Abstract: The current resonant converter according comprises a voltage converting transformer having a primary winding and a secondary winding, a switching circuit, disposed on the primary side of the transformer, for turning on and off a current supplied from an DC power to the transformer, a resonant circuit disposed adjacent to the transformer, a rectifying and smoothing circuit, disposed on the secondary side of the transformer, for supplying an output to a load, and a control circuit for controlling a switching frequency of the switching circuit, whereby the current resonant converter is operated in two modes, consisting of a first mode for prohibiting a DC current component from flowing in the primary winding and a second mode for allowing the DC current component to flow in the primary winding.

Abstract: A current resonance converter including a resonant circuit composed of an inductance Lr and a capacitor Cr, a switching element SW connected to the resonant circuit in series so as to turn on and off the resonant circuit, an oscillating circuit VCO for driving the switching element SW, a strobe pulse generating circuit SPG adapted to generate a strobe pulse after a predetermined period of time elapses from the time when the switching element SW is turned on, and a controlling circuit CTL serving to reduce an oscillation frequency derived from the voltage controlled oscillator VCO or stop oscillation of the same while the case where an electric current flows through the resonant circuit in the forward direction when a strobe pulse is generated is recognized as a case where the converter is loaded with an overload is disclosed. With this construction, the converter can be constructed in smaller dimensions with a lighter weight while assuring protection when the converter is loaded with an overload.

Abstract: A noise induced from a switching power supply source or the like is applied to a power line. The noise is classified into two kinds, one of them being normal mode noise appearing between power lines and the other one being common mode noise appearing between a power line and a ground line. Thus, a line filter is required to attenuate these noises.

Abstract: A line filter comprising a plurality of coils, one or more X capacitors is disclosed. Optionally, the line filter may comprise one or more Y capacitors. A method for constructing such a line filter is also disclosed. In one embodiment, a second X capacitor has a value approximately equal to the value of a first X capacitor if a circuit constant LT0 is less than a total inductance LT.In another embodiment, a first and third coils in combination exhibit a normal inductance of L.sub.1e, and a second and fourth coils in combination exhibit a normal mode inductance of L.sub.2e. L.sub.1e is determined at a point of intersection between a first function f1 and a second function f2, and a second capacitor has an equivalent capacitive value C.sub.X0 determined at a minimum of a third function, f3 (C.sub.X0), expressing L.sub.2e as a function of C.sub.X0.

Abstract: A power supply (ringer power supply) for a telephone exchange comprising a first switching circuit for receiving and subjecting direct current to high frequency switching by means of a switching element, a converter transformer connected to the switching circuit, a smoothing circuit connected to the secondary side of the converter transformer, a second switching circuit connected to the output stage of the smoothing circuit and used for switching the input current by means of a transistor bridge of a plurality of transistors for being alternately turned on, a direct-current bypassing diode connected between the input and output terminals of each transistor, a driving circuit for driving each of the transistors in accordance with a predetermined driving signal, and a driving signal generator circuit for generating the driving signal for setting timing to prevent the period during which a transistor is turned on from overlapping the one during which another transistor is subsequently turned on, permitting a red

Abstract: The present invention comprises a switching circuit which converts direct current electric power into a pulse; an insulative transformer which includes a primary coil for loading a generated pulse, coils for direct and alternating current outputs which are provided on the secondary coil side of the insulative transformer; an impendance circuit for controlling current which is connected with the coil for alternating the output; a control circuit which controls the switching circuit so that the output voltage of the coil for the direct current output is kept constant; and a fluorescent lamp connected with the coil for alternating the current output. The circuit can obtain the alternating current without secondary switching.

Abstract: A stabilizing power source apparatus includes a transformer with one primary and two secondary coils, a switching transistor, first and second differential amplifiers, an oscillator, and a pulse modulator. The oscillator generates a triangular wave of variable frequency. The modulator changes the pulse width and frequency of its output in accordance with a shift of a crossing point between the leading ramp of the triangular wave and the signal from the first differential amplifier. The pulse drives the switching transistor, so that the duty factor of the transistor stabilizes a DC output voltage and a switching frequency thereof stabilizes an AC output voltage. Another stabilizing power source apparatus includes a saturable reactor for stabilizing the DC output voltage and a resonance type inverter to generate a sinusoidal wave voltage.

Abstract: In a line filter having a first balun, first Y capacitors, a first X capacitor, a second balun, second Y capacitors and a second X capacitor connected between the input and output terminals of the line filter in the order named, the inductance of the first balun is larger than that of the second balun. The total capacitance of the first Y capacitors is larger than that of the second Y capacitors. The line filter can be divided into a front stage containing the first balun and a rear stage containing the second balun, the two stages being coupled via a wiring. The second balun can be constituted by a plurality of baluns.