LED driving circuit, LED driving method, and LED system

Abstract

The application provides an LED driving circuit, an LED driving method and an LED system, wherein the LED driving circuit comprises: an amplification circuit, which amplifies PWM dimming code words of different sections by different proportions to obtain preprocessed dimming code words; a digital-to-analog conversion circuit, which receives the preprocessed dimming code words and converts them into dimming voltages in a preset working interval; an adjustable current source circuit, which receives the dimming voltages and generates reference currents through voltage-to-current conversion; a current mirror circuit, which receives the reference currents and generates intermediate currents through current mirroring processing; and a current restoration module, which receives the intermediate currents and obtains LED driving currents by reducing the intermediate currents by corresponding proportions. The application solves the problem that the existing architecture cannot achieve high precision in the full range of PWM dimming code words.

Description

Technical Field

[0001] This invention relates to the field of LED driving technology, and in particular to an LED driving circuit, an LED driving method, and an LED system. Background Technology

[0002] Existing LED current drivers need to convert different PWM dimming codes into LED drive currents ranging from 0% to 100% brightness. The number of bits in the PWM dimming code determines the precision of LED brightness adjustment, while the number of bits in the configured current setting code determines the maximum brightness of the LED.

[0003] Typically, two cascaded digital-to-analog converters are used to adjust the digital input to analog output. For a detailed architecture, please refer to [reference needed]. Figure 1 ; where 11 is the digital-to-analog converter section, 12 is the adjustable current section, 13 is the current mirror section, and 14 is the operational amplifier. Because the two digital-to-analog converters are connected in series, the voltage and current variations are very large, which causes several drawbacks:

[0004] First, the common-mode level range of the operational amplifier becomes larger. When the number of bits in the PWM dimming codeword is particularly small, the common-mode level becomes smaller, the proportion of offset voltage becomes higher, and the accuracy of the LED driving current becomes worse.

[0005] Second, the range of current that needs to be mirrored in the current mirror section becomes larger. When the number of bits of the PWM dimming code is particularly small, the current becomes smaller, the current mirror operates in the subthreshold region, and the current mirroring ratio is severely distorted.

[0006] According to the formula It can be seen that the mirror ratio error ΔId / Id is contributed by the manufacturing error Δ(W / L) and threshold error ΔVth of the current mirror transistor; in the formula, the first term is a fixed error, while the second term varies with different current magnitudes due to the different values ​​of Vgs-Vth. The relationship between the mirror ratio error and the current magnitude is as follows: Figure 2 As shown in the figure, Id corresponds to the LED driving current ILED, W / L is the aspect ratio of the current mirror transistor, ΔW / L is the aspect ratio error between current mirror transistors, Vgs is the gate-source voltage of the current mirror transistor, Vth is the threshold voltage of the current mirror transistor, and ΔVth is the threshold error between current mirror transistors. It can be seen from the figure that when the driving current ILED is small, the mirror ratio error ΔId / Id is large.

[0007] It is evident that existing architectures cannot naturally achieve high accuracy across the entire range of PWM dimming codes. Traditional solutions avoid these problems through tuning, but this requires significant tuning resources, and the tuning resources and testing time increase exponentially as the number of LED current channels increases.

[0008] 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

[0009] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an LED driving circuit, an LED driving method, and an LED system to solve the problem that the existing architecture cannot achieve high precision across the entire range of PWM dimming codewords.

[0010] To achieve the above and other related objectives, the present invention provides an LED driving circuit, comprising:

[0011] An amplifier circuit amplifies the PWM dimming codewords of different sections by different ratios to obtain pre-processed dimming codewords.

[0012] The digital-to-analog converter circuit receives the preprocessed dimming codeword and converts it into a dimming voltage within a preset working range;

[0013] An adjustable current source circuit receives the dimming voltage and generates a reference current through voltage-current conversion.

[0014] A current mirror circuit receives the reference current and generates an intermediate current through current mirroring processing.

[0015] The current reduction circuit receives the intermediate current and reduces it by a corresponding ratio to obtain the LED driving current.

[0016] Optionally, the amplification circuit includes:

[0017] The segment detection module detects the segment in which the PWM dimming codeword is located to obtain a detection signal;

[0018] The segmented magnification module includes a selection unit and several magnification units with different magnification ratios.

[0019] The selection unit selects the corresponding amplification unit based on the detection signal, and the amplification unit amplifies the PWM dimming codeword by a corresponding ratio.

[0020] Optionally, when the amplification ratio is 1, the amplification unit is implemented using wires; when the amplification ratio is greater than 1, the amplification unit is implemented using a shift register.

[0021] Optionally, the adjustable current source circuit includes:

[0022] A first operational amplifier, with its first input terminal receiving the dimming voltage;

[0023] The first transistor has a control terminal coupled to the output terminal of the first operational amplifier, a first terminal coupled to the second input terminal of the first operational amplifier, and a second terminal outputting the reference current.

[0024] A first resistor is coupled between the first terminal of the first transistor and a reference ground.

[0025] Optionally, the current mirror circuit includes:

[0026] The reference module is coupled between the power supply voltage and the adjustable current source circuit;

[0027] At least one output branch, wherein each output branch is coupled to a power supply voltage and provides the intermediate current, the intermediate current being proportional to the reference current.

[0028] Optionally, the current restoration circuit includes at least one current restoration module, the current restoration module comprising:

[0029] The second resistor is coupled between the corresponding output branch and the reference ground and generates an intermediate voltage.

[0030] The second operational amplifier receives the intermediate voltage at its first input terminal;

[0031] The second transistor has a control terminal coupled to the output terminal of the second operational amplifier, a first terminal coupled to the second input terminal of the second operational amplifier, and the second terminal outputting the LED driving current.

[0032] A variable resistor unit is coupled between the first terminal of the second transistor and a reference ground.

[0033] Optionally, the variable resistor unit includes several resistor branches, and the number of resistor branches connected is controlled based on a switching signal.

[0034] Optionally, the current restoration circuit includes at least one current restoration module, the current restoration module comprising:

[0035] A reference unit is coupled between the current mirror circuit and a reference ground;

[0036] An adjustable output unit is coupled to a reference ground and outputs the LED driving current, wherein the LED driving current is proportional to the intermediate current and the ratio is adjustable.

[0037] Optionally, the adjustable output unit includes: a plurality of adjustable output branches, wherein the number of accesses for each adjustable output branch is controlled based on a switch signal.

[0038] Optionally, it also includes a decoding circuit to obtain the switching signal by decoding the PWM dimming codeword.

[0039] The present invention also provides an LED system, comprising:

[0040] LED light strings;

[0041] A voltage conversion circuit supplies power to the LED string;

[0042] The LED driving circuit described in any of the above describes the brightness adjustment of the LED string.

[0043] The present invention also provides an LED driving method, comprising:

[0044] Preprocessed dimming codewords are obtained by amplifying PWM dimming codewords in different segments at different ratios.

[0045] The preprocessed dimming codeword is converted into a dimming voltage within a preset working range;

[0046] The dimming voltage is converted from voltage to current to generate a reference current;

[0047] The reference current is subjected to current mirroring to generate an intermediate current;

[0048] The LED driving current is obtained by proportionally reducing the intermediate current.

[0049] Optionally, the method for obtaining the LED driving current includes: converting the intermediate current into an intermediate voltage, and converting the intermediate voltage into the LED driving current based on a variable resistor.

[0050] Optionally, the method for obtaining the LED driving current includes: adjusting the mirror ratio and performing current mirroring processing on the intermediate current to obtain the LED driving current.

[0051] As described above, the LED driving circuit, LED driving method, and LED system of the present invention can amplify the dimming voltage and reference current proportionally by amplifying the PWM dimming codewords of different segments at different ratios, so as to maximize the reuse of the voltage and current operating range corresponding to the last segment, thereby achieving high precision across the entire range of the PWM dimming codewords. Attached Figure Description

[0052] Figure 1 The diagram shown is a structural schematic of a traditional LED driver circuit.

[0053] Figure 2 Displayed as Figure 1 The diagram shows the image ratio error and current magnitude corresponding to the LED driving circuit shown.

[0054] Figure 3 The diagram shown is a schematic diagram of the LED driving circuit in Embodiment 1 of the present invention.

[0055] Figure 4 Displayed as Figure 3 The diagram shows an exemplary structure of an LED driver circuit.

[0056] Figure 5 The diagram shown is a schematic diagram of the LED driving circuit in Embodiment 2 of the present invention.

[0057] Figure 6 Displayed as Figure 5 The diagram shows an exemplary structure of an LED driver circuit.

[0058] Figure 7 The flowchart shown is a process for driving an LED according to Embodiment 3 of the present invention.

[0059] Figure 8 The diagram shows the invention's scaling up of PWM dimming codewords in different sections at different ratios.

[0060] Figure 9 Displayed as Figure 3 and Figure 5 The diagram shows the image ratio error and current magnitude corresponding to the LED driving circuit shown.

[0061] Figure 10 The diagram shown is a structural schematic of the LED system in Embodiment 4 of the present invention.

[0062] Component labeling: 11-Digital-to-analog converter section, 12-Adjustable current section, 13-Current mirror section, 14-Operational amplifier; 21, 31-Amplifier circuit, 211, 311-Segment detection module, 212, 312-Segmented amplification module, 2121, 3121-Selection unit, 2122, 3122-Amplifier unit, 22, 32-Digital-to-analog converter circuit, 23, 33-Adjustable current source circuit, 231, 331-First operational amplifier, 232, 332-First transistor, 233, 333-First resistor, 24, 34-Current mirror circuit, 241, 341-Reference module, 2411, 3411-Third transistor, 242, 342-Output branch, 2421 3421 - Fourth transistor; 25, 35 - Current restoration circuit; 251, 351 - Current restoration module; 2511 - Second resistor; 2512 - Second operational amplifier; 2513 - Second transistor; 2514 - Variable resistor unit; 25141 - Resistor branch; 3511 - Reference unit; 35111 - Fifth transistor; 3512 - Adjustable output unit; 35121 - Adjustable output branch; 35122 - Sixth transistor; 3513 - Third operational amplifier; 3514 - Seventh transistor; 3515 - Fourth operational amplifier; 3516 - Eighth transistor; 26, 36 - Decoding circuit; 10 - LED string; 20 - Voltage conversion circuit; 30 - LED driver circuit. Detailed Implementation

[0063] 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.

[0064] Please see Figures 3 to 10 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 illustrations 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 shape, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0065] Example 1

[0066] like Figure 3 As shown, this embodiment provides an LED driving circuit, including an amplifier circuit 21, a digital-to-analog converter circuit 22, an adjustable current source circuit 23, a current mirror circuit 24, and a current restoration circuit 25; further, it also includes a decoding circuit 26. In this embodiment, the LED driving circuit uses a resistive driving architecture as an example.

[0067] Amplification circuit 21 amplifies the PWM dimming codewords PWMset in different segments by different ratios to obtain pre-processed dimming codewords PWMA. In one embodiment, such as... Figure 4 As shown, the amplifier circuit 21 includes a segment detection module 211 and a segment amplification module 212.

[0068] The segment detection module 211 is used to detect the segment in which the PWM dimming codeword PWMset is located and obtain a detection signal. In practical applications, each segment is usually predefined based on the number of bits in the PWM dimming codeword and specific requirements, and segment detection is performed on the PWM dimming codeword.

[0069] Let M denote the number of bits in the PWM dimming codeword and X denote the number of segments, where M is a natural number greater than 1 and X is a natural number greater than 1.

[0070] When defining a segment: In the first segment, the starting value can be zero or any other value greater than zero, usually determined by specific requirements. For example, it could be 2. M 1%, which is approximately 41 for M=12, and the segment end value is 2. M-X+1 -1; In the second segment, the initial value of the segment is 2. M-X+1 The segment end value is 2 M-X+2 -1; In the third segment, the initial value of the segment is 2. M-X+2 The segment end value is 2 M-X+3 -1; In the fourth segment, the initial value of the segment is 2. M-X+3 The segment end value is 2 M-X+4 -1; and so on, until the end value of the segment is 2. M -1.

[0071] Taking M=12 and X=5 as an example, the first segment is 41~255, the second segment is 256~511, the third segment is 512~1023, the fourth segment is 1024~2047, and the fifth segment is 2048~4095; taking M=12 and X=6 as an example, the first segment is 41~127, the second segment is 128~255, the third segment is 256~511, the fourth segment is 512~1023, the fifth segment is 1024~2047, and the sixth segment is 2048~4095; of course, M and X can also be other values, and there are no major restrictions on this.

[0072] Alternatively, segment detection can be achieved by performing high-order bit judgment on the PWM dimming codeword. Taking M=12 and X=5 as an example, the process of performing high-order bit judgment on the PWM dimming codeword is as follows:

[0073] The highest bit is judged. If the highest bit is 1, it means that the segment it is in is 2048~4095, and the corresponding detection signal is output. If the highest bit is 0, the second highest bit is judged. If the second highest bit is 1, it means that the segment it is in is 1024~2047, and the corresponding detection signal is output. If the second highest bit is 0, the third highest bit is judged. If the third highest bit is 1, it means that the segment it is in is 512~1023, and the corresponding detection signal is output. This process continues until the corresponding segment is detected and the corresponding detection signal is output.

[0074] It should be noted that the segment definition above is only one feasible example and is not a limitation; in fact, other segment definition methods that meet specific needs are also applicable to this embodiment. Furthermore, the segment detection method above is also only one feasible example; other methods that can achieve segment detection are also feasible, and no further restrictions are imposed on them.

[0075] The segmented amplification module 212 includes a selection unit 2121 and several amplification units 2122 with different amplification ratios; wherein, the selection unit 2121 selects the corresponding amplification unit 2122 based on the detection signal, and the amplification unit 2122 amplifies the PWM dimming code word PWMset by the corresponding ratio.

[0076] In one example, the selection unit 2121 is implemented using a multiplexer; wherein, the control terminal of the multiplexer receives the detection signal, the fixed terminal of the multiplexer receives the PWM dimming codeword PWMset, and each selection terminal of the multiplexer is coupled to the input terminal of each amplification unit 2122 to select the corresponding amplification unit 2122 under the control of the detection signal.

[0077] The number of amplification units 2122 is determined by the number of segments X. Typically, the number of amplification units 2122 equals the number of segments X. Furthermore, the magnification ratio of each amplification unit 2122 is also related to the number of segments, where the magnification ratio of each amplification unit 2122 is 2... 0 2 1 、…、2 X-1 .

[0078] Specifically, for the amplification unit 2122 with a magnification ratio of 1, it can be implemented using wires. For the amplification unit 2122 with a magnification ratio greater than 1, it can be implemented using a shift register; for example, for the amplification unit 2122 with a magnification ratio of 2, it is implemented by shifting the shift register left by 1 bit; for the amplification unit 2122 with a magnification ratio of 4, it is implemented by shifting the shift register left by 2 bits; and for the amplification unit 2122 with a magnification ratio of 8, it is implemented by shifting the shift register left by 3 bits, wherein the low-order bits are padded with zeros.

[0079] In practical applications, when selecting the corresponding amplification unit 2122 based on the segment detection results, the amplification ratios for the first segment to the Xth segment are typically 2. X-1 、…、2 0 Each amplification unit 2122. Taking M=12 and X=5 as an example:

[0080] When the PWM dimming codeword is in the range of 0~255, the selection unit 2121 selects the amplification unit 2122 with an amplification ratio of 16 based on the detection signal, so as to amplify the PWM dimming codeword by 16 times.

[0081] When the PWM dimming codeword is located in the range of 256~511, the selection unit 2121 selects the amplification unit 2122 with an amplification ratio of 8 based on the detection signal, so as to amplify the PWM dimming codeword by 8 times.

[0082] When the PWM dimming codeword is located in the range of 512~1023, the selection unit 2121 selects the amplification unit 2122 with an amplification ratio of 4 based on the detection signal, so as to amplify the PWM dimming codeword by 4 times.

[0083] When the PWM dimming codeword is located in the range of 1024~2047, the selection unit 2121 selects the amplification unit 2122 with an amplification ratio of 2 based on the detection signal, so as to amplify the PWM dimming codeword by 2 times.

[0084] When the PWM dimming codeword is located in the range of 2048~4095, the selection unit 2121 selects the amplification unit 2122 with an amplification ratio of 1 based on the detection signal, so as to directly output the PWM dimming codeword.

[0085] The digital-to-analog converter circuit 22 receives the pre-processed dimming codeword PWMA and converts it into a dimming voltage VR within a preset operating range. In one embodiment, the digital-to-analog converter circuit 22 includes a digital-to-analog converter; wherein the number of bits of the digital-to-analog converter is determined by the number of bits M of the PWM dimming codeword PWMset, and typically, the number of bits of the digital-to-analog converter is equal to the number of bits M of the PWM dimming codeword PWMset.

[0086] The adjustable current source circuit 23 receives the dimming voltage VR and generates a reference current IR through voltage-to-current conversion. In one embodiment, such as... Figure 4 As shown, the adjustable current source circuit 23 includes a first operational amplifier 231, a first transistor 232, and a first resistor 233.

[0087] The first input terminal (e.g., non-inverting input terminal) of the first operational amplifier 231 receives the dimming voltage VR. The second input terminal (e.g., inverting input terminal) of the first operational amplifier 231 is coupled to the first terminal of the first transistor 232. The output terminal of the first operational amplifier 231 is coupled to the control terminal of the first transistor 232. The first terminal of the first transistor 232 is also coupled to the reference ground via the first resistor 233. The second terminal of the first transistor 232 outputs a reference current IR. The reference current satisfies the formula IR=VR / R1, where IR is the reference current, VR is the dimming voltage, and R1 is the resistance of the first resistor 233.

[0088] In this embodiment, the first transistor 232 is an NMOS transistor, with the control terminal being the gate terminal, the first terminal being the source terminal, and the second terminal being the drain terminal. Additionally, the first resistor 233 is an adjustable resistor to ensure high accuracy of its resistance value through adjustment; as an optional solution, the first resistor 233 can be implemented using a fixed resistor connected in series with an adjustable resistor.

[0089] The current mirror circuit 24 receives a reference current IR and generates an intermediate current IM through current mirroring. In one embodiment, such as... Figure 3 and Figure 4 As shown, the current mirror circuit 24 includes a reference module 241 and at least one output branch 242.

[0090] A reference module 241 is coupled between a power supply voltage and an adjustable current source circuit 23. In the output branches 242, each output branch 242 is coupled to the power supply voltage and provides an intermediate current IM, wherein the intermediate current IM is proportional to the reference current IR. In one example, the reference module 241 includes a third transistor 2411, and the output branch 242 includes a fourth transistor 2421. The control terminal of the third transistor 2411 is coupled to the control terminal of the fourth transistor 2421; the first terminal of the third transistor 2411 is coupled to the first terminal of the fourth transistor 2421 and receives the power supply voltage; the second terminal of the third transistor 2411 is coupled to its control terminal and receives the reference current IR; and the second terminal of the fourth transistor 2421 outputs the intermediate current IM. In this embodiment, the third transistor 2411 and the fourth transistor 2421 are PMOS transistors, with the control terminal being the gate terminal, the first terminal being the source terminal, and the second terminal being the drain terminal.

[0091] When the number of output branches 242 is greater than one, the output branches 242 are designed in parallel to output multiple intermediate currents IM, providing a corresponding number of current paths for the multiple groups of LEDs to be driven. For example, when driving two groups of LEDs, the number of output branches 242 is two, and when driving three groups of LEDs, the number of output branches 242 is three. It should be noted that in the current mirror circuit 24, the current mirror ratio is a fixed value, and the design should be based on specific requirements; there are no excessive restrictions on this.

[0092] The current reduction circuit 25 receives the intermediate current IM and reduces it proportionally to obtain the LED driving current ILED. In one embodiment, such as... Figure 3 and Figure 4 As shown, the current restoration circuit 25 includes at least one current restoration module 251, wherein the number of current restoration modules 251 is the same as the number of output branches 242 in the current mirror circuit 24.

[0093] Specifically, the current restoration module 251 includes a second resistor 2511, a second operational amplifier 2512, a second transistor 2513, and a variable resistor unit 2514.

[0094] The second resistor 2511 is coupled between the corresponding output branch 242 and the reference ground and generates an intermediate voltage VM; the first input terminal (e.g., the non-inverting input terminal) of the second operational amplifier 2512 receives the intermediate voltage VM, the second input terminal (e.g., the inverting input terminal) of the second operational amplifier 2512 is coupled to the first terminal of the second transistor 2513, the output terminal of the second operational amplifier 2512 is coupled to the control terminal of the second transistor 2513, the first terminal of the second transistor 2513 is also coupled to the reference ground via the variable resistor unit 2514, and the second terminal of the second transistor 2513 outputs the LED driving current ILED.

[0095] In this embodiment, the second transistor 2513 is an NMOS transistor, with the control terminal being the gate terminal, the first terminal being the source terminal, and the second terminal being the drain terminal. Additionally, the second resistor 2511 is an adjustable resistor to ensure high accuracy of its resistance value through adjustment; as an optional solution, the second resistor 2511 can be implemented using a fixed resistor connected in series with an adjustable resistor.

[0096] More specifically, the variable resistor unit 2514 includes several resistor branches 25141, each resistor branch 25141 controlling the number of connected resistors (e.g., the number in parallel) based on a switch signal SW, so as to achieve current restoration by adjusting the reduction ratio. Each resistor branch 25141 includes a resistor connected in series and a switch; by controlling the opening and closing of the switch, the number of connected resistors (e.g., the number of parallel resistors) is adjusted to regulate the reduction ratio.

[0097] Wherein, the LED driving current satisfies the formula ILED=VM / Req, the intermediate voltage satisfies the formula VM=IM*R2, and the intermediate current satisfies the formula IM=K1*IR, therefore ILED=(IR*K*R2) / Req; where ILED is the LED driving current, VM is the intermediate voltage, Req is the equivalent resistance of the variable resistor unit 2514, IM is the intermediate current, R2 is the resistance of the second resistor 2511, IR is the reference current, and K1 is the mirror ratio of the current mirror circuit 24.

[0098] Let the resistance in resistor branch 25141 be denoted as the third resistance, which is a unit resistance. At this time, the second resistance 2511 can be regarded as Y unit resistances connected in series. Assuming that the variable resistor unit 2514 includes Z parallel resistor branches 25141, when all the switches in the Z resistor branches 25141 are closed, ILED=(IR*K1*Y*R0) / (R0 / Z)=IR*K1*Y*Z, where IR*K1*Y is a fixed value. In this way, the current can be adjusted by adjusting the value of Z to achieve current restoration.

[0099] The specific adjustments are as follows:

[0100] When the amplification ratio is 1, closing all switches in the Z resistor branches 25141 is equivalent to keeping the reduction ratio Z constant, and the output current remains unchanged. When the amplification ratio is 2, closing half of the switches in the Z resistor branches 25141 is equivalent to changing the reduction ratio to Z / 2, thus reducing the output current by a factor of 2 and restoring the current. When the amplification ratio is 4, closing 1 / 4 of the switches in the Z resistor branches 25141 is equivalent to changing the reduction ratio to Z / 4, thus reducing the output current by a factor of 4 and restoring the current. And so on.

[0101] The decoding circuit 26 decodes the PWM dimming codeword PWMset to obtain the switching signal SW, which is used to control the switching of each resistor branch 25141 in the variable resistor unit 2514. Of course, since the detection signal is related to the PWM dimming codeword PWMset, the switching signal SW can also be obtained by decoding the detection signal; this has no substantial impact on this embodiment. In practical applications, when the number of current restoration modules 251 is greater than one, the variable resistor units 2514 in each current restoration module 251 can share the same switching signal SW.

[0102] Example 2

[0103] like Figure 5As shown, this embodiment provides an LED driving circuit, including an amplifier circuit 31, a digital-to-analog converter circuit 32, an adjustable current source circuit 33, a current mirror circuit 34, and a current restoration circuit 35; further, it also includes a decoding circuit 36. In this embodiment, the LED driving circuit takes a current-driven architecture as an example.

[0104] The amplifier circuit 31, the digital-to-analog converter circuit 32, the adjustable current source circuit 33, and the current mirror circuit 34 are the same as in Embodiment 1. For relevant details, please refer to the above text and will not be repeated here.

[0105] The current reduction circuit 35 receives the intermediate current IM and reduces it proportionally to obtain the LED driving current ILED. In one embodiment, such as... Figure 5 and Figure 6 As shown, the current restoration circuit 35 includes at least one current restoration module 351, wherein the number of current restoration modules 351 is the same as the number of output branches 342 in the current mirror circuit 34.

[0106] Specifically, the current restoration module 351 includes a reference unit 3511 and an adjustable output unit 3512. The reference unit 3511 is coupled between the current mirror circuit 34 and a reference ground; the adjustable output unit 3512 is coupled to the reference ground and outputs an LED driving current ILED, wherein the LED driving current ILED is proportional to the intermediate current IM and the ratio is adjustable. In one example, the adjustable output unit 3512 includes a plurality of adjustable output branches 35121, wherein each adjustable output branch 35121 controls the number of connected branches (e.g., the number of parallel connections) based on a switching signal SW, so as to achieve current restoration by adjusting the reduction ratio.

[0107] The reference unit 3511 includes a fifth transistor 35111. The control terminal of the fifth transistor 35111 is coupled to the control terminal of each adjustable output unit 3512. The first terminal of the fifth transistor 35111 is coupled to a reference ground. The second terminal of the fifth transistor 35111 is coupled to its control terminal and coupled to a current mirror circuit 34. The adjustable output branch 35121 includes a sixth transistor 35122 and two switches. The first terminal of the first switch serves as the control terminal of the adjustable output branch 35121. The second terminal of the first switch is coupled to the control terminal of the sixth transistor 35122 and is coupled to the first terminal of the sixth transistor 35122 via the second switch. The first terminal of the sixth transistor 35122 is coupled to a reference ground. The second terminal of the sixth transistor 35122 outputs an LED driving current ILED.

[0108] Furthermore, the current restoration module 351 also includes a third operational amplifier 3513, a seventh transistor 3514, a fourth operational amplifier 3515, and an eighth transistor 3516.

[0109] The first input terminal (e.g., non-inverting input terminal) of the third operational amplifier 3513 receives a first preset voltage VS1. The second input terminal (e.g., inverting input terminal) of the third operational amplifier 3513 is coupled to the first terminal of the seventh transistor 3514. The output terminal of the third operational amplifier 3513 is coupled to the control terminal of the seventh transistor 3514. The seventh transistor 3514 is coupled between the current mirror circuit 34 and the reference unit 3511. That is, the first terminal of the seventh transistor 3514 is coupled to the reference unit 3511, and the second terminal of the seventh transistor 3514 is coupled to the current mirror circuit 34. The reference unit 3511 is no longer directly coupled to the current mirror circuit 34. In addition, the control terminal of the fifth transistor 35111 is no longer coupled to its second terminal, but is coupled to the second terminal of the seventh transistor 3514.

[0110] The first input terminal (e.g., the non-inverting input terminal) of the fourth operational amplifier 3515 receives a second preset voltage VS2. The second input terminal (e.g., the inverting input terminal) of the fourth operational amplifier 3515 is coupled to the first terminal of the eighth transistor 3516. The output terminal of the fourth operational amplifier 3515 is coupled to the control terminal of the eighth transistor 3516. The eighth transistor 3516 is coupled to the adjustable output unit 3512. That is, the first terminal of the eighth transistor 3516 is coupled to the adjustable output unit 3512. The second terminal of the eighth transistor 3516 outputs the LED driving current ILED. The second terminal of the sixth transistor 35122 no longer outputs the LED driving current ILED.

[0111] In this embodiment, the fifth transistor 35111, the sixth transistor 35122, the seventh transistor 3514, and the eighth transistor 3516 are NMOS transistors, with the control terminal being the gate terminal, the first terminal being the source terminal, and the second terminal being the drain terminal. Alternatively, as an option, the first preset voltage VS1 and the second preset voltage VS2 are the same (typically between 100mV and 200mV) so that the operating voltages of the two operational amplifiers remain at the set values ​​under different LED drive currents, thus making the offset ratio relatively less important. By clamping the two operational amplifiers, the mirror ratio of the current mirror structure formed by the reference unit 3511 and the adjustable output unit 3512 can be made relatively accurate, thereby eliminating the influence of channel length modulation effects.

[0112] The LED driving current satisfies the formula ILED=K2*IM, and the intermediate current satisfies the formula IM=K1*IR. Therefore, ILED=K1*K2*IR, where ILED is the LED driving current, IM is the intermediate current, IR is the reference current, K1 is the mirror ratio of the current mirror circuit 34, and K2 is the mirror ratio of the current restoration module 351. K1*IR is a fixed value. Thus, the current magnitude can be adjusted by adjusting the value of K2 to achieve current restoration.

[0113] Assuming the adjustable output unit 3512 includes J parallel adjustable output branches 35121, closing the first switch and opening the second switch among the J adjustable output branches 35121 results in a mirror ratio of K2. Specifically, during adjustment:

[0114] When the amplification ratio is 1, the first switch in the J adjustable output branches 35121 is closed and the second switch is open. At this time, the mirror ratio K2 remains unchanged, and the output current remains unchanged. When the amplification ratio is 2, the first switch in the J / 2 adjustable output branches 35121 is closed and the second switch is open, while the first switch in the remaining adjustable output branches 35121 is open and the second switch is closed. At this time, the mirror ratio becomes K2 / 2, which can reduce the output current by a factor of 2, thus restoring the current. When the amplification ratio is 4, the first switch in the J / 4 adjustable output branches 35121 is closed and the second switch is open, while the first switch in the remaining adjustable output branches 35121 is open and the second switch is closed. At this time, the mirror ratio becomes K2 / 4, which can reduce the output current by a factor of 4, thus restoring the current. And so on.

[0115] The decoding circuit 36 ​​obtains the switching signal SW by decoding the PWM dimming codeword PWMset, so as to control the opening and closing of the switches of each adjustable output branch 35121 in the adjustable output unit 3512. Of course, since the detection signal is related to the PWM dimming codeword PWMset, the switching signal SW can also be obtained by decoding the detection signal, which has no substantial impact on this embodiment. It should be noted that in this embodiment, the switching signal SW includes two signals SW1 and SW2, where SW1 and SW2 are a set of complementary signals. In addition, in practical applications, when the number of current restoration modules 351 is greater than one, the adjustable output units 3512 in each current restoration module 351 can share the same switching signal SW.

[0116] Example 3

[0117] like Figure 7 As shown, this embodiment provides an LED driving method, including the following steps; wherein, the method of this embodiment can be implemented using the LED driving circuit described in Embodiment 1 or Embodiment 2.

[0118] S1, the PWM dimming codewords in different segments are amplified by different ratios to obtain pre-processed dimming codewords. Specifically, the method includes: performing segment detection on the PWM dimming codewords based on predefined segments, and amplifying the PWM dimming codewords by corresponding ratios based on the detection results to obtain pre-processed dimming codewords; for example, segment detection can be performed using a segment detection module, and amplification can be performed using a segment amplification module, as detailed in Embodiment 1, which will not be elaborated here.

[0119] S2, convert the pre-processed dimming codeword into a dimming voltage within a preset working range. For example, the pre-processed dimming codeword can be converted into a dimming voltage within a preset working range using a digital-to-analog converter, as detailed in Embodiment 1, which will not be repeated here.

[0120] S3 generates a reference current by converting the dimming voltage to a current. For example, the reference current can be obtained by converting the dimming voltage to a current using an adjustable current source circuit, as detailed in Embodiment 1, which will not be repeated here.

[0121] S4, perform current mirroring on the reference current to generate an intermediate current. For example, the intermediate current can be obtained by performing current mirroring on the reference current through a current mirror circuit, as detailed in Example 1, which will not be repeated here.

[0122] S5 reduces the intermediate current proportionally to obtain the LED driving current.

[0123] In one example, the method for obtaining the LED driving current includes: converting the intermediate current into an intermediate voltage, and converting the intermediate voltage into the LED driving current based on a variable resistor; in the process of voltage-to-current conversion of the intermediate voltage, adjusting the resistor is equivalent to adjusting the conversion ratio, and by reducing the conversion ratio based on the amplification factor, the current can be restored to obtain the LED driving current, as detailed in Example 1, which will not be repeated here.

[0124] In another example, the method for obtaining the LED driving current includes: adjusting the mirror ratio and performing current mirroring on the intermediate current to obtain the LED driving current; during the process of mirroring the intermediate current, the mirror ratio is reduced according to the magnification factor to realize the current restoration and obtain the LED driving current, as detailed in Example 2, which will not be repeated here.

[0125] In this embodiment, by amplifying the PWM dimming codewords of different segments by different proportions, the dimming voltage and reference current can be amplified proportionally. This allows the dimming voltage and reference current, originally corresponding to different segments, to reuse the voltage and current operating range corresponding to the last segment (e.g., segment 2048~4095) to the greatest extent possible. Figure 8 and Figure 9 As shown; finally, the current is restored and output.

[0126] For resistive drive architectures: This invention amplifies the equivalent voltage operating range of the two operational amplifiers, thereby reducing the offset ratio and simplifying the design. It also reduces the mirror current range of the current mirror circuit and decreases the threshold error ratio by amplifying the reference current, thus reducing the mirror ratio error. Furthermore, the offset voltage and current are controlled within the multiplexing range, significantly saving adjustment resources and inherently improving the circuit's accuracy, thereby achieving high precision across the entire PWM dimming code range. For current-driven architectures: It has roughly the same beneficial effects as the resistive drive architecture.

[0127] Example 4

[0128] like Figure 10 As shown, this embodiment provides an LED system, including an LED string 10, a voltage conversion circuit 20, and an LED driver circuit 30.

[0129] LED light string 10 is formed by connecting several LED beads in series.

[0130] The voltage conversion circuit 20 is used to power the LED string 10. In practical applications, the voltage conversion circuit 20 can be implemented using any known circuit structure, without much restriction.

[0131] The LED driving circuit 30 is used to adjust the brightness of the LED string 10; wherein the LED driving circuit 30 is implemented using the circuit structure described in Embodiment 1 or Embodiment 2.

[0132] In summary, the LED driving circuit, LED driving method, and LED system of this invention, by amplifying the PWM dimming codewords of different segments at different ratios, can proportionally amplify the dimming voltage and reference current, thereby maximizing the reuse of the voltage and current operating range corresponding to the last segment and achieving high precision across the entire range of the PWM dimming codeword. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial applicability.

[0133] 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. An LED driver circuit, comprising: An amplifier circuit amplifies the PWM dimming codewords of different sections by different ratios to obtain pre-processed dimming codewords. The digital-to-analog converter circuit receives the preprocessed dimming codeword and converts it into a dimming voltage within a preset working range; An adjustable current source circuit receives the dimming voltage and generates a reference current through voltage-current conversion. A current mirror circuit receives the reference current and generates an intermediate current through current mirroring processing. The current reduction circuit receives the intermediate current and reduces it by a corresponding ratio to obtain the LED driving current.

2. The LED driving circuit as described in claim 1, wherein, The amplifier circuit includes: The segment detection module detects the segment in which the PWM dimming codeword is located to obtain a detection signal; The segmented magnification module includes a selection unit and several magnification units with different magnification ratios. The selection unit selects the corresponding amplification unit based on the detection signal, and the amplification unit amplifies the PWM dimming codeword by a corresponding ratio.

3. The LED driving circuit as described in claim 2, wherein, When the amplification ratio is 1, the amplification unit is implemented using wires; when the amplification ratio is greater than 1, the amplification unit is implemented using a shift register.

4. The LED driving circuit as described in claim 1, wherein, The adjustable current source circuit includes: A first operational amplifier, with its first input terminal receiving the dimming voltage; The first transistor has a control terminal coupled to the output terminal of the first operational amplifier, a first terminal coupled to the second input terminal of the first operational amplifier, and a second terminal outputting the reference current. A first resistor is coupled between the first terminal of the first transistor and a reference ground.

5. The LED driving circuit as described in claim 1, wherein, The current mirror circuit includes: The reference module is coupled between the power supply voltage and the adjustable current source circuit; At least one output branch, wherein each output branch is coupled to a power supply voltage and provides the intermediate current, the intermediate current being proportional to the reference current.

6. The LED driving circuit as described in claim 1, wherein, The current restoration circuit includes at least one current restoration module, the current restoration module comprising: The second resistor is coupled between the corresponding output branch and the reference ground and generates an intermediate voltage. The second operational amplifier receives the intermediate voltage at its first input terminal; The second transistor has a control terminal coupled to the output terminal of the second operational amplifier, a first terminal coupled to the second input terminal of the second operational amplifier, and the second terminal outputting the LED driving current. A variable resistor unit is coupled between the first terminal of the second transistor and a reference ground.

7. The LED driving circuit as described in claim 6, wherein, The variable resistor unit includes several resistor branches, and the number of resistor branches connected is controlled based on a switch signal.

8. The LED driving circuit as described in claim 1, wherein, The current restoration circuit includes at least one current restoration module, the current restoration module comprising: A reference unit is coupled between the current mirror circuit and a reference ground; An adjustable output unit is coupled to a reference ground and outputs the LED driving current, wherein the LED driving current is proportional to the intermediate current and the ratio is adjustable.

9. The LED driving circuit as described in claim 8, wherein, The adjustable output unit includes several adjustable output branches, and the number of access points for each adjustable output branch is controlled based on a switch signal.

10. The LED driving circuit as described in claim 7 or 9, wherein, It also includes a decoding circuit, which obtains the switching signal by decoding the PWM dimming codeword.

11. An LED system, comprising: LED light strings; A voltage conversion circuit supplies power to the LED string; The LED driving circuit according to any one of claims 1 to 10 adjusts the brightness of the LED string.

12. An LED driving method, comprising: Preprocessed dimming codewords are obtained by amplifying PWM dimming codewords in different segments at different ratios. The preprocessed dimming codeword is converted into a dimming voltage within a preset working range; The dimming voltage is converted from voltage to current to generate a reference current; The reference current is subjected to current mirroring to generate an intermediate current; The LED driving current is obtained by proportionally reducing the intermediate current.

13. The LED driving method as described in claim 12, wherein, The method for obtaining the LED driving current includes: converting the intermediate current into an intermediate voltage, and converting the intermediate voltage into the LED driving current based on a variable resistor.

14. The LED driving method as described in claim 12, wherein, The method for obtaining the LED driving current includes: adjusting the mirror ratio and performing current mirroring processing on the intermediate current to obtain the LED driving current.

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