[Diy_efi] Re: Diy_efi Digest, Vol 3, Issue 14

[Bill Washington]

Gents,
    A possibility:
Conceptually:
                                    P&H FET (across R2)
                                     |             |
                                     |             |
Vsupply-----Inj----R1------R2-----Driver Transistor----GND

P&H FET is turned on when Driver Transistor turns off,
P&H FET turns off 'x' microseconds after Driver Transistor turns on.
This delay could be done with an Resistor/Cap circuit or, better by the 
EFI Micro making the duration programmable.

Hold current limit is set by R1 + R2,
Peak current limit is set by R1.

Peak current duration is 'x' + P & H FET switching time.
Remainder of duration to Driver off is Peak Current

Regards
Bill W




>------------------------------
>
>Date: Sun, 9 Mar 2003 17:28:26 +1300
From: "Bevan Weiss" <kaizen__ at hotmail.com>
>To: "List for general do-it-yourself EFI talk" <diy_efi at diy-efi.org>
>Subject: Re: [Diy_efi] peak-and-hold injector driver ic's
>Message-ID: <OE15niSnRMWuLn5U9T30001d2d3 at hotmail.com>
>References: <cc.1992cb67.2b9c196f at aol.com>
>Content-Type: text/plain;
>	charset="iso-8859-1"
>MIME-Version: 1.0
>Content-Transfer-Encoding: 7bit
>Precedence: list
>Reply-To: List for general do-it-yourself EFI talk <diy_efi at diy-efi.org>
>Message: 6
>
>  
>
>>my advice would be to stop worrying about current limitng and just
>>    
>>
>overbuild
>  
>
>>the circut. if you have a peak load of say 1.1amps per injector and are
>>firing one injector just go ahead and build the circut with a 4amp driver.
>>the injector wont overheat. what the issue is is with driving the gate. if
>>your using an oem ecm to drive the gate then just forget about current
>>limitng. no real point to it.
>>    
>>
>
>If I allow 4amps to pass through an injector for it's entire on time, then
>there is every likelyhod that it will melt.  I don't know of any injector
>that can take a constant 4amp current flow without getting mighty damn hot,
>and eventually failing.
>
>What I want to do is turn the injector on as fast as possible, then lower
>the current to it's minimum possible on value.  This way the design uses the
>least possible power, and also has the best possible response time.
>
>As for how the injector will be driven it will be a simple 2.5V CMOS on/off.
>I want the current limiting to be built into the actual driver itself, not
>the controller.  The controller is going to be of my own design.
>
>------------------------------
>
>  
>



_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi