battery chargers, again
in [Design]
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From: Jan Panteltje on 30 Sep 2009 14:11 On a sunny day (Wed, 30 Sep 2009 10:31:23 -0700) it happened Joerg <invalid(a)invalid.invalid> wrote in <7ihiviF315tpvU1(a)mid.individual.net>: >> How much ripple really depends on how fast it reacts. >> As it reacts very fast, it can change the drive PWM to any value within a PWM period. >> There is sort of a small analog area created. >> If you look at the PWM on the scope, once it is stabilised at the set point, you see all sort of values. >> The ripple on the output then depends on the output cap and other system parameters. >> The PWM looks irregular, but the output is really OK. > > >Irregular is ok, we even do that on purpose sometimes, for example to >dodge an EMI bullet. But hysteretic means long time-constant filters and >that can screw up the load change response. Which is often unacceptable >on my designs. Are you referring to the loop filter? There is no loop filter.
From: Joerg on 30 Sep 2009 14:17 Jan Panteltje wrote: > On a sunny day (Wed, 30 Sep 2009 10:31:23 -0700) it happened Joerg > <invalid(a)invalid.invalid> wrote in <7ihiviF315tpvU1(a)mid.individual.net>: > >>> How much ripple really depends on how fast it reacts. >>> As it reacts very fast, it can change the drive PWM to any value within a PWM period. >>> There is sort of a small analog area created. >>> If you look at the PWM on the scope, once it is stabilised at the set point, you see all sort of values. >>> The ripple on the output then depends on the output cap and other system parameters. >>> The PWM looks irregular, but the output is really OK. >> >> Irregular is ok, we even do that on purpose sometimes, for example to >> dodge an EMI bullet. But hysteretic means long time-constant filters and >> that can screw up the load change response. Which is often unacceptable >> on my designs. > > Are you referring to the loop filter? > There is no loop filter. > No, to the output filter. You can't possibly let the ripple just saunter out the banana jacks of a bench supply and pollute whatever it find downstream. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jan Panteltje on 30 Sep 2009 15:28 On a sunny day (Wed, 30 Sep 2009 11:17:34 -0700) it happened Joerg <invalid(a)invalid.invalid> wrote in <7ihlm2F3179urU2(a)mid.individual.net>: >> Are you referring to the loop filter? >> There is no loop filter. >> > >No, to the output filter. You can't possibly let the ripple just saunter >out the banana jacks of a bench supply and pollute whatever it find >downstream. All depends, 10mV is fine with me:-) You really got to come up with some numbers, else it all makes no sense,
From: John Devereux on 30 Sep 2009 15:33 John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> writes: > On Wed, 30 Sep 2009 05:30:20 +0100, John Devereux > <john(a)devereux.me.uk> wrote: > >>John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> writes: [...] >>> >>> 1.2 amps from a Lascar bench supply, overnight, is hardly >>> overcharging. Contrary to stated theory, the car works fine now. >> >>I thought we were discussing why the *battery chargers you bought* might >>refuse to charge? > > And I thought we still were. > >> How many amps were those supposed to be? > > The first ones were switchable 2/6 amps. The second pair was rated 3 > amps. All put out zero amps, which I thought was not very helpful. Do > you think maybe I'm being too demanding? They do sound pretty useless. I just like to try to understand what rationale people have for these sorts of design choices. Is it really cheaper? Afraid of being sued somehow? I'm afraid I don't quite buy your selling-more-batteries conspiracy theory, but who knows? > We just loaned the Echo to a friend who ripped the bottom out of her > BMW on a berm full of rocks. She was skeptical about driving such a > down-scale car, but now she really likes it. She may buy it for her > college-age kid. > > John > > -- John Devereux
From: Joerg on 30 Sep 2009 16:01
Jan Panteltje wrote: > On a sunny day (Wed, 30 Sep 2009 11:17:34 -0700) it happened Joerg > <invalid(a)invalid.invalid> wrote in <7ihlm2F3179urU2(a)mid.individual.net>: > >>> Are you referring to the loop filter? >>> There is no loop filter. >>> >> No, to the output filter. You can't possibly let the ripple just saunter >> out the banana jacks of a bench supply and pollute whatever it find >> downstream. > > All depends, 10mV is fine with me:-) > > You really got to come up with some numbers, else it all makes no sense, > Ok, this is the number I typically need: Not being able to show the ripple on a scope when set to 2mV/div. Good enough? Seriously, 10mV piping out would be disastrous when doing things like ultrasound experiments. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |