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TNY255 参数 Datasheet PDF下载

TNY255图片预览
型号: TNY255
PDF下载: 下载PDF文件 查看货源
内容描述: 的TinySwitch系列高效节能,低功耗离线式切换器 [TinySwitch Family Energy Efficient, Low Power Off-line Switchers]
分类和应用:
文件页数/大小: 20 页 / 498 K
品牌: POWERINT [ Power Integrations ]
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TNY253/254/255  
Safety Spacing  
Transformer  
Input Filter Capacitor  
Output Filter Capacitor  
+
HV  
SEC  
PRI  
S
D
TOP VIEW  
Y1-  
Maximize hatched copper  
Capacitor  
DC  
Out  
+
TinySwitch  
areas (  
) for optimum  
heat sinking  
CBP  
Opto-  
coupler  
S
BP  
EN  
PI-2176-071398  
Figure 13. Recommended PC Layout for the TinySwitch.  
accommodated by rating the output diode to handle the short  
circuit current. The short circuit current can be minimized by  
choosing the smallest (lowest current limit) TinySwitch for the  
required power.  
Y-Capacitor  
The placement of the Y-capacitor should be directly from the  
primary single point ground to the common/return terminal on  
the secondary side. Such placement will maximize the EMI  
benefit of the Y-capacitor.  
Layout  
Optocoupler  
Single Point Grounding  
It is important to maintain the minimum circuit path from the  
optocouplertransistortotheTinySwitchENABLEandSOURCE  
pins to minimize noise coupling.  
UseasinglepointgroundconnectionattheSOURCEpinforthe  
BYPASS pin capacitor and the Input Filter Capacitor (see  
Figure 13).  
Output Diode  
Primary Loop Area  
For best performance, the area of the loop connecting the  
secondary winding, the Output Diode and the Output Filter  
Capacitor, should be minimized. See Figure13 for optimized  
layout. In addition, sufficient copper area should be provided  
at the anode and cathode terminals of the diode to adequately  
heatsink the diode under output short circuit conditions.  
The area of the primary loop that connects the input filter  
capacitor, transformerprimaryandTinySwitchtogether, should  
be kept as small as possible.  
Primary Clamp Circuit  
A clamp or snubber circuit is used to minimize peak voltage and  
ringing on the DRAIN pin at turn-off. This can be achieved by  
using an RC snubber for less than 3 W or an RCD clamp as  
shown in Figure 13 for higher power. A Zener and diode clamp  
across the primary or a single 550V Zener clamp from DRAIN  
to SOURCE can also be used. In all cases care should be taken  
tominimizethecircuitpathfromthesnubber/clampcomponents  
to the transformer and TinySwitch.  
Input and Output Filter Capacitors  
There are constrictions in the traces connected to the input and  
output filter capacitors. These constrictions are present for two  
reasons. The first is to force all the high frequency currents to  
flow through the capacitor (if the trace were wide then it could  
flowaroundthecapacitor). Secondly,theconstrictionsminimize  
the heat transferred from the TinySwitch to the input filter  
capacitor and from the secondary diode to the output filter  
capacitor. The common/return (the negative output terminal in  
Figure13) terminal of the output filter capacitor should be  
connected with a short, low resistance path to the secondary  
winding. In addition, the common/return output connection  
should be taken directly from the secondary winding pin and  
not from the Y-capacitor connection point.  
Thermal Considerations  
CopperunderneaththeTinySwitchactsnotonlyasasinglepoint  
ground, but also as a heatsink. The hatched area shown in  
Figure13 should be maximized for good heat-sinking of  
TinySwitch and output diode.  
C
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