The circuit diagram is as follows:

The circuit diagram shows the use of a microcontroller output PWM control to adjust the current. However, the MOSFET voltage drop is too high at around 10V, and the temperature is very high. The output current is controlled to be approximately 250mA.

Solution: Even after changing to a transistor driver or totem pole drive, the voltage drop remains too high.

Note: A 1K resistor is added between 12V and the gate, which was not included in the schematic.

Question 2

I want to create a current load box with N resistors, each 0.1 ohms, with a maximum current of AC120A and maximum power of 2000W, with 14 leads on the resistors. How should I wire them?

Note: The goal is to handle relatively high currents, so I want to distribute the current across the resistors to ensure they can handle it.

Last Period's Answer:

1. After the switch is closed, the inductor charges, and then it discharges, while the capacitor charges. This cycle repeats, creating an alternating voltage and current. The output frequency of the transformer is determined by the switching rates of switches 1 and 2, and the conversion efficiency is determined accordingly.

2. At low frequencies, this resistor is somewhat comforting and unnecessary. But at high frequencies, the situation changes. The input impedance of the MOSFET will decrease, and it may become negative in a certain frequency range, leading to oscillation. To change the steepness of the control pulse and prevent oscillation, as well as reduce the voltage spikes at the collector, a suitable resistor Rg should be connected in series with the gate. As Rg increases, the conduction time lengthens, and the heat dissipation increases. As Rg decreases, di/dt increases, which may cause false conduction and damage to the device. The value of Rg should be selected based on the current capacity and voltage rating of the device, as well as the switching frequency. Typically, it ranges from a few ohms to several tens of ohms. Additionally, to prevent damage to the device due to open or damaged gate circuits, it is recommended to add a resistor Rge between the gate and the source, with a resistance value of around 10k ohms. You can find the value of Rg in the datasheet under the Td on and Td off columns.