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LNK500P-TL 参数 Datasheet PDF下载

LNK500P-TL图片预览
型号: LNK500P-TL
PDF下载: 下载PDF文件 查看货源
内容描述: 高效节能, CV或CV / CC切换为非常低的成本适配器和充电器 [Energy Efficient, CV or CV/CC Switcher for Very Low Cost Adapters and Chargers]
分类和应用:
文件页数/大小: 20 页 / 503 K
品牌: POWERINT [ Power Integrations ]
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LNK500  
Figure 5 by the addition of R3, C3 and optocoupler U1. R3  
forms a potential divider with R1 to limit the U1 collector  
emitter voltage.  
The characteristics described above provide an approximate  
CV/CC power supply output without the need for secondary  
side voltage or current feedback. The output voltage regulation  
is influenced by how well the voltage across C2 tracks the  
reflected output voltage. This tracking is influenced by the  
value of the transformer leakage inductance which introduces  
an error. Resistor R2 and capacitor C2 partially filter the  
leakage inductance voltage spike reducing this error. This  
circuitry, used with standard transformer construction  
techniques provides much better output load regulation than a  
linear transformer, making this an ideal power supply solution  
in many low power applications. If tighter load regulation is  
required, an optocoupler configuration can be used while still  
employing the constant output current characteristics provided  
by LinkSwitch.  
On the secondary side, the addition of voltage sense circuit  
componentsR4,VR1andU1LEDprovidethevoltagefeedback  
signal. In the example shown, a simple Zener (VR1) reference  
is used though a precision TL431 reference is typically needed  
to provide 5% output voltage tolerancing and cable drop  
compensation, if required. R4 provides biasing for VR1. The  
regulated output voltage is equal to the sum of the VR1 Zener  
voltage plus the forward voltage drop of the U1 LED. R5 is an  
optional low value resistor to limit U1 LED peak current due to  
output ripple. Manufacturers specifications for U1 current and  
VR1sloperesistanceshouldbeconsultedtodeterminewhether  
R5 is required.  
Optional Secondary Feedback  
U1 is arranged with collector connected to primary ground and  
emitter to the anode of D1. This connection keeps the opto in an  
electrically quietposition in the circuit. If the opto was  
Figure 6 shows a typical power supply outline schematic using  
LinkSwitchwithoptocouplerfeedbacktoimproveoutputvoltage  
regulation. On the primary side, the schematic differs from  
LinkSwitch  
D
S
V
OUT  
LNK500  
C
C1  
R5  
C2  
R1  
U1  
R4  
85-265  
VAC  
R2  
D1  
VR1  
U1  
R3  
C3  
RTN  
PI-3418-111802  
Figure 6. Power Supply Outline Schematic with Optocoupler Feedback.  
Output Voltage  
Inherent  
CC to CV  
transition  
point  
Tolerance envelope  
without optocoupler  
Typical inherent  
characteristic without  
optocoupler  
Voltage  
feedback  
threshold  
Characteristic with  
optocoupler  
Load variation  
during battery  
charging  
Output Current  
PI-2788-092101  
Figure 7. Influence of the Optocoupler on the Power Supply Output Characteristic.  
B
3/03  
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