A Powerful 30A DC Motor Driver using Power Mosfets [PWM Controlled, Half Bridge]

[Hesambook]

Please mention your opinion about this article, circuit, and PCB design. Thank you.

Article source: https://bit.ly/2LRBYXH

Abstract

DC motors are everywhere, from hobby applications to robotics and industrial areas. Therefore there is wide usage and request for suitable and powerful DC motor drivers. In this article, we will learn to build one. You can control it using a Microcontroller, an Arduino, a Raspberry Pi or even a standalone PWM generator chip. By using a proper heatsink and cooling methods, this circuit can handle currents up to 30A.

References
IR2104 Library: https://componentsearchengine.com/part.php?partID=718394

IRFP150 Library: https://www.componentsearchengine.com/part.php?partID=167938

Altium Plugin: https://www.samacsys.com/altium-designer-library-instructions

 

[std_match]

I see nothing wrong with the design, but there is some missing information.

The duty cycle can not go to 100% because the output must repeatedly go low to keep the bootstrap capacitor C3 charged.
The maximum PWM frequency is not very high for big power MOSFETs. You should probably not go higher than a few kHz, but I have no exact numbers.

 

[Hesambook]

I see nothing wrong with the design, but there is some missing information.

The duty cycle can not go to 100% because the output must repeatedly go low to keep the bootstrap capacitor C3 charged.
The maximum PWM frequency is not very high for big power MOSFETs. You should probably not go higher than a few kHz, but I have no exact numbers.

Well, No. That is the feature of the function generator which does not go to 100%. actually 100% is not a PWM anymore, it is a flat DC line.
Yes, the frequency can be increased but anyway it passed the test even with 5KHz.

 

[rbroders]

I'm not sure why you would use a half-bridge driver to run a uni-directional DC motor. When the low-side switch is on it will actually slow down the motor (acting as a brake and wasting energy). I think you would be better off using a VOM1271 and a single mosfet. It would be simpler and more efficient. Also, the device is isolated, so your signal circuitry wouldn't have to contend with motor noise coming through the grounds.


Plus you could drive it full on if you wanted (i.e. 100% PWM DC).

 

[KlausST]

Hi,

@rbroders:
A halfbridge may be a benefit, because this gives a better "duty_cycle to RPM" stability. Especially at low duty_cycle.

But you are correct... when the motor is spinning and then you immediately set the PWM to 0%, then there will be high breaking current.
Maybe too high.

But since the SD pin is fead to the header the user is free to control the motor with and without breaking.

Klaus

 

[rbroders]

Duty cycle to rpm is certainly an interesting metric.

I suppose the half bridge would reach a new lower rpm faster because of the braking action. FWIW.

However, you cannot simply feed the PWM signal to the SD input and expect the circuit to only pulse the high side switch. The boost circuit needs the low switch to turn on in order to charge the capacitor. Which drives the gate of the high side switch...