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| 型号： | FAN4800CMY |
| 厂商： | Fairchild Semiconductor |
| 文件页数： | 19/24页 |
| 文件大小： | 931K |
| 描述： | IC PFC CONTROLLER CCM/DCM 16SOIC |
| 标准包装： | 1 |
| 模式： | 连续导电（CCM），间歇导电（DCM） |
| 频率 - 开关： | 66kHz ~ 84kHz |
| 电流 - 启动： | 100µA |
| 电源电压： | 11 V ~ 16.5 V |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 16-SOIC |
| 包装： | 标准包装 |
| 其它名称： | FAN4800CMYDKR |
?2008 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN4800A/C, FAN4801/02/02L " Rev. 1.0.3
19
TriFault Detect"
To improve power supply reliability, reduce system
component count, and simplify compliance to UL 1950
safety standards, the FAN4800A/C, FAN4801/02/02L
includes TriFault Detect. 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 FAN4800A/C, FAN4801/02/02L, 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 2.75V, the PFC output
driver is shut down. The PWM section continues to
operate. The OVP comparator has 250mV of hysteresis
and the PFC does not restart until the voltage at FBPFC
drops below 2.50V. V
DD
OVP can also serve as a
redundant PFC OVP protection. V
DD
OVP threshold is
28V with 1V 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 5.7K&.
At full load, the average V
EA
needs to around 4.5V and
ripple on the VEA needs to be less than 400mV.
Choose the resistance of the sensing resistor:
(
(
)
-
?/DIV>
W?/DIV>
?/DIV>
?/DIV>
?/DIV>
=
?/DIV>
-
?/DIV>
4.5 0.7 5.7
2
2 5.6 0.7
IN
sense
K IAC Gain V
R
Line input Power
(2)
where 5.6 is V
EA
maximum output.
PFC Soft-Start
PFC startup is controlled by V
EA
level. Before FBPFC
voltage reaches 2.4V, the V
EA
level is around 2.8V. At
90V
AC
, the PFC soft-start time is 90ms.
PFC Brownout
The AC UVP comparator monitors the AC input voltage.
The FAN4800A/C, FAN4801/02 disables PFC as lower
AC input such that the VRMS is less than 1.05V. The
brownout voltage of FAN4802L is lower than
FAN4801/1S/2, such that the VRMS is less than 0.9V.
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 46 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
referred 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
,
which is the sensing resistor of the PFC boost
converter. It requires the ISENSE filter to attenuate
the energy.
2. To reduce L, the boost inductor: The ISENSE filter
also can reduce the boost inductor value since the
ISENSE filter behaves like an integrator before the
ISENSE pin, which is the input of the current error
amplifier, IEA.
The ISENSE filter is an RC filter. The resistor value of
the ISENSE 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 3mV. Design the pole of
ISENSE 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 ISENSE filter, C
FILTER
, is approximately 100nF.
Figure 46. 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 |
|---|---|
| FAN4800CNY | 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 |
| FAN4800CS | 制造商:FAIRCHILD 制造商全称:Fairchild Semiconductor 功能描述:PFC/PWM Controller Combination |
| FAN4800CSMY | 功能描述:电流型 PWM 控制器 PFC/PWM Controller Combination 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 |
| FAN4800CSNY | 功能描述:电流型 PWM 控制器 PFC/PWM Controller Combination 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 |
| FAN4800CUM | 功能描述:电流型 PWM 控制器 PFC/PWM Controller Combination 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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