Abstract: A constant current is configured to control an FET to adjust a drain current so that a detection voltage is equal to a reference voltage. A reference setter is configured to set the reference voltage to a sum of a first voltage and a second voltage. The first voltage is equal to a voltage developing across the detection resistor while a current, which has a same magnitude as a current supplied to the light source so that a current dimming level of the light source is equal to the dimming instruction value, flows through the detection resistor. The second voltage is equal to a voltage developing across the detection resistor while a second current, which has a same magnitude as a current flowing through the limiting resistor while the light source is on, flows through the detection resistor.

Abstract: A lighting device includes: a variable voltage source; a transistor which controls a current flowing through a light-emitting element; and a control circuit which causes the transistor to pass a current corresponding to a received instruction for a dimming level through the light-emitting element. When the received instruction instructs at least a predetermined dimming Level, the control circuit causes a voltage drop in the transistor to become a first voltage by controlling the variable voltage source, and when the received instruction instructs a dimming level less than the predetermined dimming level, the control circuit causes the voltage drop to become a second voltage higher than the first voltage, by controlling the variable voltage source.

Abstract: A lighting device includes: a variable voltage source; a transistor which controls a current flowing through a light-emitting element; and a control circuit which causes the transistor to pass a current corresponding to a received instruction for a dimming level through the light-emitting element. When the received instruction instructs at least a predetermined dimming level, the control circuit causes a voltage drop in the transistor to become a first voltage by controlling the variable voltage source, and when the received instruction instructs a dimming level less than the predetermined dimming level, the control circuit causes the voltage drop to become a second voltage higher than the first voltage, by controlling the variable voltage source.

Abstract: A constant current is configured to control an FET to adjust a drain current so that a detection voltage is equal to a reference voltage. A reference setter is configured to set the reference voltage to a sum of a first voltage and a second voltage. The first voltage is equal to a voltage developing across the detection resistor while a current, which has a same magnitude as a current supplied to the light source so that a current dimming level of the light source is equal to the dimming instruction value, flows through the detection resistor. The second voltage is equal to a voltage developing across the detection resistor while a second current, which has a same magnitude as a current flowing through the limiting resistor while the light source is on, flows through the detection resistor.

Abstract: The lighting control device according to the present invention includes: a power supply for operating a light source including a first light source and a second light source lower in color temperature than the first light source; and a controller for controlling the power supply. The power supply includes: a first power supply for supplying power in a first range to the first light source; and a second power supply for supplying power in a second range to the second light source. The controller controls the first and second power supplies to adjust power supplied to the first light source and power supplied to the second light source so that a color temperature of the light source is equal to a color temperature which is selected from a predetermined color adjustment range as a desired value. The first range is lower in a lower limit than the second range.

Abstract: A trigger-signal-output part sets a burst time cycle to a time period N (integer of two or more) times as long as a constant first cycle, and outputs a trigger signal M (positive integer of N or less) times during an operation period so as to synchronize it with the first cycle, and does not output the trigger signal during a stop period except the operation period of the burst time cycle. Alternatively, a trigger-signal-output part sets a burst time cycle to a time period N times as long as an output cycle of a trigger signal in an operation period, and sets the operation period to a time period M times as long as the output cycle, and sets a stop period except the operation period of the burst time cycle to a time period generated by multiplying the output cycle by a difference between N and M.

Abstract: When supplying an LED light source with a first output voltage that is equal to or higher than a threshold voltage, an LED driver causes a DC power supply to output a first DC voltage and causes a switching regulator to supply the LED light source with the first output voltage. When supplying the LED light source with a second output voltage that is below the threshold voltage, the LED driver causes the DC power supply to output a second DC voltage lower than the first DC voltage and causes the dropper regulator to supply the LED light source with the second output voltage.

Abstract: A lighting device includes at least first and second lighting circuits configured to receive electric power from a single common DC power supply. First lighting circuit includes a first output capacitor connected between output ends thereof, and a first pre-charge circuit configured to keep a voltage across first output capacitor at a first voltage for first lighting circuit, while a first light source is in OFF state. Second lighting circuit includes a second output capacitor connected between output ends thereof; and a second pre-charge circuit configured to keep a voltage across second output capacitor at a second voltage for second lighting circuit, while a second light source is in OFF state. First and second voltages are set such that a difference between a forward voltage of first light source and the first voltage agrees with a difference between a forward voltage of second light source and the second voltage.

Abstract: When supplying an LED light source with a first output voltage that is equal to or higher than a threshold voltage, an LED driver causes a DC power supply to output a first DC voltage and causes a switching regulator to supply the LED light source with the first output voltage. When supplying the LED light source with a second output voltage that is below the threshold voltage, the LED driver causes the DC power supply to output a second DC voltage lower than the first DC voltage and causes the dropper regulator to supply the LED light source with the second output voltage.

Abstract: A lighting device includes at least first and second lighting circuits configured to receive electric power from a single common DC power supply. First lighting circuit includes a first output capacitor connected between output ends thereof, and a first pre-charge circuit configured to keep a voltage across first output capacitor at a first voltage for first lighting circuit, while a first light source is in OFF state. Second lighting circuit includes a second output capacitor connected between output ends thereof, and a second pre-charge circuit configured to keep a voltage across second output capacitor at a second voltage for second lighting circuit, while a second light source is in OFF state. First and second voltages are set such that a difference between a forward voltage of first light source and the first voltage agrees with a difference between a forward voltage of second light source and the second voltage.

Abstract: The power supply device of the present invention includes a main converter and at least one sub converter connected in parallel between a pair of output ends of a DC power supply circuit for receiving power through a parallel circuit of a thyristor and a thermistor having a positive temperature coefficient. Each of the main converter and the at least one sub converter includes: a series circuit composed of a diode and a switching element and connected between the pair of output ends; a series circuit composed of a capacitor and an inductor and connected in parallel with the diode; and a drive circuit configured to drive the switching element. The main converter controls the thyristor in accordance with a voltage across a secondary winding magnetically coupled with the inductor. When a short circuit of the switching element of the at least one sub converter occurs, the drive circuit of the main converter terminates driving of the switching element of the main converter.

Abstract: A lighting device includes a step-down chopper circuit and a controller configured to control the step-down chopper circuit. The controller is configured to turn on and off a low-side switching device in the step-down chopper circuit at a fixed frequency. The controller includes an operation unit configured to determine a reference voltage value, an output unit configured to output, as a difference signal, a difference between the reference voltage value determined by the operation unit and an average value of a voltage proportional to a current flowing through the switching device, and a control circuit configured to determine an on-time period of the switching device. The control circuit includes an oscillator configured to generate a voltage signal shaped like teeth of a saw. The control circuit is configured to determine the on-time period of the switching device based on the voltage signal and the difference signal.

Abstract: The lighting control device according to the present invention includes: a power supply for operating a light source including a first light source and a second light source lower in color temperature than the first light source; and a controller for controlling the power supply. The power supply includes: a first power supply for supplying power in a first range to the first light source; and a second power supply for supplying power in a second range to the second light source. The controller controls the first and second power supplies to adjust power supplied to the first light source and power supplied to the second light source so that a color temperature of the light source is equal to a color temperature which is selected from a predetermined color adjustment range as a desired value. The first range is lower in a lower limit than the second range.

Abstract: The power supply device of the present invention includes a main converter and at least one sub converter connected in parallel between a pair of output ends of a DC power supply circuit for receiving power through a parallel circuit of a thyristor and a thermistor having a positive temperature coefficient. Each of the main converter and the at least one sub converter includes: a series circuit composed of a diode and a switching element and connected between the pair of output ends; a series circuit composed of a capacitor and an inductor and connected in parallel with the diode; and a drive circuit configured to drive the switching element. The main converter controls the thyristor in accordance with a voltage across a secondary winding magnetically coupled with the inductor. When a short circuit of the switching element of the at least one sub converter occurs, the drive circuit of the main converter terminates driving of the switching element of the main converter.

Abstract: An LED lighting device includes a step-up chopper circuit for increasing an input voltage to a prescribed DC voltage, a voltage detection circuit for detecting the DC voltage, a step-down chopper circuit for decreasing the DC voltage to apply it across a light source, a step-down chopper controlling circuit for turning on and off a switching device of the step-down chopper circuit when the DC voltage is a threshold voltage or more, and an inrush current preventing circuit having a parallel circuit of a thyristor and a thermistor. When the DC voltage is less than the threshold voltage, only the induced voltage obtained from the step-up chopper circuit is employed as a drive power supply for the thyristor. When the DC voltage is the threshold voltage or more, only the induced voltage obtained from the step-down chopper circuit is employed as the drive power supply.

Abstract: A lighting device includes a step-down chopper circuit and a controller configured to control the step-down chopper circuit. The controller is configured to turn on and off a low-side switching device in the step-down chopper circuit at a fixed frequency. The controller includes an operation unit configured to determine a reference voltage value, an output unit configured to output, as a difference signal, a difference between the reference voltage value determined by the operation unit and an average value of a voltage proportional to a current flowing through the switching device, and a control circuit configured to determine an on-time period of the switching device. The control circuit includes an oscillator configured to generate a voltage signal shaped like teeth of a saw. The control circuit is configured to determine the on-time period of the switching device based on the voltage signal and the difference signal.

Abstract: A trigger-signal-output part sets a burst time cycle to a time period N (integer of two or more) times as long as a constant first cycle, and outputs a trigger signal M (positive integer of N or less) times during an operation period so as to synchronize it with the first cycle, and does not output the trigger signal during a stop period except the operation period of the burst time cycle. Alternatively, a trigger-signal-output part sets a burst time cycle to a time period N times as long as an output cycle of a trigger signal in an operation period, and sets the operation period to a time period M times as long as the output cycle, and sets a stop period except the operation period of the burst time cycle to a time period generated by multiplying the output cycle by a difference between N and M.

Abstract: An LED lighting device includes a step-up chopper circuit for increasing an input voltage to a prescribed DC voltage, a voltage detection circuit for detecting the DC voltage, a step-down chopper circuit for decreasing the DC voltage to apply it across a light source, a step-down chopper controlling circuit for turning on and off a switching device of the step-down chopper circuit when the DC voltage is a threshold voltage or more, and an inrush current preventing circuit having a parallel circuit of a thyristor and a thermistor. When the DC voltage is less than the threshold voltage, only the induced voltage obtained from the step-up chopper circuit is employed as a drive power supply for the thyristor. When the DC voltage is the threshold voltage or more, only the induced voltage obtained from the step-down chopper circuit is employed as the drive power supply.

Abstract: A power supply includes: a step-down chopper unit for stepping down a DC voltage from a DC power source to a voltage required for lighting; and a dimming control unit which dims the light source by alternately repeating a switching ON period during which a drive signal having a frequency higher than that of the dimming signal is supplied to the switching element and a switching OFF period during which the supply of the drive signal to the switching element is stopped. Further, the power supply includes an inrush current prevention unit for preventing an inrush current occurring when the DC power source is turned on, and a compensation unit which applies a drive voltage to the thyristor in the switching OFF period.

Abstract: An LED driver circuit prevents an increase in output voltage of a DC/DC converter in an open circuit condition associated with removal or failure of an LED lighting device. A DC power source provides a first DC voltage across positive and negative voltage rails. A DC/DC converter includes a switching element which when turned ON/OFF provides a second DC voltage across first and second ends of a capacitor which further define first and second LED lighting device connection terminals. A control circuit, upon receiving a drive power signal, turns ON/OFF the switching element to provide constant current control. A power supply circuit is coupled between the second LED lighting device connection terminal and the negative voltage rail and generates the drive power signal to the control circuit during a detected lighting condition. The power supply circuit further disables the drive power signal during a detected open circuit condition.