A cartridge for use with a vaporization device comprising a first heating element, a first compartment for containment of a first vaporizable material, and a second compartment for containment of a second vaporizable material, wherein the device generates an aerosol for inhalation by a subject by heating the first vaporizable material or the second vaporizable material.

Multiple heating elements with separate vaporizable materials in an electric vaporization device

The temperature-sensitive electrical parameters (TSEPs) have been used in silicon carbide (SiC) mosfets junction temperature measurement for over-temperature protection and condition monitoring. However, the device aging can affect the TSEPs and thus leads to false ${\boldsymbol{T}}_{\boldsymbol{j}}$ measurement. In this article, the aging's impacts on various TSEPs are comprehensively investigated. Specifically, utilizing the dc power cycling test, both the gate oxide instability and package degradation are considered. Then the commercial devices with different structures are aged, and their temperature-dependent static and switching characteristics are evaluated at different aging cycles. Both the positive gate bias-induced threshold voltage shift and package degradation are observed, and their impacts on each TSEP are evaluated independently. Based on the evaluation results at various operating conditions, the temperature measurement errors due to different aging mechanisms are well summarized for each TSEP. From the dc power cycling test result, the package degradation's impact on TSEPs is found to be more significant than the gate oxide instability. It is pointed out that the aging's effect on TSEPs is an important factor that needs to be considered for accurate ${\boldsymbol{T}}_{\boldsymbol{j}}$ measurement in SiC mosfets .

Evaluation of Aging's Effect on Temperature-Sensitive Electrical Parameters in SiC mosfets

Threshold voltage ( V TH) shift due to bias temperature instability (BTI) is a well-known problem in SiC mosfet s that occurs due to oxide traps in the SiC/SiO2 gate interface. The reduced band offsets and increased interface/fixed oxide traps in SiC mosfet s makes this a more critical problem compared to silicon. Before qualification, power devices are subjected to gate bias stress tests after which V TH shift is monitored. However, some recovery occurs between the end of the stress and V TH characterization, thereby potentially underestimating the extent of the problem. In applications where the SiC mosfet module is turned off with a negative bias at high temperature, if the V TH shift is severe enough, there may be electrothermal failure due to current crowding since parallel devices lose synchronization during turn- on . In this paper, a novel method that uses the forward voltage of the body diode during reverse conduction of a small sensing current is introduced as a technique for monitoring V TH shift and recovery due to BTI. This non-invasive method exploits the increased body effect that is peculiar to SiC mosfet s due to the higher body diode forward voltage. With the proposed method, it is possible to non-invasively assess V TH shift dynamically during BTI characterization tests.

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A Novel Non-Intrusive Technique for BTI Characterization in SiC mosfet s

The long-term reliability concerns regarding the latest power devices, e.g., silicon carbide (SiC) MOSFETs, need to be well understood for their rapid and widespread deployment in industrial applications. As an effective reliability assessment, the dc power cycling test is one of the most realistic procedures providing accelerated lifetime tests. In this paper, a dc power cycling setup for SiC power MOSFETs is proposed, and the design methodology is generalized for practicing engineers. At first, the aging-independent junction temperature measurement method is identified to eliminate the laborious recalibration process. Specifically, the electrical parameter changes of commercial SiC MOSFETs are evaluated in a power cycling test. It is observed experimentally that the body diode’s voltage drop at low current and negative gate bias is unaffected by the device/package degradation. Therefore, it is selected for $T_{j}$ measurement in the proposed setup. Following that, the design considerations regarding precise parameter measurement of the device’s parameter are presented. The transient behavior of the proposed test setup is analyzed, and a simulation model is built in LTspice. Based on the model, the effects of gate timing control and paralleled capacitors are investigated for realizing accurate measurements, and the simulation results are verified experimentally in a prototype. In addition, considering the measurement delay in the conditioning circuits and the common-mode noise, the practical issues affecting the measurement accuracy in a multiple-phase setup are investigated in the experiment. Experimental results show that an accurate measurement can be achieved with the design considerations.

Design Methodology of DC Power Cycling Test Setup for SiC MOSFETs

This paper proposes a novel modulation technique for the bidirectional operation of the phase-shift full-bridge (PSFB) dc/dc power converter. The forward or buck operation of this topology is well known and widely used in medium-to-high-power dc-to-dc converters. In contrast, backward or boost operation is less typical since it exhibits large drain voltage overshoot in devices located at the secondary or current-fed side—a known problem in isolated boost converters. For that reason, other topologies of symmetric configuration are preferred in bidirectional applications. In this work, we propose a modulation technique overcoming the drain voltage overshoot of the isolated boost converter, without additional components other than the ones in a standard PSFB and still achieving full or nearly full ZVS in the primary or voltage-fed side devices along all the load range. The proposed modulation has been tested in a bidirectional 3.3 kW PSFB achieving a 98% of peak efficiency in buck mode (380 V input, 54.5 V output), and a 97.5% in boost mode (51 V input, 400 V output). This demonstrates that the PSFB converter may become a relatively simple and efficient topology for bidirectional dc-to-dc converter applications.

Modulation Scheme for the Bidirectional Operation of the Phase-Shift Full-Bridge Power Converter

An isolated boost power converter comprises a magnetically permeable multi-legged core (102) comprising first and second outer legs (132; 136) and a center leg (134) having an air gap (138) arranged therein. A boost inductor (Lboost) is wound around the center leg (134) or the first and second outer legs (132; 136) of the magnetically permeable multi-legged core (102). The boost inductor (Lboost) is electrically coupled between an input terminal (104) of the boost converter and a transistor driver (106) to be alternatingly charged and discharged with magnetic energy. A first and second series connected secondary transformer windings (SW1; SW2) with a center-tap (116) arranged in-between are wound around the first and second outer legs (132; 136), respectively, of the magnetically permeable multi-legged core (102). In a first discharge state, the magnetic energy stored in the boost inductor (Lboost) is discharged by directing a discharge current from the boost inductor through a primary transformer winding (PW1; PW2) and in a second discharge state, the magnetic energy stored in the boost inductor (Lboost) is discharged by discharging a magnetic flux through the first and second secondary transformer windings (SW1; SW2).

An isolated boost flyback power converter

This work considers an alternative method of reducing the body diode reverse recovery by taking advantage of the MOSFET body effect, and applying a bias voltage to the gate before reverse recovery. A test method is presented, allowing the accurate measurement of voltage and current waveforms during reverse recovery at high di/dt. Different bias voltages and dead times are combined, giving a loss map which makes it possible to evaluate the practical efficacy of gate bias on reducing the MOSFET body diode reverse recovery, while comparing it to the well known methods of dead time optimization. A selection of 60V devices for synchronous rectification are compared for their suitability for gate bias, while a selection of 600V devices are compared for the efficacy of gate bias for the zero voltage transition converter application. The results show that many of the tested devices benefit from greatly reduced reverse recovery after the application of gate bias.

Practical investigation of the gate bias effect on the reverse recovery behavior of the body diode in power MOSFETs

This paper investigates the feasibility of using an alternator as means of harvesting energy from a stationary exercise bicycle. A switch mode converter was designed to regulate the current in the alternator rotor winding, thus regulating the power required to pedal, and consequently the power output of the bike. The complete controller design consists of this power stage, a control circuit, a startup circuit and an overvoltage protection circuit. A functional overview of the entire controller is presented in the paper, along with in-depth descriptions of the specific subcircuits designed. The system is self-starting and does not require an external power source. There are two modes of operation: Voltage regulated 12V output for connection to a standard inverter, and unregulated output for charging of a 24V battery, with direct linear control of the rotor current, thus simulating road bike gearing. Prototype bikes were built and used at several events, and the functionality was experimentally verified.

Energy harvesting from an exercise bike using a switch-mode converter controlled generator

A new solution to the start-up and low output voltage operation of isolated boost family converters is presented. By the use of integrated magnetics and winding integration, the transformer secondary winding is re-used during start-up as a flyback winding coupled to the boost inductor. The traditional added flyback winding coupled to the boost inductor is thus eliminated from the circuit, bringing substantial cost savings, increased efficiency and simplified design. Each subinterval of the converter operation is described through electrical and magnetic circuit diagrams, and the concept is extended to other isolated boost family topologies. The principle of operation is demonstrated with a 800W isolated boost prototype, and a 1600W primary parallel series secondary isolated boost converter. Efficiency measurements of both prototypes are presented, including measurements during both start-up and normal boost operation.

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A new method for start-up of isolated boost converters using magnetic- and winding-integration

The present invention relates to a microwave powered sensor assembly for micro- wave ovens. The microwave powered sensor assembly comprises a microwave antenna for generating an RF antenna signal in response to microwave radiation at a predetermined excitation frequency. A dc power supply circuit of the microwave powered sensor assembly is operatively coupled to the RF antenna signal for extracting energy from the RF antenna signal and produce a power supply voltage. A sensor is connected to the power supply voltage and configured to measure a physical or chemical property of a food item under heating in a microwave oven chamber.

Kristian Lindberg-Poulsen

Papers

An isolated boost flyback power converter

Practical investigation of the gate bias effect on the reverse recovery behavior of the body diode in power MOSFETs

Energy harvesting from an exercise bike using a switch-mode converter controlled generator

A new method for start-up of isolated boost converters using magnetic- and winding-integration

A microwave powered sensor assembly for microwave ovens