- 您現(xiàn)在的位置：買賣IC網(wǎng) > Datasheet目錄38 > FAN6921MRMY (Fairchild Semiconductor)IC CTLR PFC/FLYBACK 16-SOICN Datasheet資料下載
參數(shù)資料
| 型號： | FAN6921MRMY |
| 廠商： | Fairchild Semiconductor |
| 文件頁數(shù)： | 19/24頁 |
| 文件大?。?/td> | 1210K |
| 描述： | IC CTLR PFC/FLYBACK 16-SOICN |
| 標準包裝： | 2,500 |
| 模式： | 臨界傳導(dǎo)（CRM） |
| 電流 - 啟動： | 10µA |
| 電源電壓： | 8.5 V ~ 25 V |
| 工作溫度： | -40°C ~ 105°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 16-SOIC（0.154"，3.90mm 寬） |
| 供應(yīng)商設(shè)備封裝： | 16-SOIC N |
| 包裝： | 帶卷 (TR) |
?2009 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN6921MR Rev. 1.0.4
19
PWM Stage
HV Startup and Operating Current (HV Pin)
The HV pin is connected to AC line through a resistor
(refer to Figure 1). With a built-in high-voltage startup
circuit, when AC voltage is applied to power system,
FAN6921MR provides a high current to charge external
V
DD
capacitor to speed up controllers startup time and
build up normal rated output voltage within three
seconds. To save power consumption, after V
DD
voltage
exceeds turn-on voltage and enters normal operation;
this high voltage startup circuit is shut down to avoid
power loss from startup resistor.
Figure 36 shows the characteristic curve of V
DD
voltage
and operating current I
DD
. When V
DD
voltage is lower
than V
DD-PWM-OFF
, FAN6921MR stops all switching
operation and turns off some internal unnecessary
circuit to reduce operating current. By doing so, the
period from V
DD-PWM-OFF
to V
DD-OFF
can be extended and
the hiccup mode frequency can be decreased to reduce
the input power in case of output short circuit. Figure 37
shows the typical waveforms of V
DD
voltage and gate
signal at hiccup mode operation.
Figure 36. V
DD
vs. I
DD-OP
Characteristic Curve
Figure 37. Typical Waveform of V
DD
Voltage and Gate
Signal at Hiccup Mode Operation
Green-Mode Operation and PFC-ON / OFF Control
(FB Pin)
Green mode mechanism is used to further reduce
power loss in the system (e.g. switching loss). It uses an
off-time modulation technique to regulate switching
frequency according to FB pin voltage. When output
loading is decreased, FB voltage becomes lower due to
secondary feedback movement and the t
OFF-MIN
is
extended. After t
OFF-MIN
(determined by FB voltage), the
internal valley detection circuit is activated to detect the
valley on the drain voltage of the PWM switch. When
the valley signal is detected, FAN6921MR outputs PWM
gate signal to turn on the switch and begin a new
switching cycle.
With green mode operation and valley detection, at light
load condition; power system can perform extended
valley switching at DCM operation and can further
reduce switching loss for getting better conversion
efficiency. The FB pin voltage versus t
OFF-MIN
time
characteristic curve is shown in Figure 38. As Figure 38
shows, FAN6921MR can narrow down to 2.25 ms t
OFF
time, which is around 440 Hz switching frequency.
Referring to Figure 1 and Figure 2, FB pin voltage is not
only used to receive secondary feedback signal to
determine gate on-time, but also determines PFC stage
on or off status. At no-load or light-load conditions, if PFC
stage is set to be off; that can reduce power consumption
from PFC stage switching device and increase
conversion efficiency. When output loading is decreased,
the FB pin voltage becomes lower and, therefore, the
FAN6921MR can detect the output loading level
according to the FB pin voltage to control the on / off
status of the PFC part.
Figure 38. V
FB
Voltage vs. t
OFF-MIN
Time Characteristic
Curve
Valley Detection (DET Pin)
When FAN6921MR operates in green mode, t
OFF-MIN
time is determined by the green mode circuit according
to FB pin voltage level. After t
OFF-MIN
time, the internal
valley detection circuit is activated. During the t
OFF
time
of PWM switch, when transformer inductor current
discharges to zero, the transformer inductor and
parasitic capacitor of PWM switch start to resonate
concurrently. When the drain voltage on the PWM
switch falls, the voltage across on auxiliary winding V
AUX
also decreases since auxiliary winding is coupled to
primary winding. Once the V
AUX
voltage resonates and
falls to negative, V
DET
voltage is clamped by the DET pin
(refer to Figure 39) and FAN6921MR is forced to flow
out a current I
DET
. FAN6921MR reflects and compares
this I
DET
current. If this source current rises to a
threshold current, PWM gate signal is sent out after a
fixed delay time (200 ns typical).
t
OFF-MIN
2.25ms
37祍
1.15V(V
G
)
2.1V(V
N
)
8祍
PFC OFF
PFC On
VCTL-PFC-ON
V
CTL-PFC-OFF
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| FAN6961SZ | IC PFC CONTROLLER DCM 8SOP |
| FAN6982MY | IC CTLR PFC CCM 14-SOICN |
| FAN7527BN | IC PFC CTRLR TRANSITION 8DIP |
| FAN7529MX | IC PFC CTRLR CRM/TRANSITION 8SOP |
| FAN7930BM | IC PFC CTLR CRITICAL CONF 8-SOIC |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| FAN6961 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Interleaved Dual BCM PFC Controllers |
| FAN6961BMY | 制造商:Fairchild Semiconductor Corporation 功能描述: |
| FAN6961DY | 功能描述:功率因數(shù)校正 IC Green mode PFC Fwd PWM Controller RoHS:否 制造商:Fairchild Semiconductor 開關(guān)頻率:300 KHz 最大功率耗散: 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel |
| FAN6961DZ | 功能描述:功率因數(shù)校正 IC Green mode PFC Fwd PWM Controller RoHS:否 制造商:Fairchild Semiconductor 開關(guān)頻率:300 KHz 最大功率耗散: 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel |
| FAN6961SY | 功能描述:功率因數(shù)校正 IC Green mode PFC Fwd PWM Controller RoHS:否 制造商:Fairchild Semiconductor 開關(guān)頻率:300 KHz 最大功率耗散: 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。