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About LNK3207D

Posted by: Omur Ceran on 11/01/2021

Hello ,
I have an technical question about LNK3207D product.
According to one of your application notes(document number=RDR-721) , There is example schematic for 5V 550mA AC/DC conversion(you can schematic at page 6, figure 3). My question is about resistor which is connected BP pin(R6). Do I have to connect it for current limiting? If I don't connect it there , can there be problem about normal working situation ?

Second question is about termal measurement.
At page 22, you made some thermal measurement. But I don't understand somewhere there. When I use my product for instant 500mA continuous current mode, will IC temperature reach 100C degree ? if so , is it normal at room temperature ? Do you have suggestion to decrease this temperature?

Third question is about input rectifiers.
If I use half bridge rectifier, can there be problem at output current ?

Best Regards,
Ömür Ceran

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Submitted by PI-Chloe on 11/04/2021

Hi Ömür Ceran

 

Question 1:

The IC can be supplied by two ways. 

          1. DRAIN voltage 

          2. BP pin 

At start up, the IC will be power up by the DRAIN voltage. 

Once the IC is power up, it will get bias in the BP pin. 

Biasing the IC in the BP pin is advantageous it will reduce the power losses in the IC. 

The resistor R6 is use to regulate the current being supplied to the IC. 

User can remove the R6. If this is the case, IC will be bias via DRAIN side. Power loss in the IC will increase due  to the internal regulator will step down the Drain voltage to 5V. 

Question 2: 

IC thermals will depend on your design. I cannot say it will reach 100degC at ambient temp. 

IC Thermal is depended on the 

     1. Package - improve thermals will be seen on G and P package.

     2. SOURCE Heatsink - the IC can be cool down via the SOURCE heatsink. Increasing copper area of the SOURCE heatsink will help to reduce thermals. 

     3. Freewheel diode D3 - use low trr diodes. Low Trr  diode will reduce the power losses of the IC.

 

Question 3: 

Yes you can use half bridge but designer needs to adjust the value of the input capacitors. (increase). 

 

Thanks 

 

regards 

PI-CHLOE