7

SEPTEMBER 1995 - REVISED SEPTEMBER 1997

TISP61060D, TISP61060P

DUAL FORWARD-CONDUCTING P-GATE THYRISTORS

PROGRAMMABLE OVERVOLTAGE PROTECTORS

PRODUCT

INFORMATION

thyristor to switch into the low-voltage on-state condition. At the end of the negative half cycle, the thyristor

switches off when the current falls below the holding current value (300 mA). Switch-off and re-clipping at

-52 V causes a second pulse of gate current. The wire current drawn by the protector is quasi-sinusoidal

During the positive a.c. voltage period (diode clipping) there is no gate current. During the negative a.c.

voltage period there are two triangular pulses of gate current, which peak at about 80 mA. This is current

However, often the supply is generated from a switching mode power supply or the SLIC supply feed has a

series diode which blocks reverse (charging) current flow to the battery. In these cases the supply can only

under high source impedance conditions (e.g. 600

Ω). In the case of the LB1201AB, it is recommended that

the supply should be able to absorb 700 mA of “wrong way” current. If the supply cannot absorb the current

then a shunt breakdown diode is recommended to provided a path for the gate current to ground (D2 in

Figure 2). High power diodes are expensive, so diode D2 is usually low power, purposely selected to fail

under this a.c. condition and protect the SLIC.

Figure 3. IC PROTECTOR POWER CROSS WAVE FORMS

Time - ms

0

5

10

15

20

-750

-500

-250

0

250

500

750

-100

-75

-50

-25

0

25

50

75

100

Time - ms

0

5

10

15

20

-60

-50

-40

-30

-20

-10

0

10

V

G

V

K

I

K

I

G

AI6XAG