I've been wondering about how to build a low noise 5V power supply for a DAC board using supercapacitors for storage.
My plan is to use two banks of two 100F 2.8V LSUC supercapacitors in series and add some low noise auto switching control to automatically alternate between the two banks of capacitors based on charge thresholds.
Initially one bank of caps would be connected to a 5.5Vdc charger only. The other pair would be connected to the DAC only. As and when the caps powering the DAC dropped to approx 4.5V (exact value tbc) the circuit would gently switch capacitor banks.
Initial calculations suggest that the caps would need to swap over once every four minutes based if the DAC draws 200mA (tbc). Of course it would be easy to increase the time intervals by increasing the capacitance.
Is this madness or is there a simple way to make it work well?
I imagine simple relay switching could be done but I thought this might be noisy (both audibly and electrically).
Any advice would be gratefully received (positive or otherwise!)
My plan is to use two banks of two 100F 2.8V LSUC supercapacitors in series and add some low noise auto switching control to automatically alternate between the two banks of capacitors based on charge thresholds.
Initially one bank of caps would be connected to a 5.5Vdc charger only. The other pair would be connected to the DAC only. As and when the caps powering the DAC dropped to approx 4.5V (exact value tbc) the circuit would gently switch capacitor banks.
Initial calculations suggest that the caps would need to swap over once every four minutes based if the DAC draws 200mA (tbc). Of course it would be easy to increase the time intervals by increasing the capacitance.
Is this madness or is there a simple way to make it work well?
I imagine simple relay switching could be done but I thought this might be noisy (both audibly and electrically).
Any advice would be gratefully received (positive or otherwise!)
the switching will be audible most probably.
use a 6v bike battery, and a cheapo float chrager. When the DAC is off, the charger should be on.
99% sure it will have enough capacity for days of listening, and no switching noise will occur. Ever.
It will be just as clean as a powersource as a supercapacitor, just cheaper, and simpler.
use a 6v bike battery, and a cheapo float chrager. When the DAC is off, the charger should be on.
99% sure it will have enough capacity for days of listening, and no switching noise will occur. Ever.
It will be just as clean as a powersource as a supercapacitor, just cheaper, and simpler.
Quite, just like the hoary 'never connected' idea - pair of synchronised switches/relays/FETs, and some additional series resistance to smooth the transition and what are you left with? At best a C-R-C supply that has a 0.5v half-wave rectified sine with a 2min period superimposed on top, and quite high series impedance (i.e. that necessary to minimise the switch noise).
Even an LM317 will do about 2orders of magnitude better there, minimum.
At least that's the view I came to on playing with similar approaches. I'd pick a supply, add a dab of R-C to filter the noise I don't want, and build a quiet reg to follow it. Boringly conventional I know.
PS edit to check numbers: two 100uF in series = 50uF, so from CV=IT you'd need to switch every 1mins to keep within your notional 0.5v tolerance.
Even an LM317 will do about 2orders of magnitude better there, minimum.
At least that's the view I came to on playing with similar approaches. I'd pick a supply, add a dab of R-C to filter the noise I don't want, and build a quiet reg to follow it. Boringly conventional I know.
PS edit to check numbers: two 100uF in series = 50uF, so from CV=IT you'd need to switch every 1mins to keep within your notional 0.5v tolerance.
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12000mAhr !!!!
What's wrong with simply referring to it as a 12Ahr battery?
The public at large are very familiar with automobile batteries that are rated in xxAhr.
But much worse,
there is no voltage information !!!!!
Even the automobile fraternity recognise that a 12V battery is needed for a 12V automobile and that a 24V automobile (truck) would need 2 off 12V batteries.
Even my Dad knew to buy a 6V battery for his VW saloon/variant.
What's wrong with simply referring to it as a 12Ahr battery?
The public at large are very familiar with automobile batteries that are rated in xxAhr.
But much worse,
there is no voltage information !!!!!
Even the automobile fraternity recognise that a 12V battery is needed for a 12V automobile and that a 24V automobile (truck) would need 2 off 12V batteries.
Even my Dad knew to buy a 6V battery for his VW saloon/variant.
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