Those pesky external power supplies....

A long time ago, power supplies used to be built into electronics products, yes they were big and heavy, but since then we have now moved on and most appliances (except for really high end audio and noise sensitive things that you would not find in your average appliance anyway) now use much smaller and lighter switched mode power supplies, so there is no excuse for having an external power supply simply just to reduce weight or size. It seems to vary from product to product and manufacturer to manufacturer. For example, I have a freeview recorder which uses a wall wart, but there is plenty of free space inside for a similar sized power supply, but my Blu ray player is a fraction of that size and has an internal power supply, whats going on? Is it just cheaper to buy a load of generic power bricks from a third party supplier and stick your own label on them or what?

I suspect with some things it may be to simplify the various approvals & regulatory compliance needed.

The 120 or 240V power supply requires various safety approval standards, while something that runs on 12V or 24V etc. is a lot simpler (but still needs some approval testing).

Offloading the high voltage side to another manufacturer can likely save quite a lot in costs & time.

It could also be to reduce the switching noise from the SMPS. Having the power supply separate means that the different plugs for different countries can be accommodated just as easily as having to supply various power leads.

I agree that it is annoying how many products don't have internal supplies. It puts more work onto the consumer to install them as a home has to be found for the power supply as well. It's a bit easier when the external power supply has a C6, C8 or C14 inlet so that a standard mains cable can be used. It can be a pain to have a whole load of wall warts around the back of the TV.

I've just refitted the TV, sound bar, PS3, satellite receiver and CD player / radio / amplifier, and there's an ethernet hub in there as well. Only the TV, the PS3 and the CD have mains inputs. Luckily none of the external power supplies are wall warts, and all have C8 inlets.

As already suggested, it's done for cheapness and convenience - and reduces the approval process for the manufacturer.

I don't think there's really any technical reason, expect perhaps in VERY rare circumstances (such as noise levels for a moving magnet pickup preamp), and I suspect then it doesn't really make much difference.

Even when the PSU is internal, it's common for most manufacturers to buy the PSU ready made from someone else - which is why it's quite common not to have schematics for the PSU's (which is annoying, because it's probably the most repairable part).

in addition to all of the above, there is cost.

Power supplies have become a commodity, and as suchmajor OEMs can have different supply vendors bid on a contract.

It is not uncommon that major vendors, the likes of HP, Dell and others, to have at least a couple of PSU sources for the same product.

Order allocation will be determined by your previous quarter metrics, which include price, on time delivery, initial quality, reliability and whatever else they can think of.

It is a very competitive market.

schmitt trigger said:

in addition to all of the above, there is cost.

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Already mentioned - although I used the word 'cheapness'

rjenkinsgb said:

I suspect with some things it may be to simplify the various approvals & regulatory compliance needed.

Click to expand...

also, building a power supply (especially a switching supply into a unit requires RFI testing and certification which is even more expensive than safety certification (and much harder to meet the standards, because a failed FCC certification for instance requires a redesign of the power supply and possibly the unit chassis/enclosure. analog supplies don't usually pass energy efficiency regulatory standards. it's easier and cheaper to buy wall warts or bricks that have already been approved.