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参数资料
| 型号： | LT3957EUHE#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING REGULATOR, PQCC36 |
| 封装： | 5 X 6 MM, LEAD FREE, PLASTIC, QFN-36 |
| 文件页数： | 8/28页 |
| 文件大小： | 359K |
| 代理商： | LT3957EUHE#PBF |
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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
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3957EUHETRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Boost, Flyback, SEPIC and Inverting Converter with 5A, 40V Switch |
| LT3957IUHE#PBF | 功能描述:IC REG MULTI CONFIG ADJ 36VQFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3957IUHE#TRPBF | 功能描述:IC REG MULTI CONFIG ADJ 36VQFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3957IUHEPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Boost, Flyback, SEPIC and Inverting Converter with 5A, 40V Switch |
| LT3957IUHETRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Boost, Flyback, SEPIC and Inverting Converter with 5A, 40V Switch |
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