A new high-efficiency stepper motor driver for old technology stepper motors

Stepper motors have been used to drive mechanical systems for many decades. Stepper motors require a current-limited multiphase driver, and techniques have evolved from simple resistive drivers to complex high efficiency, high-performance switching devices. The first high-efficiency switching designs were patented over 30 years ago and have become widely used throughout industry. This has caused a shift in driver technology from a quad-drive system to an H-bridge system, and a change in motor design from four windings to two. There are a great many older systems with the earlier motor technology still in use. Retrofitting such systems can take one of several paths: (1) Replacing the entire mechanical drive motor system, its driver, and reworking all the associated communications protocol between the driver and the outside world; (2) Choosing a high-efficiency “H”-bridge driver, reworking its communications protocol and raising the drive voltages to hazardous levels to get the older-technology motor to perform adequately; (3) Designing a high-efficiency, high-performance motor driver system that will work with older-technology motors and existing communications protocols. This paper presents a high-efficiency, high-performance stepper motor driver and that provides all the advantages of a modern motor driver, yet works with existing older-technology stepper motors. It also solves a well-known failure mode of the standard “H” bridge drive system, and will pay for itself in decreased electrical energy costs compared to an old-technology resistive driver. An application-specific communications controller and motor driver will be described to create a drop-in replacement for an existing controller-driver system.