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Old 7th February 2014, 07:11 PM   #1
el156 is offline el156  Portugal
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Default How can i have 450 Volts ?

Hi all

I have a power transfo with 230-0-230 secundary, and i need 450 volts for my next project, now, is there a simple way for me to get 450 volts DC out of this transformer ? I was thinking using a 5R4 tube that i have, and paraleling the plates, so it would be a half wave rect. so, using the 460 v secundary to the plates, would it work to have more or less 450 V on the output ? I need about 300 ma

Thanks
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Old 7th February 2014, 07:14 PM   #2
kmtang is offline kmtang  Canada
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Use a bridge rectifier across the 230-230V winding and follow by C-L-C filtering. The first C should be very small of about 0.5uF. Change the value of the first C to get you the 450V B+.

Johnny
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Old 7th February 2014, 07:28 PM   #3
el156 is offline el156  Portugal
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Quote:
Originally Posted by kmtang View Post
Use a bridge rectifier across the 230-230V winding and follow by C-L-C filtering. The first C should be very small of about 0.5uF. Change the value of the first C to get you the 450V B+.

Johnny
Thanks Kmtang, i will make a test like that, but what i really would like is a 450 V regulated supply with Mosfets, but that is far more complicated for me...maybe you know a simple schematic to do that ?

Thanks
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Old 7th February 2014, 07:38 PM   #4
M Gregg is offline M Gregg  United Kingdom
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Why not take the simple option,

B+ reducer at the bottom of the page..
http://www.geofex.com/Article_Folder...osfetfolly.htm

I guess it depends on how much current you are going to draw..
Heat dissipation in the FET..volt drop etc..

Regards
M. Gregg
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Old 7th February 2014, 07:51 PM   #5
tomchr is offline tomchr  United States
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Quote:
Originally Posted by el156 View Post
Thanks Kmtang, i will make a test like that, but what i really would like is a 450 V regulated supply with Mosfets, but that is far more complicated for me...maybe you know a simple schematic to do that ?
Have a look at my 21st Century Maida Regulator. It was designed for exactly that purpose. You'll find all the design documentation on my website (see link in my signature). I also sell PCBs for this circuit.

~Tom
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Old 7th February 2014, 07:59 PM   #6
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What's the transformer current rating? A 230-0-230 @300 mA transformer can deliver about 200 mA with a full-wave bridge with cap input, about 300 mA with choke input. Don't even think about half-wave - it's not an efficient use of transformer and other components.
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Old 7th February 2014, 08:04 PM   #7
el156 is offline el156  Portugal
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Quote:
Originally Posted by Tom Bavis View Post
What's the transformer current rating? A 230-0-230 @300 mA transformer can deliver about 200 mA with a full-wave bridge with cap input, about 300 mA with choke input. Don't even think about half-wave - it's not an efficient use of transformer and other components.
The transformer is 230-0-230 @ 500 Ma ,so is ok for what i need
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Old 7th February 2014, 08:09 PM   #8
Elvee is online now Elvee  Belgium
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Quote:
Originally Posted by el156 View Post
what i really would like is a 450 V regulated supply with Mosfets, but that is far more complicated for me...maybe you know a simple schematic to do that ?
Depends on your priorities, but if you look for decent performances and excellent resilience and survivability, this type of regulators might be an option.
Simple HV series regulators
With the right version and suitable components, they can be made to survive indefinite shorts, even with a smallish heatsink.
The general performance level is only that of a first gen maida, but this is sufficient for lots of applications, and unlike maida-type regulators, they can accept any arbitrary level of abuse (depends on your design options and components choices, of course)
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Old 8th February 2014, 12:53 AM   #9
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If you bridge rectify the end to end 460 VAC and cap. I/P filter, you get (ignoring losses) approx. 650 VDC. Hybrid bridge rectify the 460 VAC with snubbed, series wired, pairs of UF4007s on the "cold" side and a 5R4 on the "hot" side. The forward drop at 250 mA. of a 5R4 is a whopping 67 V. That loss is favorable here, as the Maida regulator will have to dissipate less power.

Energize the 5R4's filament with a CT 5 VAC winding. Take the "raw" B+ from the CT. Insert a CL90 inrush current limiting thermistor between the CT and the PSU filter. Use a 22 μF. cap., at the filter's I/P.
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Last edited by Eli Duttman; 8th February 2014 at 12:54 AM. Reason: punctuation
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Old 8th February 2014, 10:27 AM   #10
el156 is offline el156  Portugal
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Thank you very much for the advises here, i will build the circuit and see how it behaves, and maybe order 2 boards for the Maida regulator ,wich seems to be very good for my needs
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