Abstract: A lighting device includes a rectifier circuit, a conversion circuit, a constant current circuit and a control circuit. The conversion circuit includes a first series circuit, a second series circuit and a third series circuit. The conversion circuit is configured to output a DC current by on/off of a switching element being controlled by the control circuit. A high potential-side terminal of the third capacitor is electrically connected to an output terminal. The low potential-side terminal of the third capacitor is electrically connected to an output terminal, via the constant current circuit.

Abstract: Lighting apparatus includes: AC/DC converter which converts AC voltage Vac to DC voltage Vdc; DC/DC converter which converts DC voltage Vdc to a DC voltage to be applied to LED; and detection circuit which detects AC voltage Vac. DC/DC converter includes switching element, and control circuit that performs a control of repeatedly turning on and off switching element in a boundary conduction mode. Control circuit performs the control under which ON time Ton is kept from exceeding an upper limit that is previously determined, and raises the upper limit when AC voltage Vac detected by detection circuit falls below a predetermined value. ON time Ton is a period of time during which switching element is kept ON.

Abstract: A lighting device which outputs a current to a solid-state light emitting element includes: a direct current-to-direct current (DC-to-DC) converter; and an output detector which detects an output from the DC-to-DC converter, wherein the DC-to-DC converter includes: a switching element; a control device which controls the switching element in order to generate the output; and a current detector which detects a current which flows through the switching element, and if a current value of the current detected by the current detector is less than a predetermined threshold, the control device controls the switching element according to a duty cycle determined based on an output value of the output detected by the output detector, and if the current value is greater than the predetermined threshold, the control device controls the switching element according to a duty cycle lower than the duty cycle determined based on the output value.

Abstract: A light-emitting apparatus includes: a light source unit to which constant current corresponding to a dimming level is supplied from a constant current supply (dimming LED driver), and which includes a first light-emitting element column and a second light-emitting element column connected in parallel with the first light-emitting element column; a first detector circuit (resistor) which is connected in series to the first light-emitting element column, and detects a magnitude of a current flowing through the first light-emitting element column; a current adjuster circuit which adjusts a relationship of the magnitude of the current flowing through the first light-emitting element column to the constant current, based on the magnitude of the detected current; and a relationship adjuster circuit (variable resistor) which adjusts the dimming level at a changing point where a relationship of the magnitude of the current flowing through the first light-emitting element column to the dimming level changes.

Abstract: A light-emitting device includes: a first light-emitting element array including one of a single first light-emitting element or a plurality of first light-emitting elements connected in series, and having a first emission color; a second light-emitting element array including one of a single second light-emitting element or a plurality of second light-emitting elements connected in series, and having a second emission color different from the first emission color, the second light-emitting element array being connected to the first light-emitting element array in parallel; and a third light-emitting element array including one of a single third light-emitting element or a plurality of third light-emitting elements connected in series, and having a third emission color different from the first emission color and the second emission color, the third light-emitting element array being connected to the first light-emitting element array and the second light-emitting element array in series.

Abstract: An illumination system includes: a first light-emitting element column including one of a single first light-emitting element or a plurality of first light-emitting elements connected in series; a second light-emitting element column connected in parallel with the first light-emitting element column, and including one of a single second light-emitting element or a plurality of second light-emitting elements connected in series; a constant current supply that supplies a constant current to the first light-emitting element column and the second light-emitting element column which are connected in parallel; a resistor that is connected in series with the first light-emitting element column, and detects a magnitude of current flowing through the first light-emitting element column; and a current adjuster circuit that adjusts the magnitude of the current flowing through the first light-emitting element column, according to the magnitude of the current detected by the resistor.

Abstract: An illumination system includes: a first light-emitting element column in which one or more first light-emitting elements are serially connected; a second light-emitting element column connected in parallel with the first light-emitting element column, and in which one or more second light-emitting elements are serially connected; a constant current supply that supplies constant current to a light source unit including the first and second light-emitting element columns; a resistor that is connected in series with the first light-emitting element column, and detects magnitude of current flowing through at least the first light-emitting element column; a bypass circuit that passes, to the resistor, at least part of current flowing through the second light-emitting element column, when a predetermined condition is satisfied; and a current adjuster circuit that adjusts the magnitude of the current flowing through the first light-emitting element column, according to the magnitude of the current detected by the r

Abstract: A lighting device which outputs a current to a solid-state light emitting element includes: a direct current-to-direct current (DC-to-DC) converter; and an output detector which detects an output from the DC-to-DC converter, wherein the DC-to-DC converter includes: a switching element; a control device which controls the switching element in order to generate the output; and a current detector which detects a current which flows through the switching element, and if a current value of the current detected by the current detector is less than a predetermined threshold, the control device controls the switching element according to a duty cycle determined based on an output value of the output detected by the output detector, and if the current value is greater than the predetermined threshold, the control device controls the switching element according to a duty cycle lower than the duty cycle determined based on the output value.

Abstract: A lighting device includes a rectifier circuit, a conversion circuit and a control circuit. A first inductor of a first series circuit and a second inductor of a second series circuit have inductances by which a time period, during which a diode is electrically conducted, is made shorter than a half period of a resonance period of a closed loop circuit. The closed loop circuit includes a first capacitor, the first inductor, a second capacitor and a third capacitor. The control circuit is configured to control a switching element in such a manner that the switching element is turned on at fixed periods.

Abstract: A lighting device includes a constant-current circuit, a smoothing capacitor, a bypass circuit, a detection unit, and a bypass control unit. The constant-current circuit supplies a constant current to a plurality of solid-state light-emitting elements connected in series. The smoothing capacitor is connected between output terminals of the constant-current circuit. The bypass circuit is connected in parallel to one or more of the plurality of solid-state light-emitting elements. The detection unit detects whether the one or more solid-state light-emitting elements are open-circuited. When the detection unit detects that at least one of the one or more solid-state light-emitting elements is open-circuited, the bypass control unit discharges the smoothing capacitor during a discharge period to then bypass the one or more solid-state light-emitting elements through the bypass circuit.

Abstract: An illumination system includes: a first light-emitting element column including one of a single first light-emitting element or a plurality of first light-emitting elements connected in series; a second light-emitting element column connected in parallel with the first light-emitting element column, and including one of a single second light-emitting element or a plurality of second light-emitting elements connected in series; a constant current supply that supplies a constant current to the first light-emitting element column and the second light-emitting element column which are connected in parallel; a resistor that is connected in series with the first light-emitting element column, and detects a magnitude of current flowing through the first light-emitting element column; and a current adjuster circuit that adjusts the magnitude of the current flowing through the first light-emitting element column, according to the magnitude of the current detected by the resistor.

Abstract: An illumination system includes: a first light-emitting element column in which one or more first light-emitting elements are serially connected; a second light-emitting element column connected in parallel with the first light-emitting element column, and in which one or more second light-emitting elements are serially connected; a constant current supply that supplies constant current to a light source unit including the first and second light-emitting element columns; a resistor that is connected in series with the first light-emitting element column, and detects magnitude of current flowing through at least the first light-emitting element column; a bypass circuit that passes, to the resistor, at least part of current flowing through the second light-emitting element column, when a predetermined condition is satisfied; and a current adjuster circuit that adjusts the magnitude of the current flowing through the first light-emitting element column, according to the magnitude of the current detected by the r

Abstract: A lighting device includes a rectifier circuit, a conversion circuit, a constant current circuit and a control circuit. The conversion circuit includes a first series circuit, a second series circuit and a third series circuit. The conversion circuit is configured to output a DC current by on/off of a switching element being controlled by the control circuit. A high potential-side terminal of the third capacitor is electrically connected to an output terminal. The low potential-side terminal of the third capacitor is electrically connected to an output terminal, via the constant current circuit.

Abstract: A lighting device includes a rectifier circuit, a conversion circuit and a control circuit. A first inductor of a first series circuit and a second inductor of a second series circuit have inductances by which a time period, during which a diode is electrically conducted, is made shorter than a half period of a resonance period of a closed loop circuit. The closed loop circuit includes a first capacitor, the first inductor, a second capacitor and a third capacitor. The control circuit is configured to control a switching element in such a manner that the switching element is turned on at fixed periods.

Abstract: Lighting apparatus which supplies a current to solid-state light-emitting device (LED) includes: DC power supply circuit (AC/DC converter); and DC/DC converter that converts an output voltage of DC power supply circuit and applies, to solid-state light-emitting device, the output voltage converted. DC/DC converter includes: switching element; and DC/DC control circuit that performs a control of repeatedly turning ON and OFF switching element in a boundary conduction mode, and DC power supply circuit adjusts the output voltage to make a switching frequency of switching element higher than a first frequency, based on a forward voltage to be applied to solid-state light-emitting device.

Abstract: Lighting apparatus includes: AC/DC converter which converts AC voltage Vac to DC voltage Vdc; DC/DC converter which converts DC voltage Vdc to a DC voltage to be applied to LED; and detection circuit which detects AC voltage Vac. DC/DC converter includes switching element, and control circuit that performs a control of repeatedly turning on and off switching element in a boundary conduction mode. Control circuit performs the control under which ON time Ton is kept from exceeding an upper limit that is previously determined, and raises the upper limit when AC voltage Vac detected by detection circuit falls below a predetermined value. ON time Ton is a period of time during which switching element is kept ON.

Abstract: A lighting device includes a DC/DC converter (step-down chopper circuit) and a control circuit that includes a correction circuit. The correction circuit corrects the timing at which a switching element included in the DC/DC convertor is turned OFF based on a voltage value across a solid-state light-emitting element (LED unit). The correction is made such that an average value of a current flowing through an inductor included in the DC/DC converter is within a predetermined range regardless of a voltage value across the solid-state light-emitting element.

Abstract: A lighting device that lights up an LED and includes a DC power source, a buck converter and a control circuit. The buck converter includes a switching element, an inductor and a diode. The control circuit includes a current detection circuit that detects an electric current flowing through the switching element, a voltage detection circuit that detects a voltage across the inductor, a delay circuit that generates a delay time according to the voltage detected by the voltage detection circuit, and a drive circuit that generates and outputs a control signal to the switching element, the control signal turning OFF the switching element after a lapse of the delay time generated by the delay circuit from when the electric current detected by the current detection circuit reaches a predetermined current command value.

Abstract: A lighting device that is connected to a DC power source and supplies an electric current to a solid-state light-emitting element (LED) whose forward voltage ranges from Vfmin to Vfmax includes a DC/DC converter (buck converter) and a control unit. The DC/DC converter includes a switching element. The control unit turns OFF the switching element by peak current control, and when the solid-state light-emitting element to be connected to the lighting device has a forward voltage of Vfmax, turns ON the switching element in fixed cycles such that the DC/DC converter operates in BCM.

Abstract: A lighting device includes a constant-current circuit, a smoothing capacitor, a bypass circuit, a detection unit, and a bypass control unit. The constant-current circuit supplies a constant current to a plurality of solid-state light-emitting elements connected in series. The smoothing capacitor is connected between output terminals of the constant-current circuit. The bypass circuit is connected in parallel to one or more of the plurality of solid-state light-emitting elements. The detection unit detects whether the one or more solid-state light-emitting elements are open-circuited. When the detection unit detects that at least one of the one or more solid-state light-emitting elements is open-circuited, the bypass control unit discharges the smoothing capacitor during a discharge period to then bypass the one or more solid-state light-emitting elements through the bypass circuit.