参数资料
| 型号： | NCP1294EDR2G |
| 厂商： | ON Semiconductor |
| 文件页数： | 8/13页 |
| 文件大小： | 0K |
| 描述： | IC PWM CTLR FLYBACK 16SOIC |
| 标准包装： | 2,500 |
| 输出隔离： | 隔离 |
| 频率范围： | 260kHz ~ 320kHz |
| 输入电压： | 4.7 V ~ 15 V |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 16-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 16-SOIC N |
| 包装： | 带卷 (TR) |
NCP1294
APPLICATION INFORMATION
THEORY OF OPERATION
Feed Forward Voltage Mode Control
In conventional voltage mode control, the ramp signal has
fixed rising and falling slope. The feedback signal is derived
solely from the output voltage. Consequently, voltage mode
control has inferior line regulation and audio susceptibility.
Feed forward voltage mode control derives the ramp
signal from the input line, as shown in Figure 3. Therefore,
the ramp of the slope varies with the input voltage. At the
start of each switch cycle, the capacitor connected to the FF
pin is charged through a resistor connected to the input
voltage. Meanwhile, the Gate output is turned on to drive an
external power switching device. When the FF pin voltage
reaches the error amplifier output V COMP , the PWM
comparator turns off the Gate, which in turn opens the
external switch. Simultaneously, the FF capacitor is quickly
discharged to 0.3 V.
Overall, the dynamics of the duty cycle are controlled by
both input and output voltages. As illustrated in Figure 4,
with a fixed input voltage the output voltage is regulated
solely by the error amplifier. For example, an elevated
output voltage reduces V COMP which in turn causes duty
cycle to decrease. However, if the input voltage varies, the
slope of the ramp signal will react immediately which
provides a much improved line transient response. As an
example shown in Figure 5, when the input voltage goes up,
the rising edge of the ramp signal increases which reduces
duty cycle to counteract the change.
V OUT
V COMP
FF
V IN
R T C T
GATE
Figure 4. Pulse Width Modulated by Output
Current with Constant Input Voltage
V IN
V COMP
FF
I OUT
R T C T
V IN
R
Power Stage
GATE
Latch & Driver
V OUT
Feedback
GATE
Figure 5. Pulse Width Modulated by Input Voltage
with Constant Output Current
Network
C
FF
COMP
PWM
Error Amplifier
?
+
+
?
FB
Powering the IC & UVL
The Undervoltage Lockout (UVL) comparator has two
voltage references; the start and stop thresholds. During
power ? up, the UVL comparator disables V REF (which
in ? turn disables the entire IC) until the controller reaches its
V CC start threshold. During power ? down, the UVL
comparator allows the controller to operate until the V CC
stop threshold is reached. The NCP1294 requires only 50 m A
during startup. The output stage is held at a low impedance
Figure 3. Feed Forward Voltage Mode Control
The feed forward feature can also be employed to provide
a volt ? second clamp, which limits the maximum product of
input voltage and turn on time. This clamp is used in circuits,
such as Forward and Flyback converter, to prevent the
transformer from saturating. Calculations used in the design
of the volt ? second clamp are presented in the Design
Guidelines section.
state in lock out mode.
During power up and fault conditions, the Soft ? Start
clamps the Comp pin voltage and limits the duty cycle. The
power up transition tends to generate temporary duty cycles
much greater than the steady state value due to the low
output voltage. Consequently, excessive current stresses
often take place in the system. Soft ? Start technique
alleviates this problem by gradually releasing the clamp on
the duty cycle to eliminate the in ? rush current. The duration
http://onsemi.com
8
相关PDF资料 |
PDF描述 |
|---|---|
| NCP1308DR2G | IC REG CTRLR FLYBACK PWM 8-SOIC |
| NCP1337DR2G | IC REG CTRLR FLYBK ISO PWM 7SOIC |
| NCP1338DR2G | IC REG CTRLR FLYBK ISO PWM 7SOIC |
| NCP1377BP | IC CTRLR PWM CM OVP UVLO 8DIP |
| NCP1378PG | IC REG CTRLR FLYBACK PWM 7-PDIP |
相关代理商/技术参数 |
参数描述 |
|---|---|
| NCP1294EDTB16G | 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:Enhanced Voltage Mode PWM Controller |
| NCP1294EDTB16R2G | 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:Enhanced Voltage Mode PWM Controller |
| NCP1308 | 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:Power Factor Controllers |
| NCP1308DR2G | 功能描述:电流型 PWM 控制器 Quasi Resonant Current Mode PWM RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| NCP1316 | 制造商:未知厂家 制造商全称:未知厂家 功能描述: |
发布紧急采购，3分钟左右您将得到回复。