JP2012220646A - Light emitting device, driving circuit for light emitting device, and driving method of light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve display quality by preventing wrong illumination caused by parasitic capacitance of wiring or the like of a circuit.SOLUTION: A light emitting device includes: a scanning part which is connected to respective common lines C of a display part 10, selects an arbitrary common line C, and also change selections; and a driving part which is connected to respective driving lines S of the display part 10 and can drive a light emitting element connected to a common line C selected by the scanning part. The light emitting device is further equipped with charging means 41 of providing an illumination period in which the arbitrary light emitting element connected to the common line C selected by the scanning part is driven by the driving part to illuminate and a charging period for charging parasitic capacitance of the driving line S by changing the driving of the driving line S to which the arbitrary light emitting element 1 is connected into an undriven state while the common line C is selected successively to the illumination period.

Description

  The present invention relates to a light-emitting device, a light-emitting device drive circuit, and a light-emitting device driving method for controlling charge / discharge in a light-emitting device including a display unit in which driven elements such as a plurality of light-emitting elements are arranged.

  Today, light emitting diodes (LEDs) with high luminance of 1000 mcd or more have been developed for each of RGB, and large LED displays have been manufactured. This LED display has features such as being lightweight, thin and low in power consumption, and the demand is rapidly increasing as a large display that can be used outdoors. Actually, a large LED display is configured by combining a plurality of LED units according to the installation location, and the LED unit is configured by arranging RGB LED elements in a dot matrix on a substrate. The

  The LED display is provided with a drive circuit that can individually drive each LED element. Specifically, in the LED display, each LED control device for transferring display data is connected to each LED unit, and a plurality of them are connected to constitute one large display. Further, in the LED display, a dynamic drive method is used as a drive method, and specifically, the LED display is connected and driven as follows. For example, in the case of an LED unit composed of an m-row × n-column dot matrix, the anode terminals of the LED elements located in each row are commonly connected to one common line, and the cathode terminals of the LED elements located in each column Are commonly connected to one drive line. Then, the m common lines are sequentially turned on at a predetermined cycle to display. Note that the switching of the m common lines is performed, for example, via a decoder circuit based on an address signal.

  However, in the light emitting device such as the conventional LED light emitting device, when the LED element connected to the selected common line is lit, the wiring and the common line of the unselected non-lighting state are connected to the common line. There is a problem in that extra current is generated due to the residual charges accumulated in the parasitic capacitance of the connected LED elements. Due to the generation of such an excess current, the LED element that is controlled so as not to emit light may light up slightly, or the display quality may be deteriorated such that sufficient contrast cannot be obtained in the display image. It was.

  In order to solve such a problem, the applicant of the present application has developed the LED light-emitting device of Patent Document 1. This LED light-emitting device is provided with a false lighting prevention circuit 50 for each common line C as shown in FIG. In the LED light-emitting device, a plurality of LED elements are arranged in an m-row × n-column matrix as an LED display unit, the cathode terminals of the LED elements in each column are connected to the drive lines S, and the anodes of the LED elements in each row Each terminal is connected to the common line C. Further, by connecting the m switch circuits respectively connected to the common line C and the common line C specified by the address signal by the input source lighting control signal to the current source, the common line C is connected to the common line C. A current source switching circuit 20 that supplies current to the connected LED elements, a storage circuit 32 that stores n ON / OFF data that are sequentially input, and an ON period that is specified by a sink lighting control signal that is input The constant current control circuit unit 30 that drives the drive line S corresponding to the ON / OFF data stored in each storage circuit 32. This LED light emitting device is connected to a charging path for charging a residual charge generated in the LED element to the charging element when the LED element is in an OFF state, and is connected to the charging element. It has a discharge path for discharging. With this configuration, unnecessary residual charges accumulated in the LED element in the ON state of the LED element are charged into the charging element in the OFF state and discharged through the discharge path in the ON state. Even in the driving state in which the LED element is turned on, the influence of the residual charge can be substantially eliminated, and a light emitting device with high display quality can be realized.

Japanese Patent No. 3498745

  In the above-described erroneous lighting prevention circuit 50, the residual charges accumulated in the wiring of the common line itself connecting the anode terminal of the LED element and the parasitic capacitance of the LED element are discharged while the LED element is OFF. Can be eliminated. However, it has been found that this is insufficient to eliminate erroneous lighting caused by charging of the parasitic capacitance of the wiring of the drive line itself connected to the cathode terminal of the LED element. For example, as shown in FIG. 14, even if the LED light emitting device connected to the anode common type is provided with the erroneous lighting prevention circuit 50, not only the LED element 1N originally intended to be lit (shown in black in FIG. 14) but also non-lighting An unintended LED due to the energization of the LED element 1F generated by charging the parasitic capacitance of the wiring of the drive line itself to which the other LED element 1F to be turned on (indicated by hatching in FIG. 14) is connected Incorrect lighting may occur in the element 1F.

The mechanism by which such erroneous lighting occurs will be described based on the timing chart of FIG. 15 and the schematic diagrams of FIGS. In these drawings, FIG. 15 shows the timing of sending a lighting signal to the common line C and the drive line S in the LED light emitting device of FIG. Here, from the first lighting frame 0 after the power is turned on to the lighting frame N at a certain point in time, a lighting pattern is adopted in which the LED elements are switched on the diagonal line from the upper left to the lower right in each frame. FIGS. 16 to 20 are schematic diagrams illustrating lighting states in which the LED light emitting device of FIG. 14 is lit in the sections 1 ′ to 5 ′ of FIG. In these LED light emitting devices, four common lines C0 to C3 are arranged in parallel in the horizontal direction, and the erroneous lighting prevention circuit 50 and the scanning unit 21 are connected. The erroneous lighting prevention circuit 50 has a circuit configuration similar to that of FIG. The scanning unit 21 switches ON / OFF of each common line. Four LED elements are arranged on each common line, and are connected to the anode side of each LED element. In the vertical direction, four drive lines S are arranged in parallel in the vertical direction, and four LED elements are connected to each drive line S on the cathode side. Each drive line S is connected to a sink driver, and the sink driver switches ON / OFF of each drive line S. Moreover, in each drawing, the LED element 1N which should be lighted originally is shown by black, and the LED element 1F which is lighted erroneously is shown by oblique lines. Furthermore, the parasitic capacitance of the wiring of each drive line S is virtually illustrated on each drive line S as equivalent capacitors C _{S0 to} C _S3 .

Hereinafter, in the LED light emitting device of FIGS. 16 to 20, the LED elements are lit while being sequentially switched diagonally along the diagonal line from the upper left to the lower right according to the sections 1 ′ to 5 ′ shown in the timing chart of FIG. 15. explain. First, FIG. 16 shows a section 1 ′ in FIG. 15 in which the common line C0 and the drive line S0 are turned on in order to turn on the upper left LED element aA. At this time, as a result of the current flowing through the drive line S0 as indicated by the dashed arrow in FIG. 16, the LED element aA is turned on. At this time, the other drive lines _S1 to _S3 are turned off by the sink driver and should not be energized originally, but no charge is initially accumulated in the equivalent capacitors C _{S1 to} C _S3 of each drive line. For this reason, a current flows until the electric charge is accumulated in each of the equivalent capacitors C _{S1 to} C _S3 , that is, until it is charged. As a result, a current flows through the drive lines S1 to S3, and as a result, the other LED elements aB, aC, and aD connected in common with the common line C0 are also lighted slightly, resulting in erroneous lighting.

Next, in order to switch the lighting of the LED element from aA to bB in the section 2 ′ in FIG. 15, the scanning unit 21 switches the common line C0 to OFF and the common line C1 to ON as shown in FIG. At the same time, the sink driver also switches from the drive line S0 to the drive line S1. As a result, the LED element bB is turned on as a result of energization of the drive line S1 from the common line C1. At this time, no charge is accumulated in the equivalent capacitor C _S0 of the drive line S0 (even if it is accumulated, the charge is discharged when the drive line S0 is ON), so that the charge is accumulated in the equivalent capacitor C _S0. As a result, the LED line bA is erroneously turned on as a result of the drive line S0 being energized. Further, the electric charge accumulated in the equivalent capacitor C _S1 is also discharged by energizing the drive line S1.

Similarly, as shown in FIG. 18, when the common line C2 and the drive line S2 are switched on in order to turn on the LED element cC in the section 3 ′ in FIG. 15, the LED element cC is turned on and in the section 2 ′. Until the equivalent capacitor C _{S1 of the} discharged drive line S1 is charged, the drive line S1 is also energized, and the LED element cB is erroneously lit.

Similarly, as shown in FIG. 19, when the common line C3 and the drive line S3 are switched on to turn on the LED element dD in the section 4 ′ in FIG. 15, the LED element dD is turned on and the drive line S2 is turned on. Until the equivalent capacitor C _S2 is charged, the drive line S2 is also energized, and the LED element dC is erroneously lit.

Then, as shown in FIG. 20 again, when the common line C0 and the drive line S0 are switched on in order to turn on the LED element aA in the section 5 ′ in FIG. 15, the LED element aA is turned on and the drive line S3 is turned on. Until the equivalent capacitor C _S3 is charged, the drive line S3 is also energized, and the LED element aD is erroneously lit. In this section 5 ′, the drive lines S1 and S2 are not energized since the charges are already stored in the equivalent capacitors C _S1 and C _S2 in the sections 3 ′ and 4 ′ in FIG. The LED elements connected to the drive lines S1 and S2 (here, the LED elements aB and aC connected to the common line C0) are not erroneously lit.

  As described above, when the same display pattern as shown by frames 0 to N in FIG. 15 is repeatedly displayed as a result of erroneous lighting in each section, it is desired to display the original as shown in FIG. 14 by the afterimage effect. In addition to the diagonal line from the upper left to the lower right, the line is also displayed lightly below it, resulting in a ghost-like mislighting in which the display pattern appears double. Such erroneous lighting, particularly when displaying information such as characters, causes the display to blur and degrades the display quality.

  As described above, in the anode common type, due to the parasitic capacitance of the circuit wiring, not only the LED element that should originally be lit but also an unintended LED element is lit. When such erroneous lighting occurs, display quality deteriorates. In particular, if an LED element located in the vicinity of an LED element that is originally intended to be lit is erroneously lit, it is not preferable, for example, in the use of an information display for displaying a still image or character information.

  The present invention has been made in view of such conventional problems. A main object of the present invention is to provide a light-emitting device, a light-emitting device drive circuit, and a light-emitting device driving method that can avoid erroneous lighting caused by parasitic capacitance such as circuit wiring.

Means for Solving the Problems and Effects of the Invention

  In order to achieve the above object, according to the light emitting device of the first aspect of the present invention, a plurality of light emitting elements 1 arranged in a matrix and the anode terminals of the light emitting elements 1 arranged in the row direction are connected. A display unit 10 having a plurality of common lines C and a plurality of drive lines S to which cathode terminals of the light emitting elements 1 arranged in the column direction are connected, and each common line C of the display unit 10 Connected to an arbitrary common line C and connected to the scanning unit for switching the selection and each drive line S of the display unit 10 and connected to the common line C selected by the scanning unit A driving unit capable of driving the light emitting element, wherein the light emitting device further connects an arbitrary light emitting element connected to the common line C selected by the scanning unit with the driving unit. Driving point A lighting period to be driven, and following the lighting period, the driving of the driving line S to which the arbitrary light emitting element 1 is connected is brought into a non-driving state while the common line C is kept in a selected state, and the driving line S is parasitized. The charging means 41 which provides the charge period for charging a capacity | capacitance can be provided. As a result, since the parasitic capacitance can be charged during the transition period for switching from the lighting state of any light emitting element to another light emitting element, there is an advantage that the erroneous lighting prevention function can be effectively executed while the light emitting state is continued. .

  Moreover, according to the light-emitting device which concerns on a 2nd side surface, the duty ratio of an ON period can be set to the maximum in the said lighting period. Thereby, while realizing efficient lighting, an advantage that an erroneous lighting prevention function can be executed in the meantime can be obtained.

  Further, according to the light emitting device according to the third aspect, one end of each common line C is connected and the other end is grounded. The charging element constituting the discharge path and the light emitting element 1 are connected to the light emitting device. The residual charge generated in the element 1 is connected to the charging element for charging the charging element when the light emitting element 1 is in a non-lighting state, and the residual charge is connected to the light emitting element 1. And a discharge path for discharging from the charging element to the ground terminal in the lighting state. This eliminates erroneous lighting due to the parasitic capacitance of the light emitting element, while avoiding erroneous lighting due to the parasitic capacitance of the wiring that cannot be eliminated by the erroneous lighting prevention circuit.

  Furthermore, according to the light emitting device according to the fourth aspect, the light emitting element 1 can be a light emitting diode or a semiconductor laser.

  Furthermore, according to the light emitting device according to the fifth aspect, the plurality of light emitting elements 1 arranged in a matrix, the plurality of common lines C connected to the anode terminals of the light emitting elements 1 arranged in the row direction, A display unit 10 having a plurality of drive lines S to which cathode terminals of the light emitting elements 1 arranged in the direction are connected, and each common line C of the display unit 10 is connected to an arbitrary common line C. And a drive unit that is connected to each drive line S of the display unit 10 and can drive a light emitting element connected to the common line C selected by the scan unit. The light emitting device is further driven by the drive unit among the light emitting elements 1 connected to the common line C before the scanning unit switches the selection of the common line C. Once it was a light-emitting element 1 a parasitic capacitance of the connected drive line S may be provided with a charging means 41 for charging. Thus, when switching the lighting of any light emitting element to another light emitting element, the charge corresponding to the parasitic capacitance of the drive line connected to the arbitrary light emitting element is completed before the switching to the other light emitting element is completed. Since the amount can be charged in advance, it is possible to avoid a situation where any light emitting element emits light when switching to another light emitting element. As a result, it is possible to avoid a situation in which an unintentional light emitting element connected to a non-selected drive line, which has occurred in the past, is energized and erroneously lit.

  Furthermore, according to the drive circuit for a light emitting device according to the sixth aspect, the plurality of light emitting elements 1 arranged in a matrix and the plurality of common lines C connected to the anode terminals of the light emitting elements 1 arranged in the row direction. And a plurality of drive lines S connected to the cathode terminals of the light-emitting elements 1 arranged in the column direction, the drive circuit for the light-emitting device for driving the light-emitting device, and connected to each common line C The scanning unit that selects an arbitrary common line C and is connected to each driving line S and drives the light emitting element connected to the common line C selected by the scanning unit. A possible driving unit, a lighting period in which an arbitrary light emitting element connected to the common line C selected by the scanning unit is driven by the driving unit, and the common line C following the lighting period. The Charging means 41 for providing a charging period for charging the parasitic capacitance of the drive line S while keeping the drive state of the optional light emitting element 1 connected to the non-drive state. Can do. Thus, when switching the lighting of any light emitting element to another light emitting element, the charge corresponding to the parasitic capacitance of the drive line connected to the arbitrary light emitting element is completed before the switching to the other light emitting element is completed. Since the amount can be charged in advance, it is possible to avoid a situation where any light emitting element emits light when switching to another light emitting element. As a result, it is possible to avoid a situation in which an unintentional light emitting element connected to a non-selected drive line, which has occurred in the past, is energized and erroneously lit.

  Furthermore, according to the driving method of the light emitting device according to the seventh aspect, the plurality of light emitting elements 1 arranged in a matrix and the plurality of common lines C connected to the anode terminals of the light emitting elements 1 arranged in the row direction. And a plurality of drive lines S to which the cathode terminals of the light emitting elements 1 arranged in the column direction are connected, and are selected by a scanning unit connected to each common line C. A step of lighting an arbitrary light-emitting element having an anode terminal connected to the common line C with the drive line S connected to the cathode terminal of the light-emitting element as a driving state, and keeping the common line C in a selected state, Charging the drive line S as a non-driven state of the drive line S to which the arbitrary light emitting element is connected;

  The selection is switched from the common line to another common line C, and one or more other light emitting elements connected to the switched common line C are connected to the drive line S connected to the cathode terminal of the light emitting element. A step of lighting as a driving state. Accordingly, since the parasitic capacitance can be charged when switching from the lighting state of any light emitting element to another light emitting element, there is an advantage that the erroneous lighting preventing function can be effectively executed while the light emitting state is continued.

It is a block diagram which shows the light-emitting device which concerns on Embodiment 1 of this invention. It is a timing chart which shows the timing which sends a lighting signal to the common line and drive line of the LED light-emitting device of FIG. It is a schematic diagram which shows the state which the LED light-emitting device of FIG. 1 lights in the area 1 of FIG. It is a schematic diagram which shows the state which the LED light-emitting device of FIG. 1 lights in the area 2 of FIG. It is a schematic diagram which shows the state which the LED light-emitting device of FIG. 1 lights in the area 3 of FIG. It is a schematic diagram which shows the state which the LED light-emitting device of FIG. 1 lights in the area 4 of FIG. It is a schematic diagram which shows the state which the LED light-emitting device of FIG. 1 lights in the area 5 of FIG. It is a schematic diagram which shows the state which the LED light-emitting device of FIG. 1 lights in the area 6 of FIG. It is a schematic diagram which shows the state which the LED light-emitting device of FIG. 1 lights in the area 7 of FIG. It is a schematic diagram which shows the state which the LED light-emitting device of FIG. 1 lights in the area 8 of FIG. It is a schematic diagram which shows the state which the LED light-emitting device of FIG. 1 lights in the area 9 of FIG. It is a schematic diagram which shows the state turned on by avoiding mislighting with the anode common type LED light-emitting device of FIG. It is a block diagram which shows the conventional LED light-emitting device. It is a schematic diagram which shows a mode that a mislighting arises with an anode common type LED light-emitting device. It is a timing chart which shows the timing which sends out a lighting signal to a common line and a drive line in the conventional LED light-emitting device. It is a schematic diagram which shows the state which the LED light-emitting device of FIG. 14 lights in the area 1 of FIG. It is a schematic diagram which shows the state which the LED light-emitting device of FIG. 14 lights in the area 2 of FIG. It is a schematic diagram which shows the state which the LED light-emitting device of FIG. 14 lights in the area 3 of FIG. It is a schematic diagram which shows the state which the LED light-emitting device of FIG. 14 lights in the area 4 of FIG. It is a schematic diagram which shows the state which the LED light-emitting device of FIG. 14 lights in the area 5 of FIG. FIG. 21A is a schematic diagram of an LED light emitting device, and FIG. 21B is a timing chart showing an example of a lighting period and a charging period. It is a schematic diagram which shows the light-emitting device which made the light emitting element substrate and the drive circuit board | substrate separate. It is a schematic diagram which shows the light-emitting device which integrated the light emitting element board | substrate and the drive circuit board | substrate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiment described below exemplifies a light emitting device, a light emitting device driving circuit, and a light emitting device driving method for embodying the technical idea of the present invention. The driving circuit for the device and the driving method of the light emitting device are not specified as follows. Further, the present specification by no means specifies the members shown in the claims to the members of the embodiments. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the embodiments are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only. Note that the size, positional relationship, and the like of the members shown in each drawing may be exaggerated for clarity of explanation. Furthermore, in the following description, the same name and symbol indicate the same or the same members, and detailed description thereof will be omitted as appropriate. Furthermore, each element constituting the present invention may be configured such that a plurality of elements are constituted by the same member and a plurality of elements are shared by one member, and conversely, the function of one member is constituted by a plurality of members. It can also be realized by sharing. In addition, the contents described in some examples and embodiments may be used in other examples and embodiments.

  Note that in this specification, “wrong lighting” typically means unintentional lighting caused by accumulation of electric charges in a parasitic capacitance of a wiring, and may be expressed as minute lighting, pseudo lighting, or the like. However, the expression “minor” is conventional and does not specify the amount of light emission.

Hereinafter, the parasitic capacitance included in the wiring or the like is referred to as an equivalent capacitor in this specification. In this specification, the equivalent capacitor mainly indicates the parasitic capacitance of the wiring, but is not limited to this and is used with the intention of including the case caused by other factors.
(Embodiment 1)

FIG. 1 shows a block diagram of a light emitting device 100 according to Embodiment 1 of the present invention. The light emitting device 100 shown in this figure includes a display unit 10 in which the light emitting elements 1 are arranged in a matrix, a current source switching circuit 20, a constant current control circuit unit 30, a control unit 40, and an erroneous lighting prevention circuit 50. Prepare.
(Display unit 10)

The display unit 10 is configured in a grid pattern in which a plurality of common lines C are arranged in parallel in the horizontal direction and a plurality of drive lines S are arranged in parallel in the vertical direction intersecting with the common lines C. Further, by connecting a plurality of light emitting elements 1 between the common lines C and the drive lines S, the light emitting elements 1 are arranged in a matrix. In FIG. 1, common lines C correspond to rows, drive lines S correspond to columns, and a plurality of light emitting elements 1 are arranged in a matrix of m rows × n columns. The cathode terminals of the light emitting elements 1 in each column are connected to the drive line S, and the anode terminals of the light emitting elements 1 in each row are connected to the common line C, respectively. In the example of FIG. 1, the light emitting elements 1 are arranged as a display unit 10 in a matrix of 4 rows × 4 columns, but the number of rows and columns in the display unit can be arbitrarily set. It goes without saying that the same result can be obtained even if the rows and columns (vertical and horizontal) are interchanged (for example, the common lines are arranged vertically and the drive lines are arranged horizontally).
(Light emitting element 1)

As the light emitting element 1, a semiconductor light emitting element can be used, and in particular, a light emitting diode (LED) can be preferably used. However, the present invention does not limit the light-emitting element 1 to an LED, and light emission using other light-emitting elements such as a semiconductor laser, or other light-emitting elements such as an electroluminescence light-emitting device and a field emission light-emitting device (FED). The same applies to the apparatus. In this example, an example in which an LED element is used as the light emitting element 1 is described.
(Current source switching circuit 20)

  The current source switching circuit 20 constitutes a scanning unit. In the example of FIG. 1, the current source switching circuit 20 includes a scanning unit 21 and a decoder circuit 22. The scanning unit 21 is connected to each common line C of the matrix display unit 10, selects an arbitrary common line C, and controls energization of the common line C. Here, the scanning unit 21 controls ON / OFF of each common line C. The current source switching circuit 20 includes m switch circuits respectively connected corresponding to the common lines C, and by connecting the common line C specified by the address signal by the source lighting control signal to the current source, A current is supplied to the light emitting element 1 connected to the common line C.

Specifically, when the source lighting control signal is at the LOW level, the decoder circuit 22 performs ON / OFF control of the scanning unit 21 so as to connect the common line C specified by the address signal and the current source. In the current source switching circuit 20, when the source lighting control signal is at a HIGH level, the decoder circuit 22 controls the scanning unit 21 so as to disconnect all the common lines C from the current sources.
(Constant current control circuit unit 30)

  The constant current control circuit unit 30 constitutes a drive unit. In the example of FIG. 1, the constant current control circuit unit 30 includes a constant current drive unit 31, a storage circuit 32, a shift register 33, and an AND gate 34. The constant current drive unit 31 constitutes a sink driver. The constant current drive unit 31 is connected to each drive line S of the matrix display unit 10, selects an arbitrary drive line S, and controls ON / OFF of the drive line S.

  The storage circuit 32 stores n pieces of ON / OFF data that are sequentially input. The constant current control circuit unit 30 drives the drive line S corresponding to the ON / OFF data stored in each storage circuit 32 during the lighting period specified by the sink lighting control signal.

The constant current control circuit unit 30 shifts the ON / OFF data n times in synchronization with the shift clock by the shift register 33, and the ON / OFF data corresponding to each of the n drive lines S in response to the latch. Are input to the storage circuit 32 and stored. Then, the sink lighting control signal and the ON / OFF data are calculated by the AND gate 34, and the constant current drive unit 31 performs control so that a constant current flows through each drive line S during the corresponding drive pulse width.
(Control unit 40)

  The control unit 40 generates a source lighting control signal and a sink lighting control signal for controlling the current source switching circuit 20 and the constant current control circuit unit 30. The current source switching circuit 20 and the constant current control circuit unit 30 are selected by selecting an arbitrary common line C and drive line S according to the source lighting control signal and the sink lighting control signal generated by the control unit 40, respectively. The lighting state of the light emitting element 1 connected between the common line C and the drive line S is controlled.

Specifically, the control unit 40 performs LED display control with the current source switching circuit 20 and the constant current control circuit unit 30 while the source lighting control signal is at the LOW level and the sink lighting control signal is at the HIGH level. Note that while the source lighting control signal is HIGH level and the sink lighting control signal is LOW level, the display unit 10 is not connected to the current source switching circuit 20 and the constant current control circuit unit 30. Further, in the light emitting device 100, when the source lighting control signal is at the LOW level and the sink lighting control signal is at the HIGH level, the predetermined light emitting element 1 is turned on by driving the display unit 10 at a constant current, and the source lighting control signal is set to HIGH. When the level and sink lighting control signal is at the LOW level, the constant current driving of the display unit 10 is stopped.
(Incorrect lighting prevention circuit 50)

  The erroneous lighting prevention circuit 50 is connected to the current source switching circuit 20. Here, the erroneous lighting prevention circuit 50 is provided for each common line C. The erroneous lighting prevention circuit 50 is connected to the driving circuit of the scanning unit 21 that controls ON / OFF of the common line C, the charging path connected to the anode terminal of each light emitting element 1 and one end of the driving circuit, and the charging path. And a discharge path that reaches the ground terminal via the drive circuit. Here, the charging path is a path through which the residual charge in each light emitting element flows when flowing into the charging element when the common line C is in a non-energized state, and the discharging path is a state in which the common line C is in an energized state. This is a path through which the charge charged in the charging element passes when it is discharged at the ground end.

Switching of the current source switching circuit 20 is performed by a source lighting control signal, and switching of the constant current control circuit unit 30 is performed by a sink lighting control signal. When the source lighting control signal indicates lighting, the current source switching circuit 20 is driven, and when the sink lighting control signal indicates lighting, the constant current control circuit unit 30 is driven. In this driving state, the common line C designated by the address signal input in the current source switching circuit 20 is connected to the current source, and the constant current control circuit unit 30 turns on the lighting designated by the sink lighting control signal. In a period, the light emitting elements 1 connected to the common line C designated by the address signal are turned on by setting the drive line S corresponding to the ON / OFF data stored in each memory circuit 32 to the drive state. In the non-driving state, the current source switching circuit 20 and the constant current control circuit unit 30 are not driven. In this case, when the source lighting control signal and the sink lighting control signal indicate non-lighting, the charge remaining in each light emitting element 1 or its periphery is charged to the charging element through the charging path, and the source lighting is performed. When the control signal indicates lighting, the charge charged in the charging element is discharged from the ground end through the discharge path, so that there is almost no charge remaining in each light emitting element 1 or its surroundings. . Thereby, since the electric charge accumulated in the light emitting element 1 or its periphery in the lighting period is discharged in the next non-lighting period, each light emitting element is always in the non-driving state in which another common line is selected. It is possible to make a state in which unnecessary charges are not accumulated in 1 and its surroundings. Accordingly, in the light emitting device of this embodiment, lighting control can be performed without being affected by the residual charge, so that sufficient contrast can be obtained in the light emitting state, and high quality display can be achieved.
(Charging means 41)

Furthermore, the light emitting device 100 includes a charging unit 41 for preventing erroneous lighting. The charging unit 41 charges a charge amount corresponding to the parasitic capacitance of the drive line S to which the light emitting element is connected when switching the lighting of the light emitting element 1 from one light emitting element to another light emitting element. In other words, by generating a charging period for charging the parasitic capacitance, it is possible to avoid a situation in which the parasitic capacitance is charged and an erroneous lighting occurs. Such a charging unit 41 can be incorporated in a control unit that controls lighting of the light emitting element 1. For example, in the light-emitting device 100 of FIG. 1, if the light-emitting element 1 is turned on while sequentially switching from the upper left to the lower right and obliquely along the diagonal line, the timing chart as shown in FIG. As shown in FIG. 2, a charging period is provided.
(Charging period)

  Here, when switching lighting from one light-emitting element to another light-emitting element, the drive line to which the light-emitting element is connected is turned on while the common line to which the one light-emitting element is connected is turned on. Switch from OFF to OFF state. At this time, drive lines and common lines connected to other light emitting elements are not yet turned on. As a result, the parasitic capacitance of the drive line to which the one light emitting element is connected is charged through the common line within the charging period, so that the parasitic capacitance is not charged after the transition to the next lighting state. Such erroneous lighting caused by charging can be avoided. Such an operation will be described with reference to the timing chart of FIG. 2 and FIGS.

The timing chart of FIG. 2 shows the common lines C0 to C3 and the drive lines S0 to S0 when the same display pattern is repeatedly displayed from the first lighting frame 0 after the power is turned on to the lighting frame N at a certain time. The ON / OFF pattern of S3 is shown. Here, sections 1 to 8 of frame 0 and sections 2 to 9 of transition to frame 1 will be described. 3 to 11, the parasitic capacitances of the drive lines S0 to S3 are equivalently shown as equivalent capacitors C _{S0 to} C _S3 .

First, in the section 1 in FIG. 2, since the common line C0 and the drive line S0 are turned on, the LED element aA located at the upper left of the display unit 10 is turned on as shown in FIG. Here, the other LED elements aB, aC, and aD connected to the common line C0 are not energized and are not lit because the drive lines S1 to S3 are OFF. Since the equivalent capacitors C _{S1 to} C _S3, which are parasitic capacitances, are not charged after the power is turned on until the first lighting control, they are energized until they are fully charged, and the LED elements aB, aC, aD is lit slightly. This erroneous lighting occurs only in section 1 of the first frame 0 after power-on, and does not occur in subsequent frames (details will be described later).

Next, in order to turn on the LED element bB, before the common line C1 and the drive line S1 are turned on in the section 3 of FIG. 2, the charging means 41 provides the section 2 as a charging period before that. In section 2, the drive line S0 connected to the LED element aA is switched from the ON state to the OFF state while maintaining the common line C0 connected to the LED element aA. At this time, the common line C1 and the drive line S1 to which the LED element bB to be lit next is connected are not yet turned on. As a result, as shown in FIG. 4, the equivalent capacitor C _S0 of the drive line S 0 to which the LED element aA is connected is charged in the section 2.

In this way, even if the drive line S1 is turned on in addition to the common line C1 in the subsequent section 3, only the intended LED element bB is lit as shown in FIG. The other LED elements bA, bC, bD connected to are not lit. This is because the equivalent capacitors C _S0 , C _S2 , and C _S3 of the drive line connected to these are already charged. That is, the equivalent capacitor C _S0 is charged in the previous section 2, and the equivalent capacitors C _S2 and C _S3 are also charged in the section 1. For this reason, the erroneous lighting (FIG. 17) which has arisen because these equivalent capacitors are charged can be avoided effectively.

Similarly, in the section 4, the drive line S1 connected to the LED element bB is switched from the ON state to the OFF state while maintaining the ON state of the common line C1 connected to the LED element bB. As a result, as shown in FIG. 6, the equivalent capacitor C _S1 of the drive line S1 to which the LED element bB is connected is charged in the section 4. As a result, even if the equivalent capacitor C _S1 of the drive line S1 is discharged as shown in FIG. 5 in the previous section 3, the section 4 is added as a charging period, and as a result, the charging state is equivalent in the next section 5. It is possible to prevent erroneous lighting due to charging of the capacitor C _S1 .

  In the section 5, the drive line S2 is turned on in addition to the common line C2, the LED element cC is turned on as shown in FIG. 7, and the other LED elements cA, cB, connected to the same common line C2, It is possible to avoid erroneous lighting of cD.

Further, in the section 6, the drive line S2 connected to the LED element cC is switched from the ON state to the OFF state while maintaining the ON state of the common line C2 connected to the LED element cC. As a result, as shown in FIG. 8, the equivalent capacitor C _S2 of the drive line S2 connected to the LED element cC is charged in the section 6.

  In the section 7, the drive line S3 is turned on in addition to the common line C3, the LED element dD is turned on as shown in FIG. 9, and the other LED elements dA, dB, It is possible to avoid erroneous lighting of dC.

Finally, in the section 8, the drive line S3 connected to the LED element dD is switched from the ON state to the OFF state while maintaining the ON state of the common line C3 to which the LED element dD is connected. As a result, as shown in FIG. 10, the equivalent capacitor C _S3 of the drive line S 3 connected to the LED element dD is charged in the section 8.

In this way, in the frame 0, the LED elements of the matrix display unit 10 can be switched on sequentially from the upper left to the lower right. Next, when the same lighting pattern is repeated in the frame 1, the common line C0 and the drive line S0 are turned ON in the section 9 as in the section 1. At this time, as shown in FIG. 11, only the LED element aA is turned on. Here, unlike FIG. 3, the other LED elements aB, aC, and aD connected to the common line C0 are already charged with the equivalent capacitors C _{S1 to} C _S3. Does not occur. Thereafter, the same procedure as that for frame 0 is repeated, and a desired lighting pattern can be obtained while preventing erroneous lighting in frames 1 to N. As a result, in the LED light emitting device that performs dynamic lighting, it is possible to avoid the erroneous lighting as shown in FIG. 14 and only the desired LED element can be turned on as shown in FIG. Realized.

  In particular, according to this configuration, there is no need to provide a separate current source or switch for charging the equivalent capacitor for each drive line, and there is an advantage that it can be executed extremely easily. That is, no additional hardware is required for mounting, and it can be handled only by changing the control method. Therefore, it can be easily applied to an existing system and can be realized at low cost.

  The charging period is set to a time during which the equivalent capacitor can be charged. The time is appropriately adjusted according to the size of the parasitic capacitance, that is, the circuit size and scale of the light emitting device, the wiring length, the current value of the current source, the required accuracy, the response speed, and the like. That is, the charging period is set to be long when the parasitic capacitance is large, and the charging period is set to be short when the parasitic capacitance is small. As an example, in the LED light emitting device in which the LED elements of 24 rows × 48 columns shown in FIG. 21A manufactured by the present inventor are arranged, as shown in the timing chart of FIG. 4 μs. In the example of FIG. 2, each charging period is constant, but the charging period may be changed for each drive line depending on the circuit configuration.

  This method can be suitably used when the duty ratio of the ON period is maximized when performing lighting driving by PWM control. That is, an erroneous lighting prevention function can be added while performing the most efficient lighting with the entire period turned on.

  Such an erroneous lighting prevention function is particularly effective for a light emitting device having a large parasitic capacitance. For example, as shown in FIG. 22, in a light emitting device 200 in which a light emitting element substrate 12 on which a light emitting element 1 is arranged and a driving circuit board 42 on which driving circuits such as a scanning unit and a driving unit are arranged are individually configured. As a result of an increase in the length of the wiring connecting the members, the parasitic capacitance becomes relatively large and erroneous lighting tends to become remarkable. For such a circuit configuration, the erroneous lighting prevention function of the present invention works effectively. On the other hand, as shown in FIG. 23, in the light emitting device 300 in which the light emitting element 1 is arranged on the front surface side of the circuit board 13 and the driving circuit 43 is mounted on the back surface side, the parasitic capacitance caused by the wiring is relatively small. Become. However, such a circuit configuration is often used for a small display or a guide plate, and in such a light emitting device with a small display size, erroneous lighting tends to be conspicuous in relation to the size and the number of dots. Therefore, the present invention can be preferably applied to a light emitting device in which such erroneous lighting is conspicuous.

  In the above example, the display is described as the light emitting device. In particular, the present invention can provide a clear display since it can prevent erroneous lighting, and can be suitably used for applications such as character display guide boards and information display boards. However, the present invention is not limited to this, and it can be used for a moving image display, a still image display, intelligent lighting, and the like.

  As described above, various applications can be flexibly handled by using the light emitting device, the light emitting device driving circuit, and the light emitting device driving method according to the present invention. For example, it can be used as a LED display for large televisions, billboards, advertisements, traffic information, stereoscopic displays, lighting fixtures, and the like. Particularly, it is suitable for downsizing, cost reduction, automation, and design flexibility of the apparatus. Further, it can be used not only for LED light emitting devices but also for TFT liquid crystal displays in which pixels are driven by transistors.

DESCRIPTION OF SYMBOLS 100, 200, 300 ... Light-emitting device 1 ... Light-emitting element; 1N ... LED element to turn on; 1F ... Other LED element aA, aB, aC, aD, bA, bB, bC, bD, cA, cB cC, cD, dA, dB, dC, dD ... LED element 10 ... display unit 12 ... light emitting element substrate 13 ... circuit board 20 ... current source switching circuit 21 ... scanning unit 22 ... decoder circuit 30 ... constant current control circuit unit 31 ... Constant current drive unit 32 ... storage circuit 33 ... shift register 34 ... AND gate 40 ... control unit 41 ... charging means 42 ... drive circuit board 43 ... drive circuit 50 ... erroneous lighting prevention circuit C, C0 to C3 ... common lines S, S0 ~ S3 ... drive line C _S0 , C _S1 , C _S2 , C _S3 , ... equivalent capacitor

Claims (7)

A plurality of light emitting elements (1) arranged in a matrix, a plurality of common lines (C) connected to anode terminals of the light emitting elements (1) arranged in a row direction, and the light emitting elements arranged in a column direction A display unit (10) having a plurality of drive lines (S) to which the cathode terminal of (1) is connected;
Connected to each common line (C) of the display unit (10), selecting an arbitrary common line (C), and a scanning unit for switching the selection,
Connected to each drive line (S) of the display unit (10), a drive unit capable of driving a light emitting element connected to the common line (C) selected by the scanning unit,
A light emitting device comprising:
The light emitting device further includes
An arbitrary light emitting element connected to the common line (C) selected by the scanning unit, a lighting period that is driven by the driving unit to be lit, and
Following the lighting period, with the common line (C) kept in a selected state, the drive line (S) to which the arbitrary light emitting element (1) is connected is brought into a non-drive state, and the drive line (S And a charging means (41) for providing a charging period for charging the parasitic capacitance. The light-emitting device according to claim 1,
In the lighting period, the duty ratio of the ON period is set to the maximum, and the light emitting device. The light emitting device according to claim 1, further comprising:
A charging element constituting a discharge path, having one end connected to each common line (C) and the other end grounded,
A charging path connected to the light emitting element (1) and charging the charging element when the light emitting element (1) is in a non-lighting state, residual charge generated in the light emitting element (1), and
A light emitting device comprising: a discharge path connected to the charging element and discharging the residual charge from the charging element to a ground terminal in a lighting state of the light emitting element (1). The light-emitting device according to any one of claims 1 to 3,
The light emitting device, wherein the light emitting element (1) is a light emitting diode or a semiconductor laser. A plurality of light emitting elements (1) arranged in a matrix, a plurality of common lines (C) connected to anode terminals of the light emitting elements (1) arranged in a row direction, and the light emitting elements arranged in a column direction A display unit (10) having a plurality of drive lines (S) to which the cathode terminal of (1) is connected;
Connected to each common line (C) of the display unit (10), selecting an arbitrary common line (C), and a scanning unit for switching the selection,
Connected to each drive line (S) of the display unit (10), a drive unit capable of driving a light emitting element connected to the common line (C) selected by the scanning unit,
A light emitting device comprising:
The light emitting device further includes
Before the scanning unit switches the selection of the common line (C), the light emitting element (1) connected to the common line (C) is connected to the light emitting element (1) driven by the driving unit. A light emitting device comprising: charging means (41) for charging the parasitic capacitance of the drive line (S). A plurality of light emitting elements (1) arranged in a matrix, a plurality of common lines (C) connected to anode terminals of the light emitting elements (1) arranged in a row direction, and the light emitting elements arranged in a column direction A drive circuit for a light emitting device for driving a light emitting device comprising a plurality of drive lines (S) to which the cathode terminals of (1) are connected,
A scanning unit that is connected to each common line (C), selects an arbitrary common line (C), and switches the selection;
A drive unit that is connected to each drive line (S) and that can drive the light-emitting elements connected to the common line (C) selected by the scanning unit;
An arbitrary light emitting element connected to the common line (C) selected by the scanning unit, a lighting period that is driven by the driving unit to be lit, and
Following the lighting period, with the common line (C) kept in a selected state, the drive line (S) to which the arbitrary light emitting element (1) is connected is brought into a non-drive state, and the drive line (S Charging means (41) for providing a charging period for charging the parasitic capacitance of
A drive circuit for a light-emitting device, comprising: A plurality of light emitting elements (1) arranged in a matrix, a plurality of common lines (C) connected to anode terminals of the light emitting elements (1) arranged in a row direction, and the light emitting elements arranged in a column direction A drive method of a light emitting device comprising a plurality of drive lines (S) to which the cathode terminals of (1) are connected,
Arbitrary light emitting elements connected to the anode terminal to the common line (C) selected by the scanning unit connected to each common line (C), and the drive line (S) connected to the cathode element of the light emitting element. A process of lighting as a driving state;
With the common line (C) in a selected state, the drive line (S) to which the arbitrary light emitting element is connected is set in a non-driven state, and the drive line (S) is charged,
The selection is switched from the common line to another common line (C), and one or more other light emitting elements connected to the switched common line (C) are connected to the cathode element of the light emitting element. The process of lighting the drive line (S) as a drive state;
A method for driving a light emitting device, comprising:

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