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GB for Salas Reflektor-D Power Supply for Digital

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#47
I am considering one of these supplies to power a BeagleBone Black; assuming just powering the BBB and no USB peripherals, peak load is quoted as 460mA during boot up but at idle load can be closer 200mA (at 5V). As the Reflektor D is a shunt design and my understanding is that they deliver a constant current and 'burn' anything not used by the load and I'm wondering if this significantly variable load might give a problem though...

If I assume a shunt current of 75mA, added to the peak load of the BBB the total peak load will be circa 535mA @ 5V, which looks within the capability of the Reflektor D.

With the BBB at idle though the power supply will need to dissipate more watts (about 3-4 times as many) due to the lower draw of the BBB and, of course there will be other situations in between? I'm wondering if this might be too much for the devices?

Would a good compromise be to work on an expected load and accept a reduced shunt overhead during peak loads (such as at boot up)?

Or perhaps I am misunderstanding something?

Grateful for some enlightenment.

Ray
 
#48
You can set for 500mA CCS to cover the initial peak by 40mA still functioning with no transient Vout droop and let idle at 300mA average spare. With 1.2R (2-3W) R1. Chunky idle bias brings more gm (transconductance) to M2. i.e. a good thing as long as dissipation is still logical. You use the BBB for a sonic app?
 
#49
Thanks Salas.

I'm looking to use the BBB with the forthcoming Twisted Pear audio cape (Botic).

Also looking at a second Reflektor D for the Twisted Pear Buffalo III DAC, though as that has local shunt regulation modules I guess there will be only minor benefits over a conventional regulated supply.

Ray
 
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