KR100514185B1 - DC-DC Converter for electro luminescence display - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC-DC converter, and more particularly, to a DC-DC converter suitable for implementing a display device of a portable information processing device because it can improve a very small amount of power consumption and voltage conversion efficiency.

In this configuration, in the present invention, a plurality of scan lines and data lines are arranged horizontally and in a column, and a pixel portion is formed at an intersection thereof, and a cathode voltage line for supplying a power voltage and a cathode voltage for supplying the power voltage of the pixel portion is provided. An organic light emitting display device, comprising: a power supply voltage booster for boosting an input voltage; And a voltage inverting unit for boosting the input voltage to a predetermined level. The apparatus may further include a voltage divider configured to distribute the voltages output from the power voltage boosting unit and the voltage inverting unit to a predetermined level and output the voltages to the power voltage line and the cathode voltage line.

Description

DC-DC converter for organic electroluminescent display

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC-DC converter, and more particularly, to a DC-DC converter suitable for implementing a display device of a portable information processing device by reducing power consumption and improving voltage conversion efficiency.

Recently, with the spread of portable information terminals (PDAs) including mobile phones and notebook personal computers, display devices such as liquid crystal display (LCD) and electro luminescence (EL) display devices are used as display devices with low power consumption. It is becoming.

FIG. 1 illustrates an active matrix organic light emitting display device as an example of such a display device.

Reference numeral 10 denotes an organic EL panel, 11 a data driver, 12 a scan driver, 13 a pixel, 20 a DC / DC converter, and 30 a power supply unit.

The power supply unit 30 supplies power to the DC-DC converter 20, the DC / DC converter 20 boosts and outputs power, the scan driver 12 outputs a selection signal, and the data driver 11. Outputs video data. In addition, the organic EL panel 10 includes a plurality of data lines D1, D2, ... Dz and scan lines S1, S2, ... Sy connected to the data driver 11 and the scan driver 12. It is arranged on the substrate horizontally and in rows, and a plurality of pixels 13 are formed at their intersections.

When the power output from the power supply unit 30 is transferred to the DC / DC converter 20, the DC-DC converter boosts the voltage to the power voltage ELVDD line and the cathode voltage ELVSS line of the organic EL panel 10. Pass each one. The scan driver 12 transmits a selection signal to the pixel 13 through a scan line connected thereto, and the data driver 11 transmits image data to the pixel 13 through a data line.

Therefore, the organic EL panel 10 transmits a selection signal and an image signal from the scan driver 12 and the data driver 11, and the power voltage ELVDD and the cathode voltage ELVSS are supplied from the DC-DC converter 20. Display a certain image by the authorization.

The organic light emitting display device employed in a portable terminal or the like uses a low voltage such as a battery, so that the input power must be converted to a desired voltage in order to generate an organic EL lighting voltage higher than the input power. That is, in order to turn on the organic EL device, the organic EL device must have a structure of simultaneously generating the power supply voltage ELVDD and the cathode voltage ELVSS.

However, in the conventional DC-DC converter, when the input low voltage is boosted to a constant voltage and the boosted voltage is inverted to the cathode voltage ELVSS, and a loss is caused by each component of the DC-DC converter during driving. There is a problem.

Therefore, the present invention devised to solve the above problems, in the generation of the cathode voltage by boosting the input voltage to a constant voltage and inverting it to output the cathode voltage to minimize the loss of the DC-DC module voltage conversion efficiency An object of the present invention is to provide a DC-DC converter of the improved organic light emitting display device.

A configuration of the present invention for achieving the above object is a power supply line and a cathode voltage supplying a plurality of scan lines and data lines arranged horizontally and columns, the pixel portion is formed at the intersection thereof, the supply voltage of the pixel portion An organic light emitting display device comprising a cathode voltage line for supplying a voltage, comprising: a power supply voltage booster for boosting an input voltage; And a voltage inverting unit for boosting the input voltage to a predetermined level.

The apparatus may further include a voltage divider configured to distribute the voltages output from the power voltage boosting unit and the voltage inverting unit to a predetermined level and output the voltages to the power voltage line and the cathode voltage line.

The apparatus may further include a switching controller configured to control switching times of the power voltage boosting unit and the voltage inverting unit.

Here, the power voltage boosting unit and the first charging means for charging the input power; First switching means switched on to transfer input power to the first charging means; A first diode transferring a charged voltage to the first charging means; And a first capacitor that charges the voltage delivered from the first diode and delivers the voltage to the voltage divider.

In addition, when the first switching means is off, the first diode is energized, characterized in that the charging voltage of the first charging means is transmitted.

The switching controller may control the switching of the first switching means to adjust the charging voltage level of the first inductor.

Here, the voltage inverting unit and the second charging means for charging the power supply voltage; Second switching means for switching on to transfer a power supply voltage to the second charging means; A second diode which transfers the charged voltage to the second charging means when the second switching means is off; And a second capacitor that charges the voltage delivered from the second diode.

When the second switching means is turned off, the second diode, the second charging means, and the second capacitor form a closed circuit.

The voltage divider may be connected between the anode of the second diode and the cathode voltage terminal.

The switching controller may control the switching of the second switching means to adjust the charging voltage level of the second inductor.

In addition, the first switching means and the second switching means is characterized in that the polarity is opposite to each other.

Or an organic light emitting display comprising a plurality of scan lines and data lines arranged horizontally and in a column, a pixel portion formed at an intersection thereof, and a power supply voltage supplying a power supply voltage for the pixel portion and a cathode voltage line supplying a cathode voltage; An apparatus comprising: a power supply voltage booster for boosting an input power supply; A voltage inverting unit for boosting the input voltage to a predetermined level and inverting the input voltage; A voltage divider for distributing the voltages output from the power voltage booster and the voltage inverter to a predetermined level and outputting the voltages to the power voltage line and the cathode voltage line; And a switching controller for controlling switching of the power voltage boosting unit and the voltage inverting unit.

Here, the power voltage boosting unit and the first charging means for charging the input power; First switching means switched on to transfer input power to the first charging means; A first diode transferring a charged voltage to the first charging means; And a first capacitor that charges the voltage delivered from the first diode and delivers the voltage to the voltage divider.

The switching controller may control the switching of the first switching means to adjust the charging voltage level of the second inductor.

Here, the voltage inverting unit and the second charging means for charging the power supply voltage; Second switching means for switching on to transfer a power supply voltage to the second charging means; A second diode which transfers the charged voltage to the second charging means when the second switching means is off; And a second capacitor that charges the voltage delivered from the second diode and transfers the voltage delivered to the voltage divider.

Alternatively, the switching controller may control the switching of the second switching means to adjust the charging voltage level of the second inductor.

In addition, the first switching means and the second switching means is characterized in that the polarity is opposite to each other.

And a power voltage boosting unit for boosting the input power; A voltage inverting unit for boosting the input voltage to a predetermined level and inverting the input voltage; A voltage divider for distributing the voltages output from the power voltage booster and the voltage inverter to a predetermined level and outputting the voltages to the power voltage line and the cathode voltage line; And a switching controller for controlling switching of the power voltage boosting unit and the voltage inverting unit.

Wherein the power voltage boosting unit comprises: first charging means for charging the input power; First switching means switched on to transfer input power to the first charging means; A first diode transferring a charged voltage to the first charging means; And a first capacitor that charges the voltage delivered from the first diode and delivers the voltage to the voltage divider.

In addition, the voltage inverting unit and the second charging means for charging the power supply voltage; Second switching means for switching on to transfer a power supply voltage to the second charging means; A second diode which transfers the charged voltage to the second charging means when the second switching means is off; And a second capacitor that charges the voltage delivered from the second diode and delivers the voltage to the voltage divider.

In addition, the first switching means and the second switching means is characterized in that the polarity is opposite to each other.

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

2 is a circuit diagram showing a preferred embodiment of the present invention.

Reference numeral 20 is a DC-DC converter, 21 is a power voltage booster, 22 is a voltage inverter, 23 is a voltage divider, 24 is a switching controller, 25 is an input power supply, ELVDD is a power supply voltage, ELVSS is a cathode voltage, and C1. C3 is a capacitor, L1 and L2 are inductors, M1 and M2 are switching transistors, D1 and D2 are diodes, and R1 and R2 are resistors.

The DC-DC converter 20 includes a power voltage booster 21 for boosting input power to a predetermined level, a voltage inverter 22 for inverting input power, the power voltage booster 21 and the A voltage distribution unit 23 for distributing the output voltage of the voltage inverting unit 22 to a constant voltage level, a switching control unit 24 for controlling the switching transistors M1 and M2, and an input power supply unit for transmitting input power. (25). The power supply voltage ELVDD is connected to the power supply voltage ELVDD line of the pixel 13, and the cathode voltage ELVSS is connected to the cathode voltage ELVSS line of the pixel 13.

The input power supply unit 25 includes a first capacitor C1 and is connected to the power supply voltage boosting unit 21 and the voltage inverting unit 22 to transmit input power, and the power supply voltage boosting unit 21 is The input power delivered from the input power supply unit 25 is boosted to a predetermined level and transferred to the voltage distribution unit 23. The voltage inverting unit 22 boosts the input power transmitted from the input power supply unit 25 to a predetermined level, and inverts the input power to the voltage distribution unit 23. In addition, the voltage divider 23 has the power voltage boosting unit 21 and the voltage inverting unit 22 connected to an input side to distribute a boosted voltage or an inverting voltage to the power voltage terminal ELVDD. And output to the cathode voltage terminal ELVSS, respectively.

Here, the power voltage booster 21 includes a first inductor L1 connected between the input terminal Vin and the first capacitor C1. In addition, the first inductor L1 is connected to the first diode D1, and a first switching transistor M1 is connected between the anode of the first diode D1 and the first inductor L1. A voltage divider 23 is connected to the cathode of the first diode D1, and a second capacitor C2 is connected between the cathode of the first diode D1 and the voltage divider 23. The first switching transistor M1 is preferably an N-MOS field effect transistor.

In addition, the voltage inverter 22 includes a second switching transistor M2 connected to the input voltage Vin and a second diode D2 having a cathode connected to a source side of the second switching transistor M2. do. In addition, a second inductor L2 is connected between the cathode of the second diode D2 and the second switching transistor M2, and the anode side of the second diode D2 is connected through the voltage divider 23. It is connected to the cathode voltage terminal ELVSS. The third capacitor C3 is connected between the anode of the second diode D2 and the cathode voltage terminal ELVSS. Here, the second switching transistor M2 preferably uses a P-MOS field effect transistor.

The first switching transistor M1 and the second switching transistor are connected to the switching controller 24.

The voltage divider 23 also includes a first resistor R1 connected in parallel with the second capacitor C2 and a second resistor R2 connected between the power supply voltage ELVDD and the cathode voltage ELVSS. It is composed of

The operation of the DC-DC converter according to the present invention having the above configuration will be described with reference to FIGS. 3 to 5.

3 is a waveform diagram for explaining the operation of the switching transistor, Figure 4 is a waveform diagram showing the output of the power supply voltage.

The switching controller 24 applies a high signal to the N-MOS type first switching transistor M1 and the P-MOS type second switching transistor M2. Therefore, the first switching transistor M1 is turned on and the second switching transistor M2 is turned off, as shown in FIG. 3.

Therefore, as the first switching transistor M1 and the first inductor L1 form a closed circuit, the input power Vin is charged in the first inductor L1 through the first switching transistor M1. The switching controller 24 controls the duty ratio of the first switching transistor M1 to adjust the voltage charged in the first inductor L1. That is, the voltage level charged in the first inductor L1 varies according to the turn-on time of the first switching transistor M1. At this time, the first diode D1 is turned off.

Thereafter, when a predetermined time elapses, the switching controller 24 applies a low signal to the first switching transistor M1 and the second switching transistor M2. Therefore, the first switching transistor M1 is turned off and the second switching transistor M2 is turned on.

As described above, as the first switching transistor M1 is turned off, the first diode D1 is turned on to transfer the voltage across the first inductor L1 to the second capacitor C2. Therefore, the second capacitor C2 is charged with the charging voltage of the first inductor L1, and is output to the voltage divider 23. Therefore, the voltage divider 23 distributes the applied charging voltage to a predetermined level and outputs it to the power supply voltage ELVDD. At this time, the drain voltage of the first switching transistor M1 is, for example, the output side voltage is applied as 5V, and when the first switching transistor M1 is on, it is 0V, as shown in FIG.

As shown in FIG. 4, when the first switching transistor M1 is in an off state, a drain voltage of 5V, which is a voltage charged in the first inductor L1, is output, and the first switching transistor M1 is in an on state. It can be seen that the drain voltage Vd1 is 0V and the input voltage Vin is 3V. The power supply voltage ELVDD output here is obtained by Equation 1 below. Equation 1 shows an output voltage of the power voltage booster 21.

VDD = Vin / (1-D)

VDD is the output voltage, Vin is the input voltage, and D is the duty ratio.

In addition, as the second switching transistor M2 is turned on, the input voltage Vin is charged in the second inductor L2. At this time, the second diode D2 is turned off.

Similarly, the switching controller 24 controls the duty ratio of the second switching transistor M2 to adjust the voltage level charged in the second inductor L2.

Thereafter, when the second switching transistor M2 is turned off by the switching controller 24, the second diode D2, the second inductor L2, and the third capacitor C3 form a closed circuit. That is, the second diode D2 is turned on to transfer the charging voltage of the second inductor L2 to the third capacitor C3.

The third capacitor C3 transfers the charging voltage to the voltage divider 23. Therefore, the voltage divider 23 divides the applied voltage by a predetermined level and outputs the voltage to the cathode voltage ELVSS. In this case, the voltage divider 23 and the cathode voltage ELVSS are connected to the anode of the second diode D2 so that a reverse bias voltage flows through the cathode voltage ELVSS. That is, the voltage inverting unit 22 raises the input power Vin to a predetermined level and inverts it to output the cathode voltage as a negative voltage (−), the value of which is expressed by Equation 2 below. .

Vss = (D × Vin) / (1-D)

Vss is the output voltage, Vin is the input voltage (Vin), and D is the duty ratio.

The output voltage is determined by the above equation (2), and Vss < Vin in the range of D > 0.5, and Vss > In the present invention, the voltage inverting unit 22 applies a P-MOS type switching transistor M2, and converts the output voltage Vss into a negative voltage (−) by controlling the duty ratio to 0.5 or more. Output to (ELVSS). In other words, if the required cathode voltage ELVSS is -6V, the voltage inverting unit 22 boosts the input voltage Vin of 3V to 6V and inverts the negative voltage (-). This is as shown in FIG.

5 is a waveform diagram illustrating the cathode voltage ELVSS.

As shown in the drawing, when the second switching transistor M2 is turned off and the second inductor L2, the second diode D2, and the third capacitor C3 form a closed circuit, the drain voltage Vd2 becomes -6V. When the second switching transistor M2 is turned on, the drain voltage Vd2 is measured at 3V.

Although the detailed description of the present invention has been described by taking specific embodiments of the present invention as an example, the DC-DC converter according to the present invention is not limited to the organic light emitting display device, and organically within the scope not departing from the concept of the present invention. Modification or modification of various forms by those skilled in the art to which the present invention pertains to apparatuses other than the electroluminescent display device is also included in the concept of the present invention.

As described above, the DC-DC converter of the organic light emitting display device according to the present invention has a configuration suitable for the organic light emitting display device by simultaneously generating a power supply voltage and a cathode voltage. By outputting the cathode voltage by the butting to minimize the loss of the DC-DC module has the effect of improving the efficiency. In addition, the DC-DC converter according to the present invention can be applied to other devices other than the organic light emitting display because the loss as described above is minimized and the voltage conversion efficiency is excellent.

1 is a block diagram illustrating a general organic light emitting display device;

2 is a circuit diagram showing a DC-DC converter for EL lighting of an organic light emitting display device according to the present invention;

3 is a graph showing input waveforms of the first and second switching means;

4 is a measurement graph of the power supply voltage,

5 is a measurement graph of the cathode voltage.

* Description of the symbols for the main parts of the drawings *

10: organic EL panel 11: data driver

12: scan driver 13: pixel portion

20: DC / DC converter 21: power voltage booster

22: voltage inverter 23: voltage divider

ELVDD: Power Supply ELVSS: Cathode Voltage

Claims (21)

The organic light emitting display includes a plurality of scan lines, data lines arranged horizontally and in a column, pixel portions formed at intersections thereof, power supply voltage lines supplying power voltages of the pixel parts, and cathode voltage lines supplying cathode voltages. In the apparatus, A power supply voltage booster for boosting an input voltage; A DC-DC converter of an organic light emitting display device, characterized in that it comprises a voltage inverting unit for boosting the input voltage to a predetermined level. The method of claim 1, And a voltage divider for distributing the voltages output from the power voltage booster and the voltage inverter to a predetermined level and outputting the voltages to the power voltage line and the cathode voltage line. DC converter. The method of claim 1, And a switching controller for controlling switching times of the power voltage boosting unit and the voltage inverting unit. The method of claim 1, wherein the power voltage boosting unit First charging means for charging input power; First switching means switched on to transfer input power to the first charging means; A first diode transferring a charged voltage to the first charging means; And a first capacitor which charges the voltage transferred from the first diode and transfers the voltage transferred from the first diode to the voltage divider. The method of claim 4, wherein And the first diode is energized when the first switching means is turned off, so that the charging voltage of the first charging means is transferred to the DC-DC converter of the organic light emitting display device. The method of claim 4, wherein the switching control unit And controlling the switching of the first switching means to adjust the charge voltage level of the first inductor. The method of claim 1, wherein the voltage inverting unit Second charging means for charging a power supply voltage; Second switching means for switching on to transfer a power supply voltage to the second charging means; A second diode which transfers the charged voltage to the second charging means when the second switching means is off; And a second capacitor charging the voltage transmitted from the second diode. The method of claim 7, wherein And the second diode, the second charging means, and the second capacitor constitute a closed circuit when the second switching means is turned off. The method of claim 7, wherein The DC-DC converter of the organic light emitting display device, characterized in that the voltage divider is connected between the anode of the second diode and the cathode voltage terminal. The method of claim 7, wherein the switching control unit And controlling the switching of the second switching means to adjust the charging voltage level of the second inductor. The method according to claim 3 or 7, The DC-DC converter of the organic light emitting display device, wherein the first switching means and the second switching means have opposite polarities. The organic light emitting display device includes a plurality of scan lines and data lines arranged horizontally and in a column, and a pixel portion is formed at an intersection thereof, and a power supply voltage for supplying a power voltage for the pixel portion and a cathode voltage line for supplying a cathode voltage. To A power voltage booster for boosting an input power; A voltage inverting unit for boosting the input voltage to a predetermined level and inverting the input voltage; A voltage divider for distributing the voltages output from the power voltage booster and the voltage inverter to a predetermined level and outputting the voltages to the power voltage line and the cathode voltage line; And a switching controller for controlling switching of the power voltage boosting unit and the voltage inverting unit. The method of claim 12, wherein the power voltage boosting unit First charging means for charging input power; First switching means switched on to transfer input power to the first charging means; A first diode transferring a charged voltage to the first charging means; And a first capacitor which charges the voltage transferred from the first diode and transfers the voltage transferred from the first diode to the voltage divider. The method of claim 13, wherein the switching control unit And controlling the switching of the first switching means to adjust the charging voltage level of the second inductor. The method of claim 13, wherein the voltage inverting unit Second charging means for charging a power supply voltage; Second switching means for switching on to transfer a power supply voltage to the second charging means; A second diode which transfers the charged voltage to the second charging means when the second switching means is off; And a second capacitor which charges the voltage transferred from the second diode and transfers the voltage transferred to the voltage divider. 2. The method of claim 15, wherein the switching control unit And controlling the switching of the second switching means to adjust the charging voltage level of the second inductor. The method according to claim 13 or 15, The DC-DC converter of the organic light emitting display device, wherein the first switching means and the second switching means have opposite polarities. A power voltage booster for boosting an input power; A voltage inverting unit for boosting the input voltage to a predetermined level and inverting the input voltage; A voltage divider for distributing the voltages output from the power voltage booster and the voltage inverter to a predetermined level and outputting the voltages to the power voltage line and the cathode voltage line; And a switching controller for controlling switching of the power voltage boosting unit and the voltage inverting unit. The method of claim 18, wherein the power voltage boosting unit First charging means for charging input power; First switching means switched on to transfer input power to the first charging means; A first diode transferring a charged voltage to the first charging means; And a first capacitor which charges the voltage transferred from the first diode and transfers the voltage transferred from the first diode to the voltage divider. The method of claim 18, wherein the voltage inverting unit Second charging means for charging a power supply voltage; Second switching means for switching on to transfer a power supply voltage to the second charging means; A second diode which transfers the charged voltage to the second charging means when the second switching means is off; And a second capacitor which charges the voltage transferred from the second diode and transfers the voltage transferred from the second diode to the voltage divider. The method of claim 19 or 20, DC-DC converter, characterized in that the first switching means and the second switching means are opposite in polarity.