Home-built LM2575 Switching Regulator circuit.

The LM2575-ADJ step down (buck) switching regulator has an adjustable output voltage range of 1.23 to 37 volts @ 1 amp and a maximum operating input voltage of 40 volts. The regulator has an internal 52kHz fixed frequency oscillator, built in current limiting and thermal shutdown protection. The typical standby current spec is 50 uA and is achieved by turning the regulator output switch off by driving the on/off pin high.

Bench testing the LM2575 switching regulator circuit.

I have posted some test data in the table below to show the efficiency advantages over using a passive regulator. The more voltage you have to drop the greater the benefit of the switching regulator.

I became interested in the switching regulator to use it with my Chronar solar panels.


DC
V
In
Cur.
In
(mA)
Pwr
In
W
DC
V
Out
Cur.
Out
(mA)
Pwr
Out
W
Pwr
Loss
W
Load
Res.
Ohm
Reg.
Eff.

18 602 10.8 12 800 9.6 1.2 15 89%
24 456 10.9 12 800 9.6 1.3 15 88%
36 309 11.1 12 800 9.6 1.5 15 86%
18 305 5.5 12 400 4.8 0.7 30 87%
24 234 5.6 12 400 4.8 0.8 30 85%
36 163 5.9 12 400 4.8 1.1 30 82%
18 161 2.9 12 200 2.4 0.5 60 83%
24 126 3.0 12 200 2.4 0.6 60 79%
36 90 3.2 12 200 2.4 0.8 60 74%


The LM2575 switching regulator circuit pattern transfered to the circuit board.

Circuit pattern image has been transferred to circuit board with transfer material and clothes iron. Board is ready to be etched in ferric chloride.


Drawing the schematic and laying out the circuit board with CadSoft Eagle Layout software.

2575T-ADJ Switching Regulator Schematic and Board Drawings



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