jeffj@sfsup.UUCP (J.S.Jonas) (04/01/86)
[linears go hmmmmmmmmmm, but switchers go skeeeeeeeeeeee]
I am using Lamda LVS-8-12 and LUS-9-5 power supplies. Since these are
switching power supplies, do I have to supply a minimum load?
The built-in LED indicator seems to make it well behaved with no load.
Jeff 'still homebrewin' Skot
{ihnp4 | allegra | cbosgd} attunix ! jeffjpaul@axiom.UUCP (Paul O`Shaughnessy) (04/04/86)
>From: jeffj@sfsup.UUCP (J.S.Jonas) >[linears go hmmmmmmmmmm, but switchers go skeeeeeeeeeeee] >I am using Lamda LUS-8-12 and LUS-9-5 power supplies. Since these are >switching power supplies, do I have to supply a minimum load? >The built-in LED indicator seems to make it well behaved with no load. No. These Japanese manufactured switchers will operate correctly down to no load. However, they do this by reducing the duty cycle on the converter transistor, and very near no load, the circuit may begin to drop out entire cycles, effectively dropping the switching frequency. The result is the audible 'skeeeeee' that you hear. The practical consideration is the noise on your AC line (EMI, etc) and DC output. These are inexpensive supplies and they didn't blow the bank on filtering. I used the LU series, and they worked fine. I would stay away from much of the rest of Lambda's line, particularly the LY, LN, and LO series. The LU series can be second sourced by some models from Panasonic. The power supplies which require a minimum load are typically high power multichannel switchers in which a single magnetic core is used to provide power to all channels, so to ensure adequate current to the secondary channels, you must have a minimum amount of activity on the primary channel. ----------------- Paul O'Shaughnessy @ Axiom Technology, Newton, Massachusetts Home of the 'Management Team' {ihnp4,utzoo}!linus!axiom!paul (uucp) {bellcore!topaz,decvax!seismo}!harvard!axiom!paul (uucp)
larry@kitty.UUCP (Larry Lippman) (04/06/86)
In article <196@sfsup.UUCP>, jeffj@sfsup.UUCP (J.S.Jonas) writes: > > I am using Lamda LVS-8-12 and LUS-9-5 power supplies. Since these are > switching power supplies, do I have to supply a minimum load? > The built-in LED indicator seems to make it well behaved with no load. A well-designed switching power supply has good regulation and a small internal load, and therefore requires no minimum external load for stability. Lambda certainly makes well-designed power supplies. ==> Larry Lippman @ Recognition Research Corp., Clarence, New York ==> UUCP {decvax|dual|rocksanne|rocksvax|watmath}!sunybcs!kitty!larry ==> VOICE 716/688-1231 {rice|shell}!baylor!/ ==> FAX 716/741-9635 {G1, G2, G3 modes} duke!ethos!/ ==> seismo!/ ==> "Have you hugged your cat today?" ihnp4!/