Variable Switching Power Supply

This is a variable power supply with one regulated output, made by me in 2010. There were two boards: a prototype (figure 1 and figure 5) and the final release (in figures 2, 3 and 6). Both boards were made using the same schematic diagram (figure 4). The output voltage can be adjusted between 1.5 and 32 VDC by means of a potentiometer (multi turn). This device uses a LM2576T-ADJ integrated circuit. It is a high efficiency (over 80%) step-down (buck) regulator, with low power stand-by current and including an internal voltage reference with max 2% tolerance. All the power components used in this project are rated at 3A current. The integrated circuit has no heatsink, so the output current must not exceed 1A for proper use.

Figure 1
Figure 2
Figure 3

Specification:
- switch down (buck) regulated power supply
- input voltage: 230 VAC / 50 Hz
- output voltage: 1.5 - 32 VDC (adjusted by a multi turn potentiometer)
- maximum output current for safe use: 1A
- output protection with current limiter at approx. 3A
- line regulation: max 2%
- efficiency: min 80%

Figure 4
Schematic (PDF)
Figure 5
Figure 6
Figure 7

The layout is very important, without proper circuit connections, the power supply will not work. Observe the indications in datasheet, prototype layout in figure 5 and final release layout in figure 6.

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Links:
[1] - LM2576-ADJ datasheet