Need good simple 72v to 12v buck presently useing single transistor & zener.
Any suggestion please.

Thanks.

What is the 12V needed for, and why can't you just use a 12 volt battery dedicated to that purpose? You already have lots of batteries in that car...what's one more gonna hurt?

 

Kermit2

I need 12v to power pwm circuit from the 72v of the controller.

please suggest.

 

If a seperate battery is out of the question then

try this

http://www.alliedelec.com/search/productdetail.aspx?SKU=8000246

Accepts up to 76 volt input DC and gives 12 out. If you need more than an amp of output power then the prices get up into the $100 to $300 dollar range. This small unit is $23.xx plus shipping.

 

Thank Kermit2.

Specs of suggeted item is perfect, But most build from scratch. Here is pic of wat i hav presently. Please make improvment.

Thank u.

 

There are no values on the components in that drawing. I could add some color to the parts.

How can I make an improvement unless you give something that works first? Component values will determine operational parameters,which can then be adjusted to bring the performance into a range that you find acceptable.

I'm not going to build it for you...I don't need an electric gokart. I WILL help you correct problems. sketches without component values are useless to me and you as well. Build something that at least tries to work, and we will help you make it better.

 

tracking this topic with interest

 

Sorry about that here are the values.

 

Well that ones useless, even with a whole magnitude of lower resistance there isn't enough current draw to turn on those zeners

According to LTspice that is. Do YOU have the free spice program?

You can build your circuit and check it's operation and make changes and check it again, in a lot less time than breadboarding. I'm trying it out now(for the last couple of days) and it seems to work great. I have spent my whole life making stuff by breadboarding the circuits. Spice is much easier and quicker to use and doesn't let out any of the magic smoke if you hook things up wrong.

What do you get for voltages on the circuit you made the schematic from? Did you actually build it? or just want someone to check it for you, without actually building it yourself? That's okay, but you could get many more answers and figure things out quicker with a simulation program...

What say you?

 

built and tested at 48v & got 12v out (actually 15v i used a 15v zener). not tested at 72v.

Thanks i am going to chek out Spice.

 

Yes please do.

And build that circuit just like you drew it. I did and got zip for an output. Unless you count picowatts as a useable output. You are far ahead of me if you got 12 volts out of the circuit on 48 volts.

Since I was playing with spice and wanted to keep things simple with low wattage resistors and a single 2222 transistor I made a circuit that functions; according to spice at least; so here it is.

 

This circuit actually built and giving 15v from 48v, runing pwm. TRANSISTOR & 15k get a little warm.

probably replace 15v zener with a 27v, and feed the 27v in to an lm317 to get 12v reg.

 

I just had almost the same thought, but was going to suggest he put two of the 15V zeners in series and maybe use a bigger transistor, like a 3055

 

Thanks, that's a good idear will do that.