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From: "John Jardine"
Subject: Re: Constant Current Sw Regulation?
Date: Tue, 19 Nov 2002 19:53:54 -0000
NNTP-Posting-Date: 19 Nov 2002 19:42:28 GMT
X-Newsreader: Microsoft Outlook Express 5.00.2615.200
Roger N wrote in message
> On the battery charger I'm working on, it needs to be able to charge from
> 1.2V to ~20V. I prefer to use a switching regulator for efficiency. A
> description I read for a chopper stepper motor drive explained that they
> turn the switch on when the current is lower then the desired current and
> turn the switch off when it is above the desired current. Would it work
> use an op-amp circuit with hysteresis and a current sensing resistor to
> switch the transistor of a basic buck converter? For example, for 1A
> regulation, switch on at 0.95A and back off at 1.05A.
> This sounds simple enough and the switching frequency could vary depending
> on the inductor and load. Just wondering if there was any reason not to
> it this way? Thanks!
Yes it does work (and works well). Design is easy and predictable. Control
loop 'slack' which bedevils the stability of PWM setups, simply translates
into loop frequency variations.
People tend not to do it this way because it's not 'modern' enough. Why use
a simple comparitor when a more complicated PWM will do the same job ;-)
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