Zero crossing detection circuit

Details Zero crossing detection circuit Zero crossing detection circuit

2005-12-20

2005-12-20

Tran, Sihn (Department: 2646)

Telephonic communications

Supervisory or control line signaling

Using line or loop condition detection

C379S165000

Reexamination Certificate

active

06978008

ABSTRACT:
A PNPN structure thyristor and a third P-type impurity region are formed on a semiconductor substrate, and a fixed current circuit using an NPN transistor20and a resistor30is connected to a cathode terminal K and a gate terminal G of a composite element10that has a P-channel MOS transistor Q3with the third P-type impurity region as a drain connected to a PNP transistor Q1of the thyristor. If a voltage applied to the anode terminal A of the composite element10rises from 0V, initially the thyristor is on and current flows, but once the threshold voltage of transistor Q3is reached transistor Q3turns on. A short circuit then exists between the base and emitter of transistor Q3of the thyristor and current of the composite element10itself is cut off. Because of the bipolar structure it is simple to configure a small integrated circuit with a high withstand voltage. In this way, a zero crossing detection circuit is provided that has high withstand voltage characteristics, but which can be made as a small sized integrated circuit.

REFERENCES:
patent: 5875245 (1999-02-01), Miyasita et al.
patent: 3-124154 (1991-05-01), None
patent: 6-350741 (1994-12-01), None
patent: 10-75323 (1998-03-01), None

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