Power Field-Effect Transistors Control. ...

Power Field-Effect Transistors Control. Circuit Engineering. The majority of circuits of various high-frequency power electronics are nowadays built on insulated-gate field-effect transistors. Field-effect transistors have become one of the most widely-spread electronic elements and are included in many products - from microchips to integrated power circuits. Let's look at the various options of circuits that involve power field-effect transistors. Direct controller-based control. In pulse power supplies the transistor is controlled by a driver that is part of a PWM-controller. One of the few problems here is the limited output current of the driver, which leads to limited control of high-speed power transistors and excessive dissipated power in the driver. The problem can be easily addressed with a help of an external gate resistor, the size of a bridging capacitor and careful planning of the circuit elements distribution. Another popular and efficient circuit for control of a FET is a double-step stage of bipolar transistors. This circuit of a double-step driver significantly simplifies the controller's operation, because it takes up significant current surges and power dissipation. Apart from the need to place the driver next to the power switch, it also needs to be supplied with its own bridging capacitor. This driver is peculiar in that it enables mutual protection of transistors from the reverse current breakdown. The two-stage bipolar driver does not require any fuse diodes. Two-stage driver on field-effect transistors. The advantages of this driver are the same as for the previous one with bipolar transistors. However, there do exist certain drawbacks. The driver inverts the incoming signal, which requires the controller to do that too and, thus, an additional inverter needs to be used. Control of a p-channel power transistor connected in the circuit with a common source using a high-voltage metal-insulator-semiconductor complementary structured (MISCS) gate. The gates on mutually complementary transistors with the metal-insulator-semiconductor structure are the basic elements of modern microchips. In the circuit shown, the source of the p-channel transistor is connected to the positive power supply, whereas the control gate has an additional negative power supply. At low voltage on the gate output, a high-capacity power transistor would be ...