Abstract: 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.

Abstract: In semiconductor switches, erroneous firing is often a serious problem. To overcome this, a semiconductor switch is provided which includes a thyristor of PNPN structure with three PN junctions and with anode, cathode and gate electrodes, a first transistor for short-circuiting at least one PN junction of said thyristor upon its saturation, and a second transistor provided between the anode side or cathode side of the thyristor and the base of said first transistor to cause saturation of the first transistor in accordance with the voltage which is applied to the anode or cathode of the thyristor. The ratio of the time constant of the second transistor to that of said thyristor is not substantially less than 0.5. This ratio is established by using similar plane diffused patterns for the second transistor and a third transistor which is defined by three continuous layers of the thyristor.

Abstract: A semiconductor switch comprising a PNPN switch which has a four-layered PNPN structure with at least three PN-junctions, switching means for electrically short-circuiting a path between a P-type base and an N-type emitter of the PNPN switch when a transient voltage is applied between a P-type emitter and the N-type emitter of the PNPN switch, and drive means for driving the switching means, the drive means driving the switching means so that the path between the P-type base and the N-type emitter may be electrically short-circuited for a fixed time even after termination of the transient state, whereby any improper ignition of the PNPN switch is prevented even after the termination of the transient state.

Abstract: An apparatus for detecting misfire in a multicylinder internal combustion engine, comprising a sound pick-up transducer disposed in the exhaust passage of the engine or a chamber communicating with the exhaust passage for the purpose of detecting exhaust sound, an integrating circuit for integrating an electric output of the transducer in synchronism with the rotation of the engine and a comparison circuit for comparing the output of the integrating circuit with a reference signal, thereby misfire being detected on the basis of an output of the comparison circuit.