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PDF ML4828 Data sheet ( Hoja de datos )
| Número de pieza | ML4828 | |
| Descripción | BiCMOS Phase Modulation/Soft Switching Controller | |
| Fabricantes | Micro Linear | |
| Logotipo |  |
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May 1997
ML4828*
BiCMOS Phase Modulation/Soft Switching Controller
GENERAL DESCRIPTION
The ML4828 is a complete BiCMOS phase modulation
control IC suitable for full bridge soft switching converters.
Unlike conventional PWM circuits, the phase modulation
technique allows for zero voltage switching (ZVS)
transitions and square wave drive across the transformer.
The IC modulates the phases of the two sides of the bridge
to control output power.
The ML4828 can be operated in either voltage or current
mode. Both cycle-by-cycle current limit, integrating fault
detection, and soft start reset are provided. The under-
voltage lockout circuit features a 1.5V hysteresis with a
low starting current to allow off-line start up with a bleed
resistor. A shutdown function powers down the IC, putting
it into a low quiescent state.
The circuit can be operated at frequencies up to 1MHz.
The ML4828 contains four high current CMOS outputs
which feature high slew rate with low cross conduction.
FEATURES
s 5V BiCMOS for low power and high frequency
(1MHz) operation
s Full bridge phase modulation zero voltage switching
circuit with independent programmable delay times
s Current or voltage mode operation capability
s Cycle-by-cycle current limiting with integrating fault
detection and restart delay
s Can be externally synchronized
s Four 3Ω CMOS output drivers
s Under-voltage lockout circuit with 1.5V hysteresis
*Some Packages Are End Of Life
BLOCK DIAGRAM
VCC
14
SDN 19
UVLO
EA+ 10 +
EA– 9 –
ERROR
AMP
EAO 8
RAMP 11
SS 7
2.5V
1.25V
+
–
VREF
5
2.5V REF
SYNC RT CT
63 4
OSC
ISS
ΦMOD
–
+
QS
QR
Q
T
Q
RST 12
ILIM 20
1V
ILIM
+
–
IRST
FAULT
LOGIC
RQ
SQ
17
GND
DELAY A
DRIVER
18 A1
DRIVER 16 A2
DRIVER 15 B1
DELAY B
DRIVER 13 B2
12
RA RB
1
1 page  
FUNCTIONAL DESCRIPTION
PHASE MODULATOR
The ML4828 controls the power of a full bridge power
section by modulating the phases of the switches of the A
and B sides (Figure 1). The power cycle starts with A2 and
B1 high, as shown in the timing diagram (Figure 2).
1. With A2 and B1 high, Q1 and Q2 are ON. Current
flows through the primary of the transformer, and
power is delivered to the output through the secondary
winding (not shown).
2. After either the ΦMOD or ILIM comparator trips, B1
goes low, turning off Q2. Energy in the primary winding
charges the parasitic capacitances of Q2 and Q3 to
+VIN during tDB.
3. B2 goes high after time tDB, which is set by the resistor
connected from RB (pin 2) to GND. tDB should be set
large enough such that the source of Q3 has been
ML4828
charged to +VIN. At this time, Q3 turns on at zero
voltage. The transformer is now effectively shorted
through Q1 and Q3, with the primary magnetizing
current circulating in the loop formed by the
transformer primary, Q1, and Q3.
4. CLOCK then goes high and A2 goes low, while A1
remains low for time tDA, which is set by the resistor
connected from RA (pin 1) to GND. During this time,
both Q1 and Q4 are OFF. The primary magnetizing
current discharges the parasitic capacitances of Q1 and
Q4 to GND.
5. A1 goes high after time tDA. At this point, the drain of
Q4 is discharged to GND, and Q4 turns on at zero
voltage. With both Q3 and Q4 ON, a new power cycle
starts, and power is delivered to the output.
The above sequence is then repeated with the roles of
side A and B interchanged.
The ML4828 can also be used in current mode by sensing
the load current on the RAMP input (pin 11).
A2 B2
TB
+VIN
Q3 Q1
TA
B1
ML4828
A1
ILIM
B
TB
LLEAKAGE
TRANSFORMER
Q2 Q4
RSENSE
A
TA
Figure 1. Simplified diagram of Phase Modulated power Outputs.
CT
CLOCK
A2
tDA
A1
tDA
B1
tDA
tPD1
B2
tDB tPD1
tDB tPD1
tDB
B
A
Figure 2. Phase Modulation control waveforms (Shaded areas indicate a power cycle).
5
5 Page 
ML4828
ORDERING INFORMATION
PART NUMBER
ML4828CP
ML4828CS
ML4828IP
ML4828IS
TEMPERATURE RANGE
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
PACKAGE
20-Pin DIP (P20)
20-Pin DIP (S20) (EOL)
20- Pin DIP (P20) (EOL)
20- Pin SOIC (S20) (EOL)
© Micro Linear 1997 Micro Linear 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;
5,546,017; 5,559,470; 5,565,761; 5,592,128; 5,594,376; Japan: 2598946; 2619299. Other patents are pending.
Micro Linear reserves the right to make changes to any product herein to improve reliability, function or design.
Micro Linear does not assume any liability arising out of the application or use of any product described herein,
neither does it convey any license under its patent right nor the rights of others. The circuits contained in this
data sheet are offered as possible applications only. Micro Linear makes no warranties or representations as to
whether the illustrated circuits infringe any intellectual property rights of others, and will accept no responsibility
or liability for use of any application herein. The customer is urged to consult with appropriate legal counsel
before deciding on a particular application.
2092 Concourse Drive
San Jose, CA 95131
Tel: 408/433-5200
Telex: 275906
11 DS4828-01
11 Page | ||
| Páginas | Total 11 Páginas | |
| PDF Descargar | [ Datasheet ML4828.PDF ] | |
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