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| 型号： | LM5046MHX |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 540 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封装： | TSSOP-28 |
| 文件页数： | 13/32页 |
| 文件大小： | 888K |
| 代理商： | LM5046MHX |
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Where, I
m is the magnetizing current, NTR is the power
transformer’s turns ratio, I
Lpeak is the peak output filter inductor
current and C
parasitic is the parasitic capacitance at the node
SW2.
Operating State 3 (Freewheel/Passive Mode)
In the freewheel mode, unlike the conventional full-bridge
topology where all the four primary FETs are off, in the PSFB
topology the primary of the power transformer is shorted by
activating either both the top FETs (HO1 and HO2) or both of
the bottom FETs (LO1 and LO2) alternatively. In the current
CLK cycle, the top FETs HO1 and HO2 are kept on together.
Further in this mode, on the secondary side, similar to the
classic full-bridge topology the synchronous FETs are both
activated. During this state there is no energy transfer from
the primary and the filter inductor current in the secondary
freewheels through both the synchronous FETs.
Operating State 4 (Passive to Active Transition)
At the end of the switching cycle i.e. after the oscillator times
out the current CLK cycle, the primary switch HO1 and the
secondary FET SR1 are turned-off simultaneously. The volt-
age at the node SW1 begins to fall towards the GND. This is
due to the resonance between leakage inductance of the
power transformer plus any additional commutation inductor
and the parasitic capacitances at SW1. The magnetizing in-
ductor is shorted in the freewheel mode and therefore it does
not play any role in this transition. The LC resonance results
in a half-wave sinusoid whose period is determined by the
leakage inductor and parasitic capacitor. The peak of the half-
wave sinusoid is a function of the load current. The passive
to active transition time can be approximated by using the
following formula:
When tuned appropriately either by deliberately increasing
the leakage inductance or by adding an extra commutating
inductor, the sinusoidal resonant waveform peaks such that
it is clamped by the body-diode of the LO1 switch. At this in-
stant, ZVS can be realized by turning on the LO1 switch.
The switching sequence in this CLK cycle is as follows: acti-
vation of the switch LO1 turns the diagonal LO1 and HO2 on,
resulting in power transfer. The power transfer cycle ends
when PWM turns off HO2, which is followed by an active to
passive transition where LO2 is turned on. In the freewheel
mode, LO1 and LO2 are both activated. From this sequence,
it can be inferred that the FETs on the right side of the bridge
(HO2 and LO2) are always terminated by the PWM ending a
power transfer cycle and the SW2 node always sees an active
to passive transition. Further, the FETs on the left side of the
bridge (HO1 and LO1) are always turned-off by the CLK end-
ing a freewheel cycle and the SW1 node always sees a
passive to active transition.
30147863
FIGURE 10. Simplified PSFB Topology Showing the Turn-Off Mechanism
www.national.com
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LM5046
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM5046MHX/NOPB | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| LM5046SQ | 制造商:TI 制造商全称:Texas Instruments 功能描述:LM5046 Phase-Shifted Full-Bridge PWM Controller with Integrated MOSFET Drivers |
| LM5046SQ/NOPB | 功能描述:电流型 PWM 控制器 Phase-Shifted Full- Bridge PWM Cntrlr RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| LM5046SQX | 制造商:TI 制造商全称:Texas Instruments 功能描述:LM5046 Phase-Shifted Full-Bridge PWM Controller with Integrated MOSFET Drivers |
| LM5046SQX/NOPB | 功能描述:IC PWM CTRLR FULL BRIDG 28LLP RoHS:是 类别:集成电路 (IC) >> PMIC - AC-DC 转换器，离线开关 系列:PowerWise® 标准包装:1 系列:FPS™ 输出隔离:隔离 频率范围:61kHz ~ 73kHz 输入电压:8 V ~ 26 V 输出电压:650V 功率（瓦特）:12W 工作温度:-40°C ~ 115°C 封装/外壳:8-DIP（0.300"，7.62mm） 供应商设备封装:8-MDIP 包装:Digi-Reel® 其它名称:FSL206MRBNFSDKR |
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