Sanyo Electric Co., Ltd.

Sanyo Semiconductor Co., Ltd.

Semiconductor Components Industries, LLC

Nobuyuki Ohtaka

Takaaki Ishii

Tomoshi Yoshida

Ryuji Yamamoto

A light emitting element control circuit comprising: a variable current generation circuit configured to generate a variable current varying in a direction of increase or in a direction of decrease; a fixed current generation circuit configured to generate a fixed current smaller than a predetermined current of a light emitting element; and a mode setting circuit configured to selectively set a first mode of prohibiting supply of the variable current and the fixed current to the light emitting element, a second mode of supplying the variable current to the light emitting element, and a third mode of supplying the fixed current to the light emitting element, for the variable current generation circuit and the fixed current generation circuit.

Light emitting element control circuit

A light-emitting-element driving circuit is provided which comprises a voltage boosting circuit unit which supplies a boosted voltage to a light-emitting element, a current circuit unit which drives the light-emitting element with a current, a normal feedback loop path through which a voltage of the light-emitting element is input as a feedback voltage to the voltage boosting circuit unit, a backup feedback loop path through which a voltage of the light-emitting element is input as the feedback voltage to the voltage boosting circuit unit, an abnormality detection circuit unit which compares the feedback voltage which is input through the normal feedback loop path to the voltage boosting circuit unit and a predetermined determination voltage, to detect abnormality, and a switching circuit which switches from the normal feedback loop path to the backup feedback loop path when the abnormality detection circuit unit has detected the abnormality.

Light-emitting-element driving circuit

A light-emitting element driving circuit () comprises a luminosity determining unit () which determines luminosity, outputs a luminosity determination result, and outputs brightness change information, a brightness setting unit () which outputs brightness setting information and outputs brightness change information, a light-emitting element driving unit () which drives a light-emitting element with a current of a current value corresponding to the brightness setting information, a detecting and comparing unit () which compares a terminal voltage of the light-emitting element and a predetermined voltage, a voltage boost determining unit () which determines whether or not a terminal voltage of the light-emitting element is to be boosted based on at least one of the luminosity change information and the brightness change information, and a voltage boosting circuit section () which boosts the terminal voltage of the light-emitting element when it is determined that the voltage is to be boosted and does not boost the terminal voltage of the light-emitting element when it is determined that the voltage is not to be boosted.

Light-emitting element driving circuit

A semiconductor circuit () comprises a first terminal section () to be connected to a connection point of two external resistors; a second terminal section () to be connected to an external circuit; a voltage circuit section having a first terminal connected to the second terminal section (); a reference voltage circuit section () which outputs a predetermined voltage; an operational amplifier () having a first input terminal connected to the reference voltage circuit section (), a second input terminal connected to the first terminal section (), and an output terminal connected to a second terminal of the voltage circuit section; an abnormality detecting circuit which detects an abnormal voltage of the first terminal section (); a normal signal generating unit () which generates a normal signal; and a switching circuit which, when the abnormality detecting circuit detects the abnormal voltage, does not output a voltage based on the first terminal section () to the second terminal section () and instead outputs a normal voltage based on the normal signal to the second terminal section ().

Semiconductor circuit

A power voltage of a battery (including a secondary battery) mounted on a portable device drops with use or the like of the portable device. Therefore, a step-up switching voltage regulator circuit is mounted on the portable device. On the other hand, the power voltage of the battery exceeds a voltage necessary for driving the portable device sometimes when the battery is fully charged. In this case, when the step-up switching voltage regulator circuit is driven, the power is consumed in vain, and a burden is imposed on the battery. The step-up switching voltage regulator circuit of the present embodiment switches an output in accordance with the power voltage, that is, raises the power voltage supplied from the battery to a predetermined output voltage, and outputs the output voltage, when the power voltage supplied from the battery is smaller than the predetermined output voltage; on the other hand, the step-up switching voltage regulator circuit outputs the power voltage supplied from the battery as the output voltage, when the power voltage supplied from the battery is larger than the predetermined output voltage; and consequently, in the step-up switching voltage regulator circuit, the burden on the battery mounted on the portable device can be reduced.

Step-up switching voltage regulator circuit

An LED control circuit for controlling a plurality of LEDs with different emission colors comprises a counter which increments or decrements a count value at a predetermined clock in response to a count start signal externally supplied, a signal conversion circuit which converts the count value into an analog signal displaying intensity corresponding to the count value and outputs the analog signal as an output signal, a signal generation circuit which generates, based on the output signal from the signal conversion circuit and brightness data externally specified to its corresponding LED, an analog signal displaying intensity corresponding to a product of the output signal and the brightness data, and a driving circuit which drives its corresponding LED according to the analog signal output from the signal generation circuit, to gradually and simultaneously change the brightness of the LEDs in accordance with the count value.

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Kadoma, Japan

Nobuyuki Ohtaka