Considerations on External Heat Transfer in Saturated Bipolar Junction Transistors

• Published in: IEEE journal of emerging and selected topics in power electronics Vol. 12; no. 4; pp. 3967 - 3976
• Main Authors: Carotenuto, Riccardo, Iero, Demetrio, Pezzimenti, Fortunato, Della Corte, Francesco G., Merenda, Massimo
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01-08-2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Bipolar transistors; BJT heat transfer; BJT heating; BJT physical effect; BJT saturation; Circuits; Electric potential; Electrons; Emitters; Energy dissipation; Heating systems; Junction transistors; Junctions; MTBF; Rectifiers; Semiconductor devices; Thermal stress; Voltage; Voltage drop
• ISSN: 2168-6777; 2168-6785
• DOI: 10.1109/JESTPE.2024.3417526

When the BJT is deeply saturated and a resistor (R) is connected between the base and collector, the overall bipole seen through the base and emitter exhibits rectifying properties. By appropriately sizing R, only a small fraction of the current flows into the base, while the majority passes through R, causing a voltage drop almost equal to that between the base and emitter. The same current flows through the collector and emitter, resulting in a voltage drop on the order of tens of millivolts. The novelty lies in the fact that almost all the power is dissipated in R rather than in the BJT. In the presence of large currents, this leads to significantly lower power dissipation in the BJT compared to a diode of the same size. The reduced thermal stress can extend the mean time between failures (MTBFs) of the BJT. In this study, we conduct a model-based analysis of the saturated BJT rectifier, which is then validated through experimental setups. Furthermore, it is demonstrated that the power dissipated in a saturated BJT-based bridge rectifier is significantly lower than that measured in a classical bridge rectifier configuration under the same operating conditions.