CDI requires an appr. 400V DC supply
We want to be safe, so 100W power should be targetted (0.25A output current).
Input is 14V as usual.
I was thinking about CDI supplies. I built a transformer based supply earlier (somewhat lower wattage).
The best I can come up with is a simple flyback design. This has the lower part-count, beautiful simplicity (including testing!) If power was >300W a transformer based might become more attractive.
We need to use many thruhole parts in any case.
Flyback design consist of only 4 major parts:
- inductor
- switcher
- diode
- output capacitor
Inductor - (note: not transformer)
For experiments we can use 4 of these in parallel:
- 47 uHy 1.5A 0.14R 10% RAD * (BOU) RLB0914-470K 9.5
Finally we'll wind our own toroid or whatever type.
(12V / 12uH) < (16A / 16usec)
16A peak is a bit high (for the IGBT too, and definitely for the diode). 16A peak means about 16A / 2 * 12V=100W.
IGBT
similar to what we have now, but to make 400V possible, clamping at 370V is not desired.
FETdriver is needed to drive the gate at 64 usec (15625 Hz).
Diode
To get 10A diode from 5 pieces of 2 A diodes is slightly more complex than simple parallel connection because of the -2mV/K temperature coefficient, the one with lowest voltage will overheat itself. Series resistors (for each diode, maybe trace is enough) can fix that.
- BY399 (3A continuous, 600V) dropped (thruhole not justified)
- SMB footprint fast ES2J that we use all over the place is perfect
Maybe 6..7 SMB in parallel and 0.022 Ohm in series with each.
Caps
Electrolitic cap is not the best idea at 16 usec period.
It might even explode. Some testing is needed in any case. Other cap that might work:
- 2uF 450V 10% . MOTOR MP60020061 (DNA) 25x52mm M (1.4 Euro)
0.25 A * 16 usec = 4uC
4uC / 2uF = 2V (ripple)
Can I proposse another supply typology?
I don´t know if i should publish this here. I think you are decided about flyback, we are not sure about flyback for this aplication, I and a friend are making some testings with single-transistor-forward-converter, we think this is the equilibrium.
The transformer is a EE30 (30mm width), frecuency is about 300Khz for 100W.
Size is shown in picture: cdi2.jpg
There are also horizontal transformer, it is better for ecu shape.
Transistor is the same than injector (20N06) but maximum current exceed 20A and we have to select another one.
The proposed shematic are this (very provisional)
