Hitachi, Ltd.

Nippon Telegraph and Telephone Public Corporation

Fujitsu Corporation

Oki Electric Industry Co., Ltd.

Nippon Electric Co., Ltd.

Michio Tokunaga

Ichiro Ohhinata

Shinzi Okuhara

Junjiro Kitano

Hideo Mizutani

Toshio Hayashi

Kazuo Hamazato

Koichi Hasegawa

Akio Sagawa

Mitsuru Kawanami

Takaaki Osaki

Ryoichi Okada

A current supply circuit comprises a DC power feed circuit exhibiting a constant current characteristic for a power source and a constant resistance characteristic for a load, a first detecting circuit for detecting a load current or a load voltage, a DC-DC converter circuit inserted between the power source and the DC power feed circuit, a second detecting circuit for detecting an output voltage from the DC-DC converter circuit; and an operation circuit coupled at the input with the output of the first detecting circuit and the output of the second detecting circuit for controlling the DC-DC converter circuit by the output thereof. The DC-DC converter circuit is so controlled as to produce a voltage representative of the sum of a voltage drop across the load and a fixed voltage necessary for the operation of the DC power feed circuit.

Current supply circuit

A current supply circuit for a telephone exchange is disclosed in which a current-supplying current amplifier series-connected between a power supply and a load amplifys an output current of an input current supply circuit, and a driving current amplifier for driving the current-supplying current amplifier is controlled by an output of an output voltage detector parallel-connected with the load in a negative-feedback fashion to set the differential mode output impedance of the current supply circuit at a large or small value in accordance with frequency and to set the common mode output impedance at a small value; and in which a part of the output voltage detector for connecting the load to the driving current amplifier includes a diode for preventing a direct current from flowing in a opposite direction to that of a direct current from the power supply in order to suppress, independently of the state of the load, a current which flows from the load side into the driving current amplifier, whereby an increase in current is restricted and an on-off control can be conducted in a short time without impairing an essential function of the current supply circuit.

Current supply circuit for telephone exchange

A semiconductor switch circuit comprises first, second and third transistors. The complementary first and second transistors make up an inverted Darlington circuit. The third transistor with the base and collector thereof connected to the collector and base of the inverted Darlington circuit respectively makes up a positive feedback circuit with the inverted Darlington circuit. The conduction current of the switch circuit is split into two conduction currents flowing through the complementary first and second transistors making up the inverted Darlington circuit. By controlling the base current of at least one of the first and second transistors, the switch circuit is subjected to on-off control, thereby making it possible to reduce the required control power and increase the off-controllable load current.

Semiconductor switch circuit

In a semiconductor switch circuit employing at least one 4-terminal PNPN switch having a cathode gate and an anode gate for switching an AC signal, a current supplying circuit is connected to the cathode gate of the PNPN switch, and a current sinking circuit of constant-current type is connected to the current supplying circuit and the anode gate of the PNPN switch through a current change-over circuit. Depending on the potential of the PNPN switch, the current change-over circuit supplies selectively the current flowing into the current supplying circuit and the current flowing out from the anode gate of the PNPN switch to the current sinking circuit. The current supplying circuit operates as a constant-current circuit owing to the current sinking function of the current sinking circuit. The semiconductor switch circuit is simple in circuit construction and can be economically integrated into an integrated circuit form.

A semiconductor switch circuit comprises a PNPN switch with a PNPN semiconductor four-layered structure equivalently including first and second transistors and a gate terminal, a load current dividing circuit including at least one transistor, a variable impedance bypass circuit including at least one transistor, and a capacitive element. The base and the collector of the transistor included in the load current dividing circuit are connected to the cathode and the anode of the PNPN switch, respectively. The collector and the emitter of the transistor included in the variable impedance bypass circuit are connected to the P-type base of the second transistor of the PNPN switch and to the emitter of the transistor of the load-current-dividing circuit, respectively. The base of the transistor of the variable impedance bypass circuit is connected to the anode of the PNPN switch through the capacitive element and is controlled for gate turn-off operation. The PNPN switch having self-holding ability is combined with a transistor which does not have self-holding ability but current-amplifying ability to divide the load current into a current flowing through the PNPN switch and a collector current of the transistor. No large load current is imposed on the PNPN switch but most of the load current is passed through the transistors thereby to facilitate gate turn-off operation. Further, the PNPN switch is protected against the rate effect by use of the variable impedance bypass circuit. Thus both large and small load currents can be controlled with a small self-holding current.

A constant current circuit includes two characteristic-correlated PNP transistors connected to a constant voltage source and having common-connected emitters and common-connected bases and an NPN transistor. A constant current is taken out of a collector of a first PNP transistor. A collector of a second PNP transistor is connected to a base of the NPN transistor and the common-connected emitters of the first and second PNP transistors is connected to a collector of the NPN transistor to form a negative feedback circuit in the first PNP transistor, whereby when a current gain of the second PNP transistor which is characteristic corelated to the first PNP transistor is high a large amount of feedback is applied and when the current gain is low a small amount of feedback is applied so that the magnitude of the output constant current taken from the collector of the first PNP transistor is adjusted.

Constant current circuit

A semiconductor switch is composed of at least a 4-terminal PNPN switch. The cathode gate and the anode gate of the PNPN switch are connected to a current-supplying type constant-current circuit with a power supply for feeding a current into the cathode gate and to a current-sinking type constant-current circuit without any power supply for taking out a current from the anode gate, respectively. A change-over circuit is connected between both the constant-current circits for automatically selecting a path of a drive current from the current-supplying type constant-current circuit to either selected one of the cathode gate and the anode gate or the current-sinking type constant-current circuit in response to the electrical potential of the PNPN switch. The semiconductor switch circuit composed of the 4-terminal PNPN switch may be thus controlled economically with a single power supply without any wasteful power consumption.

A semiconductor switch device comprising a PNPN switch having an equivalent four-layer structure, a transistor, two impedance elements and a capacitive element, wherein the transistor and one of the impedance elements are connected in parallel with each other, the parallel circuit thus formed is connected between the P base and the N cathode of the PNPN switch, the capacitive element is connected between the base of the transistor and a terminal maintained at a constant potential, and the other impedance element is connected between the base and the emitter of the transistor, whereby the semiconductor switch has a high tolerance to dv/dt and can be closed with high sensitivity.

Semiconductor switch device

A light activated semiconductor switch device comprising a light activated PNPN switch, an impedance element, a switching element, and a capacitance element. The impedance element and switching element are connected in parallel across the cathode gate and the cathode or across the anode and the anode gate of the light activated PNPN switch, and the switching element is turned on by the current supplied through the capacitance element, so that the device can operate with improved tolerance to dv/dt and high turn-on sensitivity.

Light activated semiconductor switch device

A semiconductor bidirectional switch circuit comprises a bidirectional switch including two thyristors connected in antiparallel relationship. A bypass circuit is connected to each of the two thyristors for bypassing a part of a main current flowing through the thyristor from the anode to the cathode of the thyristor. A cathode-gate driver circuit is connected to the cathode-gate of each of the two thyristors for supplying a current thereto and a driver circuit is connected to the base of the transistor constituting each of the two bypass circuits, for extracting a current from the base, whereby the gate current of either of the thyristors is allowed to continue flowing at a low drive voltage irrespective of the amplitude of an AC signal voltage which passes through the bidirectional switch circuit so that even when the AC signal current decreases in absolute value below the self-holding current of the thyristor associated, the AC signal may be passed through the thyristor switch without being subjected to instantaneous interruptions.

Semiconductor bidirectional switch circuit

A semiconductor switch comprising a PNPN switch having an equivalently four-layer structure of p, n, p and n regions and three PN junctions; a transistor; two impedance elements and a capacitive element, wherein the transistor and one of the impedance elements is connected in parallel to each other, the parallel circuit thus formed being connected between the p base and the cathode of the PNPN switch, the capacitive element is connected between the base of the transistor and the anode of the PNPN switch, and the other impedance element is connected between the base and the emitter of the transistor, so that the obtained semiconductor switch has a high dv/dt withstandingness independent of the potential at the anode or cathode and a high breakdown voltage, can be closed with a small control current and is adapted for high speed switching.

Semiconductor switch

A semiconductor switch large in dv/dt bearing capacity regardless of the anode or cathode potential, high in breakdown voltage, capable of being closed with a small control current, and easy to be included in semiconductor integrated circuits. The semiconductor switch according to the invention comprises a PNPN switch having an equivalent PNPN four-layer construction with three junctions and an active circuit network including at least one transistor. The active circuit network combines with part of a positive feedback loop in the PNPN switch to form a negative feedback circuit network. The transistor forming part of the active circuit network is connected in such a manner as to divide one of the gate currents of the PNPN switch.

Growing community of inventors

Zushi, Japan

Michio Tokunaga