Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

50 watt voltage doubler for 6 to 12 volt motorcycle

Status
Not open for further replies.

Zeph

New Member
Hi there, I'm new to the forum. I went to electronics school about 200 yrs ago so my theory is rusty. I have a 6 volt motorcycle and want to run 12 volt lighting. I have 6 volts AC+- at the alternator. I was concidering a transformer before the regulator/rectifier but weight for a transformer that would handle that much current, (approx. 10 amps on the primary) would be prohibitive. Any ideas if I can build a doubler that would handle 50-60watts on the output at 12 volts? Thanks Zeph
 
Well, there's 3 ways to do it- a capacitive voltage doubler, a transformer, or an inductor-based DC/DC converter.

The cap doubler has many things going for it, it's theoretically lightweight, simple, and doesn't draw much idle current to stay on with no load. However I have trouble picturing the capacitors which could handle 50W. That's over 8 amps ripple current (4 amps in + 4 amps out running through the cap). Even most tantalums have ratings like 100 mA or so.

The inductor would have to be quite large, a transformer would be a better choice.
 
Your only practical solution would be rewinding the alternator for a 12V output. You'd have to replace everything (ignition coils, etc) to run of 12V.

Transformers are designed to run at a particular frequency. Your alternator puts out a frequency dependant on the engine REV's. Too wide a range here for a transformer.

You *could* use a DC to DC converter but finding a suitable one at this wattage might be an expensive alternative.

Voltage doubling with capacitors does not sound practical at these load levels.

Klaus
 
Try this
You can winding a another coil on the origial coil

Zeph said:
Hi there, I'm new to the forum. I went to electronics school about 200 yrs ago so my theory is rusty. I have a 6 volt motorcycle and want to run 12 volt lighting. I have 6 volts AC+- at the alternator. I was concidering a transformer before the regulator/rectifier but weight for a transformer that would handle that much current, (approx. 10 amps on the primary) would be prohibitive. Any ideas if I can build a doubler that would handle 50-60watts on the output at 12 volts? Thanks Zeph
 
The TDA1562 is a high power audio IC that operates in class-H.
It has a voltage doubler inside and switches the power supply voltage from normal for low levels to the doubled voltage for high levels.

Unfortunately its minimum supply voltage is 8V, not 6V.
 
I think that a boost converter is feasible. I'm looking at the MAX668 at the moment for another application and it strikes me that this IC would work well for you too. Should be OK with 60 watts as it uses an external FET, which you can tailor to the power of your application. Have a look at the examples in the data sheet.

Only thing is that homebuilding a high power boost converter is a bit tricky since the currents circulating between the FET, the diode and the output caps is very high and has fast edges with lots of high frequency energy, so you have to be quite fussy about short low impedance connections. It is often best to copy an application circuit and PCB layout given by the IC manufacturer. Sometimes it is even a good idea to buy their evaluation board and just use that.

Of course, this idea doesn't take advantage of the availability of AC, but going from 6VDC to 12VDC is pretty standard stuff, so there's lots of support out there.
 
Last edited:
Don't forget that the input voltage is 6VAC unregulated at some frequency probably between 100 Hz and 1 KHz.
 
Just use a tranformer with a 6V-0-6V secondary as an auto transformer.
 
At these frequencies it would probably work pretty well. Might want to keep track of the temperature at first, at high RPM. But then again, at high RPM there'll probably be plenty of airflow.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top