KR20110035443A - Organic electroluminescent display device and method of driving the same - Google Patents

Abstract

PURPOSE: An organic electroluminescent display device and a driving method thereof are provided to drive a DC-DC converter in a PFM mode in case of a small load and in a PWM mode in case of a large load, thereby efficiently driving the organic electroluminescent display device. CONSTITUTION: A load includes an organic electroluminescent panel(200). A voltage converting circuit converts an input voltage into an output voltage. A PFM switching controller outputs a PFM switching pulse. The PWM switching controller selectively outputs a PWM switching pulse and a PFWM switching pulse. A power supply circuit(300) converts an input voltage into an output voltage and supplies the output voltage to a load.

Description

Organic electroluminescent display device and method of driving the same

The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device and a driving method thereof.

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 electroluminescent display devices (OELD) are being utilized.

Among these flat panel display devices, the organic light emitting display device is a self-luminous display device, which has advantages of miniaturization, light weight, thinness, and low power driving, and has been widely used in recent years.

The organic light emitting display device is driven by applying the necessary power from a DC-DC converter. In general, the power supply voltage for driving the organic light emitting display device has a higher value than the input voltage input to the DC-DC converter. Therefore, the DC-DC converter is driven in a boost mode to boost the input voltage, and the boosted output voltage is supplied as a power source.

1 is a view schematically showing a conventional DC-DC converter.

As shown in the drawing, the conventional DC-DC converter 10 includes a switching control unit 11, a power supply switching transistor TP, an inductor L, a diode D, and a capacitor C. .

The conventional DC-DC converter 10 having such a configuration can boost the input voltage Vin by adjusting the on / off switching of the power switching transistor TP. That is, when the switching transistor TP is turned on, the current flowing from the input terminal is stored. After that, when the switching transistor TP is turned off, the stored current is discharged through the diode D. As a result, the voltage Vout of the output terminal rises, and the extraction voltage Vout is boosted to a voltage higher than the input voltage Vin. The capacitor C stores the boosted output voltage Vout.

Such a conventional DC-DC converter 10 controls the output voltage Vout to a predetermined range. As such, there are a pulse width modulation (PWM) method and a pulse frequency modulation (PFM) method as a method of controlling the output voltage Vout in a predetermined range. The conventional DC-DC converter 10 is driven in one of these manners.

The PWM method changes the time for turning on the power supply switching transistor TP based on the difference between the feedback voltage obtained by dividing the output voltage Vout and the PWM reference voltage. In other words, when the PWM reference voltage is higher than the feedback voltage, when the voltage difference increases, the on time, that is, the pulse width of the PWM switching pulse becomes long. On the other hand, the frequency of the PWM switching pulse is constant. In this manner, in the PWM system, the pulse width of the PWM switching pulse changes.

On the other hand, in the PFM method, the frequency of the PFM switching pulse for turning on the power supply switching transistor TP is changed based on the difference between the feedback voltage obtained by dividing the output voltage Vout and the PFM reference voltage. In other words, when the PFM reference voltage is higher than the feedback voltage, if the voltage difference increases, the frequency of the PFM switching pulse becomes high. On the other hand, the duty ratio of the PFM switching pulse is constant. In this manner, in the PFM system, the frequency of the PFM switching pulse changes.

The PWM method can be useful when the power consumption of the load is large, that is, for heavy loads. However, there is a problem in that the power conversion efficiency is low when the power consumption is small, that is, light load. That is, in the PWM system, even at a low load, a PWM switching pulse is output so that the power supply switching transistor TP performs a switching operation. Accordingly, in the case of low load, the power loss due to the switching operation is increased.

On the other hand, the PFM method can be usefully used for low loads. However, there is a problem in that the voltage conversion efficiency is low for high loads. That is, in the PFM system, in the case of high load, the frequency of the PFM switching pulse becomes high, and the power supply switching transistor TP performs the switching operation at a high frequency. Accordingly, in the case of high load, power loss due to the switching operation is increased.

Thus, the PWM method and the PFM method have advantages and disadvantages depending on the size of the load. However, the power consumption, i.e., the load of the organic light emitting display device, varies greatly depending on the type of image to be displayed. Therefore, the conventional DC-DC converter driven by one of the PWM method and the PFM method cannot be driven with high efficiency when the size of the load is greatly changed.

In order to improve this problem, DC-DC converter has been proposed to selectively use two methods depending on the size of the load by taking advantage of the PFM method and the PWM method. Hereinafter, for convenience of description, such a DC-DC converter is referred to as a PFM / PWM DC-DC converter.

2 is a view schematically showing a conventional PFM / PWM DC-DC converter.

2, the conventional PFM / PWM DC-DC converter 20 is driven in the PFM mode when the load is small. In this case, the PFM switching pulse output from the PFM switching control unit 21 is input to the power supply switching transistor TP. To this end, the selection switch SS connects the PFM switching controller 21 and the power switching transistor TP.

On the other hand, when the load is large, it is driven in the PWM mode. In such a case, the PWM switching pulse output from the PWM switching control unit 22 is input to the power supply switching transistor TP. To this end, the selection switch SS connects the PWM switching controller 22 and the power switching transistor TP.

As such, the conventional PFM / PWM DC-DC converter 20 may be selectively driven in the PFM mode and the PWM mode according to the load change. Accordingly, under low load and high load, it can be driven with high efficiency.

However, even in the case of the selective driving in the PWM mode and the PFM mode in this way, the middle load between the high load and the low load still cannot be driven with high efficiency. That is, when driving in the PWM mode under heavy load, the power loss due to the switching operation is larger than that under high load. Further, even when driving in the PFM mode under heavy load, power loss due to the switching operation is larger than that under low load.

The present invention has a problem to provide an organic light emitting display device and a driving method thereof that can improve the efficiency of the DC-DC converter.

In order to achieve the above object, the present invention is a load comprising an organic light emitting panel; And a power supply circuit converting an input voltage to supply an output voltage to the load, wherein the power supply circuit comprises: an input terminal configured to receive the input voltage; An output terminal for outputting the output voltage; A voltage conversion circuit comprising a power switching transistor, said voltage conversion circuit converting said input voltage into said output voltage; A PFM switching controller for outputting a PFM switching pulse; A PWM switching pulse synchronized with a frequency of a PWM driving pulse and a PWM switching control unit for selectively outputting a PFWM switching pulse whose pulse width is variable in synchronization with the frequency of the PFM switching pulse, wherein the PFM switching pulse and the PFWM switching pulse And the PWM switching pulses, respectively, provide an organic light emitting display device which is supplied to the power switching transistor when the load size is low, middle and high.

The voltage conversion circuit may include an inductor positioned between a node to which the power switching transistor is connected and the input terminal; A diode located between the node and the output terminal; It may further include a capacitor connected in parallel to the output terminal.

The power supply circuit includes: a PFM error amplifier for comparing the feedback voltage with respect to the output voltage and the PFM reference voltage and outputting the PFM switching controller; A PWM error amplifier which compares the feedback voltage and the PWM reference voltage and outputs the same to the PWM switching controller; A ramp wave generator for outputting a ramp wave synchronized with the frequency of the input pulse to the PWM switching controller; A pulse generator for generating the PWM driving pulse; A first selection switch for selectively connecting the pulse generator and the PFM switching controller to the ramp generator; And a second selection switch for selectively connecting the PWM switching controller and the PFM switching controller to the power switching transistor.

The power supply circuit may further include a feedback circuit connected to the output terminal in parallel to detect the feedback voltage obtained by dividing the output voltage.

In another aspect, the present invention includes the steps of generating a PFM switching pulse in the PFM switching control unit; Generating a PWM switching pulse synchronized with the frequency of the PWM driving pulse by the PWM switching controller; Generating, by a PWM switching controller, a PFWM switching pulse synchronized with a frequency of the PFM switching pulse and having a variable pulse width; Switching power supply switching transistors using the generated PFM switching pulses, PFWM switching pulses, and PWM switching pulses when the loads are low, middle, and high, respectively; Converting an input voltage input to a power supply circuit into an output voltage through switching of the power switching transistor; A method of driving an organic light emitting display device, the method comprising driving an organic light emitting panel of the load using the output voltage.

The output voltage may be a voltage obtained by boosting the input voltage.

Comparing the feedback voltage with respect to the output voltage and the PFM reference voltage and outputting the PFM switching control unit; Comparing the feedback voltage and the PWM reference voltage to output the PWM switching controller; Inputting a PFM switching pulse and a PWM driving pulse into a ramp wave generator at each of the heavy and high loads; The method may further include outputting a ramp wave synchronized with the frequency of a pulse input to the ramp wave generator to the PWM switching controller.

The feedback voltage may be a voltage obtained by dividing the output voltage.

In the present invention, the DC-DC converter is driven in PFM mode at low load and in PWM mode at high load. Accordingly, it is possible to drive with high efficiency at low load and high load.

Moreover, under heavy load, it is driven in PFWM mode. When the PFWM mode is driven, a frequency can be varied in synchronization with the PFM switching pulse, and a PFWM switching pulse can be generated in which the pulse width can be varied to switch the power supply switching transistor. Accordingly, in heavy load, the power loss due to the switching operation can be reduced as compared with the case of driving in the PWM mode, PFM mode, or PFM / PWM mode. Therefore, it becomes possible to drive with high efficiency even in heavy load.

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

3 is a view schematically illustrating an organic light emitting display device according to an embodiment of the present invention, FIG. 4 is a view showing pixels of the organic light emitting panel of FIG. 2, and FIG. 5 is a view illustrating the power circuit of FIG. 3. 6 is a diagram illustrating the control circuit of FIG. 5, and FIG. 7 is a diagram illustrating a comparator of the PWM switching controller of FIG. 6.

As illustrated, the organic light emitting display device 100 according to the embodiment of the present invention includes an organic light emitting panel 200, a panel driving circuit 250, and a power supply circuit 300. Here, the organic light emitting panel 200 and the panel driving circuit 250 for driving the same correspond to a load LOAD at the side of the power supply circuit 300.

The organic light emitting panel 200 is a display panel displaying an image. Referring to FIG. 5, in the organic light emitting panel 200, the gate line GL extending along the row direction and the data line DL extending along the column direction cross each other to define the pixel P. Referring to FIG. Such pixels P are arranged in a matrix form in the organic light emitting panel 200.

The pixel P configured in the organic light emitting panel 200 may include R (red), G (green), and B (blue) pixels. Corresponding R, G, and B image data are input to each of these R, G, and B pixels P. FIG. Here, the neighboring R, G, and B pixels P constitute one video display unit.

In each pixel P, a switching transistor Ts, a driving transistor Td, an organic light emitting diode D, and a storage capacitor C may be configured.

The switching transistor Ts is connected to the corresponding gate line and data line GL and DL. The gate terminal of the driving transistor Td is connected to the drain terminal of the switching transistor Ts. One electrode of the organic light emitting diode D may be connected to the drain terminal of the driving transistor Td. The other electrode of the organic light emitting diode D may receive a driving voltage VDD. The source terminal of the driving transistor Td may be grounded. The storage capacitor C may be connected between the gate terminal and the source terminal of the driving transistor Td. Such a structure of the pixel P is one example, and may be configured in various other structures.

The pixel P as described above is driven as follows.

The gate wiring GL is sequentially scanned frame by frame. During each scan period, a gate signal having a turn-on voltage is supplied to the gate wiring GL. On the other hand, the turn-off voltage is supplied to the gate wiring GL until the next frame is scanned. As the turn-on voltage is applied during the scan period, the switching transistor Ts is turned on.

When the switching transistor Ts is turned on, image data is applied to the data line DL in synchronization with the switching transistor Ts. The image data applied in this way passes through the switching transistor Ts of the pixel P and is applied to the driving transistor Td.

When image data is applied to the driving transistor Td, the driving transistor Td is turned on and a light emission current flows through the driving transistor Td. Here, the value of the light emission current is adjusted according to the value of the applied image data. Such a light emitting current is applied to the organic light emitting diode D, and the organic light emitting diode D emits light of luminance corresponding to the light emitting current. In other words, light of luminance corresponding to the applied image data is emitted through the organic light emitting diode D. Therefore, as the image data is adjusted, the luminance of light emitted through the organic light emitting diode D is adjusted.

On the other hand, image data applied to the driving transistor Td is stored in the storage capacitor C. Accordingly, the image data is stored in the storage capacitor C until the next scan of the pixel, and the organic light emitting diode D may emit light having the luminance corresponding to the image data until the next scan.

The driving voltage VDD for driving the organic light emitting diode D as described above is supplied from the power supply circuit 300.

The panel driving circuit 250 includes various driving circuits for driving the organic light emitting panel 200. For example, a data driver circuit for outputting image data to the data wiring DL and a gate driver circuit for outputting a gate signal to the gate wiring GL are included. And a timing control circuit for controlling the operation of the data driver circuit and the gate driver circuit. Such driving circuits also operate by receiving power from the power supply circuit 300.

As the power supply circuit 300, a DC-DC converter can be used. For example, a boost DC-DC converter that boosts the input voltage Vin may be used. In the following description, for convenience, the power supply circuit 300 may be referred to as a DC-DC converter.

DC-DC converter 300 according to an embodiment of the present invention, for example, at low load (middle load), medium load (middle load), high load (high load), respectively, PFM mode, PFWM mode, PWM mode Can be driven. The DC-DC converter 300 driven as described above will be described in more detail with reference to FIGS. 5 to 7.

The DC-DC converter 300 according to the embodiment of the present invention may include a voltage conversion circuit 310, a control circuit 320, and a feedback circuit 330.

The voltage conversion circuit 310 boosts the input voltage Vin input from the system 400 according to the switching operation, and outputs the boosted output voltage Vout to the load LOAD. To this end, the voltage conversion circuit 310 includes an inductor L, a diode DP, a capacitor CP, and a power switching transistor TP. The inductor L may be connected between the node N and the input terminal to which the power switching transistor TP is connected. The diode DP may be connected between the node N and the output terminal. The capacitor CP may be connected in parallel to the output terminal.

When the power supply switching transistor TP is turned on, the current flowing from the input terminal is stored. After that, when the power supply switching transistor TP is turned off, the current stored in the inductor L is discharged through the diode DP. As a result, the voltage Vout of the output terminal rises, and the output voltage Vout is boosted to a voltage higher than the input voltage Vin. The capacitor CP stores the boosted output voltage Vout. As described above, the voltage conversion circuit 310 boosts the input voltage Vin to generate the output voltage Vout through the switching operation of the power supply switching transistor TP.

The feedback circuit 330 is connected in parallel to the output terminal to detect the feedback voltage VF obtained by dividing the output voltage Vout. The feedback voltage VF detected as described above is transmitted to the control circuit 320. The feedback circuit 330 may be configured as a voltage divider circuit including first and second resistors R1 and R2 connected in series. In such a case, the feedback voltage VF is detected through the node between the first and second resistors.

The control circuit 320 generates a switching pulse which is a switching signal for controlling the on / off switching operation of the power switching transistor TP. Such switching pulses are output in different ways according to the low load, the heavy load, and the high load. To this end, the control circuit 320 includes a PFM controller 321, a PWM controller 322, and first and second selection switches SS1 and SS2.

The PFM control unit 321 includes a PFM error amplifier OPF and a PFM switching control unit SWF.

The PFM error amplifier OPF receives the PFM reference voltage VFref and the feedback voltage VF, and amplifies and outputs the voltage difference between these voltages. For example, the PFM reference voltage VFref and the feedback voltage VF may be input to the non-inverting terminal and the inverting terminal of the PFM error amplifier OPF, respectively.

The PFM switching controller SWF outputs the PFM switching pulse PF in response to the result output from the PFM error amplifier OPF. That is, the frequency of the PFM switching pulse PF changes according to the voltage difference between the PFM reference voltage VFref and the feedback voltage VF. For example, when the PFM reference voltage VFref is greater than the feedback voltage VF, as the voltage difference between the PFM reference voltage VFref and the feedback voltage VF increases, the frequency of the PFM switching pulse PF increases. do. On the other hand, when the PFM reference voltage VFref is less than or equal to the feedback voltage VF, the operation of the PFM switching controller SWF is stopped, and thus the PFM switching pulse PF may not be output.

In the embodiment of the present invention, the PFM switching pulse PF is used at low load and heavy load. For example, at low loads, the power supply switching transistor TP performs the switching operation by the output PFM switching pulse PF. On the other hand, under heavy load, the output PFM switching pulse (PF) is transmitted to the PWM control unit 322 and used, which will be described in more detail below.

The PWM controller 322 includes a PWM error amplifier OPW, a PWM switching controller SWW, a ramp wave generator 323, and a pulse wave generator 324.

The PWM error amplifier OPW receives the PWM reference voltage VWref and the feedback voltage VF, and amplifies and outputs the voltage difference between these voltages. For example, the PWM reference voltage VWref and the feedback voltage VF may be input to the non-inverting terminal and the inverting terminal of the PWM error amplifier OPW, respectively.

The pulse generator 324 generates a PWM driving pulse having a fixed frequency. Such a PWM driving pulse corresponds to a reference signal for driving the DC-DC converter 300 in the PWM mode.

The ramp wave generator 323 generates a ramp wave in response to an input signal. Since the ramp wave has a sawtooth shape or a triangular shape, it is also called a sawtooth wave or a triangle wave.

In the embodiment of the present invention, the ramp wave generator 323 is selectively applied to the PWM driving pulse and the PFM switching pulse PF according to the driving mode. For example, under heavy load, the PFM switching pulse PF is applied to drive the PFWM mode. In the case of high load, a PWM driving pulse is applied to drive the PWM mode. On the other hand, when the load is low, it is driven in the PFM mode, it can be applied to the PFM switching pulse (PF) or PWM driving pulse.

As such, the first selection switch SS1 may be used to selectively apply a signal to the ramp wave generator 322. For example, when the PFWM mode is driven, the first selection switch SS1 connects the ramp wave generator 323 and the PFM control unit 321 to input the PFM switching pulse PF. In the PWM mode driving, the first selection switch SS1 connects the ramp wave generator 323 and the pulse generator 324 to input the PWM driving pulse.

If the ramp wave generator 323 receives the PWM driving pulse, the ramp wave generator 323 generates a ramp wave synchronized with the PWM driving pulse. On the other hand, when the ramp wave generator 323 receives the PFM switching pulse PF, the ramp wave generator 323 generates a ramp wave synchronized with the PFM switching pulse PF. Here, since the PWM driving pulse has a fixed frequency, when the PWM driving pulse is applied, a ramp wave having a fixed frequency is generated. On the other hand, since the frequency of the PFM switching pulse PF is variable, when the PFM switching pulse PF is applied, the ramp wave and the frequency may also change according to the frequency change. As such, the ramp wave generator 323 may generate different types of ramp waves depending on the driving mode.

The PWM switching controller SWW compares the voltage output from the PWM error amplifier OPW with the ramp wave and outputs a switching pulse according to the comparison result. For example, by comparing the output voltage and the ramp wave, the power supply switching transistor TP may be turned on in a region where the ramp wave is higher than the waveform of the output voltage. Through the waveform comparison, the PWM switching controller SWW can change the pulse width of the output switching pulse. In this regard, the pulse width of the output switching pulse increases as the voltage difference between the PWM reference voltage VWref and the feedback voltage VF increases. Here, the increasing direction of the voltage difference is a direction in which the feedback voltage VF decreases based on the PWM reference voltage VWref.

The PWM switching controller SWW having the above operation includes a comparator OPC. For example, the voltage and the ramp wave output from the PWM error amplifier OPW are respectively input to the inverting terminal and the non-inverting terminal of the comparator OPC. Accordingly, the comparator OPC compares the input voltages and outputs a switching pulse.

On the other hand, as described above, since the ramp wave is changed according to the driving mode, the switching pulse output through the PWM switching control unit (SWW) also changes. For example, in the PWM mode driving, a ramp wave synchronized with a PWM driving pulse is input to the PWM switching controller SWW. Accordingly, as the switching pulse to be output, the PWM switching pulse (PW) is fixed, the frequency is fixed and the pulse width can be changed.

On the other hand, in the PFWM mode driving, the ramp wave synchronized with the PFM switching pulse PF is input to the PWM switching controller SWW. Accordingly, as the output switching pulse, the PFWM switching pulse PFW, which can be changed in both frequency and pulse width, is output.

The second selection switch SS2 selectively switches the switching pulses output through the PFM control unit 321 and the PWM control unit 322 and transmits the switching pulses to the power switching transistor TP. For example, when the PFM mode is driven, the second selection switch SS2 connects the PFM control unit 321 and the power switching transistor TP. Accordingly, the PFM switching pulse PF generated by driving the PFM mode is supplied to the power switching transistor TP, so that the power switching transistor TP switches according to the PFM switching pulse PF.

On the other hand, when driving in the PFWM mode and PWM mode, the second selection switch (SS2) is connected to the PWM control unit 321 and the power switching transistor (TP). Here, in the PFWM mode driving, the PFWM switching pulse PFW generated through the PFWM mode driving is supplied to the power switching transistor TP, and the power switching transistor TP switches the switching operation according to the PFWM switching pulse PFW. Done. In the PWM mode driving, the PWM switching pulse PW generated through the PWM mode driving is supplied to the power switching transistor TP, and the power switching transistor TP performs the switching operation according to the PWM switching pulse PW. Done.

Hereinafter, a method of driving a DC-DC converter according to an embodiment of the present invention will be described.

First, in the case of low load, the DC-DC converter 300 is driven in the PFM mode. To this end, the second selection switch SS2 is switched to connect the PFM switching controller SWF and the power switching transistor PT.

Meanwhile, the first selection switch SS1 is switched to connect the pulse generator 324 and the ramp wave generator 323. Of course, the first selection switch SS1 may be switched to connect the PFM switching controller SWF and the ramp wave generator 323. Accordingly, the PFM switching pulse PF generated by the PFM switching control unit SWF is input to the power supply switching transistor TP to control the switching operation.

Next, in the case of high load, the DC-DC converter 300 is driven in the PWM mode. To this end, the second selection switch SS2 is switched to connect the PWM switching controller SWW and the power switching transistor TP.

Meanwhile, the first selection switch SS1 is switched to connect the pulse generator 324 and the ramp wave generator 323. As a result, the PWM switching control unit SWW generates the PWM switching pulse PW synchronized with the frequency of the PWM driving pulse. The PWM switching pulses PW generated as described above are input to the power supply switching transistor TP to control the switching operation.

Next, in the case of heavy load, the DC-DC converter 300 is driven in the PFWM mode. To this end, the second selection switch SS2 is switched to connect the PWM switching controller SWW and the power switching transistor TP.

Meanwhile, the first selection switch SS1 is switched to connect the PFM switching controller SWF and the ramp wave generator 323. As a result, the PWM switching controller SWW generates the PFWM switching pulse PFW synchronized with the frequency of the PFM switching pulse. The generated PFWM switching pulse PFW is input to the power switching transistor TP to control the switching operation.

As described above, in the embodiment of the present invention, the DC-DC converter is driven in the PFM mode at low load and in the PWM mode at high load. Accordingly, it is possible to drive with high efficiency at low load and high load.

Moreover, under heavy load, it is driven in PFWM mode. When the PFWM mode is driven, a frequency can be varied in synchronization with the PFM switching pulse, and a PFWM switching pulse can be generated in which the pulse width can be varied to switch the power supply switching transistor. Accordingly, under heavy load, power loss due to the switching operation can be reduced as compared with the case of driving in the conventional PWM mode, PFM mode, or PFM / PWM mode. Therefore, it becomes possible to drive with high efficiency even in heavy load.

On the other hand, it is apparent to those skilled in the art that the terms low load, heavy load, and high load mentioned in the embodiments of the present invention are relative concepts of the magnitude of the load, rather than a fixed concept of the magnitude of the load.

Embodiment of the present invention described above is an example of the present invention, it is possible to change freely within the scope included in the spirit of the present invention. Accordingly, the invention includes modifications of the invention within the scope of the appended claims and their equivalents.

1 is a view schematically showing a conventional DC-DC converter.

Figure 2 schematically shows a conventional PFM / PWM DC-DC converter.

3 is a schematic view of an organic light emitting display device according to an embodiment of the present invention;

4 is a diagram illustrating pixels of an organic light emitting panel of FIG. 2;

5 is a view showing the power circuit of FIG.

6 shows the control circuit of FIG. 5;

FIG. 7 is a diagram illustrating a comparator of the PWM switching controller of FIG. 6. FIG.

Description of the Related Art

321: PFM control unit 322: PWM control unit

323: ramp wave generator 324: pulse generator

OPF: PFM Error Amplifier OPW: PWM Error Amplifier

SWF: PWM switching controller SWW: PWM switching controller

SS1: First Selection Switch SS2: Second Selection Switch

Claims (8)

A load including an organic light emitting panel; A power circuit converting an input voltage to supply an output voltage to the load, The power supply circuit, An input terminal for receiving the input voltage; An output terminal for outputting the output voltage; A voltage conversion circuit comprising a power switching transistor, said voltage conversion circuit converting said input voltage into said output voltage; A PFM switching controller for outputting a PFM switching pulse; A PWM switching pulse synchronized with a frequency of the PWM driving pulse, and a PWM switching control unit for selectively outputting a PFWM switching pulse whose pulse width is variable and synchronized with the frequency of the PFM switching pulse, The PFM switching pulses, the PFWM switching pulses, and the PWM switching pulses are respectively supplied to the power switching transistor when the magnitude of the load is low, middle, or high. Organic light emitting display device. The method of claim 1, The voltage conversion circuit, An inductor positioned between the node to which the power switching transistor is connected and the input terminal; A diode located between the node and the output terminal; Further comprising a capacitor connected in parallel to the output terminal Organic light emitting display device. The method of claim 1, The power supply circuit, A PFM error amplifier for comparing the feedback voltage with respect to the output voltage and the PFM reference voltage and outputting the PFM switching control unit; A PWM error amplifier which compares the feedback voltage and the PWM reference voltage and outputs the same to the PWM switching controller; A ramp wave generator for outputting a ramp wave synchronized with the frequency of the input pulse to the PWM switching controller; A pulse generator for generating the PWM driving pulse; A first selection switch for selectively connecting the pulse generator and the PFM switching controller to the ramp generator; And a second selection switch for selectively connecting the PWM switching controller and the PFM switching controller to the power switching transistor. Organic light emitting display device. The method of claim 3, wherein The power supply circuit further includes a feedback circuit connected to the output terminal in parallel to detect the feedback voltage obtained by dividing the output voltage. Organic light emitting display device. Generating a PFM switching pulse in the PFM switching controller; Generating a PWM switching pulse synchronized with the frequency of the PWM driving pulse by the PWM switching controller; Generating, by a PWM switching controller, a PFWM switching pulse synchronized with a frequency of the PFM switching pulse and having a variable pulse width; Switching the power supply switching transistor using the generated PFM switching pulses, the PFWM switching pulses and the PWM switching pulses when the loads are low, middle and high, respectively; Converting an input voltage input to a power supply circuit into an output voltage through switching of the power switching transistor; Driving the organic light emitting panel of the load using the output voltage An organic light emitting display device driving method comprising a. The method of claim 5, The output voltage is a voltage obtained by boosting the input voltage. A method of driving an organic light emitting display device. The method of claim 5, Comparing the feedback voltage with respect to the output voltage and the PFM reference voltage and outputting the PFM switching control unit; Comparing the feedback voltage and the PWM reference voltage to output the PWM switching controller; Inputting a PFM switching pulse and a PWM driving pulse into a ramp wave generator at each of the heavy and high loads; Outputting a ramp wave synchronized with the frequency of a pulse input to the ramp wave generator to the PWM switching controller; The organic light emitting display device driving method further comprising. The method of claim 7, wherein The feedback voltage is a voltage obtained by dividing the output voltage. A method of driving an organic light emitting display device.

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