Reduction In Junction Temperature Research Articles

A Reactive Power Injection Algorithm for Improving the Microgrid Operational Reliability

Stand-alone microgrids have become reliable and efficient solutions for remote areas and critical infrastructures. However, the converters within these microgrids experience long-term complex power fluctuations caused by random variations in micro sources and loads. These power fluctuations induce thermal cycling in semiconductor chips, leading to thermal fatigue failure and compromising the safety and reliability of both the converter and microgrid operation. To address this issue, this paper proposes a reactive power injection algorithm aimed at reducing the output power fluctuation of the converter. The algorithm implements reactive power injection at the converter control level, thereby restructuring the output power profile and resulting in reduced junction temperature fluctuations in IGBTs. This approach effectively mitigates thermal stress within the material layers of the module, extending the lifetime of power devices and improving the operational reliability of the microgrid. The algorithm implementation is based on the PQ control strategy, integrating the power triangle with the envelope detection technique. Furthermore, the lifetime prediction process utilizes the electro-thermal coupling model, the rainflow counting algorithm, and the Lesit model. Simulation results demonstrate that, for an active power fluctuation range of 10 kW to 80 kW and an equivalent RC time constant of 22.5 s, the algorithm achieves a significant reduction of 62.64% in the amplitude of output power fluctuation and extends the lifetime of power devices by 74.13%. The obtained data showcase the effectiveness of the algorithm in enhancing the lifetime of power devices and further improving the microgrid operational reliability under specific parameter conditions.

A 3D numerical analysis using phase change material for cooling circular light emitting diode

This paper's goal is to find the impact of incorporation of Phase Change Material (PCM) in the heat sink for improving the cooling performance of circular Light Edding Diode (LED). A 3D numerical model using Comsol Multiphysics is was created to model the PCM melting process while taking natural convection into account. The ‘‘Paraffin’’ is inserted in the central cavity of the heat sink. After validation of this model with previously published works, the effect of power input on the PCM's effectiveness was investigated. The results found that using PCM in the heat sink allowed for a reduction in junction temperature during the melting process for 11.17%, 15.59%, 18.02%, 19.54%, 20.58% and store energy of 110 kJ/kg, 129.25 kJ/kg, 148.78 kJ/kg, 168.06 kJ/kg, 187.3 kJ/kg when the circular LED is powered 1 W, 2 W, 3 W, 4 W and 5 W, respectively. This quantity of energy will be released into the surrounding space to heat it. In addition, the PCM has a notable impact on lowering the temperature but only for a brief period of time. This effect increases as the power input rises.

Thermal analysis of Si-IGBT based power electronic modules in 50kW traction inverter application

Estimation of accurate IGBT junction temperature is crucial for reliability assessment. The well-known RC lumped approach can help predict junction temperature. However, this method suffers from inaccuracy while characterizing the thermal behaviour of several IGBT modules mounted to the liquid-cooled heatsink. Specifically, the thermal challenge originates from the thermal cross-coupling and module-to-module heat spreading and the converter cooling condition. This article demonstrates a methodology to study the impact of heat spreading, thermal interface material, and massive size liquid cold-plate on the overall thermal behaviour. A case study of 50 kW traction inverter is chosen to demonstrate the benefit of early assessment of electro-thermal simulation before making costly prototype design. Power loss is initially estimated using an analytical loss model and later the estimated power loss is used in FEA (Finite Element Analysis) thermal model. This paper also compares the performance of single-phase and two-phase liquid cooling and various thermal interface materials (TIM) to determine which type of cooling system and TIM is most suitable for real applications. Simulation results suggest that combination of two-phase liquid cooling and TIM can improve the thermal performance and reduce junction temperature by 4.5%, 4.2%, 4.6% for the traction power load 30 kW, 40 kW, and 50 kW, respectively. The proposed methodology can be used as useful reference guidance for thermal design and modelling of IGBT based power converter applications.

Integrating Diamond for Cooling Electronics

III-Nitrides promise to offer high-frequency power amplifiers at higher power densities. This is attractive for realizing device platforms for 5G and beyond. It also enables integrating Si-based electronics to complement functionalities. However, to obtain the full potential of III-Nitrides one must operate these transistors at higher power densities, for which thermal management is crucial.Due to the continuous need for higher performance in various applications ranging from DC to W-band frequencies, semiconductor devices are pushed to higher power densities. This results in a higher junction temperature owing to the Joule heating in the channel resulting in device performance degradation and premature failure. Using devices based on wide-bandgap (WBG) semiconductors such as Gallium Nitride (GaN) and Gallium Oxide (GaOx) with a larger critical electric field and high-temperature tolerance, one could increase the power density. However, in order to increase the output power to the levels that is promised by these wide bandgap materials, junction temperature reduction through device-level cooling is critical. We are actively researching thermal management at device, circuit and packaging level using synthetic polycrystalline (PC) diamond. PC-diamond, at an appropriate grain size offers a TC is higher than any competing thermal vias with metals without interfering the electrical performance. Over the past 5 years we have demonstrated the potential of integrating diamond with GaN and recently achieving a record low diamond/GaN thermal boundary resistance (TBR) along with a relatively high diamond thermal conductivity (TC). This remarkable thermal performance was be achieved by maintaining the electrical performance, as demonstrated by the unharmed channel charge and mobility results.There are two key requirements for thermal management using heat spreading from the channel: first, a low thermal boundary resistance (TBR) between the hot spot in the channel and the heat spreader is required (in this study between GaN channel and diamond). Second, a low thermal resistance path to the heat-sink is crucial from the diamond layer which is directly proportional to diamond’s thermal conductivity (TC). In collaboration with Univ of Bristol, we have reported a TBR of ~3 m2K/GW, to date, known to be the lowest reported TBR for GaN HEMT technology. Diamond-GaN TBR depends strongly on the interface smoothness and the thickness of interfacial Si3N4 layer. A thinner Si3N4 resulted in lower TBR and allowed superior phonon coupling from the channel to the spreader. We have also measured a remarkably high TC for a 2 μm-thick diamond layer yielding over 650 W/m.K. The diamond grains are near isotropic in shape that allows excellent in-plane and cross-plane thermal conductivity. Achieving high TC within a thin film of diamond, grown heterogeneously, underscores the importance of our technique, since it reduces the residual stress when integrating with different materials that involves many thin layers like GaN/AlGaN HEMT epi-layers.β-Ga2O3 is an emerging ultra-wide bandgap material showing promises for both power and RF devices. However, the material’s low thermal conductivity poses to be a challenge for efficient power delivery (at any frequencies). PC diamond was successfully grown on (‾¯201)β-Ga2O3 using proper nucleation technique and thermal characterizations were conducted. A thermal conductivity (diamond + nucleation) and thermal boundary resistance at the diamond/β-Ga2O3 interface of 110 ± 33 W/mK and 30.2 ± 1.8 m2K/GW, respectively were measured.Our current results demonstrates a very promising roadmap for wide bandgap semiconductors via diamond integration.

Optimizing the heat source layout of chips using bionic method: Reduction of junction temperature

Optimizing the heat source layout to reduce the junction temperature is an important topic in the thermal design field of chips. However, the relationship between the heat source layout and the junction temperature is still ambiguous, and the optimization method suitable for actual chips is still rare, while it is quite desirable in engineering. In this work, we propose a feasible strategy to optimize the heat source layout using bionic method, and demonstrate the strategy by a flip chip ball grid array (FCBGA) case. The optimized layout can reduce the junction temperature and thermal spreading resistance by 2.38 K and 30.94%, respectively. The mechanism can be attributed to the heat dissipation advantage at the corner and edge positions of the heat source surface and the low temperature coupling between heat sources in the optimization process. This work illustrates a great promising potential of the bionic optimization method in the design of the CPU and GPU chips.

Junction Temperature Optimization Based Compensation Strategy of Modular Multilevel Railway Power Conditioner

The modular multilevel railway power conditioner (MM-RPC) can effectively improve the power quality of the railway power grid. However, since the operating conditions of MM-RPC frequently vary with the traction load, the junction temperatures of semiconductor devices fluctuate very drastically. Severe junction temperature swings can easily affect the service lifetime and reliability of the MM-RPC. In this article, a power hysteresis based on incomplete compensation control strategy is proposed. The proposed control can effectively reduce junction temperature fluctuations under complex mission profiles and increase the overall life of the system while meeting the power quality requirements. Furthermore, the effectiveness of the proposed control is verified in MATLAB/PLECS electrothermal cosimulation under a section of the load curve of the Beijing–Shanghai high-speed railway traction substation. Finally, the experimental thermal platform is built to validate the effectiveness of the proposed control strategy.

Evaluation of the thermal performance of high-power LED using magnesium oxide thin film as heat spreader

The spin coating technique was used to synthesize MgO thin film on aluminium substrates. XRD diffraction proved the presence of (200), (220) and (222) MgO phase orientations. Film thickness (370 nm), the crystal size of 17.14 nm, low surface roughness of 12.8 nm and thermal conductivity (22.68 W/mK) were recorded for MgO film sample prepared from 0.6 M concentration. A noticeable reduction in junction temperature (ΔTJ - 20.11 °C) and total thermal resistance (ΔRth-tot - 3.22 K/W) were recorded for LED fixed on 0.6 M MgO thin film sample. 8% reduction of thermal impedance was also recorded for the prepared film and proving it is free from internal structure degradation. Overall, a noticeable improvement in thermal performance of high-power LED was achieved with MgO thin film as a heat spreader and suggested it as a future alternative to the commercially available film-based heat spreader.

Effect of Phase Change Material on Dynamic Thermal Management Performance for Power Electronics Packages

Abstract High-temperature silicon carbide (SiC) die are the most critical and expensive component in electric vehicle (EV) power electronics (PE) packages and require both active and passive methods to dissipate heat during transient operation. The use of phase change materials (PCMs) to control the peak junction temperature of the SiC die and to buffer the temperature fluctuations in the package during simulated operation is modeled here. The latent heat storage potential of multiple PCM and PCM composites is explored in both single-sided and dual-sided package configurations. The results of this study show that the addition of PCM into two different styles of PE packages is an effective method for controlling the transient junction temperatures experienced during two different drive cycles. The addition of PCM in a single-sided package also serves to decrease temperature fluctuations experienced and may be used to reduce the necessary number of SiC die required for EVs, lowering the overall material cost and volume of the package by over 50%. PCM in a single-sided package may be nearly as effective as the double-sided cooling approach of a dual-sided package in the reduction of both peak junction temperature of SiC as well as controlling temperature variations between package layers.

Optimization on Thermomechanical Behavior for Improving the Reliability of Press Pack IGBT Using Response Surface Method

A press pack insulated gate bipolar transistor (PP IGBT) device consists of multiple materials. Under the influence of alternating current and clamping force, the device suffers from complex thermomechanical stress. However, the experience-based packaging design does not consider the coupling effect of junction temperature fluctuation ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta T_{\mathrm{ j}}$ </tex-math></inline-formula> ) and mechanical stress, which may not ensure the optimal thermomechanical behavior and cause the advance failure of the PP IGBT device. Thus, it is significant to provide a theoretical basis and select appropriate parameters for device packaging design. In this article, a finite-element model of a 3300-V/50-A PP IGBT device is first built and verified via experiments. The influence of principal parameters on the thermomechanical behavior is then illustrated. Next, the response surface method is proposed to reveal the significance level of each parameter. According to simulation results under different combinations of parameters, quadratic response surfaces are obtained. The combined effects of packaging parameters on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta T_{\mathrm{ j}}$ </tex-math></inline-formula> and stress are clarified. Finally, optimal results are derived and verified. An approximate 4 °C decrease in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta T_{\mathrm{ j}}$ </tex-math></inline-formula> and a 19.8% decrease in stress are achieved simultaneously in the long-time power cycling test. A 2.6 °C reduction in junction temperature is achieved under the practical high-voltage direct current (HVDC) condition.

A Novel Package-Integrated Cyclone Cooler for the Thermal Management of Power Electronics

Abstract In order for electronics packaging power density to increase, innovations and improvements in heat transfer are required. Electrification of transportation has the potential for significant fuel and energy savings. Changing to an electrified drive train requires reliable and efficient power electronics to provide power conversion between alternating current motors and direct current energy storage. For high power transportation systems like aircrafts or heavy vehicles, the power density of power electronics needs to be improved. Power density is also an enabler for high power military devices that must be used and transported via air, ground, and sea. This paper summarizes the outcome of a collaborative and multidisciplinary research effort aimed at co-designing a novel electronics cooling device that utilizes two-phase fluid flow. Two-phase flow cooling has been known for decades as well as the risks associated with it: critical heat flux (CHF), dry-out, and thermal runaway. Our research de-risks the two-phase cooling technology by swirling the flow to remove the bubbles from the wall and confining them at the core of the cooler. The combined effects of gas phase removal, enhanced nucleation, and dramatic liquid film agitation and rupture have been quantified by our experiments: double the heat transfer coefficient with only 13% increase in pressure drop. Besides advanced fluid-dynamics, our Package-Integrated Cyclone Cooler (PICCO) utilizes cutting edge packaging and additive manufacturing technology such as direct deposition of a metal substrate and circuits (dies) on a complex helical cooler that can only be manufactured via three-dimensional printing. By co-designing and testing the cooler, we have quantified the impact of the swirled flow on the junction temperature with respect to a conventional (non-swirl) two-phase-flow-cooled power electronics package. At steady-state, our post-test thermal simulations predict a junction temperature reduction from 185 °C to 75 °C at the same power dissipation. When the heat load is unsteady (United States Environmental Protection Agency Urban Drive Cycle), the junction temperature reduction is 140 °C to 60 °C.

A ᐃT j Reduced Power Module With Inbuilt Phase Change Material for Reliability Enhancement

In a harsh environment, power modules have to be subjected to deep power cycling, which causes large temperature fluctuations and, hence, leads to fatigue stresses. Reducing the junction temperature fluctuation of chips can significantly improve power module reliability. This article proposes a power module design with considerably reduced junction temperature fluctuation by using phase change material (PCM) as a part of thermal management. Cyclical power is applied to the proposed power module, and experiment results show that the reduction of junction temperature fluctuation is effective in a certain range of power periods. Thermodynamic simulations are used to illustrate the mechanism of PCM in reducing junction temperature fluctuation and the factors influencing the optimal range of power periods. With the significant reduction of junction temperature fluctuation, the reliability of the proposed power module is enhanced. The approach is significant to improve the reliability of power modules in power fluctuating conditions.

Effect of GaN-on-diamond integration technology on its thermal properties

Two different integration technologies of GaN-on-diamond are explored, direct growth of polycrystalline diamond (PCD) on GaN (sample A) and deposition of GaN on PCD (sample B). The reversed evolution of PCD grain structure is assumed for each technology, resulting in an increasing/decreasing tendency of thermal conductivity with growth thickness. Simulation of AlGaN/GaN high electron mobility transistors on PCD substrate with capped diamond is made considering anisotropic and inhomogeneous thermal conductivities of GaN and PCD, different combinations of thermal boundary resistance (TBR) values at the top diamond/GaN and bottom GaN/PCD substrate are investigated. The results show that the effect of top TBR is limited and increasing the bottom TBR from 6.5 to 100 m2K GW−1 results in a temperature rise of 80.8 °C for sample A and 85.3 °C for sample B at power dissipation of 10 W mm−1. Enlarging the thickness of capped diamond helps to reduce the junction temperature, which is more effective at small top TBR under constant bottom TBR and at large bottom TBR with fixed top TBR. In addition, increasing gate pitch is a promising solution to reduce junction temperature and a weak dependence of junction temperature on gate width is revealed.

Design of novel geometries for minichannels to reduce junction temperature of heat sinks and enhance temperature uniformity

• Numerical study is done to reduce temperature non-uniformity problem in heat sinks. • Novel combined minichannels are proposed and tested at a heat flux of 50 kW/m 2 . • Noticeable effects are detected on Δ T max,b and R t . • Maximum decrease of 11.5 K is found in Δ T max,b with η = 1.53 at Re = 900. Generally, various micro/minichannels are utilized to fabricate water-cooled heat sinks, but most of them have straight and simple geometries. To some extent, the heat sinks designed based on these geometries can dissipate the heat produced by electronic systems. However, there is still the temperature non-uniformity problem in heat sinks due to the limitation of pumping power ( P p ). In this article, several novel minichannels are designed to reduce the junction temperature of heat sinks and enhance the temperature uniformity. In these models, both the upstream and the downstream represent wavy structure with the same wave-amplitude but variable wave-lengths. To this end, 3D numerical simulations are carried out along with an experimental validation study. The coolant is water at the entrance temperature of 293 K and Reynolds number (Re) range between 100 and 900. The results show that the proposed minichannels have appreciable positive impacts on the thermal performance of heat sink, such that the maximum base temperature difference (Δ T max,b ) experiences a maximum decrease of 11.5 K, which results in a 2.35 times reduction in the total thermal resistance ( R t ). It is also found that despite a conflict between reducing R t and lowering P p , the novel minichannels show superior values of performance index ( η ) particularly at higher Re. Under the range of conditions studied, the maximum value of 1.53 is recorded for η at Re = 900.

Impact of thermal interface material on luminous flux curve of InGaAlP low-power light-emitting diodes

Purpose One major problem in the lighting industry is the thermal management of the devices. Handling of thermal resistance from solder point to the ambiance of the light-emitting diode (LED) package is linked to the external thermal management that includes a selection of the cooling mode, design of heatsink/substrate and thermal interface material (TIM). Among the significant factors that increase the light output of the of the LED system are efficient substrate and TIM. In this work, the influence of TIM on the luminous flux performance of commercial indium gallium aluminium phosphide (InGaAlP) low-power (LP) LEDs was investigated. Design/methodology/approach One batch of LEDs was mounted directly onto substrates which were glass-reinforced epoxy (FR4) and aluminium-based metal-core printed circuit boards (MCPCBs) with a dielectric layer of different thermal conductivities. Another batch of LEDs was prepared in a similar way, but a layer of TIM was embedded between the LED package and substrate. The TIMs were thermally conductive epoxy (TCE) and thermally conductive adhesive (TCA). The LED parameters were measured by using the integrated system of thermal transient tester (T3Ster) and thermal-radiometric characterization of LEDs at various input currents. Findings With the employment of TIM, the authors found that the LED’s maximum luminous flux was significantly higher than the value mentioned in the LED datasheet, and that a significant reduction in thermal resistance and junction temperature was revealed. The results showed that for a system with low thermal resistance, the maximum luminous flux appeared to occur at a higher power level. It was found that the maximum luminous flux was 24.10, 28.40 and 36.00 lm for the LEDs mounted on the FR4 and two MCPCBs, respectively. After TCA application on the LEDs, the maximum luminous flux values were 32.70, 36.60 and 37.60 lm for the FR4 and MCPCBs, respectively. Moreover, the findings demonstrated that the performance of the LED mounted on the FR4 substrate was more affected by the employment of the TIM than that of MCPCBs. Research limitations/implications One of the major problems in the lighting industry is the thermal management of the device. In many low-power LED applications, the air gap between the two solder pads is not filled up. Heat flow is restricted by the air gap leading to thermal build-up and higher thermal resistance resulting in lower maximum luminous flux. Among the significant factors that increase the light output of the LED system are efficient substrate and TIM. Practical implications The findings in this work can be used as a method to improve thermal management of LP LEDs by applying thermal interface materials that can offer more efficient and brighter LP LEDs. Using aluminium-based substrates can also offer similar benefits. Social implications Users of LP LEDs can benefit from the findings in this work. Brighter automotive lighting (signalling and backlighting) can be achieved, and better automotive lighting can offer better safety for the people on the street, especially during raining and foggy weather. User can also use a lower LED power rating to achieve similar brightness level with LED with higher power rating. Originality/value Better thermal management of commercial LP LEDs was achieved with the employment of thermal interface materials resulting in lower thermal resistance, lower junction temperature and brighter LEDs.

Improving Heat Conduction of Insulated Metal Substrate with Thermal Pyrolytic Graphite Core for SiC Power Module Packaging

TPG-core IMS concept was jointly explored in this study. Integrating high thermally conductive TPG graphite core into IMS is expected to simultaneously achieve high thermal conductivity from TPG and electrical functionalities from IMS. Nearly 2x thermal conductivity and 30% weight saving was demonstrated on TPG-core IMS compared to conventional Cu-core IMS. Significant junction temperature reduction (11°C) in steady state and power cycling was revealed by the thermal analysis as the result of improved thermal spreading in plane and through the thickness. The study also proved the manufacturability and compatibility of this TPG-core IMS structure to the existing IMS production and power module assembling. The integration of TPG and IMS paves a new packaging route to increase heat load, improve reliability, simplify module design and reduce assembling cost and number of steps.

Design, Analysis, Comparison, and Experimental Validation of Insulated Metal Substrates for High-Power Wide-Bandgap Power Modules

Abstract Direct bonded copper (DBC) substrates used in power modules have limited heat spreading and manufacturing capability due to ceramic properties and manufacturing technology. The ceramic and copper bonding is also subject to high mechanical stress due to coefficient of thermal expansion mismatch between the copper and the ceramic. For wide-bandgap (WBG) devices, it is of interest exploring new substrate technologies that can overcome some of the challenges of direct bonded copper substrates. In this technical paper, the design, analysis, and comparison of insulated metal substrates (IMSs) for high-power wide-bandgap semiconductor-based power modules are discussed. This paper starts with technical description and discussion of state-of-the-art DBC substrates with different ceramic insulators such as aluminum nitride (AlN), Al2O3, and Si3N4. Next, an introduction of IMSs and their material properties, and a design approach for SiC (silicon carbide) metal-oxide-semiconductor field-effect transistor (MOSFET)-based power modules for high-power applications is provided. The influence of dielectric thickness on the power handling capability of the substrate are also discussed. The designed IMS and DBC substrates were characterized in terms of steady-state and transient thermal performance using finite element simulation. Finally, the performance of the IMS and DBC are validated in an experimental setup under different loading and cooling temperature conditions. The simulation and experimental results showed that the IMS can provide high steady-state thermal performance for high-power modules based on SiC MOSFETs. Furthermore, the IMS provided enhanced transient thermal performance, which provided a reduced junction temperature when the module is operated at low fundamental output frequencies in traction drive systems.

Synthesis and analysis of anodic aluminum oxide-nanopore structure on Al substrates for efficient thermal management in electronic packaging

Increased heat generated in high-density electronic devices has intensified the search for advanced thermal management solutions. This urge has prompted various studies in thermal pad, liquid thermal interface material, gap fillers, and thermal coating, etc., with enhanced thermal performance. In this article, anodic aluminum oxide-nanopore (AAO-np) structure was grown on Al5052 alloy substrate electrochemically using two-step anodization process and it is used for efficient electronic packaging applications. It is observed that AAO-np substrate shows significant impact in thermal resistance (Rth) and junction temperature (Tj) of an electronic package. At 3.5 W input power with 14, 29, and 43 psi pressure condition the experimental results of AAO-np substrate resulted 15.11%, 14.58%, and 13.89% reduction in thermal resistance (ΔRth) and 15.53%, 14.85%, and 14.26% reduction in junction temperature (ΔTj) compared to bare Al5052 substrate. This enhanced thermal performance of AAO-np layer are due to high crystallinity, honeycomb-like morphology, nanopore oxide layer, and 0.35 µm rough surface which are effectively acting towards directional heat transport.

Thermal investigation of power diodes in novel integrated disc type packages

Paper focusses on electro-thermal numerical investigation of a novel disc type package for power diodes integrated with microchannel cooling system. Although the new solution ensures much lower average temperature of an electronic element, it results in much higher temperature non-uniformity obtained within the silicon structure. The distribution can be improved with the aid of redesigned microchannel cooler. The maximum junction temperature reduction of more than 25 °C is possible.

Optimization of Arrangement of LED on the PCB for High Power LED Module

LED operating under high-temperature condition badly affects reliability. To reduce junction temperature of LED is crucial. In this paper, luminous intensity and photo conversion efficient with respect to electrical power are discussed. Moreover, three arrangements for LED module are suggested, and design parameters are discussed in terms of the number of LEDs and distance between each LED. In order to evaluate thermal performance of designed the module, computer simulation was conducted. Distance between each LED is selected by 7.6, 9.6, and 13.3mm for 80, 128, and 240 LEDs, respectively and unit heat flux is calculated to be 0.47W/mm2 , 0.29W/mm2 , 0.16W/mm2 for 80, 128, and 240 LEDs, respectively. In this case, Maximum temperature on the PCB was 67.8C, 62.5C, and 57.1C for 80, 128, and 240 LEDs, respectively. The Maximum temperature and unit heat flux was reduced by 15.7% and 66%, respectively, when the number of LEDs are increased by three times. We found that the temperature between LEDs can be reduced if unit heat flux can be reduced.

Performance Comparison of Two Hybrid Si/SiC Device Concepts

Various Si/SiC hybrid device concepts aim at achieving SiC performance at a significantly reduced cost in comparison to full SiC solutions. Both the insulated-gate bipolar transistor (IGBT)(Si)/Schottky(SiC) hybrid pair and the IGBT(Si)/MOSFET(SiC) hybrid switch offer a substantial reduction in switching losses but operate quite differently. This article compares the performance of these two hybrid device concepts in a voltage source inverter (VSI). The basic operation principle, conduction, and switching characteristics of the two hybrid configurations are directly compared, and an improved power loss model is developed for these two solutions in VSI. Two single-phase VSI prototypes using these two hybrid devices are built and tested, respectively. Experimental results show that a 1200-V hybrid IGBT/MOSFET solution achieves a significant efficiency improvement and a maximum junction temperature reduction compared to the hybrid IGBT/Schottky counterpart. The hybrid IGBT/MOSFET solution achieves a 40% higher power handling capability in the 20-kHz single-phase VSI or 1.5 times higher switching frequency in the 2-kW single-phase VSI than the hybrid IGBT/Schottky solution.