- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄382500 > SG6858DZ (FAIRCHILD SEMICONDUCTOR CORP) Low-Cost, Green-Mode PWM Controller for Flyback Converters PDF資料下載
參數(shù)資料
| 型號： | SG6858DZ |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Low-Cost, Green-Mode PWM Controller for Flyback Converters |
| 中文描述： | SWITCHING CONTROLLER, 75 kHz SWITCHING FREQ-MAX, PDIP8 |
| 封裝： | GREEN, MS-001BA, DIP-8 |
| 文件頁數(shù)： | 8/13頁 |
| 文件大?。?/td> | 512K |
| 代理商： | SG6858DZ |
Product Specification
Low-Cost, Green-Mode PWM Controller for Flyback Converters
OPERATION DESCRIPTION
SG6858
System General Corp.
Version 1.2.1 (IAO33.0045.B2)
- 8 -
www.sg.com.tw www.fairchildsemi.com
September 25, 2007
SG6858 devices integrate many useful designs into one
controller for low-power switch-mode power supplies.
The following descriptions highlight some of the features
of the SG6858 series.
Start-up Current
The start-up current is only 10μA, which allows a start-up
resistor with a high resistance and a low-wattage to supply
the start-up power for the controller. A 1.5M
, 0.25W,
start-up resistor and a 10μF/25V V
DD
hold-up capacitor
are sufficient for an AC-to-DC power adapter with a wide
input range (100V
AC
to 240V
AC
).
Operating Current
The operating current has been reduced to 2.5mA. The
low operating current results in higher efficiency and
reduces the V
DD
hold-up capacitance requirement.
Green-Mode Operation
The proprietary green-mode function provides off-time
modulation to linearly decrease the switching frequency
under light-load conditions. On-time is limited to provide
stronger protection against brownouts and other abnormal
conditions. The feedback current, which is sampled from
the voltage feedback loop, is taken as the reference. Once
the feedback current exceeds the threshold current, the
switching frequency starts to decrease. This green-mode
function dramatically reduces power consumption under
light-load and zero-load conditions. Power supplies using
the SG6858 can meet even the strictest regulations
regarding standby power consumption.
Oscillator Operation
A resistor connected from the RI pin to ground generates a
constant current source used to charge an internal
capacitor. The charge-time determines the internal clock
speed and the switching frequency. Increasing the
resistance reduces the amplitude of the input current and
the switching frequency. A 95k
resistor, R
I
, results in a
50μA constant current, I
I
, and a 70kHz switching
frequency. The relationship between R
I
and the switching
frequency is:
)
(
kHz
)
(k
R
6650
PWM
f
Ω
=
(1)
Leading-Edge Blanking
Each time the power MOSFET is switched on, a turn-on
spike occurs at the sense-resistor. To avoid premature
termination of the switching pulse, a 300ns leading-edge
blanking time is built in. Conventional RC filtering can
therefore be omitted. During this blanking period, the
current-limit comparator is disabled and cannot switch off
the gate driver.
Constant Output Power Limit
When the SENSE voltage across the sense resistor, R
S
,
reaches the threshold voltage (around 0.96V), the output
GATE drive is turned off following a short propagation
delay t
PD
.
This propagation delay introduces additional current
proportional to t
PD
V
in
/L
p
. The propagation delay is nearly
constant regardless of the input line voltage V
IN
. Higher
input line voltages result in larger additional currents. At
high input line voltages, the output power limit is higher
than at low input line voltages.
To compensate for this output power limit variation
across a wide AC input range, the threshold voltage is
adjusted by adding a positive ramp (V
LIMIT_RAMP
).
This ramp signal rises from 0.80V to 0.96V, then flattens
out at 0.96V. A smaller threshold voltage forces the
output GATE drive to terminate earlier. This reduces the
total PWM turn-on time and makes the output power
equal to that of low line input. This proprietary internal
compensation ensures a constant output power limit for a
wide AC input voltage range (90V
AC
to 264V
AC
).
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SG6858TZ | Low-Cost, Green-Mode PWM Controller for Flyback Converters |
| SG6859 | Low Cost Green-Mode PWM Controller for Flyback Converters |
| SG6859DZ | Low Cost Green-Mode PWM Controller for Flyback Converters |
| SG6859TZ | Low Cost Green-Mode PWM Controller for Flyback Converters |
| SG6901A | PFC / Flyback PWM Controller |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SG6858TZ | 功能描述:IC CTRLR PWM PROG GREEN CM 6SSOT RoHS:是 類別:集成電路 (IC) >> PMIC - AC-DC 轉(zhuǎn)換器，離線開關(guān) 系列:- 標準包裝:3,000 系列:- 輸出隔離:隔離 頻率范圍:61kHz ~ 71kHz 輸入電壓:9.4 V ~ 28 V 輸出電壓:12V 功率（瓦特）:- 工作溫度:-40°C ~ 125°C 封裝/外殼:SC-74，SOT-457 供應(yīng)商設(shè)備封裝:6-TSOP 包裝:帶卷 (TR) |
| SG6859 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Low Cost Green-Mode PWM Controller for Flyback Converters |
| SG6859A | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Low-Cost, Green-Mode PWM Controller for Flyback Converters |
| SG6859A_10 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Low-Cost, Green-Mode PWM Controller for Flyback Converters |
| SG6859ADY | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Low-Cost, Green-Mode PWM Controller for Flyback Converters |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。