I usually power my beginner prototype circuits using mb102 power supply board, but it needs an external elimeter to draw power and then regulate it.

I was looking for a portable solution for my 5 volt and 3.3 volt circuit needs and came up with using a portable battery charger for mobile phones.

I tried powering up a simple transistor and LED circuit with it but it wouldn't power-up.

I feel that there is some load sensing circuit in the portable charger which doesn't detect these low power circuits.

I also tried connecting different resistors to the charger, the charger outputs 5 Volts for a few seconds and then again shuts down and doesn't stay ON continuously.

It would be really comfortable to use a portable charger since it could be charged using a phone charger and would be very handy.

What can I do to make the charger output power on low loads?


What can I do to make the charger output power on low loads?

You probably can't do anything reasonable. Charging power banks are designed to cut off power when they think the charge is done, when load drops below certain cut-off level. This condition will happen every time you connect-disconnect your project while debugging it.

  1. you can load it with proper resistor, but it will drain the bank battery quickly.

  2. you can reverse engineer your powerbank, determine what kind of PMIC (power management IC) is used, and disable this cut-off function if possible, but it is very doubtful.

  3. You need to design your own PMIC on the top of existing circuit, replace it with power management you need. This new design must have all features to charge and protect the powerbank battery, but will have no cut-off function.

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  • \$\begingroup\$ I opened the charger, its based on TP4213 IC \$\endgroup\$ – codin Nov 20 '16 at 12:50
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    \$\begingroup\$ @codin, I don't see any means to disable the low-load cut-off, nor do I see any specifications for this parameter (the datasheet is in chinese, I have no clue). Your option is to get any single-cell charger on USB-in end, and a battery backup IC (like TPS61251) from the battery to USB-out. \$\endgroup\$ – Ale..chenski Nov 20 '16 at 18:29
  • \$\begingroup\$ I managed to power up the portable charger by adding a load of 47.Ohms, when I previously tried, the resistors were of low wattage so it didnt work, but now I used 1/2 watt resistors and the resistors stay slightly warm but it works. Thanks \$\endgroup\$ – codin Nov 26 '16 at 11:42
  • \$\begingroup\$ Good. 47 Ohms means 100mA load. It sounds too high to me (for the charging purpose). Did you try 100 Ohms or 150 Ohms? What is the lowest load that works? \$\endgroup\$ – Ale..chenski Nov 26 '16 at 18:28
  • \$\begingroup\$ yes, 100mA might be high, but I don't have more high wattage resistors to try any more combinations, the smaller ones start to heat up. I will try to increase the resistance once I get hands on those resistors. \$\endgroup\$ – codin Nov 27 '16 at 11:54

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