Self-adaptive frequency modulation method, frequency modulation circuit and driving circuit

Abstract

The invention provides a self-adaptive frequency modulation method, which comprises the following steps that: pulse extraction is carried out when the duty ratio of an LED (Light Emitting Diode) driving channel is reduced to be below a preset frequency reduction threshold value, a rated number of PWM (Pulse Width Modulation) periods are taken as a group in the pulse extraction, a plurality of pulses are extracted from the PWM periods according to the duty ratio, and the number of the extracted pulses is increased along with the reduction of the duty ratio; and averagely distributing the total pulse width of the extracted pulses to the remaining pulses, and performing width compensation on the pulse widths of the remaining pulses. According to the invention, the PWM frequency can be adaptively adjusted according to the brightness of the LED, and the linearity of the dimming current is ensured while the frequency reduction is realized.

Description

Technical Field

[0001] The present invention relates to the field of electronics, and more particularly but not limited to an adaptive frequency modulation method, a frequency modulation circuit, and a driving circuit. Background Art

[0002] During the use of LEDs, a driving circuit capable of providing a constant current is required, and a dimming circuit capable of adjusting its brightness is also needed. Currently, LED dimming technologies mainly include analog dimming and PWM chopping dimming. Among them, the chopping dimming accuracy is more accurate and is widely used in switching power supplies. PWM chopping dimming adjusts the average value of the LED current by setting the frequency and duty cycle. Under the condition of constant frequency, the brightness of the LED will decrease as the duty cycle decreases. When using different PWM dimming frequencies, the corresponding advantages and disadvantages are also different. When using low-frequency PWM frequency dimming, obvious water ripples will appear in the shooting of the imaging device by the LED device, but there is a monotonic relationship between the duty cycle and the brightness under low-frequency conditions. In the prior art, the common practice to avoid the stroboscopic problem is to increase the PWM frequency. However, as the frequency increases, the problem of brightness imbalance will occur when the LED is at low brightness. Especially when the dimming depth of the LED reaches less than one-thousandth, in the case of a high PWM frequency, the actual high-level time length order of magnitude of the PWM output is small, which requires high chip performance and great design difficulty.

[0003] In the existing solution, one or more driving channels are provided in the LED driving circuit, each channel corresponding to driving one or more LED lamp circuits. An adaptive frequency modulation module is provided in the LED driving circuit, and the adaptive frequency modulation module generates different PWM dimming frequencies according to the set brightness. A first brightness threshold is provided in the system. When the set brightness is above the first brightness threshold, a fixed frequency is used as the PWM dimming frequency; when the set brightness is less than the first brightness threshold, the corresponding preset PWM dimming frequency is selected according to the brightness, and the preset PWM dimming frequency changes linearly with the brightness. The specific change relationship is as follows Figure 1 shown.

[0004] The existing solution is to detect the brightness setting value through the adaptive frequency modulation module and generate the corresponding PWM dimming frequency and output it to the driving channel to achieve the purpose of frequency reduction. Its disadvantage is that when there are multiple driving channels in the driving circuit, such as in a five-way PWM dimming application, the brightness of each path may be different, which makes the PWM chopping frequency of each path also different. Since the five channels operate at different frequencies, it is not convenient for the phase shift between channels and the design of subsequent other functions.

[0005] In view of this, a new structure or control method is needed to solve at least some of the above problems. Summary of the Invention

[0006] At least for one or more problems in the background art, the present invention provides an adaptive frequency modulation method, a frequency modulation circuit and a driving circuit, which can adaptively adjust the PWM frequency according to the brightness of the LED.

[0007] According to one aspect of the present invention, an adaptive frequency modulation method for an LED driving circuit includes:

[0008] Performing pulse extraction when the duty cycle of the LED driving channel is reduced below a preset frequency reduction threshold, where the pulse extraction is performed in groups of a rated number of PWM cycles, and a certain number of pulses are extracted from each group according to the duty cycle, and the number of extracted pulses increases as the duty cycle decreases;

[0009] Averaging the total pulse width of the extracted pulses and distributing it to the remaining pulses to perform width compensation on the pulse width of the remaining pulses.

[0010] Optionally, segmenting the duty cycle to obtain a plurality of duty cycle intervals, and each duty cycle interval corresponds to extracting different numbers of pulses, and the difference between the upper and lower limits of the duty cycle of the duty cycle interval is the width of the duty cycle interval.

[0011] Optionally, the extracted pulses are evenly distributed in each group of PWM cycles.

[0012] Optionally, the width compensation includes:

[0013] Calculating a duty cycle compensation coefficient for different duty cycle intervals based on the number of PWM cycles and the number of pulse extractions in each duty cycle interval;

[0014] Calculating a duty cycle compensation amount for each duty cycle interval based on the duty cycle compensation coefficient and the limit values of different duty cycle intervals.

[0015] Optionally, calculating the duty cycle compensation amount includes:

[0016] Taking the lower limit value of the duty cycle of different duty cycle intervals as the basis for pulse width compensation in this interval, and calculating the duty cycle compensation amount and the compensated duty cycle value as:

[0017] Duty comp =Duty L ×(N / (M-N))

[0018] Duty2=Duty1+Duty comp

[0019] In the formula, Duty comp is the duty cycle compensation amount, Duty Lis the lower limit value of the duty cycle for the duty cycle interval, N is the number of pulse extractions for the duty cycle interval, M is the number of PWM cycles, N / (M - N) is the duty cycle compensation coefficient, Duty1 is the duty cycle value before compensation, and Duty2 is the duty cycle value after compensation.

[0020] Optionally, calculating the duty cycle compensation amount includes:

[0021] Taking the integer part of the duty cycle compensation coefficient as the independent duty cycle compensation coefficient for this interval, taking the duty cycle value before compensation as the independent compensation basis for the pulse width of this interval, and calculating the independent duty cycle compensation component for this interval;

[0022] Taking the fractional part of the duty cycle compensation coefficient as the supplementary duty cycle compensation coefficient for this interval, taking the lower limit value of the duty cycle for the duty cycle interval as the supplementary compensation basis for the pulse width of this interval, and calculating the supplementary duty cycle compensation component for this interval;

[0023] Summing the independent duty cycle compensation component and the supplementary duty cycle compensation component to obtain the duty cycle compensation amount for this interval.

[0024] Optionally, calculating the duty cycle value after compensation is:

[0025] Duty2 = Duty1×(1 + floor(N / M - N)) + Duty L ×((N mod (M - N)) / (M - N))

[0026] In the formula, Duty2 is the duty cycle value after compensation, Duty1 is the duty cycle value before compensation, Duty L is the lower limit value of the duty cycle for the duty cycle interval, floor() is the floor function, mod is the modulo operation, N is the number of pulse extractions for each duty cycle interval, and M is the number of PWM cycles.

[0027] Optionally, calculating the duty cycle compensation amount includes:

[0028] Segmenting the duty cycle intervals where the current drops below a preset threshold according to the number of PWM cycles, the number of pulse extractions for the duty cycle interval, the upper limit value and the lower limit value of the duty cycle interval, and calculating the duty cycle compensation amount.

[0029] Optionally, segmenting the duty cycle interval into two segments and calculating the duty cycle value after compensation is:

[0030] When Duty L <Duty1 ≤ (Duty L + Duty H ) / 2, the duty cycle value after compensation is:

[0031] Duty2 = Duty1 × (1 + floor(N / M - N)) + Duty L × ((N mod (M - N)) / (M - N))

[0032] When (Duty L + Duty H ) / 2 < Duty1 ≤ Duty H , the duty cycle value after compensation is:

[0033] Duty2 = Duty1 × (1 + floor(N / M - N)) + ((Duty H + Duty L ) / 2) × ((N mod (M - N)) / (M - N))

[0034] In the formula, floor() is the floor function, mod is the modulo operation, Duty L is the lower limit value of the duty cycle in the duty cycle range, Duty H is the upper limit value of the duty cycle in the duty cycle range, N is the number of pulse extractions in the duty cycle range, M is the number of PWM cycles, Duty1 is the duty cycle value before compensation, and Duty2 is the duty cycle value after compensation.

[0035] Optionally, divide the duty cycle range into three segments and calculate the duty cycle value after compensation as:

[0036] When Duty L < Duty1 ≤ Duty L + (Duty H - Duty L ), the duty cycle value after compensation is:

[0037] Duty2 = Duty1 × (1 + floor(N / M - N)) + Duty L × ((N mod (M - N)) / (M - N))

[0038] When Duty L + (Duty H - Duty L ) / 3 < Duty1 ≤ Duty H - (Duty H - Duty L ), the duty cycle value after compensation is: Duty2 = Duty1 × (1 + floor(N / M - N)) + (Duty L + (Duty H - Duty L ) / 3) × ((N mod (M - N)) / (M - N))

[0039] When Duty H -(Duty H -Duty L ) / 3 < Duty1 ≤ Duty H the duty ratio after compensation is:

[0040] Duty2 = Duty1 × (1 + floor(N / M - N)) + (Duty H -(Duty H -Duty L ) / 3) × ((N mod (M - N)) / (M - N))

[0041] where floor() is the floor function, mod is the modulo operation, Duty L is the lower limit of the duty ratio of the duty ratio interval, Duty H is the upper limit of the duty ratio of the duty ratio interval, N is the number of pulse extractions in the duty ratio interval, M is the number of PWM cycles, Duty1 is the duty ratio value before compensation, and Duty2 is the duty ratio value after compensation.

[0042] According to another aspect of the present invention, an adaptive frequency modulation circuit includes:

[0043] A dimming control module for adjusting the duty ratio of the LED driving channel according to the dimming signal;

[0044] A pulse extraction module for extracting a certain number of pulses from the duty ratio in groups of a rated number of PWM cycles when the duty ratio drops below a preset frequency reduction threshold, and the number of extracted pulses increases as the duty ratio decreases;

[0045] A pulse compensation module for evenly distributing the total pulse width of the extracted pulses to the remaining pulses to perform width compensation on the pulse widths of the remaining pulses.

[0046] Optionally, the pulse compensation module includes:

[0047] A compensation coefficient calculation unit for calculating the duty ratio compensation coefficient for each duty ratio interval based on the number of PWM cycles and the number of pulse extractions in each duty ratio interval;

[0048] A compensation amount calculation unit for calculating the duty ratio compensation amount based on the duty ratio compensation coefficient and the pulse width compensation basis.

[0049] Optionally, the pulse width compensation basis is the lower limit of the duty ratio of the duty ratio interval.

[0050] Optionally, the integer part of the duty cycle compensation coefficient is the duty cycle independent compensation coefficient, and the independent compensation basis of the corresponding pulse width is the duty cycle value before compensation; the fractional part of the duty cycle compensation coefficient is the duty cycle supplementary compensation coefficient, and the supplementary compensation basis of the corresponding pulse width is the lower limit value of the duty cycle in the duty cycle interval.

[0051] Optionally, the pulse compensation module includes:

[0052] A segmented compensation unit, configured to perform segmented compensation on the duty cycle interval where the current drop exceeds a preset threshold according to the number of PWM cycles, the number of pulse extractions in the duty cycle interval, the upper limit value and the lower limit value of the duty cycle interval.

[0053] According to still another aspect of the present invention, a driving circuit includes the adaptive frequency modulation circuit as described in any one of the above.

[0054] The adaptive frequency modulation method, frequency modulation circuit and driving circuit proposed by the present invention can adaptively adjust the PWM frequency according to the LED brightness, and ensure the linearity of the dimming current while achieving frequency reduction. Description of the Drawings

[0055] The drawings are used to provide a further understanding of the present invention, and are used together with the description to explain the embodiments of the present invention, and do not constitute a limitation to the present invention. In the drawings:

[0056] Figure 1 Shows a schematic diagram of the linear change between the PWM dimming frequency and the brightness in the prior art;

[0057] Figure 2 Shows a schematic diagram of the pulse extraction result of an embodiment of the present invention;

[0058] Figure 3 Shows a schematic diagram of the simulation results of the number of pulse extractions being 1 and the number of pulse extractions being 2 in an embodiment of the present invention;

[0059] Figure 4 Shows a schematic diagram of the simulation results of the number of pulse extractions being 4 and the number of pulse extractions being 5 in an embodiment of the present invention;

[0060] Figure 5 Shows a schematic diagram of the average PWM per segment and the real-time PWM after the lower limit point compensation in an embodiment of the present invention;

[0061] Figure 6 Shows a schematic diagram of the average PWM per segment and the real-time PWM after the lower limit point compensation combined with the shift processing in another embodiment of the present invention;

[0062] Figure 7Shows a schematic diagram of the average PWM per segment and the real-time PWM after the lower limit point compensation, shift processing, and segmented processing of another embodiment of the present invention;

[0063] Figure 8 Shows the flowchart of the adaptive frequency modulation method of the present invention. Detailed implementation manners

[0064] To further understand the present invention, the preferred implementation manners of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0065] The description of this part only targets several typical embodiments, and the present invention is not limited to the scope described in the embodiments. Combinations of different embodiments, mutual replacement of some technical features in different embodiments, and mutual replacement of the same or similar prior art means and some technical features in the embodiments are also within the scope of description and protection of the present invention.

[0066] "Coupled" or "connected" in the specification includes both direct connection and indirect connection. Indirect connection is a connection through an intermediate medium, such as a connection through an electrical conduction medium such as a conductor, where the electrical conduction medium may contain parasitic inductance or parasitic capacitance, or may also be a connection through an intermediate circuit or component described in the embodiments of the specification; indirect connection may also include a connection through other active devices or passive devices on the basis of achieving the same or similar functions, such as a connection through circuits or components such as switches, signal amplification circuits, and follower circuits. "Multiple" or "plural" means two or more.

[0067] In a multi-channel, high-precision dimming drive application scenario, the adaptive frequency modulation method adopts the Pulse Skipping algorithm. After the duty cycle of the channel reaches below the frequency reduction threshold, while keeping the channel frequency unchanged, a certain number of pulses are extracted from the rated number of cycles according to the actual duty cycle of the channel (pulse extraction) to achieve a function similar to frequency reduction. At the same time, the total pulse width of the extracted pulses is evenly distributed to the remaining pulses (pulse compensation) to ensure the linearity of the dimming current. The "frequency reduction threshold" and the "rated number of cycles" mentioned in the algorithm can be flexibly configured. In this embodiment, the frequency reduction threshold is 15% and the rated number of cycles is 16 for example and demonstration.

[0068] As Figure 8 shown, the adaptive frequency modulation method includes two parts: pulse extraction and pulse compensation.

[0069] 1) Pulse extraction:

[0070] During the dimming process, pulse extraction starts when the duty cycle is reduced to less than 15%. One pulse is extracted from every 16 PWM cycles; and for every additional 1% reduction in the duty cycle, the number of extracted pulses increases by 1. As the duty cycle decreases, the number of extracted pulses gradually increases. To reduce the impact of pulse extraction on current linearity, the corresponding number of pulses is evenly extracted from every 16 pulses in each group. The specific results are as Figure 2 shown, and the simulation results are intercepted as Figure 3 , Figure 4 shown. Among them, Figure 3 15 consecutive pulses plus 1 discarded pulse in total 16 form a group, corresponding to Figure 2 the waveform with a pulse extraction amount of 16 - 1 in Figure 3 ; two sets of 7 consecutive pulses plus 1 discarded pulse in total 16, corresponding to Figure 2 the waveform with a pulse extraction amount of 16 - 2 in Figure 4 ; two sets of 3 consecutive pulses plus 1 discarded pulse (only the second set of 3 consecutive pulses plus 1 discarded pulse is drawn in Figure 2 ), corresponding to Figure 4 the waveform with a pulse extraction amount of 16 - 4 in Figure 2 ; four sets of 2 consecutive pulses plus 1 discarded pulse and one set of 3 consecutive pulses plus 1 discarded pulse in total 16, corresponding to

[0071] 2) Pulse compensation:

[0072] While pulse extraction is performed, width compensation is carried out on the remaining pulses. In theory, to ensure the accuracy of the current, the ratio of the high and low levels of the PWM waveform after pulse jumping within a group should be equal to the current duty cycle, that is: the total pulse width of the extracted pulses needs to be evenly dispersed and compensated to the pulse widths of the remaining pulses. This requires real-time calculation of the total pulse width of the extracted pulses, which has high requirements for computing power and great design difficulty.

[0073] Based on this, an embodiment of this solution adopts the lower limit point compensation method, that is: take the lower limit value (Duty L ) of the duty cycle interval in different pulse extraction quantity segments as the compensation width base number, and then calculate in combination with the pulse extraction quantity (N) in each segment and the remaining pulse quantity (16 - N) after extraction in each segment to obtain the duty cycle compensation amount Duty comp . The specific calculation formula for the duty cycle compensation amount Duty comp is:

[0074] Duty comp = Duty L × (N / (16 – N))

[0075] Duty2 = Duty1 + Duty comp

[0076] In the formula, Duty1 is the duty ratio before compensation, and Duty2 is the duty ratio after compensation.

[0077] In the method of compensating at the lower limit point, since there is a difference between the lower limit value Duty L of the duty ratio interval and the current real-time duty ratio, there is a difference in the PWM high-level time within each segment before and after compensation, resulting in a small drop in current. As the number of pulse extractions (N) increases, the coefficient multiplied by the lower limit value Duty L of the duty ratio interval becomes larger, and further causes the current drop to become more obvious. The specific simulation results are as Figure 5 shown.

[0078] To address the problem of the obvious current drop mentioned above, this solution introduces a method of shift processing, that is: simplify the duty ratio compensation amount Duty comp into a false fraction, move out the integer part of the simplification and replace the lower limit value Duty L of the duty ratio interval with the duty ratio value before compensation as the compensation basis. The true fraction part of the simplification still uses the lower limit value Duty L of the duty ratio interval as the compensation basis to reduce the error caused by the decrease in the coefficient multiplied by the lower limit value Duty L . At this time, the duty ratio value after compensation through shift processing based on the compensation at the lower limit point is:

[0079] Duty2 = Duty1 × (1 + floor(N / M - N)) + Duty L × ((N mod (M - N)) / (M - N))

[0080] In the formula, Duty2 is the duty ratio value after compensation, Duty1 is the duty ratio value before compensation, Duty L is the lower limit of the duty ratio of the duty ratio interval, floor() is the downward rounding formula, mod is the modulo operation, N is the number of pulse extractions in each duty ratio interval, and M is the number of PWM cycles.

[0081] An embodiment illustrates the shift processing with the extraction quantity N being 9 as follows:

[0082] By performing shift processing on Duty2 = Duty1 + Duty L * (9 / 7), we get Duty2 = Duty1 * 2 + Duty L * (2 / 7).

[0083] Substitute the formulas before and after the shift processing into the data respectively to calculate the duty cycle size after compensation. According to the extraction quantity of 9, from Figure 2 the lower limit value Duty of the current duty cycle range can be obtained L is 6%. Assume that the duty cycle value Duty1 before compensation is 6.8%.

[0084] Substituting into the formula before the shift processing, it can be obtained that the duty cycle value Duty2 after compensation is approximately 14.5%.

[0085] Substituting into the formula after the shift processing, it can be obtained that the duty cycle value Duty2 after compensation is approximately 15.3%.

[0086] Take the difference between the result of multiplying the duty cycle value Duty2 after compensation by the remaining pulse quantity 7 (i.e., PWM period 16 minus the pulse extraction quantity 9) and the result of multiplying the duty cycle value Duty1 before compensation by the PWM period 16, calculate the compensation error, and it can be obtained that the compensation error before the shift processing is 7.3%, and the compensation error after the shift processing is 1.7%. Thus, it can be known that the compensation error after the shift processing decreases, and the current drop decreases.

[0087] The simulation result after the shift processing is as Figure 6 shown. Compared with Figure 5 , Figure 6 there is an obvious improvement in the current drop, but there is still a small current drop in some duty cycle ranges.

[0088] For the duty cycle range where the current drop exceeds the preset threshold as described above, this solution introduces a segmented processing method. For example, Figure 5 the gray scale is adjusted from 1336 to 10 with a step of 10. The current drop corresponding to each step of the waveform should be about 2 mV, and the current drop here is about 7 mV. According to the size of the current drop, the duty cycle ranges with extraction quantities of 4, 5, 9, 11, and 13 are compensated in two segments. The specific compensation formula is:

[0089] a) If (Duty L + Duty H ) / 2 < Duty1 ≤ Duty H , then:

[0090] Duty2 = Duty1 + ((Duty L + Duty H ) / 2) × (N / (16 - N))

[0091] b) If Duty L < Duty1 ≤ (Duty L + Duty H ) / 2, then:

[0092] Duty2 = Duty1 + Duty L ×(N / (16 - N))

[0093] The duty cycle intervals with extraction quantities of 6, 7, and 10 are compensated in three segments. The specific compensation formula is:

[0094] a) If Duty H -(Duty H - Duty L ) / 3 < Duty1 ≤ Duty H , then:

[0095] Duty2 = Duty1 + (Duty H -(Duty H - Duty L ) / 3) × (N / (16 - N))

[0096] b) If Duty L +(Duty H - Duty L ) / 3 < Duty1 ≤ Duty H -(Duty H - Duty L ), then:

[0097] Duty2 = Duty1 + (Duty L +(Duty H - Duty L ) / 3) × (N / (16 - N))

[0098] c) If Duty L < Duty1 ≤ Duty L +(Duty H - Duty L ), then:

[0099] Duty2 = Duty1 + Duty L ×(N / (16 - N))

[0100] In an embodiment of this solution, based on the compensation at the lower limit point, combined with the shifting processing method and the segmented processing method, the duty cycle values after two - segment compensation are:

[0101] When Duty L < Duty1 ≤ (Duty L + Duty H ) / 2:

[0102] Duty2 = Duty1 × (1 + floor(N / 16 - N)) + Duty L×((N mod(16-N)) / (16-N))

[0103] When (Duty L +Duty H ) / 2 < Duty1 ≤ Duty H :

[0104] Duty2 = Duty1 × (1 + floor(N / 16-N)) + ((Duty H +Duty L ) / 2) × ((N mod(16-N)) / (16-N))

[0105] The duty ratio after three - stage compensation is:

[0106] When Duty L <Duty1 ≤ Duty L +(Duty H -Duty L ):

[0107] Duty2 = Duty1 × (1 + floor(N / 16-N)) + Duty L × ((N mod(16-N)) / (16-N))

[0108] When Duty L +(Duty H -Duty L ) / 3 < Duty1 ≤ Duty H -(Duty H -Duty L ):

[0109] Duty2 = Duty1 × (1 + floor(N / 16-N)) + (Duty L +(Duty H -Duty L ) / 3) × ((N mod(16-N)) / (16-N))

[0110] When Duty H -(Duty H -Duty L ) / 3 < Duty1 ≤ Duty H :

[0111] Duty2 = Duty1 × (1 + floor(N / 16-N)) + (Duty H -(Duty H -Duty L) / 3)×((N mod(16-N)) / (16-N))

[0112] One embodiment takes the duty cycle interval with a sampling quantity of 9 as an example to illustrate that the two-segment compensation formula is as follows:

[0113] a) If (Duty L +Duty H ) / 2 < Duty1 ≤ Duty H , then:

[0114] Duty2 = Duty1 × 2 + ((Duty L +Duty H ) / 2)×(2 / 7)

[0115] b) If Duty L < Duty1 ≤ (Duty L +Duty H ), then:

[0116] Duty2 = Duty1 × 2 + Duty L ×(2 / 7)

[0117] Suppose the duty cycle value Duty1 before compensation is 6.8%. According to Figure 2 , the lower limit value Duty L of the duty cycle interval obtained from the sampling quantity of 9 is 6%, and the upper limit value Duty H of the duty cycle interval is 7%. Substituting into the above compensation formula, the duty cycle value Duty2 after compensation is calculated to be approximately 15.4%. Taking the difference between the result of multiplying the duty cycle value Duty2 after compensation by the pulse remaining quantity 7 (PWM period 16 - pulse sampling quantity 9)) and the result of multiplying the duty cycle value Duty1 before compensation by the PWM period 16, the compensation error is calculated to be 1%. Compared with the compensation error of 1.7% after only performing shift processing on the basis of compensation at the lower limit point, further segment processing on the basis of compensation at the lower limit point and shift processing can further reduce the compensation error.

[0118] Combined with the above optimization processing, the final simulation result shows smooth current change, and the simulation result is as Figure 7 shown.

[0119] Those skilled in the art should know that the "high level" and "low level", "set" and "reset", "AND gate" and "OR gate", "in-phase input terminal" and "anti-phase input terminal" in the logical control involved in the specification or drawings can be interchanged or changed with each other, and the same functions or purposes as those in the above embodiments can be achieved by adjusting the subsequent logical control.

[0120] The description and application of the present invention herein are illustrative and are not intended to limit the scope of the present invention to the above embodiments. The relevant descriptions of effects or advantages, etc. involved in the specification may not be reflected in actual experimental examples due to uncertainties in specific condition parameters or other factors, and the relevant descriptions of effects or advantages, etc. are not used to limit the scope of the invention. Modifications and changes to the disclosed embodiments are possible, and various substitutions and equivalent components of the embodiments are known to those of ordinary skill in the art. Those skilled in the art should understand that the present invention can be implemented in other forms, structures, arrangements, proportions, and with other components, materials, and parts without departing from the spirit or essential characteristics of the present invention. Other modifications and changes can be made to the disclosed embodiments without departing from the scope and spirit of the present invention.

Claims

1. An adaptive frequency modulation method for an LED driving circuit, characterized in that: include: When the duty cycle of the LED driving channel is adjusted down to below a preset frequency reduction threshold, pulse extraction is performed, wherein the pulse extraction is performed by taking a rated number of PWM cycles as a group, and extracting a number of pulses from each group according to the duty cycle, wherein the number of pulses extracted increases as the duty cycle decreases; The total pulse width of the extracted pulses is evenly distributed to the remaining pulses, and the pulse width of the remaining pulses is compensated.

2. The adaptive frequency modulation method according to claim 1, characterized in that: The duty cycle is segmented to obtain a number of duty cycle intervals, each duty cycle interval corresponds to the extraction of a different number of pulses, and the difference between the upper and lower limits of the duty cycle of the duty cycle interval is the duty cycle interval width.

3. The adaptive frequency modulation method according to claim 1, characterized in that: The extracted pulses are evenly distributed in each group of PWM cycles.

4. The adaptive frequency modulation method according to claim 1 or 2, characterized in that: The width compensation includes: The duty cycle compensation coefficients of different duty cycle intervals are calculated based on the number of PWM cycles and the number of pulse extractions in each duty cycle interval; and the duty cycle compensation amount of each duty cycle interval is calculated based on the duty cycle compensation coefficients and the limits of different duty cycle intervals.

5. The adaptive frequency modulation method according to claim 4, characterized in that: Calculating the duty cycle compensation amount includes: The duty cycle lower limit value of different duty cycle intervals is used as the basis for pulse width compensation in the interval, and the duty cycle compensation amount and the duty cycle value after compensation are calculated as follows: Duty comp =Duty L ×(N / (M-N)) Duty2=Duty1+Duty comp In the formula, Duty comp Duty is the duty cycle compensation amount, L is the duty cycle lower limit of the duty cycle interval, N is the number of pulses extracted in the duty cycle interval, M is the number of PWM cycles, N / (MN) is the duty cycle compensation coefficient, Duty1 is the duty cycle value before compensation, and Duty2 is the duty cycle value after compensation.

6. The adaptive frequency modulation method according to claim 4, characterized in that: Calculating the duty cycle compensation amount includes: The integer part of the duty cycle compensation coefficient is used as the independent compensation coefficient of the duty cycle in the interval, and the duty cycle value before compensation is used as the independent compensation basis of the pulse width in the interval, and the independent compensation component of the duty cycle in the interval is calculated; The true fraction part of the duty cycle compensation coefficient is used as the duty cycle supplementary compensation coefficient of the interval, and the duty cycle lower limit value of the duty cycle interval is used as the supplementary compensation basis of the pulse width of the interval, and the duty cycle supplementary compensation component of the interval is calculated; The duty cycle independent compensation component and the duty cycle supplementary compensation component are summed to obtain the duty cycle compensation amount of the interval.

7. The adaptive frequency modulation method according to claim 6, characterized in that: The duty cycle value after the compensation is calculated as: Duty2=Duty1×(1+floor(N / M-N))+Duty L ×((N mod(M-N)) / (M-N)) In the formula, Duty2 is the duty cycle value after compensation, Duty1 is the duty cycle value before compensation, and Duty L is the lower limit of the duty cycle in the duty cycle interval, floor() is the rounding formula, mod is the modulo operation, N is the number of pulses extracted in each duty cycle interval, and M is the number of PWM cycles.

8. The adaptive frequency modulation method according to claim 5 or 6, characterized in that: Calculating the duty cycle compensation amount includes: segmenting the duty cycle interval in which the current drops below a preset threshold according to the number of PWM cycles, the number of pulse extractions in the duty cycle interval, and the upper limit and lower limit of the duty cycle interval, and calculating the duty cycle compensation amount.

9. The adaptive frequency modulation method according to claim 8, characterized in that: The duty cycle range is divided into two sections and the duty cycle value after compensation is calculated as: When Duty L <Duty1≤(Duty L +Duty H ) / 2, the duty cycle after compensation is: Duty2=Duty1×(1+floor(N / M-N))+Duty L ×((N mod(M-N)) / (M-N)) When (Duty L +Duty H ) / 2<Duty1≤Duty H When , the duty cycle after compensation is: Duty2=Duty1×(1+floor(N / M-N))+((Duty H +Duty L ) / 2)×((N mod(M-N)) / (M-N)) In the formula, floor() is the rounding down formula, mod is the modulus operation, and Duty is L Duty is the lower limit of the duty cycle interval. H is the duty cycle upper limit value of the duty cycle interval, N is the number of pulse extractions in the duty cycle interval, M is the number of PWM cycles, Duty1 is the duty cycle value before compensation, and Duty2 is the duty cycle value after compensation.

10. The adaptive frequency modulation method according to claim 8, characterized in that: The duty cycle interval is divided into three sections and the duty cycle value after compensation is calculated as follows: When Duty L <Duty1≤Duty L +(Duty H -Duty L ) / 3, the duty cycle after compensation is: Duty2=Duty1×(1+floor(N / M-N))+Duty L ×((N mod(M-N)) / (M-N)) When Duty L +(Duty H -Duty L ) / 3<Duty1≤Duty H -(Duty H -Duty L ) / 3, the duty cycle after compensation is: Duty2=Duty1×(1+floor(N / M-N))+(Duty L +(Duty H -Duty L ) / 3)×((N mod(M-N)) / (M-N)) When Duty H -(Duty H -Duty L ) / 3<Duty1≤Duty H When , the duty cycle after compensation is: Duty2=Duty1×(1+floor(N / M-N))+(Duty H -(Duty H -Duty L ) / 3)×((N mod(M-N)) / (M-N)) In the formula, floor() is the rounding down formula, mod is the modulus operation, and Duty L Duty is the lower limit of the duty cycle interval. H is the duty cycle upper limit value of the duty cycle interval, N is the number of pulse extractions in the duty cycle interval, M is the number of PWM cycles, Duty1 is the duty cycle value before compensation, and Duty2 is the duty cycle value after compensation.

11. An adaptive frequency modulation circuit, characterized in that: include: A dimming control module, used to adjust the duty cycle of the LED driving channel according to the dimming signal; A pulse extraction module, for extracting a number of pulses from a rated number of PWM cycles according to the duty cycle when the duty cycle is reduced to below a preset frequency reduction threshold, wherein the number of pulses extracted increases as the duty cycle decreases; The pulse compensation module is used to evenly distribute the total pulse width of the extracted pulses to the remaining pulses and perform width compensation on the pulse width of the remaining pulses.

12. The adaptive frequency modulation circuit according to claim 11, characterized in that: The pulse compensation module comprises: A compensation coefficient calculation unit, used for calculating a duty cycle compensation coefficient of each duty cycle interval based on the number of PWM cycles and the number of pulse extractions in each duty cycle interval; The compensation amount calculation unit is used to calculate the duty cycle compensation amount based on the duty cycle compensation coefficient and the pulse width compensation basis.

13. The adaptive frequency modulation circuit according to claim 12, characterized in that: The pulse width compensation basis is the duty cycle lower limit value of the duty cycle interval.

14. The adaptive frequency modulation circuit according to claim 12, characterized in that: The integer part of the duty cycle compensation coefficient is the duty cycle independent compensation coefficient, and the independent compensation basis of the pulse width corresponding to the duty cycle value before compensation; The true fraction part of the duty cycle compensation coefficient is the duty cycle supplementary compensation coefficient, and the corresponding pulse width supplementary compensation basis is the duty cycle lower limit value of the duty cycle interval.

15. The adaptive frequency modulation circuit according to claim 11, characterized in that: The pulse compensation module comprises: The segmented compensation unit is used to perform segmented compensation for the duty cycle interval where the current drops below a preset threshold according to the number of PWM cycles, the number of pulse extractions in the duty cycle interval, and the upper limit and lower limit of the duty cycle interval.

16. A driving circuit, characterized in that: It comprises the adaptive frequency modulation circuit as described in any one of claims 11-15.

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