The efficiency improvement of the motor driving system which accounts for 60% of energy consumption is said to be progressing with the spread of inverters, but apart from electric automobiles and trains, the penetration rate in the field using large drive systems in factories or hospitals is not necessarily high. The cause is surge current and electromagnetic noise from the power inverter. These effects cause malfunctions in the peripheral control system. Currently, various countermeasures are being taken to remove surge current and electromagnetic noise in automobiles. The inverter itself is never friendly to the environment. Generally, voltage output of the inverter is performed by pulse width modulation (PWM), which is an essential problem. For example, the main cause of electromagnetic noise is that this rectangular voltage output is a harmonic component. This leads to short life of the coil in motor driving. “Ideal motor drive is drive with sinusoidal voltage”. Therefore, an inverter output with a sinusoidal high voltage (500-1000 V) is desired. A sinusoidal wave can be obtained by blocking harmonics using a low-pass filter, but the high-voltage filter becomes extremely large when the frequency is low (10 kHz or less). With a high frequency of 1 MHz or more, the filter can be downsized, and compact and noise-free motor driving is achieved by increasing the sine wave high output inverter frequency (1 MHz or more). However, 500-1000 V inverters operating at 1 MHz or higher do not yet exist in the world.

Therefore, complementary field effect transistor (C-FET) utilizing wide band gap semiconductors (SiC, GaN, diamond) is drastically reconfigured from the type and circuit configuration of the semiconductor. Complementary inverters power C-FETs can realize MHz high speed switching. Unlike conventional inverters in which an n-type channel FET (n-FET) is connected to upper and lower arms, complementary inverters are composed of an n-FET and a p-channel FET (p-FET). In the source fixed complementary inverter (Fig.1) in which the source potential of the upper p-FET is fixed to a high potential and the source potential of the lower n-FET is fixed to a low potential, the potential of the gate drive circuit is fixed. There is no bootstrap circuit for up-down, it is suitable for high-speed operation. Due to MHz switching by complementary inverter with wide bandgap semiconductor, harmonics can be eliminated with ultra small sinusoidal filter and sinusoidal high voltage output ideal for motor driving is realized.
It contributes to the surrounding friendly power system society.

Fig.1 System of complementary wide bandgap semiconductor devices such as that used for power inverters. (H.Kawarada et al. Sci. Rep. 7, 42368, (2017)).