Hitachi, Ltd.

Hideaki Horie

Hiroshi Kimura

Akihiko Kanouda

Kenichi Onda

Nobuyoshi Mutoh

Katsunori Hayashi

Masayoshi Sato

Hideki Nihei

Syooichi Kawamata

Syuya Hagiwara

Fumio Tajima

Shigeki Morinaga

Hiroshi Kanazawa

Noriyuki Uchiyama

Shunichi Tanae

Sadamu Saito

Ryoichi Naganuma

Yasuo Abe

The invention relates to a power supply system having plural converters connected in parallel. The current of each of the plural converters is detected and each of the converters is controlled so as to match each of the converters to a maximum current value from among the detected current values. In the parallel converters, when one or more converter fails, having an output current of zero, the remaining converters are each partially charged equally to maintain the load current. Since a common bus is arranged between plural converters and plural loads, it is possible to carry out a redundant operation having a high reliability. Since a stable output can be obtained without being affected by the failed converter, a power supply system having the redundancy and the high reliability can be attained.

Power supply system for supplying electric power to a load through

A parallelized power supply system including a plurality of switching power supplies each having a circuit for limiting rush current generated when a main switch is turned on. This system can be installed in an apparatus which requires the functions such as power uninterrupted operation and live wire insertion/dismount. Each switching power supply has another power supply for driving the rush current limiter circuit and a relay circuit for supplying relay driving current and making a connection of relay contacts after a predetermined time lapse after the operation start of the switching power supply. An a.c. power is supplied via the relay contacts to each switching power supply. The relay driving time set in the rush current limiter circuit is different for each switching power supply. Accordingly, concentration and excess of rush current when the relay is driven can be suppressed, and sparks at contact pins of a connector to be otherwise generated when the switching power supply is mounted on the connector, can be eliminated so that radiation noises and connector breakage can be avoided. Each of the switching power supplies connected in parallel has a current detecting resistor connected between the low voltage side of a load and the low voltage side of a voltage regulator d.c. output, and at least one operational amplifier for detecting a change in the d.c. output, the negative power supply terminal of the operational amplifier being connected to the current detecting resistor at its one end on the load side.

Parallelized power supply system providing uninterrupted operation

A diode, a condenser and a switching element are connected to a primary winding of a flat type transformer such as a wire type transformer. A citation energy discharged during an off-condition of the switching element, namely a reset period of the transformer, is accumulated in the condenser. An output voltage is obtained from the condenser. Two system direct current voltage output can be obtained from one transformer. Since the two system direct current voltage output can be obtained from the transformer having a pair of a primary winding and a secondary winding, the volume and the weight of the transformer can be reduced and the compact and the slim of the machine apparatus being mounted can be contributed. Making the small winding ratio of the transformer, the copper loss of the transformer can be reduced. By using MOS synchronous rectification, the loss in the circuit can be reduced. It is unnecessary to select highly the switching frequency.

Multi-output DC-DC convertor

A flat transformer has a coil body. The coil body is formed by winding plural insulated conductive wires. Each of the plural insulated conductive wires has a conductor having a circular shaped cross-section, and an outer peripheral portion of the conductor is coated by an insulating coating. A part of plural insulated conductive wires is used to form a primary winding and the remainder of the plural insulated conductive wires is used to form a secondary winding. A flat transformer may also have plural coil bodies. The plural coil bodies may be wound at plural stages. A part of the plural coil bodies is may be used to form a primary winding and the remainder of plural coil bodies may be used to form a secondary winding. The flat transformer can operate stably at a high frequency with a small loss.

Flat transformer and power supply unit having flat transformer

A portable-type disk apparatus for a 3.5-inch or less optical disk implemented in a thin, light-weight and miniaturized structure having a vibration-withstanding capability. An optical head assembly is disposed stationarily while an optical disk and a spindle motor for rotating the optical disk are disposed movably in a diametrical direction of the optical disk. The spindle motor is constituted by a brushless motor of a substantially semi-circular form in cross section and having a laterally truncated portion. The optical head assembly including an optical head and a laser circuit is disposed at the side of the laterally truncated portion.

Optical disk apparatus

A linear actuator for e.g. a disk drive has a fixed member and a movable member. One of those members carries at least one track of permanent magnets extending in the direction in which the movable member is to move, with adjacent permanent magnets having alternate magnetic polarity. The other member has first and second drive parts, each having at least one pair of opposing sets of teeth. The moveable member or each track passes between those teeth. Each pair of teeth is associated with a corresponding drive coil giving the teeth a magnetic polarity so that there is a magnetic alignment between a polarity of the teeth and the permanent magnets. The drive parts are arranged so that, for any given relative position of the first and second members, the magnetic alignment of the teeth of one drive part is out of phase with the magnetic alignment of the teeth of the other part. In order to ensure that the magnetic alignments are out of phase, there may be a physical displacement between the teeth of the two drive parts. This displacement may be (m.+-.1/2).multidot.T.sub.p, where m is an integer and T.sub.p is the teeth pitch. This gives a phase displacement of 180.degree.. Alternatively, the drive parts may be aligned, and two tracks of permanent magnets be provided with the magnets thereof having opposite polarity for a given track position, or the drive current to the drive coils may be controlled to be out of phase.

Linear actuator

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Hitachi, Japan

Hideaki Horie