This paper presents a CMOS MEMS-based thermoelectric energy generator (TEG) device with an efficient heat dissipation path. For present CMOS MEMS-based thermoelectric generator devices, the output performance is greatly limited by the high thermal-contact resistance in the system. For the device proposed in the work, the silicon substrate is etched into two comb-shaped blocks thermally isolated from each other, which form the hot and cold sides. Thin-film-based thermal legs are densely located between the two blocks along the winding split line. Low internal thermal-contact resistance is achieved with the symmetrical thermal structure. When the TEG device is embedded between the heat source and heat sink, the heat loss can be well controlled with flat thermal-contact pads of the device. For a full device with 900 n/p-polysilicon thermocouples, the measured open-circuit voltage reaches as high as 146 mV K−1, and the power factor reaches almost five times higher value compared to the previously reported results. A test system integrated with a single device presents an open-circuit voltage of 110 mV K−1 when forcibly cooled by a Peltier cooler, or 26 mV K−1 when cooled by ambient air.

https://iopscience.iop.org/article/10.1088/0960-1317/22/10/105011/pdf

CMOS MEMS-based thermoelectric generator with an efficient heat dissipation path

DESCRIPTION: METAL BACKBOX: This sturdy metal backbox protects the speaker from debris and insulation. The V-9915M-5 meets the UL UUMW standard and is typically used in air plenum return ceilings. The V-9915M-5 must be ordered in multiples of 5. METAL BRIDGES: The V-9914M-5 provides a solid mounting structure for 8” ceiling speakers in 2’ x 2’ or 2’ x 4’ ceiling grids. The V-9904M-5 (picture not shown) provides a solid mounting structure for 4” ceiling speakers in 2’ x 2’ or 2’ x 4’ ceiling grids. The steel bridges prevent ceiling tile sag and are coated to inhibit rust. Both the V-9914M-5 and the V-9904M-5 must be ordered in multiples of 5. METAL RING: The V-9912M-10 provides a solid mounting structure for 8” ceiling speakers in hard ceiling types such as drywall or plaster. The steel ring is galvanized to inhibit rust. The V-9912M-10 must be ordered in multiples of 10. COMBINATION: The V-9916M is a single set combination of the above 8” speaker bridge and backbox.

/pdf/the-technical-specification-29ukg6fmnn.pdf

The Technical Specification

Miniature power semiconductor devices mounted on printed circuit boards (PCBs) are normally cooled by means of PCB vias, copper pads, and/or heatsinks. Various reference PCB thermal designs have been provided by semiconductor manufacturers and researchers. However, the recommendations are not optimal, and there are some discrepancies among them, which may confuse electrical engineers. This paper aims to develop analytical thermal resistance models for PCB vias and pads, and further to obtain the optimal design for thermal resistance minimization. First, the PCB via array is thermally modeled in terms of multiple design parameters. A systematic parametric analysis leads to an optimal trajectory for the via diameter at different PCB specifications. Then, an axisymmetric thermal resistance model is developed for PCB thermal pads where the heat conduction, convection, and radiation all exist; due to the interdependence between the conductive/radiative heat transfer coefficients and the board temperatures, an algorithm is proposed to fast obtain the board-ambient thermal resistance and to predict the semiconductor junction temperature. Finally, the proposed thermal models and design optimization algorithms are verified by computational fluid dynamics simulations and experimental measurements.

/pdf/thermal-modeling-and-design-optimization-of-pcb-vias-and-4amyec35uj.pdf

Thermal Modeling and Design Optimization of PCB Vias and Pads

In this paper,the current accelerated aging experiment was used to investigate the luminous attenuation and lifetime of the high-power white LEDs (1W). Two kinds of luminous attenuation process were found:the slow attenuation at the early stage and the fast attenuation at the late stage. Moreover,the LED lifetimes with different operating currents were calculated by the exponential fitting of the slow luminous attenuation. The result implied that the Eying model was applicable for the relation between the lifetime and the operating current. Thus,the lifetime with standard current (350 mA) was calculated as 1924 h.

Lifetime Estimation of High-Power White LEDs

This paper proposes a light-emitting diode (LED) driver based on a three-phase resonant switched capacitor (SC) converter. The LED lamp employs chip-on-board (COB) technology, as it is possible to achieve high power density. The three-phase structure provides low ripple current and reduced percent flicker. Besides, it does not use electrolytic capacitors, thus, causing the driver lifetime to increase. The converter active switches are turned off under zero current switching (ZCS) and zero voltage switching (ZVS) conditions, as efficiency is consequently increased. LED dimming is also a prominent advantage, what can be obtained by varying the switching frequency. An experimental prototype rated at 216 W has been developed in order to evaluate the performance of the proposed approach, while results are properly presented and discussed. LED dimming is possible as the output power varies from 50% to 100%. Overall efficiency and power factor are higher than 90% and 0.97 over the entire load range, respectively.

Three-Phase Resonant Switched Capacitor LED Driver With Low Flicker

The thermal conductivity of PCB structures variations according to the position of the metal layers as a function of the local copper contents and distribution are studied. The value of the parallel and serial thermal conductivity coefficient of PCB have been calculated by usage of the corresponding electrical analogs of parallel and serial resistive systems. Solutions were obtained for two PCB thicknesses. Cases with and without a copper layer on the component side were investigated. Simulated results are verified with infrared thermovision measurements.

Investigation of thermal conductivity of PCB

An approach based on design of different experiments for improvement the thermal paths in PCB through thermal vias is offered. An efficient thermal via placed on the PCB decreases the junction temperature of the package. In this paper elaborate study has been done in analyzing the effect of thermal vias and the ways to decrease the junction temperature by given number of computations. Thermal enhancement has been achieved by running the thermal simulations with and without thermal vias. Temperature profiles have been plotted in FLOTHERM. The thermal enhancement study focuses on the importance of thermal vias to a great extent. The simulation models are validated with experiments.

/pdf/pcb-thermal-design-improvement-through-thermal-vias-bzo4vfjj9e.pdf

PCB thermal design improvement through thermal vias

LEDs are not 100 % efficient at converting input power to light. Some of the energy is converted into heat and must be transferred to the ambient. Two approaches are used to assess the amount of heat generated by the LED - based on the luminous efficacy of radiation and a new one presented in the paper. To provide sufficient accuracy in thermal evaluations closer to the real operating modes for a specific LED module a new technique is developed. The aim is to evaluate the amount of heat generated during design phase of LED lighting. Experiments of LED modules are conducted to evaluate LEDs efficiency at converting input power to heat. For the heat dissipation study and thermal analysis of LED module are used non-contact temperature measurement using an infrared camera combined with computer aided thermal modelling and simulation. DOI: http://dx.doi.org/10.5755/j01.eie.22.2.8522

https://eejournal.ktu.lt/index.php/elt/article/download/8522/7557

Estimation the Amount of Heat Generated by LEDs under Different Operating Conditions

The thermal influence of the topology of the COB (Chip-on-Board) LED modules is examined. For this purpose CFD simulations of a powerful COB LED module thermal model are carried out and the thermal distribution at different locations of LED chips is analyzed. Simulation experiments are designed, using the substrates of ceramic materials - Alumina (Typical), Alumina (94 %), Alumina (96 %) and AlN. The thermal efficiency of four different structures of COB LED modules with different modes of operation and environment is examined. The simulation results are verified with thermal measurements.

/pdf/study-of-high-power-cob-led-modules-with-respect-to-topology-qs82d7cvj8.pdf

Study of High Power COB LED Modules with Respect to Topology of Chips

The aim of this work is therefore to analyze the thermal stability by lifetime accelerated tests for three different constructions of LED lighting fixtures. In result of studied we believe to provide information on the role of temperature in determining devices degradation, since in most of the cases high current and high temperatures acted as degradation driving forces. In order to high light the influence of the ageing tests on the LEDs, we firstly measured their characteristics at the initial state and than the measurements were carried out in a cyclical way after every ageing step. The accelerated current test implied a faster degradation than the constant thermal stress: even if the degradation modes were similar for both stress and appeared to be thermally activated, the high carrier flow acted as an acceleration factor on the failure of devices. These results underline that package design in terms of heat dissipation is significant for devices with longer lifetime, and essential requirement for solid state lightning market. Thermal modeling of the LED packages was done in FLOTHERM. Using an IR camera, we measured the die surface temperature of the high-power single dies in LED packages, which are heat sunk at the case.

Anna Andonova

Papers

Investigation of thermal conductivity of PCB

PCB thermal design improvement through thermal vias

Estimation the Amount of Heat Generated by LEDs under Different Operating Conditions

Study of High Power COB LED Modules with Respect to Topology of Chips

Thermal stability analysis of power LED during aging