TWI703898B - Light-emitting device, driving device and driving method thereof - Google Patents

Abstract

A light-emitting device, driving device and driving method thereof. The driving device is coupled to the load, and includes a first current source and a second current source. The first current source provides a base current to drive the load; and the second current source generates an adjustment current according to the adjustment voltage, and enables adjustment current to adjust the magnitude of the current flowing through the load.

Description

Light emitting device and its driving device

The present disclosure relates to a driving device, and more particularly to a driving device for a light emitting device.

At present, the application of various solid-state light-emitting elements has become more and more widespread. For example, light source modules in display panels, lighting devices in daily life, and indicator lights in public spaces, etc., have gradually adopted light-emitting diodes (Light Emitting Diodes). Diode, LED) as the light source. In addition, with the vigorous development of communication technology, various solid-state light-emitting elements are also used in wireless signal transmission. In particular, light-emitting diodes used as lighting can be applied to the technology of Visible Light Communication (VLC).

However, in the prior art, the optical communication driving device used to drive the light-emitting element usually has various limitations, such as: light-emitting power, modulation speed, modulation waveform, circuit complexity, and size. Therefore, how to design a driving device that solves the above-mentioned constraints is the direction that those skilled in the art are devoted to research.

The present disclosure provides a light emitting device and a driving device thereof, which can dynamically adjust the current flowing through the load.

The present disclosure provides a driving device. The driving device is coupled to the load. The driving device includes a first current source and a second current source. The first current source provides basic current to drive the load. The second current source generates an adjustment current according to the adjustment voltage, and makes the adjustment current adjust the current value flowing through the load.

The present disclosure provides a light source device including a light-emitting element and the driving device described above. The driving device described above is coupled to the light emitting element.

Based on the above, the present disclosure provides a second current source to generate an adjustment current according to the adjustment voltage, and adjust the current value flowing through the load through the adjustment current. In this way, the operating speed of the driving device in the present disclosure may not be limited to the operating speed of the first current source for generating the main driving current, which effectively improves the performance of the driving circuit.

In order to make the above-mentioned features and advantages of the present disclosure more obvious and understandable, the following specific embodiments are described in detail in conjunction with the accompanying drawings.

100, 700: drive device

110, 200, 720, 800: the first current source

120, 710: Load

130, 300, 730, 900: second current source

I _C : Basic current

I _LED : Load current

I _VLC : Adjust current

V _VLC : Adjust voltage

Rf: current sense resistor

Vf: feedback voltage

210: Reference current source

220: voltage to current circuit

2201, 310, 610, 810, 910: operational amplifier

2202, 320, 600: voltage subtractor

GND: Reference ground terminal

Is: Reference current

Vs, V _in : reference voltage

R, Rs, Rs2, R ₁ ~ R ₄ : resistance

V _o1, V _i: Voltage

V _o2 , V _o , V _o22 : output voltage

Tr, Trs: Transistor

V _bias : bias voltage

V _o12 , V _i2 : voltage

V ₊ , V _- : input voltage

E1: Endpoint

V, V ₂ : Feedback signal

FIG. 1 illustrates a block diagram of a driving device according to an exemplary embodiment of the present disclosure.

FIG. 2 illustrates a schematic diagram of a first current source according to an exemplary embodiment of the present disclosure.

FIG. 3 illustrates a schematic diagram of a second current source according to an exemplary embodiment of the present disclosure Figure.

4A to 4C illustrate schematic diagrams of signals according to an exemplary embodiment of the present disclosure.

5A and 5B illustrate schematic diagrams of signals according to an exemplary embodiment of the present disclosure.

FIG. 6 illustrates a schematic diagram of a voltage subtractor according to an exemplary embodiment of the present disclosure.

FIG. 7 illustrates a block diagram of a driving device according to another exemplary embodiment of the present disclosure.

FIG. 8 illustrates a schematic diagram of a first current source according to an exemplary embodiment of the present disclosure.

FIG. 9 illustrates a schematic diagram of a second current source according to an exemplary embodiment of the present disclosure.

10A and 10B illustrate schematic diagrams of signals according to an exemplary embodiment of the present disclosure.

FIG. 1 illustrates a block diagram of a driving device according to an exemplary embodiment of the present disclosure. Please refer to FIG. 1, the driving device 100 includes a first current source 110, a load 120, a second current source 130, and a current sensing resistor Rf. The first terminal of the first current source 110 and the first terminal of the second current source 130 are jointly coupled to the first terminal of the load 120, and the second terminal of the first current source 110 is coupled to the reference ground terminal GND, the load 120 The second terminal of the second current source 130 and the second terminal of the second current source 130 are jointly coupled to the feedback terminal of the first current source 110, and the current sensing resistor Rf is coupled between the load 120 and the reference ground terminal GND. The load current I _LED flows through the current sensing resistor Rf to generate the feedback voltage Vf. The first current source 110 can provide the basic current I _C at the first end according to the feedback voltage Vf. The second current source 130 can draw the adjustment current I _VLC from the basic current I _C through its first end, and make the current value of the load current I _LED flowing through the load 120 equal to the basic current I _C minus the adjustment current I _VLC . Further, a second current source 130 may receive the regulated voltage V _VLC, and according to the adjustment to produce an adjusted voltage V _VLC current I _VLC. Therefore, the driving device 100 can draw the adjustment current I _{VLC from} the basic current I _C according to the adjustment voltage V _VLC , and then adjust the current value of the load current I _LED flowing through the load 120.

In this embodiment, the adjustment voltage V _VLC and the adjustment current I _VLC may be proportional or inversely proportional. For example, if the adjustment voltage V _{VLC is} inversely proportional to the adjustment current I _VLC , and the adjustment voltage V _VLC is directly proportional to the load current I _LED . In this embodiment, when the adjustment voltage V _VLC is adjusted higher, the adjustment current I _VLC drawn by the second current source 130 from the basic current I _C is adjusted lower, and the load current I _LED flowing through the load 120 is adjusted higher. Conversely, when the adjustment voltage V _VLC is adjusted lower, the adjustment current I _VLC drawn by the second current source 130 from the basic current I _C is adjusted higher, and the load current I _LED flowing through the load 120 is adjusted lower.

In other embodiments of the present disclosure, the adjustment voltage V _VLC and the adjustment current I _VLC may be proportional, and the adjustment voltage V _VLC and the load current I _LED may be inversely proportional. In this embodiment, when the adjustment voltage V _VLC is adjusted higher, the adjustment current I _VLC drawn by the second current source 130 from the basic current I _C is adjusted higher, and the load current I _LED flowing through the load 120 is adjusted lower. Conversely, when the adjustment voltage V _VLC is adjusted lower, the adjustment current I _VLC drawn by the second current source 130 from the basic current I _C is adjusted lower, and the load current I _LED flowing through the load 120 is adjusted higher.

With the above-mentioned driving device 100, the embodiment of the present disclosure can dynamically control the voltage value of the adjustment voltage V _VLC to control how much adjustment current I _{VLC is} drawn from the basic current I _C , thereby controlling the current value flowing through the load 120 . For example, the driving device 100 may adjust the voltage value of the adjusting voltage V _VLC periodically to generate the periodically changing load current I _LED to drive the load 120, wherein the switching frequency of the basic current I _C is lower than the adjusting voltage V _VLC switching frequency. In addition, the above-mentioned driving device 100 has a simple structure and is easy to integrate circuits.

It should be noted that the load 120 may be a light-emitting element, and the light-emitting element may be constructed by one or more light-emitting diodes. Among them, multiple light-emitting diodes can be connected in series, in parallel with each other, or a combination of multiple series and parallel to construct a light-emitting element, and there is no fixed limit. Therefore, the above-mentioned driving device 100 can be used to drive the light-emitting element, and by dynamically adjusting the voltage value of the voltage V _VLC , the light-emitting element can generate a periodically changing light signal. In this way, ordinary electrical signals can be converted into optical signals, and can be applied to various optical communication equipment. Among them, optical signals have directivity, information security, immunity to electromagnetic interference, no need for frequency band license, and can provide Many advantages such as indoor lighting.

FIG. 2 illustrates a schematic diagram of a first current source according to an exemplary embodiment of the present disclosure. Please refer to FIG. 2, the first current source 200 includes a reference current source 210 and a voltage-to-current circuit 220. The second terminal of the reference current source 210 is coupled to the reference ground GND, the feedback terminal of the reference current source 210 is used to receive the feedback voltage Vf, and the first terminal of the reference current source 210 can generate a reference current according to the feedback voltage Vf Is. The voltage-to-current circuit 220 is coupled to the reference current source 210 and receives the reference current Is. The voltage-to-current circuit 220 generates a reference voltage Vs according to the reference current Is, and generates a basic current I _C according to the bias voltage V _bias and the reference voltage Vs.

In detail, the voltage-to-current circuit 220 includes a resistor R, a transistor Tr, an operational amplifier 2201, and a voltage subtractor 2202. The resistor R is connected in series between the first terminal of the reference current source 210 and the negative input terminal of the operational amplifier 2201. The positive input terminal of the voltage subtractor 2202 is coupled to the first terminal of the reference current source 210, and the output terminal of the voltage subtractor 2202 is coupled to the positive input terminal of the operational amplifier 2201, and the negative input terminal of the voltage subtractor 2202 is used for The bias voltage V _{bias is} received. The control terminal of the transistor Tr is coupled to the output terminal of the operational amplifier 2201, the first terminal of the transistor Tr is coupled to the negative input terminal of the operational amplifier 2201, and the second terminal of the transistor Tr is used to output the basic current I _C.

In detail, by making the resistor R receive the reference current Is, the positive input terminal of the voltage subtractor 2202 can generate the reference voltage Vs, and the voltage subtractor 2202 subtracts the reference voltage Vs and the bias voltage V _bias to generate the voltage V _o1 . Further, the reference current Is flowing through the resistor R, may be generated and the negative input terminal of a first operational amplifier transistor Tr voltage V _I 2201, wherein the resistance value of the resistor R is equal to 1 ohm example, voltage V The voltage value of _i can be equal to Vs-Is. The operational amplifier 2201 generates an output voltage V _o2 to the control terminal of the transistor Tr and the voltage according to the voltage V _o1 V _i. The transistor Tr generates a basic current I _C at the second end of the transistor Tr according to the output voltage V _o2 , wherein the current value of the basic current I _C can be equal to the current value of the reference current Is.

In the disclosed embodiment, the transistor Tr may be a PNP-type bipolar junction transistor (BJT) or a P-type field-effect transistor (Field-Effect Transistor, FET), and there is no specific limitation.

FIG. 3 illustrates a schematic diagram of a second current source according to an exemplary embodiment of the present disclosure. Please refer to FIG. 3, the second current source 300 includes a resistor Rs, a resistor Rs2, a transistor Trs, an operational amplifier 310, and a voltage subtractor 320. The resistor Rs is coupled between the negative input terminal of the operational amplifier 310 and the positive input terminal of the voltage subtractor 320. The output terminal of the voltage subtractor 320 is coupled to the positive input terminal of the operational amplifier 310, wherein the positive input terminal of the voltage subtractor 320 is used to receive the load voltage V _LED , and the negative input terminal of the voltage subtractor 320 is used to receive the adjusted voltage V _VLC . The control terminal of the transistor Trs is coupled to the output terminal of the operational amplifier 310, the first terminal of the transistor Trs is coupled to the negative input terminal of the operational amplifier 310, and the resistor Rs2 is coupled to the second terminal of the transistor Trs and the feedback Between voltage Vf.

In detail, the voltage subtractor 320 subtracts the load voltage V _LED and the adjustment voltage V _VLC to generate the voltage V _o12 . The operational amplifier 310 generates an output voltage _Vo22 to the control terminal of the transistor Trs according to the voltage _Vo12 and the voltage _Vi2 . The transistor Trs generates an adjusting current I _VLC at the second end of the transistor Trs according to the output voltage V _o22 , where the current value of the adjusting current I _VLC can be equal to the current generated based on the load voltage V _LED and the voltage _Vi2 across the resistor Rs For example, the current value of the adjustment current I _VLC can be equal to (V _LED -V _VLC )/Rs.

It is worth noting that the transistor Trs can be a PNP type bipolar junction type transistor or a P type field effect transistor. In addition, the adjustment voltage V _VLC can be a periodically modulated voltage, or suitable for any adjustable format (for example, pulse width modulation, pulse wave position modulation, pulse amplitude modulation, quadrature amplitude modulation, etc.) , And the specifications of the transistor Trs can be set according to the frequency of the adjustment voltage V _VLC .

Regarding the implementation details of the adjustment voltage V _VLC , please refer to FIG. 1 and FIG. 4A to FIG. 4C at the same time. FIG. 4A to FIG. 4C illustrate a schematic diagram of a signal according to an exemplary embodiment of the present disclosure. In FIG. 4A, the adjusting voltage V _VLC is a pulse wave modulation signal, the basic current I _C is a direct current (equal to the current value A1), and the adjusting current I _VLC is a current with a periodic square wave. By drawing the adjustment current I _VLC from the basic current I _C , the generated load current I _{LED is} also a periodic square wave current, and the current value of the load current I _LED can be equal to the current value of the basic current I _C minus the adjustment The current value of the current I _VLC .

In FIG. 4B, the adjustment voltage V _VLC is a sine wave signal, the basic current I _C is a direct current (equal to the current value A1), and the adjustment current I _VLC is a current with a periodic sine wave. By drawing the adjustment current I _VLC from the basic current I _C , the generated load current I _{LED is} also a current with a periodic sine wave, and the current value of the load current I _LED can be equal to the current value of the basic current I _C minus the adjustment The current value of the current I _{VLC (} the current value of the peak is A1). In FIG. 4C, the adjustment voltage V _VLC is a triangular wave signal, the basic current I _C is a direct current (equal to the current value A1), and the adjustment current I _VLC is a current with a periodic triangular wave. By drawing the adjustment current I _VLC from the basic current I _C , the generated load current I _{LED is} also a current with a periodic triangular wave, and the current value of the load current I _LED can be equal to the current value of the basic current I _C minus the adjustment current I _VLC current value.

Regarding the implementation details of the adjustment voltage I _VLC , please refer to Fig. 1 and Figs. 5A to 5B at the same time. In Fig. 5A, the basic current I _C is a direct current (equal to the current value A2), and the adjustment current I _VLC is a periodic string. Wave of electric current. By drawing the adjustment current I _VLC from the basic current I _C , the generated load current I _LED is a current with a periodic sine wave, and the current value of the load current I _LED can be equal to the current value of the basic current I _C minus the adjustment current I The current value of _VLC . In Figure 5B, the basic current I _C is a periodic square wave current (the current value of the basic current I _C varies between A2 and A3, and the half period is t), and the adjustment current I _VLC is periodic. Sine wave current. By drawing the adjustment current I _VLC from the basic current I _C , the generated load current I _LED is a sine wave current with a periodic and peak value that varies according to the basic current I _C , and the current value of the load current I _LED can be equal to the basic current I The current value of _C subtracts the current value of the adjustment current I _VLC .

FIG. 6 illustrates a schematic diagram of a voltage subtractor according to an exemplary embodiment of the present disclosure. Please refer to FIG. 6, the voltage subtractor 600 includes an operational amplifier 610 and a plurality of resistors R ₁ ˜R ₄ . The resistor R _{1 is} coupled between the positive input terminal of the operational amplifier 610 and the reference ground terminal GND. The resistor R _{2 is} coupled to the positive input terminal of the operational amplifier 610 and the resistor R ₁ . The resistor R _{3 is} coupled to the negative input terminal of the operational amplifier 610. The resistor R _{4 is} coupled between the negative input terminal of the operational amplifier 610 and the output terminal of the operational amplifier 610. The positive input terminal of the operational amplifier 610 can receive the input voltage V ₊ through the resistor R ₂ , and the negative input terminal of the operational amplifier 610 can receive the input voltage V ₋ through the resistor R ₃ . The voltage subtractor 600 can generate the voltage V _o according to the input voltage V ₊ and the input voltage V _- . Under the condition having the same resistance value of resistors R ₁ ~ R _4, the input voltage V _o = voltage V ₊ minus the input voltage V _-.

FIG. 7 illustrates a block diagram of a driving device according to another exemplary embodiment of the present disclosure. Please refer to FIG. 7, the driving device 700 includes a load 710, a first current source 720 and a second current source 730. The first terminal of the load 710 receives the reference voltage Vs, the second terminal of the load 710 is coupled to the first terminal of the first current source 720 and the first terminal of the second current source 730, and the second terminal of the first current source 720 And the second end of the second current source 730 is commonly coupled to the reference ground GND. The first current source 720 and the second current source 730 can respectively generate the basic current I _C and the adjustment current I _VLC . The basic current I _C and the adjustment current I _VLC generated by the first current source 720 and the second current source 730 are combined and flow through the load 710, so that the value of the current flowing through the load 710 is equal to the basic current I _C plus the adjustment current I _VLC (the load current I _{LED is} shunted at the node E1 into the basic current I _C and the adjustment current I _VLC ). Further, a second current source 730 may receive a regulated voltage V _VLC, and according to the adjustment to produce an adjusted voltage V _VLC current I _VLC. Thereby, the driving device 700 can adjust the current value of the combination of the basic current I _C and the adjustment current I _VLC , and then adjust the load current I _LED flowing through the load 710.

With the above-mentioned driving device 700, the disclosed embodiments can dynamically control the voltage value of the adjustment voltage V _VLC to control the current value of the combination of the basic current I _C and the adjustment current I _VLC , thereby controlling the current flowing through the load 710 Value size. For example, the driving device 700 can adjust the voltage value of the adjusting voltage V _VLC periodically to generate the periodically changing load current I _LED to drive the load 710, wherein the switching frequency of the basic current I _C is lower than the adjusting voltage V _VLC switching frequency. It can be known from the above description that the driving device 700 of this embodiment has a simple circuit structure and is easy to be integrated into circuits.

FIG. 8 illustrates a schematic diagram of a first current source according to an exemplary embodiment of the present disclosure. Please refer to FIG. 8, the first current source 800 includes a resistor R, a transistor Tr, and an operational amplifier 810. The negative input terminal of the operational amplifier 810 is coupled to the reference ground GND through a resistor R, and the positive input terminal of the operational amplifier 810 is used to receive the bias voltage V _bias . The control terminal of the transistor Tr is coupled to the output terminal of the operational amplifier 810, the first terminal of the transistor Tr (ie, the terminal E1) is used to receive the reference voltage V _in , and the second terminal of the transistor Tr is coupled to the operational amplifier 810's negative input.

In detail, the operational amplifier 810 generates an output voltage _Vo to the control terminal of the transistor Tr according to the bias voltage V _bias and the feedback signal V. The transistor Tr generates a basic current I _C at the second end of the transistor Tr according to the output voltage V _o to flow through the resistor R, wherein the value of the current flowing through the resistor R is equal to the voltage value of the feedback signal V divided by the value of the resistor R resistance. In operation, the voltage value of the feedback signal V is substantially equal to the voltage value of the bias voltage V _bias , and the current value of the basic current I _C can be equal to V _bias /R.

It is worth noting that the transistor Tr may be an NPN type bipolar junction type transistor or an N type field effect transistor.

FIG. 9 illustrates a schematic diagram of a second current source according to an exemplary embodiment of the present disclosure. Please refer to FIG. 9, the second current source 900 includes a resistor Rs, a transistor Trs, and an operational amplifier 910. The negative input terminal of the operational amplifier 910 is coupled to the reference ground GND via the resistor Rs, and the positive input terminal of the operational amplifier 910 is used to receive the adjustment voltage V _VLC . The control terminal of the transistor Trs is coupled to the output terminal of the operational amplifier 910, the first terminal of the transistor Trs (ie, the terminal E1) is used to receive the reference voltage V _in , and the second terminal of the transistor Trs is coupled to the operational amplifier The negative input of the 910.

Specifically, according to the adjustment of the operational amplifier 910 and the voltage feedback signal V _VLC V ₂ generates a control terminal to an output voltage V _o2 of transistor Trs. The transistor Trs generates an adjusting current I _VLC at the second end of the transistor Trs to flow through the resistor Rs according to the output voltage V _o2 , wherein the current value of the adjusting current I _VLC is equal to the voltage value of the feedback signal V ₂ divided by the resistor Rs The resistance value. In operation, the voltage value of the feedback signal V ₂ is substantially equal to the voltage value of the adjustment voltage V _VLC , and the current value of the adjustment current I _VLC can be equal to V _VLC /Rs.

It is worth noting that the transistor Trs can be an NPN type bipolar junction type transistor or an N type field effect transistor.

10A and 10B illustrate schematic diagrams of signals according to an exemplary embodiment of the present disclosure. Referring to FIG. 10A, the basic current I _C is a direct current (equal to the current value A4), and the adjustment current I _VLC is a current with a periodic sinusoidal wave. Through the combination of the basic current I _C and the adjustment current I _VLC , the combined load current I _LED is a current with a periodic sine wave, and the current value of the load current I _LED can be equal to the current value of the basic current I _C plus adjustment The current value of the current I _VLC . Please refer to Figure 10B, the basic current I _C is a periodic square wave current (the current value of the basic current I _C varies between A4 and 0, and the half period is t), and the adjustment current I _VLC is periodic. Sine wave current. Through the combination of the basic current I _C and the adjustment current I _VLC , the combined load current I _LED is a sine wave current with periodic and peak values that vary according to the basic current I _C , and the current value of the load current I _LED can be equal to the basic current The current value of I _C is added to the current value of the adjustment current I _VLC .

In this embodiment, the basic current I _C does not affect the adjustment current I _VLC obtained from the optical signal, and the adjustment current I _VLC has the advantage of high bandwidth. For example, the basic current I _C is a relatively low frequency current, the adjustment current I _VLC is a relatively high frequency current, and the load current I _LED formed by combining the basic current I _C and the adjustment current I _VLC has multiple frequencies.的current. In this way, after receiving the optical signal generated according to the load current I _LED , the obtained optical signal can be captured by a bandpass filter, and the communication data generated according to the adjustment current I _VLC can be obtained .

In summary, the present disclosure provides a second current source to generate an adjusted current according to the adjusted voltage, and adjusts the current value flowing through the load by adjusting the current. In this way, the operating speed of the driving device in the present disclosure may not be limited to the operating speed of the first current source for generating the main driving current, which effectively improves the performance of the driving circuit.

Although this disclosure has been disclosed in the above embodiments, it is not intended to limit the disclosure. Anyone with ordinary knowledge in the relevant technical field can make some changes and modifications without departing from the spirit and scope of this disclosure. Therefore, The scope of protection of this disclosure shall be subject to those defined by the attached patent scope.

100‧‧‧Drive device

110‧‧‧First current source

120‧‧‧Load

130‧‧‧Second current source

I _C ‧‧‧Basic current

I _LED ‧‧‧Load current

I _VLC ‧‧‧Adjust current

V _VLC ‧‧‧Adjust voltage

GND‧‧‧Reference ground

Rf‧‧‧Current sensing resistor

Vf‧‧‧Feedback voltage

Claims (6)

A driving device, coupled to a load, includes: a first current source that provides a basic current flowing out of the load to drive the load; and a second current source that generates a flow out of the load according to an adjusted voltage Adjust the current, and adjust the current value flowing through the load by the adjustment current, wherein the basic current and the adjustment current generated by the first current source and the second current source are divided and flowed out of the load, so that the current The magnitude of the current through the load is equal to the basic current plus the adjustment current, wherein the second current source includes: a first resistor; a first operational amplifier, the negative input of the first operational amplifier passes through the first resistor Coupled to a reference ground terminal, the positive input terminal of the first operational amplifier is used to receive the adjustment voltage; and a first transistor, the control terminal of the first transistor is coupled to the output terminal of the first operational amplifier , The first terminal of the first transistor is coupled to the second terminal of the load, and the second terminal of the first transistor is coupled to the negative input terminal of the first operational amplifier. The driving device according to claim 1, wherein the first terminal of the load receives a reference voltage, and the second terminal of the load is coupled to the first current source and the second current source. The driving device according to claim 1, wherein the first current source includes: a second resistor; a second operational amplifier, the negative input terminal of the second operational amplifier is coupled to the reference via the second resistor The ground terminal, the positive input terminal of the second operational amplifier is used to receive a bias voltage; and a second transistor, the control terminal of the second transistor is coupled to the output terminal of the second operational amplifier, the second The first terminal of the transistor is coupled to the second terminal of the load, and the second terminal of the second transistor is coupled to the negative input terminal of the second operational amplifier. The driving device described in item 1 of the scope of patent application, wherein the adjusting voltage is a pulse wave modulation signal, a sine wave signal or a triangle wave signal, and the basic current is a direct current or a periodically changing current. The driving device described in item 1 of the scope of patent application, wherein when the basic current is a periodically changing current, the switching frequency of the basic current is lower than the switching frequency of the adjustment voltage. A light source device includes: a light-emitting element; and the driving device as described in item 1 of the scope of patent application, coupled to the light-emitting element.

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