Panasonic Corporation

Matsushita Electric Industrial Co., Ltd.

Go Takata

Yasunori Yamamoto

Hideaki Mori

Daisuke Itou

Shinichiro Kataoka

Ryuji Ueda

Tsukasa Kawahara

Hideyuki Nakanishi

Takahiro Kobayashi

Toshiki Onishi

Akihiro Yamamura

Short circuit failures and open circuit failures of light-emitting elements used for the backlight in an LCD panel can be reliably and easily detected. The voltage at the node between each series-connected light-emitting element array and a drive circuit is detected as a monitored voltage. A maximum detector detects the highest and a minimum detector detects the lowest of these monitored voltages. Short circuit or open circuit failure of a light-emitting element is detected by comparing the voltage difference between the maximum detector output and the minimum detector output with a specific reference voltage.

Light-emitting element driving device

An overcurrent protection circuit includes: a determiner configured to determine whether or not the switch current exceeds a predetermined threshold, that is, the switch current is an overcurrent state when the switching element is turned ON; an OFF period setting counter configured to increase or decrease a counter output depending on a determination result of the determiner; and a drive signal generator configured to generate a drive signal of the switching element such that a length of an ON timing interval of the switching element corresponds to the counter output of the OFF period setting counter.

Overcurrent protection circuit and overcurrent protection method

The load driving apparatus according to the present invention includes a load current setting signal generating section, a load current generating section, a reference voltage generating section and a drive voltage generating section. The load current setting signal generating section generates a desired load current setting signal. The load current generating section generates a load current based on the load current setting signal to drive the load. The reference voltage generating section generates a reference voltage based on the load current setting signal. The drive voltage generating section generates a drive voltage, supplies the drive voltage to the load, generates a between-both-terminals voltage between both terminals of the load current generating section based on the drive voltage and controls the drive voltage so that the difference between the between-both-terminals voltage and the reference voltage becomes small.

Load driving apparatus

A light emitting element drive apparatus that drives light emitting elements reduces power loss caused by variability between forward voltage drops of the light emitting elements. A plurality of voltage applying sections (and; andand) generate application voltages based on a detection voltage determined based on a maximum forward voltage drop among the forward voltage drops of the light emitting element arrays (to), and apply the generated application voltages to the light emitting elements (to). Switching sections (and) switch between a plurality of voltage applying sections (and; andand) to which the light emitting element arrays (to) individually connect. Controlling sections (to) control the switching sections (and) to switch connection to minimize the difference between forward voltage drops of light emitting element arrays (to).

Light emitting element drive apparatus, planar illumination apparatus, and liquid crystal display apparatus

A reverse current detection unit detects the direction of the motor current during the synchronous rectifier period based on the polarity of the on voltage of a switching device contained in the motor current path, and outputs a reverse current detection signal representing the result of this detection to the PWM control unit. Change in the output of the PWM control unit that generates the drive signal for a particular switching device in the drive unit is controlled based on the reverse current detection signal and the energizing pattern of the drive unit is changed when motor current is detected in the synchronous rectifier period to be flowing in the opposite direction as in the urging period. The flow of motor current to the power supply is thus reduced and a rise in the power supply voltage can be prevented.

Motor drive device and drive method

A rise in the power supply voltage as a result of a sudden speed reducing command causing the motor current to flow to the power supply is prevented. The motor drive device has a drive signal generating unit for generating a drive signal by an energizing control unit, PWM control unit, and oscillation unit; a drive unit for producing drive power to drive the motor based on the drive signal; a torque control signal generating unit for generating a torque control signal specifying the motor torque; a speed detection unit for detecting the rotational speed of the motor and generating a rotational speed signal denoting motor speed information; and a decision unit for generating a speed difference detection signal denoting the difference between the torque control signal and the rotational speed signal. The drive signal generating unit is controlled based on the speed difference detection signal.

A motor driving apparatus includes a motor driver which includes a parallel circuit in which a plurality of series circuits are connected in parallel. Each of the plurality of series circuits has a high side switching device and a low side switching device connected in series. A voltage detector detects a voltage at a neutral point of the multiphase motor and outputs the detected voltage as a first detection signal. A timing detector detects a timing at which a voltage of the first detection signal equals to a reference voltage, and outputs the detected timing as a second detection signal which is used to generate a plurality of driving signals for driving switching devices in the parallel circuit.

Growing community of inventors

Hyogo, Japan

Go Takata