Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!columbia!rutgers!ucla-cs!zen!cory.Berkeley.EDU!heppell From: heppell@cory.Berkeley.EDU (Kevin G. Heppell) Newsgroups: sci.electronics Subject: Re: Choosing Cap Size in Power Supply Message-ID: <3109@zen.berkeley.edu> Date: Mon, 27-Jul-87 00:41:16 EDT Article-I.D.: zen.3109 Posted: Mon Jul 27 00:41:16 1987 Date-Received: Tue, 28-Jul-87 00:36:38 EDT References: <5705@ut-ngp.UUCP> Sender: news@zen.berkeley.edu Reply-To: heppell@cory.Berkeley.EDU.UUCP (Kevin G. Heppell) Distribution: world Organization: University of California, Berkeley Lines: 32 Keywords: bridge filter In article <5705@ut-ngp.UUCP> jjr@ngp.UUCP (Jeff Rodriguez) writes: > >I'm building a general-purpose power supply... > >How do I choose the size of capacitor to place across >the output of the rectifier? I once heard that the >rule-of-thumb is 1000 micro-F per 1 A of current. >Is that reasonable? In one of TI's applications manuals they list a graphical solution: O.H. Schade, "Analysis of Rectifier Operation", Proc. IRE., Vol. 31, 343, 1943 Basically, the desired filter (capacitor plus shunt resistance of the regulator) depends on several factors, including whether you use a full or half wave rectifier, line frequency (usu. a constant, but who knows :-), peak input (transformer voltage), and desired output voltage. I'm sorry, but I haven't worked with the method enough to give you a specific answer. The TI manual "Linear and Interface Circuits Applications", Volume 1, 1985 gives a good, _general_ discussion of basic linear regulators, their own parts notwithstanding. Disclaimer: I have no connection with TI except someone gave me a bunch of their books for free. -------------------------------------------------------------------------------- Kevin G. Heppell USNail: 784 Santa Barbara Rd. USENET: ucbvax!cory!heppell Berkeley, CA 94707-2046 arpa: heppell@cory.Berkeley.EDU (415) 528-6396