Hi Chris:
In answer to your questions about a PWB board for user-installation
in a personal computer (PC):
> 1) Is it a given that all PCs meet UL1950 or IEC 950 directly or
> indirectly?
PCs marked with any of the safety certification house certification
marks comply with an IEC 950 clone. PCs marked with the CE mark
comply with EN 60950.
PCs not marked with either mark should not be assumed to comply with
IEC 950. I understand that a PC could be assembled from readily
available parts, in which case it would not bear a suitable
certification mark, and should not be assumed to comply with IEC 950.
> 2) Would my card need to meet UL1950 for the USA market?
Yes and no. If you were to supply the complete PC with your card
installed, then your card, as a part of the PC would need to meet
UL requirements for the PC to bear the UL mark. However, if you
supply the card after the PC is sold, and for installation by the
user, then there is no "enforcement" as to whether or not the card
meets UL requirements.
UL has a certification program for such cards. Not many card
manufacturers use this program.
> If no - is there any perceived market value by meeting 1950 for
> this card?
Is there any percieved market value for ANY safety certification mark?
PC buyers do not select the PC on the basis of whether or not a safety
certification mark is on the product, let alone which one!
> 3) Would my card need to meet EN60950 (IEC 950) to satisfy the CE
> mark LVD?
There are two issues:
1) Are components permitted to use the CE mark?
The rule is no. However, some manufacturers have chosen to mark
components with the CE mark. (Keep in mind that use of the CE
mark indicates compliance with ALL of the applicable directives,
including the EMC directive.)
2) Is the card subject to the LVD?
No. The LVD does not apply to products where the voltage does
not exceed 50 V dc or rms.
> 4) Is there a market expectation to see EN60950 on a PC card in
> Europe?
Having said all this, I want to offer some comments on the true
safety of the card. First, to protect against fire, I advise you
to use a fuse in the 12 V supply line. While the 12-volt supply in
a PC is usually a wimpy supply, you can't count on it always being
a wimpy supply. Consequently, the only way you can provide positive
protection against your card overheating and causing a fire is to
provide overcurrent protection as a part of your card. Consider
that your card COULD be connected to a supply equivalent to your
car battery!
Second, the isolation transformer and spacings on the board should
be capable of withstanding a power cross occuring on the twisted
pair signal wires (external to the card and PC). You should
seriously consider complying with the requirements of IEC 950,
Clause 6. While these requirements apply to telephone connections,
any set of wires within a building are capable of a power cross.
>From your description of the product, I doubt that you would need
to do anything but comply with the dielectric strength requirements.
Best regards from San Diego,
Rich
