How to choose the input DC voltage for the device?

Question

Do it yourself

Hello!
I am developing a USB-Hub type device with external power from a purchased AC-DC power supply. The question arose - what input voltage to choose? The main supply voltage of my circuit is 5V, the power consumption is ~13.6 W. It is logical to assume that you need to select an input voltage of 5V and buy a 5V, 3A power supply. But, studying a similar device, I saw that 24V 1A comes to its input, it is immediately converted to 5V at the input and then it diverges according to the circuit. Why didn't the developers put 5V right away? On sale I see USB hubs with 5V, 12V, 24V power supply. In principle, there is a dependence, the more ports - the higher the voltage. I myself see only 1 pc of increased voltage: Less current. But 3-amp 5V power supplies exist and cost the same as 24V 0.75A. Also, with less current, it is easier and cheaper to make surge and reverse polarity protection circuits. But then you need to put an extra buck-converter.
So my question is - What are the input voltage selection criteria? And what voltage is best suited for my task (Usb hub ~ 14W)? Are there any articles on this topic?

Answer 1

3 amps for 5 volts is still too much.
There may be problems with the connector, 3 amperes is not enough, a cheap microusb, for example, will already warm up from 3 amperes, and if it oxidizes, it can even burn out. You need to thoughtfully approach the issue of the power connector, or lead the wire inside.
Also, using the built-in buck converter it is easier to control the stability of the power supply, eating directly from 5 volts you need a guaranteed high-quality power supply.
With a 12 volt supply, any unit will suit you, even if the voltage sags or interference occurs, you will be safe due to your built-in stabilizer.
If you need more than 5 volts and 1.5 amps of power, then I would advise looking at 12 volts + a step-down regulator on the device board.

Answer 2

The recommended current density for long-term use of the cable is 2 A / mm ² , the permissible one is 3 A / mm ² . Well, the voltage drop on the cable grows with the current.

Answer 3

It's not about the voltage in your device, but what voltage you pull from the PSU. In automation, 24 V is accepted, 12 V is safe. The lower the voltage, the thicker the wires should be, otherwise there will be a large drawdown on a long line.

Answer 4

yes, any source will do, the main thing is that there should be a stabilizer LM7805