Power diodes

Figure 6.14 Circuit symbol for a power diode as a switch...

Note The above switching devices by themselves or in conjunction w ith power diodes can be developed into a variety ol new devices to suit any power conversion and control application. MCTs and IGCTs arc a few such hybrid devices. For more details refer to the literature on the subject in the Further reading. 

Notes (1) Considering the firing angle = 0, the values are same for power diodes also. 

When eontrolling an a.e. maehine, the eonverter is usually a full-wave, power diode fixed-type reetifier and the Vlf is eontrolled through the IGBT inverter. For regenerative mode, the d.e. bus is eonneeted in antiparallel with a full-wave voltage-eontrolled inverter as shown in Figure 6.31. 

It is also possible to use an IGBT eonverter instead of a power diode or a thyristor eonverter. A single IGBT... 

A power diode reetifier unit feeding a fixed d.e. power to an inverter unit to control an a.c. motor, or a thyristor rectifier unit, directly controlling a d.e. motor, both contain... 

The inductance in the d.c. link may cause a reverse voltage spike across the power diodes or thyristors as a residt of the decay of the reverse current (release of its stored energy). A power deviee may be protected against such voltage spikes through tin R-C snubber circuit, as shown in Figure 6.37. (This circuit is discussed later.)... 

This is applicable to thyristor (SCR) circuits to protect all the semiconductor devices used in the switching circuit, such as diodes (also power diodes) or IGBTs, in addition to SCRs. The same protection can be applied to all the semiconductor circuits likely to experience high dv/di. 

Fig. 14-8 Circuit diagram for a dc decoupling device with silicon diodes. (KE) insulated cable end sealing, (E) grounding installation, (1) silicon power diodes.

Hefner, A., et ah, SiC Power Diodes Provide Breakthrough Performance for a Wide Range of Applications, IEEE Trans. Power Electronics, Vol. 16, 2001, pp. 273-280. McCluskey, P., et ah, Reliability of Commercial Plastic Encapsulated Microelectronics at Temperatures from 125°C to 300°C, 2000 IEEE Aerospace Conf. Proc., Vol. 5, March 18-25, 2000, pp. 445-450. 

Auerbach (37) recorded with a diode laser in a thin film of a solvent-coated polymer-metal ion salt complex (e.g., poly-2-vinylpyridine-AgNO3). Using short-duration pulses (120 ns) of 820-nm light (10 mW), he showed that high reflectivity marks could be created that could be read with a lower power diode laser. The mechanism is believed to involve thermally induced electron transfer from the polymer to the metal ion forming localized metal areas (Ag + e — Ag°). The concept is not limited to silver salts of gold, copper, and tellurium can be used. Polymers other than vinylpyridine that can form charge-transfer complexes with metal ions should function as electron-transfer binders. 

Laser therapy by low light doses shows promising results in the modulation of some cell functions. However, the mechanism behind it is still not completely understood. To explore the effect of a low-power diode laser (= 780 nm) on normal skin tissue, time-dependent contrast enhancement has been determined by MRI. It can be observed that, after biomodulation with light of low energy and low power, wound healing improves and pain is... 

Schottky power diodes with heat sinks (optional)... 

A. Courjaud, N. Deguil, F. Salin, Fligh-power diode-pumped Yb KGW utra-fast laser, Adv. Solid State Lasers 68, 161-163 (2001)... 

Frequency doubling, or SHG, as illustrated in Figure 1, is of keen interest as a means of generating new laser sources. Frequency doubling of low power diode lasers from the red or infrared into the blue comprise a prime commercial application. Device outlets include higher capacity optical storage devices, as well as more sensitive laser printers and copiers. The objective is to increase not only the molecular response p, but of course the material response Be-... 

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