www.fairchildsemi.com
ML4827
Fault-Protected PFC and PWM Controller Combo
Features
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Pin-compatible with industry-standard ML4824-1
TriFault Detect™ to conform to UL1950™ requirements
Available in 50% or 74% max duty cycle versions
Low total harmonic distortion
Reduces ripple current in the storage capacitor between
the PFC and PWM sections
Average current, continuous boost leading edge PFC
High efficiency trailing-edge PWM can be configured for
current mode or voltage mode operation
Average line voltage compensation with brown-out
control
PFC overvoltage comparator eliminates output
“runaway” due to load removal
Current fed gain modulator for improved noise immunity
Overvoltage protection, UVLO, and soft start
necessary for conformance to the safety requirements of
UL1950. A direct descendent of the industry-standard
ML4824-1, the ML4827 adds a TriFault Detect™ function to
guarantee that no unsafe conditions may result from single
component failure in the PFC. Power Factor Correction
(PFC) allows the use of smaller, lower cost bulk capacitors,
reduces power line loading and stress on the switching FETs,
and results in a power supply that fully complies with
IEC1000-3-2 specification. The ML4827 includes circuits
for the implementation of a leading edge, average current,
“boost” type power factor correction and a trailing edge,
pulse width modulator (PWM). The device is available in
two versions; the ML4827-1 (Duty Cycle
MAX
= 50%) and
the ML4827-2 (Duty Cycle
MAX
= 74%). The higher
maximum duty cycle of the -2 allows enhanced utilization of
a given transformer core’s power handling capacity. An over-
voltage comparator shuts down the PFC section in the event
of a sudden decrease in load. The PFC section also includes
peak current limiting and input voltage brown-out
protection. The PWM section can be operated in current or
voltage mode, and includes a duty cycle limit to prevent
transformer saturation.
General Description
The ML4827 is a controller for power factor corrected,
switched mode power supplies, that includes circuitry
Block Diagram
16
VEAO
VFB
15
2.5V
IAC
2
VRMS
4
ISENSE
3
RAMP 1
7
RAMP 2
8
8V
VDC
6
VCC
SS
5
DC ILIMIT
9
PULSE WIDTH MODULATOR
8V
50µA
1.25V
–
+
–
+
1
IEAO
IEA
+
0.5V
–
+
POWER FACTOR CORRECTOR
BROKEN WIRE
COMPARATOR
2.7V
OVP
+
–
2µA
VREF VCCZ
13.5V
13
VCC
VREF
7.5V
14
REFERENCE
VEA
–
+
3.5kΩ
+
–
S
–1V
+
–
Q
GAIN
MODULATOR
3.5kΩ
–
R
S
Q
PFC OUT
Q
12
PFC ILIMIT
R
OSCILLATOR
Q
DUTY CYCLE
LIMIT
S
VFB
2.5V
–
+
Q
VIN OK
1V
–
+
PWM OUT
11
R
DC ILIMIT
VCCZ
UVLO
Q
GND
10
REV. 1.0.1 6/27/01
ML4827
PRODUCT SPECIFICATION
Pin Configuration
ML4827
16-Pin PDIP (P16)
16-Pin Wide SOIC (S16W)
IEAO 1
IAC 2
ISENSE 3
VRMS 4
SS 5
VDC 6
RAMP 1 7
RAMP 2 8
16 VEAO
15 VFB
14 VREF
13 VCC
12 PFC OUT
11 PWM OUT
10 GND
9
DC ILIMIT
TOP VIEW
Pin Description
PIN
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
NAME
IEAO
I
AC
I
SENSE
V
RMS
SS
V
DC
RAMP 1
RAMP 2
DC I
LIMIT
GND
PWM OUT
PFC OUT
V
CC
V
REF
V
FB
VEAO
PFC gain control reference input
Current sense input to the PFC current limit comparator
Input for PFC RMS line voltage compensation
Connection point for the PWM soft start capacitor
PWM voltage feedback input
PFC (master) oscillator input; f
OSC
set by R
T
C
T
When in current mode, this pin functions as as the current sense input; when in
voltage mode, it is the PWM (slave) oscillator input.
PWM current limit comparator input
Ground
PWM driver output
PFC driver output
Positive supply (connected to an internal shunt regulator)
Buffered output for the internal 7.5V reference
PFC transconductance voltage error amplifier input, and TriFault Detect input
PFC transconductance voltage error amplifier output
FUNCTION
PFC transconductance current error amplifier output
Absolute Maximum Ratings
Absolute Maximum Ratings are those values, beyond which the device could be permanently damaged. Absolute maximum
ratings are stress ratings only and functional device operation is not implied.
Parameter
V
CC
Shunt Regulator Current
I
SENSE
Voltage
Voltage on any other Pin
I
REF
I
AC
Input Current
–3
GND-0.3
Min.
Max.
55
5
V
CCZ +0.3
20
10
Units
mA
V
V
mA
mA
2
REV. 1.0.1 6/27/01
PRODUCT SPECIFICATION
ML4827
Peak PFC OUT Current, Source or Sink
Peak PWM OUT Current, Source or Sink
PFC OUT, PWM OUT Energy Per Cycle
Junction Temperature
Storage Temperature Range
Lead Temperature (soldering, 10s)
Thermal Resistance (θ
JA
)
Plastic DIP
Plastic SOIC
–65
500
500
1.5
150
150
260
80
105
mA
mA
µJ
°C
°C
°C
°C/W
°C/W
Operating Conditions
Parameter
Temperature Range
ML4827CP, CS
ML4827IP, IS
Min.
0
–40
Max.
70
85
Units
°C
°C
Electrical Characteristics
Unless otherwise specified, I
CC
= 25mA, R
T
= 21.8kΩ, C
T
= 1000pF, T
A
= Operating Temperature Range (Note 1)
Symbol
Parameter
Input Voltage Range
Transconductance
Feedback Reference Voltage
Input Bias Current
Output High Voltage
Output Low Voltage
Source Current
Sink Current
Open Loop Gain
Power Supply Rejection Ratio
Current Error Amplifier
Input Voltage Range
Transconductance
Input Offset Voltage
Input Bias Current
Output High Voltage
Output Low Voltage
Source Current
Sink Current
Open Loop Gain
Power Supply Rejection Ratio
OVP Comparator
Threshold Voltage
Hysteresis
2.6
80
2.7
115
2.8
150
V
mV
V
CCZ
- 3V < V
CC
< V
CCZ
- 0.5V
∆V
IN
= ±0.5V, V
OUT
= 6V
∆V
IN
= ±0.5V, V
OUT
= 1.5V
–40
40
60
60
6.0
V
NON INV
= V
INV
, VEAO = 3.75V
–1.5
130
2
195
10
–0.5
6.7
0.6
–90
90
75
75
1.0
2
310
17
–1.0
V
µΩ
mV
µA
V
V
µA
µA
dB
dB
Ω
V
CCZ
- 3V < V
CC
< V
CCZ
- 0.5V
∆V
IN
= ±0.5V, V
OUT
= 6V
∆V
IN
= ±0.5V, V
OUT
= 1.5V
–40
40
60
60
Note 2
6.0
V
NON INV
= V
INV
, VEAO = 3.75V
Conditions
Min.
0
50
2.48
85
2.55
–1
6.7
0.6
–80
80
75
75
1.0
Typ.
Max.
7
120
2.62
–2
Units
V
µΩ
V
µA
V
V
µA
µA
dB
dB
Ω
Voltage Error Amplifier
REV. 1.0.1 6/27/01
3
Embedded System
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