International Rectifier (IR) plans to recruit one or more semiconductor suppliers to act as alternative sources for a motor control architecture that the company has developed.
To make it possible to use low-end microcontrollers as motor controllers, IR has developed a chipset that takes on most of the pulse width modulation (PWM) functions normally needed to control an AC motor. The chipset is controlled using a simple serial protocol by a separate microcontroller.
Currently, most motor designs use a high-integration microcontroller or DSP with built-in support for PWM. To handle the mathematical operations needed to implement full PWM control, these devices typically demand high clock speeds and processing performance.
Eric Persson, power IC systems design manager at IR, said: "As drives get more complex, the task of the DSP becomes greater. We aim to simplify that job.
"You can just have the DSP send simple commands to the drive through a serial port. It only has to send voltage, frequency and coordinate points. Isolation will be easier because it is just a serial interface."
Because the architecture is different to the one used today, and motor control is an area where product obsolescence is a big problem, IR has acknowledged that there will have to be multiple sources for a dedicated motor control chipset.
"It is an issue we will have to overcome. We have built alliances with other companies who will support compatible protocols," said Persson.
The first chipset will support MOSFET or IGBT power transistors. The digital PWM control section will be built on a 0.5µm, 20V process. A second version will add support for better control at low speeds.
Typically, to prevent short circuits, dead time has to be inserted whenever each transistor on either side of a half bridge is turned off. This dead time becomes more significant at low speeds leading to a loss of drive control.
IR will build in automatic dead-time compensation to let the chipset handle motors running at very low speeds.