KR101075603B1 - Electric power-converting device and display apparatus having the same - Google Patents

Abstract

Disclosed are a power conversion device having a reduced power loss, and a display device having the same. The power converter includes a DC power input unit, a DC power output unit, a first switching unit, and a second switching unit. The DC power input unit converts the first DC voltage provided from the outside into the first DC current. The DC power output unit is connected to the DC power input unit and converts the first DC current into a second DC voltage to output the same. The first switching unit is disposed between the DC power input unit and the DC power output unit to intermittently output the first DC current. The second switching unit is disposed between the first switching unit and the DC power output unit, and zero current switching the first switching unit using resonance with the first switching unit. Thus, by adding a second switching unit for zero current switching in the circuit, it is possible to prevent the occurrence of current stress and conduction loss due to switching, thereby reducing the power loss.

Description

Power conversion device and display device having the same {ELECTRIC POWER-CONVERTING DEVICE AND DISPLAY APPARATUS HAVING THE SAME}

1 is a block diagram illustrating a display device according to an exemplary embodiment of the present invention.

FIG. 2 is a block diagram illustrating in detail a driving voltage generator of the display device of FIG. 1.

3 is a circuit diagram illustrating a DC / DC converter in detail in the driving voltage generator of FIG. 2.

FIG. 4 is a circuit diagram abbreviated in order to more easily explain the circuit diagram of FIG. 3.

5A through 5F are waveform diagrams illustrating signals in the circuit diagram of FIG. 4.

<Description of the symbols for the main parts of the drawings>

50: control unit 100: data driver

200: gate driver 300: display unit

400: driving voltage generator 420: DC / DC converter

422: DC power input unit 424: DC power output unit

426: first switching unit 428: second switching unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power conversion device and a display device having the same, and more particularly, to a power conversion device having a reduced power loss due to switching and a display device having the same.

In general, a liquid crystal display (LCD) includes a display unit for displaying an image by light transmittance of a liquid crystal, a driver unit for applying a driving signal to the display unit, and a response to an externally input image signal. And a control unit controlling the driving unit, and a driving voltage generation unit applying a driving voltage to the display unit and the driving unit.

The driving voltage generator includes an AC / DC converter that converts an external AC voltage into a DC voltage and a DC / DC converter that boosts the DC voltage to generate the driving voltage. As such a DC / DC converter, a boost converter that boosts the DC voltage through a periodic change in current is widely used.

The boost converter generally includes an inductor, a switch and an output load. Looking at the operation state of the boost converter, while the switch is on (on) the DC voltage input to the boost converter is applied to both ends of the inductor to charge the current, the switch is off (off) While the charged current is applied to the output load to generate the boosted drive voltage. In this case, the switch is generally turned off when current is flowing.                         

However, when the switch is turned off while current is flowing to the switch, the switch has a problem that current stress and conduction loss are generated, and as a result, power loss is increased.

Accordingly, the technical problem of the present invention is to solve such a conventional problem, and an object of the present invention is to provide a power conversion device which reduces power loss by performing zero current switching.

Another object of the present invention is to provide a display device having the above-described power converter.

In order to achieve the above object of the present invention, a power conversion apparatus according to an embodiment includes a DC power input unit, a DC power output unit, a first switching unit and a second switching unit. The DC power input unit converts the first DC voltage provided from the outside into the first DC current. The DC power output unit is connected to the DC power input unit, and converts the first DC current into a second DC voltage to output. The first switching unit is disposed between the DC power input unit and the DC power output unit to intermittently output the first DC current. The second switching unit is disposed between the first switching unit and the DC power output unit, and performs zero current switching of the first switching unit by using resonance with the first switching unit.

In order to achieve the above object of the present invention, a power conversion apparatus according to another embodiment includes a first power conversion unit, a second power conversion unit, and a switching control unit. The first power converter converts an AC voltage into a first DC voltage. The second power converter converts the first DC voltage into a second DC voltage while performing zero current switching. The switching controller controls the second power converter.

In accordance with another aspect of the present invention, a display device includes a display unit, a driver, a driving power generator, and a controller. The display unit includes a data line and a scan line that cross each other, and displays an image by the data line and the scan line. The driver applies a source signal to the data line and applies a scan signal to the scan line. For example, the driver includes a data driver for applying a source signal to the data line and a gate driver for applying a scan signal to the scan line. The driving voltage generation unit applies a driving voltage to the display unit and the driving unit. The control unit controls the driving unit and the driving voltage generation unit by an image signal input from the outside.

According to such a power conversion device and a display device having the same, by adding a second switching unit for zero current switching in a circuit, power loss can be reduced by preventing occurrence of current stress and conduction loss due to switching.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating a display device according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the display device includes a controller 50, a data driver 100, a gate driver 200, a display unit 300, and a driving voltage generator 400.

The display unit 300 receives a source signal and a scan signal from the data driver 100 and the gate driver 200 to display an image. The display unit 300 is interposed between an array substrate on which a plurality of thin film transistors (TFTs) are formed, a color filter substrate disposed to face the array substrate, and on which a plurality of color filters are formed, and between the array substrate and the color filter substrate. Made of a liquid crystal layer.

A plurality of data lines D1, D2, ..., Dm and gate lines G1, G2, ..., Gn intersecting with each other are formed on the array substrate, and the data lines D1, D2,. Pixel regions are defined by..., Dm) and gate lines G1, G2,..., Gn, and unit pixels are formed in each of the pixel regions.

Each of the unit pixels includes a thin film transistor TFT, a liquid crystal capacitor Clc, and a storage capacitor Cst. The thin film transistor TFT includes a gate electrode, a source electrode, and a drain electrode. The gate electrode is connected to the gate lines G1, G2, ..., Gn, the source electrode is connected to the data lines D1, D2, ..., Dm, and the drain electrode is the liquid crystal capacitor. It is connected to the pixel electrode which is a 1st electrode of (Clc).

The color filter substrate includes color filters formed of color pixels corresponding to each unit pixel, and a common electrode applied with a common voltage Vcom and a second electrode of the liquid crystal capacitor Clc.

The liquid crystal capacitor Clc is defined by the pixel electrode connected to the drain electrode and the common electrode to which a common voltage Vcom is applied. In addition, the storage capacitor Cst is defined by a reference voltage line to which a storage reference voltage Vst is applied and the pixel electrode.

The data driver 100 receives the data signal Data2 and the data control signal Sync2 from the controller 50, and receives the source signal in response to the data signal Data2 and the data control signal Sync2. It is applied to the data lines D1, D2, ..., Dm. The data driver 100 converts the data signal Data2, which is a digital signal, into the source signal, which is an analog signal. In this case, the data driver 100 receives a gamma voltage Vref from the driving voltage generator 400 to display an image having an actual desired color, and based on the gamma voltage Vref, the data signal Data2) is converted into the source signal.

The gate driver 200 receives a gate control signal Sync3 from the controller 50 and transmits the scan signal to the gate lines G1, G2, ..., Gn in response to the gate control signal Sync3. ) The gate driver 200 includes a plurality of shift resistors, and the shift registers include gate on / off voltages (Von / Voff) for determining a high voltage and a low voltage of the scan signal. ) Is applied from the driving voltage generator 400.

The controller 50 receives the image signal Data1 and the control signal Sync1 from the outside, and responds to the image signal Data and the control signal Sync1 in response to the data signal Data2 and the data control signal Sync2. ), The gate control signal Sync3 and the voltage control signal Pcon are output. The data signal Data2 has an RGB color data value and is applied to the data driver 100 to represent a color of an image. The data control signal Sync2 is input to the data driver 100 to control the data driver 100, and the gate control signal Sync3 is input to the gate driver 200 to provide the gate driver 200. To control. The voltage control signal Pcon is input to the driving voltage generator 400 to control the driving voltage generator 400.

FIG. 2 is a block diagram illustrating in detail a driving voltage generator of the display device of FIG. 1.

Referring to FIG. 2, the driving voltage generator 400 receives the voltage control signal Pcon from the controller 50 and sends the voltage control signal Pcon to the driving unit and the display unit 300 by the voltage control signal Pcon. Apply the drive voltage. In this case, the driving voltage is formed in the gamma voltage Vref applied to the data driver 100, the gate on / off voltage Von / Voff applied to the gate driver 200, and the display unit 300. The common voltage Vcom is applied to the common electrode and the storage reference voltage Vst is applied to the reference voltage line.

The driving voltage generator 400 includes an AC / DC converter 410, a DC / DC converter 420, a switching controller 430, and a voltage generator 440.

The AC / DC converter 410 receives an AC voltage Vcc from the outside and outputs a first DC voltage Vi to the DC / DC converter 420. The AC / DC converter 410 includes a rectifier circuit (not shown) for rectifying the AC voltage Vcc to generate the first DC voltage Vi.

The DC / DC converter 420 is, for example, a boost converter for boosting a DC voltage by switching. The DC / DC converter 420 receives the first DC voltage Vi from the AC / DC converter 410 and outputs a second DC voltage Vo boosted by the voltage generator 440. . The DC / DC converter 420 receives a first switching signal S1 and a second switching signal S2 from the switching controller 430 to determine a boost ratio of the second DC voltage Vo.

The switching controller 430 receives the voltage control signal Pcon from the controller 50, and controls the DC / DC converter 420 in response to the voltage control signal Pcon. S1) and the second switching signal S2 are output to the DC / DC converter 420. The first switching signal S1 and the second switching signal S2 are repeated at regular intervals. The first switching signal S1 is applied to the DC / DC converter 420 to determine the magnitude of the second DC voltage Vo, and the second switching signal S2 is the DC / DC converter ( 420 is applied to generate a resonance in the DC / DC converter 420, and the DC / DC converter 420 causes zero current switching by the resonance.

The voltage generator 440 receives the second DC voltage Vo from the DC / DC converter 420 to generate the driving voltage required to actually drive the display unit 300 and the driver. The voltage generator 440 includes a gamma voltage generator 442, a gate voltage generator 444, and a common voltage generator 446.

The gamma voltage generator 442 receives the second DC voltage Vo and outputs the gamma voltage Vref to the data driver 100. The gate voltage generator 444 receives the second DC voltage Vo and outputs the gate on / off voltage Von / Voff to the gate driver 200. The common voltage generator 446 receives the second DC voltage Vo, outputs the common voltage Vcom to the common electrode, and outputs the storage reference voltage Vst to the reference voltage line. .

In FIG. 2, only one DC / DC converter 420 is illustrated. Alternatively, the driving voltage generator 400 may have a plurality of DC / DC converters 420.

3 is a circuit diagram illustrating a DC / DC converter in detail in the driving voltage generator of FIG. 2.

Referring to FIG. 3, the DC / DC converter 420 includes a DC power input unit 422, a DC power output unit 424, a first switching unit 426, and a second switching unit 428.

The DC power input unit 422 includes the first DC voltage Vi and one input inductor Li. The first DC voltage Vi is generated and applied from the AC / DC converter 410 and is connected in series with the input inductor Li.

The DC power output unit 424 includes one output diode Df, one output capacitor Co, and an output load Ro. The output diode Df is connected in series with the input inductor Li, and the output capacitor Co and the output load Ro are connected in parallel with each other and connected in series with the output diode Df. In this case, the voltage across the output load Ro is defined as a second DC voltage Vo. In addition, the output diode Df is disposed such that a current flowing through the output diode Df flows toward the output capacitor Co and the output load Ro.

The first switching unit 426 is disposed between the DC power input unit 422 and the DC power output unit 424. The first switching unit 426 includes one first transistor T1 and one first diode D1.

The first transistor T1 and the first diode D1 are connected in parallel with each other and are connected in series with the input inductor Li. In this case, the first switching signal S1 generated by the switching control unit 430 is input to the gate terminal of the first transistor T1, and the current flowing through the channel layer of the first transistor T1 is Head toward the first DC voltage Vi. In addition, the direction of the first diode D1 is determined such that a current flowing through the first diode D1 flows toward the input inductor Li.

The second switching unit 428 is disposed between the first switching unit 426 and the DC power output unit 424. The second switching unit 428 includes one resonant inductor Lr, one resonant capacitor Cr, one second transistor T2, and one second diode D2.

The resonant inductor Lr is connected in series with the input inductor Li and is disposed in parallel with the first transistor T1 and the first diode D1. The second transistor T2 and the second diode D2 are connected in parallel with each other, and are connected in series with the resonant inductor Lr. In addition, the second transistor T2 and the second diode D2 are connected in parallel with the output diode. The resonant capacitor Cr is connected in series with the second transistor T2 and the second diode D2 connected in parallel.                     

In this case, the second switching signal S2 generated by the switching controller 430 is input to the gate terminal of the second transistor T2, and the current flowing through the channel layer of the second transistor T2 is Toward the resonant inductor Lr. In addition, the direction of the second diode D2 is determined such that a current flowing through the second diode D2 flows toward the resonance capacitor Cr.

The first and second transistors T1 and T2 shown in FIG. 3 are bipolar transistors. For example, the bipolar transistor may be a bipolar junction transistor (BJT) or an insulated gate bipolar transistor (IGBT). Alternatively, the first and second transistors T1 and T2 may be metal oxide semiconductor field effect transistors (MOSFETs).

FIG. 4 is a circuit diagram abbreviated in order to more easily explain the circuit diagram of FIG. 3.

Referring to FIG. 4, the circuit of the DC / DC converter 420 is abbreviated more simply for the convenience of circuit analysis. In this case, it is assumed that the input inductor Li is sufficiently large so that the DC power input unit 422 has a constant input DC current Ii, and the output capacitor Co is also large enough so that the DC power output unit 424 is also large. It is assumed that the second DC voltage Vo is constant.

In addition, a voltage applied to both ends of the first transistor T1 is defined as a first switch voltage Vs1, and a current directed toward the first transistor T1 is defined as a first switch current Is1. The voltage across the second transistor T2 is defined as the first switch voltage Vs2, and the current directed toward the second transistor T2 is defined as the second switch current Is2. The voltage across the resonant capacitor Cr is defined as the resonant capacitor voltage Vcr, and the current directed toward the input DC current Ii through the resonant inductor Lr is defined as the resonant inductor current ILr. . A current directed toward the second DC voltage Vo through the output diode Df is defined as an output diode current IDf, and a voltage across both ends of the output diode Df is defined as an output diode voltage VDf. Furthermore, the first transistor T1 is defined as a first switch and the second transistor T2 is defined as a second switch.

Hereinafter, an operation mode of the DC / DC converter 420 will be described through waveform diagrams of signals in the DC / DC converter 420.

5A through 5F are waveform diagrams illustrating signals in the circuit diagram of FIG. 4. In detail, FIG. 5A is a waveform diagram illustrating first and second switching signals in the circuit diagram of FIG. 4, and FIG. 5B is a diagram illustrating a voltage across the first switching unit and a current applied to the first switching unit in the circuit diagram of FIG. 4. 5C is a waveform diagram illustrating a voltage across both ends of the second switching unit and a current applied to the second switching unit in the circuit diagram of FIG. 4, and FIG. 5D is a diagram illustrating a voltage across both output capacitors in the circuit diagram of FIG. 4. 5E is a waveform diagram illustrating a current applied to the resonant inductor in the circuit diagram of FIG. 4, and FIG. 5F is a voltage across both ends of the first diode and a current applied to the first diode in the circuit diagram of FIG. 4. Is a waveform diagram showing.

5A to 5F, the operation mode of the DC / DC converter 420 may include a zeroth time t0, a first time t1, a second time t2, and a third time according to the passage of time. It is divided into a time t3, a fourth time t4, a fifth time t5, a sixth time t6, a seventh time t7, and an eighth time t8.

In the case of the zero mode in which the operation time is before the zeroth time t0, both the first switching signal S1 and the second switching signal S2 are in an off state. During the zero mode, the input DC current Ii is applied to the output load Ro through the resonant inductor Lr and the output diode Df.

In a first mode in which the operation time is up to the first time t1 including the zero time t0, the first switching signal S1 is turned on. 2 switching signal S2 maintains the off state. During the first mode, the resonant inductor current ILr and the output diode current Df decrease linearly by the resonant inductor Lr, while the first switch current Is1 is linear. To increase. Accordingly, as the output diode Df is softly turned off and the first switch is softly turned on, a reverse recovery current by the first diode or the output diode is caused. Reduces the impact of.

In the second mode in which the operation time is up to and before the second time t2 including the first time t1, the input DC current Ii flows through the first switch, and the output diode Df ) Stays off. During the second mode, the same operation as that of the conventional boost converter without the second switching unit is performed.

In a third mode in which the operating time is up to the third time t3 including the second time t2, the second switch is softly turned on, and the first switch remains on. do. When the second switch is softly turned on, resonance starts between the resonant inductor Lr and the resonant capacitor Cr. Accordingly, the resonance current generated by the resonance proceeds in the order of the resonance capacitor Cr, the second switch, the resonance inductor Lr, and the first switch, and the resonance capacitor is performed at the third time t3. The voltage VCr is inverted to a negative maximum value.

In the fourth mode in which the operating time is up to the fourth time t4 including the third time t3, the resonance capacitor voltage VCr becomes a negative maximum value at the third time t3. It gradually decreases as it is reversed. During the fourth mode, the resonant current is inverted to turn on the second diode D2, and as a result, the resonant current flows through the second diode D2. Therefore, while the resonance current flows through the second diode D2, the second switch satisfies the zero current switching condition. In this case, the zero current switching condition means switching while no current flows. Further, as the resonance current gradually increases sinusoidal, the first switch current decreases sinusoidally.

In a fifth mode in which the operating time is up to the fifth time t5 including the fourth time t4, the first switch current Is1 is zero at the fourth time t4. Is reversed to a negative value. As the first switch current Is1 becomes zero, the first diode D1 is turned on so that current flows to the first diode D1. As a result, the first switch is satisfied with the zero current switching condition during the fifth mode.                     

In the case of the sixth mode in which the operation time is before the sixth time t6 including the fifth time t5, the zero current switching condition of the second switch secured in the fourth and fifth modes and the Under zero current switching conditions of the first switch, the first switch and the second switch are simultaneously turned off for ease of control.

In the seventh mode in which the operation time is before the seventh time t7 including the sixth time t6, the resonance capacitor voltage Vcr is not completely terminated at the sixth time t6. In this state, the resonant capacitor voltage Vcr has a lower value than the second DC voltage Vo. During the seventh mode, the resonance capacitor voltage Vcr is charged to the second DC voltage Vo by the input DC current Ii to complete resonance.

In the eighth mode in which the operation time is after the seventh time t7, the output diode Df is turned on in the zero voltage condition formed by resonance at the seventh time t7. During the eighth mode, the same operation as that of the conventional boost converter without the second switching unit is performed.

As described above, the DC / DC converter 420 generates the boosted second DC voltage Vo while repeatedly performing the operations of the zeroth to eighth modes.

According to an exemplary embodiment of the present invention, by adding and resonating the second switching unit 428 in the existing boost converter, the first switch and the second switch may be switched under a zero current switching condition. Accordingly, current stress and conduction loss generated when the first switch and the second switch are switched can be prevented, and as a result, power loss can be reduced.

As described above, according to the present invention, by adding the second switching unit in the existing boost converter to generate a resonance current, the first switch and the second switch may be switched under the zero current switching condition. Accordingly, current stress and conduction loss generated when the first switch and the second switch are switched can be prevented, and as a result, power loss can be reduced.

Although described above with reference to the embodiments, those skilled in the art can be variously modified and changed within the scope of the present invention without departing from the spirit and scope of the invention described in the claims below. I can understand.

Claims (8)

A DC power input unit converting a first DC voltage provided from the outside into a DC current; A DC power output unit connected to the DC power input unit and converting the DC current into a second DC voltage to output the second DC voltage; A first switching unit disposed between the DC power input unit and the DC power output unit to control the output of the first DC current; And A second switching unit disposed between the first switching unit and the DC power output unit and configured to perform zero current switching of the first switching unit by using resonance with the first switching unit, The first switching unit is connected to the DC power input unit, and connected in parallel with the first switch and the first switch to control the magnitude of the second DC voltage by intermittent the output of the first DC current by a switching cycle. And a first diode connected in series with the DC power input unit. delete The power conversion device of claim 1, wherein the first switch is a bipolar transistor. The method of claim 1, wherein the second switching unit A resonance inductor connected in parallel with the first switching unit and connected in series with the DC power input unit; A second switch connected in series with the DC power output unit and connected in series with the resonant inductor and configured to zero current switch the first switching unit by using resonance with the first switching unit; A second diode connected in parallel with the second switch and connected in series with the resonant inductor; And And a resonant capacitor connected between the second switch and the second diode and the DC power input unit. 5. The power converter of claim 4, wherein the second switch is a bipolar transistor. A first power converter converting an AC voltage into a first DC voltage; A DC power input unit for converting the first DC voltage into a DC current, a DC power output unit connected to the DC power input unit and outputting the DC current by converting the DC current into a second DC voltage, the DC power input unit and the DC power output A first switching part interposed between the first switching part and the first switching part and the direct current power output part disposed between the first switching part and the first switching part by using resonance with the first switching part; A second power conversion unit including a second switching unit for zero current switching the unit; And It includes a switching control unit for controlling the second power conversion unit, The first switching unit is connected to the DC power input unit, and connected in parallel with the first switch and the first switch to control the magnitude of the second DC voltage by intermittent the output of the first DC current by a switching cycle. And a first diode connected in series with the DC power input unit. The power converter of claim 6, further comprising a voltage generator configured to change the second DC voltage into a driving voltage and output the driving voltage. A display unit including a data line and a scan line crossing each other and displaying an image by the data line and the scan line; A driver for applying a source signal to the data line and applying a scan signal to the scan line; A DC power input unit for converting a first DC voltage provided from the outside into a DC current, a DC power output unit connected to the DC power input unit and outputting the DC current by converting the DC current into a second DC voltage, the DC power input unit and the A first switching unit disposed between a DC power output unit and intermittently outputting the output of the first DC current, and disposed between the first switching unit and the DC power output unit, by using resonance with the first switching unit; A driving voltage generation unit including a second switching unit for zero current switching the first switching unit, and applying a driving voltage to the display unit and the driving unit; And A control unit controlling the driving unit and the driving voltage generation unit by an image signal input from an external device, The first switching unit is connected to the DC power input unit, and connected in parallel with the first switch and the first switch to control the magnitude of the second DC voltage by intermittent the output of the first DC current by a switching cycle. And a first diode connected in series with the DC power input unit.

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