Switch Mode Power Supplies (SMPS) is now widely used in modern electronic equipment due to its compact design and high efficiency of about 80% or more. The switch-mode regulator circuit presented here has an efficiency of around 85%.
The IC8211 (Programmable Voltage Detectors) provides the voltage reference and regulator amplifier, while Q1 is the series pass transistor. R1 defines the output current of the IC8211, while Cl and C2 provide loop stability and also act to suppress feedthrough of input transients to the output supply. R2 and R3 determine the output voltage as follows :
The regulator circuit uses an LM117K three-terminal adjustable output positive voltage regulator in a TO-3 can. The variable voltage regulator lets you adjust the output voltage of a fixed DC power supply between 1.2 and 37 VDC, and will supply the output current in excess of 1.5 A.
These Low Voltage regulators with short circuit protection can provide 6, 7.5, and 9 V from an automobile battery supply of 13.5 V nominal, however, they will function just as well if connected to a smoothed dc output from a transformer/rectifier circuit.
Every electronic circuit will work as good as its power supply. However this is often overlooked. There are two main families of power supplies: the linear power supply and switch mode power supplies. Linear power supplies are easier to manufacture and to troubleshoot. But they have the disadvantage (especially for high power), the circuit is more complicated with the results of less power and heat faster than the switch mode power supply.