Shaving 0.5V of an smps, help wanted

[peterhenk]

I have two nice Phoenix Connector Quint-power SMPS, the 48 Volt version that can be tuned anywhere between 30 and 56 volts.

However I need these PS to drive a TI TAS5825M Amp that allows for a voltage of max 26.4V

I tweaked the voltage regulator pot a bit by lowering the resistance to ground to get a lower Voltage. This works wonders yet the internal control starts to become unhappy (warning lamp starts to blink) when I drop below 26.6 Volts, so I made sure that this is the lowest I can adjust now.

Since the difference is soo small a Buck converter or a resister network is not practical (I used a calculator and the Ohm values where tiny).

How can I shave off these 0.2V or better 0.5V to stay out of the fringes? Will adding some caps between SMPS and Amp help (all components have some resistance ;-)

Thanks for the help
Peter

 

[NickKUK]

Diode drop not work?

 

[JonSnell Electronic]

Capacitors after am SMPSU is not a good thing as it may cause instability!
Use a diode in series with the load as Nick suggests.

 

[Nisbeth]

Haven't looked at the specs for the PSU or the amp, but just thinking that when you are talking about such narrow margins what about the line/load regulation of the PSU?

Also, the absolute max. of the TAS-chip is 30V as far as I can see.

 

[peterhenk]

Thanks for all the info!!

Never looked into the diode solution! Seems relatively easy to do! Only question that remains is what kind of diode is the best to consider (led?) for this situation.

Nisbeth, I am not only 'worried' about the TAS-chip but also about the other components on the (Zoudio) board. Maybe I am making this bigger than it is?

 

[peterhenk]

This one between the + and the - of the SMPS would be a solution or am I simplifying badly?

ON Semiconductor, 25V Zener Diode 5% 5 W Through Hole 2-Pin DO-15

RS-stocknr.:
221-333
Fabrikantnummer:
1N5360BG
Fabrikant:
ON Semiconductor

 

[kodabmx]

It will probably blow up. because anything over it's zener voltage will be shorted away as heat in the diode.

Figure out how much current the device draws, and find a diode that will handle it. Put that diode in series with the load.

Since it's an amp I'm guessing you want at least a 10A part.

This one will work for you for sure though, it's a 20 amp 60 volt part: SB2060TA

 

[peterhenk]

Thanx kodabmx

BTW Love your footnote!!

 

[kodabmx]

You're welcome. Keep in mind the drop will be smaller at idle than at full blast.

If you find you really need a high drop all the time, look at high voltage diodes like 1000V. They have a larger drop all the time but will make more heat in the process - Ohm's law, right?