A stable and reliable LED driving method, driving circuit and PCB board

Abstract

The present application discloses a stable and reliable LED driving method, driving circuit and PCB board, which relates to the technical field of light source control. The method includes: establishing a control connection between a control unit, an LED load unit and a driving circuit; acquiring and storing a first delay t1 and a second delay t2 after the driving circuit and the LED load unit respectively respond to a first control signal / second control signal after the control unit outputs the first control signal and the second control signal; monitoring and responding to a load adjustment request of the LED load unit, outputting the first control signal to the driving circuit to control the circuit output, and outputting the second control signal to the LED load unit after a duration of t1-t2 to control the working state of the LED load; the above solution adjusts the output parameters of the driving circuit in advance for a set duration, so that the adjusted output current can adapt to the requirements when the LED load changes, maintain voltage stability, reduce the output ripple size, reduce the damage suffered by each light source device during frequent switching, and extend the service life.

Description

Technical Field

[0001] This application relates to the technical field of light source control, and in particular, to a stable and reliable LED driving method, driving circuit, and PCB board. Background Art

[0002] In practical applications, LED lighting driving usually uses a flyback switching power supply to provide stable voltage and current to an LED load. To simplify system control, the sampling signal at the output end of the flyback circuit is usually directly fed back to the power management chip through a feedback loop, and then the changes in the output voltage / current are monitored. The power management chip adjusts the duty cycle of the PWM signal output to the internal switching transistor of the flyback circuit according to the above changes, and then adjusts the final output of the circuit to meet the requirement of voltage stabilization. In addition, a controller (such as a single-chip microcomputer) is usually used to output a control signal to control the lighting state of the LED load.

[0003] In specific practices, to avoid damage to the MCU caused by voltage fluctuations at the driving circuit or load end, an isolation unit is usually set between the driving circuit / load end and the MCU, such as configuring an optocoupler isolation chip between the MCU and the driving circuit. However, practice shows that when the frequency conversion speed of the control signal exceeds 1 KHz, the output of an ordinary optocoupler will be severely distorted, and using a high-speed optocoupler will significantly increase the system hardware cost. At the same time, when the number of LED loads driven by a flyback switching power supply changes, such as adjusting the light source color temperature or brightness by turning on or off some LED loads, due to the response delay of the feedback loop control, the flyback circuit cannot adjust the output voltage in time, resulting in an increase in output ripple, damaging the load and circuit components, and in the long run, reducing the service life of the load and circuit components. Summary of the Invention

[0004] Aiming at the problem that ordinary optocouplers in specific practices are difficult to meet the control requirements of LEDs and frequent switching of LED light sources easily shortens their service life, a first object of this application is to provide a stable and reliable LED driving method, which can directly and accurately control the output voltage / current and output timing of the flyback circuit through an MCU via a capacitive isolation driving chip, effectively reducing the output ripple of the circuit when the LED load changes, thereby reducing the damage suffered by each light source device during frequent switching of the LED light source. At the same time, a capacitive isolation driving chip is used to replace the ordinary optocoupler, ensuring high-frequency control accuracy while effectively protecting the MCU from the influence of voltage fluctuations in the driving circuit. To implement the above LED driving method, a second object of this application is to provide a stable and reliable LED driving circuit, and finally, a PCB board printed with the above LED driving circuit is proposed for protection. The specific solutions are as follows:

[0005] A stable and reliable LED driving method includes:

[0006] Establish a control connection between the control unit, the LED load unit, and the drive circuit;

[0007] Obtain and store the first time delay t1 from when the first control signal is output from the control unit until the drive circuit responds to the first control signal, and

[0008] the second time delay t2 from when the second control signal is output from the control unit until the LED load unit responds to the second control signal;

[0009] Monitor and respond to the load adjustment request of the LED load unit, output the first control signal to the drive circuit to control the circuit output, and output the second control signal to the LED load unit after a duration of t1 - t2 to control the operating state of the LED load.

[0010] Through the above technical solution, based on the control connection between the control unit, the drive circuit, and the LED load unit, when the number of loads in the LED load unit is about to change, the output of the drive circuit is adjusted in advance for a set duration, so that the adjusted output current supply can exactly meet the requirements when the number of LED loads changes, thereby ensuring the stability of the output voltage, reducing the output ripple magnitude at the output end of the drive circuit, thereby reducing the damage suffered by each light source device during frequent switching of the LED light source, and extending the service life of each device.

[0011] Further, the LED load unit includes at least two groups of LED loads;

[0012] The LED driving method further includes:

[0013] Associatively store the compensation ripple waveform characteristics required for each LED load and its combination when adjusting the operating state;

[0014] Associatively store each compensation ripple waveform characteristic and its required compensation control parameters and the third time delay t3;

[0015] Monitor the load adjustment request of the LED load unit and generate the second control signal based on the load adjustment request;

[0016] Find the compensation ripple waveform characteristic corresponding to the above load adjustment, match and output the corresponding compensation control parameters as the third control signal to the drive circuit, and output the second control signal to the LED load unit after a duration of t1 - t3;

[0017] Wherein, the compensation control parameters are configured to adjust the PWM adjustment signal output by the internal power management chip of the drive circuit and / or the capacitance value at the output end of the drive circuit;

[0018] The compensated ripple waveform feature is configured to reduce the ripple generated due to the load change at the output end of the driving circuit.

[0019] Through the above technical solution, according to the ripple waveform feature caused by the load change in the LED load unit, the corresponding compensation control parameters can be output in advance, so that the ripple generated when different loads or their combinations change can be reduced in time.

[0020] Further, the LED driving method further includes:

[0021] Based on the theoretical filtering model at the output end of the driving circuit, obtain the optimal filtering capacitance value corresponding to different LED loads or their combinations, and store them in an associated manner;

[0022] Establish a control connection between the control unit and the filtering capacitance at the output end of the driving circuit;

[0023] Obtain and store the fourth time delay t4 from the output of the fourth control signal from the control unit to the response of the output end filtering capacitance to the fourth control signal;

[0024] According to the load adjustment request obtained by monitoring, search for and match the corresponding optimal filtering capacitance value;

[0025] Generate and output the fourth control signal according to the optimal output capacitance value, and output the second control signal to the LED load unit after a duration of t1 - t4 to control the working state of the LED load.

[0026] Through the above technical solution, before using the control unit to output a control signal to control the working state of the LED load, first change the filtering capacitance value at the output end of the driving circuit, so that its filtering parameters can be more adapted to the upcoming change of the load. Furthermore, when the output load changes instantaneously, the filtering capacitance value at the output end of the driving circuit also changes accordingly, finally reducing the ripple size, making the voltage at the output end of the driving circuit more stable, and also conducive to extending the service life of each component.

[0027] Further, the LED driving method further includes:

[0028] Statistically store the attenuation rate of the performance parameters of each component in the driving circuit and the LED load unit with the change of the usage duration;

[0029] Based on the theoretical output model of the driving circuit, combined with the current transmission time delays of each control signal and feedback signal, establish the correlation between the change of the transmission time delay and the usage duration;

[0030] Statistically calculate the usage duration of the current driving circuit and the LED load unit, and calculate and adjust the transmission time delay length of each control signal.

[0031] Through the above technical solution, when the entire LED light source system has been used for a long time and the components are aging, the control unit can still output corresponding control signals at precise time points, thereby ensuring that the ripples at the output end of the drive circuit can be effectively reduced throughout the life cycle of the entire light source, extending the service life of each component, and making the LED emit light more stably and reliably.

[0032] To implement the above LED driving method, the present application also proposes a stable and reliable LED driving circuit, including an input rectification unit, a PFC unit, a flyback driving unit, an LED load unit, and a control unit; wherein, the control unit includes:

[0033] An isolation driving module configured to implement isolation communication with an external functional unit;

[0034] A storage module configured to store a first time delay t1 from when the first control module outputs a first control signal until the flyback driving unit responds, and a second time delay t2 from when the second control module outputs a second control signal until the LED load unit responds;

[0035] A signal receiving module configured to monitor and receive an output feedback signal at the output end of the flyback driving unit and an external load adjustment request;

[0036] A first control module configured to be connected to the signal receiving module and the flyback driving unit, and configured to receive and generate and output a first control signal to adjust the output voltage of the flyback driving unit and / or the size of a filter capacitor at the output end of the flyback driving unit according to the output feedback signal or the load adjustment request;

[0037] A second control module configured to be connected to the signal receiving module and the LED load unit, and configured to receive and generate and output a second control signal to control the working state of the LED load according to the load adjustment request;

[0038] An output control module, in response to a load adjustment request output by an instruction receiving module, controls to output a first control signal to the flyback driving unit to control the circuit output, and outputs a second control signal to the LED load unit after a duration of t1 - t2 to control the working state of the LED load.

[0039] Further, the storage module is also associated with storage of:

[0040] The compensation ripple waveform characteristics, the required compensation control parameters, and the corresponding third time delay t3 required for each LED load and its combination when adjusting the working state;

[0041] The optimal filter capacitor values corresponding to different LED loads or their combinations, and the fourth time delay t4 from when the third control signal is output by the control unit until the capacitor at the output end of the flyback driving unit responds to the third control signal; and

[0042] The correlation between the changes in each signal transmission time delay and the power supply usage duration;

[0043] The control unit further includes:

[0044] A third control module, configured to be connected to the flyback driving unit, receive and respond to the output of the instruction receiving module, look up the compensated ripple waveform characteristics corresponding to the load adjustment request from the storage module, match and output a third control signal containing corresponding compensation control parameters to the flyback driving unit to improve the circuit output ripple;

[0045] A fourth control module, configured to be connected to the output capacitor of the flyback driving unit, used to receive and, according to the load adjustment request obtained by the instruction receiving module, look up and match the corresponding optimal filter capacitor value and output a fourth control signal to the flyback driving unit to improve the circuit output ripple;

[0046] A signal transmission time delay adjustment module, configured to be used for counting and, according to the usage duration of the current flyback driving unit and the LED load unit, calculating and adjusting the transmission time delay lengths of each control signal;

[0047] The output control module counts the usage duration of the current driving circuit and the LED load unit, calculates and adjusts the transmission time delay lengths of each control signal, and outputs the second control signal to the LED load unit after the t1 - t3 time period of the third control signal output, and outputs the second control signal to the LED load unit after the t1 - t4 time period of the fourth control signal output.

[0048] Further, the flyback driving unit includes:

[0049] A transformer module, including a first primary coil and its coupled first secondary coil. One end of the primary coil is electrically connected to the output end of the PFC unit, and the other end is connected to a first switching tube. A output - end filter capacitor and a load resistor are connected in parallel at both ends of the first secondary coil to form a regulated output end;

[0050] A power control module, including a power management chip U1 and a first switching tube connected thereto. The switching - tube current detection input end and the output end of the error amplifier of the power management chip U1 are both connected to the first control module for signal connection, receiving and responding to the control signal output by the first control module to control the on - off state of the first switching tube to adjust the voltage at the voltage output end;

[0051] The signal sampling module is configured between the control unit and the regulated output terminal, and includes a plurality of voltage-dividing resistors connected in series to the voltage output terminal and a sampling output circuit, which is used to collect the output voltage of the regulated output terminal and output it to the signal receiving module in the control unit via the isolation driving module;

[0052] The load driving module includes at least one energy supply transformer connected to the regulated output terminal and a second switching tube for controlling the conduction state of the energy supply transformer, and the LED load is connected to the secondary coil of the energy supply transformer;

[0053] The first control module includes a first control program sub-module loaded in the MCU. The first control program sub-module responds to the output voltage fed back by the signal sampling module, and respectively outputs a PWM voltage regulation signal and an output voltage turn-off signal to the switching tube current detection input terminal of the power management chip and the output terminal of the error amplifier based on the built-in algorithm, so as to adjust the voltage output of the regulated output terminal of the flyback driving unit.

[0054] Through the above technical solution, the control mode of the flyback driving circuit is changed from the conventional automatic feedback loop control to the control via the MCU. Thus, according to the output state of the regulated output terminal and the change of the LED load, the output voltage and waveform of the flyback driving circuit can be adjusted in advance to adapt to the frequent changes of the LED load, making the entire light source system emit light more stably and reliably.

[0055] Further, the second switching tube is controlled and connected to the signal output terminal of the second control module in the control unit through an isolation optocoupler;

[0056] The second control module includes a second control program sub-module loaded in the MCU. The second control program sub-module receives and responds to the load adjustment request output by the instruction receiving module, and outputs a PWM dimming signal to the isolation optocoupler to control the conduction state of the second switching tube.

[0057] Through the above technical solution, the control unit can quickly and efficiently adjust the brightness of each LED load in the LED load unit. Thus, the adjustment of the light source color temperature can also be realized. Since it operates independently of the first control module, the second control signal can be output after the first control signal, reducing the output ripple caused by the signal transmission delay or the component response delay being too long, and improving the voltage stability of the flyback driving unit.

[0058] Further, the isolation driving module is configured as a capacitive isolation driving chip;

[0059] The first switching tube is configured as an NMOS tube;

[0060] The power supply pin VCC of the power management chip U1 is powered by a DC power supply and is connected in series with a grounded capacitor for filtering; the inverting input pin INV of the error amplifier in the power management chip U1 is powered by a DC power supply through a resistor voltage divider; the multiplier input pin MULT in the power management chip U1 is powered by a resistor series voltage divider; the current detection input pin CS of the power management chip U1 is electrically connected to the source of the first switch tube Q5 through a sampling resistor; the voltage regulation signal output pin GD of the power management chip U1 is electrically connected to the gate of the first switch tube Q5 through a driving resistor, the drain of the first switch tube Q5 is electrically connected to the DC voltage output end of the PFC unit through the first primary coil of the transformer module, the source of the first switch tube Q5 is electrically connected to the current detection input pin CS of the power management chip U1 through a sampling resistor, and is grounded through a protection resistor;

[0061] The transformer module includes a first primary coil, an auxiliary coil and a first secondary coil coupled to the first primary coil arranged on the same side; one end of the first primary coil is electrically connected to the output end of the PFC unit, and the other end is connected to the drain of the first switch tube Q5; the first secondary coil is connected in series with a rectifier diode, and an output filter capacitor and a load resistor are connected in parallel at both ends to form a voltage-stabilized output end;

[0062] The two ends of the first primary coil are connected in parallel with a diode and a capacitor, and at the same time, an energy-consuming resistor and a diode are connected in parallel, so as to form an RCD energy-consuming circuit to reduce the voltage spike after the first switch tube Q5 is turned off; the auxiliary coil is connected in parallel with a filter capacitor via a resistor to supply power to the zero current detection pin ZCD of the power management chip U1; the current detection input pin CS of the power management chip U1 is connected in series with a resistor and a capacitor and then grounded, and at the same time, a PWM voltage regulation signal directly output by the MCU is connected via a resistor to change the output of the voltage regulation signal output pin GD;

[0063] The error amplifier output pin COMP in the power management chip U1 is connected in series with a resistor and an optocoupler and then grounded, and is also connected in parallel with a grounding capacitor;

[0064] The optical coupler is connected to the MCU control via an isolation drive module;

[0065] The voltage stabilizing output end is connected to two power supply transformers L1 and L3, one end of the secondary coils of the power supply transformers L1 and L3 are electrically connected to the corresponding LED loads respectively, and the other end is connected in series with the second switch tubes Q1 and Q3 and then grounded; the second switch tubes Q1 and Q3 are controlled and connected to the two control signal output pins of the MCU via the optical couplers U1B and U2B respectively.

[0066] The present application also discloses a PCB board, on which the stable and reliable LED driving circuit as described above is printed.

[0067] In summary, the present application includes at least one of the following beneficial technical effects:

[0068] When the number of loads in the LED load unit is about to change, the output of the drive circuit is adjusted in advance for a set duration, so that the adjusted voltage / current supply can exactly meet the requirements when the number of LED loads changes. At the same time, the filter capacitance value of the regulated output terminal is adjusted according to the load change situation, thereby reducing the output ripple magnitude at the output terminal of the drive circuit, reducing the damage suffered by each light source device during frequent switching of the LED light source, and extending the service life of each device. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 is a schematic diagram of the LED driving method of the present application;

[0070] Figure 2 is a schematic diagram of optimizing the output ripple by adjusting the capacitance value of the regulated output terminal;

[0071] Figure 3 is a schematic diagram of the overall functional modules of the LED driving circuit of the present application;

[0072] Figure 4 is a schematic diagram of the functional modules of the control unit;

[0073] Figure 5 is a schematic diagram of the circuit principle of the LED driving circuit of the present application;

[0074] Figure 6 is a schematic diagram of the circuit principle of the flyback driving unit;

[0075] Figure 7 is a schematic diagram of the circuit principle of the input rectification unit and the PFC unit;

[0076] Figure 8 is a schematic diagram of the circuit principle of the control unit.

[0077] Reference numerals: 100, input rectification unit; 200, PFC unit; 300, flyback driving unit; 310, transformer module; 320, power control module; 330, signal sampling module; 340, load driving module; 400, LED load unit; 500, control unit; 510, isolation driving module; 520, storage module; 530, signal receiving module; 540, first control module; 550, second control module; 560, third control module; 570, fourth control module; 580, output control module; 590, signal transmission delay adjustment module. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0078] The following details the embodiments of the present application, and examples of the embodiments are shown in the drawings.

[0079] In the description of this specification, the description with reference to the terms "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.

[0080] This application embodiment first discloses a stable and reliable LED driving method, as Figure 1 shown, mainly including the following steps:

[0081] S100, establish a control connection between the control unit, the LED load unit and the driving circuit;

[0082] S200, obtain and store the first time delay t1 from when the first control signal is output from the control unit until the driving circuit responds to the first control signal, and

[0083] the second time delay t2 from when the second control signal is output from the control unit until the LED load unit responds to the second control signal;

[0084] S300, monitor and respond to the load adjustment request of the LED load unit, output the first control signal to the driving circuit to control the circuit output, and output the second control signal to the LED load unit after a duration of t1 - t2 to control the working state of the LED load.

[0085] In step S100, for the specific control connection relationship between the control unit and the LED load unit, reference can be made to Figures 3 - 8 which will be described in detail in subsequent embodiments.

[0086] In step S200, after the control unit outputs a control signal, affected by the charging and discharging of components such as capacitors and inductors in the circuit, the driving circuit takes a certain amount of time to respond to the above control signal, that is, there is a certain time delay in adjusting the voltage output according to the instruction requirements of the control signal. And affected by the circuit structure, the time of the above first time delay t1 is longer than the second time delay t2.

[0087] In this specific practice, the oscilloscope and the signal generator can be connected to the driving circuit to calculate and obtain the above first time delay and second time delay, and the average value is taken as a fixed parameter and written into the program module of the control unit after multiple effective measurements.

[0088] In step S300, the control unit receives an instruction signal from the outside to adjust the operating states of the respective LED loads. For example, the light source brightness is adjusted by controlling the magnitude of the current of the LED load, or the color temperature is adjusted by adjusting the light-emitting states of multiple LED loads. In step S300, the transmission delays of the respective signals are fully considered, and a preset duration is used to adjust the output of the drive circuit, so that the adjusted output current supply can exactly meet the requirements when the number of LED loads changes. As a result, the output voltage is kept stable, the output ripple magnitude at the output end of the drive circuit is reduced, the damage suffered by each light source device during frequent switching of the LED light source is reduced, and the service life of each device is prolonged.

[0089] In practical applications, the LED load unit usually includes at least two groups of LED loads, which improves the reliability of the light source and is also convenient for adjusting the color temperature.

[0090] Therefore, the LED driving method described in the embodiments of the present application further includes the following steps:

[0091] A100, associatively storing the compensation ripple waveform characteristics required for adjusting the operating states of each LED load and its combination, and associatively storing each compensation ripple waveform characteristic, its required compensation control parameters, and the third delay t3;

[0092] A200, monitoring the load adjustment request of the LED load unit, and generating the second control signal based on the load adjustment request;

[0093] A300, finding the compensation ripple waveform characteristic corresponding to the above load adjustment, matching and outputting the corresponding compensation control parameter as the third control signal to the drive circuit, and outputting the second control signal to the LED load unit after a duration of t1 - t3.

[0094] In step A100, the compensation ripple waveform characteristic is configured to eliminate the ripple generated due to the change of the load at the output end of the drive circuit. In practical applications, first, an oscilloscope is used to obtain the waveform of the voltage at the output end of the drive circuit changing with the operating states of each LED load and its combination. Usually, within a set time after the change of the LED load, affected by the change of the load resistance at the output end of the drive circuit, for example, when more parallel-connected LED loads will cause the load resistance to decrease, this will cause the waveform output at the output end of the drive circuit to jitter and generate ripple. Different changes in LED loads will generate different types of ripple, such as the amplitude, waveform, and attenuation characteristics of the ripple, etc.; after obtaining the ripple waveform characteristics corresponding to the changes of each LED load, the waveform characteristics corresponding to the above compensation ripple can be obtained through computer processing. In an ideal embodiment, the amplitude and oscillation direction of the above compensation ripple are exactly opposite to the ripple waveform caused by the load change.

[0095] The compensation control parameter in step A100 is configured to adjust the PWM regulation signal output by the internal power management chip of the driving circuit and / or the capacitance value at the output end of the driving circuit, including outputting a PWM voltage regulation signal from the control unit to the power management chip of the driving circuit, such as outputting to the current detection pin of the switching transistor, to finely adjust the current at the output end of the driving circuit, or adjusting the instantaneous capacitance value of the filter capacitor at the output end of the driving circuit in advance through a charge-discharge loop, so that the above filter capacitor can better buffer the output voltage change of the driving circuit. In practical applications, adjusting the capacitance value of the filter capacitor can also be completed by controlling the power management chip of the driving circuit, such as changing the duty cycle of the output pulse during the charge-discharge cycle of the filter capacitor to affect the charge-discharge degree of the capacitor.

[0096] Generating the second control signal based on the load adjustment request in step A200 means directly changing the working state of each LED load by changing the control instruction output by the control unit, such as changing the current magnitude of the LED load by adjusting the internal channel width of the switching transistor connected to the LED load.

[0097] Since there are differences in the response effects of the filter capacitor at the output end of the driving circuit for different output loads, such as Figure 2 shown, the LED driving method of the embodiment of the present application further includes:

[0098] B100, based on the theoretical filter model at the output end of the driving circuit, obtaining the optimal filter capacitor value corresponding to different LED loads or their combinations, and associatively storing the LED loads or their combinations with the corresponding optimal filter capacitor values to form a two-dimensional data table.

[0099] B200, establishing a control connection between the control unit and the filter capacitor at the output end of the driving circuit.

[0100] B300, obtaining and storing the fourth time delay t4 from the output of the fourth control signal from the control unit to the completion of the response of the output end filter capacitor to the fourth control signal.

[0101] B400, according to the load adjustment request obtained by monitoring, searching for and matching the corresponding optimal filter capacitor value;

[0102] B500, generating and outputting the fourth control signal according to the optimal output capacitor value, and outputting the second control signal to the LED load unit after a duration of t1 - t4 to control the working state of the LED load.

[0103] Before using the control signal output by the control unit to control the working state of the LED load, the filtering capacitance value at the output end of the driving circuit is first changed so that its filtering parameters can be more adapted to the upcoming changes in the load. As a result, when the output load changes instantaneously, the filtering capacitance value at the output end of the driving circuit also changes accordingly, ultimately reducing the ripple magnitude, making the voltage at the output end of the driving circuit more stable, and also facilitating the extension of the service life of each component.

[0104] In practical applications, the transmission delay of each signal in the driving circuit is usually related to the parameters and operating states of each component. To ensure that the control unit can still provide precise timing control after the light source has been used for a long time, so as to minimize the ripple generated when the load changes, the LED driving method described in the embodiments of the present application further includes:

[0105] C100, statistically storing the attenuation rates of the performance parameters of each component in the driving circuit and the LED load unit with the usage duration;

[0106] C200, based on the theoretical output model of the driving circuit, combining the current transmission delays of each control signal and feedback signal, establishing the correlation between the change in the transmission delay and the usage duration;

[0107] C300, statistically storing the usage duration of the current driving circuit and the LED load unit, calculating and adjusting the transmission delay lengths of each control signal, where the control signals include the aforementioned first control signal, second control signal, third control signal, and fourth control signal.

[0108] The law of change of the performance parameters of each component with the usage duration can be obtained by looking up the performance data sheet provided by the component manufacturer. For example, after the inductor has been used for a long time, its inductance value will decrease while its resistivity will increase. The aforementioned theoretical output model can be constructed according to the actual circuit schematic diagram.

[0109] Based on the above technical solution, when the entire LED light source system has been used for a long time and the components are aging, the control unit can still output corresponding control signals at precise time points, thereby ensuring that the output ripple at the output end of the driving circuit can be effectively suppressed throughout the life cycle of the entire light source, extending the service life of each component, and making the LED emit more stably and reliably.

[0110] To implement the above LED driving method, the present application also proposes a stable and reliable LED driving circuit, as Figure 3 shown, including an input rectification unit 100, a PFC unit 200, a flyback driving unit 300, an LED load unit 400, and a control unit 500 connected in sequence.

[0111] Combined Figure 4As shown, the control unit 500 includes: an isolation driving module 510, a storage module 520, a signal receiving module 530, a first control module 540, a second control module 550, a third control module 560, a fourth control module 570, an output control module 580, and a signal transmission delay adjustment module 590.

[0112] Among them, the signal receiving module 530, the first control module 540, the second control module 550, the third control module 560, the fourth control module 570, the output control module 580, and the signal transmission delay adjustment module 590 are all program modules configured to implement relevant functions and are loaded into the control chip. In the embodiment of the present application, an STM32F103 series single-chip microcomputer (MCU) is preferably used as the control chip. The peripheral power supply and clock circuit of the above control chip are all prior arts and will not be elaborated in this embodiment. The isolation driving module 510 is implemented by a separately configured capacitive isolation driving chip, which can meet the transmission of signals with a conversion frequency exceeding 1 KHz. In the embodiment of the present application, an ISOC124P chip is preferably used to realize the isolated communication between the control chip and the external functional unit.

[0113] The storage module 520 is implemented by using the built-in memory of the MCU. In specific practice, the above storage module 520 can be implemented by an external storage chip.

[0114] In the embodiment of the present application, the storage module 520 is configured to store at least the following data contents:

[0115] The first delay t1 from the output of the first control signal by the first control module 540 to the response of the flyback driving unit 300; the second delay t2 from the output of the second control signal by the second control module 550 to the response of the LED load unit 400; the compensation ripple waveform characteristics, the required compensation control parameters, and the corresponding third delay t3 required for each LED load and its combination when adjusting the working state; the optimal filter capacitor values corresponding to different LED loads or their combinations, and the fourth delay t4 from the output of the third control signal by the control unit 500 to the response of the capacitor at the output end of the flyback driving unit 300 to the third control signal; and the correlation between the changes in each signal transmission delay and the power usage duration.

[0116] The signal receiving module 530 includes the built-in data input port of the MCU. In the present application, the INT pin and the P0 pin on the MCU are selected and configured to monitor and receive the output feedback signal at the output end of the flyback driving unit 300 and the external load adjustment request respectively.

[0117] The first control module 540 is used to control the voltage regulation signal parameters in the flyback driving unit 300, and is configured to be connected to the signal receiving module 530 and the flyback driving unit 300, and is used to receive and generate and output a first control signal according to the output feedback signal or the load adjustment request to adjust the output voltage of the flyback driving unit 300 and / or the size of the filter capacitor at the output end of the flyback driving unit 300. The second control module 550 is used to control the working state of the LED load and adjust the size of the working current, and is configured to be connected to the signal receiving module 530 and the LED load unit 400, and is used to receive and generate and output a second control signal according to the load adjustment request to control the working state of the LED load. The output control module 580 is mainly used to control the signal output time, and is configured to respond to the load adjustment request output by the instruction receiving module, control the output of the first control signal to the flyback driving unit 300 to control the circuit output, and output the second control signal to the LED load unit 400 after the time period of t1 - t2 to control the working state of the LED load.

[0118] The third control module 560 is configured to be connected to the flyback driving unit 300, receive and respond to the output of the instruction receiving module, search for the compensation ripple waveform characteristics corresponding to the load adjustment request from the storage module 520, match and output a third control signal containing the corresponding compensation control parameters to the flyback driving unit 300 to improve the circuit output ripple. The fourth control module 570 is configured to be connected to the output terminal capacitor of the flyback driving unit 300, and is used to receive and search for and match the corresponding optimal filter capacitor value according to the load adjustment request obtained by the instruction receiving module, and output a fourth control signal to the flyback driving unit 300 to improve the circuit output ripple.

[0119] The signal transmission delay adjustment module 590 is configured to be used to count and calculate and adjust the transmission delay length of each control signal according to the usage duration of the current flyback driving unit 300 and the LED load unit 400.

[0120] The output control module 580 counts the usage duration of the current driving circuit and the LED load unit 400, calculates and adjusts the transmission delay length of each control signal, and outputs the second control signal to the LED load unit 400 after the time period of t1 - t3 when the third control signal is output, and outputs the second control signal to the LED load unit 400 after the time period of t1 - t4 when the fourth control signal is output. In practical applications, the counting of the usage duration can be completed by the timing module in the MCU, that is, when the MCU is powered on and working, the timing starts, and the current timing duration is saved after power off, so as to accumulate the usage duration.

[0121] See Figure 6, the flyback driving unit 300 mainly includes a transformer module 310, a power control module 320, a signal sampling module 330, and a load driving module 340.

[0122] In the embodiment of the present application, the above-mentioned power control module 320 includes a power management chip U1 and a first switching transistor Q5 connected thereto. The above-mentioned power management chip U1 preferably uses an L6562 current-mode PWM controller chip, and the first switching transistor preferably uses an NMOS transistor. The current detection input pin CS and the error amplifier output pin COMP of the power management chip U1 are both signal-connected to the first control module 540, receive and respond to the control signal output by the first control module 540, and control the on-off state of the first switching transistor to adjust the voltage at the voltage output terminal. Combined Figure 5 and Figure 6 As shown, the specific connection method of the power control module 320 is as follows: The power supply pin VCC of the power management chip U1 is powered by a 15V DC power supply. At the same time, a filter capacitor C14 is connected in series at the power supply pin VCC to filter out low-frequency interference in the power supply voltage and ensure stable power supply; the inverting input pin INV of the error amplifier in the power management chip U1 is powered by the series voltage division of resistors R35 and R52; the multiplier input pin MULT for implementing power factor correction in the power management chip U1 is powered by the series voltage division of resistors R36 and R53. The current detection input pin CS of the power management chip U1 is electrically connected to the source electrode of the first switching transistor Q5 through a sampling resistor R37 to detect the magnitude of the current flowing through the first switching transistor Q5. The voltage regulation signal output pin GD of the power management chip U1 is electrically connected to the gate electrode of the first switching transistor Q5 through a driving resistor R28. The drain electrode of the first switching transistor Q5 is electrically connected to the DC voltage output terminal of the PFC unit 200 through the first primary coil of the transformer module 310. The source electrode is electrically connected to the CS pin of the power management chip U1 through the sampling resistor R37, and is grounded through three resistors R44, R45, and R46 connected in parallel to withstand the current output from the source electrode of the first switching transistor Q5, realizing overcurrent protection.

[0123] Combined Figure 5 and Figure 6As shown, the transformer module 310 includes a first primary coil, an auxiliary coil, and a coupled first secondary coil. One end of the first primary coil is electrically connected to the DC voltage output terminal of the PFC unit 200, and the other end is connected to the drain of the first switching transistor Q5. The two ends of the first secondary coil are connected in series with a rectifying diode D3, and then a filter capacitor C4 for the output terminal and a load resistor R11 are connected in parallel across the two ends to form a regulated output terminal V+. A diode D5 and a capacitor C2 are connected in parallel across the two ends of the first primary coil. At the same time, a resistor group composed of resistors R1, R2, R3, R4, R12, and R13 connected in series and in parallel and a diode TV1 are connected in parallel to form an RCD circuit. When the first switching transistor Q5 is turned on, current flows through the first primary coil and then through the first switching transistor Q5 to ground. The CS pin samples the magnitude of the current and then outputs a PWM voltage regulation signal from the GD pin. When the first switching transistor Q5 is turned off, the voltage in the first primary coil reverses, charges the capacitor C2 through the diode D5, and at the same time, the voltage spike is absorbed and dissipated in the form of heat through the RCD loop formed by the cooperation of the resistor group and the diode TV1, ensuring that the first switching transistor Q5 is not burned out. While a varying current passes through the first primary coil, a varying current is also generated in the auxiliary coil. After passing through a resistor R18 and a filter capacitor C5 connected in parallel, it supplies power to the zero-current detection pin ZCD of the power management chip U1, which is used to detect whether the current in the first primary coil drops to zero. In the embodiment of the present application, the CS pin of the power management chip is grounded after being connected in series with a resistor R58 and a capacitor C24. At the same time, a PWM voltage regulation signal directly output by the MCU is introduced through a resistor R60 to change the output of the GD pin. The COMP pin of the power management chip U1 is grounded after being connected in series with a resistor R57 and an optocoupler U8B. At the same time, it is grounded through a capacitor C22. The optocoupler U8B is directly controlled by the MCU through the isolation driving module 510. By controlling the conduction depth of the photosensitive triode in the optocoupler U8B, the voltage of the COMP pin changes accordingly, so that the power management chip U1 outputs a corresponding PWM voltage regulation signal to change the output voltage of the flyback driving unit 300.

[0124] Combined with Figure 6 As shown, the signal sampling module 330 is configured between the control unit 500 and the regulated output terminal, and includes voltage-dividing resistors R19 and R20 connected in series at the voltage output terminal and a sampling output circuit, which is used to sample the output voltage of the regulated output terminal and output it to the signal receiving module 530 in the control unit 500 through the isolation driving module 510. For the specific connection method, please refer to Figure 6 , which will not be elaborated here.

[0125] Figure 6 A capacitor CY1 is connected in series between the hot ground terminal GND and the cold ground terminal GNDE to improve the anti-interference ability of the circuit.

[0126] The load driving module 340 includes at least one power supply transformer connected to the regulated output terminal V+, and a second switching transistor for controlling the conduction state of the power supply transformer. The LED load is connected to the secondary coil of the power supply transformer. For simplicity of description, the embodiments of the present application will be described by taking two groups of LED loads as an example. Refer to Figure 8 , two power supply transformers L1 and L3 are connected to the regulated output terminal V+. The secondary coils of L1 and L3 are respectively electrically connected to different LED loads, and the current magnitudes of the LED loads are respectively controlled by switching transistors Q1 and Q3. The switching transistors Q1 and Q3 are respectively connected to two control signal output pins of the MCU via optocouplers U1B and U2B, thereby realizing precise independent control of the voltage and current of each LED load.

[0127] To achieve complete shutdown or voltage regulation of the load driving module 340, the regulated output terminal V+ is connected to the ground in series via a resistor R33 and a switching transistor Q12. A control signal output pin of the MCU controls the switching of the switching transistor Q12 via an isolation driving module 510, thereby controlling the voltage of the regulated output terminal V+.

[0128] In the embodiments of the present application, the first control module 540 includes a first control program sub-module loaded in the MCU or stored in an external storage chip for the MCU to retrieve. The first control program sub-module responds to the output voltage fed back by the signal sampling module 330, and respectively outputs a PWM voltage regulation signal and an output voltage shutdown signal to the switching transistor current detection input terminal and the output terminal of the error amplifier of the power management chip U1, and adjusts the voltage output of the regulated output terminal of the flyback driving unit 300. The second control module 550 includes a second control program sub-module loaded in the MCU. The second control program sub-module receives and responds to the load adjustment request output by the instruction receiving module, and outputs a PWM dimming signal to the isolation optocoupler to control the conduction state of the second switching transistor.

[0129] To meet the effective transmission of high-frequency signals, the isolation driving module 510 in the embodiments of the present application is configured as a capacitive isolation driving chip.

[0130] For the rectification unit and the PFC unit 200 structure involved in the solution of the present application, specific reference can be made to Figure 5 and Figure 7 , where after the rectification unit accesses the 220V mains power, it is rectified and filtered by the EMI module to output a 310V DC voltage, and then further regulated and adjusted after being processed by the PFC unit 200. In the embodiments of the present application, the power management chip U2 in the above PFC unit 200 also samples the L6562 chip. The circuit structures and working principles of the above two functional units have been disclosed in many prior arts and will not be elaborated here.

[0131] Finally, an embodiment of the present application also discloses a PCB board, on which the stable and reliable LED driving circuit as described above is printed to achieve stable driving of the LED load and extend the service life of each component in the light source.

[0132] 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 stable and reliable LED driving method, characterized in that: include: Establishing a control connection between the control unit (500) and the LED load unit (400) and the driving circuit; Acquiring and storing a first time delay t1 from when the control unit (500) outputs a first control signal to when the drive circuit responds to the first control signal, and A second time delay t2 from the control unit (500) outputting the second control signal to the LED load unit (400) responding to the second control signal; Monitor and respond to the load adjustment request of the LED load unit (400), output a first control signal to the driving circuit to control the circuit output, and output a second control signal to the LED load unit (400) after a time period t1-t2 to control the working state of the LED load.

2. The stable and reliable LED driving method according to claim 1, characterized in that: The LED load unit (400) comprises at least two groups of LED loads; The driving method further comprises: Associate and store the compensation ripple waveform characteristics required for each LED load and its combination when adjusting the working state; storing the waveform characteristics of each compensation ripple and the required compensation control parameters and the third time delay t3 in association; Monitoring a load adjustment request of the LED load unit (400), and generating the second control signal based on the load adjustment request; Finding the compensation ripple waveform characteristics corresponding to the load adjustment, matching and outputting the corresponding compensation control parameters as the third control signal to the driving circuit, and outputting the second control signal to the LED load unit (400) after a time period of t1-t3; Wherein, the compensation control parameter is configured to adjust the PWM regulation signal output by the power management chip inside the driving circuit and / or the capacitance value of the output end of the driving circuit; The compensating ripple waveform characteristic is configured to reduce the ripple generated by the load change at the output end of the driving circuit.

3. The stable and reliable LED driving method according to claim 1, characterized in that: The driving method further comprises: Based on the theoretical filter model of the output end of the driving circuit, the optimal filter capacitor values ​​corresponding to different LED loads or their combinations are obtained and stored in association; Establishing a control connection between a control unit (500) and a filter capacitor at an output end of a drive circuit; Acquiring and storing a fourth time delay t4 from when the control unit (500) outputs a fourth control signal to when the output-end filter capacitor completes responding to the fourth control signal; According to the load adjustment request obtained by monitoring, find the optimal filter capacitor value that matches the corresponding one; A fourth control signal is generated and outputted according to the optimal output capacitance value, and a second control signal is outputted to the LED load unit (400) after a time period t1-t4 to control the working state of the LED load.

4. The stable and reliable LED driving method according to claim 2 or 3, characterized in that: The driving method further comprises: Counting and storing the attenuation rate of the performance parameters of each component in the driving circuit and the LED load unit (400) as the usage time changes; Based on the theoretical output model of the driving circuit and in combination with the transmission delays of the current control signals and feedback signals, a correlation relationship between the transmission delay change and the usage time is established; The usage time of the current driving circuit and the LED load unit (400) is counted, and the transmission time extension of each control signal is calculated and adjusted.

5. A stable and reliable LED driving circuit, characterized in that: It comprises an input rectification unit (100), a PFC unit (200), a flyback drive unit (300), an LED load unit (400) and a control unit (500); wherein the control unit (500) comprises: An isolation driving module (510), configured to implement isolated communication with an external functional unit; A storage module (520) configured to store a first time delay t1 from the first control module (540) outputting a first control signal to the flyback drive unit (300) for responding, and a second time delay t2 from the second control module (550) outputting a second control signal to the LED load unit (400) for responding; A signal receiving module (530) configured to monitor and receive an output feedback signal from an output end of the flyback driving unit (300) and an external load adjustment request; A first control module (540) is configured to be connected to the signal receiving module (530) and the flyback drive unit (300), and is used to receive and generate and output a first control signal according to the output feedback signal or the load adjustment request to adjust the output voltage of the flyback drive unit (300) and / or the size of the filter capacitor at the output end of the flyback drive unit (300); A second control module (550) is configured to be connected to the signal receiving module (530) and the LED load unit (400), and is used to receive and generate and output a second control signal according to the load adjustment request to control the working state of the LED load; The output control module (580) controls the output of a first control signal to the flyback drive unit (300) to control the circuit output in response to the load adjustment request output by the instruction receiving module, and outputs a second control signal to the LED load unit (400) after a time period t1-t2 to control the working state of the LED load.

6. The stable and reliable LED driving circuit according to claim 5, characterized in that: The storage module (520) also stores: The compensation ripple waveform characteristics, the required compensation control parameters and the corresponding third time delay t3 required for each LED load and its combination when adjusting the working state; Optimal filter capacitance values ​​corresponding to different LED loads or combinations thereof, and a fourth time delay t4 from when the control unit (500) outputs a third control signal to when the output terminal capacitance of the flyback drive unit (300) responds to the third control signal; as well as The correlation between the change in each signal transmission delay and the power usage time; The control unit (500) further comprises: A third control module (560) is configured to be connected to the flyback drive unit (300), receive and respond to the output of the instruction receiving module, search the storage module (520) for the compensation ripple waveform characteristics corresponding to the load adjustment request, match and output a third control signal containing corresponding compensation control parameters to the flyback drive unit (300) to improve the circuit output ripple; A fourth control module (570) is configured to be connected to the output capacitor of the flyback drive unit (300), and is used to receive and search for a corresponding optimal filter capacitor value according to the load adjustment request obtained by the instruction receiving module, and output a fourth control signal to the flyback drive unit (300) to improve the circuit output ripple; A signal transmission delay adjustment module (590) is configured to calculate and adjust the transmission delay of each control signal according to statistics and the usage time of the current flyback drive unit (300) and the LED load unit (400); The output control module (580) counts the usage time of the current driving circuit and the LED load unit (400), calculates and adjusts the transmission time extension of each control signal, and outputs the second control signal to the LED load unit (400) after the third control signal is output at time t1-t3, and outputs the second control signal to the LED load unit (400) after the fourth control signal is output at time t1-t4.

7. The stable and reliable LED driving circuit according to claim 6, characterized in that: The flyback driving unit (300) comprises: A transformer module (310) comprises a first primary coil and a first secondary coil coupled thereto, one end of the primary coil being electrically connected to a DC voltage output end of a PFC unit (200), and the other end being connected to a first switch tube, and an output filter capacitor and a load resistor being connected in parallel at both ends of the first secondary coil to form a voltage-stabilized output end; A power control module (320), comprising a power management chip U1 and a first switch tube connected thereto, wherein the switch tube current detection input terminal and the output terminal of the error amplifier of the power management chip U1 are both signal-connected to the first control module (540), and receives and controls the on-off state of the first switch tube in response to a control signal output by the first control module (540) to adjust the voltage at the voltage output terminal; A signal sampling module (330) is arranged between the control unit (500) and the voltage stabilization output terminal, comprising a plurality of voltage dividing resistors and a sampling output circuit arranged in series at the voltage output terminal, and is used to collect the output voltage of the voltage stabilization output terminal and output it to the signal receiving module (530) in the control unit (500) via the isolation driving module (510); A load driving module (340) comprising at least one power supply transformer connected to a voltage stabilization output terminal and a second switch tube for controlling the conduction state of the power supply transformer, wherein the LED load is connected to a secondary coil of the power supply transformer; The first control module (540) comprises an MCU and a first control program submodule loaded therein, wherein the first control program submodule responds to the output voltage fed back by the signal sampling module (330), and based on a built-in algorithm, outputs a PWM voltage regulation signal and an output voltage shutdown signal to the switch tube current detection input terminal and the output terminal of the error amplifier of the power management chip, respectively, to adjust the voltage output of the voltage stabilization output terminal of the flyback drive unit (300).

8. The stable and reliable LED driving circuit according to claim 7, characterized in that: The second switch tube is controllably connected to the signal output end of the second control module (550) in the control unit (500) via an isolation optical coupler; The second control module (550) comprises a second control program submodule loaded in the MCU, the second control program submodule receives and responds to the load adjustment request output by the instruction receiving module, outputs a PWM dimming signal to the isolation optocoupler, and controls the conduction state of the second switch tube.

9. The stable and reliable LED driving circuit according to claim 8, characterized in that: The isolation driving module (510) is configured as a capacitive isolation driving chip; The first switch tube is configured as an NMOS tube; The power supply pin VCC of the power management chip U1 is powered by a DC power supply and is connected in series with a grounded capacitor for filtering; the inverting input pin INV of the error amplifier in the power management chip U1 is powered by a DC power supply through a resistor voltage divider; the multiplier input pin MULT in the power management chip U1 is powered by a resistor voltage divider in series; the current detection input pin CS of the power management chip U1 is electrically connected to the source of the first switch tube Q5 through a sampling resistor; the voltage regulation signal output pin GD of the power management chip U1 is electrically connected to the gate of the first switch tube Q5 through a driving resistor, the drain of the first switch tube Q5 is electrically connected to the DC voltage output end of the PFC unit (200) through the first primary coil of the transformer module (310), the source of the first switch tube Q5 is electrically connected to the current detection input pin CS of the power management chip U1 through a sampling resistor, and is grounded through a protection resistor; The transformer module (310) comprises a first primary coil, an auxiliary coil and a first secondary coil coupled to the first primary coil, which are arranged on the same side; one end of the first primary coil is electrically connected to the output end of the PFC unit (200), and the other end is connected to the drain of the first switch tube Q5; the first secondary coil is connected in series with a rectifier diode, and an output filter capacitor and a load resistor are connected in parallel at both ends to form a voltage-stabilized output end; The two ends of the first primary coil are connected in parallel with a diode and a capacitor, and at the same time, an energy-consuming resistor and a diode are connected in parallel, so as to form an energy-consuming loop after the first switch tube Q5 is turned off to reduce the voltage spike; the auxiliary coil is connected in parallel with a filter capacitor through a resistor to supply power to the zero current detection pin ZCD of the power management chip U1; the current detection input pin CS of the power management chip U1 is connected in series with a resistor and a capacitor and then grounded, and at the same time, a PWM voltage regulation signal directly output by the MCU is connected through a resistor to change the output of the voltage regulation signal output pin GD; The error amplifier output pin COMP in the power management chip U1 is connected in series with a resistor and an optocoupler and then grounded, and is also connected in parallel with a grounding capacitor; The optical coupler is connected to the MCU control via an isolation drive module (510); The voltage stabilizing output end is connected to two power supply transformers L1 and L3, one end of the secondary coils of the power supply transformers L1 and L3 are electrically connected to the corresponding LED loads respectively, and the other end is connected in series with the second switch tubes Q1 and Q3 and then grounded; the second switch tubes Q1 and Q3 are controlled and connected to the two control signal output pins of the MCU via the optical couplers U1B and U2B respectively.

10. A PCB board, characterized in that: The PCB board is printed with a stable and reliable LED driving circuit as described in any one of claims 5 to 9.

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