BUW1215 datasheet(4/7 Pages) STMICROELECTRONICS

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Reverse Biased SOA

In order to saturate the power switch and reduce

conduction losses, adequate direct base current

IB1 has to be provided for the lowest gain hFE at

100

oC (line scan phase). On the other hand,

negative base current IB2 must be provided the

transistor to turn off (retrace phase).

Most of the dissipation, especially in the deflection

application, occurs at switch-off so it is essential

to determine the value of IB2 which minimizes

power losses, fall time tf and, consequently, Tj. A

new set of curves have been defined to give total

power losses, ts and tf as a function of IB1 at 64

KHz scanning frequencies for choosing the

optimum negative drive. The test circuit is

illustrated in figure 1.

The values of L and C are calculated from the

following equations:

(IC)2 =

(VCEfly)2

ω = 2 πf =

√

L C

Where IC = operating collector current, VCEfly=

flyback voltage, f= frequency of oscillation during

retrace.

BASE DRIVE INFORMATION

BUW1215

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