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参数资料
| 型号： | LT3757HMSE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 18/36页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR PWM CM 10-MSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 1MHz |
| 电源电压： | 2.9 V ~ 40 V |
| 降压： | 无 |
| 升压： | 是 |
| 回扫： | 是 |
| 反相： | 是 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 150°C |
| 封装/外壳： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 |
| 包装： | 带卷 (TR) |
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LT3757/LT3757A
APPLICATIONS INFORMATION
V OUT N D
V OUT N D
=
FlybackConverter:SwitchDutyCycleandTurnsRatio
The flyback converter conversion ratio in the continuous
mode operation is:
= S ?
V IN N P 1 ? D
where N S /N P is the second to primary turns ratio.
Figure 8 shows the waveforms of the flyback converter
in discontinuous mode operation. During each switching
period T S , three subintervals occur: DT S , D2T S , D3T S .
During DT S , M is on, and D is reverse-biased. During
D2T S , M is off, and L S is conducting current. Both L P and
L S currents are zero during D3T S .
The flyback converter conversion ratio in the discontinu-
ous mode operation is:
= S ?
V IN N P D2
V DS
I SW
According to the preceding equations, the user has relative
freedom in selecting the switch duty cycle or turns ratio to
suit a given application. The selections of the duty cycle
and the turns ratio are somewhat iterative processes, due
to the number of variables involved. The user can choose
either a duty cycle or a turns ratio as the start point. The
following trade-offs should be considered when select-
ing the switch duty cycle or turns ratio, to optimize the
converter performance. A higher duty cycle affects the
flyback converter in the following aspects:
? Lower MOSFET RMS current I SW(RMS) , but higher
MOSFET V DS peak voltage
? Lower diode peak reverse voltage, but higher diode
RMS current I D(RMS)
? Higher transformer turns ratio (N P /N S )
The choice,
D 1
D + D2 3
(for discontinuous mode operation with a given D3) gives
the power MOSFET the lowest power stress (the product
of RMS current and peak voltage). However, in the high
output voltage applications, a higher duty cycle may be
adopted to limit the large peak reverse voltage of the
diode. The choice,
I SW(MAX)
D
D + D2
=
2
3
I D
I D(MAX)
DT S
D2T S
T S
D3T S
t
3757 F07
(for discontinuous mode operation with a given D3) gives
the diode the lowest power stress (the product of RMS
current and peak voltage). An extreme high or low duty
cycle results in high power stress on the MOSFET or diode,
and reduces efficiency. It is recommended to choose a
duty cycle, D, between 20% and 80%.
Figure 8. Waveforms of the Flyback Converter
in Discontinuous Mode Operation
3757afd
18
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3757IDD | 制造商:LINER 制造商全称:Linear Technology 功能描述:Boost, Flyback, SEPIC and Inverting Controller |
| LT3757IDD#PBF | 功能描述:IC REG CTRLR BST FLYBK INV 10DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,000 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:1MHz 占空比:50% 电源电压:9 V ~ 10 V 降压:无 升压:是 回扫:是 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 85°C 封装/外壳:8-TSSOP（0.173"，4.40mm 宽） 包装:带卷 (TR) |
| LT3757IDD#PBF | 制造商:Linear Technology 功能描述:DC-DC CONTROLLER SEPIC 1MHZ 制造商:Linear Technology 功能描述:DC-DC CONTROLLER, SEPIC, 1MHZ, DFN-10 |
| LT3757IDD#TRPBF | 功能描述:IC REG CTRLR BST FLYBK INV 10DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LT3757IDDPBF | 制造商:Linear Technology 功能描述:Boost Flyback SEPIC Controller DFN10EP |
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