In “Microcontroller drives H bridge to power a permanent-magnet dc motor,” Luca Bruno of ITIS Hensemberger Monza in Lissone, Italy, critiques the traditional approach to driving a low- to medium-power permanent-magnet dc motor using four MOSFET or bipolar transistors in an H-bridge configurations.

He shows what happens when, depending on the motor’s voltage requirements, the upper two drive signals may require electrical isolation or a level-shifter circuit to match the microcontroller’s output-voltage limitations.

To overcome this problem, he describes an alternative circuit design that drives only the H bridge’s two low-side switching transistors.