A multi-segment linear LED driving circuit, device and driving method

Abstract

This invention discloses a multi-segment linear LED driving circuit, device, and driving method. The multi-segment linear LED driving circuit includes a reference voltage input module, a current source module, a voltage control module, a current adjustment module, at least two LED strings connected in series, and at least two driving modules corresponding to the LED strings. The reference voltage input module provides a reference voltage to each driving module. The current source module provides DC current to the voltage control module. The voltage control module controls the input voltage of the driving module according to the DC current. The driving module drives the corresponding LED string to light up or turn off with a constant current according to the reference voltage, input voltage, and line voltage. The current adjustment module adjusts the constant current. The constant current of the subsequent driving module is greater than that of the preceding driving module, and when current flows through the subsequent driving module, the preceding driving module stops driving. This reduces harmonic effects and lowers the circuit implementation cost.

Description

Technical Field

[0001] The present invention relates to the field of LED technology, and in particular to a multi-segment linear LED driving circuit, device and driving method. Background Art

[0002] In traditional single-stage linear constant current LED drivers, the LED string voltage must be at least 2 / 3 of the rectifier bridge output voltage or more. High LED string voltage causes severe distortion of the current waveform flowing through the rectifier bridge, resulting in poor power factor, large harmonic distortion, and low efficiency.

[0003] The traditional multi-segment linear constant current driver needs to generate multiple reference voltages to control the current of each constant current source. Compared with the single-segment linear constant current LED driver, its efficiency, power factor value and total harmonic distortion are improved, but the sub-harmonic distortion still cannot meet the specification requirements, and generating multiple reference voltages will make the circuit implementation complicated. Increasing the number of LED light string segments can partially solve the problem of sub-harmonics, but for each additional LED light string, a constant current source is added accordingly, and the circuit implementation cost increases.

[0004] Therefore the prior art still needs to be improved and enhanced. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a multi-segment linear LED driving circuit, device and driving method, which adopts a reference voltage to control the constant current source and simplifies the peripheral circuit, thereby reducing the impact of harmonics and further reducing the circuit implementation cost.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A multi-segment linear LED driving circuit comprises a reference voltage input module, a current source module, a voltage control module, a current regulating module, at least two LED light strings connected in series, and at least two driving modules corresponding to the LED light strings; the reference voltage input module is used to provide a reference voltage for each of the driving modules; the current source module is used to provide a direct current for the voltage control module; the voltage control module is used to control the input voltage of the driving module according to the direct current; the driving module is used to drive the corresponding LED light string to light up or turn off according to the reference voltage, the input voltage and the line voltage; the current regulating module is used to regulate the constant current flowing through the corresponding LED light string; wherein the constant current of the latter driving module is greater than the constant current of the former driving module, and when the latter driving module has current passing through it, the former driving module stops driving.

[0008] In the multi-segment linear LED driving circuit, the voltage control module includes a resistor string, the resistor string includes a plurality of resistors connected in series, the upper end of the resistor string is connected to the current source module, the lower end of the resistor string is connected to the current regulation module, and the upper end tap of each resistor is respectively led out to connect the input voltage end of each driving module.

[0009] In the multi-segment linear LED driving circuit, the reference voltage input module includes a reference voltage source, and the reference voltage source is used to output a constant reference voltage to the driving module.

[0010] In the multi-segment linear LED driving circuit, the reference voltage input module includes a voltage dividing unit, and the voltage dividing unit divides the line voltage and outputs a reference voltage that changes synchronously with the line voltage to the driving module.

[0011] In the multi-segment linear LED driving circuit, the voltage divider unit includes a first resistor and a second resistor, one end of the first resistor is connected to the line voltage input terminal, the other end of the first resistor is connected to one end of the second resistor and each of the driving modules, and the other end of the second resistor is grounded.

[0012] In the multi-segment linear LED driving circuit, the driving module includes a first operational amplifier, a second operational amplifier, a third operational amplifier, a fourth operational amplifier, a first MOS tube, a second MOS tube, a third MOS tube and a fourth MOS tube; the voltage control module includes a third resistor, a fourth resistor and a fifth resistor;

[0013] The positive-phase input terminal of the first operational amplifier, the positive-phase input terminal of the second operational amplifier, the positive-phase input terminal of the third operational amplifier and the positive-phase input terminal of the fourth operational amplifier are all connected to the positive electrode of the reference voltage source; the inverting input terminal of the first operational amplifier is connected to the current source module and one end of the third resistor, and the other end of the third resistor is connected to one end of the fourth resistor and the inverting input terminal of the second operational amplifier; the other end of the fourth resistor is connected to one end of the fifth resistor and the inverting input terminal of the third operational amplifier; the other end of the fifth resistor is connected to the inverting input terminal of the fourth operational amplifier and the current regulation module; The output end of the first operational amplifier is connected to the gate of the first MOS tube, the drain of the first MOS tube, the drain of the second MOS tube, the drain of the third MOS tube and the drain of the fourth MOS tube are all connected to the output end of each of the LED light strings, and the source of the first MOS tube, the source of the second MOS tube, the source of the third MOS tube and the source of the fourth MOS tube are all connected to the current regulation module; the output end of the second operational amplifier is connected to the gate of the second MOS tube, the output end of the third operational amplifier is connected to the gate of the third MOS tube, and the output end of the fourth operational amplifier is connected to the source of the fourth MOS tube.

[0014] In the multi-segment linear LED driving circuit, the driving module includes a fifth operational amplifier, a sixth operational amplifier and a seventh operational amplifier; the voltage control module includes a sixth resistor and a seventh resistor;

[0015] The non-inverting input terminal of the fifth operational amplifier, the non-inverting input terminal of the sixth operational amplifier and the non-inverting input terminal of the seventh operational amplifier are all connected to the other end of the first resistor and one end of the second resistor, the inverting input terminal of the fifth operational amplifier is connected to the current source module and one end of the sixth resistor, the other end of the sixth resistor is connected to one end of the seventh resistor and the inverting input terminal of the sixth operational amplifier, and the other end of the seventh resistor is connected to the inverting input terminal of the seventh operational amplifier and the current regulation module; the output terminal of the fifth operational amplifier is connected to the gate of the fifth MOS tube, the output terminal of the sixth operational amplifier is connected to the gate of the sixth MOS tube, and the output terminal of the seventh operational amplifier is connected to the gate of the seventh MOS tube; the source of the fifth MOS tube, the source of the sixth MOS tube and the source of the seventh MOS tube are all connected to the current regulation module; the drain of the fifth MOS tube, the drain of the sixth MOS tube and the drain of the seventh MOS tube are respectively connected to the output terminal of each of the LED light strings.

[0016] In the multi-segment linear LED driving circuit, the current regulating module includes a constant current resistor, one end of the constant current resistor is connected to the voltage control module and the driving module, and the other end of the constant current resistor is grounded.

[0017] A driving method based on the multi-segment linear LED driving circuit as described above comprises the following steps:

[0018] The reference voltage input module provides a reference voltage for each of the driving modules;

[0019] The current source module provides a direct current to the voltage control module;

[0020] The voltage control module controls the input voltage of the driving module according to the DC current;

[0021] The driving module drives the corresponding LED light string to light up or turn off according to the reference voltage, the input voltage and the line voltage; wherein the constant current of the latter driving module is greater than the constant current of the former driving module, and when the latter driving module has current passing through it, the former driving module stops driving;

[0022] The current regulating module is used to regulate the constant current flowing through the corresponding LED light string.

[0023] A multi-segment linear LED driving device comprises the multi-segment linear LED driver as described above.

[0024] Compared with the prior art, the present invention provides a multi-segment linear LED driving circuit, device and driving method, wherein the multi-segment linear LED driving circuit comprises a reference voltage input module, a current source module, a voltage control module, a current regulating module, at least two LED light strings connected in series and at least two driving modules corresponding to the LED light strings; the reference voltage input module is used to provide a reference voltage for each of the driving modules; the current source module is used to provide a direct current for the voltage control module; the voltage control module is used to control the input voltage of the driving module according to the direct current; the driving module is used to drive the corresponding LED light string to light up or turn off according to the reference voltage, the input voltage and the line voltage constant current; the current regulating module is used to regulate the constant current flowing through the corresponding LED light string; wherein the constant current of the latter driving module is greater than the constant current of the former driving module, and when the latter driving module has current passing through it, the former driving module stops driving, and by using a reference voltage to control the constant current source and simplify the peripheral circuit, while reducing the harmonic impact, the circuit implementation cost is further reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A structural block diagram of a multi-segment linear LED driving circuit provided by the present invention;

[0026] Figure 2 A circuit schematic diagram of a multi-segment linear LED driving circuit provided by the present invention;

[0027] Figure 3 A circuit schematic diagram of a first embodiment of a multi-segment linear LED driving circuit provided by the present invention;

[0028] Figure 4 A waveform diagram of the line voltage and the constant current of the LED light string in the first embodiment of the multi-segment linear LED driving circuit provided by the present invention;

[0029] Figure 5 A circuit schematic diagram of a second embodiment of the multi-segment linear LED driving circuit provided by the present invention;

[0030] Figure 6 A waveform diagram of the line voltage and the constant current of the LED light string in the second embodiment of the multi-segment linear LED driving circuit provided by the present invention;

[0031] Figure 7 This is a flow chart of the multi-segment linear LED driving method provided by the present invention. DETAILED DESCRIPTION

[0032] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a multi-segment linear LED driving circuit, device and driving method, which adopts a reference voltage to control the constant current source and simplify the peripheral circuit, thereby reducing the impact of harmonics and further reducing the circuit implementation cost.

[0033] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] Please also read Figure 1The multi-segment linear LED driving circuit provided by the present invention includes a rectifier module 100, a reference voltage input module 200, a current source module 300, a voltage control module 400, a current regulation module 500, at least two LED light strings connected in series, and at least two driving modules 600 corresponding to the LED light strings; the input end of the rectifier module 100 is connected to the AC power supply, the output end of the rectifier module 100 is connected to the input end of the LED light string, the output end of each of the LED light strings is connected to the input end of the driving module 600, the input end of the driving module 600 is also connected to the reference voltage input module 200 and the voltage control module 400, and the output end of the driving module 600 is connected to the current regulation module 500.

[0035] In the present invention, the rectifier module 100 rectifies the AC power provided by the AC power source and then outputs a line voltage that flows through the LED light string to the driver module 600; the reference voltage input module 200 is used to provide a reference voltage for each of the driver modules 600, and the reference voltage can be a constant DC voltage or a periodic voltage signal synchronized with the line voltage output by the rectifier bridge module 100; the current source module 300 is used to provide a DC current for the voltage control module 400; the voltage control module 400 is used to control the input voltage of the driver module 600 according to the DC current, and the DC current flows through the voltage control module 400, and the two adjacent driver modules 600 are controlled by the voltage control module 400. A fixed voltage difference is maintained between them; the driving module 600 is used to drive the corresponding LED light string to light up or turn off according to the reference voltage and the input voltage constant current, and control the current flowing through the corresponding LED light string to be constant; the current regulating module 500 is used to regulate the constant current flowing through the corresponding LED light string, and control the maximum constant current flowing through the LED light string; wherein, the constant current of the latter driving module 600 is greater than the constant current of the former driving module 600, and when the latter driving module 600 has current passing through, the former driving module 600 stops driving; therefore, it is efficient to control multiple driving modules 600 by one reference voltage, and no additional sampling circuit is required, which reduces the complexity of the peripheral circuit and reduces the cost.

[0036] For further information, please also refer to Figure 2The voltage control module 400 includes a resistor string, which includes a plurality of resistors connected in series. The upper end of the resistor string is connected to the current source module 300, and the lower end of the resistor string is connected to the current regulation module 500. The upper end tap of each resistor is respectively connected to the input voltage end of each driving module 600. The current source module 300 provides a direct current to flow through each resistor in the resistor string, thereby obtaining a corresponding voltage. The input voltage of each driving module 600 is controlled by the voltage of each resistor, so that the input voltage between adjacent driving modules 600 can maintain a fixed voltage difference.

[0037] Furthermore, the current regulating module 500 includes a constant current resistor, one end of which is connected to the voltage control module 400 and the driving module 600, and the other end of which is grounded. The constant current of each driving module 600 is adjusted by setting the resistance value of the constant current resistor.

[0038] Specifically, the DC current is Ios, the reference voltage is Vref, the line voltage is Vrec, the LED light strings are LED1, LED2, LED3, ..., LEDN; the constant currents of each driving module 600 are I1, I2, I3, ..., IN, and the resistors of the resistor string are Ros1, Ros2, Ros3, ..., Ros N-1 , constant current resistor Rcs, the voltage of the resistors in the resistor string is Vdif1, Vdif2, Vdif3, ..., Vdifi; and the corresponding constant current of each driving module 600 is:

[0039]

[0040]

[0041] …

[0042] IN = Vref / Rcs - Ios;

[0043] Because Ios is much smaller than Vref / Rcs (at least two orders of magnitude), Ios can be ignored in the above items, expressed as:

[0044]

[0045]

[0046] …

[0047] IN=Vref / Rcs, wherein N is a positive integer greater than 1, i is a positive integer, and Vdifi=Ios*Ros.

[0048] After the multi-segment linear LED driving circuit enters the working state, when the line voltage Vrec output by the rectifier bridge module 100 is less than the conduction voltage Vled1 of the first LED string LED1, there is no current in the LED1 string and the LED1 string does not light up; when Vled1 < Vrec < Vled1 + Vled2, LED1 lights up and the current is I1, where Vled2 is the conduction voltage of the LED2 string; when the line voltage Vrec continues to increase to Vled1 + Vled2 < Vrec < Vled1 + Vled2 + Vled3, LED1 and LED2 light up and the current is I2, where Vled3 is the conduction voltage of the LED3 string; at the same time, the previous driving module 600, that is, the driving module 600 corresponding to providing the constant current I1, is turned off and stops driving. And so on, as the line voltage Vrec increases, more LED strings light up, and at the same time the driving modules 600 are turned off one by one. As the line voltage Vrec decreases, the number of lit LED strings decreases, and at the same time the driving modules 600 are turned on one by one. Thus, the driving control of each LED string is completed. By setting the resistance values of the resistors in the resistor string, the waveform change of the constant current is close to the waveform of the line voltage Vrec, the harmonic distortion is reduced, and the power factor is improved.

[0049] In the first embodiment of the present invention, please refer to Figure 3 , the reference voltage input module 200 includes a reference voltage source. The positive electrode of the reference voltage source is connected to each of the driving modules 600, and the negative electrode of the reference voltage source is grounded; the reference voltage source is used to output a constant reference voltage Vref to the driving module 600. Specifically, the working principle of the multi-segment linear LED driving circuit is illustrated by 4 groups of LED strings and 4 driving modules 600.

[0050] In this embodiment, the driving module 600 includes a first operational amplifier OP1, a second operational amplifier OP2, a third operational amplifier OP3, a fourth operational amplifier OP4, a first MOS transistor Q1, a second MOS transistor Q2, a third MOS transistor Q3, and a fourth MOS transistor Q4; the voltage control module 400 includes a third resistor R3, a fourth resistor R4, and a fifth resistor R5; the non-inverting input terminals of the first operational amplifier OP1, the second operational amplifier OP2, the third operational amplifier OP3, and the fourth operational amplifier OP4 are all connected to the positive pole of the reference voltage source; the inverting input terminal of the first operational amplifier OP1 is connected to the current source module 300 and one end of the third resistor R3, and the other end of the third resistor R3 is connected to one end of the fourth resistor R4 and the inverting input terminal of the second operational amplifier OP2; the other end of the fourth resistor R4 is connected to one end of the fifth resistor R5 and the inverting input terminal of the third operational amplifier OP3; the other end of the fifth resistor R5 is connected to the inverting input terminal of the fourth operational amplifier OP4 and the current regulation module 500; the output terminal of the first operational amplifier OP1 is connected to the gate of the first MOS transistor Q1, the drains of the first MOS transistor Q1, the second MOS transistor Q2, the third MOS transistor Q3, and the fourth MOS transistor are all connected to the output terminals of each LED lamp string, and the sources of the first MOS transistor Q1, the second MOS transistor Q2, the third MOS transistor Q3, and the fourth MOS transistor are all connected to the current regulation module 500; the output terminal of the second operational amplifier OP2 is connected to the gate of the second MOS transistor Q2, the output terminal of the third operational amplifier OP3 is connected to the gate of the third MOS transistor Q3, and the output terminal of the fourth operational amplifier OP4 is connected to the source of the fourth MOS transistor Q4.

[0051] In this embodiment, according to the virtual short and virtual open characteristics of each operational amplifier in each driving module 600, the current flowing through the corresponding LED lamp string is controlled to be constant. The current source module 300 provides a DC current Ios for the third resistor R3, the fourth resistor R4, and the fifth resistor R5 to respectively control the input voltages of the first operational amplifier OP1, the second operational amplifier OP2, and the third operational amplifier OP3, that is, the voltages at the inverting input terminals of each operational amplifier. The constant current resistor Rcs is used to control the negative terminal voltage of the fourth operational amplifier OP4, and by setting the resistance value of the constant current resistor Rcs, the maximum current flowing through each LED lamp string can be controlled.

[0052] When Vrec < Vled1, there is no current in the LED lamp string and all LEDs are not lit.

[0053] When Vled1 < Vrec < Vled + Vled2, the current of the LED string is Iled = I1 = [Vref - (Vdif1 + Vdif2 + Vdif3)] / Rcs, and LED1 is on. At this time, due to the virtual short characteristic of the first operational amplifier OP1, the voltage V1+ at the non-inverting input terminal is equal to the voltage V1- at the inverting input terminal, that is, V1+ = V1- = Vref.

[0054] When Vled1 + Vled2 < Vrec < Vled + Vled2 + Vled3, the current of the LED string is Iled = I2 = [Vref - (Vdif2 + Vdif3)] / Rcs, and LED1 and LED2 are on. At this time, due to the virtual short characteristic of the second operational amplifier OP2, the voltage V2+ at the non-inverting input terminal is equal to the voltage V2- at the inverting input terminal, that is, V2+ = V2- = Vref, while the voltage V1- at the inverting input terminal of the first operational amplifier OP1 is Vref + Vdif1, which is greater than the voltage V1+ = Vref at the non-inverting input terminal. Therefore, the first MOS transistor Q1 is turned off.

[0055] When Vled1 + Vled2 + Vled3 < Vrec < Vled + Vled2 + Vled3 + Vled4, the current of the LED string is Iled = I3 = (Vref - Vdif3) / Rcs, and LED1, LED2, and LED3 are on. At this time, the voltage at the inverting input terminal of the second operational amplifier OP2 is greater than the voltage at the non-inverting input terminal. Therefore, the second MOS transistor Q2 is turned off.

[0056] When Vled + Vled2 + Vled3 + Vled4 < Vrec, the current of the LED string is Iled = I4 = Vref / Rcs, and all of LED1, LED2, LED3, and LED4 are on. Correspondingly, the third MOS transistor Q3 is turned off, where Vdif1 = Ios * R3; Vdif2 = Ios * R4; Vdif3 = Ios * R5.

[0057] Because the reference voltage source only needs to generate a constant DC low voltage as the reference voltage Vref, in applications with high efficiency requirements and low harmonic distortion requirements, through the value of the constant current resistor Rcs, the maximum current of the LED string I4 = Vref / Rcs can be obtained. After setting the values of resistors R3 to R5, the currents I1, I2, and I3 are also determined and satisfy I1 < I2 < I3 < I4. Among them, the values of resistors R3 to R5 determine Vdif1 to Vdif3, and Vdif1 to Vdif3 determine the change of Iled. By setting the values of resistors R3 to R5, Iled is closer to the line voltage Vrec waveform (such as Figure 4As shown in the figure, a higher power factor and lower harmonic distortion can be obtained. The values ​​of resistors R3 to R5 are determined and will not be changed, which makes system integration easier. After integration, the chip PAD is reduced, making PCB routing easier.

[0058] In the second embodiment of the present invention, please refer to Figure 5 The reference voltage input module 200 includes a voltage dividing unit, which divides the line voltage Vrec and outputs a reference voltage Vref that changes synchronously with the line voltage Vrec to the driving module 600. The voltage dividing unit includes a first resistor R1 and a second resistor R2. One end of the first resistor R1 is connected to the line voltage input end, and the other end of the first resistor R1 is connected to one end of the second resistor R2 and each of the driving modules 600. The other end of the second resistor R2 is grounded. After the line voltage Vrec is divided by the first resistor R1, a reference voltage Vref that changes synchronously with the line voltage Vrec is obtained, thereby realizing control of each driving module 600.

[0059] In this embodiment, the working principle of the multi-segment linear LED driving circuit is described through three groups of LED light strings and three-way driving modules 600.

[0060] For details, please continue to see Figure 5 , the driving module 600 includes a fifth operational amplifier OP5, a sixth operational amplifier OP6 and a seventh operational amplifier OP7; the voltage control module 400 includes a sixth resistor R6 and a seventh resistor R7; the non-inverting input terminal of the fifth operational amplifier OP5, the non-inverting input terminal of the sixth operational amplifier OP6 and the non-inverting input terminal of the seventh operational amplifier OP7 are all connected to the other end of the first resistor R1 and one end of the second resistor R2, the inverting input terminal of the fifth operational amplifier OP5 is connected to the current source module 300 and one end of the sixth resistor R6, the other end of the sixth resistor R6 is connected to one end of the seventh resistor R7 and the inverting input terminal of the sixth operational amplifier OP6, and the seventh resistor The other end of R7 is connected to the inverting input end of the seventh operational amplifier OP7 and the current regulating module 500; the output end of the fifth operational amplifier OP5 is connected to the gate of the fifth MOS tube Q5, the output end of the sixth operational amplifier OP6 is connected to the gate of the sixth MOS tube Q6, and the output end of the seventh operational amplifier OP7 is connected to the gate of the seventh MOS tube Q7; the source of the fifth MOS tube Q5, the source of the sixth MOS tube Q6 and the source of the seventh MOS tube Q7 are all connected to the current regulating module 500; the drain of the fifth MOS tube Q5, the drain of the sixth MOS tube Q6 and the drain of the seventh MOS tube Q7 are respectively connected to the output end of each of the LED light strings.

[0061] Among them, the reference voltage is generated by dividing the line voltage by the first resistor R1 and input to the non-inverting input terminals of the fifth operational amplifier OP5, the sixth operational amplifier OP6, and the seventh operational amplifier OP7. The current source module 300 outputs a direct current to the sixth resistor R6 and the seventh resistor R7 to control the voltages at the inverting input terminals of the fifth operational amplifier OP5 and the sixth operational amplifier OP6 respectively. The constant current resistor Rcs can control the voltage at the inverting input terminal of the seventh operational amplifier OP7, and by setting the resistance value of the constant current resistor Rcs, the maximum current flowing through each LED string can be controlled.

[0062] When Vrec < Vled1, there is no current in the LED string and all LEDs are off.

[0063] When Vled1 < Vrec < Vled + Vled2, the current in the LED string is Iled = I1 = [Vref - (Vdif1 + Vdif2)] / Rcs and LED1 is on.

[0064] When Vled1 + Vled2 < Vrec < Vled + Vled2 + Vled3, the current in the LED string is Iled = I2 = (Vref - Vdif2) / Rcs, LED1 and LED2 are on, and the corresponding fifth MOS transistor Q5 is turned off.

[0065] When Vled + Vled2 + Vled3 < Vrec, the current in the LED string is Iled = I3 = Vref / Rcs, and all LEDs LED1, LED2, and LED3 are on. Correspondingly, the sixth MOS transistor Q6 is turned off; where Vdif1 = Ios * R6; Vdif2 = Ios * R7.

[0066] Specifically, since the reference voltage is generated by dividing the line voltage Vrec, the reference voltage is synchronized with the line voltage Vrec. Therefore, the smaller Vdif1 and Vdif2 are, the closer the change in Iled is to the waveform of the line voltage Vrec (such as Figure 6As shown), the smaller the harmonic distortion, the higher the power factor. However, due to the process error during mass production, the operational amplifier has an offset voltage Vosn, which limits Vdif1 and Vdif2 from being infinitely small. Only when the voltage Vn- at the inverting input terminal of the operational amplifier is greater than the voltage Vn+ at the positive input terminal of each of the operational amplifiers, can the current of the previous LED light string be turned off when there is current in the next LED light string, that is, the MOS tube of the previous path is turned off, and thus the corresponding operational amplifier Vn->Vn+ is required, and Vn-=Vref+Vdifi-Vosn, Vn+=Vref, so it is necessary to ensure that Vdifi should be greater than Vosn, and Vdifi is related to the resistance value in the resistor string. When setting the resistance value of each resistor in the voltage control module 400, it should be ensured that the corresponding voltage is greater than the offset voltage of the operational amplifier connected thereto.

[0067] Because the reference voltage Vref in this embodiment is generated by dividing the line voltage Vrec, the reference voltage Vref is synchronized with the line voltage Vrec. When the line voltage Vrec increases, the reference voltage Vref increases, and the corresponding current Iled flowing through the LED light string increases accordingly; when the line voltage Vrec decreases, the reference voltage Vref decreases, Iled decreases accordingly, and the current Iled flowing through the LED light string changes synchronously with the line voltage Vrec. Compared with the method of improving harmonic distortion by increasing the number of LED light string segments, in this embodiment, harmonic distortion is better suppressed, the power factor is higher, the circuit structure is simple and the implementation cost is low. The resistance values ​​of the sixth resistor R6 and the seventh resistor R7 are only related to the offset voltage Vosn of the corresponding connected operational amplifier. When their resistance values ​​are determined, they no longer change, which makes it easier to integrate the system. After integration, the chip PAD is reduced, which makes it easier to route the PCB. In the case of the same number of LED light strings, compared with the solution of using multiple reference voltages, using a reference voltage Vref synchronized with the line voltage Vrec can obtain better power factor and lower harmonic distortion. The fractional harmonics also meet various regulatory requirements, and there is no need to set up unnecessary and complex sampling circuits on the periphery. The structure is simple and the implementation cost is low.

[0068] The present invention also provides a multi-segment linear LED driving method. Figure 7 , including the steps of:

[0069] S100, the reference voltage input module provides a reference voltage for each of the driving modules;

[0070] S200, the current source module provides a direct current to the voltage control module;

[0071] S300, the voltage control module controls the input voltage of the driving module according to the DC current;

[0072] S400, the driving module drives the corresponding LED light string to light up or turn off according to the reference voltage, the input voltage and the line voltage; wherein the constant current of the latter driving module is greater than the constant current of the former driving module, and when the latter driving module has current passing through it, the former driving module stops driving;

[0073] S500, the current regulating module is used to regulate the constant current flowing through the corresponding LED light string.

[0074] Based on the above LED driving circuit, the present invention also provides a multi-segment linear LED driving device, including the multi-segment linear LED driving as described above. Since the multi-segment linear LED driving is described in detail above, it will not be repeated here.

[0075] In summary, the present invention provides a multi-segment linear LED driving circuit, device and driving method, wherein the multi-segment linear LED driving circuit comprises a reference voltage input module, a current source module, a voltage control module, a current regulating module, at least two LED light strings connected in series, and at least two driving modules corresponding to the LED light strings; the reference voltage input module is used to provide a reference voltage for each of the driving modules; the current source module is used to provide a direct current for the voltage control module; the voltage control module is used to control the input voltage of the driving module according to the direct current; the driving module is used to drive the corresponding LED light string to light up or turn off according to the reference voltage, the input voltage and the line voltage constant current; the current regulating module is used to regulate the constant current flowing through the corresponding LED light string; wherein the constant current of the latter driving module is greater than the constant current of the former driving module, and when the latter driving module has current passing through it, the former driving module stops driving, and by using a reference voltage to control the constant current source and simplify the peripheral circuit, while reducing the harmonic impact, the circuit implementation cost is further reduced.

[0076] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present invention, and all these changes or substitutions should fall within the protection scope of the claims attached to the present invention.

Claims

1. A multi-segment linear LED driving circuit, characterized in that: It includes a reference voltage input module, a current source module, a voltage control module, a current regulation module, at least two LED light strings connected in series, and at least two driving modules corresponding to the LED light strings; the reference voltage input module is used to provide a reference voltage for each of the driving modules; the current source module is used to provide a direct current for the voltage control module; the voltage control module is used to control the input voltage of the driving module according to the direct current; the driving module is used to drive the corresponding LED light string to light up or turn off according to the reference voltage, the input voltage and the line voltage constant current; The current regulating module is used to regulate the constant current flowing through the corresponding LED light string; wherein the constant current of the latter driving module is greater than the constant current of the former driving module, and when the latter driving module has current passing through it, the former driving module stops driving; The voltage control module comprises a resistor string, the resistor string comprises a plurality of resistors connected in series, the upper end of the resistor string is connected to the current source module, the lower end of the resistor string is connected to the current regulation module, and the upper end tap of each resistor is respectively led out to connect to the input voltage end of each driving module; The current source module provides a direct current to flow through each resistor in the resistor string, thereby obtaining a corresponding voltage, and the input voltage of each driving module is controlled by the voltage of each resistor, thereby maintaining a fixed voltage difference between the input voltages of adjacent driving modules; The current regulating module comprises a constant current resistor, one end of which is connected to the voltage control module and the driving module, and the other end of which is grounded.

2. The multi-segment linear LED driving circuit according to claim 1, characterized in that: The reference voltage input module includes a reference voltage source, and the reference voltage source is used to output a constant reference voltage to the driving module.

3. The multi-segment linear LED driving circuit according to claim 1, characterized in that: The reference voltage input module includes a voltage dividing unit, and the voltage dividing unit divides the line voltage and then outputs a reference voltage that changes synchronously with the line voltage to the driving module.

4. The multi-segment linear LED driving circuit according to claim 3, characterized in that: The voltage dividing unit includes a first resistor and a second resistor, one end of the first resistor is connected to the line voltage input terminal, the other end of the first resistor is connected to one end of the second resistor and each of the driving modules, and the other end of the second resistor is grounded.

5. The multi-segment linear LED driving circuit according to claim 2, characterized in that: The driving module includes a first operational amplifier, a second operational amplifier, a third operational amplifier, a fourth operational amplifier, a first MOS tube, a second MOS tube, a third MOS tube and a fourth MOS tube; the voltage control module includes a third resistor, a fourth resistor and a fifth resistor; The positive-phase input terminal of the first operational amplifier, the positive-phase input terminal of the second operational amplifier, the positive-phase input terminal of the third operational amplifier and the positive-phase input terminal of the fourth operational amplifier are all connected to the positive electrode of the reference voltage source; the inverting input terminal of the first operational amplifier is connected to the current source module and one end of the third resistor, and the other end of the third resistor is connected to one end of the fourth resistor and the inverting input terminal of the second operational amplifier; the other end of the fourth resistor is connected to one end of the fifth resistor and the inverting input terminal of the third operational amplifier; the other end of the fifth resistor is connected to the inverting input terminal of the fourth operational amplifier and the current regulation module; the output terminal of the first operational amplifier is connected to the gate of the first MOS tube, the drain of the first MOS tube, the drain of the second MOS tube, the drain of the third MOS tube and the drain of the fourth MOS tube are all connected to the output terminal of each of the LED light strings, and the source of the first MOS tube, the source of the second MOS tube, the source of the third MOS tube and the source of the fourth MOS tube are all connected to the current regulation module; The output end of the second operational amplifier is connected to the gate of the second MOS tube, the output end of the third operational amplifier is connected to the gate of the third MOS tube, and the output end of the fourth operational amplifier is connected to the gate of the fourth MOS tube.

6. The multi-segment linear LED driving circuit according to claim 4, characterized in that: The driving module includes a fifth operational amplifier, a sixth operational amplifier, a seventh operational amplifier, a fifth MOS tube, a sixth MOS tube and a seventh MOS tube; the voltage control module includes a sixth resistor and a seventh resistor; The non-inverting input terminal of the fifth operational amplifier, the non-inverting input terminal of the sixth operational amplifier and the non-inverting input terminal of the seventh operational amplifier are all connected to the other end of the first resistor and one end of the second resistor, the inverting input terminal of the fifth operational amplifier is connected to the current source module and one end of the sixth resistor, the other end of the sixth resistor is connected to one end of the seventh resistor and the inverting input terminal of the sixth operational amplifier, and the other end of the seventh resistor is connected to the inverting input terminal of the seventh operational amplifier and the current regulation module; the output terminal of the fifth operational amplifier is connected to the gate of the fifth MOS tube, the output terminal of the sixth operational amplifier is connected to the gate of the sixth MOS tube, and the output terminal of the seventh operational amplifier is connected to the gate of the seventh MOS tube; the source of the fifth MOS tube, the source of the sixth MOS tube and the source of the seventh MOS tube are all connected to the current regulation module; the drain of the fifth MOS tube, the drain of the sixth MOS tube and the drain of the seventh MOS tube are respectively connected to the output terminal of each of the LED light strings.

7. A driving method based on the multi-segment linear LED driving circuit according to any one of claims 1 to 6, characterized in that: The steps include: The reference voltage input module provides a reference voltage for each of the driving modules; The current source module provides a direct current to the voltage control module; The voltage control module controls the input voltage of the driving module according to the DC current; The driving module drives the corresponding LED light string to light up or turn off according to the reference voltage, the input voltage and the line voltage; wherein the constant current of the latter driving module is greater than the constant current of the former driving module, and when the latter driving module has current passing through it, the former driving module stops driving; The current regulating module is used to regulate the constant current flowing through the corresponding LED light string.

8. A multi-segment linear LED driving device, characterized in that: It comprises a multi-segment linear LED driving circuit as described in any one of claims 1-6.

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