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參數(shù)資料
| 型號(hào)： | MIC3833BWM |
| 廠商： | MICREL INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Current-Fed PWM Controllers |
| 中文描述： | 1 A SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | 0.300 INCH, SOIC-16 |
| 文件頁(yè)數(shù)： | 9/10頁(yè) |
| 文件大?。?/td> | 100K |
| 代理商： | MIC3833BWM |
April 1998
4-143
MIC3832/3833
Micrel
The push-pull cycles are synchronized to run at half of the
PWM frequency, so a soft or zero voltage switch transition
may be obtained, reducing spikes and EMI. Feeding a
sample of the PWM oscillator ramp to the current-mode
comparator along with the input current sample allows slope
compensation to be obtained for PWM duty cycles above
50%, preventing subharmonic oscillation at low input volt-
ages.
Boost-Derived Current Fed
If a regulator is designed to run at higher push-pull voltage
than the input line voltage, a step-up (boost) PWM regulator,
with an inductor switched to ground, minus the normal output
capacitor, will provide a current limited input to the push-pull
stage. In this configuration all three power switches may be
operated low-side, simplifying their drive circuitry. An input
fuse is needed to guard against short-circuits since there is no
high-side series switch.
Construction Hints
Careful prototyping techniques are required to prevent oscil-
lations. Traditional solderless breadboards are a source of
noise, and should be avoided. Use double-sided, copper-
clad boards with a large area used as a single-point ground
plane.
All timing and loop compensation capacitors and resistors
should be star connected to GND (ground). Wire lengths
along the high-current path should be kept as short as
possible, with appropriate wire gauges being used. Do not
socket the switching transistors as this can add to the voltage
drop and power losses.
Current-Fed Push-Pull SMPS
Figure 3 illustrates this basic topology, a standard push-pull
configuration where the center tap of the primary is fed with
an inductor current instead of a voltage. This constant current
reduces cross conduction and catastrophic transformer core
saturation. Push-pull topologies are often used in 100W and
larger power supplies as they allow more efficient use of the
transformer. The entire range of the B-H curve is used in a
push-pull supply, so a transformer that is one-half the size of
a transformer used in a single-ended, forward-mode topology
can be used. This topology can be extended to a full bridge
where the two 50% duty cycle stages would be used to drive
two MOSFETs each, one for each half of the bridge.
L
D1
S1
S2
S3
50%
50%
Duty Cycle
Control
Figure 3: Current-Fed Push-Pull Topology
Current-Fed Multiple-Output SMPS
Figure 4 illustrates this topology. The absence of output
inductors improves cross-regulation and simplifies the con-
struction of isolated or high-voltage output supplies.
L
D1
S1
Duty Cycle
Control
Additional
Outputs
S2
S3
50%
50%
Figure 4: Current-Fed Multiple-Output Topology
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
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| MIC3838 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:Flexible Push-Pull PWM Controller |
| MIC3838_05 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:Flexible Push-Pull PWM Controller |
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| MIC3838BMM | 功能描述:IC REG CTRLR ISO PWM 10-MSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| MIC3838BMM TR | 功能描述:IC REG CTRLR ISO PWM 10-MSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
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