Dual polarity power suppply

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Jackdaniel

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Hi..

One of my friends wants me to build him a 2.1 amp which is supposed to power from a 12V Car battery, thus the problem is i want to use tda2030a ICs (4 OF THEM<<2 for sub.wf) and it requires a DUAL POWERSUPPLY!!! so the real question is how can i get dual powersupply from that single supply battery? Any ideas/circuits?
 
You'll need a couple of boost converters, one normal polarity, the other an inverting one to generate the - voltage. Look it up here or on the web.
 
i want make it simple :C Please help me for god's sake!! bcz i assured him that it is very inexpensive and can build within a day..please help me
 
You can't simply get a -12V from a +12V supply. It requires a high power switching regulator.

If you look on page 4 of this data-sheet you will see a schematic for using the amp with a single supply voltage. Of course, the power is significantly reduced from using two supplies.

But the tda2030a does not work particularly well for automotive 12V applications. For that you should use an amplifier designed for automotive use that has a bridge type output to give the maximum power from a single 12V supply, such as the TDA7396.
 
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Thanx crutchshow, by the way i am trying to fix a switchmode power supply and found it got short circuited bcz of the one who tried to change the fuse used a copper wire intestead of fuse when it was blown! And When i tested the 3 of 4 1n4007 diodes r shorted and 400V 22uf cap also blown! And i got a MF7210D9 cap which is a black round cap and when i test it it shows short! Any help? Would be there any problem in that transformer or Power transistor? Help me
 
Hey Jack.... I work in the crane industry and some electric cranes have an "Idle Booster" when the crane is Idle there is a boost to the V+ rail... The unit is called a field generator and generates +18 / -18 from a 9 - 12 volt supply.... If you can wait till Monday I can post the circuit...BE WARNED!! some components are quite large as this can provide 3A across the 36V.
 
Did the new cap show a short before or after you put it in the new circuit? How did you test the cap for a short?

Not too likely the power transformer is bad but the power transistor could be.

What type of switchmode power supply is it?
 
Hey, I just thought of a way to get -12V form a battery, and it will only take 5 minutes. This is probably not the solution you're looking for, but it since you're in an all-fired hurry, it just might fit the bill. Get an inexpensive commerical "invertor" and a 12V power supply. Connect the inverter to your battery and plug in the 12V supply. Now use the + output for your ground and the ground output for your power rail.
 
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crutschow said:
Did the new cap show a short before or after you put it in the new circuit? How did you test the cap for a short?
Click to expand...
i used a continuity tester that made by me and i did't use a new cap but the cap used in the fried circuit has already shown short! And 1 end of the cap was connected directly to the mains and other end to a fuse!

crutschow said:
What type of switchmode power supply is it?
Click to expand...

they have printed out on the case - input :~ 220-230v AC 50/60 Hz

Output:~12V 1200mA, it was using to power a small LCD TV, now i found that the entire circuit on the PCB of the powersupply has destroyed! So now i am thinking i can Use a 12V 1.A linear transformer instead of that switch mode powersupply! Is that possible? Might i need increase amperage and use a regulator like LM317T? pls help crutchshow..
 

What's the power consumption of the TV? If it draws more than about an amp, then no, you can't use either the SMPS or a 1A transformer (by which I presume you mean a 12V, 1A DC power supply).
 
You can use any power supply, linear or switching, that provides at least 1.2A at a regulated (some wall-wort types are unregulated) 12V. You shouldn't need any additional regulator.
 
crutschow said:
You can use any power supply, linear or switching, that provides at least 1.2A at a regulated (some wall-wort types are unregulated) 12V. You shouldn't need any additional regulator.
Click to expand...

but crutchshow, how do i regulate the 12V Without using any regulators? Maybe the transformer will pass around 14v or 16V After rectification! Any idea there?
 
Jackdaniel said:
but crutchshow, how do i regulate the 12V Without using any regulators? Maybe the transformer will pass around 14v or 16V After rectification! Any idea there?
Click to expand...
I was talking about wall-worts or other types of power supplies that have build-in regulators. If you just have a transformer and rectifiers then, yes, you will need a regulator.
 
hi crutchshow,

i built the powersupply that provides 1.4 A But the powersupply is in a small case with plugs to connect to wall socket, i cant fiddle anymore components inside it so i did't put a regulator. I measured the output after bridge (without filter capacitor) and it shows about 11.98V DC and when i added a 25V 2200uf cap it shows around 18V! Is it dangerous to the load equipment as it requires only 12V? Or is it normal as the capacitor being charged? Maybe the voltage will become 12V when it connect to a load.. Pls help
 
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