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A guide I wrote to building a high voltage switched mode power supply

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profdc9

Tue Apr 05 2016, 03:44AM

Registered Member #58522 Joined: Tue Mar 15 2016, 08:33PM
Location:
Posts: 50

Hello,

I have been working with high voltage and I wrote a guide on how to build a half bridge switched mode power supply, and I included a design spreadsheet. I would welcome any comments. I personally found it difficult to assemble a lot of this information so I thought I would compile it in one place.

The files are in the reply... I accidentally uploaded an old version.

Moderator edit:
Here is the file, I accidentally uploaded an old version.
]building_a_smps.pdf[/file]
]half_bridge_spreadsheet_3.zip[/file]

Keep in mind that of course high voltage and mains voltage is dangerous and you use this at your own risk.

Thanks,

Dan

profdc9

Sat Apr 09 2016, 02:08PM

Registered Member #58522 Joined: Tue Mar 15 2016, 08:33PM
Location:
Posts: 50

This is a document describing how to build a half-bridge switched mode power supply, and make a transformer.

I have revised the document. There are a few changes to the circuit:

kVA meter was in the wrong place.
Better transient behavior when turning on and off to ensure that the half bridge does not shoot through.
Better specification of the snubbers.

Of interest, you might note that I used the following cores, which are both cheap and excellent:

(ICH) U1-1F4 3C85 type, 8 cm^2 cross section,

The following capacitors for the voltage doubler:
(CFE) 003000R00AEI

and the following capacitors for the snubbers and
C4MAHUC4220AA1J 2.2 uF 600 V polyprop
C4MAHUB3470AA0J 0.47 uF 600 V polyprop
A72QQ2150AA02K 0.015 uF 600 V polyprop

and the IGBT

Thanks for reading, let me know if you have any questions.

Best,

Dan

]building_a_smps.pdf[/file]
]half_bridge_spreadsheet_3.zip[/file]

Sulaiman

Sat Apr 09 2016, 07:51PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Nothing that I noticed wrong with your publication, some of the diagrams are excellent.

but I could not work out who your target reader is,

There are no results of any of the design aspects or even photographs etc.
this always puts me off reading too carefully as I may be wasting my time on some ones (usually incomplete) understanding.
I know that many commercial designs have significant flaws and they were designed by an elite few
(if you are lucky you will get a truly professional opinion from one of our members with commercial smpsu design success).

I saw less than I could get from datasheets and application notes other than the high voltage part
I think that you can assume that there are many general smpsu design papers
so some unique/interesting aspect of general smpsu design, in this case your transformer and hv section,
could be the main topic, adding a half-bridge driver is well covered.

With your member name starting with prof. it needs more,
references would be a good start.

Don't let my comments put you off, we all start somewhere.

When you have some working smpsu designs or preferably copies of one design.
.. torture them, learn how to protect them from torture :)
(poor ventilation, low line input voltage, over-voltage input, over-current output, continuous full power output, accidental short-circuit output etc.)
or a design for a very specific application like this hv psu
that is easy to reproduce, understand and hack by those with less electronics experience than yourself.

Looking forward to your results and measurements.

P.S. have you looked at any of the work that members here have done on switchmode hv/eht supplies ?
because I did not notice any references to some excellent work.

profdc9

Sun Apr 10 2016, 05:00PM

Registered Member #58522 Joined: Tue Mar 15 2016, 08:33PM
Location:
Posts: 50

Sulaiman,

Thanks for your feedback.

You are correct that a bibliography is warranted. That was an oversight on my part and has been corrected in the attached document.

I have added a part that explains better why I wrote the document:

"Because SMPS transformers are lighter and less expensive than mains frequency transformers, SMPS are replacing mains frequency transformers in most applications, especially those requiring high power. Unfortunately, this means that the mains frequency transformers that are currently used in high voltage experimentation, such as neon sign transformers (NST) and microwave oven transformers (MOT), are going to become increasingly difficult to find. This document was written to help the high voltage hobbyist transition to the same SMPS technology that is becoming dominant for other power electronics applications. The very popular Mazzilli/Royer flyback driver is used widely for this purpose, however, it has a problem directly using mains voltages, and has not scaled to over 1 kW of power. Furthermore, as LCD televisions are becoming dominant, the CRT flyback transformers typically used with the Mazzilli driver will become increasingly scarce as well. The half bridge configuration, which is already used in high current welders and solid state Tesla coils, is a good starting point for those who wish to work with a directly mains-powered high voltage source. Furthermore, winding a flyback transformer, while tedious, is not out of reach of the hobbyist, especially if large enough ferrite cores can be obtained."

So my target reader is the high voltage enthusiast who would like to try to build something more advanced than the Mazzilli driver. I wanted to assemble the information for others to use, and explain the important issues behind building the SMPS and the transformer.

What kind of pictures would you like to see? I personally have not found the pictures on the web sites of others that helpful, so if there is a way to make the pictures more useful, let me know. I have built up my power supplies but, at least for myself, the design principles were more useful than trying to visually reproduce what was photographed.

For the power supply, I have drawn arcs on it repeatedly, shorted the output, switched it on and off many times, and tested the overcurrent protection. I can spend several minutes melting the ends off of screws and the transistors don't get very hot. It seems to pass these tests, but the problem is that transient events that destroy it may be rare. Its very hard to guarantee (and I do not guarantee) its going to be able to tolerate any abuse.

Basically, I examined various designs such as Steve Ward's Tesla coils and other power supplies (I have links now in the bibliography), and tried to figure out what these various parts of the power supplies did so that I could build a simple supply and explain what the parts do. While I could build a SSTC for my needs, I thought it might be useful to design a substitute for the kinds of power supplies such as MOT and NST that are getting harder to find.

Anyways, I welcome further feedback. Thanks for reading!

Dan

]building_a_smps.pdf[/file]

profdc9

Wed Apr 20 2016, 12:45AM

Registered Member #58522 Joined: Tue Mar 15 2016, 08:33PM
Location:
Posts: 50

Hello again,

I added some to the document. In particular,

How to calculate the gap size in the transformer.
Additional information on winding transformers, including wire gauge table and corona avoidance.
Some minor typo fixes.

Dan

]building_a_smps.pdf[/file]
]half_bridge_spreadsheet_5.zip[/file]

profdc9

Tue Jun 07 2016, 01:12AM

Registered Member #58522 Joined: Tue Mar 15 2016, 08:33PM
Location:
Posts: 50

I added a section to my document explaining how to achieve ZVS operation with the half-bridge. Basically, I've summarized an explanation from LLC resonant converters. It's pretty elegant and I haven't seen this explanation in any of the forum posts I've encountered. I was trying to figure out why the half-bridge had low power dissipation like the Royer/Mazzilli and as I read more carefully, it became clearer to me why the half-bridge is used. I am not a power electronics person by training and so it has taken me a little time to get up to speed. I wanted to put all of these answers in the same place.

I also organized the references better as well. I hope this is useful to you. Be safe.

Dan

]building_a_smps.pdf[/file]
]half_bridge_spreadsheet_5.zip[/file]

hen918

Tue Jun 07 2016, 05:07PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

Can you add page numbers and maybe rearrange the sections, perhaps separating the circuit design and transformer design into different sections?
I would like to point out a few flaws/misconceptions, but pointing out where they are is difficult at the moment.

profdc9

Thu Jun 09 2016, 01:57PM

Registered Member #58522 Joined: Tue Mar 15 2016, 08:33PM
Location:
Posts: 50

I have reorganized the sections somewhat for the transformer design first, then the half-bridge circuit. I also added page numbers.

Best, Dan
]building_a_smps.pdf[/file]

hen918

Thu Jun 09 2016, 09:02PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

Suggestions PMed to profdc9

profdc9

Sat Jun 18 2016, 01:45AM

Registered Member #58522 Joined: Tue Mar 15 2016, 08:33PM
Location:
Posts: 50

Hello,

I have the latest version of the half-bridge document incorporating changes and reorganizing as suggested by hen918. In addition, I added a section about rectifying the high voltage on the secondary side, as well as protecting the output from voltage spikes, for example, from a Tesla coil or other spark gap device.

Thanks,

Dan
]building_a_smps.pdf[/file]
]half_bridge_spreadsheet_5.zip[/file]

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