KR20230142314A - Led driving circuit and its driving method. - Google Patents

Abstract

This embodiment relates to an LED driving circuit that adjusts the PWM driving frequency when driving a light emitting diode, and relates to a technology for changing the PWM frequency of the LED driving circuit in response to the frequency of a PWM clock signal transmitted externally or internally.

Description

LED driving circuit and its driving method {LED DRIVING CIRCUIT AND ITS DRIVING METHOD.}

This embodiment relates to an LED driving circuit and a display device including the same.

As informatization progresses, various display devices that can visualize information are being developed. Liquid crystal displays (LCD), organic light emitting diode (OLED) displays, and plasma display panels (PDP) are representative examples of display devices that have been developed or are being developed recently. These display devices are evolving to be able to properly display high-resolution images.

In LED display technology, modular LED pixels can be arranged in the required number to form one large panel. Alternatively, in LED display technology, unit panels composed of multiple LED pixels can be arranged in the required number to form one large panel structure. In this way, in LED display technology, it is possible to easily implement a large display device by expanding and arranging LED pixels as necessary.

LED display devices have the advantage of not only enlarging but also diversifying panel sizes. In LED display technology, the horizontal and vertical sizes can be adjusted in various ways according to the appropriate arrangement of LED pixels.

Meanwhile, the LED display device supplies driving current to the LED as much as the ON section of the PWM (Pulse Width Modulation) signal. The ON section of the PWM signal can be determined according to the gray level value of the LED. When controlling the LED brightness by a PWM drive control signal, a flicker phenomenon occurs, and it is necessary to properly adjust the duty ratio and frequency of the PWM drive control signal.

In addition, if an external oscillator is used in the process of driving the LED, the PWM frequency (fpwm) change is limited, and if data (bit) that determines the PWM frequency (fpwm) is added to the externally transmitted protocol, the display resolution is reduced. Problems that diminish arise. For example, if the PWM frequency is doubled in 1 frame, additional data (1 bit) for PWM generation may be allocated, reducing the display resolution by ½ times.

Against this background, the purpose of this embodiment is to store an indicator indicating the multiplier frequency of the PWM frequency in a register of the LED driving circuit during the LED driving process, thereby determining the PWM frequency (fpwm) through external data communication. The present invention provides an LED driving circuit and an operating method that can control PWM operation through internal calculations without receiving data for adjustment.

In order to achieve the above-described object, in one aspect, the present embodiment includes a current channel electrically connected to a light-emitting diode and transmitting a driving current of the light-emitting diode; and a dimming control circuit that controls the driving current of the light emitting diode according to the duty ratio of a PWM (Pulse Width Modulation) driving control signal, wherein the dimming control circuit changes the rising or falling timing of the driving current of the current channel. It is possible to provide an LED driving circuit that does this.

In order to achieve the above-described object, in another aspect, the present embodiment includes a current channel electrically connected to the light-emitting diode and transmitting a driving current of the light-emitting diode; and a dimming control circuit that controls the driving current of the light emitting diode according to the duty ratio of the PWM (Pulse Width Modulation) driving control signal; The dimming control circuit may provide an LED driving circuit that changes the frequency of the driving current in response to the number of clocks of the PWM clock signal transmitted externally or internally.

In order to achieve the above-described object, in another aspect, this embodiment includes a microcontroller unit that is connected to a plurality of current channels and generates an LED driving control signal to control the operation of a light-emitting diode that transmits light; And an LED driving circuit that generates a PWM (Pulse Width Modulation) driving control signal based on the LED driving control signal and controls the operation timing of the driving current of the light emitting diode, wherein the LED driving circuit is configured every frame. An LED driving device that changes the operation timing of the light emitting diode can be provided.

As described above, according to this embodiment, the precision of LED driving can be improved through hybrid LED driving, PWM single driving, or PAM single driving in which PWM driving and PAM driving are distinguished based on the reference current, Noise generated during the LED driving process can be reduced.

According to this embodiment, during the LED driving process, an indicator indicating the multiplier frequency of the PWM frequency is stored in the register of the LED driving circuit, and data for adjusting the PWM frequency (fpwm) is transmitted through external data communication. By controlling the PWM operation through internal calculation without receiving the LED, the LED driving accuracy can be improved and the delay problem of data communication can be effectively solved.

1 is a configuration diagram of a display device according to this embodiment.
Figure 2 is a diagram explaining a method of driving a display device according to this embodiment.
Figure 3 is a diagram illustrating a method of supplying power for each channel of a light emitting diode according to this embodiment.
Figure 4 is a diagram illustrating how the LED driving circuit according to this embodiment controls the current of the light emitting diode.
Figure 5 is a block diagram of each operating element of the LED driving circuit according to this embodiment.
Figure 6 is a diagram explaining the switch operation of the LED driving circuit according to this embodiment.
Figure 7 is a configuration diagram of a switch circuit according to this embodiment.
Figure 8 is a method explaining a method of controlling the LED driving current according to this embodiment.
Figure 9 is a diagram explaining a communication protocol for local dimming of light emitting diodes according to this embodiment.
Figure 10 is a diagram illustrating a frequency multiple stored in a register according to this embodiment.
Figure 11 is a diagram explaining a method of adjusting the frequency of a PWM drive control signal according to this embodiment.
Figure 12 is a first example diagram illustrating a communication protocol according to this embodiment.
Figure 13 is a second example diagram illustrating a communication protocol according to this embodiment.
Figure 14 is a diagram illustrating the signal flow of the logic operation circuit according to this embodiment.

1 is a configuration diagram of a display device according to this embodiment.

Referring to FIG. 1, the display device 100 includes a system on chip (SOC) 110, a timing controller (T-CON) 120, a data driving circuit 130, and a display panel 140. ), a microcontroller unit (MCU: Micro Controller Unit) 150, an LED driving circuit 160, a backlight 170, etc.

The system-on-chip (SOC) 110 may be a circuit that performs the function of a central processing unit (CPU), such as an application processor (AP) in a mobile device, and also controls the operation of the internal electronic circuit of the display device. It may be a semiconductor chip, etc. for performing calculation and control operations. The system-on-chip 110 can control the timing controller 120, the microcontroller unit 150, etc., or can define internal operations by transmitting signals to each circuit.

The timing controller (T-CON) 120 may be a circuit that controls the operation timing of the data driving circuit 130, the LED driving circuit 160, etc. Additionally, the timing controller 120 can control the data driving circuit 130 to convert image data input from the outside and generate a data voltage corresponding to the grayscale value of the pixel of the display panel 140.

The data driving circuit 130 can control the operation of the pixel 141 through the data line DL by changing the size and waveform of the data voltage in response to the control signal transmitted by the timing controller 120. For example, the data driving circuit 130 can control the operation of the polarizer disposed in the pixel 141.

The display panel 140 may be an organic light emitting diode (OLED), a liquid crystal display (LCD), etc., but may have a structure capable of receiving light by the backlight 170. Mini-LED is a miniaturization of the size of the LED used in the LCD backlight to reduce the disadvantages of the existing LCD. It requires a smaller chip than the LED driving circuit for the operation of the existing LCD and requires a large number of chips. I do it.

One pixel (P) of the panel 140 forms subpixels such as red (R), green (G), and blue (B), and determines or changes the wavelength of light transmitted through a color filter (not shown). You can.

The microcontroller unit (MCU) 150 may be a device that transmits a control signal to the LED driving circuit 160 to control the driving timing, driving current, and driving voltage of the LED. The timing controller 120 and the microcontroller unit 150 may share some functions and, if necessary, may be implemented in an integrated form for effective data operation, but are not limited thereto.

The LED driving circuit 160 may be a device for controlling the operation of a plurality of LEDs disposed in the backlight. The LED driving circuit 160 controls the operation of a switch circuit (not shown) disposed therein, and can control the timing or intensity of the driving current transmitted to the LED. The LED driving circuit 160 changes the operation of the LED based on a control signal received from the microcontroller unit 150, or changes the operation of the LED based on a signal received from another LED driving circuit. You can. If necessary, the LED driving circuit 160 can change the operation of the LED based on an algorithm or information previously stored by an internal register (not shown).

The backlight 170 may be comprised of a plurality of LEDs arranged on a substrate, and may be formed integrally with the display panel 140 or separately as needed. LEDs arranged in the backlight 170 can be individually controlled for each channel according to the LED driving circuit 160.

A configuration including the panel 140, the LED driving circuit 160, and the backlight 170 can be defined as an LED driving device (not shown).

The term light emitting diode (LED) used in this specification is used interchangeably with LED, and the meaning may be the same.

Figure 2 is a diagram explaining a method of driving a display device according to this embodiment.

Referring to FIG. 2, the system-on-chip (SOC) 110 controls the driving of the display panel 140 or the driving of the light emitting diode (LED) by the timing controller 120 or the microcontroller unit 150. You can.

The timing controller 120 can determine the operation timing of the gate driving circuit (not shown), the data driving circuit 130, and the LED driving circuit 160, and the operation timing of each circuit is determined by a sync signal (SYNC) or a serial clock signal. It can be defined in response to all or part of the rising edge or falling edge of (SCLK).

The timing controller 120 can control the operation of the pixel (P) by the gate control signal (GCS) transmitted to the gate driving circuit (not shown) and the data control signal (DCS) transmitted to the data driving circuit 130. there is. The operation of the liquid crystal polarizer changes in response to changes in the voltage of the transistor disposed on the display panel 140, and thus the ratio of transmitted light can be appropriately controlled.

The microcontroller unit 150 can change the driving voltage or driving current transmitted to the light emitting diode (LED) by the LED control signal (LCS) transmitted to the LED driving circuit 160.

The timing controller 120 and the microcontroller unit 150 may be implemented with integrated circuit configurations, or may be defined as functionally separate individual circuit configurations as needed.

Figure 3 is a diagram illustrating a method of supplying power for each channel of a light emitting diode according to this embodiment.

Referring to Figure 3, the backlight 170 can receive a driving voltage (V_LED) to one end of the LED string by a switching mode power supply (SMPS: 180), and a current channel (CH1- The brightness of the light emitting diode (LED) can be determined by flowing the driving current (I_LED) through 12).

The switching mode power supply 180 can supply the same driving voltage (V_LED) or different driving voltages (V_LED1 to V_LED12) to the first LED group (171-1) to the twelfth LED group (171-12), and the LED driving circuit A row (not shown) can control the driving current (I_LED) flowing through each LED string by adjusting the voltage at the other end of each channel. The LED of the LED string can display an image with desired brightness by irradiating light to the display panel in response to the driving current (I_LED).

The same driving current (I_LED) may flow through each channel, but different driving currents (I_LED1 to I_LED12) may flow through each channel.

The microcontroller unit 150 can adjust the timing and size of the LED driving voltage (V_LED) supplied by the switching mode power supply 180.

The number and shape of LEDs and channels formed in the backlight 170 of FIG. 3 are intended to illustrate the driving voltage and driving current of the LED, and may include various numbers and shapes of LEDs without being limited thereto.

Figure 4 is a diagram illustrating how the LED driving circuit according to this embodiment controls the current of the light emitting diode.

Referring to FIG. 4, the LED driving circuit 160 is connected to one or more current channels to control the brightness of the light emitting diode (LED).

The LED driving circuit 160 receives the LED driving control signal (CS_LED) transmitted by the microcontroller unit 150 and controls the light transmitted to the display panel by adjusting the timing or intensity of the driving current of the light emitting diode (LED). You can. The LED driving circuit 160 may control the brightness of the light emitting diode (LED) by controlling the timing or intensity of the voltage applied to the channel.

The LED driving control signal (CS_LED) can define the operation timing of the internal circuit of the LED driving circuit 160, and drives the light emitting diode flowing in the channel (CH1) by changing the state of the internal transistor of the LED driving circuit 160. Current (I_LED) can be adjusted.

For example, the LED driving control signal (CS_LED) can control the turn-on and turn-off of a switch disposed inside the LED driving circuit 160, or control the intensity or direction of the current flowing in the transistor. .

The frequency of the LED driving control signal (CS_LED) can determine the frequency of the light emitting diode driving current (I_LED) controlled by the LED driving circuit 160. For example, when the LED driving control signal (CL_LED) is a PWM driving control signal, the LED driving circuit 160 controls the driving timing of the channel current formed in the LED string - for example, the driving current of the light emitting diode (I_LED). can be adjusted. The driving current (I_LED) of the light-emitting diode may repeatedly rise or fall in response to the high-state and low-state signals of the PWM driving control signal, and this relationship can be adjusted to the frequency or timing of the PWM driving control signal to determine the driving current of the light-emitting diode. It can be understood that the frequency or timing of the driving current (I_LED) is changed.

Figure 5 is a block diagram of each operating element of the LED driving circuit according to this embodiment.

Referring to FIG. 5, the LED driving circuit 160 may include a digital logic operation circuit 161, a digital-analog converter 162, a dimming control circuit 163, a register 169, etc.

The digital logic operation circuit 161 can generate a PAM drive control signal or a PWM drive control signal by calculating a digital serial clock signal (SCLK) received from the microcontroller unit 150. The digital logic operation circuit 161 may be integrated with the PWM signal generation circuit (not shown) or may be implemented as a separate circuit, but is not limited thereto.

The digital logic operation circuit 161 operates on all or part of the serial clock signal (SCLK), local dimming signal (L/D), PWM clock signal (PWMCLK), vertical synchronization signal (VSYNC), and enable signal (SPI_EN). Logical operations - for example, AND logical operations, OR logical operations, etc. - can be performed and output. Here, the PWM clock signal (PWMCLK) can be replaced with an internal serial clock signal (SCLK) or an external vertical synchronization signal (VSYNC).

Additionally, the digital logic operation circuit 161 can control the operating duty ratio or operating frequency of the dimming control circuit 163 by generating a PWM driving control signal (CS_PWM).

The digital-analog converter 162 can convert the digital signal transmitted from the digital logic operation circuit 161 into an analog signal and transmit it to the dimming control circuit 163.

The dimming control circuit 163 can adjust the duty ratio or frequency of the PWM drive control signal at a current below the reference current value, and keep the duty ratio or frequency of the PWM drive control signal constant at a current exceeding the reference current value. . The deging control circuit 163 can define various hybrid driving conditions by utilizing a plurality of reference current values stored in the register 169.

The dimming control circuit 163 can control the operation of the LED based on the duty ratio or frequency of the PWM drive control signal. The dimming control circuit 163 can change the timing or frequency of the driving current in response to the number of clocks of the PWM clock signal transmitted externally or internally. Additionally, the dimming control circuit 163 can control the frequency of the driving current of the light emitting diode to correspond to the frequency of the PWM clock signal generated by the internal oscillator. Additionally, the dimming control circuit 163 can control the driving current of the light emitting diode based on the number of PWM clock signals transmitted from the outside.

The dimming control circuit 163 monitors the timing of the rise or fall of the driving current of the light-emitting diode in the current channel and can change the timing of the rise or fall of the driving current of the light-emitting diode. The timing of the rise or fall of the driving current of the light emitting diode may correspond to the timing and period of the PWM drive control signal or PWM clock signal determined by the digital logic operation circuit 161.

The frequency of the driving current of the light emitting diode can be defined by the operation timing of the rising, falling, and inflection of the driving current of the light emitting diode of the current channel, and this can be determined in conjunction with the frequency of the PWM driving control signal. For example, the frequency of the driving current of the light-emitting diode may be defined based on the number of rises or falls of the driving current for each frame, or the frequency of the driving current of the light-emitting diode may be defined based on the number of rises or falls within a preset time period. there is.

The register 169 stores information about the operating mode of the LED driving circuit 160 - for example, PWM driving, PAM driving, hybrid driving, etc. - or stores information about the current channel of the LED driving circuit 160. It may be a memory-type circuit that stores information, driving delay or deviation of the LED driving circuit 160, etc.

The register 169 is information about the frequency of the PWM drive control signal (CS_PWM) generated by the digital logic operation circuit 161, and may include an indicator indicating the multiplier frequency. In the register 169, an indicator indicating an integer multiple of the PWM clock signal (PWMCLK) - for example, 1, 2, 4, 8, 16, 32, 64, etc. - may be stored in the form of a parameter defined as an integer. , an indicator can be output based on the data of the frequency selection signal transmitted through the communication protocol.

The register 169 can store a first indicator and a second indicator that determine the frequency of the PWM drive control signal, and the digital logic operation circuit 161 uses the first indicator or the second indicator stored in the register 169 as a PWM clock. The frequency of the PWM drive control signal can be determined and changed by multiplying it by the frequency of the signal.

The microcontroller unit 150 or timing controller 120 may generate an LED drive control signal and transmit it to the LED drive circuit 160, and the LED drive control signal may not include data that determines the frequency of the PWM drive control signal. You can. Instead of determining the PWM driving frequency outside of the LED driving circuit 160, an indicator of the PWM frequency is stored in a register inside the LED driving circuit 160, and the PWM operation is controlled through internal calculation, which is necessary in the data communication process. You can save data quota. By utilizing the data bits saved through this, additional bits can be allocated for other data transmission.

Additionally, the flicker phenomenon occurring in the panel can be improved by the LED driving circuit 160 changing the PWM driving frequency in the above manner.

Figure 6 is a diagram explaining the switch operation of the LED driving circuit according to this embodiment.

Referring to FIG. 6, the LED driving circuit 160 may further include a first switch circuit 164 and a second switch circuit 165.

The LED driving circuit 160 is electrically connected to a light emitting diode (LED) and may include one or more current channels (CH) that transmit a driving current of the light emitting diode. For example, the first driving current (I_LED1) can be individually generated and controlled through the first channel (CH1) and the second driving current (I_LED2) can be individually generated and controlled through the second channel (CH2).

The current channel (CH) may be connected in series with a light emitting diode (LED), the first switch circuit 164, and the second switch circuit 165. The driving voltage (V_LED) or driving current (I_LED) of the light emitting diode (LED) can be changed by the operation of the first and second switch circuits 164 and 165.

The dimming control circuit 163 receives the PWM drive control signal (CS_PWM) or the PAM drive control signal (CS_PAM) from the microcontroller unit 150, and operates the operation timing or Operation states can be defined. The current channel (CH) may include a plurality of channels, and the dimming control circuit 163 may individually control the LED driving current of the plurality of channels in response to the PWM driving control signal or the PAM driving control signal.

The dimming control circuit 163 controls the operation section of the first switch circuit 164 and the second switch circuit 165 based on the driving current value of the light emitting diode (LED) or the output current value of the digital-to-analog converter (DAC). You can set the operation section of .

The dimming control circuit 163 adjusts the switching timing by outputting a PWM drive control signal to the first switch circuit 164 in the current range between the reference current value and below and 0, and exceeds the reference current value and between the maximum current value. The intensity of the driving current can be adjusted by outputting the PAM driving control signal to the second switch circuit 165 in the current range.

The first switch circuit 164 can adjust the size of the driving current of the light emitting diode according to the duty ratio or frequency of the PWM (Pulse Width Modulation) signal. For example, as the duty ratio of the PWM driving control signal decreases, the time period of the current passed through the first switch circuit 164 decreases, which can reduce the driving current (I_LED) of the light emitting diode. Depending on the turn-on timing and turn-off timing of the first switch circuit 164, the driving current of the light-emitting diode may increase and decrease at a constant cycle, and this can be averaged to define the average intensity of the driving current of the light-emitting diode.

The second switch circuit 165 can adjust the size of the driving current of the light emitting diode by receiving a PAM (Pulse Amplitude Modulation) signal. The second switch circuit 165 may receive a PAM driving control signal having an analog signal waveform or a PAM driving control signal having a digital signal waveform.

The LED drive circuit 160 individually adjusts the PWM drive control signal and the PAM drive control signal transmitted to a plurality of current channels, and controls the PWM control data for controlling the PWM drive control signal and the PAM control signal for controlling the PAM drive control signal. Data can be delivered in the same time period. In this case, the communication protocol can be simplified by simultaneously receiving PWM control data and PAM control data.

According to another embodiment of the present invention, a display device includes a plurality of light emitting diodes disposed on a panel, a switch circuit (SW) for controlling the current supplied to the light emitting diodes, and a switch circuit for controlling the turn-on and turn-off periods of the switch circuit. An LED driving circuit 160 that changes the operating current of the light emitting diode by receiving a PWM driving control signal and a PWM driving control signal that adjusts the current intensity of the switch circuit, and a hybrid in which the LED driving circuit is a mixture of PWM driving and PAM driving. It may include a microcontroller unit 150 that transmits an LED driving control signal to the LED driving circuit to perform driving.

The switch circuit (SW) is a first switch circuit 164 that changes the timing for turning on and off according to the duty ratio of the PWM driving control signal, and the driving current of the light emitting diode according to the PAM driving control signal. It may include a second switch circuit 165 that adjusts the size.

The microcontroller unit 150 can determine the PWM driving timing and PAM driving timing by time-dividing the LED driving control signal of the N-bit code (N is a natural number of 2 or more). The LED drive control signal may be a control signal that selects one of a PWM drive mode that performs PWM drive alone, a PAM drive mode that performs PAM drive alone, and a hybrid drive mode that performs a mixture of PWM drive and PAM drive. .

The LED driving circuit 160 includes a plurality of integrated circuits electrically connected to a plurality of current channels, and the plurality of integrated circuits are connected in a series structure to perform serial peripheral interface (SPI) communication so that the driving mode is sequentially updated. You can. The driving modes of a plurality of integrated circuits or a plurality of current channels are individually defined, and the driving mode may change depending on one frame or some frames.

The LED driving circuit 160 includes a plurality of current channels, and the LED driving control signal may be a signal that compensates for current deviation by individually adjusting the driving current of each current channel.

Figure 7 is a configuration diagram of a switch circuit according to this embodiment.

Referring to FIG. 7, the switch circuit (SW) may include a first switch circuit 164 and a second switch circuit 165.

The first switch circuit 164 may include a field effect transistor (T1) whose terminal is electrically connected to a current channel, and the transistor (T1) may receive a PWM driving control signal through a gate terminal. One terminal of the transistor (T1) may be connected to the current channel of the LED string, and the other terminal may be connected to the transistor (T2).

The first switch circuit 164 can change the state of the supply current (I_LED) of the light emitting diode (LED) by repeating the turn-on state or turn-off state in response to the duty ratio or frequency of the PWM driving control signal. .

The second switch circuit 165 is an operational amplifier (AMP) that receives the PAM driving control signal through a first input terminal (for example, a plus input terminal), and an electric field effect that receives the output signal of the operational amplifier through the gate terminal. It may include a transistor (T2) and a resistor (R) connected to the drain terminal of the transistor (T2).

Additionally, the operational amplifier of the second switch circuit 165 may receive the drain terminal voltage of the transistor T2 as a feedback voltage through a second input terminal (for example, a minus input terminal), and may receive the voltage of the drain terminal of the transistor T2 as a feedback voltage through a second input terminal - for example, a minus input terminal. The output signal can be determined by comparing the voltage deviation of the input terminal.

Figure 8 is a method explaining a method of controlling the LED driving current according to this embodiment.

Referring to FIG. 8, the method of controlling the LED driving current is as in the first case (CASE 1), defining the turn-on period (S1) corresponding to a certain period (S2) as a duty ratio and generating a PWM driving control signal to control the LED. You can control the brightness.

As in the second case (CASE 2), the intensity of the driving current can be increased by increasing the magnitude of the current from the first intensity (H1) to the second intensity (H2). In this case, the brightness of the LED can be changed to become brighter by increasing the signal strength while maintaining the same duty ratio compared to the first case (CASE 1).

In the third case (CASE 3), the brightness of the LED can be changed by changing the duty ratio while maintaining the first intensity (H1). The amount of current supplied to the LED can be increased according to the changed turn-on state period (S1'). By supplying current to the LED for a long period of time, the time and size of the current staying in the LED can be increased.

Figure 9 is a diagram explaining a communication protocol for local dimming of light emitting diodes according to this embodiment.

Referring to FIG. 9, a communication protocol for local dimming of a light emitting diode may include frequency selection data, local dimming data, etc.

Frequency selection data (M0 to M3) is a data set that selects the frequency for PWM driving, and can be defined by the time period that forms the period of the frequency clock signal. Frequency selection data can be transmitted and received first before transmitting and receiving local dimming data, but local dimming data can be transmitted and received and frequency selection data can be transmitted and received later.

The local dimming data (D0 to D11) may be data about the PAM driving range (D0 to D5) and data about the PWM driving range (D6 to D11). The PAM driving range can be defined for some of the 12-bit data, and the PWM driving range can be defined for the rest. Information on current deviation for PAM driving may be further included, and information on period, turn-on period, and turn-off period may be further included for PWM driving.

Figure 10 is a diagram illustrating a frequency multiple stored in a register according to this embodiment.

Referring to FIG. 10, a plurality of indicator data may be stored in the register.

The LED driving circuit 160 receives a command signal for changing the PWM frequency through an external serial interface, and uses the set PWM frequency as an external PWM clock signal (PWMCLK) or an internal PWM clock signal (PWMCLK) to control the operation delay and operation delay for each channel. The final PWM waveform can be created by reflecting the PWM duty ratio and frequency information.

In the communication protocol, when the bit allocated to frequency selection among local dimming data is 4 bits, values from 0 to 15 can be transmitted, and accordingly, indicator data corresponding to values from 0 to 15 can be stored in the register.

For example, from 0 to 6, it can have multiple values of 1, 2, 4, 8, 16, 32, and 64, and the digital logic operation circuit 161 or dimming control circuit 163 uses the reference PWM clock signal. The frequency of the final PWM drive control signal can be calculated by multiplying by the frequency multiple of .

Through this, the frequency of the PWM drive control signal can be implemented as a multiple of the internal frame rate.

For example, from 7 to 15, the default value can be a multiple of 1.

A register can store a plurality of indicators defined as natural numbers in the form of a lookup table (LUT), and a digital logic operation circuit can obtain indicators from the register. In this way, the digital logic operation circuit can change the frequency of the PWM drive control signal by multiplying the frequency of the PWM clock signal (PWMCLK) with an indicator indicating the multiplier frequency of the PWM drive control signal. .

Figure 10 is an example, and the technical idea of this embodiment is not limited thereto.

Figure 11 is a diagram explaining a method of adjusting the frequency of a PWM drive control signal according to this embodiment.

Referring to FIG. 11, the PWM drive control signal may be output in synchronization with a horizontal synchronization signal (VSYNC) transmitted externally. In this way, the timing of the driving current and driving voltage of the light emitting diode can be synchronized to the horizontal synchronization signal (VSYNC) transmitted externally.

The PWM clock signal (PWM_CLK) may be an internal or externally supplied signal, and may be a reference signal for changing the frequency of PWM frequency driving.

The PWM driving control signal supplied to the dimming control circuit 163 may be defined as a first output signal (PWM_OUT1), a second output signal (PWM_OUT2), a third output signal (PWM_OUT3), etc.

The first output signal may have a frequency 4 times that of the PWM clock signal and may have a period 1/4 times the period.

The second output signal may have a frequency twice that of the PWM clock signal and a period 1/2 times the period.

It can have a period that is 1 times the period of the PWM clock signal and can have a period that is 1 times the period.

In this way, with the same duty ratio, it is possible to effectively remove the flicker phenomenon while maintaining the same brightness by changing the frequency and cycle of PWM driving. In particular, by determining PWM driving in response to the state of the PWM clock signal transmitted internally or externally, it is possible to solve problems such as delay problems that occur in the LED driving process and problems of non-synchronization of the operation timing of multiple LEDs.

The digital logic operation circuit 161 can count the number of externally transmitted PWM clocks (PWMCLK) and perform edge counting in conjunction with the resolution required to drive the LED. If the required data is 4096 data, only the rising edge can be counted, and if the required data is 2048 data, a double edge count can be performed that counts both the rising edge and the falling edge.

In addition, the frequency of the PWM driving control signal of the LED driving circuit can be changed using the internal oscillator. In this case, the frequency of the internal PWM clock signal and the frequency of the PWM drive control signal for driving the LED can be linked.

Figure 12 is a first example diagram illustrating a communication protocol according to this embodiment.

Referring to FIG. 12, the communication protocol may include a command byte, a data byte, a dummy byte, etc.

The Command Byte may include an ID Flag bit, an ID Assign bit, a Command (CMD) bit, etc.

Command Byte is data that determines the operating state of the LED driving circuit, and may be data that selects the LED driving circuit to be operated or sets a current channel in the LED driving circuit. The command byte may set a certain value - for example, a value between 0 and 15 - with 4 bits to determine the PWM driving frequency of the LED driving circuit, but is not limited thereto.

Data Byte is data for determining the driving current operation for each channel of a plurality of LED driving circuits, and may be data for PWM driving and PAM driving of the channel.

For example, channel data in a data byte can transmit data about reference current values for PWM driving and PAM driving, or data about operating conditions for PWM driving and PAM driving defined for each channel can be individually transmitted. .

Hybrid drive mode data can be transmitted at once by transmitting PWM drive data and PAM drive data in the same time period for each channel, and a dummy section can be included to fill the time allocated to each channel.

Figure 13 is a second example diagram illustrating a communication protocol according to this embodiment.

Referring to FIG. 13, the communication protocol for each channel can transmit the PWM data section and the PAM data section by time division.

The protocol may be divided so that PWM data is transmitted and received for part of the data allocated to one channel, and PAM data is transmitted and received for the tree.

Figure 14 is a diagram illustrating the signal flow of the logic operation circuit according to this embodiment.

Referring to FIG. 14, the LED driving circuit 260 may include a digital logic operation circuit 261, a dimming control circuit 263, and a register 269.

The digital logic operation circuit 261 can determine the duty ratio or frequency of the PWM drive control signal (CS_PWM) and transmit it to the dimming control circuit 263. The dimming control circuit 263 can adjust the supply timing, rising or falling timing, frequency, etc. of the driving current of the light emitting diode according to the duty ratio or frequency of the PWM driving control signal (CS_PWM).

The digital logic operation circuit 261 generates a PWM drive control signal at an integer multiple of the frequency of the PWM clock signal (PWMCLK) based on an indicator indicating the multiplier frequency of the PWM drive control signal stored in the register 269. The duty ratio of (CS_PWM) can be changed. More effective logical operations are possible by changing the frequency of the PWM drive control signal by multiplying the frequency of the indicator and the PWM clock signal (PWMCLK). In this process, a frequency multiplier, etc. can be used. The frequency of PWM driving can be determined and changed by inputting an indicator stored in a register into a circuit that outputs a multiple of the input frequency.

The digital logic operation circuit 261 can synchronize the PWM driving control signal with the horizontal synchronization signal (VSYNC) transmitted from the timing controller through the input terminal 267 and output it. Alternatively, the digital logic operation circuit 261 may output the PWM driving control signal in synchronization with the internal PWM clock signal generated by the internal oscillator 268 - for example, the serial clock signal (SCLK).

The digital logic operation circuit 261 can determine the frequency of the PWM drive control signal by counting the number of PWM clock signals transmitted from the outside, and the dimming control circuit 263 controls the frequency of the light emitting diode in response to the frequency of the PWM drive control signal. The frequency of the driving current can be adjusted.

When the digital logic operation circuit 261 receives an external PWM clock signal with a fixed number of clocks per cycle, the rising edge or falling edge of the PWM clock signal can be counted, but the rising edge or falling edge of the PWM clock signal can be counted as needed. By counting both edges and falling edges, the frequency of the PWM drive control signal or the resolution of the display can be appropriately varied.

The digital logic operation circuit 261 can match the frequency of the PWM driving control signal with the frequency of the internal PWM clock signal generated by the internal oscillator 268.

The dimming control circuit 263 can control the supply timing of the driving current of the light emitting diode according to the duty ratio or frequency of the PWM driving control signal. Here, the frequency of the PWM driving control signal can determine the on-off timing for PWM operation.

The dimming control circuit 263 can adjust the driving current control timing to compensate for inter-channel delay of the plurality of current channels. The dimming control circuit 263 receives information about the PWM clock signal transmitted internally or the PWM clock signal transmitted externally to adjust the PWM operating frequency and at the same time compensate for the delay between channels. If an external PWM clock signal with a fixed number of clocks per cycle is received, LED dimming control can be performed by counting the number of clocks and determining the frequency of the PWM clock signal, and inside the LED driving circuit When receiving a PWM clock signal with a variable number of clocks from an oscillator, etc., a multiple of the frame rate can be linked to the PWM frequency for dimming control.

The register 269 may provide data stored in the digital logic operation circuit 261 or the dimming control circuit 263.

The register 259 can store a value that determines the frequency of the PWM driving control signal, and can store a plurality of parameters defined as natural numbers in the form of a look-up table (LUT).

The LED driving circuit 260 includes a first switch circuit (not shown) that adjusts the size of the driving current of the light-emitting diode according to the duty ratio of the PWM driving control signal, and a PAM driving control signal to adjust the size of the driving current of the light-emitting diode. It may include a second switch circuit (not shown) that controls . The first switch circuit (not shown) is a field effect (MOSFET) transistor (T1) whose terminal is electrically connected to a current channel, and can receive a PWM driving control signal through the gate terminal.

The dimming control circuit 263 can individually control the driving current of the light emitting diodes of the plurality of current channels in response to the PWM driving control signal or the PAM driving control signal.

The dimming control circuit 263 may determine the PWM operation of the first switch circuit or the PAM operation of the second switch circuit for each frame and update the frequency of the PWM driving control signal for the PWM operation.

The LED driving circuit 260 further includes a multiplexer 266 that selects one of the horizontal synchronization signal (VSYNC) transmitted from the timing controller and the internal clock signal generated by the internal oscillator and transmits it to the digital logic operation circuit 261. can do.

The multiplexer 266 determines the type of signal supplied to the digital logic operation circuit 261, and can select a PWM clock signal supplied externally or a PWM clock signal supplied internally. Through this, the operation type of the digital logic operation circuit 261 can be determined depending on the type of PWM clock signal. If the PWM clock signal is supplied externally, it may be a signal with a fixed number of clocks without an external oscillator. In this case, PWM operation control can be performed by counting the number of clocks. If the PWM clock signal is supplied internally, PWM operation control can be performed by multiplying the internal frame rate by a multiple.

The digital logic operation circuit 261 can perform double edge counting, which counts both the rising edge and the falling edge of the PWM clock signal.

The LED driving circuit 260 can change the edge counting method of the PWM clock signal in conjunction with the resolution or internal situation of the display device, and can optimize the resolution of the display device by changing the driving timing of the light emitting diode.

Claims (20)

A current channel electrically connected to the light emitting diode and transmitting a driving current of the light emitting diode; and
A dimming control circuit that controls the driving current of the light emitting diode according to the duty ratio of a PWM (Pulse Width Modulation) driving control signal,
The dimming control circuit is an LED driving circuit that changes the timing of the rise or fall of the driving current of the current channel. According to claim 1,
It includes a digital logic operation circuit that calculates the duty ratio of the PWM drive control signal to determine the timing of the rise or fall of the drive current of the light emitting diode,
The digital logic operation circuit changes the frequency of the PWM drive control signal by multiplying the frequency of the PWM clock signal (PWMCLK) with an indicator indicating the multiplier frequency of the PWM drive control signal, and An LED driving circuit that controls the rising or falling cycle of the driving current of a light emitting diode. According to claim 1,
It further includes a register for storing an indicator indicating a multiplier frequency of the PWM drive control signal,
The register stores a plurality of indicators defined as natural numbers in the form of a look-up table (LUT), and the digital logic operation circuit obtains the indicators from the register. According to claim 1,
The digital logic operation circuit outputs the PWM drive control signal in synchronization with the horizontal synchronization signal (VSYNC) transmitted from the timing controller, and synchronizes the timing of the driving current of the light emitting diode to the horizontal synchronization signal. . According to claim 1,
The LED driving circuit includes a first switch circuit that adjusts the size of the driving current of the light emitting diode according to the duty ratio of the PWM driving control signal; and
An LED driving circuit comprising a second switch circuit that receives a PAM (Pulse Amplitude Modulation) driving control signal and adjusts the size of the driving current of the light emitting diode. According to claim 5,
The dimming control circuit is an LED driving circuit that individually controls the timing of the rise or fall of the driving current of the light emitting diodes of the plurality of current channels in response to the PWM driving control signal or the PAM driving control signal. According to claim 5,
The dimming control circuit determines the PWM operation of the first switch circuit or the PAM operation of the second switch circuit for each frame, and changes the operation timing of the driving current for the PWM operation. According to claim 1,
The digital logic operation circuit outputs the PWM driving control signal in synchronization with the PWM clock signal generated by an internal oscillator, and synchronizes the timing of the driving current of the light emitting diode to the PWM clock signal. According to claim 1,
An LED driving circuit further comprising a multiplexer that selects one of a horizontal synchronization signal (VSYNC) transmitted from a timing controller and a PWM clock signal generated by an internal oscillator and transmits it to the digital logic operation circuit. According to claim 1,
The digital logic operation circuit is an LED driving circuit that performs double edge counting by counting both rising edges and falling edges of the PWM clock signal transmitted internally or externally. According to claim 1,
The dimming control circuit is an LED driving circuit that adjusts driving current control timing to compensate for inter-channel delay of a plurality of current channels. A current channel electrically connected to the light emitting diode and transmitting a driving current of the light emitting diode; and
A dimming control circuit that controls the driving current of the light emitting diode according to the duty ratio of the PWM (Pulse Width Modulation) driving control signal;
The dimming control circuit is an LED driving circuit that changes the frequency of the driving current in response to the number of clocks of the PWM clock signal transmitted externally or internally. According to claim 12,
a digital logic operation circuit that determines the duty ratio and frequency of the PWM driving control signal based on the number of clocks of the PWM clock signal and transmits the duty ratio and frequency to the dimming control circuit; and
It includes a register for storing a first indicator and a second indicator indicating a multiplier frequency of the PWM drive control signal,
The digital logic operation circuit determines the frequency of the PWM driving control signal by multiplying the first indicator or the second indicator stored in the register with the frequency of the PWM clock signal. According to claim 12,
The dimming control circuit is an LED driving circuit that controls the frequency of the driving current of the light emitting diode to correspond to the frequency of the PWM clock signal generated by the internal oscillator. According to claim 12,
The dimming control circuit is an LED driving circuit that controls the frequency of the driving current of the light emitting diode based on the number of PWM clock signals transmitted from the outside. According to claim 15,
The digital logic operation circuit is an LED driving circuit that counts both rising edges and falling edges of the PWM clock signal. A microcontroller unit that is connected to a plurality of current channels and generates an LED driving control signal to control the operation of a light emitting diode that transmits light; and
An LED driving circuit that generates a PWM (Pulse Width Modulation) driving control signal based on the LED driving control signal and controls the operation timing of the driving current of the light emitting diode,
The LED driving circuit changes the operation timing of the light emitting diode every frame. According to claim 17,
The LED driving circuit counts the number of clocks of the PWM clock signal transmitted from inside or outside the LED driving circuit, and multiplies a plurality of indicators stored in an internal register by the frequency of the PWM clock signal. An LED driving device that determines the frequency of the driving control signal and changes the timing of the rise or fall of the driving current of the light emitting diode. According to claim 17,
The LED driving circuit changes the edge counting method of the PWM clock signal in conjunction with the resolution of the display device. According to claim 17,
The LED driving circuit changes the frequency of the PWM driving control signal to an integer multiple of the frequency of the PWM clock signal generated by the internal oscillator, and uses the frequency of the PWM clock signal to determine the frequency of the driving current of the light emitting diode. LED driving device.