CN110996441B - Dimming method of LED driving device - Google Patents
Dimming method of LED driving device Download PDFInfo
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- CN110996441B CN110996441B CN201911216635.4A CN201911216635A CN110996441B CN 110996441 B CN110996441 B CN 110996441B CN 201911216635 A CN201911216635 A CN 201911216635A CN 110996441 B CN110996441 B CN 110996441B
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Abstract
The invention discloses a dimming method of an LED driving device, wherein the LED driving device comprises an LED lamp, a microprocessor and N +1 constant current source branches electrically connected with the microprocessor, and the dimming method comprises the steps that the microprocessor sets the clock frequency in the microprocessor to be GCLK and the PWM period output to each constant current source branch by the microprocessor to be Tn+1(ii) a The microprocessor determines that the input PWM subdivision gray level of each constant current source branch is gn+1＝GCLK/Tn+1Then, the sub-division gray scale of the LED driving device is G ═ N +1) Gn+1(ii) a And the microprocessor controls the PWM signal output to each constant current source branch and adjusts the current subdivision precision of the LED driving device. The embodiment of the invention can increase the LED dimming gray scale subdivision level and precision on the basis of realizing large-current driving.
Description
Technical Field
The invention relates to the field of circuits, in particular to a dimming method for realizing LED dimming gray level progression by an LED driving device for realizing constant current expansion through low-end current sampling.
Background
Because of the unique advantages of extremely high luminous efficiency and no mercury pollution, the LED is recognized as the most ideal green illumination light source at present, and the vigorous development and popularization of LED illumination become the mainstream of modern illumination development. With the advent of high power LEDs, the current driving the LEDs also ranges from the first few milliamps to tens of amps, and the LED dimming gray scale also increases from 8 bits to over 16 bits. However, the inventors of the present invention have found, in a study on the prior art, that only the accuracy of a large current can be ensured in an LED driver having a large current of several amperes to several tens of amperes, and therefore it is difficult to control the current accuracy of several milliamperes simply by increasing the dimming gradation ratio.
Disclosure of Invention
The invention provides a dimming method of an LED driving device, which aims to solve the technical problem that the existing large-current driver is difficult to realize the precision control of small current.
In order to solve the above technical problem, an embodiment of the present invention provides a dimming method for an LED driving device, where the LED driving device includes an LED lamp, a microprocessor, and N +1 constant current source branches electrically connected to the microprocessor, where N is an integer greater than or equal to 1; the input end of the LED lamp is connected with the positive electrode of a power supply, the output end of the LED lamp is respectively connected with the input end of each constant current source branch, and the output end of each constant current source branch is connected with the negative electrode of the power supply; the dimming method comprises the following steps:
the microprocessor sets the clock frequency in the microprocessor to be GCLK, and the PWM period output to each constant current source branch by the microprocessor is Tn+1；
The microprocessor determines that the input PWM subdivision gray level of each constant current source branch is gn+1＝GCLK/Tn+1Then, the sub-division gray scale of the LED driving device is G ═ N +1) Gn+1；
And the microprocessor controls the PWM signal output to each constant current source branch and adjusts the current subdivision precision of the LED driving device.
Preferably, when the microprocessor modulates the light of the LED driving device, the microprocessor outputs PWM signals to the N +1 constant current source branches one by one at a preset phase difference time interval.
Preferably, each of the constant current source branches includes a constant current source, an input end of the constant current source is connected to an output end of the LED lamp, and an output end of the constant current source is connected to a negative electrode of the power supply.
As a preferred scheme, each constant current source branch further comprises a unidirectional conduction diode connected between the LED lamp and the corresponding constant current source, an input end of the unidirectional conduction diode is connected with an output end of the LED lamp, and an output end of the unidirectional conduction diode is connected with an input end of the corresponding constant current source.
Preferably, the constant current source includes, but is not limited to, an MBI6662 driver.
Preferably, the constant current source includes, but is not limited to, a constant current source providing a constant 2A current.
Preferably, the negative electrode of the power supply is grounded.
Preferably, the dimming method of the LED driving apparatus further includes a microprocessor, and a control terminal of the microprocessor is connected to each of the constant current sources.
To sum up, the embodiment of the invention provides a dimming method of an LED driving device, which has the following beneficial effects:
the parallel connection of a plurality of constant current sources is realized through low-end current sampling, the expansion of LED driving current can be realized, and the current flowing through the LED lamp is the linear superposition of the constant current sources of N +1 constant current source branches, so that the large-current constant-current driving high-power LED circuit is realized through small-current driving combination. In addition, each constant current source can work independently and be controlled independently, and the mutual interference is avoided, so that the stability of the driving circuit can be improved.
The dimming method based on the LED driving device comprises the steps of utilizing a multi-path constant current source circuit to parallelly extend LED driving current, then carrying out independent PWM subdivision dimming on each path of constant current source, and controlling multi-path PWM signal output by a microprocessor, so that each path of PWM can be independently controlled, and the PWM modulation adopts a modulation mode with fixed period and variable pulse width, so that the output current of the constant current source and the PWM pulse width are in a direct proportion relation.
The invention adopts a multi-path PWM phase difference output method, namely, each path of PWM phase is asynchronous and has fixed phase difference, thus only one path of constant current source switch is opened to work in a certain narrow pulse output time range, and the influence of mutual crosstalk on the stability of low-gray dimming when the constant current sources work is effectively avoided.
Drawings
Fig. 1 is a flowchart illustrating steps of a dimming method of an LED driving apparatus according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of an LED driving apparatus according to an embodiment of the present invention;
fig. 3 is a circuit diagram of an LED driving apparatus according to an embodiment of the present invention;
fig. 4 is a multi-PWM equipartition phase waveform diagram of a dimming method of an LED driving apparatus according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 2 and fig. 3, an embodiment of the present invention provides an LED driving apparatus, including an LED lamp, a microprocessor, and N +1 constant current source branches electrically connected to the microprocessor, where N is an integer greater than or equal to 1;
the input end of the LED lamp is connected with the positive electrode of a power supply, the output end of the LED lamp is respectively connected with the input end of each constant current source branch, and the output end of each constant current source branch is connected with the negative electrode of the power supply ground.
In this embodiment, the parallel connection of multiple constant current sources is realized by sampling the low-end current, the expansion of the LED driving current can be realized, and the current flowing through the LED lamp is linearly superposed by the constant current sources of N +1 constant current source branches, so that the large-current constant-current driving high-power LED circuit is realized by small-current driving combination. In addition, each constant current source can work independently and be controlled independently, and the mutual interference is avoided, so that the stability of the driving circuit can be improved. The input end of the LED lamp is the anode of the LED lamp, and the output end of the LED lamp is the cathode of the LED lamp.
Based on the LED driving apparatus, the present invention provides a dimming method, as shown in fig. 1, including the following steps:
s1, setting the clock frequency in the microprocessor to GCLK and the PWM period from the microprocessor to each constant current source branch to Tn+1；
S2, the microprocessor determines PWM subdivision gray scale and the like of each constant current source branch inputGrade gn+1＝GCLK/Tn+1Then, the sub-division gray scale of the LED driving device is G ═ N +1) Gn+1；
And S3, the microprocessor controls the PWM signal output to each constant current source branch and adjusts the subdivision current precision of the LED driving device.
In this embodiment, the low-side current sampling circuit is used to realize the multi-path constant current source to expand the LED current, and then each path of constant current source is subjected to independent PWM subdivision dimming:
wherein, the clock frequency of the microprocessor is GCLK, and the PWM period is determined to be Tn+1Then PWM subdivides the class gn+1＝GCLK/Tn+1。
At a determined PWM period Tn+1Then, the higher the clock frequency of the microprocessor, the higher the PWM subdivision level, which is limited per path.
Thus, the multi-path constant current source can be realized to expand the subdivision gray level number, for example, each path of constant current source input PWM subdivision gray level is gn+1The sub-divided gray scale of the N +1 constant current sources is added to be G ═ N +1) Gn+1；
In addition, it should be noted that, in order to generate multiple paths of PWM dimming signals, the microprocessor is used to control the multiple paths of PWM signal output, so that each path of PWM independently controls the gray scale output; the PWM modulation adopts a modulation mode with fixed period and variable pulse width, so that the output current of the constant current source is in direct proportion to the PWM pulse width.
LED driving current is expanded by utilizing a plurality of paths of constant current source circuits in parallel, then independent PWM subdivision dimming is carried out on each path of constant current source, and because each path of constant current source independently drives the LED current, the total current I flowing through the LED is equal to the sum of the currents flowing through each constant current source; similarly, each path of PWM dimming independently subdivides each path of constant current source current, so that the total dimming gray level G is equal to the sum of the added PWM dimming gray levels;
in the dimming method of the LED driving circuit provided by the embodiment of the present invention, in order to generate multiple paths of PWM dimming signals, a microprocessor is used to control multiple paths of PWM signal outputs, so that each path of PWM can be independently controlled. The PWM modulation adopts a modulation mode with fixed period and variable pulse width, so that the output current of the constant current source is in direct proportion to the PWM pulse width.
When multiple paths of PWM output narrow pulse dimming signals, in order to prevent the phenomenon of micro-flicker in LED low-gray dimming caused by mutual interference between the constant current sources, the embodiment adopts a method of multiple paths of PWM phase difference output, that is, the phases of the PWM are asynchronous, and a fixed phase difference exists. Therefore, only one constant current source switch is turned on to work within a certain narrow pulse output time range, and the influence of mutual crosstalk on the stability of low-gray dimming during the work of the constant current sources is effectively avoided.
With continued reference to fig. 2, in a preferred embodiment, each of the constant current source branches includes a constant current source, an input terminal of the constant current source is connected to an output terminal of the LED lamp, and an output terminal of the constant current source is connected to a negative terminal of the power supply. Preferably, each constant current source branch further comprises a unidirectional conduction diode connected between the LED lamp and the corresponding constant current source, an input end of the unidirectional conduction diode is connected with an output end of the LED lamp, and an output end of the unidirectional conduction diode is connected with an input end of the corresponding constant current source. Through connecting a unidirectional conducting diode in each constant current source branch in series, mutual crosstalk between constant current sources can be effectively prevented, and therefore the stability of the driving circuit is improved.
As an example, when the dimming method of the LED driving apparatus has 2 constant current source branches, the input terminal of the constant current source I1 is connected to the negative terminal of the diode D1, the input terminal of the constant current source I2 is connected to the negative terminal of the diode D2, the output terminals of the constant current source I1 and the constant current source I2 are connected together to the negative terminal of the power ground, and the circuits passing through the constant current source I1 and the constant current source I2 are I1 and I2, respectively, the current I passing through the LED lamp is I1+ I2, so that the linear superposition of the driving current passing through the LED is realized through the 2 constant current sources.
When the dimming method of the LED driving device has 3 or more than 3 constant current source branches, as shown In fig. 2 and 3, and multiple constant current sources are used In a superimposed manner, the current I flowing through the LED lamp is I1+ I2+ … + In.
Referring to fig. 3, in one possible implementation, the constant current source is an MBI6662 driver, the constant current source is a constant current source providing a constant 2A current, and the dimming method of the LED driving apparatus further includes a microprocessor, a control terminal of the microprocessor is connected to each of the constant current sources, and the microprocessor can control whether the constant current sources participate in operation, so as to control the independent operation of each of the constant current sources, which does not interfere with each other, and has high circuit stability. It should be noted that the driver chip model MBI6662 and the provision of the 2A current are only one possible embodiment of the present invention, and the constant current source may have other options, and is not limited to the driver chip model MBI6662, and the constant current source is not limited to the constant current source providing only the constant 2A current.
In an embodiment of the present invention, the dimming method further includes:
and S4, the microprocessor outputs PWM signals to the N +1 constant current source branches one by one at preset phase difference time intervals when the LED driving device is subjected to dimming.
In this embodiment, when multiple PWM outputs the narrow pulse dimming signal, in order to prevent the micro-flicker phenomenon in the low-gray dimming of the LED caused by the mutual interference between the constant current sources, the multiple PWM phase difference output method is adopted, that is, the PWM phases are not synchronous, and there is a fixed phase difference.
Therefore, only one constant current source switch is switched on to work within a certain narrow pulse output time range, the influence of mutual crosstalk on the stability of low-gray dimming during the work of the constant current sources is effectively avoided, and multi-path PWM phase difference output modulation is realized.
As shown in fig. 4, the microprocessor outputs 5 equal-period T PWM signals, the phase difference Tm between every two adjacent PWM signals is T/5, the narrow pulse output time is T, and when T is much less than the PWM period T, the constant current sources are sequentially turned on for operation within the effective on-time of T, thereby avoiding the influence of crosstalk caused by simultaneous operation on the stability of small signal output.
In summary, the present invention provides a dimming method of an LED driving apparatus, which has the following functions:
1. LED driving current is expanded through the parallel connection of a plurality of paths of constant current source circuits, and the LED current flowing through the LED is linearly superposed, so that the LED current is expanded;
2. independent PWM subdivision dimming is carried out on each path of constant current source circuit, and a microprocessor is adopted to control multi-path PWM subdivision output; the PWM modulation adopts a modulation mode with fixed period and variable pulse width;
3. the total gray level number G of LED dimming subdivision is equal to the sum of the subdivision gray levels G of each constant current source;
4. each path of constant current source can work independently and is controlled independently without mutual interference;
5. each path of constant current source is isolated through a one-way conduction diode, so that mutual crosstalk between the constant current sources is prevented;
6. the multi-channel PWM adopts a microprocessor to control the output of the equal phase.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Claims (7)
1. The dimming method of the LED driving device is characterized in that the LED driving device comprises an LED lamp, a microprocessor and N +1 constant current source branches electrically connected with the microprocessor, wherein N is an integer greater than or equal to 1; the input end of the LED lamp is connected with the positive electrode of a power supply, the output end of the LED lamp is respectively connected with the input end of each constant current source branch, and the output end of each constant current source branch is connected with the negative electrode of the power supply; the dimming method comprises the following steps:
the microprocessor sets the clock frequency in the microprocessor to be GCLK, and the PWM period output to each constant current source branch by the microprocessor is Tn+1(ii) a Wherein N +1 represents the N +1 path PWM signal in the N +1 constant current source branches electrically connected with the microprocessor, and N is an integer greater than or equal to 0;
said microprocessor determining each of said constant current sourcesBranch input PWM subdivision gray scale of gn+1＝GCLK/Tn+1Then, the sub-division gray scale of the LED driving device is G ═ N +1) Gn+1；
And the microprocessor controls the PWM signal output to each constant current source branch and adjusts the current subdivision precision of the LED driving device.
2. The dimming method of an LED driving apparatus according to claim 1, wherein the method further comprises:
and when the microprocessor regulates the light of the LED driving device, the microprocessor outputs PWM signals to the N +1 constant current source branches one by one at a preset phase difference time interval.
3. The dimming method of an LED driving apparatus according to claim 1, wherein each of the constant current source branches includes a constant current source, an input terminal of the constant current source is connected to an output terminal of the LED lamp, and an output terminal of the constant current source is connected to a negative terminal of the power supply.
4. The dimming method of an LED driving apparatus according to claim 3, wherein each of the constant current source branches further comprises a unidirectional conducting diode connected between the LED lamp and the corresponding constant current source, an input terminal of the unidirectional conducting diode is connected to an output terminal of the LED lamp, and an output terminal of the unidirectional conducting diode is connected to an input terminal of the corresponding constant current source.
5. The dimming method of the LED driving apparatus according to claim 3 or 4, wherein the constant current source comprises an MBI6662 driver.
6. The dimming method of an LED driving apparatus according to claim 3 or 4, wherein the constant current source comprises a constant current source supplying a constant 2A current.
7. The dimming method of an LED driving apparatus according to claim 3, further comprising a microprocessor, wherein a control terminal of the microprocessor is connected to each of the constant current sources.
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| JP2015043041A (en) * | 2013-08-26 | 2015-03-05 | 三星ディスプレイ株式會社Ｓａｍｓｕｎｇ Ｄｉｓｐｌａｙ Ｃｏ．，Ｌｔｄ． | Electro-optic device |
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| CN103003768A (en) * | 2010-06-29 | 2013-03-27 | 株式会社理光 | Constant current circuit and light emitting diode driving device using the same |
| CN103310735A (en) * | 2013-06-27 | 2013-09-18 | 深圳市明微电子股份有限公司 | Display control method and display control system both supportive of gray level expansion |
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