What can switching supplies be used for?

[SonsOfThunder]

Uhh...can we back up a minute here?

Let's look at something REAL besides our personal opinions and possible misconceptions about switching PSUs.

Let me ask a question...how many of you have listened to a nice sounding high powered car amplifier? (brand doesn't matter, anything over 25W output is fine) If the amp is just a decent design and properly installed, it was probably quiet wasn't it? Guess what? It had a switching PSU! I have personally heard some car amps w/ switching PSUs that are DEAD quiet.

A switcher done correctly doesn't have to be terribly expensive, they can have better isolation from hum and AC line noise. You can run the freq up way high (above 20kHz) and then filter out the crap with smaller inductor and cap values. Done properly, you should need any additional linear regulation either.

I have a rough design for a switching PSU that a friend of mine did up for me for my 1567a clone...I'm slow going on it but I intend to share it with you guys when I get it done.

And using a bunch of different wall-warts allow a manuf to sell the same box in a bunch of different countries with no changes to the product!! We might joust back and forth over maybe four differnt line voltages while there are a BUNCH of standards throughout the world. Would you want to have a different unit/model number for every country where you wanted to sell your product?

hth! Peace!
Charlie

 

[dale116dot7]

The heatsink is insignificant in supplies less than 3 or so amps, but look at a linear lab supply for, say, 30 volts and 30 amps. What's the retail price of a kilowatt heatsink? It ain't cheap. Seems to me the heatsink price is close to that of the iron once you need serious heatsinking.

Tascam uses a switcher for logic and a separate linear supply for their analog stuff in their DM24 mixer. There was a grounding issue, though. At 44.1 kHz the switching supply would mix into the effects insert D-A and A-D section. I needed to add a small capacitor from the chassis to the power supply ground to fix it. I'm surprised that it never got caught in the design phase, but I'm not too worried cuz it's fixed now.

If you want to use switchers with analog, maybe check some Linear Tech app notes - there's good info on this very topic there.

-Dale