參數(shù)資料
型號： LT3957EUHE#TRPBF
廠商： LINEAR TECHNOLOGY CORP
元件分類： 穩(wěn)壓器
英文描述： SWITCHING REGULATOR, PQCC36
封裝： 5 X 6 MM, LEAD FREE, PLASTIC, QFN-36
文件頁數(shù)： 8/28頁
文件大?。?/td> 359K
代理商： LT3957EUHE#TRPBF
LT3957
16
3957f
APPLICATIONS INFORMATION
Figure 7 shows the waveforms of the yback converter
in discontinuous mode operation. During each switching
period TS, three subintervals occur: DTS, D2TS, D3TS.
During DTS, M is on, and D is reverse-biased. During
D2TS, M is off, and LS is conducting current. Both LP and
LS currents are zero during D3TS.
FLYBACK CONVERTER APPLICATIONS
The LT3957 can be congured as a yback converter for the
applications where the converters have multiple outputs,
high output voltages or isolated outputs. Due to the 40V
rating of the internal power switch, LT3797 should be used
in low input voltage yback converters. Figure 6 shows a
simplied yback converter.
The yback converter has a very low parts count for mul-
tiple outputs, and with prudent selection of turns ratio, can
have high output/input voltage conversion ratios with a
desirable duty cycle. However, it has low efciency due to
the high peak currents, high peak voltages and consequent
power loss. The yback converter is commonly used for
an output power of less than 50W.
The yback converter can be designed to operate either
in continuous or discontinuous mode. Compared to con-
tinuous mode, discontinuous mode has the advantage of
smaller transformer inductances and easy loop compen-
sation, and the disadvantage of higher peak-to-average
current and lower efciency.
Figure 7. Waveforms of the Flyback Converter
in Discontinuous Mode Operation
3957 F07
ISW
VSW
ID
t
DTS
D2TS
D3TS
ISW(MAX)
ID(MAX)
TS
Figure 6. A Simplied Flyback Converter
NP:NS
VIN
CIN
CSN
VSN
LP
D
SUGGESTED
RCD SNUBBER
ID
ISW
3957 F06
GND
SW
LT3957
LS
+
–
RSN
DSN
+
–
+
VOUT
COUT
+
Flyback Converter: Switch Duty Cycle and Turns Ratio
The yback converter conversion ratio in the continuous
mode operation is:
VOUT
VIN
=
NS
NP
D
1D
where NS/NP is the second to primary turns ratio. D is
duty cycle.
The yback converter conversion ratio in the discontinu-
ous mode operation is:
VOUT
VIN
=
NS
NP
D
D2
According to Figure 6, the peak SW voltage is:
VSW(PEAK) = VIN(MAX) + VSN
where VSN is the snubber capacitor voltage. A smaller VSN
results in a larger snubber loss. A reasonable VSN is 1.5
to 2 times of the reected output voltage:
VSN =k
VOUT NP
NS
k = 1.5 ~ 2
相關(guān)PDF資料
PDF描述
LT3957IUHE#PBF SWITCHING REGULATOR, PQCC36
LT3958IUHE#PBF SWITCHING REGULATOR, PQCC36
LT3958EUHE#PBF SWITCHING REGULATOR, PQCC36
LT3958EUHE#TRPBF SWITCHING REGULATOR, PQCC36
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LT3957IUHE#PBF 功能描述:IC REG MULTI CONFIG ADJ 36VQFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標準包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤
LT3957IUHE#TRPBF 功能描述:IC REG MULTI CONFIG ADJ 36VQFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標準包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤
LT3957IUHEPBF 制造商:LINER 制造商全稱:Linear Technology 功能描述:Boost, Flyback, SEPIC and Inverting Converter with 5A, 40V Switch
LT3957IUHETRPBF 制造商:LINER 制造商全稱:Linear Technology 功能描述:Boost, Flyback, SEPIC and Inverting Converter with 5A, 40V Switch
LT3958 制造商:LINER 制造商全稱:Linear Technology 功能描述:Monolithic High Voltage Isolated Flyback Converter No External Start-Up Resistor
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