Linear LED driving system and driving method

Abstract

The application provides a linear LED driving system and a driving method, which comprises a first LED module and a second LED module, each of which comprises a plurality of LED lamp segments connected in cascade, and the number of LED lamp segments in the first and second LED modules differs by one segment; the input end of the first LED module is connected with a bus voltage, and the output end is connected with the input end of the second LED module through a flow direction limiting module; the flow direction limiting module is configured to allow current to flow from the first LED module to the second LED module only; a switch is connected between the input end of the first LED module and the input end of the second LED module, and is closed at low voltage and is opened at high voltage; a driving control module closes the switch at low voltage, and controls the LED lamp segments in each LED module to be lit alternately in turn as the bus voltage increases; the switch is opened at high voltage, and the LED lamp segments are lit in turn and the output current is controlled as the bus voltage increases. The application reduces the design difficulty and the system cost, and improves the system efficiency and single harmonic performance.

Description

Technical Field

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

[0002] The regulation IEC61000-3-2 specifies the requirements for input current harmonics for lighting equipment with an input of 25W or more, as shown in the table below.

[0003]

[0004] For linear LED drivers, current will only flow through the LED when the input voltage is higher than the LED's forward voltage; for example... Figure 1 As shown, when the forward voltage of the LED segment is set to near 0, the output current Isin is close to a sine wave. Since the higher harmonic components of the sine wave are zero, the single harmonics are relatively low at this time, which meets the requirements of the table above. When the forward voltage of the LED is set to V1, the output current IV1 changes abruptly at the input voltage V1. When the forward voltage of the LED is set to V2, the output current IV2 changes abruptly at the input voltage V2. Simulation results show that the single harmonics of the stepped wave are prone to exceed the standard when the output current is IV1 or IV2, which fails to meet the requirements of the table above.

[0005] The lower the forward voltage of an LED, the better its THD (Total Harmonic Distortion); however, too low a forward voltage will reduce the overall system efficiency. Therefore, multi-segment LED drivers are usually used to reduce THD while improving system efficiency. However, system cost must also be considered, and the number of segments cannot be too large, otherwise multi-segment linear drivers will not have a cost advantage compared to switching drivers.

[0006] Therefore, how to balance the single harmonics of LED drivers, system efficiency, and cost has become one of the problems that urgently needs to be solved by those skilled in the art.

[0007] It should be noted that the above description of the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of the present invention and facilitating understanding by those skilled in the art. It should not be assumed that the above technical solutions are known to those skilled in the art simply because they have been described in the background section of this invention. Summary of the Invention

[0008] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a linear LED driving system and driving method to solve the problem that the single harmonic distortion, system efficiency and cost of LED driving cannot be balanced in the prior art.

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

[0010] The system comprises a first LED module, a second LED module, a flow direction limiting module, and a switch and drive control module; wherein, both the first LED module and the second LED module include a number of LED segments cascaded in sequence, and the number of LED segments in the first LED module and the second LED module differs by a certain amount;

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

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

[0013] The drive control module is connected to the output terminal of each LED segment. When the bus voltage is low, it controls the switch to close, and as the bus voltage increases, it controls the LED segments in each LED module to light up alternately. When the bus voltage is high, it controls the switch to open, and as the bus voltage increases, it controls the LED segments to light up alternately. It also controls the output current so that the output current is sinusoidal in each cycle.

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

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

[0016] Alternatively, the drive control module includes: a voltage detection unit, a control unit, and several output current adjustment units;

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

[0018] Each output current adjustment unit is connected to the output terminal of each LED segment to adjust the current at the output terminal of each LED segment.

[0019] The control unit is connected to the sampling terminal of each output current adjustment unit. It obtains a sinusoidal reference based on the bus sampling voltage and the output current sampling voltage, and generates drive control signals for each output current adjustment unit based on the output signal of the voltage detection unit and the sinusoidal reference.

[0020] Alternatively, each output current adjustment unit includes a power transistor and a sampling unit; one end of the power transistor is connected to the output terminal of the corresponding LED segment, the other end is grounded via the sampling unit, and the control terminal is connected to the output terminal of the control unit.

[0021] Alternatively, each output current regulation unit may share the same sampling unit.

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

[0023] The input terminal of the operational amplifier module is connected to the sampling terminal of each output current adjustment unit and receives the reference voltage; the output terminal 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 a multiplication operation to obtain the sinusoidal reference.

[0025] The reference voltage generator is connected to the output terminals of the multiplier and the voltage detection unit, and generates the reference voltage for each output current adjustment unit based on the magnitude of the sinusoidal reference and the bus voltage.

[0026] Each operational amplifier corresponds one-to-one with each output current adjustment unit. The input terminal of each operational amplifier is connected to the corresponding reference voltage and the corresponding output current sampling voltage to generate the drive control signal for the corresponding output current adjustment unit.

[0027] Alternatively, the linear LED driving system further 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 across the bus voltage terminals, and the connection node between the first resistor and the second resistor outputs the bus sampling voltage.

[0028] Alternatively, the flow direction limiting module is a diode, with the anode of the diode connected to the output terminal of the first LED module and the cathode connected to the input terminal of the second LED module.

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

[0030] Alternatively, when the number of LED segments is set to 5, the conduction voltage of each LED segment satisfies:

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

[0032] To achieve the above and other related objectives, the present invention also provides a linear LED driving method, implemented based on the above-described linear LED driving system, wherein the linear LED driving method includes at least:

[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 LED segments in each LED module light up alternately in sequence;

[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, each LED segment lights up in sequence.

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

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

[0037] When the switch is open, as the bus voltage increases, each LED segment turns on sequentially 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 asymmetrical segmentation and optimizes the reference voltage. When the low voltage input is applied, the system circuit no longer operates in parallel mode, but is converted to interleaved series mode. 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 transistors by reducing the number of LED segments, thereby reducing the system cost.

[0042] 3. The linear LED driving system of the present invention increases the number of conduction segments at low voltage input, thereby improving system efficiency and single harmonic performance. Attached Figure Description

[0043] Figure 1 The diagram shows the simulated output current waveforms obtained under different forward conduction voltages of the LED segment.

[0044] Figure 2 The diagram shown is a structural schematic of a linear LED driving system according to the present invention.

[0045] Figure 3 This is a schematic diagram of another structure of the linear LED driving system of the present invention.

[0046] Figure 4 The diagram shown is a schematic of the segmented LED driving system structure used in the comparative example of this invention.

[0047] Component designation explanation

[0048] 1 Linear LED Driving System

[0049] 11 First LED Module

[0050] 12 Second LED Module

[0051] 13 Flow direction restriction module

[0052] 14 Switches

[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 generation 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 Implementation

[0065] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

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

[0067] Further simulations revealed that when the forward conduction voltage of the LED is less than one-third of the peak input voltage, the single harmonic of the waveform can meet the standard. Considering system efficiency, the multi-segment linear LED in this invention is driven in at least three segments.

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

[0069] The system comprises 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. Both the first LED module 11 and the second LED module 12 include several cascaded LED segments, with the number of LED segments differing slightly between the two modules. The input terminal of the first LED module 11 is connected to the bus voltage, and its output terminal is connected to the input terminal 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 terminal of the first LED module 11 to the input terminal of the second LED module 12. The switch 14 is connected between the input terminals of the first LED module 11 and the second LED module 12, and its control terminal is connected to the output terminal of the drive control module 15. The drive control module 16 is connected to the output terminal of each LED segment. When the bus voltage is low, the control switch 14 is closed, and as the bus voltage increases, the LED segments in each LED module are lit up alternately. When the bus voltage is high, the control switch 14 is open, and as the bus voltage increases, the LED segments are lit up alternately. The output current is also controlled so that the output current is sinusoidal in each cycle.

[0070] Specifically, the total number of LED 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 segments can be configured to any odd number greater than or equal to 3; of course, the number of segments should not be too many, as the more segments there are, the higher the cost, and the specific number of segments should be set according to the actual application needs.

[0071] The present invention also provides a linear LED driving method, comprising: detecting the 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 LED segments in each LED module light up sequentially and alternately. 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 segments light up sequentially.

[0072] Example 1

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

[0074] like Figure 2 As shown, the input terminal of the first LED module 11 is connected to the bus voltage Vin, and the output terminal is connected to the input terminal 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 connected in sequence. The second LED module 12 includes a fourth LED segment LED4 and a fifth LED segment LED5 connected in sequence. The on-state voltage of each segment satisfies: 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 the optimal loss and efficiency, the conduction voltage of each lamp segment is set as follows: VLED1:VLED2:VLED3:VLED4:VLED5 = 1 / 2:1:1:1:1; when the conduction voltage of each LED is the same, the conduction voltage corresponds to the number of LEDs, that is, at this time, the number of LEDs in each lamp segment satisfies 1 / 2:1:1:1:1.

[0076] like Figure 2 As shown, 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.

[0077] Specifically, in this embodiment, the flow direction limiting module 13 is implemented using diode D1. The anode of diode D1 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. At this time, 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 practical use, any circuit structure or device that can limit the current flow direction is applicable to this invention and is not limited to this embodiment.

[0078] like Figure 2 As shown, switch 14 is connected between the input terminal of the first LED module 11 and the input terminal of the second LED module 12, and the control terminal is connected to the output terminal of the drive control module 15; when the bus voltage Vin is low, switch 14 is closed, and when the bus voltage Vin is high, 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 series alternately. That is, as the bus voltage Vin increases, the conduction sequence of each LED segment is as follows: LED1 → LED4 → LED1+LED2 → LED4+LED5 → LED1+LED2+LED3. When switch 14 is open, the LED segments are connected in series sequentially. That is, as the bus voltage Vin increases, the conduction sequence of each LED segment is as follows: 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 switching function, which will not be elaborated here.

[0080] like Figure 2 As shown, the drive control module 15 is connected to the output terminal of each LED segment to control the output current so that the output current is sinusoidal 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 segments, so that the output current is sinusoidal in each cycle (it should be noted that ideally the output current is sinusoidal in one cycle, but there will be errors in actual use; a sinusoidal shape is sufficient, i.e., meeting the single harmonic requirement), and the overall output is constant current; any circuit structure that can achieve the above function is applicable to this invention. In this embodiment, the drive control module 15 includes: a voltage detection unit 151, a first output current adjustment unit, a second output current adjustment unit, a third output current adjustment unit, a fourth output current adjustment unit, a fifth output current adjustment unit, and a control unit 152. The number of output current adjustment units is the same as the number of LED segments, and they correspond one-to-one. When the number of LED segments changes, the number of output current adjustment units is also adjusted adaptively, which will not be described in detail here.

[0082] More specifically, the voltage detection unit 151 detects the bus voltage Vin and determines whether the bus voltage Vin is low or high. As an example, the input terminal of the voltage detection unit 151 is connected to the bus voltage Vin and the reference voltage Ref. The bus voltage Vin is compared 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. 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. 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 industry-known standards. Generally, 120V bus voltage is considered low voltage, and 220V bus voltage is considered high voltage. In this example, the distinction between high voltage and low voltage is determined based on the LED turn-on voltage. That is, when the peak value of the bus voltage Vin is less than VLED1 + VLED2 + VLED3 + VLED4, it is not possible to simultaneously power the first to fourth LED segments (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 low and can only power a small number of LEDs; when the peak value of the bus voltage Vin is greater than or equal to LED1+LED2+LED3+LED4, it can simultaneously power the first to fourth LED segments (when the number of LED segments is configured as N, the peak value of the bus voltage Vin is greater than or equal to...). When the bus voltage Vin is considered to be high, it is assumed that it can power a large number of LED lights.

[0084] More specifically, the first to fifth output current adjustment units are connected one-to-one to the output terminals (OUT1, OUT2, OUT3, OUT4, OUT5) of the first to fifth LED segments respectively, and are used to adjust the current at the output terminal of each LED segment. Each output current adjustment 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 segment, and the other end is grounded to GND via the sampling unit. The control terminal is connected to the output terminal of the control unit 152. As an example, such as Figure 2 As shown, each output current adjustment 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 all output current adjustment units share the same sampling resistor Rcs. In this example, each power transistor is implemented using an NMOS transistor. The drain of each power transistor is connected to the output terminal of the corresponding LED segment, the gate is connected to the corresponding output signal of the driving unit 152, and the source is grounded to GND via the sampling resistor Rcs. In practical applications, any circuit structure capable of output current adjustment is applicable to this invention.

[0085] More specifically, the control unit 152 is connected to the sampling terminal of each output current adjustment unit. It obtains a sinusoidal reference based on the bus sampling voltage Vin and the output current sampling voltage, and generates drive control signals for each output current adjustment 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 corresponds to the number of LED segments, and the number of operational amplifiers is adaptively adjusted when the number of LED segments changes. The input terminal of the operational amplifier module 152a is connected to the sampling terminal CS (i.e., the connection node between the sampling resistor Rcs and each power transistor) of each output current adjustment unit and receives the reference voltage Ref (the comparison reference for the current sampling voltage). Its output terminal is connected to the upper plate of the compensation capacitor C1; the lower plate of the compensation capacitor C1 is grounded to GND. Multiplier 152b receives the compensation voltage on compensation capacitor C1 and the bus sampling voltage, and performs multiplication to obtain a sinusoidal reference. Reference voltage generator 152c is connected to the output terminals of multiplier 152b and voltage detection unit 151, and generates reference voltages for each output current adjustment unit based on the sinusoidal reference and the magnitude of bus voltage Vin. When switch 14 is closed, the reference voltages satisfy: Ref1 < Ref4 < Ref2 < Ref5 < Ref3; when switch 14 is open, the reference voltages satisfy: Ref1 < Ref2 < Ref3 < Ref4 < Ref5. Among them, Ref1, Ref2, Ref3, Ref4, and Ref5 are the reference voltages of the first to fifth output current adjustment units, respectively. The first to fifth operational amplifiers (OP1, OP2, OP3, OP4, OP5) correspond one-to-one with each output current adjustment unit, and their input terminals are connected to the corresponding reference voltage and the corresponding output current sampling voltage to generate the corresponding output current adjustment unit's drive control signal.

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

[0087] As another implementation of the present invention, such as Figure 2As shown, the linear LED driving system 1 also includes a bus voltage sampling module 16. The bus voltage sampling module 16 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 terminals. The connection node between the first resistor and the second resistor outputs the bus voltage sampling voltage. In practical use, any method that can sample the bus voltage is applicable to this invention and is not limited to this embodiment.

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

[0089] like Figure 2 As shown, in this embodiment, the voltage detection unit 151, the first to fifth power transistors, the working 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 a single chip. The chip's HV terminal is connected to the bus voltage Vin, the SWO terminal is connected to the control terminal of the switch 14, OUT1-OUT5 are connected to the output terminals of each LED 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 implement linear LED driving, comprising:

[0091] The bus voltage Vin is monitored. When the bus voltage Vin is low, switch 14 is closed. As the bus voltage Vin increases, each LED segment is turned on in the following order: LED1 → LED4 → LED1+LED2 → LED4+LED5 → LED1+LED2+LED3. When the bus voltage Vin is high, switch 14 is opened. As the bus voltage Vin increases, each LED segment is 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: 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: Ref1 < Ref2 < Ref3 < Ref4 < Ref5, so that each LED segment is turned on sequentially.

[0093] Example 2

[0094] like Figure 3 As shown, this embodiment provides a linear LED driving system 1. The difference from Embodiment 1 is that the first LED module 11 includes a fourth LED segment LED4 and a fifth LED segment LED5 connected in series, and the second LED module 12 includes a first LED segment LED1, a second LED segment LED2, and a third LED segment LED3 connected in series. When switch 14 is closed, the first LED module 11 and the second LED module 12 are connected in parallel; when switch 14 is open, the first LED module 11 and the second LED module 12 are connected in series. Other structures and working principles are completely the same as in Embodiment 1, and will not be described in detail here.

[0095] Comparative Example

[0096] like Figure 4 As shown in the comparative example, this invention provides a segmented LED driving system 2, including first to sixth LED segments LED1-LED6. The first LED segment LED1, the second LED segment LED2, and the third LED segment LED3 are connected in series to form a third LED module 21. The fourth LED segment LED4, the fifth LED segment LED5, and the sixth LED segment LED6 are connected in series to form a fourth LED module 22. The input terminal of the third LED module 21 is connected to the bus voltage Vin, and the output terminal is connected to the anode of diode D1. The input terminal of the fourth LED module 22 is connected to the cathode of diode D1. One end of switch SW is connected to the input terminal of the third LED module 21, and the other end is connected to the input terminal of the fourth LED module 22. The structure of the drive control module is the same as that of this invention and will not be described in detail 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 opened, achieving 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 circuits where LED1, Q1, and OP2 are located need to be balanced with the circuits where LED4, Q4, and OP5 are located (including but not limited to the same corresponding device parameters and signal magnitudes); the circuits where LED2, Q2, and OP3 are located need to be balanced with the circuits where LED5, Q5, and OP6 are located; the circuits where LED3, Q3, and OP4 are located need to be balanced with the circuits where LED6, Q6, and OP7 are located. If they are not balanced, the situation of larger current on one side and smaller current on the other side will occur. 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, where VLED1 = VLED2 = VLED3 = VLED4 = VLED5 = VLED6. That is, when the conduction voltages of each lamp bead are equal, the number of lamp beads in each lamp 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 relational expression: Ref1 = Ref4 < 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 relational expression: Ref1 < Ref2 < Ref3 < Ref4 < Ref5 < Ref6.

[0100] Figure 4 As shown, the comparative example can meet the 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 switch SW will also cause imbalance in the circuit.

[0101] As Figure 2 and Figure 3 shown, the lamp segments of the present invention do not adopt even segmentation, and work in cooperation with the reference voltages Ref1 - Ref5, no longer requiring the circuit to meet the matching property. Figure 4At low input voltage, the comparative amplifier has only three conduction segments: 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 segment of the comparative amplifier is N / 6. As the bus voltage increases, the number of LEDs in each conduction segment is N / 6→2 / 6*N→3 / 6*N. Therefore, the voltage switching range between two conduction segments is N / 6. Since the characteristic of linear LED driving is that excess voltage is borne by the constant current control transistor (power transistor), the loss range is N / 6. In this example, the present invention is illustrated by taking the number of LEDs in each segment as satisfying 1 / 2:1:1:1:1. Under low voltage input, the present invention has five conducting segments, namely LED1→LED4→LED1+LED2→LED4+LED5→LED1+LED2+LED3. Assuming 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, and 2 / 9*N respectively. As the bus voltage increases, the number of LEDs corresponding to each conducting segment is N / 9→2 / 9*N→3 / 9*N→4 / 9*N→5 / 9*N. Therefore, the switching range of the conduction voltage between two adjacent conducting segments in the present invention becomes N / 9 (less than N / 6). The switching range of the conduction voltage in this invention is smaller than that in the comparative invention, thereby reducing the loss of the two switching ranges. In addition, the maximum number of LEDs connected in series at low voltage input is changed from 3 / 6*N to 5 / 9*N, which can also improve the efficiency of the system. Furthermore, the conduction voltage is lower after the first segment is changed to N / 9, so a lower single harmonic can be obtained. At low voltage input, the number of conduction segments is effectively changed from three to five in series.

[0102] like Figure 4 As shown, the comparative amplifier uses a parallel connection at low voltage input, which limits the number of segments that can be switched on. For example... Figure 2 and Figure 3 As shown, this invention achieves interleaved series connection at low voltage input, which can increase the number of segments that are conducting in stages and improve system performance. Figure 4 As shown, the comparative example uses six LED segments connected in series under high voltage input, while the present invention uses five LED segments connected in series under high voltage input. Figure 2 and Figure 3 As shown, relatively speaking, the segmentation efficiency and single harmonic performance of the present invention are slightly worse than those of the 6-segment, but the performance difference is not significant. However, in terms of cost, the present invention can reduce one driving power transistor, and the cost of the power transistor is reduced to 5 / 6 of the original, which greatly improves the cost-effectiveness of the system.

[0103] In summary, this 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, both the first LED module and the second LED module include a plurality of LED segments cascaded in sequence, and the number of LED segments in the first LED module and the second LED module differs by a certain distance; the input terminal of the first LED module is connected to the bus voltage, and the output terminal is connected to the input terminal of the second LED module via the flow direction limiting module; the flow direction limiting module is configured to allow current to flow only from the output terminal of the first LED module to the input terminal of the second LED module; the switch is connected between the input terminals of the first LED module and the second LED module, and the control terminal is connected to the output terminal of the driving control module; the driving control module is connected to the output terminal of each LED segment, and when the bus voltage is low, it controls the switch to close, and as the bus voltage increases, it controls the LED segments in each LED module to light up alternately in sequence; when the bus voltage is high, it controls the switch to open, and as the bus voltage increases, it controls the LED segments to light up in sequence; and it controls the output current so that the output current is sinusoidal in each cycle. The linear LED driving system of this invention employs asymmetrical 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 driving power transistors is decreased, lowering system cost. Furthermore, the relatively increased number of conducting segments at low input voltage improves system efficiency and single-harmonic performance. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and possesses high industrial applicability.

[0104] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can 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 those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A linear LED driving system, characterized in that, The linear LED driving system includes at least: The system comprises a first LED module, a second LED module, a flow direction limiting module, and a switch and drive control module; wherein, both the first LED module and the second LED module include a number of LED segments cascaded in sequence, and the number of LED segments in the first LED module and the second LED module differs by a certain amount; The input terminal of the first LED module is connected to the bus voltage, and the output terminal is connected to the input terminal of the second LED module via the flow direction limiting module; the flow direction limiting module is configured to allow current to flow only from the output terminal of the first LED module to the input terminal of the second LED module; The switch is connected between the input terminal of the first LED module and the input terminal of the second LED module, and the control terminal is connected to the output terminal of the drive control module; The drive control module is connected to the output terminal of each LED segment. When the bus voltage is low, it controls the switch to close, and as the bus voltage increases, it controls the LED segments in each LED module to light up alternately. When the bus voltage is high, it controls the switch to open, and as the bus voltage increases, it controls the LED segments to light up alternately. It also controls the output current so that the output current is sinusoidal in each cycle.

2. The linear LED driving system according to claim 1, characterized in that: The first LED module includes a first LED segment, a second LED segment, and a third LED segment cascaded together, and the second LED module includes a fourth LED segment and a fifth LED segment cascaded together; or the first LED module includes a fourth LED segment and a fifth LED segment cascaded together, and the second LED module includes a first LED segment, a second LED segment, and a third LED segment cascaded together. The on-state voltage of each LED segment satisfies: VLED1 < VLED4 < VLED1 + VLED2 < VLED4 + VLED5 < VLED1 + VLED2 + VLED3, where VLED1 is the on-state voltage of the first LED segment, VLED2 is the on-state voltage of the second LED segment, VLED3 is the on-state voltage of the third LED segment, VLED4 is the on-state voltage of the fourth LED segment, and VLED5 is the on-state voltage of the fifth LED 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 several output current adjustment units; The voltage detection unit detects the bus voltage and determines whether the bus voltage is low or high. Each output current adjustment unit is connected to the output terminal of each LED segment to adjust the current at the output terminal of each LED segment. The control unit is connected to the sampling terminal of each output current adjustment unit. It obtains a sinusoidal reference based on the bus sampling voltage and the output current sampling voltage, and generates drive control signals for each output current adjustment 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, characterized in that: Each output current adjustment unit includes a power transistor and a sampling unit; one end of the power transistor is connected to the output terminal of the corresponding LED segment, and the other end is grounded through the sampling unit, and the control terminal is connected to the output terminal of the control unit.

5. The linear LED driving system according to claim 4, characterized in that: All output current regulation units share the same sampling unit.

6. The linear LED driving system according to claim 3, characterized in that: The control unit includes an operational amplifier module, a compensation capacitor, a multiplier, a reference voltage generator, and several operational amplifiers; The input terminal of the operational amplifier module is connected to the sampling terminal of each output current adjustment unit and receives the reference voltage; the output terminal 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 a multiplication operation to obtain the sinusoidal reference. The reference voltage generator is connected to the output terminals of the multiplier and the voltage detection unit, and generates the reference voltage for each output current adjustment unit based on the magnitude of the sinusoidal reference and the bus voltage. Each operational amplifier corresponds one-to-one with each output current adjustment unit. The input terminal of each operational amplifier is connected to the corresponding reference voltage and the corresponding output current sampling voltage to generate the drive control signal for the corresponding output current adjustment unit.

7. The linear LED driving system according to claim 3, characterized in that: The linear LED driving system further 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 and then connected across the bus voltage terminals. 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, with the anode of the diode connected to the output terminal of the first LED module and the cathode connected to the input terminal 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 also 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 2-8, 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 as described in any one of claims 1-10, characterized in that, The linear LED driving method includes at least the following: 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 LED segments in each LED module light up alternately in sequence; 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, each LED segment lights up in sequence.

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

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