Path: utzoo!attcan!uunet!nancy!wsrcc!wolfgang From: wolfgang@wsrcc.uucp (Wolfgang S. Rupprecht) Newsgroups: sci.electronics Subject: Re: Switched power supplies, how do they actually work ? Message-ID: <1990Oct21.173113.10031@wsrcc.uucp> Date: 21 Oct 90 17:31:13 GMT References: <17660122@hpfcdj.HP.COM> <1990Oct20.222618.2212@zoo.toronto.edu> Organization: Wolfgang S Rupprecht Computer Consulting, Washington DC. Lines: 25 >In article <17660122@hpfcdj.HP.COM> myers@hpfcdj.HP.COM (Bob Myers) writes: >>One other *disadvantage of switchers that I believe Henry forgot to mention >>is a typically atrocious power factor ... In sci.electronics you write: >Actually, I believe the problem here is common to both linears and switchers. >It's not the switching action per se, given that there is a diode bridge and >a bit of a filter capacitor in a typical switcher. Switchers are worse because they have only the input diodes and input filter capacitor impedence to limit the peak current. Normal linears have a transformer's impedence also. This actually tends to help alot, since the core usually just saturates and takes out some of the worst of the current spiking. What PS designers will most likely start doing is running with little or no input filtering. Just vary the swithing ratio to take into account the varying input voltage. -wolfgang -- Wolfgang Rupprecht uunet!{nancy,usaos,media!ka3ovk}!wsrcc!wolfgang Snail Mail Address: Box 6524, Alexandria, VA 22306-0524