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参数资料
| 型号： | FAN4800ASNY |
| 厂商： | Fairchild Semiconductor |
| 文件页数： | 13/19页 |
| 文件大小： | 860K |
| 描述： | IC CTLR COMBO PFC/PWM 16-DIP |
| 标准包装： | 30 |
| 模式： | 平均电流 |
| 频率 - 开关： | 240kHz ~ 268kHz |
| 电流 - 启动： | 30µA |
| 电源电压： | 11 V ~ 26 V |
| 工作温度： | -40°C ~ 105°C |
| 安装类型： | 通孔 |
| 封装/外壳： | 16-DIP（0.300"，7.62mm） |
| 供应商设备封装： | 16-DIP |
| 包装： | 管件 |
?2010 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN4800AS/CS/01S/02S " Rev. 1.0.2
13
Functional Description
The FAN4800AS/CS/01S/02S consist of an average
current controlled, continuous-boost, Power Factor
Correction (PFC) front-end and a synchronized Pulse
Width Modulator (PWM) back-end. The PWM can be
used in current or voltage mode. In voltage mode,
feedforward from the PFC output bus can help improve
the line regulation of PWM. In either mode, the PWM
stage uses conventional trailing-edge, duty-cycle
modulation. This proprietary leading / trailing edge
modulation results in a higher usable PFC error amplifier
bandwidth and can significantly reduce the size of the
PFC DC bus capacitor.
The synchronization of the PWM with the PFC simplifies
the PWM compensation due to the controlled ripple on
the PFC output capacitor (the PWM input capacitor).
In addition to power factor correction, a number of
protection features are built into this series. They include
soft-start, PFC over-voltage protection, peak current
limiting, brownout protection, duty cycle limiting, and
under-voltage lockout (UVLO).
Gain Modulator
The gain modulator is the heart of the PFC, as the
circuit block controls the response of the current loop to
line voltage waveform and frequency, RMS line voltage,
and PFC output voltages. There are three inputs to the
gain modulator:
1. A current representing the instantaneous input
voltage (amplitude and wave shape) to the PFC. The
rectified AC input sine wave is converted to a
proportional current via a resistor and is fed into the
gain modulator at IAC. Sampling current in this way
minimizes ground noise, required in high-power,
switching-power conversion environments. The gain
modulator responds linearly to this current.
2. A voltage proportional to the long-term RMS AC line
voltage, derived from the rectified line voltage after
scaling and filtering. This signal is presented to the
gain modulator at VRMS. The output of the gain
modulator is inversely proportional to V
RMS
(except at
unusually low values of V
RMS
, where special gain
contouring takes over to limit power dissipation of the
circuit components under brownout conditions).
3. The output of the voltage error amplifier, V
EA
. The
gain modulator responds linearly to variations in V
VEA
.
The output of the gain modulator is a current signal, in
the form of a full wave rectified sinusoid at twice the line
frequency. This current is applied to the virtual ground
(negative) input of the current error amplifier. In this way,
the gain modulator forms the reference for the current
error loop and ultimately controls the instantaneous
current draw of the PFC from the power line. The
general form of the output of the gain modulator is:
(
)
K
VRMS
0.7
V
I
I
2
EA
AC
GAINMOD
?/DIV>
?/DIV>
=
(1)
Note that the output current of the gain modulator is
limited around 159 糀 and the maximum output voltage
of the gain modulator is limited to 159 糀 x
5.7 k=0.906 V. This 0.906 V also determines the
maximum input power. However, I
GAINMOD
cannot be
measured directly from ISENSE. I
SENSE
=I
GAINMOD
I
OFFSET
and I
OFFSET
can only be measured when V
VEA
is
less than 0.5 V and I
GAINMOD
is 0 A. Typical IOFFSET is
around 31 糀 ~ 48 糀.
Selecting R
AC
for the IAC Pin
The IAC pin is the input of the gain modulator and also a
current mirror input that requires current input. Selecting
a proper resistor, R
AC,
provides a good sine wave
current derived from the line voltage and helps program
the maximum input power and minimum input line
voltage. R
AC
=V
IN
peak x 56 k&. For example, if the
minimum line voltage is 75 V
AC
, the R
AC
=75 x 1.414 x
56 k&=6 M&.
Current Amplifier Error, IEA
The current error amplifiers output controls the PFC
duty cycle to keep the average current through the boost
inductor a linear function of the line voltage. At the
inverting input to the current error amplifier, the output
current of the gain modulator is summed with a current,
which results in a negative voltage being impressed
upon the ISENSE pin.
The negative voltage on ISENSE represents the sum of
all currents flowing in the PFC circuit and is typically
derived from a current-sense resistor in series with the
negative terminal of the input bridge rectifier.
The inverting input of the current error amplifier is a
virtual ground. Given this fact, and the arrangement of
the duty cycle modulator polarities internal to the PFC,
an increase in positive current from the gain modulator
causes the output stage to increase its duty cycle until
the voltage on ISENSE is adequately negative to cancel
this increased current. Similarly, if the gain modulators
output decreases, the output duty cycle decreases to
achieve a less negative voltage on the ISENSE pin.
PFC Cycle-By-Cycle Current Limiter
In addition to being a part of the current feedback loop,
the ISENSE pin is a direct input to the cycle-by-cycle
current limiter for the PFC section. If the input voltage at
this pin is less than -1.15 V, the output of the PFC is
disabled until the protection flip-flop is reset by the clock
pulse at the start of the next PFC power cycle.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| FAN4800AU | 制造商:FAIRCHILD 制造商全称:Fairchild Semiconductor 功能描述:PFC/ PWM Controller Combination |
| FAN4800AUM | 功能描述:电流型 PWM 控制器 PFC + PWM Controller Combo 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 |
| FAN4800AUN | 功能描述:电流型 PWM 控制器 PFC + PWM Controller Combo 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 |
| FAN4800C | 制造商:FAIRCHILD 制造商全称:Fairchild Semiconductor 功能描述:PFC/PWM Controller Combination |
| FAN4800CMY | 功能描述:电流型 PWM 控制器 PWM/PFC, Avg Curr 30uA SU, 2.6mA Op 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 |
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