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參數(shù)資料
| 型號： | SI9117 |
| 廠商： | Vishay Intertechnology,Inc. |
| 英文描述： | High-Frequency Converter for Telecom Applications |
| 中文描述： | 高頻轉(zhuǎn)換器的電信應(yīng)用 |
| 文件頁數(shù)： | 14/15頁 |
| 文件大小： | 132K |
| 代理商： | SI9117 |
Si9117
Vishay Siliconix
www.vishay.com
14
Document Number: 70027
S-40750—Rev. E, 19-Apr-04
Amps
Current
Tail
Volts
1
1
1
FIGURE 13.
FIGURE 14.
SS
COMP
R
OSC
FB
C
OSC
NI
SYNC
V
REF
V
SD
V
CC
V+
I
SENSE
NC
S
D
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
C
in
C
ref
C
ss
Si9117DY
C
filt
R
filt
Tx1
R
sense
+
Choosing the Switching Frequency
When selecting the switching frequency, it is usually best to
choose the lowest possible frequency that the design solution
will accept. In PWM control topologies, the maximum switching
frequency will be strongly governed by short circuit behavior.
When a short circuit is applied to the output, the control circuit
is required to reduce the duty cycle to the smallest possible
value to maintain constant current operation (Figure 14).
Ideally, the converter should deliver 105% of the output current
within regulation and no more than 115% under short circuit. At
500 kHz, the period of conversion is 2 s and the maximum on
time is 1 s. High minimum duty ratios will result in current tails
and require rectifier oversizing to avoid destructive currents
under overload conditions.
The Si9117 has a sync-to-output delay of less than 70 ns, so
the minimum duty cycle for operation at 500 kHz would be
70 ns/1 s = 7%. This minimum should be considered when
the short circuit current is determined. Designers should note
that a shunt placed across the output of the converter is
probably not a realistic load in the event of a failure, and the real
circuit impedance will probably be substantially lower. In such
circumstances, it may be necessary to shift the frequency of
the converter to a lower value during overload. Frequency
shifting can be accomplished by altering the steady state
values of the oscillator programming components (see
oscillator section, Figure 7).
Short Circuit Behavior
Short circuit behavior is different for both common topologies,
and must be paid special attention.
In flyback converters, all windings appear in “parallel” with
each other. When one winding is shorted, all other flyback
windings are also shorted through it. In multiple output
converters, therefore, any single winding without a
separate secondary current-limiting protection will “drag
down” all the other windings. As a result, if a bias winding is
used to power the control circuit, it will stop delivering power.
When this occurs, the Si9117 depletion device will turn on
and regulate the supply rail to 9.2 V, as in its normal starting
mode. In this event, designers should calculate the
worst-case power dissipation caused by the voltage drop
across the depletion transistor at the highest applied
voltage across it and with the current flowing through it.
In forward converters, traditionally the bias winding is also
taken in forward conduction mode, but without any series
inductance. In the event of a short circuit, the pulse width is
reduced to minimum, but it is sufficient to supply enough
power to the control circuit. This is an advantage, and
avoids the problems encountered with flyback converters.
Power may also be taken in flyback mode, however, when
the duty cycle is low. There will be very little flyback voltage
present, since the applied volt/microseconds is low and the
core need not, therefore, fly back very far to reset.
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| SI9121DY-3 | High-Voltage, Non-Isolated Buck-Boost Converter for ISDN Digital Phones |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SI9117DY | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 1MHz HV Sw Mode Reg RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| SI9117DY-E3 | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 Hi Freq Converter For Telecom App RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| SI9117DY-T1 | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Hi Freq Converter For Telecom App RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| SI9117DY-T1-E3 | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 Hi Freq Converter For Telecom App RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| SI9118 | 制造商:VISHAY 制造商全稱:Vishay Siliconix 功能描述:Programmable Duty Cycle Controller |
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