Hitachi, Ltd.

Hitachi Metals, Ltd.

Hitachi Device Engineering Co., Ltd.

Hitachi Device Eng. Co., Ltd.

Hitachi Nisshin Electronics Co., Ltd.

Hisao Amano

Norikazu Tokunaga

Hiroshi Fukui

Yasuo Matsuda

Kenichi Onda

Ikuo Yamato

Shin Kimura

Masayoshi Sato

Teruaki Odaka

Takahiro Nagano

Tsutomu Yatsuo

Saburo Oikawa

Atsumi Watanabe

Kazuo Honda

Hiroo Konishi

Kouzou Watanabe

Ryuji Iyotani

Shuji Musha

Yorito Jifuku

Fumio Ogata

Sadaji Tashiro

Shoichi Noguchi

Masayoshi Satoo

A switching power supply using a step-up transformer whose impedance viewed from its primary side is different from the impedance viewed from its secondary side whereby the inductance of its primary and secondary windings are settable independently of each other.

Switching power supply

In a power conversion system, a DC voltage of a DC power supply is converted into a predetermined high-frequency voltage by an inverter, and a high-frequency low voltage generated from the inverter is converted into a high-frequency high voltage by a transformer. A high-frequency high voltage generated from a secondary winding of the transformer is converted into a predetermined low-frequency voltage by a frequency changing circuit. The commutating operation of the frequency changing circuit is performed by a control circuit in response to the output current of the frequency changing circuit and in synchronism with the starting time of the short-circuiting prevention period of the inverter. As a result, the converted output of the power conversion system is prevented from decreasing.

Pulse width modulated inverter with high-to-low frequency output

In a voltage resonance type switching power source apparatus, which has a step-up transformer, a resonance capacitor connected in series with a primary winding of the transformer, and a transistor connected in parallel with the capacitor to cause a resonant oscillation current by the on-off operation thereof, an on signal of the transistor is produced in synchronism with a second signal, which is obtained by delaying a first signal depending on a voltage induced in a detecting winding provided in the transformer by a predetermined delay time.

Voltage resonance type switching power source apparatus

A power conversion apparatus comprises an inverter for converting a voltage of a DC power source into AC power having a frequency higher than the commercial frequency, a transformer, fed by the inverter, for outputting AC power, which is adjusted at a desired voltage, a frequency converter, formed by two pairs of two gate turn-off thyristors (GTOs) connected in reverse-parallel, for converting the frequency of the AC power supplied from the transformer into the commercial frequency, and an energy regenerating device having capacitors for absorbing the energy of a spike voltage occurring due to a circuit inductance upon interruption of a current of each GTO of the frequency converter and a bridge circuit, formed by GTOs and diodes connected in reverse-paralel therewith, for switching over the direction of connecting the capacitors with a secondary winding of the transformer in accordance with the polarity of a voltage of the secondary winding in such a manner that the energy stored in the capacitors is regenerated to the transformer.

Current and frequency converter having means to reduce switching losses

A switching power supply, in which a series circuit consisting of a primary winding of a transformer and a controllable switch is connected with a DC power source and a secondary winding of the transformer is connected with a first voltage source outputting the voltage developed across the secondary winding during the on-period of the controllable switch and a second voltage source storing the exciting energy of the transformer during the off-period of the controllable switch by using the exciting inductance of the transformer as a current source, a series circuit consisting of the first and the second voltage sources being connected with a load. Owing to this construction, even if voltage-current characteristic of a load having constant voltage characteristic, such as a magnetron, vary due to variations in the temperature, etc., the output voltage is automatically compensated and a stable electric power can be supplied to the load.

A semiconductor switching device includes a row of a plurality of switching elements connected in series. The input terminal of the input-nearest switching element and the output terminal of the output-nearest switching element are connected with the input terminal and output terminal of the semiconductor switching device, respectively. A control signal is applied to the control terminal of the output-nearest switching element. The semiconductor switching device comprises a first plurality of capacitive elements each of which is connected between the output terminal of the output-nearer switching element and the control terminal of the input-nearer switching element of the adjacent switching elements among the switching element row; and a second capacitive element connected between the output terminal and input terminal of the input-nearest switching element. At least the switching elements (S.sub.2 -S.sub.n) have insulating gates, respectively.

Semiconductor switching device having plural MOSFET's, GTO's or the like

A semiconductor device such as a transistor or gate turn-off thyristor provided with a control electrode for improving the current cut-off performance, is disclosed in which an emitter layer of a semiconductor substrate is formed of a plurality of strip-shaped regions, a base layer adjacent to the strip-shaped regions is exposed to one principal surface of the semiconductor substrate together with the strip-shaped regions, one main electrode is provided on each strip-shaped region, first and second control electrodes are provided on the base layer, on one and the other sides of each strip-shaped region viewed in the direction of the width thereof, respectively, the other main electrode is provided on the second principal surface of the semiconductor substrate, and a gate terminal is not connected to the first control electrode but connected to the second control electrode, in order to draw out carriers unequally by the first and second control electrodes at a turn-off period. At the initial stage of turn-off action, carriers are drawn out mainly by the second control terminal, and a conductive region contracts so as to be limited to the first control electrode side. At the final stage of turn-off action, carriers are drawn out considerably by the first control electrode, to complete the turn-off action.

Semiconductor device with floating remote gate turn-off means

A gate circuit for gate turn-off thyristors is disclosed which includes a turn-on circuit formed of a series combination of a turn-on power source and an NPN transistor and a turn-off circuit formed of a series combination of a turn-off power source and a thyristor, and in which a PNP transistor is provided between the anode and gate of the thyristor in such a manner that the base of the NPN transistor and the base of the PNP transistor are connected to each other and a junction of these bases receives a control signal for turning on or off a gate turn-off thyristor.

Gate circuit for gate turn-off thyristor

A gate circuit for a thyristor is disclosed which includes a power supply for feeding gate-on current through a gate and cathode of the thyristor, a switching circuit connected in series with the power supply to turn the gate-on current on or off, and a diode connected between a gate ignition signal input terminal of said switching circuit and the anode of said thyristor with the cathode of said diode being coupled to said anode of said thyristor and the anode of said diode coupled to said switching circuit.

Gate circuit for thyristors

A d.c. power supply for use in microwave ovens in which an a.c. voltage having a commercial frequency is rectified and then is chopped at a high frequency by means of a switching element. The resultant voltage is smoothed before being applied to the microwave oven. The voltage level of the commercial frequency voltage is sensed to produce a control pulse the duty ratio of which becomes greater as the voltage level becomes lower. The control pulse is used to control the ON-OFF operation of the switching element. By this circuit configuration, the microwave oven is supplied with a continuously-controllable d.c. voltage having a flat waveform.

D.C. Power supply

A power supply apparatus for a resistance welder has an inverse-parallel thyristor circuit for constrolling the welding current. One of thyristors connected in inverse-parallel relationship is turned on by a first signal whose reference phase is established by a synchronizing signal which is based on a voltage wave form of an AC power source and the other thyristor is turned on by a second signal whose reference phase is established by a signal which is delayed half a period of the voltage wave form with respect to the first signal, so that integrals of positive and negative halves of the output voltage wave form of the inverse parallel thyristor circuit can always be made equal.

Power supply apparatus for resistance welder including means for

A gate circuit for use with a gate turn-off thyristor comprises a capacitor to be charged by a power source supplying a gate turn-on current. The capacitor is connected in series with a power source supplying a gate turn-off current.

A gate circuit for a gate turn-off (GTO) thyristor comprises current supply means for supplying a turn-off current to the GTO thyristor, and energy storing means for storing energy by receiving a current from the current supply means and supplying the stored energy to the GTO thyristor as the turn-on current therefor.

Gate circuit for a gate turn-off thyristor

A pair of thyristor converters are connected by a DC power transmission line, and their AC terminals are connected through tapped transformers to AC systems respectively. The output signal of a constant-current circuit in a converter control unit associated with the forward converter is selected to control the gate of the forward converter, while the output signal of a constant-voltage circuit in a converter control unit associated with the reverse converter is selected to control the gate of the reverse converter. When the reactive power is to be controlled, a reactive power signal is applied for the gate control. A voltage limit indication circuit in each control unit receives the AC terminal voltage e.sub.2 of the transformer and the DC current I.sub.d so as to increase the control angle limit with a decrease in the values of e.sub.2 and I.sub.d. When the control advance angle or control delay angle determined by the output signals of the control circuits is larger than the control angle limit, this angle is limited to the control angle limit. When the reactive power is to be controlled, the tap position of either transformer is lowered to decrease e.sub.2 and to increase the control angle limit thereby widening the controllable range of the reactive power. During the start-stop stage or during the protective operation, the output of the voltage limit indication circuit in each control unit is inhibited to permit free variations of the control angle.

DC Power transmission control

A gate controlling apparatus for a thyristor valve including a plurality of series connected thyristors controlled by a narrow gate pulse. The apparatus includes means for judging whether the thyristor valve is to be in the conductive state or not, means for detecting a forward voltage across at least one of the thyristors in the thyristor valve, and an AND circuit for generating an output at a time when an AND condition between the respective outputs of the judging means and the forward voltage detector means is satisfied. The apparatus further includes means for detecting a period of inverse voltage across at least one of the thyristors in the thyristor valve. The forward and inverse voltages may be, respectively, detected by detecting the forward and inverse voltages of specified thyristors.

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Hitachi, Japan

Hisao Amano