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參數(shù)資料
| 型號： | 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 |
| 文件頁數(shù)： | 15/22頁 |
| 文件大小： | 863K |
| 代理商： | SG6902 |
Product Specification
Green-Mode PFC / Flyback-PWM Controller
SG6902
System General Corp.
Version 1.3.1 (IAO33.0022.B3)
- 15 -
www.sg.com.tw www.fairchildsemi.com
September, 2007
Line-Voltage Detection (VRMS)
Figure 2 shows a resistive divider with low-pass filtering
for line-voltage detection on the VRMS pin. The V
RMS
voltage is used for the PFC multiplier, brownout
protection, and range control.
For brownout protection, the SG6902 is disabled with
195ms delay time if the voltage V
RMS
drops below 0.8V.
For PFC multiplier and range control, refer to the sections
below for details.
FIG.2 Line-Voltage Detection Circuit
PFC Output Voltage Control (RANGE)
For a universal input (90V
AC
~ 264V
AC
) power supplies
applying active boost PFC and flyback as a second stage,
the output voltage of PFC is usually designed around
250V at low line and 390V at high line. This is to improve
efficiency at low-line input. In SG6902, the RANGE pin
(open-drain structure) is used for the two-level output
voltage setting.
Figure 3 shows the RANGE output that programs the PFC
output voltage. The RANGE output is shorted to ground if
the V
RMS
voltage exceeds 1.95V while high impedance
(open) and the V
RMS
voltage drops below 1.6V. The
output voltages can be designed using below equations:
(
)
(
)
V
3
R
//
R
R
//
R
R
V
Ground
Range
V
3
R
R
R
V
Open
Range
C
B
C
B
A
O
B
B
A
O
×
+
=
=
×
+
=
=
---- (3)
FIG.3 Range Control Two-Level Output Voltage
Interleave Switching and Green-Mode
Operation
The SG6902 uses interleaved switching to synchronize
the PFC and flyback stages, which reduces switching
noise and spreads the EMI emissions. Figure 4 shows
off-time, T
OFF
, inserted between the turn-off of the PFC
gate drive and the turn-on of the PWM.
The off-time T
OFF
is increased in response to the
decreasing of the voltage level of FBPWM. Therefore, the
PWM switching frequency is continuously decreased to
reduce switching losses. To further reduce power losses
under extra light-load conditions, the PFC stage is turned
off with a 650ms delay time.
FIG.4 Interleaved Switching Pattern
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相關代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| 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 |
| 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 |
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