A deep flicker-free PWM dimming method

Abstract

The present invention discloses a deep flicker-free PWM dimming method, in which the dimming PWM frequency is fixed and ≥10KHz, and the dimming is performed from a maximum value to a minimum value, comprising the following steps: step 1, in the process of dimming from 100% to X1%, the driving voltage is maintained at the rated output voltage U1, and the dimming is performed in a manner of changing the duty cycle, and the corresponding duty cycle is adjusted from 100% to A%; step 2, in the process of dimming from X1% to X2%, the duty cycle of the dimming PWM is increased from A% to B%, and the driving voltage is reduced from the rated output voltage U1 to voltage U2; step 3, in the process of dimming from X2% to 0, the driving voltage is maintained at voltage U2, and the dimming is performed in a manner of changing the duty cycle, and the duty cycle of the dimming PWM is adjusted from B% to 0; wherein, B>X2.

Description

Technical Field

[0001] The invention relates to the technical field of PWM dimming, and in particular to a deep flicker-free PWM dimming method. Background Art

[0002] Existing LED dimming generally adopts PWM dimming technology, and the general dimming frequency is 500HZ-2KHZ. There is still flicker in the dimming within this frequency range, and frequency ripples will appear when shooting with a camera, which cannot meet the requirements of existing healthy lighting for flicker. The 2KHZ-10KHZ PWM dimming has a certain improvement in frequency ripples because the frequency is increased, but there will be noise in this range of dimming. The human ear is most sensitive to this range of hearing. As the frequency increases, the loss of the MOS tube increases, the heat increases, and it cannot be linear at low brightness. Generally, it cannot be distinguished below a duty cycle of 3%, and deep dimming of 0.01% cannot be achieved. In order to increase the dimming depth, most manufacturers will use frequency reduction, such as starting to reduce the frequency below 10%, and reducing the frequency to 500HZ at the lowest brightness, thus achieving a dimming depth of 0.01% and reducing MOS loss. However, the biggest problem is that there is also frequency ripple in the process of frequency conversion, and the ripple gradually increases as the frequency decreases. Summary of the invention

[0003] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a deep flicker-free PWM dimming method which is flicker-free in the entire PWM dimming range, especially at low brightness, which not only ensures the dimming depth but also improves the dimming experience.

[0004] According to the deep flicker-free PWM dimming method of the embodiment of the present invention, the dimming PWM frequency is fixed and ≥10KHz, and the dimming is from the maximum value to the minimum value, including the following steps:

[0005] Step 1: During dimming from 100% to X1%, the driving voltage is kept at the rated output voltage U1, and dimming is performed by changing the duty cycle, corresponding to the duty cycle being adjusted from 100% to A%;

[0006] Step 2, when the dimming is reduced from X1% to X2%, the duty cycle of the dimming PWM increases from A% to B%, and the driving voltage decreases from the rated output voltage U1 to voltage U2;

[0007] Step 3, during the dimming process from X2% to 0, the driving voltage is maintained at voltage U2, and dimming is performed by changing the duty cycle, and the duty cycle of the dimming PWM is adjusted from B% to 0; wherein B>X2.

[0008] The deep flicker-free PWM dimming method according to the embodiment of the present invention has at least the following beneficial effects: first, the dimming PWM frequency is fixed and ≥10KHz. In the dimming range of X1%~100%, the driving voltage is kept at the rated output voltage U1, and the dimming is performed by changing the duty cycle, corresponding to the duty cycle range of A%~100%. Since the higher the brightness, the less sensitive the human eye is to the change in brightness, the dimming in the X1%~100% section does not need to be so delicate, which can reduce the loss of the MOS tube in this section. When the dimming is reduced from X1% to X2%, the driving voltage is reduced from the rated output voltage U1 to the voltage U2, the dimming PWM frequency is fixed, and the brightness of X2% is guaranteed by increasing the PWM duty cycle. This balance point can be set at a duty cycle of B%, that is, when the dimming is reduced from X1% to X2%, the duty cycle begins to increase to maintain the brightness at X2%, and when the duty cycle increases to about B%, the driving voltage stops decreasing to stabilize at the voltage U2. When dimming continues to drop from X2% to 0, the driving voltage remains at voltage U2, and the duty cycle continues to drop from B%. Since the driving voltage drops to voltage U2 at X2%, the PWM duty cycle has reached B%. When dimming from 0 to X2%, the brightness is adjusted by adjusting the PWM duty cycle. Since the driving voltage drops to voltage U2, there is a duty cycle of B% that can be adjusted, where B is greater than X2, while conventional technology generally only has a duty cycle of X2% that can be adjusted. This is equivalent to improving the dimming fineness by B / X2 times, which is equivalent to refining the dimming depth of 0~X2%. When dimming at low brightness, the brightness changes more gently, the visual effect is better, and it is better for the health of the human eye. And because the frequency of the dimming PWM has never changed, and a fixed frequency of more than 10KHZ has been used, conventional camera tools will not produce flicker during the dimming process, and there is no noise that can be heard by the human ear.

[0009] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings;

[0011] Figure 1 It is a schematic diagram of the deep flicker-free PWM dimming method from bright to dark;

[0012] Figure 2 It is a schematic diagram of the deep flicker-free PWM dimming method from dark to bright. DETAILED DESCRIPTION

[0013] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0014] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0015] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0016] Reference Figure 1 to Figure 2 The present invention provides a deep flicker-free PWM dimming method, the dimming PWM frequency is fixed and ≥10KHz, taking brightness adjustment as an example, from the brightest to the darkest, such as Figure 1 As shown, the following steps are included:

[0017] Step 1: During dimming from 100% to X1%, the driving voltage is kept at the rated output voltage U1, and dimming is performed by changing the duty cycle, corresponding to the duty cycle being adjusted from 100% to A%;

[0018] Step 2: When dimming is reduced from X1% to X2%, the duty cycle of dimming PWM increases from A% to B%, and the driving voltage decreases from the rated output voltage U1 to voltage U2;

[0019] Step 3, during the dimming process from X2% to 0, the driving voltage is kept at voltage U2, and dimming is performed by changing the duty cycle, and the duty cycle of the dimming PWM is adjusted from B% to 0;

[0020] Among them, B>X2.

[0021] like Figure 2 , repeat the above steps 1 to 3 in reverse to get a curve graph from the darkest to the brightest.

[0022] In general embodiments, the low brightness range is 0~10%, so A=X2≤10. Of course, the values ​​of A and X2 are not limited to ≤10. The values ​​of B and X1 only need to be greater than X2. Preferably, B≥90. Therefore, in the process of dimming from 10% to 0, more than 90% of the duty cycle is adjustable, while conventionally only 10% of the duty cycle is adjustable. This is equivalent to improving the dimming fineness by more than 9 times.

[0023] Take X1=12, A=X2=10, B=90 as an example: First, the dimming PWM frequency is fixed and ≥10KHz. In the dimming range of 12%~100%, the driving voltage is kept at the rated output voltage U1, and the dimming is performed by changing the duty cycle. The corresponding duty cycle range is 12%~100%. Since the higher the brightness, the less sensitive the human eye is to the change in brightness, the dimming in the 12%~100% range does not need to be so delicate, which can reduce the loss of the MOS tube in this section. When the dimming is reduced from 12% to 10%, the driving voltage is reduced from the rated output voltage U1 to the voltage U2, and the dimming PWM frequency is fixed. The brightness of 10% is guaranteed by increasing the PWM duty cycle. This balance point can be set at a duty cycle of 90%, that is, when the dimming drops to 10%, the duty cycle begins to increase to maintain the brightness at 10%. When the duty cycle increases to about 90%, the driving voltage stops decreasing to stabilize at the voltage U2. When the dimming continues to drop from 10% to 0, the driving voltage remains at voltage U2, and the duty cycle continues to drop from 90%. Since the driving voltage drops to voltage U2 at 10%, the PWM duty cycle has reached 90%. When dimming in the range of 0~10%, the brightness is adjusted by adjusting the PWM duty cycle. Since the driving voltage drops to voltage U2, 90% of the duty cycle is adjustable, while conventional technology generally only has 10% of the duty cycle adjustable. This is equivalent to increasing the dimming fineness by 9 times, which is equivalent to refining the dimming depth of 0~10%. When dimming at low brightness, the brightness changes more gently, the visual effect is better, and it is better for the health of the human eye. And because the frequency of the dimming PWM has never changed and has always used a fixed frequency of more than 10KHZ, conventional camera tools will not produce flicker during the dimming process, and there is no noise that can be heard by the human ear.

[0024] That is, the PWM frequency remains fixed during the whole process, and a PWM frequency of more than 10KHZ is used, which will neither generate dimming noise nor dimming frequency ripple, while ensuring the dimming depth and fineness of low-brightness dimming.

[0025] The flicker-free PWM dimming method is not limited to brightness adjustment and can also be used in multi-channel applications of dimming and color temperature adjustment, such as adjusting color temperature and brightness through two-way PWM and adjusting RGB through three-way PWM.

[0026] It is easy for those skilled in the art to understand that the above preferred embodiments can be freely combined and superimposed without conflict.

[0027] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or directly or indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A deep flicker-free PWM dimming method, characterized in that: The dimming PWM frequency is fixed and ≥10KHz, and the dimming from the maximum value to the minimum value includes the following steps: Step 1: During dimming from 100% to X1%, the driving voltage is kept at the rated output voltage U1, and dimming is performed by changing the duty cycle, corresponding to the duty cycle being adjusted from 100% to A%; Step 2: When dimming is reduced from X1% to X2%, the duty cycle of dimming PWM increases from A% to B%, and the driving voltage decreases from the rated output voltage U1 to voltage U2; Step 3, during the dimming process from X2% to 0, the driving voltage is kept at voltage U2, and dimming is performed by changing the duty cycle, and the duty cycle of the dimming PWM is adjusted from B% to 0; Among them, B > X2.

2. A deep flicker-free PWM dimming method according to claim 1, characterized in that: To dim from minimum to maximum, repeat steps 1 to 3 in reverse.

3. The deep flicker-free PWM dimming method according to claim 1, characterized in that: A=X2≤10.

4. The deep flicker-free PWM dimming method according to claim 1, characterized in that: B≥90。 5. The deep flicker-free PWM dimming method according to claim 1, characterized in that: Dimming from maximum to minimum includes dimming from brightest to darkest and from highest color temperature to lowest color temperature.

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