Pieter Jacqmaer

Fast robust gate-drivers with easily adjustable voltage ranges for driving normally-on wide-bandgap power transistors

Wide-bandgap (WBG) semiconductors, such as gallium nitride (GaN), are more and more being used in switching power devices. An AlGaN/GaN/AlGaN Double Heterojunction Field Effect transistor (DHFET) was developed in previous work and needed to be tested. The used test circuit was a buck converter. This type of converter, in addition with the normally-on switching behaviour of the GaN-based transistors, requires dedicated gate drive circuitry, resulting in the development of three types of gate-drivers. This paper presents the topology and performance of these drivers. Because of the type of converter, the drivers need to be galvanically isolated. Furthermore, because the experimental GaN transistors are normally-on, the drivers need to be robust so that they apply a negative gate-to-source voltage to switch off the transistor in case an error occurs in the driver. A third requirement for the drivers is that it has to be easy to adjust the voltage levels, in order to test the devices at different gate-to-source voltage conditions. A final requirement is that it has to be possible to construct the drivers with readily available electronic components. Because the drivers are galvanically isolated, there is a parasitic isolation capacitance in the DC-DC-converter of the drivers. This gives rise to a common-mode current which possibly can disturb the operation of the driver. The article also discusses this common-mode problem.

A novel voltage clamp circuit for the measurement of transistor dynamic on-resistance

For determining the dynamic on-resistance Rdyn,on of a power transistor, the voltage and current waveforms have to be measured during the switching operation. In measurements of voltage waveforms, using an oscilloscope, the characteristics of an amplifier inside the oscilloscope are distorted when the range of the measurement channel is not set wide enough to measure both on-state and off-state voltage, resulting in failure to accurately measure the voltage waveforms. A novel voltage clamp circuit improving the accuracy of the transistor on-state voltage measurement is presented. The measurement accuracy is improved by clamping the off-state voltage across the transistor to a lower voltage that is still greater than the on-state voltage. Unlike traditional clamping circuit, the presented voltage clamp circuit does not introduce delay caused by RC time constants keeping the voltage waveform clear even during state transitions of the evaluated semiconductor device for frequencies up to 1MHz.

A hybrid electric kart with energy flow management as a student project

A hybrid electric Kart is built as a didactical project for the students of the Master of Engineering: Energy of the K.U.Leuven. In order to cope with the growing number of students, a modular hybrid electric kart is conceived. The hybrid configuration allows to diversify between several tasks that have to be addressed by the students. The tasks include a control scheme for an induction motor, a control scheme and design of a power-factor-correction converter which enables power flow between the DC-link and a gasoline generator and finally the control scheme and design of a DC/DC converter allowing bidirectional power flow between a low voltage battery and the DC-link. All control schemes are supervised by a top level control scheme which maximises efficiency. The control schemes are programmed in Matlab/Simulink. A rapid-prototyping control board runs the model made in Matlab/Simulink. The control board interfaces between the different sensors and power electronics present on the kart.

An Electromagnetic Circuit Simulator for Power Electronics

A method for solving the full equations of Maxwell for circuits with discrete nonlinear, nonideal elements is presented. To this end, the method of moments is used in combination with a classical circuit simulator. Both operate in the frequency domain. A few methods to greatly accelerate the calculations are also presented. The methods are implemented and tested in Matlab.

Accurately modelling of parasitics in power electronics circuits using an easy RLC-extraction method

A method for accurately modelling parasitics in power electronic circuits, is presented in this paper. The freeware software programs FastCap and FastHenry are used to create a model of the printed circuit board tracks, consisting of resistances, self and mutual inductances, and self and mutual capacitances. This model can be easily loaded into a standard circuit simulator such as Spice, together with models for other components, such as the diodes, transistors, coils and capacitances. Thus, the power electronic circuit can easily be simulated in the time domain, returning electrical currents and voltages typically being subject to ringing effects and overshoot.

Modelling earthing systems and cables with moment methods

Purpose – The purpose of this paper is to present a method to model earthing systems subjected to lightning strikes with a one‐dimensional moment method. This paper was conducted because an accurate method to model earthing systems subjected to lightning strikes, was deemed necessary. To name a few examples of relevant situations: supply stations of railway systems, from which also critical signalling infrastructure is fed, earthing systems of cellular phone basestations, located in the vicinity of high‐antenna towers, prone to lightning strikes, and gas and oil pipelines. There exist already methods to solve this problem, based on circuit theory, but the electromagnetic method of this work is based directly on Maxwells equations and therefore more accurate.Design/methodology/approach – The earthing electrodes and meshes are represented as wire scatterers. First, the method is outlined for scatterers in a single medium. Next, the method is extended to model to presence of the soil‐air interface layer. An...

High Frequency Analysis of a Switching Mode Power Supply

In this paper, the electromagnetic fields radiated by a buck converter are calculated with a method based upon the Method of Moments (MoM). From the field line plots of the Poynting vector field, it is seen that DC power flows from voltage source to switch. There, the DC power is transformed into high frequency (HF) power. This HF power travels partially towards the diode where it is converted back into DC power which flows to the resistive load. This means that there exists a HF channel between switch and diode. In the second part of the paper, the conditions are derived to obtain a matching between the transmitter of high frequency power (switch) and the receiver (diode) at the different ends of the HF channel. The matching eliminates the radiation of energy at the switching frequency and its harmonics and therefore contributes to a better Electromagnetic Compatibility (EMC) performance.

Application of an electromagnetic modeling method for railway grounding systems subjected to lightning strikes

This document presents the work done for the Belgian railway operator Infrabel with respect to the modeling of grounding systems. Infrabel needed information on how to design the lightning protection systems of the recently deployed GSM-R installations. There exist many methods for simulating lightning strikes on grounding systems. One of these techniques, an electromagnetic method based on Moment Methods, is used to solve the problem. The theory behind the method is described and a novel technique is presented for simulating cylindrical cables without metal sheets. The method is applied to the grounding of the Infrabel GSM-R base station. The influence of the soil conductivity, the length of cables and grounding rods and the type of lightning strike on the effectiveness of the grounding system is researched.

Design, construction and control of a quasi-resonant SMPS working at 2 MHz.

Switching mode power supplies with higher switching frequencies are, in general, smaller in size for the same power rating. Resonant converters have an advantage over PWM-type converters because they use soft switching, reducing losses and increasing the energy efficiency of the power electronic circuit. In this paper, a converter is designed having a switching frequency of more than 2 MHz. The power is regulated and varies between 15 and 50 W, at a constant output voltage of 15 V. An LLC-type topology is chosen as resonant tank, in which the parasitic transformer leakage inductance is efficiently employed. An experimental converter was built, handling 50 W at 1.4 MHz. The efficiency is 60 % at full load..