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golam

Member
Joined 2008
Hi
Very interesting site but could not understand much as my effort to translate it in English from Turkish was futile. English translation by any means or by anybody is welcome.

Hi geb, can you help in this regard, so that we can enjoy your site?

Thanks.
 
gev

gev

Member
Joined 2005
320volt.com
Pabasarak said:
Hi All

I am trying to build 750v 125W SMPS. guitar_joe, u were saying that you got some documents. can you please post them here.

my main problem is coming up with a suitable transformer. can anyone please help me with that?

Thanks
Click to expand...

Link 750v 125W SMPS http://www.siliconchip.com.au/cms/A_102096/article.html

An externally hosted image should be here but it was not working when we last tested it.



Valve circuits are not yet dead. While transistors are undoubtedly superior in most applications, the valve still offers several unique advantages. This applies first and foremost to its use in power circuits.

There exists a substantial body of opinion that valves outperform transistors in high-quality audio amplifiers, especially in the power output stages. The seriousness of these claims is reflected in the fact that some very reputable manufacturers offer valve amplifiers at the top end of their audio range. For the home constructor, reasonable-quality valve audio amplifiers can be made for a modest outlay using designs available freely on the Internet. These amplifiers are generally based on an EL34 or KT88 valve pair in the output stage, with both valves being readily available in Australia.

Another common application for valves is in the output stages of RF power amplifiers. They will operate satisfactorily at frequencies of up to about 30MHz, delivering up to 50W per valve. Their main advantage over RF power transistors, apart from being somewhat cheaper, is that they are much more tolerant of fault conditions.

When tuning a new power amplifier design, parasitic oscillations are often encountered which can easily destroy expensive RF power transistors. The valve, however, will live to see another day. Valves are therefore much more suitable for experimentation in new designs.

Although valves are readily obtainable, one of the main problems in their exploitation is the lack of suitable power supply transformers. Both the EL34 and KT88 are rated at a maximum plate voltage of 800V, with supply voltages in the order of 500-600V needed to extract maximum power and linearity. However, the only readily available high-voltage power transformers are isolating transformers, which deliver 240V, and magnetron transformers from microwave ovens, which deliver 1500V or more.

Clearly, both of these are unsuitable for our application.
 
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