MJ10023

5

Motorola Bipolar Power Transistor Device Data

SWITCHING TIMES NOTE

In resistive switching circuits, rise, fall, and storage times

have been defined and apply to both current and voltage

waveforms since they are in phase. However, for inductive

loads which are common to SWITCHMODE power supplies

and hammer drivers, current and voltage waveforms are not

in phase. Therefore, separate measurements must be made

on each waveform to determine the total switching time. For

this reason, the following new terms have been defined.

tsv = Voltage Storage Time, 90% IB1 to 10% VCEM

trv = Voltage Rise Time, 10–90% VCEM

tfi = Current Fall Time, 90–10% ICM

tti = Current Tail, 10–2% ICM

tc = Crossover Time, 10% VCEM to 10% ICM

An enlarged portion of the inductive switching waveform is

shown in Figure 7 to aid on the visual identity of these terms.

For the designer, there is minimal switching loss during

storage time and the predominant switching power losses

occur during the crossover interval and can be obtained us-

ing the standard equation from AN–222A:

PSWT = 1/2 VCCIC(tc)f

In general, trv + tfi ` tc. However, at lower test currents this

relationship may not be valid.

As is common with most switching transistors, resistive

switching is specified at 25

_C and has become a benchmark

for designers. However, for designers of high frequency con-

verter circuits, the user orinented specifications which make

this a “SWITCHMODE” transistor are the inductive switching

speeds (tc and tsv) which are guaranteed at 100_C.

2.0

5.0

10

20

40

0.4

1.0

0.02

0.05

0.1

0.2

0.5

1.0

2.0

Figure 10. Typical Turn–On Switching Times

IC, COLLECTOR CURRENT (AMPS)

2.0

5.0

10

20

40

Figure 11. Typical Turn–Off Switching Times

IC, COLLECTOR CURRENT (AMPS)

Figure 12. Thermal Response

t, TIME (ms)

1.0

0.01

0.1

0.1

1.0

10

100

10000

R

θJC(t) = r(t) RθJC

R

θJC = 0.7°C/W MAX

D CURVES APPLY FOR POWER

PULSE TRAIN SHOWN

READ TIME AT t1

TJ(pk) – TC = P(pk) R

θJC(t)

P(pk)

t1

t2

SINGLE PULSE

1000

0.02

0.05

0.1

0.2

0.5

1.0

2.0

tf

VCC = 250 V

IC/IB1 = 20

TJ = 25°C

ts

td

tr

0.4

1.0

VCC = 250 V

IC/IB1 = 20

VBE(off) = 5 V

D = 0.5

0.5

0.2

0.05

DUTY CYCLE, D = t1/t2

0.2

0.1

RESISTIVE SWITCHING