Author Topic: Connection 0V together !(High Voltage)  (Read 330 times)

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Offline QWERTYQWQ

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Connection 0V together !(High Voltage)
« on: October 24, 2019, 01:36:45 pm »
hi folks..
First of all ,im a newbie(my first post) here and im sayin all of you guys HELLO   :box: !

Nowadays im working on VFD . Since today the all project were going well so i could handle. But today(!) , i hit the wall ..... |O :palm:

The main goal is to controll FETs by DC Bus  [ from  a transformerless power supply (311Vdc) ] . Transformerless power supply works fine and doing well with it. The problem is connection of DC Bus's 0V to another power supply's 0V...

As you guys know H-bridge of the configuration's Gate terminals must drive with low voltage (in my case 20Vmax Vgs). There is also a optoisolator (totem pole) at the output of the control circuitry. The opto's Vcc must 12Vdc(the 12v is comming from smps) for driving the FET's Gate terminal and also the 0V of the SMPS should connect to 311Vdc bus's 0V.  But couldnt figure it out to connect to 0V pins together !!!!! :horse:
I have tested with my oscilloscope and i have noticed  311V peak half rectified signal between each others(as expected before). The reason why im here to solve this situation with you guys comment. How can i generate or connect 12Vdc voltage to opto's Vcc pin  ??????

Im going to be crazy right now. I tried to tell my problem as much as i can. If you guys have any advice to me , im happy to read your comments.. :-+

Thanks A Lot.QWERTY.
 

Offline Zero999

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Re: Connection 0V together !(High Voltage)
« Reply #1 on: October 25, 2019, 10:05:30 pm »
I'm sure I saw a detailed reply to the same question yesterday. Either this is a repeat, from another account or there was an error and it got deleted.

The 0V rails should all be connected to a single point. Beware that the DC bus and the output of the inverter, will be floating at the mains voltage, so you can't connect it to 0V. You need to use two channels of the oscilloscope working in differential mode to look at the output voltage.

Also note the hazards when working with transformerless power supplies, which aren't isolated from the mains.
 


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