Linear LED driving system and driving method

Abstract

The invention provides a linear LED driving system and method, and the system comprises a first LED module and a second LED module which respectively comprise a plurality of LED lamp segments which are cascaded in sequence, and the number of the LED lamp segments in the first LED module and the number of the LED lamp segments in the second LED module differ by one segment; the input end of the first LED module is connected with bus voltage, and the output end is connected with the input end of the second LED module through the flow direction limiting module; the flow direction limiting module is configured to only allow current to flow from the first LED module to the second LED module; the switch is connected between the input end of the first LED module and the input end of the second LED module, and is switched off at low voltage and high voltage; the driving control module is used for closing the switch when the voltage is low, and controlling the LED lamp sections in the LED modules to be sequentially and alternately lightened along with the increase of the bus voltage; and when the voltage is high, the switch is switched off, the LED lamp sections are controlled to be lightened in sequence along with the increase of the bus voltage, and the output current is controlled. According to the invention, the design difficulty and the system cost are reduced, and the system efficiency and the single harmonic performance are improved.

Description

Technical Field

[0001] The present invention relates to the field of LED control, and in particular to a linear LED driving system and a driving method. Background Art

[0002] Regulation IEC61000-3-2 sets out requirements for input current harmonics for lighting equipment with an input of more than 25W, as shown in the following table.

[0003]

[0004] For linear LED drivers, current will flow through the LED only when the input voltage is higher than the forward conduction voltage of the LED. Figure 1 As shown in the figure, when the forward conduction voltage of the LED lamp segment is set to close to 0, the output current Isin is close to a sine wave. Since the higher-order harmonic components of the sine wave are zero, the single harmonics are relatively low at this time, meeting the requirements of the above table; when the forward conduction voltage of the LED is set to V1, the output current IV1 suddenly changes at the input voltage V1; when the forward conduction voltage of the LED is set to V2, the output current IV2 suddenly changes at the input voltage V2; after simulation, it was found that the single harmonics of the step wave when the output current is IV1 or IV2 are likely to exceed the standard and cannot meet the requirements of the above table.

[0005] The lower the LED's forward voltage, the better the THD (Total Harmonic Distortion). However, too low a forward voltage can reduce overall system efficiency. Therefore, multi-segment LED drivers are often used to reduce THD and improve system efficiency. However, system cost must be considered, and the number of segments should be kept to a minimum. Otherwise, multi-segment linear drivers will lose their cost advantage over switching drivers.

[0006] Therefore, how to balance the single harmonic of LED driving, system efficiency and cost has become one of the problems that technicians in this field need to solve urgently.

[0007] It should be noted that the above technical background is merely provided to provide a clear and complete description of the technical solutions of the present invention and to facilitate understanding by those skilled in the art. Simply because these solutions are described in the technical background section of the present invention, it should not be assumed that the above technical solutions are well known to those skilled in the art. Summary of the Invention

[0008] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a linear LED driving system and driving method to solve the problem in the prior art that single harmonics, system efficiency and cost of LED driving cannot be taken into account at the same time.

[0009] To achieve the above objectives and other related objectives, the present invention provides a linear LED driving system, which at least includes:

[0010] A first LED module, a second LED module, a flow direction limiting module, a switch, and a drive control module; wherein the first LED module and the second LED module each include a plurality of LED light segments cascaded in sequence, and the number of LED light segments in the first LED module and the second LED module differ by one segment;

[0011] The input end of the first LED module is connected to the bus voltage, and the output end is connected to the input end of the second LED module via the flow direction limiting module; the flow direction limiting module is configured to only allow current to flow from the output end of the first LED module to the input end of the second LED module;

[0012] The switch is connected between the input end of the first LED module and the input end of the second LED module, and the control end is connected to the output end of the drive control module;

[0013] The drive control module is connected to the output end of each LED light segment. When the bus voltage is low, the switch is controlled to close. As the bus voltage increases, the LED light segments in each LED module are controlled to light up alternately in sequence. When the bus voltage is high, the switch is controlled to open. As the bus voltage increases, the LED light segments are controlled to light up in sequence. The output current is controlled so that the output current is a sine wave in each cycle.

[0014] Optionally, the first LED module includes a first LED light segment, a second LED light segment, and a third LED light segment connected in sequence, and the second LED module includes a fourth LED light segment and a fifth LED light segment connected in sequence; or the first LED module includes a fourth LED light segment and a fifth LED light segment connected in sequence, and the second LED module includes a first LED light segment, a second LED light segment, and a third LED light segment connected in sequence;

[0015] The on-state voltage of each lamp segment satisfies: VLED1<VLED4<VLED1+VLED2<VLED4+VLED5<VLED1+VLED2+VLED3, wherein VLED1 is the on-state voltage of the first LED lamp segment, VLED2 is the on-state voltage of the second LED lamp segment, VLED3 is the on-state voltage of the third LED lamp segment, VLED4 is the on-state voltage of the fourth LED lamp segment, and VLED5 is the on-state voltage of the fifth LED lamp segment.

[0016] More optionally, the drive control module includes: a voltage detection unit, a control unit and a plurality of output current adjustment units;

[0017] The voltage detection unit detects the bus voltage and determines whether the bus voltage is low voltage or high voltage;

[0018] Each output current regulating unit is connected to the output end of each LED light segment in a one-to-one correspondence, and is used to regulate the current at the output end of each LED light segment;

[0019] The control unit is connected to the sampling end of each output current regulating unit, obtains a sinusoidal reference based on the bus sampling voltage and the output current sampling voltage, and generates a driving control signal for each output current regulating unit based on the output signal of the voltage detection unit and the sinusoidal reference.

[0020] More optionally, each output current regulating unit includes a power tube and a sampling unit; one end of the power tube is connected to the output end of the corresponding LED light segment, the other end is grounded via the sampling unit, and the control end is connected to the output end of the control unit.

[0021] More optionally, each output current regulating unit shares the same sampling unit.

[0022] More optionally, the control unit includes an operational amplifier module, a compensation capacitor, a multiplier, a reference voltage generator and several operational amplifiers;

[0023] The input end of the operational amplifier module is connected to the sampling end of each output current regulating unit and receives the reference voltage, and the output end is connected to the upper plate of the compensation capacitor; the lower plate of the compensation capacitor is grounded;

[0024] The multiplier receives the compensation voltage on the compensation capacitor and the bus sampling voltage, and performs multiplication operation to obtain the sinusoidal reference;

[0025] The reference voltage generator is connected to the output end of the multiplier and the voltage detection unit, and generates a reference voltage for each output current regulating unit based on the sinusoidal reference and the magnitude of the bus voltage;

[0026] Each operational amplifier corresponds to each output current regulating unit one by one. An input terminal of each operational amplifier is connected to a corresponding reference voltage and a corresponding output current sampling voltage to generate a driving control signal of the corresponding output current regulating unit.

[0027] More optionally, the linear LED driving system further includes a bus voltage sampling module, which includes a first resistor and a second resistor, wherein the first resistor and the second resistor are connected in series and are connected at both ends of the bus voltage, and the connection node between the first resistor and the second resistor outputs the bus sampling voltage.

[0028] More optionally, the flow direction limiting module is a diode, an anode of the diode is connected to the output end of the first LED module, and a cathode of the diode is connected to the input end of the second LED module.

[0029] More optionally, the linear LED driving system further includes an AC / DC conversion module, which rectifies the AC voltage into a bus voltage.

[0030] More optionally, when the number of LED segments is set to 5, the on-state voltage of each LED segment satisfies:

[0031] VLED1:VLED2:VLED3:VLED4:VLED5=1 / 2:1:1:1:1.

[0032] To achieve the above-mentioned and other related objectives, the present invention further provides a linear LED driving method, which is implemented based on the above-mentioned linear LED driving system. The linear LED driving method at least includes:

[0033] The bus voltage is detected, and when the bus voltage is low, the switch is closed; the first LED module and the second LED module are connected in parallel, and as the bus voltage increases, the light segments in each LED module are alternately lit;

[0034] When the bus voltage is high, the switch is disconnected; the first LED module and the second LED module are connected in series, and as the bus voltage increases, the LED lamp segments are lit in sequence.

[0035] Optionally, the number of LED light segments is set to 5; when the switch is closed, as the bus voltage increases, the LED light segments are turned on in sequence in the following order:

[0036] LED1→LED4→LED1+LED2→LED4+LED5→LED1+LED2+LED3;

[0037] When the switch is off, as the bus voltage increases, the LED segments are turned on in the following order:

[0038] LED1→LED1+LED2→LED1+LED2+LED3→LED1+LED2+LED3+LED4→LED1+LED2+LED3+LED4+LED5.

[0039] As described above, the linear LED driving system and driving method of the present invention have the following beneficial effects:

[0040] 1. The linear LED driving system of the present invention adopts asymmetric segmentation and optimizes the reference voltage. When the input voltage is low, the system circuit no longer operates in parallel, but is converted to staggered series. Therefore, the system circuit does not require balanced matching, which reduces the design difficulty.

[0041] 2. The linear LED driving system of the present invention reduces the number of driving power tubes by reducing the number of LED segments, thereby reducing system costs.

[0042] 3. The linear LED driving system of the present invention relatively increases the number of conduction sections at low voltage input, thereby improving system efficiency and single harmonic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Shown is a schematic diagram of the corresponding output current waveform obtained by simulation under different forward conduction voltages of the LED lamp segment.

[0044] Figure 2 Shown is a structural schematic diagram of the linear LED driving system of the present invention.

[0045] Figure 3 Shown is another structural schematic diagram of the linear LED driving system of the present invention.

[0046] Figure 4 Shown is a schematic structural diagram of a segmented LED driving system used in a comparative example of the present invention.

[0047] Component number description

[0048] 1 Linear LED drive system

[0049] 11. First LED module

[0050] 12 Second LED module

[0051] 13 Flow direction limitation module

[0052] 14 Switch

[0053] 15 Drive control module

[0054] 151 Voltage detection unit

[0055] 152 control unit

[0056] 152a Op Amp Module

[0057] 152b multiplier

[0058] 152c Reference Voltage Generator

[0059] 153 working voltage generating unit

[0060] 16 Bus voltage sampling module

[0061] 17 AC / DC conversion module

[0062] 2-segment LED drive system

[0063] 21 Third LED module

[0064] 22 Fourth LED module DETAILED DESCRIPTION

[0065] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0066] See also Figures 2 to 4 It should be noted that the diagrams provided in this embodiment are merely schematic illustrations of the basic concept of the present invention. Therefore, the diagrams only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0067] Further simulation results show that when the forward conduction voltage of the LED is less than one-third of the peak value of the input voltage, the single harmonic of the waveform can meet the standard. Taking the system efficiency into consideration, the multi-segment linear LED in the present invention is driven in at least three segments.

[0068] The present invention provides a linear LED driving system 1, comprising:

[0069] A first LED module 11, a second LED module 12, a flow direction limiting module 13, a switch 14, and a drive control module 15 are provided. Both the first LED module 11 and the second LED module 12 include a plurality of cascaded LED segments, with the number of LED segments differing between the first and second LED modules. The input of the first LED module 11 is connected to the bus voltage, and its output is connected to the input of the second LED module 12 via the flow direction limiting module 13. The flow direction limiting module 13 is configured to allow current to flow only from the output of the first LED module 11 to the input of the second LED module 12. The switch 14 is connected between the input of the first LED module 11 and the input of the second LED module 12, with its control terminal connected to the output of the drive control module 15. The drive control module 16 is connected to the output end of each LED lamp segment. When the bus voltage is low, the control switch 14 is closed. As the bus voltage increases, the LED lamp segments in each LED module are controlled to light up alternately in sequence. When the bus voltage is high, the control switch 14 is opened. As the bus voltage increases, the LED lamp segments are controlled to light up in sequence. The output current is controlled so that the output current is a sine wave in each cycle.

[0070] Specifically, the total number of LED light segments in the first LED module 11 and the second LED module 12 can be set as needed, including but not limited to 3 segments, 5 segments, 7 segments, and 9 segments; theoretically, the total number of LED light segments can be configured to any odd number greater than or equal to 3; of course, the number of segments cannot be too many, and the more segments, the higher the cost. The specific number of segments is set according to actual application needs.

[0071] The present invention also provides a linear LED driving method, comprising: detecting a bus voltage; when the bus voltage is low, closing a switch; connecting a first LED module and a second LED module in parallel; and as the bus voltage increases, the light segments in each LED module are alternately illuminated. When the bus voltage is high, opening the switch; connecting the first LED module and the second LED module in series; and as the bus voltage increases, the LED light segments are alternately illuminated.

[0072] Example 1

[0073] like Figure 2 As shown, in this embodiment, the total number of LED light segments is set to 5.

[0074] like Figure 2 As shown, the input end of the first LED module 11 is connected to the bus voltage Vin, and the output end is connected to the input end of the second LED module 12 via the flow direction limiting module 13 .

[0075] Specifically, in this embodiment, the first LED module 11 includes a first LED segment LED1, a second LED segment LED2, and a third LED segment LED3, which are connected in cascade sequence. The second LED module 12 includes a fourth LED segment LED4 and a fifth LED segment LED5, which are connected in cascade sequence. The on-state voltage of each segment satisfies the following: VLED1 < VLED4 < VLED1 + VLED2 < VLED4 + VLED5 < VLED1 + VLED2 + VLED3, where VLED1 is the on-state voltage of the first LED segment LED1, VLED2 is the on-state voltage of the second LED segment LED2, VLED3 is the on-state voltage of the third LED segment LED3, VLED4 is the on-state voltage of the fourth LED segment LED4, and VLED5 is the on-state voltage of the fifth LED segment LED5. As an example, in order to obtain optimal loss and efficiency, the on-state voltage of each lamp segment is set to: VLED1:VLED2:VLED3:VLED4:VLED5=1 / 2:1:1:1:1; when the on-state voltage of each LED lamp bead is the same, the on-state voltage corresponds to the number of lamp beads, that is, at this time, the number of lamp beads in each lamp segment satisfies 1 / 2:1:1:1:1:1.

[0076] like Figure 2 As shown, the flow direction limiting module 13 is configured to only allow current to flow from the output end of the first LED module 11 to the input end of the second LED module 12 .

[0077] Specifically, in this embodiment, the flow direction limiting module 13 is implemented using a diode D1. The anode of the diode D is connected to the output terminal of the first LED module 11, and the cathode is connected to the input terminal of the second LED module 12. In this case, current can flow from the third LED segment LED3 to the fourth LED segment LED4, but cannot flow from the fourth LED segment LED4 to the third LED segment LED3. In actual use, any circuit structure or device that can limit the flow of current is applicable to the present invention, and is not limited to this embodiment.

[0078] like Figure 2 As shown, the switch 14 is connected between the input end of the first LED module 11 and the input end of the second LED module 12, and the control end is connected to the output end of the drive control module 15; when the bus voltage Vin is low, the switch 14 is closed, and when the bus voltage Vin is high, the switch 14 is open.

[0079] Specifically, switch 14 is used to adjust the connection relationship of the LED segments. When switch 14 is closed, the LED segments are connected in an alternating series arrangement. That is, as the bus voltage Vin increases, the LED segments are turned on in the following order: LED1 → LED4 → LED1 + LED2 → LED4 + LED5 → LED1 + LED2 + LED3. When switch 14 is open, the LED segments are connected in series. That is, as the bus voltage Vin increases, the LED segments are turned on in the following order: LED1 → LED1 + LED2 → LED1 + LED2 + LED3 → LED1 + LED2 + LED3 + LED4 → LED1 + LED2 + LED3 + LED4 + LED5. Switch 14 can be implemented using any device or circuit structure with a switching function, and a detailed description thereof is omitted here.

[0080] like Figure 2 As shown, the drive control module 15 is connected to the output end of each LED lamp segment and controls the output current so that the output current is a sine wave in each cycle.

[0081] Specifically, the drive control module 15 controls the output current of each current path according to the conduction state of different LED light segments, so that the output current is a sine wave within each cycle (it should be noted that under ideal conditions, the output current is a sine wave within a cycle, but there will be errors in actual use. It is sufficient to be similar to a sine wave, that is, to meet the single harmonic requirement), and the overall output is a constant current. Any circuit structure that can achieve the above functions is applicable to the present invention. In this embodiment, the drive control module 15 includes: a voltage detection unit 151, a first output current regulation unit, a second output current regulation unit, a third output current regulation unit, a fourth output current regulation unit, a fifth output current regulation unit, and a control unit 152. The number of output current regulation units is the same as the number of LED light segments, and they correspond one to one. When the number of LED light segments changes, the number of output current regulation units is also adaptively adjusted, which is not detailed here.

[0082] More specifically, the voltage detection unit 151 detects the bus voltage Vin and determines whether the bus voltage Vin is low voltage or high voltage; as an example, the input end of the voltage detection unit 151 is connected to the bus voltage Vin and the reference voltage Ref, and compares the bus voltage Vin with the reference voltage Ref. When the peak value of the bus voltage Vin is greater than the reference voltage Ref, the bus voltage is determined to be high voltage; when the peak value of the bus voltage Vin is less than or equal to the reference voltage Ref, the bus voltage is determined to be low voltage. In this example, the comparison reference of the bus voltage Vin and the comparison reference of the current sampling voltage are set to the same value. In actual use, the corresponding comparison references can be set separately as needed.

[0083] It should be noted that high voltage and low voltage can be determined according to the standards known in the industry. Generally, 120V bus voltage is low voltage and 220V bus voltage is high voltage. In this example, the distinction between high voltage and low voltage is determined based on the LED conduction voltage. That is, when the peak value of the bus voltage Vin is less than VLED1+VLED2+VLED3+VLED4, the first to fourth LED segments cannot be powered at the same time (when the number of LED segments is configured as N, the peak value of the bus voltage Vin is less than When N is a natural number greater than or equal to 3, the bus voltage Vin is considered to be low voltage and can only power a small number of LED lights; when the peak value of the bus voltage Vin is greater than or equal to LED1+LED2+LED3+LED4, it can power the first to fourth LED light segments at the same time (when the number of LED light segments is configured as N, the peak value of the bus voltage Vin is greater than or equal to ), the bus voltage Vin is considered to be high voltage and can power a large number of LED lights.

[0084] More specifically, the first to fifth output current regulating units are connected to the output terminals (OUT1, OUT2, OUT3, OUT4, OUT5) of the first to fifth LED light segments, respectively, for regulating the current at the output terminals of each LED light segment. Each output current regulating unit includes a power transistor and a sampling unit. One end of each power transistor is connected to the output terminal of the corresponding LED light segment, the other end is grounded GND via the sampling unit, and the control end is connected to the output terminal of the control unit 152. As an example, Figure 2 As shown, each output current regulation unit includes a first power transistor Q1, a second power transistor Q2, a third power transistor Q3, a fourth power transistor Q4, and a fifth power transistor Q5, and each output current regulation unit shares a common sampling resistor Rcs. In this example, each power transistor is implemented as an NMOS transistor. The drain of each power transistor is connected to the output terminal of the corresponding LED light segment, the gate is connected to the corresponding output signal of the driving unit 152, and the source is connected to ground GND via the sampling resistor Rcs. In actual use, any circuit structure that can achieve output current regulation is applicable to the present invention.

[0085] More specifically, the control unit 152 is connected to the sampling terminals of each output current regulating unit, derives a sinusoidal reference based on the bus sampling voltage Vin and the output current sampling voltage, and generates a drive control signal for each output current regulating unit based on the output signal of the voltage detection unit 151 and the sinusoidal reference. As an example, the control unit 152 includes an operational amplifier module 152a, a first operational amplifier OP1, a second operational amplifier OP2, a third operational amplifier OP3, a fourth operational amplifier OP4, a fifth operational amplifier OP5, a compensation capacitor C1, a multiplier 152b, and a reference voltage generator 152c. The number of operational amplifiers is the same as the number of LED segments, and corresponds one-to-one. When the number of LED segments changes, the number of operational amplifiers is also adaptively adjusted. Details are not detailed here. The input terminal of the operational amplifier module 152a is connected to the sampling terminal CS of each output current regulating unit (i.e., the connection node between the sampling resistor Rcs and each power transistor) and receives a reference voltage Ref (a comparison reference for the current sampling voltage). The output terminal is connected to the top plate of the compensation capacitor C1; the bottom plate of the compensation capacitor C1 is grounded GND. Multiplier 152b receives the compensation voltage on compensation capacitor C1 and the bus sampling voltage, performing a multiplication operation to obtain a sinusoidal reference. Reference voltage generator 152c is connected to multiplier 152b and the output of voltage detection unit 151, and generates reference voltages for each output current regulating unit based on the sinusoidal reference and the bus voltage Vin. When switch 14 is closed, each reference voltage satisfies the following conditions: Ref1 < Ref4 < Ref2 < Ref5 < Ref3; when switch 14 is open, each reference voltage satisfies the following conditions: Ref1 < Ref2 < Ref3 < Ref4 < Ref5. Ref1, Ref2, Ref3, Ref4, and Ref5 are the reference voltages for the first to fifth output current regulating units, respectively. First to fifth operational amplifiers (OP1, OP2, OP3, OP4, and OP5) correspond to each output current regulating unit, with their inputs connected to the corresponding reference voltage and the corresponding output current sampling voltage to generate a drive control signal for the corresponding output current regulating unit.

[0086] As another implementation of the present invention, Figure 2 As shown, the drive control module 15 further includes a working voltage generating unit 153 . The working voltage generating unit 153 is connected to the bus voltage Vin and converts the bus voltage Vin into a working voltage of the drive control module 15 .

[0087] As another implementation of the present invention, Figure 2As shown, the linear LED driving system 1 further includes a bus voltage sampling module 16 , which includes a first resistor R1 and a second resistor R2 . The first resistor R1 and the second resistor R2 are connected in series across the bus voltage, and the connection node between the first and second resistors outputs the bus sampled voltage. In actual use, any method capable of sampling the bus voltage is applicable to the present invention, and is not limited to this embodiment.

[0088] As another implementation of the present invention, Figure 2 As shown, the linear LED driving system 1 further includes an AC / DC conversion module 17 that receives an AC voltage AC and converts the AC voltage AC into a bus voltage Vin (in a bun wave form). In this example, the AC voltage is converted into the bus voltage based on a rectifier bridge BD1.

[0089] like Figure 2 As shown, in this embodiment, the voltage detection unit 151, the first to fifth power transistors, the operating voltage generation unit 153, the operational amplifier module 152a in the control unit 152, the first to fifth operational amplifiers (OP1-OP5), the multiplier 152b, and the reference voltage generator 152c are integrated into the chip. The HV terminal of the chip is connected to the bus voltage Vin, the SWO terminal is connected to the control terminal of the switch 14, the OUT1-OUT5 are respectively connected to the output terminals of each LED light segment, the CS terminal is connected to the sampling resistor Rcs, the COMP terminal is connected to the upper plate of the compensation capacitor C1, and the LN terminal is connected to the bus sampling voltage.

[0090] The linear LED driving system 1 of the present invention is used to realize linear LED driving, and includes:

[0091] The bus voltage Vin is detected. When the bus voltage Vin is low, the switch 14 is closed. As the bus voltage Vin increases, the LED segments are turned on in the following order: LED1 → LED4 → LED1+LED2 → LED4+LED5 → LED1+LED2+LED3. When the bus voltage Vin is high, the switch 14 is opened. As the bus voltage Vin increases, the LED segments are turned on in the following order: LED1 → LED1+LED2 → LED1+LED2+LED3 → LED1+LED2+LED3+LED4 → LED1+LED2+LED3+LED4+LED5.

[0092] Specifically, when a low voltage is input, the first LED module 11 and the second LED module 12 are connected in parallel, and the reference voltages satisfy the following: Ref1 < Ref4 < Ref2 < Ref5 < Ref3, so that the first LED module 11 and the second LED module 12 alternately reach the turn-on voltage. When a high voltage is input, the first LED module 11 and the second LED module 12 are connected in series, and the reference voltages satisfy the following: Ref1 < Ref2 < Ref3 < Ref4 < Ref5, so that the light segments are turned on in sequence.

[0093] Example 2

[0094] like Figure 3 As shown, this embodiment provides a linear LED drive system 1. This differs from the first embodiment in that a first LED module 11 includes a fourth LED segment LED4 and a fifth LED segment LED5 connected in cascade, and a second LED module 12 includes a first LED segment LED1, a second LED segment LED2, and a third LED segment LED3 connected in cascade. When a switch 14 is closed, the first LED module 11 and the second LED module 12 are connected in parallel; when the switch 14 is open, the first LED module 11 and the second LED module 12 are connected in series. The remaining structure and operating principles are identical to those of the first embodiment and are not detailed here.

[0095] Comparative Example

[0096] like Figure 4 As shown, this comparative example provides a segmented LED driver system 2, comprising first to sixth LED segments LED1-LED6. The first, second, and third LED segments LED1-LED2 are sequentially connected in series to form a third LED module 21, and the fourth, fifth, and sixth LED segments LED4, LED5, and LED6 are sequentially connected in series to form a fourth LED module 22. The input of the third LED module 21 is connected to the bus voltage Vin, and its output is connected to the anode of a diode D1. The input of the fourth LED module 22 is connected to the cathode of the diode D1. One end of a switch SW is connected to the input of the third LED module 21, and the other end is connected to the input of the fourth LED module 22. The structure of the driver control module is the same as that of the present invention and is not further described here.

[0097] Specifically, when at low voltage, the switch SW is closed, enabling the parallel connection of LED1 and LED4, the parallel connection of LED1 + LED2 and LED4 + LED5, and the parallel connection of LED1 + LED2 + LED3 and LED4 + LED5 + LED6. The diode D1 isolates the positive terminal of LED4 from the negative terminal of LED3, ensuring that current does not flow directly from the switch SW to the power transistor Q3 (i.e., the output terminal of the third LED segment LED3). When at high voltage, the switch SW is open, enabling the sequential series connection of LED1, LED2, LED3, D1, LED4, LED5, and LED6. Thus, appropriate system performance can be achieved at both low and high voltages.

[0098] However, it should be noted that when in parallel connection at low voltage, the loop where LED1, Q1, and OP2 are located needs to be balanced with the loop where LED4, Q4, and OP5 are located (including but not limited to the same corresponding device parameters and signal magnitudes); the loop where LED2, Q2, and OP3 are located needs to be balanced with the loop where LED5, Q5, and OP6 are located; the loop where LED3, Q3, and OP4 are located needs to be balanced with the loop where LED6, Q6, and OP7 are located. If not balanced, there will be a situation where the current on one side is large and the current on the other side is small. In extreme cases, one side may not work properly, resulting in overheating and abnormality on the other side.

[0099] Specifically, in this example, considering system efficiency, the LED segments are usually evenly segmented, with VLED1 = VLED2 = VLED3 = VLED4 = VLED5 = VLED6. That is, when the conduction voltages of each LED bead are equal, the number of LED beads in each segment satisfies 1:1:1:1:1:1. When the third LED module 21 is in parallel with the fourth LED module 22, the reference voltages satisfy the following relationship: Ref1 = Ref^4 < Ref2 = Ref5 < Ref3 = Ref6. When the third LED module 21 is in series with the fourth LED module 22, the reference voltages satisfy the following relationship: Ref1 < Ref2 < Ref3 < Ref4 < Ref5 < Ref6.

[0100] Figure 4 As shown, the comparative example can meet requirements such as single - harmonic and system efficiency, but there are a total of 6 segments. When in parallel connection at low voltage, the requirement for circuit matching is relatively high, and the system cost is relatively high. Additionally, when in parallel connection, the series - connected switch SW will also cause imbalance in the circuit.

[0101] As Figure 2 and Figure 3 shown, the LED segments of the present invention do not adopt even segmentation, and work in conjunction with the reference voltages Ref1 to Ref5, no longer requiring the circuit to meet matching requirements. Figure 4At low input voltage, the comparative example has only three conduction sections: LED1 → LED1 + LED2 → LED1 + LED2 + LED3, and LED4 → LED4 + LED5 → LED4 + LED5 + LED6 in parallel. Assuming the total number of LEDs is N, the number of LEDs in each section is N / 6. As the bus voltage continues to rise, the number of LEDs corresponding to each conduction section is N / 6 → 2 / 6*N → 3 / 6*N. Therefore, the conduction voltage switching range between the two conduction sections is N / 6. Due to the characteristic of linear LED drive, the excess voltage is borne by the constant current control tube (power tube), so the loss range is N / 6. In this example, the present invention is explained by taking the number of lamp beads in each lamp segment satisfying 1 / 2:1:1:1:1 as an example; when the input voltage is low, the number of conduction segments of the present invention is five segments, namely LED1→LED4→LED1+LED2→LED4+LED5→LED1+LED2+LED3; assuming that the total number of LEDs is N, the number of LEDs in each segment is N / 9, 2 / 9*N, 2 / 9*N, 2 / 9*N, 2 / 9*N, and 2 / 9*N, respectively. In the process of continuous increase in bus voltage, the number of LEDs corresponding to each conduction segment is N / 9→2 / 9*N→3 / 9*N→4 / 9*N→5 / 9*N, so the conduction voltage switching interval between two adjacent conduction segments of the present invention becomes N / 9 (less than N / 6). The on-state voltage switching interval of the present invention is smaller than that of the comparative example, thereby reducing the loss in the two-stage switching interval. In addition, the maximum number of LEDs connected in series when the input voltage is low is reduced from 3 / 6*N to 5 / 9*N, which can also improve the efficiency of the system. Moreover, after the first stage is reduced to N / 9, the on-state voltage is even lower, thereby obtaining a lower single harmonic. When the input voltage is low, the number of on-state stages is changed from three stages in series to five stages in series.

[0102] like Figure 4 As shown, the comparative example adopts a parallel connection mode at low voltage input, which limits the number of segments that can be turned on. Figure 2 and Figure 3 As shown, the present invention realizes staggered series connection at low voltage input, which can increase the number of segments that are conducted in sections and improve system performance. Figure 4 As shown, the number of LED segments connected in series in the comparative example at high voltage input is six, while the number of LED segments connected in series in the present invention at high voltage input is five. Figure 2 and Figure 3 As shown, relatively speaking, the segmented efficiency and single harmonic performance of the present invention are slightly worse than those of the six-segment system, but the performance difference is not too large; however, in terms of cost, the present invention can reduce one driving power tube, and the cost of the power tube is reduced to 5 / 6 of the original, and the cost performance of the system can be greatly improved.

[0103] In summary, the present invention provides a linear LED driving system and driving method, comprising: a first LED module, a second LED module, a flow direction limiting module, a switch, and a driving control module; wherein each of the first LED module and the second LED module includes a plurality of LED segments connected in cascade, and the number of LED segments in the first LED module and the second LED module differs by one segment; an input end of the first LED module is connected to a bus voltage, and an output end is connected to an input end of the second LED module via the flow direction limiting module; the flow direction limiting module is configured to only allow current to flow from the output end of the first LED module to the input end of the second LED module; a switch is connected between the input end of the first LED module and the input end of the second LED module, and a control end is connected to the output end of the driving control module; the driving control module is connected to the output end of each LED segment, and when the bus voltage is low, the switch is controlled to close, and as the bus voltage increases, the LED segments in each LED module are controlled to illuminate alternately in sequence; when the bus voltage is high, the switch is controlled to open, and as the bus voltage increases, the LED segments are controlled to illuminate in sequence; and the output current is controlled so that the output current forms a sinusoidal wave within each cycle. The linear LED driver system of this invention utilizes asymmetric segmentation and optimizes the reference voltage, eliminating the need for balanced matching and reducing design complexity. By reducing the number of LED segments, the number of driver power transistors is reduced, lowering system costs. At low input voltages, the number of conducting segments is relatively increased, thereby improving system efficiency and single harmonic performance. Therefore, this invention effectively overcomes the shortcomings of existing technologies and possesses high industrial value.

[0104] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A linear LED driving system, characterized in that: The linear LED driving system at least includes: A first LED module, a second LED module, a flow direction limiting module, a switch, and a drive control module; wherein the first LED module and the second LED module each include a plurality of LED light segments cascaded in sequence, and the number of LED light segments in the first LED module and the second LED module differ by one segment; The input end of the first LED module is connected to the bus voltage, and the output end is connected to the input end of the second LED module via the flow direction limiting module; the flow direction limiting module is configured to only allow current to flow from the output end of the first LED module to the input end of the second LED module; The switch is connected between the input end of the first LED module and the input end of the second LED module, and the control end is connected to the output end of the drive control module; The drive control module is connected to the output end of each LED light segment. When the bus voltage is low, the switch is controlled to close. As the bus voltage increases, the LED light segments in each LED module are controlled to light up alternately in sequence. When the bus voltage is high, the switch is controlled to open. As the bus voltage increases, the LED light segments are controlled to light up in sequence. The output current is controlled so that the output current is a sine wave in each cycle.

2. The linear LED driving system according to claim 1, wherein: The first LED module includes a first LED light segment, a second LED light segment, and a third LED light segment connected in sequence, and the second LED module includes a fourth LED light segment and a fifth LED light segment connected in sequence; or the first LED module includes a fourth LED light segment and a fifth LED light segment connected in sequence, and the second LED module includes a first LED light segment, a second LED light segment, and a third LED light segment connected in sequence; The on-state voltage of each lamp segment satisfies: VLED1<VLED4<VLED1+VLED2<VLED4+VLED5<VLED1+VLED2+VLED3, wherein VLED1 is the on-state voltage of the first LED lamp segment, VLED2 is the on-state voltage of the second LED lamp segment, VLED3 is the on-state voltage of the third LED lamp segment, VLED4 is the on-state voltage of the fourth LED lamp segment, and VLED5 is the on-state voltage of the fifth LED lamp segment.

3. The linear LED driving system according to claim 1 or 2, characterized in that: The drive control module includes: a voltage detection unit, a control unit and a plurality of output current adjustment units; The voltage detection unit detects the bus voltage and determines whether the bus voltage is low voltage or high voltage; Each output current regulating unit is connected to the output end of each LED light segment in a one-to-one correspondence, and is used to regulate the current at the output end of each LED light segment; The control unit is connected to the sampling end of each output current regulating unit, obtains a sinusoidal reference based on the bus sampling voltage and the output current sampling voltage, and generates a driving control signal for each output current regulating unit based on the output signal of the voltage detection unit and the sinusoidal reference.

4. The linear LED driving system according to claim 3, wherein: Each output current regulating unit includes a power tube and a sampling unit; one end of the power tube is connected to the output end of the corresponding LED light segment, the other end is grounded via the sampling unit, and the control end is connected to the output end of the control unit.

5. The linear LED driving system according to claim 4, characterized in that: Each output current regulating unit shares the same sampling unit.

6. The linear LED driving system according to claim 3, wherein: The control unit includes an operational amplifier module, a compensation capacitor, a multiplier, a reference voltage generator and several operational amplifiers; The input end of the operational amplifier module is connected to the sampling end of each output current regulating unit and receives the reference voltage, and the output end is connected to the upper plate of the compensation capacitor; The lower plate of the compensation capacitor is grounded; The multiplier receives the compensation voltage on the compensation capacitor and the bus sampling voltage, and performs multiplication operation to obtain the sinusoidal reference; The reference voltage generator is connected to the output end of the multiplier and the voltage detection unit, and generates a reference voltage for each output current regulating unit based on the sinusoidal reference and the magnitude of the bus voltage; Each operational amplifier corresponds to each output current regulating unit one by one. An input terminal of each operational amplifier is connected to a corresponding reference voltage and a corresponding output current sampling voltage to generate a driving control signal of the corresponding output current regulating unit.

7. The linear LED driving system according to claim 3, wherein: The linear LED driving system also includes a bus voltage sampling module, which includes a first resistor and a second resistor. The first resistor and the second resistor are connected in series at both ends of the bus voltage, and the connection node between the first resistor and the second resistor outputs the bus sampling voltage.

8. The linear LED driving system according to claim 1 or 2, characterized in that: The flow direction limiting module is a diode, an anode of the diode is connected to the output end of the first LED module, and a cathode of the diode is connected to the input end of the second LED module.

9. The linear LED driving system according to claim 1 or 2, characterized in that: The linear LED driving system further includes an AC / DC conversion module, which rectifies the AC voltage into a bus voltage.

10. The linear LED driving system according to any one of claims 2 to 8, characterized in that: When the number of LED segments is set to 5, the conduction voltage of each LED segment satisfies: VLED1:VLED2:VLED3:VLED4:VLED5=1 / 2:1:1:1:

1.

11. A linear LED driving method, implemented based on the linear LED driving system according to any one of claims 1 to 10, characterized in that: The linear LED driving method at least includes: The bus voltage is detected, and when the bus voltage is low, the switch is closed; the first LED module and the second LED module are connected in parallel, and as the bus voltage increases, the light segments in each LED module are alternately lit; When the bus voltage is high, the switch is disconnected; the first LED module and the second LED module are connected in series, and as the bus voltage increases, the LED lamp segments are lit in sequence.

12. The linear LED driving method according to claim 11, wherein: The number of LED light segments is set to 5; When the switch is closed, as the bus voltage increases, the LED segments are turned on in the following order: LED1→LED4→LED1+LED2→LED4+LED5→LED1+LED2+LED3; When the switch is off, as the bus voltage increases, the LED segments are turned on in the following order: LED1→LED1+LED2→LED1+LED2+LED3→LED1+LED2+LED3+LED4→LED1+LED2+LED3+LED4+LED5。

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