/diy_bench_power_supply_lm2596

A DIY two channel bench power supply based on Texas Instruments LM2596

Primary LanguageC++MIT LicenseMIT

DIY Bench Power Supply LM2596

There is a ton of material on the internet about DIY bench power supplies based on TI LM2576 [1], TI LM2587 [2] and TI LM2596 [3] buck/boost converters.

I used [4], [5] and [6] as a starting point for my own design.

Repository structure

/software/      Bare-metal firmware implementation with OOP approach (PlatformIO project)
/hardware/      Circuit schematics and simulations as documentation
/mechanics/     Housing design files
/misc/          Material of built version

Features

  • Two channels with on/off LED and button per channel
  • Adjustable voltage (CV)
  • Settable and adjustable current limit (CC)
  • LED indicators for enabled current limit and reached limit
  • LCD showing measured voltages, currents and current limits per channel
  • Buzzer feedback (acoustic button feedback, current limit warning)

Design / Components

  • Arduino Pro Mini as controller (mainly because of the 8 analog pins)
  • LM2596 buck converter boards [7]
  • HP notebook 90W power supply brick (19V, max. 4.74A)

Simulation

Texas Instruments does provide SPICE models for the LM2596 3.3, 5 and 12 volt version. But not for the ADJ version. Simple LTspice simulations with a modified SPICE model are located here: /hardware/ltspice/.

Modified lines to edit out the internal voltage divider (see file LM2596_5P0_TRANS.LIB).

Original lines:

...
E_U1_E5         U1_N16912605 0 VALUE { V(FB_INT, GND) }
...
R_RFB2         FB FB_INT  7.63k TC=0,0
R_RFB1         GND FB_INT  2.5k TC=0,0
...

New lines:

...
E_U1_E5         U1_N16912605 0 VALUE { V(FB, GND) }
...
*R_RFB2         FB FB_INT  7.63k TC=0,0
*R_RFB1         GND FB_INT  2.5k TC=0,0
...

Added simulations are:

  • lm2596-modified-3_3v-load-3_3-ohm-transient-10ms.asc with results
  • lm2596-modified-3_3v-load-33-ohm-transient-10ms.asc with results
  • lm2596-modified-5v-load-5-ohm-transient-10ms.asc with results
  • lm2596-modified-5v-load-50-ohm-transient-10ms.asc with results
  • lm2596-modified-17v-load-17-ohm-transient-10ms.asc with results
  • lm2596-modified-17v-load-50-ohm-transient-10ms.asc with results

Special simulation with added current limiter (not sure about results):

  • lm2596-modified-5v-load-5-ohm-transient-10ms-with-current-limiter.asc with results

Schematic

The schematic can be found at EasyEDA. I did no PCB (perfboard design is enough).

Performance of LM2596

For a detailed performance review of the LM2596 see [8].

References