DIY-WB02 display / Testing

[bcroe at juno.com]

I agree with the efficiency issue.  A switching driver would 
also have noise issues, a high price to pay for 3.4 watts.

Using a rather low resistance (large light bulb) to test the 
heater circuit is not a good idea, because it will operate 
the regulator at full current and much increased voltage
drop, tending to generate lots of heat.  A known resistor 
connected rather briefly is a better idea.  

Substituting a 0.1 ohm FET driver for the LT1086 would 
reduce the minimum device drop from 1.3 V to 0.125 V,
a reduction of 1.175V.  But this would also allow the 
voltage drop across the current sensing resistor to be 
reduced to half or even less, bringing the required 
voltage down at least 1.8 volts.  There is also an advantage
that the FET will tolerate much higher battery transients 
without breakdown.  For this however there is a price to
pay.  A couple of additional OP amps are needed to 
regulate voltage and current.  Despite that I have used 
this design for my WB cirucuits.

Bruce Roe

On Sat, 16 Mar 2002 23:16:45 -0600 Chad Clendening 
<clendenc at execpc.com> writes:

> linear:       1.2 amps at 14.5 volts =  17.4 watts
> switching  1.2 amps at 11.5   volts = 13.8 watts round to 14 watts 
> for waste.   Leaving a differance of 3.4 watts total dissipation.


> One could substitute a FET for the bipolar output.  This 
> would require modification of the V / I limiting circuitry.
> The benefit would be limited to about a 0.3 volts lower 
> requirement.
> 
> Chad

----- End of forwarded message from owner-diy_efi at diy-efi.org -----
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org