Yes, I have encountered this situation where the USB mobile power supply keeps shutting down due to low current consumption when powering a project. This is a frustrating problem, as these mobile power supplies usually have overcurrent protection mechanisms that automatically shut down when detecting low current consumption.
To solve this problem, I designed a pulse-adjustable constant current source module based on a microcontroller, operational amplifier, MOSFET, and other components. This module can be connected to USB 3 directly, providing a stable current output and avoiding the mobile power supply shutdown issue.
The working principle of this module is to use the microcontroller to monitor current consumption and adjust the output current accordingly. The operational amplifier amplifies the current signal, while the MOSFET acts as a current switch to control the output current. By doing so, we can create an adjustable constant current source that meets the project’s current requirements while avoiding the mobile power supply shutdown issue.
The design of this module is very convenient, using a convenient USB interface that is easy to integrate with the project. At the same time, it also supports USB 3 direct connection, providing high-speed data transmission. Overall, this module is a very practical solution that can help us solve the mobile power supply shutdown issue and provide a stable current output.
A quick fix to prevent mobile power banks from shutting down is to use a resistor to bridge the output, absorbing a certain amount of current. For example, using a 150R resistor can absorb an additional 33mA of current, keeping the mobile power bank running. However, some mobile power banks may require higher currents to stay on, such as 100mA, which would require a 50R 1W power resistor.
Fortunately, mobile power banks don’t need continuous current flow to stay on. In fact, a 2-second pulse every 15 seconds may be sufficient to keep them running. This technique can significantly extend the battery life of mobile power banks, making them suitable for powering small projects for weeks.
To determine the current consumption and shutdown timeout of different mobile power banks, we tested some no-name mobile power banks. The test results can help us choose the right resistor value and pulse frequency to ensure stable operation of the mobile power bank. By doing so, we can easily solve the problem of mobile power banks shutting down, providing a stable power output.
| Power bank # | Keep-alive current | Timeout |
|---|---|---|
| 1 | 100mA | 10 seconds |
| 2 | 30mA | 16 seconds |
| 3 | 10mA | 18 seconds |
The smarts of this device is an ATtiny10 which controls the on and off cycling of the constant current sink (pulse duration and interval is adjustable via firmware). The current is adjustable via a small trim potentiometer from 0mA to 140mA and the supply voltage can be anywhere from 1.8V to 5.5V.
These power bank keep-alive modules are available to buy from my Tindie store! Or they can be ordered directly from me, send an email to shop AT zakkemble.net
Designs and firmware are on my GitHub
