Please explain LPS for a noob

[batou]

Hello Folks

 

I'm about to build a computer, that will be my main PC and HTPC (until I build a lower power HTPC fully passive ... )

I will buy a SoTM USB card, Uptown Audio Regen is already ordered, and my LH Labs Pulse Sfi is already here.

 

Now I did read a lot about people using LPS for their gear: DAC, Regen, SoTM usb card, PC... Now I need to understand something, isn't the Power already linear? Isn't a normal ATX PSU for example already transforming AC to DC? Or the DACs supplied Power Supply, isn't it transforming already AC to DC? Whats the thing with the 'special' LPS?

 

How could I theoretically power all these devices with a LPS? Since they all need different V and A?

 

Thanks

[sandyk]

Now I did read a lot about people using LPS for their gear: DAC, Regen, SoTM usb card, PC... Now I need to understand something, isn't the Power already linear? Isn't a normal ATX PSU for example already transforming AC to DC? Or the DACs supplied Power Supply, isn't it transforming already AC to DC? Whats the thing with the 'special' LPS?

 

Laurent

Put simply, a Linear PSU uses an iron cored step down transformer to convert mains voltage to the lower AC voltage needed.

The output voltage is governed by the turns ratio of the primary and secondary windings, with the secondary winding having much fewer turns of wire, but of a heavier gauge wire. The resulting AC voltage is rectified by diodes and filtered by large value electrolytic capacitors, and often further filtered and regulated to the required DC voltages using Voltage Regulator I.C.s.

The attached link gives an easier to understand overview of how Switched Mode Power Supplies work than Wikipaedia, which of necessity gives more technical explanations to satisfy Engineers etc.

SMPS inject much more noise and HF rubbish back into the AC mains than a Linear PSU, and they also have HUGE start up current demands. Unlike Linear Power Supplies, they first convert the full mains voltage to a DC value, whereas Linear Power Supplies convert the stepped down AC voltage to a DC voltage.

When you switch on several SMPS devices at the same time, you need to be careful not to blow out the circuit breaker, which may need to be dimensioned to cope with this initial high current inrush.

Alex

 

an overview of switched mode power supplies or SMPS