Knowledge of instantaneous junction temperature is essential for effective health management of power converters, enabling safe operation of the power semiconductors under all operating conditions. Methods based on fixed thermal models are typically unable to compensate for degradation of the thermal path resulting from aging and the effect of variable cooling conditions. Thermosensitive electrical parameters (TSEPs), on the other hand, can give an estimate of junction temperature ${T_J}$ , but measurement inaccuracies and the masking effect of varying operating conditions can corrupt the estimate. This paper presents a robust and noninvasive real-time estimate of junction temperature that can provide enhanced accuracy under all operating and cooling conditions when compared to model-based or TSEP-based methods alone. The proposed method uses a Kalman filter to fuse the advantages of model-based estimates and an online measurement of TSEPs. Junction temperature measurements are obtained from an online measurement of the on-state voltage, ${V}_{{\bf CE(ON)}}$ , at high current and processed by a Kalman filter, which implements a predict-correct mechanism to generate an adaptive estimate of ${T_ J}$ . It is shown that the residual signal from the Kalman filter may be used to detect changes in thermal model parameters, thus allowing the assessment of thermal path degradation. The algorithm is implemented on a full-bridge inverter and the results verified with an IR camera.

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Application of Kalman Filter to Estimate Junction Temperature in IGBT Power Modules

A thermally integrated packaging structure for an all silicon carbide (SiC) power module was used to realize highly efficient cooling of power semiconductor devices through direct bonding of the power stage and a cold baseplate. The prototype power modules composed of SiC metal-oxide-semiconductor field-effect transistors and Schottky barrier diodes demonstrate significant improvements such as low-power losses and low-thermal resistance. Direct comparisons to their silicon counterparts, which are composed of insulated gate bipolar transistors and PiN diodes, as well as conventional thermal packaging, were experimentally performed. The advantages of this SiC module in efficiency and power density for power electronics systems have also been identified, with clarification of the SiC attributes and packaging advancements.

Development of Advanced All-SiC Power Modules

A multilayer planar interconnection structure was used for the packaging of liquid-cooled automotive power modules. The power semiconductor switch dies are sandwiched between two symmetric substrates, providing planar electrical interconnections and insulation. Two minicoolers are directly bonded to the outside of these substrates, allowing double-sided, integrated cooling. The power switch dies are orientated in a face-up/face-down 3-D interconnection configuration to form a phase leg. The bonding areas between the dies and substrates, and the substrates and coolers are designed to use identical materials and are formed in one heating process. A special packaging process has been developed so that high-efficiency production can be implemented. Incorporating high-efficiency cooling and low-loss electrical interconnections allows dramatic improvements in systems' cost, and electrical conversion efficiency. These features are demonstrated in a planar bond-packaged prototype of a 200 A/1200 V phase-leg power module made of silicon (Si) insulated gate bipolar transistor and PiN diodes.

A Phase-Leg Power Module Packaged With Optimized Planar Interconnections and Integrated Double-Sided Cooling

∗Power semiconductors can be modeled as a thermal network of resistors and capacitors. The thermal boundary condition of such a model is typically defined as the heat sink surface temperature, which is assumed to be constant. In reality, the heat sink surface temperature underneath the power module is not exactly known. In this paper we show how to set up a thermal model of the heat sink in form of a RC thermal equivalent network that can be directly embedded in any circuit simulator. The proposed thermal heat sink model takes into account convection cooling, thermal hotspots on the heat sink base plate, thermal time constants of the heat sink, and thermal coupling between different power modules mounted onto the heat sink. Experimental results are given and show high accuracy of the heat sink model with temperature errors below 10%.

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A Thermal Model of a Forced-Cooled Heat Sink for Transient Temperature Calculations Employing a Circuit Simulator

Existing three-dimensional (3D) integration of multi-core processor-cache system is confronted with the problem of die thermal run-away hazard. This teething problem is addressed by a real-time demand-based thermal management with non-uniform microfluidic cooling in this paper. A novel runtime temperature management is implemented to predict the real-time temperature demand based on software-sensing with prediction-and-correction. A 3D thermal model is developed to cater the real-time microfluidic thermal dynamics. An autoregressive (AR) prediction with correction is implemented by Kalman filtering to predict and correct the runtime power, which is further used to calculate the future temperature demand. With this software-sensing approach, thermal management can be performed in a cyber-physical fashion with real-time sensing, prediction-and-correction and fine-grained control. Compared to the existing works using on-chip temperature sensors, our closed-loop controller with software-sensing avoids the cost of sensor implementation and deployment. Our work analyzes and predicts the fine-grained temperature profile of multi-core processor-cache system. It enables a number of microfluidic channels to be adjusted adaptively with different flow-rates to control the system temperature proactively as opposed to the static control with a uniform flow-rate for microfluidic channels. With the proposed cyber-physical temperature management scheme, it is shown that the temperature of multi-core system is suppressed below an acceptable thermal threshold. In fact, the fine-grained flow-rate control also achieves a more even temperature distribution and saves up to 72.1% of total flow-rate compared with uniform flow-rate controls.

Cyber-physical thermal management of 3D multi-core cache-processor system with microfluidic cooling

This study presents an overview of water cooling methods used in the power electronic field. The first one uses the classical method with separated power module and cooling device. The second one deals with high reduction of conductive thermal resistance and could predominately be the final cooling solution in the near future. The last one, foreseen for future applications, consists in designing the power module and the cooling device in the silicon material, improving even more the overall thermal resistance. Each alternative may require a good knowledge of the thermal exchange laws in the heat exchanger. The Nusselt number, as a characteristic thermal parameter proposed in the literature, is not always realistic for all kinds of cooling devices. The work focuses on that correlated value determination taking into account the channel geometry, the fluid flow rate and its temperature. Then, the obtained value is used to make a real optimisation of the cooling device.

Heat transfer coefficient for water cooled heat sink: application for standard power modules cooling at high temperature

Thermal grease used in classical power module water-cooling takes 40 percent of the water-cooled heat sink thermal resistance. This part which belong to conduction phenomena can be suppressed using a direct cooling method. In this paper, the basic conduction term provided by the component packaging is firstly determined, using several methods. Then mini water-cooled channels are directly machined in a standard power module baseplate, taking into account mechanical and technological constraints. In the same way a CFD tool, FLOTHERM from Flomerics is used in order to improve equipment performances such as a low junction to ambient thermal resistance, that approaches the power module's own thermal resistance, a low pressure drop, a high dissipated power and a low gradient in coolant temperature. The equipment thermal and electrical behaviors are finally compared to a typical equipment including a power module and a cooling device mounted with thermal grease utilisation.

O. Karim

Papers

Heat transfer coefficient for water cooled heat sink: application for standard power modules cooling at high temperature

Power module integrated cooling design using CFD simulation