KR20120014768A - Dc-dc converter and display device including the same - Google Patents

Abstract

PURPOSE: A DC-DC converter and a display apparatus including the same are provided to generate desired output voltage using the small number of components. CONSTITUTION: A voltage booster(621) generates output voltage by boosting input voltage. The voltage booster includes first and second capacitors(C1,C2), a first diode(D1), and a first inductor(L1). A first electrode of the first capacitor is connected to a first electrode of the first diode. A second electrode of the first capacitor is connected to one side of the first inductor. The second capacitor is connected to the other side of the first inductor and a second electrode of the first diode.

Description

DC-DC converter and display device including the same}

The present invention relates to a DC-DC converter, and more particularly, to a DC-DC converter and a display device including the same.

As the information society develops, the demand for display devices for displaying images is increasing in various forms. Recently, liquid crystal displays (LCDs), plasma display panels (PDPs), organic fields Various flat display devices such as organic light emitting diodes (OLEDs) are being utilized.

These flat panel display apparatuses include a power generation unit for generating a voltage for driving the display panel and various driving units. Here, the power generation unit includes a DC-DC converter.

In this case, the conventional DC-DC converter has a problem in that a large number of parts must be used in order to increase the voltage. In addition, since the on period of the switching element of the DC-DC converter needs to be increased in order to increase the voltage, there is a problem that high heat generation of the switching element occurs.

The present invention relates to a DC-DC converter and a flat panel display device including the same, and has a problem in generating a desired output voltage using a small number of components.

In addition, there is a problem to improve the heat generation problem of the switching element.

In order to achieve the above object, the present invention includes a booster for boosting an input voltage to generate an output voltage, wherein the booster includes first and second capacitors, a first diode, and a first inductor. The first electrode of the first capacitor is connected with the first electrode of the first diode, the second electrode is connected with one side of the first inductor, and the second capacitor is the second electrode of the first diode. And a DC-DC converter connected to the other side of the first inductor.

The DC-DC converter further includes a second inductor, a second diode, and a third capacitor, wherein the second inductor is connected to the first electrode of the first capacitor and the first electrode of the first diode. A first electrode of the second diode is connected with a second electrode of the first capacitor and the first inductor, a first electrode of the third capacitor is connected with a second electrode of the second diode, The second electrode is grounded.

A flat panel display comprising a display panel for displaying an image, the flat panel display comprising: a booster for boosting an input voltage to generate an output voltage, wherein the booster includes first and second capacitors, a first diode, and a first inductor. And a first electrode of the first capacitor is connected with a first electrode of the first diode, a second electrode is connected with one side of the first inductor, and the second capacitor is a second of the first diode. Provided is a flat panel display including an electrode and a DC-DC converter connected to the other side of the first inductor.

The DC-DC converter further includes a second inductor, a second diode, and a third capacitor, wherein the second inductor is connected to the first electrode of the first capacitor and the first electrode of the first diode. A first electrode of the second diode is connected with a second electrode of the first capacitor and the first inductor, a first electrode of the third capacitor is connected with a second electrode of the second diode, The second electrode is grounded.

As the display panel, a liquid crystal panel, an organic light emitting panel, and a plasma display panel are used.

The DC-DC converter and the flat panel display device including the same according to the present invention have an effect of generating a desired high output voltage using fewer components than the boost converter and the charge pump converter.

1 is a schematic cross-sectional view showing a flat panel display device according to an embodiment of the present invention.
2 is a schematic cross-sectional view showing the duty ratio.
3 is a cross-sectional view schematically showing the type of DC-DC converter.
4 is a schematic cross-sectional view of a circuit of a boost converter to which a charge pump of a DC-DC converter is coupled;
5 is a schematic cross-sectional view of a circuit of a DC-DC converter according to an embodiment of the present invention.
6 is a graph schematically showing a gain value according to a duty ratio of a boost converter.
7 is a graph schematically showing gain values according to duty ratios according to types of DC-DC converters.
8 is a graph schematically illustrating a variation in gain values according to duty ratios according to types of DC-DC converters.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 is a view schematically showing a flat panel display device according to an embodiment of the present invention.

As illustrated, the flat panel display device 100 according to the embodiment of the present invention includes a display panel 200, a backlight 700, and a driving circuit unit.

The display panel 200 includes a plurality of gate lines GL extending in a row line direction and a plurality of data lines DL extending in a column line direction. The gate line GL and the data line DL cross each other to define the pixel P in a matrix form.

Each pixel P of the flat panel display apparatus 100 may include, for example, a switching thin film transistor and a storage capacitor.

The switching thin film transistor is formed at the intersection of the gate line GL and the data line DL. When the gate wiring GL is scanned and a gate signal having a turn-on voltage, for example, a gate high voltage, is applied, the switching thin film transistor is turned on. Accordingly, for example, a data voltage corresponding to the image data is applied to each pixel P. FIG.

The storage capacitor plays a role of storing the data voltage applied to the pixel P until the next frame.

As the display panel 200, a liquid crystal panel, an organic electroluminescence panel, a plasma display panel, or the like may be used.

Herein, when the liquid crystal panel is used as the display panel 200, the display panel 200 may further include a backlight 700.

The backlight 700 serves to supply light to the display panel 200. As the backlight 700, a Cold Cathode Fluorescent Lamp (CCFL), an External Electrode Fluorescent Lamp (EEFL), a Light Emitting Diode (LED), or the like may be used.

The driving circuit unit may include a timing controller 300, a gate driver 400, a data driver 500, a power generator 600, and a gamma reference voltage generator 800.

Here, the timing controller 300 inputs a video data signal RGB, a vertical synchronization signal, a horizontal synchronization signal, a clock signal, and a data enable signal TCS from an external system such as a TV system or a video card. Will receive. Although not shown, these signals may be input through an interface configured in the timing controller 300.

The timing controller 300 generates a gate control signal GCS for controlling the gate driver 400 and a data control signal DCS for controlling the data driver 500 using the input control signal TCS. do. The gate control signal GCS includes a gate start pulse (GSP), a gate shift clock (GSC), a gate output enable signal (GOE), and the like. The data control signal (DCS) includes a source start pulse (SSP), a source shift clock (SSC), a source output enable signal (SOE), and a polarity signal (POL). And the like.

The gate start pulse GSP serves to inform the start line of the screen, that is, the first line, among the 1 vertical, and the gate shift clock GSC is a switching thin film formed on the pixel P of the display panel 200. Specifies the time when the transistor is on. In addition, the gate output enable signal GOE controls the output of the gate driver 400.

In addition, the source start pulse SSP informs the start point of the data, that is, the first pixel P, from one horizontal, and the source shift clock SSC latches the data based on the rising and falling edges. (latch) In addition, the source output enable signal SOE serves to control the output of the data driver 500, and the polarity signal POL controls the data voltage of the display panel 200 to be positive (+) polarity or negative (−). It is a signal indicating the polarity to drive the polarity.

In addition, the timing controller 300 receives the image data RGB from an external system, arranges the image data RGB, and transmits the image data RGB to the data driver 500.

The data driver 500 supplies the data voltages to the plurality of data wirings DL in response to the data control signal DCS and the image data RGB supplied from the timing controller 300. That is, for example, a data voltage corresponding to the image data RGB is generated using the gamma reference voltage Vgamma, and the generated data voltage is output to the data wiring DL.

The gate driver 400 sequentially scans the plurality of gate wirings GL in response to the gate control signal GCS supplied from the timing controller 300. For example, a plurality of gate lines GL are sequentially selected during each frame, and a gate voltage is output to the selected gate lines GL. By the gate voltage, the switching thin film transistor positioned in the corresponding row line is turned on. On the other hand, the turn-off voltage is supplied to the gate line GL until the next frame is scanned so that the switching thin film transistor is maintained in the turn-off state.

The gamma reference voltage generator 800 divides the high potential common voltage and the low potential common voltage generated from the power generator 600, generates a gamma reference voltage Vgamma, and supplies the generated gamma reference voltage Vgamma to the data driver 500.

The power generator 600 generates various driving voltages necessary for driving the flat panel display 100. For example, the power supply voltage supplied to the timing controller 300, the data driver 500, and the gate driver 400, the gate high voltage and the gate low voltage supplied to the gate driver 400 are generated.

The power generator 600 may include a pulse width modulation (PWM) controller 610 and a DC-DC converter 620 as shown in FIG. 1.

The PWM controller 610 generates a PWM control signal PS and outputs it to the DC-DC converter 620.

Here, the PWM control signal PS is a square wave signal for adjusting the duty ratio of the on time and the off time of the DC-DC converter 620. Therefore, according to the on-off duty width of the PWM control signal PS, the on time of the DC-DC converter 620 is adjusted. That is, by adjusting the duty ratio of the PWM control signal PS, the level of the output voltage Vout of the DC-DC converter 620 can be adjusted to a target voltage level.

Specifically, referring to FIG. 2, the duty ratio D may be expressed by Equation (1).

Equation (1): D = Ton / T (Ton: time when switching element is on, T: switching cycle of switching element)

Therefore, when the output voltage is Vout (A), since the on period is larger than when the output voltage Vout (B), the duty ratio D becomes larger when the output voltage is Vout (A).

Hereinafter, the DC-DC converter 620 according to the embodiment of the present invention will be described in more detail with reference to FIGS. 3 to 5.

3 and 4 schematically show a circuit used as the DC-DC converter 620, and FIG. 5 schematically shows a circuit of the DC-DC converter 620 according to an embodiment of the present invention. to be.

The DC-DC converter 620 receives a power supply voltage supplied from the outside as an input voltage Vin, generates and outputs the output voltage Vout at a desired level.

As shown in FIG. 3, the DC-DC converter 620 includes, for example, a buck converter (buck-step-down) (FIG. 3A) and a boost converter (step-up) ( FIG. 3B), a buck-boost converter (FIG. 3C), and the like.

The buck converter is a converter in which the output voltage Vout is lower than the input voltage Vin. At this time, the output voltage Vout is as shown in Equation (2).

Equation (2): Output voltage (Vout) = D * Input voltage (Vin).

The boost converter is a converter in which the output voltage Vout is output higher than the input voltage Vin. At this time, the output voltage Vout is as shown in Equation (3).

Equation (3): Output voltage (Vout) = (1 / (1-D)) * Input voltage (Vin).

The buck-boost converter is a mixture of a buck converter and a boost converter. At this time, the output voltage (Vout) is as shown in equation (4).

Equation (4): Output voltage (Vout) = (D / (1-D)) * Input voltage (Vin).

Another type of DC-DC converter 620 is a boost converter with a charge pumped coupling. For convenience of description, the boost converter to which the charge pump is coupled is referred to as a charge pump converter.

The charge pump converter increases the input voltage Vin (for example, twice) to generate the output voltage Vout.

4 is a diagram schematically illustrating a circuit of a charge pump converter in which a charge pump is coupled to a boost converter (see FIG. 3A).

At this time, the relationship between the input voltage Vin and the output voltage Vout is as shown in Equation (5). Here, the value obtained by doubling the input voltage Vin of the boost converter is taken as an example.

Equation (5): Output voltage (Vout) = (2 / (1-D)) * Input voltage (Vin).

In this case, a gain value of each converter may be represented as an output voltage Vout / input voltage Vin. In other words, the gain value represents a boost ratio of the output voltage Vout to the input voltage Vin.

Comparing the gain values of the charge pump converter and the boost converter, the charge pump converter has, for example, a gain value twice as high as that of the boost converter. In order to double the output voltage using only the boost converter, the boost converter must be configured in two stages. As a result, the output voltage can be twice as high after two boosts. On the other hand, the charge pump converter adds two more capacitors and two diodes than the boost converter to obtain a gain value twice as high. Therefore, the charge pump converter can obtain a high gain value for the same duty ratio while reducing the number of parts than using a two-stage boost converter.

Hereinafter, the DC-DC converter 620 according to the embodiment of the present invention will be described in detail with reference to FIG. 5.

As shown in FIG. 5, the DC-DC converter 620 according to the embodiment of the present invention includes first and second inductors L1 and L2, first to third capacitors C1, C2 and C3, and One and two diodes D1 and D2 and a switch S may be included. Here, the second inductor L2, the first and second capacitors C1 and C2, and the first diode D1 form the boosting unit 621.

First, the connection relationship of the DC-DC converter 620 according to the embodiment of the present invention will be described.

One side of the first inductor L1 is connected to an input terminal of the input voltage Vin, and the other side thereof has a first electrode of the first capacitor C1 and a first electrode of the first diode D1, for example, an anode. ) And the switch (S). Here, for example, a FET can be used as the switch element.

One side of the second inductor L2 is connected to the second electrode of the first capacitor C1 and the first electrode of the second diode D2, for example, an anode, and the other side of the second inductor L2 is connected to the first electrode and the first electrode of the second capacitor. The second electrode of one diode D1 is connected to, for example, a cathode.

The first electrode of the first diode D1 is connected to the switch S, the first inductor L1, and the first electrode of the first capacitor C1. The second electrode, for example, the cathode of the first diode D2 is connected to the second inductor L2 and the first electrode of the second capacitor C2.

The first electrode of the second diode D2, for example, the anode is connected to the second electrode of the first capacitor C1 and the second inductor L2. The second electrode, for example, the cathode of the second diode D2 is connected to the first electrode of the third capacitor C3 and the output terminal of the output voltage Vout.

Second electrodes of the second capacitor and the third capacitor C2 and C3 are grounded.

Although not shown in FIG. 5, an arbitrary capacitor may be further included in the input terminal receiving the input voltage Vin. That is, an arbitrary capacitor may be included between the input terminal of the input voltage Vin and the first inductor L1. Such a capacitor removes a ripple component of the input voltage Vin and stabilizes the input voltage Vin.

Hereinafter, the function of each configuration of the DC-DC converter 620 according to the embodiment of the present invention will be described.

The first inductor L1 stores the input charge and boosts the input voltage Vin to a predetermined level.

The second diode D2 sends the input charge and the input voltage Vin to the output terminal of the output voltage Vout.

The third capacitor C3 removes and stabilizes the ripple component of the output voltage Vout at the output terminal. That is, a ripple component is included in the output voltage Vout in which the input voltage Vin is boosted by the high speed switching of the switch S, and serves to remove the ripple component.

The booster 621 boosts the input voltage Vin to a predetermined level to generate an output voltage Vout. The output voltage Vout may be, for example, higher than the output voltage Vout generated in the boost converter and lower than the output voltage Vout generated in the charge pump converter.

Specifically, the first diode D1, the first capacitors and the second capacitors C1 and C2 boost the input voltage Vin to a predetermined level. That is, when the input voltage Vin is boosted, it functions as a charge pump. Here, the boosted output voltage Vout may have a lower value than that of the charge pump converter, for example, and may have a higher value than that of the boost converter. Through this, the output voltage Vout having a value between the boost converter and the charge pump converter can be efficiently generated.

The second inductor L2 suppresses peak currents of the diodes D1 and D2.

The output voltage Vout of the DC-DC converter 620 having such a configuration is shown in Equation (6).

Equation (6): Output voltage (Vout) = ((1 + D) / (1-D)) * Input voltage (Vin).

Therefore, the gain value according to the duty ratio is (1 + D) / (1-D).

The gain value of the boost converter is (1 / (1-D)) and the gain value of the charge pump converter is (2 / (1-D)). Compared with the DC-DC converter 620 according to the embodiment of the present invention, it has a high gain value for the same duty ratio than the boost converter, and has a low value compared to the charge pump converter. That is, the DC-DC converter 620 according to the embodiment of the present invention can reduce the number of parts and efficiently generate the desired output voltage Vout as compared to the two-stage boost converter and the charge pump converter.

Hereinafter, the effects of the DC-DC converter 620 according to the embodiment of the present invention will be described with reference to FIGS. 7 and 8.

7 is a diagram schematically illustrating a gain value according to a duty ratio of a boost converter, a charge pump converter, and a DC-DC converter 620 according to an embodiment of the present invention, and FIG. 8 is according to the duty ratio of each converter. A diagram schematically showing a gain variation amount.

As shown in Fig. 7, the charge pump converter has the highest gain value for the same duty ratio, and the boost converter has the lowest gain value. The DC-DC converter 620 according to the embodiment of the present invention has approximately the intermediate value between the charge pump converter and the boost converter.

Here, as described above, the charge pump converter has a value of about twice as high as the gain value of the boost converter.

While boost converters can theoretically produce infinitely high output voltages (see equation (4)), stable control of the boost converter is difficult at high duty ratios. This is because, as shown in FIG. 6, the gain value changes rapidly at a high duty ratio. Therefore, in the boost converter, the duty ratio should be designed to be 0.5 to 0.7 or less, for example.

In addition, in the boost converter, the duty ratio must be increased in order to obtain a high gain value, so that the ON period of the switch, for example, the FET is long, and the FET component heat generation is increased.

In order to improve the above problems, a charge pump converter is used. By using a charge pump converter, it is possible to generate higher output voltage at the same duty ratio while reducing component count than boosting the output voltage using a two-stage boost converter.

However, if one wants a higher output voltage than the boost converter, but wants to produce a lower output voltage than the charge pump converter, there is a problem in that a charge pump converter is conventionally used.

That is, even when generating an output voltage having a gain value between the boost converter and the charge pump converter, a charge pump converter having a larger number of parts than the DC-DC converter 620 according to the embodiment of the present invention should be used. do. This wastes manufacturing costs by increasing the number of unnecessary parts. In addition, generating unnecessary voltage also wastes power.

Therefore, by using the DC-DC converter 620 according to the embodiment of the present invention, it is possible to obtain a high gain value for the same duty ratio, while reducing the number of parts than the two-stage boost converter and the charge pump converter. That is, it is possible to generate the desired output voltage Vout more efficiently (e.g., a gain value that is higher than the boost converter and lower than the charge pump converter).

In addition, as shown in FIG. 8, the gain variation amount according to the duty ratio is the highest in the boost converter, the lowest in the charge pump converter, and the DC-DC converter 620 according to the embodiment of the present invention sets the intermediate value thereof. Will have

The DC-DC converter 620 may be stably driven as the amount of gain variation due to the duty ratio is low.

Accordingly, the DC-DC converter 620 according to the embodiment of the present invention may have a higher gain value for the same duty ratio while driving more stably than the boost converter.

In addition, compared with the charge pump converter, there is an effect that the number of parts can be reduced and the desired output voltage Vout can be efficiently generated.

Here, the DC-DC converter 620 according to the embodiment of the present invention may be referred to as a current controlled charge pumping boost converter.

The duty ratio of the DC-DC converter 620 and the gain variation amount according to the duty ratio are shown as an example.

Boost Converter: D = 0.8, dG / dD = 25

2. Charge pump converter: D = 0.6, dG / dD = 12.5

CCC-Boost Converter: D = 0.67, dG / dD = 18

As described above, the DC-DC converter 620 according to the embodiment of the present invention can efficiently generate a desired output voltage Vout by using a small number of components, and generates heat of a switch, for example, a FET. It will provide an effect that can be improved.

The embodiments of the present invention described above are examples of the present invention, and modifications can be made freely within the scope of the present invention. Accordingly, the invention includes modifications of the invention within the scope of the appended claims and their equivalents.

100: flat panel display 200: display panel
600: power generator 620: DC-DC converter
621: booster
D: Diode C: Capacitor L: Inductor
Vin: Input Voltage Vout: Output Voltage

Claims (5)

A booster for boosting an input voltage to generate an output voltage,
The boosting unit,
A first and a second capacitor, a first diode, and a first inductor,
The first electrode of the first capacitor is connected to the first electrode of the first diode, the second electrode is connected to one side of the first inductor,
The second capacitor is connected to the second electrode of the first diode and the other side of the first inductor.
DC-DC converter.
The method of claim 1,
The DC-DC converter further includes a second inductor, a second diode, and a third capacitor,
The second inductor is connected to a first electrode of the first capacitor and a first electrode of the first diode,
A first electrode of the second diode is connected to a second electrode of the first capacitor and the first inductor,
The first electrode of the third capacitor is connected to the second electrode of the second diode, and the second electrode is grounded.
DC-DC converter.
In the flat panel display device comprising a display panel for displaying an image,
A booster for boosting an input voltage to generate an output voltage,
The boosting unit,
A first and a second capacitor, a first diode, and a first inductor,
The first electrode of the first capacitor is connected to the first electrode of the first diode, the second electrode is connected to one side of the first inductor,
The second capacitor is connected to the second electrode of the first diode and the other side of the first inductor.
Flat panel display device including a DC-DC converter.
The method of claim 3, wherein
The DC-DC converter further includes a second inductor, a second diode, and a third capacitor,
The second inductor is connected to a first electrode of the first capacitor and a first electrode of the first diode,
A first electrode of the second diode is connected to a second electrode of the first capacitor and the first inductor,
The first electrode of the third capacitor is connected to the second electrode of the second diode, and the second electrode is grounded.
Flat panel display device including a DC-DC converter.
The method of claim 3, wherein
The display panel,
Liquid crystal panel, organic light emitting panel, plasma display panel
Flat Panel Display.

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