Essay on Power Semiconductor Devices

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Power Semiconductor Devices

Introduction

Today there are many power semiconductor devices used in different applications of power conversion. The diode is one of the oldest semiconductors devices and is still wildly used today in power electronics. Diodes are found in virtually all power converts in one form or another. For this reason our discussion will be focused on the application of power diodes. Power Diodes are two terminal electronic devices that permit current flow in predominantly one direction. Diodes are composed of differently doped silicon or germanium bounded together at a junction.

Purpose

As an Electrical Engineering specializing in Power Electronics it is important to understanding the application of
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If the voltage differential reverses, conduction stops. In practice diodes have a small forward voltage drop of between 0.5 and 1.5 Volts. The heat generated in the diode is proportional to the current through the diodes times the voltage drop across the diode.

Diodes are found in virtually all in AC drives and Power converters in one form or another. They are used as rectifiers, current steerers, protection devices from reverse voltage, and to clamp voltage at defined levels. Their location and rating depends on current configuration. The forward surge maximum ( IFSM ) rating is the maximum current that a diode can handle as a transient. The IFSM rating of a typical D6 power diode is up to 190 Amps with a maximum junction temperature of around 180ºC. The typical forward voltage drop across a germanium diode is 0.2 Volts and for silicon diode is 0.7 Volts. Various types of diodes are available to match application requirements.

Schottky diodes are created by bonding a metal, such as platinum or aluminum, to a n-type silicon. Their primary advantages are very low forward voltage drop and switching speeds of up to less then 100 picoseconds. Schottky diodes are ideal for the output stages of a switching power supplies and use in very high frequency applications. The little reverse recovery time they exhibit is primarily dictated by their capacitance rather then their minority carrier recombination. This characteristic allows for minimal current
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