Fujitsu Corporation

Toshiyuki Matsuyama

Kyuichi Takimoto

Seiya Kitagawa

Hidekiyo Ozawa

Takashi Matsumoto

Mitsuo Saeki

Hidetoshi Yano

Yoshiaki Sano

Yoshihiro Nagaya

Koichi Inatomi

A direct-current to direct-current conversion (DC/DC) apparatus includes a control circuit having an error amplifier for voltage control, basing the conversion 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 of the output voltage of a DC/DC result and a voltage signal of a lower potential among the plurality of reference voltage signals and carries out the pulse width modulation control. Furthermore, the control circuit includes a circuit for discharging charges corresponding to the output voltage of the DC/DC result when a power supply to the control circuit is turned off.

DC to DC converter producing output voltage exhibit rise and fall characteristics independent of load thereon

A direct-current to direct-current conversion (DC/DC) apparatus includes a control circuit having an error amplifier for voltage control, basing the conversion 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 carries out the pulse width modulation control. Furthermore, the control circuit includes a circuit for discharging charges corresponding to the output voltage of the DC/DC result when a power supply to the control circuit is turned off.

DC to DC converter producing output voltage exhibiting rise and fall characteristics independent of load thereon

A regulator circuit capable of accurately adjusting output voltage anywhere in a current region and maintaining optimum output voltage by correcting setting of a predetermined voltage to be regulated depending on a value of charging current. An output terminal of an amplifier is connected to a reference voltage terminal through a resistance element. When charging current does not flow, detection voltage 0V. Consequently, voltage of a reference power source is divided between a resistance element R and parallel resistance elements R and R When charging current flows and detection voltage is outputted, the detection voltage is divided by resistance elements R and R whereby corrected voltage depending on a value of charging current is generated. Even if voltage drop occurs between a charging-control-device output terminal and a battery terminal, control voltage of output voltage is appropriately adjusted so that a battery terminal can keep full charging voltage.

Regulator circuit and control method thereof

There is intended to provide an overvoltage-protective device capable of protecting a power system from overvoltage not destructively without using a fuse. An alarm signal from an MOS transistor Tr , a structural element of a DC/DC converter , is inputted to a switching circuit , a structural element of the AC/DC converter . In case an alarm signal keeps high-level potential without indicating overvoltage-state, the switching circuit connects a output current detecting circuit having the smaller gain G to an output voltage detecting circuit as well as a feedback circuit A, thereby to set large output-power-supply capability. In case an alarm signal inverses to low-level potential indicating overvoltage-state, the switching circuit connects a output current detecting circuit having the larger gain G to the output voltage detecting circuit as well as the feedback circuit A, thereby to set small output-power-supply capability. Thus, overvoltage at the DC/DC converter can be avoided.

Overvoltage-protective device for power system, AC/DC converter and DC/DC converter constituting the power system

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.

Battery charge control circuit, battery charging device, and battery charge control method

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.

DC-to-DC converter circuit having a power saving mode

A switch circuit has an input terminal and an output terminal and when turned on, provides a voltage at its input terminal to its output terminal. A transistor is connected between the input and output terminals. A gate drive circuit is connected to the gate of the transistor and provides a gate drive signal to the gate. The gate drive circuit, in response to a first control signal, causes the gate drive signal to have one of a first voltage derived from an input voltage at the input terminal and a low potential voltage. A back gate drive circuit is connected to a back gate of the transistor and provides a back gate drive signal to the back gate. The back gate drive signal controls a voltage applied to the back gate of the transistor depending on whether the transistor is turned on or off. The switch circuit may be used to selectively supply battery power to a portable electronic device.

Switch circuit with back gate voltage control and series regulator

A DC-DC converter generally includes a supply circuit, a charge circuit, and a control unit connected to the charge circuit. The charge circuit receives the input current and supplying a charge current to the battery. The control unit controls the charge current according to the results of comparisons between various currents and voltages and corresponding threshold levels. The control unit, which may be constructed on a single-chip semiconductor substrate, includes a differential charge controller, a charge current controller, a charge voltage controller, and a dynamic charge controller. These elements respectively compare the input current, the charge current, the charge voltage and an input voltage from the external DC power supply with a threshold values and control the charge current and charge voltage according to a result of the comparisons.

DC-DC converter and semicondutor integrated circuit device for DC-DC converter

A DC-DC converter includes a main switching device and a synchronous switching connected in series between a power supply and a ground, and a drive control circuit for supplying a first drive signal to the main switching device and a second drive signal to the synchronous switching device to alternately activate and deactivate the main switching device and the synchronous switching device. A detection circuit is connected to the synchronous switching device for detecting a malfunction of the synchronous switching device, such as a short-circuit, and generates a detection signal when a malfunction is detected. A protection circuit is connected to the detection circuit and the drive control circuit and inhibits the first and second drive signals in response to the detection signal. The drive control circuit, the detection circuit and the protection circuit are all formed on a single semiconductor substrate.

DC-DC converter and controller for detecting a malfunction therein

A DC&mdash;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.

Controller for DC-DC converter

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. Furthermore, the control circuit includes a circuit for discharging charges corresponding to the output voltage of the DC/DC result when a power supply to the control circuit is turned off. By the constitution, it is possible to easily realize power turn-on/turn-off sequence controls without requiring any special logic circuit, and thus to control rise/fall characteristics of the output voltage without depending on the load.

DC to DC converter producing output voltage exhibiting rise and fall

A DC--DC converter includes an offset comparator that compares an output voltage with a reference voltage in parallel with an error amplification circuit, which also compares the output voltage with the reference voltage. The offset comparator has a predetermined offset voltage set between its input terminals so that the offset comparator outputs a high signal when the voltage difference between its inputs exceeds the predetermined level. The output of the offset comparator is input, along with the error amplification circuit output, into a PWM comparator. The signal output by the offset voltage comparator allows the DC--DC converter to more quickly respond to a sudden increase in current consumption by a connected load. In responding to the increased current draw, the DC--DC converter quickly converges back at the reference voltage, such that the DC--DC converter provides a very stable output voltage.

Method for controlling the output voltage of a DC-DC converter

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.

Growing community of inventors

Kasugai, Japan

Toshiyuki Matsuyama