Is there a better or best adj. voltage regulator??

[AudioJohn]

The big question is - what are we trying to protect?

With a zener diode in place of D1 to limit the differential voltage to less than 40 volts across the LM317 - the current to the zener must be limited - or it will fail short circuit!
This will protect the regulator, but will allow high voltage, unregulated current to pass to the load.

The moist common problem when building, experimenting or testing a new circuit is an accidental short circuit to earth - so under this condition - we want all components to survive and carry on working when the short is removed!

Later, during its service life, components might fail - an output capacitor might go short - but there is not much else to go wrong on the supply side of a Phantom circuit.

I limit the zener current with a 680R resistor, but this also limits the current to the regulator under normal operation - so the circuit I have designed is only good to feed one or two Phantom channels.

I always have an additional capacitor (10uF) from pin 1 of the regulator to earth to greatly improve ripple rejection - and it is then essential to have another protection diode across R2 (240R) - positive towards the 48 volt output.

 

[owel]

Download the 317 datasheet. It's all in there.

Two (2) protection diodes, 10uf cap to improve ripple, etc.

Also, take care that the Vin-Vout difference is less than 37Volts. Otherwise, the 317 will not regulate.

 

[ENS Audio]

So in reference to the Green PSU does there need to be a diode (located between the pair of 1000uf caps just in back of the 4 way connector). need to be in the opposite direction of the other diodes, or should it be in the same direction as the other diodes, or....do I even need one there.

The older PSU PCB layout doent show the diode im referring to, so would anyone be able to clarify what the issue is with the pcb layout??

I remember reading on a few Green Pre threads of this issue and with there lacking much clarification on what is the proper design or maybe Im just dense in the head :?

 

[peterc]

All the diodes face the same way, as do all the caps. Easier to build!

The top left diode & the diode between the 2 x 1000 uF caps are the 2 protection diodes discussed above & also shown in the datasheet.

It is good to have them in circuit.

I have also blown 317's in this circuit by accidentally shorting the 317 output to gnd. I assume this produces the effect mentioned by audiojohn, & draws too much current through the reg & toasts it.

Peter

 

[ENS Audio]

[quote author="Dan Kennedy"]I've used 317l's as phantom regulators for years, in thousands of units with no problems, but you do need to limit the voltage differential from in to out, so a zener in the D1 position takes care of the problem.

I think I'm using a 28v part in the current units, whatever a 1N4750 is. I'm not where I can look at a parts list right now, and the memory is only so good.[/quote]

So a 1N4750 would do the trick?? Ok cool, I'll try that

Thanks,

 

[dale116dot7]

TL783CKC

 

[raysolinski]

The 37 volts on the regular old 317 is the differential between the input and output, not the maximum voltage. If you have 60V and are regulating to 48 you should be fine..Phantom is such a small current draw that the heat disapation should be minimal..just make sure your protection diodes are there and you don't have a short...I have a few old breadboarded phantom supplies based on Keith's units that have been running for 3 years (daily) with no problems..and no heatsinks! Although they are only powering 1 or 2 mics (20ma max current draw)...

Ray

 

[dale116dot7]

But if you have the possibility of a short, a protected reg like the one I mentioned might be worth it. Though I use LM317HV's for my phantom supplies.