Fumiya Hattori

A Novel High-Efficiency Gate Drive Circuit for Normally Off-Type GaN FET

A novel drive circuit suitable for next generation semiconductor, GaN-FET (Gallium Nitride Field Effect Transistor), have been proposed and discussed in this paper. Drive loss is also analyzed on respective methods. Furthermore, the problem which is loss increase one of body diode in GaN-FET has been pointed out, and a novel active discharged type gate drive circuit suitable for GaN-FET is proposed. Its operating principles and low loss operation are discussed and evaluated effectiveness from the experimental point of view.

An analysis of false turn-on mechanism on power devices

Currently, driving power circuits at high switching frequency is performed in order to downsize and lighten switching power supplies. Along with it, wide band gap semiconductor devices, GaN and SiC, have attracted attention. However, there is a great constrain related to the false turn-on phenomenon produced by gate noise because these wide band gap semiconductor devices have low threshold voltage. If the false turn-on phenomenon occurs, the efficiency of the power supply decreases. Therefore, this paper analyzes the gate noise performance using simulation and experimental tests focusing on the parasitic inductance of the power devices terminals. As a result, it was found that the gate noises can be related to the recovery current of the body diodes. Additionally, this analysis was theorized by the comparison between the experimental results and the theoretical equation using an equivalent circuit.

Capacitor-Less Gate Drive Circuit Capable of High-Efficiency Operation for Non-Insulating-Gate GaN FETs

Recently, Gallium Nitride (GaN) power devices have become very attractive because of their high power density. GaN FETs, however, differ from MOSFETs, and it is possible that GaN-based power electronics circuits show lower efficiency than Si-based circuits because of their unique characteristics. A capacitor-less gate drive circuit is proposed as a solution. This paper shows the effectiveness of a capacitor-less gate circuit in terms of gate drive loss, reverse conduction loss, and recovery loss, and compares it with capacitor-type gate drive circuits for GaN FETs. Drive loss analysis of an inverted gate drive circuit showing the lowest losses among capacitor-type gate drive circuits and a capacitor-less gate drive circuit was made to examine the differences between them. The results show that higher efficiency operation is obtained by applying a capacitor-less gate drive circuit to simple test circuits.

Proposal and analysis of gate drive circuit suitable for GaN-FET

This paper proposes a novel gate-drive circuit suitable for the GaNFET. The gate-drive makes GaNFET turn-off sufficiently and also reduce a loss in the reverse conduction time which the reverse drain-source current flows to GaNFET at off-state. Moreover, the losses caused by the recovery phenomenon are compared the proposed gate-drive circuit with the conventional gate-drive circuit. In addition, a detailed loss analysis of the proposed gate-drive circuit is stated in this paper. Furthermore, the validity of the proposed circuit is evaluated and discussed from the experimental point of view.

Design method considering magnetic saturation issue of coupled inductor in interleaved CCM boost PFC converter

The demand of high power Continuous Conduction Mode (CCM) Power Factor Correction (PFC) converter installed in charging devices for Electric and Hybrid Vehicles has grown in the recent years. In these converters, the inductor often appears as the largest component, consequently, the CCM boost PFC converter using coupled inductors is well-known as one of the topologies that can achieve miniaturization and weight reduction of the inductors. However, the change of the magnetic flux during a half cycle of the input AC voltage has not yet been analyzed in detail. Therefore, the cause of the difference of the magnetic saturation is not known. In the case of non-coupled inductor, the magnetic saturation occurs at a point of the peak inductor current. In contrast, in the case of the coupled inductor, the magnetic saturation occurs at a different point than the inductor current peak. In this paper, the change of the magnetic flux in a half cycle of the input AC voltage is analyzed. Additionally, the novel design method of the coupled inductor considering the maximum magnetic flux is proposed. Finally, the validity of the novel design method is confirmed by experimental tests.

Drive loss analysis and comparison of capacitor-less gate drive circuit for GaN FETs with capacitor type gate drive circuits

Galluim-Nitride(GaN) power devises have a potential to achieve higher efficiency operation than Silicon(Si) ones such as MOS FETs and IGBTs. However, the characteristic of GaN FETs is different from MOS FETs, and thus, there is the possibility that GaN-based power electronics circuits shows more losses than Si-based ones. To resolve this problem, some of the gate drive circuits for GaN FETs are proposed and one of them is called capacitor-less gate drive circuit. This paper presents drive losses analysis of the capacitor-less gate drive circuit. Furthermore, the drive losses of the capacitor-less gate drive circuit are compared with capacitor-type gate drive circuit experimentally.

Multi-resonant gate drive circuit of isolating-gate GaN HEMTs for tens of MHz

Research of power supplies for megahertz (MHz) class applications such as a semiconductor manufacturing apparatus, induction heater and wireless transfer is carried out. A liner amplifier is generally used for MHz class applications. The loss of the power devices on a liner amplifier is theoretically high. To reduce the loss, the class E and Φ 2 inverters are proposed, and some of the resonant gate drive circuits (GDC) are utilised at those of the gate port. However, the control signal of the GDC becomes complicated due to the additional switches. Moreover, the switches in the GDC perform the hard-switching, and the drive loss can thus be increased. In this study, a multi-resonant gate drive circuit is proposed, and its design method is introduced. It can generate the trapezoidal wave gate-to-source voltage with the simple control signal, and zero voltage switching operation is achieved at the switches of the gate drive circuit. First, its operation is experimentally verified. Secondly, the drive loss is also compared with that of the conventional circuit. Furthermore, its operation with the class E inverter with a cascode GaN high-electron-mobility transistor (HEMT) is confirmed at the switching frequency 13.56 MHz.

Reduce of electric ner-field intensity by a shield box in wireless power transfer via field resinance coupling

Wireless Power transfer using electric field can realize highly efficient electrical power transmission and the transmission units are thin and light. However, the transmission system produces large electric field intensity and the electric field noise can make other electronic devices malfunction. A shield box is greatly effective to reduce the electric intensity 60dB without a decline of transmission efficiency. The distance between the shield box and the transmission unit should be a half of the transmission distance between a transmitter and a receiver. The shield box can attenuate the intensity behind the box less than 100V/m in case of 1kW transmission.

Basic experiment study on misalignment characteristic of electrical resonance coupling wireless power transfer

This paper describes lateral misalignment characteristics of electrical resonance coupling wireless power transfer (ERC-WPT) from experimental points of view. A dead zone is an important factor for ERC-WPT because ERC-WPT cannot transfer electric power in the zone. Electrical coupling units that are composed of 2 electrodes lined up laterally have a dead zone. The dead zone exists near outer edge areas of the electrodes and certain distant areas.

Mid-range kHz electric resonance coupling wireless power tranfser

This paper describes mid-range electrical resonance wireless power transfer in kHz range. Wireless power transfer using electrical field is minor since this method is understood only for close-range applications. However, our experimental units, the resonance frequency of which is 85 kHz, achieved 180 mm distance power transmission by vector network analyzer (VNA) measurement while keeping peak efficiency 68 %. In case of frequency response analyzer (FRA) measurement, the units can transfer power the most to the load at 300 mm but the efficiency is low. The closer the distance between the units, the better the efficiency is.