參數(shù)資料
型號(hào)： NCP1239
廠商： ON SEMICONDUCTOR
英文描述： Low−Standby High Performance PWM Controller
文件頁(yè)數(shù)： 16/38頁(yè)
文件大?。?/td> 1145K
代理商： NCP1239
NCP1239
http://onsemi.com
16
APPLICATION INFORMATION
The NCP1239 includes all necessary features to help
building a rugged and safe switchmode power supply. The
following details the major benefits brought by
implementing the NCP1239 controller:
Currentmode
operation
compensation:
implementing peak current mode control,
the NCP1239 offers an internal ramp compensation signal
that can easily be summed up to the sensed current.
Subharmonic oscillations can thus be fought via the
inclusion of a simple resistor,
500 mV Current Sense threshold for Over Power Limit
(NCP1239F):
the NCP1239 operating in current mode, the
circuit Pin 10 monitors the current to modulate its level
according to the power demand. Due to the ramp
compensation, one must generally note that the Pin 10
voltage is not the exact image of the inductor current. A
precise current limitation being essential, the NCP1239
features a separate current sense pin (Pin 9) for an accurate
overcurrent detection. The low threshold of this protection
(500 mV) avoids excessive losses in the current sense
resistor and improves the efficiency. In addition, Pin 9
sources a current that proportional to the highvoltage rail,
compensates the currentsense and turn off delays at high
line. A resistor inserted between Pin 9 and the sensing
resistor offsets the Pin 9 currentsense information to build
a precise overload protection, independent of the mains
input.
Large V
CC
operation:
the NCP1239 offers an extended
V
CC
range up to 36 V, bringing greater flexibility in Flyback
or Forward applications.
Internal highvoltage startup switch:
reaching low
levels of standby power represents a difficult exercise when
the controller requires an external, lossy, resistor connected
to the bulk capacitor. Due to an internal logic, the controller
disables the highvoltage current source after startup which
no longer hampers the consumption in noload situations.
Skipcycle capability:
a continuous flow of pulses is not
compatible with noload standby power requirements.
Slicing the switching pattern in bunch of pulses drastically
reduces overall losses but can, in certain cases, bring
acoustic noise in the transformer. Due to a skip operation
taking place at low peak currents only, no mechanical noise
appears in the transformer. Furthermore, the skip threshold
is made programmable to allow the best tradeoff between
noise and efficiency.
Standby Detect/Shutdown of the PFC frontstage:
The
NCP1239 incorporates an internal logic that is able to detect
a standby situation. Pin1 state changes in accordance to the
with
internal
ramp
detected mode (standby or normal mode). Simply connect a
pnp transistor between the NCP1239 V
CC
and the PFC
controller one and drive it using Pin 1, to enable the PFC
stage in normal mode and disable it in standby.
SoftStart:
the capacitor connected to Pin 6 provides a
softstart sequence that precludes the main power switch
from being stressed upon startup. The same voltage is also
used to perform frequency jittering and timing for the fault
condition detection.
Major Fault Detection:
the circuit detects when Pin 3
voltage exceeds 2.4 V. When this occurs, the NCP1239
considers that a major fault is present and as a consequence,
the circuit gets permanently latchedoff. In this mode, the
circuit needs the V
CC
to go down below 4.0 V to reset, for
instance when the user unplugs the SMPS. This capability
is mainly intended to detect an overvoltage condition or/and
an overheating of the application that would be sensed by
a thermistor.
Brownout detection:
by monitoring the level on Pin 5
during normal operation, the controller protects the SMPS
against low mains conditions. When the Pin 5 voltage falls
below 250 mV, the controllers stops pulsing until this level
goes back to 500 mV to prevent any instability.
Shortcircuit protection:
shortcircuit and especially
overload protections are difficult to implement when a
strong leakage inductance affects the transformer (the
auxiliary winding level does not properly collapse
…
). Here,
every time the feedback pin is at its maximum (higher than
5.0 V practically), an error flag is asserted and the circuit
activates a timer that is programmed by the Pin 6 capacitor.
If Pin 6 reaches 4.3 V while the error flag is still present, the
controller stops the pulses and goes into a latchoff phase,
operating in a lowfrequency burstmode. As soon as the
fault disappears, the SMPS resumes its operation. The
latchoff phase can also be initiated, more classically, when
V
CC
drops below UVLO (11.2 V typical).
Adjustable frequency and Internal dithering for
improved EMI signature:
Pin 4 offers a means to precisely
adjust the switching frequency through a simple resistor to
ground. Frequency operation is allowed up to 250 kHz. By
modulating the internal switching frequency with the Pin 6
sawtooth (100 Hz with 390 nF), natural energy spread
appears and softens the controller’s EMI signature.
5.0 V reference voltage:
a 5.0 V regulator is provided to
help biasing any external circuitry in the vicinity of the
controller. This reference voltage can typically supply up to
10 mA.
相關(guān)PDF資料
PDF描述
NCP1239FDR2 Low−Standby High Performance PWM Controller
NCP1239FDR2G Low−Standby High Performance PWM Controller
NCP1239VDR2 Low−Standby High Performance PWM Controller
NCP1239VDR2G Low−Standby High Performance PWM Controller
NCP1271 Soft−Skip Mode Standby PWM Controller with Adjustable Skip Level and External Latch
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
NCP1239D 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Low-Standby High Performance PWM Controller
NCP1239F 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:AC-DC Offline Switching Controllers/Regulators
NCP1239FDR2 功能描述:電流型 PWM 控制器 Low Standby Power RoHS:否 制造商:Texas Instruments 開(kāi)關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
NCP1239FDR2G 功能描述:電流型 PWM 控制器 Low Standby Power High Performance PWM RoHS:否 制造商:Texas Instruments 開(kāi)關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
NCP1239V 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:AC-DC Offline Switching Controllers/Regulators
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