1, low-voltage application

When using 5V power supply, if the traditional totem pole structure is used at this time, because the be of the transistor has a voltage drop of about 0.7V, the actual final voltage applied to the gate is only 4.3V. At this time, there are certain risks in choosing MOS transistors with a nominal gate voltage of 4.5V, and the same problems will occur when using 3V or other low-voltage power supplies.

2. Wide voltage application

The input voltage is not a fixed value, it will change with time or other factors. This change leads to the instability of the driving voltage provided by PWM circuit to MOS transistor. In order to make MOS transistors safe under high gate voltage, many MOS transistors have built-in voltage regulators to forcibly limit the amplitude of gate voltage. In this case, when the supplied driving voltage exceeds the voltage of the regulator, it will lead to large static power consumption. At the same time, if the gate voltage is simply reduced by the principle of resistance voltage division, the MOS transistor will work well when the input voltage is relatively high, but when the input voltage is reduced, the gate voltage is insufficient, resulting in incomplete conduction, thus increasing power consumption;

3. Dual voltage application

In some control circuits, the logic part uses a typical digital voltage of 5V or 3.3V, while the power part uses a voltage of 12V or even higher. These two voltages are connected in * * * ground mode. This puts forward a requirement that a circuit should be used so that the low-voltage side can effectively control the high-voltage side MOS tube, and the high-voltage side MOS tube will also face the problems mentioned in 1 and 2.