Light emitting diode driving device and method for generating driving signal therefor

Abstract

A light-emitting diode driving device using (M+N) bit control signals may be configured to include: a sigma-delta modulation unit that receives the M bit control signals and generates a 1 bit modulation signal; a first summing unit that sums the N1 bit control signals among the N bit control signals and the modulation signal to generate a first summing signal; and a driving unit that receives the first summing signal and generates the driving signal.

Description

Technology Field

[0001] The embodiments disclosed in this specification relate to a light-emitting diode driving device and a method for generating the driving signal thereof. Background Technology

[0002] Sigma-delta modulation can be used to convert a digital signal into a high-frequency 1-bit stream.

[0003] Korean Patent Publication No. 10-2009-0040772 (hereinafter referred to as the 'prior art') discloses a lighting control device using digital sigma delta.

[0004] However, if the brightness of lighting such as LEDs is controlled only by the pulse width of the output of the sigma-delta modulator (200-1 to 200-n) as in the prior art, there is a limit to the resolution of the brightness of lighting such as LEDs, and flicker is likely to occur. In order to increase the resolution of the brightness of lighting and reduce flicker using only the output of the sigma-delta modulator (200-1 to 200-n), it is necessary to increase the frequency of the reference clock used in the sigma-delta modulator (200-1 to 200-n). However, if the frequency of the reference clock is increased, the error in the accuracy of the output of the sigma-delta modulator (200-1 to 200-n) increases.

[0005] In addition, the peak-to-peak level of the amplitude of the pulses output to the LED driver (300-1 to 300-n) is high, so the EMI (Electro Magnetic Interference) is high. The problem to be solved

[0006] The embodiments disclosed in this specification are embodiments intended to solve the technical problems described above, and the purpose is to provide a light-emitting diode driving device capable of achieving high resolution, low flicker, and low EMI (Electro Magnetic Interference) while adopting a sigma-delta modulation scheme, and a method for generating the driving signal said device. means of solving the problem

[0007] A light-emitting diode driving device using a (M+N) bit control signal according to a first embodiment and a second embodiment includes: a sigma-delta modulation unit that receives the M bit control signal and generates a 1 bit modulation signal; a first summing unit that sums the N1 bit control signal among the N bit control signals and the modulation signal to generate a first summing signal; and a driving unit that receives the first summing signal and generates a driving signal.

[0008] The above M is a natural number greater than or equal to 2, the above N1 is a natural number greater than or equal to 1, and the above N is a natural number greater than or equal to N1.

[0009] In addition, the driving signal of the light-emitting diode driving device according to the first and second embodiments corresponds to a signal obtained by summing a reference level signal determined by the N-bit control signal and a pulse activation frequency signal determined by the M-bit control signal.

[0011] The driving unit of the light-emitting diode driving device according to the second embodiment comprises: a first decoder that decodes the first summing signal to generate a first thermometer code; a second decoder that decodes the N2 bits of the control signal among the N bits of the control signal to generate a second thermometer code; a first converter that converts the first thermometer code into an analog signal to generate a first analog signal; a second converter that converts the second thermometer code into an analog signal to generate a second analog signal; and a third summing unit that sums the first analog signal and the second analog signal to generate the driving signal.

[0012] The above N2 is a natural number greater than or equal to 1, and the above N has the same value as the sum of the above N1 and the above N2.

[0013] The driving unit of the light-emitting diode driving device according to the second embodiment generates the driving signal by summing the first analog signal, which is obtained by converting the first summing signal into an analog signal, and the second analog signal, which is obtained by converting the N2 bits of the control signal among the N bits of the control signal into an analog signal. Effects of the invention

[0014] According to the light-emitting diode driving device and the method for generating the driving signal thereof of the embodiments disclosed in this specification, high resolution, low flicker, and low EMI (Electro Magnetic Interference) can be achieved while adopting a sigma-delta modulation scheme. Brief explanation of the drawing

[0015] FIG. 1 is a configuration diagram of a light-emitting diode driving device according to a first embodiment. Figure 2 is an example of a waveform of a driving signal. FIG. 3 is a configuration diagram of a light-emitting diode driving device according to a second embodiment. FIG. 4 is a correspondence table between a binary code and a thermometer code according to one embodiment. Specific details for implementing the invention

[0016] Hereinafter, a light-emitting diode driving device and a method for generating a driving signal thereof according to embodiments of the present disclosure will be described in detail with reference to the attached drawings. It is understood that the following embodiments of the present disclosure are merely for the purpose of embodying the present disclosure and do not limit or restrict the scope of the rights of the present disclosure. Anything that can be easily inferred by a person skilled in the art to which the present disclosure pertains from the detailed description and embodiments of the present disclosure is interpreted as falling within the scope of the rights of the present disclosure.

[0018] Terms such as “…part,” “…unit,” etc., as used in this specification refer to a unit that processes at least one function or operation, which may be implemented in hardware using various components such as an application-specific integrated circuit (“ASIC”), implemented in software executed by a microprocessor or similar device, or implemented as a combination of hardware and software.

[0020] A light-emitting diode driving device (100, 200) according to embodiments of the present disclosure generates a driving signal (S_D) of a light-emitting diode using a (M+N) bit control signal (CON(M+N)). Among the (M+N) bits, the N bit control signal (CON(N)) is a higher bit than the M bit control signal (CON(M)), M is a natural number greater than or equal to 2, and N is a natural number greater than or equal to 1. The (M+N) bit control signal (CON(M+N)) corresponds to a signal that controls the brightness of the corresponding light-emitting diode.

[0022] When driving multiple light-emitting diodes, multiple light-emitting diode driving devices (100, 200) according to multiple embodiments of the present disclosure can be used in parallel, and a lighting device or display can be implemented by multiple light-emitting diodes.

[0024] FIG. 1 shows a configuration diagram of a light-emitting diode driving device (100) according to a first embodiment.

[0025] As can be seen from FIG. 1, the light-emitting diode driving device (100) according to the first embodiment is configured to include a sigma-delta modulation unit (110), a first summing unit (120), and a driving unit (130).

[0026] The sigma-delta modulation unit (110) receives an M-bit control signal (CON(M)) by means of a sigma-delta modulation method according to a reference clock (not shown) and generates a quantized 1-bit modulation signal. Similar to Pulse Width Modulation, the sigma-delta modulation unit (110) outputs a 1-bit modulation signal in the form of a bit stream by adjusting the pulse activation frequency according to the value of the M-bit control signal (CON(M)). That is, the higher the value of the M-bit control signal (CON(M)), the higher the frequency at which the pulse becomes high, and the lower the value of the M-bit control signal (CON(M)), the lower the frequency at which the pulse becomes high.

[0027] Specifically, the sigma-delta modulation unit (110) may be configured to include a quantizer (111), a feedback signal generator (112), and a second summer (113).

[0028] The quantizer (111) receives the second summing signal and generates a quantized 1-bit modulated signal.

[0029] In addition, the feedback signal generator (112) receives the lower M bit signal, excluding the quantized 1-bit modulation signal among the second summing signals from the quantizer (111), and generates a feedback signal. The feedback signal generator (112) receives Z from the modulation signal. -1 A feedback signal is generated by delaying the lower M bit signal by multiplying it. For example, the feedback signal generator (112) can generate a feedback signal by delaying the lower M bit signal by 1 reference clock.

[0030] The second summer (113) generates a second summer signal of (M+1) bits by summing an M-bit control signal (CON(M)) and a feedback signal. Since the second summer (113) continuously performs summing through the feedback loop, the M-bit control signal (CON(M)) is accumulated. That is, the second summer (113) accumulates the input digital signal, the M-bit control signal (CON(M)), through several stages and integrates it through the second summer (113).

[0032] The first summing unit (120) sums the N1-bit control signal among the N-bit control signals (CON(N)) and the modulation signal output from the sigma-delta modulation unit (110) to generate a first summing signal, which is a (N1+1)-bit signal. Here, all N bits become N1 bits, so N and N1 are identical.

[0033] The driving unit (130) receives a first summing signal and generates a driving signal (S_D). The driving unit (130) may include a decoder (not shown) that decodes an N1-bit binary digital signal to generate a thermometer code, and a converter (not shown) that receives the thermometer code and converts it into an analog signal. However, the driving unit (130) may receive the first summing signal and generate the driving signal (S_D) without a separate decoder.

[0035] Figure 2 shows an example of the waveform of the driving signal (S_D).

[0036] The driving signal (S_D) corresponds to a signal obtained by summing a reference level signal determined by an N-bit control signal (CON(N)) and a pulse activation frequency signal determined by an M-bit control signal (CON(M)).

[0037] That is, the driving signal (S_D) is a pulse of amplitude at the unit level of the N-bit control signal (CON(N)) from a reference level signal determined by the value of the N-bit control signal (CON(N)), and the activation frequency of the corresponding pulse is determined by the value of the M-bit control signal (CON(M)). Here, the unit level is the smallest difference value between the reference level signals.

[0039] FIG. 3 shows a configuration diagram of a light-emitting diode driving device (200) according to a second embodiment.

[0040] As can be seen from FIG. 3, the light-emitting diode driving device (200) according to the second embodiment is configured to include a sigma-delta modulation unit (210), a first summing unit (220), and a driving unit (230).

[0041] The configuration of the light-emitting diode driving device (200) according to the second embodiment, having the same name as the configuration of the light-emitting diode driving device (100) according to the first embodiment, has the same features unless otherwise described.

[0042] However, in the light-emitting diode driving device (200) according to the second embodiment, N is separated into N1 and N2. That is, N has a value equal to the sum of N1 and N2, and the N2 bit corresponds to a higher bit than the N1 bit. Here, N1 and N2 are natural numbers greater than or equal to 1.

[0043] The sigma-delta modulation unit (210) receives an M-bit control signal (CON(M)) by means of a sigma-delta modulation method according to a reference clock (not shown) and generates a quantized 1-bit modulation signal. Specifically, the sigma-delta modulation unit (210) may be configured to include a quantizer (211), a feedback signal generator (212), and a second summer (213).

[0044] The first summing unit (220) sums the N1 bit control signal and the modulation signal among the N bit control signals (CON(N)) to generate a first summing signal, which is a (N1+1) bit signal.

[0045] The driving unit (230) receives a first summing signal and generates a driving signal (S_D).

[0047] Below, the driving unit (230) of the light-emitting diode driving device (200) according to the second embodiment will be described in detail.

[0048] The driving unit (230) converts a first summing signal into an analog signal to generate a first analog signal, converts an N2 bit control signal among N bits of a control signal (CON(N)) into an analog signal to generate a second analog signal, and generates a driving signal (S_D) by summing the first analog signal and the second analog signal. N2 is a natural number greater than or equal to 1, and N has the same value as the sum of N1 and N2.

[0049] Specifically, the driving unit (230) may be configured to include a first decoder (231), a second decoder (232), a first converter (233), a second converter (234), and a third summer (235).

[0050] The first decoder (231) receives a first summing signal and decodes it to generate a first thermometer code. Additionally, the second decoder (232) receives an N2-bit control signal among the N-bit control signals (CON(N)) and decodes it to generate a second thermometer code. That is, the first decoder (231) and the second decoder (232) can each be implemented using a thermometer decoder and can generate a Gray code called a thermometer code.

[0051] The first converter (233) receives a first thermometer code and converts it into an analog signal to generate a first analog signal. Additionally, the second converter (234) receives a second thermometer code and converts it into an analog signal to generate a second analog signal. The first converter (233) and the second converter (234) output an analog current signal.

[0052] The third summer (235) generates a driving signal (S_D) by summing the first analog signal and the second analog signal. That is, the first converter (233) and the second converter (234) output analog current signals, and the third summer (235) sums the currents that are the outputs of the first converter (233) and the second converter (234).

[0053] The waveform of the driving signal (S_D) of the light-emitting diode driving device (200) according to the second embodiment can also be shown in the same form as FIG. 2.

[0055] The light-emitting diode driving device (100, 200) according to the first and second embodiments has a multi-bit sigma-delta structure, which is theoretically capable of realizing the best resolution relative to the operating speed and minimizing the current fluctuation range in the time domain, making it a structure that is very suitable for controlling lighting such as light-emitting diodes.

[0057] However, the light-emitting diode driving device (200) according to the second embodiment has the following features by further improving the multi-bit sigma-delta structure of the light-emitting diode driving device (100) according to the first embodiment.

[0058] In the multi-bit sigma-delta structure of the light-emitting diode driving device (100) according to the first embodiment, since +1 and +0 operate continuously alternately in the time domain, this part must have only a minimum current error (toggling, glitch) to guarantee the best image quality. For example, this issue can be resolved if the entire bit output from the first summing unit (110) in the light-emitting diode driving device (100) according to the first embodiment is processed into a thermometer code using a decoder. However, even if the entire bit is assumed to be 10 bits, 2 10 -1 = 1023 physical lines and a huge number of decodings are required.

[0059] However, in the light-emitting diode driving device (200) according to the second embodiment, a compromise between decoder size and performance can be found by separating the N-bit control signal (CON(N)) into N1 bits and N2 bits for processing, and processing each with a separate decoder (231, 232).

[0060] In a structure where an N-bit control signal (CON(N)) is separated into N1 bits and N2 bits, when performing a sigma-delta operation, a point may occur where the entire N2 bit is toggled. For example, assuming 0111(N2) + 1111(N1) + 1 or + 0 (sigma-delta modulator), a very bad point may occur as 1000,0000 <-> 0111 + 1111.

[0062] FIG. 4 shows a correspondence table between a binary code and a thermometer code according to one embodiment.

[0063] Binary codes have weights in powers of two, offering the advantage of allowing digital circuits to be implemented simply and compactly. However, because the changes between bits—that is, transitions—are very large, if these changes are transferred directly to analog circuits, they can have a significant adverse effect on the performance of the final output, potentially leading to image quality degradation. Nevertheless, in digital circuits, even with many transitions, there are no issues other than slight current consumption.

[0064] As can be seen from Fig. 4, a point occurs where four binary codes toggle simultaneously, such as between '0111' and '1000', and the current weight is 2 4 +2 2 +2 1 +1 = 31. A change in weight occurs.

[0065] In contrast, in a thermometer code, 1 bit carries the meaning of only 1 level. Therefore, it has a minimal weight change corresponding to the amount of data change, which is positive for the final output. However, for a thermometer code, the decoder size and the number of physical lines of thermometer bits are 2 n There is a disadvantage that it grows exponentially by a factor of two.

[0067] However, the toggle point shown in FIG. 4 is a singularity that occurs due to a carry operation in a digital control method, and this phenomenon does not occur if a third summer (235) that sums currents in analog, such as the light-emitting diode driving device (200) according to the second embodiment, is used. Therefore, by allocating an additional bit to N1 bits and summing the currents in the third summer (235), it is possible to improve the optimal decoder (231, 232) size and performance.

[0069] Below, a method for generating a driving signal (S_D) of a light-emitting diode according to the first embodiment will be described.

[0070] The method for generating a driving signal (S_D) of a light-emitting diode according to the first embodiment is implemented by the light-emitting diode driving device (100) according to the first embodiment described above, so it is obvious that it includes all features of the light-emitting diode driving device (100) according to the first embodiment without separate explanation.

[0071] A method for generating a driving signal (S_D) of a light-emitting diode according to the first embodiment generates the driving signal (S_D) of the light-emitting diode using a control signal (CON(M+N)) of (M+N) bits.

[0072] Specifically, a method for generating a driving signal (S_D) of a light-emitting diode according to a first embodiment comprises: receiving an M-bit control signal (CON(M)) and generating a 1-bit modulation signal (S110); summing the N1-bit control signal and the modulation signal among an N-bit control signal (CON(N)) to generate a first summed signal (S120); and receiving the first summed signal and generating a driving signal (S_D) (S130).

[0073] M is a natural number greater than or equal to 2, N1 is a natural number greater than or equal to 1, and N has the same value as N1.

[0074] Specifically, step S110 includes: receiving a second summing signal and generating a 1-bit modulation signal (S111); receiving a lower M-bit signal other than the 1-bit modulation signal among the second summing signals and generating a feedback signal (S112); and summing an M-bit control signal (CON(M)) and the feedback signal to generate a second summing signal (S113).

[0075] The driving signal (S_D) corresponds to a signal obtained by summing a reference level signal determined by an N-bit control signal (CON(N)) and a pulse activation frequency signal determined by an M-bit control signal (CON(M)).

[0077] Below, a method for generating a driving signal (S_D) of a light-emitting diode according to a second embodiment will be described.

[0078] The method for generating a driving signal (S_D) of a light-emitting diode according to the second embodiment is implemented by the light-emitting diode driving device (200) according to the second embodiment described above, so it is obvious that it includes all features of the light-emitting diode driving device (200) according to the second embodiment without separate explanation.

[0079] A method for generating a driving signal (S_D) of a light-emitting diode according to a second embodiment generates the driving signal (S_D) of the light-emitting diode using a control signal (CON(M+N)) of (M+N) bits.

[0080] Specifically, the method for generating a driving signal (S_D) of a light-emitting diode according to the second embodiment includes: receiving an M-bit control signal (CON(M)) and generating a 1-bit modulation signal (S210); summing the N1-bit control signal and the modulation signal among an N-bit control signal (CON(N)) to generate a first summed signal (S220); and receiving the first summed signal and generating a driving signal (S_D) (S230).

[0081] M is a natural number greater than or equal to 2, N1 is a natural number greater than or equal to 1, and N is a natural number greater than or equal to N1.

[0082] Specifically, step S210 includes: receiving a second summing signal and generating a 1-bit modulation signal (S211); receiving a lower M-bit signal other than the 1-bit modulation signal among the second summing signals and generating a feedback signal (S212); and summing an M-bit control signal (CON(M)) and the feedback signal to generate a second summing signal (S213).

[0083] Specifically, the driving signal (S_D) corresponds to a signal obtained by summing a reference level signal determined by an N-bit control signal (CON(N)) and a pulse activation frequency signal determined by an M-bit control signal (CON(M)).

[0085] In step S230, a first sum signal is converted into an analog signal to generate a first analog signal, and an N2-bit control signal among the N-bit control signals (CON(N)) is converted into an analog signal to generate a second analog signal, and the first analog signal and the second analog signal are summed to generate a driving signal (S_D). N2 is a natural number greater than or equal to 1, and N has the same value as the sum of N1 and N2.

[0086] Specifically, step S230 includes: a step of receiving a first summing signal and decoding it to generate a first thermometer code (S231); a step of receiving and decoding an N2-bit control signal among an N-bit control signal (CON(N)) to generate a second thermometer code (S232); a step of receiving the first thermometer code and converting it into an analog signal to generate a first analog signal (S233); a step of receiving the second thermometer code and converting it into an analog signal to generate a second analog signal (S234); and a step of summing the first analog signal and the second analog signal to generate a driving signal (S_D) (S235).

[0088] As described above, according to the light-emitting diode driving device (100, 200) and the method for generating the driving signal of the embodiments disclosed in this specification, it can be seen that by using a multi-bit sigma-delta structure, the best resolution relative to the operating speed can be realized, thereby reducing flicker, and the current fluctuation range in the time domain can be minimized, so that the light-emitting diode can be driven at low EMI (Electro Magnetic Interference). Explanation of the symbols

[0089] 100, 200: Light Emitting Diode Driver 110, 210: Sigma-delta modulation section 120, 220: First summing section 130, 230: Driving unit 111, 211: Quantizer 112, 212: Feedback signal generator 113, 213: Second summer 231: 1st decoder 232: 2nd decoder 233 : 1st Converter 234 : 2nd Converter 235 : 3rd summer

Claims

Claim 1 A light-emitting diode driving device utilizing (M+N) bit control signals, comprising: a sigma-delta modulation unit that receives the M bit control signal and generates a 1 bit modulation signal having a unit level amplitude and a pulse activation frequency determined according to the value of the M bit control signal; a first summing unit that sums the N1 bit control signal among the N bit control signals and the modulation signal to generate a first summing signal; and a driving unit that receives the first summing signal and generates a driving signal; wherein the driving signal corresponds to a signal obtained by summing a reference level signal determined by the N bit control signal and the modulation signal, and the unit level corresponds to the degree of increase of the reference level signal when the value of the N bit control signal increases by 1, and M is a natural number greater than or equal to 2, N1 is a natural number greater than or equal to 1, and N is a natural number greater than or equal to N1. Claim 2 A light-emitting diode driving device according to claim 1, wherein the driving unit comprises: a first decoder that decodes the first summed signal to generate a first thermometer code; a second decoder that decodes the N2 bits of the control signal among the N bits of the control signal to generate a second thermometer code; a first converter that converts the first thermometer code into an analog signal to generate a first analog signal; and a second converter that converts the second thermometer code into an analog signal to generate a second analog signal; wherein N2 is a natural number greater than or equal to 1, and N has a value equal to the sum of N1 and N2. Claim 3 In paragraph 2, the driving unit further comprises a third summer that generates the driving signal by summing the first analog signal and the second analog signal. A light-emitting diode driving device. Claim 4 delete Claim 5 A light-emitting diode driving device according to claim 1, wherein the driving unit generates the driving signal by summing the first analog signal converted into an analog signal and the second analog signal converted into an analog signal of the N-bit control signal, wherein N2 is a natural number greater than or equal to 1 and N has the same value as the sum of N1 and N2. Claim 6 A method for generating a driving signal for a light-emitting diode using a (M+N) bit control signal, comprising: (a) receiving the M bit control signal and generating a 1-bit modulation signal having a unit level amplitude and determining the pulse activation frequency according to the value of the M bit control signal; (b) adding the N1 bit control signal among the N bit control signals and the modulation signal to generate a first sum signal; and (c) receiving the first sum signal and generating the driving signal; wherein the driving signal corresponds to a signal obtained by adding a reference level signal determined by the N bit control signal and the modulation signal, and the unit level corresponds to the degree of increase of the reference level signal when the value of the N bit control signal increases by 1, and M is a natural number greater than or equal to 2, N1 is a natural number greater than or equal to 1, and N is a natural number greater than or equal to N1. Claim 7 A method for generating a driving signal according to claim 6, wherein step (c) comprises: (c-1) decoding the first summed signal to generate a first thermometer code; (c-2) decoding the N2 bits of the control signal among the N bits of the control signal to generate a second thermometer code; (c-3) converting the first thermometer code into an analog signal to generate a first analog signal; and (c-4) converting the second thermometer code into an analog signal to generate a second analog signal; wherein N2 is a natural number greater than or equal to 1, and N has a value equal to the sum of N1 and N2. Claim 8 A method for generating a driving signal according to claim 7, wherein step (c) further comprises (c-5) a step of summing the first analog signal and the second analog signal to generate the driving signal. Claim 9 delete Claim 10 A method for generating a driving signal according to claim 6, wherein in step (c), the driving signal is generated by summing the first analog signal converted into an analog signal and the second analog signal converted into an analog signal of the N-bit control signal, wherein N2 is a natural number greater than or equal to 1 and N has the same value as the sum of N1 and N2.

Images