Description:

• Input voltage: 24VAC (RMS)
• Output voltage: 3.64VDC ~ 16VDC
• Current rating: 1A
• Ripple: 24mV
• Buck converter IC: LM2575

Components:

• 1N4007 x 4 -> Bridge rectifier
• 100uF 50V capacitor -> Input capacitor
• 10uF 35V capacitor -> Input capacitor
• LM2575 -> Buck converter IC
• 330uH inductor -> Delivers energy to the load while the IC switch is OFF
• 1N5815 Schottky diode -> Directs current while the IC switch is OFF
• 330uF 50V capacitor -> Output capacitor
• 10uF 35V capacitor -> Output capacitor
• 2k resistor -> Used for programming the output voltage
• 10k potentiometer -> Used for programming the output voltage
• 1k resistor -> Used for programming the output voltage
• 22uH inductor -> Part of the LC circuit to further smooth output voltage ripple
• 100uF 50V capacitor -> Part of the LC circuit to further smooth output voltage ripple

Schematic

Gallery

Top View

Bottom View

3.6Vout

16Vout

Notes

• Input capacitors should be as close as possible to the input pin. This is to avoid stray inductance that becomes present as leads get longer.
• Feedback line should be kept short to avoid picking up noise from the surrounding circuits.
• Vout = Vref(1+R1/R2), where Vref = 1.23V. R1 has the lowest value of 2kOhm, which ensures the minimum voltage 3.6V. R1 can increase by turning the potentiometer.
• Single point grounding was supposed to be implemented to eliminate ground loop, but it was difficult to do in prototype board.
• Soldering job is a lot cleaner with higher quality soldering iron.

Reference

LM2575 datasheet
https://www.onsemi.com/pub/Collateral/LM2575-D.PDF