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Increased productivity in industrial processes can be achieved by dynamic and accurate positioning of servo drives. Therefore, improvement of servo drive dynamics using latest technologies in the key components such as inverter, control system and position measuring device are investigated. Using Gallium Nitride (GaN) or Silicon Carbide (SiC) semiconductors for motor inverters enables energy efficient operation up to pulse width modulation (PWM) frequencies of 500 kHz. This allows motor filters with small component sizes. As a result, high motor efficiency, low torque ripple, high control bandwidth and almost ideal sinusoidal output voltages are achieved. Experiments on a 200 kHz Gallium Nitride inverter with sine wave motor filter show a current control loop bandwidth of 3.2 kHz and almost ideal sinusoidal phase voltages. The achieved bandwidths of the speed and position control loops are 318 Hz and 106 Hz, respectively.
We present low-cost, high-efficient electromagnetic coupling between open ring geometry and a so-called butterfly structure on standard printed circuit boards (FR4) for the purpose of short range wireless data and power transfer at an UHF resonance frequency of 868 MHz. The components of the transfer system are characterized by simulation and experiments in terms of associated scattering parameters. Characterizing the efficiency of the coupled resonators, RF signal power transmission is examined for high power transfer as well as for low power DC supply utilizing a voltage doubler rectifier. With an enhanced butterfly structure coupler, unmodulated RF power transmission of 17.3 W is achieved with an efficiency of more than 95%. Furthermore, signal transmission of Pulse-Width-Modulated (PWM) signals with frequencies up to 5 MHz is demonstrated.
Recent development of GaN power transistors with blocking voltages up to 650V enables novel power electronics applications with outstanding performance in high-frequency operation. This paper demonstrates a class E power amplifier with 13.56MHz switching frequency for inductively coupled DC power supplies. Continuous wave output power up to 200W is achieved with 95% Power Added Efficiency (PAE).
We present inductive power transfer (IPT) with a half-bridge converter based on differential relaxation self-oscillation. The oscillation dynamics of the converter automatically adapts to variation in the inductive coupling link and changes in the load, respectively. Design equations based on theoretical circuit analysis reveals a high power transfer efficiency (>90%) for alteration of coupling distance in the strong coupling regime. A prototype system employing GaN-HEMTs confirms the theoretically predicted characteristics of the proposed circuit.
This paper proposes an ultra-low inductance half-bridge switching cell with substrate integrated 650V GaN bare dies. A vertical parallel-plate waveguide structure with 100 μm layer thickness results in a commutation loop inductance of 0.5 nH resulting in a negligible drain-source voltage overshoot in the inductive load standard pulse test. On the other hand reliable circuit operation requires an assessment of the isolation strength of the thin dielectric layer in the main commutation loop, because critical high local electric fields might occur between the pads. Measurements of the dielectric breakdown voltage followed by a statistical failure analysis provide a characteristic life of 14.7 kV and a 10% quantile of 13.5kV in the Weibull fitted data. This characteristic life depends strongly on the ambient temperature and drops to 4.1kV at 125°C. Additionally, ageing tests show an increasing in dielectric breakdown voltage after 500h, 1000h and 2000h at 125°C high-temperature storage due to resin densification processes.
A gate drive circuit for gallium nitride (GaN) enhancement mode (e-mode) transistors is presented, which avoids parasitic turn-on of the power devices in the halfbridge configuration. New e-mode GaN devices turn on at very low threshold voltages between 1V and 2V. This makes the transistors highly sensitive to spurious turn-on and thus reduces the required safety margin of the gate drive signals. To avoid this parasitic turn-on, a very low gate loop impedance is required. This prevents the halfbridge against bridge shorts during the switching events and guarantees stable gate drive control with increased switching efficiency. The new gate drive circuit is developed in a SPICE simulation environment and verified in a prototype setup by a double pulse test. The simulation matches very well with the experimental result and demonstrates the suppression of parasitic semiconductor turn-on with the proposed gate drive. Furthermore the dissipated switching energy is reduced, compared to a standard gate drive circuit. High DCDC converter efficiency of 98.67% at 1kW output power is achieved by using the driving circuit for a buck converter prototype with 200kHz switching frequency.
Gallium Nitride (GaN) semiconductor devices are promised to be a good alternative to Silicon (Si) semiconductors in future motor inverters for variable frequency drives (VFDs). They combine low on state resistance and low switching losses with a high blocking voltage capability. Compared to actual inverters based on insulated gate bipolar transistors (IGBTs) the pulse width modulation (PWM) frequency for efficient operation can be increased by a factor of 5 to 10, extending the PWM frequency range up to 500 kHz. This allows the use of motor filters with small component size. As a result, high motor efficiency, low torque ripple, high control bandwidth and nearly ideal sinusoidal output voltages are achieved. Therefore this inverters can be used for high speed spindle motors and dynamic servo drives. This paper focus on the design of a hybrid sine wave filter consisting of an analog and a digital part. The filter is optimized to achieve low power loss and high current control bandwidth. A 3-phase GaN motor inverter operating at 200 kHz PWM frequency at 400 V DC-link voltage verifies the system design.
Power cycling and temperature endurance test of a GaN switching cell with substrate integrated chips
(2019)
We present a reliability study of a half-bridge switching cell with substrate integrated 650 V GaN HEMTs. Power Cycling Testing with a ΔTj of 100 K has revealed thermo-mechanically induced failures of contact vias after more than 220 kcycles. The via failure mode of contact opening is confirmed by reverse-bias pulsed IV-measurements to be primarily triggered by a ΔTj imposed thermal gradient and not by a high Tj. The chip electrical characteristics, however, remained unaffected during Power Cycling. Furthermore, a High Temperature Storage test at 125 °C for 5000 h has shown no changes in the electrical performance of substrate integrated GaN HEMTs.