Patents by Inventor Seiya Kitagawa
Seiya Kitagawa has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Patent number: 6452364Abstract: A battery charge control circuit, a battery charging device, and a battery charge control method for controlling the charging of a battery are provided. A power source supplies a current to a load, and a battery also supplies a current to the load. If the current supply capacity of the power source is restricted when the power source charges the battery, the charging of the battery is not stopped. Thus, a wrong operation can be avoided, and more reliable battery charging can be performed.Type: GrantFiled: March 22, 2000Date of Patent: September 17, 2002Assignee: Fujitsu LimitedInventors: Mitsuo Saeki, Seiya Kitagawa, Hidekiyo Ozawa, Toshiyuki Matsuyama
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Patent number: 6445164Abstract: The present invention provides a battery charging/discharging method for effectively using the battery energy of a power supply apparatus with a plurality of chargeable batteries. The power supply apparatus in which batteries are connected in parallel to the node of an external power source and a load comprises a charge/discharge monitor unit for judging whether the external power source is in a state where a load is driven and sufficient voltage to charge the batteries is outputted or in a state where sufficient voltage is not outputted and a discharge current should be supplied from the batteries to the load, switches inserted in series with each of the batteries, and an on/off control unit for controlling the on/off operation of the switches according to the output of the charge/discharge monitor unit and the charging/discharging state of each battery.Type: GrantFiled: January 18, 2001Date of Patent: September 3, 2002Assignee: Fujitsu LimitedInventor: Seiya Kitagawa
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Patent number: 6420858Abstract: A DC-to-DC converter circuit having a power saving mode, and which achieves a high conversion efficiency without using a sense resistance. The DC-to-DC converter circuit includes a triangular wave generation circuit to generate a triangular wave signal and a differential amplifier to receive the triangular wave signal and to generate an output signal. A main switching element is provided to turn ON and OFF an input voltage, and a synchronous commutating switching element is provided to perform synchronous commutation of a load current. A detection device detects whether an output voltage of the main switching element is larger than an input voltage of the main switching element. A control device operates in a power saving mode to reduce a drive voltage of the main switching element in response to the detection device detecting that the output voltage of the main switching element is larger than the input voltage.Type: GrantFiled: December 21, 1999Date of Patent: July 16, 2002Assignee: Fujitsu LimitedInventors: Seiya Kitagawa, Toshiyuki Matsuyama, Hidekiyo Ozawa
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Patent number: 6414403Abstract: A power unit having a built-in battery to supply voltage from the battery over a long period of time by utilizing fully the capabilities of the built-in battery. The power unit supplies electric power to a load even when a battery with a higher battery voltage than the external power source voltage is used by charging the battery from an external power source even when the external power source voltage is lower than the battery voltage. By charging the battery when electric power is supplied to a load from an external power source, the power unit supplies electric power to the load from the battery when the supply of electricity from an external power source is cut off. The power unit includes a having converter to boost output voltage from the battery and to supply the voltage to the load when the battery is discharged and the external power source voltage is higher than the battery voltage.Type: GrantFiled: September 23, 1998Date of Patent: July 2, 2002Assignee: Fujitsu LimitedInventors: Seiya Kitagawa, Mitsuo Saeki, Hidekiyo Ozawa
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Publication number: 20020057073Abstract: The present invention provides a battery charging/discharging method for effectively using the battery energy of a power supply apparatus with a plurality of chargeable batteries. The power supply apparatus in which batteries are connected in parallel to the node of an external power source and a load comprises a charge/discharge monitor unit for judging whether the external power source is in a state where a load is driven and sufficient voltage to charge the batteries is outputted or in a state where sufficient voltage is not outputted and a discharge current should be supplied from the batteries to the load, switches inserted in series with each of the batteries, and an on/off control unit for controlling the on/off operation of the switches according to the output of the charge/discharge monitor unit and the charging/discharging state of each battery.Type: ApplicationFiled: January 11, 2002Publication date: May 16, 2002Inventor: Seiya Kitagawa
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Publication number: 20010020802Abstract: A power unit having a built-in battery to supply voltage from the battery over a long period of time by utilizing fully the capabilities of the built-in battery. The power unit supplies electric power to a load even when a battery with a higher battery voltage than the external power source voltage is used by charging the battery from an external power source even when the external power source voltage is lower than the battery voltage. By charging the battery when electric power is supplied to a load from an external power source, the power unit supplies electric power to the load from the battery when the supply of electricity from an external power source is cut off. The power unit includes a having converter to boost output voltage from the battery and to supply the voltage to the load when the battery is discharged and the external power source voltage is higher than the battery voltage.Type: ApplicationFiled: September 23, 1998Publication date: September 13, 2001Inventors: SEIYA KITAGAWA, MITSUO SAEKI, HIDEKIYO OZAWA
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Publication number: 20010007417Abstract: The present invention provides a battery charging/discharging method for effectively using the battery energy of a power supply apparatus with a plurality of chargeable batteries. The power supply apparatus in which batteries are connected in parallel to the node of an external power source and a load comprises a charge/discharge monitor unit for judging whether the external power source is in a state where a load is driven and sufficient voltage to charge the batteries is outputted or in a state where sufficient voltage is not outputted and a discharge current should be supplied from the batteries to the load, switches inserted in series with each of the batteries, and an on/off control unit for controlling the on/off operation of the switches according to the output of the charge/discharge monitor unit and the charging/discharging state of each battery.Type: ApplicationFiled: January 18, 2001Publication date: July 12, 2001Inventor: Seiya Kitagawa
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Patent number: 6204633Abstract: The present invention provides a battery charging/discharging method for effectively using the battery energy of a power supply apparatus with a plurality of chargeable batteries. The power supply apparatus in which batteries are connected in parallel to the node of an external power source and a load comprises a charge/discharge monitor unit for judging whether the external power source is in a state where a load is driven and sufficient voltage to charge the batteries is outputted or in a state where sufficient voltage is not outputted and a discharge current should be supplied from the batteries to the load, switches inserted in series with each of the batteries, and an on/off control unit for controlling the on/off operation of the switches according to the output of the charge/discharge monitor unit and the charging/discharging state of each battery.Type: GrantFiled: August 24, 1998Date of Patent: March 20, 2001Assignee: Fujitsu LimitedInventor: Seiya Kitagawa
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Patent number: 6194875Abstract: A DC—DC converter generates a system output current and a battery charging current. The converter has an output transistor connected between an AC adapter, which provides a supply current, and a terminal at which the battery charging current is provided. A control circuit generates a duty control signal used to activate and deactivate the output transistor in order to adjust the battery charging current. The control circuit includes a voltage detection circuit that compares a DC power supply voltage of the AC adapter with a first reference voltage and generates a differential voltage signal from the comparison result. A PWM comparison circuit is connected to the voltage detection circuit and compares the differential voltage signal with a triangular wave signal to generate the duty control signal which has a duty ratio corresponding to the comparison result.Type: GrantFiled: October 7, 1999Date of Patent: February 27, 2001Assignee: Fujitsu LimitedInventors: Kyuichi Takimoto, Toshiyuki Matsuyama, Hidekiyo Ozawa, Seiya Kitagawa
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Patent number: 6169392Abstract: A DC—DC converter circuit for performing DC—DC conversion by switching an input voltage on and off achieves high conversion efficiency while, at the same time, making it possible to supply low voltages. The DC—DC converter circuit includes: a level shift circuit which generates a voltage that is lower than the input voltage by a predetermined voltage; a power supply generating circuit which generates a floating power supply having a magnitude equal to the difference between the input voltage and the output voltage of the level shift circuit; a capacitor which is charged up by the floating power supply generated by the power supply generating circuit; and a driver circuit which supplies the charged voltage of the capacitor as a driving voltage to the main switching device in accordance with the operation control signal.Type: GrantFiled: December 14, 1999Date of Patent: January 2, 2001Assignee: Fujitsu LimitedInventor: Seiya Kitagawa
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Patent number: 6147477Abstract: A direct-current to direct-current conversion (DC/DC) apparatus includes a control circuit having an error amplifier for voltage control and controlling a direct-current to direct-current conversion based on a pulse width modulation control using an output of the error amplifier. The error amplifier inputs a voltage signal corresponding to an output voltage of a DC/DC result and a plurality of reference voltage signals. The DC/DC apparatus also includes a soft start capacitor to provide one of the plurality of reference voltage signals. The error amplifier amplifies a difference between the voltage signal corresponding to the output voltage of a DC/DC result and a voltage signal of a lower potential among the plurality of reference voltage signals and, based on the amplified output, carries out the pulse width modulation control.Type: GrantFiled: June 27, 1997Date of Patent: November 14, 2000Assignee: Fujitsu LimitedInventors: Mitsuo Saeki, Hidetoshi Yano, Hidekiyo Ozawa, Seiya Kitagawa, Toshiyuki Matsuyama, Takashi Matsumoto, Kyuichi Takimoto, Yoshiaki Sano
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Patent number: 6091234Abstract: A DC-DC convertor is used as a power source for an electronic apparatus. In this converter, a synchronous rectification transistor is provided in parallel with a flywheel diode. A control circuit of the converter is configured in such a way that a synchronous rectification transistor isolating unit for compulsorily turning off the synchronous rectification transistor for a predetermined fixed period of time, at the activation time of the DC--DC convertor, is included.Type: GrantFiled: July 30, 1998Date of Patent: July 18, 2000Assignee: Fujitsu LimitedInventor: Seiya Kitagawa
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Patent number: 5966003Abstract: A control circuit for controlling an output voltage of a DC--DC converter which supplies power to various semiconductor device, such as a processor and a memory, by way of an output transistor. The control circuit drives the output transistor in response to an external control signal. The control circuit gradually reduces an operating time of the output transistor by performing a discharge operation in response to the external control signal being inactive.Type: GrantFiled: February 3, 1998Date of Patent: October 12, 1999Assignee: Fujitsu LimitedInventors: Kyuichi Takimoto, Takashi Matsumoto, Toshiyuki Matsuyama, Seiya Kitagawa
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Patent number: 5898234Abstract: A power supply unit includes a charger composed of a switch for enabling and disabling a charge current and a charge control unit for controlling the switch in accordance with the charge current, the switch being provided in a path shared by the charge current and a discharge current and including a power feed status detection unit for detecting a normal supply voltage of an external power supply source, an absence of a supply of a voltage from the external power supply source, and a drop in a voltage supplied by the external power supply source, and the charge control unit controlling charging of the electric battery by controlling the switch while the power feed status detection unit detects the normal supply voltage of the external power supply source, closing the switch when the power feed status detection unit detects an absence of a supply of a voltage from the external power supply source or a drop in a voltage supplied by the external power supply source, so as to form a discharge path connecting theType: GrantFiled: December 3, 1996Date of Patent: April 27, 1999Assignee: Fujitsu LimitedInventor: Seiya Kitagawa
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Patent number: 5831418Abstract: A converter for converting a DC voltage not stabilized, such as the terminal voltage of a battery, into a stable DC voltage, comprising a voltage comparison unit (2 in FIG. 1) and an operation changeover control unit (3). The voltage comparison unit (2) compares an input voltage and an output voltage. The operation changeover control unit (3) controls the changeover of the operations of the DC/DC converter (1) so that the DC/DC converter (1) may perform a step-down operation as the operation of a step-down type converter when the input voltage is higher than the output voltage as the result of the comparison, and that it may perform a step-up operation as the operation of a step-up type converter when the output voltage is higher than the input voltage. Thus, losses in the smoothing reactor and smoothing capacitor of the step-up/down converter are suppressed to enhance the efficiency thereof.Type: GrantFiled: July 8, 1997Date of Patent: November 3, 1998Assignee: Fujitsu Ltd.Inventor: Seiya Kitagawa