Impact of Gamma Radiation on Dynamic RDSON Characteristics in AlGaN/GaN Power HEMTs
GaN high-electron-mobility transistors (HEMTs) are promising next-generation devices in the power electronics field which can coexist with silicon semiconductors, mainly in some radiation-intensive environments, such as power space converters, where high frequencies and voltages are also needed. Its wide band gap (WBG), large breakdown electric field, and thermal stability improve actual silicon performances. However, at the moment, GaN HEMT technology suffers from some reliability issues, one of the more relevant of which is the dynamic on-state resistance (R) regarding power switching converter applications. In this study, we focused on the drain-to-source on-resistance (R) characteristic…
Power system consumption model using SPICE
Space missions have very stringent mass, volume and also power budgets. This requires very precise knowledge of the power consumption of the whole satellite, not only peak power but also static and long term dynamic power. This calculation becomes very complex if all the operational modes (long term dynamic changes) are taken into account, including the different environmental situations. The power budget of any Power Converter Module (PCM), which includes not only the DC/DC converter but also the distribution unit, depends on the power it delivers and on external factors like temperature and input voltage. We propose to use a linear SPICE model using electronic models of discrete component…
Electron Emission of Pt: Experimental Study and Comparison With Models in the Multipactor Energy Range
Experimental data of secondary emission yield (SEY) and electron emission spectra of Pt under electron irradiation for normal incidence and primary energies lower than 1 keV are presented. Several relevant magnitudes, as total SEY, elastic backscattering probability, secondary emission spectrum, and backscattering coefficient, are given for different primary energies. These magnitudes are compared with theoretical or semiempirical formulas commonly used in the related literature.
On the design of a multiple-output DC/DC converter for the PHI experiment on-board of solar orbiter
Power converters for experiments that have to fly on board space missions (satellite, launchers, etc.) have very stringent requirements due to its use in a very harsh environment. The selection of a suitable topology is therefore not only based on standard requirements but additional more strict ones have also to be fulfilled. This work shows the design procedure followed to build the Power Converter Module (PCM) for the Polarimetric and Helioseismic Imager (SO/PHI), experiment on board the Solar Orbiter Satellite. The selected topology has been a Push-Pull, for a power level of approximately 35 W and with seven output voltages. Galvanic isolation is needed from primary to secondary, but no…
Novel test bed for induction heating power supplies
Power supplies used in induction heating industrial applications must be entirely tested after its manufacturing in order to assure its security and reliability by means of a full power running test of several hours of duration. Nowadays this test is done with a dissipative load which implies a large waste of energy. This paper proposes a new high efficiency test system for induction heating generators. It incorporates a regenerative electronic load which allows an extraordinary improvement of the efficiency of this test with an important economical and ecological benefit.
Isolated two-stage passive PFC rectifier for the Radioisotope Stirling Generator
This paper describes an isolated, passive power factor correction rectifier devised for low-voltage, large-inductance, single-phase alternator, like the one used in the Radioisotope Stirling Generator. The power converter splits into two independent stages, the front-end rectifier corrects the power factor by adding a series capacitor in the AC line. Further, the rectifier, thanks to the alternator inductance, behaves as a constant-current source that powers a current-fed, zero voltage and zero current switching push-pull stage. This approach takes advantage of all parasitic elements to increase power density while keeping simple and reliable. Full description and analysis is given as well …
High-Efficiency Regulation Method for a Zero-Current and Zero-Voltage Current-Fed Push–Pull Converter
A new high-efficiency regulation method for a zero-current and zero-voltage current-fed push-pull converter is presented. The method proposed is based on the use of a controlled transformer as a post-regulator, which adds or subtracts an additional voltage to the output filter of the converter. An auxiliary regulator, which only handles a percentage of the output power, controls this transformer, and therefore, results in much higher efficiency than a normal preregulator would have. The novelty of the presented converter is that regulation is achieved without affecting the zero-voltage and zero-current switching in any working conditions. Small- and large-signal models of the converter have…
Failure Rate Measurement on Silicon Diodes Reverse Polarized at High Temperature
This paper calculates the failure rate on reversed polarized silicon diodes with the aim to justify, experimentally, the rules of the European Space Agency (ESA) which are referred to the component life’s extension, the reliability increase and the end of life performance enhancement, by using oversized devices (derating rules). In order to verify the derating rules, 80 silicon diodes are used, which are reverse polarized in a high temperature environment. The diodes are divided in 4 groups of 20 diodes, applying a different voltage to each group, in order to relate the failure rate to the applied derating rule. The experiment described in this paper is developed using a temperature acceler…
Optimized Topology for High Efficiency Battery Discharge Regulator
In the following years power levels of 20 kW to 50 kW will be demanded by the telecommunication satellites. It is not possible to keep 0.5 kW modules with up to 100 modules in parallel and, therefore, higher power modules must be used. A higher bus voltage seems also necessary and any voltage below 150 V and above 100 V could meet the needs. In addition, new optimized topologies that process only a part of the total power delivery can be employed to improve the efficiency. In this article, design guidelines and experimental results of a high efficiency battery discharge regulator (BDR) module based on parallel power processing are given.
Evaluation of Gallium Nitride Transistors in Electronic Power Conditioners for TWTAs
The aim of this paper is to evaluate the benefits of replacing Si Mosfets transistors with enhancement mode GaN transistors in a Half-Bridge Zero Voltage and Zero Current Switching Power Switching Converter (ZVZCPS). This converter is usually used as power supply of the travelling-wave tube amplifiers (TWTAs) in aerospace applications. In this paper, firstly the converter is theoretically analyzed, obtaining its operation, losses and efficiency equations, these equations are used to obtain optimizations maps based on the main system parameters. In this way, the ideal design parameters can be visually obtained. These optimization maps are the key to quantify the potential benefits of GaN tra…
New Power Conditioning System for Battery-free Satellite Buses with Maximum Power Point Tracking
The purpose of this paper is describe a new conception of Power Conditioning Unit (PCU) developed to fulfill the requirements of BepiColombo Electronic Propulsion module. This load bus has very tough specification especially regarding transient response during total load switch-off ("beam out") which has to be less than 2% of the bus voltage. The conception we propose, is the new Sequential Switching Shunt Maximum Power Regulator (S3MPR) consisting in a S3R, to keep the SA voltage at its Maximum Power Point (MPP) followed by a Boost regulator to produce a constant 100V to supply the Electronic Propulsion (EP). This concept may also be of interest for other future missions involving high pow…
Soft switched interleaved boost converters used as high-power battery discharge regulator for space power systems
In the following years the telecommunication satellites will have a much greater power demand than nowadays. One reason for this is that the geostationary orbit required by this kind of satellites is becoming too crowded. Probably power levels of l0 kW to l00 kW will be the standard and with life duration of 25 years. It is not possible to keep 0.5 kW modules with more than 100 in parallel and therefore higher power modules (5 kW) must be used. A higher bus voltage seems also necessary and keeping a safety limit of 150 V, any voltage below it and above 100 V could meet the needs. In this paper we will propose a topology that fits the application: two soft switched interleaved boost converte…
Prototyping and Characterization of 1.2KV SIC Schottky Diodes for TWTA Application: The Challenge to Meet the User Specification
Novel zero-current-transition circuit for three-phase buck rectifiers
ZCT circuits have already been proposed in the past and are becoming more and more popular in high power rectifiers and inverters where bipolar devices have to be used (IGBTs or even BJTs). Although ZCT techniques have already been applied to three-phase boost type topologies, no ZCT circuits have been proposed for three-phase buck-type topologies. The authors propose a new load independent ZCT circuit for a three-phase buck-type rectifier which achieves high noise reduction, voltage stress reduction and zero current transitions to almost all transitions of the rectifier's switches including the additional auxiliary switches.
Dynamic $\mathrm{R}_{\mathrm{ON}}$ evaluation of commercial GaN HEMT under different switching and radiation conditions
This paper focus on the study of dynamic resistance $(\mathrm{R}_{\mathrm{dyn}})$ over commercial Gallium Nitride High Electromobility Transistors (GaN HEMTs) devices. The first part shows a study of the main mechanism causing $\mathrm{R}_{\mathrm{dyn}}$ , showing that depending on the structure, stress time, voltage applied and switching conditions, the $\mathrm{R}_{\mathrm{dyn}}$ can suffer a relevant increase. Also, it is demonstrated how the use of soft-switching conditions can alleviate trapping effects. Finally, due to the interest over these devices for future space applications, the effects of gamma radiation over the $\mathrm{R}_{\mathrm{dyn}}$ has been studied.
Unstable behaviour of normally-off GaN E-HEMT under short-circuit
The short-circuit capability of power switching devices plays an important role in fault detection and the protection of power circuits. In this work, an experimental study on the short-circuit (SC) capability of commercial 600 V Gallium Nitride enhancement-mode high-electron-mobility transistors (E-HEMT) is presented. A different failure mechanism has been identified for commercial p-doped GaN gate (p-GaN) HEMT and metal-insulator-semiconductor (MIS) HEMT. In addition to the well known thermal breakdown, a premature breakdown is shown on both GaN HEMTs, triggered by hot electron trapping at the surface, which demonstrates that current commercial GaN HEMTs has requirements for improving the…
Hydrogen back-up power system with photovoltaic direct energy transfer regulation and interleaved boost for space applicattions
This work details a power conditioning unit for photovoltaic/hydrogen based energy systems in space applications. The power conversion techniques applied are similar to the ones used on photovoltaic/battery space power systems. A direct energy transfer photovoltaic regulator is devised for feeding two outputs; the first output corresponds to the main unregulated battery bus and the second output sets a power path to feed an electrolyser. A modular fuel cell converter completes the system and operates when photovoltaic energy is not available or load demand exceeds the generated photovoltaic power, providing electrical power from a fuel cell. An ancillary battery, located in the main bus, di…
Study of the Audio Susceptibility in Parallel Power Processing With a High-Power Topology
In this paper, the audio susceptibility characteristic of a high-efficiency nonisolated topology that processes only a part of the total power delivery is analyzed. Since the proposed topology presents a direct path from input to output, the effect of the input voltage ripple at the output voltage has been studied. The effect on the audio susceptibility of the values and disposition of the components and the effect of their parasitic elements must be taken into account. Due to this study, the analytical expression of the audio susceptibility and the design criteria to improve it have been obtained.
Bidirectional high-power high-efficiency non-isolated step-up DC-DC converter
This paper presents the results of a high-efficiency high-power (5kW) non-isolated bidirectional DC-DC converter. High efficiency, high stability and simplicity are the main goals, and no galvanic isolation is required. The proposed topology is a new BOOST converter with output filter where input and output inductors are coupled together which can be designed to be a minimum phase system. This topology provides therefore input and output current filtering, reducing noise and need of additional filters. Its bidirectionality reduces mass in many applications like in charge/discharge subsystems and lowers cost and component count. This converter is useful with any system that needs backup batt…
Stability improvement of isolated multiple-output DC/DC converter using coupled inductors
Coupling output inductors is a very popular solution when designing a multiple-output DC/DC system. Space-borne circuits are one of the areas where a custom DC/DC converter design with coupled inductors could be preferred to have a detailed design of all variables. Output voltage regulation can be improved using coupled output inductors on a multiple-output DC/DC converter, and, as demonstrated in this paper, it provides an enhanced stability. This paper presents the small signal analysis of a push-pull converter with seven outputs having all its output inductors coupled together and compares it theoretically to the uncoupled version to demonstrate the stability improvement. The theoretical…
A Comparative Performance Study of a 1200 V Si and SiC MOSFET Intrinsic Diode on an Induction Heating Inverter
This paper presents a comparison of the behavior of the intrinsic diode of silicon (Si) and silicon carbide (SiC) MOSFETs. The study was done for 1200 V Si and SiC MOSFETs. The data sheet from manufacturers shows the characteristics of MOSFET' intrinsic diode when gate source voltage (VGS) is 0 V. There are applications where the MOSFET' intrinsic diode is used while VGS is different than 0 V. One of these applications is induction heating, where depending on the load and the regulation system, the diode can conduct a significant part of the inverter current. In most applications which use the MOSFET' intrinsic diode, the turn ON of the intrinsic diode happens at VGS = 0 V. After a blanking…
Benefits and Drawbacks of A High Frequency Gan Zvzcps Converter
This paper presents the benefits and drawbacks of replacing the traditional Si Mosfets transistors with enhancement mode GaN transistors in a Half-Bridge Zero Voltage and Zero Current Switching Power Switching (ZVZCPS) converter. This type of converters is usually used as Electronic Power Converters (EPC) for telecommunication satellites travelling-wave tube amplifiers (TWTAs). In this study, firstly the converter is theoretically analysed, obtaining its operation, losses and efficiency equations. From these equations, optimizations maps based on the main system parameters are obtained. These optimization maps are the key to quantify the potential benefits of GaN transistors in this type of…
Thermal Analysis of the Solar Orbiter PHI Electronics Unit
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300°C SiC Blocking Diodes for Solar Array Strings
Silicon Carbide 300V-5A Ni and W Schottky diodes with high temperature operation capability (up to 300°C) have been fabricated. This paper reports on the stability tests (ESA space mission to Mercury, BepiColombo requirements) performed on these diodes. A DC current stress of 5A has been applied to these diodes at 270°C for 800 hours. These reliability tests revealed both, degradation at the Schottky interface (forward voltage drift) and at the diode top surface due to Aluminum diffusion (bond pull strength degradation). The use of W as Schottky metal allows eliminating the forward voltage drift producing stable metal–semiconductor interface properties. Nevertheless, SEM observations of the…
Phase Margin Degradation of a Peak Current Controlled Converter at Reduced Duty Cycle
An inner current loop is frequently used in many switching power supplies to achieve higher stability and a good current sharing. Nevertheless, some problems derived from its practical implementation can be encountered. One problem is related to the need of filtering of the sensed current and was discovered by the authors in the implementation of a 500 W converter, when peak current control was applied by sensing the switch current. This paper will demonstrate mathematically that an RC filter not only filters out the noise but also can cause a degradation of the phase margin, especially, if the needed duty cycle is close to zero. The main reason for it is the severe distortion of the curren…
Design of Zero-Ripple-Current Coupled Inductors With PWM Signals in Continuous Conduction Mode
Coupled inductors are widely used in multiple outputs and interleaved dc–dc converters. Also filters often use coupled inductors as their inductive part. A generalized design procedure is proposed in this article focused on current ripple minimization and applicable to coupled inductors exposed to pulsewidth modulation signals and in continuous conduction mode. The design provides a very large inductance for all windings but one. Compared to other designs, it adapts to the existing magnetic properties of the magnetic device changing only the inductance ratio, simplifying the design and manufacturing process. It is based on the equivalent inductance value and its divergences. The only assump…
Zero Ripple Current with Coupled Inductors in Continuous Conduction Mode under PWM Signals
This article presents a generalized analysis to explain current ripple of an $m$ windings coupled inductor with a given coupling factor $k_{ij}$ for each pair of windings and then studies more in detail its use in the continuous conduction mode and with pulsewidth modulated signals. To determine the current ripple, a generalized expression of the equivalent inductance of each winding is calculated, including the influence of voltage unbalance. In the ideal case, the equivalent inductance shows that the current ripple can only become $m$ times smaller than that with uncoupled inductors. But in the unbalanced case, some divergences of the equivalent inductance appear that are responsible for …
High Temperature SiC Blocking Diodes for Solar Array
This paper presents the results of an experimental investigation of the performance of 300V-5A Silicon Carbide Ni and W Schottky diode operating in the range between -170°C to 270°C. We have developed these diodes as blocking diodes, for solar cell array protection in order to fulfill the BepiColombo mission specifications. An electro-thermal characterization has been performed taking into account the harsh condition of the mission (high temperature range and electrical stress). The destructive and non-destructive tests have assured that the designed SiC diodes are able to support the electro-thermal limits. A reliability test has also been performed to investigate the stability of forward …
Integrating New Open Source Assessment Tools into dotLearn LMS
The convergence process initiated by the European Higher Education Space (EHES) has changed the approach to the teaching and learning process focusing largely on monitoring the progress of the student. This task can be simplified with the proper use of tools integrated in the universities’ Learning Management Systems (LMS). Most of these platforms have modules for managing the evaluation and to create online examinations. However, they do not tend to contemplate ways of evaluation depending on the subjects taught. This chapter presents a tool for continuous evaluation of a variety of subjects and their integration into a LMS based on open source. In the University of Valencia’s particular c…
Using Pulse Density Modulation to Improve the Efficiency of IGBT Inverters in Induction Heating Applications
This paper analyses a high power (50 kW), high frequency (150 kHz) voltage fed inverter with a series resonant load circuit for industrial induction heating applications which is characterized by a full bridge inverter made with IGBT and the power control based on pulse density modulation (PDM). This power control strategy allows that the inverter works close to the resonance frequency for all output power levels. In this situation zero-voltage switching (ZVS) and zero-current switching (ZCS) conditions are performed and the switching losses are minimized. The results are verified experimentally using a prototype for induction hardening applications. A comparative study between the PDM and …
Multi-pulse characterization of trapping/detrapping mechanisms in AlGaN/GaN high electromobility transistors
GaN high-electro mobility transistors (HEMTs) are among the most promising candidates for use in high-power, high-frequency, and high-temperature electronics owing to their high electrical breakdown threshold and their high saturation electron velocity. The applications of these AlGaN/GaN HEMTs in power converters are limited by the surface trapping effects of drain-current collapse. Charge-trapping mechanisms affect the dynamic performance of all GaN HEMTs used in power switching applications. This study analyzes the dynamic resistance of GaN HEMTs and finds that the effects of dynamic resistance can be suppressed by controlling switching conditions and on-off cycles.