GaN design drives 200V AC servos at 99 percent efficiency

GaN design drives 200V AC servos at 99 percent efficiency

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By Nick Flaherty

The reference design uses TI’s LMG3410 600-V, 12-A GaN power module with an integrated FET, gate driver and protection, announced last year. The GaN module allows the design to switch up to 5x faster than silicon FETs, while achieving efficiency levels greater than 98 percent at 100 kHz and greater than 99 percent at 24 kHz pulse width modulation (PWM) frequency. 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 100 kHz significantly helps improve torque ripple when used with low-inductance motors.

The GaN inverter power stage easily interfaces with microcontrollers such as TI’s TMS320F28379D drive control system-on-chip to help dynamically adjust voltage frequency and achieve ultra-fast current loop control. This uses the new DesignDRIVE Fast Current Loop software with a sub-cycle PWM that helps push current-loop performance in servo drives to less than 1 microsecond, potentially tripling motor torque response.

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.

The high-efficiency power stage delivers 98 percent efficiency at 100 kHz PWM and 99 percent at 24 kHz PWM, reducing the size of the heat sink. The fast switching transition of under 25 ns without any switch node voltage ringing reduces EMI and the GaN FET power module allows for fast and easy PCB layout and small form-factor design.

Download the reference design at


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