Lighting device

Abstract

[Problem] To provide a lighting device having high power utilization efficiency. [Solution] A lighting device (10) comprises a rectifier circuit (12), a light-emitting diode (14), a switching circuit (16), and a control circuit (18). The switching circuit (16) is connected to both ends of the light-emitting diode (14). The switching circuit (16) is provided with switch elements (22) and an interconnection circuit (24). The control circuit (18) controls a switch (26) in accordance with the voltage rectified by the rectifier circuit (12). By controlling the switch (26), the control circuit (18) connects the plurality of light-emitting diodes (14) in series, in parallel, or in series-parallel.

Description

lighting equipment

[0001] The present invention relates to a lighting device equipped with a light-emitting diode.

[0002] Patent Document 1 listed below discloses a circuit that changes the connection method of light-emitting diodes depending on the input voltage. Depending on the input voltage, a plurality of light-emitting diodes are connected in series, parallel, or series-parallel.

[0003] However, the circuit of Patent Document 1 can only be changed in three stages, which may cause a difference between the input voltage and the potential of the light-emitting diode, resulting in poor power utilization efficiency.

[0004] Patent Publication No. 2012-243755

[0005] An object of the present invention is to provide a lighting device with good power utilization efficiency.

[0006] The lighting device of the present invention includes a rectifier circuit that rectifies the output of an AC power supply, a plurality of light-emitting diodes to which the voltage rectified by the rectifier circuit is applied, a switching circuit including a switch that switches the plurality of light-emitting diodes between series connection, parallel connection, and series-parallel connection by switching the switch, and a control circuit that controls the switching of the switch. Under the control of the control circuit, some of the light-emitting diodes are sometimes connected in parallel or series-parallel and the remaining light-emitting diodes are sometimes connected in series with the parallel- or series-parallel-connected light-emitting diodes, and there are times when the potential difference between some of the parallel- or series-parallel-connected light-emitting diodes differs from the potential difference between the remaining series-connected light-emitting diodes, and the control circuit maintains the plurality of light-emitting diodes in a connection state corresponding to the peak voltage from the start of control until the voltage rectified by the rectifier circuit reaches the first peak voltage.

[0007] The lighting device of the present invention includes a rectifier circuit that rectifies the output of an AC power supply, a plurality of light-emitting diodes to which the voltage rectified by the rectifier circuit is applied, a switching circuit including a switch that switches the plurality of light-emitting diodes between a series connection, a parallel connection, or a series-parallel connection by switching the switch, a control circuit that controls the switching, a first semiconductor substrate on which the light-emitting diodes are formed, and a second semiconductor substrate on which the switching circuit and the control circuit are formed and made of a material different from that of the first semiconductor substrate. Under the control of the control circuit, some of the light-emitting diodes are connected in parallel or series-parallel, and the remaining light-emitting diodes are connected in series to the parallel-connected or series-parallel-connected light-emitting diodes. The first semiconductor substrate and the second semiconductor substrate face each other, and the light-emitting diodes and the switching circuit are ohmically connected at the opposing portions of the first semiconductor substrate and the second semiconductor substrate, and the other portions are joined with a resin.

[0008] In the lighting device of the present invention, when the areas of the junctions of the first and second semiconductor substrates are the same, the second semiconductor substrate has a space in which extension circuits other than the switching circuit and the control circuit can be formed.

[0009] In the lighting device of the present invention, the first semiconductor substrate uses gallium nitride, and the second semiconductor substrate uses a silicon wafer for semiconductor ICs.

[0010] According to the present invention, by connecting light emitting diodes in series, parallel, or series-parallel, it is possible to make the potential difference of the light emitting diodes close to the rectified voltage, thereby reducing power loss.

[0011] 1 is a block diagram showing the circuit configuration of a lighting device of the present invention; FIG. 2 is a diagram showing the circuit configuration of a switch element; FIG. 3 is a diagram showing the rectified voltage with a solid line and the potential of a light-emitting diode with a dotted line; (a) is a diagram showing the connection state of light-emitting diodes at times T1 to T2 and T11 to T12, and (b) is a diagram showing the connection state of light-emitting diodes at times T2 to T3 and T10 to T11; (a) is a diagram showing the connection state of light-emitting diodes at times T3 to T4 and T9 to T10, and (b) is a diagram showing the connection state of light-emitting diodes at times T4 to T5 and T8 to T9; (a) is a diagram showing the connection state of light-emitting diodes at times T5 to T6 and T7 to T8, and (b) is a diagram showing the connection state of light-emitting diodes at times T6 to T7; and FIG. 4 is a diagram showing another configuration of a switch element.

[0012] The lighting device of the present invention will be described with reference to the drawings. A plurality of embodiments will be described, but overlapping portions may be described in one embodiment and omitted in other embodiments.

[0013] First Embodiment A lighting device 10 of the present invention shown in FIGS. 1 and 2 includes a rectifier circuit 12, a light-emitting diode 14, a switching circuit 16, and a control circuit 18. The rectifier circuit 12 is a rectifier circuit 12a, a light-emitting diode 14b, a switching circuit 16c, and a control circuit 18c.

[0014] The rectifier circuit 12 is a half-wave or full-wave rectifier circuit using diodes. The voltage of the AC power supply 20 is rectified by the rectifier circuit 12. The rectified voltage is applied to the light-emitting diode 14. While an electrolytic capacitor, a transformer, and the like are generally used to adjust the voltage applied to the light-emitting diode, the lighting device 10 does not use such components, thereby simplifying the lighting device 10.

[0015] The lighting device 10 includes a plurality of light-emitting diodes 14. The plurality of light-emitting diodes 14 are connected in series, in parallel, or in a series-parallel configuration, and the connection state is switched according to the input voltage.

[0016] A switching circuit 16 is connected across the light emitting diode 14. The switching circuit 16 includes a switch element 22 and an interconnection circuit 24.

[0017] The switch element 22 includes a plurality of switches 26 (FIG. 2). The switches 26 are elements that can be electronically turned on and off, such as FETs. The plurality of switches 26 in the switch element 22 are connected in parallel. The gate of each switch 26 is connected to the control circuit 18, and the switch 26 is turned on and off by a signal input from the control circuit 18 to the switch 26. One of the plurality of switches 26 is controlled to be on. One switch 26 connects the light-emitting diode 14 and the interconnection circuit 24.

[0018] The interconnection circuit 24 is provided with a plurality of wires for connecting the light-emitting diodes 14 in series, parallel, or series-parallel. The plurality of wires are connected to switches 26. The wires connected to the switches 26 that are turned on are able to supply power to the light-emitting diodes 14. By changing the switches 26 that are turned on, the wires for supplying power to the light-emitting diodes 14 are changed. By selecting the switches 26, the plurality of light-emitting diodes 14 can be connected in series, parallel, or series-parallel. Although two interconnection circuits 24 are shown in FIG. 1, the wires in the two interconnection circuits 24 may be connected to each other.

[0019] The number of switches 26 and the wiring structure of the interconnection circuit 24 may be changed as appropriate depending on the number of light-emitting diodes 14. As the number of light-emitting diodes 14 increases, the number of switches 26 and the number of wirings also increase.

[0020] The control circuit 18 is a circuit for controlling the on / off of the switch 26. The control circuit 18 can be configured with an IC. The control circuit 18 controls the switch 26 in accordance with the voltage rectified by the rectifier circuit 12. A voltmeter is provided for measuring this voltage. The voltmeter may use a Hall element, or may be configured so that a potential is directly input to the control circuit 18. The control circuit 18 controls the switch 26, thereby connecting the plurality of light-emitting diodes 14 in series, parallel, or series-parallel.

[0021] The series, parallel or series-parallel connection of the light-emitting diodes 14 is determined according to the rectified voltage. The connection state of the light-emitting diodes 14 is switched so that the potential of each light-emitting diode 14 is constant or approximately constant.

[0022] For example, suppose there are eight light-emitting diodes 14, each with a rated voltage of x (V). The peak voltage of the rectified voltage is 6x (V) (see FIG. 3). The connection states between times T1-T2 and T11-T12 are shown in FIG. 4(a), the connection states between times T2-T3 and T10-T11 in FIG. 4(b), the connection states between times T3-T4 and T9-T10 in FIG. 5(a), the connection states between times T4-T5 and T8-T9 in FIG. 5(b), the connection states between times T5-T6 and T7-T8 in FIG. 6(a), and the connection states between times T6-T7 in FIG. 6(b). Each light-emitting diode 14 is connected so that its rated voltage is equal to or less than x (V). Note that the period between T6 and T7 is the peak voltage, and may be a very short period.

[0023] When the rectified voltage is less than or equal to x (V), all of the light-emitting diodes 14 are connected in parallel (see FIG. 4). On the other hand, when the rectified voltage is at its peak, the number of light-emitting diodes 14 connected in series is greatest. In either case, the voltage applied to each light-emitting diode 14 is less than the rated voltage.

[0024] Some of the light-emitting diodes 14 may be connected in parallel or series-parallel, with the remaining light-emitting diodes 14 connected in series to these light-emitting diodes 14. The potential difference between the parallel-connected or series-parallel-connected portions may be different from the potential difference between the remaining series-connected portions. For example, from time T5 to T6, there are light-emitting diodes 14 connected in series and light-emitting diodes 14 connected in parallel. A potential difference of 3x (V) occurs in the parallel-connected portions, and a potential difference of 2x (V) occurs in the series-connected portions. An imbalance in the potential difference occurs between the series-connected portions and the parallel-connected portions. By creating an imbalance in the potential difference, the difference between the rectified voltage and the voltage applied to the light-emitting diodes 14 is reduced, making it less likely that losses will occur.

[0025] Some of the light-emitting diodes 14 may be connected in parallel or in series-parallel, and the remaining light-emitting diodes 14 may also be connected in parallel or in series-parallel, or these may be connected in series. Between times T3 and T4, there are parallel-connected portions and series-parallel-connected portions, which are connected in series. The parallel-connected portions and the series-parallel-connected portions may have different potential differences, which are x (V) and 2x (V) in FIG. 5(a).

[0026] In Figure 3, the potential difference occurring in each of the sections divided by dotted lines in Figures 4 to 6 is shown by dotted lines. By dividing the light-emitting diodes 14 into unbalanced groups and connecting them in series, parallel, or series-parallel, it is possible to make the rectified voltage and the potential difference of the light-emitting diodes 14 closer together. In the above explanation, there are eight light-emitting diodes 14, so in Figure 3 there are some places where the difference between the potential of the light-emitting diodes 14 and the rectified voltage is large. However, as the number of light-emitting diodes 14 increases, the number of series, parallel, and series-parallel connection patterns also increases, and the potential difference becomes smaller.

[0027] Since multiple light-emitting diodes 14 can be connected in an unbalanced manner, the duration of each connection state may vary. For example, in FIG. 3, the periods T5 to T6 and T7 to T8 are long, while the period T6 to T7 is short.

[0028] As described above, in order to facilitate switching the connections of the light-emitting diodes 14, the number of light-emitting diodes 14 is an even number, preferably a power of two.

[0029] The control circuit 18 controls the light-emitting diodes 14 to be in a predetermined connection state from the start of control until the rectified voltage reaches the first peak voltage. Specifically, the connection state of the light-emitting diodes 14 at the peak voltage is set. In the above example, the connection state of the light-emitting diodes 14 is set to the state shown in FIG. 6(b). This is set to the state that maximizes the number of series connections. By controlling the light-emitting diodes 14 to be in the most series connections, the light-emitting diodes 14 are protected.

[0030] Once the first peak voltage has passed after the start of control, the connection state of the light emitting diode 14 is switched in accordance with the rectified voltage as described above.

[0031] As described above, the present invention switches the connection of the light-emitting diodes 14 according to the rectified voltage, thereby applying a voltage that matches the rated voltage of the light-emitting diodes 14 to the light-emitting diodes 14 without using electrolytic capacitors or the like. By imbalancing the potential difference across each light-emitting diode 14, the potential difference across the entire light-emitting diodes can be made closer to the rectified voltage, thereby improving power utilization efficiency. When the light-emitting diodes 14 are first connected, they can be protected by being connected in a state that allows the rectified voltage to reach its peak voltage. Unlike chopper-type switching power supplies, no noise is generated, eliminating the need for noise countermeasures.

[0032] [Embodiment 2] The present invention may include a current control circuit. The current flowing through the light-emitting diode 14 may be adjusted by the current control circuit. For example, a current control circuit may be connected between the interconnection circuit 24 in FIG. 1 and ground, between the AC power supply 20 and the interconnection circuit 24, or between other components of the circuit shown in FIG. 1 and ground. The current control circuit may be configured with a transistor, a resistor, a constant current diode, or the like.

[0033] The potential generated in the current control circuit may be used as a power source for the control circuit 18. The power source for the control circuit 18 can be generated while adjusting the current flowing through the light-emitting diode 14, resulting in an energy-saving circuit. The potential generated in the light-emitting diode 14 may be used as a power source for the control circuit 18.

[0034] [Embodiment 3] The switch 26 provided in the switch element 22 may be replaced with a digital decoder. The connection structure of the light-emitting diodes 14 is input to the switch element 22 as a digital signal from the control circuit 18. This makes it possible to reduce the number of wires routed from the control circuit 18 to the switch element 22. When the light-emitting diodes 14 are arranged in one direction (lengthwise), securing the wiring area becomes an issue if the width direction is narrow, but by reducing the number of wires, it becomes easier to arrange them in one direction.

[0035] [Embodiment 4] The switching circuit 16 is not limited to the switch element 22 and the interconnection circuit 24 described in embodiment 1. For example, it may be a switch element 28 connected between two light-emitting diodes 14 shown in FIG.

[0036] The switch element 28 includes a first switch 30, a second switch 32, and a third switch 34. The first switch 30 may be a FET connected between the anodes of the light-emitting diodes 14. The second switch 32 may be a FET connected between the cathodes of the light-emitting diodes 14. The two FETs may be n-type MOSFETs. The third switch 34 may be a diode connecting the cathodes and anodes of adjacent light-emitting diodes 14. The anode of the diode is connected to the cathode of the light-emitting diode 14 in the preceding stage and the connection terminal of the second switch 32, and the cathode of the diode is connected to the anode of the light-emitting diode 14 in the following stage and the connection terminal of the first switch 30.

[0037] When the first switch 30 and the second switch 32 are turned on, adjacent light-emitting diodes 14 are connected in parallel. When the first switch 30 and the second switch 32 are turned off, adjacent light-emitting diodes 14 are connected in series.

[0038] The control circuit 18 inputs signals to the gates of the first switch 30 and the second switch 32, turning the first switch 30 and the second switch 32 on and off. The configuration of the control circuit 18 is not limited as long as it can control the switches 30 and 32.

[0039] The third switch 34 may be a FET. When the first switch 30 and the second switch 32 are turned on, the third switch 34 is turned off. When the first switch 30 and the second switch 32 are turned off, the third switch 34 is turned on. Although the first switch 30 and the second switch 32 use n-type MOSFETs, the third switch 34 may use a p-type MOSFET, or vice versa.

[0040] [Embodiment 5] In Fig. 1, there is one light-emitting diode 14 sandwiched between two switch elements 22. There may be a plurality of light-emitting diodes 14 sandwiched between two switch elements 22. The plurality of light-emitting diodes 14 sandwiched between two switch elements 22 may be connected in series, parallel, or series-parallel. The connection of the plurality of light-emitting diodes 14 can be switched between series, parallel, and series-parallel. The same applies to Fig. 7.

[0041] Sixth Embodiment The lighting device 10 may be configured with a first semiconductor substrate on which the light-emitting diodes 14 are formed and a second semiconductor substrate on which the switching circuit 16 and the control circuit 18 are formed. The light-emitting diodes 14 on the first semiconductor substrate and the switching circuit 16 on the second semiconductor substrate are ohmically connected by a low-resistance metal (such as an aluminum-nickel alloy).

[0042] The first and second semiconductor substrates are made of different materials. The first semiconductor substrate uses gallium nitride, while the second semiconductor substrate uses a silicon wafer for semiconductor ICs. The first and second semiconductor substrates face each other, and the terminals of the light-emitting diode 14 and the terminals of the switch 22 are joined by ohmic contact, with the remaining parts joined with resin (adhesive).

[0043] [Embodiment 7] The circuits formed on the second semiconductor substrate can be more integrated than the light-emitting diodes 14 on the first semiconductor substrate. When the areas of the junctions between the first and second semiconductor substrates are the same, empty space is likely to be formed on the second semiconductor substrate. Circuits (extension circuits) other than the circuits described above may be formed in that empty space. For example, a communication circuit may be formed on the second semiconductor substrate as an extension circuit. The communication circuit may be a circuit for wireless communication such as Wi-Fi or Bluetooth (registered trademark). The lighting device 10 is often installed on a ceiling or the top of a wall, where there are few obstacles to wireless communication radio waves. An antenna may be attached to the lighting device 10 of the present invention to function as a communication device. The communication circuit may also be used to send and receive control signals to the control circuit 18.

[0044] The extension circuit formed in the empty space of the second semiconductor substrate may be a circuit other than a communication circuit. For example, a sensor circuit may be used. The sensor circuit may be at least one of a human sensor, an infrared sensor, a temperature sensor, and a light sensor. The light-emitting state of the light-emitting diode 14 may be controlled according to the presence of people, temperature, illuminance, etc. in the space where the lighting device is installed.

[0045] The sensor circuit formed in the empty space of the second semiconductor substrate may be an acceleration sensor. If the lighting device 10 is a portable device, the acceleration sensor may detect the angle of the lighting device 10 and change the light-emitting state of the light-emitting diode 14. The acceleration sensor may be configured using MEMS (Micro Electro Mechanical Systems).

[0046] The extension circuit formed in the empty space of the second semiconductor substrate may be a circuit for driving a microphone, a speaker, or both. The microphone and speaker are attached to the lighting device 10. By installing the lighting device 10 in a high place such as a ceiling, there are fewer obstacles to sound when sound enters the microphone or comes out of the speaker.

[0047] The expansion circuit is not limited to the above-mentioned circuit, but may be any other circuit.

[0048] In addition, the present invention can be implemented in various forms with various improvements, modifications, and changes made based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

[0049] 10: Lighting device 12: Rectifier circuit 14: Light-emitting diode 16: Switching circuit 18: Control circuit 20: AC power supply 22, 28: Switch element 24: Interconnection circuit 26, 30, 32, 34: Switch

Claims

1. A lighting device comprising: a rectifier circuit that rectifies the output of an AC power source; a plurality of light-emitting diodes to which the voltage rectified by the rectifier circuit is applied; a switching circuit including a switch that switches the connection of the plurality of light-emitting diodes between series, parallel, or series-parallel by switching the switch; and a control circuit that controls the switching of the switch; wherein, under the control of the control circuit, some of the light-emitting diodes are connected in parallel or series-parallel, and the remaining light-emitting diodes are connected in series to the parallel- or series-parallel-connected light-emitting diodes, and there are times when the potential difference between some of the parallel- or series-parallel-connected light-emitting diodes differs from the potential difference between the remaining series-connected light-emitting diodes, and the control circuit maintains the connection state of the plurality of light-emitting diodes at the time of the peak voltage from the start of control until the voltage rectified by the rectifier circuit reaches the first peak voltage.

2. The lighting device of claim 1, further comprising a current control circuit for controlling the current flowing through said light emitting diode, and the potential generated in said current control circuit or the potential generated in said light emitting diode is used as a power source for the control circuit.

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