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| 型号： | FAN4801SMY |
| 厂商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 0.5 A POWER FACTOR CONTROLLER WITH POST REGULATOR, 268 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | 0.150 INCH, GREEN, MS-012AC, SOIC-16 |
| 文件页数： | 6/19页 |
| 文件大小： | 577K |
| 代理商： | FAN4801SMY |
2010 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN4800AS/CS/01S/02S Rev. 1.0.1
14
FA
N
4800A
S/C
S
/01S/02S
—
PFC/PWM
Controller
Combination
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 2.75V, 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 2.5V.
VDD OVP can also serve as a redundant PFC OVP
protection. VDD OVP threshold is 28V with 1V hysteresis.
Selecting PFC Rsense
Rsense is the sensing resistor of the PFC boost converter.
During the steady state, line input current x Rsense equals
IGAINMOD x 5.7k.
At full load, the average VVEA needs to around 4.5V and
ripple on the VEA pin needs to be less than 400mV.
Choose the resistance of the sensing resistor:
(
)
()
4.5 0.7
5.7
2
25.6 0.7
_
IN
SENSE
KIAC Gain V
R
Line Input
Power
×
Ω ×
×
=
×
(2)
where 5.6 is VVEA maximum output voltage.
PFC Soft-Start
PFC startup is controlled by VVEA level. Before the
FBPFC voltage reaches 2.4V, the VVEA level is around
2.8V. At 90VAC, the PFC soft-start time is 90ms.
PFC Brownout
The AC UVP comparator monitors the AC input voltage.
The PFC is disabled as AC input lowers, causing VRMS to
be less than 1.05V.
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 Rsense 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 Rsense, the sensing
resistor of the PFC boost converter. It requires the
ISENSE filter to attenuate the energy.
2. To reduce inductance, 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 IOFFSET x
RFILTER can generate a negative offset voltage of IEA.
Selecting an RFILTER equal to 50 keeps the offset of the
IEA less than 3mV. Design the pole of the ISENSE filter at
fPFC/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,
CFILTER, is approximately 100nF.
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 |
|---|---|
| FAN4801SNY | 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 |
| FAN4802 | 制造商:FAIRCHILD 制造商全称:Fairchild Semiconductor 功能描述:PFC/PWM Controller Combination |
| FAN4802L | 制造商:FAIRCHILD 制造商全称:Fairchild Semiconductor 功能描述:PFC/PWM Controller Combination |
| FAN4802LMY | 功能描述:电流型 PWM 控制器 PWM PFC 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 |
| FAN4802LNY | 功能描述:电流型 PWM 控制器 PWM PFC 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 |
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