CN114158158A - Self-adaptive constant current control method and self-adaptive constant current circuit - Google Patents
Self-adaptive constant current control method and self-adaptive constant current circuit Download PDFInfo
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Abstract
The invention discloses a self-adaptive constant current control method and a self-adaptive constant current circuit, wherein the method comprises the following steps: acquiring the instantaneous voltage of the cathode of the LED lamp string and comparing the instantaneous voltage with a first preset voltage and a second preset voltage respectively; the first preset voltage is greater than the second preset voltage; adjusting the magnitude of the LED lamp string driving current according to the difference value between the instantaneous voltage and the first preset voltage or the difference value between the instantaneous voltage and the second preset voltage until the instantaneous voltage is between the second preset voltage and the first preset voltage; detecting the minimum voltage of the instantaneous voltage in each period, and adjusting the magnitude of the LED lamp string driving current according to the difference value of the minimum voltage and the second preset voltage until the minimum voltage is equal to the second preset voltage; and stopping adjusting the LED lamp string driving current and keeping outputting the LED lamp string driving current. The invention achieves the aim of removing ripple current.
Description
Technical Field
The invention relates to the technical field of light emitting diode lighting, in particular to a self-adaptive constant current control method and a self-adaptive constant current circuit.
Background
A Light-Emitting Diode (LED) dc power supply generally supplies power to an LED after being filtered by a capacitor. However, the LED dc power supply still fluctuates after being filtered by the capacitor, that is, the LED current fluctuates along with the voltage fluctuation at the two ends of the capacitor, and there is a current ripple, so that the brightness of the LED changes with the change of the LED current, and if a user is in such light for a long time, the user feels fatigue.
Accordingly, the prior art is yet to be improved and developed.
Disclosure of Invention
In view of the above-mentioned deficiencies of the prior art, an object of the present invention is to provide an adaptive constant current control method and an adaptive constant current circuit, so as to solve the problem that the current ripple still exists after the current ripple is filtered by a capacitor in the conventional LED dc power supply.
The technical scheme of the invention is as follows:
an adaptive constant-current control method, comprising:
acquiring the instantaneous voltage of the cathode of the LED lamp string and comparing the instantaneous voltage with a first preset voltage and a second preset voltage respectively; the first preset voltage is greater than the second preset voltage;
adjusting the magnitude of the LED lamp string driving current according to the difference value between the instantaneous voltage and the first preset voltage or the difference value between the instantaneous voltage and the second preset voltage until the instantaneous voltage is between the second preset voltage and the first preset voltage;
detecting the minimum voltage of the instantaneous voltage in each period, and adjusting the magnitude of the LED lamp string driving current according to the difference value of the minimum voltage and the second preset voltage until the minimum voltage is equal to the second preset voltage;
and stopping adjusting the LED lamp string driving current and keeping outputting the LED lamp string driving current.
The step of obtaining the instantaneous voltage of the cathode of the LED lamp string and comparing the instantaneous voltage with the first preset voltage and the second preset voltage respectively comprises the following steps:
and presetting the first preset voltage and the second preset voltage.
In a further configuration of the present invention, the step of adjusting the magnitude of the driving current of the LED light string according to the difference between the instantaneous voltage and the first preset voltage or the difference between the instantaneous voltage and the second preset voltage until the instantaneous voltage is between the second preset voltage and the first preset voltage includes:
when the instantaneous voltage is greater than the first preset voltage, increasing the LED lamp string driving current;
and when the instantaneous voltage is less than the second preset voltage, reducing the driving current of the LED lamp string.
The invention further provides that the step of adjusting the magnitude of the driving current of the LED light string according to the difference between the instantaneous voltage and the first preset voltage or the difference between the instantaneous voltage and the second preset voltage further comprises:
when the instantaneous voltage is greater than the first preset voltage, the greater the difference between the instantaneous voltage and the first preset voltage is, the faster the speed of increasing the driving current of the LED lamp string is;
when the instantaneous voltage is smaller than the second preset voltage, the smaller the difference between the instantaneous voltage and the second preset voltage is, the faster the speed of reducing the driving current of the LED lamp string is.
The invention is further configured that the step of detecting the minimum voltage of the instantaneous voltage in each period, and adjusting the magnitude of the driving current of the LED light string according to the difference between the minimum voltage and the second preset voltage until the minimum voltage is equal to the second preset voltage includes:
when the minimum voltage is greater than the second preset voltage, increasing the LED lamp string driving current;
and when the minimum voltage is less than the second preset voltage, reducing the driving current of the LED lamp string.
According to a further development of the invention, the minimum voltage is the minimum voltage of a cycle preceding the instantaneous voltage.
The invention further provides that the step of adjusting the magnitude of the driving current of the LED light string according to the difference between the instantaneous voltage and the first preset voltage or the difference between the instantaneous voltage and the second preset voltage until the instantaneous voltage is between the second preset voltage and the first preset voltage further comprises:
and if the instantaneous voltage is equal to the minimum voltage of the previous period and the ripple wave of the previous period is in a reduction stage, stopping adjusting the LED lamp string driving current and keeping outputting the LED lamp string driving current.
The invention further provides that the step of adjusting the magnitude of the driving current of the LED light string according to the difference between the instantaneous voltage and the first preset voltage or the difference between the instantaneous voltage and the second preset voltage until the instantaneous voltage is between the second preset voltage and the first preset voltage further comprises:
and if the instantaneous voltage is greater than the minimum voltage of the previous period and the ripple wave of the previous period is not in a reduction stage, stopping adjusting the LED lamp string driving current and keeping outputting the LED lamp string driving current.
Based on the same inventive concept, the invention also provides an adaptive constant current circuit, which adopts the adaptive constant current control method and comprises a sampling module, an operational logic module and a digital control current source; wherein,
the sampling module is connected with the arithmetic logic module and is used for acquiring the instantaneous voltage of the cathode of the LED lamp string and converting the instantaneous voltage into a digital signal to the arithmetic logic module;
the operation logic module is also connected with the digital control current source, and is used for performing logic operation according to the digital signal output by the sampling module so as to respectively compare the instantaneous voltage with a first preset voltage and a second preset voltage, adjusting the magnitude of the LED lamp string driving current according to the difference value of the instantaneous voltage and the first preset voltage or the difference value of the instantaneous voltage and the second preset voltage, adjusting the magnitude of the LED lamp string driving current according to the difference value of the minimum voltage of the previous period of the instantaneous voltage and the second preset voltage, and outputting a digital signal of an operation logic result to the digital control current source;
and the digital control current source adjusts the magnitude of the LED lamp string driving current according to the digital signal of the operation logic result.
In a further aspect of the present invention, the adaptive constant current circuit further comprises: a direct current power supply and a filter capacitor;
the direct-current power supply is connected with the LED lamp string and used for supplying power to the LED lamp string;
the filter capacitor is connected with the direct current power supply in parallel and is used for filtering the power supply voltage output by the direct current power supply.
The invention provides an adaptive constant current control method and an adaptive constant current circuit, wherein the method comprises the following steps: acquiring the instantaneous voltage of the cathode of the LED lamp string and comparing the instantaneous voltage with a first preset voltage and a second preset voltage respectively; the first preset voltage is greater than the second preset voltage; adjusting the magnitude of the LED lamp string driving current according to the difference value between the instantaneous voltage and the first preset voltage or the difference value between the instantaneous voltage and the second preset voltage until the instantaneous voltage is between the second preset voltage and the first preset voltage; detecting the minimum voltage of the instantaneous voltage in each period, and adjusting the magnitude of the LED lamp string driving current according to the difference value of the minimum voltage and the second preset voltage until the minimum voltage is equal to the second preset voltage; and stopping adjusting the LED lamp string driving current and keeping outputting the LED lamp string driving current. The LED lamp string driving current is regulated when the minimum value of the instantaneous voltage is detected to be equal to the preset minimum voltage, and the output of the LED lamp string driving current is maintained, so that the aim of removing ripple current is fulfilled.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
Fig. 1 is a circuit diagram of a conventional LED string driving circuit.
Fig. 2 is a circuit schematic diagram of a conventional LED string adaptive constant current circuit.
FIG. 3 is a flow chart of the adaptive constant current control method of the present invention.
FIG. 4 is a timing diagram of the LED string drive current regulation according to the present invention.
FIG. 5 is a flow chart of an embodiment of the adaptive constant current control method according to the present invention.
Fig. 6 is a circuit schematic of the adaptive constant current circuit of the present invention.
Fig. 7 is a circuit schematic of a digitally controlled current source in one embodiment of the invention.
Fig. 8 is a circuit schematic of a digitally controlled current source in another embodiment of the present invention.
Detailed Description
The present invention provides an adaptive constant current control method and an adaptive constant current circuit, and in order to make the purpose, technical scheme and effect of the present invention clearer and clearer, the present invention is further described in detail below by referring to the attached drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the embodiments and claims, the articles "a", "an", "the" and "the" may include plural forms as well, unless the context specifically dictates otherwise. If there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature.
It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or wirelessly coupled. As used herein, the term "and/or" includes all or any element and all combinations of one or more of the associated listed items.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
The inventor researches and finds that the LED direct current power supply DC generally supplies power to the LED after being filtered by a capacitor C1, as shown in FIG. 1. However, the LED dc power supply still fluctuates after being filtered by the capacitor C1, that is, the LED current fluctuates along with the voltage fluctuation at the two ends of the capacitor, and there is a current ripple, so that the brightness of the LED changes with the change of the LED current, and if the user is in such light for a long time, the user feels fatigue. In order to solve the above problems, an adaptive constant current circuit is usually added to reduce the ripple amplitude of the current ripple. As shown in fig. 2, the current of the conventional adaptive constant current circuit is controlled by the voltage at both ends of the filter capacitor C2, and the voltage on the filter capacitor C2 is obtained by sampling the voltage of the negative electrode of the LED through the voltage regulator tube DZ1, and since the voltage of the negative electrode of the LED fluctuates along with the voltage fluctuation of the filter capacitor C1, the ripple cannot be completely eliminated although the filter capacitor C2 has a filtering function. In addition, the maximum voltage of the cathode of the LED can only be limited within a preset value in the conventional adaptive constant-current circuit, and the minimum voltage of the cathode of the LED is not limited, so that if the capacitance value of the filter capacitor C1 is larger, the minimum voltage of the cathode of the LED is larger, so that the power consumption lost on the switching tube Q1 is larger, the system efficiency is reduced, the lamp generates heat, a radiator needs to be added for cooling, and the service life of a device in a high-temperature state for a long time is also reduced.
In order to solve the technical problems, the invention provides a self-adaptive constant current control method, which comprises the steps of sampling the instantaneous voltage output by the cathode of an LED lamp string, adjusting the drive current of the LED lamp string according to the acquired instantaneous voltage, stopping adjusting the drive current of the LED lamp string when the minimum value of the instantaneous voltage is detected to be equal to the preset minimum voltage, and maintaining the output of the drive current of the LED lamp string so as to achieve the purpose of removing ripple current. In addition, the LED lamp string driving current is regulated and controlled through the minimum value of the instantaneous voltage, the problem of power consumption loss caused by the fact that the driving current of the LED is controlled through the maximum value of ripples in the traditional constant current circuit is solved, and therefore power consumption can be reduced, and lighting effect is improved.
Referring to fig. 3 to 5, the present invention provides a preferred embodiment of an adaptive constant current control method.
As shown in fig. 3 and 4, the adaptive constant current control method provided by the present invention includes the steps of:
s100, acquiring the instantaneous voltage of the cathode of the LED lamp string and comparing the instantaneous voltage with a first preset voltage and a second preset voltage respectively; the first preset voltage is greater than the second preset voltage;
specifically, the first preset voltage Vmax and the second preset voltage Vmin are preset, where the second preset voltage Vmin is smaller than the first preset voltage Vmax. In the process of adjusting the driving current Iled of the LED lamp string, sampling an instantaneous voltage Vd output by a cathode of the LED lamp string through an ADC module (analog-to-digital conversion module), converting the sampled instantaneous voltage Vd into a digital signal and sending the digital signal to an arithmetic logic module, comparing the instantaneous voltage Vd with a first preset voltage Vmax and a second preset voltage Vmin by the arithmetic logic module, and obtaining the difference value between the instantaneous voltage Vd and the first preset voltage Vmax and the difference value between the instantaneous voltage Vd and the second preset voltage Vmin.
S200, adjusting the magnitude of the LED lamp string driving current Iled according to the difference value between the instantaneous voltage and the first preset voltage or the difference value between the instantaneous voltage and the second preset voltage until the instantaneous voltage is between the second preset voltage and the first preset voltage;
specifically, when the instantaneous voltage Vd is greater than the first preset voltage Vmax, the LED string driving current Iled is increased, and the larger the difference between the instantaneous voltage Vd and the first preset voltage Vmax is, the faster the LED string driving current Iled is increased, so as to accelerate the adjustment of the LED string driving current Iled. When the instantaneous voltage Vd is smaller than the second preset voltage Vmin, the LED lamp string driving current Iled is reduced, and the smaller the difference value between the instantaneous voltage Vd and the second preset voltage Vmin is, the faster the LED lamp string driving current Iled is reduced, so that the regulation of the LED lamp string driving current Iled is accelerated. After iteration, the range of the instantaneous voltage Vd fluctuates between the first preset voltage Vmax and the second preset voltage Vmin, namely Vmin is not less than Vd and not more than Vmax, so that the first stage of LED string driving current Iled regulation, namely the rapid regulation stage, is completed.
S300, detecting the minimum voltage of the instantaneous voltage in each period, and adjusting the magnitude of the LED lamp string driving current according to the difference value of the minimum voltage and the second preset voltage until the minimum voltage is equal to the second preset voltage;
specifically, when the LED string driving current Iled enters the micro-regulation stage from the fast regulation stage, that is, when the instantaneous voltage Vd is between the first preset voltage Vmax and the second preset voltage Vmin, the minimum voltage Vdmin in each period of the instantaneous voltage Vd is further detected, where the minimum voltage Vdmin is the minimum voltage of a previous period of the instantaneous voltage Vd. And when the minimum voltage Vdmin is greater than the second preset voltage Vmin, increasing the LED lamp string driving current Iled, and when the minimum voltage Vdmin is less than the second preset voltage Vmin, decreasing the LED lamp string driving current Iled, after regulation for several cycles, making the minimum value of the instantaneous voltage Vd equal to the second preset voltage Vmin, and then entering a stabilization stage.
And S400, stopping adjusting the LED lamp string driving current and keeping outputting the LED lamp string driving current.
Specifically, after the LED lamp string driving current Iled enters the stable regulation stage, the regulation of the LED lamp string driving current Iled is stopped, and the LED lamp string driving current Iled is kept to be output, so that the purpose of removing ripple current is achieved.
In some embodiments, the step S200 further includes:
step 201, if the instantaneous voltage is equal to the minimum voltage in the previous period and the ripple in the previous period is in a reduction stage, stopping adjusting the LED light string driving current and keeping outputting the LED light string driving current.
Specifically, after the LED string driving current Iled is adjusted in the fast adjustment stage, if the instantaneous voltage Vd is equal to the minimum voltage Vdmin in the previous period and the ripple in the previous period is in the reduction stage, the adjustment of the LED string driving current Iled is stopped, and the LED string driving current Iled is kept being output.
In some embodiments, the step S200 further includes:
s202, if the instantaneous voltage is larger than the minimum voltage in the previous period and the ripple wave in the previous period is not in a reduction stage, stopping adjusting the LED lamp string driving current and keeping outputting the LED lamp string driving current.
Specifically, after the adjustment of the LED string driving current Iled enters the fine adjustment stage, if the instantaneous voltage Vd is greater than the minimum voltage Vdmin in the previous period and the ripple in the previous period is not in the reduction stage, the adjustment of the LED string driving current Iled is stopped, and the LED string driving current Iled is kept being output.
Therefore, according to the self-adaptive constant current control method provided by the invention, the instantaneous voltage output by the cathode of the LED lamp string is sampled, the LED lamp string driving current is regulated according to the collected instantaneous voltage, the LED lamp string driving current is stopped being regulated when the minimum value of the instantaneous voltage is detected to be equal to the preset minimum voltage, and the LED lamp string driving current is kept being output, so that the purpose of removing ripple current is achieved, the brightness of the LED cannot be changed along with the change of the LED current, and the situation that fatigue is caused by the difference of users under the light of the driving current with current ripples for a long time is avoided. In addition, the LED lamp string driving current is regulated and controlled through the minimum value of the instantaneous voltage, the problem of power loss caused by the fact that the traditional constant current circuit controls the LED driving current through the maximum value of ripples is solved, and therefore power consumption can be reduced and light efficiency is improved.
For a better understanding of the present invention, the following description will be made by way of a process for adjusting the optimum driving current of the LED string.
Referring to fig. 5, fig. 5 is a schematic flowchart illustrating an embodiment of an adaptive constant current control method according to the present invention, in fig. 5, Vdpre is a value of an instantaneous voltage Vd sampled last time, charge _ flag is a ripple rising stage flag, 1 represents that a ripple is in a rising stage, and 0 represents that a ripple is in a falling stage. The method specifically comprises the following steps:
s1, initializing the system, wherein the Vdpre is initially assigned to 0, the charge _ flag is initially assigned to 1, and the step S2 is carried out);
s2, sampling the Vd voltage value once, and going to step S3);
s3) judging whether Vd is larger than Vmax, if so, increasing the output current and going to step S5), otherwise, going to step S4);
s4) judging whether Vd is smaller than Vmin, if so, reducing the output current and going to step S5), otherwise, going to step S5);
s5) judging whether Vd is larger than Vdpre, if so, going to step S6), otherwise, assigning the charge _ flag to 0, and going to step S9);
s6) judging whether the charge _ flag is equal to 0, if yes, assigning Vdpin to Vdpre, assigning the charge _ flag to 1 (representing that the ripple is changed from a descending stage to an ascending stage, the previous period is ended, the new period is started, and the current Vdpre is the minimum value of the previous period), and going to step S7), otherwise, going to step S9);
s7) judging whether Vdmin is larger than Vmin, if so, increasing the output current and going to step S9); otherwise to step S8);
s8) judging whether Vdmin is smaller than Vmin, if so, reducing the output current and carrying out step S9); otherwise, keeping the output current and going to step S9);
s9) assigning Vdpre to Vd (one sampling is completed), returning to step S2) to sample Vd once again.
Referring to fig. 6, in some embodiments, the present invention further provides an adaptive constant current circuit, which employs the adaptive constant current control method described above, including: the circuit comprises a direct current power supply DC, a filter capacitor C1, a sampling module 100, an operation logic module 200 and a digital control current source 300. The sampling module 100 is connected to the arithmetic logic module 200, and the sampling module 100 is configured to obtain an instantaneous voltage of a cathode of the LED string and convert the instantaneous voltage into a digital signal, which is sent to the arithmetic logic module 200; the arithmetic logic module 200 is further connected to the digital control current source 300, and the arithmetic logic module 200 is configured to perform a logic operation according to the digital signal output by the sampling module 100, to compare the instantaneous voltage with a first preset voltage and a second preset voltage, respectively, and adjust the magnitude of the LED string driving current according to the difference between the instantaneous voltage and the first preset voltage or the difference between the instantaneous voltage and the second preset voltage, and adjust the magnitude of the LED string driving current according to the difference between the minimum voltage of the previous period of the instantaneous voltage and the second preset voltage, and output a digital signal of an arithmetic logic result to the digital control current source 300; the digital control current source 300 adjusts the magnitude of the driving current of the LED lamp string according to the digital signal of the operation logic result; the direct-current power supply DC is connected with the LED lamp string and used for supplying power to the LED lamp string; the filter capacitor C1 is connected in parallel with the DC power supply DC, and the filter capacitor C1 is used for filtering the power supply voltage output by the DC power supply DC.
Specifically, the arithmetic logic control module 200 may be a control unit or an application specific integrated circuit. The power voltage output by the DC power supply DC is filtered by the filter capacitor C1, and is subjected to ripple removal by the adaptive constant current circuit composed of the sampling module 100, the operation logic module 200, and the digital control current source 300, and then supplies power to the LED light string.
Referring to fig. 7, in some embodiments, the digitally controlled current source 300 may be composed of a digital-to-analog conversion unit DAC and a voltage-controlled current source, wherein the voltage-controlled current source includes an operational amplifier U1, a switch Q1, a feedback resistor Rcs, and the like. The operation logic result output by the operation logic module 200 is input to the digital-to-analog conversion unit DAC, the digital signal is converted into an analog signal, and then an analog voltage Vs is output, and the voltage-controlled current source controls the magnitude of the output current according to the analog voltage Vs. It should be noted that the digitally controlled current source is a mature prior art, and thus is not described herein again.
Referring to fig. 8, in some embodiments, the digitally controlled current source 300 may further comprise a reference current source, a plurality of current mirror output tubes (SW1, SW2, SWk) and a plurality of switch tubes (Q1, Q2, Q3). The operation logic control module 200 controls the number of output tubes of the current mirror according to the output operation logic result, thereby controlling the mirror proportion of the current mirror and realizing the control of the output of the driving current of the LED lamp string. It should be noted that the digitally controlled current source is a mature prior art, and thus is not described herein again.
In summary, the adaptive constant current control method and the adaptive constant current circuit provided by the present invention include: acquiring the instantaneous voltage of the cathode of the LED lamp string and comparing the instantaneous voltage with a first preset voltage Vmax and a second preset voltage respectively; the first preset voltage is greater than the second preset voltage; adjusting the magnitude of the LED lamp string driving current according to the difference value between the instantaneous voltage and the first preset voltage or the difference value between the instantaneous voltage and the second preset voltage until the instantaneous voltage is between the second preset voltage and the first preset voltage; detecting the minimum voltage of the instantaneous voltage in each period, and adjusting the magnitude of the LED lamp string driving current according to the difference value of the minimum voltage and the second preset voltage until the minimum voltage is equal to the second preset voltage; and stopping adjusting the LED lamp string driving current and keeping outputting the LED lamp string driving current. The LED lamp string driving current is regulated when the minimum value of the instantaneous voltage is detected to be equal to the preset minimum voltage, and the output of the LED lamp string driving current is maintained, so that the aim of removing ripple current is fulfilled. In addition, the LED lamp string driving current is regulated and controlled through the minimum value of the instantaneous voltage, the problem of power loss caused by the fact that the traditional constant current circuit controls the current of the LED through the maximum value of ripples is solved, and therefore power consumption can be reduced and light efficiency is improved.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.
Claims (10)
1. An adaptive constant current control method, comprising:
acquiring the instantaneous voltage of the cathode of the LED lamp string and comparing the instantaneous voltage with a first preset voltage and a second preset voltage respectively; the first preset voltage is greater than the second preset voltage;
adjusting the magnitude of the LED lamp string driving current according to the difference value between the instantaneous voltage and the first preset voltage or the difference value between the instantaneous voltage and the second preset voltage until the instantaneous voltage is between the second preset voltage and the first preset voltage;
detecting the minimum voltage of the instantaneous voltage in each period, and adjusting the magnitude of the LED lamp string driving current according to the difference value of the minimum voltage and the second preset voltage until the minimum voltage is equal to the second preset voltage;
and stopping adjusting the LED lamp string driving current and keeping outputting the LED lamp string driving current.
2. The adaptive constant current control method according to claim 1, wherein the step of obtaining the instantaneous voltage of the cathode of the LED string and comparing the instantaneous voltage with the first preset voltage and the second preset voltage respectively comprises:
and presetting the first preset voltage and the second preset voltage.
3. The adaptive constant current control method according to claim 1, wherein the step of adjusting the magnitude of the LED string driving current according to the difference between the instantaneous voltage and the first preset voltage or the difference between the instantaneous voltage and the second preset voltage until the instantaneous voltage is between the second preset voltage and the first preset voltage comprises:
when the instantaneous voltage is greater than the first preset voltage, increasing the LED lamp string driving current;
and when the instantaneous voltage is less than the second preset voltage, reducing the driving current of the LED lamp string.
4. The adaptive constant current control method of claim 3, wherein the step of adjusting the magnitude of the LED string drive current according to the difference between the instantaneous voltage and the first preset voltage or the difference between the instantaneous voltage and the second preset voltage further comprises:
when the instantaneous voltage is greater than the first preset voltage, the greater the difference between the instantaneous voltage and the first preset voltage is, the faster the speed of increasing the driving current of the LED lamp string is;
when the instantaneous voltage is smaller than the second preset voltage, the smaller the difference between the instantaneous voltage and the second preset voltage is, the faster the speed of reducing the driving current of the LED lamp string is.
5. The adaptive constant current control method of claim 1, wherein the steps of detecting a minimum voltage of the instantaneous voltage in each cycle and adjusting the magnitude of the LED string driving current according to a difference between the minimum voltage and the second predetermined voltage until the minimum voltage is equal to the second predetermined voltage comprise:
when the minimum voltage is greater than the second preset voltage, increasing the LED lamp string driving current;
and when the minimum voltage is less than the second preset voltage, reducing the driving current of the LED lamp string.
6. The adaptive constant current control method according to claim 1, wherein the minimum voltage is a minimum voltage of a period before the instantaneous voltage.
7. The adaptive constant current control method according to claim 6, wherein the step of adjusting the magnitude of the LED string driving current according to the difference between the instantaneous voltage and the first preset voltage or the difference between the instantaneous voltage and the second preset voltage until the instantaneous voltage is between the second preset voltage and the first preset voltage further comprises:
and if the instantaneous voltage is equal to the minimum voltage of the previous period and the ripple wave of the previous period is in a reduction stage, stopping adjusting the LED lamp string driving current and keeping outputting the LED lamp string driving current.
8. The adaptive constant current control method according to claim 6, wherein the step of adjusting the magnitude of the LED string driving current according to the difference between the instantaneous voltage and the first preset voltage or the difference between the instantaneous voltage and the second preset voltage until the instantaneous voltage is between the second preset voltage and the first preset voltage further comprises:
and if the instantaneous voltage is greater than the minimum voltage of the previous period and the ripple wave of the previous period is not in a reduction stage, stopping adjusting the LED lamp string driving current and keeping outputting the LED lamp string driving current.
9. A self-adaptive constant current circuit is characterized by comprising a sampling module, an operational logic module and a digital control current source; wherein,
the sampling module is connected with the arithmetic logic module and is used for acquiring the instantaneous voltage of the cathode of the LED lamp string and converting the instantaneous voltage into a digital signal to the arithmetic logic module;
the operation logic module is also connected with the digital control current source, and is used for performing logic operation according to the digital signal output by the sampling module so as to respectively compare the instantaneous voltage with a first preset voltage and a second preset voltage, adjusting the magnitude of the LED lamp string driving current according to the difference value of the instantaneous voltage and the first preset voltage or the difference value of the instantaneous voltage and the second preset voltage, adjusting the magnitude of the LED lamp string driving current according to the difference value of the minimum voltage of the previous period of the instantaneous voltage and the second preset voltage, and outputting a digital signal of an operation logic result to the digital control current source;
the digital control current source adjusts the magnitude of the LED lamp string driving current according to the digital signal of the operation logic result;
the adaptive constant current circuit employs the adaptive constant current control method according to any one of claims 1 to 8.
10. The adaptive constant current circuit of claim 9, further comprising: a direct current power supply and a filter capacitor;
the direct-current power supply is connected with the LED lamp string and used for supplying power to the LED lamp string;
the filter capacitor is connected with the direct current power supply in parallel and is used for filtering the power supply voltage output by the direct current power supply.
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