BUH1215 Datasheet, PDF (4/7 Pages) STMicroelectronics – HIGH VOLTAGE FAST-SWITCHING NPN POWER TRANSISTOR

BUH1215
Reverse Biased SOA
BASE DRIVE INFORMATION
In order to saturate the power switch and reduce
conduction losses, adequate direct base current
I_B1 has to be provided for the lowest gain h_FE at
100 ^oC (line scan phase). On the other hand,
negative base current I_B2 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 I_B2 which
minimizes power losses, fall time tf and,
consequently, T_j. 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:
1
2
L
(I_C)²
=
1
2
C
(V_CEfly)²
ω
=
2
πf
=
1
√LC
Where I_C = operating collector current, V_CEfly=
flyback voltage, f= frequency of oscillation during
retrace.
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