CN102006698A - Control method and light emitting device capable of avoiding flicker effect - Google Patents

Abstract

The present invention discloses a control method and a light emitting device capable of avoiding flickering effect. The control method capable of avoiding flickering effect is used in a light emitting light source module, and comprises detecting a change of a driving current flowing through the light emitting light source module to generate a current detection signal; adjusting a variable reference voltage according to the current detection signal; obtaining a feedback voltage from the light emitting light source module; generating a voltage control signal according to the feedback voltage and the variable reference voltage; and generating an output voltage according to the voltage control signal to drive the light emitting light source module.

Description

Control method and light emitting device capable of avoiding flicker effect

technical field

The invention relates to a control method and a light emitting device, in particular to a control method and a light emitting device capable of dynamically detecting load current to avoid the flicker effect.

Background technique

With the advent of the energy crisis and the rising awareness of environmental protection, the demand for energy conservation and environmental protection has become a topic of widespread concern around the world. Compared with traditional light sources, light-emitting diodes (Light Emitting Diode, LED) have the advantages of power saving, long component life, no mercury, rich color gamut, no need to warm up the lamp time, and fast response. Therefore, light-emitting diodes have been used It is widely used as a light source for display and lighting. In addition, light-emitting diodes can be made into extremely small or arrayed components due to their small size, light weight, impact resistance, suitability for mass production, and easy adaptation to application requirements. Therefore, light-emitting diodes are not only used in various outdoor displays In addition to traffic signal lights, it can also be applied to various electronic products or portable products, such as the screen backlight of LCD monitors, mobile phones, portable computers and personal digital assistants.

Please refer to FIG. 1 , which is a schematic diagram of a conventional LED driving circuit 10 . The LED driving circuit 10 is used to drive an LED light source module 102 . As shown in FIG. 1 , the LED light source module 102 includes m parallel LED groups C ₁ -C _m , and each LED string includes n serially connected LEDs. The LED driving circuit 10 includes a voltage converter 104 , a current source 106 , a pulse width modulation unit 108 and a control unit 110 . The voltage converter 104 is used to provide a driving voltage V _D to the LED light source module 102 . The current source 106 is used to provide driving currents _{ID1 -IDm} to the LED light source module 102 . The pulse width modulation unit 108 is used for performing a dimming procedure according to a dimming signal _SD . Generally speaking, there are corresponding headroom voltages (Headroom voltage) V _HR1 ˜V _HRm on the path of each LED group C ₁ ˜C _m , indicating that on the path of each LED group C ₁ ˜C _m , it can be The voltage value used by the current source 106 . In practical applications, in order to stably control the brightness and power consumption of the LEDs, the current flowing through the LEDs is usually kept stable (that is, the driving currents _{ID1 ˜IDm} are kept stable). However, due to the impact of non-ideal factors in the process or any other factors, the voltages across the light emitting diodes are not completely the same, resulting in the headspace voltages V _HR1 -V _HRm being different. In this case, the head space voltage is too high or too low, which will have a bad influence on the LED driving circuit 10. For example, if the head space voltage is too high, too much voltage will be consumed in the current source 106. On the contrary, if the voltage of the headspace is too low, the current source 106 will operate in an inappropriate state and cannot stably provide the required driving current.

Therefore, in FIG. 1 , in the prior art, the negative feedback control unit 110 is used to control the voltage converter 104 to change the driving voltage V _D to adjust the head space voltage to an appropriate constant value. The control unit 110 includes a voltage selector 112 , an error amplifier 114 and a conversion controller 116 . The voltage selector 112 is coupled to the output terminals of each LED group C ₁ -C _m , and is used to select one of the head space voltages V _HR1 -V _HRm as a feedback voltage V _FB , and feed back The voltage V _FB and a preset reference voltage V _REF are respectively input to the negative input terminal and the positive input terminal of the error amplifier 114 . The error amplifier 114 generates an error signal S _E according to the difference between the feedback voltage V _FB and the preset reference voltage V _REF . The conversion controller 116 generates a control signal S _C according to the error signal S _E to control the voltage converter 104 to perform voltage conversion to output the driving voltage V _D . That is to say, when the head space voltages V _HR1 ˜V _HRm corresponding to each LED group C ₁ ˜C _m are too low, the error amplifier 114 will generate an error signal S _E to the conversion controller 116 , and the conversion controller 116 Further, the voltage converter 104 increases the driving voltage V _D by using the control signal S _C . In this way, under the condition that the driving currents I _D1 ˜I _Dm are constant and the voltages across the light emitting diodes do not change, the control unit 110 controls to increase the driving voltage V _D , and the head space voltage V _HR1 ~V _HRm will also increase accordingly, and there is a positive relationship between the two, the same reason, and vice versa. In other words, under the stable supply of driving currents I _D1 ˜I _Dm , the LED driving circuit 10 can lock the voltage of the head space at a reasonable voltage value (ie, the preset reference voltage V _REF ).

However, in many cases, the current through the LED still has current variation. For example, when performing a dimming program, it is usually used to adjust the current through the LED (that is, to adjust the driving current _ID1 ~ I _Dm size) to change the brightness of the LED. In this case, since the driving currents I _D1 ˜I _Dm will change, the voltage across the light emitting diode will change accordingly. Therefore, in the aforementioned prior art, if the driving voltage V _D is only adjusted by comparing with the fixed preset reference voltage V _REF , the driving voltage V _D may not be raised in real time due to the lengthy feedback tracking time. During the feedback tracking period, the current source 106 cannot provide sufficient driving current due to insufficient headspace voltage, and the light emitting diode will flicker.

Contents of the invention

Therefore, the main purpose of the present invention is to provide a control method and a light emitting device which can avoid the flicker effect.

The present invention discloses a control method capable of avoiding the flicker effect, which is used in a luminous light source module, including detecting the variation of a driving current flowing through the luminous light source module to generate a current detection signal; according to the current detection signal, adjusting a variable reference voltage; obtaining a feedback voltage from the light emitting source module; generating a voltage control signal according to the feedback voltage and the variable reference voltage; and generating an output voltage according to the voltage control signal to and drive the luminescent light source module.

The present invention also discloses a light emitting device, comprising: a voltage converter, used to convert an input voltage into an output voltage according to a voltage control signal; a light emitting source module, coupled to the voltage converter; a variable a current source, coupled to the light emitting source module, for providing a driving current to drive the light emitting source module; and a control unit, coupled to the light emitting source module and the voltage converter, for receiving from the light emitting source module, Obtain a feedback voltage, and detect the variation of the driving current flowing through the light emitting source module to generate a current detection signal; wherein, the control unit adjusts a variable reference voltage according to the current detection signal, and adjusts a variable reference voltage according to the The feedback voltage and the variable reference voltage generate the voltage control signal to the voltage converter.

The present invention also discloses a control method capable of avoiding the flicker effect, which is used in a light-emitting light source module, including: detecting the change of a driving current provided by a variable current source to generate a current detection signal; according to the A current detection signal is used to adjust a variable reference voltage; a feedback voltage is obtained from the luminescent light source module; a voltage control signal is generated according to the feedback voltage and the variable reference voltage; and a voltage control signal is generated according to the voltage control signal output voltage to drive the luminescent light source module.

The present invention also discloses a light emitting device, comprising: a voltage converter, used to convert an input voltage into an output voltage according to a voltage control signal; a light emitting source module, coupled to the voltage converter; a variable a current source, coupled to the light emitting source module, used to generate a driving current to drive the light emitting source module; and a control unit, coupled to the variable current source and the voltage converter, used to generate a driving current from the light emitting source module , obtain a feedback voltage, and detect the variation of the driving current provided by the variable current source to generate a current detection signal; wherein, the control unit adjusts a variable reference voltage according to the current detection signal , and generate the voltage control signal to the voltage converter according to the feedback voltage and the variable reference voltage.

Description of drawings

FIG. 1 is a schematic diagram of a conventional LED driving circuit.

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

FIG. 3 is a schematic diagram of a process in Embodiment 1 of the present invention.

FIG. 4 is a schematic diagram of a light emitting device according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of an embodiment of a variable current source in FIG. 4 .

FIG. 6 is a schematic diagram of a process in Embodiment 1 of the present invention.

FIG. 7 is a schematic diagram of an embodiment of the reference voltage converter in FIG. 2 .

FIG. 8 is a schematic diagram of an embodiment of the reference voltage converter shown in FIG. 4 .

Description of reference symbols

10 LED drive circuit

102 LED light source module

104, 202, 402 voltage converter

106 Current source

108 Pulse Width Modulation Unit

110 Control unit

112, 210, 410 voltage selector

114, 218, 418 error amplifier

116, 220, 420 conversion controller

20, 40 Lighting device

204, 404 Luminescent light source module

206, 406 variable current source

208, 408 control unit

212, 412 Current detector

214, 414 computing unit

216, 416 Reference voltage converter

30, 60 Process

300, 302, 304, 306, 308,

310, 312, 602, 604, 606,

608, 610, 612 steps

502 variable current mirror

504 Current drive components

C ₁ ~C _m LED group

I _D1 ～I _Dm driving current

I _L1 ～I _Lm load current

_VD driving voltage

V _FB feedback voltage

V _HR1 ～V _HRm head space voltage

V _IN input voltage

V _REF preset reference voltage

V _{REF_V} variable reference voltage

S _C voltage control signal

S _E error voltage signal

S _L current detection signal

S _V reference voltage conversion signal

Detailed ways

Please refer to FIG. 2 , which is a schematic diagram of a light emitting device 20 according to an embodiment of the present invention. The lighting device 20 includes a voltage converter 202 , a lighting source module 204 , a variable current source 206 and a control unit 208 . Wherein, the light emitting device 20 can be applied to any kind of light source. The voltage converter 202 is used to convert an input voltage V _IN into an output voltage V _D according to a voltage control signal S _C , so as to provide it to the light emitting source module 204 . The light source module 204 is coupled to the voltage converter 204 . It should be noted that, in this embodiment, the light emitting source module 204 includes LED groups C ₁ -C _m , but it is not limited thereto, and there may be only one LED group. On the other hand, since the LED is a current-driven component, its luminous brightness is directly proportional to the magnitude of the driving current, that is, the larger the driving current, the greater the luminous brightness of the LED. Generally speaking, in order to achieve the same brightness requirement by requiring the same current flowing through each LED, in this embodiment, each LED group includes n LEDs coupled in series, but the LEDs The groups C ₁ -C _m are not limited to n light-emitting diodes connected in series, in other words, each light-emitting diode group may only include a single light-emitting diode. In addition, the variable current source 206 is coupled to the light emitting source module 204 for providing load currents I _L1 -I _Lm flowing through each light emitting diode group to drive the light emitting source module 204 . The control unit 208 is coupled to the light source module 204 and the voltage converter 202, and is used to obtain a feedback voltage V _FB from the light source module 204, and detect the change of the load current I _L1 ˜I _Lm flowing through the light source module 204 , to generate a current detection signal S _L . Next, the control unit adjusts a variable reference voltage V _{REF_V} according to the current detection signal _SL , and generates a voltage control signal S _C to the voltage converter 202 according to the feedback voltage V _FB and the variable reference voltage V _{REF_V} . In other words, the control unit 208 detects the change of the load current I _L1 ˜I _Lm flowing through the light source module 204 in real time to dynamically adjust the variable reference voltage V _{REF_V} , and then controls the voltage converter 202 to convert an appropriate output voltage V in real time. _D , to provide to the light source module 204 .

For further description of the control unit 208 , please continue to refer to FIG. 2 . The control unit 208 includes a voltage selector 210 , a current detector 212 , a computing unit 214 , a reference voltage converter 216 , an error amplifier 218 and a conversion controller 220 . The voltage selector 210 is coupled to the light emitting source module 204 for selecting the feedback voltage V _FB from the head space voltages V _HR1 ˜V _HRm corresponding to the LED groups C ₁ ˜C _m . The current detector 212 is coupled to the light source module, and is used to detect the change of the load current I _L1 ˜I _Lm to generate a current detection signal S _L . The computing unit 214 is coupled to the current detector 212 and used for generating a reference voltage conversion signal S _V according to the current detection signal _SL . The reference voltage converter 216 is coupled to the computing unit 214 and used for generating a variable reference voltage V _{REF_V} according to the reference voltage conversion signal S _V . Therefore, when the current detection signal _SL indicates that the load currents I _{L1 ˜ILm} vary, the computing unit 214 will notify the reference voltage converter 216 to generate the required variable reference voltage V _{REF_V} through the reference voltage conversion signal S _V . For example, when the current detection signal indicates that the load current I _L1 ˜I _Lm becomes larger, the calculation unit 214 will notify the reference voltage converter 216 to increase the variable reference voltage V _{REF_V} ; similarly, when the current detection signal indicates that the load current I When _L1 ˜I _Lm becomes smaller, the reference voltage converter 216 is notified to decrease the variable reference voltage V _{REF_V} .

Furthermore, a positive input terminal and a negative input terminal of the error amplifier 218 are respectively coupled to the reference voltage converter 216 and the voltage selector 210 for generating an error according to the variable reference voltage V _{REF_V} and the feedback voltage V _FB . Voltage signal S _E . The switching controller 220 is coupled between an output terminal of the error amplifier 218 and the voltage converter 202 for generating a voltage control signal S _C according to the error voltage signal S _E to provide to the voltage converter. In this case, when the feedback voltage V _FB is greater than or less than the variable reference voltage V _{REF_V} , the error amplifier 218 will generate an error voltage signal _SE to notify the conversion controller 220 according to the difference between the two, and the conversion controller Based on this, the 220 generates a voltage control signal S _C to increase or decrease the output voltage V _D . In short, the control unit 208 can detect the change of the load current in real time, and then dynamically adjust the reference voltage input to the error amplifier 218 to achieve real-time and effective feedback tracking to the proper output voltage V _D .

Therefore, in the present invention, the control unit 208 can detect the change of the load current I _L1 ˜I _Lm flowing through the light source module 204 in real time to dynamically adjust the variable reference voltage V _{REF_V} , and then control the voltage converter 202 to convert an appropriate voltage in real time. the output voltage V _D . In this way, when the load current changes, it is possible to effectively prevent the head space voltage from being compressed to too low, so that the variable current source 206 cannot provide enough load current, which will cause the light source module 204 to flicker. , and will not consume too much voltage on the variable current source 206 due to the high head space voltage, thereby reducing the overall voltage conversion efficiency.

Regarding the operation of the light emitting device 20 , please refer to FIG. 3 , which is a schematic diagram of a process 30 according to Embodiment 1 of the present invention. Process 30 includes the following steps:

Step 300: start.

Step 302: Detect the variation of the load currents I _L1 -I _Lm flowing through the light source module 204 to generate a current detection signal S _L .

Step 304: Adjust a variable reference voltage V _{REF_V} according to the current detection signal _SL .

Step 306 : Obtain a feedback voltage V _FB from the light source module 204 .

Step 308: Generate a voltage control signal S _C according to the feedback voltage V _FB and the variable reference voltage V _{REF_V} .

Step 310: Generate an output voltage V _D to drive the light source module 204 according to the voltage control signal S _C .

Step 312: end.

The process 30 is used to illustrate the operation mode of the light emitting device 20 , and the detailed description and related changes can refer to the foregoing description, and will not be repeated here.

In addition, the control unit 208 can also dynamically adjust the variable reference voltage V _{REF_V} by directly detecting the current variation of the variable current source, and then control the voltage converter 202 to convert an appropriate output voltage V _D in real time. Please refer to FIG. 4 , which is a schematic diagram of a light emitting device 40 according to an embodiment of the present invention. It is worth noting that since components with the same names in the light emitting device 20 in FIG. 2 and the light emitting device 40 in FIG. The connection relationship of the components is shown in FIG. 4 , which will not be repeated here. The lighting device 40 includes a voltage converter 402 , a lighting source module 404 , a variable current source 406 and a control unit 408 . The control unit 408 includes a voltage selector 410 , a current detector 412 , a computing unit 414 , a reference voltage converter 416 , an error amplifier 418 and a conversion controller 420 . Wherein, the difference from the light emitting device 20 in FIG. 2 is that the current detector 412 is coupled to the variable current source 406 . The current detector 412 is used to detect the change of the load current generated by the variable current source 406 to generate the current detection signal S _L to dynamically adjust the variable reference voltage V _{REF_V} . In addition, please refer to FIG. 5 , the variable current source 406 may further include a variable current mirror 502 and a current driving component 504 . The variable current mirror 502 is coupled to the current detector 412 for generating load currents I _L1 ˜I _Lm . The current driving component 504 is coupled to the variable current mirror 502 and the light emitting diode groups C ₁ -C _m of the light emitting source module 404, and is used to control and provide load current I _{L1 -ILm} to the light emitting diode group C of the light emitting source module ₁ ~ C _m . In other words, the control unit 408 can directly detect the change of the current on the variable current mirror 502 to control the voltage converter 402 to convert a proper output voltage V _D in real time. In addition, in this embodiment, the control unit 408 is directly coupled to the variable current mirror 502, but not limited thereto, the control unit 408 can also directly detect other components of the variable current source 406 (such as the current driving component 504) In other words, the control unit 408 can dynamically detect the current change of any component of the variable current source 406 to obtain the change of the load current I _L1 ˜I _Lm . On the other hand, in terms of circuit design, the control unit 408 and the variable current source 406 can be integrated on the same chip. In this way, the aforementioned operation mode can be realized inside the chip, and the prevention of transistor generation can be realized in real time. The purpose of flicker effect.

Regarding the operation of the light emitting device 40 , please refer to FIG. 6 , which is a flowchart of a process 60 according to Embodiment 1 of the present invention. Process 60 comprises the following steps:

Step 600: start.

Step 602: Detect the variation of the load currents I _L1 ˜I _Lm provided by the variable current source 406 to generate a current detection signal S _L .

Step 604: Adjust a variable reference voltage V _{REF_V} according to the current detection signal _SL .

Step 606: Obtain a feedback voltage V _FB from the light source module 404 .

Step 608: Generate a voltage control signal S _C according to the feedback voltage V _FB and the variable reference voltage V _{REF_V} .

Step 610: Generate an output voltage V _D to drive the light source module 404 according to the voltage control signal S _C .

Step 612: end.

The process 60 is used to illustrate the operation mode of the light emitting device 40 , and the detailed description and related changes can refer to the foregoing description, and will not be repeated here.

It is worth noting that the above-mentioned embodiment is only an example of the present invention, and those skilled in the art can make appropriate modifications according to actual needs. For example, since the reference voltage converters 216 and 416 are used to provide various The voltage value makes the variable reference voltage V _{REF_V} variable. Therefore, various voltage values required can be generated in any form. As shown in FIG. 7 and FIG. 8 , the reference voltage converters 216 and 416 can be implemented by multiplexers 702 and 802 respectively. The multiplexers 702 and 802 convert the signal S _V according to the reference voltage to obtain a preset reference voltage A variable reference voltage V _{REF_V} is selected by switching among V _{REF_1} -V _{REF_z} . In addition, the voltage selectors 210 and 410 can select the feedback voltage V _FB from the head space voltages V _HR1 ˜V _HRm according to any rules. For example, the voltage selector 210 can select the smallest head space voltage from the head space voltages V _HR1 ˜V _HRm as the feedback voltage VFB. On the other hand, the calculation units 214 and 414 will perform logic calculations to obtain a reasonable reference voltage value according to the change of the load current I _L1 ˜I _Lm , for example, according to the number of current changes, the amount of current change, or the average change of the overall current Quantity, to evaluate and calculate a corresponding reference voltage value. The computing unit 214, 414 can generate a current detection signal _SL according to the current change when at least one load current changes or at a specific time interval. In addition, the variable current source 406 can change the current provided to the light emitting source module 404 according to a dimming signal according to system requirements, so as to adjust the light emitting brightness of the LEDs on the light emitting source module 404 .

To sum up, the present invention detects the change of the load current I _L1 ˜I _Lm flowing through the light source module in real time through the control unit to dynamically adjust the variable reference voltage V _{REF_V} , and then controls the voltage converter to convert the appropriate voltage in real time. output voltage V _D . In this way, when the load current changes, the variable current source 206 cannot provide enough load current due to the compression of the head space voltage to be too small, which will cause the light source module to flicker. It will not consume too much voltage on the variable current source 206 due to the high voltage of the head space, thereby reducing the overall voltage conversion efficiency.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the claims of the present invention shall fall within the scope of the present invention.

Claims (38)

1. A control method capable of avoiding the flicker effect, for a luminescent light source module, comprising: Detecting changes in a driving current flowing through the light emitting source module to generate a current detection signal; adjusting a variable reference voltage according to the current detection signal; obtaining a feedback voltage from the luminescent light source module; generating a voltage control signal according to the feedback voltage and the variable reference voltage; and According to the voltage control signal, an output voltage is generated to drive the luminescent light source module. 2. The control method according to claim 1, wherein the light emitting source module comprises a plurality of LED groups, and the driving current is composed of a plurality of load currents flowing through each of the plurality of LED groups. 3. The control method according to claim 2, wherein the step of detecting the change of the driving current flowing through the light-emitting light source module to generate the current detection signal is to detect a change in at least one of the plurality of load currents When, the current detection signal is generated according to the change of the at least one changed load current. 4. The control method as claimed in claim 2, wherein the step of obtaining the feedback voltage from the light emitting source module is to select the minimum head space voltage from a plurality of head space voltages corresponding to the plurality of light emitting diode groups The space voltage is the feedback voltage. 5. The control method of claim 1, wherein the feedback voltage is selected from head space voltages corresponding to the light emitting source module. 6. The control method according to claim 1, wherein the step of adjusting the variable reference voltage according to the current detection signal is to increase the variable reference voltage when the current detection signal indicates that the driving current becomes larger. 7. The control method according to claim 1, wherein the step of adjusting the variable reference voltage according to the current detection signal is to decrease the variable reference voltage when the current detection signal indicates that the driving current becomes smaller. 8. The control method according to claim 1, wherein the step of adjusting the variable reference voltage according to the current detection signal comprises: generating a reference voltage conversion signal according to the current detection signal; and The variable reference voltage is generated according to the reference voltage conversion signal. 9. A lighting device, comprising: a voltage converter for converting an input voltage into an output voltage according to a voltage control signal; a luminescent light source module coupled to the voltage converter; a variable current source, coupled to the light emitting source module, for providing a driving current to drive the light emitting source module; and A control unit, coupled to the light emitting source module and the voltage converter, used to obtain a feedback voltage from the light emitting source module, and detect the change of the driving current flowing through the light emitting source module to generate a current detection signal; Wherein, the control unit adjusts a variable reference voltage according to the current detection signal, and generates the voltage control signal to the voltage converter according to the feedback voltage and the variable reference voltage. 10. The light emitting device according to claim 9, wherein the light emitting source module comprises a plurality of LED groups, and the driving current is composed of a plurality of load currents flowing through each of the plurality of LED groups. 11. The light emitting device of claim 10, wherein each LED group of the plurality of LED groups comprises a plurality of LEDs connected in series. 12. The lighting device according to claim 10, wherein the control unit generates the current detection signal according to a variation of the at least one load current when detecting that at least one of the plurality of load currents changes. 13. The lighting device of claim 10, wherein the control unit selects the smallest head space voltage as the feedback voltage from a plurality of head space voltages corresponding to the plurality of LED groups. 14. The lighting device of claim 9, wherein the control unit comprises: a voltage selector, coupled to the light emitting source module, for selecting the feedback voltage from a plurality of headspace voltages corresponding to the light emitting source module; A current detector, coupled to the light emitting light source module, is used to detect the change of the driving current flowing through the light emitting light source module, so as to generate the current detection signal; an arithmetic unit, coupled to the current detector, for generating a reference voltage conversion signal according to the current detection signal; A reference voltage converter, coupled to the computing unit, used to convert a signal according to the reference voltage to generate the variable reference voltage; an error amplifier, coupled to the voltage selector and the reference voltage converter, for generating an error voltage signal according to the feedback voltage and the variable reference voltage; and A conversion controller, coupled to the error amplifier and the voltage converter, is used to generate the voltage control signal according to the error voltage signal to provide to the voltage converter. 15. The lighting device of claim 14, wherein the voltage selector selects the smallest head space voltage from the plurality of head space voltages as the feedback voltage. 16. The light emitting device of claim 14, wherein the calculation unit adjusts the variable reference voltage higher when the current detection signal indicates that the driving current becomes larger. 17. The light emitting device according to claim 14, wherein the computing unit lowers the variable reference voltage when the current detection signal indicates that the driving current becomes smaller. 18. A control method capable of avoiding the flicker effect, used for a light source module, comprising: Detecting a change in a driving current provided by a variable current source to generate a current detection signal; adjusting a variable reference voltage according to the current detection signal; obtaining a feedback voltage from the luminescent light source module; generating a voltage control signal according to the feedback voltage and the variable reference voltage; and According to the voltage control signal, an output voltage is generated to drive the luminescent light source module. 19. The control method according to claim 18, wherein the light emitting source module includes a plurality of LED groups, and the driving current includes a plurality of load currents for providing each of the plurality of LED groups. 20. The control method according to claim 19, wherein the step of detecting the change of the drive current provided by the variable current source to generate the current detection signal is to detect at least one of the plurality of load currents When a change occurs, the current detection signal is generated according to the change of the at least one changed load current. 21. The control method as claimed in claim 19, wherein the step of obtaining the feedback voltage from the light-emitting source module is to select a minimum head space voltage from a plurality of head space voltages corresponding to the plurality of light-emitting diode groups The space voltage is the feedback voltage. 22. The control method of claim 18, wherein the feedback voltage is selected from head space voltages corresponding to the light emitting source module. 23. The control method according to claim 18, wherein the step of adjusting the variable reference voltage according to the current detection signal is to increase the variable reference voltage when the current detection signal indicates that the driving current increases. 24. The control method of claim 18, wherein the step of adjusting the variable reference voltage according to the current detection signal is to decrease the variable reference voltage when the current detection signal indicates that the driving current becomes smaller. 25. The control method according to claim 18, wherein the step of adjusting the variable reference voltage according to the current detection signal comprises: generating a reference voltage conversion signal according to the current detection signal; and According to the reference voltage conversion signal, the variable reference voltage is generated. 26. A lighting device comprising: a voltage converter for converting an input voltage into an output voltage according to a voltage control signal; a light emitting source module coupled to the voltage converter; a variable current source, coupled to the light emitting source module, for generating a driving current to drive the light emitting source module; and a control unit, coupled to the variable current source and the voltage converter, for obtaining a feedback voltage from the light-emitting light source module, and detecting the variation of the driving current provided by the variable current source, to generate a current detection signal; Wherein, the control unit adjusts a variable reference voltage according to the current detection signal, and generates the voltage control signal to the voltage converter according to the feedback voltage and the variable reference voltage. 27. The light emitting device according to claim 26, wherein the light emitting source module comprises a plurality of LED groups, and the driving current is composed of a plurality of load currents flowing through each of the plurality of LED groups. 28. The light emitting device of claim 27, wherein each LED group of the plurality of LED groups comprises a plurality of LEDs connected in series. 29. The light emitting device according to claim 27, wherein the control unit generates the current detection signal according to a variation of the at least one load current when detecting that at least one of the plurality of load currents changes. 30. The lighting device of claim 27, wherein the control unit selects the smallest head space voltage as the feedback voltage from a plurality of head space voltages corresponding to the plurality of LED groups. 31. The lighting device of claim 26, wherein the variable current source can generate the driving current according to the requirement of the lighting source module. 32. The light emitting device of claim 26, wherein the variable current source can generate the driving current according to a dimming signal. 33. The light emitting device of claim 26, wherein the variable current source comprises: a variable current mirror, coupled to the control unit, for generating the driving current; and A current driving component, coupled to the variable current mirror and the light emitting source module, is used to control and provide the driving current to the light emitting source module. 34. The light emitting device as claimed in claim 26, wherein the control unit can detect the variation of the current provided by the variable current mirror to generate a cover current detection signal. 35. The lighting device of claim 26, wherein the control unit comprises: a voltage selector, coupled to the light emitting source module, for selecting the feedback voltage from a plurality of headspace voltages corresponding to the light emitting source module; A current detector, coupled to the variable current source, is used to detect the variation of the driving current generated by the variable current source to generate the current detection signal; an arithmetic unit, coupled to the current detector, for generating a reference voltage conversion signal according to the current detection signal; A reference voltage converter, coupled to the computing unit, used to convert a signal according to the reference voltage to generate the variable reference voltage; an error amplifier, coupled to the voltage selector and the reference voltage converter, for generating an error voltage signal according to the feedback voltage and the variable reference voltage; and A conversion controller, coupled to the error amplifier and the voltage converter, is used to generate the voltage control signal according to the error voltage signal to provide to the voltage converter. 36. The light emitting device of claim 35, wherein the voltage selector selects the smallest head space voltage from the plurality of head space voltages as the feedback voltage. 37. The light emitting device according to claim 35, wherein the calculation unit adjusts the variable reference voltage up when the current detection signal indicates that the driving current becomes larger. 38. The light emitting device of claim 35, wherein the calculation unit lowers the variable reference voltage when the current detection signal indicates that the driving current becomes smaller.

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