From: John Woodgate
Subject: Re: PSU ripple current
Date: Wed, 15 Jan 2003 09:07:07 +0000
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Wed, 15 Jan 2003 12:22:16 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that Mike Monett
wrote (in <3E24D301.2A73@sneakemail.com>)
about 'PSU ripple current', on Tue, 14 Jan 2003:
>I just put this in SPICE. The ripple current is similar to a half sine
>wave followed by a flat discharge. The shape of the half sine changes
>with any change to the circuit, including leakage inductance of the
>transformer, source resistance, load current, and of course, cap value.
You can get different shapes depending on the ripple amplitude. SPICE
allows you to explore all these possibilities
>Although the charge current can change shape dramatically, it never
>resembles a square wave, or even comes close.
It does if the ripple amplitude is small - less than 5% of the d.c.
The charging voltage waveform is the tip of a (approximate, but very
close if there is little leakage inductance in the transformer) sine
wave of much higher frequency than the supply: you can see this if you
display the ripple voltage and the diode current simultaneously. For
very short charging times ( = small ripple voltage), this tip is close
to a straight line. The discharge waveform is exponential, but again,
for small ripple voltages it is nearly linear.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
PLEASE do NOT copy news posts to me by E-MAIL!