What's a good way to find power transformers whose no-load dissipation is small enough to meet the sub-1-watt "vampire power" requirements of Energy Star / IEC 62301?
I haven't found any comparison-shopping websites which list this information, nor DigiKey / Mouser / etc. And my vendor of choice, Block Transformers, seems to say the best transformer they can sell me, dissipates 0.9 watts in the transformer alone! Leaving not much at all for the wakey-uppie electronics the transformer supplies.
I've got a small 3VA transformer whose primary is permanently connected to the AC mains whether the power switch is on or off. It powers a teeny splash of stuff that uses a few milliwatts listening to the remote control, waiting for someone to press the PowerOn button, etc. I want to meet Energy Star / IEC 62301 requirements for teeny tiny "vampire power" levels, but it seems the power transformer is getting in my way.
What's the standard solution? What does Cambridge Audio do? What does NAD do?
If you're wondering, why 3VA? the answer is: because when the equipment finally is turned on, and we're no longer aiming for sub-1-watt, this transformer supplies 1.5 watts to the coils of the 15 ampere relays associated with mains-power-enable, soft-start, and other such items.
I haven't found any comparison-shopping websites which list this information, nor DigiKey / Mouser / etc. And my vendor of choice, Block Transformers, seems to say the best transformer they can sell me, dissipates 0.9 watts in the transformer alone! Leaving not much at all for the wakey-uppie electronics the transformer supplies.
I've got a small 3VA transformer whose primary is permanently connected to the AC mains whether the power switch is on or off. It powers a teeny splash of stuff that uses a few milliwatts listening to the remote control, waiting for someone to press the PowerOn button, etc. I want to meet Energy Star / IEC 62301 requirements for teeny tiny "vampire power" levels, but it seems the power transformer is getting in my way.
What's the standard solution? What does Cambridge Audio do? What does NAD do?
If you're wondering, why 3VA? the answer is: because when the equipment finally is turned on, and we're no longer aiming for sub-1-watt, this transformer supplies 1.5 watts to the coils of the 15 ampere relays associated with mains-power-enable, soft-start, and other such items.
This is thinking outside the box and not answering your question, but...
Why use a transformer at all? How about something like a supercapacitor or battery to run the power-sipping wakey-uppey circuitry? This can be recharged after wake up, or automatically wake up only the charging circuitry at the intervals needed to charge up the storage. Zero power usage otherwise...
Why use a transformer at all? How about something like a supercapacitor or battery to run the power-sipping wakey-uppey circuitry? This can be recharged after wake up, or automatically wake up only the charging circuitry at the intervals needed to charge up the storage. Zero power usage otherwise...
The power switch could be "off" for 6 months, long enough to completely discharge a battery or a supercap. The other think-outside-the-box solution, which churns my stomach, is to use an off the shelf, Energy Star compliant, little bitty SMPS mobile phone charger module. A tiny few milliwatts of no-load power dissipation, but +5VDC @ 1 amp when you need it. Bleah.
part 1 of answer
part 2 of answer
part 3 of answer
part 4 of answer which costs $237 more than part 3.
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These transformers have .3 W loss.
BLOCK Transformatoren-Elektronik GmbH :::: Products :::: Transformers :::: Product Details
Your existing transformer has to much magnetizing current. I looked for, but did not find a low power transformer with a 130 to 135 VAC pri that would have lower magnetizing current at 120 VAC.
The next best thing would be to add an inductor in series with the primary winding to lower your magnetizing power. At these power levels you might find a affordable 60 Hz inductor.
Well last idea, if you want a specific mounting style, VA and power loss. You could have one wound. 20 years ago this would have cost around $30, today i do not know.
BLOCK Transformatoren-Elektronik GmbH :::: Products :::: Transformers :::: Product Details
Your existing transformer has to much magnetizing current. I looked for, but did not find a low power transformer with a 130 to 135 VAC pri that would have lower magnetizing current at 120 VAC.
The next best thing would be to add an inductor in series with the primary winding to lower your magnetizing power. At these power levels you might find a affordable 60 Hz inductor.
Well last idea, if you want a specific mounting style, VA and power loss. You could have one wound. 20 years ago this would have cost around $30, today i do not know.
Try to think more creatively... when the battery has discharged to some minimum charge level it wakes up the charging system (only) just long enough to recharge and then puts it to sleep again. You could maintain this indefinitely.
Thank You! That solves my problem quite handily. I think I will let other people explore the other ideas that have been put forward here in this thread.
Gratefully,
Mark Johnson
You didn't answer my question that is does the transformer have any power factor correction. If not then a small capacitor across the primary will reduce this vampire power loss. And no I don't know how to calculate this value.
Woody I gave you a link to the AVB transformer's datasheet, here it is once more . I'm afraid I don't know any more about the transformer than this; haven't bought one, haven't measured one. However now that I'm aware of the RKD line of 15 & 30 VA transformers linked by member powerbob, with much improved no-load losses, my interest in the AVB line has diminished. Nevertheless thanks for the idea.
I've discovered that Amveco's catalog actually lists this information in their product selection tables.
So does Talema's catalog.
Just flip to the section on PC-mount transformers (the ones in blue packages) and look at the data. Very handy!
Well for my knowledge standby consumption for AC-adapters in the US is restricted nowadays to 100mW according to energy level 6.
To reduce magnetizing current significantly, you could connect an european 230V transformer to the 117V line.
An option we Europeans do not have!🙁
To reduce magnetizing current significantly, you could connect an european 230V transformer to the 117V line.
An option we Europeans do not have!🙁
Europeans could use two 230V transformers with their primaries connected in series, and achieve the same result (at double the cost). Be sure to arrange the windings' phase dots the right way round.
Have you looked at RECOM AC/DC converters? I know this is what Toni (diyAudio member astx) will be using for the next version of his housekeeping circuit in order to meet European standby energy dissipation regulations.
1W and 2W available. http://www.mouser.com/ds/2/468/RAC01_02-SC-16262.pdf
1W and 2W available. http://www.mouser.com/ds/2/468/RAC01_02-SC-16262.pdf
In the Amveco datasheet, they show an example comparison for an EI vs their toroid.
I am guessing that the 1.5W gives the magnetizing current using W/Vac and that current times the primary resistance gives the 0.6mW of dissipation in the copper. Does the core have a dissipation loss (it gets warm) when the secondary is open circuit?.
Is there any other "loss"?
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Hi Mark, is it EMI/RFI that churns your stomach regarding using one of these?
Yes EMI, and the very idea of putting a 100 kHz SMPS inside the same box as analog circuitry handling microvolt signals. Maybe a Faraday cage might relieve my queasiness.
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