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| 型号： | FAN4800ASNY |
| 厂商： | Fairchild Semiconductor |
| 文件页数： | 14/19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
14
TriFault Detect"
To improve power supply reliability, reduce system
component count, and simplify compliance to UL1950
safety standards; the FAN4800AS/CS/01S/02S includes
TriFault Detect" technology. This feature monitors
FBPFC for certain PFC fault conditions.
In a feedback path failure, the output of the PFC could
exceed safe operating limits. With such a failure, FBPFC
exceeds its normal operating area. Should FBPFC go too
low, too high, or open; TriFault Detect" senses the error
and terminates the PFC output drive.
TriFault Detect is an entirely internal circuit. It requires no
external components to serve its protective function.
PFC Over-Voltage Protection
In the FAN4800AS/CS/01S/02S, the PFC OVP
comparator serves to protect the power circuit from being
subjected to excessive voltages if the load changes
suddenly. A resistor divider from the high-voltage DC
output of the PFC is fed to FBPFC. When the voltage on
FBPFC exceeds 2.75 V, the PFC output driver is shut
down. The PWM section continues to operate. The OVP
comparator has 250 mV of hysteresis and the PFC does
not restart until the voltage at FBPFC drops below 2.5 V.
V
DD
OVP can also serve as a redundant PFC OVP
protection. V
DD
OVP threshold is 28 V with 1 V hysteresis.
Selecting PFC R
sense
R
sense
is the sensing resistor of the PFC boost converter.
During the steady state, line input current x R
sense
equals
I
GAINMOD
x 5.7 k&.
At full load, the average V
VEA
needs to around 4.5 V and
ripple on the VEA pin needs to be less than 400 mV.
Choose the resistance of the sensing resistor:
(
)
(
)
4.5 0.7 5.7
2
2 5.6 0.7
_
_
IN
SENSE
K IAC Gain V
R
Line Input Power
?/DIV>
┳
?/DIV>
?/DIV>
?/DIV>
=
?/DIV>
?/DIV>
(2)
where 5.6 is V
VEA
maximum output voltage.
PFC Soft-Start
PFC startup is controlled by V
VEA
level. Before the
FBPFC voltage reaches 2.4 V, the V
VEA
level is around
2.8 V. At 90 V
AC
, the PFC soft-start time is 90 ms.
PFC Brownout
The AC UVP comparator monitors the AC input voltage.
The PFC is disabled as AC input lowers, causing V
RMS
to
be less than 1.05 V.
Error Amplifier Compensation
The PWM loading of the PFC can be modeled as a
negative resistor because an increase in the input voltage
to the PWM causes a decrease in the input current. This
response dictates the proper compensation of the two
transconductance error amplifiers. Figure 26 shows the
types of compensation networks most commonly used for
the voltage and current error amplifiers, along with their
respective return points. The current-loop compensation
is returned to VREF to produce a soft-start characteristic
on the PFC. As the reference voltage increases from 0V,
it creates a differentiated voltage on IEA, which prevents
the PFC from immediately demanding a full duty cycle on
its boost converter. Complete design is discussed in
application note AN-6078SC.
There is an RC filter between R
sense
and ISENSE pin.
There are two reasons to add a filter at the ISENSE pin:
1. Protection: During startup or inrush current conditions,
there is a large voltage across R
sense
, the sensing
resistor of the PFC boost converter. It requires the
I
SENSE
filter to attenuate the energy.
2. To reduce inductance, L, the boost inductor. The
I
SENSE
filter also can reduce the boost inductor value
since the I
SENSE
filter behaves like an integrator before
the ISENSE pin, which is the input of the current error
amplifier, IEA.
The I
SENSE
filter is an RC filter. The resistor value of the
I
SENSE
filter is between 100 & and 50 & because I
OFFSET
x
R
FILTER
can generate a negative offset voltage of IEA.
Selecting an R
FILTER
equal to 50 & keeps the offset of the
IEA less than 3 mV. Design the pole of the I
SENSE
filter at
f
PFC
/6, one sixth of the PFC switching frequency, so the
boost inductor can be reduced six times without
disturbing the stability. The capacitor of the I
SENSE
filter,
C
FILTER
, is approximately 100 nF.
Figure 26. Compensation Network Connection for
the Voltage and Current Error Amplifiers
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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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