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參數(shù)資料
| 型號： | LM5045SQ |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 540 kHz SWITCHING FREQ-MAX, QCC28 |
| 封裝： | 5 X 5 MM, LLP-28 |
| 文件頁數(shù)： | 8/28頁 |
| 文件大?。?/td> | 610K |
| 代理商： | LM5045SQ |
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Synchronous Rectifier Control
Outputs (SR1 & SR2)
Synchronous rectification (SR) of the transformer secondary
provides higher efficiency, especially for low output voltage
converters, compared to the diode rectification. The reduction
of rectifier forward voltage drop (0.5V - 1.5V) to 10mV -
200mV VDS voltage for a MOSFET significantly reduces
rectification losses. In a typical application, the transformer
secondary winding is center tapped, with the output power
inductor in series with the center tap. The SR MOSFETs pro-
vide the ground path for the energized secondary winding and
the inductor current. From Figure 5 it can be seen that when
the HO1/LO2 diagonal is turned ON, power transfer is en-
abled from the primary. During this period, the SR1 MOSFET
is enabled and the SR2 MOSFET is turned-off. The sec-
ondary winding connected to the SR2 MOSFET drain is twice
the voltage of the center tap at this time. At the conclusion of
the HO1/LO2 pulse, the inductor current continues to flow
through the SR2 MOSFET body diode. Since the body diode
causes more loss than the SR MOSFET, efficiency can be
improved by minimizing the T2 period while maintaining suf-
ficient timing margin over all conditions (component toler-
ances, etc.) to prevent the shoot-through current. When HO2/
LO1 enables power transfer from the primary, the SR2 MOS-
FET is enabled and the SR1 MOSFET is off.
During the freewheeling period, the inductor current is almost
equally shared between both the SR1 and SR2 MOSFETs
which effectively shorts the transformer secondary. The SR2
MOSFET is disabled before HO1/LO2 is turned-on. The SR2
MOSFET body diode continues to carry about the half induc-
tor current until the primary power raises the SR2 MOSFET
drain voltage and reverse biases the body diode. Ideally,
dead-time T1 would be set to the minimum time that allows
the SR MOSFET to turn off before the SR MOSFET body
diode starts conducting.
The SR drivers are powered by the REF regulator and each
SR output is capable of sourcing 0.1A and sinking 0.4A peak.
The amplitude of the SR drivers is limited to 5V. The 5V SR
signals enable the LM5045 to transfer SR control across the
isolation barrier either through a solid-state isolator or a pulse
transformer. The actual gate sourcing and sinking currents for
the synchronous MOSFETs are provided by the secondary-
side bias and gate drivers.
T1 and T2 can be programmed by connecting a resistor be-
tween RD1 and RD2 pins and AGND. It should be noted that
while RD1 effects the maximum duty cycle, RD2 does not.
The RD1 and RD2 resistors should be located very close to
the device. The formula for RD1 and RD2 resistors are given
below:
If the desired dead-time for T1 is 60ns, then the RD1 will be
20 k
.
30145436
FIGURE 5. Synchronous Rectifier Timing Diagram
www.national.com
16
LM5045
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| LM5046SQ | SWITCHING CONTROLLER, 540 kHz SWITCHING FREQ-MAX, QCC28 |
| LM5046MHX | SWITCHING CONTROLLER, 540 kHz SWITCHING FREQ-MAX, PDSO28 |
| LM5067SDX-2 | 2-CHANNEL POWER SUPPLY SUPPORT CKT, DSO10 |
| LM5067SD-2 | 2-CHANNEL POWER SUPPLY SUPPORT CKT, DSO10 |
| LM555H | PULSE; RECTANGULAR, TIMER, MBCY8 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM5045SQ/NOPB | 功能描述:電流型 PWM 控制器 Full-Bridge PWM Cntrlr 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 |
| LM5045SQX | 制造商:TI 制造商全稱:Texas Instruments 功能描述:Full-Bridge PWM Controller with Integrated MOSFET Drivers |
| LM5045SQX/NOPB | 功能描述:IC PWM CTRLR FULL BRIDG 28LLP RoHS:是 類別:集成電路 (IC) >> PMIC - AC-DC 轉(zhuǎn)換器，離線開關(guān) 系列:PowerWise® 標(biāo)準(zhǔn)包裝:1 系列:FPS™ 輸出隔離:隔離 頻率范圍:61kHz ~ 73kHz 輸入電壓:8 V ~ 26 V 輸出電壓:650V 功率（瓦特）:12W 工作溫度:-40°C ~ 115°C 封裝/外殼:8-DIP（0.300"，7.62mm） 供應(yīng)商設(shè)備封裝:8-MDIP 包裝:Digi-Reel® 其它名稱:FSL206MRBNFSDKR |
| LM5046 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Input operating range: 36V to 75V Line UVLO (34V/32V on/off) |
| LM5046_1 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Input operating range: 36V to 75V Line UVLO (34V/32V on/off) |
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