TLP 250 isolated power supply

[vinu gopalakrishnan]

Hi freinds, ...I am doing a three phase inverter. For the 3 phase bridge, There are six tlp 250 optocouplers, driving IGBTs. So to avoid common ground problem we need isolated power supply for tlp..right?? But i'm not sure how many?
Four 15v transformers are enough isn't it? In which three of them for the top three high side optocouplers...and one for the bottom three optocouplers....
is this the way??? please help..

 

[eiphan]

TLP250 gives you isolation. You do not need isolation transformer. Power supply using NME1215 from murata will work. You can use that power supply to high side of TLP250 as well as gate drive.

 

[vinu gopalakrishnan]

the transformers are for supply vcc to tlp. they are not isolation transformers.

 

[eiphan]

But if you use TLP250, you still need gate driver. Why not you use HCPL3180? It is isolated gate driver. You just need to provide 6 gate drivers power supply only.

 

[pplus]

So to avoid common ground problem we need isolated power supply for tlp..right?? But i'm not sure how many?
Four 15v transformers are enough isn't it? In which three of them for the top three high side optocouplers...and one for the bottom three optocouplers....

You needed 4 isolated power supply for tlp. One for DC- and other three for DC+.

 

[vinu gopalakrishnan]

TLP 250 is a optocoupler+gate driver

 

[pplus]

And how it changed the number of power supplies?

 

[Tahmid]

TLP 250 is a optocoupler+gate driver

Yes. This means that you don't need additional driver circuitry or additional isolation circuitry. What you do need, like you mentioned, are isolated power supplies. You'll need one isolated power supply for each high-side IGBT. One common power supply will be sufficient for the three low-side IGBTs. So, that means, you'll need four isolated power supplies.

So, you can use four transformers. Make sure you rectify the AC output to DC and filter it. You should also add a voltage regulator to keep the voltage stable. A simple 7812 or 7815 will be okay. Keep in mind the lowest possible input AC voltage and the corresponding lowest possible output voltage from the transformer. Select the voltage regulator accordingly.

Hope this helps.
Tahmid.

 

[vinu gopalakrishnan]

Ok...thanks a lot..Tahmid:smile: