LIGHTING DEVICE

Abstract

A lighting device having: a first light source including at least one first light-emitting unit having a first light emission color; a second light source including at least one second light-emitting unit having a second light emission color; a resistor connected in series to the first light source; and a switching element connected in series to the second light source, current flowing to the first light source being converted into a control voltage by the resistor, and current flowing to the switching element being controlled by the control voltage.

Claims

1-5. (canceled)

6. A lighting device characterized by having: a first light source including at least one first light-emitting unit having a first light emission color; a second light source including at least one second light-emitting unit having a second light emission color; a resistor connected in series to only the first light source from among the first light source and the second light source; and a switching element connected in series to the second light source, and being able to turn off current flowing to the second light source in accordance with a predetermined range for a current amount for the first light source, current flowing to the first light source being converted into a control voltage by the resistor, current flowing to the switching element being controlled by the control voltage, and a color temperature emitted across all light sources including the first light source and the second light source thereby becoming variable.

7. The lighting device according to claim 6, wherein a field-effect transistor or a thyristor is used as the switching element.

8. The lighting device according to claim 6, wherein the first light source, the second light source, the resistor, and the switching element are mounted on the same printed substrate.

9. The lighting device according to claim 6, wherein a plurality of irradiation units including the first light source, the second light source, the resistor, and the switching element are connected in series or parallel.

10. A lighting device characterized by having: a first light source including at least one first light-emitting unit having a first light emission color; a second light source including at least one second light-emitting unit having a second light emission color; and a resistor connected in series to the first light source, quantities of the first light-emitting unit and the second light-emitting unit being the same, and quantities of light-emitting elements connected in series in the first light source and the second light source being different.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0028] FIG. 1 is a diagram depicting a configuration of a lighting device according to a first embodiment of the present invention.

[0029] FIG. 2 is a graph depicting simulation results for the lighting device according to the first embodiment of the present invention.

[0030] FIG. 3 is a drawing depicting a configuration of a lighting device according to a second embodiment of the present invention.

[0031] FIG. 4 is a drawing depicting a configuration of a lighting device according to a third embodiment of the present invention.

[0032] FIG. 5 is a drawing depicting a schematic configuration of an LED substrate according to a fourth embodiment of the present invention.

[0033] FIG. 6 is a drawing depicting another example of a schematic configuration of the LED substrate according to the fourth embodiment of the present invention.

[0034] FIG. 7 is a drawing depicting a configuration of a lighting device according to a first conventional example.

[0035] FIG. 8 is a schematic graph depicting a Kruithof curve.

[0036] FIG. 9 is a drawing depicting a configuration of a lighting device according to a second conventional example.

[0037] FIG. 10 is a graph depicting simulation results for the lighting device according to the second conventional example.

[0038] FIG. 11 is a drawing depicting a configuration of a lighting device according to a third conventional example.

[0039] FIG. 12 is a graph depicting simulation results for the lighting device according to the third conventional example.

[0040] FIG. 13 is a drawing depicting a schematic configuration of an LED substrate according to a conventional example.

[0041] FIG. 14 is a drawing depicting a schematic configuration of an LED substrate according to a conventional example.

[0042] FIG. 15 is a drawing depicting a configuration of a lighting device according to a fifth embodiment of the present invention.

[0043] FIG. 16A is a graph depicting simulation results for the lighting device according to the fifth embodiment of the present invention.

[0044] FIG. 16B is a graph depicting simulation results for the lighting device according to the fifth embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

[0045] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First Embodiment

[0046] An LED lighting device according to a first embodiment of the present invention will be described using FIGS. 1 and 2.

[0047] An LED lighting device 100 according to the present embodiment depicted in FIG. 1 is a lighting device that operates with an alternating-current power source 101 as a power source. The LED lighting device 100 has a power source circuit 110 that generates a direct-current voltage for driving LEDs from the alternating-current power source 101, and an irradiation unit 120 that is provided with the LEDs.

[0048] The power source circuit 110 drives the irradiation unit 120 and causes light to be emitted using an anode line 111 and a cathode line 112. Although not especially depicted, some kind of dimming function is provided in the power source circuit 110, and the current that drives the irradiation unit 120 can be controlled.

[0049] The irradiation unit 120 has: an LED light source 130 formed by a plurality of LED packages (an example of a light-emitting unit) 131 that have a first light emission color being connected in series; a second LED light source 140 formed by a plurality of LED packages 141 that have a second light emission color being connected in series; a switching element Q1 that is an N-channel MOS-FET (field-effect transistor); and a resistor R1.

[0050] A connection point where the anode sides of each of the LED light source 130 and the LED light source 140 are connected is connected to the anode line 111. The cathode side of the LED light source 130 is connected to one end of the resistor R1. The cathode side of the LED light source 140 is connected to the drain of the switching element Q1. A node N1 that is a connection point between the LED light source 130 and the resistor R1 is connected to the gate of the switching element Q1. A connection point between the other end of the resistor R1 and the source of the switching element Q1 is connected to the cathode line 112.

[0051] The operation when the driving current of the irradiation unit 120 is changed will be described.

[0052] The current that flows to the LED light source 130 and the current that flows to the resistor R1 are substantially equal. Furthermore, the current that flows to the LED light source 140 and the current that flows to the switching element Q1 are substantially equal. Thus, the current that flows to the irradiation unit 120 becomes the sum of the current that flows to the LED light source 130 and the current that flows to the LED light source 140.

[0053] When the current that flows to the irradiation unit 120 is small, the current that flows to the LED light source 130 and the current that flows to the LED light source 140 are both small. The current that flows to the resistor R1 is also small, and therefore there is almost no difference between the potential of the node N1 and the potential of the cathode line 112. The switching element Q1 is an N-channel MOS-FET having the gate connected to the node N1, and therefore almost no current can be passed in a state in which the voltage between the gate and source is small. Consequently, almost no current is passed to the LED light source 140, whereas current flows to the LED light source 130.

[0054] From here, when the current that flows to the irradiation unit 120, in other words, the current that flows to the LED light source 130, is increased, the current that flows to the resistor R1 increases, and the voltage between the node N1 and the cathode line 112 increases in proportion thereto. When this voltage increases to a certain extent and reaches a voltage at which the switching element Q1 turns on, the switching element Q1 passes current. In other words, current flows not only to the LED light source 130 but also to the LED light source 140.

[0055] Generally, the on-resistance of a MOS-FET is extremely small, and therefore, when the current that flows to the irradiation unit 120 is additionally increased in a state in which the switching element Q1 is on, the current that flows to the LED light source 140 can be increased compared to the LED light source 130.

[0056] Summarizing the above explanation, when the current that flows to the irradiation unit 120 is small, in other words, when the illuminance of the emitted light is low, only the LED light source 130 emits light; however, when the current increases, in other words, as the illuminance of the emitted light increases, it becomes possible for the LED light source 140 to also emit light, and the proportion of current that flows to the LED light source 140 gradually increases. In the case where the LED light source 130 is a white light source having a low color temperature and the LED light source 140 is a white light source having a high color temperature, an operation results in which light is emitted at a low color temperature when the illuminance is low, and light is gradually emitted at a high color temperature as the illuminance increases.

[0057] Simulation results calculated from the configuration of the irradiation unit 120 of the LED lighting device 100 are depicted in FIG. 2. The notation method for this graph is similar to the previous FIG. 10. The resistance value of the resistor R1 connected to the LED light source 130 is adjusted in such a way that effects are easily understood. Almost no current flows to the LED light source 140 until the switching element Q1 turns on, and it is therefore possible to ensure a greater difference in current between the LED light source 130 and the LED light source 140.

[0058] It should be noted that the quantities of LED packages included in the LED light source 130 and the LED light source 140, the series/parallel connection method therefor, and the like are not particularly restricted to the examples described above, and a single LED package may be used rather than a plurality thereof.

Second Embodiment

[0059] Next, an LED lighting device according to a second embodiment of the present invention will be described using FIG. 3. An LED lighting device 300 the configuration of which is depicted in FIG. 3 has a similar function to the LED lighting device 100 (FIG. 1, first embodiment). An irradiation unit 320 of the LED lighting device 300 has a different configuration from the irradiation unit 120 of the LED lighting device 100.

[0060] Similar to the irradiation unit 120, the irradiation unit 320 has the LED light source 130 and the LED light source 140. The irradiation unit 320 also has a resistor R3 that is connected in series to the anode side of the LED light source 130, and a switching element Q3 that is a P-channel MOS-FET connected in series to the anode side of the LED light source 140.

[0061] The operation when the driving current of the irradiation unit 320 is changed is substantially similar to that of the irradiation unit 120. The resistor R3 and the switching element Q3 for controlling current are connected to the anode side, and therefore a P-channel type of MOS-FET rather than an N-channel type is used for the switching element. When the voltage drop caused by the resistor R3 increases to a certain extent or more, the switching element Q3 turns on, and therefore the behavior is similar to that of the irradiation unit 120.

[0062] According to the aforementioned operation, similar to the LED lighting device 100, the LED lighting device 300 can also emit light at a low color temperature when the illuminance is low, and gradually emit light at a high color temperature as the illuminance increases.

Third Embodiment

[0063] Next, an LED lighting device according to a third embodiment of the present invention will be described using FIG. 4.

[0064] In an LED lighting device 400 depicted in FIG. 4, LED packages 142 having two LED elements connected in series therein are used in the LED light source 140. In the LED light source 130 and the LED light source 140, the quantities of LED packages are the same (eight as an example in FIG. 4); however, the quantities of the LED elements connected in series are different, and therefore the forward voltage is different. A resistor R4 is connected to the LED light source 130, which has a low forward voltage. This irradiation unit is equivalent to the LED lighting device 1100 (FIG. 11) in terms of circuitry apart from the quantity of LEDs, and therefore, with the same scheme, the ratio of the current that flows to the LED light source 130 changes in accordance with the driving current that flows to an irradiation unit 420, and the color temperature of the emitted light changes. In other words, it is possible to cause the color temperature to change in accordance with illuminance.

Fourth Embodiment

[0065] An LED substrate of an LED lighting device according to the present invention will be described using FIGS. 5 and 6.

[0066] FIG. 5 depicts a schematic diagram of an LED substrate corresponding to the irradiation unit 120 (FIG. 1, first embodiment). In the LED substrate depicted in FIG. 5, eight LED packages 131, eight LED packages 141, the resistor R1, and the connector C1 are mounted on a printed substrate PB1. The LED packages 131 and the LED packages 141 are mounted equally in an alternating manner, and therefore color irregularities and luminance irregularities can be suppressed to the minimum. Furthermore, the work for connecting an anode and cathode can be easily performed by merely inserting a harness into the connector C1. An LED substrate depicted in FIG. 6 also has a configuration similar to that in FIG. 5; however, the LED packages 131 and the LED packages 141 are arranged in a staggered manner. Thus, surface irradiation is possible with a single substrate, and color irregularities can be suppressed to the minimum by implementing an equally staggered arrangement.

[0067] In the LED substrate depicted in FIG. 5, the quantities of the LED packages 131 and LED packages 141 are the same, and therefore the LED packages arranged at both ends are different. Consequently, when a plurality of these LED substrates are arranged horizontally side-by-side, different LEDs are arranged at the boundaries between adjacent substrates, and color irregularities are unlikely to occur. By arranging a plurality of LED substrates side-by-side in this way, a longer linear light source can be obtained while suppressing the occurrence of color irregularities. Furthermore, in the case where these LED substrates are arranged vertically side-by-side to obtain surface irradiation, the LED packages 131 and LED packages 141 of adjacent substrates may be swapped around. In this way, two types of LED packages can be arranged in a staggered manner. This kind of configuration is possible since the quantities of the LED packages are the same.

[0068] When a plurality of the LED substrates depicted in FIG. 6 are arranged vertically and horizontally side-by-side, the substrate boundaries also form an arrangement in which two types of LED packages are staggered. Consequently, considerable surface irradiation can be obtained by merely arranging the same substrates side-by-side. In the case where the quantities of the two types of LED packages are different, invariably there are portions where a staggered arrangement is not achieved, which therefore causes color irregularities. However, if the quantities of the two types of LED packages are the same, a staggered arrangement can be achieved, and therefore color irregularities are unlikely to occur.

[0069] Color irregularities are unlikely to occur even when a plurality of the LED substrates depicted in FIGS. 5 and 6 are arranged side-by-side vertically and/or horizontally. When a plurality of substrates are used, control is possible not only by means of a method in which driving is performed separately from the power source circuit 110 (FIG. 1) but also by connecting a plurality of irradiation units 120 in parallel or in series.

[0070] Furthermore, this kind of LED substrate can be realized with the irradiation unit 320 (FIG. 3, second embodiment) or the irradiation unit 420 (FIG. 4, third embodiment) in exactly the same manner as with the irradiation unit 120.

<Others>

[0071] Embodiments of the present invention have been described hereinabove; however, the scope of the present invention is not restricted thereto, and it is possible for various alterations to be added and carried out without deviating from the gist of the present invention.

[0072] For example, in the embodiments of the present invention described hereinabove, the two types of LED light sources each had LED packages connected in one line; however, a similar effect can be obtained even if a plurality of lines are connected in parallel. By adjusting the quantity of lines, it is possible to adjust the overall light emission intensity of the LED light sources.

[0073] Furthermore, in the aforementioned lighting device of the first or second embodiment, another resistor may be additionally added and connected in series to the resistor that is connected in series to the LED light sources. According to this kind of configuration, it is possible to alter the change in the proportion of current that flows to the LED light sources after the switching element has turned on.

[0074] Furthermore, in the aforementioned lighting device of the first or second embodiment, it is possible for the locations where the switching element and the resistor are inserted and the voltage that controls the switching element to be changed within the path along which each thereof is connected in series. If this kind of configuration is adopted, there is an improvement in the degree of freedom with respect to component arrangement when these elements are arranged on a printed substrate.

[0075] Furthermore, in the aforementioned lighting device of the first or second embodiment, the quantities of the LED packages in the LED light source 130 and the LED light source 140 may be different. Furthermore, in the aforementioned lighting device of the first or second embodiment, similar to the lighting device of the aforementioned third embodiment, LED packages having different quantities of LED elements connected in series may be used. These can be decided taking into consideration the voltage and current required to drive the irradiation unit, the change in the proportion of current that flows to the LED light sources, the arrangement of the LED packages, and the like.

[0076] Furthermore, for the switching element used in the present invention, it is possible to use an element other than the N-channel MOS-FET or the P-channel MOS-FET described as examples. For example, in the case where a junction FET or a relay is used, a similar function can be realized in a circuit configuration similar to that of a MOS-FET. Furthermore, it is also possible to use a bipolar transistor or a photocoupler. In addition, it is also possible to use a thyristor or a triac, and in these cases, lighting devices having different feelings of use can be realized.

[0077] An LED lighting device 500 depicted in FIG. 15 is an example of a circuit configuration in which a thyristor is used as a switching element. A thyristor S1 is prevented from turning on due to minute fluctuations in gate voltage such as noise, and therefore fluctuations in voltage and current are controlled with the addition of a resistor R6 and a capacitance C2.

[0078] FIG. 16 constitutes simulation results indicating examples of the behavior of an LED lighting device 500. FIG. 16A constitutes behavior in the case where current is increased from a state in which the lighting is off. First, the potential of the node N1 is equal to a cathode voltage 112 and therefore the thyristor S1 is off, and consequently all of the current of an irradiation unit 520 flows to the LED light source 130 without current flowing to the LED light source 140. When the current of the LED light source 130 increases to a certain extent, the current of a resistor R5 also increases, and therefore the potential of the node N1 rises. The node N1 is connected to the gate of the thyristor S1 by way of the resistor R6, and therefore when the potential of the node N1 rises to a certain extent, the gate current of the thyristor S1 increases and the thyristor S1 turns on. The thyristor S1 continues to be on until the current is interrupted, and therefore current flows to both the LED light source 130 and the LED light source 140 in this state.

[0079] FIG. 16B constitutes simulation results for when the current of the irradiation unit 520 is gradually decreased from a state in which the thyristor S1 is on. First, the thyristor S1 is in an on state; however, when the current of the irradiation unit 520 decreases, the current of the LED light source 130 and the LED light source 140 also decreases. When the current of the LED light source 140, in other words, the anode current of the thyristor S1, is equal to or less than the holding current, the thyristor S1 turns off. Thus, all of the current of the irradiation unit 520 flows to the LED light source 130.

[0080] Owing to the aforementioned operation, from a state in which the LED lighting device 500 is off, first, current passes to only the LED light source 130, and when this current increases to a certain extent, current also flows to the LED light source 140, and therefore the color temperature changes drastically. Conversely, when the current of the irradiation unit is decreased, up to a certain point the LED light source 140 also passes current and therefore the color temperature does not change very much; however, when the current of the irradiation unit has decreased to a certain extent, switching is performed in such a way that current is no longer passed to the LED light source 140 and current is passed only to the LED light source 130, and therefore the color temperature changes drastically. In this way, by implementing a lighting device which has color temperature characteristics that exhibit hysteresis with respect to increases/decreases in current, it is possible to realize, with a simple circuit configuration, behavior in which a plurality of color temperatures are switched discretely.

[0081] In addition, in the LED lighting device 500, by deliberately causing the forward voltages of the LED light source 130 and the LED light source 140 to be significantly different, for example, it is possible to adjust the balance between the current passed by the LED light source 130 and the LED light source 140. When the forward voltage of the LED light source 140 becomes sufficiently lower than the forward voltage of the LED light source 130, for example, behavior occurs in which for the most part only the LED light source 130 is lit when the thyristor is off, and for the most part only the LED light source 140 is lit when the thyristor is on.

[0082] By implementing the configuration of the LED light sources of the configuration according to the present invention as a nested structure, it is possible to realize changes in a wide variety of color temperatures. It is also possible for the configurations of lighting devices according to the present invention having different behaviors as in the LED lighting device 500 and the LED lighting device 100, for example, to be mixed. If the LED light source 130 of the LED lighting device 500 is made to have a configuration such as that of the irradiation unit 120 exemplified in the LED lighting device 100 rather than an LED arrangement having a single color temperature, a behavior is exhibited in which the color temperature changes according to the current value even in a region in which only the LED light source 130 of the LED lighting device 500 is lit. By implementing a configuration having a similar nested structure and using a thyristor as the switching element, it is also possible for three or more types of color temperature to be made to change discretely in accordance with current. It goes without saying that it is also possible for the structure of the irradiation unit of the present invention and the structure of an irradiation unit according to conventional technology (for example, the structure of the irradiation unit 920 indicated in the LED lighting device 900) to be nested and combined.

[0083] Furthermore, only a configuration having components mounted on a printed substrate is exemplified as an irradiation unit hereinabove; however, by providing some of the components within a power source, for example, components having comparatively large dimensions can also be used without giving consideration to optical hindrance. Furthermore, by mounting at least some of the components other than the LEDs making up the irradiation unit in the same package as the LEDs, it is possible to simplify the configuration and to realize a lighting device that is easily assembled.

REFERENCE SIGNS LIST

[0084] 100, 300, 400, 500 LED lighting device (the present invention) [0085] 700, 900, 1100 LED lighting device (conventional) [0086] 101 Alternating-current power source [0087] 110 Power source circuit [0088] 111 Anode line [0089] 112, 113 Cathode line [0090] 120, 320, 420, 520, 720, 920, 1120 Irradiation unit [0091] 130, 140 LED light source [0092] 131, 141, 142 LED packages [0093] R1, R3, R4, R5, R6, R9, R11 Resistor [0094] Q1, Q3 Switching element [0095] C1, C2, C11 Connector [0096] PB1, PB11 Printed substrate [0097] S1 Thyristor