RESONANCE EFFECTS FOR EVERYONE TO SHARE

[najman100]

@Najman100,

Looks great. :-)

But why trim the PCB? I designed the PCB so that you can mount the transistors
two ways. One, standing up and mounted to a heat sink. Or, lying down bolted to a L shape
alu. profile. Then the Alu. profile can be bolted to a bigger heat sink.

I some cases the user want to use a low load and then the PCB itself will be the heat sink.
That is way I have copper under the transistors. Same goes for the 7805 regulator. The PCB
will be the heat sink.

@TinselKoala,

You can always add a couple of wires to get your LED display. I did not put in anything extra
because I want the circuit to use as little power as possible.

Groundloop.

i did that for 2 reasons one is for the heat sink second for making 4 pcbs from the same pcb boaed i could not find bigger an di do not want to wist 3 board so  with 2 i will have 8 .6 for all of us and 2 in case i fkup in the process .
Najman 

[Groundloop]

@najman100,

I understand. Your doing a great job. :-)

Groundloop.

[Chris31]

@Chris31,

If you have tested this and find that it will protect the mos drivers, then why not.

Can you make a simple drawing and post it here?

Although Transient Voltage Suppressor (TVS) will do a wonderful job of protecting mosfets, they also kill any over unity
in the circuit, I think? Better blow some transistors and get over unity results than have a stable circuit that runs forever
without any o/u. Please share your thoughts about this.

Groundlop.

Hi

Its easier for me to show a link of a circuit based on an IR bridge driver. Although its not using the same part number but it essentially (should  ) have the same drive circuitry.

http://www.molla.org/DIY-CDI/SC-DIY-CDI-article-hires.pdf

If you check out the inverter circuit, you will see pin 6 of the chip is connected to a 22ohms, 22k and a diode. On my circuit Im only using 22ohms + diode. The article I read says to add 22ohms resistor, I did that and it seems to work fine, being a bit too cautious I added the diode as well anyway. I couldnt find the apps note, I remember reading it saying it was from IR and/or motorola.

Im using IR2109 on my CDI, without the resistor it kept blowing up.

As for the TVS protection, you are right, thing is when I set mine up thinking the internal diode across was enough the circuit was blown within 5 seconds. Powered by 340V DC rectified mains driving an ignition coil result is dead transistors + drivers within 5 seconds, those transistors are not cheap 

Well I dunno what to say really, I guess its better to protect them first so you can get the hang of it, once you feel the circuit is running well and all tuned up, you can always remove the TVS one by one to see if you gonna get OU 

Worst thing is, circuit kept blowing up and you could hardly perform any test, it could be very off putting. 

[Chris31]

I agree about the TVS potentially killing the "interesting" effects.
I usually put an additional fast diode across the source and drain of each mosfet, even though they have internal diodes, to channel the flyback pulse away from the transistor. But I feel the same way about these as I do about the TVS.
The driver chips are supposed to control the timing of the MOSFETS so that shoot-thru (both on) and no-current (both off) times are minimized. Other controller chips like the Intersil HIP 4081A have the capability to fine-tune these parameters.
There's some good stuff about power dissipation in MOSFET h-bridges in the Intersil application note:
http://www.intersil.com/data/an/an9405.pdf

Yes I seen those chips, but I like the IR products more for some reason Plenty of flavours to choose from. One can also add diode+cap+resistor on the gate to increase the dead time.

[Chris31]

Groundloop

Just a suggestion here,

I think there are alot of interest in this circuit, for easy replication, why not redesign for single sided PCB?

16F84 can be alittle bit expensive as well, why not use the more recent and common parts from microchip with ICSP for easy reprogramming?

Its probably too late now but maybe in the next revision, just a thought