EP1237140B1 - Circuit for driving a display - Google Patents

Description

The invention relates to a circuit arrangement for controlling a VFD, LED or LCD display.

Such displays are e.g. Widely used in small electrical appliances. They serve et al to display the time or the temperature. For electronic cooker timers You will also find signs for the set on such displays Operating mode of the stove or oven or for other functions such as Alarm or radio reception. A numeric display (for example, for the time) will be here usually realized by means of 7-segment display.

The control of such displays is carried out according to the nature of the respective Display (VFD, LED, LCD) different. In a vacuum fluorescence display (VFD) is behind the numbers to be displayed, a heated cathode. The individual, corresponding segments of the different (7-segment) digits are each connected in parallel with each other and form the anodes. Between the heated cathodes and the segments serving as anodes grids are mounted, each extending over the area of a digit. A segment of a given digit lights up when both the corresponding to this segment anode as well as this paragraph corresponding Grid are on positive voltage. Via a multiplex control of the segments and the digits is thus every single segment of each one Number separately controllable.

For a light-emitting diode (LED) display, the individual segments are the digits each formed by individual LEDs. The individual, corresponding to each other Segments of different numbers are in turn parallel to each other interconnect and form the cathode, while the different digits (digits) form the anodes. Again, each segment by means of multiplex control be addressed separately.

The difference in the control between VFD and LED display exists Firstly, that the VFD has either positive voltage at the terminals or no voltage is applied while to the terminals of the LED indicator positive (for numbers) or negative (for segments) or no voltage applied becomes. On the other hand, a VFD with a relatively high voltage of 16 up to 30V, but low power operated from 0.1 to 2 mA, while an LED indicator only a small voltage of about 2 V, but a larger current of 2 needed up to 20 mA.

The control of a liquid crystal display (LCD), however, takes place fundamentally different. These are passive elements, which are on a the Ambient light backscattering substrate are applied. Is attached to such Element applied an electrical voltage, the contained in it Crystals, which absorbs the ambient light at this point, why the element appears dark. To maintain this effect for a long time However, the element must be reloaded again and again (approximately every 100 ms) become. The voltage applied to the element must have a certain value Exceed minimum value to effect alignment of the crystals.

An LCD is now constructed so that up to 3 segments parallel to each other are interconnected and so form the one electrode. The other electrode is going through formed three back electrodes (COM), each one of the three with each other associated with parallel interconnected segments. This way is also here again a multiplex control possible. However, here are the individual Connections of the display not only two voltage values (positive or negative and zero), but also voltage intermediate values (in the case described 1/3 and 2/3 of the voltage), so that a targeted reloading of individual elements without Influencing the other elements is possible.

While the control of a VFD and an LED display is similar and with sufficient generous dimensioning of the components with a Drive circuit is accomplished, is for the activation of a LCD a fundamentally different drive circuit necessary. on the other hand however, it would be desirable to have a single drive circuit which is suitable for VFD, LED and LCD displays. This would be an increased component standardization, a reduction of the Expenses for logistics and warehousing as well as a more flexible reaction on customer requests result.

A circuit for driving various types of displays is from the Datasheet of NEC "S11543EJ2V0DS00, FIP / LCD Static Display Driver μPD6320 / μPD6321, October 1996, XP-002198520 " There disclosed circuit has a combined VFD / LCD driver and a separate LED driver, with a part of the outputs of the VFD / LCD driver connected to part of the outputs of the LED Driver are. The information which type of display is controlled by the circuit is to be due to the circuit in the form of a hardware coding at. With the circuit, a LED display can be multiplexed and a VFD or LCD display statically driven become. The disadvantages of the circuit are the limited drive capacity and the necessary hardware coding.

In the data sheet "FEDL9002-03, LCD Driver with Keyscan Function MSM9006-01, -02, September 2000, XP-002198521 "of the company OKI is a LCD drivers are described on which in addition to a LCD display yet a single light emitting diode can be connected.

The NEC Datasheet "IC-3307, 1 / 4- to 1/11-Duty FIP (VFD) Controller / Driver μPD16312, March 1997, XP-002198522 "describes a circuit with a VFD driver and a separate LED driver, in which a VFD display and an LED display to separate outputs can be connected. So this is one Compilation of two display driver circuits.

It is an object of the present invention, starting from the indicated Prior art to provide a drive circuit, which to control both a VFD and LED as well as an LCD display in capable.

This object is achieved by a circuit arrangement having the features of claim 1. Describe the claims 2 to 8 Embodiments and developments of the invention.

The ability to control a VFD, LED and LCD display becomes thereby achieved that at least two control blocks are provided, wherein one of the control blocks necessary for an LCD display control signals generated and the other for a VFD or LED or both Displays necessary control signals generated. The control signals of Control blocks are fed to a common driver block, the corresponding control signals for the VFD / LED display from these control signals and for the LCD display and to the corresponding one Display passes on.

The VFD, LED and LCD displays are controlled by means of a multiplex drive. In a ROM block, with a control logic is in operative connection, is stored, which control mode (e.g., VFD 5x Multiplex, LED 7x Multiplex, LCD 3x Multiplex) is.

In development of the invention, three control blocks are provided by each one for the LCD, the VFD and the LED display the necessary Provides control signals.

Furthermore, one or more memory elements may be provided be assigned to each of the individual control blocks.

In an embodiment of the invention, the driver module has a plurality of driver elements each of which is connected to one of the VFD, LED or VFD ports LCD display is connected to this terminal and a corresponding drive signal supplies.

Furthermore, it is preferably provided that each driver element with each of the Control blocks is connected, giving it all for driving the connection the necessary control signals are supplied to the connected display.

The control signals of the control blocks in the driver elements are preferably such interconnects the connection of the connected display with the appropriate one Drive signal is supplied. This interconnection takes place in the development of Invention depending on the type of connected display.

Preferably, the control logic, the at least one memory element and the Control blocks executed digitally, while the driver block executed analog is.

Figur 1

ein Blockschaltbild einer erfindungsgemäßen Schaltungsanordnung,

Figur 2a

die Anzeige eines VFD- bzw. LED-Displays,

Figur 2b

den zeitlichen Verlauf der Ansteuersignale für ein VFD- bzw. LED- Display,

Figur 3a

die Anzeige eines LCD,

Figur 3b

den zeitlichen Verlauf der Ansteuersignale eines LCD und

Figur 4

den prinzipiellen Schaltungsaufbau eines Treiberelementes.

In the following, an embodiment of the invention will be explained in more detail with reference to the drawing. Show it:

FIG. 1

a block diagram of a circuit arrangement according to the invention,

FIG. 2a

the display of a VFD or LED display,

FIG. 2b

the time profile of the drive signals for a VFD or LED display,

FIG. 3a

the display of an LCD,

FIG. 3b

the timing of the drive signals of an LCD and

FIG. 4

the basic circuit structure of a driver element.

A circuit arrangement 1 for driving a VFD, LED or LCD display 2 has a data receiver 3, which for the control of the Display receives necessary data from a microprocessor 4, which the data receiver 3 simultaneously supplied with a time 4.1. The data receiver 3 forwards the received data to a control logic 5. The control logic 5 checked the received data and decodes it by being received from the Data addresses, control words and commands extracted. The commands contain the actual display data. This display data is sent to a data memory 6 passed on and saved there. They remain stored unchanged as long as until the display is to be changed. Then new display data will appear in the Data memory 6 stored.

Furthermore, the control logic 5 a first control block 7, which of the generation of control signals necessary for an LCD display, and a second one Control block 8, which the generation of necessary for a VFD or LED display Control signals are used to indicate which drive mode is set (e.g. VFD / LED 5x, 6x or 7x multiplex, LCD 3x multiplex, night reduction or load shedding; see below). The selected mode is in the ROM block 9, which is in operative connection with the control logic 5.

Depending on whether an LCD or VFD / LED mode is set, the control block becomes 7 or the control block 8 active. Based on him from the data memory. 6 provided display data generates the active control block 7 or 8 in usual and further explained in more detail below way for the respective display. 2 necessary control signals COM 1 to 3 and S 1 to 13 (LCD) or G 1 to 7 and S 1 to 9 (VFD / LED) (see below).

The control signals from the control block 8 still go through the level shifter 10, in which, in the presence of a VFD mode, the levels of the control signals of usual 3.3 V to be necessary for a VFD 30 V raised. In the event of a LED mode, this level increase is not necessary. The information about the set mode receives the level shifter 10 as well as the control blocks 7 and 8 from the control logic 5.

The control signals of the control blocks 7 and 8 then go to the driver block 11. This has individual driver elements 11.1 to 11.16. These received the respective control signals of the control block 7 or 8, process them and give in this for the display 2 suitable form to this. Every one of them is Driver elements 11.1 to 11.16 connected to one terminal of the display 2.

Alternatively, it is also possible that both control blocks 7 and 8 regardless of set mode are active at any time. In this case, however, it is necessary that the driver elements 11.1 to 11.16 control signals depending on the set mode (LCD or VFD / LED) received only from one of the control blocks 7 and 8. The corresponding information receive the driver elements 11.1 to 11.16 directly from the control logic 5.

Furthermore, the control logic 5 still controls a reset circuit 12 for the microprocessor 4, a buzzer circuit 13 for a buzzer 14 and a driver 15 for driving relays 16 and 17. In addition, it should be noted that a power supply for the individual components of the circuit arrangement 1 for the sake of clarity is not drawn; the power supply takes place but in the usual way.

FIG. 2a shows the luminous segments of a VFD or an LED display. With a designated segments are connected in parallel with each other and with the terminal S1 connected, the elements denoted by b with the terminal S2, etc. The terminals G1 to G7 are each connected to the one via a digit (possibly with adjacent symbols).

The control of such a display will now be explained with reference to Figure 2b in which the timing of the at the terminals S1 to S9 and G1 to G7 applied signals is shown in excerpts. During the period t1 is at both the terminal S1 and the terminal G1 a signal, i. tension at. Thus, the segment a of the digit illuminates that to the Connection G1 connected grille heard. In the period t2 that becomes the Connection G2 associated grid driven, but here are no segments controlled, so that the number belonging to G2 remains dark. The connected to G3 Grid belonging symbols a and b light up again, however, because of the Terminals S1 and S2 during the period t3 in each case a signal is applied.

In the present case, seven grids are driven, so that the cycle time composed of the periods t1 to t7. It is thus hereby a 7x multiplex. When the G6 and G7 lattices disappear would reduce the cycle time accordingly, it would be a 5 times Given multiplex.

The control for an LED display is basically as straight described, except that at the terminals S1 to S9 instead of a positive one negative Voltage applied.

In Figure 3a, the display elements of an LCD are shown. Up to three of each Display elements are interconnected in parallel and to the terminals S1 connected to S13. The back electrodes of the three elements are respectively connected to the Connection COM 1, COM 2 or COM 3 connected.

In Figure 3b, the timing of the connections COM 1, COM 2 and COM 3 and signals applied to the terminal S12 signals, where it is a standard method for controlling an LCD. The Andes Terminals S1 to S13 are opposite to those at COM 1, COM 2 and COM 3 applied opposite polarity, so that e.g. at the upper display element S12 a voltage corresponding to COM 1 minus S12 is present at the middle display element S12 corresponding to COM 2 minus S12 and at the lower display element S12 corresponding to COM 3 minus S12. The Voltage differences, which at the upper display element (corresponding to COM 1 minus S12) are too small for the crystals to align could. There is thus no display. At the middle and lower Display element, however, occur large voltage differences of 2 U, which is why here an alignment of the crystals and thus a display is made.

FIG. 4 now shows a basic circuit diagram in the driver elements 11. 1 to 11 respectively contained interconnection for generating the drive signals for the display 2. In the VFD or LED mode from the control block 8, the switches 18 and 19 driven by digital signals W4 and W0. If desired at output A, i. at the corresponding terminal of the display 2, a signal, i. Voltage applied, so is closed via a digital signal W4, the switch 18, while the Switch 19 as well as the switches 20, 21 and 22 remain open. Using a VFD display is now the voltage U present at the output A ' 30 V, when using an LED display only about 2 V. Set at the output no signal, so no voltage applied, the switch 18 is opened and the Switch 19 closed by a digital signal W0. Thus, over the (corresponding dimensioned) switches 18 and 19 for a VFD or LED element suitable signal can be generated. The information as to whether a voltage U ' of 30V or only 2V use (according to the control a VFD or an LED display), the respective driver element 11.1 to 11.16 received either from the level shifter 10 or the control logic 5 directly (see Figure 1).

For controlling an LCD element, the switches 19, 20, 21 and 22 are used. By closing the corresponding switch by means of the associated, from the control block 7 coming digital signal W0, W1, W2 or W3, the Voltage at the output A to 0, 1/3 U, 2/3 U or U are regulated, where U typically 3.3V.

In this way, by controlling the appropriate switch by the the control blocks 7 and 8 coming digital signals W0, W1, W2, W3 and W4 on one and the same output or terminal A both an LCD and a VFD and LED element are controlled.

The control logic 5, the memory element 6 and the control blocks 7 and 8 of the Circuit 1 are executed digitally while the driver module 11 is carried out analogously with the driver elements 11.1 to 11.16. The whole Circuit arrangement 1 is designed as an integrated circuit (IC). In these IC are also the reset circuit 12, the buzzer circuit 13 and the relay driver 15 integrated.

Claims (9)

1. Switching device (1) for activating a VFD, LED or LCD display (2)
   with a data receiver (3) which receives the data required for activating the display (2) from a central unit (4),
   with a control logic (5) which checks the data received from the data receiver (3) and extracts display data from them,
   with at least one memory element (6) in which the current display data are stored,
   with at least two control blocks (7, 8) which have a data connection to at least one memory element (6), for generating the control signals required for the display, depending on the display data stored in least one memory element (6) and on the VFD, LED or LCD activation mode selected,
   wherein the first control block (7) is designed so that it supplies the control signals required for an LCD display,
   and the second control block (8) is designed so that it supplies the control signals required for a VDF or an LED display or for both a VFD and an LED display,
   and also with a common drive component (11) to which the control signals are supplied from the control blocks (7) and (8), which component generates from these control signals suitable activation signals for the VFD, LED and/or LCD displays, and transmits them to the corresponding display (2),
   characterised in that the VFD, LED and LCD displays are activated by means of a multiplex activation system,
   and in that the switching device exhibits a ROM block (9) which is actively connected to the control logic (5) and in which is stored information on which multiplex activation mode has been selected and whether a VFD, an LED or an LCD activation system has been selected.
2. Switching device according to Claim 1,
   wherein three control blocks are provided, and wherein the first supplies the control signals required for the LCD display, the second the signals required for the VFD display and the third the signals required for the LED display.
3. Switching device according to Claim 1 or 2,
   wherein several memory elements (6) are provided which are assigned to the LCD and the VFD/LED control block (7, 8) and to the LCD, VFD and LED control block respectively.
4. Switching device according to one of Claims 1 to 3,
   wherein the drive component (11) exhibits several drive elements (11.1-11.16) and wherein each drive element (11.1-11.16) is connected to a connection of the VFD, LED or LCD display (2) and the corresponding activating signal is supplied to this connection.
5. Switching device according to Claim 4,
   wherein each drive element (11.1-11.16) is connected to each of the control blocks (7, 8) so that it receives the control signals required for activating one of the connections of the VFD, LED or LCD displays (2).
6. Switching device according to Claim 5, wherein
   the control signals from the control blocks (7, 8) are connected in the drive elements (11.1-11.16) so that the appropriate activating signal is supplied to the connection of the VFD, LED or LCD display (2).
7. Switching device according to Claim 6, wherein
   the control signals are connected in the drive elements (11.1-11.16) according to the nature of the connected display (2).
8. Switching device according to one of the preceding claims, wherein the control logic (5), at least one of the memory elements (6) and the control blocks (7, 8) are designed so that they operate digitally, whilst the drive component (11) is designed for analogue operation.
9. Switching device according to one of the preceding claims, wherein the entire switching device (1), with data receiver (3), control logic (5), memory element (6), control blocks (7, 8), drive component (11) and ROM block (9), is designed as an integrated circuit (IC).

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