CN109392217B

CN109392217B - Light emitting element drive circuit and control method thereof

Info

Publication number: CN109392217B
Application number: CN201810650830.7A
Authority: CN
Inventors: 黄意文
Original assignee: Richtek Technology Corp
Current assignee: Richtek Technology Corp
Priority date: 2017-08-14
Filing date: 2018-06-22
Publication date: 2020-11-03
Anticipated expiration: 2038-06-22
Also published as: CN109392217A

Abstract

The invention provides a light emitting element driving circuit and a control method thereof. The light emitting device driving circuit for driving a light emitting device circuit includes: a switching power supply circuit and a current regulating circuit. The current regulation circuit includes: the multi-section direct current control circuit is used for respectively determining the conduction or non-conduction of a plurality of sub direct current supply circuits according to the direct current dimming signal so as to supply direct current to the light-emitting element circuit; and a switching current control circuit for operating one of the PWM switches to supply PWM current to the light emitting device circuit according to the PWM dimming signal; the direct current and the pulse width modulation current are superposed and then flow through the light-emitting element circuit, so that the brightness of the light-emitting element circuit is adjusted according to the direct current dimming signal and the pulse width modulation dimming signal.

Description

Light emitting element drive circuit and control method thereof

Technical Field

The present invention relates to a light emitting device driving circuit and a control method thereof, and more particularly, to a light emitting device driving circuit having a dimming function and a control method thereof.

Background

Fig. 1A shows a schematic diagram of a prior art Light Emitting Diode (LED) driving circuit 100. As shown in fig. 1A, the LED driving circuit 100 drives the LED circuit 10. The LED driving circuit 100 includes a power control circuit 11, a power stage circuit 12, a feedback circuit 13, and a current control circuit 14. The power control circuit 11 is electrically connected to the feedback circuit 13 to receive a feedback signal FB related to the output voltage Vout and generate an operation signal GATE for operating the power switch in the power stage circuit 12, so as to convert the input voltage Vin into the output voltage Vout for supplying power to the LED circuit 10. The brightness of the LED circuit 10 is controlled by the output current Iout, and when the LED driving circuit 100 has a dimming function, the current control circuit 14 has a pin to receive a dimming signal; the dimming signal may adjust an average value of the output current Iout to adjust the brightness of the LED circuit 10. The power stage circuit 12 may be a synchronous or asynchronous buck, boost, buck boost, or flyback power stage circuit, as shown in fig. 2A-2K.

In the prior art, there are two ways to adjust the brightness of the LED circuit 10. One is an analog dimming mode, and the other is a digital dimming mode. The analog dimming manner is to adjust the level of the output current Iout by the current control circuit 14 according to the received dimming signal. As shown in fig. 1B, the current control circuit 14 adjusts the output current Iout to a level between 0 and the maximum current Imax according to the dimming signal, and adjusts the level of the output current Iout according to the dimming signal, so as to achieve the purpose of dimming. The higher the level of the output current Iout flowing through the LED circuit 10, the higher the luminance of the LED circuit 10.

On the other hand, in the digital dimming method, the current control circuit 14 generates a Pulse Width Modulation (PWM) signal according to the dimming signal, and the signal waveform thereof is as shown in fig. 1C. The current control circuit 14 adjusts the time (on time Ton) that the pwm signal is at the high level H to adjust the duty ratio (duty ratio), and further adjusts the time that the output current Iout is at the current maximum value Imax, thereby adjusting the brightness of the LED circuit 10. For example, the brightness of the LED circuit 10 is related to the average value of the output current Iout. The average value of the output current Iout is the current maximum value Imax multiplied by the duty ratio, i.e. the on-time Ton divided by the period time Tdim. Generally, the minimum on-time ton (min) is about tens of nanoseconds (ns) to tens of microseconds (us), and thus the switching frequency of the operation signal is about hundreds of hertz (Hz) to thousands of Hz.

The above-mentioned prior art digital dimming method has at least the disadvantages of low frequency flicker (low frequency flicker) and audio noise (audio noise) when applied. In addition, the on-response time of the LED circuit 10 is slowed down as the output current Iout is increased, which reduces the dimming resolution. On the other hand, another prior art analog dimming method has a disadvantage of causing color drift (color drift) of the light emitting device circuit.

In view of the above, the present invention provides a light emitting device driving circuit and a control method thereof, which are directed to overcome the problems of flicker, noise, and low resolution of the light emitting device, and avoid color shift of the light emitting device without reducing the resolution of the dimming method.

Disclosure of Invention

In order to achieve the above object, in one aspect, the present invention provides a light emitting device driving circuit for driving a light emitting device circuit, including: a switching power supply circuit for controlling at least one of the power switches according to a feedback signal to convert an input voltage into an output voltage for supplying power to the light emitting device circuit; and a current regulation circuit comprising: a multi-stage DC current control circuit for determining the conduction or non-conduction of a plurality of sub-DC current supply circuits according to a DC dimming signal to supply a DC current to the light emitting element circuit; and a switching current control circuit for operating one of the PWM switches to supply a PWM current to the light emitting device circuit according to a PWM dimming signal; after the direct current and the pulse width modulation current are superposed, a light emitting element current is generated and flows through the light emitting element circuit, so that the brightness of the light emitting element circuit is adjusted according to the direct current dimming signal and the pulse width modulation dimming signal.

In a preferred embodiment, each of the sub-dc supply circuits supplies a sub-dc when turned on, and the sub-dc provided by the turned on sub-dc supply circuits are superimposed to form the dc current, and each of the sub-dc is not lower than a unit current, and an average current of the pwm current is not higher than the unit current.

In the aforementioned embodiment, each of the sub-dc currents is preferably constant.

In a preferred embodiment, the multi-stage dc current control circuit includes: a DC switch electrically connected to the light emitting element circuit for controlling the DC channel; a switch control circuit coupled to the DC switch for controlling the DC switch according to a reference voltage; the plurality of sub-direct current supply circuits are electrically connected with the direct current switch and used for respectively determining to conduct and not conduct one of the sub-direct current switches according to the direct current dimming signal so as to respectively supply or not supply a sub-direct current, and the direct current is formed after the sub-direct current provided by the conducted sub-direct current supply circuits is superposed.

In a preferred embodiment, the switching current control circuit comprises: the PWM switch is coupled with the light-emitting element circuit and is used for operating according to the PWM dimming signal so as to supply the PWM current; and a PWM switch control circuit coupled to the PWM switch for controlling the PWM switch according to a reference voltage.

In a preferred embodiment, the switching current control circuit comprises: a power stage circuit for operating the at least one power switch according to an operation signal to supply power to the light emitting device circuit; a control circuit coupled to the power stage circuit for generating the operation signal according to a feedback signal related to the output voltage; and a feedback signal generating circuit coupled to the power stage circuit and the control circuit for generating the feedback signal according to the output voltage.

In a preferred embodiment, the sub-dc supply circuit is a current source circuit or a current sink circuit.

From another perspective, the present invention also provides a method for controlling a light emitting device driving circuit, wherein the light emitting device driving circuit is configured to drive a light emitting device circuit, the method comprising: controlling at least one power switch according to a feedback signal to convert an input voltage into an output voltage to supply power to the light-emitting element circuit; respectively determining the conduction or non-conduction of a plurality of sub-DC current supply circuits according to a DC dimming signal so as to supply a DC current to the light-emitting element circuit; and operating a PWM switch to supply a PWM current to the light emitting device circuit according to a PWM dimming signal; after the direct current and the pulse width modulation current are superposed, a light emitting element current is generated and flows through the light emitting element circuit, so that the brightness of the light emitting element circuit is adjusted according to the direct current dimming signal and the pulse width modulation dimming signal.

In a preferred embodiment, the step of determining whether the plurality of sub-dc current supply circuits are turned on or off respectively according to a dc dimming signal to supply a dc current to the light emitting device circuit includes: providing a direct current switch electrically connected with the light-emitting element circuit for controlling the direct current channel; controlling the DC switch according to a reference voltage; and respectively determining to conduct and not conduct a sub-DC switch in the sub-DC supply circuit according to the DC dimming signal so as to respectively supply or not supply a sub-DC, and forming the DC after the sub-DC provided by the conducted sub-DC supply circuit is superposed.

In a preferred embodiment, the step of operating a pwm switch to supply a pwm current to the light emitting device circuit according to a pwm dimming signal comprises: operating the pwm switch to supply the pwm current according to the pwm dimming signal; and controlling the PWM switch to operate in a saturation region according to a reference voltage.

In a preferred embodiment, the step of controlling at least one power switch according to a feedback signal to convert an input voltage into an output voltage for supplying power to the light emitting device circuit comprises: according to an operation signal, operating the at least one power switch to supply power to the light-emitting element circuit; generating the operation signal according to a feedback signal related to the output voltage; and generating the feedback signal according to the output voltage.

The purpose, technical content, features and effects of the invention will be more easily understood through the following detailed description of specific embodiments.

Drawings

FIG. 1A shows a schematic diagram of a prior art LED driver circuit 100;

FIG. 1B is a schematic diagram showing the waveforms of the output current Iout and the operation signal GATE in the prior art;

FIG. 1C shows a signal waveform diagram of an output current Iout and a level diagram of a maximum current Imax in the prior art;

FIGS. 2A-2K illustrate synchronous or asynchronous buck, boost, buck-boost, boost-buck, and flyback power stage circuits;

FIG. 3 shows a first embodiment of the invention;

FIG. 4 shows a second embodiment of the present invention;

FIG. 5 shows a third embodiment of the invention;

FIGS. 6A-6B illustrate a fourth embodiment of the present invention;

fig. 7 is a schematic diagram showing signal waveforms of the dc current ILED _ dc, the pwm current ILED _ pwm, the pwm signal Gpwm, and the light emitting element current ILED according to the present invention;

fig. 8 shows a fifth embodiment of the present invention.

Detailed Description

The drawings in the present disclosure are schematic and are intended to show the coupling relationship between circuits and the relationship between signal waveforms, and the circuits, signal waveforms and frequencies are not drawn to scale.

Fig. 3 shows a first embodiment of the invention. As shown, the light emitting device driving circuit 200 is used for driving the light emitting device circuit 20, and includes a switching power supply circuit 21 and a current regulating circuit 22. The switching power supply circuit 21 is configured to control at least one of the power switches according to the feedback signal FB to convert the input voltage Vin into the output voltage Vout, so as to supply power to the light emitting device circuit 20.

The switching power supply circuit 21 includes a power stage circuit 211, a control circuit 213, and a feedback signal generating circuit 215. The power stage circuit 211 is used for operating at least one of the power switches according to the operation signal GATE to supply power to the light emitting device circuit 20. The power stage circuit 211 may be a synchronous or asynchronous buck, boost, buck boost, or flyback power stage circuit, as shown in fig. 2A-2K. The control circuit 213 is coupled to the power stage circuit 211 for generating the operation signal GATE according to the feedback signal FB related to the output voltage Vout. The feedback signal generating circuit 215 is coupled to the power stage circuit 211 and the control circuit 213 for generating the feedback signal FB according to the output voltage Vout.

The current adjusting circuit 22 includes a multi-stage dc current control circuit 221 and a switching current control circuit 222. The multi-stage dc current control circuit 221 is used for determining conduction or non-conduction of a plurality of sub-dc current supply circuits 2211 therein according to the dc dimming signal, so as to supply the dc current ILED _ dc to the light emitting device circuit 20. The sub dc currents Idc1 provided by the sub dc current supply circuits 2211 may be the same current or different currents. When each sub-dc current supply circuit 2211 is turned on, the sub-dc currents Idc1 are supplied, and the sub-dc currents Idc1 provided by the turned-on sub-dc current supply circuits 2211 are superimposed to form the dc current ILED _ dc, and each sub-dc current Idc1 is not lower than the unit current Iunit, and an average current of the pulse width modulated current ILED _ pwm is not higher than the unit current Iunit. In a preferred embodiment, the sub-dc current Idc1 is constant (fixed current).

The switching current control circuit 222 is used for operating a pwm switch (not shown, described in detail later) according to the pwm dimming signal to supply a pwm current ILED _ pwm to the light emitting device circuit 20. After the direct current ILED _ dc and the pulse width modulation current ILED _ pwm are superimposed, a light emitting device current ILED is generated and flows through the light emitting device circuit 20, so that the brightness of the light emitting device circuit 20 is adjusted according to the direct current dimming signal and the pulse width modulation dimming signal.

Fig. 4 shows a second embodiment of the invention. Referring to fig. 4, an embodiment of the current regulator circuit 22 according to the present invention is shown. As shown in fig. 4, the current regulating circuit 22 includes: a multi-stage DC current control circuit 221 and a switching current control circuit 222. The multi-stage dc current control circuit 221 is configured to determine whether the plurality of sub-dc

current supply circuits

2211, 2212, and 2213 therein are turned on or off (the number of the sub-dc current supply circuits is plural, in this embodiment, 3 sub-dc current supply circuits are taken as an example) according to the dc dimming signal, so as to supply the dc current ILED _ dc to the light emitting device circuit 20. The switching current control circuit 222 is configured to generate a Pulse Width Modulation (PWM) signal Gpwm according to the PWM dimming signal to operate a pulse width modulation switch (not shown, described in detail later) thereof, so as to supply a pulse width modulation current ILED _ PWM to the light emitting device circuit 20. The direct current ILED _ dc and the pwm current ILED _ pwm are superimposed to generate a lighting device current ILED, which flows through the lighting device circuit 20, so as to adjust the brightness ILED _ dcILED _ pwm of the lighting device circuit 20 according to the direct current dimming signal and the pwm dimming signal.

As shown, the sub-dc supply circuit 2211 includes a switch SW1 and a drawing circuit CS1, for example, and generates a sub-dimming signal dimm1 according to the dc dimming signal to determine whether the switch SW1 is turned on or off, and further determine whether to generate a sub-dc current Idc1 as a part of the dc current ILED _ dc, wherein the sub-dc current Idc1 is, for example but not limited to, a constant value. The sub-dc current supply circuit 2212 includes, for example, a switch SW2 and a drawing circuit CS2, and generates a sub-dimming signal dimm2 according to the dc dimming signal to determine whether the switch SW2 is turned on or off, and further determine whether to generate a sub-dc current Idc2 as a part of the dc current ILED _ dc, wherein the sub-dc current Idc2 is, for example, but not limited to, a constant value. The dc current control circuit 2213 includes, for example, a switch SW3 and a drawing circuit CS3, and generates a sub-dimming signal dimm3 according to the dc dimming signal to determine whether the switch SW3 is turned on or off, and further determine whether to generate a sub-dc current Idc3 as a part of the dc current ILED _ dc, wherein the sub-dc current Idc3 is, for example but not limited to, a constant value. The sub-dc currents Idc1, Idc2, and Idc3 are all no lower than the pulse width modulation current ILED _ pwm. Assuming that the sub-dc

current supply circuits

2211, 2212 and 2213 are turned on, the sub-dc currents Idc1, Idc2 and Idc3 are added to form the dc current ILED _ dc, and each of the sub-dc currents Idc1, Idc2 and Idc3 is not lower than the unit current Iunit, and an average current of the pulse width modulated current ILED _ pwm is not higher than the unit current Iunit.

It should be noted that, according to the present invention, the plurality of sub dc current supply circuits can respectively provide different sub dc currents to be superimposed to the required dc current, and of course, the plurality of dc current control circuits can also provide the same sub dc current to be superimposed to the required dc current. In addition, according to the present invention, the manner of controlling and generating the sub-dc current and the pwm current by the sub-dc current supply circuit and the switching current control circuit is different. The sub-dc supply circuit controls and generates the sub-dc, for example, by a linear control such as a linear regulator (LDO) or a transistor. The switching current control circuit controls and generates the PWM current by switching at least one PWM switch with the PWM signal to regulate the PWM current. In a preferred embodiment, the frequency of the PWM signal according to the present invention is, for example, but not limited to, higher than 20kHz to avoid the audio frequency range.

It is noted that the present invention provides advantages over the prior art, including: according to the present invention, the multi-stage dc dimming mode and the PWM signal switching dimming mode are combined to adjust the brightness of the light emitting device circuit, so as to obtain a higher brightness resolution and avoid the disadvantages of the prior art. Wherein, the multi-stage DC dimming mode can select a coarse-adjustment brightness from the brightness of the light-emitting element circuit with higher brightness level difference in a coarse-adjustment mode; compared with the prior art, the PWM signal switching dimming mode can generate PWM current in a fine adjustment mode on the basis of direct current based on coarse adjustment brightness so as to precisely adjust the brightness of the light-emitting element circuit at higher switching frequency. Therefore, the luminance resolution of the light-emitting element circuit can be improved, low-frequency flicker and audio noise (20 Hz-20 kHz) caused by low frequency of PWM signal switching dimming can be avoided, the reaction time is shortened, and the color deviation of the light-emitting element circuit can be avoided.

Fig. 5 shows a third embodiment of the invention. As shown, the multi-stage dc current control circuit 221 includes a plurality of sub-dc current supply circuits 2211, dc current switches 2218 and switch control circuits 2216. The dc switch 2218 is electrically connected to the light emitting device circuit 20 for controlling the passage of the dc current ILED _ dc. The switch control circuit 2216 is coupled to the dc switch 2218 for controlling the dc switch 2218 according to a reference voltage. A plurality of dc current control circuits 211, electrically connected to the dc current switch 2218, for respectively determining to turn on and turn off the dc sub-switches according to the dc dimming signal, so as to respectively supply or not supply the sub-dc current Idc1 as a part of the dc current ILED _ dc.

Fig. 6A-6B show a fourth embodiment of the present invention. The present embodiment shows that the sub dc current supply circuit 2211 can be a current source circuit or a current drawing circuit. As shown in fig. 6A, the sub dc current supply circuit 2211 may be a current source circuit. As shown in fig. 6B, the sub dc current supply circuit 2211 may be a current drawing circuit. The current source circuit and the current drawing circuit are well known to those skilled in the art and will not be described herein.

Fig. 7 shows signal waveforms of the dc current ILED _ dc, the pulse width modulation current ILED _ pwm, the pulse width modulation signal Gpwm, and the light emitting element current ILED according to the present invention. For example, the multi-stage dc current control circuit adjusts the brightness of the light emitting device circuit in a coarse adjustment manner by using a multi-stage dc dimming manner, for example, the multi-stage dc current control circuit includes 3 sub-dc current supply circuits, each of which can provide a maximum value ILEDmax of 25% of the light emitting device current ILED, that is, the sub-dc current Idc1 is 25% of the maximum value ILEDmax, where the unit current Iunit is 25% of the maximum value ILEDmax.

For example, two sub dc current supply circuits are selected to be conductive and one sub dc current supply circuit is selected to be non-conductive, that is, the dc current ILED _ dc is the maximum value ILEDmax of 50% of the light emitting element current ILED, and is supplied to the light emitting element circuit 20. The switching current control circuit, according to the dimming signal, switches the dimming mode with the PWM signal to precisely adjust the brightness of the light emitting device circuit, for example, selects a pulse width modulation current ILED _ PWM with an on time Ton of 105.1 nanoseconds (ns) and a cycle time Td of 38.46 microseconds (us) (with a frequency of 26kHz), that is, an duty ratio (duty ratio) of 1/256 (the resolution of the PWM signal switching dimming mode is, for example, 8 bits), and an amplitude of 25% of the maximum value ILEDmax of the light emitting device current ILED to provide the light emitting device circuit 20. Summing the dc current ILED _ dc and the PWM current ILED _ PWM, the light emitting element current ILED is obtained as shown in the figure, which has an average current of 50.098% of the maximum value ILEDmax of the light emitting element current ILED. When the duty ratio is at the maximum value 1, the average current of the pulse-width modulation current ILED _ pwm is at the maximum value ILEDmax 25%, is equal to the unit current Iunit, and is not greater than the unit current Iunit, that is, the average current of the pulse-width modulation current ILED _ pwm is not greater than the unit current Iunit. As can be seen from the above example, in this case, the dimming resolution is 1/256 of the maximum value ILEDmax of the light emitting device current ILED, and the above-mentioned disadvantages of the prior art are avoided. Of course, the sub dc current supply circuit may also provide a smaller current, such as, but not limited to, 12.5% of the maximum value ILEDmax of the light emitting element current ILED, i.e., 12.5% of the sub dc current Idc1, where the unit current Iunit is 12.5% of the maximum value ILEDmax. Fig. 8 shows a fifth embodiment of the present invention. This embodiment shows a more specific embodiment of the current regulating circuit 22. As shown, in the present embodiment, the multi-stage dc control circuit 221 has four

sub-dc supply circuits

2211, 2212, 2213 and 2214, which can respectively provide different sub-dc currents, such as but not limited to: 1.25 milliamps (mA), 2.5 milliamps (mA), 5 milliamps (mA) and 10 milliamps (mA). The four sub-DC

current supply circuits

2211, 2212, 2213 and 2214 are turned on and off to combine a DC current ILED _ dc of 0 to 18.75 milliamperes (mA). The pulse width modulation current ILED _ pwm can be set to be adjustable to 0 to 1.25 milliamperes (mA), so that the direct current ILED _ dc and the pulse width modulation current ILED _ pwm are accumulated, the light emitting device current ILED can be adjusted to 0 to 20 milliamperes (mA), and the switching current control circuit 222 can be utilized to make the current adjusting circuit 22 have a high-resolution dimming function.

In the multi-stage dc current control circuit 221, the switch control circuit 2216 includes, for example and without limitation, an amplifying circuit as shown in the figure, and ensures that the transistor switching elements in the dc current switch 2218 operate in the saturation region according to the reference voltage Vref to provide a stable dc current ILED _ dc.

In the switching current control circuit 222, the pwm switch 2228 is coupled to the light emitting device circuit 20 for being operated according to the pwm dimming signal to supply the pwm current ILEDpwm. The pwm switch control circuit 2226 is coupled to the pwm switch 2228, and is used for controlling the pwm switch 2228 to operate in a saturation region according to the reference voltage Vref, so as to provide a stable pwm current ILED _ pwm.

As shown, the reference current supply circuit 23 provides a reference current Iref by, for example, a current source, and provides a stable reference current Iref by an amplifying circuit according to a reference voltage Vref. The PWM dimming signal is a Pulse Width Modulation (PWM) signal, and the pulse width modulation current ILEDpwm is adjusted by different duty ratios (duty ratios) to change an average current of the pulse width modulation current ILEDpwm, so as to adjust the brightness of the light emitting device circuit 20.

The present invention has been described with respect to the preferred embodiments, but the above description is only for the purpose of making the content of the present invention easy to understand for those skilled in the art, and is not intended to limit the scope of the present invention. The embodiments described are not limited to separate applications, but may be applied in combination. For example, in the embodiments, two circuits or elements directly connected to each other are illustrated, and other circuits or elements not affecting the main function may be inserted; for another example, the light emitting element is not limited to the Light Emitting Diode (LED) shown in each embodiment, but may be other light emitting circuits, such as but not limited to an LED array including a plurality of LEDs connected in series, an LED array including a plurality of LED strings connected in parallel, or other light emitting element strings or light emitting element arrays. For another example, the PMOS device shown in the embodiment can be replaced by an NMOS device, and the NMOS device can be replaced by a PMOS device, and only the processing manner of the circuit for the signal needs to be modified correspondingly. As another example, variations in all embodiments may be used interchangeably, e.g., the FIG. 6A embodiment may correspond to other embodiments (e.g., without limitation, the first, second, third, or fifth embodiments), and so on. For another example, the present invention is not limited to a circuit for Direct Current (DC) power source-Direct Current (DC) power source conversion, but may be applied to a circuit for Alternating Current (AC) power source-Direct Current (DC) power source conversion. Further, equivalent variations and combinations are contemplated by those skilled in the art within the spirit of the present invention, and the term "processing or computing or generating an output result based on a signal" is not limited to the signal itself, and includes, if necessary, performing voltage-to-current conversion, current-to-voltage conversion, and/or scaling on the signal, and then processing or computing the converted signal to generate an output result. The present invention has been described with respect to the preferred embodiments, but the above description is only for the purpose of making the content of the present invention easy to understand for those skilled in the art, and is not intended to limit the scope of the present invention. Equivalent variations will occur to those skilled in the art, within the same spirit of the invention.

Claims

1. A light emitting device driving circuit for driving a light emitting device circuit, comprising:

a switching power supply circuit for controlling at least one of the power switches according to a feedback signal to convert an input voltage into an output voltage for supplying power to the light emitting device circuit; and

a current regulation circuit comprising:

a multi-stage DC current control circuit for determining the conduction or non-conduction of a plurality of sub-DC current supply circuits according to a DC dimming signal to supply a DC current to the light emitting element circuit; and

a switching current control circuit for operating one of the PWM switches to supply a PWM current to the light emitting device circuit according to a PWM dimming signal;

after the direct current and the pulse width modulation current are superposed, a light emitting element current is generated and flows through the light emitting element circuit, so that the brightness of the light emitting element circuit is adjusted according to the direct current dimming signal and the pulse width modulation dimming signal.

2. The light-emitting device driving circuit according to claim 1, wherein each of the sub-dc supply circuits supplies a sub-dc when turned on, and the sub-dc supplied by the turned-on sub-dc supply circuits are superimposed to form the dc current, and each of the sub-dc is not lower than a unit current, and an average current of the pwm currents is not higher than the unit current.

3. The light-emitting device driving circuit according to claim 2, wherein each of the sub-direct currents is constant.

4. The light emitting device driving circuit according to claim 1, wherein the multi-stage dc current control circuit comprises:

a DC switch electrically connected to the light emitting element circuit for controlling the DC channel;

a switch control circuit coupled to the DC switch for controlling the DC switch according to a reference voltage;

the plurality of sub-direct current supply circuits are electrically connected with the direct current switch and used for respectively determining to conduct and not conduct one of the sub-direct current switches according to the direct current dimming signal so as to respectively supply or not supply a sub-direct current, and the direct current is formed after the sub-direct current provided by the conducted sub-direct current supply circuits is superposed.

5. The light-emitting element driving circuit according to claim 1, wherein the switching current control circuit comprises:

the PWM switch is coupled with the light-emitting element circuit and is used for operating according to the PWM dimming signal so as to supply the PWM current; and

a PWM switch control circuit coupled to the PWM switch for controlling the PWM switch according to a reference voltage.

6. The light-emitting device driver circuit according to claim 1, wherein the switching power supply circuit comprises:

a power stage circuit for operating the at least one power switch according to an operation signal to supply power to the light emitting device circuit;

a control circuit coupled to the power stage circuit for generating the operation signal according to a feedback signal related to the output voltage; and

a feedback signal generating circuit coupled to the power stage circuit and the control circuit for generating the feedback signal according to the output voltage.

7. The light-emitting device driving circuit according to claim 1, wherein the sub-dc current supply circuit is a current source circuit or a current sink circuit.

8. A control method of a light-emitting device driving circuit, wherein the light-emitting device driving circuit is used for driving a light-emitting device circuit, the control method of the light-emitting device driving circuit comprises:

controlling at least one power switch according to a feedback signal to convert an input voltage into an output voltage to supply power to the light-emitting element circuit;

respectively determining the conduction or non-conduction of a plurality of sub-DC current supply circuits according to a DC dimming signal so as to supply a DC current to the light-emitting element circuit; and

operating a PWM switch according to a PWM dimming signal to supply a PWM current to the light emitting device circuit;

9. The method according to claim 8, wherein each of the sub-DC supply circuits supplies a sub-DC when turned on, and the sub-DC supplied by the turned-on sub-DC supply circuits are superimposed to form the DC, and each of the sub-DC is not lower than a unit current, and an average current of the PWM current is not higher than the unit current.

10. The method according to claim 8, wherein each of the sub-DC currents is constant.

11. The method according to claim 8, wherein the step of determining whether the plurality of sub-dc current supply circuits are turned on or off respectively according to a dc dimming signal to supply a dc current to the light emitting device circuit comprises:

providing a direct current switch electrically connected with the light-emitting element circuit for controlling the direct current channel;

controlling the DC switch according to a reference voltage;

and respectively determining to conduct and not conduct a sub-DC switch in the sub-DC supply circuit according to the DC dimming signal so as to respectively supply or not supply a sub-DC, and forming the DC after the sub-DC provided by the conducted sub-DC supply circuit is superposed.

12. The method according to claim 8, wherein the step of supplying a PWM current to the light emitting device circuit according to a PWM dimming signal to operate a PWM switch comprises:

operating the pwm switch to supply the pwm current according to the pwm dimming signal; and

the PWM switch is controlled to operate in a saturation region according to a reference voltage.

13. The method according to claim 8, wherein the step of controlling at least one power switch to convert an input voltage to an output voltage according to a feedback signal to supply power to the light emitting device circuit comprises:

according to an operation signal, operating the at least one power switch to supply power to the light-emitting element circuit;

generating the operation signal according to a feedback signal related to the output voltage; and

the feedback signal is generated according to the output voltage.

14. The method according to claim 8, wherein the sub-DC supply circuit is a current source circuit or a current sink circuit.