Schottky diodes have several common and important currents

In actual engineering practice, Schottky diodes are often used in circuits that convert AC voltage to DC voltage. They are also often used as voltage stabilizing circuits, limiting circuits, and freewheeling circuits. Select a few common and important currents to analyze.

1. It plays a freewheeling role in the inductance of switching power supplies and inductive loads such as relays. This function is very practical.

Switch A and switch B are implemented using PFET and NFET switches, respectively, to form a synchronous buck regulator. The word "synchronous" means using a FET as a low-side switch. Buck regulators that use Schottky diodes instead of low-side switches are called the "asynchronous"(or asynchronous) type. When dealing with low power, synchronous buck regulators are more effective because the voltage drop of FETs is lower than that of Schottky diodes, which is mainly determined by Rds(on). However, when the inductor current reaches zero, if the bottom FET is not released, the light-load efficiency of the synchronous converter will be reduced, and additional control circuitry will increase the complexity and cost of the IC. Schottky diodes can be used as freewheeling diodes. The Schottky PN junction is special, which makes it have a very small junction capacitance and stores little charge. Therefore, this junction has a very fast switching speed and can be used for high-speed clamping. The characteristics of Schottky diodes are: very fast switching speed and extremely short reverse recovery time. Therefore, switching diode low-voltage high-current rectifying diode can be made.

2. Analog water flow simulation of Schottky diode effect

Voltage is often simulated as water pressure, and the function of a Schottky diode can also be simulated similar to water flow. The relative current of the Schottky diode is like a one-way valve. When biased in forward direction, as long as the bias voltage exceeds the threshold voltage, the valve will open and water can flow smoothly; when biased in reverse direction, the valve cannot be opened. No water flows through.

3. Schottky rectifying diode

By using the unidirectional conductivity of Schottky diodes, alternating current with alternating directions can be converted into pulsating direct current in a single direction.