9

SEPTEMBER 1995 - REVISED SEPTEMBER 1997

TISP61060D, TISP61060P

DUAL FORWARD-CONDUCTING P-GATE THYRISTORS

PROGRAMMABLE OVERVOLTAGE PROTECTORS

PRODUCT

INFORMATION

energy capability. Second, the series gate diodes have been changed to transistor buffers. The maximum

from the positive voltage diode conduction has been diverted to the gate terminal which subtracts from the

normal gate current. In most cases, this allows any previously used SLIC supply rail shunt protection diode to

be removed. Although the SLIC supply is taken to a terminal that is internally connected to transistor bases,

the terminal is still designated as the gate terminal, G.

Figure 6 shows the high impedance a.c. waveforms for the TISP61060. As the TISP61060 replaces the IC

based protector’s gate diode with a transistor, the peak gate current is reduced by over 50 times. In addition

there is a compensating negative gate current flow during diode conduction. The TISP61060 has the

maximum value of peak gate current specified and so allows for designer to design for limit conditions. Most

IC protectors do not specify this parameter. Figure 7 shows the improvement due to the TISP61060. These

plots show the full cycle average gate current against rms a.c. voltage. The IC based protector has a

substantial positive gate current which will always charge the SLIC supply, possibly causing an overvoltage.

The TISP61060 has a negative gate current and so cannot overvoltage the SLIC.

Figure 6. TISP61060 HIGH IMPEDANCE POWER CROSS CLIPPING WAVE FORMS

Time - ms

0

5

10

15

20

-300

-200

-100

0

100

200

300

-10

-8

-6

-4

-2

0

2

4

6

8

10

Time - ms

0

5

10

15

20

-60

-50

-40

-30

-20

-10

0

10

V

G

V

K

I

K

I

G

I

G

I

K

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