Patent Publication Number: US-10332452-B2

Title: OLED panel and power driving system associated to same

Description:
BACKGROUND 
     Technical Field 
     The present invention relates to a panel and a power driving system thereof, and in particular, to an organic light-emitting diode (OLED) panel and a power driving system associated to same. 
     Related Art 
     It is well known that, as compared with a conventional thin film transistor liquid crystal display (TFT LCD) panel, display technologies of active matrix organic light-emitting diode (AMOLED) panels have the advantages of being brighter, having a wider color gamut, and being more energy-saving. Therefore, for smartphones or smartwatches, there has been a tendency of replacing TFT LCD panels with OLED panels. 
     Referring to  FIG. 1 ,  FIG. 1  is a schematic diagram of a conventional OLED panel. An OLED panel  100  includes: an AMOLED  110  and a data driver  120 . The data driver  120  includes: a boost circuit  122  and a source driver  124 . Certainly, the OLED panel  100  further includes a gate driver and a timing controller. Details are not described herein again. 
     Generally, to enable the AMOLED  110  to work normally, a positive supply voltage OVDD, which is between approximately 4 V and 5 V (such as 4.6 V), and a negative voltage source OVSS, which is approximately −2.4 V, are provided to the AMOLED  110 . In addition, the source driver  124  receives a higher voltage Data_high (such as 5.6 V) and a lower voltage Data_low (such as 3.3V), and generates a data output signal SDout to the AMOLED  110 . In other words, a data range of the data output signal SDout is 2.3 V, that is, a voltage difference between the data high voltage Data_high and the data low voltage Data_low (5.6 V-3.3 V=2.3 V). 
     In addition, an input voltage Vin received by the boost circuit  122  ranges from approximately 2.7 V to 3.6 V. Therefore, the boost circuit  122  needs to boost the input voltage Vin first, and generate the data high voltage Data_high and the data low voltage Data_low that are needed by the source driver  124 . Generally, the boost circuit  122  includes at least one charge pump, configured to increase the input voltage Vin by a fixed multiple. 
     For example, the boost circuit  122  convertes a 2.8 V input voltage Vin double to a 5.6 V data high voltage Data_high, and then supplies the data high voltage Data_high to the source driver  124 . 
     Referring to  FIG. 2 ,  FIG. 2  is a schematic diagram of a power driving system of a conventional OLED panel. Because the AMOLED  110  needs a relatively great loading current during operation, a circuit board  200  needs at least two power chips. As shown in the figure, the circuit board  200  includes: an analog power IC  210  and an OLED power IC  220 . 
     The OLED power IC  220  receives a battery voltage Vbat, generates a positive supply voltage OVDD and a negative supply voltage OVSS, and supplies to the AMOLED  110  of the OLED panel  100 . 
     Further, the analog power IC  210  receives the battery voltage Vbat, generates an input voltage Vin, and supplies to all drivers, such as the data driver  120  and a gate driver (not shown), of the OLED panel  100 . Therefore, the power driving system of a conventional OLED panel is a power driving system having two chips. 
     Basically, when a smartphone or a smartwatch is in a standby state, the analog power IC  210  and the OLED power IC  220  still need to supply a quiescent current. In this way, a power driving system having two chips consumes power due to the quiescent current. In addition, in the conventional OLED panel  100 , the boost circuit  122  in the data driver performs a boost operation on the input voltage Vin, and causes additional power consumption on, for example, a 2×Vin or 3×Vin level. 
     SUMMARY 
     An embodiment of the present invention relates to an OLED panel, including a data driver and an AMOLED. The data driver may receive an input voltage and generate a data output signal. The AMOLED receives a positive supply voltage and a negative supply voltage, and emits light according to the data output signal. The input voltage and the positive supply voltage are substantially the same. 
     An embodiment of the present invention relates to a power driving system of an OLED panel, including an OLED panel and a circuit board. The circuit board is provided with a power chip thereon, and the power chip receives a battery voltage and generates a positive supply voltage, a negative supply voltage, and an input voltage. The circuit board may be electrically connected to the OLED panel, and the input voltage and the positive supply voltage are substantially the same. 
     An embodiment of the present invention relates to an OLED panel, including an OLED pixel circuit, a data driver and a circuit board. The OLED pixel circuit includes an OLED, and has an anode and a cathode. The data driver is electrically connected to the OLED pixel circuit. The circuit board has a power chip. The power chip has an input pin, a first output pin, a second output pin, and a third output pin. The first output pin is electrically connected to the data driver. The second output pin is electrically to the anode terminal. The third output pin is electrically connected to the cathode terminal. 
     To better understand the foregoing and other aspects of the embodiments of the present invention, preferred embodiments accompanied with figures are described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating a conventional OLED panel; 
         FIG. 2  is a schematic diagram illustrating a power driving system of a conventional OLED panel; 
         FIG. 3A  and  FIG. 3B  are schematic diagrams illustrating a pixel circuit applied to an OLED panel and relevant signals thereof according to an embodiment of the present invention; 
         FIG. 4  is a schematic diagram illustrating an OLED panel according to an embodiment of the present invention; and 
         FIG. 5  is a schematic diagram illustrating a power driving system of an OLED panel according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 3A  and  FIG. 3B ,  FIG. 3A  and  FIG. 3B  are schematic diagrams illustrating a pixel circuit applied to an OLED panel and relevant signals thereof according to an embodiment of the present invention. 
     A pixel circuit  300  includes a plurality of transistors, an OLED, and a compensation circuit  310 . A first terminal of a transistor M 1  receives a positive supply voltage OVDD, and a gate is electrically connected to the compensation circuit  310 . A first terminal of a transistor M 6  is electrically connected to a second terminal of the transistor M 1 , and a gate receives a control signal EM. An anode terminal of the OLED is electrically connected to a second terminal of the transistor M 6 , and a cathode terminal is electrically connected to a negative supply voltage OVSS. A first terminal of a transistor M 4  receives a data output signal SDout, a gate receives a control signal S 2 , and a second terminal of the transistor M 4  is electrically connected to the compensation circuit  310 . A first terminal of a transistor M 5  is electrically connected to the second terminal of the transistor M 4 , a gate receives the control signal EM, and a second terminal of the transistor M 5  receives a reference voltage Vref. A first terminal of a transistor M 7  is electrically connected to the compensation circuit  310 , a gate receives a control signal S 1 , and a second terminal receives the reference voltage Vref. 
     The compensation circuit  310  includes a capacitor C and transistors M 2  and M 3 . One terminal of the capacitor C is electrically connected to the second terminal of the transistor M 4 , and another terminal of the capacitor C is electrically connected to the gate of the transistor M 1 . The first terminal of the transistor M 2  is electrically connected to the gate of the transistor M 1 , the gate receives a control signal S 2 , and the second terminal of the transistor M 2  is electrically connected to the first terminal of the transistor M 7 . The first terminal of the transistor M 3  is electrically connected to the first terminal of the transistor M 7 , the gate receives the control signal S 2 , and the second terminal of the transistor M 3  is electrically connected to the second terminal of the transistor M 1 . 
     According to this embodiment of the present invention, the compensation circuit  310  in the pixel circuit  300  is configured to compensate for a threshold voltage of the transistor M 1 . Further, the reference voltage Vref is an adjustable bias signal. When the data output signal SDout is generated, an OLED current holed generated by the transistor M 1  is enabled to be proportional to (SDout-Vref) 2 . 
     As shown in  FIG. 3B , before a time point t 1 , the control signal EM is on a low level, the control signals S 1  and S 2  are on a high level, and the second terminal of the transistor M 4  has the reference voltage Vref. Between the time point t 1  and a time point t 2 , the control signals EM, S 1 , and S 2  are all on a high level, and the second terminal of the transistor M 4  is maintained at the reference voltage Vref. Between the time point t 2  and a time point t 3 , the control signal S 1  is on a low level, and the control signals EM and S 2  are on a high level, so that the transistor M 7  provides the reference voltage Vref to the compensation circuit  310 . 
     Between the time point t 3  and a time point t 4 , the control signals S 1  and S 2  are on a low level, and the control signal EM is on a high level, so that the transistor M 4  provides the data output signal SDout to the compensation circuit  310 . Between the time point t 4  and a time point t 5 , the control signal S 2  still keep a low level, and the control signals S 1  and EM are on a high level, so that the compensation circuit  310  performs threshold voltage compensation. Between the time point t 5  and a time point t 6 , the control signals S 1 , S 2 , and EM are all on a high level, so that compensation for the transistor M 1  is completed. At a time point t 6 , the control signal EM is on a low level, and the control signals S 1  and S 2  are on a high level, so that the transistor M 1  generates an OLED current holed and sends it to the OLED. The OLED current holed is approximately equal to β×(SDout-Vref) 2 , and β is a device parameter of the transistor M 1 . 
     According to the foregoing description, it can be known that attributes of the pixel circuit  300  of this embodiment of the present invention are derived from the OLED current holed, which depends on a difference between the data output signal SDout and the reference voltage Vref. To maintain light-emitting attributes of the OLED, a substantially same OLED current bled needs to be formed. Therefore, to maintain light-emitting attributes of the OLED, a substantially same voltage difference between the data output signal SDout and the reference voltage Vref needs to be maintained. In this case, a lower operating level of the OLED is obtained by further adjusting a value of the reference voltage Vref. For example, when the same light-emitting attributes of the OLED are maintained and the reference voltage Vref is reduced, an operating voltage of the data output signal SDout also is adjusted to a lower voltage region. When the reference voltage Vref is 1 V, the data high voltage Data_high is adjusted to 2.8 V and the data low voltage Data_low is 0.5 V. It results an operating range of the data output signal SDout is also maintained at 2.3 V. 
     However, according to the foregoing voltage instances, when the data high voltage Data_high is 2.8 V and the data low voltage Data_low is 0.5 V, the data driver does not need a boost circuit to increase the input voltage Vin, and power consumption of the data driver is effectively reduced. The pixel circuit  300  shown in  FIG. 3A  is an embodiment of the present invention, but the present invention is not limited thereto. Specifically, the pixel circuit  300  is considered to be a circuit that has the reference voltage Vref as a DC offset signal attribute, and adjusts the reference voltage Vref. Therefore, if other pixel circuits have same attributes, the reference voltage Vref can also be easily adjusted, so as to affect an operating voltage of the data output signal SDout. 
     Referring to  FIG. 4 ,  FIG. 4  is a schematic diagram illustrating an OLED panel according to an embodiment of the present invention. An OLED panel  400  includes: an AMOLED  410  and a data driver  420 . The data driver  420  further includes a voltage step-down circuit  422  and a source driver  424 . In addition, the OLED panel  400  further includes a gate driver and a timing controller. However, details are not described herein again. 
     In this embodiment of the present invention, when an operating voltage of a data output signal SDout generated by the data driver  420  is adjusted to a low voltage, an input voltage Vin received by the data driver  420  is reduced. In this way, the input voltage Vin not only can be provided to the data driver  420  to form the data output signal SDout, but also can be provided for a positive supply voltage OVDD of the AMOLED  410 . For example, the positive supply voltage OVDD of the AMOLED  410  is approximately 3.3 V, and the negative supply voltage OVSS. According to the embodiment of  FIG. 3A , the data high voltage Data_high of the operating voltage range of the data output signal SDout is 2.8 V, and the data low voltage Data_low of the operating voltage range of the data output signal SDout is 0.5 V, so that the operating voltage (2.8 V to 0.5 V) of the data output signal SDout is less than the positive supply voltage OVDD (3.3 V). In this way, when the data driver  420  receives the 3.3 V of the input voltage Vin, a proper operating voltage provided to generate the data output signal SDout. At the same time, the input voltage Vin also is provided to the AMOLED  410  as the positive supply voltage OVDD. 
     Specifically, referring to the embodiment of  FIG. 4 , the data driver  420  includes the voltage step-down circuit  422  and the source driver  424 , and the data driver  420  receives the input voltage Vin to generate the data output signal SDout. The positive supply voltage OVDD is greater than or substantially equal to the operating voltage range of the data output signal SDout. That is, the positive supply voltage OVDD is respectively greater than or substantially equal to the data high voltage Data_high and the data low voltage Data_low. Therefore, the data driver  420  is provided with the voltage step-down circuit  422  to buck the input voltage Vin to form the data high voltage Data_high and the data low voltage Data_low. As compared with the conventional OLED panel, in the OLED panel  400  of this embodiment of the present invention, the data driver  422  does not need a boost circuit to increase the input voltage Vin, so that power consumption of the OLED panel  400  is effectively reduced. 
     Specifically, in this embodiment, the voltage step-down circuit  422  uses a low dropout regulator (LDO) to convert the input voltage Vin into a data high voltage Data_high and a data low voltage Data_low. For ease of description,  FIG. 4  of this embodiment shows and expresses a signal or voltage connection relationship rather than metal wiring of actual objects. 
     Referring to  FIG. 5 ,  FIG. 5  is a schematic diagram illustrating a power driving system of an OLED panel according to an embodiment of the present invention. Because an input voltage Vin on an OLED panel  400  is substantially the same as a positive supply voltage (OVDD), for example, approximately 3.3V, a power chip is disposed on a circuit board  500 , and such a single power chip can provide three groups of power supplies to the OLED panel  400 . As shown in the figure, the circuit board  500  combined with the OLED panel  400  includes: a power chip  520 . In this embodiment, the circuit board  500  is a printed circuit board (PCB) or a flexible printed circuit (FPC) board, but the present invention is not limited thereto. The circuit board  500  also is any carrier provided with metal wiring or capable of transmitting or conducting an electric signal. 
     In other words, the power chip  520  receives a battery voltage Vbat, and generates a positive supply voltage OVDD and a negative supply voltage OVSS, to provide them to an AMOLED  410 . In the embodiment of the invention, an OLED power IC  520  also generates an input voltage Vin to provide it to a data driver  420 . In this embodiment of the  FIG. 5 , the power chip  520  includes a buck boost converter, an input terminal as the battery voltage Vbat and three output terminals as the input voltage Vin, the positive supply voltage OVDD, and the negative supply voltage OVSS. The input voltage Vin is substantially the same as the positive supply voltage OVDD. However, the present invention is not limited thereto. Different circuits is used according to different designs, to achieve the function that the input voltage Vin can be substantially the same as the voltage of the positive supply voltage OVDD. 
     Specifically, in this embodiment, the power chip  520  includes an input pin  530 , a first output pin  531 , a second output pin  532 , and a third output pin  533 . The battery voltage Vbat is transmitted to an input pin  530 , and various voltages are generated by means of the power chip  520  to be provided to the OLED panel  400 . The first output pin  531  correspondingly generates the input voltage Vin,the second output pin  532  correspondingly generates the positive supply voltage OVDD, and the third output pin  533  correspondingly generates the negative supply voltage OVSS. Voltages formed by the first output pin  531  and the second output pin  532  are substantially the same. In this embodiment, when the same voltage is generated by different two pins, it results the two pins with the same voltage is separately controlled in timings to facilitate application to the OLED panel  400 . As compared with the power driving system of the conventional OLED panel, the OLED panel  400  in the embodiment of the present invention needs only three groups of power supplies to work normally. That is, the power driving system of the OLED panel in the embodiment of the present invention is a power driving system having 1 IC and 3 channels. 
     According to the foregoing description, it is known that the advantage of the embodiments of the present invention lies in providing an OLED panel and a power driving system associated to same. On the OLED panel, the data driver  420  only needs to buck the input voltage Vin, and does not need to boost the input voltage Vin, to reduce power consumption. 
     In addition, the reference voltage Vref is appropriately adjusted by means of the pixel circuit, so as to make the positive supply voltage OVDD of the AMOLED substantially the same as the input voltage Vin. In this way, the power driving system in the embodiment of the present invention is a power driving system having 1 IC and 3 channels. 
     Further, the voltage values mentioned above are not intended to limit the present invention. A person skilled in the art may make modifications according to voltage values mentioned in the OLED panel and power driving system that are disclosed in the present invention and implement the present invention. In addition, the connection, electrical connection, coupling, electrical coupling, and the like mentioned above are considered as direct relationships only when they are particularly described to be direct, such as direct connection, that is, there is no other object therebetween. 
     Based on the above, the present invention is disclosed through the foregoing embodiments; however, these embodiments are not intended to limit the present invention. A person of ordinary skill in the technical field to which the present invention belongs can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention is subject to the appended claims.