Power supply for AMP in CAR

[nanopoylos]

HI THERE.
we all know that we can build amps for home use .
I would like to construct an amp for use in my car , with 12V supply .
Inorder to achieve many Watts , we should raise the voltage of the car battery to 40 or ever 70 volts .
As i know we should use a power converter .
I would like to have a diagramm or an idea of how i can do it .

 

[EDY2]

Check this out

http://sound.westhost.com/project89.htm

Cheers ;D

 

[MP1]

Another way would be to take the power inverter diagram from the projects section of this site and modify it.
I am referring to this project-->
http://www.electronics-lab.com/projects/power/018/index.html

Method 1:
Instead of using a tansformer that steps the voltage up by 10, use one which will step it up by 3 or 4. This is accomplished by the number of windings on the primary vs the number of windings on the secondary. You do not have to modify a transformer, they come in different types. Once you have the correct voltage out (or close), rectify it for DC and regulate it or use a voltage divider to tweak it in to the exact voltage you want.

Method 2:
Another way to accomplish what you want with this circuit is to use a voltage divider on the 12VDC to make it only 4 volts. Since this is a 10 times step up circuit, you will have 40 volts AC.
At the output of the transformer, you just run it through a diode to rectify it and add a large cap to smooth out the remaining AC.

Method 3:
Use the circuit "as is", run the output through the diode rectifier and add a cap for ripple rejection (DC voltage), then use a voltage divider or regulator circuit to trim it down to the voltage you desire. This could be done with zener diodes and resistors.

If you need a bipolar supply, you can run the output of the transformer through a bridge and get -40 as well as the +40 volts.

So you see, there are some choices.

MP

 

[hotwaterwizard2]

The problem with this design is Current handling capability.
The project you are looking at is only about 5 amps and a 100 watt Amplifier needs about 20 amps. You should make sure the transformer is 20 amps or better and use about 8 of the 2N3055 transistors 4 and 4 hooking three in parallel with each original.
Also see my post on the subject.

http://www.electronics-lab.com/forum/index.php?board=22;action=display;threadid=222

 

[hotwaterwizard2]

Here is what I have so far:

 

[MP1]

You will need some current limiting power resistors on the emitter side of the power transistors unless you are going to use MosFets. The reason this is done is because power transistors like the 2N3055 are not matched. Current will flow through them differently from one to the next. Because of this, when you parallel them together like this, you will have one that will be less resistive than the others and will take all of the current load and overheat itself. The power resistors are a safeguard. Something in the 0.1 to 0.22 ohm range with a fairly good watt rating will work.

MP

 

[hotwaterwizard2]

Show me where to put these resistors.

 

[MP1]

Cut the connection of the emitter to ground. Put 1 each between the emitter leg of the transistor to ground. You will not even know they are there as far as amplification of your circuit. But if they are not there and the system draws a lot of current, you could have a melt down.

MP

 

[ante1]

Hi MP.

I

 

[MP1]

I would not leave them out.
Why should the current run through these 2N3055s equally? There is nothing there to cause it. There is no balance here. The resistors will cause current to flow equally through all of them. If 1 2N3055 is doing all the work because it has the least resistance, you have a problem, don't you agree?

MP

 

[hotwaterwizard2]

Something like this?

View attachment 35140

 

[ante1]

Hi MP.

I agree to that, but even if one resistor (transistor) is smaller they are all in parallel. I don

 

[hotwaterwizard2]

For the sake of this discussion you may want to read this info:

http://www.qsl.net/xq2fod/Electron/Ps20/Ps20.html

 

[MP1]

Yes, that is exactly what I meant. The diagram in the article you have posted also gives a little better detail regarding the reason behind this.

MP

 

[hotwaterwizard2]

I found my original drawing with better resolution and modified it. Here is my new working diagram. This circuit has not been tested yet it is a concept drawing for R&D purposes.

View attachment 35143

 

[Kasamiko]

Hi hotwaterwizard,
The schematic you attached seems interesting..can you tell me the value of transformer you used?? and the two oscillator transistors??
Thanks.

 

[hotwaterwizard2]

I haven't built this yet. I am working on the design with help from people like you. I am thinking about 2N2222 or 2N2222a. As for the Transformer I am thinking about a Toroid hand built transformer with a center tap secondary for a split power supply = + 40v

 

[ante1]

Hi MP & hotwaterwizard !

I, we checked the link and it was nice reading, lots of good thinking and valuable info. But this project is a linear one and stubborn as I am I still state that switch mode is very different from linear. You don

 

[MP1]

Yes, I work in the consumer electronics industry. I have also seen the amazing things that the industry gets away with. :Consumer electronics is not based on good design. It is based on how much money the company can make. If you can leave out several 20 cent parts and sell several hundred thousand units that will still make it past the warranty period, then it is considered a good thing. The goal is met. One should never base good design on this. One can always base good profit on this.
The only thing the resistors will do is control the amount of current flowing and insure that all paths to ground have the same resistance. When you have several paths to ground all open at the same time, the flow is going to take the least resistive path. That is a built in law with electronics.
I appreciate your stubborness. In fact, I respect you for standing on your opinion. If you want to research this further, please show me an engineering article which backs up your claim.
By the way, the MOSFETs are different. You do not need resistors on them.
MP