If you use inductive smoothing you need to recover the energy from the choke
hence freewheel diode. Make the choke big enough the current goes continious
and you can get to 200mV ripple in 120V with a single stage of L / C

STeve

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
David VanHorn
Sent: 12 September 2006 21:18
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Triac / SCR pre regulator

>
>
> > I did that in a printer design, wasn't hard.  Basically, take a "light
> > dimmer" sort of circuit, and apply the output of a voltage comparator,
> so
> > that if your voltage is high enough, you skip the next
> half-cycle.  Bridge
> > rectifier on the front end, and SCR between that and the filter cap.
>
> Maybe the SCR in front of the bridge on the AC path, or two thyristors
> as half bridge and two diodes as other half bridge. Else how you fired
> off the SCR as long there is no zero cross (or lower than sustaining
> current of the SCR) current on the filter capacitor ?



The SCR turns off when the output of the bridge won't keep enough current
into the filter cap.
There is not a zero-cross on the output of the bridge, but output current
DOES go to zero every half-cycle.
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