Showing papers on "Junction temperature published in 2014"

Real-Time Temperature Estimation for Power MOSFETs Considering Thermal Aging Effects

Abstract: This paper presents a novel real-time power-device temperature estimation method that monitors the power MOSFET's junction temperature shift arising from thermal aging effects and incorporates the updated electrothermal models of power modules into digital controllers Currently, the real-time estimator is emerging as an important tool for active control of device junction temperature as well as online health monitoring for power electronic systems, but its thermal model fails to address the device's ongoing degradation Because of a mismatch of coefficients of thermal expansion between layers of power devices, repetitive thermal cycling will cause cracks, voids, and even delamination within the device components, particularly in the solder and thermal grease layers Consequently, the thermal resistance of power devices will increase, making it possible to use thermal resistance (and junction temperature) as key indicators for condition monitoring and control purposes In this paper, the predicted device temperature via threshold voltage measurements is compared with the real-time estimated ones, and the difference is attributed to the aging of the device The thermal models in digital controllers are frequently updated to correct the shift caused by thermal aging effects Experimental results on three power MOSFETs confirm that the proposed methodologies are effective to incorporate the thermal aging effects in the power-device temperature estimator with good accuracy The developed adaptive technologies can be applied to other power devices such as IGBTs and SiC MOSFETs, and have significant economic implications

Modulation Methods for Neutral-Point-Clamped Wind Power Converter Achieving Loss and Thermal Redistribution Under Low-Voltage Ride-Through

Abstract: The three-level neutral-point (NP)-clamped (3L-NPC) converter is a promising multilevel topology in the application of megawatt wind power generation systems. However, the growing requirements by grid codes may impose high stress and even give reliability problem to this converter topology. This paper investigates the loss and thermal performances of a 10-MW 3L-NPC wind power inverter undergoing low-voltage ride-through (LVRT) operation. A series of new space vector modulation methods is then proposed to relocate the thermal loading among the power switching devices. It is concluded that, with the proposed modulation methods, the thermal distribution in the 3L-NPC wind power inverter undergoing LVRT becomes more equal, and the junction temperature of the most stressed devices can be also relieved. Also, the control ability of the dc-bus NP potential, which is one of the crucial considerations for the 3L-NPC converter, is even more improved by the proposed modulation methods.

Dynamic and static behavior of packaged silicon carbide MOSFETs in paralleled applications

Abstract: There is little work done to study the nuances related to paralleling the higher speed SiC Mosfet devices when compared to Si devices. This paper deals with the parallel operation of packaged silicon carbide (SiC) MOSFETs. The parameters that affect the static and dynamic current sharing behavior of the devices have been studied. We also investigate the sensitivity of those parameters to the junction temperature of the devices. The case temperature difference for paralleled MOSFETs has been experimentally measured on a SEPIC converter for different gate driver resistance and different switching frequency, the results show the current and temperature can be well balanced for the latest generation of SiC MOSFETs with low gate driver resistance.

Characterization and Scalable Modeling of Power Semiconductors for Optimized Design of Traction Inverters with Si- and SiC-Devices

Abstract: Silicon carbide (SiC) based power semiconductors are expected to contribute to an increase in inverter efficiency, switching frequencies, maximum permissible junction temperature, and system power density. This paper presents a comparison of silicon (Si) and SiC device technologies for the use in hybrid electric vehicle traction inverters. SiC-JFETs and SiC-MOSFETs are characterized and a scalable loss and scalable thermal modeling approach is used to find the optimum chip area for each Si or SiC traction inverter. This procedure also provides a proper technical comparison of the semiconductor technologies. The progressed simulations using standardized drive cycles and thermal-electrical coupled semiconductor models permit an inverter performance evaluation close to real load situations, leading to an improved estimation of the benefit which can be expected from systems utilizing SiC technology. This paper concludes that the SiC devices can lead to a reduction in chip area and semiconductor losses by more than 50% at the same time in hard switching applications with partial load dominated mission profiles.

High Temperature Stability and the Performance Degradation of SiC MOSFETs

Abstract: SiC MOSFET devices have great potentials in future high temperature power electronics applications due to their possible higher thermal runaway temperature compared with other SiC power semiconductor devices. In this paper, the high temperature stability of SiC MOSFETs is investigated by experiments and Saber simulations. The maximum steady-state junction temperature of the SiC MOSFET is measured to exceed 250 °C and saber simulations based on experimental model estimate that the thermal runaway temperatures are close to 300 °C. In addition, performance degradation of SiC MOSFETs during high-temperature operation is observed and discussed. Experimental results show that the degradation happens during both the high temperature storage (maximum 5% RON increment) and high temperature operation process (maximum 15% RON increment). The degradations are found to recover to a close-to-initial level after 1 h recovery time at the room temperature.

Improving Power Converter Reliability: Online Monitoring of High-Power IGBT Modules

Abstract: The real-time junction temperature monitoring of a high-power insulated-gate bipolar transistor (IGBT) module is important to increase the overall reliability of power converters for industrial applications. This article proposes a new method to measure the on-state collector-emitter voltage of a high-power IGBT module during converter operation, which may play a vital role in improving the reliability of the power converters. The measured voltage is used to estimate the module average junction temperature of the high and low-voltage side of a half-bridge IGBT separately in every fundamental cycle of the current by calibrating them at load current. The measurement is very accurate and also measures the voltage at the middle of a pulse-width modulation (PWM) switching. A major objective is that this method is designed to be implemented in real applications. The performance of this technique is measured in a wind power converter at a low fundamental frequency. To illustrate more, the test method as well as the performance of the measurement circuit are also presented. This measurement is also useful to indicate failure mechanisms such as bond wire lift-off and solder layer degradation. The measurements of and rise in the junction temperature after five million cycles of normal operation of the converter are also presented.

High-output-power 255/280/310 nm deep ultraviolet light-emitting diodes and their lifetime characteristics

Abstract: 255/280/310 nm deep ultraviolet light-emitting diodes (DUV LEDs) suitable for high-current operation are reported. Newly developed 1 mm sized chips are installed in a commercial package with a two-series configuration. At a forward current of 350 mA, we measured powers of 45.2, 93.3, and 65.8 mW for the 255, 280, and 310 nm LEDs, respectively. The corresponding external quantum efficiencies per serial circuit were 1.3, 3.0, and 2.4%, and successful chip scalability was demonstrated. The 50% lifetime of the 280 nm LED die was estimated to be 3000 h at a junction temperature of 30 °C.

An All-SiC High-Frequency Boost DC–DC Converter Operating at 320 °C Junction Temperature

Abstract: This letter presents the design, prototype development, operation, and testing of an 800 kHz, 1 kW, 800 V output boost dc–dc converter module that integrates SiC MOSFET and SiC Schottky diode die. It is observed that when the device loss is dominated by switching loss, the steady-state junction temperature of SiC MOSFET can reach as high as 320 °C. This is the highest self-heated junction temperature operation of SiC power devices under room temperature ambient reported in the literature. The high-frequency switching characteristics and high-temperature thermal reliability of the assessed converter are evaluated in detail. A solder-molten phenomenon during high junction temperature operation is detected and the die-attachment material is thus improved to enhance the high-temperature thermal reliability of the converter module. This study shows that the high-frequency capability of a gate driver and high-temperature die-attachment technology can be limiting factors preventing SiC power devices from operating at higher junction temperatures.

Thermoelectric Cooling for Power Electronics Circuits: Modeling and Active Temperature Control

Abstract: This paper discusses the modeling and application of thermoelectric cooling (TEC) in power electronics circuits. To investigate the benefits and challenges of using TEC, a temperature-dependent thermoelectric model which includes both power electronics circuits and TEC device is presented. With this model, both steady-state and small signal analyses can be carried out, and this paper is more focused on the steady-state part. For the steady-state analysis, the results have identified the allowed operation range which could be used as guidelines for system design. Also, with TEC device, the case temperature and junction temperature of power electronics switches can be dynamically controlled. Therefore, the switches' thermal cycling problem could be alleviated, and the switch lifetime and overall system reliability will be improved. Both simulation and experimental results are presented in this paper to verify the analysis.

A high temperature silicon carbide MOSFET power module with integrated silicon-on-insulator based gate drive

Abstract: This paper presents a board-level integrated silicon carbide (SiC) mosfet power module for high temperature and high power density application. Specifically, a silicon-on-insulator (SOI)-based gate driver capable of operating at 200 °C ambient temperature is designed and fabricated. The sourcing and sinking current capability of the gate driver are tested under various ambient temperatures. Also, a 1200 V/100 A SiC mosfet phase-leg power module is developed utilizing high temperature packaging technologies. The static characteristics, switching performance, and short-circuit behavior of the fabricated power module are fully evaluated at different temperatures. Moreover, a buck converter prototype composed of the SOI gate driver and SiC power module is built for high temperature continuous operation. The converter is operated at different switching frequencies up to 100 kHz, with its junction temperature monitored by a thermosensitive electrical parameter and compared with thermal simulation results. The experimental results from the continuous operation demonstrate the high temperature capability of the power module at a junction temperature greater than 225 °C.

Thermal impedance model of high power IGBT modules considering heat coupling effects

Abstract: Thermal loading of Insulated Gate Bipolar Transistor (IGBT) modules is important for the reliability performance of power electronic systems, thus the thermal information of critical points inside module like junction temperature must be accurately modeled and predicted. Usually in the existing thermal models, only the self-heating effects of the chips are taken into account, while the thermal coupling effects among chips are less considered. This could result in inaccurate temperature estimation, especially in the high power IGBT modules where the chips are allocated closely to each other with large amount of heat generated. In this paper, both the self-heating and heat-coupling effects in the of IGBT module are investigated based on Finite Element Method (FEM) simulation, a new thermal impedance model is thereby proposed to better describe the temperature distribution inside IGBT modules. It is concluded that the heat coupling between IGBT and diode chips strongly influence the temperature distribution inside IGBT module, and this effect can be properly modeled/predicted by the proposed thermal impedance model.

A simple differential steady-state method to measure the thermal conductivity of solid bulk materials with high accuracy

Abstract: Accurate measurements of thermal conductivity are of great importance for materials research and development. Steady-state methods determine thermal conductivity directly from the proportionality between heat flow and an applied temperature difference (Fourier Law). Although theoretically simple, in practice, achieving high accuracies with steady-state methods is challenging and requires rather complex experimental setups due to temperature sensor uncertainties and parasitic heat loss. We developed a simple differential steady-state method in which the sample is mounted between an electric heater and a temperature-controlled heat sink. Our method calibrates for parasitic heat losses from the electric heater during the measurement by maintaining a constant heater temperature close to the environmental temperature while varying the heat sink temperature. This enables a large signal-to-noise ratio which permits accurate measurements of samples with small thermal conductance values without an additional heater calibration measurement or sophisticated heater guards to eliminate parasitic heater losses. Additionally, the differential nature of the method largely eliminates the uncertainties of the temperature sensors, permitting measurements with small temperature differences, which is advantageous for samples with high thermal conductance values and/or with strongly temperature-dependent thermal conductivities. In order to accelerate measurements of more than one sample, the proposed method allows for measuring several samples consecutively at each temperature measurement point without adding significant error. We demonstrate the method by performing thermal conductivity measurements on commercial bulk thermoelectric Bi2Te3 samples in the temperature range of 30–150 °C with an error below 3%.

Online junction temperature measurement via internal gate resistance during turn-on

Abstract: A new method for junction temperature measurement of power semiconductor switches is presented. The measurement exploits the temperature dependent resistance of the temperature sensitive electrical parameter (TSEP): the internal gate resistance. This dependence can be observed during the normal switching transitions of an IGBT or MOSFET, and as a result the presented method uses the integral of the gate voltage during the turn-on delay. A measurement circuit can be integrated into a gate driver with no modification to converter or gate driver operation and holds significant advantages over other TSEP based measurement methods, primarily being: an absence of any dependence on operating conditions such as load current, and the potential to achieve higher sensitivity (20mV/C or more) than alternative TSEPs.

Color Variation Reduction of GaN-Based White Light-Emitting Diodes Via Peak-Wavelength Stabilization

Abstract: The color, electrical, and thermal properties of LED devices are highly dependent on one another. The peak wavelength of GaN-based white LED shifts in opposite directions under the influences of current and junction temperature change. This affects the correlated color temperature (CCT). Importantly, duty cycle control for LED dimming does not provide constant color (against conventional wisdom). An analysis model that links the peak wavelength, electrical, and thermal properties of LED devices is proposed. The color-shift trend of the LED with respect to the changes in its thermal and electrical operating conditions is described. The stabilized CCT performance of a dc or a bilevel-driven LED over a dimming range is found to be a result of the complex interactions between the selected current levels, duty cycle, thermal resistances of the heatsink and device, heat dissipation conversion ratio, and the physical parameters of the LED device. The predicted color variation is verified by experimental results, which demonstrate that the CCT stabilization of an LED with a dc drive requires less thermal energy than that with a bilevel drive. For a given thermal design, the reduction in CCT variation during light intensity change is possible via the combined adjustment of the current level and its duty cycle over the dimming operation.

Analysis and characterization of thermal transport in GaN HEMTs on Diamond substrates

Abstract: The emergence of Gallium Nitride-based High Electron Mobility Transistor (HEMT) technology has proven to be a significant enabler of next generation RF systems. However, thermal considerations currently prevent exploitation of the full electromagnetic potential of GaN in most applications, limiting HEMT areal power density (W/mm 2 ) to a small fraction of electrically limited performance. GaN on Diamond technology has been developed to reduce near junction thermal resistance in GaN HEMTs. However, optimal implementation of GaN on Diamond requires thorough understanding of thermal transport in GaN, CVD diamond and interfacial layers in GaN on Diamond substrates, which has not been thoroughly previously addressed. To meet this need, our study pursued characterization of constituent thermal properties in GaN on Diamond substrates and temperature measurement of operational GaN on Diamond HEMTs, employing electro-thermal modeling of the HEMT devices to interpret and relate data. Strong agreement was obtained between simulations and HEMT operational temperature measurements made using two independent thermal metrology techniques, enabling confident assessment of peak junction temperature. The results support the potential of GaN on Diamond to enable a 3X increase in HEMT areal dissipation density without significantly increasing operational temperature. Such increases in HEMT power density will enable smaller, higher power density Monolithic Microwave Integrated Circuits (MMICs).

A real time measurement of junction temperature variation in high power IGBT modules for wind power converter application

Abstract: paper presents a real time measurement of on-state forward voltage and estimating the junction temperature for a high power IGBT module during a power converter operation. The power converter is realized as it can be used for a wind turbine system. The peak of the junction temperature is decreased at higher fundamental frequency due to change in on-state time from the change in output frequency. The junction temperature is estimated using the on-state collector- emitter voltage of the IGBT module. Lower output frequency is thermally a higher stressing zone for wind power con- verters, hence the low frequency range is considered from 6Hz to 20Hz; the corresponding on-state collector-emitter voltage and junction temperature are presented. The estimation of junction temperature is compared with finite element based thermal simulations. The peak temperatures at different frequencies are compared between measurement and si- mulation results. The measurement technique desinged to be implementable for field application.

An effective heat propagation path-based online adaptive thermal model for IGBT modules

Abstract: The information of junction temperature is crucial for operation management of IGBT modules In practice, junction temperature is typically estimated by using an electrothermal model IGBT modules are subject to various aging processes during operation, some of which, eg substrate solder crack, changes the thermal impedance of an IGBT module However, in the literature little work has included the aging effects into online thermal behavior modeling of IGBT modules This paper proposes an Effective Heat Propagation Path (EHPP)-based online adaptive thermal model for IGBT modules, where the EHPP is proposed to quantify the impact of substrate solder cracks on the heat propagation inside the IGBT modules A straightforward relationship between substrate solder crack and the degree of nonuniformity of case temperature distribution is established Based on the EHPP, the parameters of a thermal network, eg, a Cauer thermal network, are adjusted online to track the thermal behavior changes of the IGBT modules caused by substrate solder cracks, leading to an adaptive thermal model The proposed adaptive thermal model is validated by comparing with finite element analysis (FEA) simulation results for a commercial IGBT module

Sensing power MOSFET junction temperature using gate drive turn-on current transient properties

Abstract: Junction temperature sensing for high-bandwidth power MOSFET junction temperature protection is usually achieved on the power converter’s high power side, by directly monitoring the power switches with additional temperature detectors. This requires special considerations for high voltage, high current, high temperature, and EMI protection. This paper presents a new method applied on the power converter’s low power side (MOSFET gate drive) so that junction temperature sensing can be integrated into MOSFET gate drive. For the purpose of demonstrating MOSFET junction temperature sensing, a push–pull gate drive is applied to a switching current divider circuit. The gate drive turn-on current transient waveform is used for MOSFET junction temperature estimation. A “gate drive-MOSFET” switching dynamic model is implemented indicating the mechanisms of MOSFET gate drive output dynamics. Modeling includes gate-drive push–pull output, gate drive output parasitics, power MOSFET intrinsic parameters, PCB parasitics, and load parasitics. LTSpice simulation of this model is studied and compared with experimental results.

Switching Loss Analysis of 4.5-kV–5.5-kA IGCTs Within a 3L-ANPC Phase Leg Prototype

Abstract: Three-level active neutral-point-clamped (NPC) (3L-ANPC) voltage-source converters (3L-ANPC-VSCs) enable additional switch states and commutations compared to the three-level NPC voltage-source converters (3L-NPC-VSCs). They are used to overcome one important disadvantage of the 3L-NPC-VSC, the unequal semiconductor loss distribution. With an accurate switching model (obtained directly from the measurements), it is possible to improve the junction temperature distribution among the power devices, increasing the 3L-ANPC-VSC output power and/or increasing the frequency and/or decreasing the derating of the converter. This paper presents the characterization of a 4.5-kV-5.5-kA integrated gate-commutated thyristor (IGCT) within a 3L-ANPC phase leg. A quantitative analysis of the switching losses using 5SHY55L4500 IGCTs and D1961SH45T press-pack diodes for a current range from 1 to 4.5 kA and junction temperatures between 25 ° C and 125 ° C is presented. The 3L-ANPC phase leg performs 32 different commutations. Each commutation exhibits different switching losses, as a result of the different commutation paths and their stray inductances. This switching energy range is presented and quantified. Finally, a simplified switching loss model considering the maximal switching losses in terms of the commutation current and the junction temperature is presented.

Modeling the Influence of Selected Factors on Thermal Resistance of Semiconductor Devices

Abstract: In this paper, the analytical description of the nonlinear thermal model of the semiconductor device considering the influence of the selected factors on its thermal resistance is proposed. The worked out nonlinear thermal model considers the influence of such factors as length of metal leads, solder area, dimensions of the heat-sink, ambient temperature, and dissipated power on the efficiency of heat transfer between the chip and the surrounding. The correctness of the worked out thermal model is verified experimentally for the selected types of semiconductor devices operating in different cooling conditions. In all the considered cases, the good agreement of the results of calculations and measurements is obtained.

High power SiC inverter module packaging solutions for junction temperature over 220°C

Abstract: The SiC based high power 3 phase inverter module with double side cooling structure was developed. By applying flipchip bonding of SiC based high power DMOSFET device on DBC substrate, the source and gate bonding could be achieved. The drain interconnection was done by copper clip attach. The developed structure can provide the flat structure for both top and bottom surfaces, which can be effectively utilized for double side cooling design for high power heat dissipation. In addition to power module design with double side cooling capability, the high temperature endurable material set which can endure over 220°C device junction temperature such as high temperature interconnection, encapsulation and TIM (thermal interface materials) are developed and identified. Through the thermal, mechanical, electrical modeling & characterization and the reliability test for the developed functional test vehicles, the author could demonstrate the possibility of flip-chip based double side cooling capable high power module structure which can be utilized to high power and high temperature endurable applications for future wide band-gap device such as SiC and GaN based inverter modules.

Reduced junction temperature control during low-voltage ride-through for single-phase photovoltaic inverters

Abstract: Future photovoltaic (PV) inverters are expected to comply with more stringent grid codes and reliability requirements, especially when a high penetration degree is reached, and also to lower the cost of energy. A junction temperature control concept is proposed in this study for the switching devices in a single-phase PV inverter in order to reduce the junction temperature stress, and thus to achieve improved reliability of a PV inverter. The thermal stresses of the switching devices are analysed during low-voltage ride-through operation with different levels of reactive power injection, allowing an optimal design of the proposed control scheme with controlled mean junction temperature and reduced junction temperature swings. The effectiveness of the control method in terms of both thermal performance and electrical performance is validated by the simulations and experiments, respectively. Both test results show that single-phase PV inverters with the proposed control approach not only can support the grid voltage recovery in low-voltage ride-through operation but also can improve the overall reliability with a reduced junction temperature.

An IGBT Driver Concept with Integrated Real-Time Junction Temperature Measurement

Abstract: This paper presents an IGBT driver concept that is suitable to measure the junction temperature of a conventional IGBT power module during inverter operation. Thereby the temperature of the internal gate resistor is determined by superimposing the negative gate voltage with a highfrequency, sinusoidal identification signal. New aspects are the parallel feeding in of the identification voltage into an existing IGBT driver circuit and the generation of an ADC compatible sensor voltage using a fast rectifier and an offset compensation. The driver concept is easy to realize and enables junction temperature measurement without affecting the IGBT switching behavior and the regular inverter operation. On the basis of the theoretical backgrounds this paper presents the subsystems of the driver concept and discusses its technical feasibility. First measurement results found the remaining noise of the temperature measurement to be smaller than +- 1 Celsius. In the introduction existing approaches to measure the junction temperature are reviewed and valued regarding their usability during inverter operation.

Simultaneous online estimation of junction temperature and current of IGBTs using emitter-auxiliary emitter parasitic inductance

Abstract: A novel method is presented for online estimation of the junction temperature (Tj) of semiconductor chips in IGBT modules, based on the voltage drop (VEE') across the parasitic inductor that exists between the main emitter (E) and auxiliary emitter (E) terminals. The peak amplitude of the voltage drop (VEE') was found to depend on the junction temperature at a known current and DC link voltage. Also, the collector current can be estimated simultaneously, by integrating VEE' without the use of any additional sensors. Measurement circuits were implemented to estimate Tj and the current, and their results are discussed. The results of these measurement circuits when implemented in a real power electronic (PE) converter to estimate Tj and current in real time are also presented. This method opens up a full set of new opportunities for engineers and designers to better understand the behavior and performance of high power modules in real PE applications.

Experimental switching frequency limits of 15 kV SiC N-IGBT module

Abstract: This paper presents extensive experimental switching characteristics of a state-of-the-art 15 kV SiC N-IGBT (0.32 cm 2 active area) up to 10 kV, 10 A and 175°C. The influence of the thermal resistance of the module package, cooling mechanism, and the increased energy loss with temperature are investigated for determining the switching frequency limits of the IGBT. Detailed FEM analysis is conducted for extracting the thermal resistance of each layer in the 15 kV module from the IGBT junction to the base plate, and then down to the ambient. Using this thermal information and the experimental switching data, the inductive switching frequency limits are analytically evaluated for liquid and air cooling cases with 660 W/cm 2 and 550 W/cm 2 power dissipation densities respectively, considering 150°C as maximum junction temperature. The air cooling power dissipation density of the 15 kV IGBT is experimentally validated using a dc-dc boost converter at 10 kV, 6.4 kW output and 550 W/cm 2 under steady state operating conditions. The gate resistances used for the entire experiments are R G(ON) = 20 Ω and R G(OFF) = 10 Ω.