JP2009223145A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device capable of maintaining a display state of a display element even when trouble of a circuit including a monitor element is caused. <P>SOLUTION: The display device includes: a monitor circuit 2 for supplying a current to a monitor element Ex from a constant current source 1 and detecting a forward voltage value Vf of the monitor element at such a time; and a driving power source circuit 3 for supplying first voltage Vc1 generated in accordance with the forward voltage value detected by the monitor circuit to the display element arranged on a display panel 7 as driving voltage. Furthermore, the display device includes a fault detection means 4 for detecting a fault of the monitor element or the monitor circuit, and a driving voltage switching means 5 for switching the driving voltage to second voltage Vc2 other than the first voltage when the fault detection means detects the fault. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a driving technique for a display panel in which a large number of self-luminous elements are arranged as display pixels, for example, in a matrix form, and in particular, it is possible to suppress changes in light emission characteristics caused by changes with time of the self-luminous elements. Related to the display device.

  With the widespread use of mobile phones and portable information terminals (PDAs), there is an increasing demand for display panels that have a high-definition image display function and that can be thin and achieve low power consumption. Liquid crystal display panels have been adopted in many products as display panels that satisfy these requirements. On the other hand, in recent years, a display panel using an organic EL element that takes advantage of the characteristic of being a self-luminous element has been put into practical use, and this is drawing attention as a next-generation display panel that replaces a conventional liquid crystal display panel.

  The organic EL element is basically configured by sequentially laminating a transparent electrode made of, for example, ITO, a light emitting functional layer made of an organic material, and a metal electrode on a transparent substrate such as glass. The light emitting functional layer is a single layer of an organic light emitting layer, or a two-layer structure comprising an organic hole transport layer and an organic light emitting layer, or a three layer structure comprising an organic hole transport layer, an organic light emitting layer and an organic electron transport layer. In some cases, a multilayer structure in which an electron or hole injection layer is inserted between these appropriate layers may be used.

  FIG. 1 shows the light emission static characteristics of such an organic EL element. According to this, as shown in FIG. 1A, the organic EL element emits light with a luminance L substantially proportional to the drive current I, and the drive voltage V becomes the light emission threshold voltage as shown by the solid line in FIG. When Vth is equal to or higher than Vth, the current I suddenly flows to emit light.

  In other words, when the drive voltage is equal to or lower than the light emission threshold voltage Vth, almost no current flows through the EL element and no light is emitted. Therefore, as shown by a solid line in FIG. 1 (c), the EL element has a luminance characteristic in which the emission luminance L increases as the value of the voltage V applied thereto increases in the light emission possible region that is higher than the threshold voltage Vth. It has the characteristic which becomes.

  On the other hand, it is known that the organic EL element described above changes the physical properties of the element due to long-term use, and the forward voltage Vf increases. For this reason, as shown in FIG. 1B, the organic EL element changes in the VI characteristic in the direction indicated by the arrow (characteristic indicated by the broken line) according to the actual use time, and thus the luminance characteristic also decreases. Will do. In addition, the above-described organic EL element also has a problem of causing variations in initial luminance due to, for example, variations in vapor deposition at the time of film formation of the element, thereby expressing luminance gradation faithful to the input video signal. It becomes difficult to do.

  Furthermore, it is also known that the luminance characteristics of the organic EL element change as shown by a broken line in FIG. That is, the EL element has a characteristic that in the light emission possible region larger than the above-described light emission threshold voltage, the light emission luminance L increases as the value of the voltage V applied thereto increases, but the light emission threshold voltage decreases as the temperature increases. Become. Therefore, the organic EL element becomes capable of emitting light with a small applied voltage as the temperature rises, and has a luminance temperature dependency such that it is bright at high temperatures and dark at low temperatures even when the same applied voltage capable of emitting light is applied.

  In addition, the above-described EL element has a problem that the light emission efficiency with respect to the driving voltage varies depending on the light emission color, and each color of R (red), G (green), and B (blue) that can be put into practical use at present. As shown in FIG. 1D, in the initial stage, the EL elements emitting EL respectively emit light with high G efficiency and B with the lowest light emission efficiency. Each of the EL elements that emit R, G, and B also has a change with time and temperature dependency as shown in FIGS. 1B and 1C.

  The above-described change with time and temperature dependence are particularly prominent when the EL element is driven at a constant voltage. This is because the forward impedance of the element changes depending on the cumulative driving time and the surrounding environment, and the current flowing through the EL element changes accordingly.

  Therefore, in addition to the EL elements arranged on the display panel for performing light emission display, a monitor EL element for measuring the forward voltage Vf is provided, and the forward voltage Vf obtained from the monitor EL element is used. Patent Documents 1 to 3 disclose that the driving voltage supplied from the power supply unit is controlled.

According to the configuration disclosed in Patent Documents 1 to 3, the driving voltage provided from the power supply unit is controlled in response to the change of the EL element with time and the change of the environmental temperature, and the change of the light emission characteristics due to the change of the EL element with time, etc. Can be suppressed. Further, according to this configuration, it is possible to always ensure a voltage value necessary for light emission driving of the EL element, and it is possible to reduce an extra voltage margin, so that it is possible to improve power supply utilization efficiency.
JP 2004-252036 A JP 2005-107003 A JP 2006-79077 A

  Incidentally, in the invention disclosed in Patent Document 1, the anode potential (forward voltage Vf) of the monitor element is used as a feedback voltage to control the drive voltage applied to the display element. For this reason, when a failure occurs in the monitor element, for example, when the monitor element is short-circuited, a display element (organic EL element) is used to detect the cathode potential of the monitor element (for example, a low potential such as a ground potential) as a feedback voltage. There is a problem that the drive voltage supplied to the power source is extremely lowered and display cannot be performed.

  Further, the invention disclosed in Patent Document 2 described above is a display element that is also used as a monitor element, and is supplied to the display element by a feedback operation when any of the monitor elements is in an open state. In order to prevent an excessive increase in the driving voltage, the operation of the switching regulator that generates the driving voltage supplied to the display element is stopped. According to this, when any one of the monitor elements is in an open state, the drive voltage value supplied to the display element becomes almost zero, so that the display operation becomes impossible.

  Further, the invention disclosed in Patent Document 3 has a function of automatically cutting off the current supply to the shorted monitor element when the monitor element is in a short circuit state. There is no function of notifying the user of the occurrence of the failure of the element, and when the circuit including the switch connected to the monitor element breaks down, the problem that the display is not normally performed similarly occurs.

  The inventions disclosed in Patent Documents 1 to 3 described above all take measures to lower the drive voltage applied to the display element in order to protect the circuit when a failure occurs in the monitor element or the like. When a failure occurs in the monitor element or the like, the display is turned off.

  By the way, in a display device adopted for medical equipment, aircraft instruments, and the like, the degree of influence on human life is extremely large when the display is turned off. Therefore, stricter reliability is required for display than display devices used in consumer devices such as mobile phones and car audio, and improvements in this respect are desired.

  The present invention has been made on the basis of the above-described viewpoints, and not only the above-described short state of the monitor element but also a monitor that detects the open state of the monitor element and the forward voltage value of the monitor element. Provided a display device capable of maintaining the display state of a display element, although it is in a state different from a desired display state (e.g., light emission luminance) at the time of occurrence of a circuit failure, and that a failure has occurred It is an object of the present invention to provide a function for prompting repair or replacement of the display device by having means for informing the user.

  A preferable basic form of the display device according to the present invention made to solve the above-described problem is, as described in claim 1, a plurality of display elements contributing to display and a display constituted by the plurality of display elements. A screen, at least one monitor element that does not contribute to display, a monitor circuit that detects a forward voltage value of the monitor element when a current is supplied to the monitor element, and the forward direction detected by the monitor circuit A display device comprising a drive power supply circuit for supplying a first voltage generated according to a voltage value as a drive voltage to the plurality of display elements, wherein the failure detects a failure of the monitor element or the monitor circuit When the failure is detected by the detection means and the failure detection means, the drive voltage is switched to a second voltage other than the first voltage. Characterized in that and a obtain driving voltage switching means.

  Hereinafter, a display device according to the present invention will be described based on embodiments shown in the drawings. FIG. 2 is a block diagram showing the first embodiment. The monitor element Ex includes a constant current source 1 driven by a voltage source Vcc and a cathode terminal connected to a reference potential point. A constant current is supplied from the constant current source 1 to the anode terminal.

  The monitor element Ex is preferably an element having the same electrical characteristics (same specifications) as the organic EL element E1 constituting the display pixel described later. Preferably, the monitor element Ex is formed simultaneously with a part of the same display panel by the same manufacturing process together with the later-described organic EL element E1 constituting the display pixel.

  The forward voltage Vf of the monitor element Ex is generated by applying the constant current to the anode terminal of the monitor element Ex, and this is supplied to the monitor circuit 2. The monitor circuit 2 is configured by, for example, a sampling hold circuit, and an output based on the forward voltage Vf held thereby is configured to be supplied to the drive power supply circuit 3.

  The drive power supply circuit 3 is composed of, for example, a switching regulator that uses a battery as a power supply, and operates to control the output voltage Vc1 according to a control voltage based on the forward voltage Vf output from the monitor circuit 2. To do. The output voltage Vc1 is referred to as a first voltage, and the first voltage Vc1 is configured to be supplied to the drive voltage switching means 5.

The drive voltage switching means 5 is composed of, for example, an analog switch such as an FET, and normally drives the first voltage Vc1 provided from the drive power supply circuit 3 to display pixels arranged on the display panel 7. It is comprised so that it may supply as a voltage. Accordingly, display pixels, which will be described later, disposed on the display panel 7 are driven to be lit by a drive voltage provided from the drive power supply circuit 3 based on the forward voltage Vf obtained by the monitor element Ex.
Therefore, display pixels, which will be described later, arranged on the display panel 7 are driven to emit light without depending on changes with time and environmental temperature.

  The display panel 7 has an active matrix type display panel in which a large number of display pixels are arranged in a matrix form in the vertical and horizontal directions. The pixel structure of a display pixel is shown. That is, the pixel configuration drawn in the display panel 7 shows the most basic configuration example when an organic EL element is used as a display element, and includes a control transistor T1, a drive transistor T2, and a charge retention. Capacitor Cs and organic EL element E1 functioning as a light emitting element.

  Then, in synchronization with the gate control pulse from the gate driver 8 supplied to the gate of the control transistor T1, the organic EL element E1 is based on the data signal from the data driver 9 supplied to the source of the control transistor T1. Are selectively lit.

  On the other hand, a control voltage (hereinafter also referred to as a monitor output) output from the monitor circuit 2 is configured to be supplied to the failure detection means 4. The failure detection unit 4 has a function of receiving a monitor output and detecting a failure of a circuit configuration including the monitor element Ex and the monitor circuit 2.

  When the failure detection means 4 detects a failure in the circuit configuration including the monitor element Ex and the monitor circuit 2, the drive voltage switching means 5 is controlled to be switched, and the first power supplied from the drive power supply circuit 3 is controlled. It operates to switch from the voltage Vc1 to the second voltage source Vc2 that is a fixed voltage. The fixed voltage by the second voltage source Vc2 is set to a predetermined value that can drive each display pixel disposed on the display panel 7 to light. Thereby, the display pixels arranged on the display panel 7 are driven to be lit by the fixed voltage from the second voltage source Vc2.

  FIG. 3a shows a first example of the failure detection means 4 shown in FIG. The failure detection means 4 shown in FIG. 3 includes one voltage comparator Co1, and the voltage comparator Co1 includes a reference voltage input terminal Co1a, a signal voltage input terminal Co1b, and a comparison result output terminal Co1c. A reference voltage Va (hereinafter also referred to as a first reference voltage) is supplied to the reference voltage input terminal Co1a, and the aforementioned monitor output is supplied to the signal voltage input terminal Co1b. When the voltage of the signal voltage input terminal Co1b becomes higher than the voltage of the reference voltage input terminal Co1a, that is, when the monitor output becomes larger than the value of the reference voltage Va, the comparison result output terminal Co1c Acts to output a logic signal A indicating a fault condition.

  FIG. 3b shows a second example of the failure detection means 4 shown in FIG. Like the first example, it is composed of one voltage comparator Co2, and includes a reference voltage input terminal Co2a, a signal voltage input terminal Co2b, and a comparison result output terminal Co2c. A reference voltage Vb (hereinafter also referred to as a second reference voltage) is supplied to the reference voltage input terminal Co2a, and the monitor output described above is supplied to the signal voltage input terminal Co2b. When the voltage of the signal voltage input terminal Co2b is lower than the voltage of the reference voltage input terminal Co2a, that is, when the voltage of the monitor output is lower than the reference voltage Vb, the comparison result output terminal Co2c indicates a failure state. A logic signal B is output.

  FIG. 4 shows a third example of the failure detection means 4 shown in FIG. The failure detection means 4 shown in FIG. 4 has a configuration in which the comparator Co1 shown in FIG. 3a and the comparator Co2 shown in FIG. 3b are combined and a logic circuit is further added. One comparator Co1 performs the same function as the comparator Co1 shown in FIG. 3a. The other comparator Co2 performs the same function as the comparator Co2 shown in FIG. 3b. The relationship between the first reference voltage Va and the second reference voltage Vb is Va> Vb. The comparison result output terminals Co1c and Co2c of the two comparators are connected to the gate of the logic circuit OR1, and when a logic signal indicating a failure state is output from at least one of the comparison result output terminals, the output terminal of the logic circuit A logic signal C indicating a failure state is output.

  Therefore, according to the configuration of the failure detection means 4 shown in FIG. 4, when the monitor output is larger than the value of the reference voltage Va and when the monitor output is larger than the value of the second reference voltage Vb. When the value becomes small, the logic signal C indicating the failure state is outputted from the output terminal of the logic circuit OR1. That is, according to the configuration of the failure detection means 4 shown in FIG. 4, the presence / absence of a failure and the failure mode can be detected.

  FIG. 5 illustrates a failure state occurring in the monitor element Ex and the monitor circuit 2 and a failure detection operation detected by the failure detection means 4 shown in FIGS. 5 includes a transistor T3 in addition to the circuit configuration including the monitor element Ex and the monitor circuit 2 shown in FIG. 2, and the source electrode and the drain electrode of the transistor T3 are connected to the constant current source 1, the monitor element Ex, and the like. Is inserted between.

  The transistor T3 is provided in order to make the average lighting time of the organic EL element E1 constituting each display pixel arranged in the display panel 7 substantially coincide with the energization time to the monitor element Ex. In addition, a pulse width modulation (PWM = Pulse Width Modulation) signal is supplied to the gate of the transistor T3.

  Thereby, it is possible to make the temporal change of the forward voltage Vf obtained by the monitor element Ex substantially coincide with the temporal change of the average forward voltage of each EL element E1 in the display panel 7. Therefore, it is possible to obtain a good compensation characteristic of the drive voltage provided from the drive power supply circuit 3 to each display pixel arranged on the display panel 7.

  In the configuration shown in FIG. 5, failure modes in the circuit configuration including the monitor element Ex and the monitor circuit 2 include disconnection at locations Da, Db, and Dc shown in FIG. It is conceivable that Ex is in an open state and the monitor element Ex is short-circuited.

  According to the configuration of the failure detection means 4 constituted by one voltage comparator Co1 shown in FIG. 3, the comparator in each of the open state of the transistor T3, the disconnection at the position indicated by Dc in FIG. 5, and the open state of the monitor element Ex A logic signal A is output from Co1. Thereby, the drive voltage switching means 5 shown in FIG. 2 operates so as to select the second voltage source Vc2.

  According to the above-described failure mode, the first voltage Vc1 generated from the drive power supply circuit 3 is in a high voltage state, causing a problem that the display pixels arranged in the display panel 7 are damaged. However, since the display panel 7 is supplied with the second voltage source Vc2, compensation for temperature and aging cannot be obtained, but the display pixels arranged on the display panel 7 continue to emit light. It will be.

  Next, according to the configuration of the failure detection means 4 configured by the two voltage comparators Co1 and Co2 shown in FIG. 4, in the first comparator Co1, as in the example shown in FIG. In each of the disconnection at the position indicated by Dc in FIG. 5 and the open state of the monitor element Ex, the logic signal A is output from the comparator Co1, and the logic signal C is output from the logic circuit OR1. Thereby, the drive voltage switching means 5 shown in FIG. 2 operates so as to select the second voltage source Vc2, and the same operation effect as the example shown in FIG. 3 can be obtained.

  In the second comparator Co2, the constant current source 1 is open (open), the wire is broken at the locations indicated by Da and Db in FIG. 5, the monitor element Ex is short-circuited, and the transistor T3 is short-circuited. , The comparator Co2 outputs a logic signal B, and the logic circuit OR1 outputs a logic signal C. As a result, the drive voltage switching means 5 shown in FIG. 2 operates to select the second voltage source Vc2.

  According to the above-described failure mode, the first voltage Vc1 generated from the drive power supply circuit 3 is in a low voltage state, and it becomes impossible to drive each display pixel arranged in the display panel 7 to emit light. Invite. However, since the display panel 7 is supplied with the second voltage source Vc2, compensation for temperature and aging cannot be obtained, but the display pixels arranged on the display panel 7 continue to emit light. It will be.

  FIG. 6 is a block diagram showing a second embodiment of the display device according to the present invention. In the embodiment shown in FIG. 6, failure notification means indicated by reference numeral 6 is added to the configuration shown in FIG. 2, and the other configuration is the same as that shown in FIG. Therefore, in FIG. 6, each block that performs the same function as each part shown in FIG. 2 is denoted by the same reference numeral, and the description thereof is omitted.

  The failure notification means 6 shown in FIG. 6 is configured to operate when receiving the above-described logic signal A, logic signal B, or logic signal C provided from the failure detection means 4. That is, the failure notification means 6 operates in synchronization with the drive voltage switching means 5 selecting the second voltage source Vc2.

  The failure notifying means 6 may be a means for notifying by sound from a buzzer or announcing by sound using a speaker, means for notifying by light using a photoelectric conversion element such as a light emitting diode, or a predetermined alarm message on a display panel. A means such as superimposing a part of 7 can be adopted. As a result, a failure occurs in a part of the circuit configuration including the monitor element Ex and the monitor circuit 2, and it is notified that the display panel 7 is lit and driven by the fixed voltage from the second voltage source Vc2.

  When the failure detecting means 4 employs a configuration capable of detecting the presence / absence of a failure and a failure mode as shown in FIG. 4, the failure notifying means 6 discriminates the logic signal A or the logic signal B described above. The failure mode can be specified. Therefore, the failure notification means 6 can be configured to perform different notification operations according to the specified failure mode.

  The embodiments described above are premised on a display device using a monochrome display panel using so-called monochromatic light-emitting elements as display pixels. Therefore, when a color image is to be displayed using this type of light emitting element typified by the organic EL element, for example, R (red), G (green), and B (blue) which are the three primary colors of light. ) For each color pixel, a single color display pixel is configured.

  In this case, since the EL elements constituting the R, G, and B sub-pixels have different luminous efficiencies as described above, and the lighting time and the lighting brightness differ depending on the display image, A difference occurs in the degree of change with time. Further, the EL elements constituting each sub-pixel have different characteristics in temperature-dependent elements of the respective emission colors.

  Therefore, in the apparatus using the display panel for displaying a color image as described above, the monitor element, the monitor circuit, the drive power supply circuit, the failure detection means, and the drive voltage switching means corresponding to the emission color of each element are provided. It is desirable that With the above-described configuration, it is possible to effectively suppress the color balance collapse that occurs in response to a change with time and a change in temperature.

  FIG. 7 shows a third embodiment of the present invention that can be suitably employed in an apparatus using a color display panel having the R, G, and B sub-pixels described above. In the embodiment shown in FIG. 7, when a failure is detected by the failure detection means corresponding to one emission color, the drive voltage switching means is a monitor corresponding to another emission color in which no failure is detected. It operates to switch to the second voltage detected by the circuit.

  That is, in the embodiment shown in FIG. 7, as described above, the monitor element Ex, the monitor circuit 2, and the drive power supply circuit 3 corresponding to the light emission color of each element constituting the subpixel are provided, respectively, and further the R subpixel. Corresponding to the failure detection means 4 and a drive voltage switching means 5 which is subjected to switching control by the failure detection means 4. In FIG. 7, each block that performs the same function as each unit shown in FIG. 2 is indicated by the same reference numeral, and the R, G, and B reference signs are added to the end of each reference numeral.

  In the configuration shown in FIG. 7, the failure detection means 4 receives the output of the monitor circuit 2R corresponding to the R sub-pixel. When a failure occurs in the circuit configuration including the monitor element Ex (R) and the monitor circuit 2R, the drive voltage switching unit 5 receives the logic signal indicating the above-described failure state from the failure detection unit 4 and receives the offset. The output from the circuit 10 </ b> B or 10 </ b> G is selected as the second voltage Vc <b> 2, and this is applied to the R sub-pixel arranged on the display panel 7 as a drive voltage.

  The offset circuits 10B and 10G are set so that the outputs from the drive voltage sources 3B and 3G corresponding to the B and G subpixels are set to appropriate voltage levels corresponding to the R subpixels. To shift.

  Thus, according to the configuration shown in FIG. 7, when a failure occurs in the circuit configuration including the monitor element Ex (R) and the monitor circuit 2R corresponding to the R subpixel, it corresponds to the B or G subpixel. The output of the driving power supply circuit 3B or 3G to be operated operates as the second voltage Vc2. Further, by performing the level shift by the offset circuit 10B or 10G, it is possible to obtain temperature dependence and temporal change characteristics that are more approximate to the R sub-pixel.

  In the configuration shown in FIG. 7, the failure detection means 4 is connected to the monitor circuit 2R corresponding to the R sub-pixel. The failure detection means 4 is the same for the B and G sub-pixels. Can be provided. Also in the embodiment shown in FIG. 7, it is possible to use the output of the failure detection means 4 to drive the failure notification means 6 as shown in FIG.

  FIG. 8 shows a fourth embodiment of the present invention that can be suitably employed in an apparatus using a color display panel having R, G, and B subpixels. In FIG. 8, the blocks having the same functions as those shown in FIG. 7 are denoted by the same reference numerals, and therefore the description thereof is omitted.

  In the embodiment shown in FIG. 8, the monitor outputs of the monitor circuits 2R, 2G, 2B corresponding to R, G, B are supplied to the drive voltage switching means 5, respectively. The drive voltage switching means 5 is configured to be switched by the output of the failure detection means 4 detected by the monitor output of the monitor circuit 2R corresponding to R.

  That is, the failure detection means 4 monitors the output of the monitor circuit 2R, and in a normal state where no failure is detected, the drive voltage switching means 5 supplies the output of the monitor circuit 2R to the drive power supply circuit 3R as shown in FIG. To work. Accordingly, the drive power supply circuit 3R supplies the first drive voltage Vc1 based on the output of the monitor circuit 2R to each pixel corresponding to R. The outputs of the monitor circuits 2B and 2G are supplied to the drive power supply circuits 3B and 3G, respectively, and the drive voltages from the drive power supply circuits 3B and 3G are supplied to the subpixels corresponding to B and G.

  In the configuration shown in FIG. 8, when the failure detection means 4 that monitors the output of the monitor circuit 2R detects a failure of the monitor element Ex (R) or the like, the drive voltage switching means 5 outputs the output of the monitor circuit 2B or 2G. Is selected and supplied to the drive power supply circuit 3R. Thus, even in the configuration shown in FIG. 8, when a failure occurs in the circuit configuration including the monitor element Ex (R) corresponding to the R subpixel and the monitor circuit 2R, it corresponds to the B or G subpixel. The drive power supply circuit 3R operates so as to generate a drive voltage by using the output of the monitor circuit.

  In the configuration shown in FIG. 8, the failure detection means 4 is connected to the monitor circuit 2R corresponding to the R sub-pixel. The failure detection means 4 corresponds to the B and G sub-pixels in the same manner. Can be provided. Also in the embodiment shown in FIG. 8, it is possible to use the output of the failure detection means 4 to drive the failure notification means 6 as shown in FIG.

  In the above-described embodiment, an example in which an organic EL element is used as a light-emitting element constituting each pixel has been described. However, the present invention is applied to a display device using another light-emitting element having temporal change and temperature dependency as a pixel. By doing so, the same operational effects can be enjoyed.

It is a figure which shows the various characteristics of an organic EL element. 1 is a block diagram showing a first embodiment of a display device according to the present invention. FIG. 3 is a circuit configuration diagram showing a first example of the failure detection means shown in FIG. 2. It is the circuit block diagram which showed the 2nd example of the failure detection means similarly. It is the circuit block diagram which similarly showed the 3rd example of the failure detection means. It is a circuit block diagram explaining the aspect of the failure which generate | occur | produces in a monitor element and a monitor circuit. It is the block diagram which showed 2nd Embodiment of the display apparatus concerning this invention. It is the block diagram which similarly showed 3rd Embodiment. It is the block diagram which similarly showed 4th Embodiment.

Explanation of symbols

1, 1R, 1G, 1B Constant current source 2, 2R, 2G, 2B Monitor circuit 3, 3R, 3G, 3B Drive power supply circuit 4 Failure detection means 5 Drive voltage switching means 6 Failure notification means 7 Display panel 8 Gate driver 9 Data Driver E1 Light emitting element (organic EL element)
Ex monitor element

Claims (8)

A plurality of display elements contributing to display; a display screen constituted by the plurality of display elements; at least one monitor element not contributing to display; and an order of the monitor elements when current is supplied to the monitor elements. A monitor circuit that detects a directional voltage value; and a drive power supply circuit that supplies a first voltage generated according to the forward voltage value detected by the monitor circuit as a drive voltage to the plurality of display elements. Display device,
A failure detection means for detecting a failure of the monitor element or the monitor circuit; and a drive voltage for switching the drive voltage to a second voltage other than the first voltage when the failure is detected by the failure detection means. A display device comprising switching means.   The display device according to claim 1, further comprising failure notifying means for notifying a failure of the monitor element or the monitor circuit.   The failure notification means is configured to notify the failure by emitting a sound or light, or by displaying on at least a part of the display screen. The display device described in 1.   A plurality of display elements having different emission colors are provided as the plurality of display elements, and the monitor element, the monitor circuit, the drive power supply circuit, the failure detection means, the drive corresponding to the emission color of each display element The display device according to claim 1, further comprising a voltage switching unit.   The value of said 2nd voltage is set to the predetermined value which can carry out lighting drive of the said some display element, The any one of Claim 1 thru | or 4 characterized by the above-mentioned. Display device.   When a failure is detected by the failure detection means corresponding to one emission color, the drive voltage switching means is the second detected by the monitor circuit corresponding to another emission color in which no failure is detected. The display device according to claim 4, wherein the display device is switched to the voltage.   The failure detection means is configured to determine a failure by comparing the forward voltage value detected by the monitor circuit with a predetermined reference voltage. The display device according to any one of 6.   8. The reference voltage is set in a plurality of types, and the failure detection means is configured to identify a failure mode according to a comparison result between the forward voltage and the plurality of reference voltages. The display device described in 1.

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