There are three very different approaches to creating high-voltage rectifiers. Two approaches involve connecting a number of lower-voltage single-junction diodes in series. The simplest, called a high-voltage stack, consists of the required number
of diodes tied end to end. However, when creating a series string, it is important
to consider such factors as voltage sharing, junction temperature, and matching
reverse-recovery characteristics.
To account for these factors, compensation networks consisting of resist/capacitor strings are frequently employed. The resulting network, called an R/C-compensated
diode string, is usually used in applications where the power exceeds 30 watts. At lower
power levels, such as those encountered in CRT power supplies, multi-junction diodes
are used.
Deep-diffused junctions are ideal for high-voltage multi-junction diodes. The greatest advantage of the multi-junction process is the capability of stacking diodes at the wafer stage, thus allowing high-temperature bonding and reducing metallization between wafers to almost zero. Moreover, fabricating all the diode junctions on the same wafer provides a simple method of matching junction characteristics.
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