TFS764HG

Hi,

Could you plese send your shematic. You can attach the file at file attachements tab.

Short EN pin to ground if you don't want to use standby stage.

Redards,

PI-NANO 

Hi PI-NANO, attached my schematic. Sorry but the item "File Attachments" in Firefox Web browser is not enabled, I needed to install another browser to send the files to you. Thanks, EUGENIO

Hi,

How are you deriving 16V Aux Supply.  

Is there some additional circuit that is missing in the schematic that you had sent?

Transformer pins 7,8,9  was connected to ground  in the schematic, but at the output there is a 0V net. Are these two connected together?

Please send the PIXls fiel for your design.

Regards,

PI-NANO 

Hi,I have an auxiliary source of 16V to power the TFS764 and PFC, the ground and 0V are connected, are the same point. The line connecting the two points disappeared, probably in the conversion to pdf. Pixlr has been updated and  don´t have the TFS 764 only TFS2 line, Please, the calculation is the same? If not how to do this calculation? Thanks,

Hi,

The maximum contineous power that TFS764 can supply is about 344W at 50 deg C ambient and 414W at 25 deg C.

Your output power is way too higher. I am not sure how much forced air cooling you have. If you have very good cooling the max that you can design is 414W.

I would recommend you to use TFS7708 instead of TFS764 if you are in early stages of design.

I could get the TFS764 design with the PIXLS spread sheet. Please download the latest version of the PIXLS software at following location.

http://www.powerint.com/en/design-support/pi-expert-design-software

I looked at the spread sheet that you have attached, There are lot of warnings that have been ignored.

5 turns for secondary is way low for 18V output.

Finally your magnetizing inductance is too low. Your transformer design is not good. That is the reason for the clamp to burn.

If you still want go with TFS764 then we can work on the spredsheet design and send it back to you. If you need any further help please contact our field office in your geographical location.

http://www.powerint.com/en/company/sales-information/worldwide-sales-support-locations

Regards,

PI-NANO 

Hi,

Ok, I understand about the power continues. The power was reduced with current 18A and 18V Clamp and the reaction was also burning.

Yes, I have a forced air fan and the heatsink and the thermal resistance is less than 0.6°C / W.

I have 500pcs of TFS764 in my inventory, I have another 100pç of PCB mounted.

Reduce the current and make anothertransformer, the spreadsheet shows NO WARNINGS. The spreadsheet calculated with 5 turns, I change to 6 turns, another output inductor as your spreadsheet and clamp keeps burning and now TFS764 explodes.

The inductance in promary measured with 1kHz is 8mH.

Can I use a spreadsheet to calculate the transformer TFS2?

Please, help me.

Thanks,

Hi,

For this power level at 66Khz switching frequency, you might need about 20mH-25mH magnetizing inductance. Smaller magnetizing can cause lot of dissipation in the clamp circuit. I am not exatly sure why it is suggesting such lower no. turns for particular designs. we will look into the spredsheet to see if there are any problems.

I would suggest you to try 9 turns on secondary and 77turns on primary. Yoou should get the magnetizing inductance about 20mH-25mH. I have also observed that you are using, ultrafast diode UF4007 for the clamp doide, I would suggest you to try a slow diode (like 1N4007). Slow diode recovers some of the energy back and the zener/TVS dissipation will come down.

Please let me know the result.

Regards,

PI-NANO