6. This is implemented by sensing the voltage at
pin VSENSE with respect to a reference voltage of
3.15V. A VSENSE voltage higher than 3.15V will
immediately reduce the output duty cycle, bypassing
the normal voltage loop control. This results in a lower
input power to reduce the output voltage V
OUT
. A
VSENSE voltage higher than 3.25V will immediately
turn off the gate, thereby preventing damage to bus
capacitor.
3.5 Frequency Setting
The switching frequency of the PFC converter can be
set with an external resistor R5 at FREQ pin as shown
Figure 10. The pin voltage V
FREQ
is typically 1.7V. The
corresponding capacitor for the oscillator is integrated
in the device and the R5/frequency relationship is given
at the “Electrical Characteristic” section. The
recommended operating frequency range is from
50kHz to 250kHz. As an example, a R5 of 33kW at pin
FREQ will set a switching frequency F
SW
of 136kHz
typically.
Figure 10 Frequency Versus R
FREQ
V
ISENSE
-0.61V -0.75V -1.04V
Normal
Operation
SOC PCL
P
OUT
(rated)
IC’s
State
0
P
OUT
(max)
P
OUT
rated( ) V
INMIN
0.61
R1 2×
-------------------
´=
P
OUT
max( ) V
INMIN
0.75
R1 2×
-------------------
´=
ISENSE
ICE2PCS01/G
R1
R2
I
INDUCTOR
OP1
1.43x
Current Limit
300ns
C2
Deglitcher
TurnOff
Driver
1.5V
Full-wave
Rectifier