Stable and reliable LED driving method, driving circuit and PCB

Abstract

The invention discloses a stable and reliable LED driving method, a driving circuit and a PCB, and relates to the technical field of light source control, and the method comprises the steps: building the control connection between a control unit and an LED load unit and between the control unit and the driving circuit; acquiring and storing a first time delay t1 and a second time delay t2 for the driving circuit and the LED load unit to respectively respond to the first control signal / the second control signal after the first control signal and the second control signal are output from the control unit; the control circuit is used for monitoring and responding to a load adjusting request of the LED load unit, outputting a first control signal to the driving circuit to control circuit output, and outputting a second control signal to the LED load unit to control the working state of the LED load after t1-t2; according to the scheme, the duration is set in advance to adjust the output parameter of the driving circuit, so that the adjusted output current can adapt to the requirement when the LED load changes, the voltage is maintained to be stable, the output ripple is reduced, the damage to each light source device during frequent switching is reduced, and the service life is prolonged.

Description

Technical Field

[0001] The present 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 drivers usually use flyback switching power supplies to provide stable voltage and current to LED loads. In order to simplify system control, the sampling signal at the output of the flyback circuit is usually directly fed back to the power management chip through a feedback loop to monitor changes in the output voltage / current. The power management chip adjusts the duty cycle of the PWM signal output to the switch tube inside the flyback circuit according to the above changes, and then adjusts the final output of the circuit to achieve voltage stabilization requirements. In addition, a controller (such as a single-chip microcomputer) is usually used to output a control signal to control the light-emitting state of the LED load.

[0003] In practice, in order to prevent voltage fluctuations at the drive circuit or load end from damaging the MCU, an isolation unit is usually set between the drive circuit / load end and the MCU, such as configuring an optocoupler isolation chip between the MCU and the drive circuit. However, practice shows that when the control signal frequency conversion speed exceeds 1KHz, the output of ordinary optocouplers will be seriously distorted, and the use of high-speed optocouplers will significantly increase the system hardware cost. At the same time, when the number of LED loads driven by the flyback switching power supply changes, such as by turning on or off certain LED loads to adjust the color temperature or brightness of the light source, due to the response delay of the feedback loop control, the flyback circuit cannot adjust the output voltage in time, which leads to an increase in output ripple, causing damage to the load and circuit components, and in the long run, it will reduce the service life of the load and circuit components. Summary of the invention

[0004] In view of the problem that ordinary optocouplers are difficult to meet the control requirements of LEDs in specific practices and that frequent switching of LED light sources can easily shorten their service life, the first purpose of this application is to provide a stable and reliable LED driving method, which directly controls the output voltage / current and output timing of the flyback circuit through the MCU via a capacitive isolation driver chip, which can effectively reduce the output ripple of the circuit when the LED load changes, thereby reducing the damage to each light source device when the LED light source is frequently switched on and off. At the same time, the capacitive isolation driver chip is used to replace the ordinary optocoupler to ensure high-frequency control accuracy while effectively protecting the MCU from the influence of voltage fluctuations in the driving circuit. In order to implement the above-mentioned LED driving method, the second purpose of this application is to provide a stable and reliable LED driving circuit, and finally proposes to protect a PCB board printed with the above-mentioned LED driving circuit. The specific scheme is as follows: A stable and reliable LED driving method, comprising: Establishing a control connection between the control unit and the LED load unit and the drive circuit; Acquire and store a first time delay t1 from when the control unit outputs a first control signal to when the drive circuit responds to the first control signal, and A second time delay t2 from when the control unit outputs the second control signal to when the LED load unit responds to the second control signal; Monitor and respond to the load adjustment request of the LED load unit, 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 after a time period t1-t2 to control the working state of the LED load.

[0005] Through the above technical solution, based on the control connection between the control unit and 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 by setting the duration in advance, so that the adjusted output current supply can just meet the demand when the number of LED loads changes, thereby ensuring the stability of the output voltage and reducing the output ripple size at the output end of the drive circuit, thereby reducing the damage to each light source device when the LED light source is frequently switched on and off, and extending the service life of each device.

[0006] Further, the LED load unit includes at least two groups of LED loads; The LED driving method further includes: 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, and generating the second control signal based on the load adjustment request; Find the compensation ripple waveform characteristics corresponding to the load adjustment, match and output the corresponding compensation control parameters as the third control signal to the driving circuit, and output the second control signal to the LED load unit after the time 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.

[0007] Through the above technical solution, the corresponding compensation control parameters can be output in advance according to the ripple waveform characteristics caused by the load change in the LED load unit, so that the ripples generated by different loads or their combination changes can be reduced in time.

[0008] Furthermore, the LED driving method further includes: 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 the control unit and the filter capacitor at the output end of the drive circuit; Acquire and store a fourth time delay t4 from when the control unit 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 after a time period t1-t4 to control the working state of the LED load.

[0009] Through the above technical solution, before using the control unit to output a control signal to control the working state of the LED load, the filter capacitor value at the output end of the drive circuit is first changed so that its filter parameters can be more adapted to the changes that are about to occur in the load, thereby causing the filter capacitor value at the output end of the drive circuit to change accordingly at the moment the output load changes, thereby ultimately reducing the ripple size and making the voltage at the output end of the drive circuit more stable, which is also beneficial to extending the service life of various components.

[0010] Furthermore, the LED driving method further includes: Count and store the attenuation rate of performance parameters of each component in the drive circuit and LED load unit 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 LED load unit is counted, and the transmission time extension of each control signal is calculated and adjusted.

[0011] Through the above technical solution, when the entire LED light source system has been used for a long time and the components have aged, the control unit can still output the corresponding control signal at a precise time point, thereby ensuring that the ripple at the output end of the driving circuit can be effectively reduced throughout the life cycle of the light source, extending the service life of each component and making the LED light emission more stable and reliable.

[0012] In order to implement the above-mentioned 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: An isolation driver module, configured to implement isolated communication with an external functional unit; A storage module configured to store a first time delay t1 from when the first control module outputs a first control signal to when the flyback drive unit responds, and a second time delay t2 from when the second control module outputs a second control signal to when the LED load unit responds; A signal receiving module configured to monitor and receive an output feedback signal from an output end of the flyback drive unit and an external load adjustment request; A first control module is configured to be connected to the signal receiving module and the flyback driving unit, 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 and / or the size of the filter capacitor at the output end of the flyback driving unit; A second control module, configured to be connected to the signal receiving module and the LED load unit, and 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, in response to the load adjustment request output by the instruction receiving module, controls the output of 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 time period t1-t2 to control the working state of the LED load.

[0013] Furthermore, the storage module 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; The optimal filter capacitance value corresponding to different LED loads or their combination, and the fourth time delay t4 from the control unit outputting the third control signal to the output end capacitance of the flyback drive unit responding to the third control signal; and The correlation between the change in each signal transmission delay and the power usage time; The control unit also includes: a third control module, configured to be connected to the flyback drive unit, receive and respond to the output of the instruction receiving module, search the compensation 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 drive unit to improve the circuit output ripple; a fourth control module, configured to be connected to the output capacitor of the flyback drive unit, to receive and search for a corresponding optimal filter capacitor value according to the load adjustment request obtained by the instruction receiving module, and to output a fourth control signal to the flyback drive unit to improve the circuit output ripple; The signal transmission delay adjustment module is configured to calculate and adjust the transmission delay of each control signal according to the current usage time of the flyback drive unit and the LED load unit; The output control module counts the usage time of the current driving circuit and the LED load unit, calculates and adjusts the transmission time extension of each control signal, and outputs the second control signal to the LED load unit after the third control signal is output at time t1-t3, and outputs the second control signal to the LED load unit after the fourth control signal is output at time t1-t4.

[0014] Furthermore, the flyback driving unit includes: The transformer module comprises a first primary coil and a first secondary coil coupled thereto, wherein 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 switch tube, and an output filter capacitor and a load resistor are connected in parallel at both ends of the first secondary coil to form a voltage-stabilized output end; A power control module, 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, and receives and responds to the control signal output by the first control module to control the on-off state of the first switch tube to adjust the voltage at the voltage output terminal; The signal sampling module is arranged between the control unit and the voltage stabilization output terminal, and includes 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 in the control unit via the isolation driving module; A load driving module, comprising at least one power supply transformer connected to the 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 the secondary coil of the power supply transformer; The first control module includes a first control program submodule loaded in the MCU. The first control program submodule responds to the output voltage fed back by the signal sampling module, and based on the 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, thereby adjusting the voltage output of the voltage stabilization output terminal of the flyback drive unit.

[0015] Through the above technical solution, the control mode of the flyback drive circuit is changed from conventional automatic feedback loop control to MCU control. Therefore, the output voltage and waveform of the flyback drive circuit can be adjusted in advance according to the output state of the voltage stabilization output terminal and the changes in the LED load, so that it can adapt to the frequent changes of the LED load, making the entire light source system emit light more stably and reliably.

[0016] Furthermore, the second switch tube is controllably connected to the signal output terminal of the second control module in the control unit via an isolation optical coupler; The second control module includes 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.

[0017] Through the above technical solution, the control unit can quickly and efficiently adjust the brightness of each LED load in the LED load unit, thereby realizing the adjustment of the color temperature of the light source. Since it operates independently from the first control module, the second control signal can be output after the first control signal, thereby reducing the output ripple caused by signal transmission delay or component response delay, and improving the voltage stability of the flyback drive unit.

[0018] Furthermore, the isolation driving module 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 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; 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; 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; 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; 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.

[0019] The present application also discloses a PCB board, on which the stable and reliable LED driving circuit as described above is printed.

[0020] In summary, the present application includes at least one of the following beneficial technical effects: When the number of loads in the LED load unit is about to change, the output of the drive circuit is adjusted by setting the duration in advance, so that the adjusted voltage / current supply can just meet the demand when the number of LED loads changes. At the same time, the filter capacitor value of the voltage regulator output end is adjusted according to the load change, thereby reducing the output ripple size of the output end of the drive circuit, reducing the damage to each light source device when the LED light source is frequently switched on and off, and extending the service life of each device. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of the LED driving method of the present application; Figure 2 This is a schematic diagram of optimizing the output wave based on adjusting the capacitance value of the voltage stabilization output terminal; Figure 3 It is an overall schematic diagram of the functional modules of the LED driving circuit of the present application; Figure 4 It is a schematic diagram of the functional modules of the control unit; Figure 5 It is a circuit principle schematic diagram of the LED driving circuit of the present application; Figure 6 It is a schematic diagram of the circuit principle of the flyback drive unit; Figure 7 It is a schematic diagram of the circuit principle of the input rectifier unit and the PFC unit; Figure 8 It is a schematic diagram of the circuit principle of the control unit.

[0022] Attached figure numbers: 100, input rectification unit; 200, PFC unit; 300, flyback drive unit; 310, transformer module; 320, power supply control module; 330, signal sampling module; 340, load drive module; 400, LED load unit; 500, control unit; 510, isolation drive 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

[0023] Embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings.

[0024] In the description of this specification, the description with reference to the terms "certain embodiments", "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0025] The present application embodiment first discloses a stable and reliable LED driving method, such as Figure 1 As shown, it mainly includes the following steps: S100, establishing a control connection between the control unit and the LED load unit and the drive circuit; S200, acquiring and storing a first time delay t1 from when the control unit outputs a first control signal to when the drive circuit responds to the first control signal, and A second time delay t2 from when the control unit outputs the second control signal to when the LED load unit responds to the second control signal; S300, monitor and respond to the load adjustment request of the LED load unit, 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 after a time period t1-t2 to control the working state of the LED load.

[0026] In step S100, the specific control connection relationship between the control unit and the LED load unit can be found in Figure 3-Figure 8 This will be described in detail in the subsequent examples.

[0027] In step S200, after the control unit outputs the control signal, affected by the charging and discharging of components such as capacitors and inductors in the circuit, the drive circuit needs to spend a certain amount of time to respond to the above control signal, that is, there is a certain delay in adjusting the voltage output according to the instruction requirements of the control signal, and affected by the circuit structure, the first delay t1 is longer than the second delay t2.

[0028] In this specific practice, the oscilloscope and the signal generator can be connected to the driving circuit to calculate and obtain the first delay and the second delay. After multiple effective measurements, the average value is taken as a fixed parameter and written into the program module of the control unit.

[0029] In step S300, the control unit receives an external command signal to adjust the working state of each LED load, such as adjusting the brightness of the light source by controlling the current of the LED load, or adjusting the color temperature by adjusting the light-emitting state of multiple LED loads. In step S300, the transmission delay of each signal is fully considered, and the duration is set in advance to adjust the output of the drive circuit, so that the adjusted output current supply can just meet the demand when the number of LED loads changes, thereby keeping the output voltage stable, reducing the output ripple size of the output end of the drive circuit, reducing the damage to each light source device when the LED light source is frequently switched on and off, and extending the service life of each device.

[0030] In practical applications, an LED load unit usually includes at least two groups of LED loads, which improves the reliability of the light source and facilitates the adjustment of the color temperature.

[0031] To this end, the LED driving method described in the embodiment of the present application further includes the following steps: A100, storing in association the compensation ripple waveform characteristics required by each LED load and its combination when adjusting the working state, and storing in association the compensation ripple waveform characteristics and the compensation control parameters required by them and the third delay t3; A200, monitoring a load adjustment request of the LED load unit, and generating the second control signal based on the load adjustment request; A300, searching for the compensation ripple waveform characteristics corresponding to the above 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 after the time duration t1-t3.

[0032] In step A100, the compensating ripple waveform feature is configured to reduce the ripple generated by the load change at the output end of the driving circuit. In practical applications, firstly, the waveform of the voltage at the output end of the driving circuit that changes with the working state of each LED load and its combination is obtained through an oscilloscope. Usually, within a set time after the LED load changes, it is affected by the change of the load resistance at the output end of the driving circuit. For example, more LED loads connected in parallel will cause the load resistance to decrease, which will cause the waveform output at the output end of the driving circuit to jitter and generate ripples. Changes in different LED loads will generate different types of ripples, such as the amplitude, waveform and attenuation characteristics of the ripples. After obtaining the ripple waveform features corresponding to the changes in each LED load, the waveform features corresponding to the above-mentioned compensating ripples can be obtained through computer processing. In an ideal embodiment, the amplitude and oscillation direction of the above-mentioned compensating ripples are exactly opposite to the ripple waveform caused by the load change.

[0033] The compensation control parameters in step A100 are configured to adjust the PWM regulation signal output by the power management chip inside the driving circuit and / or the capacitance value at the output end of the driving circuit, including a control unit outputting a PWM voltage regulation signal to the power management chip of the driving circuit, such as outputting to the current detection pin of the switch tube, to fine-tune 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 the charge and discharge circuit, so that the above-mentioned filter capacitor can better buffer the output voltage change of the driving circuit. In practical applications, the capacitance value of the filter capacitor can also be adjusted by the power management chip that controls the driving circuit, such as changing the duty cycle of the output pulse during the charge and discharge cycle of the filter capacitor to affect the charge and discharge degree of the capacitor.

[0034] 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 size of the LED load by adjusting the internal channel width of the switch tube connected to the LED load.

[0035] Because the filter capacitor at the output end of the drive circuit has different response effects to different output loads, such as Figure 2 As shown, the LED driving method of the embodiment of the present application further includes: B100, based on the theoretical filtering model of the output end of the driving circuit, obtains the optimal filtering capacitance values ​​corresponding to different LED loads or their combinations, and associates the LED loads or their combinations with the corresponding optimal filtering capacitance values ​​to form a two-dimensional data table.

[0036] B200, establishes a control connection between the control unit and the filter capacitor at the output end of the drive circuit.

[0037] B300, obtaining and storing a fourth time delay t4 from when the control unit outputs a fourth control signal to when the output-end filter capacitor completes responding to the fourth control signal.

[0038] B400, according to the load adjustment request obtained by monitoring, finds the optimal filter capacitor value that matches the corresponding one; B500, generating and outputting a fourth control signal according to the optimal output capacitance value, and outputting a second control signal to the LED load unit after a time period t1-t4 to control the working state of the LED load.

[0039] The above technical solution first changes the filter capacitance value at the output end of the driving circuit before using the control unit to output a control signal to control the working state of the LED load, so that its filter parameters can be more adapted to the changes that are about to occur in the load, thereby causing the filter capacitance value at the output end of the driving circuit to change accordingly at the moment the output load changes, thereby ultimately reducing the ripple size, making the voltage at the output end of the driving circuit more stable, and also helping to extend the service life of various components.

[0040] In practical applications, the delay of each signal transmission in the driving circuit is usually related to the parameters and operating status of each component. In order to ensure that the control unit can still provide accurate timing control after the light source is used for a long time to minimize the ripple generated when the load changes, the LED driving method described in the embodiment of the present application also includes: C100, counts and stores the attenuation rate of performance parameters of each component in the drive circuit and LED load unit as the usage time changes; C200, based on the theoretical output model of the driving circuit, combined with the transmission delay of each current control signal and feedback signal, establishes a correlation relationship between the transmission delay change and the usage time; C300, counting the usage time of the current driving circuit and the LED load unit, and calculating and adjusting the transmission time extension of each control signal, wherein the control signal includes the aforementioned first control signal, second control signal, third control signal and fourth control signal.

[0041] The law of how the performance parameters of each component change with the use time can be found through the performance data table provided by the component manufacturer. For example, after the inductor is used for a long time, its inductance value will decrease and its resistivity will increase. The above theoretical output model can be constructed based on the actual circuit schematic.

[0042] Based on the above technical solution, when the entire LED light source system has been used for a long time and the components have aged, the control unit can still output the corresponding control signal at a precise time point, thereby ensuring that the output ripple at the output end of the driving circuit can be effectively suppressed throughout the life cycle of the light source, extending the service life of each component and making the LED light emission more stable and reliable.

[0043] In order to realize the above LED driving method, the present application also proposes a stable and reliable LED driving circuit, such as Figure 3 As shown, it includes an input rectifying unit 100, a PFC unit 200, a flyback driving unit 300, an LED load unit 400 and a control unit 500 which are connected in sequence.

[0044] Combination Figure 4 As 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.

[0045] 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 configured as program modules that can realize related functions and are loaded into the control chip. The implementation method of this application preferably uses the STM32F103 series single-chip microcomputer (MCU) as the control chip. The peripheral power supply and clock circuit of the above-mentioned control chip are all existing technologies and are not repeated in this implementation method. The isolation drive module 510 is implemented by a separately configured capacitive isolation drive chip, which can meet the transmission of signals with a conversion frequency exceeding 1KHz. In the implementation method of this application, the ISOC124P chip is preferably used to realize the isolated communication between the control chip and the external functional unit.

[0046] The storage module 520 is implemented by the built-in memory of the MCU. In specific practice, the storage module 520 can be implemented by a peripheral storage chip.

[0047] In the implementation manner of the present application, the storage module 520 is configured to store at least the following data contents: The first time delay t1 from the first control module 540 outputting the first control signal to the flyback drive unit 300 responding; the second time delay t2 from the second control module 550 outputting the second control signal to the LED load unit 400 responding; the compensation ripple waveform characteristics, required compensation control parameters and corresponding third time delay t3 required for each LED load and its combination when adjusting the working state; the optimal filter capacitance value corresponding to different LED loads or their combinations, and the fourth time delay t4 from the control unit 500 outputting the third control signal to the output end capacitance of the flyback drive unit 300 responding to the third control signal; and the correlation between the changes in each signal transmission delay and the power usage time.

[0048] The signal receiving module 530 includes a built-in data input port of the MCU. The present application selects the INT pin and the P0 pin on the MCU, which are respectively configured to monitor and receive the output feedback signal of the output end of the flyback drive unit 300 and the external load adjustment request.

[0049] The first control module 540 is used to control the voltage regulation signal parameters in the flyback drive unit 300, and 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 load adjustment request to adjust the output voltage of the flyback drive unit 300 and / or the filter capacitor size at the output end of the flyback drive unit 300. The second control module 550 is used to control the working state of the LED load and adjust the working current size, 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 drive unit 300 to control the circuit output, and output the second control signal to the LED load unit 400 after the time t1-t2 to control the working state of the LED load.

[0050] The 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 compensation ripple waveform characteristics corresponding to the load adjustment request from the storage module 520, match and output the third control signal containing the corresponding compensation control parameter to the flyback drive unit 300 to improve the circuit output ripple. The fourth control module 570 is configured to be connected to the output capacitor of the flyback drive unit 300, receive and according to the load adjustment request obtained by the instruction receiving module, search and match the corresponding optimal filter capacitor value and output the fourth control signal to the flyback drive unit 300 to improve the circuit output ripple.

[0051] The signal transmission delay adjustment module 590 is configured to calculate and adjust the transmission delay of each control signal according to statistics and the current usage time of the flyback driving unit 300 and the LED load unit 400.

[0052] 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 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. In practical applications, the usage time can be counted by the timing module in the MCU, that is, the timing starts when the MCU is powered on, and the current timing time is saved after the power is turned off, so as to accumulate the usage time.

[0053] See also 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 .

[0054] In the embodiment of the present application, the power control module 320 includes a power management chip U1 and a first switch tube Q5 connected thereto. The power management chip U1 preferably adopts an L6562 current mode PWM controller chip, and the first switch tube preferably adopts an NMOS tube. The current detection input pin CS and the error amplifier output pin COMP of the power management chip U1 are both connected to the first control module 540 signal, and receive and respond to the control signal output by the first control module 540 to control the on-off state of the first switch tube to adjust the voltage at the voltage output end. Figure 5 and Figure 6As 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, and 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 to ensure stable power supply; the inverting input pin INV of the error amplifier in the power management chip U1 is powered by resistors R35 and R52 in series for voltage division; the multiplier input pin MULT for power factor correction in the power management chip U1 is powered by resistors R36 and R53 in series for voltage division. 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 R37, and is used to detect the current flowing through the first switch tube Q5. 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 via a driving resistor R28, the drain of the first switch tube Q5 is electrically connected to the DC voltage output end of the PFC unit 200 via the first primary coil of the transformer module 310, the source is electrically connected to the CS pin of the power management chip U1 via the sampling resistor R37, and is grounded via three parallel resistors R44, R45, and R46 to withstand the current output from the source of the first switch tube Q5 to achieve overcurrent protection.

[0055] Combination 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 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 D3, and then an output filter capacitor C4 and a load resistor R11 are connected in parallel at both ends to form a regulated output terminal V+. The two ends of the first primary coil are connected in parallel with a diode D5 and a capacitor C2, and 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 switch tube Q5 is turned on, the current flows through the first primary coil and to the ground through the first switch tube Q5. The CS pin collects the current and then outputs a PWM voltage regulation signal from the GD pin; when the first switch tube Q5 is turned off, the voltage in the first primary coil is reversed, and the capacitor C2 is charged through the diode D5. At the same time, the RCD loop formed by the resistor group and the diode TV1 absorbs and dissipates the voltage spike in the form of heat to ensure that the first switch tube Q5 is not burned. While a variable current passes through the first primary coil, the auxiliary coil will also generate a variable current. A resistor R18 is connected in parallel with a filter capacitor C5 to supply 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 connected in series with a resistor R58 and a capacitor C24 and then grounded, and 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 connected in series with a resistor R57 and an optocoupler U8B to ground, and at the same time, it is grounded through a capacitor C22. The optocoupler U8B is directly controlled by the MCU via the isolation driver module 510. By controlling the conduction depth of the phototransistor in the optocoupler U8B, the voltage of the COMP pin changes accordingly, thereby causing the power management chip U1 to output a corresponding PWM voltage regulation signal to change the output voltage of the flyback driver unit 300.

[0056] Combination Figure 6 As shown, the signal sampling module 330 is configured between the control unit 500 and the voltage stabilization output terminal, including voltage dividing resistors R19 and R20 arranged in series at the voltage output terminal and a sampling output circuit, which 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. For the specific connection method, please refer to Figure 6 , I will not go into details here.

[0057] Figure 6 A capacitor CY1 is connected in series between the hot ground terminal GND and the cold ground terminal GNDE to improve the circuit's anti-interference capability.

[0058] The load driving module 340 includes at least one power supply transformer connected to the voltage stabilization output terminal V+ and a second switch tube 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 present application embodiment takes two groups of LED loads as an example for description. Figure 8 The voltage-stabilized output terminal V+ is connected to two power transformers L1 and L3. The secondary coils of L1 and L3 are electrically connected to different LED loads, and the current of the LED loads is controlled by the switch tubes Q1 and Q3. The switch tubes Q1 and Q3 are controlled by the two control signal output pins of the MCU through the optocouplers U1B and U2B, respectively, so as to achieve precise and independent control of the voltage and current of each LED load.

[0059] In order to achieve complete shutdown or voltage regulation of the load driving module 340, the voltage-stabilized output terminal V+ is connected to the ground in series via the resistor R33 and the switch tube Q12, and a control signal output pin of the MCU controls the switch of the above-mentioned switch tube Q12 via the isolation driving module 510, thereby controlling the voltage of the voltage-stabilized output terminal V+.

[0060] In the embodiment of the present application, the first control module 540 includes a first control program submodule loaded in the MCU or stored in an external storage chip for MCU to retrieve. The first control program submodule responds to the output voltage fed back by the signal sampling module 330, and based on the 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 U1, respectively, to adjust the voltage output of the voltage stabilization output terminal of the flyback drive unit 300. The second control module 550 includes a second control program submodule loaded in the MCU, and 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.

[0061] In order to ensure the effective transmission of high-frequency signals, the isolation driving module 510 in the embodiment of the present application is configured as a capacitive isolation driving chip.

[0062] For details about the rectifier unit and PFC unit 200 structure involved in the present application solution, please refer to Figure 5 and Figure 7 , wherein the rectifier unit is connected to the 220V mains and then filtered by the EMI module to output a 310V DC voltage, which is then further stabilized and adjusted by the PFC unit 200 before output. In the implementation of the present application, the power management chip U2 in the PFC unit 200 also uses the L6562 chip. The circuit structure and working principle of the above two functional units have been disclosed in many prior arts and will not be described here.

[0063] Finally, an embodiment of the present application further discloses a PCB board, on which is printed the stable and reliable LED driving circuit as described above, so as to achieve stable driving of the LED load and extend the service life of various components in the light source.

[0064] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify 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 includes: 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 includes: 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 includes: 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 when the first control module (540) outputs a first control signal to when the flyback drive unit (300) responds, and a second time delay t2 from when the second control module (550) outputs a second control signal to when the LED load unit (400) responds; 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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