Fujitsu Corporation

Fujitsu Semiconductor Limited

Fujitsu Microelectronics Limited

Fijitsu Limited

Yoshihiro Nagaya

Kyuichi Takimoto

Toshiyuki Matsuyama

Takashi Matsumoto

Takehito Doi

Koichi Inatomi

Yukinori Maekawa

Keita Sekine

Jun Kawajiri

A DC-DC converter for converting an input voltage and generating an output voltage. The DC-DC converter includes an adjustment resistor. A control circuit generates a control signal and includes an external terminal to which the adjustment resistor is externally connected. A switching transistor is connected to the control circuit and turned on or off in accordance with the control signal. The control circuit includes an oscillator that generates an oscillation signal. The control circuit generates the control signal based on the oscillation signal and a signal that is in accordance with an output voltage or output current of the DC-DC converter. The oscillator monitors a first amount of current flowing through the external terminal of the control circuit and generates the oscillation signal in a cycle that is accordance with the monitoring result.

DC-DC converter with oscillator and monitoring function

To present a DC-DC converter efficient in conversion and not requiring an external diode. The DC-DC converter includes a main NMOS transistor FETas a main switching device, a driver DVHfor driving a gate terminal of the main NMOS transistor FET, a capacitor Cconnected between a source terminal of the main NMOS transistor FETand a power source terminal of the driver DVH, and an NMOS transistor FETconnected between a route leading to an input power source and the power source terminal of the driver DVH. The NMOS transistor FETdoes not conduct when the main NMOS transistor FETconducts, and conducts when the main NMOS transistor FETdoes not conduct.

DC-DC converter

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

An oscillator circuit for efficiently generating a triangular wave signal having multiple phases. The oscillator circuit includes capacitors, each having two terminals and having a voltage between the two terminals. The capacitors include a first capacitor. A plurality of charge/discharge switching circuits are connected to the first capacitor. Each of the charge/discharge switching circuits generates a switching signal for an associated one of the switches to control the charging and discharging of the associated capacitor. The switching signals of the charge/discharge switching circuits have different phases. Each of the charge/discharge switching circuits receives a first capacitor voltage between the terminals of the first capacitor and compares the first capacitor voltage with a first reference voltage and a second reference voltage to generate the switching signal that has a predetermined phase. A triangular wave signal is generated at one of the two terminals of each of the capacitors. The triangular wave signals have different phases.

Oscillator circuit

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 duty ratio setting circuit includes a triangular waveform oscillation circuit for generating a triangular waveform signal and an error amplifying circuit that compares a detection voltage with a reference voltage and generates a control voltage based on the difference between the compared voltages. A comparator is connected to the oscillation circuit and the amplifying circuit and compares the voltage of the triangular waveform signal with the control voltage, and generates a first rectangular waveform signal having a predetermined duty ratio based on the comparison. A pulse signal generator generates a pulse signal having a predetermined pulse width and which is synchronized with the triangular waveform signal. A logic circuit connected to the comparator and the pulse signal generator receives the first rectangular waveform signal and the pulse signal and generates a second rectangular waveform signal. The second rectangular waveform signal has a maximum duty ratio based on the pulse width of the pulse signal when the duty ration of the first rectangular waveform signal exceeds the maximum duty ratio.

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Kasugai, Japan

Yoshihiro Nagaya