THERMAL SIMULATION OF POWER LED DIODE IN COMSOL ENVIRONMENT
The aim of this paper is to build a dynamic thermal model of power LED for simulation environment COMSOL. The dynamic thermal model was based on technical and application manufacturer's data of power light emitting diode. In this way the assembled electrical and thermal model of power LED was simulated in a dynamic process of load within Comsol simulation program. The simulation results have been subjected to verification in the real environment. Measurements of the real LED showed good agreement with the simulation results. 1 Principle of power LED Technical solutions of advanced power LEDs make them suitable for their widespread use in lighting techniques. The reason is their high efficiency of conversion of electrical energy to optical as well as their long life. Despite these positive properties, power LEDs have quite large electrical losses that are transformed into heat. It is necessary to take thermal energy of electrical losses from the LED chip into the environment through effective heat sink. The contribution offers an opportunity to obtain the basic information about a thermal field of specific power LED HUEY JANN ELECTRONIC HPB8C49KYWHB [8] simulated in the COMSOL Multiphysics program [1]. Fig. 1 shows a construction of a power LED (right) and the same diode with the addition of sink (left). Power dissipation heats the LED chip and the diode housing. It is needed to dissipate a heat outside the LED chip so as not to damage components (maximum junction temperature Tj must not exceed 150 ° C). LED power dissipation is related to the specific output of LED, which has a value of 125 Lm / W at an ambient temperature Ta = 25 ° C. 2 Heat dissipation Power dissipation, which is released into the environment in the form of thermal energy, occurs in a volume of semiconductor device by the action of flowing current. It is primarily the loss in a permeable state (voltage drop at the part and forward current). For the power LED, it is necessary to set the dissipation. The common formula is used to calculate active power in integral form [4]:     0 1 t P v t i t dt T    (1) where v(t), i (t) are the instantaneous values of relevant electrical quantities, and T is their period. The product of v(t). i(t) represents the so-called instantaneous power, which is an important indicator of
Optimization procedure for selection of active components of DC-DC converter's thermal simulation model
The power electronic system which contains printed circuit board is comprised from set of passive and active components. Active electronic components are represented as source of thermal energy which arises from power loss of given device. By capturing the surface's temperature of whole electronic system through thermo vision measurement, and by consequent picture analysis of thermo frames, it is possible to identify active components. The aim of this article is development of methodology for optimal selection of mentioned active components for thermal simulation model of given electronic system. The main reason of component minimization is optimization of model's thermal analysis. That means, the computation of thermal field of investigated system may be accelerated due to lower interactions between active and non active components, whereby pre-defined accuracy of heat transfer shall be achieved.
A study of the local tissue reactions in man to cortisone and compound F. VI. Histopathological studies of the local effect of compound F in normal and pathologic skin of man.
After our previous negative studies (1) of the local effect of cortisone acetate in the skin of man, a year ago, a parallel study of 17-hydroxycorticosterone-21-acetate, Compound F, was outlined. Theoretically, Compound F should be the active steroid. It was so suggested by Rothman (2), that in all probability Compound F and not cortisone would be active locally in the skin of man.