CN117479380A - Stroboflash-free LED driven dimming system and method - Google Patents

Stroboflash-free LED driven dimming system and method Download PDF

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Publication number
CN117479380A
CN117479380A CN202311721452.4A CN202311721452A CN117479380A CN 117479380 A CN117479380 A CN 117479380A CN 202311721452 A CN202311721452 A CN 202311721452A CN 117479380 A CN117479380 A CN 117479380A
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China
Prior art keywords
duty ratio
control signal
control
signal
control unit
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CN202311721452.4A
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Chinese (zh)
Inventor
白磊
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Shanghai Fu Lift Lighting Technology Co ltd
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Shanghai Fu Lift Lighting Technology Co ltd
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Priority to CN202311721452.4A priority Critical patent/CN117479380A/en
Publication of CN117479380A publication Critical patent/CN117479380A/en
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/32—Pulse-control circuits
    • H05B45/325—Pulse-width modulation [PWM]
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/10—Controlling the intensity of the light
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • H05B45/59—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits for reducing or suppressing flicker or glow effects

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  • Circuit Arrangement For Electric Light Sources In General (AREA)

Abstract

The invention discloses a dimming system and a dimming method driven by a stroboscopic-free LED, which belong to the field of illumination and comprise the following steps: the duty ratio signal is obtained after an external PWM input signal is received, the duty ratio signal is compared with a duty ratio preset interval, when the duty ratio signal falls in the duty ratio preset interval, the brightness control of the LED is realized by only adjusting the duty ratio of the MOS tube so as to control the output current, when the duty ratio signal does not belong to the duty ratio preset interval, the PWM control signal frequency and the PWM control signal period are controlled by the duty ratio control unit and the period control unit, the number of periods passing through a certain period is controlled, the more accurate control of the output current is realized, and the control gray level of the driving circuit is improved on the premise that the dimming process is free of stroboscopic.

Description

Stroboflash-free LED driven dimming system and method
Technical Field
The invention relates to the field of illumination, in particular to a dimming system and method driven by a stroboscopic-free LED.
Background
With the improvement of life quality and health care of people, people are paying more attention to lamplight stroboscopic effect, and low-frequency lamplight stroboscopic effect can have influence on human health and safety, especially on eyes. The stroboscopic is the stroboscopic that causes when the light modulation appointed gray scale, the LED lamp pearl electric current changes, and is irrelevant with frequency. The non-stroboscopic state indicates that the current flowing through the LED lamp beads does not change drastically (current is cut off) when dimming is performed to designate any gray level, and thus the stroboscopic state is not caused. The stroboscopic-free dimming technology is suitable for conventional household and commercial illumination, is also suitable for high-speed cameras (frame frequency is greater than 2K) used for photography and scientific research, and ensures that films and photos shot by the high-speed cameras are free of stripes.
In the process of implementing the present invention, the inventor finds that at least the following technical problems exist in the prior art:
at present, in order to realize strobe-free dimming, a method for adjusting a reference voltage of a comparator to perform strobe-free dimming is generally adopted, but the gray level of the method is still too low to meet the requirement of users on low brightness.
Disclosure of Invention
In order to solve the above problems, the present invention aims to provide a dimming technology driven by a stroboscopic-free LED, which aims to achieve full-range stroboscopic-free dimming while increasing the gray level from 100 to 1000 or more.
To achieve the above technical object, the present application provides a dimming system driven by a stroboscopic-free LED, including:
the PWM input unit is used for acquiring a PWM dimming signal of an external control circuit, judging the duty ratio of the PWM dimming signal by counting the high level and the low level, and generating duty ratio information, wherein the external control circuit represents an external LED circuit formed by serially connected lamp beads;
the error amplifier is used for generating comparison information after comparing and amplifying the feedback voltage of the MOS tube source electrode of the external LED circuit with the set reference voltage and inputting the comparison information into the DC-DC control unit;
the DC-DC control unit is used for generating a first control signal and a second control signal according to the duty ratio information and the comparison information;
the duty ratio control unit is used for generating a constant-current duty ratio control signal according to the first control signal and constant-current working frequency and duty ratio information corresponding to the PWM dimming signal;
and the period control unit is used for counting the constant-current duty ratio control signal according to the second control signal and controlling the passing period number.
Preferably, one end of the error amplifier is connected to a reference voltage unit for generating a reference voltage;
the other end of the error amplifier is connected with the source electrode of the MOS tube and used for obtaining feedback voltage.
Preferably, the duty ratio control unit is further configured to set a control policy of the constant current working frequency according to a preset duty ratio, generate a trigger condition of the control policy, and generate a constant current duty ratio control signal according to the control policy of the constant current working frequency corresponding to the trigger condition met by the first control signal, where the preset duty ratio is 1% -10%.
Preferably, the duty ratio control unit is further configured to adjust the PWM dimming signal according to a control policy of a constant current operating frequency corresponding to a trigger condition satisfied by the first control signal, so as to implement strobe-free driving control on the external LED circuit, where a duty ratio of the PWM dimming signal corresponding to the first control signal is greater than or equal to a preset duty ratio.
Preferably, the period control unit is further configured to perform period control on the constant current duty cycle control signal output by the duty cycle control unit according to a control policy of the constant current working frequency corresponding to the triggering condition met by the second control signal, where a duty cycle of the PWM dimming signal corresponding to the second control signal is smaller than a preset duty cycle.
Preferably, the duty ratio control unit is further configured to adjust the constant current operating frequency corresponding to the PWM dimming signal according to the requirement when the duty ratio of the PWM dimming signal is lower than the preset duty ratio according to the linear relationship between the duty ratio of the PWM dimming signal and the preset duty ratio, improve the constant current operating frequency, and keep the duty ratio of the PWM dimming signal unchanged, so as to generate the constant current duty ratio control signal.
Preferably, the period control unit is configured to control a number of pass periods of the constant current duty control signal.
The invention also discloses a dimming method driven by the stroboscopic-free LED, which comprises the following steps of:
acquiring a PWM dimming signal and a feedback voltage of an external LED circuit, and generating a first control signal and a second control signal according to duty ratio information of the PWM dimming signal and comparison information of the feedback voltage and a set reference voltage;
when the duty ratio of the PWM dimming signal is smaller than the preset duty ratio, the passing cycle number of the constant-current duty ratio control signal is controlled through the first control signal and the second control signal;
when the duty ratio of the PWM dimming signal is larger than or equal to the preset duty ratio, the passing cycle number of the constant-current duty ratio control signal is not controlled through the first control signal.
The invention discloses the following technical effects:
according to the invention, the duty ratio signal is obtained after the external PWM input signal is received, and compared with the duty ratio preset interval, when the duty ratio signal falls in the duty ratio preset interval, the brightness control of the light emitting unit is realized by only adjusting the duty ratio of the MOS tube to control the output current passing through the light emitting unit, when the duty ratio signal does not belong to the duty ratio preset interval, the PWM control signal frequency and the PWM control signal period are controlled by the duty ratio control unit and the period control unit, the number of periods passing through a certain period is controlled, the more accurate control of the output current is realized, and the lowest brightness level of the light emitting unit is improved on the premise that no stroboscopic effect is ensured in the dimming process.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of an integrated circuit for strobe-free LED drive dimming according to an embodiment of the present invention;
fig. 2 is a schematic flow chart of the method of the invention.
Detailed Description
For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application, which are generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present application, as provided in the accompanying drawings, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present application without making any inventive effort, are intended to be within the scope of the present application.
As shown in fig. 1-2, the present invention provides a dimming system driven by a stroboscopic-free LED, comprising:
the PWM input unit is used for acquiring a PWM dimming signal of an external control circuit, judging the duty ratio of the PWM dimming signal by counting the high level and the low level, and generating duty ratio information, wherein the external control circuit represents an external LED circuit formed by serially connected lamp beads;
the error amplifier is used for generating comparison information after comparing and amplifying the feedback voltage of the MOS tube source electrode of the external LED circuit with the set reference voltage and inputting the comparison information into the DC-DC control unit;
the DC-DC control unit is used for generating a first control signal and a second control signal according to the duty ratio information and the comparison information;
the duty ratio control unit is used for generating a constant-current duty ratio control signal according to the first control signal and constant-current working frequency and duty ratio information corresponding to the PWM dimming signal;
and the period control unit is used for counting the constant-current duty ratio control signal according to the second control signal and controlling the passing period number.
Still preferably, one end of an error amplifier of the dimming system provided by the present invention is connected to a reference voltage unit for generating a reference voltage;
the other end of the error amplifier is connected with the source electrode of the MOS tube and used for obtaining feedback voltage.
Still preferably, the duty ratio control unit of the dimming system provided by the invention is further configured to set a control policy of the constant current working frequency according to a preset duty ratio, generate a trigger condition of the control policy, and generate a constant current duty ratio control signal according to the control policy of the constant current working frequency corresponding to the trigger condition met by the first control signal, where the preset duty ratio is 1% -10%.
Still preferably, the duty ratio control unit of the dimming system provided by the invention is further configured to adjust the PWM dimming signal according to a control policy of the constant current operating frequency corresponding to the triggering condition satisfied by the first control signal, so as to implement strobe-free driving control on the external LED circuit, where the duty ratio of the PWM dimming signal corresponding to the first control signal is greater than or equal to a preset duty ratio.
Still preferably, the period control unit of the dimming system provided by the invention is further configured to perform period control on the constant current duty cycle control signal output by the duty cycle control unit according to a control policy of the constant current working frequency corresponding to the triggering condition met by the second control signal, where the duty cycle of the PWM dimming signal corresponding to the second control signal is smaller than a preset duty cycle.
Still preferably, the duty ratio control unit of the dimming system provided by the invention is further configured to adjust the constant current operating frequency corresponding to the PWM dimming signal according to the requirement when the duty ratio of the PWM dimming signal is lower than the preset duty ratio according to the linear relation between the duty ratio of the PWM dimming signal and the preset duty ratio, improve the constant current operating frequency, keep the duty ratio of the PWM dimming signal unchanged, and generate the constant current duty ratio control signal.
Still preferably, the period control unit of the dimming system provided by the present invention is used for controlling the number of passing periods of the constant current duty cycle control signal.
Still preferably, according to the functional design of the cycle control unit of the dimming system provided by the present invention, the amplitude of the adjustment may be further adjusted according to a multiple or linear relation between the duty ratio of the PWM dimming signal and a preset duty ratio, and according to a multiple or linear relation of the constant current operating frequency corresponding to the PWM dimming signal, so as to be used as a data reference for controlling the passing cycle number of the constant current duty ratio control signal.
The invention discloses a dimming method driven by a stroboscopic-free LED, which comprises the following steps of:
acquiring a PWM dimming signal and a feedback voltage of an external LED circuit, and generating a control signal according to duty ratio information of the PWM dimming signal and comparison information of the feedback voltage and a set reference voltage;
based on the control signal, generating a constant-current duty ratio control signal and a period control signal according to the relation between the duty ratio of the PWM dimming signal and a preset duty ratio, wherein the preset duty ratio is 1% -10%;
when the duty ratio of the PWM dimming signal is smaller than the preset duty ratio, the passing cycle number of the constant current duty ratio control signal is controlled;
when the duty ratio of the PWM dimming signal is larger than or equal to the preset duty ratio, the passing cycle number of the constant current duty ratio control signal is not controlled.
Further preferably, according to the dimming method disclosed by the invention, the first control signal and the second control signal are generated according to the duty ratio information of the PWM dimming signal and the comparison information of the feedback voltage and the set reference voltage by acquiring the PWM dimming signal and the feedback voltage of the external LED circuit; when the duty ratio of the PWM dimming signal is smaller than the preset duty ratio, the passing cycle number of the constant-current duty ratio control signal is controlled through the first control signal and the second control signal; when the duty ratio of the PWM dimming signal is larger than or equal to the preset duty ratio, the passing cycle number of the constant-current duty ratio control signal is not controlled through the first control signal.
Example 1: an integrated circuit structure for implementing the strobe-free LED driving dimming technique of the present invention, as shown in fig. 1, includes:
PWM input unit: and receiving an external PWM input, counting the high level and the low level to judge the current duty ratio, and respectively transmitting the duty ratio information to a post-stage circuit in a voltage or data mode.
DC-DC control unit: duty cycle information from the PWM input is received and compared with comparison information from the error amplifier. After the two information are processed, two paths of signals are output to the period control unit and the duty ratio control unit respectively.
And the duty ratio control unit is used for: and receiving the control signal transmitted by the DC-DC control unit, and outputting the signal to the period control unit according to the preset frequency and the duty ratio information.
A period control unit: and receiving the control signal transmitted by the DC-DC control unit, and receiving the duty ratio and the frequency/period signal transmitted by the duty ratio control unit. And outputting the duty ratio signal to the MOS tube according to the preset working period and the stop period.
An error amplifier: the positive end is input as the reference voltage of the reference voltage unit, the negative end is input as the feedback voltage from an external circuit, and the signal is transmitted to the DC-DC control unit after being amplified. The signals input by the positive terminal and the negative terminal of the error amplifier can be interchanged in different topologies.
Reference voltage unit: a reference voltage is generated for comparison to an error amplifier.
According to the structure of the integrated circuit, the principle of the dimming method for realizing the driving of the LED without stroboscopic is as follows:
when the input PWM detected by the PWM input unit is high duty ratio (such as more than or equal to 1%), the signal is transmitted to the DC-DC control unit.
When the input PWM duty ratio is 1% -100%, only the duty ratio control unit is used. The cycle control unit is disabled and passes directly. And the strobe-free dimming of 1% -100% is realized.
When the input PWM duty ratio is less than 1%, for example, 0.1% -1% or 0.01% -1%, the DC-DC control unit outputs signals respectively to control the duty ratio control unit and the period control unit to act so as to realize dimming of less than 1%. The following is detailed:
when the PWM input unit detects that the duty ratio of the input PWM dimming signal is lower than 1%, the duty ratio of the control duty ratio control unit is controlled to be unchanged by the output signal, and meanwhile the period control unit acts.
For example, when the PWM input unit detects that the duty ratio of the input PWM dimming signal is 0.5%, the DC-DC control unit outputs a control signal to the duty ratio control unit, and outputs a control signal when the dimming is 1%, the DC-DC control unit outputs a control signal to the period control unit, so that the signal output by the duty ratio control unit passes through 5 periods within 10 periods, and the 5 periods are shielded, thereby achieving the purpose of outputting 0.5% driving output current.
Optionally, when the cycle control unit acts on, improve constant current operating frequency, prevent the condition that the lamp pearl is cut off to appear, and original freewheel time is enough when 1 time, consequently only 5 cycle work in 10 cycles, the freewheel time of inductance is also enough, guarantees that the electric current of lamp pearl can not break, can not produce the stroboscopic.
And by analogy, the PWM input unit detects that the input PWM duty ratio is 0.1%, the DC-DC control unit outputs a control signal to the period control unit, and the signal output by the duty ratio control unit passes through only 1 period in 10 periods, so that the aim of driving output current by 0.1% is fulfilled.
Similarly, when the PWM input unit detects that the input PWM duty ratio is 0.01%, the DC-DC control unit sends out a signal to control the duty ratio control unit to output a control signal for dimming to 1%, and the frequency is optionally increased by 100 times under the condition that the duty ratio is unchanged. The DC-DC control unit sends out signals to enable the period control unit to pass through only 1 period in 100 periods, so that the purpose of driving and outputting 0.01% current is achieved.
Through the method, 1% -100% dimming is realized through duty ratio dimming, and 1% -100% dimming is realized on the basis of 1% through controlling the passing rate of output duty ratio signals. Thereby realizing a gray level of 100x100 = 10000 steps.
The invention can improve the gray level to 1000 level or above while the whole dimming process of the lamp is free from stroboscopic, and is commonly used in the technical fields of desk lamps, industrial cameras, high-speed photography and scientific research illumination.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
In the description of the present invention, it should be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims (8)

1. A strobe-free LED driven dimming system, comprising:
the LED lamp comprises a PWM input unit, a control unit and a control unit, wherein the PWM input unit is used for acquiring a PWM dimming signal of an external control circuit, judging the duty ratio of the PWM dimming signal by counting high and low levels and generating duty ratio information, and the external control circuit represents an external LED circuit formed by serially connected lamp beads;
the error amplifier is used for generating comparison information after comparing and amplifying the feedback voltage of the MOS tube source electrode of the external LED circuit with the set reference voltage and inputting the comparison information into the DC-DC control unit;
a DC-DC control unit for generating a first control signal and a second control signal according to the duty ratio information and the comparison information;
the duty ratio control unit is used for generating a constant-current duty ratio control signal according to the first control signal, the constant-current working frequency corresponding to the PWM dimming signal and the duty ratio information;
and the period control unit is used for counting the constant current duty ratio control signal according to the second control signal and controlling the passing period number.
2. The strobe-free LED-driven dimming system of claim 1, wherein:
one end of the error amplifier is connected with a reference voltage unit for generating a reference voltage;
the other end of the error amplifier is connected with the source electrode of the MOS tube and used for acquiring the feedback voltage.
3. The strobe-free LED-driven dimming system of claim 2, wherein:
the duty ratio control unit is further configured to set a control strategy of a constant current working frequency according to a preset duty ratio, generate a trigger condition of the control strategy, and generate the constant current duty ratio control signal according to the control strategy of the constant current working frequency corresponding to the trigger condition met by the first control signal, where the preset duty ratio is 1% -10%.
4. A strobe-free LED driven dimming system as claimed in claim 3, wherein:
the duty ratio control unit is further configured to adjust the PWM dimming signal according to a control policy of the constant current operating frequency corresponding to the trigger condition that the first control signal meets, so as to implement strobe-free driving control on the external LED circuit, where a duty ratio of the PWM dimming signal corresponding to the first control signal is greater than or equal to a preset duty ratio.
5. A strobe-free LED driven dimming system as claimed in claim 3, wherein:
the period control unit is further configured to perform period control on the constant current duty cycle control signal output by the duty cycle control unit according to a control policy of the constant current working frequency corresponding to the trigger condition satisfied by the second control signal, where a duty cycle of the PWM dimming signal corresponding to the second control signal is smaller than a preset duty cycle.
6. The strobe-free LED-driven dimming system of claim 5, wherein:
the duty ratio control unit is further configured to adjust a constant current operating frequency corresponding to the PWM dimming signal according to a requirement when the duty ratio of the PWM dimming signal is lower than a preset duty ratio according to a linear relation between the duty ratio of the PWM dimming signal and the preset duty ratio, improve the constant current operating frequency, and keep the duty ratio of the PWM dimming signal unchanged, so as to generate the constant current duty ratio control signal.
7. The strobe-free LED-driven dimming system of claim 6, wherein:
the period control unit is used for controlling the passing period number of the constant current duty ratio control signal.
8. A strobe-free LED driven dimming method, comprising the steps of:
acquiring a PWM dimming signal and a feedback voltage of an external LED circuit, and generating a first control signal and a second control signal according to duty ratio information of the PWM dimming signal and comparison information of the feedback voltage and a set reference voltage;
when the duty ratio of the PWM dimming signal is smaller than a preset duty ratio, the passing cycle number of the constant-current duty ratio control signal is controlled through the first control signal and the second control signal;
when the duty ratio of the PWM dimming signal is larger than or equal to a preset duty ratio, the passing cycle number of the constant-current duty ratio control signal is not controlled through the first control signal.
CN202311721452.4A 2023-12-14 2023-12-14 Stroboflash-free LED driven dimming system and method Pending CN117479380A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202311721452.4A CN117479380A (en) 2023-12-14 2023-12-14 Stroboflash-free LED driven dimming system and method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202311721452.4A CN117479380A (en) 2023-12-14 2023-12-14 Stroboflash-free LED driven dimming system and method

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Publication Number Publication Date
CN117479380A true CN117479380A (en) 2024-01-30

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