LTC3722-1 LINER [Linear Technology], LTC3722-1 Datasheet - Page 10

• Manufacturer Part Number: LTC3722-1
• Description: Synchronous Dual Mode Phase Modulated Full Bridge Controllers
• Manufacturer: LINER [Linear Technology]

LTC3722-1/LTC3722-2
TI I G DIAGRA
Phase Shift Full-Bridge PWM
Conventional full-bridge switching power supply topolo-
gies are often employed for high power, isolated DC/DC
and off-line converters. Although they require two addi-
tional switching elements, substantially greater power and
higher efficiency can be attained for a given transformer
size compared to the more common single-ended forward
and flyback converters. These improvements are realized
since the full-bridge converter delivers power during both
parts of the switching cycle, reducing transformer core
loss and lowering voltage and current stresses. The full-
bridge converter also provides inherent automatic trans-
former flux reset and balancing due to its bidirectional
drive configuration. As a result, the maximum duty cycle
range is extended, further improving efficiency. Soft switch-
ing variations on the full-bridge topology have been pro-
posed to improve and extend its performance and applica-
tion. These zero voltage switching (ZVS) techniques ex-
10
OPERATIO
W
RAMP
COMP
OUTA
OUTB
OUTC
OUTD
OUTE
OUTF
NOTE: SHADED AREAS CORRESPOND TO POWER DELIVERY PULSES.
U
U
W
COMP
PASSIVE LEG
DELAY
SYNC TURN OFF
DELAY (PROGRAMMABLE)
ploit the generally undesirable parasitic elements present
within the power stage. The parasitic elements are utilized
to drive near lossless switching transitions for all of the
external power MOSFETs.
LTC3722-1/LTC3722-2 phase shift PWM controllers pro-
vide enhanced performance and simplify the design task
required for a ZVS phase shifted full-bridge converter. The
primary attributes of the LTC3722-1/LTC3722-2 as com-
pared to currently available solutions include:
1) Truly adaptive and accurate (DirectSense technology)
ZVS with programmable timeout.
Benefit: higher efficiency, higher duty cycle capability,
eliminates external trim.
2) Fixed ZVS capability.
Benefit: enables secondary side control and simplifies
external circuit.
SYNC TURN OFF
DELAY (PROGRAMMABLE)
ACTIVE LEG
DELAY
COMP
3722 TD
372212i