May 1997
ML4822*
ZVS Average Current PFC Controller
GENERAL DESCRIPTION
The ML4822 is a PFC controller designed specifically for
high power applications. The controller contains all of the
functions necessary to implement an average current
boost PFC converter, along with a Zero Voltage Switch
(ZVS) controller to reduce diode recovery and MOSFET
turn-on losses.
The average current boost PFC circuit provides high
power factor (>98%) and low Total Harmonic Distortion
(THD). Built-in safety features include undervoltage
lockout, overvoltage protection, peak current limiting, and
input voltage brownout protection.
The ZVS control section drives an external ZVS MOSFET
which, combined with a diode and inductor, soft switches
the boost regulator. This technique reduces diode reverse
recovery and MOSFET switching losses to reduce EMI and
maximize efficiency.
FEATURES
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Average current sensing, continuous boost, leading
edge PFC for low total harmonic distortion and near
unity power factor
Built-in ZVS switch control with fast response for high
efficiency at high power levels
Average line voltage compensation with brownout
control
Current fed gain modulator improves noise immunity
and provides universal input operation
Overvoltage comparator eliminates output “runaway”
due to load removal
UVLO, current limit, and soft-start
Precision 1% reference
*This Part Is End Of Life As Of August 1, 2000
BLOCK DIAGRAM
(Pin configuration shown for 14-pin package)
VEAO
1
8
GND
2
IEAO
OVP
VCC
VCCZ
13.5V
2.7V
12
FB
14
2.5V
IAC
4
VRMS
5
ISENSE
3
RTCT
6
–
+
VEA
R+
FB
+
–
+
GAIN
MODULATOR
R–
IEA
+
–
–
I LIMIT
–1V
S
Q
+
–
R
PFC OUT
11
OSC
VCCZ
REF
S
R
Q
Q
ZVS OUT
10
13
REF
S
R
Q
Q
ZV SENSE
7
+
–
–
PWR GND
9
1
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
