Injector Driver Module

[Jose Rodriguez]

Mike, thanks for the response.

  Yes, there is the method of doing PWM to hold the injector current. And that solves the power dissipation problem.

  But it creates a HUGE problem with electromagnetic radiation (EMI), since the injector coil's current will be switched on/off, creating 6A peaks and big inductor spikes.

  In order to reduce the EMI, shielded cables, etc etc would be needed, that could make the module very expensive or not practical.

  Regards,

Jose

>>> Mike Morrin <mikem at southern.co.nz> 08/10/98 01:20PM >>>
At 11:17 AM 8/10/98 -0700, Jose  Rodriguez wrote:
>  There are mainly two types of injector coils: the saturated and the
peak-and-hold ones.
>  The saturated coils typically have 16 ohms resistance and yes, if I used
them the power dissipation would be greatly reduced on the injector driver
side, specially since I could saturate my drivers, so the power would be
negligible.
>
>  If most OEM coils are saturated, that would explain why they can do it
with such small heatsinks. I wish I could put the module in the interior,
but that is not an option.
>
>  Unfortunately, I am currently being forced to use the peak and hold
coils (1.5..2.3 ohms), because the injectors are to deliver a very high
mass flow, and work over -40..125C. I am told the saturated coils can not
reliably work under those conditions.

I thought I saw somewhere a circuit which generated the hold current by PWM
of the injector current, so the drivers were always saturated or off.  I
cannot remeber where I saw it, or whether it just used the internal
iductance of the injector, or an extra external inductor.

regards,

Mike