JP2004207654A - Illuminator and driver circuit for illumination - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illuminator capable of preventing the occurrence of uneven illuminance and the breaking of a light-emitting element. <P>SOLUTION: A first circuit in which an LED row 25 connecting 32 pieces of LED bare chips D<SB>11</SB>, D<SB>13</SB>to D<SB>45</SB>and D<SB>47</SB>in series and a constant current circuit 53 are connected in series, and a second circuit in which the LED row 26 connecting the 32 pieces of LED bare chips D<SB>81</SB>, D<SB>83</SB>to D<SB>55</SB>and D<SB>57</SB>in series and the constant current circuit 54 are connected in series, are connected in parallel with a common power supply. Accordingly, since each light-emitting element row can be controlled in a constant current independently, the trouble does not occur that a large current is made to flow through one row, a small amount of a current is only made to flow through the other rows, the distribution of light is unbalanced, and the LED bare chips are damaged by the large current because one constant current circuit is only mounted as conventional devices even when the temperature of the light-emitting sections is increased in the case of a lighting. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lighting device configured by connecting two or more light emitting element columns each having a plurality of light emitting elements connected in series to a common power supply, and an illumination driving circuit for lighting the light emitting elements. In particular, the present invention relates to improvement of a driving circuit for controlling a light emitting element at a constant current.
[0002]
[Prior art]
Conventionally, display devices and the like using a large number of light emitting diodes (LEDs) as light emitting units have been developed. The LED drive circuit of such a device employs a configuration in which a plurality of LEDs are connected in series. However, there is a case where all the LEDs cannot be connected in series due to the power supply voltage. A configuration in which a plurality of devices connected in series are connected in parallel is adopted. For example, if 50 LEDs with a forward voltage Vf of 4 (V) are connected, and if the input voltage is 100 (V), only 25 LEDs can be connected in series in one column, and 2 This is because they must be connected in parallel to the columns.
[0003]
When connected in parallel, the number of LEDs is usually the same in each column (for example, see Patent Document 1). This is because, in the conventional LED drive circuit, a current output from one current source is distributed to and supplied to the LEDs in each column connected in parallel. If the number of LEDs in a row is the same, the total value (combined resistance value) of the internal resistances of the LEDs in each row becomes almost the same, and almost the same amount of current can flow in each row. This is because variation in the amount of light emission can be reduced.
[0004]
[Patent Document 1]
Japanese Utility Model Registration No. 3016636 [0005]
[Problems to be solved by the invention]
However, when an LED drive circuit such as the above-described conventional display device is applied to a lighting device, an excessive current flows in one of the columns connected in parallel, causing illuminance unevenness, LED may be destroyed. This is for the following reason. That is, in order to increase the amount of light emission in the lighting device as much as possible, a larger current than the display device or the like, for example, about 20 (mA) in the display device, and a large current of about 40 (mA) is continuously applied to the LED. Therefore, the LED easily generates heat, and the light emitting portion easily becomes high in temperature. In general, LEDs have a characteristic that the internal resistance decreases as the temperature rises, and that the variation in the resistance value of each LED increases at higher temperatures.
[0006]
Therefore, when the temperature rises due to heat generation, the variation in the resistance value of each LED increases, and the variation causes the difference in the combined resistance value in each row to be larger than at low temperatures. In that case, more current flows into the column with the smaller combined resistance value than before, and in that column, the amount of current of each LED increases due to the increase in current, but the amount of heat generated also increases and the temperature rises, The combined resistance value decreases, and more current flows. On the other hand, in a column having a large combined resistance value, only a small amount of current flows and the amount of light decreases. As a result of this repetition, a large difference occurs in the amount of light emission in each row, and as a result, the light distribution becomes unbalanced, causing uneven illuminance on the irradiation target surface, or the LED in the row in which the current is excessive becomes excessive. It will be destroyed.
[0007]
The present invention has been made in view of such a problem, and provides an illumination device and an illumination drive circuit that can prevent illuminance unevenness from occurring or a light emitting element from being destroyed. Aim.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a lighting device according to the present invention is a lighting device configured by connecting two or more light emitting element arrays each having a plurality of light emitting elements connected in series to a common power supply in parallel. The number of light emitting elements in each light emitting element row is the same, and each light emitting element row is provided with a constant current circuit connected in series with the light emitting element in the light emitting element row.
[0009]
As a result, each light emitting element row can be independently controlled with a constant current, so that even if the light emitting section becomes hot at the time of lighting, only one constant current circuit is provided as in the related art. A large current does not flow in one row, and only a small amount of current flows in the other row, so that the light distribution is not unbalanced, and the large current does not cause a problem such as damage to the LED bare chip.
[0010]
Further, the constant current circuit includes a current adjusting unit. This makes it possible to adjust the amount of current flowing through the light emitting element array to an arbitrary value.
Further, the light emitting device is a light emitting diode.
Further, the illumination driving circuit of the present invention is an illumination driving circuit for driving an illumination light source including a plurality of light emitting element arrays in which the same number of light emitting elements are connected in series. A circuit for connecting the element arrays in parallel is provided, and the circuit is provided with a constant current circuit connected in series to the light emitting elements of the light emitting element arrays for each of the connected light emitting element arrays. It is characterized by.
[0011]
As a result, the light emitting element rows of each row can be independently controlled with a constant current. Even if the light emitting section becomes hot at the time of lighting, only one constant current circuit is provided as in the related art. A large current does not flow in one row and a small amount of current flows in the other row, so that the light distribution is not unbalanced and the large current does not cause a problem such as damage to the LED bare chip.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view illustrating a configuration example of a lighting device 1 according to an embodiment, and is partially cut away for convenience of description.
As shown in FIG. 1, a lighting device 1 is a substitute for a general incandescent light bulb, and reflects a diffused light of a light emitted from the lighting unit 2 and the lighting unit 2 as a lighting light source. The secondary optical system 3 serving as a reflection shade for guiding forward (upward in the figure), the case 4, and housed in the case 4, emit light from the LED bare chips D _{11 to} D ₈₈ (see FIG. 2) serving as light emitting elements of the lighting unit 2. A drive circuit board 5 (broken line) and a base 6 are provided. The base 6 has the same size (standard) as that used for general lighting bulbs such as incandescent bulbs.
[0013]
The drive circuit board 5 is connected to the lighting unit 2 via the lead wires 21 to 24, and also connected to the base 6 via the lead wires 71 and 72, and is connected to an external commercial power supply (here, AC100V) from the base. 6 is supplied to the lighting unit 2 by converting AC power inputted through the DC power supply 6 into DC power. Since the lighting unit 2 serving as a light source is a plate-like body, the size of the device itself (especially, the entire length) can be reduced with respect to an incandescent lamp or the like.
[0014]
FIG. 2 is a plan view of the lighting unit 2.
As shown in the figure, the lighting unit 2 includes a plurality of (here, 64) LED bear chips D _{11 to} D _{88 on} a metal base printed wiring board (hereinafter, simply referred to as “printed wiring board”) 20. (The symbols will be described later) are multi-point light sources arranged regularly, and are used as a surface light source by causing these LED bare chips to emit light at the same time.
[0015]
FIG. 3 is a cross-sectional view of the lighting unit 2 taken along line AA in FIG.
As shown in the figure, the printed wiring board 20 is a multilayer (here, two layers) printed wiring board based on a metal plate 28. The printed wiring board 20, the surface of the insulating plate 30 and 32 made of an inorganic filler-containing thermosetting resin, the wiring pattern (FIG made of metal, as a pattern for the LED bare chips D ₁₁ connected, 44A, 40A, 40H Are formed on the metal plate (in this case, an aluminum plate) 28.
[0016]
On the other hand, LED bare chips D ₁₁ is an LED bare chip InGaN system in which the cubic shape, an LED bare chip of single-sided electrode type having both the anode electrode and the cathode electrode on one surface. This configuration is the same for the other 63 LED bare chips.
In the present embodiment, an alumina composite substrate using alumina as the inorganic filler and epoxy resin as the thermosetting resin is used for the insulating plates 30 and 32. Further, copper (Cu) is used for the wiring pattern. The filler used is not limited to alumina, and may be any filler having high thermal conductivity that efficiently transfers the heat generated from the LED bare chip to the metal plate 28 during lighting. For example, silica or boron nitride can be used. Further, the wiring pattern is not limited to copper, and gold (Au) or the like can be used.
[0017]
FIG. 4 is a plan view of the substrate 36, and FIG. 5 is a plan view of the substrate 34.
As shown in FIG. 4, in the formation region of the wiring pattern 40 formed on the insulating plate 32 of the substrate 36, 64 LED bare chips D ₁₁ to D ₈₈ are orderly mounted in a matrix of 8 rows and 8 columns. The mounting position of each LED bare chip is indicated by a symbol Cnm (n indicates the number of rows, m indicates the number of columns, and each is an integer of 1 to 8). In accordance with this, the LED bare chip mounted at each mounting position is represented by Dnm. That is, the LED bare chip mounted at the mounting position of the n-th row and the m-th column is Dnm.
[0018]
The wiring pattern 40 is for connecting the LED bare chips in the odd-numbered columns and the LED bare chips in the even-numbered columns in each row in series.
The wiring patterns 40A, 40B, 40C, and 40D are used as power supply terminals. The lead 21 is connected to the wiring pattern 40A, the lead 22 is connected to the wiring pattern 40B, the lead 23 is connected to the wiring pattern 40C, and the lead 24 is connected to the wiring pattern 40D. 5 receives the DC power.
[0019]
The wiring pattern formed on the substrate 34 shown in FIG. 5 is a pattern that is interlayer-connected to the wiring pattern 40 via a via hole (indicated by a small “○” in FIGS. 4 and 5).
As described above, the wiring pattern 44 further connects the series-connected odd-numbered LED bear chips and the series-connected even-numbered LED bear chips in series in each row. That is, the LED bare chips are connected in series for each row. For example, if the first line, in the order of _{D 11, D 13, D 15} , D 17, D 12, D 14, D 16, D 18, LED bare chips are connected to each other in series.
[0020]
The wiring pattern 44 further connects the first to fourth rows of the LED bare chips connected in series for each row in series in the order of row numbers, and the fifth to eighth rows have the same row numbers. Connect in series in order. That is, 32 from the first row first column to the fourth row 8 column LED bare chips D ₁₁ to D ₄₈ (hereinafter, these LED bare chips is referred to as a "first group".) Is D _11, D ₁₃ · · · D ₁₈ , D ₂₂ , D ₂₄ ... D ₂₈ , D ₂₁ ... D ₂₇ , D ₃₁ ... D ₄₃ , D ₄₅ , and D ₄₇ are connected in series in this order (see reference numeral 25 in FIG. 6), 32 from 5 row first column to the 8 rows and 8 column LED bare chips D ₅₁ to D ₈₈ (hereinafter, these LED bare chips is referred to as a "second group".) is _{D 81, D 83, D 85} , _{D 87, D 82, D 84} ··· D 88, D 72, D 74 ··· D 58, D 51, D 53, D 55, in the order of D ₅₇ are connected in series (code 6 26 reference).
[0021]
In this case, among the first group, and the anode electrode of the first row and first column of the LED bare chips D ₁₁ (not shown), the wiring pattern 40A is connected, the cathode of the fourth row 7 column of LED bare chips D ₄₇ an electrode (not shown), a wiring pattern 40E is connected to the wiring pattern 40E is adapted to be connected to the wiring pattern 40B via the wiring pattern 44B, LED bare chips D ₁₁ is the high potential side terminal, LED The bare chip D ₄₇ is the lower potential side terminal.
[0022]
Further, among the second group, and the anode electrode 8 row and first column of the LED bare chips D ₈₁ (not shown), a wiring pattern 40D are connected, the cathode electrode of the fifth line 7 column of LED bare chips D ₅₇ ( and not shown), it is connected to the wiring pattern 40F is, the wiring pattern 40F is adapted to be connected to the wiring pattern 40C through the wiring pattern 44C, LED bare chips D ₈₁ is the high potential side terminal, LED bare chips D ₅₇ is the lower potential end.
[0023]
FIG. 6 is a diagram illustrating a circuit configuration of the lighting device 1.
As shown in the figure, a rectifier circuit 51 composed of a diode bridge for full-wave rectification of a commercial AC power supply (AC 100 V), a smoothing circuit 52 composed of an electrolytic capacitor for smoothing the rectified DC current, and a smoothed DC current Are used as a common power supply, LED strings 25 and 26 as light emitting element strings connected in parallel to the common power supply, a constant current circuit 53 connected in series with the LED string 25, and a LED connected in series with the LED string 26. And a constant current circuit 54.
[0024]
LED row 25, the first 32 LED bare chips D ₁₁ to D ₄₈ in the group is a circuit connected in series, LED string 26, 32 of the LED included in the second group bare chip D ₅₁ to D ₈₈ is a circuit connected in series.
The rectifier circuit 51, the smoothing circuit 52, and the constant current circuits 53 and 54 are arranged on the drive circuit board 5. That is, the drive circuit board 5 is a circuit of a portion excluding the LED arrays 25 and 26 of the illumination unit 2, and a circuit as an illumination drive circuit for connecting the LED arrays 25 and 26 in parallel to a common power supply. It has a configuration.
[0025]
Note that points T and U in the figure are portions corresponding to connection terminals with the lead wires 71 and 72 of the drive circuit board 5. Point P is a portion corresponding to wiring pattern 40A, and point Q is a portion corresponding to wiring pattern 40B. The point R is a portion corresponding to the wiring pattern 40D, and the point S is a portion corresponding to the wiring pattern 40C. On the other hand, points P'Q'R'S 'indicate portions corresponding to connection terminals of the lead wires 21, 22, 24, and 23 with the lighting unit 2 of the drive circuit board 5, and the point between PP and P' is shown. A lead wire 22 is connected between the lead wires 21 and Q-Q ', a lead wire 24 is connected between R-R' and a lead wire 23 is connected between SS and S '.
[0026]
The constant current circuit 53 is formed of a known circuit in which a fixed resistor 62 and a variable resistor 63 as current adjusting means are connected to an output terminal Vout of a three-terminal regulator 61, and the current I flowing through the LED array 25 is always constant. It is controlled to be constant. On the other hand, the constant current circuit 54 is the same as the constant current circuit 53 and includes a three-terminal regulator 65, a fixed resistor 66, and a variable resistor 67, and the current I flowing through the LED array 26 is always constant. Control. The value of the current I is about 40 (mA) here, which is much larger in a case where the current I is normally used for a display device or the like than in a case where the current I is about 20 (mA). The magnitude of the current I is finely adjusted by the variable resistors 63 and 67 in each column. As a result, almost the same current I flows through the LED arrays 25 and 26.
[0027]
The number of connected LED bare chips in one row is determined based on the power supply voltage, the operating voltage of the constant current circuit, and the like. That is, the maximum voltage after rectification is “Vmax”, the ripple voltage when the output after rectification and smoothing includes ripple is “Vrp”, the forward voltage of one LED bare chip is “Vf”, and the operation of the constant current circuit. Assuming that the voltage is “Vreg”, the number “n” of LED bare chips can be obtained using the formula: n = {Vmax− (Vrp + Vreg)} / Vf.
[0028]
In the case of the configuration example of the present embodiment, since the commercial power supply is AC100 (V), if the input maximum voltage is AC110 (V) in consideration of voltage fluctuation (10%), the rectified maximum voltage Vmax is: It is approximately DC 155 (V). The LED bare chip has a forward voltage Vf of about 4.0 (V), and the constant current circuit has an optimum operating voltage of about 24 (V). If the ripple voltage Vrp is set to about 3 (V) in view of a margin, the number n is 32 (pieces) from the above equation. That is, when a circuit is configured using the LED bare chip, the constant current circuit, and the like having the above specifications, the maximum number of LED bare chips that can be connected in series in a row is 32. In the case of a lighting device, since a higher luminous intensity is required, it is desirable to connect as many LED bare chips as possible, and in that sense, the maximum number can be regarded as an optimum number. The same can be said for another column connected in parallel, so that a configuration in which 32 LED bare chips are connected in series for each column is optimal.
[0029]
In the case of a configuration in which each column is independently controlled at a constant current, the number of LED bare chips can be changed for each column. However, since the same voltage is applied to each column as a common power supply and the same current I flows, in a column having a small number of LED bare chips, light energy that would be obtained if a current originally flows through the small number of LED bare chips is used. The constant current circuits in the row merely convert the heat to waste, and the efficiency becomes extremely poor for use as a lighting device. Therefore, it is most efficient to set the same number in each row (the maximum number that can be connected).
[0030]
Thus, in the circuit configuration of the present embodiment, the optimal number of LED bare chips is 64 (2 rows), 96 (3 rows)... The size is determined in consideration of the size of the plate, the luminous intensity required for the lighting device, and the like. Here, this is a case where the present invention is used for a lighting device that substitutes for a general light bulb such as an incandescent light bulb, and the necessary luminous intensity is secured by using 64 LED bare chips.
[0031]
As described above, the lighting apparatus 1 of the present embodiment includes a circuit in which the constant current circuit 53 is connected in series to the LED string 25 and a circuit in which the constant current circuit 54 is connected in series to the LED string 26 in parallel with the common power supply. , It is possible to perform independent constant current control in each column. Therefore, even if the light-emitting portion composed of a large number of LED bare chips having a certain degree of variation in internal resistance becomes hot at the time of lighting, only one constant current circuit is provided as in the related art. A large current flows in one row, and a small amount of current flows in the other row, resulting in unbalanced light distribution and a large current that causes damage to the LED bare chip.
[0032]
Since the number of LED bare chips is the same (the maximum number that can be connected to one column) in each column, there is an effect that the circuit efficiency and the luminous efficiency when viewed as a lighting device can be improved.
In this embodiment, the number of LED bare chips in one row is 32 from the above equation. However, if the values of Vf, Vrp, etc. are different, the numbers are naturally different. The number and the number of columns are determined.
[0033]
(Modification)
As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and the following modified examples can be considered.
(1) In the above-described embodiment, an example of the circuit configuration when the commercial power supply is AC100 (V) has been described. However, even if the voltage is other than that, for example, AC120 (V), AC230 (V), or the like, The value of “Vmax” is obtained according to the voltage, and the optimal number of LED bare chips can be obtained by applying the value to the above equation.
[0034]
(2) When the input power supply is a direct current (DC) power supply such as DC48 (V), DC24 (V), and DC12 (V), there is basically no need to provide a rectifier circuit, a smoothing circuit, and the like. The circuit configuration can be made smaller and simpler. In this case, if it is not necessary to consider the ripple voltage Vrp, the above equation can be expressed as n = (DC input voltage V−Vreg) / Vf.
[0035]
(3) In the above embodiment, the constant current circuits 53 and 54 are arranged on the low potential side of the LED strings 25 and 26, but may be arranged on the high potential side, for example. In addition, a configuration in which a constant current circuit is interposed between two adjacent LED bare chips, a first group includes, for example, a circuit configuration in which D ₁₃ , a constant current circuit 53, D _15. You can also. In short, it is only necessary for each column to have a circuit configuration in which the LED bare chips in the column and the constant current circuit are connected in series.
[0036]
(4) In the above-described embodiment, an example in which the same specifications are used as the LED bare chips has been described. However, in each column, the number n of the LED bare chips is the same, and the total value of Vf is substantially the same. In this case, LED bear chips of different specifications, for example, having different emission colors can be connected in the same row. Specifically, for each column, for example, a configuration in which the same number of LED bare chips of red, green, and blue emission colors are connected in series can be considered. In this case, for example, if the LED bare chips are connected in series so that the adjacent ones emit different colors, it becomes easy to mix the colors, and it can be used as a lighting device that emits light closer to white. .
[0037]
(5) In the above embodiment, an example was described in which a single-sided electrode type bare LED chip having both an anode electrode and a cathode electrode on one surface was used. However, the LED is a resin-molded LED or the like. Needless to say, it is not limited to bare chips. Further, the present invention can be applied to a lighting device using a double-sided electrode type LED having an anode electrode on one surface and a cathode electrode on the other surface. Further, in the above, an example in which an LED is used as a light emitting element has been described. However, the present invention can be applied to a general light emitting element having the same resistance characteristics as an LED.
[0038]
(6) In the above embodiment, as an example of a lighting device, a lighting device that replaces a general incandescent light bulb is disclosed. However, the lighting device to which the driving circuit is applied is not limited thereto. The present invention can be applied to a driving circuit such as a flashlight.
(7) In the above embodiment, an example in which the present invention is applied to a lighting device has been described. However, a lighting driving circuit, that is, a circuit for driving each LED bare chip of the lighting unit 2 (the driving circuit board 5) ).
[0039]
【The invention's effect】
As described above, the lighting device according to the present invention is a lighting device configured by connecting two or more light-emitting element rows in which a plurality of light-emitting elements are connected in series to a common power supply, The number of light emitting elements in each light emitting element row is the same, and each light emitting element row is provided with a constant current circuit connected in series with the light emitting element in the light emitting element row. As a result, each light emitting element row can be independently controlled with a constant current, so that even if the light emitting section becomes hot at the time of lighting, only one constant current circuit is provided as in the related art. A large current does not flow in one row, and only a small amount of current flows in the other row, so that the light distribution is not unbalanced, and the large current does not cause a problem such as damage to the LED bare chip.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a configuration example of a lighting device 1;
FIG. 2 is a plan view of the lighting unit 2. FIG.
FIG. 3 is a cross-sectional view of the lighting unit 2 taken along line AA in FIG.
FIG. 4 is a plan view of a substrate 36 of the printed wiring board 20.
FIG. 5 is a plan view of a substrate 34 of the printed wiring board 20.
FIG. 6 is a diagram showing a circuit configuration of the illumination device 1.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Illumination device 2 Illumination unit 5 Drive circuit board 25, 26 LED string 53, 54 Constant current circuit 61, 65 Three-terminal regulator 62, 66 Fixed resistor 63, 67 Variable resistor

Claims (4)

A lighting device configured by connecting two or more light-emitting element rows in which a plurality of light-emitting elements are connected in series to a common power supply,
A lighting device, wherein the number of light emitting elements in each light emitting element row is the same, and a constant current circuit connected in series with the light emitting element in the light emitting element row is provided for each light emitting element row. The lighting device according to claim 1, wherein the constant current circuit includes a current adjusting unit. 3. The lighting device according to claim 1, wherein the light emitting element is a light emitting diode. An illumination drive circuit for driving an illumination light source including a plurality of light-emitting element rows in which the same number of light-emitting elements are connected in series,
A circuit for connecting each light-emitting element array in parallel to a common power supply, wherein the circuit includes, for each of the connected light-emitting element arrays, a constant current circuit connected in series with the light-emitting element of the light-emitting element array; An illumination drive circuit, comprising:

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