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I'm concerned about the delay of a typical relay used in this circuit:

circuit

  • DC: voltage from a low quality switching regulator.
  • R : high wattage current limiting resistor.
  • Cap : group of parallel capacitors. Summing to 8.6 mF
  • UVLO : Enables the DC-DC buck regulator when satisfactory voltage is reached (i.e. when caps are charged to a predetermined voltage)
  • MCU : triggers a relay to bypass the R.

Does this circuit work in practice to limit inrush current?

Elementronics
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  • 1) why do you need such a large (8.6 mF) smoothing cap? 2) the DC supply on the left, maybe it can already handle a large inrush current without issue? Maybe it cannot deliver a very high current in the first place? 3) connecting so much capacitance (8.6 mF again) to the output of a DCDC converter might be asking for trouble. DCDC converters generally don't like that. 4) Why not use a PTC to limit the inrush current? – Bimpelrekkie Jun 29 '21 at 07:27
  • 1.Caps are moslty there as the main voltage supply suffers from repetitive large dips (caused by upstream heavy load switches). 2. The DC supply actually isn't of high quality has no high-current/short protection. 3. Won't limiting inrush current solve this problem? 4. Read PTC/NTC are not stable, and also add another heat source to my circuit. – Elementronics Jun 29 '21 at 07:41

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