ml4826cs-2 Fairchild Semiconductor, ml4826cs-2 Datasheet

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ml4826cs-2

Manufacturer Part Number
ml4826cs-2
Description
Ml4826 Pfc And Dual Output Pwm Controller Combo
Manufacturer
Fairchild Semiconductor
Datasheet

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Part Number:
ML4826CS-2
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ML
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Part Number:
ML4826CS-2
Manufacturer:
MICROLINEAR
Quantity:
20 000
Features
• Internally synchronized PFC and PWM in one IC
• Low total harmonic distortion
• Low ripple current in the storage capacitor between the
• Average current, continuous boost, leading edge PFC
• High efficiency trailing edge PWM with dual totem-pole
• Average line voltage compensation with brown-out
• PFC overvoltage comparator eliminates output “runaway”
• Current-fed multiplier for improved noise immunity
• Overvoltage protection, UVLO, and soft start
Block Diagram
ML4826
PFC and Dual Output PWM Controller Combo
19
10
2
4
3
8
7
9
6
5
PFC and PWM sections
outputs
control
due to load removal
I AC
V FB
V RMS
I SENSE
RAMP 1
R T C T
RAMP 2
V DC
SS
DC I LIMIT
2.5V
V CC
50µA
8V
+
8V
-
VEA
VEAO
MODULATOR
1.5V
GAIN
20
11
3.5kΩ
AGND
3.5kΩ
+
-
-
+
IEA
IEAO
8V
-
+
OSCILLATOR
1
+
-
POWER FACTOR CORRECTOR
2.5V
V FB
PULSE WIDTH MODULATOR
+
-
V IN OK
DUTY CYCLE
General Description
The ML4826 is a high power controller for power factor
corrected, switched mode power supplies. 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 specifi-
cations. The ML4826 includes circuits for the implementa-
tion of a leading edge, average current “boost” type power
factor correction and a trailing edge, pulse width modulator
(PWM) with dual totem-pole outputs.
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 at up to 250kHz and includes a duty cycle limit
to prevent transformer saturation.
LIMIT
2.7V
1V
-1V
PFC I LIMIT
+
-
OVP
+
+
-
-
DC I LIMIT
V CCZ
V CCZ
13.5V
www.fairchildsemi.com
UVLO
R
S
S
S
R
S
R
T
Q
Q
Q
Q
Q
Q
Q
Q
REFERENCE
REV. 1.0.5 2/14/02
7.5V
17
PGND
V CC2
V CC
PFC OUT
PWM 2
PWM 1
PGND
V REF
V CC2
18
15
16
14
13
12

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ml4826cs-2 Summary of contents

Page 1

ML4826 PFC and Dual Output PWM Controller Combo Features • Internally synchronized PFC and PWM in one IC • Low total harmonic distortion • Low ripple current in the storage capacitor between the PFC and PWM sections • Average current, ...

Page 2

ML4826 Pin Configuration Pin Description PIN NAME 1 IEAO PFC transconductance current error amplifier output 2 I PFC gain control reference input Current sense input to the PFC current limit comparator SENSE 4 V Input for PFC ...

Page 3

PRODUCT SPECIFICATION Absolute Maximum Ratings Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum rat- ings are stress ratings only and functional device operation is not implied. Parameter V Shunt Regulator Current CC ...

Page 4

ML4826 Electrical Characteristics Unless otherwise specified 25mA Operating Temperature Range (Note 1) A Symbol Parameter Output High Voltage Output Low Voltage Source Current Sink Current Open Loop Gain Power Supply Rejection Ratio OVP Comparator ...

Page 5

PRODUCT SPECIFICATION Electrical Characteristics Unless otherwise specified 25mA Operating Temperature Range (Note 1) A Symbol Parameter Load Regulation Total Variation Long Term Stability PFC Minimum Duty Cycle Maximum Duty Cycle Output Low Voltage Output ...

Page 6

ML4826 Typical Performance Characteristics 250 200 150 100 (V) Voltage Error Amplifier (VEA) Transconductance (g Variable Gain Control Transfer Characteristic 20 IEAO VEAO V FB VEA IEA 3.5kΩ 2.5V ...

Page 7

ML4826 Functional Description The ML4826 consists of an average current controlled, continuous boost Power Factor Corrector (PFC) front end and a synchronized Pulse Width Modulator (PWM) back end. The PWM can be used in either current or voltage mode. In ...

Page 8

ML4826 The output of the gain modulator is a current signal, in the form of a full wave rectified sinusoid at twice the line frequency. This current is applied to the virtual-ground (negative) input of the current error amplifier. In ...

Page 9

PRODUCT SPECIFICATION nonlinearity such that under steady-state operating condi- tions the transconductance of the error amplifi local minimum. Rapid perturbations in line or load conditions will cause the input to the voltage error amplifier (V ate from ...

Page 10

ML4826 current transformer in the primary of the output stage, and is thereby representative of the current flowing in the con- verter’s output stage which provides cycle-by- LIMIT cycle current limiting, is typically connected to RAMP 2 ...

Page 11

PRODUCT SPECIFICATION 4 x IN4148 I T3 SENSE 200:1 x Former Figure 4. Slope Compensation and Current Sense There are a number of different ways to supply V ML4826. The method suggested in Figure 5, is one which keeps the ...

Page 12

ML4826 RECTIFIED 20V 22kΩ MJE200 Q1 PN2222 18Ω ML4826 1µF RTN Figure 5. V Bias Circuitry 39kΩ 1500µF GATE DRIVE PRODUCT SPECIFICATION V BIAS V CC 1µF ML4826 RTN Figure 6. V ...

Page 13

PRODUCT SPECIFICATION VIN DC REF OSC U4 Figure 8. Typical Trailing Edge Control Scheme VIN – REF RAMP OSC CLK U4 Figure 9. Typical Leading Edge Control Scheme. REV. 1.0.5 ...

Page 14

ML4826 Figure 10. 48V 300W Power Factor Corrected Power Supply 14 PRODUCT SPECIFICATION REV. 1.0.5 2/14/02 ...

Page 15

PRODUCT SPECIFICATION Mechanical Dimensions 20 PIN 0.060 MIN (1.52 MIN) (4 PLACES) 0.170 MAX (4.32 MAX) 0.125 MIN (3.18 MIN) REV. 1.0.5 2/14/02 inches (millimeters) Package: P20 20-Pin PDIP 1.010 - 1.035 (25.65 - 26.29) 0.240 - ...

Page 16

... NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. LIFE SUPPORT POLICY FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems ...

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