Motor performance improvement with GaN power switches

Permanent-magnet synchronous motors designed for high speed or motors with a lower inductance often need a high PWM frequency to reduce current ripple and achieve optimum motor performance. End-equipment examples include hair dryers, air blowers and pumps.

Higher current ripple in the motor winding can cause unwanted torque ripple, increased copper and core losses, and inaccuracies in the average motor current sensed during switching.

MOSFET- or IGBT-based IPMs are typically rated for usage at 20kHz; however, they are normally used at a lower switching frequency (6kHz to 16kHz) because of high switching losses. With GaN offering much lower switching losses even at a lower dv/dt, it is possible to switch at a much higher frequency to improve motor efficiency and performance.

Figure 3 shows the functional block diagram of the DRV7308, which integrates predrivers for all GaN FETs with slew-rate control of phase-node voltages. The DRV7308 helps achieve more than 99% inverter efficiency for a three phase-modulated, field oriented control-driven 250W motor-drive application in a quad flat no-lead (QFN) 12mm-by-12mm package, eliminating the need for a heat sink.