CN111770604B

CN111770604B - Light emitting device and control method thereof

Info

Publication number: CN111770604B
Application number: CN201910249905.5A
Authority: CN
Inventors: 许仲*; 张裕宽; 吴恩铭
Original assignee: Lextar Electronics Corp
Current assignee: Lextar Electronics Corp
Priority date: 2019-03-29
Filing date: 2019-03-29
Publication date: 2022-11-25
Anticipated expiration: 2039-03-29
Also published as: CN111770604A

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

The present disclosure relates to a device and a control method, and more particularly, to a light emitting device and a control method thereof.

Background

Light-emitting diodes (LEDs) are widely used in backlight and lighting products. The intensity of the LED light can be changed by adjusting the current passing through the LED or by changing the ratio of the on-time to the off-time (i.e., duty cycle) of the circuit connected to the LED. Therefore, a light-emitting device comprising two or more LEDs with different color temperatures can control the overall brightness of the light-emitting device and the color temperature of mixed light by respectively adjusting the current passing through the LEDs or the duty cycle of the LEDs so as to meet the requirements of different applications.

In order to control the brightness and color temperature of the light emitting device including the LEDs, in the driving circuit disclosed in chinese patent CN105101543B or CN105491761a, the current control circuit adjusts the current for driving the LEDs in response to a Pulse Width Modulation (PWM) signal, wherein 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 is increased accordingly so that the driving current is increased to increase the brightness. Conversely, when the required brightness is to be reduced, the duty cycle of the PWM is correspondingly reduced so that the drive current is reduced to reduce the brightness.

In the above-mentioned CN105101543B or CN105491761a, the whole circuit structure is required to have an adjustable or variable current control circuit to control the brightness or color temperature by responding to the PWM signal to control the current. Further, how to simplify the above control process and reduce the software and hardware costs is an important issue for those skilled in the art.

Disclosure of Invention

Some embodiments of the present disclosure relate to a light emitting device, which includes 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 for emitting light rays with different color temperatures. The first switch units are respectively coupled to the at least two light-emitting modules and are used for respectively responding to the switching of the first control signals so as to control the conduction states of the at least two corresponding 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 period of conducting the second switch unit. 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 working period of the plurality of 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 also used for adjusting the working period of the second control signal to modulate the brightness of the mixed light of the at least two light emitting modules.

In some embodiments, the control signal generating circuit turns on the at least two light emitting modules according to a ratio of duty cycles of the first control signals by controlling the first switching units.

In some embodiments, the light emitting 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 between the at least two light emitting modules and a signal conversion circuit.

In some embodiments, the light emitting 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 conducting states of the at least two light emitting modules simultaneously by controlling the second switch unit.

In some embodiments, the second switch unit is turned on for a longer time than the first switch units.

In some embodiments, 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.

Another embodiment of the present disclosure relates to 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 the at least two corresponding light-emitting modules; turning on or off the plurality of first switching units in response to the second control signal through a second switching 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 working period of the second control signal to modulate the brightness of the mixed light of the at least two light-emitting modules.

In some embodiments, the method for controlling a light emitting 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 method for controlling a light emitting device, wherein the first control signals and the second control signals are pulse width modulation signals.

Drawings

The foregoing and other objects, features, advantages and embodiments of the disclosure will be more readily understood from the following description taken in conjunction with the accompanying drawings in which:

fig. 1 is a schematic view of a light emitting device according to an embodiment of the present disclosure;

fig. 2 is a schematic waveform diagram illustrating a plurality of first control signals and a plurality of second control signals according to an embodiment of the disclosure;

fig. 3 is a flowchart illustrating a method for controlling a light emitting device according to an embodiment of the disclosure;

fig. 4 is a schematic diagram illustrating a light emitting device according to another embodiment of the disclosure; and

fig. 5 is a schematic view illustrating a light emitting device according to another embodiment of the disclosure.

Detailed Description

All terms used herein have their ordinary meaning. The definitions of the above-mentioned words in commonly used dictionaries, any use of the words discussed herein in the context of this specification is by way of example only and should not be construed as limiting the scope or meaning of the present disclosure. Likewise, the present disclosure is not limited to the various embodiments shown in this specification.

As used herein, the terms "comprising," including, "" having, "" containing, "and the like are open-ended terms that mean" including, but not limited to. Further, as used herein, "and/or" includes any and all combinations of one or more of the associated listed items.

In addition, when an element is referred to as being "connected" or "coupled" herein, it can be electrically connected or coupled. "connected" or "coupled" may also be used to indicate that two or more elements are in mutual engagement or interaction. In addition, although terms such as "first," "second," … are used herein to describe various elements, such terms are used only to distinguish elements or operations described in the same technical terms. Unless the context clearly dictates otherwise, the terms do not specifically refer or imply an order or sequence nor are they intended to limit the invention.

Please refer to fig. 1. Fig. 1 is a schematic diagram of a light emitting device 10 according to an embodiment of the present disclosure. As shown in fig. 1, the light emitting device 10 includes a signal conversion circuit 100, a control signal generation circuit 120,

first switch units

140a and 140b,

light emitting modules

160a and 160b, and a second switch unit 180. In terms of connection, the signal conversion circuit 100 is coupled to the

light emitting modules

160a and 160b, the control signal generation circuit 120 is coupled to the

first switch units

140a and 140b, the

first switch units

140a and 140b are coupled between the second switch unit 180 and the

light emitting modules

160a and 160b, and the second switch unit 180 is coupled to the

first switch units

140a and 140b and the control signal circuit 120.

In some embodiments, the signal conversion circuit 100 may be a light-emitting diode (LED) driving circuit, and may be implemented by a dc power supply or an ac-to-dc circuit. The control signal generating circuit 120 may be a Micro Controller Unit (MCU), a microprocessor (microprocessor), a Central Processing Unit (CPU), an Application Specific Integrated Circuit (ASIC), a logic circuit, or other similar components or combinations thereof. The

first switch units

140a, 140b and the second switch unit 180 may be implemented by transistor switches, including field effect transistors, bjts or other devices with switching functions. The

light emitting modules

160a and 160b may be implemented by a combination of one or more LED units, or may be any light emitting elements with fixed color temperature. The above embodiments are only for the purpose of easy understanding of the present invention, but the embodiments of the present invention are not limited thereto.

In operation, the signal conversion circuit 100 is used to generate current to be inputted to the

light emitting modules

160a and 160b, respectively. The

light emitting modules

160a and 160b respectively emit light rays with different color temperatures (e.g., warm white light 2700K, cold white light 6500K, etc.). The control signal generating circuit 120 is configured to generate a plurality of first control signals S1 and S2 and a second control signal PS to control the

first switch units

140a and 140b and the second switch unit 180. The

first switch units

140a and 140b are used for respectively responding to the first control signals S1 and S2 to switch so as to control the conducting states of the corresponding

light emitting modules

160a and 160b. The second switch unit 180 is switched in response to the second control signal PS to control the

first switch units

140a and 140b to operate during the period when the second switch unit 180 is turned on; the control signal generating circuit 120 is further configured to adjust a duty cycle (duty cycle) of the first control signals S1 and S2 and the second control signal PS to modulate the color temperature and the brightness of the light mixed by the

light emitting modules

160a and 160b.

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

Please refer to fig. 2. Fig. 2 is a schematic waveform diagram illustrating the first control signals S1 and S2 and the second control signal PS according to an embodiment of the disclosure. In some embodiments, the first control signals S1 and S2 and the second control signal PS may be Pulse Width Modulation (PWM) signals. The interaction between the first control signals S1 and S2 and the second control signal PS will be described in detail later.

For a better understanding of the present disclosure, the detailed operation of the light emitting device 10 of fig. 1 will be discussed in conjunction with the embodiments of fig. 2 and 3. Fig. 3 is a flowchart illustrating a method 30 for controlling a light emitting device according to an embodiment of the disclosure. In some embodiments, the lighting apparatus control method 30 shown in fig. 3 can be applied to the lighting apparatus 10 shown in fig. 1, but is 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 generating circuit 120 is further configured to receive a setting signal CS, and generate the first control signals S1 and S2 and the second control signal PS according to a target Correlated Color Temperature (CCT) and a target luminous flux included in the setting signal CS. In some embodiments, the setting signal CS is generated when a user operates a lamp, a wall switch, a mobile device, a remote controller, etc. having 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 the warm white light is about 2700K, and the color temperature of the cool white light is about 6500K. When the user selects the device 10 to emit a specific color temperature and/or brightness through the dimming control interface to emit the setting signal CS, assuming that the user selects the target color temperature to be 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 to 6500K light, for example 65.8% and 34.2% respectively, in the light to be mixed with 4000K correlated color temperature according to a mixing ratio table, and similarly, if the light to be mixed with 5500K correlated color temperature is to be mixed, the ratio of 2700K light to 6500K light is 26.3% and 73.7% respectively, and so on. It should be noted that the above embodiments are only for the purpose of easy understanding of the present disclosure, but the embodiments of the present disclosure are not limited thereto. In addition, a person skilled in the art can understand the operation of the light mixing ratio table and adjust the light mixing ratio table according to the practical application requirement, and therefore further description is omitted here for brevity.

The operation of the above embodiment will be described next. Please refer to fig. 2 and fig. 3 together. As shown in fig. 2, for example, after obtaining the ratio of the 4000K light to be mixed, wherein the 2700K light is proportional to the 6500K light, the control signal generating circuit 120 generates the first control signals S1 and S2 for respectively controlling the

first switch units

140a and 140b, wherein the first control signals S1 and S2 have the same frequency, and correspondingly controls the first switch unit 140a and the first switch unit 140b to respectively turn on the light emitting module 160a and the light emitting module 160b according to the obtained ratio for mixing light. For example, the duty cycle of the first control signal S1 for correspondingly controlling the first switch unit 140a to turn on the light emitting module 160a is 65.8%, and the duty cycle of the first control signal S2 for correspondingly controlling the first switch unit 140b to turn on the light emitting module 160b is 34.2%. In this way, the light emitting device 10 can control the

light emitting modules

160a and 160b to achieve the target color mixing correlated color temperature through the first control signals S1 and S2.

Furthermore, as shown in fig. 2, the first control signals S1, S2 have a period (period) T1, and the second control signal PS has a period T2, i.e. the frequency of the first control signals S1, S2 is different from the frequency of the second control signal PS. In some embodiments, since the second switch unit 180 is coupled to the

first switch units

140a and 140b, when the second switch unit 180 is on (i.e., on, conducting), the

first switch units

140a and 140b are on, and the whole light-emitting device 10 is in a conducting state to emit light (as a portion framed by a dotted line in fig. 2); when the second switch unit 180 is off (i.e., off or off not working), no matter the state of the first control signals S1 and S2 indicates on or off, the

first switch units

140a and 140b are not driven because the whole light-emitting device 10 is in the off state, in other words, the control signal generating circuit 120 can control the second switch unit 180 to simultaneously switch the on state of the light-emitting

modules

160a and 160b through the second control signal PS, so as 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, assuming that the period T2 of the second control signal PS is 10 times the period T1 of the first control signals S1 and S2 (i.e., T2=10xT 1), and the sum of the luminous fluxes of the light emitted by the

light emitting modules

160a and 160b in the period T1 of the first control signals S1 and S2 is I1, and the target luminous flux I2 is 5 times the period I1, the control signal generating circuit 120 generates the second control signal PS having a duty cycle of 50%, that is, the second switch unit 180 is turned on in the first 50% of the period T2, so that the

first switch units

140a and 140b operate during the period when the second switch unit 180 is turned on, that is, the

first switch units

140a and 140b are turned on for 5 periods T1, and thus the total luminous flux (brightness) of the light emitting device 10 in this period is 5 times the period I1, and reaches the target luminous flux I2. In addition, in this embodiment, the time for turning on the second switch unit 180 is longer than the time for turning on the

first switch units

140a and 140b, so as to control the overall brightness of the light emitting device 10. In 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 of the second control signal PS, so as to achieve more precise light mixing control. It should be noted that the above embodiments are only examples for easily understanding the present invention, but the embodiments of the present invention are not limited thereto.

Following step S310, in step S320, the

first switch units

140a and 140b are switched to control the conducting states of the corresponding

light emitting modules

160a and 160b in response to the first control signals S1 and S2, respectively. In some embodiments, as in the embodiment of mixing light with a color temperature of 4000K, 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%, and then the

first switch units

140a and 140b will simultaneously turn on the

light emitting modules

160a and 160b for 65.8% and 34.2% of the time in each period T1, respectively.

Next, according to step S330, the second switch unit 180 responds to the second control signal PS to control the

first switch units

140a and 140b to operate during the period when the second switch unit 180 is turned on. Continuing with the above embodiment, taking the example that the period T2 of the second control signal PS is 10 times the period T1 of the first control signals S1 and S2, and the second control signal PS has a duty cycle of 50%, the second switch unit 180 is turned on during the first 50% of the period T2 and turned off during the last 50% of the period T2, and accordingly the

first switch units

140a and 140b are turned on during the first 50% of the period T2 and turned off during the last 50% of the period T2, as indicated by the dashed line in fig. 2. In other words, the

first switch units

140a and 140b are switched in response to the first control signals S1 and S2 only during the time when the second switch unit 180 is turned on (on), and the

first switch units

140a and 140b are both turned off (off) during the time when the second switch unit 180 is turned off (off), 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, the target correlated color temperature and the target luminous flux contained in the setting signal CS can be adjusted to apply the light-emitting device 10 with adjustable light-emitting correlated color temperature and brightness to a specific use situation. Therefore, in step S340, the duty cycle of the first control signal S1, S2 is adjusted by the control signal generating circuit 120 to modulate the color temperature of the light mixed by the

light emitting modules

160a, 160b. For example, in some embodiments, when the light emitting device 10 emitting light with a color temperature of 4000K is adjusted to emit light with a color temperature of 3000K, the control signal generating circuit 120 may 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% to generate light with a color temperature of 3000K after mixing. The above examples are only for the convenience of understanding the present disclosure, but the present disclosure 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 light mixed by the

light emitting modules

160a and 160b. For example, in some embodiments, when the light emitting device 10 emitting the original light with the luminous flux I2 is adjusted to emit light 1.5 times brighter than the luminous flux I2, the control signal generating circuit 120 may adjust the duty cycle of the second control signal PS from 50% to 75% to generate light 1.5 times brighter than the original light emitting state after mixing light.

Please refer to fig. 4. Fig. 4 is a schematic diagram illustrating a light-emitting device 40 according to another embodiment of the disclosure. With respect to the embodiment of fig. 4, for ease of understanding, like elements to those in fig. 1 will be labeled with like reference numerals. Unless there is a need to explain the cooperative relationship with the elements shown in fig. 4, the specific operation of like elements that have been discussed in detail in the above paragraphs is omitted here for the sake of brevity. In addition, the lighting device control method 30 shown in fig. 3 can also be applied to the lighting device 40 shown in fig. 4.

As shown in fig. 4, different from fig. 1, the light emitting device 40 includes different light emitting modules 160a to 160n and first switch units 140a to 140n, wherein the first switch units 140a to 140n include transistors M1 to Mn, control terminals of the transistors M1 to Mn are coupled to the control signal generating circuit 120, first terminals of the transistors are coupled to corresponding ones of the light emitting modules 160a to 160n, second terminals of the transistors are coupled to a first terminal of a transistor PM, a control terminal of the transistor PM is coupled to the control signal generating circuit 120, and a second terminal of the transistor PM is grounded. The first switch units 140a to 140n are coupled between the second switch unit 180 and the light emitting modules 160a to 160n, and are configured to receive the plurality of first control signals S1 to Sn from the control signal generating circuit 120, and respectively switch in response to the first control signals S1 to Sn to control the conducting states of the corresponding light emitting modules 160a to 160 n. The second switch unit 180 is coupled to each of the first switch units 140a to 140n, and configured to receive the second control signal PS from the control signal generating circuit 120, and switch in response to the second control signal PS to control the first switch units 140a to 140n to operate during the period when the second switch unit 180 is turned on.

Specifically, in some embodiments, the light emitting modules 160a to 160n may be a single LED unit with different color temperatures or a combination of a plurality of LED units connected in series, for example, the light emitting modules 160a, 160c, and 160d may be 2700K, 3000K, 5700K, 6500K, and the like, which is not limited herein. The control signal generating circuit 120 generates the first control signals S1 to Sn and the second control signal PS according to a light mixing ratio table and a target correlated color temperature (e.g. 4500K) included in the setting signal, so that the first switch units 140a to 140n are switched in response to the first control signals S1 to Sn to control the on states of the corresponding light emitting modules 160a to 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 units 140a to 140n to operate in the on period of the second switch unit 180 to achieve the target light flux (brightness). In addition, the operation of the light mixing ratio table can be understood and adjusted according to the practical application requirement by those skilled in the art, which can be generated from simulation calculation or analysis experiment results, and therefore, further description is omitted here for brevity.

Please refer to fig. 5. Fig. 5 is a schematic diagram illustrating a light-emitting device 10 according to another embodiment of the disclosure. With respect to the embodiment of fig. 5, for ease of understanding, like elements to those in fig. 1 will be labeled with like reference numerals. Unless needed to explain the cooperative relationship with the elements shown in fig. 5, the specific operations of similar elements that have been discussed in detail in the above paragraphs are omitted here for the sake of brevity. In addition, the light-emitting device control method 30 shown in fig. 3 can also be applied to the light-emitting device 10 shown in fig. 5.

As shown in fig. 5, different from fig. 1, the light emitting device 40 includes a second switch unit 180 coupled between the

light emitting modules

160a and 160b and a signal conversion circuit 100, 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 units

140a and 140b to operate during the period when the second switch unit 180 is turned on, and at the same time, the

first switch units

140a and 140b are switched in response to the first control signals S1 and S2 received from the control signal generating circuit 120, respectively, to control the on states of the corresponding

light emitting modules

160a and 160b. Specifically, in some embodiments, when the light emitting device 10 adjusts the light emitting light to have the target correlated color temperature through the first control signals S1 and S2, the control signal generating circuit 120 adjusts the duty cycle of the second control signal PS according to the target luminous flux, for example, 50%, so that the driving current of the signal converting circuit 100 can flow into the

light emitting modules

160a and 160b in a state where the second switching unit 180 is turned on, whereas the driving current of the signal converting circuit 100 does not flow into the

light emitting modules

160a and 160b in a state where the second switching unit 180 is not turned on (except for the 50% duty cycle), and by the above operation of controlling the on-time (duty cycle), the light emitting device 10 can be driven to emit light to reach the target luminous flux.

It should be noted that, in the light emitting device control method 30 of the present disclosure, the on state of the light emitting module may be controlled according to step S320 to adjust the correlated color temperature of the light emitting device, or the first switch unit may be controlled according to step S330 to operate during the on period of the second switch unit to adjust the brightness of the light emitting device. The various operations under the lighting device control method 30 may be suitably added, replaced, omitted, or performed in a different order without departing from the manner and scope of operation of the various embodiments of this disclosure.

In summary, the present disclosure provides a light emitting device and a method for controlling the light emitting device, which can simultaneously adjust the color temperature and brightness of light emitted by the light emitting device without additional current control circuit or complicated color mixing algorithm by controlling the on-time (duty cycle) of a plurality of first switch units respectively coupled to the light emitting module and a second switch unit coupled to each first switch unit.

Although the present disclosure has been described with reference to particular embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the disclosure, and therefore, the scope of the disclosure is to be determined by the appended claims.

Claims

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.