Abstract: A switching power supply is designed so that a switching frequency deviates from a predetermined range before an output voltage deviates from a predetermined voltage range due to degradation of a choke coil and an output capacitor. The switching power supply designed in that manner is provided with a switching frequency monitoring unit which monitors a switching waveform. By checking if the operating frequency is within a predetermined tolerance, it is determined whether the switching power supply is normally operating or not.

Abstract: A switching power supply is designed so that a switching frequency deviates from a predetermined range before an output voltage deviates from a predetermined voltage range due to degradation of a choke coil and an output capacitor. The switching power supply designed in that manner is provided with a switching frequency monitoring unit which monitors a switching waveform. By checking if the operating frequency is within a predetermined tolerance, it is determined whether the switching power supply is normally operating or not.

Abstract: A digitally controlled power supply of the present invention comprises: a power unit outputting an output voltage, first and second feedback signals; a first A/D converter outputting a digital feedback signal and a first monitoring signal; a second A/D converter outputting a second monitoring signal; a driver outputting the gate signal; a digital controller for power supply control comprising a PWM circuit and a first failure detection signal output unit outputting a first failure detection signal when the first monitoring signal is not within a predetermined range; a digital controller for monitoring comprising a second failure detection signal output unit which outputs a second failure detection signal when the second monitoring signal is not within a predetermined range; and an alarm output unit outputting an alarm when at least either the first or second failure detection signal is output.

Abstract: An induction heating coil having little high-frequency loss and producing little hast is easily manufactured by covering a conductor with a first insulating material to form a wire, then bundling and twisting such wires to form a stranded wire, covering the outer surface of the stranded wire with a second insulating material to form a coil wire, winding the coil wire a certain number of turns into a coil portion having a certain shape. The end portion of the coil portion and a connecting portion are heated with Joule heat while applying pressure to the end portion at the same time, so that the first and second insulating materials are fused and pressure-bonded to the conductor. Thus a terminal portion for the external connection of the coil portion is fixed while keeping the electrical connection with the conductor. Accordingly, an induction heating coil of low cost and stable quality can be easily manufactured.

Abstract: An induction heating coil having little high-frequency loss and producing little hast is easily manufactured by covering a conductor with a first insulating material to form a wire, then bundling and twisting such wires to form a stranded wire, covering the outer surface of the stranded wire with a second insulating material to form a coil wire, winding the coil wire a certain number of turns into a coil portion having a certain shape. The end portion of the coil portion and a connecting portion are heated with Joule heat while applying pressure to the end portion at the same time, so that the first and second insulating materials are fused and pressure-bonded to the conductor. Thus a terminal portion for the external connection of the coil portion is fixed while keeping the electrical connection with the conductor. Accordingly, an induction heating coil of low cost and stable quality can be easily manufactured.

Abstract: The present invention relates to an epoxy resin composition for FRP that will be used for fishing rods, golf club shafts, and the like, a prepreg that is an intermediate material made up of an epoxy resin composition combined with reinforcing fibers, and a tubular molded article obtained using it. The epoxy resin composition for FRP of the present invention comprises (A) a bisphenol A-type epoxy resin, (B) an epoxy resin having oxazolidone rings, and (C) a curing agent. By using the epoxy resin composition for FRP of the present invention, a prepreg quite excellent in handleability and a tubular molded article improved in flexural strength in the longitudinal direction and crushing strength in the diametrical direction can be obtained.