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參數(shù)資料
| 型號(hào)： | SI9122A |
| 廠商： | Vishay Intertechnology,Inc. |
| 英文描述： | 500-kHz Half-Bridge DC/DC Controller With Integrated Secondary Synchronous Rectification Drivers |
| 中文描述： | 500千赫半橋DC / DC變換器與集成的次級(jí)同步整流驅(qū)動(dòng)器控制器 |
| 文件頁數(shù)： | 10/15頁 |
| 文件大?。?/td> | 241K |
| 代理商： | SI9122A |
Si9122A
Vishay Siliconix
www.vishay.com
10
Document Number: 73492
S–51921—Rev. A, 12-Sep-05
Current Limit
Current mode control providing constant current operation is
achieved by monitoring the differential voltage between the
CS1and CS2 pins which are connected across a primary
low-side sense resistor. Once this differential voltage exceeds
the 100-mV trigger point, the voltage on the C
L_CONT
pin is
pulled lower at a rate proportional to the excess voltage and the
value of the external capacitor connected between the
C
L_CONT
pin and ground. If the voltage between CS1 and CS2
exceeds 150 mV the C
L_CONT
capacitor is discharged rapidly
resulting in minimum duty cycle and frequency immediately.
Lowering the C
L_CONT
voltage results in PWM control of the
output drive being taken over by the current limit control loop.
Current control works to initially reduce the switching duty
cycle down to D
MIN
(12.5%). Further reduction in the duty
cycle is accompanied by a reduction in switching frequency at
a rate proportional to the duty cycle. This prevents the on time
of the primary drivers from falling below 100 ns, thereby
avoiding “current tailing”. Frequency reduction will then occur
until the operating frequency reaches 20% of the nominal
frequency, yielding a duty cycle as low as 2.5% during output
overloads.
With constant current mode control of on time and with
reduced operating frequency, protection of the MOSFET
switches is increased during fault conditions. Minimum duty
cycle and reduced frequency switching continues for the
duration of the fault condition. The converter reverts to voltage
mode operation immediately whenever the primary current
fails to reach the limit level. C
L_CONT
clamps to 6.5 V when not
in current limit.
The soft-start function does not apply under current limit as this
would constitute hiccup mode operation.
V
IN
Voltage Monitor –V
INDET
The chip provides a means of sensing the voltage of V
IN
, and
withholding operation of the output drivers until a minimum
voltage of V
REF
(3.3 V, 300-mV hysteresis), is achieved. This
is achieved by choosing an appropriate resistive tap between
the ground and V
IN
, and comparing this voltage with the
reference voltage. When the applied voltage is greater than
V
REF
, the output drivers are activated as normal. V
INDET
also
provides the input to the voltage feed forward function.
However, if the divided voltage applied to the V
INDET
pin is
greater than V
CC
–0.3 V, the high-side driver, D
H
, will stop
switching until the voltage drops below V
CC
–0.3 V. Thus, the
resistive tap on the V
IN
divider must be set to accommodate
the normal V
CC
operating voltage to avoid this condition.
Alternatively, a zener clamp diode from V
INDET
to GND may
also be used.
Shutdown Mode
If V
INDET
is forced below the lower V
SD
threshold, the device
will enter SHUTDOWN mode. This powers down all
unnecessary functions of the controller, ensures that the
primary switches are off, and results in a low level current
demand from the V
IN
or V
CC
supplies.
C
0.5 F
C
2 nF
GND
V
CC
PNP Ext
REG_COMP
V
REF
V
IN
V
INEXT
Figure 5.
High-Voltage Pre-Regulator Circuit
HV
DMOS
14.5 V
R
EXT
(Si9122A)
Auxillary
V
CC
–
+GM
C
EXT
+
–
AV
A
V
150 mV
–
+GM
Peak Detect
Blank
CS1
CS2
I
0 – 240 A (nom)
I
120 A (nom)
AV
V
OFFSET
OSC
C
L_CLAMP
R
EXT
C
L_CONT
Figure 6 .
Current Limit Circuit
A
V
100 mV
V
CC
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SI9122A_08 | 制造商:VISHAY 制造商全稱:Vishay Siliconix 功能描述:500-kHz Half-Bridge DC/DC Controller with Integrated Secondary Synchronous Rectification Drivers |
| SI9122ADLP-T1-E3 | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 500kHz DC/DC Controller 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 |
| SI9122ADQ-T1-E3 | 功能描述:DC/DC 開關(guān)控制器 500kHz DC/DC Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| SI9122DLP-T1-E3 | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 500kHz DC/DC Controller 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 |
| SI9122DQ | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 500kHz DC/DC Controller 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 |
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