Junction Temperature Variation Research Articles

Ferroelectric Field Effect Transistors–Based Content‐Addressable Storage‐Class Memory: A Study on the Impact of Device Variation and High‐Temperature Compatibility

Hafnium oxide (HfO2)‐based ferroelectric field effect transistors (FeFETs) revolutionize the emerging nonvolatile memory area, especially with the potential to replace flash memories for several applications. In this article, the suitability of FeFET memories is investigated, especially FeFET‐based content addressable memory (CAM) cells, as storage‐class memory under junction temperature variations. FeFETs with silicon oxynitride interfacial layer are fabricated and characterized at various temperatures, varying from room temperature to 120 °C. Although the memory window, numbers of programmable states, and endurance deteriorate at high temperatures, FeFETs show excellent robustness in data retention, write latency, and read stability at all temperatures, especially for binary operation. Finally, system‐level simulations using a Simulation Program with Integrated Circuit Emphasis software using experimental data are conducted to gauge the robustness of the data‐search operation using the CAM array under different temperatures. Despite temperature‐variation‐induced changes in FeFET devices, it is observed that binary CAM cells perform robust and unerring search operations for storing and searching data at temperatures up to 120 °C.

A novel integrated monitoring method for MPPF capacitor and IGBT junction temperature of half‐bridge modules

AbstractCapacitance and Insulated gate bipolar transistor (IGBT) junction temperature are two critical healthy parameters for modular multilevel converters (MMC) sub‐modules (SMs) condition monitoring. This paper proposes an integrated monitoring method for capacitance degradation and IGBT junction temperature variation. By measuring multiple characteristics of the same port voltage, the capacitance and the junction temperature can be obtained simultaneously, which greatly simplifies the measurement unit required for condition evaluation and realizes the submodule‐level condition monitoring at a lower cost. The capacitance is characterized by voltage changes during capacitor discharging and the junction temperature is monitored by capacitor voltage overshoot (peak value) during IGBT turn‐off. Theoretical analysis and experimental results verify the effectiveness of the proposed method and articulated the influence of load current, SM capacitor pre‐discharge voltage, and junction temperature. Moreover, an online data‐acquisition circuit for time‐specific capacitor voltage characterization is devised.

Thermal Behaviors of Thyristors in Repetitive Pulsed Power Applications

The temperature is closely related to the operating state of the thyristors in repetitive pulsed power applications. To study the thermal behaviors of the thyristor at high blocking voltage and repetition discharge frequency, the thermal calculation model, including the electrothermal model and the finite-element method (FEM) model, is established. The model is based on the practical conditions, the internal structure of the thyristor, and the heat transfer mechanism and is validated by comparing the experimental and calculation results. By the model, the transient junction temperature variation and the mathematical model among blocking voltage, repetition frequency, and junction temperature are obtained. The model presented is capable of evaluating the thermal behaviors, calculating the junction temperature of the thyristors in repetitive pulsed power applications, and providing optimal suggestions for the reliable operation of the pulsed power sources.

Online monitoring and correction method of threshold voltage in SiC MOSFET power cycling test

This paper presents an online monitoring and correction method of threshold voltage in SiC MOSFET power cycling test. The results of online monitoring of threshold voltage are coupled with both the effect of the degradation of SiC MOSFET chip and the effect of junction temperature variation caused by the degradation of the package. The proposed correction method can eliminate the influence of the junction temperature variation. And the effect of the chip degradation on the threshold voltage can be well reflected in the corrected results. The experimental results prove the effectiveness of the proposed method.

Comparison of junction temperature variations of IGBT modules under DC and PWM power cycling test conditions

Comparison of junction temperature variations of IGBT modules under DC and PWM power cycling test conditions

Electro-Thermal Modeling of Power IGBT Module Cooled by A Heat Pipe Cooling System

This paper deals with the development of an electro-thermal model of an Insulated Gate Bipolar Transistor (IGBT) with a water-cooled heat pipe cooling system. Firstly, a thermal model of the heat pipe cooling system is proposed. Then, an electro-thermal model of the IGBT is developed to predict the junction temperature variations in transient operation. The thermal model of the IGBT is determined on the base of the thermal-capacitance lumped method. The electrical model of the IGBT is developed by considering the effect of the junction temperature on its static electrical parameters. Finally, the electro-thermal model is considered in a boost converter application. The model predictions show the effectiveness of the heat pipe cooling system for different commutation frequencies. It is proved that the heat pipe cooling system can keep the junction temperature of the IGBT at values allowing safe operation.

Loss study and reliability analysis of a new reconfigurable fault‐tolerant multilevel inverter topology

A high reliable inverter with photovoltaic systems improves the efficiency and longevity of the entire system. Recent research emphasises on developing new fault-tolerant multilevel inverter (FTMLI) topologies. However, these topologies are not able to maintain rated voltage and power with a minimum switch count under switch fault conditions. This study proposes a new multilevel inverter with a reduced device count, which can handle both single switch fault and multi-switch fault by preserving its rated voltage and power. Sine-carrier-based level-shifted pulse-width modulation is used to generate control signals. The carriers are reconfigured based on the type and location of the fault. The loss contribution of each switch is calculated in all modes of operation by considering variations in junction temperature using a Powersim (PSIM) thermal model tool. This study helps to choose an appropriate heat sink for the switches. The reliability density function is calculated using a Markov chain model. A comparative study is presented to assess the notable benefits of the proposed topology over other existing similar topologies. The experimental results from the laboratory prototype are provided to verify the efficacy and practicality of the proposed FTMLI configuration.

A Thermal Estimation Method for IGBT Module Adaptable to Operating Conditions

This letter proposes a novel junction temperature estimation method for the IGBT module to adapt to various operating conditions and improve the computing efficiency. By using the superposition theorem and odd/even mode analysis, the input power loss is decomposed into the even and odd mode loss. Further, the thermal model considering the thermal coupling between the upper and lower arms is equivalently decomposed into the even and odd mode thermal model according to the structure symmetry. The odd mode power loss is the cause of the thermal coupling between the upper and lower arms, and the odd mode junction temperature variation is used as an indicator to measure the thermal coupling. Based on the frequency domain analysis, the dividing line for operating condition with weak thermal coupling and strong thermal coupling can be obtained. Finally, experimental results verify the validity of the theoretical analysis and the accuracy of the proposed thermal estimation method.

Red-shift effect in multi-color LEDs based visible light communication

Visible light communication (VLC) is a short range wireless optical communication system that provides lighting and data transmission, simultaneously. Besides lighting, in order to obtain high data rates, color-shift keying (CSK) which modulates the intensity of light using multi-color light emitting diodes (LEDs) has been introduced in IEEE 802.15.7 VLC standard. In CSK-based VLC (VLC-CSK) systems, some parameters of LEDs such as junction temperature is affected by physical and operation conditions. Junction temperature variations change the power spectral density (PSD) of LEDs, which is known as red-shift effect. In this study, the red-shift effect is examined for the first-time in VLC-CSK systems. The obtained numerical results show that the red-shift effect may dramatically reduce the performance of optical communication system. To eliminate the negative effect of red-shift, an effective solution based on the power normalization is proposed at the receiver side.

Aging Effect Analysis of PV Inverter Semiconductors for Ancillary Services Support

PV inverters can provide reactive power while generating active power. An ongoing microgrid implementation at Duke Energy actively engages non-utility PVs to generate/absorb reactive power in support of ancillary services to increase microgrid resiliency during extreme events. PV systems are requested to provide reactive power support: 1) in response to grid voltage variation to better regulate the local voltage; or 2) in response to utility incentives, such as following Transactive Energy System (TES) incentives. However, providing ancillary services might shorten the lifetime expectation of PV inverter semiconductors. This paper summarizes the potential impacts on a PV inverter semiconductor's lifetime when providing ancillary services. The analysis presented in this research work shows that providing reactive power support will increase the mean junction temperature and the junction temperature variation of the inverter diodes. This increased junction temperature will eventually lead to shorter diode lifetime. The lifetime estimation of semiconductors is briefly reviewed. The power losses of PV inverter semiconductors are derived as a support analysis to the junction temperature calculation. In addition, the impact of the filtering inductor on the semiconductor current distribution is discussed. The theoretical analysis presented in this research work is supported by simulation results.

Device Screening Strategy for Balancing Short-Circuit Behavior of Paralleling Silicon Carbide MOSFETs

This paper studies the spread of key electrical parameters of Silicon Carbide (SiC) MOSFET devices and its effect on the short-circuit (SC) behaviors. Device screening strategies are proposed to reduce the variation of the SC behaviors among the parallel-connected devices. Firstly, thirty discrete SiC devices from same production lot are characterized in terms of threshold voltage, transconductance, and on-resistance. The maximum variations of these device parameters are 0.5V, 1.41S and 25m ${\Omega } $ , respectively. The SC tests are performed individually on each device. The variations of SC peak current, SC energy, and SC junction temperature among these devices are 40A, 0.06J and 77°C. Furthermore, the effect of each parameter on SC behaviors variations is discussed. Based on the offset effect of parameters variation and the single transfer curves variation (TCV), a novel device screening strategy is developed. The variation of SC behavior of paralleling devices can be reduced by using the developed device screening strategy. This paper aims to provide guidelines on device screening for paralleling SiC MOSFETs.

Analytical Study on Junction Temperatures of GaInN and AlGaN Ultraviolet Light Emitting Diodes.

Junction temperatures of GaInN and AlGaN UV LEDs are analytically investigated in this paper. GaInN and AlGaN UV LEDs have a wide variety of applications such as lighting, displays, spectrofluometry, photocatalytic processes, and high resolution optics. An analytical method is employed to analyze the junction temperature variations of GaInN and AlGaN UV LEDs with injection currents. The junction temperature is related to material properties, quantum efficiency, thermal resistance, and series resistance of LEDs. The results of GaInN and AlGaN UV LEDs predicted by this study agree with these obtained from emission peak shift method and forward voltage method.

Role of Threshold Voltage Shift in Highly Accelerated Power Cycling Tests for SiC MOSFET Modules

In silicon carbide (SiC) power MOSFETs, threshold voltage instability under high-temperature conditions has potential reliability threats to long-term operation. In this paper, the threshold voltage shifts caused by the instability mechanisms in accelerated power cycling tests for SiC MOSFETs are investigated. In conventional power cycling tests, the positive threshold voltage shift can cause successive ON-state resistance increases, which can sequentially increase junction temperature variations gradually under fixed test conditions. In order to distinguish the increased die voltage drop from the bond wire resistance degradation, an independent measurement method is used during the power cycling tests. As the number of cycle increases, SiC die degradation can be observed independently of bond wire increases during the tests. It is studied that the SiC die degradation is associated with the threshold voltage instability mechanisms. Unlike the bond wire lift-off failure, the die degradation and the related die resistance increase can stop the power cycling test earlier than expected. In addition, a new test protocol considering the die degradation is proposed for the power cycling test. By means of power device analyzer, the failure mechanism and the degradation performance of SiC MOSFETs before and after the power cycling test are compared and discussed. Finally, experimental results confirm the role of threshold voltage shifting and identify different failure mechanisms.

Analysis of thermal and optical characteristics of light-emitting diode on various heat sinks

ABSTRACT Light-emitting diodes (LED) are widely used in today’s world due to its less power consumption and its high luminance capacity. Around 20–30% of energy is converted to light energy and 70–80% of energy is dissipated as heat. The excessive increase in temperature causes failure of LED. An effective thermal management is required for the proper heat dissipation in LED. In this study, the heat dissipation and the optical characteristics of the 16 W LED are studied using different types of aluminium heat sinks. The variation of case and junction temperature and the optical characteristic of LED is measured for different heat sinks. It was observed that heat sink with higher surface area shows the best result in terms of lower case and junction temperature. The higher luminous intensity was observed for the parallel fin type 1 heat sink due to the higher surface area.

The Influence of Junction Temperature Variation of LED on the Lifetime Estimation During Accelerated Aging Test

In this paper, seven LED lamps are selected to investigate how the junction temperature (Tj) of LED varies during the step-stress temperature accelerated aging test. The ambient temperatures are 80 °C and 70 °C for the first and second step of the aging test, respectively, and the total aging time is 2180 h. A non-contact method for monitoring junction temperatures of samples, by the ratio of white light energy to blue light energy (W/B), is applied. Experimental measurements show that the W/B ratio and Tj satisfy good linear relationship during the aging for all samples. Then, the junction temperatures are acquired at eight typical points of aging time which are used to eliminate the impact of Tj variation on the estimation of the decay rate and accelerated lifetime. It is shown that the estimated lifetime is longer than that acquired by the traditional method. The estimation errors of the accelerated lifetimes by the traditional method are in a range from 12.8% to 18.6% under the aging temperature of 80 °C and from 12.5% to 20.3% under the aging temperature of 70 °C for the seven samples. The estimation accuracy of the decay rates and accelerated lifetimes of LED lamps in the step-stress accelerated aging test is improved by the proposed methodology to a certain extent.

Optical and thermal performance of nitride-based thin-film flip-chip light-emitting diodes

Nitride-based light-emitting diodes (LEDs) were fabricated based on initial patterned sapphire substrate by thin film (TF) and flip-chip (FC) techniques. An enhancement of 7.7% in light output power was first obtained by optimizing the p-type contact layer. Then, periodic patterned surface was optimized by wet etching after removal of the sapphire substrate, and the light output power of the TFFC-LEDs was enhanced by 19.8% as compared to that of the TFFC-LEDs with original patterned surface. The device performance characteristic including illuminant pattern, emission wavelength movement and junction temperature variation of the optimized TFFC-LEDs were shown as compared with commercialized LEDs. The results indicate that the TFFC-LEDs possess uniform current distribution and lower junction temperature, thus show promising applications in various areas such as automotive lighting, illegal capture and solid-state lighting.

Experimental investigation of heat transfer characteristics of the LED module using passive heat sinks

ABSTRACT Light-emitting diode (LED) has several advantages and applications due to energy efficiency, versatility, performance, and long life. LED converts only 20–30% of the power input into light, converting the remaining 70–80% of the energy into heat that must be conducted from the LED die to the underlying circuit board, heat sinks, and housings. Improper thermal management will lead to an increase in the junction temperature above the safe limit, thus leading to premature failure of the LED. The present investigation aims to study the variation of case and junction temperature for three types of heat sinks, namely, diagonal, cylindrical, and spiral using 16 W LED. Light output in terms of lux is measured. Experiments were conducted by varying currents from 100 to 300 mA. It was observed that the spiral heat sink has the least junction temperature and thermal resistance among the three heat sinks at all current ratings.

Investigation and Emulation of Junction Temperature for High-Power IGBT Modules Considering Grid Codes

Grid-connected converters in wind turbine systems play a more active role in the future power grid dispatching for fulfilling specified grid codes. Hence, the diversified demands and faults from grid sides bring more intense thermal fatigue to the power modules. This paper proposes an investigation method for junction temperature (T j ) variation considering grid code constraints in laboratory environment. For the most cases of 690-V wind power systems, an MW-level H-bridge test setup with energy circulation is established. In the case of particular grid code requirements and T j control strategy, the equivalent voltage and current stresses can be reproduced and applied to the inspected insulated gate bipolar transistor (IGBT) power modules. To investigate the real-time T j under specific work conditions derived by grid codes, turn-off delay time-based thermal electrical sensitive parameter method is used for T j estimation. Consequently, a test procedure for the safe operation boundary of power converter using T j limitation as a new criterion is proposed. Finally, three types of typical operation conditions for a 1.5-MVA power converter are chosen for the validation of the proposed method. The typical conditions under grid code requirements can be reproduced and the corresponding real-time T j variation can be extracted. With the T j acknowledge, the safe operation boundary and parameter optimizations of IGBT modules can be determined by real T j instead of case temperature.

Analysis and Modeling of Thermal-Electric Coupling Effect of High-Power Monolithically Integrated Light-Emitting Diode

A 2-D thermal-electric coupling model has been developed, which enables us to evaluate the current distribution of monolithically integrated light-emitting diode (MI-LED). Based on the experimental IR images, the current distributions have been evaluated for the MI-LEDs on two types’ heat sinks. For the MI-LED on poor thermal conductive chip-on-board heat sink, although there is a large junction temperature variation of 40 °C all over the chip, the current only varies from −16% to 11% due to the high parasitic series resistance and the topological design of MI-LED. The experiments show that the impact of the heat-crowding-induced uneven current distribution on the wall-plug efficiency is negligible at a power density of 1 W/mm2. The average junction temperature is still the dominant issue. With a high thermal conductive copper heat sink, the average junction temperature could be suppressed below 50 °C, and there is no obvious heat crowding and uneven current distribution observed.

Increasing the reliability of wind turbines using condition monitoring of semiconductor devices: a review

The majority of electrical failures in wind turbines occur in the generator-side semiconductor devices. This is due to temperature swings affecting the layers of insulated-gate bipolar transistors in different ways; these effects are aggravated by the variation of wind speed. The implementation of accurate on-line condition monitoring mainly relies on on-line tracking of the temperature variation of components. The maximum temperature stress is observed at the junction terminal of the devices, which cannot be easily measured. Additionally, it is difficult to track the exact dynamic of temperature due to the slow response of sensors. Thus, several methods have been presented in the technical literature to estimate the junction temperature of the semiconductor devices. Each method has merits and disadvantages in terms of accuracy and complexity, as failure mechanisms have their own effects on the variation of junction temperature and some or all of the electrical parameters. Therefore, detection algorithms have to determine the root cause of the temperature variation. This study comparatively reviews the condition monitoring methods presented so far and gives directions on the future steps that should be addressed by research in this area.