Texas Instruments Inc (TI) has launched a three-phase, gallium nitride (GaN)-based inverter reference design that helps engineers build 200V, 2kW AC servo motor drives and next-generation industrial robotics with fast current-loop control, higher efficiency, more accurate speed, and torque control.
The three-phase high-frequency GaN inverter reference design features TI’s newest LMG3410 600V, 12A GaN power module with an integrated FET, gate driver and protection (launched in April 2016). The GaN module allows the design to switch up to five times faster than silicon FETs, while achieving efficiency levels greater than 98% at 100kHz and greater than 99% at 24kHz pulse width modulation (PWM) frequency, the firm says. With GaN, designers can optimize switch performance to reduce power loss in the motor, and downsize the heat-sink to save board space. Operating the inverter at 100kHz significantly helps to improve torque ripple when used with low-inductance motors.
The GaN inverter power stage interfaces with microcontrollers (MCU), including TI's TMS320F28379D drive control system-on-chip to help dynamically adjust voltage frequency and achieve ultra-fast current loop control.
TI has also introduced its new DesignDRIVE Fast Current Loop software with sub-cycle PWM update techniques that help to push current-loop performance in servo drives to less than 1μs (potentially tripling motor torque response). The Fast Current Loop software is said to outperform traditional MCU-based current-loop solutions, and is available free with controlSUITE software.
In addition to the GaN module, the reference design relies on TI’s AMC1306 isolated delta-sigma modulators with current sensing to increase motor control performance. TI’s ISO7831 digital isolator also provides reinforced isolation between the MCU and the design's six PWMs.
