The diode is the simplest bipolar semiconductor device. It comprises p-type and n-typesemiconductor
materials brought together, usually after diffusion or implantation, to form a (step or abrupt) junction as shown in figures 2.1a and 2.3a.
پسورد : 4power
Passive turn-on and turn-off snubber circuits for the IGBT transistor, the GCT and the GTOthyristor have been considered in chapter 7. These snubber circuits modify the device I-V switching trajectory and in so doing reduce the device transient losses. Snubber circuit action involves temporary energy stored in either an inductor or capacitor. In resetting these passive components it is usual to dissipate the stored energy in a resistor as heat. At high frequencies these losses (being proportional to frequency) may become a limiting factor because of the difficulties associated with equipment cooling. Instead of dissipating the switching-aid circuitstored energy, it may be viable to recover the energy back into the dc supply or into the load, or both. Two classifications of energy recovery circuits exist, either passive or active. A passive recovery circuit involves only passive components such as L and C while active recovery techniques involve extra switching devices, as in a switched-mode power supply, smps.
پسورد : 4power
Soft magnetic materials are used extensively in power electronic circuits, as voltage and current transformers, saturable reactors, magnetic amplifiers, inductors, and chokes. These magnetic devices may be required to operate at only 50/60 Hz, or at frequencies down to dc or over 1 MHz.
پسورد : 4power
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