LED Power Control Method and Control Circuit

Abstract

The present invention relates to the technical field of LED power control, and discloses an LED power control method and a control circuit. The method includes: obtaining a sampling signal of a sampled LED load to obtain an LED current value; calculating an adjustment coefficient according to the LED current value and a preset current threshold, and using the adjustment coefficient to adjust the duty cycle of a pulse width modulation signal output to the LED load; outputting the pulse width modulation signal to the LED load so that the LED current value continuously approaches the current threshold or is within a preset range. The present invention regulates the current of the LED load through a feedback control method, outputs a monotonically changing adjustment coefficient according to the comparison result between the sampled LED current value and the first current threshold, and uses the adjustment coefficient to adjust the duty cycle of the pulse width modulation signal, so that the LED load can quickly operate within a limited power range.

Description

Technical Field

[0001] The present invention relates to the technical field of LED power control, and in particular to an LED power control method and a control circuit. Background Art

[0002] In the prior art, when using a light-emitting diode (LED) as a lighting fixture, the light-emitting diode is generally driven in a constant-current manner, and the brightness of the light-emitting diode is controlled in a pulse width modulation (PWM) manner. Using a light-emitting diode for lighting has significant advantages such as high luminous efficiency, obvious energy-saving effect, long lifespan, and no pollution.

[0003] Currently, most existing LED lighting products use a hardware method to limit the maximum current, which will cause waste of costs; some products also use a software method to limit the maximum current. Although it can save costs, a corresponding number of LED loads need to be matched for the system. When the number of loads increases or the specifications change, the current-limiting mechanism will become ineffective. Summary of the Invention

[0004] The object of the present invention is to provide an LED power control method and a control circuit to solve one or more technical problems existing in the prior art, and at least provide a beneficial choice or create conditions.

[0005] In a first aspect, an LED power control method is provided, including the following steps:

[0006] Obtain a sampling signal of a sampled LED load to obtain an LED current value;

[0007] Calculate an adjustment coefficient according to the LED current value and a preset current threshold, and use the adjustment coefficient to adjust the duty cycle of the pulse width modulation signal output to the LED load; wherein, the adjustment coefficient is a coefficient for adjusting the LED current value to approach the current threshold or fall within a preset range;

[0008] Output a pulse width modulation signal to the LED load so that the LED current value continuously approaches the current threshold or falls within a preset range.

[0009] Further, the step of obtaining a sampling signal of a sampled LED load to obtain an LED current value specifically includes the following steps:

[0010] Obtain the voltage difference across the sampling circuit, and calculate the LED current value according to the voltage difference across the sampling circuit and the resistance value of the sampling circuit.

[0011] Further, the step of calculating an adjustment coefficient according to the LED current value and a preset current threshold specifically includes the following steps:

[0012] Determine whether the LED current value is greater than the first current threshold within the detection period;

[0013] If so, calculate the adjustment coefficient of the current detection period using the adjustment coefficient of the previous detection period, so that the adjustment coefficients of each detection period change continuously and monotonically before the LED current value is lower than the first current threshold, and output the pulse width modulation signal to the LED load to control the LED current value to decrease;

[0014] If not, when the duration that the LED current value continuously is less than the first current threshold is greater than the preset duration, use the adjustment coefficient of the previous detection period as the calculation period to calculate the adjustment coefficient of the current self-recovery period, so that the adjustment coefficients of each self-recovery period change continuously and monotonically before the LED current value is higher than the first current threshold, and output the pulse width modulation signal to the LED load to control the LED current value to increase; wherein, the self-recovery period is greater than the detection period.

[0015] Further, calculating the adjustment coefficient according to the LED current value and the preset current threshold specifically includes the following steps:

[0016] Determine whether the LED current value is within the range between the first current threshold and the second current threshold within the detection period;

[0017] If so, use the adjustment coefficient of the previous detection period as the adjustment coefficient of the current detection period;

[0018] If not, when the LED current value is greater than the first current threshold, calculate the adjustment coefficient of the current detection period using the adjustment coefficient of the previous detection period, so that the adjustment coefficients of each detection period change continuously and monotonically before the LED current value is lower than the first current threshold, and output the pulse width modulation signal to the LED load to control the LED current value to decrease; when the duration that the LED current value is less than the second current threshold is greater than the preset duration, use the preset self-recovery period as the calculation period, and calculate the adjustment coefficient of the current self-recovery period using the adjustment coefficient of the previous detection period, so that the adjustment coefficients of each self-recovery period change continuously and monotonically before the LED current value is higher than the second current threshold, and output the pulse width modulation signal to the LED load to control the LED current value to increase;

[0019] Wherein, the self-recovery period is greater than the detection period, and the first current threshold is greater than the second current threshold. Further, the first current threshold and the second current threshold satisfy the following relationship:

[0020] 0.01D1 ≤ D2 < D1;

[0021] Wherein, D1 represents the first current threshold, and D2 represents the second current threshold.

[0022] Further, calculating the adjustment coefficient of the current detection period by using the adjustment coefficient of the previous detection period specifically includes the following steps: performing a difference operation or a summation operation on the adjustment coefficient of the previous detection period and the first operation coefficient to calculate the adjustment coefficient of the current detection period;

[0023] Calculating the adjustment coefficient of the current self - recovery period by using the adjustment coefficient of the previous detection period of the self - recovery period specifically includes the following steps: performing a difference operation or a summation operation on the adjustment coefficient of the previous detection period of the self - recovery period and the second operation coefficient to calculate the adjustment coefficient of the current self - recovery period;

[0024] When the adjustment coefficient is positively correlated with the duty cycle of the adjusted pulse - width modulation signal, perform a difference operation on the adjustment coefficient of the previous detection period and the first operation coefficient, and perform a summation operation on the adjustment coefficient of the previous detection period of the self - recovery period and the second operation coefficient, where 0 < C ≤ 1, 0 < C1 ≤ 1, 0 < C2 ≤ 1;

[0025] When the adjustment coefficient is negatively correlated with the duty cycle of the adjusted pulse - width modulation signal, perform a summation operation on the adjustment coefficient of the previous detection period and the first operation coefficient, and perform a difference operation on the adjustment coefficient of the previous detection period of the self - recovery period and the second operation coefficient, where 1 ≤ C < +∞, 0 < C1 < +∞, 0 < C2 < +∞;

[0026] Wherein, C represents the adjustment coefficient, C1 represents the first operation coefficient, and C2 represents the second operation coefficient.

[0027] Further, the duration during which the adjustment coefficients of each detection period continuously and monotonically change before the LED current value is lower than the first current threshold satisfies the following relationship:

[0028] T1 = a×(C MAX1 - C MIN1 ) ;

[0029] Wherein, T1 represents the duration during which the adjustment coefficients of each detection period continuously and monotonically change, and its unit is seconds, 0 < a ≤ 3, C MAX1 represents the value of the adjustment coefficient of the detection period at the beginning of the monotonic change, and C MIN1 represents the value of the adjustment coefficient of the detection period at the end of the monotonic change.

[0030] Further, the duration during which the adjustment coefficients of each self - recovery period continuously and monotonically change satisfies the following relationship:

[0031] T2 = b×(C MAX2 - C MIN2 ) ;

[0032] Wherein, T2 represents the duration during which the adjustment coefficients of each self - recovery period continuously and monotonically change, and its unit is seconds, b > 60, CMAX2 represents the value of the adjustment coefficient of the self-recovery period at the beginning of the monotonic change, C MIN2 represents the value of the adjustment coefficient of the self-recovery period at the end of the monotonic change.

[0033] In a second aspect, a LED power control circuit is provided, including a sampling circuit, a control circuit and a driving circuit. The control circuit is respectively connected to the sampling circuit and the driving circuit, and the sampling circuit and the driving circuit are used to connect to a LED load;

[0034] The sampling circuit is used to sample the LED load;

[0035] The control circuit is used to obtain the sampling signal of the LED load sampled by the sampling circuit to obtain the LED current value; and periodically calculate the adjustment coefficient according to the LED current value and a preset current threshold, and use the adjustment coefficient to adjust the duty cycle of the pulse width modulation signal output to the LED load; wherein, the adjustment coefficient is a coefficient for adjusting the LED current value to approach the current threshold or be within a preset range;

[0036] The driving circuit is used to output a pulse width modulation signal to the LED load so that the LED current value continuously approaches the current threshold or is within a preset range.

[0037] Further, the LED power control circuit is connected to at least two groups of LED loads;

[0038] Each of the LED loads is connected in parallel;

[0039] The sampling circuit samples the aggregation point of each LED load;

[0040] The number of the driving circuits is the same as the number of the LED loads, and one driving circuit outputs a pulse width modulation signal to one LED load;

[0041] The control circuit outputs the pulse width modulation signals adjusted by the same adjustment coefficient to each driving circuit.

[0042] Advantages of the present invention: By means of a feedback control method, the current of the LED load is regulated. According to the comparison result between the sampled LED current value and the first current threshold, an adjustment coefficient showing a monotonic change is output, and the duty cycle of the pulse width modulation signal is adjusted by using the adjustment coefficient, so that the LED load can quickly operate within a limited power range. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is one of the flowcharts of the LED power control method provided by an embodiment of the present invention.

[0044] Figure 2 is the second flowchart of the LED power control method provided by an embodiment of the present invention.

[0045] Figure 3 This is the third flowchart of the LED power control method provided by the embodiments of the present invention.

[0046] Figure 4 This is one of the schematic structural diagrams of the LED power control circuit provided by the embodiments of the present invention.

[0047] Figure 5 This is the second schematic structural diagram of the LED power control circuit provided by the embodiments of the present invention.

[0048] Figure 6 This is the third schematic structural diagram of the LED power control circuit provided by the embodiments of the present invention. Detailed implementation manners

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the present invention will be further described below in conjunction with the embodiments and the accompanying drawings.

[0050] Here, the exemplary embodiments will be described in detail, and the examples are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all the implementation manners consistent with the present disclosure. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0051] According to a first aspect of the present invention, an LED power control method is provided.

[0052] As Figure 1 described, an LED power control method provided by the embodiments of the present invention specifically includes the following steps:

[0053] An LED power control method provided by the embodiments of the present invention, as Figure 1 shown, specifically includes the following steps:

[0054] S100. Obtain a sampling signal of the sampled LED load to obtain an LED current value.

[0055] S200. Calculate an adjustment coefficient according to the LED current value and a preset current threshold, and use the adjustment coefficient to adjust the duty cycle of the pulse width modulation signal output to the LED load.

[0056] S300. Output a pulse width modulation signal to the LED load so that the LED current value continuously approaches the current threshold or is within a preset range.

[0057] Among them, the adjustment coefficient is a coefficient for adjusting the LED current value to approach the current threshold or fall within a preset range. The adjustment coefficient is operated on with a pulse width modulation signal to obtain the pulse width modulation signal to be output. The duty cycle of the pulse width modulation signal output after the operation is in a proportional relationship with the duty cycle of the original pulse width modulation signal. In this way, the duty cycle of the pulse width modulation signal can be dynamically changed through the real-time changing adjustment coefficient, thereby adjusting the LED current value, and the LED current value continuously approaches the current threshold or falls within the preset range.

[0058] Optionally, the initial value of the adjustment coefficient can be a value set in advance or input by the user, or the adjustment coefficient at the time of the previous power-down, etc.

[0059] A method for controlling the power of an LED provided by an embodiment of the present invention samples the current information of an LED load through a sampling circuit, determines the LED current value through signal conversion after obtaining the sampling signal of the sampling circuit, compares the real-time LED current value with a preset current threshold, calculates the currently required adjustment coefficient according to each comparison result, and uses the adjustment coefficient to adjust the duty cycle of the pulse width modulation signal output to the LED load. When the LED current value is greater than the current threshold, the calculated adjustment coefficient is used to adjust the pulse width modulation signal to reduce the LED current value. On the contrary, when the LED current value is less than the current threshold, the calculated adjustment coefficient is used to adjust the pulse width modulation signal to increase the LED current value, so as to achieve constant power drive for the LED load.

[0060] Optionally, the sampling circuit samples the current of the LED load by generating a voltage drop when current flows through a resistor. Step S100 specifically includes the following steps:

[0061] Obtain the voltage difference across the sampling circuit, and calculate the LED current value according to the voltage difference across the sampling circuit and the resistance value of the sampling circuit.

[0062] More specifically, use the ADC of the single-chip microcomputer to obtain the voltage difference across the sampling circuit in real time, and calculate the LED current value based on Ohm's law after averaging the obtained multiple voltage differences.

[0063] Further, as Figure 2 described, in one embodiment, the calculating the adjustment coefficient according to the LED current value and the current threshold specifically includes the following steps:

[0064] S210. Judge whether the LED current value is greater than the first current threshold within the detection period.

[0065] In the above step S210, if the judgment result is yes, execute step S220; if the judgment result is no, execute step S230.

[0066] S220. Calculate the adjustment coefficient for the current detection period using the adjustment coefficient of the previous detection period, so that the adjustment coefficients of each detection period change continuously and monotonically before the LED current value is lower than the first current threshold, and output the pulse width modulation signal to the LED load to control the decrease of the LED current value.

[0067] S230. When the duration for which the LED current value continuously remains less than the first current threshold is greater than the preset duration, use the adjustment coefficient of the previous detection period to calculate the adjustment coefficient for the current self - recovery period with the preset self - recovery period as the calculation period, so that the adjustment coefficients of each self - recovery period change continuously and monotonically before the LED current value is higher than the first current threshold, and output the pulse width modulation signal to the LED load to control the increase of the LED current value.

[0068] Wherein, the self - recovery period is greater than the detection period.

[0069] The detection period and the self - recovery period are timed separately. The detection period and the self - recovery period are set to different durations, and the duration of the self - recovery period is greater than the duration of the detection period. After the LED current value is obtained in real - time, the LED current value is continuously compared with the set first current threshold, and the time interval between two adjacent comparisons is a detection period. At the start of a detection period, the current LED current value is compared with the set first current threshold. The comparison result between the LED current value and the first current threshold within the detection period is used as the basis for adjusting the adjustment coefficient. When the LED current value is greater than the first current threshold, the adjustment coefficient is updated in each detection period. Specifically, the adjustment coefficient for the current detection period is calculated based on the adjustment coefficient of the previous detection period. When the duration for which the LED current value continuously remains less than the first current threshold is greater than the preset duration, the adjustment coefficient is updated in the self - recovery period, that is, the adjustment coefficient for the current detection period is calculated based on the adjustment coefficient of the previous detection period, so that the rising rate and the falling rate of the LED current value are different.

[0070] Preferably, the preset duration is equal to the duration of the self - recovery period.

[0071] More specifically, the step of calculating the adjustment coefficient for the current detection period using the adjustment coefficient of the previous detection period specifically includes the following steps: perform a difference operation or a summation operation on the adjustment coefficient of the previous detection period and the first operation coefficient to calculate the adjustment coefficient for the current detection period; the step of calculating the adjustment coefficient for the current self - recovery period using the adjustment coefficient of the previous detection period specifically includes the following steps: perform a difference operation or a summation operation on the adjustment coefficient of the previous detection period of the self - recovery period and the second operation coefficient to calculate the adjustment coefficient for the current self - recovery period.

[0072] When the adjustment coefficient is positively correlated with the duty cycle of the adjusted pulse width modulation signal, when calculating the difference between the adjustment coefficient of the detection period and the first operation coefficient, the adjustment coefficient of the self-recovery period is calculated by summing with the second operation coefficient, where 0 < C ≤ 1, 0 < C1 ≤ 1, and 0 < C2 ≤ 1;

[0073] When the adjustment coefficient is negatively correlated with the duty cycle of the adjusted pulse width modulation signal, when calculating the sum of the adjustment coefficient of the detection period and the first operation coefficient, the adjustment coefficient of the self-recovery period is calculated by taking the difference with the second operation coefficient, where 1 ≤ C < +∞, 0 < C1 < +∞, and 0 < C2 < +∞;

[0074] Among them, C represents the adjustment coefficient, C1 represents the first operation coefficient, and C2 represents the second operation coefficient.

[0075] Exemplarily, to further illustrate the LED power control method provided by the embodiments of the present invention, the following takes the application of this LED power control method in practice as an example for illustration.

[0076] After power-on, determine the initial adjustment coefficient, and based on the initial adjustment coefficient, regulate the duty cycle of the pulse width modulation signal output to the LED load to control the current flowing through the LED load. A sampling circuit for sampling the LED load is set in the circuit network of the LED load. The sampling circuit continuously outputs the currently sampled sampling signal to the ADC terminal of the single-chip microcomputer, and after analog-to-digital conversion and calculation, the LED current value is obtained.

[0077] The single-chip microcomputer compares the current LED current value with the first current threshold within each preset detection period, outputs the corresponding adjustment coefficient according to the comparison result, and then uses this adjustment coefficient to adjust the duty cycle of the pulse width modulation signal, so that the duty cycles of the pulse width modulation signals before and after adjustment are in proportion, that is:

[0078] PWM1 = C × PWM0;

[0079] Among them, PWM1 represents the adjusted pulse width modulation signal, PWM0 represents the pulse width modulation signal before adjustment, and C represents the adjustment coefficient (0 ≤ C ≤ 1).

[0080] For the determination of the adjustment coefficient, when the LED current value is greater than the first current threshold within the detection period, subtract the first operation coefficient from the adjustment coefficient calculated in the previous detection period to calculate the adjustment coefficient of the current detection period, so that the adjustment coefficients in each detection period before the LED current value is less than the first current threshold or before the current adjustment coefficient is reduced to 0 show a monotonically decreasing change, that is:

[0081] C N = C N-1 - C1;

[0082] Among them, C N represents the adjustment coefficient of the current detection period, and C N-1 represents the adjustment coefficient of the previous detection period. C1 represents the first operation coefficient;

[0083] During the detection period, when the LED current value is less than the first current threshold, the adjustment coefficient calculated in the previous self - recovery period is added with the second operation coefficient to calculate the adjustment coefficient of the current self - recovery period, so that the adjustment coefficients of each detection period show a monotonically increasing change before the LED current value reaches the first current threshold or before the current adjustment coefficient increases to 1. That is:

[0084] C M = C M-1 + C2;

[0085] Among them, C M represents the adjustment coefficient of the current self - recovery period, C M-1 represents the adjustment coefficient of the previous self - recovery period, and C2 represents the second operation coefficient.

[0086] It should be noted that the detection period and the self - recovery period are timed independently. To prevent the phenomenon that the LED current value exceeds the first current threshold during the self - recovery process, it is set that the duration of the detection period is less than the duration of the self - recovery period. The LED current value and the first current threshold are compared once in each detection period. When the judgment result is that the LED current value is greater than the first current threshold, the adjustment coefficient of the previous detection period is used to calculate the adjustment coefficient of the current detection period, and the adjustment coefficients of each detection period change continuously and monotonically before the LED current value is lower than the first current threshold, so that the LED current value gradually decreases with the change of the adjustment coefficient and approaches the first current threshold. When the judgment result is that the LED current value is less than the first current threshold, if the timing has not reached the start stage of the self - recovery period, the adjustment coefficient will not be adjusted. If the situation that the LED current is less than the first current threshold continues until the start of the self - recovery period, the adjustment coefficient of the previous detection period at the start of the self - recovery period is used to calculate the adjustment coefficient of the self - recovery period, so that the LED current value gradually increases with the change of the adjustment coefficient and approaches the first current threshold.

[0087] For example, it is set that the duration of the detection period is 5 milliseconds and the duration of the self - recovery period is 500 milliseconds. The LED current value and the first current threshold are compared every 5 milliseconds. If it is detected that the LED current value is less than the first current threshold at the 50 - millisecond stage, since the self - recovery period (500 milliseconds) has not been reached, the LED current value will not be restored by adjusting the adjustment coefficient, and the adjustment coefficient remains unchanged. When the LED current continues to be less than the first current threshold until the self - recovery period (500 milliseconds), it enters the self - recovery period, and the adjustment coefficient is adjusted after entering the self - recovery period to increase the LED current value.

[0088] Further, to prevent the duration of the LED current value being greater than the first current threshold from being too long, the duration during which the adjustment coefficient of each detection period continuously and monotonically changes satisfies the following relationship:

[0089] T1 = a × (C MAX1 - C MIN1 );

[0090] Wherein, T1 represents the duration during which the adjustment coefficient of each detection period continuously and monotonically changes, and its unit is seconds, 0 < a ≤ 3, C MAX1 represents the value of the adjustment coefficient of the detection period at the beginning of the monotonic change, C MIN1 represents the value of the adjustment coefficient of the detection period at the end of the monotonic change.

[0091] Exemplarily, during the process of the adjustment coefficient continuously and monotonically decreasing, when the adjustment coefficient decreases from 1 to 0, the total duration of the detection periods corresponding to the continuous and monotonic change of the adjustment coefficient does not exceed 3 seconds. At the same time, in order not to cause a jitter phenomenon, the frequency of the decrease of the adjustment coefficient needs to be greater than 50 HZ (that is, the coefficient is decreased every 0 - 20 MS). Preferably, the duration of each detection period is 5 milliseconds, and the value of the first operation coefficient is 0.005.

[0092] Further, to prevent the output effect from being abnormal due to the too fast self - recovery of the LED current value, the speed of increasing the coefficient needs to be relatively slow. The duration of calculating the adjustment coefficient of the current self - recovery period using the adjustment coefficient of the previous self - recovery period satisfies the following relationship:

[0093] T2 = b × (C MAX2 - C MIN2 );

[0094] Wherein, T2 represents the duration during which the adjustment coefficient of each self - recovery period continuously and monotonically changes, and its unit is seconds, b > 60, C MAX2 represents the value of the adjustment coefficient of the self - recovery period at the beginning of the monotonic change, C MIN2 represents the value of the adjustment coefficient of the self - recovery period at the end of the monotonic change.

[0095] Exemplarily, during the process of the adjustment coefficient continuously and monotonically increasing, when the adjustment coefficient increases from 0 to 1, the total duration of the detection periods corresponding to the continuous and monotonic change of the adjustment coefficient is not shorter than 1 minute. At the same time, in order not to cause a jitter phenomenon, the single - time proportion of the increase of the coefficient cannot exceed 0.001. Preferably, the duration of each self - recovery period is 500 milliseconds, and the value of the second operation coefficient is 0.001.

[0096] In another embodiment, it can also be to use the following calculation method to adjust the duty cycle of the pulse - width modulation signal so that the duty cycles of the pulse - width modulation signals before and after the adjustment are in proportion, that is:

[0097]

[0098] Among them, PWM1 represents the adjusted pulse width modulation signal, PWM0 represents the pulse width modulation signal before adjustment, and C represents the adjustment coefficient (1 ≤ C ≤ +∞).

[0099] During the detection period, when the LED current value is greater than the first current threshold, use the adjustment coefficient obtained in the previous detection period plus the first operation coefficient, that is:

[0100] C N = C N-1 + C1;

[0101] Among them, C N represents the adjustment coefficient of the current detection period, C N-1 represents the adjustment coefficient of the previous detection period, and C1 represents the first operation coefficient;

[0102] During the detection period, when the LED current value is less than the first current threshold, use the adjustment coefficient obtained in the previous self - recovery period minus the second operation coefficient, that is:

[0103] C M = C M-1 - C2;

[0104] Among them, C M represents the adjustment coefficient of the current self - recovery period, C M-1 represents the adjustment coefficient of the previous self - recovery period, and C2 represents the second operation coefficient.

[0105] Furthermore, as Figure 3 described, in another embodiment, the calculating the adjustment coefficient according to the LED current value and the current threshold specifically includes the following steps:

[0106] S240. Judge whether the LED current value is within the range between the first current threshold and the second current threshold during the detection period.

[0107] In the above step S240, if the judgment result is yes, execute step S250; if the judgment result is no, execute step S260.

[0108] S250. Use the adjustment coefficient of the previous detection period as the adjustment coefficient of the current detection period.

[0109] S260. When the LED current value is greater than the first current threshold, calculate the adjustment coefficient of the current detection period using the adjustment coefficient of the previous detection period, so that the adjustment coefficients of each detection period change continuously and monotonically before the LED current value is lower than the first current threshold, and output the pulse width modulation signal to the LED load to control the LED current value to decrease; when the duration that the LED current value is less than the second current threshold is greater than the preset duration, use the preset self - recovery period as the calculation period, and calculate the adjustment coefficient of the current self - recovery period using the adjustment coefficient of the previous detection period, so that the adjustment coefficients of each self - recovery period change continuously and monotonically before the LED current value is higher than the second current threshold, and output the pulse width modulation signal to the LED load to control the LED current value to increase.

[0110] Among them, the self - recovery period is greater than the detection period, and the first current threshold is greater than the second current threshold.

[0111] In this embodiment, by presetting the first current threshold and the second current threshold to form three current intervals, when the LED current value is greater than the first current threshold or less than the second current threshold, the adjustment coefficient is adjusted, that is, when the LED current value is too large or too small, the adjustment coefficient is adjusted, and when the LED current is greater than the second current threshold and less than the first current threshold, the adjustment coefficient is maintained unchanged, avoiding the phenomenon of flicker and jitter of the LED load during the constant - power process. Specifically, when the LED current value is greater than the first current threshold, the LED current value is reduced by adjusting the adjustment coefficient, and the adjustment coefficients of each detection period change continuously and monotonically before the LED current value is lower than the first current threshold. When the LED current value is less than the second current threshold, the LED current value is increased by adjusting the adjustment coefficient, and the adjustment coefficients of each detection period change continuously and monotonically before the LED current value is higher than the second current threshold. The adjustment process of making the adjustment coefficient change continuously and monotonically is the same as that of the above - mentioned embodiment, and will not be elaborated here.

[0112] Preferably, the first current threshold and the second current threshold satisfy the following relationship:

[0113] 0.01D1 ≤ D2 < D1;

[0114] Among them, D1 represents the first current threshold, and D2 represents the second current threshold.

[0115] According to the second aspect of the present invention, a kind of LED power control circuit 200 is provided.

[0116] As Figure 4 described, the first kind of LED power control circuit 200 provided by the embodiment of the present invention includes a sampling circuit 100, a control circuit 200 and a driving circuit 300. The control circuit 200 is respectively connected to the sampling circuit 100 and the driving circuit 300. The sampling circuit 100 and the driving circuit 300 are used to connect to the LED load 400;

[0117] The sampling circuit 100 is used to sample the LED load 400;

[0118] The control circuit 200 is used to obtain the sampling signal of the LED load 400 sampled by the sampling circuit 100 to obtain the LED current value; and periodically calculate the adjustment coefficient according to the LED current value and the current threshold, and use the adjustment coefficient to adjust the duty cycle of the pulse width modulation signal output to the LED load 400; wherein, the adjustment coefficient is a coefficient for adjusting the LED current value to approach the current threshold or be within a preset range;

[0119] The driving circuit 300 is used to output a pulse width modulation signal to the LED load 400 so that the LED current value continuously approaches the current threshold or is within a preset range.

[0120] Among them, the control circuit 200 includes a single-chip microcomputer. Preferably, the single-chip microcomputer is a single-chip microcomputer of the MM32F series.

[0121] Further, the obtaining the sampling signal of the sampled LED load to obtain the LED current value specifically includes the following steps:

[0122] Obtain the voltage difference across the sampling circuit, and calculate the LED current value according to the voltage difference across the sampling circuit and the resistance value of the sampling circuit.

[0123] Further, the calculating the adjustment coefficient according to the LED current value and the preset current threshold specifically includes the following steps:

[0124] Judge whether the LED current value is greater than the first current threshold within the detection period;

[0125] If so, calculate the adjustment coefficient of the current detection period using the adjustment coefficient of the previous detection period, so that the adjustment coefficients of each detection period continuously and monotonically change before the LED current value is lower than the first current threshold, and the pulse width modulation signal output to the LED load controls the LED current value to decrease;

[0126] If not, when the duration that the LED current value is continuously less than the first current threshold is greater than the preset duration, use the adjustment coefficient of the previous detection period as the calculation period with the preset self-recovery period to calculate the adjustment coefficient of the current self-recovery period, so that the adjustment coefficients of each self-recovery period continuously and monotonically change before the LED current value is higher than the first current threshold, and the pulse width modulation signal output to the LED load controls the LED current value to increase; wherein, the self-recovery period is greater than the detection period.

[0127] Further, the calculating the adjustment coefficient according to the LED current value and the preset current threshold specifically includes the following steps:

[0128] Determine whether the LED current value is within the range of the first current threshold and the second current threshold during the detection period;

[0129] If so, use the adjustment coefficient of the previous detection period as the adjustment coefficient of the current detection period;

[0130] If not, when the LED current value is greater than the first current threshold, use the adjustment coefficient of the previous detection period to calculate the adjustment coefficient of the current detection period, so that the adjustment coefficients of each detection period change continuously and monotonically before the LED current value is lower than the first current threshold, and output the pulse width modulation signal to the LED load to control the LED current value to decrease; when the duration that the LED current value is less than the second current threshold is greater than the preset duration, use the preset self - recovery period as the calculation period, and use the adjustment coefficient of the previous detection period of the self - recovery period to calculate the adjustment coefficient of the current self - recovery period, so that the adjustment coefficients of each self - recovery period change continuously and monotonically before the LED current value is higher than the second current threshold, and output the pulse width modulation signal to the LED load to control the LED current value to increase;

[0131] Wherein, the self - recovery period is greater than the detection period, and the first current threshold is greater than the second current threshold. Further, the first current threshold and the second current threshold satisfy the following relationship:

[0132] 0.01D1 ≤ D2 < D1;

[0133] Wherein, D1 represents the first current threshold, and D2 represents the second current threshold.

[0134] Further, the specific steps of using the adjustment coefficient of the previous detection period to calculate the adjustment coefficient of the current detection period include the following: perform a difference operation or a summation operation on the adjustment coefficient of the previous detection period and the first operation coefficient to calculate the adjustment coefficient of the current detection period;

[0135] The specific steps of using the adjustment coefficient of the previous detection period of the self - recovery period to calculate the adjustment coefficient of the current self - recovery period include the following: perform a difference operation or a summation operation on the adjustment coefficient of the previous detection period of the self - recovery period and the second operation coefficient to calculate the adjustment coefficient of the current self - recovery period;

[0136] When the adjustment coefficient is positively correlated with the duty cycle of the adjusted pulse width modulation signal, perform a difference operation on the adjustment coefficient of the previous detection period and the first operation coefficient, and perform a summation operation on the adjustment coefficient of the previous detection period of the self - recovery period and the second operation coefficient, 0 < C ≤ 1, 0 < C1 ≤ 1, 0 < C2 ≤ 1;

[0137] When the adjustment coefficient is negatively correlated with the duty cycle of the adjusted pulse width modulation signal, the adjustment coefficient of the previous detection period is used for summation operation with the first operation coefficient, and the adjustment coefficient of the previous detection period of the self-recovery period is used for difference operation with the second operation coefficient, where 1 ≤ C < +∞, 0 < C1 < +∞, and 0 < C2 < +∞;

[0138] Among them, C represents the adjustment coefficient, C1 represents the first operation coefficient, and C2 represents the second operation coefficient.

[0139] Furthermore, the duration during which the adjustment coefficients of each detection period continuously and monotonically change before the LED current value is lower than the first current threshold satisfies the following relationship:

[0140] T1 = a × (C MAX1 - C MIN1 );

[0141] Among them, T1 represents the duration during which the adjustment coefficients of each detection period continuously and monotonically change, and its unit is seconds, where 0 < a ≤ 3, C MAX1 represents the value of the adjustment coefficient of the detection period at the beginning of the monotonic change, and C MIN1 represents the value of the adjustment coefficient of the detection period at the end of the monotonic change.

[0142] Furthermore, the duration during which the adjustment coefficients of each self-recovery period continuously and monotonically change satisfies the following relationship:

[0143] T2 = b × (C MAX2 - C MIN2 );

[0144] Among them, T2 represents the duration during which the adjustment coefficients of each self-recovery period continuously and monotonically change, and its unit is seconds, where b > 60, C MAX2 represents the value of the adjustment coefficient of the self-recovery period at the beginning of the monotonic change, and C MIN2 represents the value of the adjustment coefficient of the self-recovery period at the end of the monotonic change.

[0145] As Figure 5 described above, the second LED power control circuit 200 provided by the embodiments of the present invention.

[0146] The sampling circuit 100 includes a sampling resistor unit R3. One end of the sampling resistor unit R3 is used to connect to the LED load 400 and to the control circuit 200, and the other end of the sampling resistor unit R3 is grounded. The control circuit 200 determines the LED current value by detecting the voltage difference across the sampling resistor unit R3 and the resistance value of the sampling resistor unit R3.

[0147] The driving circuit 300 includes a switching transistor Q1, a first driving resistor unit R1, and a second driving resistor unit R2. The first end of the switching transistor Q1 is used to connect to the LED load 400. The second end of the switching transistor Q1 is connected to the sampling circuit 100. The triggering end of the switching transistor Q1 is connected to one end of the first driving resistor unit R1. The other end of the first driving resistor unit R1 is respectively connected to the control circuit 200 and one end of the second driving resistor unit R2. The other end of the second driving resistor unit R2 is grounded. The control circuit 200 outputs a pulse width modulation signal to the driving end of the switching transistor Q1, so that the conduction degree of the switching transistor Q1 changes with the duty cycle of the pulse width modulation signal, thereby regulating the current of the LED load 400.

[0148] As Figure 6 described above, the third LED power control circuit 200 provided by the embodiments of the present invention.

[0149] The LED power control circuit 200 provided by the embodiments of the present invention is connected to three groups of LED loads 400. Among them, the LED loads 400 are connected in parallel. The sampling circuit 100 samples the aggregation point of each LED load 400. The number of driving circuits 300 is the same as the number of LED loads 400. One driving circuit 300 outputs a pulse width modulation signal to one LED load 400. The control circuit 200 outputs the pulse width modulation signals obtained by adjusting with the same adjustment coefficient to each driving circuit 300.

[0150] The control circuit 200 controls each LED load 400 simultaneously, and outputs the pulse width modulation signals obtained by adjusting with the same adjustment coefficient to each driving circuit 300, so that the rising and falling ratios of the LED current values of each LED load 400 are the same, so that there is no obvious difference in the display effects among the LED loads 400. When the LED loads 400 are of different colors respectively, the effect that the display color will not change when the LED current value changes can be achieved.

[0151] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combinations of these technical features do not conflict, they should all be considered as the scope recorded in this specification.

[0152] In this article, the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion. In addition to including the listed elements, it may also include other elements not expressly listed.

[0153] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims described above.

Claims

1. An LED power control method, characterized in that, Including the following steps: Obtain a sampling signal of the sampled LED load to get the LED current value; Calculate an adjustment coefficient according to the LED current value and a preset current threshold, and use the adjustment coefficient to adjust the duty cycle of the pulse-width modulation signal output to the LED load; wherein, the adjustment coefficient is a coefficient for adjusting the LED current value to approach the current threshold or fall within a preset range; The calculating the adjustment coefficient according to the LED current value and the preset current threshold specifically includes the following steps: Judge whether the LED current value is greater than a first current threshold within a detection period; If so, calculate the adjustment coefficient of the current detection period using the adjustment coefficient of the previous detection period, so that the adjustment coefficients of each detection period continuously and monotonically change before the LED current value is lower than the first current threshold, and the pulse-width modulation signal output to the LED load controls the LED current value to decrease; If not, when the duration for which the LED current value continuously remains less than the first current threshold is greater than a preset duration, use the adjustment coefficient of the previous detection period as the calculation period to calculate the adjustment coefficient of the current self-recovery period, so that the adjustment coefficients of each self-recovery period continuously and monotonically change before the LED current value is higher than the first current threshold, and the pulse-width modulation signal output to the LED load controls the LED current value to increase; wherein, the self-recovery period is greater than the detection period; Output a pulse-width modulation signal to the LED load so that the LED current value continuously approaches the current threshold or falls within a preset range.

2. The LED power control method according to claim 1, wherein The obtaining a sampling signal of the sampled LED load to get the LED current value specifically includes the following steps: Obtain the voltage difference across the sampling circuit, and calculate the LED current value according to the voltage difference across the sampling circuit and the resistance value of the sampling circuit.

3. The LED power control method according to claim 1, wherein The calculating the adjustment coefficient according to the LED current value and the preset current threshold specifically includes the following steps: Judge whether the LED current value is within the range between the first current threshold and the second current threshold within a detection period; If so, use the adjustment coefficient of the previous detection period as the adjustment coefficient of the current detection period; If not, when the LED current value is greater than the first current threshold, calculate the adjustment coefficient of the current detection period using the adjustment coefficient of the previous detection period, so that the adjustment coefficients of each detection period continuously and monotonically change before the LED current value is lower than the first current threshold, and the pulse-width modulation signal output to the LED load controls the LED current value to decrease; when the duration for which the LED current value is less than the second current threshold is greater than a preset duration, use the preset self-recovery period as the calculation period and calculate the adjustment coefficient of the current self-recovery period using the adjustment coefficient of the previous detection period, so that the adjustment coefficients of each self-recovery period continuously and monotonically change before the LED current value is higher than the second current threshold, and the pulse-width modulation signal output to the LED load controls the LED current value to increase; wherein, the self-recovery period is greater than the detection period, and the first current threshold is greater than the second current threshold.

4. The LED power control method according to claim 3, wherein, The first current threshold and the second current threshold satisfy the following relationship: ； Among them, represents the first current threshold value, represents the second current threshold value.

5. The LED power control method according to claim 1 or 3, characterized in that Calculating the adjustment coefficient of the current detection period by using the adjustment coefficient of the previous detection period specifically includes the following steps: performing a difference operation or a summation operation on the adjustment coefficient of the previous detection period and the first operation coefficient to calculate the adjustment coefficient of the current detection period; Calculating the adjustment coefficient of the current self-recovery period by using the adjustment coefficient of the previous detection period specifically includes the following steps: performing a difference operation or a summation operation on the adjustment coefficient of the previous detection period of the self-recovery period and the second operation coefficient to calculate the adjustment coefficient of the current self-recovery period; When the adjustment coefficient is positively correlated with the duty cycle of the adjusted pulse width modulation signal, perform a difference operation on the adjustment coefficient of the previous detection period and the first operation coefficient, and perform a summation operation on the adjustment coefficient of the previous detection period of the self-recovery period and the second operation coefficient. , , ; When the adjustment coefficient is negatively correlated with the duty cycle of the adjusted pulse width modulation signal, perform a summation operation on the adjustment coefficient of the previous detection period and the first operation coefficient, and perform a difference operation on the adjustment coefficient of the previous detection period of the self-recovery period and the second operation coefficient. , , ; Among them, represents a regulation coefficient, represents a first operation coefficient, represents a second operation coefficient.

6. The LED power control method according to claim 1 or 3, characterized in that The duration of the continuous monotonic change of the adjustment coefficient of each detection period before the LED current value is lower than the first current threshold satisfies the following relationship: ； Among them, represents the duration during which the adjustment coefficient of each detection period changes continuously and monotonically, and its unit is seconds, , represents the value of the adjustment coefficient of the detection period at the beginning of the monotonic change, represents the value of the adjustment coefficient of the detection period at the end of the monotonic change.

7. The LED power control method according to claim 1 or 3, characterized in that The duration of the continuous monotonic change of the adjustment coefficient of each self-recovery period satisfies the following relationship: ； Among them, represents the duration during which the adjustment coefficient of each recovery period changes continuously and monotonically, and its unit is seconds. , represents the value of the adjustment coefficient of the self-recovery period at the beginning of the monotonic change. represents the value of the adjustment coefficient of the self-recovery period at the end of the monotonic change.

8. An LED power control circuit, characterized in that, Including a sampling circuit, a control circuit, and a driving circuit, the control circuit is respectively connected to the sampling circuit and the driving circuit, and the sampling circuit and the driving circuit are used to connect to the LED load; The sampling circuit is used to sample the LED load; The control circuit is used to obtain the sampling signal of the LED load sampled by the sampling circuit to obtain the LED current value; And periodically calculating an adjustment coefficient according to the LED current value and a preset current threshold, and using the adjustment coefficient to adjust the duty cycle of the pulse width modulation signal output to the LED load; wherein, the adjustment coefficient is a coefficient for adjusting the LED current value to approach the current threshold or be within a preset range; Calculating the adjustment coefficient according to the LED current value and the preset current threshold specifically includes the following steps: Judging whether the LED current value is greater than the first current threshold within the detection period; If so, calculating the adjustment coefficient of the current detection period by using the adjustment coefficient of the previous detection period, so that the adjustment coefficients of each detection period continuously and monotonically change before the LED current value is lower than the first current threshold, and the pulse width modulation signal output to the LED load controls the LED current value to decrease; If not, when the duration of the LED current value continuously being less than the first current threshold is greater than the preset duration, using the adjustment coefficient of the previous detection period as the calculation period to calculate the adjustment coefficient of the current self-recovery period with a preset self-recovery period, so that the adjustment coefficients of each self-recovery period continuously and monotonically change before the LED current value is higher than the first current threshold, and the pulse width modulation signal output to the LED load controls the LED current value to increase; wherein, the self-recovery period is greater than the detection period; The driving circuit is used to output a pulse width modulation signal to the LED load so that the LED current value continuously approaches the current threshold or is within a preset range.

9. The LED power control circuit according to claim 8, wherein, The LED power control circuit is connected to at least two groups of LED loads; Each of the LED loads is connected in parallel; The sampling circuit samples the aggregation point of each LED load; The number of the driving circuits is the same as the number of the LED loads, and one driving circuit outputs a pulse width modulation signal to one LED load; The control circuit outputs the pulse width modulation signals adjusted by the same adjustment coefficient to each driving circuit.

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