Sharp Kabushiki Kaisha Corporation

Atsushi Kanamori

Hirohisa Warita

Takayuki Shimizu

Takeshi Murata

Hideo Matsuda

Katsumi Inaba

Tsutomu Satoh

Kazufumi Oki

Yoshiki Ikuta

Hiroyuki Shoji

Mitsuru Mariyama

Yasuhiro Maruyama

Tadamasa Kimura

An LED drive circuit that is connectable to a phase control type of light adjuster and receives a voltage based on an a.c. voltage to drive an LED load, the LED drive circuit has a structure which includes: an adjustment signal generation portion that generates an adjustment signal in accordance with a characteristic of a phase control type of light adjuster which is connected to the LED drive circuit; and an adjustment portion that receives the adjustment signal to adjust a characteristic for driving the LED load.

LED drive circuit and LED illumination apparatus

An LED drive circuit that is connectable to an a.c. power supply via a phase control type light adjuster and drives an LED load, including a discharge portion that consumes energy of a resonance phenomenon generated by a light adjuster capacitance component of the phase control type light adjuster and a light adjuster inductance component of the phase control type light adjuster when a current holding portion of the phase control type light adjuster is turned on.

LED drive circuit and LED illumination light

There is provided an LED drive circuit that can be connected to an alternating-current power supply through a phase control dimmer and that drives an LED load, the LED drive circuit including: an LED current control circuit; a capacitance component and a resistance component that are connected in series between an input of the LED current control circuit and a reference potential; a switch element that is connected to both ends of the resistance component; and a switch control portion that turns off the switch element for a given period of time after a timing when the phase control dimmer is turned on and that turns on the switch element after the given period of time elapses.

LED drive circuit and LED illumination unit

Provided is an LED driving circuit (), including: an impedance detecting section () for detecting an impedance value of a phase-control type dimmer (); and an impedance adjusting section () for adjusting an impedance of the LED driving circuit () based on the impedance value detected by the impedance detecting section ().

LED driving circuit, LED illumination appliance, LED illuminator, and LED illumination system

An LED drive circuit connectable to a phase control type light adjuster includes a first reference voltage generation portion that generates a first reference voltage, a second reference voltage generation portion that generates a second reference voltage according to a phase angle of the light adjuster, an input voltage detection portion that detects a size relationship between an input voltage and a threshold value voltage, a current draw-out portion that draws out a current in accordance with the first reference voltage or the second reference voltage from an electricity supply line that supplies electricity to an LED drive portion, and a switch portion that in accordance with a detection result by the input voltage, detection portion, performs switching between an output from the first reference voltage generation portion to the current draw-out portion and an output from the second reference voltage generation portion to the current draw-out portion.

LED drive circuit and LED illumination apparatus using the same

An LED drive circuit is provided that can be connected to an alternating current power source via a phase-control light controller and drives an LED load. The LED drive circuit includes: a switching power source portion having a switching element, a switching current detection portion that detects a switching current, and an LED current detection portion that detects an LED current; a first subtraction portion that subtracts a given value from an output of the switching current detection portion; a first determination portion that determines, through computation on a plurality of externally inputted voltages, a target value to which the switching current is limited; a second subtraction portion that subtracts a given value from an output of the LED current detection portion; a second determination portion that determines, through computation on a plurality of externally inputted voltages, a target value of the LED current; a switching current limitation portion that, if a result of the subtraction by the first subtraction portion exceeds a result of the determination by the first determination portion, switches off the switching element so as to limit the switching current; and an LED current control portion that drives the switching element to control the LED current so that a result of the subtraction by the second subtraction portion coincides with a result of the determination by the second determination portion.

LED drive circuit and LED illumination component using the same

Provided is an LED driver circuit, to be connected to an AC power supply via a phase-control dimmer, for driving an LED load, including: a switching power supply part including a switching element and a switching current detection part; an LED current detection part; a first control part for controlling and switching the switching element so that a switching current has a desired current value based on a detection signal of the switching current detection part; a second control part for controlling and switching the switching element so that an LED current has a desired current value based on a detection signal of the LED current detection part; and a switch part for switching between control performed by the first control part when the phase-control dimmer is set to high brightness dimming and control performed by the second control part when the phase-control dimmer is set to low brightness dimming.

LED driver circuit and LED lighting device using the same

An LED drive circuit is provided that is connectable to a phase-control light controller and drives an LED load by use of a voltage obtained by rectifying a phase-controlled alternating current voltage inputted from the phase-control light controller. The LED drive circuit includes: a first phase angle detection portion that detects a phase angle in a present cycle; a second phase angle detection portion that detects a phase angle in a cycle preceding the present cycle by at least one cycle; a bias portion that generates a detection signal by adding a predetermined delay time to a phase angle obtained by averaging the phase angle detected by the first phase angle detection portion and the phase angle detected by the second phase angle detection portion; and a drive portion that starts current supply to the LED load at timing based on the detection signal generated by the bias portion.

LED drive circuit, LED illumination component, LED illumination device, and LED illumination system

An LED drive circuit in which an alternating voltage is input and an LED is driven, and which is capable of connecting to a phase control dimmer. The LED circuit is provided with a current extractor for extracting a current from a power supply feed line for feeding an LED drive current to the LED; and an extraction timing adjuster for operating the current extractor for a predetermined period of time after the start of a voltage fluctuation in the power supply feed line, the voltage fluctuation accompanying output oscillation of the phase control dimmer.

LED drive circuit, LED illumination fixture, LED illumination device, and LED illumination system

An LED drive circuit in which an alternating voltage is input and an LED is driven, and which can be connected to a phase control dimmer The LED drive circuit is provided with an edge detector for detecting an edge of the output voltage of the phase control dimmer; and a current extractor for extracting a current from a current feed line for feeding an LED drive current to the LED; wherein the value of the current extracted from the current feed line by the current extractor is varied in accordance with the detection results of the edge detector.

An LED drive circuit in which an alternating voltage from a phase control dimmer is input and an LED is driven. The LED drive circuit comprises a phase angle detector for detecting the phase angle at which a phase control element inside the phase control dimmer switches from off to on; a switching power supply for feeding a current to the LED; a switching element connected in series to the LED; and a controller for controlling the switching power supply and the switching element in accordance with the output of the phase angle detector; wherein the controller places the switching element in an always-on state in a case in which the phase angle detected by the phase angle detector is equal to or less than a predetermined value, and the controller pulse-drives the switching element in a case in which the phase angle detected by the phase angle detector is greater than the predetermined value.

LED drive circuit, dimming device, LED illumination fixture, LED illumination device, and LED illumination system

A bootstrap circuit for a step-down chopper regulator IC includes an LDMOS transistor having a gate and a source connected to output terminals of a constant voltage circuit and a drain connected to a leader terminal of a boot voltage, and a bootstrap control circuit that performs control of turning on and off the LDMOS transistor so as to support high-speed oscillation without requiring expensive process and realize a stable step-down chopping action with a wide input voltage range.

Semiconductor device, step-down chopper regulator, and electronic equipment

In a switching power supply circuit, completion of discharging of a capacitance provided in a soft-start circuit requires a period longer than a cycle with which an activating/deactivating portion switches switching control operation of a driving portion (which performs switching control to turn on/off a switching device provided in a stepping-up DC-DC converter) between an activated state and a deactivated state. Moreover, the soft-start circuit is prevented from performing soft-start operation until discharging of the capacitance is completed. Furthermore, the activating/deactivating portion prevents the switching control operation of the driving portion from being switched from the deactivated state to the activated state from a time point that constant voltage feeding operation of a constant voltage portion (which feeds, to a comparing portion that sends an output signal to the driving portion, a constant voltage as the drive voltage) is switched from the deactivated state to the activated state until a predetermined period elapses.

Switching power supply circuit and electronic apparatus provided therewith

A switching power supply apparatus produces an output voltage by smoothing a pulsating voltage obtained by switching an input direct-current voltage with a switching device. The switching power supply apparatus has a current detection circuit that outputs a detection current that varies in proportion to the switch current flowing through the switching device, an overcurrent detection circuit that detects an overcurrent by comparing the detection current with a set current previously set so as to correspond to the overcurrent detection level and that, on detection of an overcurrent, feeds a reset signal to a flip-flop for controlling the switching of the switching device to turn the switching device off, and a second current compensation circuit that superimposes a compensation current on the detection current fed to the overcurrent detection circuit to produce a compensated current.

Switching power supply apparatus and electric applianance therewith

The voltage booster type switching power supply circuit is provided with a drive circuit for controlling a switching element, a start/stop circuit for turning the drive circuit on and off according to a brightness control signal for adjusting a brightness of a light source of a liquid crystal display device, an output voltage detection circuit for detecting whether the output voltage is greater than a predetermined voltage and feeding out a result as a comparison result signal, and a soft-start circuit that does not operate when the comparison result signal is active on the rising edge of the brightness control signal, and that operates so as to increase the output voltage gradually when the comparison result signal is inactive on the rising edge of the brightness control signal.

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Osaka, Japan

Atsushi Kanamori