CN111770604B - Light emitting device and control method thereof - Google Patents

Abstract

A light emitting device and a control method thereof. The light-emitting device comprises at least two light-emitting modules, a plurality of first switch units, a second switch unit and a control signal generating circuit. The light emitting module is used for emitting light rays with different color temperatures. The first switch units are respectively coupled to the corresponding light emitting modules and switched in response to a plurality of first control signals to control the conduction states of the light emitting modules. The second switch unit is used for responding to the second control signal to switch so as to control the first switch unit to work in the period of conducting the second switch unit. The control signal generating circuit is coupled with the first switch unit and the second switch unit and used for generating a first control signal and a second control signal and respectively adjusting the work periods of the first control signal and the second control signal so as to adjust the color temperature and the mixed light brightness of the mixed light of the at least two light-emitting modules. Thus, the purpose of adjusting the luminous color temperature and the brightness of the light-emitting device can be achieved through a simple device structure.

Description

Light emitting device and control method thereof

technical field

This case relates to a device and a control method, and in particular to a light emitting device and a control method thereof.

Background technique

Light-emitting diodes (light-emitting diodes, LEDs) have been widely used in backlighting and lighting products. The luminous intensity of the LED can be changed accordingly by adjusting the passing current or changing the ratio of the on-time and off-time of the circuit connected to the LED (that is, the duty cycle). Therefore, a light-emitting device including two or more LEDs with different color temperatures can control the overall brightness of the light-emitting device and the color temperature after light mixing to meet the needs of different applications by adjusting the current through the LEDs or the duty cycle of the LEDs. .

In order to control the brightness and color temperature of a light-emitting device including LEDs, in the driving circuit disclosed in Chinese patent CN105101543B or CN105491761A, the current control circuit responds to a pulse width modulation (Pulse WidthModulation, PWM) signal to adjust the current used to drive the LED The size of the PWM signal is generated according to the required brightness or color temperature. When the required brightness is to be increased, the duty cycle of the PWM signal will be increased accordingly to increase the driving current to increase the brightness. Relatively, when the required brightness is to be reduced, the duty cycle of the PWM will be correspondingly reduced so that the driving current is reduced to reduce the brightness.

In the overall circuit structure of the above-mentioned prior application CN105101543B or CN105491761A, an adjustable or variable current control circuit is required to control the brightness or color temperature by controlling the current in response to the PWM signal. Furthermore, how to simplify the above-mentioned control process and reduce the cost of hardware and software is an important task for the relevant technical personnel.

Contents of the invention

Some embodiments of the present application relate to a light emitting device, which is characterized by comprising at least two light emitting modules, a plurality of first switch units, a second switch unit, and a control signal generating circuit. At least two light emitting modules emit lights with different color temperatures. A plurality of first switch units are respectively coupled to the at least two light-emitting modules, and are used for switching in response to a plurality of first control signals to control the conduction states of the corresponding at least two light-emitting modules. A second switch unit is used for switching in response to a second control signal, so as to control the operation of the plurality of first switch units during the conduction period of the second switch unit. A control signal generation circuit, coupled to the plurality of first switch units and the second switch unit, for generating the plurality of first control signals and the second control signal to control the plurality of first The switch unit and the second switch unit; wherein the control signal generating circuit is further used to adjust the duty cycle of the plurality of first control signals to adjust the color temperature of the light mixing of the at least two light emitting modules, and the control signal generating circuit is used in combination with The duty cycle of the second control signal is adjusted to adjust the brightness of the mixed lights of the at least two light emitting modules.

In some embodiments, the light-emitting device is characterized in that the control signal generating circuit controls the plurality of first switch units to turn on the at least two light-emitting modules according to a ratio, and the ratio is the ratio of the plurality of first The ratio of the duty cycle of the control signal.

In some embodiments, the lighting device is characterized in that the plurality of first switch units are coupled between the second switch unit and the at least two light emitting modules, or the second switch unit is coupled to Between the at least two light emitting modules and a signal conversion circuit.

In some embodiments, the lighting device is characterized in that the plurality of first control signals have the same frequency, and the frequency of the plurality of first control signals is different from the frequency of the second control signal.

In some embodiments, the light emitting device is characterized in that the control signal generating circuit switches the conduction states of the at least two light emitting modules simultaneously by controlling the second switch unit.

In some embodiments, the lighting device is characterized in that the conduction time of the second switch unit is longer than the conduction time of the plurality of first switch units.

In some embodiments, the lighting device is characterized in that the control signal generating circuit is further used to receive a setting signal, and generate the multiple a first control signal and the second control signal.

Some other embodiments of this application relate to a method for controlling a light emitting device, which is characterized by comprising the following steps: generating a plurality of first control signals and a second control signal; a first switch unit to control the conduction state of at least two corresponding light-emitting modules; a second switch unit responds to the second control signal to turn on or off the plurality of first switch units; adjust the plurality of first switch units; The duty cycle of the first control signal is used to adjust the color temperature of the mixed light of the at least two light-emitting modules; and the duty cycle of the second control signal is adjusted to adjust the brightness of the mixed light of the at least two light-emitting modules.

In some embodiments, the light emitting device control method is characterized in that the plurality of first control signals have the same frequency, and the frequency of the plurality of first control signals is different from the frequency of the second control signal.

In some embodiments, the method for controlling a light emitting device is characterized in that the plurality of first control signals and the second control signal are pulse width modulation signals.

Description of drawings

In order to make the above and other objects, features, advantages and embodiments of the present disclosure more comprehensible, the accompanying drawings are described as follows:

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

FIG. 2 is a schematic diagram showing waveforms of a plurality of first control signals and a second control signal according to an embodiment of the present application;

FIG. 3 is a flowchart illustrating a method for controlling a light emitting device according to an embodiment of the present application;

FIG. 4 is a schematic diagram of a light emitting device according to another embodiment of the present application; and

FIG. 5 is a schematic diagram of a light emitting device according to another embodiment of the present application.

Detailed ways

All terms used herein have their ordinary meanings. The definitions of the above-mentioned words in commonly used dictionaries, and the use examples of any words discussed here in the content of this specification are only examples, and should not limit the scope and meaning of the disclosure. Likewise, the disclosure is not limited to the various embodiments shown in this specification.

The words "comprising", "including", "having", "containing" and so on used herein are all open terms, meaning "including but not limited to". In addition, "and/or" used herein includes any one and all combinations of one or more items in the relevant listed items.

In addition, herein, when an element is referred to as "connected" or "coupled", it may mean "electrically connected" or "coupled". "Connected" or "coupled" may also be used to indicate that two or more elements cooperate or interact with each other. In addition, although terms such as "first", "second", ... etc. are used herein to describe different elements, these terms are only used to distinguish elements or operations described with the same technical terms. Unless clearly indicated by the context, the terms do not imply any particular order or sequence, nor are they intended to be limiting of the invention.

Please refer to Figure 1. FIG. 1 is a schematic diagram of a light emitting device 10 according to an embodiment of the present invention. As shown in FIG. 1 , the light emitting device 10 includes a signal converting circuit 100 , a control signal generating circuit 120 , first switch units 140 a and 140 b , light emitting modules 160 a , 160 b and a second switch unit 180 . In terms of connection, the signal conversion circuit 100 is coupled to the light emitting modules 160a, 160b, the control signal generating circuit 120 is coupled to the first switch unit 140a, 140b, and the first switch unit 140a, 140b is correspondingly coupled to the second switch unit 180 Between the light emitting modules 160a and 160b, the second switch unit 180 is coupled to the first switch units 140a and 140b and the control signal circuit 120 at the same time.

In some embodiments, the signal conversion circuit 100 may be a light-emitting diode (light-emitting diode, LED) driving circuit, implemented by a DC current source or an AC-to-DC circuit. The control signal generating circuit 120 may be a microprocessor unit (Microcontroller Unit, MCU), microprocessor (microprocessor), central processing unit (CPU), application specific integrated circuit (application specific integrated circuit, ASIC), logic circuit or other Similar elements or combinations of the above elements are implemented. The first switch units 140 a , 140 b and the second switch unit 180 can be realized by transistor switches, including field effect transistors, bipolar junction transistors or other components with switching functions. The light-emitting modules 160a and 160b can be implemented by a combination of one or more LED units, or any light-emitting element with a fixed color temperature. The above embodiments are only for the purpose of easy understanding of the present case, but the embodiments of the present case are not limited here.

In terms of operation, the signal conversion circuit 100 is used to generate current to be input into the light emitting modules 160a and 160b respectively. The light emitting modules 160a and 160b respectively emit light with different color temperatures (such as warm white light 2700K, cool white light 6500K, etc.). The control signal generation circuit 120 is used for generating a plurality of first control signals S1 , S2 and a second control signal PS to control the first switch units 140 a , 140 b and the second switch unit 180 . The first switch units 140a, 140b are used to switch respectively in response to the first control signals S1, S2, so as to control the conduction states of the corresponding light emitting modules 160a, 160b. The second switch unit 180 is used to switch in response to the second control signal PS to control the first switch unit 140a, 140b to work during the conduction period of the second switch unit 180; wherein the control signal generating circuit 120 is further used to adjust the first control The duty cycle of the signals S1, S2 and the second control signal PS is used to adjust the color temperature and brightness of the mixed light of the light emitting modules 160a, 160b.

In some embodiments, the first switch unit 140a includes a transistor M1, the first switch unit 140b includes a transistor M2, and the second switch unit 180 includes a transistor PM, wherein the control terminal of the transistor M1 is coupled to the control signal generating circuit 120, and the transistor M1 The first end of the transistor M1 is coupled to the light-emitting module 160a, the second end of the transistor M1 is coupled to the first end of the transistor PM, the control end of the transistor M2 is coupled to the control signal generating circuit 120, the first end of the transistor M2 is coupled to the light-emitting module 160b, the transistor M2 The second terminal of M2 is coupled to the first terminal of the transistor PM, the control terminal of the transistor PM is coupled to the control signal generating circuit 120 , and the second terminal of the transistor PM is grounded.

Please refer to Figure 2. FIG. 2 is a schematic waveform diagram of the first control signals S1 , S2 and the second control signal PS according to an embodiment of the present application. In some embodiments, the above-mentioned first control signals S1 , S2 and the second control signal PS may all be pulse width modulation (Pulse Width Modulation, PWM) signals. The interaction relationship between the first control signals S1 , S2 and the second control signal PS will be described in detail later.

In order to better understand the present application, the detailed operation of the light emitting device 10 in FIG. 1 will be discussed in conjunction with the embodiments in FIG. 2 and FIG. 3 . FIG. 3 is a flowchart illustrating a method 30 for controlling a light emitting device according to an embodiment of the present application. In some embodiments, the lighting device control method 30 shown in FIG. 3 can be applied to the lighting device 10 shown in FIG. 1 , but not limited thereto.

As shown in FIG. 3 , the light emitting device control method 30 includes steps S310 , S320 , S330 , S340 and S350 . In step S310, the control signal generation circuit 120 is further configured to receive a setting signal CS, and generate a first control signal according to a target correlated color temperature (Correlated Color Temperature, CCT) and a target luminous flux contained in the setting signal CS. S1, S2 and the second control signal PS. In some embodiments, the setting signal CS is generated when a user operates a lamp, wall switch, mobile device, remote controller, etc. that includes a dimming control interface. For example, the light emitting device 10 includes a light emitting module 160a emitting warm white light and a light emitting module 160b emitting cool white light. For example, the color temperature of warm white light is about 2700K, and the color temperature of cool white light is about 6500K. When the user chooses to emit a specific color temperature and/or brightness from the light emitting device 10 through the dimming control interface, the setting signal CS is sent. Assuming that the user selects a target color temperature of 4000K, the setting signal CS will include the target correlated color temperature. At this time, the control signal generating circuit 120 can obtain the ratio of 2700K light and 6500K light among the light with 4000K correlated color temperature to be mixed according to a light mixing ratio table, for example, they are 65.8% and 34.2% respectively. For light with a color temperature, the proportions of 2700K light and 6500K light are, for example, 26.3% and 73.7%, respectively, and so on. It should be noted that the above implementation manners are only for the purpose of easy understanding of the present case, but the implementation manners of the present case are not limited here. In addition, those skilled in the art can understand the operation of the light-mixing ratio table and adjust the light-mixing ratio table according to actual application requirements, so for the sake of brevity, further description is omitted here.

Next, the operation of the above-mentioned embodiment will be described. Please refer to Figure 2 and Figure 3 together. As shown in FIG. 2, for example, after obtaining the ratio of 2700K light to 6500K light to be mixed with 4000K light, the control signal generation circuit 120 generates the first control signal S1 for controlling the first switch units 140a, 140b respectively. , S2, wherein the first control signals S1 and S2 have the same frequency, and control the first switch unit 140a and the first switch unit 140b to turn on the light emitting module 160a and the light emitting module 160b respectively according to the ratio obtained for light mixing. For example, correspondingly controlling the first switch unit 140a to turn on the first control signal S1 of the light-emitting module 160a has a duty cycle of 65.8%, and correspondingly controlling the first switch unit 140b to turn on the first control signal S2 of the light-emitting module 160b Its duty cycle is 34.2%. In this way, the light emitting device 10 can control the light emitting modules 160a, 160b to achieve the target color-mixing correlated color temperature through the first control signals S1, S2.

In addition, as shown in FIG. 2, the first control signal S1, S2 has a period (period) T1, and the second control signal PS has a period T2, that is, the frequency of the first control signal S1, S2 is different from that of the second control signal PS. Frequency of. In some embodiments, since the above-mentioned second switch unit 180 is coupled to the first switch unit 140a, 140b, when the second switch unit 180 is turned on (that is, on, conduction), the first switch unit 140a, 140b The state of the second switch unit 180 is on, and the light-emitting device 10 is turned on as a whole to emit light (the part framed by the dotted line in FIG. 2 ); The state of a control signal S1, S2 indicates on or off, because the lighting device 10 is in a non-conductive state and does not drive the first switch unit 140a, 140b. In other words, the control signal generating circuit 120 can be controlled by the second control signal PS The second switch unit 180 simultaneously switches the conduction states of the light emitting modules 160 a and 160 b to further control the brightness of the light emitting device 10 .

Continuing with the above-mentioned embodiment, specifically, according to step S310 , the control signal generating circuit 120 generates the second control signal PS according to the target luminous flux contained in the setting signal CS. For example, referring to FIG. 2 , in some embodiments, it is assumed that the period T2 of the second control signal PS is 10 times the period T1 of the first control signal S1, S2 (ie T2=10xT1), and the light emitting modules 160a, 160b The sum of the luminous fluxes of the light emitted in the period T1 of the first control signal S1 and S2 is I1, and the target luminous flux I2 is 5 times of I1, then the control signal generating circuit 120 will generate the second control signal with a duty cycle of 50%. PS, that is, the second switch unit 180 is turned on during the first 50% of the period T2, so that the first switch units 140a, 140b work during the period when the second switch unit 180 is turned on, that is, the first switch units 140a, 140b 140b is turned on for 5 periods T1, so that the overall luminous flux (brightness) of the light emitting device 10 within this period is 5 times of I1, reaching the target luminous flux I2. In addition, further speaking, in this embodiment, the conduction time of the second switch unit 180 is longer than the conduction time of the first switch units 140a and 140b, so as to control the overall brightness of the light emitting device 10 . In some other embodiments, the frequency of the first control signal S1, S2 is greater than the frequency of the second control signal PS, wherein the frequency of the first control signal S1, S2 is an integer multiple of the frequency PS of the second control signal, so that Achieve more precise mixed light control. It should be noted that the above embodiments are only examples for easy understanding of the invention of the present case, but the implementation manner of the present case is not limited thereto.

Following step S310, in step S320, the first switch units 140a, 140b are switched in response to the first control signals S1, S2 to control the conduction states of the corresponding light emitting modules 160a, 160b. In some embodiments, as in the aforementioned embodiment where light with a color temperature of 4000K is to be mixed, the duty cycle of the first control signal S1 may be 65.8% and the duty cycle of the first control signal S2 may be 34.2%, then the first switch unit 140a , 140b will simultaneously turn on the light emitting modules 160a, 160b for 65.8% and 34.2% of the time in each period T1.

Next, according to step S330 , the second switch unit 180 responds to the second control signal PS to control the first switch units 140 a and 140 b to work during the conduction period of the second switch unit 180 . Continuing the above-mentioned embodiment, taking the period T2 of the second control signal PS as 10 times the period T1 of the first control signals S1 and S2, and the second control signal PS having a duty cycle of 50% as an example, the second switch unit 180 Turn on during the first 50% of the period T2 and turn off during the last 50% of the time, correspondingly make the first switch unit 140a, 140b conduct on during the first 50% of the period T2 and turn off during the last 50% of the time turn off, as indicated in the dotted box in Figure 2. In other words, only when the second switch unit 180 is turned on (on), the first switch units 140a, 140b will switch in response to the first control signals S1, S2, and the second switch unit 180 will be turned off (off). During the time, the first switch units 140a, 140b are both in the off state, so that the control signal generating circuit 120 can control the light emitting device 10 to reach the target luminous flux (brightness).

In some embodiments, in order to make the above-mentioned light emitting device 10 with adjustable luminous correlated color temperature and brightness applicable to specific usage scenarios, the target correlated color temperature and target luminous flux included in the setting signal CS may be adjusted. Therefore, in step S340 , the duty cycles of the first control signals S1 and S2 are adjusted by the control signal generating circuit 120 to adjust the color temperature of the light mixing of the light emitting modules 160 a and 160 b. For example, in some embodiments, when it is desired to adjust the light emitting device 10 with a color temperature of 4000K to emit light with a color temperature of 3000K, the control signal generating circuit 120 can adjust the duty cycle of the first control signal S1 from 65.8% to 92.1%. , and adjust the duty cycle of the first control signal S2 from 34.2% to 7.9%, so as to generate light with a color temperature of 3000K after light mixing. The above examples are only for the convenience of understanding the content of this case, but this case is not limited thereto.

Next, in step S350 , the duty cycle of the second control signal PS is adjusted by the control signal generating circuit 120 to modulate the brightness of the mixed light of the light emitting modules 160 a and 160 b. For example, in some embodiments, when it is desired to adjust the light emitting device 10 that originally emits light with a luminous flux I2 to emit light that is 1.5 times brighter than the luminous flux I2, the control signal generating circuit 120 can change the duty cycle of the second control signal PS from Adjust from 50% to 75% to produce light that is 1.5 times brighter than the original light after mixing.

Please refer to Figure 4. FIG. 4 is a schematic diagram of a light emitting device 40 according to another embodiment of the present application. Regarding the embodiment of FIG. 4 , the same elements as in FIG. 1 will be marked with the same reference symbols for ease of understanding. Unless there is a need to explain the cooperative relationship with the elements shown in FIG. 4 , for the sake of brevity, specific operations of similar elements that have been discussed in detail in the above paragraphs are omitted here. In addition, the light emitting device control method 30 shown in FIG. 3 can also be applied to the light emitting device 40 in FIG. 4 .

As shown in FIG. 4, different from FIG. 1, the light-emitting device 40 includes different light-emitting modules 160a-160n and first switch units 140a-140n, wherein the first switch units 140a-140n include transistors M1-Mn, transistors M1- The control terminals of Mn are coupled to the control signal generating circuit 120, the first terminals are respectively coupled to a corresponding one of the light emitting modules 160a-160n, and the second terminals are coupled to the first terminal of the transistor PM, and the control of the transistor PM The terminal is coupled to the control signal generating circuit 120, and the second terminal is grounded. The first switch units 140a-140n are coupled between the second switch unit 180 and the light-emitting modules 160a-160n, and are used to receive a plurality of first control signals S1-Sn from the control signal generating circuit 120, and respond to the first control signals respectively. The signals S1-Sn are switched to control the conduction states of the corresponding light-emitting modules 160a-160n. The second switch unit 180 is coupled to each of the first switch units 140a˜140n for receiving the second control signal PS from the control signal generating circuit 120 and switching in response to the second control signal PS to control the first switch unit 140a˜140n. The switch units 140 a - 140 n work during the conduction period of the second switch unit 180 .

Specifically, in some embodiments, the light-emitting modules 160a-160n can be single LED units with different color temperatures or a combination of multiple LED units connected in series. , 5700K, 6500K, etc., there is no limit in this case. The control signal generation circuit 120 generates the first control signals S1-Sn and the second control signal PS according to a light mixing ratio table and the target correlated color temperature (for example, 4500K) and target luminous flux contained in the setting signal, so that the first switch units 140a- 140n is switched in response to the first control signal S1-Sn to control the conduction state of the corresponding light-emitting modules 160a-160n to achieve the target correlated color temperature, and the second switch unit 180 is switched in response to the second control signal PS to control the first switch The units 140 a - 140 n work during the conduction period of the second switch unit 180 to achieve the target luminous flux (brightness). In addition, the light mixing ratio table can be generated by simulation calculation or analysis of experimental results. Those skilled in the art can understand the operation of the light mixing ratio table and adjust the light mixing ratio table according to its actual application requirements. Therefore, for the sake of brevity, further details are omitted here. instruction of.

Please refer to Figure 5. FIG. 5 is a schematic diagram of a light emitting device 10 according to another embodiment of the present application. Regarding the embodiment of FIG. 5 , the same elements as in FIG. 1 will be marked with the same reference symbols for ease of understanding. Unless there is a need to explain the cooperative relationship with the elements shown in FIG. 5 , for the sake of brevity, specific operations of similar elements that have been discussed in detail in the above paragraphs are omitted here. In addition, the lighting device control method 30 shown in FIG. 3 can also be applied to the lighting device 10 shown in FIG. 5 .

As shown in FIG. 5 , the difference from FIG. 1 is that a second switch unit 180 included in the light emitting device 40 is coupled between the light emitting modules 160a, 160b and a signal converting circuit 100 for receiving from the control signal generating circuit 120 The second control signal PS is switched in response to the second control signal PS to control the first switch unit 140a, 140b to work during the conduction period of the second switch unit 180, and the first switch unit 140a, 140b is used to respectively respond The first control signals S1 and S2 received from the control signal generating circuit 120 are switched to control the conduction states of the corresponding light emitting modules 160a and 160b. Specifically, in some embodiments, when the light emitting device 10 adjusts the luminous light to have a target correlated color temperature through the first control signals S1 and S2, the control signal generation circuit 120 adjusts the duty cycle of the second control signal PS according to the target luminous flux, For example, 50%, so that in the state where the second switch unit 180 is turned on, the driving current of the signal conversion circuit 100 can flow into the light emitting modules 160a, 160b; ) state, the driving current of the signal conversion circuit 100 does not flow into the light emitting modules 160a, 160b, and through the above operation of controlling the conduction time (working cycle), the light emitting device 10 can be driven to emit light to reach the target luminous flux.

It is worth noting that in the method 30 for controlling the light emitting device of this application, the conduction state of the light emitting module can be controlled first according to step S320 to adjust the correlated color temperature of the light emitting device, or the first switch unit and the second switch unit can be controlled first according to step S330 Working during the conduction period to adjust the brightness of the light-emitting device, this case does not set a limit on the implementation sequence. Relatively, according to the invention content of this case, since the brightness is not adjusted by increasing or decreasing the current flowing through the LED, naturally there will be no Unexpected color temperature shift when increasing or decreasing the current flowing through the LED light-emitting module to adjust the brightness. Various operations in the light emitting device control method 30 may be appropriately added, replaced, omitted or executed in a different order without departing from the operation methods and scope of the embodiments of the present application.

To sum up, this application provides a light emitting device and a control method for the light emitting device, by controlling a plurality of first switch units respectively coupled to the light emitting module and a second switch unit coupled to each first switch unit The conduction time (duty cycle) can simultaneously adjust the luminous color temperature and brightness of the luminous device without needing an additional current control circuit or a complex color mixing algorithm.

Although this case has disclosed the above in the way of implementation, it does not limit this case. Anyone who is familiar with this technology can make various changes and modifications without departing from the spirit and scope of this case. Therefore, the protection scope of this case should be determined according to the The scope defined by the appended claims shall prevail.

Claims (10)

1. A light emitting device, comprising:

at least two light emitting modules for emitting light rays with different color temperatures;

the first switch units are respectively coupled with the at least two light-emitting modules and used for respectively responding to the switching of a plurality of first control signals so as to control the conducting state of the corresponding at least two light-emitting modules;

the second switch unit is used for responding to a second control signal for switching so as to control the plurality of first switch units to work in the conducting period of the second switch unit, wherein the at least two light-emitting modules simultaneously emit light in the conducting period of the second switch unit; and

a control signal generating circuit, coupled to the first switch units and the second switch units, for generating the first control signals and the second control signals to control the first switch units and the second switch units;

the control signal generating circuit is further used for adjusting the duty cycles of the first control signals to modulate the color temperature of the mixed light of the at least two light-emitting modules, and the control signal generating circuit is used for adjusting the duty cycles of the second control signals to modulate the brightness of the mixed light of the at least two light-emitting modules.

2. The apparatus of claim 1, wherein the control signal generating circuit controls the first switch units to turn on the at least two light emitting modules according to a ratio of duty cycles of the first control signals.

3. The light-emitting device according to claim 1, wherein the plurality of first switch units are coupled between the second switch unit and the at least two light-emitting modules, or the second switch unit is coupled between the at least two light-emitting modules and a signal conversion circuit.

4. The apparatus of claim 1, wherein the plurality of first control signals have the same frequency, and the frequency of the plurality of first control signals is different from the frequency of the second control signal.

5. The apparatus of claim 1, wherein the control signal generating circuit controls the second switch unit to switch the on states of the at least two light emitting modules simultaneously.

6. The light-emitting device of claim 1, wherein the second switch unit is turned on for a longer time than the first switch units.

7. The lighting device as claimed in claim 1, wherein the control signal generating circuit is further configured to receive a setting signal and generate the plurality of first control signals and the plurality of second control signals according to a target correlated color temperature and a target luminous flux included in the setting signal.

8. A method for controlling a light emitting device, comprising:

generating a plurality of first control signals and a second control signal;

respectively responding to the first control signals to switch the first switch units so as to control the conduction states of at least two corresponding light-emitting modules;

responding to the second control signal through a second switch unit to turn on or turn off the plurality of first switch units, wherein the at least two light-emitting modules emit light simultaneously in the period of turning on the second switch unit;

adjusting the working periods of the first control signals to adjust the color temperature of the mixed light of the at least two light-emitting modules; and

adjusting the duty cycle of the second control signal to modulate the brightness of the light mixed by the at least two light-emitting modules.

9. The method of claim 8, wherein the first control signals have the same frequency, and the frequency of the first control signals is different from the frequency of the second control signal.

10. The method of claim 8, wherein the first control signals and the second control signals are pulse width modulation signals.

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