Rohm Co., Ltd.

Tetsuro Hashimoto

Isao Yamamoto

Yoshikazu Sasaki

Tsutomu Ishino

Osamu Yanagida

Hiroyuki Ishikawa

Shigekane Matsui

Akihito Ito

A control circuit of a DC/DC converter includes: a driver turning on a switching transistor and turning off a rectifying transistor in on state, turning off the switching transistor and turning on the rectifying transistor in off state, and turning off the switching transistor and turning off the rectifying transistor in high impedance state; and a switching controller controlling the on state, the off state and the high impedance state, wherein the switching controller repeats a process including: transitioning to the off state when predetermined condition is satisfied in the on state; transitioning to the high impedance state with zero-cross of coil current flowing into an inductor as trigger in the off state; measuring variable time per cycle and transitioning to the off state with time-up as trigger; and transitioning to the on state when feedback voltage corresponding to output voltage of the DC/DC converter decreases to lower threshold voltage.

DC/DC converter for providing function of noise countermeasures, control circuit thereof, control method thereof, and electronic apparatus including the DC/DC converter

A slew rate control device for controlling a slew rate, includes: a setting part configured to set a voltage value used to determine the slew rate; and a control part configured to control the slew rate, based on the voltage value set by the setting part, so that the slew rate becomes slower as an output voltage of a power supply approaches from a transition starting voltage to a target voltage.

Device and method for controlling slew rate

A battery charging circuit is used by being connected to a direct-current power source. The battery charging circuit includes a control transistor, a backflow prevention transistor and a charging controller. The control transistor is disposed in a charging path between the direct-current power source and a battery, and is configured to control a direct-current voltage from the direct-current power source, and to output controlled direct-current voltage as a charging voltage. The backflow prevention transistor is disposed in the charging path, and is configured to output the charging voltage to the battery, and to be turned off when an electric current flows backward from the battery to the direct-current power source. The charging controller is configured to turn on the backflow prevention transistor when charging of the battery starts, and to turn on the control transistor after a fixed period of time elapses from a start of the charging.

Battery charging circuit with backflow prevention transistor, portable electronic device and semiconductor integrated circuit with backflow prevention transistor

A start-up circuit receives a start-up signal instructing start-up of an equipment mounted with the circuit, and executes a predetermined sequence when start-up is instructed by the start-up signal. An oscillator generates a clock signal. A sequence circuit receives the start-up signal and a clock signal output from the oscillator, measures time by counting the clock signal when the start-up signal transits to a predetermined level, and executes a predetermined event at a predetermined timing. The oscillator operates for a period where the start-up signal is at the predetermined level if the start-up signal is at the predetermined level during the period the power key of the equipment mounted with the circuit is being pushed.

Start-up circuit and start-up method

A battery charging controller according to the present invention controls battery charging in response to a charging-control signal sent from a CPU, and includes an starting controller which is started upon a detection of an insertion of an AC adapter, and which then starts a regulator at a predetermined timing by using a regulator control signal. The regulator is started upon a detection of the regulator control signal, and thereafter starts the CPU by using an starting signal. The CPU is started upon a detection of the starting signal.

Battery charging controller and portable electronic device

An under voltage lock out circuit which monitors an input voltage and executes a predetermined sequence when the input voltage satisfies a predetermined condition may include a voltage comparison unit which compares the input voltage and a predetermined threshold voltage, and outputs a comparison signal; a logic circuit which receives the comparison signal output from the voltage comparison unit and a start-up signal instructing start-up of an equipment mounted with the under voltage lock out circuit, and asserts a sequence control signal when start-up is instructed by the start-up signal in a state the input voltage is higher than the threshold voltage; and a sequence circuit which executes a predetermined sequence when the sequence control signal is asserted, wherein the predetermined threshold voltage is switched according to the sequence control signal.

Under voltage lock out circuit and method

A voltage comparison unit compares a battery voltage with a predetermined threshold voltage, and outputs a comparison signal. A sequence circuit receives the comparison signal and a start-up signal instructing start-up of equipment mounted with a UVLO circuit, and executes a predetermined sequence when start-up is instructed by the start-up signal in a state the battery voltage is higher than the threshold voltage. A voltage control unit switches the threshold voltage based on the comparison signal and the start-up signal.

A battery is charged by using in series a constant-voltage DC power supply with current limit function and a constant voltage circuit which has a differential comparator circuit and whose current limit value is variable. Following a period of charging with the current of current limit value by the constant-voltage DC power supply, a period is provided in correspondence with the state of charging of the battery, for charging with a current limit value of the constant voltage circuit which is smaller than that current limit value. The detection of the charging state of the battery is effected by a comparison between a current value of a current source of a differential comparator circuit and a differential output of that differential comparator circuit. It enables to reduce electric power consumed by the control transistor of the constant voltage circuit and to reduce the allowable loss required for the control transistor.

Growing community of inventors

Kyoto, Japan

Tetsuro Hashimoto