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Understanding a split-mode power supply.

It's not at all uncommon to see switchers that are secondary-side linear-regulated only. I worked on a mixer / PA just a couple of weeks ago which had a full blown switcher in it. The main rails for the output stages had no regulation at all, and were completely dependant on the input line voltage. The low rails for the preamps had only simple linear regulators. At first, I thought this was a little odd, but of course, it is actually quite common for the main 'big' rails not to be regulated in this sort of kit, when it uses a conventional transformer-based supply. So what was the advantage of complicating things by using a switcher ? I can only assume that it's primarily because it's a portable item of band equipment, so it makes it much lighter to carry around. A lot of other kit uses switchers these days because of the energy efficiency, particularly when they are put into a 'sleep' mode, but an A/C unit ? It's beyond me why it would be worth the added complication of a switcher over a linear, given the energy-gulping nature of the appliance in the first place, and the potentially hostile environment that it has got to work in ...

Arfa

Reply to
Arfa Daily
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Though the PS and basic electronics are running 24/7, not just when the A/C is running.

Maybe a hypothesis of yours applies here - they got a good deal on transformers suitable for use in a switch mode PS.

Of if I were being cynical, which of course, I never am, I might suspect that it was to ensure that the boards were uneconomic to repair (except DIY), thus increasing the market for replacement boards.

Although I don't know how much a replacement costs, because 3 days after I asked, Daikin still haven't replied to my email.

Sylvia.

Reply to
Sylvia Else

It's possible that the original is just a flame-proof part - not advertised as 'fusible' by the part mfr. You'll easily find these as

6R2 in 5% and 2% ranges.

The fact is that metal film resistor values below ~ 18R in 1/4 watt and 10R in 1/2 watt are demonstrably fusible, under a certain range of conditions, providing the coating is flame resistant. This characteristic is often used to establish predictable single fault abnormal behavior, where the overstress is predictably high under the expected fault. It doesn't work as well for slower, lower voltage fault surges.

If you want to know if the part you've selected is suitable, run tests with a few samples by attaching them to the end of a line cord and plugging them into the applicable line voltage, making sure that they are located in a suitable container of some sort. The result may suprise you - often the fusing event may be hardly audible for some constructions.

This is only normally practical if you have access to parts in volume, and control over the purchasing specification.

RL

Reply to
legg

That would be most likely for that purpose.

put

Or the reason a lot of gear uses SMP these days, easier to supply various countries differing mains voltages. (Another major factor of less shipping weight would apply to air-conditioners)

MrT.

Reply to
Mr.T

Oops, that should be "wouldn't".

MrT.

Reply to
Mr.T

"Arfa Daily"

** Such amplifier supplies are actually push pull, square wave inverters.

It is not possible to have regulated output without the using an active PFC/regulator stage prior to the main inverter.

Also, because the inverter's output IS a square wave, full wave rectification produces a pure DC voltage.

** Major sales gimmick.
** The big joke is that at least 95% of all such amplifiers are permanently installed in venues.

Plus musos love to buy the heaviest tube amps they can find and use them with heaviest speakers ever made.

...... Phil

Reply to
Phil Allison

I would also agree. I've been doing commercial repair long before smps arrived.

Reply to
Meat Plow

I obtained a second hand ex-library copy for a few dollars plus postage. Interesting reading.

Judging by the book's condition - mint - I'd have to wonder whether it was ever even looked at.

Sylvia.

Reply to
Sylvia Else

Which Library? I've seen mint books in some TAFE libraries that are of the same vintage.

Reply to
terryc

Erie Community College, Williamsville, New York state, USA.

The postage cost more than the book did.

I'll probably get an email from them now saying it was stolen and that they want it back :(

Sylvia.

Reply to
Sylvia Else

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