Lülituskaotused

Lülituskaotused, also known as switching losses, are energy dissipated during the switching transitions of semiconductor devices like transistors and diodes in power electronic circuits. These losses occur because semiconductor devices are not ideal switches; they have finite switching times, meaning they transition from an on-state to an off-state, or vice versa, over a period of time rather than instantaneously.

During these transitions, both voltage across and current through the switching device are significant simultaneously, leading to power dissipation. Specifically, when a device turns on, there is a brief period where it conducts current but hasn't fully reached its low on-state resistance, and when it turns off, there's a period where it carries current while its voltage is rising towards its off-state value. These simultaneous voltage and current phases result in power loss, which is converted into heat.

The magnitude of switching losses depends on several factors, including the switching frequency, the device's switching speed, the voltage and current levels, and the presence of parasitic capacitances and inductances in the circuit. Higher switching frequencies generally lead to increased switching losses, as the device undergoes more transitions per unit time.

Minimizing switching losses is crucial in power electronics for improving efficiency and reducing thermal management challenges. Techniques like soft switching, where the switching transitions occur at zero voltage or zero current, or using devices with faster switching speeds and lower parasitic elements, can help to reduce these energy losses.