###### Abstract  
The supply of energy with the correct parameters to electrical appliances is possible with the use of energy converters. When a direct current is required, rectifier bridges are needed. These can be made using rectifier diodes. The problem of excessive junction temperatures in power diodes, which are used to build rectifier bridges and power converters, was recognized. For this reason, research work was carried out to create a model of a rectifier diode placed on a heat sink and to analyze the heat dissipation from the junction of this diode under forced convection conditions. The results obtained from the simulation work were compared with the results of thermographic temperature measurements. The boundary conditions chosen for the simulation work are presented. A method is also presented that determined the convection coefficient under forced convection conditions. The difference between the simulation results and the results of the thermographic measurements was found to be 0.1 \({}^{\circ}\)C, depending on the power dissipated at the junction and the air velocity around the diode. diode; energy converter; FEM; heat sink; rectifier diode; rectifier bridge; thermal conductivity; temperature distribution thermography +
Footnote †: journal:  
_Applied_  
Footnote †: journal:  
There are three ways to measure the junction temperature of a semiconductor diode:  
- Methods based on thermal sensitive parameter (TSP);  
- Methods which use contact sensors;  
- Methods which use non-contact sensors. Electrical methods (based on TSP) involve determining the junction temperature of a semiconductor diode from the relationship between the temperature of the diode Tj and the conduction voltage VF. This is a method that is difficult to use. The relationship Tj = f(VF) is specific to the junction in question [16]. In order to designated this relationship, it is necessary to put the diode in the measurement circuit (outside the device containing this diode) and determine the characteristics. Because of this, the use of this method is troublesome. Contact methods (which use contact sensors) require the temperature sensor to be applied to the case. Several temperature sensors are commonly used. Among the simplest of these are the thermocouple [17], the thermistor [18], and the thermoresistor [19]. The use of a thermocouple requires a device to compensate for the cold junction. This device can be found on a multimeter [20]. The thermistor has nonlinear characteristics that make it difficult to make a measurement. The use of any contact temperature sensor has an important disadvantage: the thermal conductivity relationship between the sensor case and the diode case is unknown. In addition, this conductivity depends on the temperature of the diode case. The result of the measurement of the contact temperature also depends on the contact force of the sensor case to the diode case [21]. Another significant disadvantage is the risk of electrical shock. These disadvantages can be avoided by using thermographic measurements. Such a measurement involves determining the temperature of a diode case by analyzing the optical radiation reaching the radiation detectors in the thermal imaging camera. The thermal imaging measurement is not free of disadvantages. Its value depends on the emissivity factor value [22], the reflected temperature [23], the distance between the camera lens and the object under observation [24], the ambient temperature [25], the temperature of the external optical system [26], the transmission of the external optical system [27], and the relative humidity [28]. In addition, the result of a thermographic temperature measurement depends on the fuzziness of the recorded thermogram [29] and the location of the observation. The thermographic measurement of the temperature of the diode case does not allow for the direct measurement of the semiconductor junction temperature. A measurement on the surface of the case is possible.