Rohm Co., Ltd.

Junichi Hagino

Kenichi Fukumoto

Hiroki Kikuchi

Shingo Haruta

Akira Aoki

Shinsuke Takagimoto

Satoshi Maejima

Toshikazu Takei

Goang-Woo Nam

A semiconductor integrated circuit for driving a light emitting element forms at least part of a light emitting element driving device configured to change the number of light emitting elements that are lit among a plurality of light emitting elements connected in series. The semiconductor integrated circuit includes a variable resistor controller configured to increase the resistance value of a variable resistor connected in series with the plurality of light emitting elements immediately before, or at the same time as, the time point at which the number of light emitting elements that are lit is reduced.

Semiconductor integrated circuit for driving light emitting element, light emitting element driving device, light emitting device, and vehicle

A semiconductor device includes an external terminal, a switching output stage that performs switching drive of a terminal voltage at the external terminal, an output control unit arranged to generate a drive signal for the switching output stage according to an input pulse signal, a counter arranged to count the number of pulses of the input pulse signal so as to generate a mask signal, a logical gate arranged to mask the input pulse signal according to the mask signal, and a comparator arranged to compare the terminal voltage with a predetermined threshold value voltage so as to generate a reset signal of the counter.

Semiconductor device

A rectifier IC includes, in a single package, a transistor chip in which a transistor is integrated, a controller chip that detects a drain voltage (VD) and a source voltage (VS) of the transistor so as to perform ON/OFF control of the transistor, and functions as secondary side rectifier means of an insulation type switching power supply. The controller chip turns on the transistor when VD is lower than VS and turns off the transistor when VD is higher than VS. The insulation type switching power supply includes a transformer supplied with an input voltage, a control unit that controls primary side current of the transformer according to a feedback signal, a rectifying and a smoothing unit that rectifies and smooths a secondary side voltage of the transformer so as to generate an output voltage, and an output feedback unit that generates the feedback signal according to the output voltage.

Rectifier IC and insulation type switching power supply using the same

An insulated synchronous rectification DC/DC converter is provided. A feedback circuit drives a light-emitting element of a first photocoupler such that the output voltage Vof the DC/DC converter approaches a target voltage. A primary side controller is coupled to a light-receiving element of the first photocoupler, so as to switch on and off a switching transistor according to a feedback signal V. A synchronous rectification controller controls a synchronous rectification transistor. Upon detecting the occurrence of a switching-incapable state in the synchronous rectification transistor, a protection circuit instructs the primary side controller to stop the switching operation of the switching transistor.

Insulated synchronous rectification DC/DC converter including a protection circuit to judge occurrence of a switching-incapable state

A primary-side controller comprises a feedback (FB) terminal coupled to a light-receiving element of a photocoupler so as to receive a feedback signal from the photocoupler, and a current detection (CS) terminal that receives a current detection signal that corresponds to a voltage drop across a sense resistor R. The primary-side controller includes a current mode modulator that generates a control pulse based on the voltage at the FB terminal and the voltage at the CS terminal. The primary-side controller is configured to be switchable between a normal mode and a burst mode. When the electrical state of the DC/DC converter satisfies a predetermined condition, a burst mode adjustment circuit inhibits transition to the burst mode, or otherwise forces transition from the burst mode to the normal mode.

Insulated DC/DC converter

An error signal generating unit is configured such that (i) in a calibration period, the error signal generating unit is set to a first state in which it amplifies an error signal by amplifying a difference between a predetermined first reference voltage and the lowest one from among multiple first detection voltages, and such that (ii) after the calibration period, the error signal generating unit is set to a second state in which it generates the error signal by amplifying a difference between a second detection voltage and a second reference voltage. A reference voltage setting unit holds, as the second reference voltage, the largest value of the second detection voltage detected in the calibration period.

Control circuit and control method for illumination apparatus

A current drive circuit capable of reducing the influence of temperature variation or individual deviation is provided. An output transistor is a PNP bipolar transistor, and has an emitter connected to a cathode of an LED string. A current control resistor is disposed between a collector of the output transistor and a ground terminal. An output terminal of an error amplifier is connected to a base of the output transistor, a first input terminal of the error amplifier is connected to a connection point of the output transistor and the current control resistor, and a reference voltage is applied to a second input terminal of the error amplifier. The error amplifier enables a sink current sunk from the output terminal to flow to the current control resistor.

LED backlight driving circuit for LCD panels

A driving circuit for a light emitting element is disclosed. The driving circuit includes a DC-DC converter configured to generate a drive voltage between a first line and a second line; a current driver, configured to be connected to the light emitting element in series between the first line and the second line, configured to supply a drive current to the light emitting element; a protection resistor configured to be connected to the light emitting element in series between the first line and the current driver; and a controller configured to control the DC-DC converter such that a first detection voltage, which corresponds to a voltage between both ends of the current driver, approaches a predetermined reference voltage and perform a predetermined protection process if the drive voltage between the first line and the second line exceeds a predetermined first threshold voltage.

Driving circuit of light emitting element, and light emitting device and electronic apparatus including the light emitting element

A positive counter starts counting, starting with an initial value, upon receiving a positive edge of a dimming pulse signal. A negative edge counter starts counting, starting with an initial value, upon receiving a negative edge of the dimming pulse signal. For each i-th (2&#x2266;i&#x2266;n) channel, the phase shift amount is calculated by multiplying a period count value that indicates the period of the dimming pulse signal by (i&#x2212;1)/n. When the count value matches the phase shift amount, a burst control signal is switched to a first level. When the count value matches the phase shift amount, the burst control signal is switched to a second level.

Phase shift controller

A pulse width modulated dimming pulse signal PWM is input to a control input terminal P. A standby terminal Preceives a standby signal STB that indicates switching between a standby state and an operating state of a current drive circuit. A burst dimming terminal BS is provided to each of eight respective channels. Each burst dimming terminal BS receives a voltage at one terminal (cathode) of a corresponding LED string. When the voltage level of the standby signal STB is included in a first voltage range, a burst controlleris set to an all channel common mode, and when it is included in a second voltage range, the mode is set to a phase shift mode &#x3c6;. The burst controllerset to the phase shift mode &#x3c6;automatically sets the phase shift angle according to the number of connected LED strings

Current drive circuit for light emitting diode

A charge-discharge circuit charges or discharges a capacitor having a fixed electric potential at one end. A first comparator compares an output voltage of the capacitor with a first threshold voltage and outputs a first comparison signal in accordance with a comparison result. An edge detecting circuit detects an edge of a synchronization signal input from the outside and having a frequency of about &#xbd; of a triangular-wave signal generated by the triangular-wave generating circuit, and outputs an edge detection signal that will be at a predetermined level for each of the detected edges. A charge-discharge controller receives the first comparison signal that is output from the first comparator and the edge detection signal that is output from the edge detecting circuit, and switches between a charge state and a discharge state of the charge-discharge circuit in accordance with a level transition of these signals. A voltage of the capacitor is output as a triangular-wave signal.

Triangular-wave generating circuit synchronized with an external circuit

A switching circuit includes multiple transistors connected to the primary winding of a transformer, and alternately applies an input voltage and a ground voltage to the primary winding according to the ON/OFF operations of the transistors. Multiple ballast capacitors are respectively provided to multiple fluorescent lamps. One terminal of each ballast capacitor is connected to the secondary winding so as to form a common terminal. The other terminal thereof is connected to the fluorescent lamp. A first capacitor and a second capacitor are arranged in this order in series between an connection node that connects the fluorescent lamp to be monitored and the corresponding ballast capacitor and the ground terminal. An abnormal state judging unit compares the voltage at the connection node that connects the first capacitor and the second capacitor with a predetermined threshold voltage.

Inverter apparatus

A soft start circuit generates a soft start voltage which changes over time when light emission of an EEFL is started. A pulse modulator receives a feedback voltage that corresponds to the output voltage of an inverter and the soft start voltage, and adjusts the duty ratio of a pulse signal PWM such that these two voltages match one another using a feedback operation. A striking control circuit monitors an error signal which is asserted when an abnormal state occurs. In a case in which the error signal has been asserted at a detection timing after the soft start voltage has reached a target voltage, the striking control circuit resets and restarts the soft start circuit. A driver controls the switching of the voltage at the primary coil of a transformer according to the pulse signal received from the pulse modulator.

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Kyoto, Japan

Junichi Hagino