A single-wire power supply system, method and smart screen capable of adaptively adjusting chopping time

Abstract

This invention relates to a single-wire power supply system, method, and smart screen with adaptive chopping time adjustment, comprising the following modules: a zero-crossing detection unit, connected between the live wire input and output, for detecting the zero-crossing point of the mains signal and outputting a zero-crossing signal; the zero-crossing detection unit includes a hysteresis comparator circuit for shaping the mains signal to output a stable zero-crossing signal; a main control unit, connected to the output of the zero-crossing detection unit, for acquiring the arrival time t1 of the zero-crossing signal cycle by cycle, and adaptively adjusting the chopping duration within the current mains cycle according to the arrival time t1 to generate a chopping control signal; and a switching unit, connected between the live wire input and output and controlled by the main control unit to be on or off periodically driven by the chopping control signal to control the power extraction process.

Description

Technical Field

[0001] This invention relates to the field of single-wire power supply, specifically to a single-wire power supply system, method, and smart screen that adaptively adjusts the chopping time. Background Technology

[0002] In existing homes, for ease of wiring and to save on cable length, installation workers typically install wiring boxes with only a live wire inlet and outlet, without providing a separate neutral wire. Traditional mechanical switch panels for controlling lights also do not require a neutral wire. However, with the development and widespread adoption of smart homes, a single live wire power supply scheme is generally used to power smart home control panels. This scheme relies solely on the live wire inlet and outlet for power, making it well-suited for older residential areas and ordinary homes where a neutral wire is unavailable.

[0003] In existing smart switch panel products with a single live wire power supply scheme, the general approach uses the zero-crossing point of the mains voltage as a reference, employing switching mechanisms such as MOSFETs to periodically extract a portion of the mains voltage to maintain a stable DC-DC voltage at the downstream end, thus meeting the load requirements of the smart switch panel. However, this approach has the following drawbacks: Question 1: Users' homes will connect various devices with different loads. When high-power appliances or inductive appliances are turned on, they will affect the waveform of the mains power, which in turn will affect the single live wire power supply scheme, causing the voltage to drop, resulting in device restarts or black screens. Question 2: Secondly, some electrical appliances that have not passed national standards or certifications will also pollute the mains voltage waveform. These devices often have high noise levels and cover a wide frequency band, making it difficult to filter out interference and affecting the chopping timing. Question 3: Due to the limitations of the microcontroller's clock accuracy, there will be a deviation in the control time from receiving the zero-crossing signal waveform to controlling the chopping duration. The mains voltage changes the most around the zero-crossing point. If the chopping deviation between the two points is 0.5ms, the corresponding voltage will differ by tens of volts, causing the chopping amplitude to change and resulting in unstable load capacity. Question 4: When the load connected to the power supply circuit of the smart switch is a power supply topology with a large electrolytic capacitor at the front end, the chopping voltage will decrease cycle by cycle because this type of topology will affect the phase of the mains current, eventually causing the voltage to drop and making it impossible to obtain power stably and reliably for a long time.

[0004] The purpose of this invention is to design an adaptive chopping time adjustment single-wire power supply system, method, and smart screen to address the problems existing in the prior art. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a single live wire power supply system, method, and smart screen with adaptive chopping time adjustment, which can effectively solve at least one of the problems existing in the prior art.

[0006] The technical solution of this invention is: A single-wire power supply system with adaptive chopping time adjustment. Includes the following modules: A zero-crossing detection unit is connected between the live wire inlet and the live wire outlet. It is used to detect the zero-crossing point of the mains signal and output a zero-crossing signal. The zero-crossing detection unit includes a hysteresis comparator circuit, which is used to shape the mains signal to output a stable zero-crossing signal. The main control unit is connected to the output of the zero-crossing detection unit and is used to acquire the arrival time t1 of the zero-crossing signal cycle by cycle, and adaptively adjust the chopping duration in the current mains power cycle according to the arrival time t1 to generate a chopping control signal. The switching unit is connected between the live wire inlet and the live wire outlet and is controlled to be turned on or off by the main control unit. It is driven by the chopper control signal to perform periodic switching on and off to control the power supply process.

[0007] Furthermore, the zero-crossing detection unit includes a comparator U1. The positive input terminal of the comparator U1 is connected to the reference voltage VREF through a resistor R12. The positive input terminal of the comparator U1 is connected to the output terminal of the comparator U1 through a resistor R11. The negative input terminal of the comparator U1 is connected to the mains sampling signal. The positive terminal of the comparator U1 is connected to the positive power supply voltage VCC. The negative terminal of the comparator U1 is grounded.

[0008] Furthermore, the zero-crossing detection unit includes a step-down circuit connected between the live wire input and live wire output. The output of the step-down circuit is connected to a low-pass filter circuit, and the output of the low-pass filter circuit is connected to a level conversion circuit. The level conversion circuit converts the output waveform of the low-pass filter circuit into a square wave signal containing the zero-crossing point of the mains power.

[0009] Furthermore, the level conversion circuit includes an NPN transistor Q1. The base (B) of the NPN transistor Q1 is connected to the output terminal of the low-pass filter circuit through a current-limiting resistor R9. The collector (C) of the NPN transistor Q1 is connected to the positive power supply voltage VCC through a pull-up resistor R10. The emitter (E) of the NPN transistor Q1 is grounded, and the collector (C) of the NPN transistor Q1 is connected to the negative input terminal of the comparator U1. The conduction and cutoff characteristics of the NPN transistor Q1 convert the output waveform of the low-pass filter circuit into a square wave signal with a high level before and after the zero-crossing point of the mains power. The main control unit uses the falling edge time of the square wave signal as the arrival time t1.

[0010] Furthermore, the main control unit is configured with an initial basic chopping duration, which includes the disconnection duration T1 and the closing duration T2 that control the switching unit to perform sequentially within the chopping cycle; The main control unit performs adaptive chopping duration adjustment cyclically during operation. The adaptive chopping duration adjustment includes the following steps: Obtain the arrival time t1 of the zero-crossing signal in the current cycle, and calculate the time interval between the end of the closing duration T2 of the previous cycle and the arrival time t1 of the current cycle. If the time interval is within the preset reference duration, then the disconnection duration T1 and the closure duration T2 of the current cycle remain unchanged; If the time interval is less than the minimum value of the reference duration, then the disconnection duration T1 is extended; If the time interval is greater than the maximum value of the reference duration, then the disconnection duration T1 is shortened.

[0011] Furthermore, if the time interval is less than the minimum value of the reference duration, then after extending the disconnection duration T1, the following steps are performed: If the time interval is less than the minimum value of the reference duration for a consecutive preset number of times, the extended closing duration T1 will be reset to the initial opening duration T1.

[0012] Furthermore, if the time interval is greater than the maximum value of the reference duration, shortening the disconnection duration T1 includes: If the time interval is greater than the reference duration and the time interval is less than 10ms, then the disconnection duration T1 is shortened. If the time interval is greater than the reference duration and the time interval is greater than 10ms, then the disconnection duration T1 remains unchanged.

[0013] Further, after obtaining the arrival time t1 of the zero-crossing signal in the current cycle, before calculating the time interval between the end of the closing duration T2 of the previous cycle and the arrival time t1 of the current cycle, the following is executed: Determine whether the arrival time t1 of the zero-crossing signal in the current cycle is after the closing time T2 of the switching unit in the previous cycle. If not, block the current arrival time t1 and end the current cycle.

[0014] Further, after calculating the time interval between the end point of the previous cycle's closing duration T2 and the arrival time point t1 of the current cycle, execute: Determine whether the time interval is greater than the preset waiting time; otherwise, block the current time point t1 and end the current loop.

[0015] A further method for adaptively adjusting the chopping time in a single live wire power supply is provided, comprising the following steps: Obtain the arrival time t1 of the zero-crossing signal in the current cycle, and calculate the time interval between the end of the closing duration T2 of the previous cycle and the arrival time t1 of the current cycle. If the time interval is within the preset reference duration, then the disconnection duration T1 and the closure duration T2 of the current cycle remain unchanged; If the time interval is less than the minimum value of the reference duration, then the disconnection duration T1 is extended; If the time interval is greater than the maximum value of the reference duration, then the disconnection duration T1 is shortened.

[0016] Furthermore, a smart screen is provided, which includes the aforementioned single-wire power supply system with adaptive chopping time adjustment.

[0017] Therefore, the present invention provides the following effects and / or advantages: This application utilizes a combination of hardware and software methods to enhance the stability of zero-crossing signal output. Simultaneously, it optimizes the software logic to mitigate the impact of mains noise, appliance surges, and self-interference, reducing the load's influence on single-wire devices and ensuring compatibility with most commercially available loads. It fundamentally solves the voltage drop and blackout issues that occur when single-wire devices operate under prolonged loads. Based on the original circuit design, it optimizes the single-wire chopper logic at a lower cost, enabling stable long-term load operation. Even under simulated mains interference and appliance surges, it ensures no voltage drop, achieving reliable power supply.

[0018] This application optimizes the zero-crossing circuit in hardware and adds a hysteresis comparator circuit, which can filter out mains noise interference waveforms, prevent malfunctions, provide the main control with an accurate and stable mains zero-crossing point, provide a basis for the subsequent chopping starting point, and can greatly improve circuit stability. This application sets up special judgment logic for equipment or electrical appliances that pollute the mains power grid. Even if a few noise or surge voltages of such loads pass through the filtering and hysteresis comparator circuits set in the hardware, the logic added in the software can effectively prevent voltage drops caused by interference. This application provides a software solution for adaptive chopping logic based on zero-crossing point judgment. The main controller receives the zero-crossing signal, judges and calculates it to obtain the accurate chopping time value, and then drives the MOSFET to chop periodically. A stable chopping voltage can be obtained in each cycle, ensuring that the entire system can operate stably over a long period of time. This application fully considers the impact of the large capacitive load connected to the single-fire device on its performance. It sets a condition that if the time deviation between two consecutive judgments is less than a preset value, no compensation will be performed. This avoids the cycle-by-cycle decrease in chopping time and voltage drop, maintains voltage stability, increases the load adaptability of the single-fire device, and can adapt to more complex types of electrical appliances. It avoids the embarrassing situation where users have to replace electrical appliances because the single-fire device cannot adapt to the load, improves user satisfaction, and realizes in-situ replacement of smart panels.

[0019] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained through the structures particularly pointed out in the description and the drawings.

[0020] It should be understood that the above summary and the following detailed description of the invention are exemplary and explanatory, and are intended to provide further explanation of the invention as claimed. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the system framework provided for one embodiment of the present invention.

[0022] Figure 2 This is the circuit diagram for the zero-crossing detection unit.

[0023] Figure 3 The circuit diagram for generating the reference voltage VREF.

[0024] Figure 4 This is a flowchart illustrating the operation of the main control unit.

[0025] Figure 5 A flowchart illustrating the adaptive chopping duration adjustment process. Detailed Implementation

[0026] To facilitate understanding by those skilled in the art, the present invention will now be described in further detail with reference to the embodiments: refer to Figure 1A single-wire power supply system with adaptive chopping time adjustment. Includes the following modules: A zero-crossing detection unit is connected between the live wire inlet and the live wire outlet. It is used to detect the zero-crossing point of the mains signal and output a zero-crossing signal. The zero-crossing detection unit includes a hysteresis comparator circuit, which is used to shape the mains signal to output a stable zero-crossing signal. The main control unit is connected to the output of the zero-crossing detection unit and is used to acquire the arrival time t1 of the zero-crossing signal cycle by cycle, and adaptively adjust the chopping duration in the current mains power cycle according to the arrival time t1 to generate a chopping control signal. The switching unit is connected between the live wire inlet and the live wire outlet and is controlled to be turned on or off by the main control unit. It is driven by the chopper control signal to perform periodic switching on and off to control the power supply process.

[0027] The structure of the single-wire power supply system in this embodiment is as follows: Figure 1 As shown, the zero-crossing detection unit is the core component of this embodiment. It is connected to the live wire input and output, monitors the periodic mains power signal, and feeds back the periodic zero-crossing signal to the main control unit for processing. The main control unit is mainly responsible for turning the lights on and off and adaptively processing the chopping duration to maintain the normal power supply of the entire device. The switching unit is mainly composed of a MOSFET and external circuitry. It is controlled by the main control unit and switches periodically. The switching unit is also connected between the live wire input and output. When the switching unit is closed, it conducts the live wire input and output, thereby shielding the zero-crossing detection unit and the main control unit. When the switching unit is open, it draws power from the live wire input and output to the zero-crossing detection unit and the main control unit.

[0028] Hysteresis comparator circuits can maintain the output level unchanged when the input signal is slightly disturbed, thereby filtering out mains noise interference waveforms, preventing malfunctions, providing the main controller with an accurate and stable mains zero-crossing point, providing a basis for the subsequent chopping start point, and greatly improving circuit stability.

[0029] Furthermore, due to the influence of load on circuit performance, such as a large capacitive load causing the voltage waveform phase to lag significantly behind the current waveform phase, and the possibility of reverse discharge from the capacitive load into the circuit during the switching unit's turn-off period, the zero-crossing time of the hysteresis comparator output may be offset. Generally, this offset will delay the actual arrival time of the mains voltage at zero. Therefore, the main control unit needs to adaptively adjust based on the arrival time t1 to compensate for or regulate the chopping duration, ensuring sufficient chopping time.

[0030] Furthermore, the zero-crossing detection unit includes a comparator U1. The positive input terminal of the comparator U1 is connected to the reference voltage VREF through a resistor R12. The positive input terminal of the comparator U1 is connected to the output terminal of the comparator U1 through a resistor R11. The negative input terminal of the comparator U1 is connected to the mains sampling signal. The positive terminal of the comparator U1 is connected to the positive power supply voltage VCC. The negative terminal of the comparator U1 is grounded.

[0031] Furthermore, the zero-crossing detection unit includes a step-down circuit connected between the live wire input and live wire output. The output of the step-down circuit is connected to a low-pass filter circuit, and the output of the low-pass filter circuit is connected to a level conversion circuit. The level conversion circuit converts the output waveform of the low-pass filter circuit into a square wave signal containing the zero-crossing point of the mains power.

[0032] Furthermore, the level conversion circuit includes an NPN transistor Q1. The base (B) of the NPN transistor Q1 is connected to the output terminal of the low-pass filter circuit through a current-limiting resistor R9. The collector (C) of the NPN transistor Q1 is connected to the positive power supply voltage VCC through a pull-up resistor R10. The emitter (E) of the NPN transistor Q1 is grounded, and the collector (C) of the NPN transistor Q1 is connected to the negative input terminal of the comparator U1. The conduction and cutoff characteristics of the NPN transistor Q1 convert the output waveform of the low-pass filter circuit into a square wave signal with a high level before and after the zero-crossing point of the mains power. The main control unit uses the falling edge time of the square wave signal as the arrival time t1.

[0033] refer to Figure 2The zero-crossing detection unit circuit shown in the figure has R4, R5, R6, and R7 as voltage divider resistors with the same resistance value. Their main function is to bear the high voltage of the mains power and limit the current. After being divided together with resistor R8, the voltage of the mains power is reduced to within the maximum allowable BE voltage of the NPN transistor Q1. The scaling ratio is approximately τ = R8 / (R4+R5) = R8 / (R6+R7). Inductor L1 and capacitor C1 together form a low-pass filter circuit, which allows low-frequency mains signals to pass through and can filter out high-frequency noise interference from the mains power. Since the B terminal of the NPN transistor Q1 needs a changing voltage input, the capacitance value of C1 should not be set too large, generally set to the pF to nF level. At the same time, the cutoff frequency of the low-pass filter circuit is set in a reasonable range according to the spectrum range of the mains noise. Then, the inductance value L = 1 / ((2πf)^2×C) is obtained from the formula for the cutoff frequency f of the second-order low-pass filter circuit. Resistor R9 is the current-limiting resistor for the base (B) of NPN transistor Q1. Adjusting the input current at the base (B) ensures that NPN transistor Q1 operates in the saturation region, stabilizing the VIN output waveform and reducing transistor delay. The collector (C) of NPN transistor Q1 is pulled up to VCC through resistor R10 to provide drive current and is also connected to the negative input terminal of amplifier U1 as the signal input; the emitter (E) is directly connected to the non-isolated ground plane.

[0034] The comparator U1 is connected as follows: Figure 2 As shown. The relevant calculation formulas for comparator U1 are as follows: When the input voltage VIN < the positive input voltage V+, comparator U1 outputs a high level VCC. At this time, VOUT1 = R11 × VREF / (R11 + R12) + R12 × VCC / (R11 + R12); When the input voltage VIN > the positive input voltage V+, the comparator outputs a low level, and at this time VOUT2 = R11 × VREF / (R11 + R12); Typically, when the system VCC voltage is 5V, and a high-level output greater than 2.5V and a low-level output less than 1.5V is required (i.e., VOUT1=2.5V, VOUT2=1.5V), the circuit parameters can be calculated as follows: R11:R12=4:1, VREF=2V, and R11=100KΩ, R12=25KΩ can be selected. Its input and output characteristics are as follows: when the input VIN is a high-level signal, the circuit output VOUT is a low-level signal. When external signal interference causes a momentary drop in VIN, as long as its level does not fall below 1.5V, the output VOUT can still maintain a low-level signal, thereby achieving the purpose of filtering out interference signals and preventing an incorrect zero-crossing signal from being given to the main controller, which could cause chopper logic errors and lead to voltage drops.

[0035] refer to Figure 3The reference voltage VREF generation circuit can output the voltage after passing through the optocoupler from the isolated power supply VDD. Resistor R13 is connected in parallel between pins 1 and 2 of the primary side of the optocoupler to provide a minimum current to the Zener diode. The voltage then passes through the Zener diode D1 and the current-limiting resistor R14 in series. When the VDD voltage is constant, the voltage and current across the Zener diode D1 are fixed. Since the primary side of U2 is equivalent to a light-emitting diode, its voltage drop is also fixed. Therefore, adjusting the value of R14 can control the current through the primary side of U2, so that the secondary side of U2 is in a reasonable amplification region.

[0036] The specific formula derivation is shown below. For the primary circuit of the optocoupler: Since the resistance of R13 is very large, the current through R13 can be ignored. Let the voltage across the primary of U2 be VLED, the voltage across Zener diode D1 be VD1, the voltage across R14 be VR14, and the current be I1. Then we have VDD = VLED + VD1 + VR14 and VR14 = R14 × I1. Checking the device datasheet, we know that there is a definite relationship between the optocoupler current and VLED, and between the Zener diode current and VD1. According to the parameters of the optocoupler, the secondary current I2 = CTR × I1 is obtained. Therefore, the secondary reference voltage VREF = VR15 = R15 × I2 = R15 × CTR × I1 can be obtained. The reason for using the isolated power supply VDD as the reference power supply instead of directly using VCC to obtain VREF through voltage division is that the isolated power supply VDD has less ripple than the non-isolated power supply VCC, and the obtained VREF is more stable and reliable.

[0037] Further, refer to Figure 3-4 The main control unit is configured with an initial basic chopping duration, which includes the disconnection duration T1 and the closing duration T2 that control the switching unit to perform sequentially within the chopping cycle. The main control unit performs adaptive chopping duration adjustment cyclically during operation. The adaptive chopping duration adjustment includes the following steps: Obtain the arrival time t1 of the zero-crossing signal in the current cycle, and calculate the time interval between the end of the closing duration T2 of the previous cycle and the arrival time t1 of the current cycle. If the time interval is within the preset reference duration, then the disconnection duration T1 and the closure duration T2 of the current cycle remain unchanged; If the time interval is less than the minimum value of the reference duration, then the disconnection duration T1 is extended; If the time interval is greater than the maximum value of the reference duration, then the disconnection duration T1 is shortened.

[0038] In this embodiment, the adjustment of the basic chopping duration by the main control unit is one of the core improvements. The basic chopping duration refers to the control duration of the main control unit on the switching unit after receiving the zero-crossing signal output by the zero-crossing detection unit and obtaining the arrival time t1. This includes the sequentially occurring disconnection duration T1 and closing duration T2. ​​That is, within one chopping cycle, after obtaining the arrival time t1, the main control unit first controls the switching unit to disconnect for a duration of T1, and then close for a duration of T2.

[0039] Specifically, in this embodiment, when the main control unit receives the light-on command, it enters the on-state chopping state. Initially, a Tick value is set, which is generally defined as the minimum time interval of the main control unit chip, for example, 50µs. Then, the disconnection duration T1 is set to the duration of the gate low level of the switching unit, and T2 is set to the duration of the gate high level of the switching unit. Afterward, the main control unit reads the arrival time t1 of the zero-crossing signal fed back by the zero-crossing signal circuit. Here, t1 serves as the core basis for adjusting the chopping duration and affects the judgment of the entire chopping logic.

[0040] Specifically, the basic chopping duration can be assigned as follows: T1 = n1 × Ticks, T2 = n2 × Ticks; the reference duration is set to TB = m × Ticks, with a range of [n × Ticks, N × Ticks]. After obtaining the arrival time t1, the time interval t2 between the arrival time t1 and the end of the upward cycle closing duration T2 is calculated, and the relationship between the time interval t2 and the reference duration is determined. If n×Ticks≤t2≤N×Ticks, this step determines that the arrival time t1 is within the expected range. Due to the influence of parameters such as the accuracy of the main control clock, device discreteness, temperature changes, and component delays, the arrival time t1 varies within a certain range each time. Therefore, the specific values ​​of n and N need to be obtained by statistically analyzing a large number of devices under different environments and temperatures. To ensure that the generation time of the normal zero-crossing signal falls within this range, the initial T1 and T2 remain unchanged, and the values ​​of T1 and T2 are output to the main program. When t2 < n × Ticks, that is, if the time interval is less than the minimum value of the reference duration, it means that the abnormal arrival time t1 occurs earlier than the normal zero-crossing signal time. In this case, it is necessary to extend the current period T1 and reset the chopping time points respectively: T1 = n1 × Ticks + (m × Ticks - t2) and T2 = n2 × Ticks. At this time, the extension of T1 is the difference between the minimum value of the reference duration and the time interval.

[0041] When t2 > N×Ticks, that is, if the time interval is greater than the maximum value of the reference duration, it indicates that the abnormal arrival time t1 is later than the normal zero-crossing signal time. At this time, it is necessary to reduce the current period T1 and reset the chopping time point: T1 = n1×Ticks - (t2 - m×Ticks). In this case, the amount of shortening T1 is the difference between the minimum value of the reference duration and the time interval.

[0042] Furthermore, if the time interval is less than the minimum value of the reference duration, then after extending the disconnection duration T1, the following steps are performed: If the time interval is less than the minimum value of the reference duration for a consecutive preset number of times, the extended closing duration T1 will be reset to the initial opening duration T1.

[0043] In this step, after determining the minimum value of the time interval being less than the baseline duration, the number of times this situation occurs is recorded. If the number of occurrences is less than a preset number, the extended disconnection duration T1 can be output. If the number of occurrences is greater than the preset number, it indicates that multiple cycles and the current cycle simultaneously enter the step of extending the disconnection duration T1. This situation corresponds to the impact of a large capacitive load connected to the single-fire device on its performance. To avoid the chopping time decreasing cycle by cycle and the voltage dropping, it is necessary to restore the initial baseline chopping duration, that is, to restore T1 and T2 to: T1 = n1 × Ticks and T2 = n2 × Ticks, so that the system returns to a normal cycle and maintains voltage stability. This step can increase the load adaptability of the single-fire device and is compatible with most lighting fixtures on the market. The preset number of occurrences can be set to 2.

[0044] Furthermore, if the time interval is greater than the maximum value of the reference duration, shortening the disconnection duration T1 includes: If the time interval is greater than the reference duration and the time interval is less than 10ms, then the disconnection duration T1 is shortened. If the time interval is greater than the reference duration and the time interval is greater than 10ms, then the disconnection duration T1 remains unchanged.

[0045] In this step, it is necessary to determine whether the value of t2 has overflowed. If t2 has overflowed beyond the normal range, the mains power cycle is 20ms, and there are 2 zero-crossing signals in one cycle. Then the value of t2 must satisfy t2 < 10ms. If it exceeds this range, it means that there is an abnormality in the zero-crossing signal statistics. It is necessary to skip the chopping of the current cycle and wait for the zero-crossing signal of the next cycle before chopping.

[0046] Further, after obtaining the arrival time t1 of the zero-crossing signal in the current cycle, before calculating the time interval between the end of the closing duration T2 of the previous cycle and the arrival time t1 of the current cycle, the following is executed: Determine whether the arrival time t1 of the zero-crossing signal in the current cycle is after the closing time T2 of the switching unit in the previous cycle. If not, block the current arrival time t1 and end the current cycle.

[0047] In this step, the main control unit determines whether the validity of the arrival time point t1 is required, which is used to determine whether the previous chopping was completed. If so, it proceeds to the subsequent adaptive chopping duration adjustment judgment; otherwise, it can jump out of the current loop and directly use the initial basic chopping duration.

[0048] Further, after calculating the time interval between the end point of the previous cycle's closing duration T2 and the arrival time point t1 of the current cycle, execute: Determine whether the time interval is greater than the preset waiting time; otherwise, block the current time point t1 and end the current loop.

[0049] In this step, it is determined whether the time interval t2 satisfies t2 > preset waiting time. If so, the next step is continued. This is because, in the actual circuit, after the switching unit switches the state in the previous cycle, the zero-crossing signal needs to wait between 600us and 700us (depending on the specific component parameters of the circuit) due to factors such as software execution time, transistor delay, and comparator delay. If the zero-crossing signal appears when the gate is turned low, it is because of the impact of the switching of the MOS transistor itself. The impact voltage of the device itself causes the zero-crossing signal to malfunction, resulting in the generation of abnormal zero-crossing signals, which also needs to be shielded.

[0050] A further method for adaptively adjusting the chopping time in a single live wire power supply is provided, comprising the following steps: Obtain the arrival time t1 of the zero-crossing signal in the current cycle, and calculate the time interval between the end of the closing duration T2 of the previous cycle and the arrival time t1 of the current cycle. If the time interval is within the preset reference duration, then the disconnection duration T1 and the closure duration T2 of the current cycle remain unchanged; If the time interval is less than the minimum value of the reference duration, then the disconnection duration T1 is extended; If the time interval is greater than the maximum value of the reference duration, then the disconnection duration T1 is shortened.

[0051] This method works on the same principle as the aforementioned single-wire power supply system with adaptive chopping time adjustment.

[0052] Furthermore, a smart screen is provided, which includes the aforementioned single-wire power supply system with adaptive chopping time adjustment.

[0053] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0054] This 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 block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can 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, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0055] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0056] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0057] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. A single-wire power supply system with adaptive chopping time adjustment, characterized in that: Includes the following modules: A zero-crossing detection unit is connected between the live wire inlet and the live wire outlet. It is used to detect the zero-crossing point of the mains signal and output a zero-crossing signal. The zero-crossing detection unit includes a hysteresis comparator circuit, which is used to shape the mains signal to output a stable zero-crossing signal. The main control unit is connected to the output of the zero-crossing detection unit and is used to acquire the arrival time t1 of the zero-crossing signal cycle by cycle, and adaptively adjust the chopping duration in the current mains power cycle according to the arrival time t1 to generate a chopping control signal. The switching unit is connected between the live wire inlet and the live wire outlet and is controlled to be turned on or off by the main control unit. It is driven by the chopper control signal to perform periodic switching on and off to control the power supply process.

2. The single-wire power supply system with adaptive chopping time adjustment according to claim 1, characterized in that: The zero-crossing detection unit includes a comparator U1. The positive input terminal of the comparator U1 is connected to the reference voltage VREF through a resistor R12. The positive input terminal of the comparator U1 is connected to the output terminal of the comparator U1 through a resistor R11. The negative input terminal of the comparator U1 is connected to the mains sampling signal. The positive terminal of the comparator U1 is connected to the positive power supply voltage VCC. The negative terminal of the comparator U1 is grounded.

3. A single-wire power supply system with adaptive chopping time adjustment according to claim 2, characterized in that: The zero-crossing detection unit includes a step-down circuit connected between the live wire input and live wire output. The output of the step-down circuit is connected to a low-pass filter circuit, and the output of the low-pass filter circuit is connected to a level conversion circuit. The level conversion circuit converts the output waveform of the low-pass filter circuit into a square wave signal containing the zero-crossing point of the mains power.

4. A single-wire power supply system with adaptive chopping time adjustment according to claim 3, characterized in that: The level conversion circuit includes an NPN transistor Q1. The base (B) of the NPN transistor Q1 is connected to the output of the low-pass filter circuit through a current-limiting resistor R9. The collector (C) of the NPN transistor Q1 is connected to the positive power supply voltage VCC through a pull-up resistor R10. The emitter (E) of the NPN transistor Q1 is grounded. The collector (C) of the NPN transistor Q1 is connected to the negative input of the comparator U1. The conduction and cutoff characteristics of the NPN transistor Q1 convert the output waveform of the low-pass filter circuit into a square wave signal with a high level before and after the zero-crossing point of the mains power. The main control unit uses the falling edge time of the square wave signal as the arrival time t1.

5. A single-wire power supply system with adaptive chopping time adjustment according to claim 1, characterized in that: The main control unit is configured with an initial basic chopping duration, which includes the opening duration T1 and closing duration T2 that control the switching unit to perform sequentially within the chopping cycle. The main control unit performs adaptive chopping duration adjustment cyclically during operation. The adaptive chopping duration adjustment includes the following steps: Obtain the arrival time t1 of the zero-crossing signal in the current cycle, and calculate the time interval between the end of the closing duration T2 of the previous cycle and the arrival time t1 of the current cycle. If the time interval is within the preset reference duration, then the disconnection duration T1 and the closure duration T2 of the current cycle remain unchanged; If the time interval is less than the minimum value of the reference duration, then the disconnection duration T1 is extended; If the time interval is greater than the maximum value of the reference duration, then the disconnection duration T1 is shortened.

6. A single-wire power supply system with adaptive chopping time adjustment according to claim 5, characterized in that: If the time interval is less than the minimum value of the reference duration, then after extending the disconnection duration T1, the following steps are performed: If the time interval is less than the minimum value of the reference duration for a consecutive preset number of times, the extended closing duration T1 will be reset to the initial opening duration T1.

7. A single-wire power supply system with adaptive chopping time adjustment according to claim 5, characterized in that: If the time interval is greater than the maximum value of the reference duration, then shortening the disconnection duration T1 includes: If the time interval is greater than the reference duration and the time interval is less than 10ms, then the disconnection duration T1 is shortened. If the time interval is greater than the reference duration and the time interval is greater than 10ms, then the disconnection duration T1 remains unchanged.

8. A single-wire power supply system with adaptive chopping time adjustment according to claim 5, characterized in that: After obtaining the arrival time t1 of the zero-crossing signal in the current cycle, and before calculating the time interval between the end of the closing duration T2 of the previous cycle and the arrival time t1 of the current cycle, the following steps are performed: Determine whether the arrival time t1 of the zero-crossing signal in the current cycle is after the closing time T2 of the switching unit in the previous cycle; otherwise, block the current arrival time t1 and end the current cycle; and / or, After calculating the time interval between the end point of the previous cycle's closing duration T2 and the arrival time point t1 of the current cycle, execute: Determine whether the time interval is greater than the preset waiting time; otherwise, block the current time point t1 and end the current loop.

9. A single-wire power supply method with adaptive chopping time adjustment, characterized in that: Includes the following steps: Obtain the arrival time t1 of the zero-crossing signal in the current cycle, and calculate the time interval between the end of the closing duration T2 of the previous cycle and the arrival time t1 of the current cycle. If the time interval is within the preset reference duration, then the disconnection duration T1 and the closure duration T2 of the current cycle remain unchanged; If the time interval is less than the minimum value of the reference duration, then the disconnection duration T1 is extended; If the time interval is greater than the maximum value of the reference duration, then the disconnection duration T1 is shortened.

10. A smart screen, characterized in that: The invention comprises a single-wire power supply system with adaptive chopping time adjustment as described in any one of claims 1-9.

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