參數(shù)資料
型號(hào)： SG6902
廠商： Fairchild Semiconductor Corporation
英文描述： Green-Mode PFC / Flyback-PWM Controller
中文描述： 綠色模式PFC /反激式，PWM控制器
文件頁(yè)數(shù)： 14/22頁(yè)
文件大?。?/td> 863K
代理商： SG6902
Product Specification
Green-Mode PFC / Flyback-PWM Controller
OPERATION DESCRIPTION
The highly integrated SG6902 is designed for power
supplies with boost PFC and flyback PWM. It requires
very few external components to achieve green-mode
operation and versatile protections / compensation.
SG6902
System General Corp.
Version 1.3.1 (IAO33.0022.B3)
- 14 -
www.sg.com.tw www.fairchildsemi.com
September, 2007
The patented interleave-switching feature synchronizes
the PFC and PWM stages and reduces switching noise. At
light loads, the switching frequency is continuously
decreased to reduce power consumption. If output loading
is reduced, the PFC stage is turned off to further reduce
power consumption.
The
average-current-mode control. The patented switching
charge multiplier-divider provides a high-degree noise
immunity for the PFC circuit. The proprietary
multi-vector output voltage control scheme provides a
fast transient response in a low-bandwidth PFC loop, in
which the overshoot and undershoot of the PFC voltage
are clamped. If the feedback loop is broken, the SG6902
shuts off PFC to prevent extra-high voltage on output.
Programmable two-level output voltage control reduces
the PFC output voltage at low line input to increase the
efficiency of the power supply.
PFC
function
is
implemented
by
For the flyback PWM, the synchronized slope
compensation ensures the stability of the current loop
under continuous-mode operation. Built-in line-voltage
compensation maintains constant output power limit.
Hiccup operation during output overloading is also
guaranteed. To prevent the power supply from drawing
large current during start-up, the start-up for PFC stage is
delayed
11.5ms
after the operation of PWM stage.
In addition, SG6902 provides complete protection
functions, such as brownout, over-voltage, and RI pin
open/short protections.
Start-up
Figure 1 shows the start-up circuit of the SG6902. A
resistor R
AC
is utilized to charge V
DD
capacitor through S1.
The turn-on and turn-off thresholds are fixed internally at
16V/10V. During start-up, the hold-up capacitor must be
charged to 16V through the start-up resistor to enable
SG6902. The hold-up capacitor continues to supply V
DD
before the energy can be delivered from auxiliary winding
of the main
transformer. V
DD
must not drop below 10V
during this start-up process. This UVLO hysteresis
window ensures that hold-up capacitor is adequate to
supply V
DD
during start-up. Since SG6902 consumes less
than
25μA start-up current, the value of R
AC
can be large
to reduce power consumption. One 10μF capacitor should
hold enough energy for successful start-up. After start-up,
S1 switches so that the current I
AC
is the input for PFC
multiplier. This helps reduce circuit complexity and
power consumption.
FIG.1 Start-up Circuit
Switching Frequency and Current
Sources
The switching frequency can be programmed by resistor
R
I
connected between RI and GND. The relationship is:
(kHz)
)
(k
R
1560
F
I
OSC
=
-----------
(1)
For example, a 24k
resistor for R
I
results in a 65kHz
switching frequency. Accordingly, a constant current, I
T
,
flows through R
I
:
(mA)
)
(k
R
1.2V
I
I
T
=
----------------
(2)
I
T
is used to generate internal current reference.
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
SG6902SZ 功能描述:開關(guān)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(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel
SG6903SZ 功能描述:開關(guān)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(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)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
SG6905SY 制造商:Rochester Electronics LLC 功能描述: 制造商:Fairchild Semiconductor Corporation 功能描述:
SG6905SZ 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 Grn Mode PFC/Forward 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(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel
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