Patent Application
20090026972
The present invention relates to a light emitting unit including a plurality of semiconductor light emitting devices formed on a same substrate and a lighting apparatus.
A light emitting unit including a plurality of semiconductor light emitting devices on a same substrate is hitherto been known.
For example, as shown in
When AC power Pe shown in
However, the light emitting unit 200 of the aforementioned Patent Literature 1 is provided with only the two voltage input terminals 203a and 203b and can handle only a single voltage. Accordingly, if voltage higher than specified voltage is applied to the voltage input terminals 203a and 203b, overvoltage applied to the individual semiconductor light emitting devices 201a and 201b causes current exponentially increased to flow through the semiconductor light emitting devices 201a and 201b. This gives damage in the semiconductor light emitting devices 201a and 201b or shortens the life thereof. On the contrary, if voltage lower than the specified voltage is applied to the voltage input terminals 203a and 203b, the semiconductor light emitting devices 201a and 201b do not emit light or, if emitting light, the emitted light is weak.
Moreover, even if forward voltage is applied to the semiconductor light emitting devices 201a and 201b, the semiconductor light emitting devices 201a and 201b cannot be turned on while the applied voltage is less than a certain threshold value Vt. Accordingly, even if the AC power Pe shown in
The present invention was made to solve the aforementioned problems, and an object of the present invention is to provide a light emitting unit and a lighting apparatus which can handle different voltages or to provide a light emitting unit with any of the semiconductor light emitting devices being on for long time.
To achieve the aforementioned object, an invention according to claim 1 is a semiconductor light emitting unit, including: N light emitting arrays (N>=2) each including one or a plurality of semiconductor light emitting devices formed on a same substrate, the light emitting arrays having same specified voltage; and at least (N+1) voltage input terminals provided corresponding to ends of the individual light emitting arrays. The voltage input terminals allow the light emitting arrays to be brought into serial or parallel connections to each other in order that the specified voltage is applied to each light emitting array.
An invention according to claim 2 is the light emitting unit of claim 1 in which each of the light emitting arrays includes a same number of the semiconductor light emitting devices.
An invention according to claim 3 is the light emitting unit of any one of claims 1 and 2, in which each of the light emitting arrays includes the 2M semiconductor light emitting devices and the M semiconductor light emitting devices are connected to allow current to flow therethrough in a direction opposite to that of the remaining M semiconductor light emitting arrays.
An invention according to claim 4 is the light emitting unit of any one of claims 1 to 3, in which the number of the light emitting arrays is two and the number of the voltage input terminals is three.
A invention according to claim 5 is a lighting apparatus, including: a light emitting unit having N light emitting arrays (N>=2) having one or a plurality of semiconductor light emitting devices formed on a same substrate, the light emitting arrays having same specified voltage, and at least (N+1) voltage input terminals provided corresponding to ends of the individual light emitting arrays; and switching controller switching the voltage input terminals. According to voltage applied to the light emitting unit, the switching controller causes the light emitting arrays to be connected in parallel or in series to set voltage applied to each of the light emitting arrays to the specified voltage and automatically switches the voltage input terminals to which the voltage is inputted.
An invention according to claim 6 is a light emitting unit including: three light emitting arrays each including one or a plurality of semiconductor light emitting devices formed on a same substrate; and three power input terminals which are provided at ends of the respective light emitting arrays and are supplied with a three-phase AC power supply. The power input terminals are individually supplied with three types of AC power with different phases.
An invention according to claim 7 is the light emitting unit according to claim 6, in which the other ends of the three light emitting arrays are electrically connected to each other and grounded.
An invention according to claim 8 is the light emitting unit according to any one of claims 6 and 7, in which at least any one of the three light emitting arrays is supplied with voltage not less than a threshold voltage necessary to light the light emitting array.
An invention according to claim 9 is the light emitting unit according to any one of claims 6 to 8, in which each of the light emitting arrays includes the 2M semiconductor light emitting devices and the M semiconductor light emitting devices are connected to allow current to flow therethrough in a direction opposite to that of the remaining the M semiconductor light emitting devices.
An invention according to claim 10 is the light emitting unit according to any one of claims 6 to 9, in which each of the light emitting arrays includes a same number of the semiconductor light emitting devices.
According to the light emitting unit of the present invention, by providing the (N+1) or more voltage input terminals corresponding to the ends of the N light emitting arrays, according to the applied voltage, the voltage input terminals connected to the power supply can be selected and the voltage input terminals can be connected to each other. This allows the light emitting arrays to be connected in series or in parallel and connected to a power supply. Accordingly, the specified voltage of the light emitting arrays can be supplied to each light emitting array. For different applied voltages, it is possible to prevent damage of the semiconductor light emitting device of the light emitting arrays due to overvoltage and moreover and to prevent non-light emission of the semiconductor light emitting devices due to low voltage, thus allowing the semiconductor light emitting devices to emit properly.
Moreover, according to a lighting apparatus of the present invention, the switching controller capable of switching the voltage input terminals of the light emitting unit is provided. The voltage input terminals to which the voltage is inputted can be therefore automatically connected to the power supply or connected to each other based on the applied voltage. Accordingly, a user can easily connect the lighting apparatus to a power supply regardless of the applied voltage.
According to the light emitting unit of the present invention, the three power input terminals provided at the ends of the light emitting arrays are supplied with three types of AC power with different phases from the three-phase AC power supply. It is therefore possible to increase time when the voltage not less than the threshold voltage of the light emitting arrays is applied to at least one of the light emitting arrays. Accordingly, the time when at least one of the three light emitting arrays is lighted can be increased. It is therefore possible to increase lighting time of the lighting apparatus and to prevent flickering.
Hereinafter, a description is given of a first embodiment of the present invention with reference to the drawings.
As shown in
As shown in
As shown in
Each of the light emitting arrays 21a and 21b is configured to handle a voltage of 100 V (specified voltage). Accordingly, the two light emitting arrays 21a and 21b connected in series can handle a voltage of 200 V.
As shown in
The p sides of the six semiconductor light emitting devices 23a are connected to the n sides of the adjacent semiconductor light emitting devices 23a by the wiring films 24 so that the six semiconductor light emitting devices 23a are connected in series. The p sides of the six semiconductor light emitting devices 23b are connected to the n sides of the adjacent semiconductor light emitting devices 23b by the wiring films 24 so that the six semiconductor light emitting devices 23b are also connected in series. In other words, the six semiconductor light emitting devices 23a and the remaining six semiconductor light emitting devices 23b are connected in series so that current flows in directions opposite to each other.
Accordingly, even in the case where reverse voltage is applied to the semiconductor light emitting devices 23a, forward voltage is applied to the other semiconductor light emitting devices 23b, and current flows through the other semiconductor light emitting devices 23b. On the contrary, even in the case where reverse voltage is applied to the semiconductor light emitting devices 23b, forward voltage is applied to the other semiconductor light emitting devices 23a, and current flows through the other semiconductor light emitting devices 23a.
In other words, even when the light emitting unit 3 is connected to the AC power supply P, forward voltage is applied to any ones of the semiconductor light emitting devices 23a and 23b to allow current to flow therethrough. Accordingly, any ones of the semiconductor light emitting devices 23a and 23b can be always turned on.
Moreover, auxiliary wiring films 24a are provided across the wiring films 24 connecting pairs of the semiconductor light emitting devices 23a and 23b and adjacent pairs of the semiconductor light emitting devices 23a and 23b.
Next, the semiconductor light emitting devices 23a and 23b are described with reference to
Each of the semiconductor light emitting devices 23a and 23b includes the substrate 31 and a semiconductor stack 32 formed on the substrate 31. The semiconductor stack 32 includes a low temperature buffer layer 33, a high temperature buffer layer 34, an n-type semiconductor layer 35, an MQW active layer 36, a p-type semiconductor layer 37, and a transparent electrode 38.
The low temperature buffer layer 33 is composed of a GaN layer with a thickness of about 0.005 to 0.1 μm. The high temperature buffer layer 34 is composed of an undoped GaN layer with a thickness of about 1 to 3 μm. The high temperature buffer layer 34 is semi-insulating for insulation of the semiconductor light emitting devices 23a and 23b.
The n-type semiconductor layer 35 includes an about 1 to 5 μm thick contact layer composed of an n-GaN layer doped with Si as an n-type dopant and a confinement layer composed of an n-AlGaN layer. Part of the MQW active layer 36, p-type semiconductor layer 37, and transparent electrode 38 are etched so as to expose a part of the contact layer of the n-type semiconductor layer 35.
The MQW active layer is composed of a multi-quantum well structure with a thickness of about 0.05 to 0.3 μm. Specifically, the MQW active layer 36 has a band gap energy smaller than that of the confinement layer and includes three to eight pairs of about 1 to 3 nm thick well layers of In0.13Ga0.87N and barrier layers composed of about 10 to 20 nm thick GaN layers which are stacked on each other.
The p-type semiconductor layer 37 has a thickness of about 0.2 to 1.0 μm and includes a confinement layer composed of a p-AlGaN layer and a contact layer composed of a p-GaN layer.
The transparent electrode 38 is capable of transmitting light emitted by the MQW active layer 36 and is formed on the upper surface of the p-type semiconductor layer 37. The transparent electrode 38 is composed of a 0.01 to 0.5 μm thick ZnO layer. The transparent electrode 38 may be composed of ITO, an thin alloy layer of Ni and Au, or the like.
Isolation trenches 39 with a width of about 0.6 to 5 μm are formed between adjacent pairs of the semiconductor light emitting devices 23a and 23b by etching a part of the high temperature buffer layer 34, the n-type semiconductor layer 35, the MQW active layer 36, the p-type semiconductor layer 37, and the transparent electrode 38. In the isolation trenches 39, insulating films 40 composed of SiO2 are formed for insulation of the adjacent semiconductor light emitting devices 23a and 23b.
As shown in
The voltage input terminals 22a to 22c are composed of Fe—Ni plating or Cu—Ni plating. The voltage input terminals 22a and 22c are connected to ends of the light emitting arrays 21a and 21b through pad electrodes 25a and 25c. The voltage input terminal 22b is connected through the pad electrode 25b to a part connected to the ends of the light emitting arrays 21a and 21b. The voltage input terminals 22a to 22c are connected to the pad electrodes 25a to 25c through Au or Al wires.
The light emitting unit 3 is manufactured by a known semiconductor manufacturing method or the like.
Next, a description is given of operations of the lighting apparatus 1 when the lighting apparatus 1 is connected to 200 V and 100 V AC power supplies with reference to
First, as shown in
Next, as shown in
On the other hand, as shown in
The light emitting unit 3 according to the present invention, as described above, includes the three voltage input terminals 22a to 22c corresponding to the two light emitting arrays 21a and 21b. It is therefore possible to select the voltage input terminals 22a to 22c connected to the AC power supply P or connect the voltage input terminals 22a to 22c to each other according to the supplied voltage.
The light emitting unit 3 can be connected to the AC power supply P with the light emitting arrays 21a and 21b connected to each other in series or in parallel. Accordingly, voltage applied to each of the light emitting arrays 21a and 21b can be 100 V as the specified voltage of the light emitting arrays 21a and 21b. It is therefore possible to apply a same voltage to the light emitting arrays 21a and 21b despite the difference supplied voltage. Accordingly it is possible to prevent heat generation and damage of the semiconductor light emitting devices 23a and 23b due to overvoltage and emit light at equal illuminance.
Moreover, the lighting apparatus 1 according to the present invention is provided with the switching controller 2 which is capable of automatically switching connections between the voltage input terminals 22a to 22c of the light emitting unit 3 and the AC power supply. Accordingly, based on the applied voltage, the voltage input terminals 22a to 22c to which the voltage is applied can be automatically connected to the AC power supply P and the voltage input terminals 22a to 22c are connected to each other. A user can therefore easily connect the lighting apparatus 1 to the AC power supply P regardless of the supplied voltage.
Next, a description is given of a second embodiment of the present invention with reference to the drawings.
As shown in
As shown in
The p-sides of the semiconductor light emitting devices 23a are connected to the n-sides of the adjacent semiconductor light emitting devices 23a through the wiring films 24 so that the five semiconductor light emitting devices 23a are connected in series. The p-sides of the semiconductor light emitting devices 23b are connected to the n-sides of the adjacent semiconductor light emitting devices 23b through the wiring films 24 so that the five semiconductor light emitting devices 23b are also connected in series. The six semiconductor light emitting devices 23a and the remaining six semiconductor light emitting devices 23b are connected in series so that current flows in the opposite directions.
Accordingly, even when reversed voltage is applied to the semiconductor light emitting devices 23a, forward voltage not less than the threshold voltage Vt is applied to the other semiconductor light emitting devices 23b, and current flows through the semiconductor light emitting devices 23b. On the contrary, even when reversed voltage is applied to the semiconductor light emitting devices 23b, forward voltage not less than the threshold voltage Vt is applied to the other semiconductor light emitting devices 23a, and current flows through the semiconductor light emitting devices 23b.
Moreover, the auxiliary wiring films 24a are provided across the wiring films 24 which individually connect pairs of the semiconductor light emitting devices 23a and 23b and adjacent pairs of the semiconductor light emitting devices 23a and 23b.
Next, the semiconductor light emitting devices 23a and 23b are described with reference to
Each of the semiconductor light emitting devices 23a and 23b includes the substrate 31 and a semiconductor stack 32 formed on the substrate 31. The semiconductor stack 32 includes a low temperature buffer layer 33, a high temperature buffer layer 34, an n-type semiconductor layer 35, an MQW active layer 36, a p-type semiconductor layer 37, and a transparent electrode 38.
The low temperature buffer layer 33 is composed of a GaN layer with a thickness of about 0.005 to 0.1 μm. The high temperature buffer layer 34 is composed of an undoped GaN layer with a thickness of about 1 to 3 μm. The high temperature buffer layer 34 is semi-insulating for insulation of the semiconductor light emitting devices 23a and 23b.
The n-type semiconductor layer 35 includes an about 1 to 5 μm thick contact layer composed of an n-GaN layer doped with Si as an n-type dopant and a confinement layer composed of an n-AlGaN layer. Part of the MQW active layer 36, p-type semiconductor layer 37, and transparent electrode 38 are etched so as to expose a part of the contact layer of the n-type semiconductor layer 35.
The MQW active layer is composed of a multi-quantum well structure with a thickness of about 0.05 to 0.3 μm. Specifically, the MQW active layer 36 has a band gap energy smaller than that of the confinement layer and includes three to eight pairs of about 1 to 3 nm thick well layers of In0.13Ga0.87N and barrier layers composed of about 10 to 20 nm thick GaN layers which are stacked on each other.
The p-type semiconductor layer 37 has a thickness of about 0.2 to 1.0 μm and includes a confinement layer composed of a p-AlGaN layer and a contact layer composed of a p-GaN layer.
The transparent electrode 38 is capable of transmitting light emitted by the MQW active layer 36 and is formed on the upper surface of the p-type semiconductor layer 37. The transparent electrode 38 is composed of a 0.01 to 0.5 μm thick ZnO layer. The transparent electrode 38 may be composed of ITO, an thin alloy layer of Ni and Au, or the like.
Isolation trenches 39 with a width of about 0.6 to 5 μm are formed between adjacent pairs of the semiconductor light emitting devices 23a and 23b by etching a part of the high temperature buffer layer 34, the n-type semiconductor layer 35, the MQW active layer 36, the p-type semiconductor layer 37, and the transparent electrode 38. In the isolation trenches 39, insulating films 40 composed of SiO2 are formed for insulation of the adjacent semiconductor light emitting devices 23a and 23b.
As shown in
Voltage input terminals 122a to 122c are composed of Fe—Ni plating or Cu—Ni plating. The power input terminal 122a is connected through the pad electrode 25a to an end of the light emitting array 121a and the other end of the light emitting array 121c. The power input terminal 122b is connected through the pad electrode 25b to an end of the light emitting array 121b and the other end of the light emitting array 121a. The power input terminal 122c is connected through the pad electrode 25c to an end of the light emitting array 121c and the other end of the light emitting array 121b. The power input terminals 122a to 122c are connected to the pad electrodes 25a to 25c through Au or Al wires.
The power input terminals 122a to 122c are connected to output terminals 112a to 112c of a three-phase AC power supply P, respectively. The three-phase AC power supply thus supplies AC powers with different phases to the individual light emitting arrays 121a to 121c through the power input terminals 122a to 122c.
The aforementioned light emitting unit 101 is manufactured by a known semiconductor manufacturing method or the like.
Next, a description is given of an operation of the light emitting unit 101 which is connected to the three-phase AC power supply P supplied to a motor or the like with reference to
AC powers Pa, Pb, and Pc shown in
First, as shown in
Next, as shown in
Accordingly, any one or two of the light emitting arrays 121a to 121c can keep lighted, and the light emitting unit 101 can be always lighted. It is therefore possible to prevent flickering and the like of the light emitting unit 101.
Hereinabove, the present invention is described in retail using the embodiments, but it is apparent to those skilled in the art that the present invention is not limited to the embodiments described in the specification. The present invention can be carried out as modified and changed modes without departing from the spirit and scope of the invention defined by the description of claims. Accordingly, the description of this specification is for illustrative purposes and does not impose any limitation on the present invention. A description is given below of modifications obtained by partially changing the embodiment.
For example, in the aforementioned first embodiment, the light emitting unit 3 is configured to be included in the lighting apparatus 1 but may be configured to be a separate unit.
Moreover, in the first embodiment, both of the light emitting arrays 21a and 21b light up also when the light emitting unit 3 is connected to the 100 V AC power supply. However, the light emitting unit 3 may be configured so that any one of the light emitting arrays 21a and 21b lights up when the light emitting unit 3 is connected to the 100 V AC power supply. In such a case, any one of the voltage input terminals 22a and 22c voltage supplied to the light emitting array 121a becomes Vt or less, and the light emitting array 121a turns off. However, the light emitting array 121c is continuously lighted, and the light emitting unit 101 does not black out.
Next, as shown in
Next, as shown in
The operation described above is repeated thereafter, thus allowing any one or two of the three light emitting arrays 121a to 121c to be always lighted.
As described above, the light emitting unit 101 according to the present invention is provided with the three light emitting arrays 121a to 121c and the three power input terminals 122a to 122c at the ends of the respective light emitting arrays 121a to 121c for connection of the three-phase AC power supply P, so that three powers with different phases can be supplied to the light emitting arrays 121a to 121c. This allows any one or two of the light emitting arrays 121a to 121c to be always supplied with voltage whose absolute value is not and the voltage input terminal 22b should be connected to the 100V AC power supply.
In the first embodiment, the light emitting unit 3 is provided with the two light emitting arrays 21a and 21b, but the light emitting unit may be provided with three or more light emitting arrays. For example, like a first modification shown in
Next, with reference to
As shown in
Next, as shown in
In this state, the voltage input terminals 52a and 52e and the voltage input terminals 52d and 52h are connected to the AC power supply P100 through the input terminals 54a and 54b, respectively. Accordingly, the specified voltage of 50 V is applied to each of the light emitting arrays 51a to 51d, and the light emitting arrays 51a to 51d can normally operate.
Next, as shown in
In this state, the switching controller 2A connects the voltage input terminals 52a, 52c, 52e, and 52g and the voltage input terminals 52b, 52d, 52f, and 52h to the AC power supply P50 through the input terminals 54a and 54b, respectively. The specified voltage of 50 V is thus applied to each of the light emitting arrays 51a to 51d, and the light emitting arrays 51a to 51d can normally operate.
In the aforementioned embodiment, the description is given of the lighting apparatus 1 and light emitting unit 3 which are connected to an AC power supply. However, the present invention may be applied to a lighting apparatus and a light emitting unit which are connected to a DC power supply. For example, in a light emitting unit 3B of a second modification shown in
Next, a description is given of an operation of the lighting apparatus 1B having the aforementioned light emitting unit 3B when the specified voltage of the light emitting arrays 61a and 61b is 100 V. The lighting apparatus 1B includes a switching controller 2B having input terminals 63a and 63b which are connected to a DC power supply P′200 or P′100 and output terminals 64a to 64d which are connected to the voltage input terminals 62a to 62d.
As shown in
As shown in
Moreover, the numbers of light emitting arrays and voltage input terminals should not be especially limited to those of the aforementioned first embodiment. The number of voltage input terminals should be not less than (N+1) when the number of light emitting arrays is N (N>=2).
Furthermore, the configurations and numbers of the semiconductor light emitting devices 23a and 23b shown in the aforementioned first embodiment are just examples and can be properly changed depending on the desired supplied voltage.
In the first embodiment, the power supplies of 100 V and 200 V are switched. However, the switching may be performed based on another voltage value between 100 and 200 V, for example 110 V while all the light emitting arrays are not caused to emit light.
In the aforementioned second embodiment, the other ends of the light emitting arrays 121a, 121b, and 121c are connected to the power input terminals 122b, 122c, and 122a, respectively, but the light emitting unit may be configured as shown in
The configurations and numbers of the semiconductor light emitting devices 23a and 23b shown in the aforementioned second embodiment are just examples and can be properly changed depending on the desired supplied voltage.
In the second embodiment, the threshold voltage Vt is set so that the light emitting unit 101 is always lighted but may be set so that the light emitting unit 101 temporarily blacks out.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-369551 | Dec 2005 | JP | national |
| 2005-369561 | Dec 2005 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2006/325403 | 12/20/2006 | WO | 00 | 6/20/2008 |
