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Linear or SMPS?

I was thinking of changing a wallwart 12v 1000mA PS from linear to SM, as the latter is more efficient, but now I'm not so sure.

What is the no-load power consumption of each type? I understand from Wikipedia that a SWPS must operate with a minimum current, so needs a dummy load when it is not being used.

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In that case, depending on the full and standby consumption of the device being powered, the SMPS may actually cost more to run if the SMPS "standby" consumption is higher than the equivalent linear supply. It will, of course, depend on the relative full/standby operation times, but I assume there is a crossover point where one type of power supply will cost less to run in the long term than the other.

Also, I have generally assumed that SMPS efficiency is in the region of

70%+, whereas linear efficiency is only 30 - 40%. However, this 1250mA multi-voltage SMPS has an efficiency of only 51%
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. To be fair, the higher-power version (2500mA) has an efficiency of 75%.

Does that mean there is little point in going to an SMPS if the power consumption if on the low side? Or will it always win out in terms of cost of operation?

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Jeff
Reply to
Jeff Layman
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Here in the UK electricity is about $.24 per kWh. As to whether or not it is important, even at the US cost, 3 or 4 would save over $100 a year. Would you turn down a $100 bill if one was offered to you? That's the trouble with continuous small costs, we never bother to work out what the total is over a long period of time!

Now that is an interesting observation, considering the cost of metals these days.

--
Jeff
Reply to
Jeff Layman

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