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Old 12th February 2003, 07:14 PM   #1
audioPT is offline audioPT  Portugal
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Unhappy 12 to 35-0-35V

Hi!

I've read Rod's project for 12 to V-0-V convertion.

But I need more power.

Anyone know where I can find schematics or datasheets?

I'm interested in making 6ch power amp for my car (2 front, 2 rear and 2 bridgeable for the sub)

Thanks in advance

Pedro Martins
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Old 12th February 2003, 08:22 PM   #2
JBL is offline JBL  Canada
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How much power the converter on rod site can esealy go to 300 watt of output and probably more with more MOSFET in parralel and big enough core.

or just build two of them and split the amps on two power supply.
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Old 12th February 2003, 09:05 PM   #3
blmn is offline blmn  Brazil
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Pedro,

As JBL said, more fets, a bigger core (sometimes the same core can be used) and attention to the rectifiers and filtering I suppose it might work. Some adjusts in compensation network, snnubers and dead time might be necessary to improve efficiency and stability.

I designed a switchmode power supply very similar to Rod´s one, using SG3525 pwm controller and, using the same topology, with 3 MTP50N06 mosfets per phase it pumped out almost 1KW to the power amps! Lots of cooper on pcb´s SHORT tracks (it drains near 85A from the battery!!!) and a very careffuly layout are mandatory.

Saudações
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Old 12th February 2003, 09:12 PM   #4
audioPT is offline audioPT  Portugal
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Hi blmn!

Thanks 4 that!

When I have all done, I'll post here the schematics and the pcb layout!

With large tracks!! of course!

Translation to portuguese:
Obrigado por isso!
Quando estiver tudo feito, coloco aqui o esquema e o circuito impresso!
Com pistas bem largas, claro!

Cumprimentos
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Old 12th February 2003, 09:16 PM   #5
audioPT is offline audioPT  Portugal
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Forgot this:

The layout of the amplifier:Click the image to open in full size.
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Old 13th February 2003, 12:26 AM   #6
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Quote:
Originally posted by audioPT
Forgot this:

The layout of the amplifier:Click the image to open in full size.
Try to move your filter caps to the left and right of your transformer. this should help to reduce the trace lengths of your high current leads. This in turn will reduce total leakage inductance.

If you have a scope, great. If not, get one, get a good one... ...you'll need it.

There will be two critical things you will need to test for. Overvoltage on the switching devices due to fast turn off times in your switching transistors is one of them. To have any efficiency, you will want relativley low voltage fets (50 or 60 volts) because they have lower Rds-on resistances. But, any leakage inductance and fast switch times will kill your devices.

Also, you will need to watch dead time of your switching devices. If one of the devices is still on when the other turns off, you will cause an effective shorting on your transformer, thus inducing large current draws that may cause damage to the fets (otherwise known as cross conduction)

Keep in mind both of these are opposing problems, as the solution to one may be the cause of the other!

I'm sure we are all willing to offer help, if you are serous about the project. Keeps us updated on your progress! I personally would like to hear about it as you go.

-Dan

P.S. I have a pic of my supply in my introduction thread... ...if you're intrested. (Around 2Kw from 12 Volts)
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Old 13th February 2003, 12:33 AM   #7
JBL is offline JBL  Canada
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Hmm look like alot of capacitor for a switch mode power supply
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Old 13th February 2003, 12:13 PM   #8
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Originally posted by JBL
Hmm look like alot of capacitor for a switch mode power supply
Wonder what the loop response is like... ...fast or slow...
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Old 13th February 2003, 07:54 PM   #9
audioPT is offline audioPT  Portugal
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It's only a first drawing...

Bt thanks anyway for the advice
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Old 13th February 2003, 08:44 PM   #10
blmn is offline blmn  Brazil
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Don´t cry Pedro,

You can use these quantity of capacitors in the 12V input with no problems, in large capacitance values. Use 105C temperature types.

And regarding output filtering, you can use many paralell low capacitance value low esr 105C types.

I think you are able to mantain your fine drawing, if you want to, but you have to take care of capacitors position and the others tips of dkempai .

Saudações,
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