It's a boost converter running from 9v to 80V. The transistor drive allows
me to switch the output on and off. Target output is 50V into 500Ohms

Wayne

-----Original Message-----
From: Russell McMahon [mailto:apptech@paradise.net.nz] 
Sent: 10 January 2005 10:30
To: Microcontroller discussion list - Public.
Subject: Re: [EE] boost converters and current


> I currently have a little discreet boost converter circuit running
> at
> 80V.(boost converter with a logic switch keep voltage at 80V. It 
> feeds into
> a transistor push/pull output driver which allows me to switch the 
> output.
> My current problem is current. Unloaded the system runs at 80V, with 
> a
> 500Ohm load on the output it drops to around 20V. I want to increase 
> this to
> around 40V, do I play with the output driver, or increase the boost
> converter voltage to 100V+??? Or something else???

The question does not make sense. One has to read between the lines 
and guess (possibly incorrectly) what you really want.

If the input is 80v and the target output is 40v then it is a buck 
converter OR something else, but not a boost converter.
Can you give a clear statement of input voltage and target output 
voltage (and anything else relevant that you can think of).

eg
Where does the 80v come from? - is it boosted from eg 12 volts (in 
which case it WOULD possibly be a boost converter.
What output voltage do you want (40 volts?)
What power do you want? (40^2/500 = 3.2 watts?)
What is it powering.

IF you want to go from eg 12v to 40v then one can design a converter 
that does that more or less irrespective of the load. It should not 
need to rise to 80v unloaded unless you want it to for some reason.


        RM 

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