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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)： | 17/26頁 |
| 文件大小： | 277K |
| 代理商： | NCP1562A |
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NCP1562A, NCP1562B
http://onsemi.com
17
In some instances it may be desired to latch (instead of
auto re-start) the NCP1562 after a cycle skip event is
detected. This can be easily achieved by adding an external
latch. Figures 35 and 36 show an implementation of an
integrated and a discrete latch, respectively. In general the
circuits work by pulling CSKIP to V
REF
, preventing it from
reaching V
CSKIP(valley)
once the CSKIP voltage reaches the
turn on threshold of the latch. The external latch is cleared
by bringing the UVOV voltage below V
UV
and disabling
V
REF
.
V
REF
C
REF
CSKIP
C
CSKIP
OUTY
V
CC
INA
OE
MC74VHC1GT126
Figure 38. External Latch Implemented using
ON Semiconductor's MiniGate Buffer
The latch in Figure 38 consists of a TTL level tri-state
output buffer from ON Semiconductor's MiniGate
family. The enable (OE) and output (OUTY) terminals are
connected to CSKIP and the V
CC
and INA pins are
connected to V
REF
. The output of the buffer is in a high
impedance mode when OE is low. Once a continuous
current limit condition is detected, the CSKIP timer is
enabled and CSKIP begins charging. Once the voltage on
CSKIP reaches the enable threshold of the buffer, the
output of the buffer is pulled to V
REF
, latching the CSKIP
timer. The OE threshold of the buffer is typically 1.5 V.
V
REF
C
REF
C
CSKIP
CSKIP
BSS84L
M2
24.9 k
2N7002L
R
pull-up
M1
Figure 39. External Latch Implemented using
Discrete N and P-Channel MOSFETs
A latch implemented using discrete N and P-channel
MOSFETs is shown in Figure 39. The latch is enabled once
the CSKIP voltage reaches the threshold of M1. Once M1
turns on, it pulls low the gate of M2. CSKIP is then pulled
to V
REF
by M2. It is important to size R
pull-up
correctly. If
R
pull-up
is too big, it will not keep M2 off while V
REF
charges. This will cause the controller to latch during initial
power-up. In this particular implementation the turn on
threshold of M1 is 2 V and R
pull-up
is sized to 24.9 k
Ω
.
Leading Edge Blanking
The current sense signal is prone to leading edge spikes
caused by the power switch transitions. The current signal
is usually filtered using an RC low–pass filter to avoid
premature triggering of the current limit circuit. However,
the low pass filter will inevitably change the shape of the
current pulse and also add cost and complexity. The
NCP1562 uses LEB circuitry that blocks out the first 70 ns
(typ) of each current pulse. This removes the leading edge
spikes without altering the current waveform. The blanking
period is disabled during soft-start as the blanking period
may be longer than the startup duty cycle. It is also disabled
if the output of the Saturation Comparator is low, indicating
that the output is not yet in regulation. This occurs during
power up or during an output overload condition.
Supply Voltage and Startup Circuit
The NCP1562 internal startup regulator eliminates the
need for external startup components. In addition, this
regulator increases the efficiency of the supply as it uses no
power when in the normal mode of operation, but instead
uses power supplied by an auxiliary winding. The
NCP1562 incorporates an optimized startup circuit that
reduces the requirement of the supply capacitor,
particularly important in size constrained applications.
The startup regulator consists of a constant current
source that supplies current from the input line voltage
(V
in
) to the supply capacitor on the V
AUX
pin (C
AUX
). The
startup current (I
start
) is typically 10 mA.
Once C
AUX
is charged to 10.3 V (V
AUX(on)
), the startup
regulator is disabled and the outputs are enabled if there are
no UV, OV, cycle skip or thermal shutdown faults. The
startup regulator remains disabled until the lower voltage
threshold (V
AUX(off1)
) of 8.0 V is reached. Once reached,
the startup circuit is enabled. If the bias current requirement
out of C
AUX
is greater than the startup current, V
AUX
will
discharge until reaching the lower voltage threshold
(V
AUX(off2)
) of 7.0 V. Upon reaching V
AUX(off2)
, the
outputs are disabled. Once the outputs are disabled, the bias
current of the IC is reduced, allowing V
AUX
to charge back
up. This mode of operation allows a dramatic reduction in
the size of C
AUX
as not all the power required for startup
needs to be stored by C
AUX
. This mode of operation is
known as Dynamic Self Supply (DSS). Figure 40 shows the
relationship between V
AUX(on)
, V
AUX(off1)
, V
AUX(off2)
and
UV. As shown in Figure 40, the outputs are not enabled
until the UV fault is removed and V
AUX
reaches V
AUX(on)
.
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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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