JP2012195252A - Lighting device and lighting fixture using the lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting device which suppresses electrical stress applied to a light source at the time of intermittent lighting, and a lighting fixture using the lighting device.SOLUTION: Even during a period T1 when the light source is turned off in the intermittent lighting operation, a turning-off voltage V1 has the same direction as that of a lighting voltage V2 outputted when the light source is turned on, and also has a voltage value low in such a degree that no current flows to the light source. Since a capacity component of the light source is charged in advance by this turning-off voltage V1, an inrush current generated when the light source is started to be turned on is suppressed and the electrical stress applied to the light source is suppressed as compared to a case where an input voltage Vx to the light source during the period T1 is made 0 V.

Description

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

  Conventionally, there has been provided an illumination device that can change the light output of the light source (the time average value of the luminous flux, the amount of light per unit time) by changing the on-duty when the light source is intermittently lit (for example, Patent Document 1). The frequency of the intermittent lighting is set to a sufficiently high frequency that the blinking of the light source cannot be recognized by human eyes.

  In the illumination device as described above, when a light source that is lit by DC power, such as an organic EL element or a light emitting diode element, is used as a light source, a voltage input to the light source (hereinafter referred to as a “load voltage”). .) Vx and the current (hereinafter referred to as “load current”) current Ix input to the light source are rectangular waves as shown in FIG.

  Conventionally, during the intermittent lighting, the load voltage Vx is set to a constant value high enough to turn on the light source during a period (hereinafter referred to as “on period”) T2 during which the light source is turned on, and the light source is turned off. During the period (hereinafter referred to as “off period”) T1, the load voltage Vx was set to 0V.

JP 2007-265805 A

  However, when the load voltage Vx is set to 0 V during the off period T1 as described above, the load current Ix becomes relatively large due to the inrush current immediately after the start of the on period T2, so that the electrical stress applied to the light source is reduced. It tends to be relatively large. Examples of the inrush current include a charging current for charging a capacitance component of the light source.

  The present invention has been made in view of the above-described reasons, and an object thereof is to provide an illuminating device that can suppress electrical stress applied to a light source during intermittent lighting and a luminaire using the illuminating device. .

  The illumination device of the present invention includes a light source that is turned on when a DC voltage is input, and a lighting unit that is capable of intermittent lighting operation for intermittently lighting the light source, and the lighting unit turns the light source on in the intermittent lighting operation. Even during the light-off period, the light-off voltage is output in the same direction as the light-up voltage output when turning on the light source, and the light-off voltage is low enough to prevent current from flowing through the light source. To do.

  In this illuminating device, the extinguishing voltage may be the highest voltage in a range where no current flows through the light source.

  Further, in the above illumination device, the lighting unit includes a power source during extinguishing that continuously outputs the voltage for extinguishing to the light source, and a lighting unit that intermittently outputs the voltage for lighting to the light source. You may have a power supply.

  Furthermore, in the above-described lighting device, the lighting power source may make the output current constant during a period in which the light source is turned on in the intermittent lighting operation.

  Alternatively, in the illumination device described above, the lighting unit may include a single switching power supply that can switch an output voltage.

  In the illumination device, the lighting unit may change a duration of a period during which the light source is lit in the intermittent lighting operation, and a duration of a period during which the light source is lit in the intermittent lighting operation. The shorter the is, the higher the turn-off voltage may be.

  Furthermore, in the above-described lighting device, the lighting unit may vary a lighting voltage output to the light source during a period of lighting the light source in the intermittent lighting operation, and the lower the lighting voltage is, the lower the lighting voltage is. The extinguishing voltage may be lowered.

  In the illumination device, the lighting unit may change the intermittent lighting cycle, and may lower the extinguishing voltage as the intermittent lighting cycle is longer.

  Furthermore, in the illumination device, the light source includes one or more light emitting elements, the number of light emitting elements constituting the light source is variable, and the number of light emitting elements connected between the output terminals of the lighting unit. The lighting unit may be configured to lower the turn-off voltage as the number of light emitting elements detected by the number detecting unit is smaller.

  Further, in the above-described illumination device, the lighting device further includes a surge detection unit that detects a temporary increase width of the output current of the lighting unit immediately after the lighting of the light source is started, and the lighting unit is detected by the surge detection unit. The turn-off voltage may be changed as needed so that the rising width falls within a predetermined range.

  Furthermore, in the above illumination device, the light source may include one or more organic EL elements.

  The lighting fixture of the present invention includes any one of the lighting devices described above and a fixture main body that holds the lighting device.

  According to the present invention, since the capacitance component of the light source is charged in advance by the extinguishing voltage during the period when the light source is extinguished in the intermittent lighting operation, compared with a case where no voltage is output to the light source during the period when the light source is extinguished. Inrush current at the start of lighting of the light source is suppressed, and electrical stress applied to the light source is suppressed.

It is explanatory drawing which shows the example of the waveform of the negative overvoltage Vx and the load current Ix in this invention. It is a circuit block diagram which shows the same as the above. It is explanatory drawing which shows an example of the relationship between the negative overvoltage Vx and load current Ix in the same as the above. It is explanatory drawing which shows the example of the waveform of the output voltage Va of the power supply at the time of light extinction same as the above, the output voltage Vb of the power supply at the time of lighting, and the negative overvoltage Vx. It is a circuit block diagram which shows the example of a change same as the above. It is a circuit block diagram which shows the principal part of another example of a change same as the above. It is a circuit block diagram which shows another example of a change same as the above. (A) (b) is a circuit block diagram which shows the light source of another modified example same as the above, (a) shows the state where four light emitting elements are connected, (b) shows the connection of three light emitting elements. Indicates the state that has been performed. It is a circuit block diagram which shows the light source of another modified example same as the above. (A) (b) shows the example of the waveform of the negative overvoltage Vx and the load current Ix in another modification example same as the above, respectively, (b), the duration of the ON period T2 is made longer than (a). The waveform in the state is shown. (A) (b) shows the example of the waveform of the negative overvoltage Vx and the load current Ix in another modification example same as the above, respectively, (b) is a state in which the turn-off voltage V1 is made lower than (a) The waveform at is shown. It is a disassembled perspective view which shows an example of the lighting fixture using the same as the above. It is explanatory drawing which shows the example of the waveform of the negative overvoltage Vx and the load current Ix in a prior art example.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  As shown in FIG. 2, the illumination device of the present embodiment lights a light source 1 that is turned on by DC power. As such a light source 1, for example, a light emitting element such as a light emitting diode element or an organic EL element, or a light emitting diode array or an organic EL array in which a plurality of such light emitting elements are connected can be used.

  Here, the relationship between the load voltage Vx input to the light source 1 and the load current Ix flowing through the light source 1 is shown in FIG. As can be seen from FIG. 3, if the load voltage Vx is less than a predetermined voltage (so-called turn-on voltage) Von, the load current Ix does not flow and does not light up.

  In the present embodiment, the power source 21 at the time of turn-off that continuously outputs a voltage V1 at which the light source 1 is not turned on (hereinafter referred to as “light-off voltage”) V1 to the light source 1 and the light source 1 are turned on. A lighting power source 22 capable of intermittent lighting operation for intermittently outputting a voltage (hereinafter referred to as “lighting voltage”) V2 to the light source 1 is provided. In other words, the lighting unit 2 in the present embodiment includes a power supply 21 when turned off and a power supply 22 when turned on. The turn-off voltage V1 is a positive voltage that is lower than the turn-on voltage Von (that is, the same direction as the voltage that turns on the light source 1), and the turn-on voltage V2 is a voltage that is higher than the turn-on voltage Von (for example, the rating of the light source 1). Voltage). The off-time power supply 21 and the on-time power supply 22 are connected to the light source 1 via backflow prevention diodes D1 and D2, respectively. In other words, the higher one of the output voltage Va of the power supply 21 when turned off and the output voltage Vb of the power supply 21 when turned on is input to the light source 1 and becomes the load voltage Vx. FIG. 4 shows an example of the waveforms of the output voltage Va of the power source 21 when turned off, the output voltage Vb of the lighting light source 22 and the negative overvoltage Vx.

  Furthermore, the present embodiment includes a diode bridge 4 that full-wave rectifies AC power input from an external AC power supply 3 and a capacitor C0 that smoothes the DC output of the diode bridge 4.

  The lighting power source 22 includes a voltage conversion circuit 23 that converts the voltage value of DC power obtained by smoothing the DC output of the diode bridge 4 by the capacitor C0, and a switch Q1 that turns on and off the power supply from the voltage conversion circuit 23 to the light source 1. And a drive circuit 24 for driving the switch Q1. A known semiconductor switch can be used as the switch Q1. As the voltage conversion circuit 23, for example, a known switching power supply such as a buck converter (step-down chopper circuit) can be used.

  That is, the light source 1 is intermittently lit by the drive circuit 24 repeatedly driving the switch Q1 on and off. Further, in the present embodiment, a current detection comprising a resistor Rd connected in series to the light source 1 and an amplifier circuit that inputs a voltage obtained by amplifying the voltage across the resistor Rd (that is, a voltage corresponding to the load current Ix) to the drive circuit 24. Part 25. The drive circuit 24 drives the switch Q1 on and off with an on-duty such that the time average value of the load current Ix is set to a predetermined target value in accordance with the voltage input from the current detection unit 25. Since the drive circuit 24 as described above can be realized by a well-known technique using, for example, a microcomputer, detailed illustration and description thereof are omitted.

  As the light source 21 at the time of extinguishing, a battery or a known switching power source may be used. When a switching power supply is used as the power supply 21 at the time of extinguishing, it is possible to change the extinguishing voltage V1. Further, when a switching power supply is used as the off-time power supply 21, the lighting power supply 22 and the unlit power supply 21 may share power, and the power supply for the unlit power supply 21 is separate from the power supply of the lighting power supply 22. It is good.

  According to the above configuration, as shown in FIG. 1, the negative overvoltage Vx corresponding to the extinguishing voltage V1 is ensured even during the off period T1 when the light source 1 is extinguished, whereby the capacitance component of the light source 1 is charged in advance. Therefore, compared with the case where the negative overvoltage Vx is set to 0 V during the off period T1, the inrush current at the start of the on period T2 is suppressed, and thus the electrical stress applied to the light source 1 is suppressed. In particular, when the light source 1 includes an organic EL element, the above-mentioned effect is also relatively large because the capacitance component of the light source 1 is relatively large.

  By the way, as a method of suppressing the inrush current at the start of the ON period T2, there is a method of inserting a current limiting resistor or an inductor in the power supply path to the light source 1. However, when a current limiting resistor is inserted into the power supply path to the light source 1, power loss due to the current limiting resistor continuously occurs while the light source 1 is turned on. Further, when an inductor is inserted in the power supply path to the light source 1, the rise and fall of the negative overvoltage Vx becomes dull due to the time constant of the inductor. There is a possibility that the proportional relationship between the light output of the light source 1 and the light output of the light source 1 may be impaired, and it becomes difficult to strictly control the light output of the light source 1. In the present embodiment, the power loss can be reduced as compared with the case where a current limiting resistor is inserted in the power supply path to the light source 1, and the light source 1 is compared with the case where an inductor is inserted in the power supply path to the light source 1. Strict control of the light output can be facilitated.

  The drive circuit 24 is not limited to the above, and for example, as shown in FIG. 5, the switch Q1 may be driven to turn on / off in conjunction with a rectangular-wave dimming signal input from the outside. . The dimming signal indicates the light output of the light source 1, and the higher the indicated light output, the higher the on-duty. The drive circuit 24 shown in FIG. 5 achieves insulation between input and output by the photocoupler PC, and drives the switch Q1 with a rectangular-wave drive signal Vg having an H level voltage value set to a predetermined voltage Vcc. .

  In the example of FIG. 5, the output of the current detection unit 25 is input to the voltage conversion circuit 23. The voltage conversion circuit 23 uses the output of the current detection unit 25 during the ON period T2, and the load current Ix The feedback operation is performed so as to keep the constant. That is, the lighting unit 2 keeps the load current (that is, the output current to the light source 1) Ix constant during the on period T2, which is a period during which the light source 1 is lit.

  Further, in the example of FIG. 5, the light source 1 includes a series circuit of four light emitting elements 11. As each light emitting element 11, for example, an organic EL element can be used.

  Here, when the dimming signal is not a rectangular wave as described above but a voltage signal having a voltage value corresponding to the instructed optical output, the drive circuit 24 receives the input voltage as shown in FIG. An appropriate rectangular wave generation circuit 241 that generates an on-duty rectangular wave corresponding to the value may be used. Such a rectangular wave generation circuit 241 is commercially available as an integrated circuit.

  Further, instead of separately providing the light source 21 for turning off and the power source 22 for turning on, the lighting unit 2 may be composed of one switching power source as shown in FIG. The lighting unit 2 in FIG. 7 includes a known buck converter connected between the DC output terminals of the diode bridge 4 that performs full-wave rectification on the input power from the AC power supply 3. That is, the lighting unit 2 in FIG. 7 includes a series circuit of a switching element Q2, an inductor L1, and a capacitor C1 connected between the DC output terminals of the diode bridge 4, and a cathode at a connection point between the switching element Q2 and the inductor L1. A diode D3 having an anode connected to a DC output terminal on the low voltage side of the diode bridge 4 and a drive circuit 26 for repeatedly turning on and off the switching element Q2 are connected, and both ends of the capacitor C1 are output terminals. . The drive circuit 26 performs a feedback operation in which the on-duty of the switching element Q2 is changed as needed so that the output voltage (that is, the voltage across the capacitor C1 and the load voltage Vx) is a predetermined target voltage. The target voltage is the turn-off voltage V1 during the off period T1, and the turn-on voltage V2 during the on period T2. Further, the drive circuit 26 receives a dimming signal that instructs the light output of the light source 1, and increases the on-duty T2 / (T1 + T2) of intermittent lighting as the light output instructed by the dimming signal is higher.

  When the lighting unit 2 is configured by a single switching power supply as shown in FIG. 7, the number of parts is reduced as compared with the case where the light-off power source 21 and the light-up power source 22 are separately provided as shown in FIGS. Manufacturing cost can be reduced. However, in the example of FIG. 7, since a certain time is required for switching between the turn-off voltage V1 and the turn-on voltage V2 due to the time constant of the capacitor C1 or the like, the intermittent turn-on duty T2 / (T1 + T2) The proportional relationship between the light output of the light source 1 may be impaired. On the other hand, when the light-off power source 21 and the light-on power source 22 are separately provided as shown in FIG. 2 and FIG. 5, compared with the example of FIG. Therefore, there is an advantage that the proportional relationship between the on-duty T2 / (T1 + T2) of intermittent lighting and the light output of the light source 1 is not easily lost.

  Further, the number of connected light emitting elements 11 may be changeable. Specifically, for example, each light emitting element 11 is individually detachable using a known connector. When the light emitting elements 11 are connected in series as in the examples of FIGS. 5 and 7, if the number of the light emitting elements 11 is variable as described above, as shown in FIGS. In addition, instead of the removed light emitting element 11, it is necessary to provide each light emitting element 11 with an appropriate switch 12 that constitutes a feeding path to another light emitting element 11. In the above case, the appropriate lighting voltage V2 varies depending on the number of the light emitting elements 11 to be connected. Therefore, at least the lighting voltage V2 needs to be changeable. Specifically, a number detection circuit (not shown) for detecting the number of the light emitting elements 11 is provided, and the voltage conversion circuit 23 and the back converter 26 increase the lighting voltage V2 as the number detected by the number detection circuit increases. To do. The number detection circuit may detect the number of light emitting elements 11 based on the impedances of both ends of the light source 1 or detect the number of switches 12 that are turned off as the number of light emitting elements 11. In any case, since it can be realized by a well-known technique, detailed illustration and description are omitted.

  By the way, from the viewpoint of suppressing the temporary increase width (hereinafter referred to as “surge current value”) Is of the load current Ix immediately after the start of the ON period T2, the turn-off voltage V1 is within a range where the light source 1 is not turned on. It is desirable that the voltage be as high as possible.

  On the other hand, from the viewpoint of suppressing electrical stress applied to the circuit components of the lighting unit 2 and from the viewpoint of suppressing power consumption in the lighting unit 2, it is desirable that the turn-off voltage V1 be as low as possible. At this time, the minimum amount of the turn-off voltage V1 to be secured varies depending on the way of thinking and various conditions. Therefore, a configuration in which the extinguishing voltage V1 is automatically changed may be employed. The change of the turn-off voltage V1 is achieved by changing the target voltage in the drive circuit 26 in the example of FIG. Further, even when the light-off power source 21 and the light-on power source 22 are separately provided as in the example of FIG. 2 and the example of FIG. 5, the direct-current power supply circuit that can change the output voltage Va as the light-off power source 21. If (for example, a well-known switching power supply) is used, the turn-off voltage V1 can be changed.

  Hereinafter, a specific mode of changing the turn-off voltage V1 will be described.

  For example, when a light source 1 having a plurality of light emitting elements 11 connected in series as shown in FIGS. 8A and 8B is used, the number of light emitting elements 11 detected by the number detection circuit is small. It is desirable that the turn-off voltage V1 be lowered in accordance with the decrease in the turn-on voltage Von of the light source 1 as a whole.

  Further, when a light source 1 having a plurality of light emitting elements 11 connected in parallel as shown in FIG. 9 is used, the turn-on voltage Von of the light source 1 as a whole does not change depending on the number of light emitting elements 11. Even if the number of eleven is changed, it is not necessary to change the lighting voltage V2. However, when the number of light emitting elements 11 decreases, the surge current value Is decreases even if the current flowing through each light emitting element 11 does not change. Therefore, if it is desired to reduce the surge current value Is to a certain level or less in order to suppress electrical stress applied to the circuit components of the lighting unit 2, it is desirable to reduce the turn-off voltage V1 as much as possible as shown in FIG. Even when the light emitting elements 11 are connected in parallel to each other, it is desirable that the turn-off voltage V1 be lowered as the number of the light emitting elements 11 decreases.

  Here, in general, the light source 1 that is turned on by DC power has a higher light output (light flux) as the load current Ix increases. Therefore, the greater the surge current value Is, the greater the difference between the actual light output of the light source 1 and the intended light output. If the surge current value Is is constant, the ratio of the actual light output of the light source 1 to the intended light output becomes shorter as the individual on-period (that is, the duration of the lighting state of the light source 1 in intermittent lighting) T2 is shorter. Will become bigger. Therefore, the shorter the individual on-period T2, the higher the minimum turn-off voltage V1 required to keep the above ratio below a certain level. Therefore, as shown in FIGS. 10A and 10B, a configuration in which the lighting unit 2 increases the turn-off voltage V1 as the individual on-period T2 is shorter may be employed. In the example of FIGS. 10A and 10B, the length of each off period T1 is constant, and the light output of the light source 1 is changed only by changing the length of the on period T2. That is, in the example of FIG. 10, the longer the intermittent lighting cycle T1 + T2, the lower the turn-off voltage V1.

  As a method of changing the light output of the light source 1, a method of changing the lighting voltage V2 in addition to a method of changing the on-duty T2 / (T1 + T2) of intermittent lighting is also conceivable. Further, for example, the above two methods are combined such that a rough change of the light output is achieved by changing the on-duty T2 / (T1 + T2) and a fine adjustment of the light output is achieved by changing the lighting voltage V2. It is also possible. When the lighting voltage V2 is changed as described above, the lower the lighting voltage V2, the smaller the surge current value Is. Therefore, the lower the lighting voltage V2, the lower the minimum in order to keep the surge current value Is below a certain level. The necessary turn-off voltage V1 becomes low. Therefore, as shown in FIGS. 11A and 11B, the lighting unit 2 may lower the turn-off voltage V1 as the turn-on voltage V2 is lower.

  Further, a surge detection means (not shown) for detecting the surge current value Is is provided, and the lighting unit 2 sets the turn-off voltage V1 so that the surge current value Is detected by the surge detection means falls within a predetermined range. It may be changed at any time. For example, the lighting unit 2 increases the turn-off voltage V1 if the surge current value Is exceeds the upper limit value of the predetermined range, and turns off the voltage if the surge current value Is is lower than the lower limit value of the predetermined range. Lower V1. Since the surge detecting means as described above can be realized by a well-known technique, detailed illustration and description are omitted.

  The various changes of the turn-off voltage V1 as described above may be continuous changes in which the turn-off voltage V1 is always changed if the conditions are slightly different, or for a condition having a certain range. The step-by-step change may be such that the extinguishing voltage V1 is constant. Moreover, you may combine the said various changes. For example, a configuration may be employed in which the lighting unit 2 employs the lowest one of the lighting voltages V2 determined by a plurality of determination methods. Further, for example, when the lighting voltage V2 is lowered to some extent, the extinguishing voltage V1 may be temporarily set to zero. Of course, in any of the above cases, the upper limit value of the turn-off voltage V1 is set to a value that is low enough that no current flows through the light source 1 (that is, lower than the turn-on voltage Von of the light source 1).

  The lighting unit 2 continuously outputs the lighting voltage V2 to the light source 1 in addition to the intermittent lighting operation according to the input dimming signal or the like (that is, the on-duty is set to 100%). There may be a possibility of performing a continuous lighting operation.

  The various lighting devices described above can be used in a lighting fixture 5 as shown in FIG. The lighting fixture 5 of FIG. 12 includes a case 51 that houses and holds the lighting unit 2 and the diode bridge 4, and a fixture body 50 that holds the case 51 and the four light emitting elements 11 that constitute the light source 1. Since the lighting fixture 5 as described above can be realized by a well-known technique, detailed illustration and description thereof are omitted.

DESCRIPTION OF SYMBOLS 1 Light source 2 Lighting part 5 Lighting fixture 11 Light emitting element 21 Power supply at the time of extinction 22 Power supply at the time of lighting 50 Appliance main body V1 Voltage for extinguishing V2 Voltage for lighting

Claims (12)

A light source that is turned on when a DC voltage is input;
A lighting unit capable of intermittent lighting operation for intermittently lighting the light source,
The lighting unit is a turn-off voltage in the same direction as a turn-on voltage output when turning on the light source even during a period in which the light source is turned off in the intermittent lighting operation, and no current flows through the light source. A lighting device characterized in that it outputs a voltage for extinguishing that is low.   The lighting device according to claim 1, wherein the turn-off voltage is the highest voltage in a range where no current flows through the light source.   The lighting unit includes: a power supply for extinguishing that continuously outputs the voltage for extinguishing to the light source; and a power source for lighting that intermittently outputs the voltage for lighting to the light source. The lighting device according to claim 1 or 2.   The lighting device according to claim 3, wherein the lighting power source makes an output current constant during a period in which the light source is turned on in the intermittent lighting operation.   The lighting device according to claim 1, wherein the lighting unit includes one switching power supply that can switch an output voltage. The lighting unit is configured to change a duration of a period for lighting the light source in the intermittent lighting operation,
The lighting device according to claim 1, wherein the turn-off voltage is increased as the duration of the period during which the light source is turned on in the intermittent lighting operation is shorter. The lighting unit is configured to change a lighting voltage output to the light source during a period of lighting the light source in the intermittent lighting operation,
The lighting device according to claim 1, wherein the lighting voltage is lowered as the lighting voltage is lower. The lighting unit is configured to change a cycle of the intermittent lighting,
The lighting device according to any one of claims 1, 6, and 7, wherein the longer the intermittent lighting cycle, the lower the turn-off voltage. The light source comprises one or more light emitting elements,
The number of light emitting elements constituting the light source is variable,
Comprising a number detecting means for detecting the number of light emitting elements connected between the output ends of the lighting unit;
9. The lighting device according to claim 1, wherein the lighting unit lowers the turn-off voltage as the number of light emitting elements detected by the number detection unit is smaller. . Surge detecting means for detecting a temporary rise width of the output current of the lighting unit immediately after the lighting of the light source is started,
The said lighting part changes the said voltage for light extinction at any time so that the said raise range detected by the said surge detection means may be contained in a predetermined range, The any one of Claims 1, 6-9 characterized by the above-mentioned. The lighting device described in 1.   The lighting device according to claim 1, wherein the light source includes one or more organic EL elements.   A lighting fixture comprising: the lighting device according to any one of claims 1 to 11; and a fixture main body that holds the lighting device.

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