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Author Topic: AC-DC Power  (Read 5461 times)

John Roberts {JR}

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Re: AC-DC Power
« Reply #20 on: August 06, 2014, 10:57:26 am »



Another plus to DC supply-DC dimming should be a lot less electrically noisy.  Mechanical DC switches are noisier and harder to design well-but solid state switching for DC is a natural.

But then, what would Mike do without ground loops and AC hum to chase down?
I am not so sure that DC dimming is so quiet. To do it efficiently involve PWM not unlike AC lamp dimmers but running at a much higher frequency. Arguably the higher frequency dimming could be easier to filter out but still must be managed.

Dimming that does not involve switching would involve active pass devices to scrub off voltage, and those pass elements would dissipate heat and waste power.

In fact while not cheap some recording studios use variacs (variable transformers) to dim lights efficiently and quietly.   

JR
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Stephen Swaffer

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Re: AC-DC Power
« Reply #21 on: August 08, 2014, 10:51:25 pm »

 To be totally "outside the box", I suppose one could avoid non-linear loads in AC-DC conversion by using something similar to a rotary phase converter-an AC motor driving a DC generator.  Though I imagine efficiency would take a pretty good hit.

On the larger wire for 12 VDC thought.  Obviously it takes 10 times the current at 12 VDC to convey the same energy as 120 VAC rms.  Right now, LEDs are averaging roughly 1/7th of the energy for the same lumens as incandescent lamps or metal halides (a rough approximation from recommendations I am getting on application).  So a fully loaded circuit might take a little larger wire to run LEDs on the lower voltage vs incandescents on the higher voltage.

I was told yesterday by my supplier that current LEDs are running about 100 lumens/watt.  A major manufacturer has a prototype ready to field test that is doing 200 lumens/watt and another in the lab that is showing 303 lumens/watt. Supposedly the theory said 300 lumens/watt was the limit.  If there is substance to this information, then we still have a ways to go before the potential for LED technology is reached. So the question becomes-invest now or wait 6 months?
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Steve Swaffer

Frank DeWitt

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Re: AC-DC Power
« Reply #22 on: August 09, 2014, 03:14:32 pm »

  So the question becomes-invest now or wait 6 months?

I think this is a eternal question on every subject.  Christ, wife, car guitar mixer LED Lights.

If you need it invest now  (Everyone needs Christ)
If you don't, wait 6 months
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Jonathan Johnson

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Re: AC-DC Power
« Reply #23 on: August 11, 2014, 01:42:43 am »

A major manufacturer has a prototype ready to field test that is doing 200 lumens/watt and another in the lab that is showing 303 lumens/watt. Supposedly the theory said 300 lumens/watt was the limit.
Seems to me that the theoretical limit would be when all of the energy used is transformed into visible light, resulting in no heating of the element or supporting electronics. I don't know how many lumens/watt that would be.
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Re: AC-DC Power
« Reply #23 on: August 11, 2014, 01:42:43 am »


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