ML4833
TRANSCONDUCTANCE AMPLIFIERS
The PFC voltage feedback amplifier is implemented as an
operational transconductance amplifier. It is designed to
have low small signal forward transconductance such that
a large value of load resistor (R1) and a low value
ceramic capacitor (<1µF) can be used for AC coupling
(C1) in the frequency compensation network. The
compensation network shown in Figure 3 will introduce a
zero and a pole at:
f
Z
=
1
2
π
R
1
C
1
f
P
=
1
2
π
R
1
C
2
(2)
Figure 3. Compensation Network
PVFB/OVP
18
2.5V
–
+
R1
C2
C1
L
SW2
RA
V
OUT
EMI
FILTER
R
SENSE
PIFB
OUT A
SINE
–A
+
R
–
S
SINE
OSC
RAMP
V TO I
+
CLK
VREF1
PEAO
–
CLK
Q
SW1
RB
INVERTER
LAMP
NETWORK
L
A
M
P
L
A
M
P
2
14
18
PVFB/OVP
PFC OUT
10
C
RAMP
R1
C
RAMP
C1
C2
1
PEAO
Figure 2. ML4833 PFC Controller Section
7
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
