Powering a USB hub: safely distributing current from a shared power supply

[dk8moore]

Hello there!

I'm building a MIDI instrument with USB ports to control (or be controlled by) other MIDI devices.
I'm using a Teensy 4.1 as microcontroller.

From my (in)experience, initially I thought connecting a passive USB hub to the Teensy could do the trick, but then I realized I didn't consider the limited power that the Teensy - very reasonably - can output to power external USB devices through its USB host module.

So now I'm wondering about what could be the most reasonable approach to transform my passive USB hub into an active one, using the same external power supply that is currently powering the Teensy - which is a regulated 5V 3A power supply I found on a DIY website. The power supply has a trimmer to change the output voltage by ±2V.

Let's say that while a 2A fuse could probably solve all my problems, I'd like to understand if there are better options maybe involving some specific circuits to limit the current drawn by a part of the system: ideally I'd like to be sure that the USB hub can potentially draw 2A from the power supply but not more than that, leaving enough room (1A) to power the Teensy and all the other modules in the rest of the system.

What would you guys suggest for my case scenario?

Thanks in advance.

 

[BradtheRad]

The principle of transistor usage says we can apply a bias, causing the component to permit no more than a certain amount of Amperes through a load. You'd need to determine which type (NPN or PNP) and which bias network suits your purpose.

 

[eddienel10]

uno online​

Hello there!

I'm building a MIDI instrument with USB ports to control (or be controlled by) other MIDI devices.
I'm using a Teensy 4.1 as microcontroller.

From my (in)experience, initially I thought connecting a passive USB hub to the Teensy could do the trick, but then I realized I didn't consider the limited power that the Teensy - very reasonably - can output to power external USB devices through its USB host module.

So now I'm wondering about what could be the most reasonable approach to transform my passive USB hub into an active one, using the same external power supply that is currently powering the Teensy - which is a regulated 5V 3A power supply I found on a DIY website. The power supply has a trimmer to change the output voltage by ±2V.

Let's say that while a 2A fuse could probably solve all my problems, I'd like to understand if there are better options maybe involving some specific circuits to limit the current drawn by a part of the system: ideally I'd like to be sure that the USB hub can potentially draw 2A from the power supply but not more than that, leaving enough room (1A) to power the Teensy and all the other modules in the rest of the system.

What would you guys suggest for my case scenario?

Thanks in advance.

To convert your passive USB hub into an active one, you can connect your 5V 3A power supply to the hub while using a power management IC or a dedicated current-limiting circuit to cap the hub's power draw at 2A. This way, you ensure that the remaining 1A is reserved for the Teensy and other components, providing stable and safe operation for the entire system.