ML4826IP-2 Micro Linear, ML4826IP-2 Datasheet

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ML4826IP-2

Manufacturer Part Number
ML4826IP-2
Description
PFC and dual output PWM controller combo
Manufacturer
Micro Linear
Datasheet
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
specifications. The ML4826 includes circuits for the
implementation of a leading edge, average current “boost”
type power factor correction and a trailing edge, pulse
width modulator (PWM) with dual totem-pole outputs.
The device is available in two versions; the ML4826-1
(f
Doubling the switching frequency of the PWM allows the
user to design with smaller output components while
maintaining the optimum operating frequency for the PFC.
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.
BLOCK DIAGRAM
PWM
19
10
2
4
3
8
7
9
6
5
I AC
V FB
V RMS
I SENSE
RAMP 1
R T C T
RAMP 2
V DC
SS
DC I LIMIT
2.5V
= f
V CC
PFC
50µA
) and the ML4826-2 (f
8V
8V
+
-
VEA
VEAO
MODULATOR
PFC and Dual Output PWM Controller Combo
1.5V
GAIN
20
11
3.5k
AGND
3.5k
+
PWM
-
+
-
IEA
IEAO
8V
+
-
= 2 x f
(-2 VERSION ONLY)
OSCILLATOR
1
PFC
+
-
2.5V
V FB
).
POWER FACTOR CORRECTOR
PULSE WIDTH MODULATOR
+
-
x 2
V IN OK
* This Part Is End Of Life As Of August 1, 2000
DUTY CYCLE
FEATURES
LIMIT
Internally synchronized PFC and PWM in one IC
Low total harmonic distortion
Reduced ripple current in the storage capacitor
between the PFC and PWM sections
Average current, continuous boost, leading edge PFC
High efficiency trailing edge PWM with dual
totem-pole outputs
Average line voltage compensation with brown-out
control
PFC overvoltage comparator eliminates output
“runaway” due to load removal
Current-fed multiplier for improved noise immunity
Overvoltage protection, UVLO, and soft start
2.7V
1V
-1V
PFC I LIMIT
+
-
OVP
+
+
-
-
DC I LIMIT
V CCZ
V CCZ
13.5V
UVLO
R
S
S
T
R
R
S
S
Q
Q
Q
Q
Q
Q
Q
Q
REFERENCE
7.5V
17
ML4826*
PGND
V CC2
V CC
PFC OUT
PWM 2
PWM 1
PGND
V CC2
V REF
June 1997
18
15
16
14
13
12
1

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ML4826IP-2 Summary of contents

Page 1

PFC and Dual Output PWM Controller Combo 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 ...

Page 2

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

Page 3

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. V Shunt Regulator Current .................................. 55mA CC I Voltage ...

Page 4

ML4826 ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER OVP COMPARATOR Threshold Voltage Hysteresis PFC I COMPARATOR LIMIT Threshold Voltage PFC I - Gain Modulator Output) LIMIT Delay to Output DC I COMPARATOR LIMIT Threshold Voltage Input Bias Current Delay to Output V OK ...

Page 5

ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER PFC Minimum Duty Cycle Maximum Duty Cycle Output Low Voltage Output High Voltage Rise/Fall Time PWM Duty Cycle Range Output Low Voltage Output High Voltage Rise/Fall Time SUPPLY Shunt Regulator Voltage (V CCZ V Load Regulation ...

Page 6

ML4826 TYPICAL PERFORMANCE CHARACTERISTICS 250 200 150 100 (V) Voltage Error Amplifier (VEA) Transconductance (g 20 VEAO V FB VEA IEA 3. 2. GAIN ...

Page 7

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 voltage ...

Page 8

ML4826 FUNCTIONAL DESCRIPTION 3) The output of the voltage error amplifier, VEAO. The gain modulator responds linearly to variations in this voltage. The output of the gain modulator is a current signal, in the form of a full wave rectified ...

Page 9

FUNCTIONAL DESCRIPTION Error Amplifier Compensation The PWM loading of the PFC can be modeled as a negative resistor; an increase in input voltage to the PWM causes a decrease in the input current. This response dictates the proper compensation of ...

Page 10

ML4826 FUNCTIONAL DESCRIPTION PFC RAMP (RAMP1) The intersection of RAMP1 and the boost current error amplifier output controls the PFC pulse width. RAMP1 can be generated in a similar fashion to the R The current error amplifier maximum output voltage ...

Page 11

FUNCTIONAL DESCRIPTION Volts peak. The composite waveform feeding the RAMP2 pin for the PWM consists of the reflected output current signal along with the transformer magnetizing current and the slope compensation signal. Equation 8 describes the composite signal feeding RAMP2, ...

Page 12

ML4826 FUNCTIONAL DESCRIPTION current source. The circuit guarantees that the maximum operating current is available at all times and minimizes the worst case power dissipation in the IC. Other methods such as a simple series resistor are possible, but can ...

Page 13

SW2 VIN RL SW1 DC C1 RAMP REF – DFF + VSW1 RAMP R Q – OSC D CLK Q CLK U4 Figure 8. Typical Trailing Edge Control Scheme. ...

Page 14

ML4826 Figure 10. 48V 300W Power Factor Corrected Power Supply 14 ...

Page 15

PHYSICAL DIMENSIONS 20 PIN 0.060 MIN (1.52 MIN) (4 PLACES) 0.170 MAX (4.32 MAX) 0.125 MIN (3.18 MIN) 0.498 - 0.512 (12.65 - 13.00) 20 PIN 0.024 - 0.034 0.050 BSC (0.61 - 0.86) ...

Page 16

... PART NUMBER ML4826CP-1 ML4826CP-2 ML4826CS-1 ML4826CS-2 ML4826IP-1 ML4826IP-2 ML4826IS-1 ML4826IS-2 © Micro Linear 1997 is a registered trademark of Micro Linear Corporation Products described in this document may be covered by one or more of the following patents, U.S.: 4,897,611; 4,964,026; 5,027,116; 5,281,862; 5,283,483; 5,418,502; 5,508,570; 5,510,727; 5,523,940; ...

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