An LED lighting drive control method and system

Abstract

The present application discloses an LED lighting drive control method and system, which relates to the technical field of light source control. The method includes: obtaining at least two control parameters that affect the duty cycle of the PWM signal inside the flyback circuit; establishing a first feedback loop between the feedback signal output end of the flyback circuit and one of the control parameter input ends, and a second feedback loop from the feedback signal output end through an external control unit to the remaining control parameter input ends; obtaining the safety threshold of the peak voltage at the output end of the flyback circuit; collecting the voltage feedback signal and comparing it with the safety threshold: if it is not higher than the safety threshold, maintaining the activation state of the first feedback loop, otherwise activating the second feedback loop simultaneously, and adjusting the duty cycle and change rate of the PWM signal based on the two-way feedback signals. The above solution uses multiple control parameters to cooperate to more precisely and quickly adjust the duty cycle and change rate of the PWM signal, so that the output peak voltage value is within the safe range, protecting the load and circuit components from impact and improving the stability of the circuit output.

Description

Technical Field

[0001] This application relates to the technical field of light source control, and particularly to an LED lighting drive control method and system. Background Art

[0002] The flyback converter is a common switching power supply topology and is widely used in various electronic devices. It realizes voltage conversion and isolation functions through the charging and discharging of energy storage elements, and has the advantages of simple structure, stable output, low cost, etc. Therefore, it has been widely used in power system components such as LED drivers and communication devices to provide stable voltage and current for each load.

[0003] The flyback circuit basically consists of a transformer, a switching transistor, a diode, an output filter inductor, and a capacitor, etc. Its working principle mainly includes two stages: the energy storage stage and the energy transfer stage. In the energy storage stage: when the switching transistor is turned on, the input voltage is applied to the primary side of the transformer, and the transformer stores energy; at the same time, the diode is reverse-biased and does not conduct. In the energy transfer stage: when the switching transistor is turned off, the magnetic field of the transformer collapses, generating a high-voltage pulse, inducing an output voltage on the secondary side, and the diode conducts, transferring energy to the load. Based on the above basic circuit structure, in order to ensure that the output voltage of the circuit remains stable, a feedback loop is usually configured between the output end of the flyback circuit and the power management chip. The power management chip can adjust the duty cycle of the switching transistor according to the output voltage or current sampling signal at the output end of the flyback circuit, that is, adjust the output of the secondary coil of the transformer by adjusting the on-off duration of the current in the primary coil of the transformer.

[0004] To simplify the control, the output voltage of the flyback circuit is usually sampled by resistor series voltage division, and the feedback voltage is output to the inverting input terminal of the internal error amplifier of the power control chip. After comparison with the internal reference voltage, an error signal is generated, and then the voltage value at the inverting output terminal of the error amplifier is adjusted. Finally, combined with the switching transistor current feedback signal, a PWM signal with a specific duty cycle is generated to control the on-off state of the switching transistor. Among them, the duty cycle D of the PWM signal is positively correlated with the ratio of the voltage value Vcomp at the inverting output terminal of the error amplifier and the switching transistor current feedback value Vcs, that is, D∝Vcomp / Vcs.

[0005] In practical applications, the output load of a flyback circuit is usually not constant. For example, when driving LED lighting, in order to adjust the lighting brightness or color temperature, it is necessary to change the number of LED loads or the lighting power. Taking a flyback circuit built into a charger as an example, when no load is connected, the duty cycle of the PWM signal controlling the switching transistor is about 2%. When the load output current is 0.4 A, the duty cycle of the PWM signal is about 10%. When the load output current is 0.8 A, the duty cycle of the PWM signal is about 15%. And when the load output current becomes 1.3 A, the duty cycle of the PWM signal correspondingly becomes about 20%. Combining the working principle of the flyback circuit and the above PWM signal duty cycle control principle, it can be seen that once the output load changes, the output current of the circuit will also change suddenly, and the sudden change of the output current will cause the output ripple peak to become steeper, impacting the load, and even burning out the load in severe cases.

[0006] In summary, it can be seen that how to reduce the ripple peak at the output end when the output load of the flyback circuit changes is crucial for improving the output stability of the circuit and extending the service life of the load and circuit components. Summary of the Invention

[0007] Aiming at the problem that when the output load of the flyback circuit changes in practical applications, the peak voltage generated at the output end is likely to impact the load and circuit components, affecting the output stability of the circuit and shortening the service life of the load and circuit components, a first object of this application is to provide a LED lighting drive control method, which can stabilize the circuit output when the output load changes greatly, while reducing the peak voltage and protecting the load and components. To achieve the above drive control method, a second object of this application is to provide a LED lighting drive control system, and the specific scheme is as follows:

[0008] A LED lighting drive control method includes:

[0009] Obtaining at least two control parameters affecting the duty cycle of the PWM signal based on the circuit structure, where the PWM signal is used to control the conduction state of the switching transistor inside the flyback circuit;

[0010] Establishing a first feedback loop between the feedback signal output end of the flyback circuit and one of the control parameter input ends, and a second feedback loop from the feedback signal output end through an external control unit to the remaining control parameter input ends;

[0011] Obtaining and storing the safety threshold of the peak voltage at the output end of the flyback circuit;

[0012] Collecting the voltage feedback signal at the feedback signal output end and comparing it with the safety threshold:

[0013] If the voltage feedback signal is not higher than the safety threshold, maintain the activation state of the first feedback loop, and adjust the duty cycle of the PWM signal according to the feedback signal of the first feedback loop;

[0014] If the voltage feedback signal is higher than the safety threshold, activate the second feedback loop, and adjust the duty cycle and its change rate of the PWM signal according to the feedback signals of the first feedback loop and the second feedback loop.

[0015] Through the above technical solution, when the peak voltage caused by the change of the output load of the flyback circuit is within the safety threshold, that is, when the above peak voltage will not have too much impact on the load, based on the first feedback loop and using a control parameter to feedback and adjust the duty cycle of the PWM signal to maintain the stability of the output voltage; when the peak voltage caused by the change of the output load of the flyback circuit exceeds the safety threshold, the second feedback loop is activated on the basis of the first feedback loop, and the duty cycle and its change rate of the PWM signal are adjusted more accurately and quickly by using the changes of multiple control parameters, so that the output peak voltage value is always within the safe range, thereby protecting the load and circuit components from impact, improving the stability of the circuit output, and extending the service life of the load and circuit components.

[0016] Further, a signal processing circuit module with fixed parameters is configured in the first feedback loop, which is used to receive and, according to the voltage feedback signal and based on the processing result of the signal processing circuit module, feedback and output corresponding control parameters in real time to adjust the duty cycle of the PWM signal;

[0017] A comparator module is configured in the second feedback loop, which is used to receive the voltage feedback signal and compare it with the safety threshold. If the voltage feedback signal is higher than the safety threshold, a comparison result signal is output to an external control unit. The external control unit receives and responds to the comparison result signal, collects the output of the feedback signal output end, and generates corresponding control parameters according to the built-in algorithm to adjust the duty cycle and its change rate of the PWM signal;

[0018] Among them, the change rate of the PWM signal duty cycle includes the change trend and change speed of the duty cycle.

[0019] Through the above technical solution, the signal processing circuit module configured in the first feedback loop can respond quickly and stably to the change of the voltage feedback signal. At the same time, the peak voltage generated when the duty cycle of the PWM signal is adjusted will not cause a destructive impact on the circuit components and the load, while the second feedback loop compares the voltage feedback signal with the safety threshold and calls the corresponding signal processing algorithm or established output method to output control parameters according to the comparison result.

[0020] Further, the method further includes:

[0021] Obtain and store the output current and PWM signal duty cycle corresponding to different output loads, as well as the correlation between different duty cycle change rates and peak voltage fluctuation ranges when the output load is adjusted;

[0022] Compare the voltage feedback signal with the safety threshold. If the voltage feedback signal is higher than the safety threshold, obtain and, according to the adjustment request of the current output load, find the duty cycle corresponding to the PWM signal after the adjustment is completed, and calculate the required duty cycle change rate in combination with the current PWM signal duty cycle;

[0023] According to the duty cycle change rate, gradually adjust the control parameter value of the second feedback loop in the external control unit and output it.

[0024] When the output load of the flyback circuit changes greatly in a short time, the duty cycle of the PWM signal in the traditional control method will also change rapidly, resulting in an excessive peak voltage at the output end. Through the above technical solution, based on the control of the first feedback loop, the change rate of the PWM signal duty cycle can be adjusted as needed, so that the output current at the output end of the flyback circuit changes more smoothly, reducing the peak voltage value and the impact on the load and circuit components.

[0025] Further, the method further includes:

[0026] Obtain and store the interference waveform data at the output end of the flyback circuit;

[0027] Establish a signal connection between the feedback signal output end and the external control unit;

[0028] Compare the voltage feedback signal with the safety threshold. If the voltage feedback signal is higher than the safety threshold, increase the sampling frequency of the voltage feedback signal by the external control unit;

[0029] Compare the sampling curve of the voltage feedback signal with the interference waveform data to determine whether the peak voltage in the voltage feedback signal is an interference signal:

[0030] If it is an interference signal, maintain the state where the first feedback loop is activated and the second feedback loop is in a dormant state, and adjust the duty cycle of the PWM signal according to the feedback signal of the first feedback loop;

[0031] If it is not an interference signal, activate the second feedback loop, and adjust the duty cycle and its change rate of the PWM signal according to the feedback signals of the first feedback loop and the second feedback loop.

[0032] Through the above technical solution, the sampling frequency of the voltage feedback signal can be increased, and it can be determined whether the current voltage feedback signal is an interference signal based on the change curve of multiple sampling points within a short sampling duration. Thereby, interference can be excluded, the error adjustment of the duty cycle of the PWM signal can be avoided, and the stability of the output voltage can be maintained.

[0033] Further, the method further includes:

[0034] Obtain and store the change trend of each type of spike voltage waveform itself;

[0035] Obtain and store the correlation relationship between each type of spike voltage waveform and the change rate of the duty cycle of the adapted PWM signal;

[0036] Generate a feedback waveform curve based on the feedback signal obtained by high-frequency sampling, determine the spike voltage category according to the change trend, and find the change rate of the duty cycle of the adapted PWM signal;

[0037] According to the change rate of the duty cycle of the adapted PWM signal, gradually adjust the control parameter value of the second feedback loop in the external control unit and output it.

[0038] Through the above technical solution, the control unit can be used to analyze the feedback voltage signal, especially to analyze the spike voltage waveform, predict its change trend, and predict in advance the change rate of the duty cycle required to reduce the above spike voltage according to the above change trend, quickly make adjustments to the duty cycle of the PWM signal, and avoid excessive spike voltage amplitude, which may cause damage to the load and circuit components.

[0039] Further, obtaining and storing the output current and PWM signal duty cycle corresponding to different output loads, the correlation relationship between different duty cycle change rates and the spike voltage fluctuation range during output load adjustment, and the interference waveform data at the output end of the flyback circuit are all completed by a signal generator, an oscilloscope combined with a PC;

[0040] Obtaining the change trend of each type of spike voltage waveform itself includes adjusting the output load in different electromagnetic environments and temperature environments, and then using an oscilloscope to collect the spike voltage waveform data when the output load changes, and obtaining the change trend of each type of spike voltage waveform itself through data fitting;

[0041] Obtaining the correlation relationship between each type of spike voltage waveform and the change rate of the duty cycle of the adapted PWM signal includes:

[0042] Adjust the output load of the flyback circuit and record the corresponding spike voltage waveforms for each load adjustment;

[0043] When adjusting the output load of the flyback circuit, adjust the on-off state of the switching tube with different change rates of the PWM signal duty cycle, and record the corresponding spike voltage waveforms for each load adjustment;

[0044] Select the duty cycle change rate of the PWM signal corresponding to the peak voltage with the smallest amplitude as the duty cycle change rate of the PWM signal adapted to the peak voltage waveform of the current category.

[0045] Through the above technical solution, the peak voltage waveform corresponding to the output load change, the duty cycle and the change rate of the PWM signal for reducing the above peak voltage amplitude can be accurately obtained. By storing the above data information in the control unit, the corresponding PWM signal duty cycle and its change rate can be quickly matched according to the output load change, thereby controlling the amplitude of the output peak voltage and protecting the load and circuit components from impact.

[0046] An LED lighting drive control system includes an input rectification unit, a PFC unit, a flyback circuit unit, a load unit, and an external control unit;

[0047] The flyback circuit unit includes a transformer module, a power control module, and an output feedback module;

[0048] At least two feedback loops and a loop state control sub-module are configured in the output feedback module;

[0049] The first feedback loop is configured to be from the feedback signal output end of the flyback circuit to the first PWM control signal input end in the power control module, so as to adjust the duty cycle of the PWM signal according to the voltage feedback signal to control the conduction state of the switching tube;

[0050] The second feedback loop is configured to be from the feedback signal output end of the flyback circuit through the external control unit to the second PWM control signal input end, so as to cooperate with the first feedback loop according to the voltage feedback signal to adjust the duty cycle of the PWM signal to control the conduction state of the switching tube;

[0051] The loop state control sub-module is configured to collect the voltage feedback signal at the feedback signal output end and compare it with a safety threshold:

[0052] If the voltage feedback signal is not higher than the safety threshold, the activation state of the first feedback loop is maintained, and the duty cycle of the PWM signal is adjusted according to the feedback signal of the first feedback loop;

[0053] If the voltage feedback signal is higher than the safety threshold, the second feedback loop is activated, and the duty cycle and the change rate of the PWM signal are adjusted according to the feedback signals of the first feedback loop and the second feedback loop.

[0054] Further, the loop state control sub-module includes:

[0055] A first comparator, one of its comparison input terminals is electrically connected to the feedback signal output terminal through a voltage-dividing resistor, the other comparison input terminal is electrically connected to a first reference voltage, the comparison output terminal is connected to the negative electrode of an optocoupler emitter, the positive electrode of the optocoupler emitter is electrically connected to a power supply, and the optocoupler receiver is located between the first PWM control signal input terminal and the ground;

[0056] A second comparator, one of its comparison input terminals is electrically connected to the feedback signal output terminal through a voltage-dividing resistor, the other comparison input terminal is electrically connected to a second reference voltage, and the comparison output terminal is electrically connected to the first signal input pin of an external control unit through an isolation drive chip;

[0057] The first signal output pin of the external control unit is signal-connected to the second PWM control signal input terminal, and the external control unit receives and responds to the output result of the second comparator, and outputs control parameters to the second PWM control signal input terminal based on a built-in algorithm.

[0058] Further, a signal connection exists between the second signal input pin of the external control unit and the feedback signal output terminal;

[0059] A data storage unit is configured or externally connected in the external control unit for storing: the output current and the PWM signal duty cycle corresponding to different output loads, the correlation between different duty cycle change rates and the spike voltage fluctuation range during output load adjustment, the interference waveform data at the output end of the flyback circuit, and the change trend of various spike voltage waveforms themselves;

[0060] The external control unit is configured with:

[0061] An interference elimination module configured to obtain the interference waveform data at the output end of the flyback circuit, compare the voltage feedback signal with the safety threshold, if the voltage feedback signal is higher than the safety threshold, increase the sampling frequency of the voltage feedback signal, compare the sampling curve of the voltage feedback signal with the interference waveform data, and determine whether the spike voltage in the voltage feedback signal is an interference signal: if it is an interference signal, maintain the state where the first feedback loop is activated and the second feedback loop is dormant, and adjust the duty cycle of the PWM signal according to the feedback signal of the first feedback loop;

[0062] A control parameter value generation module configured to generate a feedback waveform curve based on the feedback signal obtained by high-frequency sampling, determine the spike voltage category according to the change trend, find the duty cycle change rate of the PWM signal adapted thereto, and generate the control parameter value and output strategy of the second feedback loop according to the adapted duty cycle change rate of the PWM signal.

[0063] This application includes at least one of the following beneficial technical effects:

[0064] Two feedback loops are set between the feedback signal output terminal of the flyback circuit and the power management chip. When the spike voltage caused by the change of the output load of the flyback circuit is within the safety threshold, that is, when the spike voltage will not have too much impact on the load, the duty cycle of the PWM signal is feedback-regulated based on the first feedback loop and with a control parameter to maintain the stability of the output voltage. When the spike voltage caused by the change of the output load of the flyback circuit exceeds the safety threshold, the second feedback loop is activated on the basis of the first feedback loop, and the duty cycle and its change rate of the PWM signal are adjusted more precisely and quickly by using the changes of multiple control parameters, so that the output spike voltage value is always within the safety range, thereby protecting the load and circuit components from impact, improving the stability of the circuit output, and extending the service life of the load and circuit components. Description of the Drawings

[0065] Figure 1 is the overall schematic diagram of the LED lighting drive control method of this application;

[0066] Figure 2 is the schematic diagram of the method for finding and matching control parameters according to the spike voltage category;

[0067] Figure 3 is the schematic diagram of the method for excluding spike interference signals and correctly matching control parameters;

[0068] Figure 4 is the structural block diagram of the LED lighting drive control system of this application;

[0069] Figure 5 is the functional framework schematic diagram of the flyback circuit unit;

[0070] Figure 6 is the circuit principle schematic diagram of the flyback circuit unit.

[0071] Reference Signs: 100, input rectification unit; 200, PFC unit; 300, flyback circuit unit; 310, transformer module; 320, power control module; 330, output feedback module; 400, load unit; 500, external control unit; 600, first feedback loop; 700, second feedback loop. Detailed Embodiment

[0072] The following details the embodiments of this application, and the examples of the embodiments are shown in the drawings.

[0073] In the description of this specification, the description referring to terms such as "certain embodiments", "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiments or examples are included in at least one embodiment or example of this application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0074] An embodiment of this application discloses an LED lighting drive control method. As Figure 1 shown, it mainly includes the following steps:

[0075] S100, obtaining at least two control parameters that affect the duty cycle of the PWM signal based on the circuit structure, where the PWM signal is used to control the conduction state of the switching transistor inside the flyback circuit;

[0076] S200, establishing a first feedback loop between the feedback signal output terminal of the flyback circuit and one of the control parameter input terminals, and a second feedback loop from the feedback signal output terminal through an external control unit to the remaining control parameter input terminals;

[0077] S300, obtaining and storing the safety threshold of the peak voltage at the output terminal of the flyback circuit;

[0078] S400, collecting the voltage feedback signal at the feedback signal output terminal and comparing it with the safety threshold:

[0079] S410, if the voltage feedback signal is not higher than the safety threshold, maintaining the activation state of the first feedback loop and adjusting the duty cycle of the PWM signal according to the feedback signal of the first feedback loop;

[0080] S420, if the voltage feedback signal is higher than the safety threshold, activating the second feedback loop and adjusting the duty cycle and its change rate of the PWM signal according to the feedback signals of the first feedback loop and the second feedback loop.

[0081] In the above step S100, the control parameters that affect the duty cycle of the PWM signal can be analyzed through the flyback circuit structure. For example, through the magnitude of the current of the switching transistor, the magnitude of the voltage at the feedback signal output terminal, etc. In practical applications, the above control parameters will correspond to the corresponding control parameter input terminals on the power management chip. For example, the CS pin in the L6562 chip is used to detect the current flowing through the switching transistor, and the COMP pin is used to detect the voltage feedback signal at the feedback signal output terminal. Finally, the duty cycle is jointly determined by Vcomp and Vcs. Similarly, the INV pin also determines the duty cycle of the PWM signal.

[0082] In step S200, in order to be able to quickly respond to the voltage / current change at the output end of the flyback circuit and adjust the output of the PWM signal, a signal processing circuit module with fixed parameters is configured in the first feedback loop. The signal processing circuit module is used to receive and, based on the voltage feedback signal and the processing result of the signal processing circuit module, feedback and output corresponding control parameters in real time to adjust the duty cycle of the PWM signal. In the above design scheme of the first feedback loop, the feedback signal output from the feedback signal output end does not pass through the control unit and is directly processed by the signal processing circuit module, which can improve the signal feedback speed and enable the power management chip to make a quick response.

[0083] Correspondingly, in the embodiment of the present application, a comparator module is configured in the second feedback loop, which is used to receive the voltage feedback signal and compare it with a safety threshold. The above safety threshold is a voltage value, and the spike voltage below this safety threshold is considered not to cause a damaging impact on the circuit components and the load. In practical applications, the above threshold can be set as needed. In the embodiment of the present application, if the voltage feedback signal is higher than the safety threshold, the comparator module outputs a comparison result signal to the external control unit. The external control unit receives and responds to the comparison result signal, collects the output of the feedback signal output end, and generates corresponding control parameters according to the built-in algorithm to adjust the duty cycle and its change rate of the PWM signal.

[0084] The above control parameters refer to specific control parameter values, such as Vcs.

[0085] The change rate of the PWM signal duty cycle includes the duty cycle change trend and the change speed. For example, the time period required for the PWM signal duty cycle to change from 2% to 20%, and the number of intermediate duty cycles during the change process, etc. In practice, directly jumping from a 2% duty cycle to a 20% duty cycle in a short time will cause the current in the transformer coil to increase sharply, and then generate a relatively high spike voltage at the secondary output end. However, if the duty cycle changes from 2% to 10% and then increases to 20%, the amplitude of the generated spike voltage will be slightly smaller. By precisely controlling the change rate of the PWM signal duty cycle, the amplitude of the spike voltage can be greatly reduced, so that the output spike voltage value is always within the safe range, thereby protecting the load and circuit components from impact, improving the stability of the circuit output, and extending the service life of the load and circuit components.

[0086] In practical applications, when the output load of the flyback circuit changes greatly in a short time, the duty cycle of the PWM signal will also change rapidly, resulting in an excessive spike voltage at the output end. In order to be able to precisely control the duty cycle of the PWM signal and avoid too long response delay, such as Figure 2As shown, the LED lighting drive control method disclosed in the embodiments of the present application further includes the following steps:

[0087] A100, obtaining and storing the correlation relationship between the output current and the duty cycle of the PWM signal corresponding to different output loads;

[0088] A200, obtaining and storing the correlation relationship between different duty cycle change rates and the peak voltage fluctuation range when the output load is adjusted;

[0089] A300, comparing the voltage feedback signal with the safety threshold:

[0090] A311, if the voltage feedback signal is higher than the safety threshold, obtaining and, according to the adjustment request of the current output load, finding the duty cycle corresponding to the PWM signal after the adjustment ends, and calculating and generating the required duty cycle change rate in combination with the current duty cycle of the PWM signal;

[0091] A312, gradually adjusting the control parameter value of the second feedback loop in the external control unit according to the duty cycle change rate and outputting it.

[0092] A321, if the voltage feedback signal is not higher than the safety threshold, maintaining the sleep state of the second feedback loop.

[0093] In practical applications, the load adjustment request is usually received by the external control unit. For example, the external control instruction signal is received by using the wireless communication antenna module, and then parsed by the MCU into the corresponding circuit control instruction and output to the load unit to control the working state of the load. Therefore, in step A311 above, obtaining the adjustment request of the current load can be directly obtained through the external control unit. And since the external control unit itself serves as the relay unit of the second feedback loop, therefore, combining steps A312 and A313, the external control unit can output the circuit control instruction to the load unit after finding and calculating the corresponding control parameter value according to the load adjustment request, thereby greatly shortening the response delay of the second feedback loop in the active state.

[0094] The above technical solution can, on the basis of the control of the first feedback loop, adjust the change rate of the duty cycle of the PWM signal as needed, thereby making the output current at the output end of the flyback circuit change more smoothly, reducing the peak voltage value, and reducing the impact on the load and circuit components.

[0095] Optimally, as Figure 3 shown, the method of the present application further includes:

[0096] B100, obtaining and storing the interference waveform data at the output end of the flyback circuit;

[0097] B200, establish a signal connection between the feedback signal output terminal and the external control unit;

[0098] B300, compare the voltage feedback signal with the safety threshold:

[0099] B311, if the voltage feedback signal is higher than the safety threshold, increase the sampling frequency of the external control unit for the voltage feedback signal;

[0100] B312, compare the sampling curve of the voltage feedback signal with the interference waveform data to determine whether the spike voltage in the voltage feedback signal is an interference signal:

[0101] B3121, if it is an interference signal, maintain the state where the first feedback loop is active and the second feedback loop is dormant, and adjust the duty cycle of the PWM signal according to the feedback signal of the first feedback loop;

[0102] B3122, if it is not an interference signal, activate the second feedback loop, and adjust the duty cycle and its change rate of the PWM signal according to the feedback signals of the first feedback loop and the second feedback loop;

[0103] B320, if the voltage feedback signal is not higher than the safety threshold, maintain the dormant state of the second feedback loop.

[0104] The activation and dormancy determination criteria for the above-mentioned second feedback loop are as follows: after the voltage feedback signal is input to the external control unit, whether the external control unit outputs corresponding control parameters to the control parameter input terminal of the power control chip, that is, whether the signal transmitted in the second feedback loop will contribute to the change of the duty cycle of the PWM signal.

[0105] In the above technical solution, by increasing the sampling frequency of the voltage feedback signal, it is possible to determine whether the current voltage feedback signal is an interference signal based on the change curve of multiple sampling points within a short sampling duration, thereby eliminating interference, avoiding incorrect adjustment of the duty cycle of the PWM signal, and maintaining the stability of the output voltage.

[0106] Based on the settings of steps B200 and B311, the LED lighting drive control method described in this application further includes the steps:

[0107] C100, obtain and store the change trend of each type of spike voltage waveform itself;

[0108] C200, obtain and store the correlation between each type of spike voltage waveform and the change rate of the duty cycle of the adapted PWM signal;

[0109] C300, generate a feedback waveform curve based on the feedback signal obtained by high-frequency sampling, determine the spike voltage category according to the change trend, and find the change rate of the duty cycle of the PWM signal adapted to it;

[0110] C400. Gradually adjust the control parameter value of the second feedback loop in the external control unit according to the duty cycle change rate of the adapted PWM signal and output it.

[0111] In step C100, the change trend of the spike voltage waveform includes but is not limited to the fluctuation curve shape and trend of the spike voltage waveform.

[0112] Through the above technical solution, the control unit can analyze the feedback voltage signal, especially analyze the spike voltage waveform, predict its change trend, and predict in advance the duty cycle change rate required to reduce the above spike voltage according to the above change trend, quickly make adjustments to the duty cycle of the PWM signal, improve the response speed, and avoid excessive spike voltage amplitude, which may cause damage to the load and circuit components.

[0113] In the embodiment of the present application, obtaining the output current and PWM signal duty cycle corresponding to different output loads, the correlation between different duty cycle change rates and the spike voltage fluctuation range when the output load is adjusted, and the interference waveform data at the output end of the flyback circuit are all completed by a signal generator, an oscilloscope and a PC. In specific operations, adjust the output load, such as changing the number of connected LED loads through a switching transistor, then input specific control parameters to the control parameter input end of the power management chip U1 by using the signal generator, and at the same time collect and store the output voltage waveform at the output end of the flyback circuit by using the oscilloscope. Finally, the control parameters and voltage waveform data are output to the PC for storage.

[0114] Obtaining the change trend of each type of spike voltage waveform itself includes adjusting the output load in different electromagnetic environments and temperature environments, and then using an oscilloscope to collect the spike voltage waveform data when the output load changes, and obtaining the change trend of each type of spike voltage waveform itself through data fitting.

[0115] In the method of the present application, obtaining the duty cycle change rate of each type of spike voltage waveform and the adapted PWM signal includes:

[0116] Adjust the output load of the flyback circuit and record the corresponding spike voltage waveform for each load adjustment.

[0117] When adjusting the output load of the flyback circuit, adjust the on-off state of the switching transistor by using different duty cycle change rates of the PWM signal, and record the corresponding spike voltage waveform for each load adjustment.

[0118] Select the duty cycle change rate of the PWM signal corresponding to the spike voltage with the minimum amplitude as the duty cycle change rate of the PWM signal adapted to the current type of spike voltage waveform.

[0119] The above technical solution can accurately obtain the corresponding spike voltage waveform when the output load changes, reduce the duty cycle and change rate of the PWM signal for reducing the above spike voltage amplitude. By storing the above data information in the control unit, the corresponding duty cycle and its change rate of the PWM signal can be quickly matched according to the output load change, improving the response speed.

[0120] To implement the above LED lighting drive control method, an embodiment of the present application also discloses an LED lighting drive control system.

[0121] As Figure 4 shown, the system includes an input rectification unit 100, a PFC unit 200, a flyback circuit unit 300, a load unit 400, and an external control unit 500 that are connected in sequence.

[0122] The input end of the input rectification unit 100 is connected to 220V alternating current, and after passing through the EMI filtering module and the rectification module, 310V direct current is output. The direct current flowing out of the input rectification unit 100 enters the PFC unit 200 for power factor optimization and correction, and a stable direct current voltage is output to the flyback circuit unit 300. After being stepped down and regulated by the flyback circuit unit 300, it is output to the load unit 400. There are already many public disclosures in the prior art regarding the circuit structures and working principles of the input rectification unit 100 and the PFC unit 200, and will not be elaborated here.

[0123] In the embodiment of the present application, in combination with Figure 5 、 Figure 6 shown, the flyback circuit unit 300 includes a transformer module 310, a power supply control module 320, and an output feedback module 330.

[0124] In the embodiment of the present application, the above power management chip U1 preferably uses an L6562 chip. The transformer module 310 includes a primary coil, an auxiliary coil, and a secondary coil. One end of the primary coil is electrically connected to the output end of the PFC unit 200, and the other end is grounded in series with a switching tube. A spike ablation module is connected in parallel outside the primary coil, including several series-parallel resistors and a reverse diode. When the voltage in the primary coil reverses, the above series-parallel resistors and the reverse diode form a spike ablation circuit to eliminate the energy in the form of heat. The gate of the switching tube is electrically connected to the PWM signal output end (GD pin) of the power management chip U1, and adjusts its own conduction state in response to the PWM signal output by the power management chip U1.

[0125] In the L6562 power management chip, the duty cycle of the PWM signal is positively correlated with the ratio of Vcomp and Vcs, that is, D ∝ Vcomp / Vcs. Therefore, in the embodiment of the present application, Vcomp and Vcs are used as the aforementioned control parameters.

[0126] In combination withFigure 5 As shown, at least two feedback loops and a loop state control sub-module are configured in the output feedback module 330. For ease of explanation, two feedback loops are taken as an example in the embodiments of the present application. The first feedback loop 600 is configured to be from the feedback signal output end of the flyback circuit to the first PWM control signal input end in the power control module 320, so as to adjust the duty cycle of the PWM signal according to the voltage feedback signal to control the conduction state of the switching tube. The above-mentioned first PWM control signal input end is configured as the COMP pin of the power management chip U1. The second feedback loop 700 is configured to be from the feedback signal output end of the flyback circuit through the external control unit 500 to the second PWM control signal input end, so as to cooperate with the first feedback loop 600 according to the voltage feedback signal to adjust the duty cycle of the PWM signal to control the conduction state of the switching tube. The above-mentioned second PWM control signal input end is configured as the CS pin of the power management chip U1, and the PWM signal is output by the external control unit 500 for adjustment and control.

[0127] The loop state control sub-module is configured to collect the voltage feedback signal at the feedback signal output end and compare it with a safety threshold. If the voltage feedback signal is not higher than the safety threshold, the activation state of the first feedback loop 600 is maintained, and the duty cycle of the PWM signal is adjusted according to the feedback signal of the first feedback loop 600. If the voltage feedback signal is higher than the safety threshold, the second feedback loop 700 is activated, and the duty cycle and its change rate of the PWM signal are adjusted according to the feedback signals of the first feedback loop 600 and the second feedback loop 700.

[0128] Specifically, an output filter capacitor C4 and a load resistor R11 are connected in parallel at the feedback signal output end of the flyback circuit. The loop state control sub-module includes a first comparator A1 and a second comparator A2. As Figure 6As shown in the figure, the inverting input terminal of the first comparator A1 is electrically connected to the feedback signal output terminal of the flyback circuit through a voltage dividing resistor R19, the non-inverting input terminal is electrically connected to the first reference reference voltage (5V DC voltage) through a voltage dividing resistor R31, the comparison output terminal is connected to the negative electrode of a diode D7, the positive electrode of the diode D7 is connected to the negative electrode of the emitting end of an optocoupler, and the positive electrode of the emitting end of the optocoupler is electrically connected to a power supply (+12). The receiving end of the optocoupler is located between the COMP pin of the power management chip U1 and the ground, and a resistor R57 is connected in series and a filter capacitor C22 is connected in parallel. In addition, the negative electrode of the emitting end of the optocoupler is also electrically connected to the comparison output terminal of a third comparator A3 through a diode D16. The inverting input terminal of the above-mentioned third comparator A3 is electrically connected to the output terminal V+ of the flyback circuit through a resistor R74, and the inverting input voltage is obtained after voltage division by a voltage dividing resistor R79. The non-inverting input terminal of the third comparator A3 is electrically connected to the VOB signal output pin of the isolation drive chip through resistors R87, R83 and filter capacitors C31, C32. The above VOB signal is output from the external control unit 500. Combining the above circuit structure, the voltage magnitude of the feedback signal output terminal of the flyback circuit will directly affect the conduction depth of the optocoupler, and then affect the voltage of the COMP pin, and finally realize the adjustment of the duty cycle of the PWM signal output by the power management chip U1. Similarly, the VOB signal output by the external control unit 500 can also adjust the conduction depth of the optocoupler when the voltage of the voltage feedback signal remains unchanged.

[0129] As Figure 6 shown, the inverting input terminal of the second comparator A2 is electrically connected to the feedback signal output terminal through a voltage dividing resistor R20 and filtered by a capacitor C19. The non-inverting input terminal is electrically connected to the second reference reference voltage through a voltage dividing resistor R27. In the embodiment of the present application, the first reference reference voltage and the second reference reference voltage are the same voltage. The comparison output terminal of the second comparator A2 is pulled up by a pull-up resistor R21 and then electrically connected to the first signal input pin VIC of the external control unit 500 through an isolation drive chip.

[0130] In the embodiment of the present application, the external control unit 500 preferably adopts an MCU control module. The first signal output pin of the MCU is connected to the second PWM control signal input terminal, that is, the CS pin signal of the power management chip U1. The first signal output pin outputs a PWM control signal and outputs it to the CS pin through a drive resistor R58. Thus, the duty cycle of the PWM signal inside the power management chip U1 is changed by changing Vcs.

[0131] The load unit 400 includes multiple groups of LEDs. The above LED load is controlled by the MCU through the cooperation of a switching tube and an optocoupler. For other circuit structures of the flyback circuit unit 300 and the load unit 400, reference can be made to Figure 6 , which will not be elaborated here.

[0132] In the embodiment of the present application, a signal connection is provided between the second signal input pin and the feedback signal output end on the MCU. In practical applications, the above-mentioned second signal input pin can directly reuse the VIC pin.

[0133] In the embodiment of the present application, a data storage unit is configured or externally connected in the MCU for storing: the output current and PWM signal duty cycle corresponding to different output loads, the correlation between different duty cycle change rates and peak voltage fluctuation ranges when the output load is adjusted, the interference waveform data at the output end of the flyback circuit, and the change trends of various peak voltage waveforms themselves.

[0134] Based on the above data storage unit, an interference elimination module and a control parameter value generation module are also configured in the MCU.

[0135] The interference elimination module is configured to obtain the interference waveform data at the output end of the flyback circuit, compare the voltage feedback signal with the safety threshold. If the voltage feedback signal is higher than the safety threshold, increase the sampling frequency of the voltage feedback signal, compare the sampling curve of the voltage feedback signal with the interference waveform data, and determine whether the peak voltage in the voltage feedback signal is an interference signal: if it is an interference signal, maintain the state where the first feedback loop 600 is activated and the second feedback loop 700 is in a dormant state, and adjust the duty cycle of the PWM signal according to the feedback signal of the first feedback loop 600.

[0136] The control parameter value generation module is configured to generate a feedback waveform curve based on the feedback signal obtained by high-frequency sampling, determine the peak voltage category according to the change trend, find the duty cycle change rate of the PWM signal adapted to it, and generate the control parameter value and output strategy of the second feedback loop 700 according to the adapted duty cycle change rate of the PWM signal.

[0137] The above control parameter output strategy includes the output value and the interval time, that is, the duty cycle of the PWM signal in the flyback circuit can be smoothly transitioned from the initial value to the target value, thereby reducing the peak voltage at the output end of the flyback circuit.

[0138] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A LED lighting drive control method, characterized in that: include: Acquire at least two control parameters that affect the duty cycle of a PWM signal based on the circuit structure, wherein the PWM signal is used to control the conduction state of a switch tube inside the flyback circuit; Establishing a first feedback loop between the feedback signal output terminal of the flyback circuit and one of the control parameter input terminals, and a second feedback loop from the feedback signal output terminal to the remaining control parameter input terminals via the external control unit; Obtain and store a safety threshold of a peak voltage at an output end of a flyback circuit; The voltage feedback signal at the feedback signal output terminal is collected and compared with the safety threshold: If the voltage feedback signal is not higher than the safety threshold, maintaining the activation state of the first feedback loop, and adjusting the duty cycle of the PWM signal according to the feedback signal of the first feedback loop; If the voltage feedback signal is higher than the safety threshold, the second feedback loop is activated, and the duty cycle and the change rate of the PWM signal are adjusted according to the feedback signals of the first feedback loop and the second feedback loop.

2. The LED lighting drive control method according to claim 1, characterized in that: A signal processing circuit module with fixed parameters is configured in the first feedback loop, and is used to receive and output corresponding control parameters in real time based on the voltage feedback signal and the processing result of the signal processing circuit module to adjust the duty cycle of the PWM signal; The second feedback loop is provided with a comparator module, which is used to receive the voltage feedback signal and compare it with the safety threshold, and output a comparison result signal to the external control unit if the voltage feedback signal is higher than the safety threshold, and the external control unit receives and responds to the comparison result signal to collect the output of the feedback signal output terminal and generates corresponding control parameters according to the built-in algorithm to adjust the duty cycle and change rate of the PWM signal; The PWM signal duty cycle change rate includes the duty cycle change trend and change speed.

3. The LED lighting drive control method according to claim 2, characterized in that: The method further comprises: Acquire and store the output current and PWM signal duty cycle corresponding to different output loads, and the correlation between the different duty cycle change rates and the peak voltage fluctuation range when the output load is adjusted; Compare the voltage feedback signal with the safety threshold. If the voltage feedback signal is higher than the safety threshold, obtain and find the duty cycle corresponding to the PWM signal after the adjustment is completed according to the adjustment request of the current output load, and calculate and generate the required duty cycle change rate in combination with the current PWM signal duty cycle; According to the duty cycle change rate, the control parameter value of the second feedback loop is gradually adjusted in the external control unit and outputted.

4. The LED lighting drive control method according to claim 1, characterized in that: The method further comprises: Acquire and store interference waveform data at the output end of the flyback circuit; Establishing a signal connection between the feedback signal output terminal and the external control unit; Comparing the voltage feedback signal with a safety threshold, and if the voltage feedback signal is higher than the safety threshold, increasing the sampling frequency of the voltage feedback signal by the external control unit; Compare the sampling curve of the voltage feedback signal with the interference waveform data to determine whether the peak voltage in the voltage feedback signal is an interference signal: If it is an interference signal, the first feedback loop is kept activated and the second feedback loop is kept dormant, and the duty cycle of the PWM signal is adjusted according to the feedback signal of the first feedback loop; If it is not an interference signal, the second feedback loop is activated, and the duty cycle and the change rate of the PWM signal are adjusted according to the feedback signals of the first feedback loop and the second feedback loop.

5. The LED lighting driving control method according to claim 4, characterized in that: The method further comprises: Obtain and store the changing trends of various peak voltage waveforms; Acquire and store the correlation between various peak voltage waveforms and the duty cycle change rate of the adapted PWM signal; A feedback waveform curve is generated based on the feedback signal obtained by high-frequency sampling, the peak voltage category is determined according to the change trend, and the PWM signal duty cycle change rate adapted thereto is found; According to the adapted PWM signal duty cycle change rate, the control parameter value of the second feedback loop is gradually adjusted in the external control unit and output.

6. The LED lighting driving control method according to claim 5, characterized in that: Obtaining various peak voltage waveforms and the adapted PWM signal duty cycle change rate includes: Adjust the output load of the flyback circuit and record the corresponding peak voltage waveform during each load adjustment; When adjusting the output load of the flyback circuit, different PWM signal duty cycle change rates are used to adjust the on-off state of the switch tube, and the corresponding peak voltage waveform during each load adjustment is recorded; The PWM signal duty cycle change rate corresponding to the peak voltage with the smallest amplitude is selected as the PWM signal duty cycle change rate adapted for the current category of peak voltage waveform.

7. The LED lighting driving control method according to claim 6, characterized in that: The signal generator, oscilloscope and PC are used to obtain and store the output current and PWM signal duty cycle corresponding to different output loads, the correlation between the duty cycle change rate and the peak voltage fluctuation range when the output load is adjusted, and the interference waveform data at the output end of the flyback circuit. Obtaining the changing trends of various types of spike voltage waveforms includes adjusting the output load in different electromagnetic environments and temperature environments, and then using an oscilloscope to collect the spike voltage waveform data when the output load changes, and obtaining the changing trends of the above-mentioned various types of spike voltage waveforms through data fitting.

8. An LED lighting drive control system, characterized in that: It comprises an input rectification unit (100), a PFC unit (200), a flyback circuit unit (300), a load unit (400) and an external control unit (500); The flyback circuit unit (300) comprises a transformer module (310), a power supply control module (320) and an output feedback module (330); The output feedback module (330) is configured with at least two feedback loops and a loop state control submodule; The first feedback loop (600) is configured to feedback a signal output terminal of the flyback circuit to a first PWM control signal input terminal in the power control module (320), and is used to adjust the PWM signal duty cycle according to the voltage feedback signal to control the conduction state of the switch tube; The second feedback loop (700) is configured to feedback the signal output terminal of the flyback circuit via the external control unit (500) to the second PWM control signal input terminal, so as to coordinate with the first feedback loop (600) according to the voltage feedback signal to adjust the PWM signal duty cycle to control the conduction state of the switch tube; The loop state control submodule is configured to collect the voltage feedback signal at the feedback signal output terminal and compare it with a safety threshold: If the voltage feedback signal is not higher than the safety threshold, maintaining the activation state of the first feedback loop (600), and adjusting the duty cycle of the PWM signal according to the feedback signal of the first feedback loop (600); If the voltage feedback signal is higher than the safety threshold, the second feedback loop (700) is activated to adjust the duty cycle of the PWM signal and its change rate according to the feedback signals of the first feedback loop (600) and the second feedback loop (700).

9. The LED lighting drive control system according to claim 8, characterized in that: The loop state control submodule includes: a first comparator, wherein one comparison input terminal is electrically connected to the feedback signal output terminal via a voltage-dividing resistor, another comparison input terminal is electrically connected to the first reference voltage, a comparison output terminal is connected to the negative electrode of an optical coupler transmitting terminal, the positive electrode of the optical coupler transmitting terminal is electrically connected to a power supply, and the optical coupler receiving terminal is located between the first PWM control signal input terminal and ground; A second comparator, one comparison input terminal of which is electrically connected to the feedback signal output terminal via a voltage-dividing resistor, the other comparison input terminal of which is electrically connected to a second reference base voltage, and the comparison output terminal of which is electrically connected to a first signal input pin of an external control unit (500) via an isolation driving chip; The first signal output pin of the external control unit (500) is signal-connected to the second PWM control signal input terminal, and the external control unit (500) receives and responds to the output result of the second comparator, and outputs a control parameter to the second PWM control signal input terminal based on a built-in algorithm.

10. The LED lighting drive control system according to claim 9, characterized in that: A signal connection is provided between the second signal input pin of the external control unit (500) and the feedback signal output terminal; The external control unit (500) is configured with or externally connected to a data storage unit for storing: output currents and PWM signal duty cycles corresponding to different output loads, correlations between different duty cycle change rates and peak voltage fluctuation intervals when the output load is adjusted, interference waveform data at the output end of the flyback circuit, and change trends of various peak voltage waveforms themselves; The external control unit (500) is configured with: An interference elimination module is configured to obtain interference waveform data at the output end of the flyback circuit, compare the voltage feedback signal with the safety threshold, and if the voltage feedback signal is higher than the safety threshold, increase the sampling frequency of the voltage feedback signal, compare the sampling curve of the voltage feedback signal with the interference waveform data, and determine whether the peak voltage in the voltage feedback signal is an interference signal; if it is an interference signal, maintain the first feedback loop (600) in an activated state and the second feedback loop (700) in a dormant state, and adjust the duty cycle of the PWM signal according to the feedback signal of the first feedback loop (600); The control parameter value generation module is configured to generate a feedback waveform curve based on the feedback signal obtained by high-frequency sampling, determine the peak voltage category according to the change trend, find the PWM signal duty cycle change rate that matches it, and generate the control parameter value and output strategy of the second feedback loop (700) according to the matched PWM signal duty cycle change rate.

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