LED driving system and method

Abstract

An LED driving system (100, 500) and a method (600) are provided. The LED driving system (100, 500) includes a conversion circuit (110) configured to convert a first voltage (Vdd) to a second voltage (Vdv) having a voltage difference (Vgs) from the first voltage (Vdd) based on a control input, a drive circuit (120) connected to the conversion circuit (110) and configured to receive the second voltage (Vdv) and generate an output signal (PWM_OUT) based on the second voltage (Vdv), and a control circuit (130) connected to the drive circuit (120) and configured to control the brightness of an LED (140) based on the output signal (PWM_OUT).

Description

[Technical Field]

[0001] The present disclosure relates generally to display technology, and more particularly to LED driving systems and methods. [Background technology]

[0002] The gradation of an LED display primarily determines the brightness gradation level at which content such as photos and video images are displayed. Brightness is the measurable quality of light that corresponds to brightness. The brightness of each LED pixel can be adjusted, and the fineness of adjustment is the gradation level of the display. The higher the gradation level, i.e., the more brightness levels there are, the more detailed and colorful the displayed image can be.

[0003] The light-emitting unit includes red, green, and blue LEDs and a driving circuit. A driving chip commonly used to provide the driving circuit includes a chip incorporating a serial-parallel shift register unit and an output latch unit. The control input signals of the driving chip include data (R, G, B), a shift pulse (e.g., provided by a clock (CLK)), a latch pulse (e.g., provided by a strobe), etc.

[0004] Generally, the LED current is linearly adjusted to change the brightness of the LED. A method for adjusting the gradation of the LED by adjusting the number of pulses is also disclosed. However, for a better display effect, it is necessary to be able to finely adjust the gradation level. Summary of the Invention

[0005] An embodiment of the present disclosure provides an LED driving system that includes: a conversion circuit configured to convert a first voltage to a second voltage having a voltage difference from the first voltage based on a control input; a drive circuit connected to the conversion circuit and configured to receive the second voltage and generate an output signal based on the second voltage; and a control circuit connected to the drive circuit and configured to control brightness of an LED based on the output signal.

[0006] Furthermore, an embodiment of the present disclosure provides a method for driving an LED, the method including converting a first voltage to a second voltage having a voltage difference from the first voltage based on a control input, generating an output signal based on the second voltage, and controlling brightness of the LED based on the output signal.

[0007] Embodiments and various aspects of the present disclosure are set forth in the following detailed description and accompanying drawings, in which various features are not drawn to scale. [Brief explanation of the drawings]

[0008] [Figure 1] 1 shows a schematic diagram of the structure of an exemplary LED driving system according to some embodiments of the present disclosure. [Figure 2] 10 illustrates an example relationship between a second voltage and an output signal according to some embodiments of the present disclosure. [Figure 3] 1 illustrates an example relationship between an input PWM signal and an output signal according to some embodiments of the present disclosure. [Figure 4] 10 illustrates another example relationship between a second voltage and an output signal according to some embodiments of the present disclosure. [Figure 5] 1 shows another schematic diagram of an exemplary LED driving system structure according to some embodiments of the present disclosure. [Figure 6] 1 shows a flowchart of an exemplary method for driving an LED according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] Reference will now be made in detail to exemplary embodiments, some examples of which are illustrated in the accompanying drawings. The following description will refer to the accompanying drawings, in which like numbers in different figures represent the same or similar elements unless otherwise indicated. The implementations set forth in the following description of exemplary embodiments do not represent all implementations consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with aspects related to the present invention as set forth in the appended claims. Certain aspects of the present disclosure are described in further detail below. If terms and definitions provided herein conflict with terms and / or definitions incorporated by reference, the terms and definitions provided herein shall control.

[0010] FIG. 1 shows a schematic diagram of the structure of an exemplary LED driving system 100 according to some embodiments of the present disclosure. Referring to FIG. 1, the LED driving system 100 includes a conversion circuit 110, a driving circuit 120, a control circuit 130, and an LED 140. An input of the driving circuit 120 is connected to an output of the conversion circuit 110. A first input of the control circuit 130 is connected to the output of the driving circuit 120, and an output of the control circuit 130 is connected to the LED 140 to control the brightness (e.g., gray scale) of the LED 140. In some embodiments, the conversion circuit 110 and the control circuit 130 are both connected to an operating voltage Vdd. In some embodiments, the conversion circuit 110 may include a control input pin VSET for receiving multiple bits representing a control input as an input. The conversion circuit 110 may be implemented by a chip.

[0011] The conversion circuit 110 is configured to convert a first voltage, i.e., an operating voltage Vdd, to a second voltage Vdv based on a control input received at a pin VSET. The second voltage Vdv has a voltage difference Vgs with the first voltage Vdd. The first voltage Vdd, i.e., the operating voltage, may be, for example, +5V. The second voltage Vdv is lower than the first voltage Vdd, for example, in the range of +2V to +3V. Once the range of the second voltage Vdv is determined, the variation range of the voltage difference Vgs is determined, where Vgs = Vdd - Vdv. In this example, the variation range of the voltage difference Vgs is a 1V variation interval, i.e., 3V - 2V = 1V. The variation range of the voltage difference Vgs can be quantized and adjusted according to the control input. Therefore, different values of the second voltage Vdv can be generated by adjusting the control input to different levels. In some embodiments, the control input is set by several bits, for example, the control input is configured by a pin VSET of the chip. The VSET pin can be configured to receive 8 bits, 10 bits, 12 bits, or the like, representing the control input. VSET is a multi-bit input, and the control input can be received as a binary combination. For example, in the case of an 8-bit input, VSET<7:0> can range from (00000000) to (11111111). In this example, if the 1V fluctuation range of the voltage difference Vgs is quantized by 8 bits (e.g., the pin VSET configured to receive is an 8-bit pin), the voltage difference range (e.g., 1V) is divided into 256 levels, and the voltage fluctuation of each level is 1 / 256V. Correspondingly, the conversion circuit 110 can output 256 voltage values of the second voltage Vdv through conversion. For example, when VSET<7:0>=(00000000), the voltage difference Vgs has a minimum value, e.g., 2V. When VSET<7:0>=(111111111), the voltage difference Vgs has a maximum value, for example, 3 V. In some embodiments, when a 1 V variation range of the voltage difference Vgs is quantized with 10 bits, the voltage difference range is divided into 1024 levels, and the voltage variation of each level is 1 / 1024 V.Correspondingly, the conversion circuit 110 can output 1024 voltage values of the second voltage Vdv through conversion. In some embodiments, when a 1V fluctuation range of the voltage difference Vgs is quantized with 12 bits, the range of the voltage difference is divided into 4096 levels, and the voltage fluctuation of each level is 1 / 4096 V. Correspondingly, the conversion circuit 110 can output 4096 voltage values of the second voltage Vdv through conversion. Therefore, the conversion circuit 110 can convert the second voltage Vdv to different magnitudes and output them based on the control input.

[0012] The drive circuit 120 is connected to the conversion circuit 110 and configured to generate an output signal based on the second voltage Vdv. For example, the output signal of the drive circuit 120 varies as a function of the second voltage Vdv. For example, FIG. 2 shows an example relationship between the second voltage Vdv and the output signal of the drive circuit 120 according to some embodiments of the present disclosure. As shown in FIG. 2, the voltage of the output signal of the drive circuit 120 tracks the second voltage Vdv. As the second voltage Vdv increases, the output signal increases, and as the second voltage Vdv decreases, the output signal decreases. In some embodiments, the output signal of the drive circuit 120 may be a digital signal, for example, a pulse-width modulation (PWM) signal. Referring again to FIG. 1, the drive circuit 120 is connected to receive an input PWM signal PWM_IN. The drive circuit 120 is configured to determine an output signal PWM_OUT based on the input signal PWM_IN and the second voltage Vdv. The duty cycle of the output signal PWM_OUT is determined based on the input signal PWM_IN. The high level of the output signal PWM_OUT may be the same as the voltage of the input signal PWM_IN; in this example, the voltage of PWM_IN is the same as the operating voltage Vdd. In some embodiments, the voltage of PWM_IN may be different from the operating voltage Vdd. The low level of the output signal PWM_OUT is determined based on the operating voltage Vdd and the second voltage Vdv. FIG. 3 shows an example relationship between the input PWM signal and the output signal PWM_OUT according to some embodiments of the present disclosure. As shown in FIG. 3, the output signal PWM_OUT has the same duty cycle and frequency as the duty cycle and frequency of the input signal PWM_IN. The high level of the output signal PWM_OUT is equal to the operating voltage Vdd, and the low level of the output signal PWM_OUT is equal to the second voltage Vdv. FIG. 4 shows another example relationship between the second voltage Vdv and the output signal PWM_OUT according to some embodiments of the present disclosure. More specifically, Fig. 4 shows the input signal PWM_IN, the second voltage Vdv, and the output signal PWM_OUT. As shown in Fig. 4, the low level of the output signal PWM_OUT changes depending on the second voltage Vdv.As described above, the second voltage Vdv can be adjusted to different magnitudes, and therefore the output signal PWM_OUT can be changed to different magnitudes.

[0013] In some embodiments, the duty cycle of the output signal PWM_OUT can be adjusted within one pulse cycle, i.e., the ratio between the output high level Vdd and the output low level Vdv within one pulse cycle can be adjusted. For example, by adjusting the duty cycle of the input signal PWM_IN, the duty cycle of the output signal PWM_OUT can be adjusted. Therefore, the brightness of the LED can also be controlled by this adjustment.

[0014] 1, the control circuit 130 is connected to the drive circuit 120 and configured to control the brightness (e.g., gray scale for display) of the LED 140 based on the output signal PWM_OUT. The control circuit 130 controls the output current I out Generates an output current I out can control the brightness of the LED 140. The output current I out When is low, the brightness of LED 140 is low and the output current I out When is high, the brightness of the LED 140 is high. The output current I that can be generated by the control circuit 130 out The more levels there are, the finer the gradation can be realized. The output signal PWM_OUT can be changed to different magnitudes, for example, 256 levels, 1024 levels, or 4096 levels, so that the output current I generated based on the output signal PWM_OUT can be out The output current I for controlling the brightness of the LED 140 can also be adjusted to different magnitudes (e.g., levels). out The multiple levels of resolution significantly improve the definition of the display.

[0015] In some embodiments, the control circuit 130 may further be connected to an operating voltage Vdd. outis determined by comparing the output signal with the operating voltage Vdd. In this example, the variation range of the voltage difference Vgs between the operating voltage Vdd and the second voltage Vdv is quantized into many levels, and the low level of the output signal PWM_OUT is equal to Vdv, so that the output current I is directly determined by the voltage difference Vgs. out By quantizing more precisely, the resolution of the display can be improved.

[0016] In some embodiments, the LED 140 may be any color LED, for example, the LED 140 is any of a white LED, a red LED, a blue LED, or a yellow LED.

[0017] FIG. 5 shows another schematic diagram of the structure of an exemplary LED driving system 500 according to some embodiments of the present disclosure. Referring to FIG. 5, the LED driving system 500 includes the aforementioned conversion circuit 110 and driving circuit 120 configured as shown in FIG. 1 . The system 500 further includes a control circuit 130 implemented as a MOS (metal-oxide semiconductor) transistor 131. The source of the MOS transistor 131 is connected to a first voltage Vdd, the gate of the MOS transistor 131 is connected to the output of the driving circuit 120, and the drain of the MOS transistor 131 is connected to the LED 140. In the system 500, the LED 140 includes a diode 141. The drain of the MOS transistor 131 is connected to the positive terminal of the diode 141. The negative terminal of the diode 141 is connected to ground Vss. When the output signal PWM_OUT of the driving circuit 120 is at a low level, Vgs=Vdd-Vdv, and the MOS transistor 131 is turned on. By adjusting the setting (e.g., digital value) of VSET, the range of variation of Vgs can be quantized to a number of levels, e.g., 256, 1024, 4096, etc. In system 500, the voltage difference Vgs between the source and gate of MOS transistor 131 determines the output current I flowing through LED 140. out By adjusting the voltage difference Vgs, different values of I out You can get different I outWhen current flows through the LED 140, it can produce different brightnesses. The conversion circuit 110 is configured to adjust the low level Vdv of the output signal PWM_OUT, which can be quantized by 8 bits, 10 bits, and 12 bits. Therefore, a large number of low level Vdv values can be obtained. This makes brightness adjustment (e.g., gray scale of image display) more precise. The drive circuit 120 is configured to adjust the duty cycle of the output signal PWM_OUT within one pulse cycle by adjusting the duty cycle of the input signal PWM_IN. By adjusting the duty cycle of the output signal PWM_OUT, the output current I out can be adjusted, and therefore the brightness of the LED 140 can be adjusted.

[0018] 6 shows a flowchart of an exemplary LED driving method 600 according to some embodiments of the present disclosure. The method 600 can be performed by the LED driving system 100. As shown in FIG. 6, the method 600 includes steps 602 to 608.

[0019] In step 602, the first voltage Vdd is converted to a second voltage Vdv having a voltage difference based on the control input. The second voltage Vdv has a voltage difference Vgs with the first voltage Vdd. The first voltage Vdd may be an operating voltage, for example, +5V. The second voltage Vdv is lower than the first voltage Vdd, for example, in the range of +2V to +3V. Once the range of the second voltage Vdv is determined, the fluctuation range of the voltage difference Vgs is determined. In this example, the fluctuation range of the voltage difference Vgs is in the range of 1V, i.e., 3V-2V=1V.

[0020] In step 604, the variation range of the voltage difference is quantized based on the digital value of the control input. The variation range of the voltage difference Vgs can be quantized and adjusted by the control input. Therefore, different values of the second voltage Vdv can be generated by adjusting the control input. In some embodiments, the control input is set by several bits, for example, the control input is set by one or more pins VSET of the chip. VSET may be an 8-bit, 10-bit, or 12-bit pin, etc., that can be determined by chip selection. VSET is a multi-bit input, and the control input can be received as a binary combination. For example, in the case of an 8-bit input, VSET<7:0> may range from (00000000) to (11111111). In this example, if the variation range of 1V of the voltage difference Vgs is quantized by 8 bits (e.g., the pin VSET receives 8 bits), the voltage difference range (e.g., 1V) is divided into 256 levels, and the voltage variation of each level is 1 / 256V. Correspondingly, the conversion circuit 110 can output 256 voltage values of the second voltage Vdv through conversion. When the 1V fluctuation range of the voltage difference Vgs is quantized using 10 bits, the voltage difference range is divided into 1024 levels, and the voltage fluctuation of each level is 1 / 1024V. Correspondingly, the conversion circuit 110 can output 1024 voltage values of the second voltage Vdv through conversion. When the 1V fluctuation range of the voltage difference Vgs is quantized using 12 bits, the voltage difference range is divided into 4096 levels, and the voltage fluctuation of each level is 1 / 4096V. Correspondingly, the conversion circuit 110 can output 4096 voltage values of the second voltage Vdv through conversion. Therefore, the conversion circuit 110 can convert and output second voltages Vdv having different magnitudes based on the control input.

[0021] In step 606, an output signal is generated based on the second voltage Vdv. For example, the output signal PWM_OUT is changed based on the second voltage Vdv. For example, as shown in FIG. 2, the voltage of the output signal tracks the second voltage Vdv. When the second voltage Vdv increases, the output signal increases, and when the second voltage Vdv decreases, the output signal decreases. In some embodiments, the output signal may be a digital signal, such as a PWM signal. An input PWM signal PWM_IN may be another input of the drive circuit 120. The output signal PWM_OUT is determined based on the input signal PWM_IN and the second voltage Vdv. The duty cycle of the output signal PWM_OUT is determined based on the input signal PWM_IN. The high level of the output signal PWM_OUT may be the same as the voltage of the input signal PWM_IN. In this example, the voltage of PWM_IN is the same as the operating voltage Vdd. In some embodiments, the voltage of PWM_IN may be different from the operating voltage Vdd. The low level of the output signal PWM_OUT is determined based on the operating voltage Vdd and the second voltage Vdv. For example, the output signal PWM_OUT may have the same duty cycle and frequency as the duty cycle and frequency of the input signal PWM_IN. As shown in FIG. 3, the high level of the output signal PWM_OUT is equal to the operating voltage Vdd, and the low level of the output signal PWM_OUT is equal to the second voltage Vdv. In some embodiments, as shown in FIG. 4, the low level of the output signal PWM_OUT varies depending on the second voltage Vdv. As described above, the second voltage Vdv can be adjusted to different magnitudes, thereby changing the output signal to different magnitudes.

[0022] In some embodiments, the duty cycle of the output signal PWM_OUT can be adjusted within one pulse cycle, i.e., the ratio between the output high level Vdd and the output low level Vdv within one pulse cycle can be adjusted. For example, the duty cycle of the output signal PWM_OUT can be adjusted by adjusting the duty cycle of the input signal PWM_OUT. Therefore, the brightness of the LED can also be controlled by this adjustment.

[0023] In step 608, the brightness of the LED is controlled based on the output signal. LED is based on the output signal that can control the brightness of the LED 140. The current I LED When is low, the brightness of LED 140 is low and the current I LED When the current I is high, the brightness of the LED 140 is high. LED The more levels that can be achieved, the higher the gradation definition. The brightness of the LED 140 is determined by the current I LED The output signal can be changed to a different magnitude, for example, 256 levels, 1024 levels, or 4096 levels, so that the current I generated based on the output signal LED The current I for controlling the brightness of the LED 140 can also be adjusted to different magnitudes (e.g., levels). LED The multiple levels of resolution significantly improve the definition of the display.

[0024] In some embodiments, the current I LED is determined by comparing the output signal with the operating voltage Vdd. In this example, the variation range of the voltage difference Vgs between the operating voltage Vdd and the second voltage Vdv is quantized into many levels, and the low level of the output signal is equal to Vdv, so that the current I is directly determined by the voltage difference Vgs. LED can be quantized more accurately, resulting in a more detailed display.

[0025] It should be noted that relational terms herein, such as "first" and "second," are used merely to distinguish one entity or operation from another and do not require or imply any actual relationship or order between those entities or operations. Furthermore, the words "comprising," "having," "containing," and "including," as well as other similar forms, are intended to be equivalent in meaning and open-ended in that the one or more items following any one of these words are not meant to be an exhaustive listing of such one or more items, nor are they meant to be limited to only the listed one or more items.

[0026] As used herein, unless otherwise stated, the term "or" includes all possible combinations unless impracticable. For example, if it is stated that a database can include A or B, then the database can include A, or B, or A and B, unless otherwise stated or impracticable. As a second example, if it is stated that a database can include A, B, or C, then the database can include A, or B, or C, or A and B, or A and C, or B and C, or A, B, and C, unless otherwise stated or impracticable.

[0027] In the foregoing specification, embodiments have been described with reference to numerous specific details that may vary from implementation to implementation. Certain adjustments and modifications can be made to the described embodiments. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims. Additionally, the order of steps depicted in the figures is for illustrative purposes only and is not intended to limit the scope to any particular order of steps. Thus, one of ordinary skill in the art will recognize that steps can be performed in different orders while still performing the same method.

[0028] The drawings and specification disclose illustrative embodiments. However, many variations and modifications to these embodiments are possible. Thus, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. a conversion circuit configured to convert a first voltage to a second voltage having a voltage difference from the first voltage based on a control input; a driver circuit coupled to the converter circuit and configured to receive the second voltage and generate an output signal based on the second voltage; a control circuit connected to the drive circuit and configured to control the brightness of the LED based on the output signal; An LED driving system comprising:

2. 2. The LED driving system of claim 1, wherein the variation range of the voltage difference is quantized by the digital value of the control input.

3. 3. The LED driving system of claim 2, wherein when the variation range is quantized by 8 bits, the variation range is divided into 256 levels, when the variation range is quantized by 10 bits, the variation range is divided into 1024 levels, and when the variation range is quantized by 12 bits, the variation range is divided into 4096 levels.

4. 4. The LED driving system of claim 1, wherein the driving circuit is connected to receive an input signal, and the output signal is generated based on the input signal and the second voltage.

5. 5. The LED driving system of claim 4, wherein the input signal is an input pulse width modulation (PWM) signal and the output signal is an output PWM signal.

6. 6. The LED driving system of claim 5, wherein the output PWM signal includes a high level at the first voltage and a low level at the second voltage during a pulse cycle.

7. 7. The LED driving system according to claim 5, wherein the duty cycle of the output PWM signal is adjustable within a pulse cycle.

8. 8. The LED driving system of claim 1, wherein the control circuit includes a metal-oxide-semiconductor (MOS) transistor, a source of the MOS transistor connected to receive the first voltage, a gate of the MOS transistor connected to an output of the driving circuit, and a drain of the MOS transistor connected to the LED.

9. 9. The LED driving system of claim 8, wherein the voltage difference between the first voltage and the second voltage is equal to the voltage difference between the source and the gate of the MOS transistor.

10. 10. The LED driving system of claim 8 or 9, wherein the brightness of the LED is controlled based on the current output from the drain.

11. The LED driving system according to any one of claims 1 to 10, wherein the LED is one of a white LED, a red LED, or a blue LED.

12. converting a first voltage to a second voltage having a voltage difference from the first voltage based on a control input; generating an output signal based on the second voltage; controlling the brightness of the LED based on the output signal; An LED driving method comprising:

13. after converting the first voltage to the second voltage based on a control input; quantizing the range of variation of the voltage difference based on the digital value of the control input; The method of claim 12 further comprising:

14. 14. The method of claim 13, wherein when the variation range of the voltage difference is quantized by 8 bits, the variation range is divided into 256 levels, when the variation range is quantized by 10 bits, the variation range is divided into 1024 levels, and when the variation range is quantized by 12 bits, the variation range is divided into 4096 levels.

15. Generating the output signal based on the second voltage includes: generating the output signal based on the second voltage and an input signal; The method of any one of claims 12 to 14, further comprising:

16. 16. The method of claim 15, wherein the input signal is an input pulse width modulated (PWM) signal and the output signal is an output PWM signal.

17. 17. The method of claim 16, wherein the output PWM signal includes a high level at the first voltage and a low level at the second voltage during a pulse cycle.

18. 18. The method of claim 16 or 17, wherein the duty cycle of the output PWM signal is adjustable within a pulse cycle.

19. After generating the output signal based on the second voltage, the method further comprises: controlling the current of the LED based on the output signal; further comprising controlling the brightness of the LED based on the output signal controlling the brightness of the LED based on the current; further comprising: The method according to any one of claims 12 to 18.

20. 20. The method of claim 19, wherein the brightness of the LED is positively correlated with the current.

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