Re: Power Supply keep blowing


w_tom wrote:
> 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'.

The protection circuit often isn't in a 'separate and distinct'
package, regardless of the supply's price or quality, examples being
high quality Fortrons using the Fairchild KA3511 chip and relying on
its over/under voltage sense inputs (this manufacturer claims its ATX
supplies do have OVP) and low quality generic supplies built around the
SG6105 ATX controller. I've also seen many generics where the OVP was
in a 'separate and distinct' LM339 quad comparator chip. And I've
never see an ATX supply containing crowbars as part of the OVP
circuitry to block voltage spikes generated by inductor saturation, and
I doubt even PC Power & Cooling supplies have them. Can you cite an
ATX power supply brand that does or that meets your minimum standards
of acceptable quality?

.

Relevant Pages

  • Re: Power Supply keep blowing
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