I needed power supply (step down converter) for my big project with minimal 2A current and fixed output voltage (3.3V) or adjustable output voltage. I wanted higher efficiency and that’s why I chose switching power supply with LM2576 circuit.
I designed the circuit so I could replace LM2576 with fixed output voltage (3.3V, 5V, 12V etc.) for LM2576 with adjustable output voltage.
If you want to use fixed output voltage, replace the resistor R2 for 0R value and resistor R1 will not be involved. If you want tu use adjustable version (1.23 – 37V), you calculate values of resistor in the datasheet.
The efficiency of 3.3V version is 75%, 5V 77%, 12V 88% and adjustable version is 77%.
The board is ready for 2 input capacitors, the first with 5mm lead spacing and diameter up to 13mm and second capacitor with 5mm lead spacing and diameter up to 9mm. The output capacitors are same as input capacitors.
Input and output has SMD capacitor with 0805 case. Recommended capacity is 100nF.
If you use Low-ESR capacitors, the efficiency of converter is higher and voltage ripple is lower.
Karel Pansky – http://plus.google.com community: “elektronika bastlen? programov?n? DIY”
The board is designed for 2 types inductors – SMD or THT – toriod. The connectors have 5mm lead spacing.
As the schottky’s diode can be used SS34A or SK36A – must be SMA package (if you have happiness, you can use SMB or SMC package).
The jumper SJ2 must be closed. I will control the power supply from microcontroller.
The dimension of prototype is right, but I couldn’t buy right components in the shop. I had to buy another types of components.
Schematic of power supply:
Approximate measurement of power supply.
I couldn’t measure voltage ripple because I don’t have better measurement devices.
Layout components:
PCB (1200DPi):
Pictures of prototype:
