Mini 360 DC/DC converter : avoid !

 

For the spot welder replacement board, i wanted to use a DC/DC converter to lower the 12v input voltage to something smaller (5V).

The aim is to avoid heat and lower the current consumption, so that there will be no problem when the spot welding happens.


The original boards consume about 10 mA, the STM32F1 based one consumes about 50 mA.

I happened to have several of those mini 360 DC/DC converters. They are based on MP2307.

The bluepill needs about 50 mA at 5v idling.

The DC/DC is powered by 12V, outputs 5V  and needs ...70 mA!

WTF ?

I tested it with no load at all, still ~70 mA

Changing the self and/or the output cap and/or the load makes the consumption varies a lot, between 7mA to 80 mA+load.

Additionally the output oscillates , +- 0.5v at high frequency.


From what i could see with a quick check, it needs a self/cap/... tuned to the input/output/load settings and if you dont have the right ones it will heat up and have a very bad efficiency.

So unless you know you are in the good spot for those DC/DC converter, better to avoid them.

A 7805 will work as well without the hashing noise.


Edit :  i checked the self : 10 uH, the output cap is 10 uF, they are ~  in line with the datasheet


Edit : The datasheet actually asks for ~ 50 uf output cap and indeed putting a big electrolytic cap in addition to the 10uF ceramic does help a lot

Comments

  1. UnknownSeptember 25, 2021 at 7:46 AM

    Is it the MP2307 version or the M1584 one?
    See here:
    https://groups.google.com/g/sheffield-hardware-hackers/c/wgkXAE_sAvI/m/37VQNSPbAQAJ

    ReplyDelete

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