Re: Help! Peak-hold injector driver design

[steve ravet <sravet@arm.com>]

This is really a question for diy-efi or efi-332....  The answer is yes,
there are chips that do exactly that.  One is the 1949 from National
Semiconductor.  The efi-332 list has designed/built 2 driver boards
based on this chip, capable of driving ignition or injector coils, and a
3rd universal one is in the works, that will drive peak and hold or
saturated type coils.  Check the WWW page, there's likely to be a group
purchase soon.

You description of the operation is correct, except that I think linear
regulation is used rather than PWM

--steve

Lou wrote:
> 
> Hello,
> 
>   Dose anyone have a good design for driving peak-hold Fuel injectors?
> Is there any chips out there made specifically to do this? From what I
> understand
> the design of the peak-hold injector is such that it has a low impedance
> (1-3ohms)
> and therefore draws many (~4) amps, but, you cannot run this injector at
> large duty
> cycles if you sustain the 4ish amps it will draw short-circuited. Instead,
> (if I understand
> this...) the goal of a peak-and-hold driver is to initially draw
> full-current to open the injector,
> but then use  a FAST PWM scheme, or some other method, to current-limit the
> overall
> injector drive current to 1/3 or less of the short-circuit current that the
> injector would normally
> draw. Do i understand this? or am I just  a silly confused hot-rodder?
> 
>    any help or suggestions would be very much appreciated.

-- 
Steve Ravet
steve.ravet@arm.com
ARM,Inc.
www.arm.com
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