DC to DC Converter

Available space appears too small for a 500W converter (well none that i'm aware of). Is it perhaps possible to run the system off a 24V battery system instead, and use a much smaller 24-12V converter to power the 12V side of your system? Otherwise you may need to add an external 500W power supply.

Good afternoon

Have you thought about going mechanical? I have a 12V to 24V motor Generator made by Allied Signal lying on the shelf at home and it is about 13cm (L) x 6cm (D)cylindrical. My local Jaycar parts shop has 12 and 24 v DC motors which would couple together with a belt which are capable of 500W and they are very cheap and would fit within your space. Alternatively have you considered a simple Flip Flop driving a voltage doubler circuit folowed by a rectifier?

500W at 12V is ~41A. Jaycar hobby motors are not capable of this (the largest size they do is 12V 107W), so you would need 5 of them (=poor overall energy density). The efficiency is also too low (the DC motor alone would take up 1/2 the available space and only has an efficiency of <=71%). This type of small scale generation/conversion is not used anymore except for some very niech applications.

RF transmitters draw a lot of current during trasmit. As an example, our 12V 25W 500MHz transmitter draws about 7A during transmit. Hell, I had an application with a GSM mobile router that drew over 30W during transmit. Simple voltage doubler circuits cannot handle the current.

yes, a 90% efficient converter at 500 watts = 50 watts waste heat(although you might be able to get a device from a specialist supplier that is as high as 95% efficient. That means contacting MIL SPec suppliers in the USA/Europe and they will cost big $$

. It seems as if you had to go to 24 volt RF power FETS as you could not do it with 12 volt units because of the need for 50 ohms out and 500 watts. Try designing for an output impedance of 25 ohms and add an output transformer. That way you may be able to get 12 volt devices good for 500W...unless I am off on a tangent?

Thanks for your answers.. I need a reliable product with high efficiency. I can't design for 25 ohms the impedance must be 50 ohms. I can't use any mechanical solution.

EMI is very important for me. Converter must not be affected from high RF..Exactly, i would like to know mil. spec. supplier which has this product. But time is the other important parameter for me so i haven't any time for research. Because of this i asked to you, maybe one of you used before smilar product. Price isn't my priority for now. But if it'll be around 200-300 $, i'll be happy. I would like to say my quantity will be high..

note: dear Colin Wonfor, i'm not "sir" you can send to me information about your design nursel.yildirim@atelarge.com.. thanks for your sharing..

kind regards..

Dear Sir,

I have a working circuit if you would like a copy please let me have were to send it.

Regards CJ

Hi,

Have just registered but can't log in so hope this gets to you. Am retired psu engr in UK - spent 32 years trying to make psu systems work in military vehicles and aircraft.

Some mnfctrs make such psu s for vehicle use and are therefore very cheap. Can't find examples at present but will mail again if i find one. They untilize a non-isolated boost topology (Common -ve rail). Good news is this topology is very efficient and should be about 95% in a decent design. Bad news is that they are electrically noisy on the output side (quiet on the input side). You could make such a device up fairly easily using National Semiconductor LM3478 chip which does most of the design for you. If you look at the data sheet at www.national.com you will find a lot of helpful stuff. Such a boost design using this chip should achieve around 95% efficiency provided you don't use a silly high frequency and choose sensible fets.

Cheers,

Wayne Giles

You're really pushing your power density here. Have you thought about an isolated 12V to 12V converter, and commoning the positive output to the negative input. This will halve the power output requirement of the converter. Just a thought.

you can add capaciter bank, 30 v volt 600 micro farad to increace the voltage

How will this increase the voltage? Also, 600uF is FAR, FAR to small for even holding up the 24V of a RF transmitter during transmit (=high current draw), and don't get me started about the poor energy density compared to a converter.

Try VICOR, or DATEL, or BETA-DYNE. I've used these converters in the past.

I used vicor VJ-00 series for another application so i know this converters(beta-dyne, powerone, powerstax..etc. too) i must use master/slave operation because of power requriment but it'll be many unit so @12V input all of them're unapplicable for me. Thanks for suggestions.. i see there is only one way. I have to have custom design. Time is too short but i'll try..

with my thanks again..

you must use the power supply in some military equipment. This small size of power can be implemented by flat transformer at hf convert frequency. say 100khz to 500khz or even up to Mhz. there are serval modules on our market. how high size do you wanted?

Dear Friend,

My company has developed a DC - DC Convertor which looks to satisfy your requirements, although more information will be required regarding interfaces, height, working temperature etc.

If you would like to contact me at d2m.solutionsltd@btopenworld.com I would be pleased to help.

Regards

Melvyn

Hello fellow guest,

I was just wondering what the name of your company is. Do you guys have a web site?