Can a single buck converter be used for converting both 12V and 24V input to a constant 12V output DC to be fed into a 12V DC motor?

Question

My target is to design a low-cost PCB to run a 12V DC motor. I do need to have 2 input sources, a 12VDC and a 24VDC. What is the best way to achieve this using a single board? Can I use a single buck converter to convert both 12V and 24V into a 12V regulated output? This will be the input to 12V DC motor. Is there a better way to do it cost effectively? I want to keep the price below 5$ per board.

Answer 1

I do need to have 2 input sources, a 12VDC and a 24VDC.

Common sense dictates that if you have a 12 volt input voltage then, that will naturally become the 12 volt feed to the motor. If you only have a 24 volt input supply then use a buck converter to drop it to 12 volts for the motor feed.

Is there a better way to do it cost effectively?

I don't think so.

I want to keep the price below 5$ per board.

That may not be possible if you need a powerful buck converter and, you shop at expensive places and, your design is difficult to test and, your circuit board is difficult to make. Cost doesn't just include component parts but also labour.

Answer 2

The following circuit will allow either 12V input, 15V-24V input, or both at the same time time. The exact range will depend on the buck convertor. If you know the the "24V input" is a constant 24 volts, you can replace the buck convertor with a 50% duty cycle oscillator. That should get the design a bit cheaper (no inductors and SMPS controllers necessary).

^{simulate this circuit – Schematic created using CircuitLab}