Author Topic: power supplies in series or Paralell?  (Read 626 times)

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Offline DmeadsTopic starter

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power supplies in series or Paralell?
« on: November 14, 2019, 09:04:17 pm »
Hi!

I have a question about hooking up power supplies. I am building an H bridge inverter.

I am borrowing power supplies from my school to test it.

the gate drivers are isolated on the Hbridge side and have a separate ground for the logic supply.

The logic supply is coming from an arduino/battery set up (so isolated). The power supplies are the grounded through the electronics to mains ground.

I will attatch the positive end of the power supplies to the different inputs. 12V to driver and 40V to H bridge.
the negative inputs will be attatched to the ground of the isolated side of the gate driver. (see pic)

My question is, will this not blow up my power supplies? I dont want it to harm them because I have messed with a similar set up and the power supplies went all wonky like they were shorting each other out or something.

thanks.

 

Offline soldar

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Re: power supplies in series or Paralell?
« Reply #1 on: November 14, 2019, 09:30:03 pm »
You draw two black boxes so it is impossible to say. If everything is correct then everything is correct. If not, not.
All my posts are made with 100% recycled electrons and bare traces of grey matter.
 

Offline DmeadsTopic starter

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Re: power supplies in series or Paralell?
« Reply #2 on: November 14, 2019, 09:37:10 pm »
gate driver is UCC21222 from TI and using IRFZ44N mosfets
 

Offline soldar

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Re: power supplies in series or Paralell?
« Reply #3 on: November 15, 2019, 12:33:37 am »
Yeah, that's not gonna work. You would need two separate floating 12 V PSU or a high side bootstrap driver.

I see that is taken directly from a TI application example. Maybe I am mistaken but I cannot see how it can work.


Sorry, didn't pay enough attention. It IS a bootstrap. And It says it right there. I wasn't paying attention.
Well, It should work.

I would test it with no load and with the PSUs current seriously limited so it will not blow anything up. Check that you are getting the on and off times right and very especially that both are not on simultaneously as that would cause shoot-through from the 40 V PSU.

I have not studied the IC in detail. Are you absolutely certain it cannot enable both transistors at the same time? Because that would short circuit the 40 V PSU.

What PSU was overloaded?

Do you understand well how it is supposed to work?

I designed and built a very similar circuit but with gates so it was foolproof. Look at the waveforms. It is crucial that you have dead time between one switching off and the other switching on or you will have shoot through.
« Last Edit: November 15, 2019, 01:07:58 am by soldar »
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Offline DmeadsTopic starter

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Re: power supplies in series or Paralell?
« Reply #4 on: November 15, 2019, 03:26:21 am »
Ya the IC has programmable dead time (makes sure inputs never overlap) which I will use. I will try with no load and PSU current limited. thanks.
 


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