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參數(shù)資料
| 型號： | NCP1562A |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | High Performance Active Active Clamp/Reset PWM Controller Controller(高性能有效Clamp/Reset PWM控制器) |
| 中文描述： | 高性能主動有源鉗位/復(fù)位PWM控制器控制器（高性能有效鉗位/復(fù)位的PWM控制器） |
| 文件頁數(shù)： | 15/26頁 |
| 文件大小： | 277K |
| 代理商： | NCP1562A |
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NCP1562A, NCP1562B
http://onsemi.com
15
DETAILED OPERATING DESCRIPTION
The NCP1562x is a family of voltage mode controllers
designed for dc-dc converters requiring high-efficiency
and low parts count. These controllers incorporate two in
phase outputs with an adjustable overlap delay. The main
output is designed for driving a forward converter primary
MOSFET. The secondary output is designed for driving an
active clamp circuit MOSFET, a synchronous rectifier on
the secondary side, or an asymmetric half bridge circuit.
Two distinctive features of the NCP1562 are the
soft-stop and a cycle skip overcurrent detector with a time
threshold. The soft-stop powers down the converter in a
controlled manner after a fault is detected. The cycle skip
timer disables the converter if a continuous overcurrent
condition is present.
The NCP1562 reduces component count and system size
by incorporating high accuracy on critical specifications
such as programmable maximum duty cycle, undervoltage
detector and overcurrent threshold. Additional features
found in the NCP1562 include line feedforward,
bidirectional frequency synchronization up to 1.0 MHz,
cycle-by-cycle current limit with leading edge blanking
(LEB), independent under and overvoltage detectors,
internal startup circuit and soft-start.
SOFT-STOP AND SOFT-START
The NCP1562 incorporates a novel soft-stop and
soft-start architecture that combines soft-start and
soft-stop functions on a single pin.
Soft-stop reduces the duty cycle until it reaches 0% once
a fault is detected. By slowly reducing the duty cycle during
power down, the active clamp capacitor (C
clamp
) is
discharged. This prevents oscillations between the power
transformer and C
clamp
, and ensures the converter turns off
in a predictable state.
Soft-start slowly increases the duty cycle during power
up allowing the controller to gradually reach steady state
operation. Combined, both features reduce system stress
and power surges.
The duty cycle is controlled by comparing the SS
capacitor voltage (V
SS
) to the Feedforward (FF) Ramp.
Soft-start or soft-stop is implemented by slowly charging
or discharging the capacitor on the SS pin. OUT1 is
disabled once the FF Ramp exceeds V
SS
. The soft-start
charge current is 10 A and the soft-stop discharge current
is 100 A, guaranteeing a faster turn OFF time.
The converter enters a soft-stop sequence if an
undervoltage, overvoltage, cycle skip or thermal shutdown
condition is detected. Once the converter enters the
soft-stop mode, it will stay in soft-stop mode until V
SS
reaches 0.2 V even if the fault is removed prior to reaching
0.2 V.
The preset 1:10 charge:discharge ratio can be reduced by
placing an external resistor between the V
REF
and SS pins.
The resistor should be sized such that the total charge
current does not exceed 100 A. Otherwise the converter
will not be able to complete a soft-stop sequence.
Depending on the converter state, a soft-stop sequence
is handled differently to ensure the fastest response time
and prevent system malfunction. If a soft-stop sequence
starts before V
SS
exceeds the maximum voltage clamp of
the FF Ramp (typ. 3.0 V) and the PWM Comparator (V
EA
)
is not yet controlling the duty cycle, a controlled discharge
of C
SS
commences immediately, as shown in Figure 34.
However, if V
EA
is controlling the duty cycle, C
SS
is
discharged until soft-stop sets a duty cycle equal to the duty
cycle set by V
EA
. A controlled discharge commences
afterwards, as shown in Figure 35. If V
SS
exceeds the FF
Ramp and the V
EA
is not controlling the duty cycle, V
SS
is
forced to the peak voltage of the FF Ramp, before starting
a controlled discharge of C
SS
, as shown in Figure 36. The
duty cycle set at the beginning of the soft-stop event never
exceeds the duty cycle prior to the soft-stop event.
Figure 34. Soft-Stop Before Soft-Start
is Complete and V
EA
is Open.
(V
EA
is not controlling the duty cycle)
V
EA
V
SS
FF Ramp
Figure 35. Soft-Stop Behavior when V
EA
Controls the Duty Cycle.
V
SS
V
X
= V
EA
- V
f
V
EA
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| NCP1562A WAF | 制造商:ON Semiconductor 功能描述: |
| NCP1562ADBR2G | 功能描述:電壓模式 PWM 控制器 HI PERF RESET PWM CONTLR RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| NCP1562ADR2G | 功能描述:電壓模式 PWM 控制器 HI PERF RESET PWM CONTLR RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| NCP1562BDBR2G | 功能描述:電壓模式 PWM 控制器 HI PERF RESET PWM CONTLR RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| NCP1562BDR2G | 功能描述:電壓模式 PWM 控制器 HI PERF RESET PWM CONTLR RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
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