May 1997
ML4819*
Power Factor and PWM Controller “Combo”
GENERAL DESCRIPTION
The ML4819 is a complete boost mode Power factor
Controller (PFC) which also contains a PWM controller.
The PFC circuit is similar to the ML4812 while the PWM
controller can be used for current or voltage mode control
for a second stage converter. Since the PWM and PFC
circuits share the same oscillator, synchronization of the
two stages is inherent. The outputs of the controller IC
provide high current (>1A peak) and high slew rate to
quickly charge and discharge MOSFET gates. Special care
has been taken in the design of the ML4819 to increase
system noise immunity.
The PFC section is of the peak current sensing boost type,
using a current sense transformer or current sensing
MOSFETs to non-dissipatively sense switch current. This
gives the system overall efficiency over average current
sensing control method.
The PWM section includes cycle by cycle current limiting,
precise duty cycle limiting for single ended converters,
and slope compensation.
FEATURES
s
s
s
s
s
s
s
s
s
Two 1A peak current totem-pole output drivers
Precision buffered 5V reference (±1%)
Large oscillator amplitude for better noise immunity
Precision duty cycle limit for PWM section
Current input gain modulator improves noise immunity
Programmable Ramp Compensation circuit
Over-Voltage comparator helps prevent output
“runaway”
Wide common mode range in current sense
compensators for better noise immunity
Under-Voltage Lockout circuit with 6V hysteresis
* Some Packages Are Obsolete
BLOCK DIAGRAM
20
C
T
–
3
2
R
GM OUT
OVP
5V
+
–
S
Q
4
5
EA OUT A
INV A
5V
+
–
ERROR
AMP
I
EA
R
V
CC
OUT A
S
Q
PGND A
16
17
6
19
I
SINE
GND
GAIN MODULATOR
I
MULT
+
5V
–
–
1
I
SENSE
A
+
POWER FACTOR
CONTROLLER
+
12
RAMP COMP
SLOPE
COMPENSATION
+
–
–
P
eS
as
le
10
R
T
824
Ml4
ee
OSC
New
for
1V
ns
sig
De
7
PWM
CONTROLLER
DUTY CYCLE
I
LIM
11
I
SENSE
B
0.7V
PWM B
V
CC
9
8
OUT B
PGND B
14
13
UNDER
VOLTAGE
LOCKOUT
V
REF
V
CC
18
15
1
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
