A two-wire ac double-color LED dimming and color adjusting method and device based on phase-cut edge encoding

Abstract

This invention discloses a two-wire AC dual-color LED dimming and color-tuning method and device based on phase-cut edge encoding, belonging to the field of LED AC dimming control technology. This method utilizes the phase and neutral lines of the AC power supply to simultaneously transmit power supply energy and dimming / color-tuning control information. The controller outputs leading-edge and trailing-edge phase-cut waveforms within half a cycle or a full cycle of the power frequency AC waveform. The phase-cut edge type represents the target color channel, and the phase-cut conduction ratio represents the brightness value of the corresponding color channel. At the lighting device end, the input AC power is rectified, stepped down, and regulated to form DC power. The MCU samples the phase-cut waveform, and after waveform shaping, edge recognition, median filtering, and proportional analysis, obtains the brightness values ​​of the first and second color channels, respectively. Two high-frequency PWM drive signals are then output to drive the corresponding LED groups. This scheme achieves independent dimming and color-tuning of dual-color LEDs without adding control lines, and reduces perceptible flicker caused by direct power frequency phase-cut drive through high-frequency PWM drive, while improving adaptability to mains power fluctuations and waveform distortion.

Description

[0001] This invention belongs to the field of LED lighting dimming control technology, specifically relating to a two-wire AC dual-color LED dimming and color-tuning method and device based on phase-cut edge encoding, which is particularly suitable for lighting systems that require power supply and control via two AC power lines and achieve independent dimming and color-tuning of dual-color LEDs. Background Technology

[0002] LED lighting systems are widely used in aquaculture, planting, commercial lighting, industrial lighting, and residential lighting scenarios. In some large-area lighting scenarios, the large number of lamps and long wiring distances place high demands on installation costs, control reliability, and ease of maintenance.

[0003] Among existing AC LED dimming methods, phase-cut dimming is a common solution. The controller adjusts the load input power by changing the conduction angle of the AC waveform. Traditional phase-cut dimming mainly includes two methods: leading-edge phase-cut and trailing-edge phase-cut, and is typically used for single-channel brightness adjustment.

[0004] However, existing technologies have at least the following problems: 1. Traditional phase-cut dimming directly changes the input energy of the LED driver, which can easily cause light output fluctuations related to the power frequency at low brightness. 2. Ordinary two-wire dimming can usually only transmit single brightness information, making it difficult to achieve independent dimming of dual-color LED light groups without adding control lines; 3. Fluctuations in mains voltage, frequency shifts, and waveform distortions may cause errors in phase angle identification, resulting in brightness deviations; 4. If the phase-cutting waveform is misinterpreted as a valid color light control signal during the power-on startup phase, it may cause abnormal color light during startup. 5. If there is a lack of current limiting or slow start measures, a large inrush current may be generated when the bus capacitor is charging or the LED driver circuit is starting.

[0005] Therefore, it is necessary to provide a new two-wire AC dual-color LED dimming and color-tuning technology that can transmit dual-color control information through the AC power supply line without adding control circuitry, and convert it into a stable high-frequency PWM drive signal at the lamp end. Summary of the Invention

[0006] The purpose of this invention is to provide a two-wire AC dual-color LED dimming and color tuning method and apparatus based on phase-cut edge encoding, in order to solve or improve the problems of existing two-wire phase-cut dimming, such as difficulty in achieving independent dimming of dual colors, mains power fluctuation affecting resolution stability, direct driving of power frequency phase-cutting easily generating perceptible flicker, and possible misjudgment of color light control signals during the startup phase. Technical solution

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A two-wire AC dual-color LED dimming and color tuning method based on phase-cut edge encoding includes: The controller supplies power to the lighting device through the phase and neutral lines of the AC power supply, and forms a phase-cutting modulation waveform in the AC waveform, so that the power supply line can transmit power supply energy and control information simultaneously. The controller outputs leading-edge and trailing-edge phase-cutting waveforms within multiple power frequency half-cycles or cycles. The phase-cutting edge type is used to represent the target color light channel, and the phase-cutting conduction ratio is used to represent the brightness value of the target color light channel. The lighting device rectifies, steps down, and stabilizes the input AC power to form DC power. The MCU at the lighting device end samples the phase-cut waveform, and after waveform shaping, edge recognition, median filtering and scaling, obtains the brightness values ​​of the first color light channel and the second color light channel respectively. The MCU outputs two PWM drive signals to drive the first color LED group and the second color LED group respectively.

[0008] In one implementation, the leading edge phase-cutting waveform corresponds to the first color light channel, and the trailing edge phase-cutting waveform corresponds to the second color light channel.

[0009] In another implementation, the correspondence between the leading edge phase-cutting waveform and the trailing edge phase-cutting waveform and the color light channel can be preset by the controller or MCU.

[0010] In a preferred embodiment, the controller constructs a data frame using two consecutive power frequency cycles. The first cycle employs a leading-edge phase-cutting method, with its conduction ratio representing the brightness of the first color light channel; the second cycle employs a trailing-edge phase-cutting method, with its conduction ratio representing the brightness of the second color light channel. After receiving the complete data frame, the MCU at the lighting device updates the duty cycle of the two PWM drive signals respectively.

[0011] In another implementation, a data frame can be constructed using multiple consecutive half-cycles, where the first half-cycle or the first group of half-cycles represents the brightness of the first color light channel, and the second half-cycle or the second group of half-cycles represents the brightness of the second color light channel.

[0012] The MCU at the lighting device end can identify the phase cutting type based on one or more parameters, such as zero crossing point, conduction start point, turn-off end point, and voltage slope change point, and calculate the conduction ratio based on the position of the phase cutting edge relative to the zero crossing point.

[0013] To reduce the impact of mains power fluctuations and sampling interference, the MCU can perform median filtering, mean filtering, or outlier removal on the phase ratio values ​​obtained from multiple cycles.

[0014] During the power-on startup phase, the controller can output a preset power supply waveform without carrying valid color channel encoding information, or it can refrain from sending valid leading or trailing edge phase-cutting data within a preset startup time. The MCU maintains both PWM outputs in a preset initial state during startup, and updates the duty cycle of the two PWM outputs only after detecting stable and valid phase-cutting encoded data.

[0015] The lighting device end can also limit the power-on inrush current through current limiting circuits, constant current drive gradual rise control, bus capacitor pre-charge control, or PWM duty cycle gradual rise control. Beneficial effects

[0016] Two-wire transmission of dual-color control information: This invention uses the phase-cutting edge type to represent the color light channel and the phase-cutting conduction ratio to represent the brightness value, so that the AC power supply line can simultaneously carry power supply and dual-color dimming control information without the need for additional control lines.

[0017] Supports independent dimming and color adjustment for dual-color LEDs: By transmitting brightness data of different color light channels through leading edge phase cutting and trailing edge phase cutting respectively, the MCU at the lamp end can latch and output two PWM drive signals respectively, realizing independent control of the two color lights.

[0018] Reduce perceptible flicker caused by direct driving of power frequency phase cut: This invention analyzes the phase cut waveform into a control signal at the lamp end, and then drives the LED lamp group through high-frequency PWM, so that the LED light output does not change directly with the power frequency phase cut waveform, thereby reducing the risk of perceptible flicker.

[0019] Improve anti-interference capability: By waveform shaping, edge recognition, median filtering and outlier removal, the impact of mains voltage fluctuations, frequency offset, waveform distortion and switching noise on dimming resolution results can be reduced.

[0020] Improve the color light abnormality problem during startup: No valid color light code is sent during startup. The MCU only updates the PWM output after detecting a stable and valid code, which can reduce the color light abnormality caused by misinterpretation during power-on.

[0021] Reduce the risk of power-on inrush current: By using current limiting, pre-charging, constant current ramp-up or PWM ramp-up methods, the inrush current generated during bus capacitor charging or LED driver startup can be reduced. Attached Figure Description

[0022] Figure 1 This is a block diagram of the overall structure of the two-wire AC dual-color LED dimming and color-tuning system of the present invention.

[0023] Figure 2 This is a block diagram of the internal structure of the lighting device of the present invention.

[0024] Figure 3 This is a flowchart of the phase-cutting modulation process at the control end of the present invention.

[0025] Figure 4 This is a flowchart of the lamp terminal signal demodulation process of the present invention.

[0026] Figure 5 This is a schematic diagram of the leading edge and trailing edge phase-cutting waveforms of the present invention.

[0027] Figure 6 This is a schematic diagram illustrating the relationship between the duty cycle of the dual-channel PWM drive and the brightness of the present invention.

[0028] Figure 7 This is a schematic diagram of the current change during the startup phase of the present invention.

[0029] Figure 8 This is a schematic diagram of the parallel two-wire connection of multiple lamps according to the present invention.

[0030] in: 1. Mains power interface; 2. Controller; 3. Lighting devices; 4. Phase line; 5. Neutral line; 6. Rectifier unit; 7. Step-down and voltage-regulating unit; 8. MCU control unit; 9. Dual-channel PWM drive unit; 10. First color LED light group; 11. Second color LED light group; 12. Leading-edge phase-cutting waveform; 13. Trailing edge phase-cutting waveform; 14. Waveform after shaping; 15. First PWM drive signal; 16. Second PWM drive signal. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Example 1: Dimming and Color Adjustment Method for Two-Wire Dual-Color LEDs

[0032] like Figure 1 and Figure 8 As shown, in this embodiment, the controller 2 is connected to one or more lighting devices 3 via phase line 4 and neutral line 5. Phase line 4 and neutral line 5 serve as both power supply lines and control information transmission lines.

[0033] Controller 2 is connected to a 220V / 50Hz AC power supply. In other embodiments, it can also be applied to a 110V / 60Hz or other industrial frequency AC power supply systems.

[0034] The controller 2 internally includes a zero-crossing detection circuit, an MCU control circuit, and a phase-cutting execution circuit. The phase-cutting execution circuit can use a thyristor, MOSFET, IGBT, or other controllable power switching devices.

[0035] The controller 2 generates a phase-cutting modulation waveform based on the first color light brightness value and the second color light brightness value set by the user.

[0036] In this embodiment, the following encoding method is used: Two consecutive power frequency cycles are used as a group of data frames; The first power frequency cycle uses leading-edge phase cutting, and its conduction ratio represents the brightness value of the first color LED group 10; The second power frequency cycle uses trailing edge phase cutting, and its conduction ratio represents the brightness value of the second color LED group 11.

[0037] For example, when the brightness of the first color light is set to 30% and the brightness of the second color light is set to 70%, controller 2 outputs a leading-edge phase-cut waveform corresponding to 30% brightness in the first cycle and a trailing-edge phase-cut waveform corresponding to 70% brightness in the second cycle. After parsing this data frame, the MCU at the lighting device end updates the duty cycle of the first PWM channel to the value corresponding to 30% brightness and updates the duty cycle of the second PWM channel to the value corresponding to 70% brightness.

[0038] Before the next data frame arrives, the MCU keeps the two brightness values ​​obtained from the previous data frame unchanged.

[0039] In other implementations, multiple half-cycles can be used as data frames. For example, the positive half-cycle transmits the brightness of the first color light channel, and the negative half-cycle transmits the brightness of the second color light channel. Alternatively, a complete data frame can be composed of a start flag cycle, a first color light data cycle, a second color light data cycle, and a check cycle.

[0040] like Figure 5 As shown, the leading edge phase-cutting waveform 12 and the trailing edge phase-cutting waveform 13 have different phase-cutting edge characteristics. The MCU control unit 8 can identify the phase-cutting type and calculate the conduction ratio based on the shaped phase-cutting waveform 14. Example 2: Lamp Demodulation and PWM Driving

[0041] like Figure 2 and Figure 4As shown, the lighting device 3 includes a rectifier unit 6, a step-down regulator unit 7, an MCU control unit 8, a dual-channel PWM drive unit 9, a first-color LED lamp group 10, and a second-color LED lamp group 11.

[0042] Rectifier unit 6 is used to convert the input alternating current into pulsating direct current. Rectifier unit 6 can be a bridge rectifier circuit.

[0043] The buck regulator unit 7 is used to convert the rectified voltage into a DC voltage suitable for the operation of the MCU, driver circuit, and LED lamp assembly. The buck regulator unit 7 can adopt a flyback power supply, a buck switching power supply, a constant current drive power supply, or other isolated or non-isolated power supply structures.

[0044] The MCU control unit 8 acquires the phase-cut waveform of the input AC power or rectified AC power through a sampling circuit. The sampling circuit may include resistor voltage divider, current limiting protection, optocoupler isolation, comparator shaping, or ADC sampling circuit.

[0045] The MCU control unit 8 performs the following processing: 1. Obtain a zero-crossing point or equivalent periodic reference point; 2. Filter and shape the sampled waveform; 3. Detect voltage rising edge, falling edge, or abrupt slope changes; 4. Determine whether the phase cutting type is leading-edge phase cutting or trailing-edge phase cutting; 5. Calculate the phase-cut conduction ratio; 6. Perform median filtering on the analytical values ​​of multiple consecutive periods; 7. Determine the target color channel based on the phase-cutting edge type; 8. Update the brightness value of the corresponding color channel according to the phase switching ratio; 9. Output the PWM drive signal corresponding to the duty cycle.

[0046] The frequency of the PWM drive signal is higher than the power frequency. In this embodiment, the PWM frequency is 25kHz. This frequency is only a preferred value; in other embodiments, the PWM frequency can also be from 2kHz to 40kHz.

[0047] By using high-frequency PWM drive, the average current of the LED lamp group is controlled by the PWM duty cycle, rather than directly driven by the power frequency phase-cut waveform, thereby reducing perceptible flicker.

[0048] like Figure 6 As shown, the duty cycles of the first PWM drive signal 15 and the second PWM drive signal 16 correspond to the brightness values ​​of the first and second color light channels, respectively. Example 3: Start-up Control

[0049] During the power-on startup phase, in order to avoid the waveform distortion at the moment of startup being misjudged as valid color light control information by the MCU, the controller 2 does not send valid leading edge phase-cut or trailing edge phase-cut encoded data within the preset startup time.

[0050] During this stage, controller 2 can output a fully conducting power supply waveform, a preset fixed conducting waveform, or other power supply waveforms that do not carry valid color light channel encoding information.

[0051] During the startup phase, the MCU control unit 8 of the lighting device keeps the two PWM outputs in a preset initial state, such as keeping them off, outputting at a low duty cycle, or slowly increasing according to a preset slope.

[0052] Meanwhile, the lighting device can limit the inrush current through one or a combination of the following methods: 1. Input current-limiting resistor or NTC current limiter; 2. Bus capacitor pre-charge circuit; 3. Constant current drive current gradually increases; 4. PWM duty cycle gradually increases; 5. MOSFET soft conduction control.

[0053] After the MCU continuously detects a preset number of valid phase-coded data frames, it updates the duty cycle of the first PWM and the second PWM based on the parsing results.

[0054] By using the above-mentioned startup control method, the abnormal color light caused by misinterpretation during the startup phase can be reduced, and the impact of power-on shock on power devices and LED lamp groups can be reduced.

[0055] like Figure 7 As shown, soft-start control can gradually increase the current during the startup phase to reduce the instantaneous inrush current.

Claims

1. A dimming and color-tuning method for two-wire AC dual-color LEDs based on phase-cut edge encoding. characterized in that Includes the following steps: S1, the controller supplies power to the lighting device through the phase line and neutral line of the AC power supply, and forms a phase-cut modulation waveform on the phase line and neutral line, so that the power supply line can simultaneously carry power supply energy and dimming and color adjustment control information; S2, the controller outputs leading edge phase-cutting waveforms and trailing edge phase-cutting waveforms within multiple half-cycles or multiple cycles of the power frequency AC waveform, wherein the phase-cutting edge type is used to represent the target color light channel, and the phase-cutting conduction ratio is used to represent the brightness value of the target color light channel; S3, the lighting device rectifies, steps down, and regulates the input AC power to form a DC power supply for the MCU control unit, PWM drive unit, and LED lamp group; S4, the MCU control unit samples the phase-cut waveform of the input AC power or rectified power, and performs waveform shaping, phase-cut edge recognition and phase-cut ratio analysis on the sampled data to obtain the brightness values ​​of the first color light channel and the second color light channel respectively; S5, the MCU control unit outputs two PWM drive signals based on the obtained brightness values ​​of the first color light channel and the second color light channel, respectively driving the first color light LED group and the second color light LED group.

2. The method according to claim 1 Its features are: The leading edge phase-cutting waveform corresponds to the first color light channel, and the trailing edge phase-cutting waveform corresponds to the second color light channel; or, the correspondence between the leading edge phase-cutting waveform and the trailing edge phase-cutting waveform and the color light channel is determined by a preset configuration.

3. The method according to claim 1 Its features are: The controller forms a set of data frames with multiple consecutive power frequency half cycles or power frequency cycles, and the data frames include at least the brightness data of the first color light channel and the brightness data of the second color light channel. Among them, the brightness data of the first color light channel is represented by the conduction ratio of the leading edge phase-cutting waveform, and the brightness data of the second color light channel is represented by the conduction ratio of the trailing edge phase-cutting waveform; After receiving the data frame, the MCU control unit updates the PWM duty cycle of the first color light channel and the second color light channel respectively.

4. The method according to claim 3 Its features are: In a set of data frames, the brightness value of the first color light channel is transmitted using the leading edge phase-cutting method in the first power frequency cycle or the first half cycle, and the brightness value of the second color light channel is transmitted using the trailing edge phase-cutting method in the second power frequency cycle or the second half cycle. The MCU control unit maintains the brightness values ​​of the first and second color channels obtained from the parsing of the previous data frame until the next data frame arrives.

5. The method according to claim 1 Its features are: The MCU control unit identifies leading-edge phase-cut waveforms and trailing-edge phase-cut waveforms by detecting at least one of the voltage rising edge, falling edge, turn-on start time, turn-off end time, or voltage slope abrupt change point in the sampled waveform. The phase-cutting conduction ratio is calculated based on the time position of the phase-cutting edge relative to the zero-crossing point or the equivalent period reference point.

6. The method according to claim 1 Its features are: The waveform shaping includes removing or correcting glitch, short-term dip, abnormal peak or distorted segment in the sampled waveform; The phase ratio analysis includes performing median filtering, mean filtering, or outlier removal on the phase ratio values ​​obtained from multiple consecutive half-cycles or cycles to reduce the impact of mains power fluctuations, noise interference, or sampling errors on the brightness analysis results.

7. The method according to claim 1, characterized in that: The frequency of the two PWM drive signals is 2kHz to 40kHz, preferably 20kHz to 30kHz; The MCU control unit adjusts the duty cycle of the two PWM drive signals according to the brightness values ​​of the first and second color light channels obtained by analysis, so as to control the average current or average light output of the corresponding LED group.

8. The method according to claim 1 Its features are: During the light-on startup phase, the controller outputs a preset power supply waveform that does not carry color light channel encoding information, or does not output valid leading-edge phase-cutting or trailing-edge phase-cutting modulation data within a preset time. During the startup phase, the MCU control unit maintains the two PWM drive signals in a preset initial state. After detecting stable and valid phase-cutting encoded data, it updates the two PWM drive signals according to the obtained brightness value. Furthermore, during the startup phase, the lighting device limits the power-on inrush current through at least one of the following methods: current limiting circuit, constant current drive gradual increase control, bus capacitor pre-charge control, or PWM duty cycle gradual increase control.

9. A two-wire AC dual-color LED dimming and color-tuning device based on phase-cut edge encoding. characterized in that include: The system includes a rectifier unit, a buck regulator unit, an MCU control unit, a dual-channel PWM drive unit, a first-color LED group, and a second-color LED group. The input terminal of the rectifier unit is connected to the phase line and neutral line of the AC power supply, and the output terminal of the rectifier unit is connected to the step-down voltage regulator unit. The step-down and voltage-regulating unit is used to output DC power to power the MCU control unit, the dual-channel PWM drive unit, the first color LED group, and the second color LED group; The MCU control unit includes a sampling module, a waveform shaping module, a phase-cutting analysis module, and a PWM output module; The sampling module is used to sample the phase-cut waveform of the input AC power or the rectified AC power; The waveform shaping module is used to denoise and shape the sampled waveform; The phase-cutting analysis module is used to identify the phase-cutting edge type and calculate the phase-cutting conduction ratio to obtain the brightness value of the corresponding color light channel; The PWM output module is used to output two PWM drive signals, which drive the first color LED group and the second color LED group respectively via the dual-channel PWM drive unit.

10. The apparatus according to claim 9 Its features are: The MCU control unit is configured to parse and latch the brightness values ​​of the first color light channel and the second color light channel respectively, using multiple half-cycles or cycles of the power frequency as a group of data frames; The MCU control unit is also configured to perform median filtering, mean filtering, or outlier removal on the phase ratio values ​​obtained from multiple consecutive half-cycles or cycles. The MCU control unit is also configured to keep the two PWM drive signals in a preset initial state during the power-on startup phase, and to update the duty cycle of the two PWM drive signals after detecting valid phase-cutting encoded data.

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