Re: SMPS - effects of casing

From: TP (name_at_usenet.com)
Date: 01/21/05 

Date: Fri, 21 Jan 2005 07:14:51 -0600

They are my designs. I'm seeing similar problems in two very
different designs. Widely
different voltages and currents, different controllers and
frequencies, grounded and ungrounded cases. So what I am interested
in is general replies and perhaps specific anecdotes of similar
difficulties and solutions.

On 21 Jan 2005 04:29:39 -0800, "PeteS" <ps@fleetwoodmobile.com> wrote:

>You don't say whether this is your design or someone else's, or if the
>metal case is grounded.
>
>Whatever those things, the odds-on cause of your problem is poor layout
>perhaps with poor design in the loop compensation network.
>
>Switchmode supplies require great attention to layout (and indeed
>should be modeled at the layout level if you have the tools) for both
>stability and EMI issues.
>
>If you designed the circuit, can you identify the key parameters (Vin
>range, Vout, Iout range, Cin, Cout, controller?
>
>Cheers
>Pete
>
>TP wrote:
>> I have seen changes in behavior of switchmode power supplies when
>> installed in a metal case as opposed to out of the case on the bench.
>> This includes switching instability and increased current
>consumption.
>> I would be interested in the insights and experiences of others in
>> this area.

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