Changing output voltage of existing LNK6666E design from 12Volt to 5Volt

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Hi, I have perfectly working design of Constant Voltage 12V - 5Amp flyback design in LNK6666E chip with following specs:
Input Voltage range: 190-265V AC
Output Voltage: 12V (constant)
Output Current: 5Amp
Ferrite Core used: EE28 gapped core (AL230 Gap). Brand: Cosmo Ferrites
I would like to know what changes needs to be made so that I can use the same circuit to give 5Volt - 10Amp output?

Another thing I wanted to ask is that there is a limitation in the PIExpert tool where output current higher than 10Amp cannot be entered. However, I would like to design 5Volt(CV) - 20Amp & 5Volt(CV) - 40Amp flyback SMPS as well. Please guide me into the right direction for procuring these designs as well.
Awaiting your earnest reply.

Hi Kunal88del,

 

Can you send me the PIXLs that you used for the 12V 5A design?

The critical components that will have to be changed are the LinkSwitch-HP device, transformer and the power devices.

A 200W design may not be possible because that is not recommended in the datasheet. The power handling capability will depend on the thermal and power stress of the device.

Are you open to use some other device or a different topology if applicable?

 

Regards,

PI-Picard 

 

 

 

 

 

Hello,
Thanks Pi-Picard for posting a reply on the above query however I was not able to check it until today. You will be glad to know that we have modified our existing 12Volt - 5Amp LNK6666E design to give 5Volt - 10Amp output & its working fine.

Now, the question remains which device & topology to use for 5Volt-20Amp, 5Volt-40Amp & 5Volt-60Amp designs? If I am not wrong then we will have to switch to Forward Converter topology. However, I would like to stick to Flyback topology for atleast 5Volt-20Amp if at all it is possible else Forward Converter topology will also be fine with me.

Please share your valuable inputs so that we can take it forward. Thanks

Hi,

It will depend on your efficiency requirements and how well heat is taken off the device via heatsinking. You can use Flyback generally for 100W and below, but can also be used above 100W. The LinkSwitch-HP family is only guaranteed to work within specifications for up to 117W if the input voltage is 230Vac. For better performance you need to incorporate a PFC as an input stage to the Flyback topology. For 300W, you may use a PFC stage and 2-Fet forward depending on your efficiency requirements. The device family that you can use is the HyperPFS or TFS family.

Go to the PI website, under the design support, then reference designs and then parametric search. Search by power rating and it will you several recommendations of which devices to use and the topology.

Regards,
PI-Picard

Hi,
Thank your for your valuable feedback. Let me ask specifically then, can we use the following Power Integration value for:
1.) LNK6666E for 5Volt - 10Amp in flyback topology without PFC at 230V AC with heat sinking & efficiency requirement of upto 80%
2.) LNK6666E for 5Volt - 20Amp in flyback topology without PFC at 230V AC with heat sinking & efficiency requirement of 80%
3.) TOP271E for 5Volt - 20Amp in flyback topology without PFC at 230V AC with heat sinking & efficiency requirement of 80%
4.) For 5Volt - 40Amp & 60Amp, I tried doing parametric search for Hiperswitch & TFSswitch but I couldn't find complete design support that has 230V AC input with PFC & 2step forward topology, as recommended earlier by you. Please guide for the same.
Awaiting your earnest reply.

Hi Kunal,

1) For the 5V 10A, at 230Vac you may use LNK6666E with enough heat sinking. But I don't have data if fit can provide 80% efficiency. You may try and test. You need to be using high efficient output rectifier diodes.
2) For the 100W at 230Vac I would suggest to use LNK6xx7E as recommended in the data sheet. You may opt for LNK666E but you need to use fairly large heat sink, but we don't guarantee you will achieve at least 80%.
3) Yes, you may use TOP271E for 100W with good heatsinking and again you need to use high efficient devices. I don't have a design to share with you for 5V 100W. You may use the PIExpert tool or the PIXls and see if it fits your requirement.
4) Check this datasheet on HyperLCS if ok with you.

Hi Kunal,

Here is the link for the HyperTFS with two switch forward.

https://ac-dc.power.com/products/hiper-family/hipertfs-2/

Regards,
PI-Picard

Hi Kunal,

I also need to know how you implemented? Is changing the feedback resistor enough or do we have to rewind the transformer?

Thanks for any help.

Hi Thanibee,

You need to redesign transformer in order to regulate output voltage to 24V.
Please use online PI XLs Designer v10.2 tool to redesign the transformer.
Since power level is is higher, I recommend to size heat sink appropriately.