Abstract: A switching power supply includes a switching element, a diode, a choke coil, a comparator-detector, and a drive circuit. A first resistor and a second resistor are connected in series between one end of the choke coil and the ground, and the connection point thereof is connected to one input end of the comparator-detector. A third resistor and a parallel circuit including a fourth resistor and a capacitor are connected in series between the other end of the choke coil and the ground, and the connection point thereof is connected to the other input end of the comparator-detector. In addition, the output end of the comparator-detector is connected to the input end of the drive circuit, and the output end of the drive circuit is connected to the control end of the switching element.

Abstract: A power circuit for rectifying and smoothing a commercial voltage to obtain a direct-current voltage. The power circuit comprises a smoothing choke coil inductance varying circuit for variably controlling an inductance value of a smoothing choke coil within a smoothing circuit. The smoothing choke coil inductance varying circuit flows a current through a secondary winding of the smoothing choke coil to provide induction based on an output voltage from a diode bridge such that an inductance value of a primary winding of the smoothing choke coil is at the maximum when the output voltage from the diode bridge is zero volt, is reduced with an increase in the output voltage, reaches a predetermined value when the output voltage is at the maximum, and is increased with a reduction in the output voltage.

Abstract: The DC power supply circuit has a bleeder circuit 3 connected in parallel to a smoothing capacitor C1. The bleeder circuit 3 is adapted to permit electric current to pass therethrough when a voltage developed across the terminals of the smoothing capacitor C1 exceeds a set voltage that is a voltage set within a voltage range from an output voltage value, at which an output current has a maximum value, to an output voltage value, at which an output current is 0.

Abstract: A circuit comprises at least one electronic switch which is operatively connected to an inductive load, is intended to be driven by means of an on-off signal and, in an enabled condition, can connect the load to a direct-current voltage supply, at least one freewheeling circuit branch which comprises a diode and can recirculate the transient current which flows through the load each time the switch is disabled, and a filtering circuit connected between the diode and the voltage supply and comprising a parallel capacitor connected to the diode and a series inductor connected between the diode and the voltage supply. The freewheeling circuit branch and the filtering circuit are connected substantially in series with one another in a circuit branch which is operatively connected in parallel with the load.

Abstract: The unified constant-frequency integration (UCI) control method of the invention is based on one-cycle control. It employs an integrator with reset as its core component along with a few logic and linear components to control the pulse width of a three-phase rectifier, active power filter, or grid-connected inverter so that the three phase current draw from, or the current output to, the utility line is sinusoidal. The UCI control employs constant switching frequency and operates in continuous conduction mode (CCM) that is desirable for industrial applications.

Abstract: A laser diode system comprising a voltage source, an inductor connected to the output of the voltage source, an integrator circuit connected in series with the inductor, and a laser diode. The integrator circuit filters out noise from the voltage source, and includes a first resistor, an amplifier, a second resistor, and first and second capacitors. The second capacitor has one lead connected to the input lead of the inductors and the other lead attached to the input of the first resistor. The output lead of the first resistor is connected to the negative input lead of the amplifier, and to the input lead of the first capacitor. The positive input lead of amplifier OP is connected to the output of the inductor (and the anode of the laser diode). The outputs of amplifier and the first capacitor are connected to the input of the second resistor, which has an output connected to the anode of the laser diode. The cathode of laser diode is tied to circuit common.

Abstract: A switching power supply wherein an inductor device is connected to the center tap of a primary winding of a transformer with a switching device provided to apply high frequency signals to the transformer concurrently with a rectified smoothed input signal applied to the primary winding concurrently by another inductor device so that the secondary winding of the transformer produces a DC output signal which is free of harmonic current and whereby the switching power supply power factor is improved.

Abstract: The invention relates to a circuit arrangement for providing a unit recognizing system combined with energy supply. The system includes a unit recognizer combined with energy supply (EE) and an energy source with variable frequency (FMG). The unit recognizing module combined with energy supply (EE) includes a supply block (3) and between this and the energy source with variable frequency (FMG) a further filter block (1) and a potential separating block (2).

Abstract: A DC high voltage generator includes an AC power supply, an AC-DC rectifier and means to stabilize the DC high voltage generator against load variations. The stabilizer means uses at least two electro-magnetically coupled resonant circuits, which compensate the load variations at an operating frequency in such a way that the output voltage is essentially constant.

Abstract: A circuit arrangement for generating representations of supply voltages that includes a first path that receives control signals, the first path having a subtracter for forming a difference signal from two of the control signals and a low pass filter to receive the difference signal. A second path receives the control signals, the second path includes a second low pass filters that passes frequencies higher than the first low pass filter does. Output signals of the first and second paths are fed to a combination network which, as a function of the difference between the output signals of the first and second paths, passes on the output signals of one of the first and second paths.

Abstract: A filter for a direct current voltage converter includes chokes L1, L2 and capacitors C1, C21. The filter is connected between the feeding source and the direct voltage converter, and an auxiliary alternating voltage source U.sub.H connected in series with the capacitor C1 has the same alternating voltage amplitude as the interference voltage U.sub.C1 at 180.degree. phase angle rotation.

Abstract: A circuit for, and method of, reducing a preload current required to maintain a duty cycle of an asymmetrical DC/DC converter and a DC/DC converter incorporating the circuit or the method. In one embodiment, the circuit includes an auxiliary inductor, coupled in series with an output capacitor of the converter in an output current doubler thereof, that reduces ripple current in the output current doubler and thereby maintains the duty cycle.

Abstract: In a load-side filter of an n-phase converter circuit arrangement, the capacitors are arranged in at least two n-phase capacitor groups, one of which is hard-grounded and the other of which is grounded with a high impedance via a grounding resistor.

Abstract: A converter output filter for an induction drive system is provided. The converter output filter (40) comprises an L-R-C network (41) that can be coupled between each converter output (38a, 38b, and 38c) of a converter (16b) and a DC-link midpoint node (35) of the converter (16b). Each L-R-C network (41) comprises an inductive element (42a, 42b, and 42c), a resistive element (44a, 44b, and 44c), and a capacitive element (46a, 46b, and 46c) coupled in series. An electrical device (18) can be coupled to the L-R-C network (41) between the respective inductive element (42a, 42b, and 42c) and the respective resistive element (44a, 44b, and 44c).

Abstract: A pump supporting inductor (L1) is added to a half-bridge oscillator circ for a low-pressure discharge lamp (E) having a capacitive pump path, which inductor improves the pumping action of the pump path and its frequency response. Furthermore, an additional capacitor (C1) is connected between the pump path and the power supply path connected thereto, which capacitor acts as a trapezoidal capacitor in conjunction with the pump path and further improves the frequency response of the pump path.

Abstract: A power-line filter for operation with a converter is provided having a regulated voltage source and sinusoidal phase currents, with the power-line filter helping to eliminate interference voltages particularly in the frequency range from 2 kHz to 150 kHz, which are normally not taken into account. The leakage currents to ground, in this context, can be minimized to the point that it is possible to operate the converter in an (AC/DC sensitive) Interference Filter (IF) protective circuit-breaker.

Abstract: A filter scheme for a battery power plant for supplying power to a load includes positive and negative voltage bus bars each having an input and an output, the output adapted to be connected to the load. A capacitor is connected between the bus bars adjacent to the output of power plant, and an inductor is connected to either one of the bus bars adjacent to the output of the power plant to reduce bus voltage transients.

Abstract: An electromagnetic interference (EMI) filter, method of manufacturing therefor and power converter employing the EMI filter. In one embodiment, the EMI filter includes (1) a filter circuit board located outside a chassis and having an aperture that receives therethrough a bus bar extending from within the chassis, (2) a capacitor, mounted on the filter circuit board and coupled to the bus bar, that receives from the bus bar at least a portion of EMI induced into the bus bar from within the chassis and (3) a conductor, mounted on the filter circuit board and coupled between the capacitor and the chassis, that receives the portion from the capacitor and returns the portion to ground via the chassis.

Abstract: In a smoothing circuit for a switching power supply having a reactor and a capacitor, the circuit includes a resistor connected in series to the capacitor, a MOSFET connected parallel to the resistor, and a control circuit for turning the MOSFET on only when the voltage at both ends of the resistor increases or decreases to reach reference voltages. Thus, the output waveform is changed from a triangular wave to a sine wave in order to reduce the harmonic components contained in the output ripple. An output noise is reduced stably without reducing efficiency.

Abstract: The present invention provides an improved power factor and lower harmonic distortion in the power supply circuit of a high frequency discharge lamp. An "extra" circuit path is provided so that the driving power to the lamp will "see" a load that significantly reduces the harmonic distortion and tends to cause the power factor to approach "1". In a preferred embodiment of the invention this is accomplished by providing a third capacitor with which the load circuit forms an in-series resonance circuit with the discharge lamp and its associated current-limiting inductance. The new circuit arrangement provides a high frequency current passage not provided in known lighting circuits of this type that raises the power factor and lowers harmonic distortion.

Abstract: In a circuit where a power converter (1) that is connected to a motor is also connected at its input terminals (2, 3) to a d.c. power supply system (U.sub.DC) and where at least one condenser (C) is connected in parallel to the power converter (1) connected to the motor and at least one line reactor (L) is connected in series to the condenser (C), a reduction in the harmonic currents fed back into the d.c. power supply system (U.sub.DC) by the power converter (1) connected to the motor above a predetermined minimum frequency is achieved without unnecessarily overdimensioning the condenser (C) and the line reactor (L) due to the fact that the line reactor (L) has at least one tapping point (4) to which at least one RC circuit (5) is connected in parallel to the condenser (C), where the RC circuit (5) has at least one capacitor (C.sub.1) and at least one resistor (R.sub.1) connected in series with it.

Abstract: Disclosed is a new single-phase passive harmonic filter for one or more nonlinear loads. The filter improves the total system performance by drastically reducing the line side current harmonics generated by nonlinear loads. The filter includes two inductive portions across one of which is connected a tuning capacitor. The parallel combination of one inductive portion with the tuning capacitor forms a series tuned filter configuration while the second inductive portion is used for harmonic attenuation. A shunt capacitor is employed for shunting higher order harmonic components. A single-phase passive voltage regulator provides the needed voltage bucking to prevent over voltage at the load terminals of the filter. The filter provides an alternate path for the harmonic currents generated by nonlinear loads. The over voltage caused by the increased capacitive reactance is controlled by either capacitor switching or by the use of the passive voltage regulator or a combination of the two.

Abstract: A voltage converter having a voltage intermediate circuit and an invertor connected to the output of the voltage intermediate circuit. The invertor produces a three-phase AC voltage at its output and is connected to the output terminals of the voltage converter by a filter arrangement. The filter arrangement includes a filter inductor connected in series with the output terminal and the filter capacitor connected between the output terminal and a common capacitor star point. Attenuation of the DC system is achieved by having the capacitor star point connected to the voltage intermediate circuit by way of an RC element having a capacitor and a resistor.

Abstract: A method and apparatus for maintaining relatively low ripple current in a dc-dc converter while minimizing the size of an inductive line filter utilizes a transformer having at least a pair of secondary windings in which the secondary windings are selected to have different numbers of winding turns depending on the specific design of the ideal duty factor at which the converter will be operated. In addition, the converter is provided with an active pre-load which establishes a continuous conduction current when load current is below some selected minimum value in order to provide control stability during light load conditions without converter oscillations.

Abstract: A battery charging system detects a secondary battery terminal voltage and selectively controls a first switch to connect/disconnect a series-connected smoothing capacitor and resistor to ground to present an impedance greater than the battery impedance and further controls a second switch to connect/disconnect a charging control circuit in series between the voltage supply and the secondary battery being charged.

Abstract: For use with a boost converter having first, second and third input inductors, a switching network, method of reducing input current total harmonic distortion (THD) associated with the boost converter, and boost converter employing the switching network and method. In one embodiment, the switching network includes a first switch coupled between corresponding rails of the boost converter. The switching network also includes first, second and third L-C resonant networks wye-coupled to a common node and coupled to the first, second and third input inductors, respectively. The first switch and the first, second and third L-C resonant networks cooperate to create resonant voltages across, and induce phase currents through, the first, second and third input inductors to reduce input current THD associated with the boost converter.

Abstract: An electrical filter apparatus for an electrostatic precipitator, wherein the filter apparatus is a T-type or pi-type filter electrically connected to a high voltage output of an electrostatic precipitator power supply and an electrostatic precipitator electrode. The T-type filter comprises a first inductor electrically connected to the high voltage output and a capacitor that is also electrically connected to ground. A second inductor is connected to the first inductor and the electrostatic precipitator electrode. In another embodiment, a two-stage inductor assembly is provided having a third inductor member defined by a plurality of turns of a continuous length of wire, and a fourth inductor member defined by a plurality of ferrite beads in end-to-end relationship.

Abstract: The alternative power system provides microprocessor grade, filtered output power capable of replacing standard NiCad battery packs in portable electronic devices. The invention makes use of capacitor banks comprised of capacitors having different values, whereby the individual capacitors act as individual filters to substantially eliminate all transients which are present in the source of power, which is typically provided by rechargeable batteries on a host system, such as a forklift or hand truck.

Abstract: An access device having an input port for connecting to an upstream section of a coaxial distribution cable and an output port for connecting to a downstream section of a coaxial distribution cable, and provides isolation of an RF communication signal from an AC power signal for access by subscriber network service equipment. The access device also includes power conditioning of the AC signal to provide a DC operating voltage over a separate output to operate the respective subscriber network service equipment.

Abstract: For use in a split-boost converter having a DC input, first and second outputs, a power train interposed between the DC input and the first and second outputs, a damped electromagnetic interference (EMI) filter circuit and method of reducing the EMI. In one embodiment, the EMI filter circuit includes (1) an EMI filter interposed between the power train and the second output, the EMI filter subject to oscillation from line disturbances arriving at the DC input and (2) a conductive path, coupling a rail of the second output to the DC input, that routes at least a portion of the line disturbances from the DC input directly to the second output to damp the oscillation of the EMI filter.

Abstract: Disclosed is a new single-phase passive harmonic filter for one or more nonlinear loads. The filter improves the total system performance by drastically reducing the line side current harmonics generated by nonlinear loads. The filter includes single-phase integrated inductances with an appropriately placed tap across which is connected a tuning capacitor. The combination of the inductance up to the tap position and the tuning capacitor form a series tuned filter configuration while the remainder of the integrated inductance is used for harmonic attenuation. A shunt capacitor is employed for shunting higher order harmonic components. A single-phase passive voltage regulator provides the needed voltage bucking to prevent over voltage at the load terminals of the filter. The filter provides an alternate path for the harmonic currents generated by nonlinear loads.

Abstract: Matrix filters useful in low-noise power distribution systems include arrays of capacitors and inductors with interleaved interconnections in an high density interconnect structure so as to achieve nearly ideal performance, i.e., such that capacitor and inductor parasitics are minimized. The matrix filters are bi-directional which help to isolate different load modules by attenuating the switching noise of associated power converters as well as the noise generated by digital loads.

Abstract: In order to avoid filter excitations of subharmonics or intermediate harmonics, that is to say of oscillations in the frequency range between integral harmonics of the mains frequency (f.sub.N), in the case of an attenuation resistor (R1, R3, R3') in parallel with a series resonant circuit comprising a filter inductor (L1, L3) in series with a filter capacitor (C1, C31, C31'), the resistance is dimensioned in such a way that a current gain of the filter (F1-F3) at its frequency pole points with an AC mains (1) is not greater than 6-fold. Double low-pass filters (F1, F2) and high-pass filters (F3) with attenuation resistors (R1, R3, R3') are particularly suitable as filters (F1, F3).

Abstract: The battery charger comprises a power factor correcting and voltage regulating apparatus having an inductor through which current is modulated by a modulator to obtain an efficient regulation and an efficient power factor correction. According to a first embodiment, the modulator comprises two rectifying elements connected to two controllable high frequency bidirectional switch elements. According to a second embodiment, the modulator comprises a rectifying element connected to a controllable high frequency switch. According to a third embodiment, an efficient battery charger is provided. It comprises an inverter including four controllable high frequency bidirectional switch elements connected in a bridge configuration. According to a fourth embodiment, a two-part battery charger is provided. It has an indicator for indicating quality of the coupling between the two parts thereof. According to a fifth embodiment, a two-part battery charger is provided.

Abstract: A power factor improving circuit capable of obtaining a high power factor for a power supply circuit and at the same time of achieving a smaller size and lower cost of the power supply apparatus by a simple construction. To accomplish this object, a choke coil L1 is connected between the higher potential side output terminal of a rectifier 1 and the primary winding N1 of a transformer T of a converter circuit 2, and one end of a smoothing capacitor C1 is connected to a connecting point between the choke coil L1 and the primary winding N1 of the transformer T. The other end of the smoothing capacitor C1 is connected to the cathode of a first diode D1, to the anode of a second diode D2 and to the anode of a third diode D3.

Abstract: The invention relates to a circuit arrangement for operating a low-pressure discharge lamp. The circuit arrangement according to the invention comprises means X for supplying the low-pressure discharge lamp, provided with means X1 for generating a current of changing polarity. The circuit arrangement also comprises a feedback network which together with the means X and the low-pressure discharge lamp forms a control loop for controlling a lamp condition parameter. A low-pass filter is included in the control loop. The feedback network is provided with means M for generating a signal m which represents the instantaneous value of the lamp condition parameter, means C for comparing the signal m with a reference signal d, and means S for controlling the means X in dependence on the result of the comparison.

Abstract: A DC to DC converter including a resonant switching circuit (13, 51 , 115, 151, 125, 153); an impedance matching circuit (53) responsive to the resonant switching circuit; a rectifier circuit (55) responsive to the impedance matching circuit; an output filter circuit (57) responsive to rectifier circuit for providing a filtered DC to DC converter voltage output; and a varactor diode circuit (27, 29, 31, 61) responsive to the filtered DC to DC converter voltage output for controlling the impedance matching circuit such that the filtered DC to DC converter output voltage is substantially constant.

Abstract: An isolated, high impedance, DC current source is provided from a readily available AC type source. The DC current source includes an isolating transformer which receives the AC source signal and provides an isolated AC voltage signal therefrom, a resonant low pass filter which is tuned to the frequency of the AC type source and which takes the AC isolated voltage signal and generates therefrom an AC current source signal, and a rectifier which rectifies the AC current source signal to provide a DC current source signal. A voltage limiting clamp is preferably coupled to the rectifier in order to limit the output voltage to a desired level. The resonant low pass filter is preferably comprised of two substantially equally valued inductors coupled to respective poles of the secondary winding of the isolating transformer, and a capacitor which is coupled to both of the inductors.

Abstract: A filter module for a frequency converter comprises a filter circuit housed in a casing adapted for connection to the converter. The filter module includes an input filter and an output filter so arranged that input terminals for connection to the AC line voltage and output terminals for connection to an electric motor are disposed on a common side of the casing and so that the connections between the frequency converter and the filter module are disposed on a side of the casing which in use faces the converter.

Abstract: A high frequency AC/AC converter apparatus with power factor correction includes an AC/DC converter circuit part to provide power factor correction and a DC/AC inverter circuit part to produce a high frequency AC signal for operation of a load, for example, a discharge lamp. The AC/DC converter circuit part includes a diode and an inductor. The converter apparatus utilizes first and second semiconductor controlled switching devices, one of which is common to each part of the overall converter apparatus. A single control circuit controls both parts of the converter apparatus by controlling the switching of the first and second semiconductor switching devices. There are two possible control techniques, constant duty ratio control or duty ratio sweeping control. A voltage clamp circuit inhibits undesired oscillation of the diode voltage.

Abstract: A power supply includes a power converter 2 for generating an output voltage to be supplied to a load 3 from a power source 4, a filter 5 connected between power converter 2 and load 3, and a controller 10 for controlling the power converter 2, in which controller 10 applies a voltage instruction value v.sub.r applied as an input to circuitry which implements an operation element A defined as: ##EQU1## subtracts the output voltage from instruction voltage v.sub.r, and applies the difference to power converter 2.

Abstract: A ballast filter in which the ballast can operate at a total harmonic distortion of power line current of less than 10%. Power dissipated by the filter when at a THD of less than 10% is relatively low. The input impedance of the ballast is chosen to be no greater than twice the equivalent filter impedance of a front end filter and no less than the equivalent filter impedance/1.5. The filter includes a transformer having a core which at times operates within the non-linear region of its B-H curve under nominally rated ballast load conditions.

Abstract: A power supply which incorporates a high frequency inverter and which is suitable for use in conjunction with a florescent lamp. The power supply comprises a full wave rectifier (10) and a reservoir capacitor (12) connected across the rectifier for the purpose of providing successive half-cycles of the voltage waveform V2 across the capacitor with a minimum instantaneous voltage level greater than zero. A solid state switching device (14) and an oscillator (15) are connected in circuit with the reservoir capacitor. The oscillator generates a gating signal to the switching device. The switching device is arranged to provide an output voltage V4 which has a frequency determined by the applied gating signal V3 and which has a peak amplitude value which varies over successive cycles with the waveform of the voltage V2 across the reservoir capacitor.

Abstract: To insure high power factor for the operating circuit of a low-pressure discharge lamp, especially of miniature fluorescent lamps, a high-frequency active rectifier bridge (D1-D4) is provided which interrupts charging of a smoothing capacitor (C2), which smoothing capacitor supplies an inverter circuit (WR) in the switching rhythm of the inverter. A storage choke or inductance (L1), a negative feedback capacitor (CG) and an auxiliary capacitor (CS) are coupled to the high-frequency rectifier bridge (D1-D4) which, together with the inductance insure an approximately sinusoidal current being taken from a power network, with a power factor of 0.98 or higher. Preferably, the circuit includes voltage dividers (R8, R9, R11; R15, R16, R17) which are coupled to a voltage sensitive trigger circuit (DI, TH) to turn OFF alternate switching of transistors (T1, T2) of the inverter (WR) in case excess supply voltage or operating voltages of the lamp are sensed.

Abstract: An inverter device is connected to output ends of a full-wave rectifier for full-wave recification of an AC input voltage from an AC power source, and includes an inductance component in a loop formed with a load circuit including an LC resonance series for charging a DC power-source capacitor through one of a pair of switching elements, whereby a high input power factor is maintained while reducing any distortion of input current, and a control of the switching elements which function to restrain any rush current can be simplified.

Abstract: An improved EMI filter design is provided for an inverter operated dynamoelectric machine. A lossy balun wound choke is connected between a power supply in the form of a bridge rectifier and the inverter. The choke acts as a source resistance. Using the choke as the source resistance, an equiripple approximation to linear phase filter is derived. The filter is placed on the input side of the bridge rectifier. A method of designing an EMI filter for use in conjunction with an inverter operated dynamoelectric machine.

Abstract: A resonant power supply for use in conjunction with power transistor switching circuits. In one embodiment, a series-connected LC resonant circuit is coupled to the high voltage pulsed output of the power transistors and designed to draw power from the pulsed output and deliver the same to a low voltage output capacitor at which a low voltage output is provided. The low voltage output is regulated by a zener diode connected in parallel with the output capacitor. A starting resistor of a relatively high value, typically in the Megohm range, supplies initial charge to the output capacitor to permit the first switching event to occur so that the resonant power supply can begin to provide power. The resonant frequency of the LC circuit is significantly higher than the maximum switching frequency of the power transistors, enabling the resonating high frequency wave forms of the LC circuit to supply repeated charge bursts to the output capacitor.

Abstract: A switching power source apparatus for producing power signals. The apparatus includes a rectification circuit for rectifying received alternating voltage signals, a smoothing circuit for smoothing the rectified signals and a switching power supply circuit for producing the power signals. The apparatus may include a circuit for extracting low voltage signals from the switching power supply circuit and for superposing such low voltage signals on the smoothed rectified signals so as to reduce a ripple component present in the smoother rectified signals. The smoothing circuit and the switching power supply circuit may utilize a common switching device and/or a common frequency switching signal.

Abstract: A Variable Frequency Drive Power Center incorporating a new passive Harmonic Filter in an improved housing structure for Variable Frequency Drives (VFDs). The new harmonic filter improves the overall system performance by drastically reducing the line side current harmonics generated by all VFDs. The harmonic filter includes a series inductance, a parallel capacitance, and a buck transformer. The filter provides a low impedance path for the harmonic currents generated by VFD and therefore prevents them from flowing into the input ac power lines. The filter also improves the input power factor of the VFD system because of its increased inductive reactance under full-load conditions. Although the filter causes an overvoltage across the VFD terminals because of its increased capacitive reactance at the fundamental frequency this problem is overcome by using the buck transformer.

Abstract: A smoothing device for a power supply is provided comprising a rectifier for rectifying an output of an alternating current power supply and at least a pair of electrolytic capacitors for smoothing an output of said rectifier. The pair of electrolytic capacitors have a non-polarized structure in which a pair of electrode foils each having an oxide film on a surface are wound into a roll with a separator containing an electrolyte interposed therebetween. A pair of electrodes are connected to each of said pair of electrode foils. At least one of the pair of electrodes has a mark for distinguishing them from each other. The pair of electrolytic capacitors are so connected that magnetic fluxes generated by said electrode foils are cancelled with each other.