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參數資料
| 型號： | SG6901A |
| 廠商： | Fairchild Semiconductor Corporation |
| 元件分類： | 基準電壓源/電流源 |
| 英文描述： | PFC / Flyback PWM Controller |
| 中文描述： | 功率因數校正/反激式PWM控制器 |
| 文件頁數： | 14/18頁 |
| 文件大小： | 716K |
| 代理商： | SG6901A |
Product Specification
PFC / Flyback PWM Controller
Interleave Switching
SG6901A
System General Corp.
Version 1.0.1 (IAO33.0062.B0)
- 14 -
www.sg.com.tw www.fairchildsemi.com
September 26, 2007
The SG6901A uses interleaved switching to synchronize
the PFC and flyback stages, which reduces switching
noise and spreads the EMI emissions. Figure 3 shows
off-time, T
OFF
, inserted between the turn-off of the PFC
gate drive and the turn-on of the PWM.
FIG.3 Interleaved Switching Pattern
PFC Operation
The purpose of a boost active power factor corrector (PFC)
is to shape the input current of a power supply. The input
current waveform and phase follow that of the input
voltage. Average-current-mode control is utilized for
continuous-current-mode operation for the PFC booster.
With the innovative multi-vector control for voltage loop
and switching charge multiplier-divider for current
reference, excellent input power factor is achieved with
good noise immunity and transient response. Figure 4
shows the total control loop for the average-current-mode
control circuit of SG6901A.
The current source output from the switching charge
multiplier-divider can be expressed as:
(μA)
V
V
I
K
I
2
RMS
EA
AC
MO
×
×
=
------------
(4)
As shown in Figure 4, the current output from IMP pin,
I
MP
, is the summation of I
MO
and I
MR1
. I
MR1
and I
MR2
are
identical fixed-current sources used to pull high the
operating point of the IMP and IPFC pins since the
voltage across R
S
goes negative with respect to ground.
Constant current sources I
MR1
and I
MR2
are typically 60μA.
Through the differential amplification of the signal across
R
S
, better noise immunity is achieved. The output of
IEA
is
compared with an internal sawtooth and the pulse width
for PFC is determined. Through the average current-mode
control loop, the input current I
S
is proportional to I
MO
:
S
S
2
MO
I
R
I
R
×
=
×
--------------------
(5)
According to Equation 5, the minimum value of R
2
and
maximum of R
S
can be determined since I
MO
should not
exceed the specified maximum value.
There are different concerns in determining the value of
the sense resistor R
S
. The value of R
S
should be small
enough to reduce power consumption, but large enough to
maintain the resolution. A current transformer (CT) may
be used to improve efficiency of high-power converters.
To achieve good power factor, the voltage for V
RMS
and
V
EA
should be kept as constant as possible, according to
Equation 4. Good RC filtering for V
RMS
and narrow
bandwidth (lower than the line frequency) for voltage
loop are suggested for better input current shaping. The
transconductance error amplifier has output impedance
Z
O
and a capacitor C
EA
(1μF ~ 10μF) should be connected
to ground. This establishes a dominant pole f1 for the
voltage loop:
EA
O
1
C
Z
2
1
f
×
×
=
π
----------------------
(6)
The average total input power can be expressed as:
AC
EA
2
RMS
V
EA
AC
RMS
V
2
RMS
V
EA
AC
RMS
V
MO
I
RMS
V
(rms)
IN
I
(rms)
I
×
IN
R
V
2
V
R
Vin
V
V
Pin
×
=
×
×
∝
×
×
∝
∝
×
=
----------------
(7)
From Equation 7, V
EA
, the output of the voltage error
amplifier, controls the total input power and the power
delivered to the load.
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| SG6902 | Green-Mode PFC / Flyback-PWM Controller |
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相關代理商/技術參數 |
參數描述 |
|---|---|
| SG6901ASZ | 功能描述:開關變換器、穩(wěn)壓器與控制器 PFC/Flyback PWM Controller RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| SG6902 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Green-Mode PFC / Flyback-PWM Controller |
| SG6902SZ | 功能描述:開關變換器、穩(wěn)壓器與控制器 Grn Mode PFC/Flyback PWM Controller RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| SG6903SZ | 功能描述:開關變換器、穩(wěn)壓器與控制器 Highly-Integrated Grn Mode PWM Cntrl RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| SG6905 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Green mode PFC/Flyback-PWM Controller |
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