KR102587489B1 - POWER SUPPLYING APPARATUS FOR Electroluminescent Display Device - Google Patents

Abstract

According to an embodiment of the present specification, a power supply device for an electroluminescence display device for changing a first level voltage to a second level voltage different from the first level voltage is provided. This power supply device includes an inductor connected to an input voltage terminal where the first level voltage is input; an output control switch connected between the inductor and a base voltage terminal; A control unit that generates a pulse width modulation signal to control the on/off operation of the output control switch; a comparison unit that compares the second level voltage and a reference voltage and outputs the comparison result to the control unit; And a noise improvement unit that alleviates the noise component in the output of the comparison unit according to the time constant value, but varies the time constant value in the display drive for reproducing the input image and the sensing drive for sensing the driving characteristics of the pixel. do.

Description

POWER SUPPLYING APPARATUS FOR Electroluminescent Display Device}

This specification relates to a power supply device for an electroluminescent display device.

Electroluminescent display devices are roughly divided into inorganic light emitting display devices and organic light emitting display devices depending on the material of the light emitting layer. Among these, the active matrix type organic light emitting display device includes an organic light emitting diode (hereinafter referred to as "OLED") that emits light on its own, has a fast response speed, and has high luminous efficiency, brightness and It has the advantage of a large viewing angle.

OLED, a self-luminous device, includes an anode electrode and a cathode electrode, and an organic compound layer formed between them. An organic light emitting display device arranges pixels, each including an OLED and a driving TFT (Thin Film Transistor), in a matrix form and adjusts the luminance of the image implemented in the pixels according to the gradation of the image data. The driving TFT controls the driving current flowing through the OLED according to the voltage applied between its gate electrode and source electrode (hereinafter referred to as “gate-source voltage”). The amount of light emitted and brightness of OLED are determined depending on the driving current.

The electroluminescent display device includes a power supply device that generates driving power required for operation. The power supply device is integrated into one integrated circuit (hereinafter referred to as “IC”). Hereinafter, an IC with a built-in power supply device will be referred to as a power IC. When the power voltage switch of the electroluminescent display device is turned on, the input voltage of the power IC rises. The power IC generates an output when its internal logic is activated. In other words, the power IC starts operating when the input voltage is above a certain level and sequentially generates output according to a predetermined sequence control order.

The output of a power IC is affected by load changes. In addition to display driving to reproduce input images, electroluminescent display devices include sensing driving to sense the driving characteristics of pixels. During sensing driving, the load on the output terminal of the power IC is greater than when driving the display.

If the load change is large like this, noise occurs due to the instantaneous peak current flowing in the inductor of the power IC. Because the screen is turned off during sensing operation, even slight noise can be easily perceived emotionally.

Therefore, this specification provides a power supply device for an electroluminescent display device that improves emotional quality by suppressing power IC noise due to load changes.

The tasks of this specification are not limited to the tasks mentioned above, and other tasks not mentioned can be clearly understood by those skilled in the art from the description below.

According to an embodiment of the present specification, a power supply device for an electroluminescence display device for changing a first level voltage to a second level voltage different from the first level voltage is provided. This power supply device includes an inductor connected to an input voltage terminal where the first level voltage is input; an output control switch connected between the inductor and a base voltage terminal; A control unit that generates a pulse width modulation signal to control the on/off operation of the output control switch; a comparison unit that compares the second level voltage and a reference voltage and outputs the comparison result to the control unit; And a noise improvement unit that alleviates the noise component in the output of the comparison unit according to the time constant value, but varies the time constant value in the display drive for reproducing the input image and the sensing drive for sensing the driving characteristics of the pixel. do.

The noise improvement unit changes the time constant value in the display drive and the sensing drive depending on the low-potential pixel voltage applied to the pixel.

The low-potential pixel voltage is input as a first voltage in the display drive, and is input as a second voltage higher than the first voltage to prevent unnecessary light emission of the pixel in the sensing drive.

The noise improvement unit increases the time constant value in the sensing drive in which the low-potential pixel voltage of the second voltage is input compared to the display drive in which the low-potential pixel voltage of the first voltage is input.

The noise improvement unit includes a resistor R connected between the output terminal of the comparison unit and node N1; a capacitor C connected between the node N1 and the base voltage terminal; a switch SW1 connected between the node N1 and the node N2 and turned on/off according to the low-potential pixel voltage; and a capacitor Ca connected between the node N2 and the base voltage terminal. Here, the switch SW1 is turned off according to the low-potential pixel voltage of the first voltage in the display driving, and is turned on according to the low-potential pixel voltage of the second voltage in the sensing driving.

The noise improvement unit includes a resistor Ra connected between the output terminal of the comparison unit and node N3; a switch SW2 connected between the output terminal of the comparison unit and node N3 and turned on/off according to the low-potential pixel voltage; a resistor R connected between the node N3 and the node N4; and a capacitor C connected between the node N4 and the base voltage terminal. Here, the switch SW2 is turned on according to the low-potential pixel voltage of the first voltage in the display driving, and is turned off according to the low-potential pixel voltage of the second voltage in the sensing driving.

The noise improvement unit includes a resistor Ra connected between the output terminal of the comparison unit and node N5; a switch SW2 connected between the output terminal of the comparison unit and node N5 and turned on/off according to the low-potential pixel voltage; a resistor R connected between the node N5 and the node N6; a capacitor C connected between the node N6 and the base voltage terminal; a switch SW1 connected between the node N6 and the node N7 and turned on/off in the opposite direction of the switch SW2 according to the low-potential pixel voltage; and a capacitor Ca connected between the node N7 and the base voltage terminal. Here, the switch SW1 is turned off according to the low-potential pixel voltage of the first voltage in the display driving, and is turned on according to the low-potential pixel voltage of the second voltage in the sensing driving. In addition, the switch SW2 is turned on according to the low-potential pixel voltage of the first voltage in the display driving, and is turned off according to the low-potential pixel voltage of the second voltage in the sensing driving.

During the sensing operation, the screen of the display panel remains turned off.

The sensing driving is performed during a power-on sequence period before the display driving starts, or during a power-off sequence period after the display driving ends.

Embodiments of the present specification reduce the sensitivity of the feedback voltage by increasing the RC value only during sensing operation, thereby reducing peak current flowing in the inductor and unnecessary noise resulting therefrom, thereby improving emotional quality. Since the screen is not displayed during sensing operation, even if the sensitivity of the feedback voltage is decreased by increasing the RC value, it is not a problem because defects such as screen abnormalities are not recognized.

The effects according to the embodiments of the present specification are not limited to the contents exemplified above, and further various effects are included in the present specification.

1 is a block diagram showing an electroluminescence display device according to an embodiment of the present specification.
Figure 2 is a diagram showing an example of the configuration of a pixel capable of sensing operation and a data driving circuit.
Figure 3 is a diagram showing the power-on sequence period and power-off sequence period during which sensing driving is performed.
Figure 4 is a diagram showing a power supply device according to an embodiment of the present specification.
Figure 5 is a diagram showing the voltage transfer ratio according to the duty of the output control switch in the power supply device of Figure 4.
FIG. 6 is a diagram showing that the low-potential driving voltage during sensing driving is different compared to the low-potential driving voltage during display driving.
Figures 7 to 9 are diagrams showing various implementation examples of the noise improvement unit of Figure 4.
Figure 10 is a diagram showing simulation results for power IC noise and inductor peak current before and after noise improvement.

The advantages and features of the present specification and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present specification is not limited to the embodiments disclosed below and will be implemented in various different forms, but the present embodiments only serve to ensure that the disclosure of the present specification is complete, and that common knowledge in the technical field to which this specification pertains is provided. It is provided to fully inform those who have the scope of the invention, and this specification is only defined by the scope of the claims.

The shape, size, ratio, angle, number, etc. disclosed in the drawings for explaining the embodiments of the present specification are illustrative, and the present specification is not limited to the matters shown. Like reference numerals refer to like elements throughout the specification. Additionally, in describing the present specification, if it is determined that a detailed description of related known technologies may unnecessarily obscure the gist of the present specification, the detailed description will be omitted. When 'includes', 'has', 'consists of', etc. mentioned in the specification are used, other parts may be added unless '~ only' is used. When a component is expressed in the singular, the plural is included unless specifically stated otherwise.

When interpreting a component, it is interpreted to include the margin of error even if there is no separate explicit description.

In the case of a description of a positional relationship, for example, if the positional relationship between two parts is described as 'on top', 'on top', 'at the bottom', 'next to ~', 'right next to' Alternatively, there may be one or more other parts placed between the two parts, unless 'directly' is used.

First, second, etc. may be used to describe various elements, but these elements are not limited by these terms. These terms are merely used to distinguish one component from another. Accordingly, the first component mentioned below may be the second component within the technical idea of the present specification.

Like reference numerals refer to substantially like elements throughout the specification.

The features of various embodiments of the present specification can be partially or entirely combined or combined with each other, and various technological interconnections and operations are possible, and each embodiment may be implemented independently of each other or together in a related relationship. there is.

Hereinafter, various embodiments of the present specification will be described in detail with reference to the attached drawings. In the following embodiments, the description will focus on an organic light emitting display device including an organic light emitting material. However, it should be noted that the technical idea of the present specification is not limited to organic light emitting display devices, but can be applied to inorganic light emitting display devices including inorganic light emitting materials.

1 is a block diagram showing an electroluminescence display device according to an embodiment of the present specification. Figure 2 is a diagram showing an example of the configuration of a pixel capable of sensing operation and a data driving circuit. And, Figure 3 is a diagram showing the power-on sequence period and power-off sequence period during which sensing driving is performed.

Referring to FIGS. 1 to 3, the electroluminescence display device according to an embodiment of the present specification includes a display panel 10, a timing controller 11, a data driving circuit 12, a gate driving circuit 13, and a host system ( 14), and a power supply circuit 15.

The display panel 10 is provided with a plurality of pixels (PXL) and first signal lines 20 and 30 that intersect each other. The first signal lines 20 include data lines DL that supply analog data voltages to the pixels PXL, and sensing lines SL that sense driving characteristics of the pixels PXL. However, the driving characteristics of the pixels PXL may be sensed through the data lines DL, and in this case, the sensing lines SL can be omitted. The first signal lines 30 may include, but are not limited to, first and second gate lines GL1 and GL2 that supply gate signals to the pixels PXL. A scan signal (SCAN) may be supplied to the first gate lines (GL1), and a sensing signal (SEN) may be supplied to the second gate lines (GL2).

The pixels (PXL) of the display panel 10 are arranged in a matrix form to form a pixel array. Each pixel (PXL) may be connected to one of the data lines (DL), one of the sensing lines (SL), and the gate lines (GL1 and GL2). A high-potential pixel voltage (EVDD) and a low-potential pixel voltage (EVSS) are supplied to each pixel (PXL).

Each pixel (PXL) may have a circuit structure that can sense the driving characteristics of the driving TFT (DT). However, the pixel circuit can be modified in various ways other than those presented in the description of the embodiments of this specification. It should be noted that the technical idea of this specification is not limited to the connection configuration of the pixel circuit. For example, the pixel (PXL) may further include a plurality of switch TFTs (ST1, ST2) and a storage capacitor (Cst) in addition to the OLED and the driving TFT (DT). The first switch TFT (ST1) may be turned on/off according to the scan signal (SCAN), and the second switch TFT (ST2) may be turned on/off according to the sensing signal (SEN). A storage capacitor (Cst) is connected to node Ng and node Ns.

The timing controller 11 can temporally separate sensing driving and display driving according to a predetermined control sequence. Here, the sensing drive is a drive to sense the electrical characteristics of the driving TFT and update the compensation value accordingly, and the display drive is a drive to display an image by writing input image data (DATA) reflecting the compensation value into the display panel 10. It's driving. By the control operation of the timing controller 11, the sensing drive is performed in the Power On Sequence Period (X1) before the display drive starts, or in the Power Off Sequence Period (X1) after the display drive ends. It can be performed in Sequence Period (X2). The power-on sequence period (X1) refers to the period from when the system power is applied (PON) until the screen is turned on, and the power-off sequence period (X2) refers to the period from when the screen is turned off until the system power is released (POFF). means the period of

Meanwhile, sensing driving may be performed in an idle driving state, that is, in a state in which only the screen of the display device is turned off while the system power is being applied, such as standby mode, sleep mode, or low power mode. The timing controller 11 can detect standby mode, sleep mode, low power mode, etc. according to a predetermined detection process and control various operations for sensing driving.

The timing controller 11 operates based on timing signals such as the vertical synchronization signal (Vsync), horizontal synchronization signal (Hsync), dot clock signal (DCLK), and data enable signal (DE) input from the host system 14. A data control signal (DDC) for controlling the operation timing of the data driving circuit 12 and a gate control signal (GDC) for controlling the operation timing of the gate driving circuit 13 can be generated. The timing controller 11 may generate different control signals (DDC, GDC) for display driving and control signals (DDC, GDC) for sensing driving.

The gate control signal (GDC) includes a gate start pulse, gate shift clock, etc. The gate start pulse is applied to the gate stage that produces the first output and controls that gate stage. The gate shift clock is a clock signal commonly input to the gate stages and is a clock signal for shifting the gate start pulse.

The data control signal (DDC) includes a source start pulse, a source sampling clock, and a source output enable signal. The source start pulse controls the data sampling start timing of the data driving circuit 12. The source sampling clock is a clock signal that controls the sampling timing of data based on the rising or falling edge. The source output enable signal controls the output timing of the data driving circuit 12.

The timing controller 11 may include a data compensation unit. The data compensation unit calculates a compensation value that can compensate for changes in the electrical characteristics of the driving TFT (DT) based on the sensing data (SD) input from the sensing unit (SU) during sensing operation, and updates this compensation value in the memory. You can. The data compensation unit reads the compensation value from the memory when driving the display, corrects the image data (DATA) with this compensation value, and then supplies the corrected image data (DATA) to the data driving circuit 12. The compensation value stored in the memory can be updated each time the sensing is driven, and thus the deviation in the electrical characteristics of the driving TFT (DT) can be easily compensated.

The data driving circuit 12 includes at least one data driver IC. This data driver IC is equipped with multiple digital-to-analog converters (hereinafter referred to as DACs) connected to each data line (DL). The DAC of the data driver IC converts the image data (DATA) into a display data voltage according to the data control signal (DDC) applied from the timing controller 11 when driving the display and supplies it to the data lines DL. Meanwhile, the DAC of the data driver IC can generate a data voltage for sensing according to the data control signal (DDC) applied from the timing controller 11 during sensing operation and supply it to the data lines DL.

The data driver IC includes a plurality of sensing units (SU) and an analog-to-digital converter (hereinafter referred to as ADC). Each sensing unit (SU) is connected one-to-one to the sensing line (SL) and sequentially connected to the ADC according to the sampling order. Each sensing unit (SU) may be implemented as a current sensing type such as a current integrator or current comparator, or may be implemented as a voltage sensing type such as a sample and holder. The ADC can convert the sensing voltage input from the sensing unit (SU) into sensing data (SD) and output it to the data compensation unit.

The gate driving circuit 13 may generate a gate signal based on the gate control signal (GDC) during sensing operation and then supply the gate signal to the gate lines GL1 and GL2 sequentially or non-sequentially. One line sensing on time is determined by the gate signal applied during sensor operation. The 1-line sensing on time is the time allocated to sensing only the pixels (P) of one specific color among the pixels (PXL) of multiple colors arranged in 1 pixel line. Pixels (PXL) of a specific color may be pixels (PXL) of any one color among R, G, and B pixels, and pixels of any one color among R, G, B, and W pixels ( PXL). Therefore, in order to sense all of the pixels (PXL) of multiple colors arranged in one pixel line, one line sensing on time may be required three or four times.

The gate driving circuit 13 may generate a gate signal based on the gate control signal (GDC) when driving the display and then sequentially supply the gate signal to the gate lines (GL1 and GL2).

The power supply circuit 15 starts operating when the input voltage (Vin) supplied from the host system 14 is above the under voltage protection (Under Voltage Lock Out, hereinafter referred to as “UVLO”) level, and is delayed for a predetermined time. Output is generated from then on. The power supply circuit 15 includes a power IC and can output VGH, SVDD, EVDD, etc. VGH may be a gate high voltage set above the threshold voltage of the TFTs included in the pixel (PXL). VGH is supplied to the gate driving circuit 13. SVDD is a high-potential power supply voltage to be supplied to the gamma divider circuit of the data driving circuit 12 that generates positive/negative gamma reference voltages. EVDD is the high potential pixel voltage to be input to the pixels (PXL). The input voltage (Vin) of the power supply circuit 15 may be a voltage of 12V. The input voltage (Vin) rises from 0V to 12V when the power voltage switch of the liquid crystal display device is turned on to operate the power IC, and falls from 12V to 0V when the power voltage switch is turned off to operate the power IC. make it stop

The power supply circuit 15 boosts the input voltage Vin and outputs a higher voltage. During sensing operation, the load change on the output terminal of the power IC is greater than when driving the display, so noise may occur due to the momentary peak current flowing in the inductor of the power IC during sensing operation. Because the screen is turned off during sensing operation, even slight noise can be easily perceived emotionally. This specification proposes a noise improvement unit to suppress power IC noise due to load changes. This will be described later with reference to FIGS. 4 to 10.

Figure 4 is a diagram showing a power supply circuit according to an embodiment of the present specification. Figure 5 is a diagram showing the voltage transfer ratio according to the duty of the output control switch in the power supply circuit of Figure 4. And, FIG. 6 is a diagram showing that the low-potential driving voltage during sensing driving is different compared to the low-potential driving voltage during display driving.

Referring to FIG. 4, the power supply circuit 15 according to an embodiment of the present specification may be implemented as a step-up converter, for example, as a boost converter.

The power supply circuit 15 includes an inductor (L), a diode (D), an output control switch (FET), a control unit 151, a comparison unit (COMP), an output capacitor (CO), and a noise improvement unit 152. Including a first level input voltage (hereinafter Vin) and outputting a second level output voltage (hereinafter Vout) higher than the first level. As an example, this output voltage (Vout) may be a high potential power supply voltage (SVDD) to be supplied to the gamma divider circuit of the data driving circuit 12.

The inductor (L) is a current accumulation element whose one side is connected to the input voltage terminal (IT) where Vin is input, and the other side is connected to node XY.

The diode (D) has an anode connected to node XY and a cathode connected to the output voltage terminal (OT).

The output control switch (FET) may be implemented as a field effect transistor connected between node XY and the ground voltage terminal (GND). When the output control switch (FET) is turned on, current is accumulated in the inductor (L), and when the output control switch (FET) is turned off, the current in the inductor (L) is output to the output voltage terminal (OT).

The control unit 151 generates a pulse width modulation signal (PWM) to control the on/off operation of the output control switch (FET). The output terminal of the control unit 151 is connected to the gate electrode of the output control switch (FET).

The comparison unit (COMP) is a feedback circuit that compares Vout and the reference voltage (REF) and transmits the comparison result to the control unit 151. The control unit 151 maintains Vout constant by controlling the duty of the PWM signal according to the comparison result from the comparison unit (COMP). The duty of the PWM signal means the on-duty that can turn on the output control switch (FET). The voltage transfer ratio (Vout/Vin) is proportional to the duty of the PWM signal, as shown in FIG. 5. In other words, as the duty of the PWM signal increases, Vout increases. Meanwhile, the output of the comparison unit (COMP) and the duty of the PWM signal may have an inverse relationship. The comparator (COMP) reduces the duty of the PWM signal by increasing the comparison output (feedback voltage) when Vout becomes higher than the target value. Conversely, when Vout becomes lower than the target value, it lowers the comparison output (feedback voltage) to increase the duty of the PWM signal. By doing so, Vout can be maintained at the target value.

The output capacitor (CO) is connected between the output voltage terminal (OT) and the base voltage terminal (GND).

The noise improvement unit 152 alleviates the noise component included in the output (feedback voltage) of the comparator (COMP) according to the time constant value (RC value). Even if the time constant value (RC value) is set to an appropriate value considering various conditions such as output voltage/current and line status of the power supply path, when the load changes, an instantaneous peak current flows in the inductor (L). , which may result in noise. The sensitivity and noise of the feedback voltage can be determined depending on the time constant value (RC value). If the time constant value (RC value) is set small, the sensitivity of the feedback voltage can improve and the stability of Vout can be improved. However, because the instantaneous peak current flowing in the inductor (L) increases, wavy noise increases. You can. Conversely, if the time constant value (RC value) is set large, the instantaneous peak current and wavy noise flowing through the inductor (L) will be reduced, but the sensitivity of the feedback voltage will worsen, reducing the stability of Vout and causing problems with image display. You can.

Accordingly, the noise improvement unit 152 controls the time constant value (RC value) differently during display driving and sensing driving. Since an image is displayed when the display is driven, the stability of Vout is more important than noise. On the other hand, during sensing operation, no image is displayed and the screen remains off, so reducing noise is more important in terms of emotional quality than the stability of Vout. Accordingly, the noise improvement unit 152 controls the time constant value (RC value) to be relatively low when driving the display, and controls the time constant value (RC value) to be relatively high when driving the sensing.

The noise improvement unit 152 controls the time constant value (RC value) differently during display driving and sensing driving based on the low potential pixel voltage (EVSS). As shown in FIG. 6 , the low-potential pixel voltage (EVSS) is input as a first voltage (V1) during display driving, and is input as a second voltage (V2) higher than the first voltage (V1) during the sensing driving period (TS). The reason for increasing the low potential pixel voltage (EVSS) during sensing driving is to prevent unnecessary light emission from the OLED while the electrical characteristics of the driving TFT are being sensed.

The noise improvement unit 152 may control the time constant value (RC value) by including a switch that is turned on/off according to the low potential pixel voltage (EVSS). Since the noise improvement unit 152 uses the low-potential pixel voltage (EVSS) as a control signal for the switch, no additional signal is required and design is easy.

Figures 7 to 9 are diagrams showing various implementation examples of the noise improvement unit of Figure 4.

Referring to FIG. 7, the noise improvement unit 152 may control the time constant value (RC value) by including a switch SW1 that is turned on/off according to the low potential pixel voltage (EVSS).

The noise improvement unit 152 includes a resistor R connected between the output terminal (NO) of the comparator (COMP) and node N1, a capacitor C connected between node N1 and the base voltage terminal (GND), and a resistor R connected between node N1 and node N2. It may include a switch SW1 that is connected and turned on/off according to the low-potential pixel voltage (EVSS), and a capacitor Ca connected between the node N2 and the ground voltage terminal (GND). Switch SW1 can be implemented with NMOS.

Here, the switch SW1 is turned off according to the low-potential pixel voltage (EVSS) of the first voltage (V1) in the display drive, and is turned on according to the low-potential pixel voltage (EVSS) of the second voltage (V2) in the sensing drive. do. The total capacitance of the capacitors C and Ca increases when switch SW1 is turned on compared to when switch SW1 is turned off. Accordingly, the noise improvement unit 152 can control the time constant value (RC value) to be relatively higher during sensing driving than when driving the display, thereby reducing wavy noise and improving emotional quality.

Referring to FIG. 8, the noise improvement unit 152 may control the time constant value (RC value) by including a switch SW2 that is turned on/off according to the low potential pixel voltage (EVSS).

The noise improvement unit 152 has a resistor Ra connected between the output terminal (NO) of the comparator (COMP) and node N3, and a low-potential pixel voltage (EVSS) connected between the output terminal (NO) of the comparator (COMP) and node N3. ) may include a switch SW2 that is turned on/off, a resistor R connected between node N3 and node N4, and a capacitor C connected between node N4 and the ground voltage terminal (GND). Switch SW2 can be implemented in PMOS.

Here, switch SW2 is turned on according to the low-potential pixel voltage (EVSS) of the first voltage (V1) in display driving, and turned off according to the low-potential pixel voltage (EVSS) of the second voltage (V2) in sensing driving. do. The total impedance of the resistors R and Ra increases when switch SW1 is turned off compared to when switch SW1 is turned on. Accordingly, the noise improvement unit 152 can control the time constant value (RC value) to be relatively higher during sensing driving than when driving the display, thereby reducing wavy noise and improving emotional quality.

Referring to FIG. 9, the noise improvement unit 152 may control the time constant value (RC value) by including switches SW1 and SW2 that are turned on/off according to the low potential pixel voltage (EVSS).

The noise improvement unit 152 has a resistor Ra connected between the output terminal (NO) of the comparator (COMP) and node N5, and a low-potential pixel voltage (EVSS) connected between the output terminal (NO) of the comparator (COMP) and node N3. ), a switch SW2 that is turned on/off, a resistor R connected between node N5 and node N6, and a capacitor C connected between node N6 and the base voltage terminal (GND), and a low potential connected between node N6 and node N7. It may include a switch SW1 that is turned on/off in contrast to the switch SW2 according to the pixel voltage (EVSS), and a capacitor Ca connected between the node N7 and the base voltage terminal (GND). Switch SW1 may be implemented with NMOS, and switch SW2 may be implemented with PMOS.

Here, the switch SW1 is turned off according to the low-potential pixel voltage (EVSS) of the first voltage (V1) in the display drive, and is turned on according to the low-potential pixel voltage (EVSS) of the second voltage (V2) in the sensing drive. do. The total capacitance of the capacitors C and Ca increases when switch SW1 is turned on compared to when switch SW1 is turned off. Accordingly, the noise improvement unit 152 can control the time constant value (RC value) to be relatively higher during sensing driving than when driving the display, thereby reducing wavy noise and improving emotional quality.

In addition, switch SW2 is turned on according to the low-potential pixel voltage (EVSS) of the first voltage (V1) in display driving, and is turned off according to the low-potential pixel voltage (EVSS) of the second voltage (V2) in sensing driving. do. The total impedance of the resistors R and Ra increases when switch SW1 is turned off compared to when switch SW1 is turned on. Accordingly, the noise improvement unit 152 can control the time constant value (RC value) to be relatively higher during sensing driving than when driving the display, thereby reducing wavy noise and improving emotional quality.

Figure 10 is a diagram showing simulation results for noise and inductor peak current before and after noise improvement.

Referring to FIG. 10, as described in the embodiments of this specification, if the time constant value is controlled to be relatively high during sensing driving compared to display driving, the instantaneous peak current flowing in the inductor is reduced and noise due to wavy noise is also reduced. As a result, by applying the noise improvement method presented in this specification, unnecessary noise can be effectively reduced without concerns about screen defects, etc., thereby significantly improving emotional quality.

Through the above-described content, those skilled in the art will be able to see that various changes and modifications can be made without departing from the technical idea of the present specification. Therefore, the technical scope of the present specification is not limited to the content described in the detailed description of the specification, but should be determined by the scope of the patent claims.

10: display panel 15: power supply circuit
151: Control unit 152: Noise improvement unit

Claims (12)

In the power supply device of an electroluminescence display device for changing a first level voltage to a second level voltage different from the first level voltage,
an inductor connected to an input voltage terminal where the first level voltage is input;
an output control switch connected between the inductor and a base voltage terminal;
A control unit that generates a pulse width modulation signal to control the on/off operation of the output control switch;
a comparison unit that compares the second level voltage and a reference voltage and outputs the comparison result to the control unit; and
A noise improvement unit that alleviates the noise component in the output of the comparison unit according to the time constant value, but varies the time constant value in display driving for reproducing the input image and sensing driving for sensing the driving characteristics of the pixel; ,
A power supply device for an electroluminescent display device in which the output of the comparator and the duty of the pulse width modulation signal are inversely proportional. According to claim 1,
The noise improvement unit,
A power supply device for an electroluminescent display device that varies the time constant value in the display drive and the sensing drive depending on the low-potential pixel voltage applied to the pixel. According to claim 2,
The low-potential pixel voltage is input as a first voltage in the display driving, and the low-potential pixel voltage is input as a second voltage higher than the first voltage to prevent unnecessary light emission of the pixel in the sensing driving. According to claim 3,
The noise improvement unit,
A power supply device for an electroluminescent display device that increases the time constant value in the sensing drive in which the low-potential pixel voltage of the second voltage is input compared to the display drive in which the low-potential pixel voltage of the first voltage is input. . According to claim 4,
The noise improvement unit,
Resistor R connected between the output terminal of the comparison unit and node N1;
a capacitor C connected between the node N1 and the base voltage terminal;
a switch SW1 connected between the node N1 and the node N2 and turned on/off according to the low-potential pixel voltage; and
Includes a capacitor Ca connected between the node N2 and the base voltage terminal,
The switch SW1 is,
A power supply device for an electroluminescent display device that is turned off according to the low-potential pixel voltage of the first voltage in the display driving and turned on in accordance with the low-potential pixel voltage of the second voltage in the sensing driving. According to claim 4,
The noise improvement unit,
Resistor Ra connected between the output terminal of the comparison unit and node N3;
a switch SW2 connected between the output terminal of the comparison unit and node N3 and turned on/off according to the low-potential pixel voltage;
a resistor R connected between the node N3 and the node N4; and
Includes a capacitor C connected between the node N4 and the base voltage terminal,
The switch SW2 is,
A power supply device for an electroluminescent display device that is turned on according to the low-potential pixel voltage of the first voltage in the display driving and turned off in accordance with the low-potential pixel voltage of the second voltage in the sensing driving. According to claim 4,
The noise improvement unit,
Resistor Ra connected between the output terminal of the comparison unit and node N5;
a switch SW2 connected between the output terminal of the comparison unit and node N5 and turned on/off according to the low-potential pixel voltage;
a resistor R connected between the node N5 and the node N6;
a capacitor C connected between the node N6 and the base voltage terminal;
a switch SW1 connected between the node N6 and the node N7 and turned on/off in the opposite direction of the switch SW2 according to the low-potential pixel voltage; and
Includes a capacitor Ca connected between the node N7 and the base voltage terminal,
The switch SW1 is,
In the display driving, it is turned off according to the low-potential pixel voltage of the first voltage, and in the sensing driving, it is turned on according to the low-potential pixel voltage of the second voltage,
The switch SW2 is,
A power supply device for an electroluminescent display device that is turned on according to the low-potential pixel voltage of the first voltage in the display driving and turned off in accordance with the low-potential pixel voltage of the second voltage in the sensing driving. According to claim 1,
A power supply device for an electroluminescent display device in which the screen of the display panel remains turned off during the sensing operation. According to claim 1,
The sensing drive is,
A power supply device for an electroluminescent display device, which is performed in a power-on sequence period before the display driving starts or in a power-off sequence period after the display driving ends. In the power supply device of an electroluminescence display device for changing a first level voltage to a second level voltage different from the first level voltage,
an inductor connected to an input voltage terminal where the first level voltage is input;
an output control switch connected between the inductor and a base voltage terminal;
A control unit that generates a pulse width modulation signal to control the on/off operation of the output control switch;
a comparison unit that compares the second level voltage and a reference voltage and outputs the comparison result to the control unit; and
A noise improvement unit that alleviates the noise component in the output of the comparison unit according to the time constant value, but varies the time constant value in display driving for reproducing the input image and sensing driving for sensing the driving characteristics of the pixel; ,
The noise improvement unit controls the value of the time constant when driving the display to be relatively lower than when driving the sensing, and controls the value of the time constant when driving the sensing to be relatively higher than when driving the display. Power supply for the display device. In the power supply device of an electroluminescence display device for changing a first level voltage to a second level voltage different from the first level voltage,
an inductor connected to an input voltage terminal where the first level voltage is input;
an output control switch connected between the inductor and a base voltage terminal;
A control unit that generates a pulse width modulation signal to control the on/off operation of the output control switch;
a comparison unit that compares the second level voltage and a reference voltage and outputs the comparison result to the control unit; and
A noise improvement unit that alleviates the noise component in the output of the comparison unit according to the time constant value, but varies the time constant value in display driving for reproducing the input image and sensing driving for sensing the driving characteristics of the pixel; ,
The noise improvement unit is a power supply device for an electroluminescence display device that controls the value of the time constant during the sensing drive to be higher than when the display is driven based on a low-potential pixel voltage applied to the pixel. In the power supply device of an electroluminescence display device for changing a first level voltage to a second level voltage different from the first level voltage,
an inductor connected to an input voltage terminal where the first level voltage is input;
an output control switch connected between the inductor and a base voltage terminal;
A control unit that generates a pulse width modulation signal to control the on/off operation of the output control switch;
a comparison unit that compares the second level voltage and a reference voltage and outputs the comparison result to the control unit; and
A noise improvement unit that alleviates the noise component in the output of the comparison unit according to the time constant value, but varies the time constant value in display driving for reproducing the input image and sensing driving for sensing the driving characteristics of the pixel; ,
The noise improvement unit is a power supply device for an electroluminescent display device that varies the time constant value based on a voltage value in which the low-voltage pixel voltage of the sensing drive is higher than the low-voltage pixel voltage of the display drive.