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I am trying to use a cheap DC-DC boost converter I got from ebay. I need about 300 mA at 3.3 V.

The ebay spec is:

  • Input voltage 0.8 ~ 3.3 V, output 3.3 V
  • Maximum output current: 500 mA
  • Start Voltage 0.8 V, Output Current 10 mA
  • INPUT 1-1.5 V, OUTPUT 3.3 V 50-110 mA
  • INPUT 1.5-2 V, OUTPUT 3.3 V 110-160 mA
  • INPUT 2-3 V, OUTPUT 3.3 V 160-400 mA
  • INPUT above 3 V, OUTPUT 3.3 V 400-500 mA

enter image description here

When I connected a 250 Ω resistor from Vo to GND and measured current and voltage I got the following:

Vin Vo Icc measured (not 13mA)
2 V 3.3 V 48 mA
2.5 V 3.3 V 38 mA
3 V 3.3 V 30 mA

For 50 Ω resistor I measured 300+ mA with Vo around 1.2 V.

Is this correct to test by connecting the resistor to GND? If yes, are those things really junk and out of spec?

Velvet
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vg6
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    Never trust anything you buy from dubious sources like unknown sellers on ebay or amazon. Buy electronic parts from digikey, mouser, newark, arrow, etc. – Hearth Oct 15 '23 at 00:27
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    There is no way you can have 1.2V across a 50 ohm resistor produce >300mA of current. Something is wrong with your measurement. – user1850479 Oct 15 '23 at 00:30
  • I mean measuring the current from power supply to dc-dc. i think, the dc-dc is consuming all that current, not being able to boost. i have the following connections : power_supply -> DVM -> dc-dc Vin -> dc-dc Vout -> resistor -> gnd. – vg6 Oct 15 '23 at 01:04
  • I guessed i got "owned" by junk vendors – vg6 Oct 15 '23 at 01:12
  • I remeasured with current meter placed between the dc-dc output and the resistor. With 30 ohm, Vo was 2.9V with Vin=2V and current was about 95mA. Not what they claim with Vo supposedly 3.3V and current 110mA. I returned it at Amazon and got immediate refund with no need to return. – vg6 Oct 15 '23 at 04:13

1 Answers1

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So here is the deal. I did have bad setup as @user1850479 noted. I set current limit on power supply to about 400mA, but for Vin range from 2.5V to 3.2V dc-dc draws from 900mA to 630mA. So, the power supply was limiting , therefore i saw drooping Vo not as 3.3V, but 1.2 or 2V. With that, though, i still cannot use the dc-dc, because:

  1. Input current spikes to 1A for a good second before "settling" to 600mA to 900mA.
  2. Vo goes from 3.4V to 3.6V for Vin from 2.8V to 3.3V.

So, this would not be good for battery based application or if your component cannot handle voltage above 3.3V.

vg6
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