TWI758657B - A driving circuit and light-emitting device using the same - Google Patents

Abstract

This application discloses a driving circuit and light-emitting device using the same. The driving circuit includes an external control unit, a digital control unit, a trigger unit and a current source. The digital control unit generates an internal control signal. The trigger unit generates a trigger signal to control the current source according to the internal control signal.

Description

A drive circuit and a light-emitting device using the drive circuit

The present invention relates to a driving circuit of a light-emitting device, and more particularly, to a circuit for adjusting the light intensity of the light-emitting device by using a digital control unit.

With the development of technology, more and more devices in daily life use light-emitting diodes (LEDs) as light sources. In order to be more widely used in daily life, some light sources are equipped with dimmers that can adjust the brightness, so that users can change the intensity of the light source according to the needs of the environment. Common dimmers can be divided into digital dimming methods and analog dimming methods. Compared with the digital dimming method, although the analog dimming method does not require a digital controller, it is limited by the dimmer (such as a TRIAC dimmer) used in the analog dimming method. The maintenance current is required to maintain the normal operation of the dimmer, which leads to the situation that the current through the dimmer is lower than the maintenance current of the dimmer, causing the dimmer to turn off abnormally, causing the light source to flicker. . Therefore, the present invention hereby proposes a digital dimming method, which not only avoids flickering at low brightness, but also improves the stability of the dimming method.

The invention discloses a driving circuit which can be connected to a power source, comprising a digital control unit, a trigger unit, a current source, and a resistor. The digital control unit provides a first current signal, the trigger unit is electrically connected to the digital control unit and receives the first current signal and the second current signal from the power source, and the current source is electrically connected to the trigger unit.

1000, 1002, 2000: Lighting installations

300, 302, 320: drive circuit

110, 111: Power

10: External control unit

12: Digital control unit

14, 15: Trigger unit

16, 160: current source

18: Light source

Ca: Capacitance

Di: Diode

R: resistance

Q1, Q2, Q3: Transistor

Si1: the first control signal

Si2: the second control signal

Si3: the third control signal

FIG. 1A is a circuit diagram of a light emitting device according to an embodiment of the present invention.

FIG. 1B is a waveform diagram of the second control signal.

FIG. 2 is a circuit diagram of a light emitting device according to an embodiment of the present invention.

FIG. 3 is a circuit diagram of a light emitting device according to an embodiment of the present invention.

FIG. 1A is a circuit diagram of a light emitting device 1000 according to an embodiment of the present invention. The light emitting device 1000 includes a light source 18 and a driving circuit 300 . The driving circuit 300 has an external control unit 10 , a digital control unit 12 , a trigger unit 14 and a current source 16 . The current source 16 is a constant current source and includes a transistor Q1 . The transistor Q1 may be a high electron mobility transistor (HEMT), more specifically a depletion type high electron mobility field effect transistor. Transistor (Depletion-mode HEMT). The transistor Q1 has a gate electrode G1, a drain electrode D1 and a source electrode S1. The drain electrode D1 is electrically connected to the light source 18 , and the gate electrode G1 is electrically connected to the trigger unit 14 .

x

1；0

y

1；(x+y)

1。並根據 材料的不同，發光二極體可以發射峰值波長在610nm和650nm之間的紅色光、峰值波長在495nm和570nm之間的綠色光、峰值波長在450nm和495nm之間的藍色光、峰值波長在400nm和440nm之間的紫色光或峰值波長在200nm和400nm之間的紫外線光。在一實施例中，發光二極體具有一發光層，以及一形成於發光層之上的波長轉換材料，波長轉換材料包含了量子點材料、螢光粉材料或其二者之組合。其中，螢光粉材料可以包含黃綠色螢光粉、紅色螢光粉或藍色螢光粉。黃綠色螢光粉包含YAG、TAG，矽酸鹽，釩酸鹽，鹼土金屬硒化物，及金屬氮化物。紅色螢光粉包括氟化物(例如K₂TiF₆：Mn⁴⁺或K₂SiF₆：Mn⁴⁺)、矽酸鹽、釩酸鹽、鹼土金屬硫化物、金屬氮氧化物、及鎢酸鹽和鉬酸鹽的混合物。藍色螢光粉包括BaMgAl₁₀O₁₇：Eu²⁺。量子點材料可以是硫化鋅、硒化鋅、碲化鋅、氧化鋅、硫化鎘、硒化鎘、碲化鎘、氮化鎵、磷化鎵、硒化鎵、銻化鎵、砷化鎵、氮化鋁、磷化鋁、砷化鋁、磷化銦、砷化銦、碲、硫化鉛、銻化銦、碲化鉛、硒化鉛、碲化锑、ZnCdSeS、CuInS、CsPbCl₃、CsPbBr₃、CsPbI₃。在一實施例中，包含波長轉換材料的發光二極體可以發出一白光。例如，在顯示器的背光模組中，白光的色溫介於10000K~20000K之間，且在CIE1931色度圖中具有一色點座標(x、y)，其中，0.27≦x≦0.285；0.23≦y≦0.26。在另一實施例中，例如，在通用照明的場合中，發光二極體發出的白光具有一色溫介於2200~6500K(例如2200K、2400K、2700K、3000K、5700K、6500K)且在CIE1931色度圖中具有一色點座標(x、y)位於7階麥克亞當橢圓(MacAdam ellipse)內。 The light source 18 includes one or more light-emitting diodes, and the light-emitting diodes may include a semiconductor layer composed of a group III-V semiconductor material to emit non-coherent light, such as a group III-V semiconductor material such _{as AlxInyGa 1-xy)} N or Al _x In _y Ga _(1-xy) P, where 0

x

1;0

y

1; (x+y)

1. And depending on the material, light-emitting diodes can emit red light with peak wavelengths between 610nm and 650nm, green light with peak wavelengths between 495nm and 570nm, blue light with peak wavelengths between 450nm and 495nm, peak wavelengths between 495nm and 570nm. Violet light between 400nm and 440nm or ultraviolet light with a peak wavelength between 200nm and 400nm. In one embodiment, the light-emitting diode has a light-emitting layer, and a wavelength conversion material formed on the light-emitting layer, and the wavelength conversion material includes a quantum dot material, a phosphor material, or a combination thereof. The phosphor material may include yellow-green phosphor, red phosphor or blue phosphor. Yellow-green phosphors include YAG, TAG, silicates, vanadates, alkaline earth metal selenides, and metal nitrides. Red phosphors include fluorides (eg K ₂ TiF ₆ : Mn ⁴⁺ or K ₂ SiF ₆ : Mn ⁴⁺ ), silicates, vanadates, alkaline earth metal sulfides, metal oxynitrides, and tungstates and molybdate mixture. The blue phosphor includes BaMgAl ₁₀ O ₁₇ : Eu ²⁺ . The quantum dot material can be zinc sulfide, zinc selenide, zinc telluride, zinc oxide, cadmium sulfide, cadmium selenide, cadmium telluride, gallium nitride, gallium phosphide, gallium selenide, gallium antimonide, gallium arsenide, Aluminum Nitride, Aluminum Phosphide, Aluminum Arsenide, Indium Phosphide, Indium Arsenide, Tellurium, Lead Sulfide, Indium Antimonide, Lead Telluride, Lead Selenide, Antimony Telluride, ZnCdSeS, CuInS, CsPbCl ₃ , CsPbBr ₃ , CsPbI ₃ . In one embodiment, the light emitting diode including the wavelength converting material can emit a white light. For example, in a display backlight module, the color temperature of white light is between 10000K and 20000K, and there is a color point coordinate (x, y) in the CIE1931 chromaticity diagram, where 0.27≦x≦0.285; 0.23≦y≦ 0.26. In another embodiment, for example, in the case of general lighting, the white light emitted by the light-emitting diode has a color temperature ranging from 2200K to 6500K (such as 2200K, 2400K, 2700K, 3000K, 5700K, 6500K) and has a CIE1931 chromaticity In the figure, the coordinates (x, y) of a color point are located in a MacAdam ellipse of order 7 (MacAdam ellipse).

As shown in FIG. 1A , if the operating voltages of different elements in the light emitting device 1000 are different, the light emitting device 1000 can be respectively connected to power sources 110 and 111 suitable for the needs of the individual elements. In one embodiment, the operating voltage of the digital control unit 12 is 5V, and the power supply 110 can provide a voltage of 3V to 15V, such as 3.3V, Voltages of 5V, 7V, and 12V; the operating voltage of the light source 18 is 110V, and the power supply 111 can provide voltages of 70V to 230V, such as 80V, 96V, and 115V. Connecting components that require different operating voltages to their respective power sources not only makes the power supply more efficient, but also avoids mutual interference between components, which affects the stability of the components when they are operated. In one embodiment, the light-emitting device 1000 further includes an AC-DC voltage conversion circuit (not shown) connected to the commercial power, and converts the commercial power into a power source 110 and/or a power source 111, for example, the commercial power is 110V, 220V or 240V alternating current.

In the light emitting device 1000 , the digital control unit 12 generates a second control signal Si2 according to a first control signal Si1 from the external control unit 10 . The second control signal Si2 is input to the trigger unit 14 . The trigger unit 14 generates a third control signal Si3 according to the second control signal Si2, and uses the third control signal Si3 to control the current source 16 to be turned on or off. The first control signal Si1 is an external control signal, the second control signal Si2 is an internal control signal, and the third control signal Si3 is a trigger signal. Since the brightness of the light emitting diode is related to the current flowing through it, by controlling the on or off state of the current source 16 , the current flowing through the light source 18 can be determined for a period of time, so as to achieve the effect of adjusting the luminous intensity of the light emitting device 1000 .

The external control unit 10 can be a wired device or a wireless device, and is used for receiving the user's instruction to generate the first control signal Si1. In one embodiment, the external control unit 10 is a wired device, such as a variable resistor or a sensor, which is connected to the digital control unit 12 through a physical line to transmit the first control signal Si1 to the digital control unit 12 . In one embodiment, the external control unit 10 is a wireless device that transmits the first control signal Si1 to the digital control unit 12 through wireless transmission, such as a Bluetooth module or an IoT device. In one embodiment, the digital control unit 12 is a Microcontroller Unit (MCU) for generating a second control signal Si2 according to the first control signal Si1, and the second control signal Si2 has a pulse width Modulation (Pulse Width Modulation; PWM) signal. More specifically, the digital control unit 12 adjusts the signal characteristic of the second control signal Si2 according to the first control signal Si1, and the signal characteristic includes a duty ratio. As the duty ratio is lower, the current source 16 The longer the on time of the light source 18 is, the longer the light source 18 emits time, and the higher the brightness provided by the light emitting device 1000 is. Please refer to Figure 1B and related paragraphs for details.

In general, the lighting time of the light source 18 is determined by controlling the on or off of the current source 16 to achieve the effect of dimming. Wherein, by turning on or off the current source 16 through a switching frequency higher than the human eye perceptible switching frequency (eg, a frequency greater than 50, 60, 120 Hz), the human eye can avoid discomfort caused by the flickering of the light emitting device 1000 . In other words, the light emitting device 1000 sequentially generates the second control signal Si2 and the third control signal Si3 according to the first control signal Si1 to turn on or off the current source 16, wherein the frequencies of the second control signal Si2 and the third control signal Si3 are higher than the switching frequency perceptible to the human eye.

In the light emitting device 1000, the transistor Q1 in the current source 16 is a depletion type high electron mobility field effect transistor, so the trigger unit 14 provides a third control signal Si3 including a negative voltage to turn on or off the transistor Q1. Specifically, the trigger unit 14 includes a negative voltage generator or a clamping circuit for generating a third control signal Si3 including a negative voltage according to the second control signal Si2. Referring to FIG. 1A , the trigger unit 14 includes a capacitor Ca electrically connected to the digital control unit, and a diode Di connected to the capacitor Ca and the transistor Q1 . The voltage ranges of the third control signal Si3 and the second control signal Si2 are different. For example, the voltage range of the second control signal Si2 is 0V~5V, while the voltage range of the third control signal Si3 is -5V~0V, so that the voltage range including the negative voltage The third control signal Si3 enables or disables the transistor Q1.

FIG. 1B is a waveform diagram of the second control signal Si2 in an embodiment of FIG. 1A. Figure 1B includes five waveforms such as waveforms (a) to (e), which represent waveforms of the second control signal Si2 with responsibility ratios of 0%, 25%, 50%, 75%, and 100%, respectively. With the difference of the duty ratio, the waveform of the second control signal Si2 also changes from the state of the low voltage (VL) in the waveform (a) representing the duty ratio 0% to the high voltage (VH), for example, it becomes a representative A waveform with a 25% responsibility ratio (b), a waveform with a representative responsibility ratio of 50% (c), a waveform with a representative responsibility ratio of 75% (d), or a representative responsibility ratio of 100% waveform (e). In the light emitting device 1000, the trigger unit 14 generates a third control signal Si3 according to the second control signal Si2, and the frequency of the third control signal Si3 is the same or approximately the same as the second control signal Si2, but the responsibility of the third control signal Si3 The ratio is different from the second control signal Si2. In terms of frequency, the frequency difference between the third control signal Si3 and the second control signal Si2 is less than 5% of one of the frequencies. In terms of responsibility ratio, the sum of the responsibility ratios of the two signals Si2 and Si3 is approximately equal to 100%. For example, in the light-emitting device 1000, when the second control signal Si2 is the waveform (b) and the responsibility ratio is 25%, the responsibility ratio of the third control signal Si3 is approximately 75%; When (b) is adjusted to waveform (d), the responsibility ratio of the third control signal Si3 is also adjusted from 75% to 25%. In one embodiment, the sum of the responsibility ratios of the two signals Si2 and Si3 ranges from 90% to 110%. The higher the duty ratio of the second control signal Si2 is, the lower the duty ratio of the third control signal Si3 is, the shorter the time for the light source 18 to emit light in one cycle, the darker the brightness of the light-emitting device 1000; on the contrary, the second control signal Si3 The lower the duty ratio of the signal Si2 is, the higher the duty ratio of the third control signal Si3 is, the longer the light source 18 emits light in one cycle, the brighter the brightness of the light emitting device 1000 is. To sum up, the light emitting device 1000 can receive the user's instruction from the external control unit 10 to generate the corresponding first control signal Si1 to control the duty ratio of the second control signal Si2, and then control the current source 16 through the third control signal Si3, so as to The light emission brightness of the light emitting device 1000 is changed.

In one embodiment, a resistor (not shown) is further disposed between the light source 18 and the power source 111 to adjust the current flowing through the light source 18 . In one embodiment, a resistor and/or a capacitor is further arranged between the power source 111 and the current source 16, so that the resistor and/or the capacitor and the light source 18 are connected in series or in parallel to adjust the current flowing through the light source 18, and to filter out impurities. The information makes the lighting condition of the light source 18 more stable. In one embodiment, a resistor (not shown) and/or a capacitor (not shown) is further disposed between the source S of the transistor Q1 and the ground potential in the current source 16 to adjust the current flowing through the transistor Q1.

FIG. 2 is a light emitting device 1002 according to an embodiment of the present invention. The light emitting device 1002 includes a light source 18 and a driving circuit 302 . The driving circuit 302 includes an external control unit 10 , a digital control unit 12 , a trigger unit 14 , a resistor R and a current source 160 . The current source 160 includes a transistor Q1 and a transistor Q2 connected in parallel. The transistors Q1 and Q2 may be high electron mobility field effect transistors, more specifically depletion type high electron mobility field effect transistors. The transistor Q1 has a gate electrode G1, a drain electrode D1 and a source electrode S1, and the transistor Q2 has a gate electrode G2, a drain electrode D2 and a source electrode S2. The transistor Q1 and the transistor Q2 are connected in parallel, so that the drain electrodes D1 and D2 are electrically connected to the light source 18 , the source electrodes S1 and S2 are connected to each other, and the gate electrodes G1 and G2 are connected to the trigger unit 14 together. Please refer to the above paragraphs for the descriptions of the components in the light-emitting device 1002 and the light-emitting device 1000 with the same or similar numbers and names, and how the light-emitting device 1002 receives the user's command through the external control unit 10 to generate the first control signal Si1, and then Please also refer to the above paragraphs for the operation flow of controlling the luminous intensity of the light source 18 via the second control signal Si2 and the third control signal Si3 generated by the digital control unit 12 and the trigger unit 14 . In the light emitting device 1002, the current source 160 including the transistors Q1 and Q2 can provide more current to the light source 18 to increase the luminous intensity. In one embodiment, a resistor R is set between the power supply 110 and the trigger unit 14 to provide another additional current (current signal) to the trigger unit 14 . The current signal can provide more current, so that the capacitor Ca in the trigger unit 14 can receive more charges, so as to output the current to the transistors Q1 and Q2 more stably. One end of the resistor R is connected to the power supply 110 , and the other end is electrically connected to the digital control unit 12 and the trigger unit 14 at the same time. Through the setting of the resistor R, the trigger unit 14 not only receives the second control signal Si2, but also receives the current signal passing through the resistor R. As mentioned above, the current signal can provide more charge to the capacitor Ca, so as to provide a more stable output current to the transistors Q1 and Q2. In one embodiment, the current value of the current signal is greater than the current value of the second control signal Si2, for example, the second control signal Si2 is 100mA, and the current signal is 1A. In other words, if the current amount of the second control signal Si2 cannot meet the requirements of the transistors Q1 and Q2, the current signal can be used to supplement the requirements. Here, the current signal can provide more charge to the capacitor Ca to output a more stable current to the power supply. Crystal Q1, Q2. Therefore, the capacitor Ca in the trigger unit 14 can receive the current signal (ie the second control signal Si2 ) from the digital control unit 12 and The current signal from the power supply 110 can store more charges due to receiving a plurality of current signals, so that the capacitor Ca will not be caused by insufficient charge stored in the capacitor Ca during the period when the transistors Q1 and Q2 are turned on. The third control Abnormality of signal Si3. For example, it should be the third control signal Si3 with a duty ratio of 75%. Because the amount of charge stored in the capacitor Ca is not enough, it transitions from a high-voltage state to a low-voltage state in advance, such as a case where the duty ratio is 60%. In this case, the responsibility ratio is abnormal, which will cause the transistors Q1 and Q2 to be turned off in advance, so that the brightness of the light-emitting device 1002 is abnormal. It is worth noting that when the trigger unit 14 is connected with more transistors, the capacity of the capacitor Ca must be increased to store more charges and stably output current to the connected transistors. In this case, it is more likely to cause an abnormal situation of the third control signal Si3 due to insufficient charge stored in the capacitor Ca. Therefore, it is more necessary to set the resistor R as shown in Figure 2 to increase the input to the trigger unit. 14 current flow. Wherein, the value of the resistor R can be changed with the required amount of current. If the amount of current input to the trigger unit 14 is to be increased, the resistor R with a lower value is set. On the other hand, to avoid excessive current passing through the resistor to generate excess heat, the resistor R with a larger value is set instead, and the current is reduced under the circumstance that the third control signal Si3 can be prevented from being abnormal. In other embodiments, the resistor R can be set in the light-emitting device 1000 of FIG. 1A to connect the power supply 110 and the trigger unit 14 , so that the capacitor Ca in the trigger unit 14 can receive the current signal from the digital control unit 12 ( That is, the second control signal Si2) and the current signal passing through the resistor R to store more charges, so as to avoid the abnormal brightness phenomenon that the transistor Q1 is turned off in advance.

In one embodiment, a resistor (not shown) is further disposed between the light source 18 and the power source 111 to adjust the current flowing through the light source 18 . In one embodiment, a resistor and/or a capacitor is further arranged between the power source 111 and the current source 160, so that the resistor and/or the capacitor is connected in parallel with the light source 18 to adjust the current flowing through the light source 18, which can filter out noise and allow The lighting condition of the light source 18 is more stable. In one embodiment, a resistor (not shown) and/or a capacitor (not shown) is further disposed between the sources S1 and S2 of the transistors Q1 and Q2 in the current source 160 and the ground potential to adjust the flow through the transistors The current of Q1 and Q2.

FIG. 3 is a light emitting device 2000 according to an embodiment of the present invention. The light-emitting device 2000 includes a light source 18 and a driving circuit 320 . The driving circuit 320 has an external control unit 10 , a digital control unit 12 , a trigger unit 15 and a current source 160 . Please refer to the foregoing paragraphs for the description of the elements in the light-emitting device 2000 and the light-emitting device 1000 with the same or similar reference numerals and names. The trigger unit 15 includes a transistor Q3. The transistor Q3 may be a metal oxide semiconductor field effect transistor (MOSFET), more specifically, an enhancement type high electron mobility field effect transistor. -mode MOSFET). The transistor Q1 has a gate electrode G1, a drain electrode D1 and a source electrode S1, and the transistor Q3 has a gate electrode G3, a drain electrode D3 and a source electrode S3. In the light emitting device 2000, the transistor Q1 in the current source 160 is connected in series with the transistor Q3, so that the gate G1 of the transistor Q1 is connected to the ground potential, the drain D1 is electrically connected to the light source 18, and the source S1 is connected to the electrical potential. The drain D3 of the transistor Q3 is connected, the gate G3 of the transistor Q3 is connected to the digital control unit 12, the drain D3 is connected to the source S1 of the transistor Q1, and the source S3 is connected to the ground potential. In the light emitting device 2000 , the digital control unit 12 generates a second control signal Si2 according to a first control signal Si1 from the external control unit 10 , and the second control signal Si2 is input to the trigger unit 15 . In one embodiment, the digital control unit 12 and the trigger unit 15 further have a resistor, and the voltage value and/or the current value of the second control signal Si2 can be adjusted through the setting of the resistor. The trigger unit 15 receives the second control signal Si2, and adjusts the on or off of the transistor Q3 according to the second control signal Si2, thereby adjusting the light-emitting time length of the light source 18 in one cycle. More specifically, when the transistor Q3 receives the second control signal Si2 and is turned on, the current passes through the light source 18 , the current source 160 (the transistor Q1 in the inside) and the trigger unit 15 (the transistor Q3 in the inside) in sequence, so that the The light emitting device 2000 may emit light. On the other hand, when the transistor Q3 is turned off after receiving the second control signal Si2, the current cannot pass through the trigger unit 15 (the transistor Q3 in it), so that the light emitting device 2000 cannot emit light. Therefore, in the light-emitting device 2000, the duration of the conduction time of the trigger unit 15 (the transistor Q3 in the digital control unit 12) can be adjusted directly according to the second control signal Si2 generated by the digital control unit 12, so as to change the duration of the light-emitting time of the light source 18 in one cycle. , to achieve the effect of changing the brightness. That is to say, the higher the responsibility ratio of the second control signal Si2 is, the higher the duty ratio of the light source 18 is to emit light in one cycle. The longer the time, the higher the brightness of the light emitting device 1000; on the contrary, the lower the duty ratio of the second control signal Si2, the shorter the time the light source 18 emits light in one cycle, the lower the brightness of the light emitting device 1000. It is worth noting that, since the transistor Q3 can be directly controlled by the second control signal Si2, there is no need to convert the second control signal Si2 by another device (eg, the trigger unit 14).

The above-mentioned embodiments are only to illustrate the technical ideas and characteristics of the present invention, and the purpose is to enable those who are familiar with the art to understand the content of the present invention and implement it accordingly. It should not be used to limit the patent scope of the present invention. That is, all equivalent changes or modifications made according to the spirit disclosed in the present invention should still be covered by the patent scope of the present invention.

1000: Lighting Device

300: Drive circuit

110, 111: Power

10: External control unit

12: Digital control unit

14: Trigger unit

16: Current source

18: Light source

Ca: Capacitance

Di: Diode

Q1: Transistor

D1: drain

G1: Gate

S1: source

Si1: the first control signal

Si2: the second control signal

Si3: the third control signal

Claims (7)

A driving circuit includes: a digital control unit providing a first current signal, wherein the first current signal is a pulse width modulation (PWM) signal; a trigger unit electrically connected to the digital control unit and receiving the a first current signal; and a current source electrically connected to the trigger unit; wherein the trigger unit includes a negative voltage generator, and the negative voltage generator includes a diode and a capacitor, and the diode is electrically connected The current source and the capacitor are electrically connected to the digital control unit. The driving circuit of claim 1, wherein the frequency of the first current signal is higher than the switching frequency perceptible to human eyes. The driving circuit of claim 1 of the claimed scope includes a resistor, wherein one end of the resistor is connected to a power source, and the other end of the resistor is electrically connected to the digital control unit and the trigger unit at the same time. The driving circuit of claim 1, wherein the current source comprises a depletion type high carrier mobility transistor. The driving circuit of claim 1, wherein the current source comprises two depletion type high carrier mobility transistors connected in parallel. The driving circuit of claim 1 further comprises an external control unit, wherein the external control unit generates an external control signal to adjust the signal characteristic of the first current signal. The driving circuit of claim 6, wherein the signal characteristic of the first current signal includes a first duty ratio.

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