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參數(shù)資料
| 型號： | SG6846A |
| 廠商： | Fairchild Semiconductor Corporation |
| 英文描述： | Highly Integrated Green-Mode PWM Controller |
| 中文描述： | 高度集成的綠色模式PWM控制器 |
| 文件頁數(shù)： | 9/13頁 |
| 文件大?。?/td> | 494K |
| 代理商： | SG6846A |
Product Specification
Highly Integrated Green-Mode PWM Controller
SG6846A
System General Corp.
Version 1.1.1 (IAO33.0059.B1)
- 9 -
www.sg.com.tw www.fairchildsemi.com
September 26, 2007
OPERATION DESCRIPTION
Start-up Operation
The turn-on/turn-off thresholds are fixed internally at
16.5V/10.5V. To enable the SG6846A during start-up,
the hold-up capacitor must first be charged to 16.5V
through the start-up resistor.
The hold-up capacitor continues to supply V
DD
before
energy can be delivered from the auxiliary winding of the
main transformer. The V
DD
must not drop below 10.5V
during this start-up process. This UVLO hysteresis
window ensures that the hold-up capacitor can
adequately supply V
DD
during start-up.
The typical start-up current is only 8μA, which allows a
high-resistance,
low-wattage
minimize power loss. A 1.5M
Ω
/0.25W start-up resistor
and a 10μF/25V V
DD
hold-up capacitor are sufficient for
a universal input range.
start-up
resistor
to
The required operating current has been reduced to
3.7mA, which enables higher efficiency and reduces the
V
DD
hold-up capacitance requirement.
Green-Mode Operation
The proprietary green-mode function provides off-time
modulation to continuously decrease the switching
frequency under light-load conditions. Maximum
on-time is limited to provide protection against abnormal
conditions. To further reduce power consumption under
zero-load condition, the PWM oscillator is completely
turned off and the power supply enters burst-mode. This
green-mode function dramatically reduces power
consumption under light-load and zero-load conditions.
Power supplies using the SG6846A can meet even the
most restrictive international regulations regarding
standby power consumption.
Oscillator Operation
A resistor connected from the RI pin to GND generates a
reference current source used to determine the PWM
frequency. Increasing the resistance decreases the
amplitude of the current source and reduces the PWM
frequency. Using a 26k
Ω
resistor results in a
corresponding
relationship between R
I
and the switching frequency is:
65kHz
switching
frequency.
The
)
(k
I
R
1690
(kHz)
PWM
f
Ω
=
----------------------------
(1)
If an open-circuit or short-circuit to ground occurs at the
RI pin, the internal protection circuit immediately shuts
down the controller.
Two-Level Over-Current Protection
The cycle-by-cycle current limiting shuts down the PWM
immediately when the switching current is over the
peak-current threshold. Additionally, when the switching
current is higher than two thirds the peak-current
threshold, the internal counter counts down. When the
total accumulated counting time is more than around
1600ms (R
I
=26k
), the controller is latched off the
internal counter counting up. When the switching current
is lower than two thirds of the peak current threshold, the
internal counter counts down. When the total
accumulated counting time is more than about 1700ms
(R
I
=26k
), the controller is latched off.
This two-level OCP protection and up/down counter are
especially designed for SMPS with surge current for
printers, scanners, motor drivers, etc.
Constant Output Power Limit
For constant output power limit over a universal
input-voltage range, the peak-current threshold is
adjusted by the voltage of the VIN pin. Since the VIN pin
is connected to the rectified AC input line voltage
through the resistive divider, a higher line voltage
generates a higher V
IN
voltage. The threshold voltage
decreases as the V
IN
voltage increases, making the
maximum output power at high-line input voltage equal
to that at low-line input.
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| SG6846ACSZ | Highly Integrated Green-Mode PWM Controller |
| SG6846ALSZ | Highly Integrated Green-Mode PWM Controller |
| SG6858 | Low-Cost, Green-Mode PWM Controller for Flyback Converters |
| SG6858DZ | Low-Cost, Green-Mode PWM Controller for Flyback Converters |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SG6846A_08 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Highly Integrated Green-Mode PWM Controller |
| SG6846ACSY | 功能描述:電流型 PWM 控制器 Highly Integrated Gr Mode PWM Contrl RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| SG6846ACSZ | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Highly Integrated Green-Mode PWM Controller |
| SG6846ALSY | 功能描述:電流型 PWM 控制器 Highly Integrated Gr Mode PWM Contrl RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| SG6846ALSZ | 功能描述:電流型 PWM 控制器 Highly-Integrated Green-Mode PWM RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
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