[Diy_efi] Re: peak-and-hold injector driver ic's

[Marcell Gal]

Hi, 

Klaus Allmendinger writes:
> be wrong in something as simple as the attached design?

simplicity: exellent 

I also thought about the emitter-follower design
driven by a CMOS gate.
But would CD40106 not burn at 14 V supply? Maybe a diode
at GND and another at VCC can effectively decrease its
supply without having much effect on FET operation.
(if it worx, my circuit can use the same and get rid of a few
components). 

> Example: 1.2 Ohm Injector, 12V battery voltage, 1A hold current. R-Limit =
> 10.8 Ohm. 

So in hold mode efficiency is about 10%. Much worse than
with pulse-mode flyback current limiting.
Adding those 8 simple components (sum ~ $1) worth
the efficiency, I think: 

http://x-dsl.hu/genboard/injector/ 

I uploaded injdrive2.pdf
(thanx to Alexei Pavlov for his valuable comments) 

injdrive and injdrive2 are very similar.
There is a small difference around Q4.
Some will like one, others the other. injdrive2 has a little higher 
dissipation, but
setting values might be simpler since margins are higher. The same PCB can 
be designed that can be populated
either way. Look at injdrive.txt for more info. 

Marcell
-- 
+36 70 2 654 789 

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