Question One:

Three-terminal transistor + MOS

MOS alone

Question One:

What are the advantages of using a three-terminal transistor with MOS compared to using MOS alone, considering that the battery is a single cell with a full charge of 4.2V, which is a low voltage?

Question Two:

In a flyback power supply, the secondary Schottky rectifier diode shorts, causing the primary MOSFET to burn out as soon as power is applied. What could be the reason for this? Initially, it was thought that the short-circuit protection of the power supply did not work, but the MOSFET was not burned out when there was a positive and negative short circuit at the output terminal, indicating that the power supply protection worked in that case. If the short-circuit protection did not work, what other circuit components could be related to this issue?

Previous Answer:

1. Replacing the 10N60 with an IRF540 transistor allows for full conduction. The IRF540 has a lower on-state resistance than the 10N60, so at the same voltage, the IRF540 has a smaller voltage drop, reducing the temperature of the MOSFET. Additionally, the electrical parameters of the IRF540 are more suitable for the application, resulting in better performance when using the IRF540.

2. Using a series-parallel connection of N 0.1Ω resistors can achieve the power rating required. However, this approach is cumbersome. It is recommended to use a self-tuned regulator as a dummy load, which can be adjusted at any time and is inexpensive. Another option is to use an electronic load (consisting of a thyristor) with a wide adjustment range, which can also feed back to the grid for energy savings.