JPS62237844A - Drive circuit for display of key telephone system - Google Patents

Abstract

PURPOSE:To stabilize the lighting brightness regardless of the display state by sending a drive signal turning on sequentially repetitively switch elements inserted at each column of a light emitting element array at a prescribed period. CONSTITUTION:A control circuit CNT1 sends trigger signals a-c at each same connection order at each column of groups G1-Gm corresponding to a light emitting diode LED extinguished in reponse to the display state synchronously with prescribed periods T1-T2. Thus, the DC component is blocked by capacitors C11-Cnm and a pulse trigger signal is obtained regardless of the DC potential difference at the side of thyristors SR11-SRnm with respect to the power return and fed to the gate of the thyristor SR. Only when transistors Q1-Qm are turned on while the SR receiving the trigger is turned on, the state is held, the corresponding LED is shortcircuited for the extinguishing. While the SR not receiving the trigger signal is not turned on, the corresponding LED is lighted for the display.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a display drive circuit for a button telephone device.

[Conventional technology]

A button telephone (hereinafter referred to as ST) is equipped with a large number of indicator lights for each 8T in order to display the outside line status, busy 8T, status of various functions, etc. A display driving circuit is used for lighting or blinking the ST simultaneously or individually.

7tjL, when each indicator light is connected to the power supply individually,
Since the required power supply current increases when lighting simultaneously, multiple light emitting elements are connected in series and connected to a power supply, and switching elements are individually connected in parallel with each light emitting element, and these switching elements are turned on and off. proposed a method to control the energization of light-emitting elements and determine the display status, and the
Details are disclosed in Japanese Patent Publication No. 10205, Japanese Patent Publication No. 57-12347, etc.

[Problems that the invention attempts to solve]

However, in the case of the above-mentioned method, among the light-emitting elements connected in series, those that do not perform a light-emitting display are short-circuited to the switching element, which causes the energizing current to change depending on the display status. In order to stabilize the luminance by keeping this constant, it is necessary to switch one diagonal resistor in the main device, or to switch a constant voltage diode to compensate for the applied voltage, which complicates the circuit configuration. Along with this, recently,
There are 2 units in each 8T that independently control the display.
Problems arise such as difficulty in applying recent buttons to plugging devices.

[Elaborate means to solve problems]

In order to solve the above-mentioned problem, the present invention is constructed by the following means.

That is, in the above-mentioned display drive circuit, there are a plurality of light emitting elements each connected in series, and a plurality of rows of light emitting elements connected in parallel to the power supply, and a group of light emitting elements connected in parallel with each light emitting element. with a constant thyristor connected as
A coupling means for blocking direct current to the gate of each thyristor and giving a pulse-like firing signal to each thyristor, a constant current means inserted between the light emitting element group and the power source, and a coupling means for each row of the light emitting element group. A driving signal is sent to repeatedly turn on the switching element inserted in the light emitting element and the valley switching element sequentially and repeatedly at a constant period, and to each coupling means in the valley plane-connection order in each column of the light emitting element group. On the other hand, a control means is provided which sends out an ignition signal corresponding to the display status for each connection order in synchronization with a fixed period.

[For production]

As a result, dynamic lighting is achieved by sequentially and repeatedly turning on each switching element using a drive signal, and short-circuiting of the F-light emitting elements is performed when each thyristor is turned on by a firing signal, thereby determining the display situation. In addition, the constant current means maintains the current flowing at a constant level, and the luminance becomes stable regardless of the display situation.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to figures showing embodiments.

Figure 1 is a circuit diagram, Figure aK2 is a timing chart showing waveforms of various parts in Figure 1, and Figure 4 shows light emitting diodes (hereinafter referred to as light emitting diodes) as light emitting elements connected in series with the same polarity. LED) LDH-
LDnt to LDlm-LDnmlC constitute a plurality of rows of light emitting element groups Gl""Gm, which are connected in parallel to the power source V, and %LED-LDII-
Thyristors 5RII-8Rnm are each connected in parallel to the LDnm in a forward direction with respect to the power supply +V, and resistors R11 to Rnm are connected between these gates and candos, and , capacitors CLI to Cnm as coupling means are inserted in series, and are commonly connected to each open connection in each column of each light emitting element group G l "" am, and a control circuit C
Hereinafter, they are connected to the output ports R1 to Rn of CNT) 1, respectively.

Also, on the power supply return side of each light emitting element group Gl=Gm, transistors C and below, between the collector and emitter of TR) Qx-Qm, and emitter resistors Rel to Rem are inserted respectively, and each TR-Q A bias resistor Rbl"'=Rbm is connected between the collector and base of t~Qm, and a diode is connected in series with each of them with the same polarity and in the forward direction with respect to the forward bias of the base. Da11Dbt to DamsDbm are connected, and the bases of TR-Ql to Qm are respectively connected to the output capacitors C1 to cm of CNT1.

Note that the details of the circuit are shown only for the light emitting element group Gl,
Although the others are omitted, blocks 11 to 11 within the dotted line
rtm all have the same configuration and similar block 10
1 to 10 m all have the same configuration.

In addition, blocks 101 to 10In are TR・Ql"
``'Qm operates as a switching element, and
Based on the forward voltage of the diode Da1, Dbr-Dams Dbm, it operates as a constant current circuit by series feedback with the resistor Re1 ""RemK, and one circuit functions as a switching element and a constant current means. It is designed to exhibit both functions at the same time.

On the other hand, CNT using microprocessor and memory etc.
1, which is omitted in the figure, takes in the operation outputs of the 7 switches and the keyboard through the following path, transmits these conditions as operation data to the main control unit [(hereinafter referred to as KSU), and receives control data from the KSU. The lighting status of LEDllLDll-LDnm is controlled according to the internal world of the decoder 1, and each part in the ST is controlled.From the output ports R1 to Rn, each light emitting element! western cl
t-ignition signals (a) to (c) are sent to the capacitors C1l to cnm of -am according to the display status for each connection order, and the output ports C1 to Cn are sent by branching of clock pulses, etc. The generated multiphase drive signal is)
〜(f) is sent out at the same time.
Accordingly, TR-01 to TR-9m of blocks 101 to 10m are turned on sequentially and repeatedly, and the circuits of each group G1 to Gm are individually completed, and the instantaneous drive signals (d) to (0) are turned on. A constant current passes through each individual.

CNT1 is in a dimmed state depending on the display situation.
Corresponding to ED, firing signals (a) to (c) are transmitted at a constant period 'rl for each same connection order in each column of each group at""cm.
-These are connected to capacitor C in order to transmit in synchronization with T2.
11= CnmK L , the DC component is blocked, and a pulsed firing signal is applied to the gate of thyristor 8R1t-sRnm, regardless of the DC potential difference on the thyristor 5RII~sanm side with respect to the power return path. , the applied SR of this turns on and T R-
This state is maintained only while Qt-QITI is active, and the corresponding LED is short-circuited to dim the light, whereas ignition 1'Fji (a) to (C) are not given. SR is turned on, corresponding. LgD emits light to perform display.

In the example shown in Fig. 2, the LED-LDII dims and dims in period 'ri' due to the ignition signals (a) to (C).
LED-LD21. LDnl emits light with a period of 1゛2
Then, Lh:D-LD12 and LED2 are dimmed, LE
The D-LD 22 emits light, and the other LEDs are similarly controlled, and by repeating this process at high speed, the display situation is determined.

Even if the number of LgDs to be energized is different for each column of each group Gl to Gm, or the number of LgDs to be energized for each column is changed according to changes in display conditions, the constant current effect of blocks 101 to 10m Therefore, the applied current is always constant, and the luminance of light emission does not change.

FIG. 3 and FIG. 4 are circuit diagrams showing another embodiment, in which TR-Qt to Qm as switching elements and a constant current circuit (hereinafter referred to as CIC) 2 are provided respectively, and ClC2?
While commonly inserted to the power supply +V side, blocks 201 to 2
0 m (D T R-Q 1 to Q m f each group G1-
The blocks 201 to 20m are inserted into the power supply return path for each column of Gm, and the configuration of the blocks 201 to 20m is simplified compared to FIG. 1 by making ClC2 common.

In addition, in FIG. 4, it is assumed that no drive signal is sent from the CNT 1, and only pulses with a constant period T are sent from the output port co, and a counter (hereinafter referred to as CUT) 3 that performs counting in a ring is used to perform multiple counts. Generate phase pulses and use them as drive signals (d) to (f) to blocks 201 to 2
In this case, CNT1
The required number of output ports is reduced, and the larger the number of columns in groups G1-Gm, the more effective it becomes.

In contrast, by serially energizing and dynamically driving each LED-LDII-LDnm, the required power supply current for display does not increase, and the energizing current remains constant regardless of the number of LgDs emitting light, and the luminance is stabilized. , and the purpose can be fully achieved with a simple configuration.

Well, it becomes possible to independently configure all the circuits within the ST, making it suitable for use in the recent electronic 7tST.

However, as a light emitting element, a light bulb or the like may be used in addition to an LED, and a pulse transformer or the like may be used as a coupling means, and as a constant current means and a switching element, a light bulb or the like may be used, depending on the conditions. If you select one, you can use 8 each as a control means as well as workmanship! Various modifications are possible, such as the possibility of using a combination of logic circuits.

〔Effect of the invention〕

As is clear from the above description, if the present invention is implemented, it is possible to use a six-insertion system that can drive a large number of light emitting elements with stable luminance depending on the display situation, with a configuration that can be easily and locally provided. A remarkable effect can be obtained in the button telephone device.

[Brief explanation of drawings]

The figures show an embodiment of the present invention, with FIG. 1 being a circuit diagram, and FIG. 2 being a timing chart showing waveforms at the troughs in FIG.
FIG. 3 and FIG. 4 are circuit diagrams showing other embodiments. 1...CNT (control circuit), 2...CIC (constant current circuit), 3...CUT (kakunta), LDII
~LDnm...-LID (light emitting diode), 5R
II~Sml # ” ' ” Sairyuta, C11A+
Cml... Capacitor, Q1~Qln... Person-TR
() transistor), R+11-Rnl s Rb 1,
Rel~Item...Fist resistor, Dal s D
blm --m diode, (a) to (c)... ignition signal, (d) to (f)... drive signal, Tt-T2
・・・Constant cycle.

Claims (1)

[Claims] In a display drive circuit provided for each button telephone of a button telephone device, a plurality of rows of light emitting elements each consisting of a plurality of light emitting elements connected in series and connected in parallel to a power supply, and each of the light emitting elements and a thyristor connected in parallel to each of the thyristors, a coupling means for blocking a DC component to the gate of each of the thyristors and providing a pulsed ignition signal to each of the thyristors, and a coupling means inserted between the light emitting element group and the power source. a constant current means, a switching element inserted in each column of the light emitting element group, and a driving signal that sequentially and repeatedly turns on each switching element at a constant period; A button telephone characterized in that it is provided with a control means for sending out the firing signal corresponding to the display status in synchronization with the fixed period to each of the coupling means of each of the same connection order in the row for each connection order. Device display drive circuit.