For this Project I wanted to make a PSU. I had found a Brute force PSU Made for a CB. Its original specs were 13V @4 Amps. I opened her up and gutted it. I saved The transformer and plan on using the case. I was originally going to use a Linear Regulator, but then I got a job, and Bought the parts for a SMPS PSU.
Why SMPS? SMPS Stands for Switch mode Power Supply. SMPS's Are way more efficient than their Linear Counterparts, because there isnt much loss in the components. You can think of a linear Regulator as a variable Resistor. If there is a large input voltage, The regulator has to drop a Large Voltage and pass the same current as if it were running from a smaller voltage. This means there is a Large Power Loss if your Output is very Low or your input it very High. SMPS address's this by using switching regulation. Instead of acting like a resistor, SMPS's use switching to control an Inductor to buck, boost or invert the Output. Efficiency's are Now ranging from 80 to 95% Versus 40 to 50% for Linear Regulators.
However, Everything is not without cost. SMPS are a bit Bigger, but if you compare this with the physical size of the needed heatsink for the same linear counter part (along with the transformer) SMPS becomes a better option. Linear Maybe cheaper, But the Cost for this project is $16. I have the filter caps that I got from a friend sometime ago.
For this Project I am going to use the LM2679 Simple Switcher Buck Regulator. The Simple switcher family is meant to be simple, and not complex, Like the LM780X Family. Pretty much Plug and Play. I am also using Through hole, since SMD parts might be a bit hard to come by.
The Only difference in my version is the fact I am using a Pot for R1 to adjust Voltage. I may Add in a pot at Radj to adjust current also.
C in: (not including Filter Caps)
Radj (limits Peak Current)
And of course the IC cost $6.50 or So
Total Cost is $16. Not bad for a homemade Lab PSU.
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