JP5857214B2 - LED lighting device and lighting apparatus using the same - Google Patents

Description

  The present invention relates to an LED lighting device and a lighting fixture using the same.

  Conventionally, there has been an LED lighting device using an LED as a light source and a lighting fixture including the LED lighting device (see, for example, Patent Document 1).

  In the LED lighting device disclosed in Patent Document 1, an AC power supply is full-wave rectified by a rectifier, then stepped down to a constant voltage by a step-down chopper circuit, and then converted from a constant current circuit connected to the output terminal of the step-down chopper circuit to the LED. A constant current was supplied to light the LED.

JP 2009-33098 A

  By the way, in the LED lighting device of Patent Document 1, a constant current is passed through the LED by a constant current circuit. However, the forward current flowing through the LED is fed back so that the forward current becomes a predetermined target value. There is also an LED lighting device provided with a power supply circuit for controlling the output.

  FIG. 4 shows an example of an LED lighting device that feedback-controls a forward current flowing in the LED. The LED lighting device includes a rectifier circuit 2, an insulating flyback converter 3, a smoothing capacitor 4, a light emitting diode (hereinafter referred to as a “light emitting diode”). LED) 5).

  The rectifier circuit 2 performs full-wave rectification on the commercial AC power supply 1 and converts it into direct current, and the direct-current voltage that has been full-wave rectified by the rectifier circuit 2 is output to the isolated flyback converter 3.

  The insulating flyback converter 3 includes an insulating transformer 6, a switching element 7 made of, for example, an FET, and a diode 8. The primary winding of the insulating transformer 6 is connected between the output terminals of the rectifier circuit 2 via the switching element 7 and the current detection unit 10. A smoothing capacitor 4 is connected between both ends of the secondary winding of the insulating transformer 6 via a diode 8, and an LED 5 and a current detection unit 9 are connected between both ends of the smoothing capacitor 4. The switching element 7 is controlled to be turned on / off by a drive signal S2 input from the control circuit unit 11.

  In the insulation type flyback converter 3, when the switching element 7 is turned on, a switching current I2 flows through the primary winding of the insulation transformer 6, and electric energy is converted into magnetic energy. At this time, no current flows on the secondary side of the insulating transformer 6 due to the polarity of the diode 8, and magnetic energy is accumulated in the insulating transformer 6. After that, when the switching element 7 is turned off, the magnetic energy accumulated in the insulating transformer 6 during the ON period of the switching element 7 is reconverted into electric energy and discharged from the secondary side of the insulating transformer 6 to charge the smoothing capacitor 4. To do. When the switching element 7 is periodically turned on / off, a DC voltage insulated from the primary side is generated on the secondary side of the insulating transformer 6, and a DC voltage V <b> 1 generated between both ends of the smoothing capacitor 4. Is applied to the LED 5 and the LED 5 is lit.

  A control signal S1 for determining a target value of an output current (forward current I1 of the LED 5) and detection signals of the current detection units 9 and 10 are input to the control circuit unit 11 from the outside. The current detection unit 9 includes a resistor connected in series with the LED 5, for example, detects a forward current I 1 flowing through the LED 5, and outputs a signal having a magnitude corresponding to the forward current to the control circuit unit 11. The current detection unit 10 includes, for example, a resistor connected in series with the switching element 7, detects the switching current I 2 flowing through the switching element 7, and outputs a signal having a magnitude corresponding to the switching current I 2 to the control circuit unit 11. To do. Based on the control signal S1 and the detection signals from the current detection units 9 and 10, the control circuit unit 11 controls the operation of the switching element 7 so that the forward current I1 of the LED 5 becomes a target value.

  Here, from the state in which the LED 5 is turned off, whether the power is turned on or the control signal S1 is switched, the control circuit unit 11 starts the switching operation of the isolated flyback converter 3, and the LED 5 is turned on. The operation when switching to the lighting state will be described. FIG. 5 shows an ideal change over time of the output voltage on the secondary side during the switching from the unlit state to the lit state, that is, the applied voltage V1 to the LED 5 and the forward current I1 flowing through the LED 5.

  At time t1, when the isolated flyback converter 3 starts the switching operation from the stopped state, the output voltage on the secondary side, that is, the applied voltage V1 of the LED 5, starts to rise from about 0V. When the applied voltage V1 reaches the lighting start voltage Vf0 of the LED 5 at time t1, the forward current I1 starts to flow through the LED 5, and thereafter, the forward current I1 matches the target value If corresponding to the control signal S1. The control circuit unit 11 controls the operation of the switching element 7 and the voltage applied to the LED 5 is also stabilized at the voltage Vf.

  However, the waveform diagram of FIG. 5 shows an ideal operation, and actually the operation is as shown in the waveform diagram of FIG. 6A is a waveform diagram of the voltage V1 applied to the LED 5 (that is, the output voltage of the isolated flyback converter 3), FIG. 6B is a waveform diagram of the forward current I1, and FIG. It is a wave form diagram of switching current I2.

  The LED 5 is not lit from time t1 to time t2 when the control circuit unit 11 causes the switching element 7 to start the switching operation, and the forward current I1 is approximately 0A. In this period, since the actual value is insufficient with respect to the target value If of the forward current I1, the control circuit unit 11 increases the applied voltage V1 to the LED 5 rapidly, so that the switching current flowing through the switching element 7 is adjusted. The switching operation is performed in an operation mode that is maximum within the range. In this operation mode (hereinafter referred to as the maximum load mode), the ON period of the switching element 7 is longer than that during steady lighting (after time t3 in FIG. 6), and the peak value of the switching current I2 is also higher than during steady lighting. Become.

  Thereafter, when the applied voltage V1 rises and reaches the lighting start voltage Vf0 at time t2, the forward current I1 flowing through the LED 5 increases rapidly, and a forward current I1 of Ifmax that greatly exceeds the target value If flows through the LED 5. become. At this time, when the current detection unit 9 detects that an excessive forward current Ifmax flows, the control circuit unit 11 stops the switching operation of the switching element 7 based on the detection result of the current detection unit 9. When the switching element 7 is turned off, the forward current I1 rapidly decreases, and at time t3, the forward current I1 decreases to Ifmin which is lower than the target value If. When the current detection unit 9 detects that the forward current I1 has fallen below the target value If, the control circuit unit 11 resumes the switching operation of the switching element 7 based on the detection result of the current detection unit 9. Let Thereby, after the time t3, the forward current I1 is controlled to the target value If, the LED 5 is switched to the steady lighting operation, and the control circuit unit 11 continuously performs the switching operation of the switching element 7.

  By the way, the LED has a characteristic that the forward voltage does not change much compared to the forward current after the forward voltage becomes equal to or higher than a certain value and the forward current I1 starts to flow. That is, as shown in FIG. 6A, when the applied voltage V1 to the LED 5 reaches the lighting start voltage Vf0 and the forward current I1 starts to flow, the applied voltage V1 also decreases slightly due to the drop of the forward current I1. It can be said that the applied voltage V1 is substantially constant at the lighting start voltage Vf0. This means that when the applied voltage V1 increases transiently, the forward current I1 greatly increases compared to the fluctuation of the applied voltage V1, and as a result, the brightness of the LED 5 also changes greatly.

  Due to the change in the forward current I1 of the LED 5 generated by this series of operations, the LED 5 is lit brightly for a moment, and after that, the brightness of the LED 5 suddenly becomes dark and then brightens to the target level. Therefore, the change in the light output becomes a flash, and there is a problem that the user feels visually uncomfortable. Note that the greater the difference in operation between the maximum load mode from time t1 to time t2 and the steady load mode after time t3, and the greater the delay time until the feedback signal of the forward current I1 is reflected in the circuit operation. The peak value of the forward current I1 generated when the applied voltage V1 reaches the lighting start voltage Vf0 increases, and the visual discomfort felt by the user tends to increase correspondingly.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an LED lighting device that reduces flash light generated when switching from a light-off state to a light-on state, and a lighting fixture using the same. It is to provide.

In order to solve the above-mentioned problems, an LED lighting device according to the present application is a switching power supply that converts an input from a DC power supply to a DC voltage having a desired voltage value by switching the input from the DC power supply and supplies a drive current to the LED. A current detection unit that detects a forward current flowing through the LED, and a control circuit unit that controls a switching operation of the switching element so that a detection current of the current detection unit becomes a target value in a steady lighting state. The control circuit unit is configured to start the switching operation of the switching power supply unit to turn on the LED in the off state until the applied voltage to the LED increases to the lighting start voltage. After providing the first switching period in which the ON time of the switching element is relatively long, the ON time of the switching element A second switching period that is relatively shorter than the first switching period is provided, and the control circuit unit sets a period until a predetermined time elapses from the time when the switching operation is started as the first switching period, When the predetermined time elapses, the second switching period is switched .

In addition, the LED lighting device of the present application converts the input from the DC power supply with a switching element to convert it to a DC voltage of a desired voltage value, and supplies a driving current to the LED, and the LED A current detection unit that detects a forward current flowing; a control circuit unit that controls a switching operation of the switching element so that a detection current of the current detection unit becomes a target value in a steady lighting state; and an application to the LED A voltage detection unit that detects a voltage, and the control circuit unit starts the switching operation of the switching power supply unit in order to turn on the LED in the off state. Until a first switching period in which the on-time of the switching element is relatively long, On-time of the switching element is provided a relatively shorter second switching period as compared with the first switching period, the control circuit unit, the detection voltage of the voltage detecting unit from the time when said switching operation is started is the lighting the time to reach a lower predetermined threshold voltage than the start voltage and the first switching period, the detected voltage is configured to switch the second switching period exceeds the threshold voltage, the threshold voltage is constant It is a value of 50% or more and 80% or less of the voltage applied to the LED in the lighting state.

  The lighting fixture of this application is provided with one of the LED lighting devices mentioned above.

  ADVANTAGE OF THE INVENTION According to this invention, the flash which generate | occur | produces when switching from a light extinction state to a lighting state can be reduced, and the visual discomfort given to a user by generation | occurrence | production of a flash can be reduced.

It is a circuit diagram of the LED lighting device of this embodiment. It is an operation | movement waveform diagram same as the above, (a) is a waveform diagram of switching current, (b) is a waveform diagram of drive signal S2, (c) is a waveform diagram of lighting power. It is a wave form chart at the time of switching from a light extinction state same as the above, (a) is a wave form figure of an applied voltage to LED, (b) is a wave form figure of a forward current, (c) is a wave form figure of switching current. It is. It is a circuit diagram of the conventional LED lighting device. It is an ideal waveform figure at the time of switching from a light extinction state same as the above to a lighting state, (a) is a waveform figure of an applied voltage to LED, and (b) is a wave form chart of a forward current. It is an actual waveform diagram at the time of switching from the unlit state to the lit state as above, (a) is a waveform diagram of the voltage applied to the LED, (b) is a waveform diagram of the forward current, (c) is a waveform of the switching current. It is a waveform diagram.

  The LED lighting device of this embodiment and the lighting fixture using the same will be described with reference to the drawings.

  FIG. 1 is a circuit diagram of an LED lighting device. The LED lighting device includes a rectifier circuit 2, an insulating flyback converter 3, a smoothing capacitor 4, and an LED (light emitting diode) 5 as main components. Yes. In the LED lighting device of this embodiment, two LEDs 5 are connected in series as a load, but the number of LEDs is not limited to two, and may be one or three or more, A plurality of LEDs may be connected in parallel.

  The rectifier circuit 2 performs full-wave rectification on the commercial AC power supply 1 and converts it into direct current. The direct-current voltage rectified by the rectifier circuit 2 is output to the insulation type flyback converter 3. Here, the rectifier circuit 2 constitutes a DC power supply that supplies DC power to the isolated flyback converter 3 serving as a switching power supply.

  The insulating flyback converter 3 serving as a switching power supply unit includes an insulating transformer 6, a switching element 7, and a diode 8. The primary winding of the insulating transformer 6 is connected between the output terminals of the rectifier circuit 2 via the switching element 7 (for example, composed of FET) and the current detection unit 10. A smoothing capacitor 4 (for example, a large-capacity electrolytic capacitor) is connected between both ends of the secondary winding of the insulating transformer 6 via a diode 8, and an LED 5 and a current detection unit 9 are connected between both ends of the smoothing capacitor 4. It is connected. Further, a voltage detector 15 that detects the level of the output voltage (voltage V1 applied to the LED 5) and a predetermined threshold voltage is connected between the output terminals of the insulating flyback converter 3. The switching power supply unit is not limited to the insulating flyback converter 3 and may be of other circuit types.

  The switching element 7 of the insulating flyback converter 3 is controlled to be turned on / off by the drive signal S2 input from the control circuit unit 11. When the switching element 7 is turned on by the drive signal S2 from the control circuit unit 11, a switching current I2 flows through the primary winding of the insulating transformer 6, and electric energy is converted into magnetic energy. At this time, no current flows on the secondary side of the insulating transformer 6 due to the polarity of the diode 8, and magnetic energy is accumulated in the insulating transformer 6. Thereafter, when the switching element 7 is turned off by the drive signal S2, the magnetic energy accumulated in the insulating transformer 6 during the ON period of the switching element 7 is reconverted into electric energy, and is released from the secondary side of the insulating transformer 6 and smoothed. The capacitor 4 is charged. When the switching element 7 is periodically turned on / off, a DC voltage insulated from the primary side is generated on the secondary side of the insulating transformer 6, and a DC voltage generated between both ends of the smoothing capacitor 4 is generated. Applied to the LED 5, the LED 5 lights up.

  Next, the control circuit unit 11 will be described. The control circuit unit 11 includes a control signal S1 for determining a target value of the output current (forward current I1 of the LED 5) from the outside, detection signals from the current detection units 9 and 10, and detection output from the voltage detection unit 15. Have been entered. The current detection unit 9 includes a current detection resistor connected in series with the LED 5, for example, and outputs a signal having a magnitude corresponding to the forward current I 1 to the control circuit unit 11. The current detection unit 10 includes, for example, a current detection amount resistor connected in series with the switching element 7, and outputs a signal having a magnitude corresponding to the switching current I 2 to the control circuit unit 11. The voltage detection unit 15 includes a voltage dividing circuit 12, a reference power supply 13, and a comparator 14. The voltage dividing circuit 12 is composed of a series circuit of resistors 12a and 12b connected between the output terminals of the isolated flyback converter 3, and has a voltage dividing ratio according to the ratio between the resistance value of the resistor 12a and the resistance value of the resistor 12b. The voltage V1 applied to the LED 5 is divided. The comparator 14 compares the divided voltage divided by the voltage dividing circuit 12 with the reference voltage of the reference power supply 13, and if the divided voltage is higher than the reference voltage, the comparator 14 outputs an H level signal. Is lower than the reference voltage, an L level signal is output to the control circuit unit 11. Note that the reference voltage of the reference power supply 13 is set to a value corresponding to the above threshold voltage, and if the applied voltage V1 is higher than the threshold voltage, the output of the voltage detector 15 becomes H level, and the applied voltage V1 is the threshold value. If the voltage is lower than the voltage, the output of the voltage detector 15 is at the L level.

  The control circuit unit 11 can adjust the output power of the isolated flyback converter 3 (that is, the lighting power supplied to the LED 5) by changing the ON time (ON duty or switching frequency) of the switching element 7. . 2 shows operation waveforms in two lighting modes M1 and M2 having different lighting power levels, FIG. 2A is a waveform diagram of the switching current I2, FIG. 2B is a waveform diagram of the drive signal S2, and FIG. (C) is a waveform diagram of the lighting power W1. Further, the left side in FIG. 2 is an operation waveform in the lighting mode M1 where the lighting power W1 is relatively large, and the right side in FIG. 2 is an operation waveform in the lighting mode M2 where the lighting power W1 is relatively small. From the operation waveform of FIG. 2, in the lighting mode M1 where the lighting power W1 is large, the ON period of the switching element 7 is longer and the peak value of the switching current I2 is higher than in the lighting mode M2 where the lighting power W1 is small. As described above, when the switching element 7 is turned on, a current flows through the primary winding of the insulating transformer 6 through the switching element 7, whereby electric energy is converted into magnetic energy and accumulated in the insulating transformer 6. Thereafter, when the switching element 7 is turned off, the magnetic energy accumulated in the insulating transformer 6 when the switching element 7 is turned on is reconverted into electric energy and released from the secondary side. Since the transformer has the property of storing energy as the current flowing in the winding increases, the current flowing in the primary winding of the insulating transformer 6 and the switching element 7 gradually increases when the switching element 7 is turned on. Further, as the current increases, the energy stored in the insulating transformer 6 and released to the secondary side of the insulating transformer 6 also increases. Therefore, the lighting mode M1 in which the ON period is longer and the peak value of the switching current I2 is larger. However, the lighting power W1 is larger than that in the lighting mode M2.

  The control signal S1 input to the control circuit unit 11 is a PWM signal obtained by modulating the ON time of a pulse signal having a predetermined frequency according to the target value of the forward current I1 flowing through the LED 5. The control circuit unit 11 is configured so that the actual value of the forward current I1 detected by the current detection unit 9 matches the signal level of the DC reference signal generated from the control signal S1 (target value of the forward current I1). The driving signal S2 output to the switching element 7 is adjusted to adjust the lighting power. That is, when the peak value of the switching current I2 detected by the current detection unit 10 exceeds the threshold value determined based on the difference between the target value and the actual value of the forward current I1, the control circuit unit 11 performs switching. The element 7 is turned off.

  To summarize the above operation, the control circuit unit 11 compares the signal level of the reference signal obtained from the control signal S1 input from the outside with the detection signal of the current detection unit 9, and in the steady lighting state, the order of the LEDs 5 is compared. The threshold for turning off the switching element 7 is changed so that the direction current I1 becomes a level corresponding to the control signal S1, and the on-time (that is, the lighting power W1) is controlled thereby. On the other hand, when the LED 5 is switched from the unlit state to the lit state, since the forward current I1 does not flow through the LED 5, the control circuit unit 11 operates the switching element 7 in the maximum load mode to reduce the applied voltage V1 for a short time. However, when the applied voltage V1 rises to a predetermined threshold voltage, the output power of the isolated flyback converter 3 is reduced to reduce the flashing when switching from the unlit state to the lit state. To do. Therefore, in this embodiment, the detection output of the voltage detection part 15 which detects the applied voltage V1 applied to LED5 is input into the control circuit part 11. FIG. The comparator 14 of the voltage detector 15 compares the level of the voltage obtained by dividing the applied voltage V1 with the voltage dividing circuit 12 with the reference voltage (voltage set corresponding to the threshold voltage) given from the reference power supply 13. When the voltage obtained by dividing the applied voltage V1 exceeds the reference voltage, the output of the comparator 14 is switched from the L level to the H level. In the control circuit unit 11, the threshold value of the switching current I2 described above is switched according to the output of the voltage detection unit 15. When the output of the voltage detection unit 15 is switched from the L level to the H level (that is, the applied voltage V1 is the threshold value). When the voltage is exceeded, the threshold value of the switching current I2 is switched to a lower value than before, and the output power is reduced.

  Here, the operation of the LED lighting device will be described based on the waveform diagram of FIG. 3A is a waveform diagram of the applied voltage V1 to the LED 5, FIG. 3B is a waveform diagram of the forward current I1 flowing through the LED 5, and FIG. 3C is a waveform of the switching current I2 flowing through the switching element 7. FIG. It is a waveform diagram.

  At time t11, when the LED lighting device is turned on or the control signal S1 input from the outside is switched, the control circuit unit 11 switches the switching element 7 so that the LED 5 is turned off. Start operation. The applied voltage V1 increases as the switching operation starts, but the LED 5 is not lit until time t13 when the applied voltage V1 reaches the lighting start voltage Vf0, and the forward current I1 is approximately 0A. is there. Until the applied voltage V1 reaches a predetermined threshold voltage Vf1 (for example, about 80% of the applied voltage Vf0 in the steady lighting state) (time t11 to t12), the control circuit unit 11 includes the voltage detector 15 An L level signal is input, and the control circuit unit 11 operates the switching element 7 in the maximum load mode that maximizes the ON time within the adjustment range. Thereby, in the period from time t11 to t12, the applied voltage V1 rises rapidly compared to the subsequent period (time t12 to t13). Thereafter, when the applied voltage V1 to the LED 5 exceeds the threshold voltage Vf1 at time t12, an H level signal is input from the voltage detection unit 15 to the control circuit unit 11, and the control circuit unit 11 is input from the voltage detection unit 15. The threshold value of the switching current I2 is limited to a lower value than the period (time t11 to t12) based on the received signal. As a result, the period from time t12 to when the LED 5 is turned on (this period is the second switching period T2) compared to the period from time t11 to time t12 (this period is the first switching period T1). Since the on-time of the switching element 7 is switched to a short time, the increasing rate of the applied voltage V1 becomes gradual compared with the first switching period T1. At time t13 when the applied voltage V1 reaches the lighting start voltage Vf0, when the current starts to flow through the LED 5, the forward current I1 of the LED 5 rises sharply, and the current Ifmax exceeding the target value If of the forward current I1 instantaneously Will flow. However, in the second switching period T2, the peak value of the switching current I2 is reduced and the difference from the steady lighting state is reduced by switching to a time with a shorter on-time compared to the first switching period T1. The difference in output power between the second switching period T2 and the steady lighting state is also small. Therefore, since the peak Ifmax of the forward current I1 generated when switching from the unlit state to the lit state can be reduced as compared with the conventional case, the flash generated when the LED 5 switches from the unlit state to the lit state is suppressed and given to the user. Visual discomfort can be suppressed.

  As described above, the LED lighting device of the present embodiment includes the switching power supply unit (consisting of the insulating flyback converter 3), the current detection unit 9, and the control circuit unit 11. The switching power supply unit converts the input from the DC power supply (consisting of the rectifier circuit 2) by the switching element 7 to convert the input to a DC voltage having a desired voltage value, and supplies a drive current to the LED 5. The current detection unit 9 detects a forward current flowing through the LED 5. The control circuit unit 11 controls the switching operation of the switching element 7 so that the detection current of the current detection unit 9 becomes a target value in the steady lighting state. In addition, the control circuit unit 11 starts the switching operation of the switching power supply unit in order to light the LED 5 in the extinguished state until the voltage V1 applied to the LED 5 increases to the lighting start voltage Vf0. After the first switching period T1 having a relatively long on-time, the second switching period T2 having a relatively short on-time of the switching element 7 as compared with the first switching period T1 is provided.

  Thereby, in the second switching period T2, the output power from the switching power supply unit to the LED is reduced by shortening the on-time of the switching element as compared with the first switching period. The peak value of the forward current I1 generated when switching to can be reduced. Accordingly, it is possible to reduce the flash that is generated when the light is switched from the light-off state to the light-on state, and it is possible to reduce visual discomfort given to the user due to the generation of the flash light.

  In this LED lighting device, a period from when the control circuit unit 11 starts the switching operation until the detection voltage of the voltage detection unit 15 reaches a predetermined threshold voltage Vf1 lower than the lighting start voltage Vf0 is a first switching period. It is also preferable to switch to the second switching period T2 when T1 is set and the detection voltage exceeds the threshold voltage Vf1.

  For example, when switching from the first switching period T1 to the second switching period T2 when a predetermined time elapses from the time when the switching operation is started, a circuit component such as a capacity decrease of a capacitor constituting a timer circuit that counts the predetermined time is used. There is a possibility that the timing of switching to the second switching period T2 may fluctuate due to, for example, charge remaining in the capacitor due to degradation or power supply opening / closing, but when the detection voltage exceeds the threshold voltage Vf1, the second switching period T2 is reached. Since the switching is performed, it is possible to surely switch to the second switching period T2 before reaching the lighting start voltage, and it is possible to reliably reduce the occurrence of flash.

  In this LED lighting device, the threshold voltage is preferably 50% or more and 80% or less of the voltage applied to the LED in the steady lighting state.

  As a result of actual device studies, by setting the threshold voltage to a value that is 50% or more and 80% or less of the voltage applied to the LED in the steady lighting state, the flash generated when switching from the unlit state to the lit state is reliably reduced. it can. If the threshold voltage is too low, the time until the applied voltage reaches the lighting start voltage becomes long and the time until the LED 5 lights up becomes slow. However, by setting the threshold voltage to 50% or more, the LED 5 There is also an advantage that the adverse effect that the time until lighting is too long is less likely to occur.

  In the above embodiment, when the applied voltage V1 reaches the threshold voltage Vf1, the control circuit unit 11 switches from the first switching period T1 to the second switching period T2, but the control circuit unit 11 starts the switching operation. It is also preferable that the period from when the predetermined time elapses until the predetermined time elapses is the first switching period T1, and when the predetermined time elapses, the period is switched to the second switching period T2.

  In this case, the first switching period T1 to the second switching period T2 can be achieved by adding a relatively simple circuit such as using the time constant of the RC circuit or sharing the clock of the microcomputer used for other control. It is possible to reduce the flash generated when switching from the extinguished state to the lit state by detecting the timing of switching to.

  Moreover, the lighting fixture of this embodiment is comprised by attaching LED5 which is a light source, and the above-mentioned LED lighting device which lights LED5 to the fixture main body (not shown), for example.

  Thereby, it is possible to reduce the flash generated when switching from the light-off state to the light-on state, and to realize a lighting fixture that suppresses the visual discomfort given to the user.

  The lighting fixture is not limited to a ceiling-mounted type, but may be a pendant-type fixture body that is suspended from the ceiling, holding the LED 5 and the above-described LED lighting device, or a fixture that is attached to a wall. The main body may hold the LED 5 and the LED lighting device described above, or the stand-type instrument main body may hold the LED 5 and the LED lighting device described above.

1 Commercial AC power supply 2 Rectifier circuit (DC power supply)
3 Insulated flyback converter (switching power supply)
5 LED
7 Switching element 9, 10 Current detection unit 11 Control circuit unit 15 Voltage detection unit

Claims (3)

A switching power supply unit that converts the input from the DC power supply to a DC voltage of a desired voltage value by switching with a switching element and supplies a driving current to the LED;
A current detector for detecting a forward current flowing in the LED;
A control circuit unit that controls a switching operation of the switching element so that a detection current of the current detection unit becomes a target value in a steady lighting state;
The control circuit unit is configured to start the switching operation of the switching power supply unit in order to turn on the LED in the extinguished state until the applied voltage to the LED increases to the lighting start voltage. Providing a second switching period in which the on-time of the switching element is relatively shorter than the first switching period .
The control circuit unit sets a period until a predetermined time elapses from the time when the switching operation is started as the first switching period, and switches to the second switching period when the predetermined time elapses. Lighting device. A switching power supply unit that converts the input from the DC power supply to a DC voltage of a desired voltage value by switching with a switching element and supplies a driving current to the LED;
A current detector for detecting a forward current flowing in the LED;
A control circuit unit that controls a switching operation of the switching element so that a detection current of the current detection unit becomes a target value in a steady lighting state;
A voltage detection unit for detecting a voltage applied to the LED,
The control circuit unit is configured to start the switching operation of the switching power supply unit in order to turn on the LED in the extinguished state until the applied voltage to the LED increases to the lighting start voltage. Providing a second switching period in which the on-time of the switching element is relatively shorter than the first switching period.
The control circuit unit sets a period from when the switching operation is started until the detection voltage of the voltage detection unit reaches a predetermined threshold voltage lower than the lighting start voltage as the first switching period, and the detection voltage Is configured to switch to the second switching period when the threshold voltage is exceeded,
The LED lighting device , wherein the threshold voltage is a value of 50% to 80% of a voltage applied to the LED in a steady lighting state . A lighting fixture comprising the LED lighting device according to claim 1.

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