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Author Topic: transformerless AC to DC 300v 1A power supply  (Read 5409 times)
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2N5109
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« on: August 01, 2010, 11:38:05 23:38 »

In these days of power control chips and switching power supplies is there any way to design a 300 volt 1 amp DC power supply without a transformer?  It should run off of 110v AC, 60 cycles.  It could use high voltage capacitors.  

Thanks for any help,

--2N5109
« Last Edit: August 05, 2010, 02:20:39 14:20 by 2N5109 » Logged
solutions
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« Reply #1 on: August 02, 2010, 09:06:59 09:06 »

You could do a charge pump with the caps to double or triple the voltage, but there's no way you'll get 300W out of it.
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Old_but_Alive
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« Reply #2 on: August 02, 2010, 09:49:12 09:49 »

is there a valid reason why you dont want to use a transformer ?
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oldvan
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« Reply #3 on: August 02, 2010, 10:44:44 10:44 »

Need more info:  300V but how much allowable ripple?  Does it need to be regulated?  How much sag is allowable?
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Triodethom
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« Reply #4 on: August 02, 2010, 02:31:15 14:31 »

is there a valid reason why you dont want to use a transformer ?
even switching power supplies us one be it  smaller because of the higher frequency . It has the advantage of limited band pass that is a good thing in this case as well as a voltage step up effect.  Current cd players use a switching unit then a transformer then a regulation stage.
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DarkClover
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« Reply #5 on: August 02, 2010, 05:12:38 17:12 »

Just do a search on the internet for basic knowledge of switching power supplys
and I'm sure there is a project which fit to your specification or at least gives
you the basement and some knowhow.
Then you just have to calculate it for your values.

There are a lot of (non)adjustable high power switching supplys from many
different manufacturer. They have up to 500V with almost 30A or more.
So it sure is possible to build one with 300V and  1A even with easy optainable
electronic parts.

Have a look at this:

« Last Edit: August 04, 2010, 02:44:38 14:44 by DarkClover » Logged

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2N5109
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« Reply #6 on: August 02, 2010, 06:37:17 18:37 »

Thanks for pointing out the Wikipedia link, I would not have thought there would be such detail there and it makes sense even with the "Wiki-filter" on.  It looks like I will have to insert at least one inductor based on the considerations of energy losses in charging capacitors given in the other link.  

This supply can have up to 4volts peak-to-peak ripple and regulate up to 10v from no load to full load.  The application is to power a MOSFET RF amplifier (200watts out) for a small portable HF radio transceiver which runs off 110vac.  It could use ferrite magnetics but I was thinking there might be some unique AC chopping/multiplying and rectifying circuit available nowadays.  I am not too familiar with up to date power supply technology.  


--2N5109
« Last Edit: August 05, 2010, 02:19:06 14:19 by 2N5109 » Logged
Old_but_Alive
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« Reply #7 on: August 02, 2010, 06:56:50 18:56 »

I think this is well beyond you.

Mike
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dikris
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« Reply #8 on: August 02, 2010, 07:43:28 19:43 »

read about power factor correcors. A popular,old IC that does this is UC3854, but there are many others
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2N5109
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« Reply #9 on: August 04, 2010, 04:59:18 04:59 »

My knowledge is more in the area of analog and RF design but there may be applications of impedance matching of RF circuits to 60 cycle circuits for power correction.  This is getting at a high power active inductor.  How about using an active inductor but building it with high power devices.  Could this be used instead of the series inductor in a boost regulator?  I  am not a power supply or Electric Power Engineer.  There is such a thing as non Foster impedance matching of antennas using active devices.  
« Last Edit: August 05, 2010, 02:19:47 14:19 by 2N5109 » Logged
carbontracks
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« Reply #10 on: August 04, 2010, 02:31:28 14:31 »

active inductors can never replace the functionality of real inductors in power supplies.  While active inductors simulate the impedance characteristics of an inductor, they cannot store energy, which is the purpose of an inductor in a power supply.

There's no way to escape having some kind of inductor/transformer in you design unless you can accept either terrible efficiency or terrible regulation.
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« Reply #11 on: August 04, 2010, 02:43:46 14:43 »

The higher the switching frequency the smaller the inductor. Why is a small inducor such a problem ?
There are many calculation softwares around the internet (a big bunch is freeware) which help you
calculate the inductor values and so on.
I'm not a inductorspecialist but they are needed like resistors and capacitors Wink
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2N5109
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« Reply #12 on: August 05, 2010, 02:31:51 14:31 »

ok I think I got it.  You use a real inductor to temporarily store energy from a voltage source, then route the current through a rectifier.  Topology is convenient for MOSFET devices and diodes for switching and rectifying.  This cannot be done without real inductors.  End of story. 
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nordiceng
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« Reply #13 on: April 30, 2013, 04:01:43 16:01 »

why you don't need transformer
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« Reply #14 on: May 01, 2013, 12:52:33 00:52 »

I take it that there are no high voltage isolation issues.

Normally to meet safety requirements for equipment running off mains electricity, a transformer of some kind is usually the simplest and cheapest approach.
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