JP2014022067A - Lighting device and illuminating fixture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting device capable of dimming more smoothly, and that is suitable for digital control.SOLUTION: A lighting device 1 lightening an LED 15 at a brightness depending on a light-control signal, comprises: a lighting circuit 10 including an inductor 14, a switching element 13, and a diode 12; and a control circuit 20 repeatedly outputting a burst that is a pulse train for turning on the switching element 13 at a constant cycle to control the switching element 13. The burst includes a first pulse for turning on the switching element 13 that has a pulse width of a first ON period, and a second pulse for turning on the switching element 13 that has a pulse width of a second ON period. The control circuit 20 controls the number of the first pulses, and the number of the second pulse or the pulse width of the second pulse included in one burst, depending on the light-control signal from exterior.

Description

  The present invention relates to a lighting device for lighting solid light emitting elements such as light emitting diodes and organic EL elements and a lighting fixture using the same, and more particularly to a lighting device for lighting solid light emitting elements with brightness according to a dimming signal.

  In recent years, lighting fixtures using solid light emitting elements such as light emitting diodes (LEDs) or organic EL elements have become widespread as lighting fixtures with low power consumption and long life.

  Conventionally, for example, a technique disclosed in Patent Document 1 has been proposed as a lighting device for lighting a solid state light emitting device with brightness according to a dimming signal.

  FIG. 17 is a circuit diagram showing a configuration of a power supply assembly for an LED illumination module disclosed in Patent Document 1. As shown in FIG. The power supply assembly includes a control switch 101 for supplying a constant current to the LED lighting module 102. A dual switching signal composed of a low frequency burst of high frequency pulses is supplied to the control switch 101. By changing the low-frequency component of the dual switching signal, the average current flowing through the LED lighting module 102 is changed, thereby changing the light intensity of the LED lighting module 102.

  That is, the AND gate 107 calculates the logical product of the PWM signal indicating the period of the low frequency burst and the high frequency pulse train, and the operation result is supplied to the control switch 101 as a dual switching signal. Therefore, by adjusting the duty ratio of the PWM signal, the number of high-frequency pulses included in one burst of the dual switching signal changes, so the average current flowing through the LED lighting module 102 is changed.

JP 2006-511078 gazette

  However, the technique disclosed in Patent Document 1 has a problem that dimming cannot be performed smoothly.

  FIG. 18 is a diagram for explaining a problem in the technique of Patent Document 1. FIG. 18A shows waveforms of “PMW signal”, “drive signal”, and “load current”. The “PMW signal” is a signal input to the AND gate 107. The “drive signal” is a dual switching signal (a series of high frequency pulses included in one burst) output from the AND gate 107. The “load current” is a current that flows through the LED lighting module 102. FIG. 18B is a graph showing the intensity of light output from the LED illumination module 102 when the duty ratio of the PWM signal is changed. As can be seen from FIG. 18, even when the duty ratio of the PWM signal is continuously changed, the number of high-frequency pulses included in one burst changes in integer units. As a result, the light output from the LED illumination module 102 changes discretely (stepwise) corresponding to the change in the number. Therefore, the technique of Patent Document 1 cannot perform dimming smoothly. In particular, when dimming with a low luminous flux, since the rate of change in the light output of the LED illumination module 102 is relatively large, the roughness of the dimming becomes conspicuous.

  In recent years, control circuits have been digitized due to improvements in CPU performance. As for power supply devices such as DC / DC converters and inverters, power supply devices equipped with control ICs such as dedicated microcomputers (microcomputers) for digital control and DSPs (Digital Signal Processors) have been developed and are widely used in the market. . Therefore, it is desired that the lighting device also includes a circuit suitable for digital control.

  Therefore, the present invention has been made in view of such a situation, and an object of the present invention is to provide a lighting device and a lighting fixture that can adjust light more smoothly and are suitable for digital control.

  In order to achieve the above object, a lighting device according to an embodiment of the present invention is a lighting device that lights a solid state light emitting element with brightness according to a dimming signal, and is connected in series with a DC voltage as an input. An inductor and a switching element; a diode for regenerating energy stored in the inductor when the switching element is off; a lighting circuit that generates a current to be passed through the solid state light emitting element; and the switching element A control circuit for controlling the switching element by repeatedly outputting a burst, which is a train of pulses to be turned on, at a constant period, and the burst has a pulse width of a first on period for turning on the switching element. A first pulse and a second pulse having a pulse width of a second on-period for turning on the switching element; And the control circuit controls the number of the first pulse and the number of the second pulse or the pulse width of the second pulse included in one burst according to the dimming signal. .

  Here, as a more specific configuration of the control circuit, the control circuit includes a burst timer that determines the fixed period, and a first memory circuit that stores the number of the first pulses determined according to the dimming signal. , A second memory circuit that stores the number or width of the second pulses determined according to the dimming signal, the number of the first pulses stored in the first memory circuit, and the second memory unit. A pulse generation circuit that generates a burst for one time composed of the second pulse having the stored number or pulse width, and repeatedly outputs the generated burst at a period determined by the burst timer. Also good.

  The second on-period is preferably smaller than the first on-period.

  Further, as an order of outputting pulses, the control circuit may output the second pulse after outputting the first pulse to the switching element in one burst, or the control circuit may In one burst, the first pulse may be output after the second pulse is output to the switching element.

  Also, as a second pulse control method, the number of the second pulses included in one burst is 1, and the control circuit is included in one burst according to the dimming signal. The number of the first pulses to be controlled and the pulse width of the second pulse may be controlled.

  Further, as another control method of the second pulse, the control circuit, according to the dimming signal, the number of the first pulse included in one burst and the first pulse included in one burst. The number of two pulses may be controlled.

  Further, an AC-DC converter or a DC-DC converter that generates the DC voltage may be provided.

  The DC voltage is an output of an AC-DC converter, and the control circuit preferably outputs the burst repeatedly at a frequency of 600 Hz or a multiple of 600 Hz.

  In addition, this invention can be implement | achieved not only as a lighting device but as a lighting fixture provided with the said lighting device.

  According to the present invention, a lighting device and a lighting fixture that can adjust light more smoothly and are suitable for digital control are provided.

  Therefore, the practical value of the present invention is extremely high in the present day when lighting fixtures using solid-state light-emitting elements with low power consumption and long life have become widespread.

Circuit diagram of lighting device according to Embodiment 1 of the present invention Timing chart showing the operation of the lighting device Timing chart showing operation of lighting device according to first modification Timing chart showing the operation of the lighting device according to the second modification realized using two counters Timing chart showing the operation of the lighting device according to the second modified example realized by using one counter Timing chart showing operation of lighting device according to third modification Circuit diagram of lighting device according to Embodiment 2 of the present invention Timing chart showing the operation of the lighting device Circuit diagram of lighting device according to Embodiment 3 of the present invention Timing chart showing operation in continuous mode of the lighting device Timing chart showing the operation of the lighting device in discontinuous mode Circuit diagram of lighting device according to fourth modification Circuit diagram of lighting apparatus according to fifth modification Circuit diagram of lighting device according to sixth modification Circuit diagram of lighting device according to seventh modification The figure which shows the structural example of the lighting fixture in embodiment of this invention The circuit diagram which shows the structure of the electric power feeding assembly for the conventional LED lighting module Illustration for explaining problems in the prior art

  Hereinafter, a lighting device and a lighting fixture according to the present invention will be specifically described with reference to the drawings. Note that each of the embodiments and modifications described below is a specific example of the present invention. The numerical values, shapes, materials, constituent elements, arrangement positions and connection forms of the constituent elements, operation timings, and the like shown in the following embodiments and modifications are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments and modifications, constituent elements that are not described in the independent claims indicating the highest concept are described as optional constituent elements.

(Embodiment 1)
First, the lighting device according to Embodiment 1 of the present invention will be described.

  FIG. 1 is a circuit diagram of lighting device 1 according to Embodiment 1 of the present invention. In this figure, a DC voltage source 11 for supplying a DC voltage to the lighting device 1 and a solid state light emitting element (here, LED 15) to be lit are also shown (for other embodiments). The same).

  The lighting device 1 is a device that lights the LED 15 with brightness according to a dimming signal given from the outside, and includes a lighting circuit 10 and a control circuit 20 that controls the lighting circuit 10.

  The lighting circuit 10 is a circuit that generates a current (load current) that flows through the LED 15, and includes a diode 12, a switching element 13, and an inductor 14. The switching element 13 is an NMOS transistor, for example. The LED 15, the inductor 14, and the switching element 13 are connected in series to the DC voltage source 11. The diode 12 regenerates the energy accumulated in the inductor 14 when the switching element 13 is off, and forms a circuit loop with the LED 15 and the inductor 14 so as to supply the current due to the regeneration to the LED 15. With this connection, in this embodiment, the lighting circuit 10 forms a step-down chopper circuit that generates a voltage obtained by stepping down the voltage from the DC voltage source 11 and outputs the voltage to the LED 15.

  The control circuit 20 is a circuit that repeatedly outputs a burst, which is a train of pulses for turning on the switching element 13, at a constant period. That is, the control circuit 20 controls the switching element 13 by repeatedly outputting a drive signal for one cycle including a burst on period and a burst off period at a constant frequency. In one burst (burst on period), the first pulse having the pulse width of the first on period for turning on the switching element 13 and the second on period for turning on the switching element 13 (<first on period) And a second pulse having a pulse width of. Then, according to the dimming signal, the control circuit 20 determines the number of first pulses included in one burst and the number of second pulses (number of second pulses included in one burst) or second. The pulse width of the pulse (in this embodiment, the pulse width) is controlled. Specifically, in the present embodiment, the control circuit 20 outputs a number of first pulses corresponding to the dimming signal to the switching element 13 and then has one pulse width corresponding to the dimming signal. The second pulse is output. The dimming signal is an analog signal such as a voltage corresponding to the brightness of the LED 15, for example.

  For this purpose, the control circuit 20 includes a drive circuit 21, an RS flip-flop 22, an OR gate 23, a zero current detection circuit 24, a Ton timer 25, a pulse number counter 26, a burst timer 27, a memory 28, and a dimming level reading unit 29. Prepare.

  The zero current detection circuit 24 is an example of a current detection circuit that detects a current flowing through the switching element 13 or the inductor 14. In the present embodiment, the zero current detection circuit 24 outputs a pulse when detecting that the current flowing through the inductor 14 becomes zero using a sensor inductively coupled to the inductor 14.

  The burst timer 27 is an example of a timer that determines a burst repetition period. In the present embodiment, the burst timer 27 outputs a pulse at a frequency of 600 Hz or a multiple of 600 Hz. The reason why the burst repetition frequency is 600 Hz or a multiple of 600 Hz is to avoid various adverse effects caused by the commercial power supply. For example, as will be described later, when an AC-DC converter that generates a DC voltage from a commercial power supply (frequency is 50 Hz or 60 Hz) is used as the DC voltage source 11, a ripple of 100 Hz or 120 Hz is generated on the generated DC voltage. Can occur. Due to the interference caused by the ripple, the load current may fluctuate, and the light output of the LED 15 may flicker. Therefore, by making the repetition frequency of the burst the least common multiple of the ripple frequency that can be generated (100 Hz or 120 Hz) or a multiple thereof (600 Hz or a multiple of 600 Hz), the light output of the LED 15 becomes almost constant, and due to ripple interference. Flicker is suppressed.

  The OR gate 23 is a gate that outputs a logical sum of the pulse from the zero current detection circuit 24 and the pulse from the burst timer 27 (that is, allows both pulses to pass).

  The RS flip-flop 22 is an example of a pulse generation circuit that generates a first pulse and a second pulse that form a burst. In the RS flip-flop 22, the output signal from the OR gate 23 is input to the set terminal S, the output signal from the Ton timer 25 is input to the reset terminal R, and a pulse (first pulse and second pulse) is output from the output terminal Q. ) Is output.

  The drive circuit 21 has a voltage necessary for driving the pulse (first pulse and second pulse) output from the RS flip-flop 22 to drive the control terminal (for example, the gate terminal of the NMOS transistor) of the switching element 13. Convert to drive signal. Then, the drive circuit 21 outputs the converted drive signal to the control terminal of the switching element 13.

  The dimming level reading unit 29 includes the number n of first pulses that include the magnitude of a dimming signal (for example, an analog signal that indicates the brightness of the LED 15) given from the outside, and the second number The pulse width Ton2 of the pulse is converted to a numerical value Nton2. Then, the dimming level reading unit 29 writes the converted number n and the numerical value Nton2 in the memory 28. The dimming level reading unit 29 repeats the above conversion at a constant cycle. When the dimming signal changes in size, the dimming level reading unit 29 generates the number n and the numerical value Nton2 corresponding to the dimming signal after the change. Write to.

  The memory 28 stores the number n and the numerical value Nton2 written by the dimming level reading unit 29. The stored number n is output to the pulse number counter 26, and the stored numerical value Nton2 is stored. Output to the Ton timer 25.

  The pulse number counter 26 is a counter that counts down each time a pulse is output from the RS flip-flop 22 after setting a value (n + 1) obtained by adding 1 to the number n output from the memory 28 as a preset. The pulse number counter 26 outputs the stored count value to the Ton timer 25, and outputs a signal to the zero current detection circuit 24 when the count value becomes zero to operate the zero current detection circuit 24. Stop. The pulse counter 26 is reset by a pulse from the burst timer 27, and repeats the preset and countdown.

  The Ton timer 25 is a timer that outputs a pulse after a predetermined time has elapsed since a new count value was input from the pulse number counter 26. The Ton timer 25 has a preset (fixed) first on-period Ton1 until the count value output from the pulse number counter 26 becomes 1 (that is, until the count value changes from n + 1 to 1). Functions as a timer for timing. On the other hand, after the count value output from the pulse number counter 26 becomes 1, the Ton timer 25 measures the period corresponding to the numerical value Nton2 output from the memory 28 (that is, the second on-period Ton2). Functions as a timer.

  The memory 28 and the pulse number counter 26 constitute a first memory circuit that stores the number of first pulses determined according to the dimming signal. In addition, the memory 28 and the Ton timer 25 constitute a second storage circuit that stores the number or pulse width (in this embodiment, pulse width) of the second pulse determined according to the dimming signal. The RS flip-flop 22 constitutes a pulse generation circuit. The pulse generation circuit generates a burst composed of the number of first pulses stored in the first storage circuit and the second pulse of the number or pulse width stored in the second storage unit, and the generated burst Is repeatedly output at a cycle determined by the burst timer 27.

  Next, operation | movement of the lighting device 1 in this Embodiment comprised as mentioned above is demonstrated.

  FIG. 2 is a timing chart showing the operation of the lighting device 1 in the present embodiment. Here, waveforms of “burst timer”, “drive signal”, “pulse number counter”, “Ton timer value”, and “L current (= LED current)” are shown. In the figure, “burst timer” indicates a pulse (a pulse generated at a period corresponding to 600 Hz or a multiple of 600 Hz) output from the burst timer 27. “Drive signal” indicates an output signal from the drive circuit 21. “Pulse number counter” indicates a count value output from the pulse number counter 26 to the Ton timer 25. The “Ton timer value” indicates a timer value counted by the Ton timer 25. “L current (= LED current)” indicates a load current flowing through the inductor 14 (and the LED 15).

  In this figure, according to the dimming signal, 4 is written in the memory 28 as the number n of the first pulses included in one burst, and the numerical value Nton2 that specifies the pulse width Ton2 of the second pulse is Ton2. A case where a numerical value Nton2 satisfying = 0.8 × Ton1 is written is shown.

  When a pulse from the burst timer 27 is input to the set terminal S of the RS flip-flop 22, the RS flip-flop 22 is set and a high level is output from its output terminal Q. At the same time, when a pulse from the burst timer 27 is input to the pulse number counter 26, the pulse number counter 26 is reset and preset to n + 1 (= 5).

  The Ton timer 25 that has received the notification of the count value outputs a signal to the reset terminal R of the RS flip-flop 22 after the first on-period Ton1 has elapsed from the notification. As a result, the RS flip-flop 22 is reset and a low level is output from its output terminal Q. As a result, the first pulse (that is, the first pulse) is generated from the RS flip-flop 22 and is output from the drive circuit 21 to the control terminal of the switching element 13 as a drive signal. Further, the count value of the pulse number counter 26 is counted down by 1 (from 5 to 4).

  The switching element 13 is turned on only for the period of the pulse width of the first pulse output from the drive circuit 21 and then turned off. As a result, the current flowing through the inductor 14 (and the LED 15) increases while the switching element 13 is on and flows as a regenerative current while the switching element 13 is off, but decreases. Go. Therefore, the current flowing through the inductor 14 (and the LED 15) has a triangular waveform as shown in FIG.

  When the current flowing through the inductor 14 becomes zero (that is, when the regenerative current becomes zero), this is detected by the zero current detection circuit 24, and the pulse from the zero current detection circuit 24 is transmitted via the OR gate 23 to the RS flip-flop. Is input to the set terminal S of the terminal 22. As a result, a current flows through the inductor 14 in the critical mode, and the rising edge of the second pulse (that is, the first pulse) (High level from the output terminal Q of the RS flip-flop 22) is output. As described above, the control circuit 20 includes the zero current detection circuit 24 that detects that the current flowing through the inductor 14 becomes zero. Then, the control circuit 20 generates the first pulse and the second pulse so that the current starts to flow through the inductor 14 immediately after the zero current detection circuit 24 detects that the current has become zero, and the switching element 13 Turn on. Thereafter, such pulse generation is repeated until the count value in the pulse number counter 26 becomes 1. As a result, four first pulses having a pulse width of the first on-period Ton1 are generated.

  When the count value of the pulse number counter 26 becomes 1, the Ton timer 25 starts with the second on-period Ton2 (here, the first on-period Ton1 × 0.8) from the timer that counts the first on-period Ton1 so far. Switch to a timer that counts As a result, for the fifth pulse, one pulse (that is, the second pulse) having the pulse width of the second on-period Ton2 is generated.

  Such pulse generation in one burst is repeated at a frequency determined by the burst timer 27. In other words, a driving signal for one cycle composed of a burst on period in which the first pulse and the second pulse are generated and a burst off period in which no pulse is output is repeatedly generated at a frequency determined by the burst timer 27, and switching is performed. It is supplied to the element 13.

  As described above, according to the present embodiment, the number of first pulses included in one burst and one second pulse following those first pulses according to the magnitude of the dimming signal. The pulse width is adjusted. That is, one burst is composed of an integer number of first pulses and one second pulse having a pulse width smaller than the pulse width of the first pulse. Therefore, compared to the conventional dimming method in which one burst is composed of only an integer number of first pulses, the average current flowing through the LED 15 is adjusted in finer increments, and dimming smoother than before is realized. The

  The pulse width of the second pulse is proportional to the wave height of the current flowing through the inductor 14 (and the LED 15) (the height of the triangular waveform). Therefore, the integrated value of current corresponding to the brightness of the LED 15 (the area of the triangular waveform) is proportional to the square of the pulse width of the second pulse. Therefore, in consideration of such a relationship (a relationship between the pulse width of the second pulse and the integrated value of the current), the dimming level reading unit 29 includes the magnitude of the dimming signal in one burst. The value is converted into a numerical value Nton2 that specifies the number n of the first pulses and the pulse width Ton2 of the second pulse. As a result, the magnitude of the dimming signal is adjusted to be proportional to the integrated value (or average current) of the current flowing through the LED 15 in one burst.

  Further, according to the present embodiment, the control circuit 20 determines the magnitude of the dimming signal from the number of first pulses included in one burst and the number of second pulses (included in one burst). The number of second pulses) or the pulse width of the second pulse. Therefore, such a control circuit 20 can be realized by a digital control circuit using a counter and a timer. Further, in the present embodiment, the magnitude of the dimming signal is digitized and stored in the memory 28, and the counter and timer are controlled according to the stored digital value, and the average current flowing through the LED 15 is adjusted. Therefore, the lighting device 1 in the present embodiment has a circuit configuration suitable for digital control. As described above, by implementing the lighting device 1 according to the present embodiment using the counter, timer, or interrupt function of the control IC such as a microcomputer, a complicated arithmetic circuit design is not required.

  From the above, according to the present embodiment, a lighting device that can adjust light smoothly and is suitable for digital control is realized.

  Note that lighting devices according to various modifications can be realized by slightly modifying the lighting device 1 according to the present embodiment.

  For example, in the first embodiment, in one burst, after n first pulses having a predetermined pulse width of the first on-period Ton1 are output, the first burst is determined depending on the dimming signal. One second pulse having a pulse width of 2 on periods Ton2 was output. However, the output order of the first pulse and the second pulse may be reversed (first modification).

  That is, as shown in the timing chart of FIG. 3, in one burst, after a second pulse having a pulse width determined depending on the dimming signal is output, a predetermined pulse width is set. N first pulses may be output.

  In order to realize such a lighting device according to the first modification, the function of the Ton timer 25 in the lighting device 1 shown in FIG. 1 may be changed. That is, when the first count value is output from the pulse number counter 26, the Ton timer 25 according to the first modification operates a timer that counts the second on-period Ton2. Thereafter, a timer for counting the first on-period Ton1 is operated until a count value of zero is output from the pulse number counter 26. As a result, the lighting device operates at a timing as shown in FIG. As a result, as in the first embodiment, the average current flowing through the LED 15 is adjusted in fine increments according to the dimming signal. Therefore, according to the present modification, as in the first embodiment, a lighting device that can adjust light more smoothly than in the past and is suitable for digital control is realized.

  As a second modification, the number of second pulses included in one burst may be changed in place of the pulse width of the second pulse, depending on the dimming signal. That is, in the first embodiment, the number of second pulses included in one burst is constant (one), and the pulse width changes depending on the dimming signal, but instead, The pulse width (Ton2) of the second pulse may be constant and the number thereof may be changed depending on the dimming signal.

  In order to realize such a lighting device according to the second modification, the functions of the dimming level reading unit 29, the pulse number counter 26, and the Ton timer 25 in the lighting device 1 shown in FIG. That is, the dimming level reading unit 29 according to the second modification converts the magnitude of the dimming signal into the number of first pulses n1 and the number of second pulses n2 included in one burst, The converted numbers n1 and n2 are written in the memory 28. The pulse number counter 26 according to the second modification includes a first counter that counts the number of first pulses and a second counter that counts the number of second pulses. The number n1 stored in the memory 28 is preset in the first counter, and the number n2 stored in the memory 28 is preset in the second counter. The count value of the first counter is output from the pulse number counter 26 to the Ton timer 25, and when the count value becomes zero, the count value of the second counter is subsequently output. The Ton timer 25 operates a timer that counts a predetermined (fixed) first on-period Ton1 while the count value of the first counter is output from the pulse number counter 26. Then, while the count value of the second counter is output from the pulse number counter 26, the Ton timer 25 measures a predetermined (fixed) second on-period Ton2 (<first on-period Ton1). Start the timer.

  Thereby, the lighting device according to the second modification that operates at the timing as shown in FIG. 4 is realized. 4, “pulse number counter 1” and “pulse number counter 2” indicate the count value of the first counter and the count value of the second counter of the pulse number counter 26, respectively. Here, the second on-period Ton2 = the first on-period Ton1 × 0.2 is set, the first counter is preset with 4 as the number n1, and the second counter is preset with 3 as the number n2. The timing in the case is shown.

  Even in the control method according to the second modification, the number of first pulses and the number of second pulses included in one burst are determined depending on the magnitude of the dimming signal. . As a result, as in the first embodiment, the average current flowing through the LED 15 is adjusted in small increments according to the dimming signal. Therefore, according to the present modification, as in the first embodiment, a lighting device that can adjust light more smoothly than in the past and is suitable for digital control is realized.

  In addition, although this 2nd modification was implement | achieved using two counters (a 1st counter, a 2nd counter), you may implement | achieve with one counter.

  For example, as in the first embodiment, the pulse number counter 26 has one counter, presets the total value (n1 + n2) of the number n1 and the number n2 stored in the memory 28, and counts down. . However, the Ton timer 25 switches from the timer that counts the first on-period Ton1 to the timer that counts the second on-period Ton2 when the count value output from the pulse number counter 26 reaches n2.

  As a result, the lighting device operates at a timing as shown in FIG. In FIG. 5, when the “pulse number counter” reaches n2 (= 3), the “Ton timer value” is switched from the first on-period Ton1 to the second on-period Ton2.

  Thus, even in the control method using only one counter (FIG. 5), as a result, as in the control method using two counters (FIG. 4), the average current passed through the LED 15 in response to the dimming signal Is adjusted in small increments to achieve smooth dimming.

  Moreover, you may implement | achieve as a 3rd modification as a lighting device which reversed the output order of the 1st pulse and 2nd pulse in a 2nd modification.

  That is, as shown in the timing chart of FIG. 6, in one burst, first, n2 (here, 3) second pulses having a pulse width of the second on-period Ton2 (<first on-period Ton1). A pulse is output. Thereafter, n1 (here, 4) first pulses having a pulse width of the first on-period Ton1 are output.

  In order to realize such a lighting device according to the third modification, the functions of the pulse number counter 26 and the Ton timer 25 in the lighting device according to the second modification may be changed. That is, the pulse number counter 26 according to the third modification first outputs the count value of the second counter, and when the value becomes zero, subsequently outputs the count value of the first counter. The Ton timer 25 operates a timer that counts the second on-period Ton2 while the count value of the second counter is output from the pulse number counter 26. While the count value of the first counter is output from the pulse number counter 26, the Ton timer 25 operates a timer that counts the first on-period Ton2.

  As a result, the lighting device operates at the timing as shown in FIG. 6, and as a result, the average current passed through the LED 15 is adjusted in fine steps according to the dimming signal, as in the second modification. Therefore, according to the present modification, as in the second modification, a lighting device that can adjust light more smoothly than in the past and is suitable for digital control is realized.

(Embodiment 2)
Next, a lighting device according to Embodiment 2 of the present invention will be described.

  FIG. 7 is a circuit diagram of lighting device 2 according to Embodiment 2 of the present invention.

  The lighting device 2 is a device that lights the LED 15 with brightness according to a dimming signal, and includes a lighting circuit 10a and a control circuit 20a that controls the lighting circuit 10a. In this lighting device 2, the lighting circuit 10 a includes a resistor 32 in addition to the components of the lighting circuit 10 of the first embodiment. The control circuit 20a includes a comparator 30 and a reference voltage generation unit 31 instead of the Ton timer 25 in the control circuit 20 of the first embodiment. In the following, the same components as those in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and differences from the first embodiment will be mainly described.

  In the present embodiment, as a method for controlling the pulse widths of the first pulse and the second pulse, a comparator method is adopted instead of the timer method in the first embodiment. In this comparator method, the current flowing through the switching element 13 or the inductor 14 (in this embodiment, the switching element 13) is compared with a reference value.

  The resistor 32 provided in the lighting circuit 10 a is an example of a current detection circuit that detects a current flowing through the switching element 13 or the inductor 14. In the present embodiment, the resistor 32 is connected in series with the switching element 13 in order to detect the current flowing through the switching element 13 (the resistance value is R1).

  The comparator 30 in the control circuit 20a is an example of a comparator that compares the current detected by the current detection circuit (resistor 32) with a reference value. Here, the comparator 30 compares the voltage at both ends of the resistor 32 with the reference voltage generated by the reference voltage generator 31 and outputs the result to the reset terminal of the RS flip-flop 22.

  The reference voltage generation unit 31 is a circuit that generates a reference value used for comparison in the comparator 30, and supplies the reference voltage Vref to the comparator 30 here. The reference voltage generator 31 is a first reference voltage that is set in advance (fixed) until the count value output from the pulse counter 26 becomes 1 (that is, until the count value changes from n + 1 to 1). Vref1 is generated. Then, after the count value output from the pulse number counter 26 becomes 1, the reference voltage generator 31 outputs the second reference voltage Vref2 (<first reference voltage Vref1) corresponding to the numerical value Nth2 output from the memory 28. ). Here, the first reference voltage Vref1 is set to a value such that the pulse width of the pulse output from the RS flip-flop 22 becomes the first on-period Ton1 in the first embodiment.

  In the present embodiment, the dimming level reading unit 29 includes the number n of first pulses that include the size of a dimming signal (for example, an analog signal) supplied from the outside in one burst, and The second reference voltage Vref2 is converted into a numerical value Nth2 that designates the second reference voltage Vref2. Then, the dimming level reading unit 29 writes the converted number n and the numerical value Nth2 in the memory 28. The memory 28 stores the number n and the numerical value Nth2 written by the dimming level reading unit 29. The stored number n is output to the pulse number counter 26, and the stored numerical value Nth2 is stored. Output to the reference voltage generator 31.

  In the present embodiment, the memory 28 and the reference voltage generation unit 31 are configured such that the number or the pulse width of the second pulse determined according to the dimming signal (in the present embodiment, the pulse width, more strictly, the second pulse). A second memory circuit that stores a numerical value Nth2) that specifies the reference voltage Vref2 is configured.

  Next, the operation of the lighting device 2 in the present embodiment configured as described above will be described.

  FIG. 8 is a timing chart showing the operation of the lighting device 2 in the present embodiment. Here, waveforms of “burst timer”, “drive signal”, “pulse number counter”, “Vref value”, and “L current (= LED current)” are shown. “Burst timer” indicates a pulse output from the burst timer 27. “Drive signal” indicates an output signal from the drive circuit 21. “Pulse number counter” indicates a count value output from the pulse number counter 26 to the reference voltage generator 31. The “Vref value” indicates a reference voltage output from the reference voltage generator 31. “L current (= LED current)” indicates a load current flowing through the inductor 14 (and the LED 15).

  In this figure, according to the dimming signal, 4 is written in the memory 28 as the number n of the first pulses included in one burst, and Ton2 = 0 as the numerical value Nth2 specifying the second reference voltage Vref2 A case where a numerical value Nth2 satisfying .8 × Ton1 is written is shown.

  Until the count value of the pulse number counter 26 changes from 5 to 1, the reference voltage generator 31 generates the first reference voltage Vref 1 and outputs it to the comparator 30. The comparator 30 outputs a signal to the reset terminal of the RS flip-flop 22 when the voltage generated in the resistor 32 exceeds the first reference voltage Vref1. As a result, four first pulses having a pulse width of the first on-period Ton1 (= Vref1 / R1) are generated from the RS flip-flop 22, and these pulses are output to the switching element 13 via the drive circuit 21. Is done. Thereby, as shown in FIG. 8, a current having four triangular waveforms flows through the inductor 14 (and the LED 15).

  When the count value of the pulse number counter 26 becomes 1, the reference voltage generator 31 generates the second reference voltage Vref2 corresponding to the numerical value Nth2 output from the memory 28 and outputs it to the comparator 30. The comparator 30 outputs a signal to the reset terminal of the RS flip-flop 22 when the voltage generated by the resistor 32 exceeds the second reference voltage Vref2. As a result, one second pulse having a pulse width of the second on-period Ton2 (= Vref2 / R1) is generated from the RS flip-flop 22, and these pulses are output to the switching element 13 via the drive circuit 21. Is done. As a result, as shown in FIG. 8, the inductor 14 (and the LED 15), after a current having four triangular waveforms, flows a current having one triangular waveform having a small wave height.

  As described above, also in the comparator method according to the present embodiment, the number of the first pulses included in one burst and the first pulses according to the magnitude of the dimming signal, as in the first embodiment. The pulse width of one second pulse subsequent to is adjusted. That is, one burst is composed of an integer number of first pulses and one second pulse having a pulse width narrower than the first pulse. As a result, it is possible to adjust the average current flowing through the LED 15 in finer increments than in the conventional dimming method in which one burst is composed of only an integer number of first pulses. Therefore, according to the present embodiment, as in the first embodiment, a lighting device that can adjust light more smoothly than in the past and is suitable for digital control is realized.

  Also in the present embodiment, the control circuit 20a includes the zero current detection circuit 24, and the current flows through the inductor 14 in the critical mode, as in the first embodiment.

(Embodiment 3)
Next, a lighting device according to Embodiment 3 of the present invention will be described.

  FIG. 9 is a circuit diagram of lighting device 3 according to Embodiment 3 of the present invention.

  The lighting device 3 is a device that lights the LED 15 with brightness according to a dimming signal, and includes a lighting circuit 10a and a control circuit 20b that controls the lighting circuit 10a. In the lighting device 3, the control circuit 20b includes a monostable multivibrator 35 instead of the zero current detection circuit 24 in the control circuit 20a of the second embodiment. Hereinafter, a description will be given focusing on differences from the second embodiment.

  In the first and second embodiments, the current flows through the inductor 14 in the critical mode. However, in the present embodiment, the current flows through the inductor 14 in the continuous mode. That is, in the present embodiment, the control circuit 20b generates and switches the first pulse and the second pulse so that the current flowing through the inductor 14 starts to increase until the current flowing through the inductor 14 becomes zero due to regeneration. The element 13 is turned on. For this purpose, the control circuit 20 b includes a monostable multivibrator 35.

  When a signal from the comparator 30 is input, the monostable multivibrator 35 outputs a pulse to the OR gate 23 after a predetermined time has elapsed from that point. The certain time here is shorter than the time from when the regenerative current starts to flow to the inductor 14 until it becomes zero.

  Next, operation | movement of the lighting device 3 in this Embodiment comprised as mentioned above is demonstrated.

  FIG. 10 is a timing chart showing the operation of the lighting device 3 in the present embodiment. Here, signals similar to those in FIG. 8 are shown. However, here, as can be seen from the waveform of “L current (= LED current)”, when the switching element 13 is turned off and the regenerative current starts to flow through the inductor 14, the current value decreases to a preset current value. The time constant or inductance value of the monostable multivibrator 35 is set so that the switching element 13 is turned on and the current flowing through the inductor 14 starts to increase.

  As described above, even in the current mode in the continuous mode in the present embodiment, as in the first and second embodiments, one burst is an integer number of firsts according to the magnitude of the dimming signal. It is composed of a pulse and one second pulse having a pulse width narrower than that of the first pulse. Therefore, compared to the conventional dimming method in which a single burst consists of only an integer number of first pulses, the average current flowing through the LED 15 can be adjusted in finer increments, resulting in smoother dimming. Is done.

  It should be noted that by changing the time constant or the inductance value of the monostable multivibrator 35 in the present embodiment, the current method in the discontinuous mode can be easily realized. That is, the time constant or inductance value of the monostable multivibrator 35 is set larger than the value in the third embodiment. Specifically, when a signal from the comparator 30 is input, a pulse is output to the OR gate 23 after a time larger than the time from the time until the time when the regenerative current becomes zero. The time constant or inductance value of the stable multivibrator 35 is set.

  Accordingly, the control circuit 20b can control the switching element 13 as shown in the timing chart of FIG. That is, after the current flowing through the inductor becomes zero due to regeneration, the current starts to flow through the inductor after a certain period.

  As described above, in the present embodiment as well, in the same way as in the first and second embodiments, the number of the first pulses included in one burst and the first pulses thereof according to the magnitude of the dimming signal. The pulse width of one second pulse subsequent to is adjusted. That is, one burst is composed of an integer number of first pulses and one second pulse having a pulse width narrower than the first pulse. As a result, it is possible to adjust the average current flowing through the LED 15 in finer increments than in the conventional dimming method in which one burst is composed of only an integer number of first pulses. Therefore, according to the present embodiment, as in the first and second embodiments, a lighting device that can adjust light more smoothly than in the past and is suitable for digital control is realized.

  Although the lighting device according to the present invention has been described based on the first to third embodiments, the lighting device according to the present invention can be realized in other forms.

  For example, the lighting device according to the present invention may include an AC-DC converter that converts an AC voltage into a DC voltage or a DC-DC converter that converts a DC voltage into a desired DC voltage (fourth modification).

  FIG. 12 is a circuit diagram of the lighting device 4 according to the fourth modified example. Here, as a DC voltage source for supplying a DC voltage to the lighting device 1 (2, 3) in the first to third embodiments, a DC voltage source constituted by an AC power supply 40, an AC-DC converter 41, and a capacitor 42 is used. It is shown.

  The AC power supply 40 is, for example, an AC 100V commercial power supply. The AC-DC converter 41 is a rectifier circuit such as a diode bridge that converts AC power into DC power and a converter circuit such as a boost chopper. The capacitor 42 is an electrolytic capacitor or the like that smoothes the output voltage from the AC-DC converter 41.

  With the lighting device 4 according to the fourth modified example, a lighting device that operates with an AC power source and can smoothly dim light is realized.

  In the first to third embodiments, the LED 15 is lit by pulse driving using a triangular waveform current, but may be driven by a direct current obtained by smoothing the triangular waveform current (fifth modification). .

  FIG. 13 is a circuit diagram of the lighting device 5 according to the fifth modified example. Here, the lighting device 1 (2, 3) in the first to third embodiments is provided with a capacitor 43 connected in parallel with the LED 15. As a result, the voltage at both ends of the LED 15 is smoothed by the capacitor 43 and the ripple of the load current that can occur when an AC-DC converter is used as the DC voltage source 11 is suppressed.

  Therefore, the lighting device 5 according to the fifth modified example implements a lighting device that can suppress flickering of the light output of the LED 15 and can smoothly adjust the light.

  In the first to third embodiments, the lighting circuit forms a step-down chopper circuit that generates a voltage obtained by stepping down the DC voltage from the DC voltage source 11 and outputs the voltage to the LED 15. It may also be possible (sixth modification).

  FIG. 14 is a circuit diagram of the lighting device 6 according to the sixth modified example. Here, in the lighting circuit of the lighting device 1 (2, 3) in the first to third embodiments, the lighting device 6 including the capacitor 43 connected in parallel with the LED 15 and the lighting circuit constituting the boosting chopper circuit is provided. It is shown.

  That is, in the lighting circuit 10 b of the lighting device 6, the inductor 14 and the switching element 13 are connected in series to the DC voltage source 11. The diode 12 regenerates the energy stored in the inductor 14 when the switching element 13 is off, and supplies the current due to the regeneration to the LED 15 with the inductor 14, the LED 15, and the DC voltage source 11. A loop is formed. The capacitor 43 is connected in parallel with the LED 15. With this connection, in this modification, a voltage obtained by boosting the voltage from the DC voltage source 11 is generated in the capacitor 43, and the boosted voltage is applied to the LED 15.

  Therefore, the lighting device 6 according to the sixth modification realizes a lighting device that can drive the LED 15 with a DC voltage obtained by boosting the DC voltage from the DC voltage source 11 and can smoothly dim the light.

  The configuration of the lighting circuit is not limited to the configuration of the step-down chopper circuit or the step-up chopper circuit, and may be a configuration of a step-up / step-down chopper circuit (seventh modification).

  FIG. 15 is a circuit diagram of the lighting device 7 according to the seventh modified example. Here, the lighting circuit of the lighting device 1 (2, 3) in the first to third embodiments is provided with a capacitor 43 connected in parallel with the LED 15 and a lighting device including a lighting circuit that constitutes a step-up / step-down chopper circuit. 7 is shown.

  That is, in the lighting circuit 10 c of the lighting device 7, the inductor 14 and the switching element 13 are connected in series to the DC voltage source 11. The diode 12 regenerates the energy stored in the inductor 14 when the switching element 13 is off, and forms a circuit loop with the inductor 14 and the LED 15 so as to supply the current due to the regeneration to the LED 15. Yes. The capacitor 43 is connected in parallel with the LED 15. With this connection, in this modification, a voltage obtained by boosting or stepping down the voltage from the DC voltage source 11 is generated in the capacitor 43, and the voltage after stepping up or stepping down is applied to the LED 15.

  Therefore, the lighting device 7 according to the seventh modification realizes a lighting device that can drive the LED 15 with a DC voltage obtained by stepping up or down the DC voltage from the DC voltage source 11 and can smoothly dim the light. .

(Embodiment 4)
Next, the lighting fixture in Embodiment 4 of this invention is demonstrated.

  The lighting fixture in this Embodiment is provided with the lighting device in any one of the said Embodiment 1-3 and a modification.

  (A) of FIG. 16 is a figure which shows an example of the lighting fixture in this Embodiment, ie, the structure of the lighting fixture 8 of the power supply installation type which has arrange | positioned the lighting device 51 separately from the light source part 53. As shown in FIG. The lighting fixture 8 includes a lighting device 51, a light source unit 53, and a lead wire 57 that connects them. Here, a state in which the instrument body 50 that houses the light source unit 53 is embedded in the ceiling 58 is shown. In the following description, the expressions “upper” and “lower” mean the upper direction and the lower direction in FIG.

  The instrument body 50 is made of a metal such as aluminum die casting, for example, and is formed in a bottomed cylindrical shape having an open lower end. A light source unit 53 including a plurality of (three in the drawing) LEDs 15 and a substrate 54 on which each LED 15 is mounted is disposed on the upper bottom portion inside the instrument body 50. Each LED 15 is arranged so that the light irradiation direction is downward in order to irradiate the external space with light from the lower end of the instrument body 50. In addition, a translucent plate 56 for diffusing light from each LED 15 is provided in the opening at the lower end of the instrument body 50. On the back surface (upper surface) of the ceiling 58, the lighting device 51 is disposed at a place different from the fixture body 50. The lighting device 51 and the light source unit 53 are wired with a lead wire 57 via a connector 60.

  The lighting device 51 is a device that houses any one of the lighting devices of the first to third embodiments and the modified examples.

  FIG. 16B is a diagram showing another example of the lighting fixture in the present embodiment, that is, the configuration of the power supply-integrated lighting fixture 9 in which the lighting device 51 is built in the fixture main body 50 together with the light source unit 53. .

  In this configuration, a heat radiating plate 61 made of an aluminum plate or a copper plate is disposed on the upper surface of the substrate 54 in contact with the instrument body 50. Thereby, the heat generated in each LED 15 can be released to the outside through the heat radiating plate 61 and the instrument main body 50.

  As described above, according to the lighting device and the lighting fixture in the embodiment and the modified example, the number of the first pulses included in one burst and the burst for one time according to the magnitude of the dimming signal. The number of second pulses or the pulse width of the second pulses included in the. As a result, it is possible to adjust the average current flowing through the LED 15 in finer increments than in the conventional dimming method in which one burst is composed of only an integer number of first pulses.

  Further, according to the lighting device and the lighting fixture in the embodiment and the modified example, the magnitude of the dimming signal is digitized and stored in the memory 28, and the counter, the timer, and the like are controlled according to the stored digital value. The average current flowing through the LED 15 is adjusted. As a result, a complicated arithmetic circuit design can be avoided by realizing the lighting device according to the present embodiment and the modification using a counter, timer, or interrupt function of a control IC such as a microcomputer.

  As described above, according to the lighting device and the lighting fixture in the above-described embodiment and modification, a lighting device that can adjust light smoothly and is suitable for digital control is realized.

  As mentioned above, although the lighting device and lighting fixture apparatus which concern on this invention were demonstrated based on embodiment and its modification, this invention is not limited to these embodiment and modification. As long as it does not deviate from the gist of the present invention, various modifications conceived by those skilled in the art are applied to the present embodiments and modifications, and forms constructed by combining components in different embodiments and modifications are also included in the present invention. It may be included within the scope of one or more embodiments.

  For example, in the above embodiment, in order to make the pulse width of the second pulse smaller than the pulse width of the first pulse, second on-period Ton2 <first on-period Ton1 or second reference voltage Vref2 <first The relationship of the reference voltage Vref1 was established. However, this relationship is not necessarily required. Even if the magnitude relationship is reversed, the dimming level reading unit 29 takes into account the relationship, and the dimming level reading unit 29 includes the number n of the first pulses that include the dimming signal in one burst and the second on-period Ton2. Alternatively, it may be converted into a numerical value specifying the second reference voltage Vref2. As a result, smooth dimming can be realized as compared with the conventional case in which one burst is composed of only an integer number of first pulses.

  In the first to third embodiments, the number of second pulses or the pulse width of the second pulse included in one burst is changed according to the dimming signal. Both may be changed. Thereby, although the control is slightly complicated, the average current flowing through the LED 15 can be adjusted in finer increments.

  It should be noted that which of the number of second pulses and the pulse width is adjusted according to the dimming signal may be selected and determined as appropriate. Also, which of the first pulse and the second pulse is output first may be selected and determined as appropriate. In addition, which of the current modes (critical mode / continuous mode / discontinuous mode) to employ may be selected and determined as appropriate. The configuration of the lighting circuit (step-down chopper circuit / step-up chopper circuit / step-up / step-down chopper circuit) may be selected and determined as appropriate. Further, the presence or absence of a converter circuit (AC-DC converter / DC-DC converter) may be selected and determined as appropriate. The presence or absence of a capacitor that smoothes the voltage applied to the LED 15 may also be selected and determined as appropriate. Furthermore, you may implement | achieve various forms of lighting devices and a lighting fixture using the same by combining what was selected arbitrarily from each selection matter.

  INDUSTRIAL APPLICABILITY The present invention can be used as a lighting device for lighting a solid light emitting element such as a light emitting diode and an organic EL element and a lighting fixture using the lighting device, for example, a lighting fixture embedded in a ceiling.

DESCRIPTION OF SYMBOLS 1-7 Lighting device 8, 9 Lighting fixture 10, 10a-10c Lighting circuit 11 DC voltage source 12 Diode 13 Switching element 14 Inductor 15 LED
20, 20a, 20b Control circuit 21 Drive circuit 22 RS flip-flop 23 OR gate 24 Zero current detection circuit 25 Ton timer 26 Pulse number counter 27 Burst timer 28 Memory 29 Dimming level reading unit 30 Comparator 31 Reference voltage generation unit 32 Resistance 35 Monostable Multivibrator 40 AC Power Supply 41 AC-DC Converter 42, 43 Capacitor 50 Appliance Main Body 51 Lighting Device 53 Light Source Unit 54 Substrate 56 Translucent Plate 57 Lead Wire 58 Ceiling 60 Connector 61 Heat Sink

Claims (10)

A lighting device for lighting a solid state light emitting element with brightness according to a dimming signal,
A current that flows through the solid-state light emitting element, including an inductor and a switching element connected in series with a DC voltage as an input, and a diode for regenerating energy stored in the inductor when the switching element is off A lighting circuit that generates
A control circuit for controlling the switching element by repeatedly outputting a burst, which is a train of pulses for turning on the switching element, at a constant period;
The burst includes a first pulse having a pulse width of a first on period for turning on the switching element and a second pulse having a pulse width of a second on period for turning on the switching element,
The control circuit controls the number of the first pulses included in one burst and the number of the second pulses or the pulse width of the second pulses according to the dimming signal. The control circuit includes:
A burst timer for determining the fixed period;
A first memory circuit for storing the number of the first pulses determined according to the dimming signal;
A second memory circuit for storing the number or pulse width of the second pulse determined according to the dimming signal;
A burst for one time composed of the number of the first pulses stored in the first memory circuit and the number of the second pulses stored in the second memory unit or the pulse width is generated and generated. The lighting device according to claim 1, further comprising: a pulse generation circuit that repeatedly outputs the burst at a period determined by the burst timer. The lighting device according to claim 1, wherein the second on-period is smaller than the first on-period. The lighting device according to claim 3, wherein the control circuit outputs the second pulse after outputting the first pulse to the switching element in one burst. The lighting device according to claim 3, wherein the control circuit outputs the first pulse after outputting the second pulse to the switching element in one burst of the burst. The number of the second pulses included in one burst is 1,
6. The control circuit according to claim 1, wherein the control circuit controls the number of the first pulses and the pulse width of the second pulse included in one burst according to the dimming signal. The lighting device described. The control circuit controls the number of the first pulses included in one burst and the number of the second pulses included in one burst according to the dimming signal. The lighting device according to any one of 5. The lighting device according to claim 1, further comprising an AC-DC converter or a DC-DC converter that generates the DC voltage. The DC voltage is an output of an AC-DC converter,
The lighting device according to claim 1, wherein the control circuit repeatedly outputs the burst at a frequency of 600 Hz or a multiple of 600 Hz.   A lighting fixture comprising the lighting device according to any one of claims 1 to 9.

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