Gigahertz Current Measurement for Wide Band-gap Devices

In order to improve efficiency and reduce circuit size the switching speeds of semiconductor power devices are being reduced. This is being achieved by the use of wide band-gap semiconductor devices. Traditional current measurement techniques are unable to accurately measure these new high speed switching edges, due to a lack of bandwidth and high insertion inductance. In this paper a 1.6 GHz bandwidth, scalable current, SMD shunt based current probe is developed for switching and steady state current measurements in wide band-gap power devices. By designing this shunt with an extremely low insertion inductance of less than 10 pH it is ensured that the measurement circuit has negligible impact on switching device operation

Design of a SiC-Based Switched CCM/TCM Inverter for High-speed Machine Drive with Low PWM-Induced Current Ripple

This paper presents the design of a SiC-based inverter for high-speed machine using a continuous conduction mode (CCM) and triangular conduction mode (TCM) switched switching scheme. The implementation of the switched TCM and CCM on machine drive are explored analytically in the context of PWM-induced current quality and efficiency, based on which, an improved switched switching strategy is employed. According to the difference in uneven current ripple distribution of TCM and CCM, the proposed strategy alternates between TCM and CCM in one line cycle for an enhanced current ripple and efficiency performance

Split Parallel Semibridge Switching Cells for Full-Power-Range Efficiency Improvement

This paper proposes a positively-coupled-inductor (PCI) based paralleling scheme for semi-bridge switching cells which are formed by power MOSFETs and diodes. Both the semi-bridge switching cell and the inductor are split into two parallel parts, and thus, a small differential-mode inductance is formed between the midpoints of the parallel semi-bridge switching cells. A time-delay-based modulation strategy is applied to generate a controllable circulating current which enables all active switches to achieve the zero-current switching (ZCS) or zero-voltage switching (ZVS), and all diodes to achieve ZCS turn-off. Accordingly, the switching loss and the reverse-recovery loss can be significantly reduced. The operating principle of the proposed paralleling scheme is characterized by two complementary operation modes: desynchronized mode with soft-switching (lower switching loss) and synchronized mode with lower conduction loss. Compared with conventional soft-switching schemes, this solution features zero auxiliary switches, constant switching frequency, and improved full-power-range efficiency enabled by the dual operation modes. Furthermore, design guidelines of the PCIs are presented where a novel winding arrangement is proposed and verified to obtain a controllable differential mode (DM) inductance. The operation principles and advantages of the proposed paralleling structure are comprehensively validated on both Buck and Boost dc-dc converters with both Si and SiC power MOSFETs and diodes

Optically Triggered Self-Adaptive Zero Voltage Switching

Zero voltage switching (ZVS) is useful to increase power electronics efficiency but difficult to achieve due to the nonlinear parasitic capacitance of the power semiconductors and varying load current. This letter proposes a self-adaptive ZVS method by using the intrinsic electroluminescence (EL) property of SiC mosfets to automatically adjust the switching frequency in every switching cycle to retain the optimal ZVS in varying load current. A sensing circuit is developed to digitally utilize the EL to trigger ZVS and embodied in a customized PCB-embedded half-bridge power module. Experimental results demonstrate the effectiveness of the proposed optically triggered self-adaptive ZVS in a Buck converter. The proposed method is compatible with conventional PWM gate drives for various power electronic devices and applications

Hybrid-Mode Adaptive Zero-Voltage Switching for Single-Phase DC-AC Conversion with Paralleled SiC MOSFETs

State-of-the-art soft-switching modulations such as critical conduction mode (CrM) and Triangular Current Mode (TCM) increase the conduction loss of power semiconductors and require variable switching frequencies, thus these soft-switching methods are seldom used in high-power DC-AC conversion. To achieve soft-switching while maintaining low RMS currents, this article proposes a Hybrid Quadrilateral and Continuous Current Mode (HQCCM) modulation for general high-frequency single-phase DC-AC conversion based on paralleled SiC MOSFETs. The proposed HQCCM adaptively operates in soft-switching Quadrilateral Current Mode (QCM) or hard-switching Continuous Conduction Mode (CCM) in one AC line cycle depending on the instantaneous AC load current. Thus, high efficiencies can be achieved over the full power range. This HQCCM modulation features adaptive soft-switching, constant switching frequency, compatibility to line filter and is applicable for high-power applications. A 4.4-kW single-phase DC-AC inverter is developed and tested to verify the advantages of the HQCCM. This article is accompanied by a video demonstrating the effectiveness of the proposed HQCCM in varying load scenarios