50Vdc - 300Vdc to 15Vdc

In message , dated Wed, 2 Aug 2006, snipped-for-privacy@gmail.com writes

Once again, HOW MUCH CURRENT? That profoundly affect your choice of techniques.

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OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

You can buy this from any broad-line distributor - most small universal switching power supplies just diode rectify mains AC into a reservoir capacitor, and use a switching regulator to get 15V DC (or 5V or 3,3V as required). At least some of them let you by-pass the rectifier.

You need a decent text-book on switching regulator design - I've got Abraham I. Pressman's "Switching Power Supply Design" ISBN: 0070522367 which is still in stock at Amazon nine years after it was first published.

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Bill Sloman, Nijmegen

John Woodgate ha escrito:

Hi, thanks for your fast asnwer, the current is ver low, the maximum it could be 1 Amp, i have been looking for schemes to obtain the 15v but the only ones that i have seen have and input not bigger than 40v.

snipped-for-privacy@ieee.org ha escrito:

Do you think that my problem is difficult to resolve? if is difficult to do i'll desist, and i will buy something that do it, i have seen some schemes that converts 40v to 15v using a zener and some capacitors, but i'm not sure if i can do the same with a input variable and with a maximum value of 300v.

Thanks for all your response.

In message , dated Wed, 2 Aug 2006, snipped-for-privacy@gmail.com writes

For you to do it yourself, yes. 300 V in, 15 V at 1 A out, that's 285 W that's go to go somewhere in a linear system. You need a switch-mode system (even though I don't like them - nasty complicated things). And you don't stand a chance of designing one with such a wide input voltage range. That requires a very skilled designer.

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

--- If you want a 15 volt output which can supply 1 ampere into a load, then that means that if you place a linear regulator between the

300V source and the 15V load, the regulator must drop the voltage from 300 to 15, while allowing 1A to pass into the load. That means the regulator must dissipate:

Vin - Vout 285V P = ------------ = ------ = 285 watts I 1A

Find a DC to DC converter which will do what you want and you'll be miles ahead than if you tried to design it yourself. Perhaps light years, even.

-- John Fields Professional Circuit Designer

1A at 15V from a 300V source isn't a low current. If you wanted to use a linear regulator. you'd have to be able to dissipate 285W in the series element. This is difficult.

A switching regulator can offer efficienies of 95% and higher, which would mean that you would need to dissipate less than a watt in your switching series element, which is a lot easier to manage.

Switching regulators are relatively tricky, but - as I said - they are a mass market product, so you should be able to buy an integrated circuit that does most of the work. I've not worked in the area, but Supertext does appear to have that kind of part

Here's hopng that we can get some advice from somebody who has worked on this sort of circuit.

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Bill Sloman, Nijmegen

try the viper from st.com

martin

Hi, thanks for all your answers, i explain for what i'm going to use the ciruit, sorry for not explain before. The circuit is needed for an inverter, the inverter uses a power supply that is going to be in a range of 50v to 300v, and to drive the igbt's i use a ir2110, that needs a 15v supply reference to the same ground than the 300v, i'm not going to make the 300 v power supply, i will buy one, and my idea is connect the power supply to the inverter and using a dc converter obtain my 15v to the ir2110, another solution is from the 220Vac source of the 300v power supply, obatin the 15V using a transformer and a 7815 or something similar, this is much easier but i'm not sure if the 15v that i obtain from the 7815 are reference to the same ground than the

300v. I said that i need to obtain a 1 amp current, i think that the two ir2110 (there are 4 igbt's), aren't going to consume that current, and it will be lower. I hope that everybody understand what i mean.

snipped-for-privacy@ieee.org ha escrito:

Hi, thanks for your answer, that circuit is ideal for my case, and i have been looking for some applications, and i have found this

and is not a difficult circuit, and i think i could do it by myself. Thanks for the help.

martin griffith ha escrito:

Thanks for your answer martin, i have been looking for the viper, and it's another good solution, the viper support a 265Vac input that in dc is 375, i think if finally i use the dc converter, i will use the viper, st has excellent information about them.

Finally, thanks again for all your answers

Our pleasure. It often takes longer to get the right advice, and we don't always get the original poster coming back and saying what they are going to do, though we really do appreciate it.

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Bill Sloman, Nijmegen

He could use a water cooled linear. It would be easier for the unskilled in the mysteries of switchers.

How well regulated does the 15V need to be? Do you have the room for an assembly the size of a 2 drawer filing cabinet?

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kensmith@rahul.net   forging knowledge

Hell. He could use an air-colled linear, if he split the current path into a sufficiently large number of parallel elements, but to a large extend that would be swapping the mysteries of heat dissipation for the mysteries of switchers - heat sinks don't perhaps offer the same breadth of opportunity to get things wrong that you can find in switchers, but I blew up my share of TIP3055 power transistors working out how to get rid of 800W into a water-cooled heat-sink after making exactly that choice back in 1972.

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Bill Sloman, Nijmegen

Ken Smith ha escrito:

Hi, thakns for your answer, the 15v according to the ir2110 datahset, it must be between 10V and 20V, and yes i got a room with that size.

I think that i'm killing butterflies with boms, this is a common expression here in my country spain, and i hope that everybody understan what i mean, i only need a 15V supply for my ir2110, i got a

300 v power supply for the inverter, and i need to get 15v reference to the same ground that the 300v, the 300v power supply is connected to the power line (220Vac), if i get my 15v from the 220Vac using a transformer and a 7815, the 15V that i get, will be 15v reference to the 300v ground?, i hope that everybody understand me, sorry if my english sounds a little bad, thanks again for all your answers.

Ken Smith ha escrito:

- Ocultar texto de la cita -

- Mostrar texto de la cita -

Hi, thakns for your answer, the 15v according to the ir2110 datahset, it must be between 10V and 20V, and yes i got a room with that size.

I think that i'm killing butterflies with boms, this is a common expression here in my country spain, and i hope that everybody understan what i mean, i only need a 15V supply for my ir2110, i got a

300 v power supply for the inverter, and i need to get 15v reference to the same ground that the 300v, the 300v power supply is connected to the power line (220Vac), if i get my 15v from the 220Vac using a transformer and a 7815, the 15V that i get, will be 15v reference to the 300v ground?, i hope that everybody understand me, sorry if my english sounds a little bad, thanks again for all your answers.

I have looking for ac/dc converters and i have seen this

that circuit adapts perfect to my case, and is not very expensive

30=80.

In message , dated Thu, 3 Aug 2006, snipped-for-privacy@gmail.com writes

It will if you connect the ground sides of the 15 V DC and the 300 V together. I'm really worried that if you have to ask that question, you are trying to work a long way ahead of your technical insight. I think you need local assistance, not help from 1000-plus kilometres away.

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

John Woodgate ha escrito:

Of course it will if i connect both ground sides, but my question is i connect the 300V power supply, and with the same connector, i connect to the transformer and the 7815, then the grounds will be the same? i suppose that yes, but i preffer to ensure me.

In message , dated Thu, 3 Aug 2006, snipped-for-privacy@gmail.com writes

I'm sorry to have to emphasise the point, but your response is nonsense and you need local help.

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

It's not necessary to be english to understand your problem.

The ground is just a name for a wire. Usualy the ground coud be connected to the earth potential (called also protective ground) but is not allways necessary So, you may use without any fear a different power supply from 220V ac (with transformer, rectifier, filter and a 15V stabiliser) and connect the "-15V wire" named say "local 15V ground " with your 300V DC "ground" wire.

In that way you have a common ground and a +15V for your driver. The transformer used for this power supply must met insulation requirements (at least 1000V dielectric isolation between primary and secondary) and if indeed you need 15V/1A, the 7815 must be a 3A TO3 package mounted on the heatsink because it need at least +4V more than 15Vdc (so it will dissipate at least 4V*1A = 4W at minimum main value and much more when the main voltage is at maximum value (the power main supply could be

220V -15% +10%)

greetings, Vasile

sounds like some sort of "buck converter" would fit the bill

google for "switched mode" "buck converter" and "design" and you should get a few leads.

Bye. Jasen

if it's from a transformer you can typically reference it to any one point you wish. with a DC-DC converter you typically end up with the same ground as the supply.

The DC-DC convertter sounds like more fun, but using a prefabricated 15V supply will be easier.

Bye. Jasen