Is there any correlation between MOSFET power loss and diode loss?

Is there any correlation between MOSFET power loss and diode loss?

Is there any correlation between MOSFET power loss and diode loss? Switch Mode Power Supply (SMPS), also known as Switching Power Supply or Switching Converter, is a high-frequency electrical energy conversion device and a type of power supply.

Switching losses include conduction losses and cutoff losses. Conduction loss refers to the power loss generated by a power transistor from cutoff to conduction. Cut off loss refers to the power loss generated by a power transistor when it transitions from conduction to cutoff. Switching loss, including turn on loss and turn off loss, is often discussed in both hard switching and soft switching. The so-called turn on loss refers to the voltage of a non ideal switching transistor that does not immediately drop to zero when it is turned on, but has a falling time, and its current does not immediately rise to the load current, but also has a rising time. During this period, there is an overlap between the current and voltage of the switching transistor, which results in losses, known as turn-on losses.

By analogy, the reason for the shutdown loss can be derived, which will not be further elaborated here. Another meaning of switch loss is that in a switching power supply, when switching large MOS transistors, parasitic capacitors need to be charged and discharged, which can also cause losses.

In the process of device design selection, it is necessary to perform preliminary calculations on the operating losses of MOSFETs (the so-called preliminary calculations refer to using the parameters provided in the device specification book, the calculated values and expected waveforms of the operating circuit, and applying formulas for theoretical approximation calculations without being able to test various operating waveforms).

Generally speaking, power MOSFETs and diodes are basic components in electronic product design and electrical circuit systems. Their electronic components themselves have extreme parameters such as conductivity resistance and working environment. So, how do electronic engineers grasp the performance quality of power consumption and service life of electronic components, as well as the losses of power MOSFETs and diodes?

Electronic product designers and engineering assistants need to consider two different situations, namely the worst-case scenario of electronic product operation and the actual working environment of the device. Starting from the procurement brand and selection of electronic components, select the correct components for circuit products, and then find technical parameter values that are close to and consistent with the actual application in the electronic component specification book, such as the selection of MOS transistor channel type, current and voltage values.

The loss of diode switches is actually a very important indicator. The self heating damage on the working circuit of electronic components, as well as the heating caused by losses due to external DC power, can all cause instantaneous and local heating and damage to a certain extent. For example, calculating the thermal resistance between the semiconductor junction of packaged devices and the environment, assessing the conduction loss of power MOS transistors in the event of damage to built-in diodes, and calculating the heat dissipation requirements of the system.