ML4833

7

Figure 2. ML4833 PFC Controller Section

+

–

–

+

L

A

M

P

L

A

M

P

LAMP

NETWORK

INVERTER

RA

SW2

L

SW1

SINE

RB

EMI

FILTER

14

2

PIFB

C1

C2

R1

OUT A

PVFB/OVP

18

–A

S

VREF1

OSC

SINE

RAMP

CLK

PFC OUT

CLK

RQ

V TO I

PEAO

10

PEAO

1

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

RC

f

RC

ZP

==

1

2

1

2

11

1 2

ππ

(2)

–

+

18

2.5V

PVFB/OVP

R1

C1

C2

Figure 3. Compensation Network