Jan Heijkamp said:
I am building a cdi ignition for my motorbike.
There is enough available on the web but I can not find how to make a dc/dc
converter that is small enough to place on a motorbike. What I have found
has a large transformer.
I need a dc/dc 12/200V converter and the power is approximately 20 watt.
Knows anyone how to build this converter?
ive built a few of these many years ago while I was at Uni for my suzuki
gs550, some more reliable than others, I managed to get one down close to
the size of a cigerette packet but this was too small and was unreliable as
it got hot.
if you look at several of the ferrite manafacturers you find data sheets for
their cores wich give tables for the size of the transformer you need versus
operating frequency. you should be able to get quite small for 20w.
especialy as you can go quite high frequency with a mosfet where as i was
having to use discrete darlintgon setup.
i used the circular pot core for my designs, and an auto transformer style
winding.
I used 2 gates of a cmos hex inverter IC as a simple relaxation oscilator to
control the switching transistor wich sensed when the colector voltage of
the transistor fell below 12v to switch it on, it also sensed when the
capacitor voltage reached full voltage.
the other 4 gates to control the 2 firing signals for the thyristors - two
coils for 4 cylinders as motorbikes dont have distributors like cars.
the charge per cycle design is interesting here but the size of inductor you
would need to store 0.1 joules every cycle is rather large i would think.
Colin =^.^=