JP2000187464A - Device and method for driving matrix - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a matrix driving device to detect a current of a matrix element with high accuracy with a circuit scale kept unchanged even if the matrix is increased in size, and to control the current excellently. SOLUTION: This matrix driving device drives matrix elements 1 through a cathode driving circuit 2 and an anode driving circuit 3 according to an instruction from a control device 5. In that case, a current detecting cycle of the matrix elements 1 is included in a driving cycle of the matrix elements, and the currents flowing through individual elements are sequentially detected by a current detecting circuit 6 at each n-line driving on the common side of the cathode, and are inputted to the control device 5. And, the driving current of an elements is controlled according to the detected current value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matrix device driving device in which a large number of light emitting devices are arranged in a matrix, and more particularly to a matrix driving device and a matrix driving method incorporating a current detection cycle.

[0002]

2. Description of the Related Art In order to display more information by combining a large number of light emitting elements such as LEDs and organic ELs, generally, a matrix drive system in which the elements are arranged in a matrix and time-divisionally lit is adopted. . FIG. 9 is an equivalent circuit diagram showing an example of the matrix element 1 in such a matrix drive system.

FIG. 9 shows a case where the cathode side is a common side and the anode side is a segment, where (n, 0), (n-1, 0).
.. The light emitting elements of each pixel of (0, m) are arranged in a matrix. A cathode (common) line and an anode (segment) line are connected to each light emitting element.

FIG. 10 is a block diagram showing a configuration of a conventional driving device for driving the above-mentioned matrix element 1. As shown in FIG. In the figure, reference numeral 2 denotes a cathode drive circuit, 3 denotes an anode drive circuit, 4 denotes a current detection circuit for detecting a current flowing through each anode line, and is constituted by a plurality of current detectors connected to each anode line.
Reference numeral 5 denotes a control device that controls each of the drive circuits 2 and 3 based on input information and information from the current detection circuit 4.

In a matrix display device, when a display element requires current control, a current detector is generally connected to each anode line (when the cathode side is common) as shown in FIG.

At the time of driving, the potential of the cathode 0 (common 0) line is set to the ground potential, the anode on the 0 line which needs lighting is set to the driving voltage, and the anode to be turned off is set to the ground potential. Then, the current is detected by each of the current detectors described above, and the drive voltage is directly controlled in accordance with the detected value to perform constant current control.

When the driving time of the cathode 0 line ends, the same operation is performed on the cathode 1 line. At this time, the lighting time of one line is 1 / n if the cathode is n lines, and is generally called 1 / n duty.

[0008]

However, in the conventional driving device for a matrix element as described above,
Since the current detecting means is added to each line, the circuit becomes complicated and expensive. In particular, when the matrix size becomes large, the circuit scale becomes large and the device becomes large.

The present invention has been made in view of the above-mentioned problems, and enables a highly accurate current detection with a simple and inexpensive configuration. Even if the matrix size becomes large, the circuit scale remains unchanged. Therefore, it is an object of the present invention to provide a matrix driving device and a matrix driving method that can perform good current control.

[0010]

A matrix driving apparatus and a matrix driving method according to the present invention are configured as follows.

(1) In a driving device for a light emitting element in a matrix configuration, current detecting means for detecting a current flowing through the light emitting element, and controlling a driving current of the light emitting element detecting the current in accordance with the detected current. Control means,
The current flowing through each light emitting element is sequentially detected in accordance with the driving cycle of the light emitting element.

(2) In the method of driving a light emitting element in a matrix configuration, currents flowing through individual light emitting elements are sequentially detected in accordance with the driving cycle of the light emitting elements, and the light emission is detected according to the detected current. The driving current of the element is controlled.

[0013]

FIG. 1 is a block diagram showing the configuration of a first embodiment of the present invention. The same reference numerals as in FIG. 10 denote the same components.

In FIG. 1, reference numeral 1 denotes a matrix element (light emitting element) such as an LED, which has a configuration similar to that of FIG. Reference numerals 2 and 3 denote a cathode drive circuit and an anode drive circuit connected to the cathode line and the anode line, respectively, which are controlled by a control device (control means) 5. Reference numeral 6 denotes a current detecting circuit (current detecting means) for detecting a current flowing through the matrix element 1. The control device 5 sequentially inputs detection values of the current flowing through the individual elements 1 in accordance with the driving cycle of the matrix element 1. The driving current of the element 1 that has detected the current is controlled.

In the driving method of this embodiment, the control is performed by inserting a current detection cycle into the driving cycle on the assumption that the driving current does not change greatly in a short time in the matrix driving of the current control type element. Thus, current detection can be performed at low cost and with high accuracy regardless of the matrix size.

That is, similarly to the above-mentioned conventional method, the line of the common 0 is set to the ground potential, and the driving voltage is applied to the anode of the lighting element on the line 0 and the ground potential is applied to the light-off element. Then, at this time, current detection is not performed, and after driving for n lines, a current detection cycle is started.
Perform current detection.

In the first current detection cycle, the current of the element (0, 0) shown in FIG. 9 is detected. That is, with the common (cathode) 0 as the ground potential, the segment (anode) 0 as the detection voltage, and other than the segment 0 (1 to m) as the ground potential, the current flowing through the element (0, 0) by the current detection circuit 6 To detect.

In the next current detection cycle, after n-line driving, current detection is performed on the element (0, 1) in the same manner as described above. At this time, the aforementioned lighting time (duty cycle)
Is 1 / (n + 1).

Next, the operation of the above-described drive cycle and current detection cycle will be described in detail with reference to FIGS. Here, the case of the matrix of the common 2 and the segment 2 shown in FIG. 2 will be described. In FIG. 2, D _{00 to} D
Reference numeral ₁₁ denotes an LED as a light emitting element.

FIG. 3 shows the operation timing in the above matrix. Here, the cathode rays C ₀ ,
The voltage of C ₁ and anode lines S ₀ , S ₁ and each line (C ₀ ,
Shows a lighting driving timing of C _1), and the current detection timing of D ₀₀ to D _11, the timing signals from the shift register (see FIG. 4, FIG. 5) of the cathode driving circuit 2 and the anode driving circuit 3 will be described later I have.

FIG. 4 is a block diagram showing an example of the anode drive circuit 3. In the figure, 11 is a shift register for outputting a timing signal for measurement (for current detection), 12 is a shift register for outputting a drive pulse whose pulse width is controlled, 13 is a subtraction counter for counting the pulses of the shift register 12,
14 is an AND gate; 15 is a flip-flop (F / F); 16 is an AND gate to which signals from the flip-flop 15 and the shift register 11 are input;
Is an inverter for inverting the signal from the shift register 11, and 18 is a flip-flop 15 and the shift register 11
Is an AND gate to which a signal from is input.

The shift registers 11 and 12, the subtraction counter 13 and the flip-flop 15 receive a timing clock (CLOCK), and the subtraction counter 13 receives a load (LOAD) signal. Then, the outputs of the inverter 17 and the AND gate 18 are input to the gates of the FETs Q1 and Q2 connected in series.
The drive voltage Vd and the detection voltage Vs are output to the anode of the matrix element 1 from the connection point between ETQ1 and Q2. The output of the AND gate 16 is input to the gate of the FET Q3, and the drive voltage Vd is output through the FET Q3.

FIG. 5 is a block diagram showing an example of the cathode drive circuit 2. This circuit has a shift register 19 for outputting a timing signal for display, and an output of the shift register 19 is inverted by an inverter 20 to connect a series-connected FET.
Input to the gates of Q4 and Q5. And this FE
The drive voltage Vd is output to the cathode of the matrix element 1 from the connection point between TQ4 and Q5.

FIG. 6 is a block diagram showing an example of the current detection circuit 6. This circuit has a measuring resistor R1 through which a current from the cathode driving circuit 2 flows. The voltage across the resistor R1 is input to the A / D converter 21 to be converted into a signal, and the detection signal is input to the control device 5. are doing.

As described above, in this embodiment, the current detection cycle is inserted into the drive cycle of the matrix element 1 for control, so that a highly accurate current detection can be performed with a simple and inexpensive configuration. Even if the matrix size becomes large, good current control can be performed without changing the circuit scale.

The voltage Vs at the time of detection may be lower than the drive voltage Vd. In addition, even when gradation control is performed, the control method of this embodiment is effective.

FIG. 7 is a diagram showing the configuration of the second embodiment of the present invention, and the same reference numerals as in FIG. 1 denote the same components. In the figure, reference numeral 7 denotes a power supply for the drive voltage Vd, and 8 denotes a power supply for the detection voltage Vs.

In the above embodiment, an example was described in which the anode side is common, but the cathode side may be common as in this embodiment. Even with such a configuration, the same operation and effect can be obtained.

FIG. 8 is a flowchart showing the operation of the above-described embodiment. The control shown in this flowchart is executed by the control device 5 according to a predetermined program.

First, display data is developed based on the input information (S1), and the segment line m = 0 (S
2), common line (unlit) n '= 0 (S3), and common line (lit) n = 0 (S4). And n
The line data is set, and a drive voltage is applied to the segment to be lit (displayed), and a ground potential is applied to the other segments (S5).

Next, a ground potential is applied to the common n-line, and a drive voltage is applied to the other common lines (S6). After a predetermined ON time (S7) has elapsed (S7), a drive voltage is applied to the common n-line (S6). S8). And n = n + 1
(S9), and when n exceeds a predetermined number N (S1).
0), and a drive voltage is applied to the segment m line (S1).
1), a ground potential is applied to the common n 'line (S1
2).

Thereafter, a current detection cycle is started, current detection is performed (S13), and m = m + 1 is set (S14).
If m exceeds a predetermined number M (S15), n '= n' + 1 is set (S16). When n ′ exceeds N (S
17), n ′ = 0 is set (S18), and the above operation is repeated.

[0033]

As described above, according to the present invention, it is possible to detect the current of a matrix element with high accuracy with a simple and inexpensive configuration, and to maintain the circuit scale even if the matrix size becomes large. There is an effect that good current control can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a matrix.

FIG. 3 is an explanatory diagram showing operation timings of the matrix in FIG. 2;

FIG. 4 is a configuration diagram showing an example of an anode drive circuit.

FIG. 5 is a configuration diagram illustrating an example of a cathode drive circuit.

FIG. 6 is a configuration diagram illustrating an example of a current detection circuit.

FIG. 7 is a configuration diagram of a second embodiment of the present invention.

FIG. 8 is a flowchart showing the operation of the embodiment.

FIG. 9 is an equivalent circuit diagram illustrating an example of a matrix element.

FIG. 10 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Matrix element (light emitting element) 2 Cathode drive circuit 3 Anode drive circuit 5 Control device (control means) 6 Current detection circuit (current detection means)

Claims (2)

[Claims] 1. A driving device for a light emitting element having a matrix configuration, wherein current detecting means for detecting a current flowing through the light emitting element, and control for controlling a driving current of the light emitting element detecting the current in accordance with the detected current. Means for sequentially detecting a current flowing through each light emitting element in accordance with a driving cycle of said light emitting element. 2. A method of driving a light-emitting element having a matrix configuration, wherein currents flowing through individual light-emitting elements are sequentially detected in accordance with a driving cycle of the light-emitting element, and the current is detected in accordance with the detected current. A matrix driving method, wherein the driving current is controlled.