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LadyN

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Joined: 26/01/2019
Location: United States
Posts: 408

Posted: 04:50pm 03 Jun 2019

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While I wait on parts to build a transformer baaed inverter, I have been having good luck configuring devices to run off HVDC.

However, there are a few PSUs that use PFC that will not start on DC input: Apple MBP charger, XBox, Desktop SMPS all have PFC

I have been looking around for theory and operation of PFC PSUs and am not having good luck on tutorials that go into enough detail. The closest I found are:

https://www.nuvation.com/resources/article/power-supply-basics-active-power-factor-correction

https://www.allaboutcircuits.com/technical-articles/how-the-boost-pfc-converter-circuit-improves-power-quality/

(remove the spaces in the links above to visit them)

I was able to get some idea that most of these PFCs are Boost convertors that take the grid voltage and boost it to ~400 VDC: that is good news because I can do that too.

My hope is to bypass the initial PFC bit and tap into the HVDC rail so that these PSUs now run off the PV array

Questions:

1. How well would these PFC PSUs run off MSW inverters?
2. Are these PFC PSUs specifically designed with the assumption that they will be working off sine input?
2. Are there some tutorials that go into enough details on theory and operation of these PFC PSUs? Most SMPS websites that have schematics (that I know of) do not reverse engineer PFC PSUs unfortunately

hotwater
Senior Member

Joined: 29/08/2017
Location: United States
Posts: 120

Posted: 05:52pm 03 Jun 2019

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They are just a boost converter with variable power that follows the sine wave making the load look like a resistor. and they typically don't like DC. However, some wall warts have a voltage doubler to make rectified DC and that could be the reason they don't work.

While the power company likes them, PFC supplies waste more power doing a double conversion.

LadyN

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Joined: 26/01/2019
Location: United States
Posts: 408

Posted: 08:04pm 03 Jun 2019

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hotwater said They are just a boost converter with variable power that follows the sine wave making the load look like a resistor. and they typically don't like DC

Hey!

Very glad to hear from you again. Hope you got all the paperwork done?

I actually think this project (modding PFC PSUs to run off PV direct) might be a great idea for you to post on given that you have hacked non PFC flyback convertors to work on PV DC before and have got great success.

The Xbox PSU is capable of hundreds of Watts and can be purchased for a few dollars - so it's way more powerful than the 72V adapters and for the same price.

So as not to damage my brothers Xbox PSU, I have purchased a 175W (12V@15A!) Xbox PSU for $4 from Goodwill and am happy to work with you on this project. You can find the same PSUs for same if not less price

hotwater
Senior Member

Joined: 29/08/2017
Location: United States
Posts: 120

Posted: 09:18pm 03 Jun 2019

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I don't see that happening. I'm not enamored with those power supplies and typically they run very high voltage on the switching so not applicable with anything I'm using at camp. My next planned project is to get a LG washer to run off 60V DC.

BenandAmber
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Joined: 16/02/2019
Location: United States
Posts: 961

Posted: 10:44pm 03 Jun 2019

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Hot water are you talkin about the LG inverter style washing machines with the direct drive Motors

If so I've got some parts here I think I have two of them inverter boards

be warned i am good parrot but Dumber than a box of rocks

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