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README.md

README.md

#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

MP2307 datasheet

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