Miscellaneous active electrical nonlinear devices – circuits – and – External effect – Light
Reexamination Certificate
2000-05-23
2001-07-10
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
External effect
Light
C327S515000, C250S551000
Reexamination Certificate
active
06259308
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Japanese Patent Application No. 11-158946, filed Jun. 7, 1999, the entire subject matter of which is incorporated herein of reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an optical coupling semiconductor switching circuit which is operated by an optical signal.
2. Description of the Related Art
An optical coupling semiconductor switching circuit in the related art, which is operated by optical signals, includes a light detector, an impedance circuit, and a semiconductor switching device such as a FET transistor that is connected to electrical circuits. When the light detector receives light from a light emitting device, the light detector changes a light signal to an electric signal to generate voltage. The voltage, which is output from the light detector, is input to the impedance circuit. The semiconductor switching device is operated when the semiconductor switching device receives the voltage as a gate voltage from the light detector via the impedance circuit.
Since the impedance circuit is in a high impedance state when the voltage is applied to an input terminal of the impedance circuit, the voltage at the input terminal can be output effectively from first and second output terminals of the impedance circuit with little loss. Therefore, the semiconductor switching device whose gate is connected to the first output terminal is operated without fail. Further, while the light detector does not receive light so that the voltage is not applied to the input terminal of the impedance circuit, the impedance circuit is in low-impedance state. Thus, the connection of the impedance circuit is short-circuited between its output terminals. In this situation, as the charge at the gate of the semiconductor switching device rapidly discharges, the gate voltage falls rapidly. Therefore, speedy operation of the semiconductor switching device can be performed.
In the related art, it is required that a plurality of electrical circuits are operated by a single light signal. In this case, the same number of optical coupling semiconductor switching circuits as electrical circuits is formed. Each optical coupling semiconductor switching circuit has a light detector, an impedance circuit and a switching device, and is connected to respective electrical circuit. Thus, the overall circuit is both large and complicated.
SUMMARY OF THE INVENTION
An objective of the invention is to resolve the above-described problem and to provide an optical coupling semiconductor switching circuit having a simple structure, which operates a plurality of an electrical circuits with a single light signal.
The objective is achieved by an optical coupling semiconductor switching circuit to be coupled to a light emitting device for controlling electrical circuits, including a light detector generating voltage in response to light from the light emitting device, a low loss impedance circuit having a first and a second output terminal, which is connected to the light detector to receive the voltage from the light detector, and a plurality of switching devices in parallel connected between the output terminals. Each switching device includes a pair of transistors each having a gates connected to the first output terminal, and an optical rectifier that is activated by light from the light emitting device. The rectifier has a cathode connected to a source of each transistor and an anode connected to the second input terminal.
REFERENCES:
patent: 5013926 (1991-05-01), Aizawa
patent: 5138177 (1992-08-01), Morgan et al.
patent: 5910738 (1999-06-01), Shinobe et al.
Dinh Paul
Mimura Junichi
OKI Electric Industry Co., Ltd.
Wells Kenneth B.
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