參數(shù)資料
型號: LTC3722-1
廠商: Linear Technology Corporation
英文描述: Synchronous Dual Mode Phase Modulated Full Bridge Controllers
中文描述: 同步相位調(diào)制的雙模式全橋控制器
文件頁數(shù): 20/28頁
文件大?。?/td> 319K
代理商: LTC3722-1
LTC3722-1/LTC3722-2
20
372212i
4. Using two CS transformers summed together.
5. Choose a CS transformer optimized for high frequency
applications.
Phase Modulator (LTC3722-1)
The LTC3722-1 phase modulation control circuitry is
comprised of the phase modulation comparator and logic,
the error amplifier, and the soft-start amplifier (see Fig-
ure12). Together, these elements develop the required
phase overlap (duty cycle) required to keep the output
voltage in regulation. In isolated applications, the sensed
output voltage error signal is fed back to COMP across the
input to output isolation boundary by an optical coupler
and shunt reference/error amplifier (LT
1431) combina-
tion. The FB pin is connected to GND, forcing COMP high.
The collector of the optoisolator is connected to COMP
Figure 12. Phase Modulation Circuitry (LTC3722-1)
650mV
12
μ
A
3722 F11
R
S
Q
R
S
Q
+
+
+
+
Q
Q
C
D
B
A
CLK
CLK
CLK
1.2V
V
REF
SOFT-START
AMPLIFIER
ERROR
AMPLIFIER
TOGGLE
F/F
PHASE
MODULATION
LOGIC
PHASE
MODULATION
COMPARATOR
FROM
CURRENT
LIMIT
COMPARATOR
BLANKING
FB
COMP
SS
R
LEB
CS
14.9k
50k
OPTIONAL
FILTERING
N:1
MB
SOURCE
MD
SOURCE
CURRENT
TRANSFORMER
R
SLOPE
RAMP
CS
R
S
1922 F10
Figure 11. Current Transformer Sense Circuitry
directly. The voltage COMP is internally attenuated by the
LTC3722-1. The attenuated COMP voltage provides one
input to the phase modulation comparator. This is the
current command. The other input to the phase modula-
tion comparator is the RAMP voltage, level shifted by
approximately 650mV. This is the current loop feedback.
During every switching cycle, alternate diagonal switches
(MA-MD or MB-MC) conduct and cause current in an
output inductor to increase. This current is seen on the
primary of the power transformer divided by the turns
ratio. Since the current sense resistor is connected be-
tween GND and the two bottom bridge transistors, a
voltage proportional to the output inductor current will be
seen across R
SENSE
. The high side of R
SENSE
is also
connected to CS, usually through a small resistor (R
SLOPE
).
When the voltage on CS exceeds either (COMP/5.2)
–650mV, or 270mV, the overlap conduction period will
terminate. During normal operation, the attenuated COMP
voltage will determine the CS trip point. During start-up, or
slewing conditions following a large load step, the 270mV
CS threshold will terminate the cycle, as COMP will be
driven high, such that the attenuated version exceeds the
270mV threshold. In extreme conditions, the 650mV
threshold on CS will be exceeded, invoking a soft-start/
restart cycle.
OPERATIOU
相關(guān)PDF資料
PDF描述
LTC3722EGN-1 Synchronous Dual Mode Phase Modulated Full Bridge Controllers
LTC3722EGN-2 Synchronous Dual Mode Phase Modulated Full Bridge Controllers
LTC1922-1 Synchronous Dual Mode Phase Modulated Full Bridge Controllers
LTC1696 Synchronous Dual Mode Phase Modulated Full Bridge Controllers
LTC3722-2 Synchronous Dual Mode Phase Modulated Full Bridge Controllers
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