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Project Notes

#211 BuckConverterModules

Test a range of low-cost buck converter modules

Notes

There are many super-cheap buck converter modules available, many based on the LM2596S-ADJ. This is the place I record any notes on the individual units I get to see.

Four so far:

  • Module 1 - LM2596S 2.6-30V Buck Module
  • Module 2 - LM2596S 1.23V-30V Buck Module
  • Module 3 - XL4015 1.25V-36V Buck Module
  • Module 4 - MP2307DN 1.0V-17V Buck Module

Module 1 - LM2596S 2.6-30V Buck Module

The example I’m using is similar to this seller listing. Typical price USD$0.93 with free shipping.

module_1

Buck circuit comprises:

  • LM2596S-ADJ (as marked, but behaves more like an LM2576 - see note below)
  • 330µH output inductor
  • 220µF output capacitor

Performance:

  • minimum voltage achieved in practice: 2.56V
  • switching frequency appears to be in the ~50kHz range rather than the 150kHz per datasheet(??)
  • switching spikes around 30-40mV

Conclusion

This is one of the most common modules, but quite noisy and can’t regulate to very low voltages.

It also behaves more like an LM2576:

  • the 330µH inductor is also more suited to a standard LM2576 topology rather than the 33µF recommended for the LM2596.
  • the apparent switching frequency is closer to the LM2576 52kHz rather than the LM2596’s 150kHz.
  • so is this a fake or QC-fail LM2596S-ADJ? Possibly, if my scope traces are reliable.

module_1_test

module_1_scope

Module 2 - LM2596S 1.23V-30V Buck Module

The example I’m using is similar to this seller listing. Typical price USD$0.79 with free shipping.

module_2

Buck circuit comprises:

  • LM2596S-ADJ (as marked, but behaves more like an LM2576 - see note below)
  • 470µH output inductor
  • 220µF output capacitor

Performance:

  • minimum voltage achieved in practice: 1.22V
  • switching frequency appears to be ~50kHz, not 150kHz per LM2596 specs.
  • switching spikes under 10mV

Conclusion

Performance is pretty good, but this does not appear to be a genuine LM2596S-ADJ.

  • the 470µH inductor is also more suited to a standard LM2576 topology rather than the 33µF recommended for the LM2596.
  • the apparent switching frequency is closer to the LM2576 52kHz rather than the LM2596’s 150kHz.
  • so is this a fake or QC-fail LM2596S-ADJ? Possibly, if my scope traces are reliable.

module_2_test

module_2_scope

Module 3 - XL4015 1.25V-36V Buck Module

The example I’m using is similar to this seller listing. Typical price USD$2.68 with free shipping.

module_3

Board comprises:

  • XL4015E5 with toroidal inductor and capacitors as per datasheet recommendations
  • digital voltmeter with pushbuttons to switch display on/off and select input/output voltage for display

Performance: up with the best. There’s no scope capture below because despite my best attempts, the output voltage remained flat as a board (no detectable ripples or spikes .. just the normal noise floor)

module_3_test

Module 4 - MP2307DN 1.0V-17V Buck Module

The example I’m using is similar to this seller listing. Typical price USD$0.51 (USD$5.06 for 10) with free shipping.

module_4

Board comprises:

  • MP2307 monolithic buck converter with standard support circuits per datasheet recommendations
  • pretty small package!

Performance: quite impressive for the size. There’s no scope capture below because despite my best attempts, the output voltage remained flat as a board (no detectable ripples or spikes .. just the normal noise floor)

module_4_test

Test Bed Construction

Breadboard

In the test configuration, I have the buck converters adjusted to ~3V output, and two blue LEDs in parallel form the load. the LEDs have a forward voltage Vf of ~3V.

The Schematic

Credits and References

About LEAP#211 Power
Project Source on GitHub Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is my personal collection of electronics projects, usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting (IMHO!).

The projects are usually inspired by things found wild on the net, or ideas from the sources such as:

Feel free to borrow liberally, and if you spot any issues do let me know. See the individual projects for credits where due. There are even now a few projects contributed by others - send your own over in a pull request if you would also like to add to this collection.