Fujitsu Corporation

Fujitsu Microelectronics Limited

Akira Haraguchi

Takashi Matsumoto

Kyuichi Takimoto

Hidekiyo Ozawa

Masaya Tsukamoto

A circuit for controlling charging includes a transistor provided on a charging path between a position of a charging terminal and a position of a battery, an input voltage detecting circuit configured to detect a potential of a point on the charging path coupled to the charging terminal's side of the transistor, and a drive circuit configured to control an ON resistance of the transistor between a conductive state and a nonconductive state in response to the potential detected by the input voltage detecting circuit.

Charge control that keeps constant input voltage supplied to battery pack

A control circuit for controlling an output voltage of a DC/DC converter. The control circuit includes a pulse signal generation circuit which generates a pulse signal for controlling the output voltage of the DC/DC converter, and a drive signal generation circuit which generates first and second drive signals using the pulse signal such that a main switching element and a synchronous switching element are turned ON and OFF alternately at different timings. The drive signal generation circuit generates the first drive signal which has substantially the same pulse width as that of the pulse signal to improve ON-duty characteristics of the main switching element.

Control circuit for DC/DC converter

A constant-voltage power supply circuit includes a constant-voltage output unit and an output current restriction unit. The constant-voltage output unit includes an output transistor and controls the transistor based on output voltage from the output transistor to maintain the output voltage constant. The output current restriction unit restricts output current of the constant-voltage output unit. When the overcurrent detection unit detects that current flowing through the output transistor that is an overcurrent flowing continuously for a predetermined time, the output current restriction unit executes an output current restriction operation. This configuration prevents the output voltage from decreasing after an overcurrent control operation.

Constant-voltage power supply circuit

The present invention aims to provide a differential voltage amplifier circuit capable of preventing narrowing of an input voltage allowable range, making unnecessary the calculation of correction by an MPU or the like, reducing an influence due to a change in temperature and detecting a high-accuracy differential voltage. Upon a short circuit between input paths, an output voltage of a differential amplifier at the short circuit therebetween is held in a capacitor. Upon differential voltage amplification, a subtraction circuit section performs a process for subtraction between the output voltage held in the capacitor and a bias voltage. An output voltage is applied to a bias voltage terminal, and an output voltage obtained by multiplying the difference between input voltages by an amplification factor AV with the applied output voltage as the reference is outputted via an output terminal for a differential voltage amplifier circuit section.

Differential voltage amplifier circuit

There are provided a DC/DC converter control circuit and a DC/DC converter system having high degree of freedom of mounting and achieving the following matters: (1) housing a DC/DC converter control circuit in a package miniaturized by reducing the number of terminals; and (2) starting-up a power saving mode in response to an input of an external control signal to a DC/DC converter system. A frequency setting terminal (RT) is connected to a resistance element RT and a switching sectionin series, between the terminal and ground voltage. An external control signal CTL is inputted to the switching sectionWhen an external control signal CTL turns off the switching sectionconnection to the ground voltage is opened and an oscillation driving sectiondoes not operate. Thereby, power saving mode is kept. When the switching sectionis turned on, connection to the ground voltage is closed and the oscillation driving sectionstarts up. Subsequently, a bias control sectionstarts up and bias condition toward the resistance element RT is controlled. Thereby oscillation frequencies approximate to a setting value. Control of power saving mode can be thus carried out without a dedicated terminal for an external control signal CTL.

DC/DC converter control circuits and DC/DC converter systems with power saving mode in accordance with an external control signal

A DC&mdash;DC converter in which no operational instability occurs and ranges of input and output voltages are wide, an electric appliance using such DC&mdash;DC converter, and a duty-ratio setting circuit in which no operational instability occurs and ranges of input and output voltages of a converter circuit can be widen in controlling the converter circuit are provided. A DC&mdash;DC converter has a converter circuit , an output voltage detection circuit and a duty-ratio setting circuit . An error amplifier circuit compares Vref with Vd to output a control voltage Vfb. A pulse-width modulator circuit compares a triangular-wave voltage Vct with the control voltage Vfb to output a first pulse signal PWO. A second-pulse generator circuit outputs a second pulse signal PSO having a predetermined on-duty ratio. A selector circuit selects the first pulse signal PWO or the second pulse signal PSO according to the control voltage Vfb to output the selected signal to a transistor M as a rectangular-wave signal PS.

DC-DC converter, duty-ratio setting circuit and electric appliance using them

A charge/discharge control circuit for controlling charging and discharging of a secondary battery that includes a cell. The charge/discharge control circuit includes an overdischarge detection circuit for detecting an overdischarged state of the battery, and an overcharge detection circuit for detecting an overcharged state of the battery. A discharge control switch is deactivated in the overdischarged state. A first charge control switch is deactivated in the overdischarged state. A second charge control switch is activated in the overdischarged state. A current-limiting circuit is connected in series with the second charge control switch for limiting the charging current when charging is performed.

Charge/discharge control circuit and secondary battery

A charge and discharge circuit that reduces the power consumption at charging and discharging without shortening the life of secondary batteries is described. The charge and discharge circuit includes charge current control circuits connected in parallel to the secondary batteries for performing bypass control of a charge current supplied to the secondary batteries. A potential difference detection circuit detects a voltage difference between the secondary batteries and controls the charge current control circuits in accordance with the voltage difference to selectively bypass the charge current supplied to the secondary batteries.

Charge circuit that performs charge control by comparing a plurality of battery voltages

A discharge control circuit that securely prevents an over discharge of a battery. The control circuit includes a discharge control switch connected to the battery for cutting off a discharge current of the battery in response to a discharge stop signal. A control circuit is connected to the battery and the discharge control switch generates the discharge stop signal for deactivating the discharge control switch when a voltage of at least one cell reaches a lower limit. The control circuit includes a switch holding circuit for continuously supplying the discharge stop signal to the discharge control switch for a predetermined time after the discharge stop signal is generated regardless of the cell voltage.

Discharge control circuit of batteries

One end of a resistor R,is connected to a charger detection terminal OCV and the other end of the resistor R,is connected to a base terminal of an NPN type bipolar transistor Q,of open collector structure to thereby supply a driving bias current. An emitter terminal of the transistor Q,is connected to a reference potential and a collector terminal of the transistor Q,is connected to a gate terminal COUT of a charge control P type FET,. Not only the resistor R,but also a collector terminal of an NPN type bipolar transistor Q,of an open collector structure is connected to the base terminal of the transistor Q,. An emitter terminal of the transistor Q,is connected to the reference potential and an overcharge control signal from an overcharge control circuit,is connected to a base terminal of the transistor Q,. If a voltage of not less than a predetermined voltage value is applied to the charger detection terminal OCV, the transistor Q,is turned on and makes the charge control P type FET,conductive to thereby charge a battery. When receiving the overcharge control signal, the transistor Q,is turned on, bypasses a bias current of the transistor Q,supplied from the charger detection terminal OCV and turns off the transistor Q,to thereby prohibit charge operation.

Growing community of inventors

Kasugai, Japan

Akira Haraguchi