Hi there,

I'm trying to design a voltage regulation circuit with a steady 12V output for a motor. The motor will be powered from a 11V - 14V battery (voltage depends on how much the battery is charged). The motor draws 0.5A without load and < 6A with load (in specification). However, I only managed to make it draw 2.5A with nominal load. But, for the sake of safety, let's say it will draw around 6A so I need an IC that can handle this.

I found a TI IC with sufficient specifications (10A) (LM25118) with a convenient HTSSOP package.

My question is, is this IC actually sufficient for my purpose or am I missing something? This is my first time dealing with switching regulators and it looks a little bit intimidating, so I rather asked first.

Are there any other options to get a steady 12V, 6A (max. current) at my output?

Any suggestions?

Thank you for your time.

- Dave

 

Why do you need a steady 12V for your motor? Motors are not critical in their power requirements. If it is an automotive device, the voltage "naturally" varies over that range with no problems. One thing you will be well advised to include is a low voltage lock out, probably with a bit of a delay to allow motor start surges, to protect the battery from over discharge.

 

I think you are thinking about this with a non optimized angle. You are thinking about designing a regulated power supply to control your motor, when in reality what you need to do is use a motor driver/controller which will in essence regulate the motor power for you. But before I go on, I need to point out you have two issues and you should get rid of one of them. The two issues are:

1. You want to control a motor with a voltage regulator.
2. You want to regulate the voltage output to 12V even when the battery voltage is less.

To tackle issue #2 you would need a Buck Boost converter. Whether this is OK for low current applications (such as say gate driving, digital logic) it would be preposterously expensive to drive a motor. To do a 6A Buck Boost would be insane! Heck even a 200 mA Buck Boost is in the pricey side of things... So I highly recommend you steer away from the idea of regulating the voltage up from an 11V input because at the end of the day, I don't think you need it.

The other issue is way easier to solve. You want to generate a voltage regulator to drive your motor. If you use a conventional motor driver, you will not need to do this! For example, most current chopper H Bridges are in essence a "Buck Converter" with the motor being the inductor. That is, they regulate current so the motor sees the voltage required to sustain that current. You can also regulate voltage by specifying the duty cycle. That way, the motor sees a voltage directly proportional to the input voltage and duty cycle. If the battery voltage decreases, you increase the duty cycle and so on.

This is a problem which is super easy to solve with a motor drive chip. And there is a pentillion of those out there, so you are in luck! BTW, you never specified which kind of motor you wanted to drive. But I guess it is a brushed DC motor, so there are tons of drivers out there to choose from.

 

Why do you think you need a regulated voltage? Do you think this will regulate the speed? Hint: it will not.

Bob

 

Hey everyone,

first of all, thanks for your input. I guess I rushed things a bit, not thinking clearly about it all - first time working with a motor, honestly.

Yes, I'm using a brushed DC motor and a TI driver IC for it.

I now realize why I don't need the 12V regulator... I mean, it's logical, not sure how I missed this.

My setup now consists of a 5V buck regulator for ICs and a microcontroller and a V-I-measuring IC (measuring battery voltage to adjust PWM regulation and to cut power to the motor if battery goes below a voltage threshold).