JP2016162654A - Lighting device and luminaire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting device that has a broad lighting control range and suppress flicker and wobble of output current at a light controlling transition period.SOLUTION: A lighting device 1 for supplying current to a solid light-emitting element (LED2) has a full-wave rectification circuit 19, a buck-boost type DC/DC converter 20 to which full-wave-rectified current is supplied from the full-wave rectification circuit 19 and which has a switching element 14, and a control circuit 10 for performing on and off control on the switching element 14. The control circuit 10 controls the switching element 14 in a current critical mode when the effective value of the output current is adjusted to a predetermined threshold value or more, controls the switching element 14 in a discontinuous mode when the effective value of the output current is adjusted to a value less than the threshold value, and changes the switching frequency discontinuously so that the effective value of the output current varies continuously when the control mode of the switching element 14 is switched between the current critical mode and the discontinuous mode.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a lighting device for supplying a current to a solid-state light emitting element such as an LED (Light Emitting Diode) and a lighting fixture using the same.

  LEDs are used as light sources for lighting devices and the like because of their high efficiency and long life. In an illuminating device using an LED, a dimming method is generally used in which the light output is adjusted by adjusting the magnitude of a current supplied to the LED. As a lighting device capable of adjusting the magnitude of the current supplied to the LED, a lighting device using a step-up / step-down DC / DC converter such as a SEPIC (Single Ended Primary Inverter Converter) circuit has been proposed (for example, Patent Document 1). . For example, by inputting the output voltage of the full-wave rectifier circuit to a step-up / step-down DC / DC converter, it is possible to improve the power factor and realize a dimmable lighting device.

JP 2012-221700 A

  In a step-up / step-down DC / DC converter such as a SEPIC circuit, the magnitude of the output current is adjusted using a continuous mode in which current is continuously output or a discontinuous mode having a period in which no current is output.

  When the current critical mode, which is an example of the continuous mode, is used, the output current is reduced by shortening the switching period of the step-up / step-down DC / DC converter. However, it is difficult to set the switching period to a predetermined value (for example, about 500 nsec) or less due to a delay time in a control circuit that controls the DC / DC converter. For this reason, in the DC / DC converter using the current critical mode, the output current cannot be adjusted to a predetermined current or less. In other words, the dimming width is narrow in the current critical mode.

  On the other hand, when the discontinuous mode is used, the length of the period for outputting the current and the length of the period for not outputting the current can be freely adjusted. The output current can be adjusted to a small value. However, in the discontinuous mode, even if it is attempted to continuously adjust the output current of the DC / DC converter by continuously changing the current output period, the magnitude of the output current flickers and fluctuates. Therefore, the output current cannot be adjusted continuously. This is because the output current oscillates freely during a period in which no current is output, and the magnitude of the output current varies according to the phase of the free oscillation at the moment when the output of the current is resumed.

  The present invention has been made to solve such a problem, and a lighting device having a wide range of dimming and capable of suppressing flickering and rattling of an output current in a dimming transition period, and It aims at providing the lighting fixture using it.

  In order to achieve the above object, an aspect of the lighting device according to the present invention includes a full-wave rectifier circuit that full-wave rectifies an alternating current supplied from an AC power supply, and a full-wave rectified current from the full-wave rectifier circuit. A step-up / step-down DC / DC converter that is supplied and includes a switching element, and a control circuit that controls on and off of the switching element. The control circuit controls the switching element in the current critical mode when the effective value of the output current from the DC / DC converter is adjusted to a value equal to or greater than a predetermined threshold value. On the other hand, when the effective value of the output current is adjusted to a value less than the threshold value, the switching element is controlled in the discontinuous mode. Further, the control circuit discontinuously changes the switching frequency of the switching element so that the effective value of the output current is continuously changed when the control mode of the switching element is switched between the current critical mode and the discontinuous mode. To change.

  According to the present invention, it is possible to provide a lighting device that has a wide range of dimming and that can suppress flickering and rattling of an output current in a dimming transition period, and a lighting fixture using the same.

It is a circuit diagram of the lighting device which concerns on embodiment, and a lighting fixture provided with the same. It is the circuit diagram which extracted the principal part of the DC / DC converter which concerns on embodiment. It is a graph which shows the outline | summary of the time waveform of the electric current which flows into the switching element in the case of being controlled by the current critical mode of the DC / DC converter which concerns on embodiment. It is a graph which shows an example of the time waveform of the electric current which flows into each element of the DC / DC converter which concerns on embodiment. It is a graph which shows an example of the time waveform of the electric current which flows into the switching element of the lighting device which concerns on embodiment. It is a graph which shows another example of the time waveform of the electric current which flows into the switching element of the lighting device which concerns on embodiment. It is a graph which shows the relationship between the switching frequency of the switching element of the lighting device which concerns on embodiment, and the effective value of output current.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Each of the embodiments described below shows a preferred specific example of the present invention. Accordingly, the numerical values, shapes, materials, components, arrangement positions and connection forms of components, steps (steps), order of steps, and the like shown in the following embodiments are merely examples and are intended to limit the present invention. is not. Therefore, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims showing the highest concept of the present invention are described as optional constituent elements.

  Each figure is a schematic diagram and is not necessarily illustrated strictly. Moreover, in each figure, the same code | symbol is attached | subjected to the substantially same structure, The overlapping description is abbreviate | omitted or simplified.

(Embodiment)
[Entire configuration of lighting device and lighting apparatus]
First, the whole structure of the lighting device and lighting fixture which concern on embodiment is demonstrated using drawing.

  FIG. 1 is a circuit diagram of a lighting device 1 according to the present embodiment and a lighting fixture 4 having the same. FIG. 1 also shows an AC power supply 3 that supplies an AC current to the lighting device 1.

  As shown in FIG. 1, the lighting fixture 4 according to the present embodiment includes a lighting device 1 and an LED 2.

  The LED 2 is a solid state light emitting element supplied with current from the lighting device 1. Each LED 2 may be composed of a single LED chip, or may be composed of a plurality of LED chips connected in series or in parallel.

  The lighting device 1 is a device that is connected to an AC power source 3 and supplies a current to the LED 2. As shown in FIG. 1, the lighting device 1 includes a full-wave rectifier circuit 19, a DC / DC converter 20, and a control circuit 10.

  The AC power source 3 is a power source that outputs an AC voltage, and is a system power source such as a commercial power source that outputs an AC voltage of 100 V to 242 V, for example.

  The full-wave rectifier circuit 19 is a circuit that full-wave rectifies an alternating current supplied from the AC power supply 3. The full-wave rectifier circuit 19 is composed of, for example, a diode bridge.

  The DC / DC converter 20 is a step-up / step-down type DC / DC converter that is supplied with a full-wave rectified current from the full-wave rectifier circuit 19 and includes the switching element 14. The output current of the DC / DC converter 20 is supplied to the LED 2. In the present embodiment, the DC / DC converter 20 has a SEPIC type configuration. As shown in FIG. 1, in addition to the switching element 14, the DC / DC converter 20 includes a first inductor 11, a second inductor 12, a first capacitor 13, a second capacitor 15, a diode 16, and a third inductor. The capacitor 17 and the resistor 18 are provided.

  A connection mode of each element constituting the DC / DC converter 20 will be described with reference to FIG. As shown in FIG. 1, the first capacitor 13 is connected to the output terminal of the full-wave rectifier circuit 19. The first series circuit 31 in which the first inductor 11 and the switching element 14 are connected in series is connected to the output terminal of the full-wave rectifier circuit 19. A second series circuit 32 in which the second capacitor 15, the diode 16 and the third capacitor 17 are connected in series is connected to both ends of the switching element 14. One end of the second inductor 12 is connected to the connection point between the second capacitor 15 and the diode 16, and the other end is connected to the connection point between the switching element 14 and the third capacitor 17. Further, the voltage output to the third capacitor 17 is applied to the LED 2. The resistor 18 has one end connected to a connection point between the third capacitor 17 and the second inductor 12 and the other end connected to an output terminal on the low potential side of the lighting device 1.

  The switching element 14 is an element that switches based on a signal output from the control circuit 10 (that is, repeats ON and OFF). In the present embodiment, the switching element 14 is configured by an n-channel MOSFET (Metal-Oxide Semiconductor Field-Effect Transistor).

  The control circuit 10 is a circuit that controls on and off of the switching element 14 of the DC / DC converter 20. The control circuit 10 is composed of, for example, a microcomputer. The control circuit 10 includes a terminal DS, a terminal VD, a terminal ZCD, and a terminal FB as input terminals. Further, the control circuit 10 includes a terminal GD as an output terminal.

  The terminal DS is a terminal to which a dimming signal is input from the outside of the lighting device 1. Based on the dimming signal input from the terminal DS, the control circuit 10 controls the switching element 14.

  The terminal VD is a terminal to which the voltage output from the full wave rectifier circuit 19 is input. By controlling the switching element 14 according to the voltage input from the terminal VD, the magnitude of the current supplied to the LED 2 is constant even when the output voltage of the AC power supply 3 is changed from 100 V to 240 V, for example. It can be.

  The terminal ZCD is a terminal to which a signal corresponding to the current flowing through the diode 16 is input. The control circuit 10 detects that the current flowing through the diode 16 has become zero based on the signal input from the terminal ZCD.

  The terminal FB is a terminal to which a signal corresponding to the current flowing through the LED 2 is input. In the present embodiment, a voltage applied to the resistor 18 is used as the signal. Based on the signal input from the terminal FB, the control circuit 10 feedback-controls the switching element 14 so that the magnitude of the current flowing through the LED 2 becomes a value corresponding to the dimming signal.

  The terminal GD is a terminal for outputting a control signal to the switching element 14. The control circuit 10 adjusts the output current from the lighting device 1 by adjusting the timing at which the switching element 14 is turned on and off.

[Basic operation of lighting device]
Next, the basic operation of the lighting device 1 will be described with reference to the drawings.

  FIG. 2 is a circuit diagram in which main parts of the DC / DC converter 20 according to the present embodiment are extracted.

  FIG. 3 is a graph showing an outline of a time waveform of the current I14 flowing through the switching element 14 when the DC / DC converter 20 according to the present embodiment is controlled in the current critical mode. In FIG. 3, the current I16 flowing through the diode 16 is also indicated by a broken line.

  In the circuit shown in FIG. 2, the input voltage, the input current, the output voltage, and the output current are denoted as V1, I1, V2, and I2, respectively. Hereinafter, an outline of the operation of the DC / DC converter 20 when controlled in the current critical mode will be described.

  When the DC / DC converter 20 is controlled in the current critical mode, the current I14 flowing through the switching element 14 changes with time as shown by the solid line waveform shown in FIG. The dotted line shown in FIG. 3 shows the outline of the time waveform of the input voltage V1, and is sinusoidal as shown in FIG. Specifically, the operation in the current critical mode will be described. When the switching element 14 is in the ON state, a current flows from the first inductor 11 and the second capacitor 15 to the switching element 14. The flowing current I14 increases. When the switching element 14 is on, a reverse bias is applied to the diode 16 and no current flows through the diode 16. However, also in this case, a current is output from the DC / DC converter 20 as the third capacitor 17 is discharged.

  On the other hand, when the switching element 14 is switched to the off state after the predetermined on-time Ton has elapsed, the first inductor 11 and the second inductor 12 output current, so that the switching element 14 is turned on. Release the energy stored during the state. As a result, a current flows from the second inductor 12 to the diode 16. The current I16 flowing through the diode 16 changes in a time waveform as shown by a broken line in FIG. 3, and decreases as the energy stored in the second inductor 12 decreases. When the control circuit 10 detects that the current I16 flowing through the diode 16 has become zero, the control circuit 10 outputs a signal for turning on the switching element 14. When the switching element 14 is in an off state, the DC / DC converter 20 outputs a current obtained by smoothing the current flowing through the diode 16.

  In the current critical mode, the control circuit 10 repeats the operation of controlling the switching element 14 on and off as described above. As a result, the current waveforms of the currents I14 and I16 flowing through the switching element 14 and the diode 16, respectively, are sawtooth as shown in FIG.

  Next, the operation in each case where the DC / DC converter 20 is controlled in the current critical mode and the discontinuous mode will be described in detail with reference to the drawings.

  FIG. 4 is a graph showing an example of a time waveform of a current flowing through each element of the DC / DC converter 20 according to the present embodiment. In FIG. 4, currents I11, I12, and I14 flowing through the first inductor 11, the second inductor 12, and the switching element 14 are shown. In FIG. 4, the current I16 flowing through the diode 16 is also shown by a broken line. In FIG. 4, the effective value of the current flowing through the first inductor 11 and the second inductor 12 is indicated by a one-dot chain line. FIG. 4 shows an example of a time waveform when the DC / DC converter 20 is controlled in the discontinuous mode.

  Regardless of the mode in which the DC / DC converter 20 is controlled, if the switching element 14 is in the ON state, the first inductor 11 and the second inductor 12 are respectively connected as shown in FIG. The flowing currents I11 and I12 increase. During this time, a current I14 corresponding to the sum of the currents I11 and I12 flows through the switching element 14.

  The switching element 14 is maintained in the on state for the on time Ton and then switched to the off state by the control circuit 10. When the switching element 14 is in an off state, each inductor outputs a current, thereby releasing energy stored when the switching element 14 is in an on state. During this time, the currents I11 and I12 decrease from the peak current values Ip1 and Ip2, respectively. Further, since the current output from the second inductor 12 flows through the diode 16, the current I16 flowing through the diode 16 also decreases in the same manner as the current flowing through the second inductor 12 (the broken line time waveform shown in FIG. 4). reference).

  Here, when the DC / DC converter 20 is controlled in the current critical mode, as described above, when the control circuit 10 detects that the current I16 flowing through the diode 16 becomes zero, the control circuit 10 The signal which turns 14 into an ON state is output. Thereafter, similarly, the DC / DC converter 20 repeats the operations in the above-described on state and off state. That is, when the time required for the current I16 to become zero from the time when the switching element 14 is switched to the off state is Toff1, the switching period T1 in the current critical mode is the sum of the on time Ton and the off time Toff1. Become.

  On the other hand, when the DC / DC converter 20 is controlled in the discontinuous mode, the control circuit 10 switches the switching element 14 until the predetermined time Toff2 has elapsed even after the current I16 flowing through the diode 16 becomes zero. Keep it off. After the current I16 becomes zero, the magnitudes of the currents I11 and I12 flowing through the first inductor 11 and the second inductor 12, respectively, are predetermined values (Ib and -Ib in the example shown in FIG. 4). Vibrates around the center. FIG. 4 does not show the state of current oscillation. As described above, in the discontinuous mode, the OFF time Toff (= Toff1 + Toff2) of the switching element 14 is longer than the time Toff1 required until the current I16 becomes zero after the switching element 14 is switched to the OFF state. Is long. The switching period T in the discontinuous mode is the sum of the on time Ton and the off time Toff.

  Subsequently, a current value flowing through each element of the DC / DC converter 20 will be described in detail. In the example shown in FIG. 4, when the switching element 14 is in the on state, the current I11 flowing through the first inductor 11 increases from the current value Ib to the current value Ip1. Further, the increase amount Ipp1 (= Ip1-Ib) of the current I11 is expressed by the following formula 1.

  Here, L1 is the inductance of the first inductor 11, Ton is the ON time of the switching element 14, and Toff1 is the time from when the switching element 14 is switched to the OFF state until the current flowing through the diode 16 becomes zero. The time required is shown respectively.

  Similarly, when the switching element 14 is in the ON state, the current I12 flowing through the second inductor 12 increases from the current value −Ib to the current value Ip2. Here, the increase amount Ipp2 (= Ip2 + Ib) of the current I12 is expressed by the following equation 2.

  Here, L2 represents the inductance of the second inductor 12. Further, as described above, the current I14 flowing through the switching element 14 is equal to the sum of the currents flowing through the first inductor 11 and the second inductor 12, respectively. Therefore, the maximum value of the current I14 flowing through the switching element 14 can be expressed as Ipp1 + Ipp2.

[Lighting device control mode switching operation]
Subsequently, the control mode switching operation of the lighting device 1 according to the present embodiment will be described. In the present embodiment, the control circuit 10 controls the switching element 14 in the current critical mode when the effective value Ioeff of the output current from the DC / DC converter 20 is adjusted to a value equal to or higher than a predetermined threshold value Ith. To do. On the other hand, when the effective value Ioeff of the output current is adjusted to a value less than the threshold value Ith, the control circuit 10 controls the switching element 14 in the discontinuous mode. Further, when switching the control mode of the switching element 14 between the current critical mode and the discontinuous mode, the switching frequency f of the switching element 14 is discontinuously changed so that the effective value Ioeff of the output current is continuously changed. To change. Hereinafter, the control mode switching operation will be described with reference to the drawings.

  FIG. 5 is a graph showing an example of a time waveform of the current I14 flowing through the switching element 14 of the lighting device 1 according to the present embodiment. In FIG. 5, the current I16 flowing through the diode 16 is also shown by a broken line. In FIG. 5, the effective value Ioeff of the output current of the lighting device 1 is indicated by a one-dot chain line. As can be seen from the effective value Ioeff of the output current shown in FIG. 5, (a) to (d1) in FIG. 5 are cases where the lighting device 1 is operated to have different output currents (that is, dimming degrees). Current waveform is shown. Further, the output current decreases in order from (a) to (d1) in FIG. 5 (that is, the dimming degree increases).

  In the lighting device 1 according to the present embodiment, when the effective value Ioeff of the output current is equal to or greater than the threshold value Ith, as shown in FIGS. The switching element 14 of the DC converter 20 is controlled in the current critical mode. In the current critical mode, the control circuit 10 adjusts the output current by adjusting the on-time Ton of the switching element 14.

  On the other hand, in the lighting device 1 according to the present embodiment, when the effective value Ioeff of the output current is less than the threshold value Ith, as shown in (c) and (d1) of FIG. The switching element 14 of the DC / DC converter 20 is controlled in a discontinuous mode. In the example shown in FIG. 5, the control circuit 10 adjusts the on-time Ton of the switching element 14 while maintaining the switching period in the discontinuous mode at a constant value (Tc). The effective value Ioeff of is adjusted.

  The method for adjusting the output current in the discontinuous mode is not limited to this. Another method for adjusting the output current in the discontinuous mode will be described with reference to the drawings.

  FIG. 6 is a graph showing another example of a time waveform of the current I14 flowing through the switching element 14 of the lighting device 1 according to the present embodiment. In FIG. 6, as in FIG. 5, the current I16 flowing through the diode 16 is indicated by a broken line, and the effective value Ioeff of the output current of the lighting device 1 is indicated by a one-dot chain line. As can be seen from the effective value Ioeff of the output current shown in FIG. 6, the lighting device 1 is operated so as to have different output currents (that is, dimming degrees) in (c) and (d2) of FIG. The current waveform for the case is shown. In addition, the output current is smaller in the case of (d2) than in the case of (c) in FIG. 6 (that is, the dimming degree is deeper).

  In the example shown in FIG. 6, the control circuit 10 adjusts the effective value Ioeff of the output current by adjusting the switching period while keeping the ON time Ton of the switching element 14 constant. In the example shown in (d) of FIG. 6, the control circuit 10 sets the effective value Ioeff of the output current of (c) by setting the switching period to a switching period Td2 longer than the switching period Tc in the case of (c). It is reduced from the case.

  Note that the output current control method in the discontinuous mode of the control circuit 10 is not limited to the method described above. For example, the control circuit 10 may adjust the effective value of the output current by adjusting both the switching period and the on-time Ton.

  Next, the operation at the time of switching the control mode of the lighting device 1 will be described with reference to the drawings.

  FIG. 7 is a graph showing the relationship between the switching frequency f of the switching element 14 of the lighting device 1 according to the present embodiment and the effective value Ioeff of the output current. FIG. 7 also shows a human audible range (about 20 Hz to 20 kHz) and an infrared communication band (about 35 kHz to 40 kHz) used for a remote control or the like.

  First, the case where the lighting device 1 decreases the effective value Ioeff of the output current from the maximum value to the threshold value Ith will be described. As indicated by the straight line from point A to point B in FIG. 7, the control circuit 10 of the lighting device 1 increases the switching frequency f while controlling the switching element 14 in the current critical mode, thereby increasing the output current. The effective value Ioeff is decreased. As described above, the lighting device 1 controls the switching element 14 in the current critical mode when the effective value Ioeff of the output current is equal to or greater than the threshold value Ith. Flicker can be suppressed.

  Next, a case where the lighting device 1 decreases the effective value Ioeff of the output current from the threshold value Ith to less than the threshold value Ith will be described. As described above, the control circuit 10 switches the control mode from the current critical mode to the discontinuous mode. Here, when the control mode is switched between the current critical mode and the discontinuous mode, as shown by the points B and C in FIG. 7, the switching is performed so that the effective value of the output current is continuously changed. The switching frequency of the element 14 is changed discontinuously. Accordingly, the effective value Ioeff of the output current of the lighting device 1 continuously changes even in the dimming transition period in which the dimming degree from the point B to the point C in FIG. 7 is changed.

  When the lighting device 1 changes the effective value Ioeff of the output current below the threshold value Ith, for example, as shown by the straight line from the point C to the point D1 in FIG. The output current is reduced by shortening (see the above-mentioned matters for (c) and (d1) in FIG. 5). Further, as indicated by a broken line from point C to point D2 in FIG. 7, the output current may be decreased by increasing the switching frequency f while keeping the on-time Ton constant (the matters described above with reference to FIG. 6). See). As described above, when the effective value Ioeff of the output current of the lighting device 1 is changed below the threshold value Ith, the DC / DC converter 20 is controlled in the discontinuous mode, which is deeper than in the case of controlling in the current critical mode. Dimming is possible.

  Here, a method for changing the switching frequency discontinuously so as to continuously change the effective value of the output current will be described. In the current critical mode, the effective value Ioeff1 of the output current of the lighting device 1 is expressed by the following expression 3.

  Here, Vac and Lc in Equation 3 above represent the effective voltage value of the AC power supply 3 and the combined inductance of the first inductor 11 and the second inductor 12, respectively. The combined inductance Lc is expressed by the following expression 4.

  A is represented by the following formula 5.

  Here, Voeff represents an effective value of the output voltage of the lighting device 1.

  On the other hand, in the discontinuous mode, the effective value Ioeff2 of the output current of the lighting device 1 is expressed by the following expression 6.

  Here, η indicates the circuit efficiency (output power / input power) of the DC / DC converter 20.

  From the above equations 3 to 6, parameters (on time Ton and switching period T) when the control mode is switched between the current critical mode and the discontinuous mode can be obtained. For example, when switching from the current critical mode to the discontinuous mode, the effective value Ioeff2 of the output current at the time of switching is substituted into Equation 6, and the on-time Ton and the switching period T are determined so that Equation 6 is satisfied. it can. Since the peak value of the current flowing through the switching element 14 is determined by the on-time Ton, for example, the on-time Ton is determined based on the current resistance characteristics of the switching element 14 and the switching period T corresponding to the on-time Ton is set. It can be determined from Equation 6. Further, by setting the on-time Ton to be equal to or less than the maximum value of the on-time Ton used in the current critical mode, it is possible to suppress the current resistance characteristics required for the switching element 14. That is, the withstand current characteristic required for the switching element 14 can be made comparable to the withstand current characteristic of the switching element used in the SEPIC type DC / DC converter controlled only in the current critical mode.

  Conversely, when switching from the discontinuous mode to the current critical mode, the on-time Ton can be determined by substituting the effective value Ioeff1 of the output current at the time of the switching into Equation 3.

  Further, the band of the switching frequency f is close to the infrared communication band as shown in FIG. When the switching frequency f is in the infrared communication band, the lighting device 1 may generate noise that adversely affects infrared communication used by a remote controller or the like. Therefore, as shown in FIG. 7, when the effective value Ioeff of the output current is equal to or greater than the threshold value Ith, the control circuit 10 sets the switching frequency f to a frequency larger than the infrared communication band. On the other hand, when the effective value Ioeff of the output current is less than the threshold value Ith, the control circuit 10 sets the switching frequency f to a frequency less than the infrared communication band.

  Further, the switching frequency f is close to the audible range. When the switching frequency f is in the audible range, the lighting device 1 sounds. Therefore, as shown in FIG. 7, the control circuit 10 sets the switching frequency f to a frequency higher than the audible range.

[Effects, etc.]
As described above, the lighting device 1 according to the present embodiment is supplied with the full-wave rectifier circuit 19, the full-wave rectified current from the full-wave rectifier circuit 19, and the step-up / step-down DC having the switching element 14. / DC converter 20 and control circuit 10 are provided. When the effective value Ioeff of the output current from the DC / DC converter 20 is adjusted to a value equal to or greater than a predetermined threshold value Ith, the control circuit 10 controls the switching element 14 in the current critical mode. On the other hand, when the effective value Ioeff of the output current is adjusted to a value less than the threshold value Ith, the switching element 14 is controlled in the discontinuous mode. Further, the control circuit 10 switches the switching frequency of the switching element 14 so as to continuously change the effective value Ioeff of the output current when the control mode of the switching element 14 is switched between the current critical mode and the discontinuous mode. Is changed discontinuously.

  Thereby, in the lighting device 1, when the effective value Ioeff of the output current is less than the threshold value Ith, the control circuit 10 controls the switching element 14 in the discontinuous mode, so that deep dimming can be realized. That is, in the lighting device 1, the range of dimming can be widened. In the lighting device 1, when the effective value Ioeff of the output current is equal to or greater than the threshold value Ith, the control circuit 10 controls the switching element 14 in the current critical mode. Suppression can be suppressed.

  In the lighting device 1 according to the present embodiment, the DC / DC converter 20 includes the first capacitor 13, the second capacitor 15, the third capacitor 17, the first inductor 11, and the second capacitor. The inductor 12 and the diode 16 are further provided. The first capacitor 13 is connected to the output terminal of the full-wave rectifier circuit 19. The first series circuit 31 in which the first inductor 11 and the switching element 14 are connected in series is connected to the output terminal of the full-wave rectifier circuit 19. A second series circuit 32 in which the second capacitor 15, the diode 16 and the third capacitor 17 are connected in series is connected to both ends of the switching element 14. One end of the second inductor 12 is connected to the connection point between the second capacitor 15 and the diode 16, and the other end is connected to the connection point between the switching element 14 and the third capacitor 17. Further, the voltage output to the third capacitor 17 is applied to the LED 2.

  Moreover, in the lighting device 1 according to the present embodiment, the control circuit 10 may set the switching frequency f to a frequency larger than the infrared communication band when the effective value Ioeff of the output current is equal to or greater than the threshold value Ith. In addition, when the effective value Ioeff of the output current is less than the threshold value Ith, the control circuit 10 may set the switching frequency f to a frequency less than the infrared communication band.

  Thereby, the bad influence with respect to the infrared communication by the noise which generate | occur | produces from the lighting device 1 can be suppressed.

  Moreover, in the lighting device 1 according to the present embodiment, the control circuit 10 may set the switching frequency f to a frequency higher than the audible range.

  Thereby, it can suppress that the lighting device 1 sounds.

(Variations, etc.)
As mentioned above, although the lighting device and lighting fixture which concern on this invention were demonstrated based on embodiment, this invention is not limited to these embodiment.

  For example, in the above embodiment, the SEPIC type DC / DC converter is used as the step-up / step-down type DC / DC converter, but the invention is not limited to this. For example, a flyback type DC / DC converter may be used.

  Further, in the above embodiment, the configuration for controlling the on-time Ton of the switching element 14 based on the signal corresponding to the current flowing through the LED 2 is used. It is not limited to. For example, since the output current of the lighting device 1 depends on the input voltage to the DC / DC converter 20 as understood from the above formulas 1 and 2, the switching current is switched based on the detected value of the input voltage. The on-time of the element 14 may be controlled.

  In each of the above embodiments, the LED 2 is used as the solid light emitting element, but an organic EL (Electro-Luminescence) element may be used.

  In addition, the present invention can be realized by various combinations conceived by those skilled in the art for each embodiment, or by arbitrarily combining the components and functions in each embodiment without departing from the spirit of the present invention. This form is also included in the present invention.

1 lighting device 2 LED (solid state light emitting device)
3 AC power supply 4 Lighting fixture 10 Control circuit 11 First inductor 12 Second inductor 13 First capacitor 14 Switching element 15 Second capacitor 16 Diode 17 Third capacitor 19 Full wave rectifier circuit 20 DC / DC converter 31 First series circuit 32 Second series circuit

Claims (5)

A lighting device that is connected to an AC power source and supplies current to a solid state light emitting device,
A full-wave rectification circuit for full-wave rectification of an alternating current supplied from the alternating-current power supply;
A step-up / step-down DC / DC converter that is supplied with a full-wave rectified current from the full-wave rectifier circuit and includes a switching element;
A control circuit for controlling on and off of the switching element,
The control circuit controls the switching element in a current critical mode when the effective value of the output current from the DC / DC converter is adjusted to a value equal to or greater than a predetermined threshold value, and the effective value of the output current is controlled. Is adjusted to a value less than the threshold, the switching element is controlled in a discontinuous mode, and when the control mode of the switching element is switched between the current critical mode and the discontinuous mode, A lighting device that discontinuously changes a switching frequency of the switching element so as to continuously change an effective value of the output current. The DC / DC converter is
A first capacitor, a second capacitor, a third capacitor, a first inductor, a second inductor, and a diode;
The first capacitor is connected to an output terminal of the full-wave rectifier circuit,
The first series circuit in which the first inductor and the switching element are connected in series is connected to the output terminal of the full-wave rectifier circuit,
A second series circuit in which the second capacitor, the diode, and the third capacitor are connected in series is connected to both ends of the switching element,
The second inductor has one end connected to a connection point between the second capacitor and the diode, and the other end connected to a connection point between the switching element and the third capacitor,
The lighting device according to claim 1, wherein a voltage output to the third capacitor is applied to the solid state light emitting device. The control circuit includes:
If the effective value of the output current is greater than or equal to the threshold, the switching frequency is set to a frequency greater than the infrared communication band,
The lighting device according to claim 1, wherein when the effective value of the output current is less than the threshold, the switching frequency is set to a frequency less than an infrared communication band. The lighting device according to claim 1, wherein the control circuit sets the switching frequency to a frequency larger than an audible range. The lighting device according to any one of claims 1 to 4,
A lighting fixture comprising the solid-state light emitting element.

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