IN Brief:
- EPC91124 uses EPC2361 GaN transistors and supports 35A RMS continuous phase current, while EPC91125 supports 30A RMS.
- Both 79 × 80mm boards operate from 18–80V DC, with 100kHz normal PWM switching and a stated 150kHz maximum.
- Integrated Hall-effect sensors offer 250kHz bandwidth, supporting current feedback for field-oriented motor control.
Efficient Power Conversion (EPC) has introduced two 100V gallium nitride three-phase inverter evaluation boards for brushless motor control. The EPC91124 and EPC91125 operate from an 18–80V DC supply and support pulse-width modulation at frequencies up to 100kHz under their normal operating specifications, allowing developers to assess GaN switching performance in industrial motion-control applications.
The two boards share a 79 × 80mm footprint and include gate drivers, current sensing, voltage monitoring, temperature measurement and connections for external motor controllers. Their principal differences concern the power transistors used and the corresponding current ratings.
EPC91124 incorporates the EPC2361 enhancement-mode GaN transistor, which has a typical on-resistance of 0.75mΩ. The board is rated for continuous phase current up to 35A RMS and peak current of 45A RMS under the manufacturer’s specified conditions.
EPC91125 uses the EPC2367, with typical on-resistance of 1.2mΩ. Its corresponding ratings are 30A RMS continuous and 40A RMS peak. These are evaluation-board specifications and should not be confused with the drain-current ratings of individual power transistors.
Both designs use a three-phase inverter arrangement, in which power transistors control the voltage applied to each motor winding from a common DC bus. The switching sequence determines the phase currents that produce torque in a brushless DC or permanent-magnet synchronous motor.
Pulse-width modulation adjusts the effective voltage applied to the windings by changing the conducting interval within each switching period. The motor’s inductance smooths the current between switching events, while winding resistance and back electromotive force influence the current available under different speeds and loads.
Increasing PWM frequency reduces the time between switching events. Under comparable conditions, this can reduce the change in winding current during each cycle, potentially lowering ripple and improving the behaviour of the current-control system.
The frequency increase also creates additional switching events. Each transition dissipates energy and can generate electrical interference, so the selected operating frequency must balance current ripple, semiconductor losses, thermal requirements and the control system’s response.
EPC specifies operation up to 100kHz for the new evaluation boards, with a maximum PWM frequency of 150kHz. The higher limit should not be interpreted as a continuously qualified operating point under all current and thermal conditions.
The manufacturer has configured the gate-drive circuits to limit voltage slew rate to approximately 10V/ns rather than pursuing the fastest switching transitions available from the GaN devices. Controlling the rate of voltage change can reduce some sources of electromagnetic interference and overshoot associated with rapid switching.
Slower transitions introduce their own trade-offs because voltage and current may overlap for longer during switching. The appropriate gate-drive configuration therefore depends on the permissible switching loss, the converter’s parasitic inductance and the electromagnetic compatibility requirements of the intended equipment.
Integrated Hall-effect current sensors provide feedback with a specified bandwidth of 250kHz, sensitivity of 13.2mV/A and a measurement range of approximately ±125A. Their output allows external motor controllers to monitor phase current and adjust the inverter switching pattern.
Current measurement is central to field-oriented control, which regulates the components of motor current associated with magnetic flux and torque. The controller uses measured currents together with information about rotor position to calculate the voltage commands required for the desired motor operation.
Measurement bandwidth, sampling timing and sensor accuracy affect the control system’s ability to reconstruct current behaviour. At higher switching frequencies, care is also required to distinguish the motor-current waveform from switching noise introduced by the power stage.
The evaluation boards incorporate phase-voltage and DC-bus monitoring, temperature measurement and onboard housekeeping supplies. These functions support characterisation of the inverter and provide information that can be used by external control and protection circuitry.
Connections for encoder and Hall-effect rotor-position feedback allow different motor-control strategies to be evaluated. EPC identifies compatibility with controller families including Microchip dsPIC, Texas Instruments C2000, STMicroelectronics STM32 and Renesas RA8T2.
The boards do not remove the need to develop and validate the control firmware. Current-loop tuning, fault handling, rotor-position processing and protection behaviour depend on the selected motor, controller and application requirements.
Thermal design is another constraint. Power transistors, PCB conductors and other components dissipate heat according to the operating current and switching conditions. Continuous operation at high phase current must therefore be assessed against the cooling arrangement rather than inferred solely from the device’s nominal ratings.
EPC provides schematics, bills of materials and Gerber files to support evaluation and development. The reference boards are priced at US$690 for EPC91124 and US$680 for EPC91125 in the company’s announcement, with immediate availability reported through DigiKey and Mouser.
Both products are evaluation platforms rather than production-qualified industrial motor drives. Their common mechanical format and integrated measurement functions allow developers to compare two GaN power-stage configurations before determining the electrical, thermal and safety requirements of an application-specific inverter.
