Hitachi, Ltd.

Shinzi Okuhara

Ichiro Ohhinata

Michio Tokunaga

Mitsuru Kawanami

Tatsuya Kamei

Masayoshi Suzuki

Masaaki Kusano

Mitsuo Matsuyama

Yoshikazu Hosokawa

Tetsuo Takeshita

Takuzi Mukaemachi

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.

Semiconductor switch circuit

A semiconductor switch has a pair of PNPN switches connected in an inverse-parallel mode and each includes a switching circuit for protection against the rate effect. Each switch has its gate terminal multi-connected through a capacitive element to provide a terminal, which is connected to the output terminal of a control circuit for generating a voltage pulse in a repetitive manner to bear the difference of potential between the PNPN switches and a capacitive element by means of the capacitive element and to drive the PNPN switches with the aid of a variation of voltage produced in the control circuit.

Semiconductor switch

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 plurality of PNPN switches, each permitting current flow in either, i.e., positive or negative, direction, are arranged at the cross points between the rows and the columns of the speech paths so as to form a matrix. The gate trigger terminal of each PNPN switch is connected with a gating current circuit having a high impedance, which circuit is adapted to control ON and OFF operations of the switch. A plurality of means are provided to selectively turn the gate current circuits on and off so that gate current is supplied continuously for the gate terminal of any desired PNPN switch at least for the time during which the corresponding cross point of the matrix is to be electrically bridged.

Semiconductor channel switch

A stable semiconductor switch comprising a PNPN switch, a transistor, a driving device, and diodes. The PNPN switch is composed of four-layered PNPN structure and has three PN-junctions, an anode, an anode gate, a cathode gate, and a cathode. The collector and the emitter of the transistor are connected to the cathode gate and the cathode of the PNPN switch, respectively. The driving device has its one end connected to the anode gate of the PNPN switch and its other end connected to the base of the transistor so as to drive the transistor in transient state. The diodes are connected between the driving device and the emitter of the transistor in a manner so that, when the PNPN switch is controlled to fire and a back current tends to flow through the PNPN switch temporarily, the back current does not flow through the transistor so as to prevent the transistor from causing any abnormal actions such as oscillation.

A plurality of sets of thyristors, each set consisting of two thyristors connected in inverse parallel configuration, are arranged in the form of a matrix to provide a switch of balanced or unbalanced type. A control circuit is provided which feeds successive pulses or light energy whose repetition rate is higher than the frequency of the ac signal such as a ringing signal passing through the speech paths, to the thyristors at a cross-point to be closed, during the time required for exchange operation. In this way, a speech path switch can be constituted of semiconductor elements and ringing, dialing and hooking signals can be treated together with speech signals.

Semiconductor speech path switch

A light-emitting diode element comprises a semiconductor wafer including a pair of a p-type semiconductor region and an n-type semiconductor region forming a pn junction, an inclined first electrode provided on at least one of the peripheral edges of the surface of one of the semiconductor regions in the semiconductor wafer, and a flat second electrode provided on the surface of the other semiconductor region. A light-emitting diode device is provided in which a plurality of such light-emitting diode elements are respectively received in a plurality of openings of a substrate having a first wiring conductor group and a second wiring conductor group electrically connected to the first and second electrodes respectively of the light-emitting diode elements by a low-melting metal. Thus, these light-emitting diode elements can be mounted on the single substrate in a high package density, and the light-emitting diode device of simple construction can be easily assembled.

Light-emitting diode element and device

A semiconductor switch of a PNPN structure comprises a PNPN switch of an equivalently four-layered structure including a P-type anode, N-type cathode, N-type gate and P-type gate, a first NPN transistor, a second PNP transistor, a level shifting circuit, and an impedance element, wherein the impedance element is connected between the collector and emitter of the first transistor, the first transistor has its collector and emitter connected to the P-type gate and N-type cathode respectively, and the second transistor has its emitter and base connected to the P-type anode and N-type gate, respectively, and has its collector connected to the base of the first transistor through the level shifting circuit. In this arrangement, the first transistor is driven by the current flowing through a PN junction at the end on the side of the anode of the PNPN switch and the level shifting circuit, so that the semiconductor switch has a great dv/dt withstanding power, operates with high sensitivity, has a high breakdown voltage in both directions and facilitates the setting of circuit constants.

A semiconductor switch assuring the easy formation of a semiconductor integrated circuit and having high control sensitivity while maintaining high dv/dt - immunity, which comprises a PNPN switch of an equivalently four-layered structure including at least three PN-junctions, an anode and a cathode, switching means including a control terminal and connected with the PNPN switch to shunt one of the three PN-junctions at either one end of the PNPN switch, amplifying means, and a capacitive element for differentiating a voltage applied between the anode and the cathode of the PNPN switch to allow a current to flow into the control terminal of the switching means through the amplifying means, so that the switching means is driven by the current thereby to short-circuit the one of three PN-junctions.

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.

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Fujisawa, Japan

Shinzi Okuhara