ML4819 Datasheet, PDF (1/15 Pages) Fairchild Semiconductor – Power Factor and PWM Controller “Combo”

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.
BLOCK DIAGRAM
FEATURES
s Two 1A peak current totem-pole output drivers
s Precision buffered 5V reference (±1%)
s Large oscillator amplitude for better noise immunity
s Precision duty cycle limit for PWM section
s Current input gain modulator improves noise immunity
s Programmable Ramp Compensation circuit
s Over-Voltage comparator helps prevent output
“runaway”
s Wide common mode range in current sense
compensators for better noise immunity
s Under-Voltage Lockout circuit with 6V hysteresis
10 ^RT
OSC
CT
20
RAMP COMP
12
SLOPE
COMPENSATION
1 ^{ISENSE A}
POWER FACTOR
+ ^CONTROLLER
5V
–
–
3 ^{GM OUT}
2 ^OVP
+
5V
–
4 ^{EA OUT A}
5 ^{INV A}
+
5V
–
ERROR
AMP
IEA
ISINE
6
GND
19
GAIN MODULATOR
IMULT
PWM
CONTROLLER
R
SQ
R
SQ
DUTY CYCLE ₇
ILIM ₁₁
1V
ISENSE B ₉
0.7V
PWM B ₈
VCC
OUT B
14
PGND B
13
UNDER
VOLTAGE
LOCKOUT
VREF ₁₈
VCC ₁₅
VCC
OUT A ₁₆
PGND A ₁₇
REV. 1.0 10/10/2000