Re: Power Supply keep blowing
- From: w_tom <w_tom1@xxxxxxxxxxx>
- Date: Wed, 28 Dec 2005 14:41:08 -0500
If all but the cheapest supplies contain circuitry meant to
protect against overvoltage, then why do so many supplies not
have it? The Intel spec is quite blunt about this function
that was defacto standard 30 years ago:
> The overvoltage sense circuitry and reference shall reside
> in packages that are separate and distinct from the regulator
> control circuitry and reference. No single point fault shall
> be able to cause a sustained overvoltage condition on any or
> all outputs. The supply shall provide latch-mode overvoltage
> protection ...
How does one know overvoltage protection (OVP) is missing?
The 'separate and distinct' packages don't exist. If a power
supply does not specifically and in writing claim to have OVP,
then it's a sure bet, the overvoltage protection does not
exist. Missing OVP is common in cheapest supplies that only
cost $60 full retail - a very low price. To get prices lower,
essential functions must be 'forgotten'.
Did they forget an essential function? Well, where is that
function listed in numerical specs? If the function (ie
overvoltage protection) is not specifically listed, then it
probably is not provided. Those written specifications - what
they do and do not say - are damning facts. No long list of
written numerical specs? Then that supply may not have OVP
and a long list of other essential functions.
This specifically not possible - does not meet Intel specs
because it is not overvoltage protection:
> ... circuitry meant to protect against overloads, overvoltage,
> and undervoltage because the controller ICs contain those
> functions ...
One major reason for OVP: controller IC may fail. A failed
controller IC therefore IS a reason for separate OVP circuitry
- as Intel demands. Intel is blunt for good reason:
> The overvoltage sense circuitry and reference shall reside
> in packages that are separate and distinct from the regulator
> control circuitry and reference.
One way to reduce that retail price below a so competitive
$60? Forget the OVP.
Why would power supplies keep failing? Without technical
details such as meter readings and what internal part is
damaged, then every answer is only speculation. But if that
supply is missing essential functions, then it also will not
provide that long list of written and numerical specs.
bryanlove@xxxxxxxxx wrote:
> All but the cheapest supplies contain circuitry meant to protect
> against overloads, overvoltage, and undervoltage because the controller
> ICs contain those functions, but the protection often doesn't work
> correctly because the design wasn't debugged thoroughly enough or built
> with adequate components.
>
> High volume (1M-12M units/annum) and Chinese labor allow good supplies
> to retail for under $60, and Fortron-Source Power proves this
> constantly with some of the best products on the market. OTOH some
> high priced supplies have low quality because their marketers emphasize
> cosmetics (windows, glowing fans, sheathed cables) over functional
> design
.
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