Rohm Co., Ltd.

Noboru Kagemoto

Isao Yamamoto

Kyoichiro Araki

Sachito Horiuchi

Ichiro Yokomizo

Shozo Miyagawa

Yoshiyuki Karasawa

Hideki Miyoshi

In a soft start period after power-on, a voltage regulating apparatus checks LED by LED to determine whether the LED is mounted on a position to receive a drive voltage. After the soft start period, the voltage regulating apparatus monitors the driving status of each of the plurality of LEDs. When it is determined as a result of monitoring that the driving status of at least one of the LEDs is improper, the voltage regulating apparatus increases the drive voltage. In this process, the monitoring on an LED determined to be unmounted as a result of a mount checking process is invalidated. With this, it is ensured that a result of monitoring on the LED unmounted is prevented from affecting the increasing of the drive voltage.

Voltage regulating apparatus supplying a drive voltage to a plurality of loads

A charge pump circuit boosts a voltage of a battery so as to generate a drive voltage for an LED. A constant current circuit generates a constant current to feed through the LED. A monitoring circuit monitors a cathode potential of the LED, i.e., a voltage across the constant current circuit. A control circuit receives a result of monitoring from the monitoring circuitand increases a step-up ratio of the charge pump circuit when the voltage across the constant current circuit drops below a minimum voltage that guarantees a constant current. The control circuit sets an externally requested constant current value in the constant current circuit. When a change from a large current to a small current is requested, the control circuit returns the step-up ratio of the charge pump circuit to 1.0.

Boost controller capable of step-up ratio control

Trimming by disconnecting a fuse connected in parallel to a feedback resistor of an amplifier circuit would cause a variation in voltage value due to a remaining resistance component. A voltage generator circuit is provided therein with a D/A converter circuit of an R-2R ladder resistor network type circuit. The D/A converter circuit is provided with a first switch circuit to an eighth switch circuit, corresponding to each bit, which are switched to set a digital value. Each switch circuit, which is provided with a fuse for providing a fixed voltage value, allows the fuse to be disconnected to fix the voltage value to a value obtained by inverting the initial value. The setting circuit controls the switching operation of each switch circuit, thereby simulating an electrical state of a fuse being disconnected before the fuse is actually disconnected.

Method and circuit for producing trimmed voltage using D/A converter circuit

An electronic apparatus includes a display device () and a drive device () for driving the display (). The display device () is equipped with light emitting elements () such as LEDs driven at high voltages. The display device () has a multiplicity of light emitting element series each supplied at one end thereof with a high voltage (Vh) higher than a given power supply voltage (Vdd). The drive device () has drivers () each having one end connected to a respective terminal to which a corresponding one of said multiple light emitting elements series is connected. The drivers are turned ON and OFF in accordance with instruction signals (SS) such that, when turned ON, they provide currents to the series connected. The drive device () also has a multiplicity of bypass current source () for providing the light emitting element series with currents not sufficient to activate the series for emission of light when corresponding drivers are turned OFF. The drive device can be constructed using ICs that are designed to operate at low voltages, thereby facilitating reduction of electric power loss by the electronic apparatus.

Light emitting element drive device and electronic device light emitting element

A cellular phone in which a data storage means can be installed while meeting the requirements for a compact and lightweight design, imposed on the cellular phone, different types of batteries are selectively used on the basis that a battery used in the cellular phone is removable. That is, when a data storage means is to be additionally provided in the cellular phone, a battery having such a specially designed structure that can be installed together with a data storage memory in the cellular phone, is used with the cellular phone. When the cellular phone should preferentially be compact and lightweight, a standard battery conforming to the compact design requirement is used with the cellular phone.

Cellular phone in which memory is removably installable due to the removability of battery, and battery recharger capable of supporting date write to cellular phone memory

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Kanagawa, Japan

Noboru Kagemoto