here is a question: i have a computer PS and as you know it has +5V output at many amps(20A in my case), and i don't use this at full power, not even 1A. so my question is can i connect a SMPS i want to buy(wich has Uin=5-35V, Uout=1.2-30V/3A) to the 5V of the computer power suply?
does it work switch mode to switch mode? the second PS i want to use is DC/DC type.
an another question: if i power my circuits from a SMPS do i get any interference or noise in audio circuits from the suply?
can i use a SMPS as a suply for a power audio amp, i mean how does a SMPS react to fast chages of load and current?
hope someone knows tha answers i just suspect.

 

"can i connect a SMPS i want to buy(wich has Uin=5-35V, Uout=1.2-30V/3A) to the 5V of the computer power suply?"

Yes. The output of the SMPS is dc and the input to your dc/dc converter is dc, so they're compatible. Note that the output of your converter appears to be as much as 30v at 3a which is 90 watts. Your computer supply is good for 5v at 20 amps, which is 100 watts. You may not be able to run the converter at full output if you have much load already on your 5v supply.


"if i power my circuits from a SMPS do i get any interference or noise in audio circuits from the suply?"

In general, no, as long as you have decent filtering at the output of the SMPS. The preamps will be most vulnerable to noise on the power supply output, but good decoupling (electrolytic AND ceramic capacitors in parallel) should take care of that. Consider the fact that most computers have sound cards -- do they appear to have noise on their outputs?


"can i use a SMPS as a suply for a power audio amp, i mean how does a SMPS react to fast chages of load and current?"

Anytime you use a regulated power supply on a load with high peak current demands, you may have problems. Even a raw dc supply with no regulation will have problems if it doesn't have enough short-term energy storage capacity. A regulated supply can also go into a semi-permanent shutdown mode with an overcurrent spike to protect itself and the load and may have to be turned off to reset it. Adding a pile of bulk capacitance to the output of the supply will help you over those short-term spikes, however the supply may also balk at charging a lot of capacitance, too! You'll have to experiment to see what works. In general, the farther away from the supply limits that you stay, the better off you'll be.

Dean

__________________
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

R.I.P.

 

thanks! this is what i waited for! an answer from a real professional!