Circuit for driving a display

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

Such displays are as prevalent in small electrical appliances. they serve inter alia, to display the time or the temperature. In electronic cooker timers can be found on such displays additionally mark for the set Mode the stove or oven or for other features such as Alarm or radio reception. A digital display (eg for time) is here usually realized by means of 7-segment display.

The control of such display is performed in accordance with the nature of the Display (VFD, LED, LCD) differently. In a vacuum fluorescent display (VFD) is located behind the digits displayed a heated cathode. The individual, mutually corresponding segments of different (7-segment) digits are each connected in parallel with each other and form the anodes. Between the heated cathodes and anodes serving as segments are grid mounted, each extending over the area of ​​a digit. A segment of a certain point then lights up when both the This segment corresponding anode and the corresponding paragraph of this Grid lie on positive voltage. About a multiplex driving of the segments and the numbers (digits) is thus each individual segment each Paragraph controlled separately.

In a light-emitting diode display (LED), the individual segments of the figure each formed by individual light-emitting diodes. The individual, mutually corresponding Segments of the various digits are again parallel to each other interconnected and form the cathode, while the various digits (counts) form the anodes. Again, each segment by multiplex driving be addressed separately.

The difference in activation between VFD and LED display is firstly that the VFD to the terminals either positive voltage or no voltage is applied, while to the terminals of the LED display positive (for numbers) or negative (in segments) or no voltage is applied becomes. On the other hand, a VFD having a relatively high voltage of 16 to 30 V, but a low current of 0.1 operated to 2 mA, while an LED display only a small voltage of about 2 V, but a larger power of 2 to 20 mA required.

The control of a liquid crystal display (LCD) will be made fundamentally different. There are passive elements which the on Ambient light back-scattering surface are applied. Is at such a Element applying an electric voltage, the target of the contained in it Crystals, whereby the ambient light is absorbed at this point, why the element appears dark. To this effect a long time upright receive the item but must always be transhipped (about every 100 ms) will. The voltage is thereby applied to the element has a certain exceed a minimum value in order to effect alignment of the crystals.

An LCD is now constructed such that up to 3 segments parallel to one another are interconnected and thus form an electrode. The other electrode is three return electrodes (COM) is formed, which each one of the three together parallel-connected segments are allocated. In this way, also here again a multiplex driving possible. However, here are the individual Connectors for the display not only two voltage values ​​(positive or negative and zero), but also intermediate voltage values ​​(in the case described 1/3 and 2/3 of the voltage), so a targeted individual elements without reloading Influencing of the other elements is possible.

While the control of a VFD and an LED display is similar and at sufficiently generous dimensioning of the components with a drive circuit is bewerkstelligbar, is a principle for controlling an LCD other drive circuit required. On the other hand, however, it would be desirable to to have a single drive circuit, which flexibly for VFD, LED and LCD display is suitable. This would allow increased component standardization, a reduction of the expenses for logistics and warehousing as well result in a more flexible response to customer requests.

It is therefore an object of the present invention, starting identified by the to provide state of the art, a drive circuit, which both to drive VFD and LED as well as an LCD display is capable of.

This object is achieved by a circuit arrangement having the features of fulfilled claim 1. The claims 2 to 8 describe embodiments and developments of the invention.

The ability to control a VFD, LED and LCD display, is characterized achieved that at least two control blocks are provided, one of said Control blocks generates the necessary for a LCD display control signals and the other necessary for a VFD or LED or both ads generates control signals. The control signals of the control blocks are a common supplied driver module, the corresponding one of these control signals generates control signals for the VFD / LED indicator and the LCD display and forwards them to the appropriate display.

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

Further may be provided one or more memory elements, the are respectively assigned to the individual control blocks.

In an embodiment of the invention, the driver module has a plurality of driving elements on each of which each having a terminal of the VFD, LED or LCD display is connected and this connection a corresponding control signal supplies.

Furthermore, it is preferably provided that each driver element of every Control blocks is associated, so that it all for the control of the terminal the connected display necessary control signals are supplied.

Preferably, the control signals of the control blocks in the driver elements in such a way interconnected that the terminal of the connected display select the ideal Driving signal is supplied. This interconnection is a development of the Invention depending on the nature of the connected display.

Preferably, the control logic, the memory element at least one, and which are Control blocks performed digitally, the driver module executed during analog is.

In the following, with reference to the drawing, an embodiment of the invention are explained in detail. Show it:<dl tsize="8"><dt>figure 1</dt><dd>a block diagram of an inventive circuitry,</dd><dt>figure 2a</dt><dd>the display of a VFD or LED displays,</dd><dt>figure 2b</dt><dd>the timing of the drive signals for a VFD or LED display;</dd><dt>3a</dt><dd>the display of an LCD,</dd><dt>3b</dt><dd>the timing of the driving signals of an LCD and</dd><dt>figure 4</dt><dd>the basic circuit configuration of a driver element.</dd></dl>

A circuit arrangement 1 for driving a VFD, LED or LCD display 2 comprises a data receiver 3 which for the control of Display necessary data from a microprocessor 4 receives that data recipients to 3 simultaneously supplied with a time 4.1. The data receiver 3 outputs the received data to a control logic 5 further. checks the control logic 5 the received data and decodes it by received from the Data addresses, control words and commands extracted. The commands include actual display data. This display data to a data storage 6 be stored there. You will be saved unchanged, should be changed to the display. Then new display data in the be Data memory 6 is stored.

Further divides the control logic 5 a first control block 7 which the forming serving of required for an LCD display control signals, and a second Control block 8, which required the creation of a VFD or LED display Control signals used, with which driving mode is set (eg, VFD / LED 5x, 6x or 7x multiplex, LCD 3x multiplex, night setback or load shedding; see below). The selected mode is in the ROM block 9 stored, which communicates with the control logic 5 in operative connection.

Depending on whether an LCD or VFD / LED mode is set, the control block 7 or the control block 8 active. On the basis of it from the data memory 6 provided display data generated by the active control block 7 or 8 in the usual and in more detail below, the manner explained for the respective display 2 necessary control signals COM 1 to 3, and S 1 to 13 (LCD) or G 1 to 7 and 1 S to 9 (VFD / LED) (see also below).

Scroll through the control signals from the control block 8 nor the level shifter 10, in which in case of a VFD mode, the level of the control signals from conventional 3.3V be raised to the necessary for a VFD 30V. In the event of an LED mode, this level increase is not necessary. The information about the selected mode is replaced by the level shifter 10 as well as the control blocks 7 and 8 by the control logic. 5

The control signals of the control blocks 7 and 8, then pass to the driver block 11. This includes individual driver elements 11.1 to 11:16. This received the respective control signals of the control block 7 or 8 process, this give and it appropriately for display 2 to form these further. In this case, each of the Driver elements 11.1 to 11:16 each connected to a terminal of the display. 2

Alternatively, it is also possible that both control blocks 7 and 8 independently from set mode are active at all times. In this case, however, it is necessary that the driver elements 11.1 to 11:16 control signals depending on the selected mode (LCD or VFD / LED) received by only one of the control blocks. 7 and 8 The appropriate information to obtain the driver elements 11.1 to 11:16 directly from the control logic fifth

Furthermore, the control logic 5 controls nor 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 various components of the circuit arrangement 1 the sake of clarity is not shown; the power supply is However, in a conventional manner.

2a shows the light segments of a VFD and an LED display. With a designated segments are connected in parallel with each other and with the terminal S1 connected to the designated b elements to the terminal S2, etc. The terminals G1 to G7 are connected to the over a digit (possibly connected to standing next to icons) extending grid.

The triggering of such a display is now described with reference to Figure 2b be, in which the temporal course of the at terminals S1 to S9 and G1 is shown from G7 signals present in extracts. During the period t1 lies both at the terminal S1 and the terminal G1 a signal, ie, voltage at. The segment will light a that point, which at about the G1 connected grid belongs. In the period t2 that is to Terminal driven G2 corresponding grid, however, are here no segments driven, so that the belonging to G2 digit remains dark. The connected to the G3 However lattice associated symbols a and b are light up again, because of the Terminals S1 and S2 during the time period t3 respectively a signal is present.

In the present case seven grids are actuated so that the cycle time composed of the periods t1 to t7. It is therefore to a 7 fold multiplex. belonging When to G6 and G7 omission grid the cycle time could be reduced accordingly, it would be a 5-fold given multiplex.

The activation of an LED display basically proceeds as just described, except that a negative at the terminals S1 to S9 take a positive Voltage.

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

In figure 3b is the time course of and at the terminals COM 1, COM 2 COM 3 and applied to the terminal S12 signals shown, which is is a standard method of driving an LCD. The Andes Terminals S1 to S13 are signals present, compared to at COM 1 COM 2 and COM oppositely poled 3 applied signals so as to the upper display element S12 a voltage corresponding to COM 1 minus S12 rests on the central display element S12 corresponding COM 2 minus S12 and on the lower display element S12 corresponding COM 3 minus S12. The Voltage differences, which at the upper display element (corresponding COM 1 minus S12) occur, are too small for that to align the crystals could. There thus no display takes place. In the middle and lower Display element, however, there are major differences in voltage of 2 U, which is why here an alignment of the crystals and hence a display.

Figure 4 shows a block diagram of the driver elements 11.1 to 11:16 Interconnection respectively contained for generating the control signals for the display 2. VFD or LED mode are the control block 8, the switch 18 and 19 driven by digital signals W4 and W0. Target at the output A, that is on corresponding terminal of the display 2, a signal, ie voltage applied so is closed by a digital signal W4 of the switch 18, while the Switch 19 as well as the switches 20, 21 and 22 remain open. Using a VFD is now present at the output A voltage U ' 30 V, using a LED display only about 2 V. target at the output no signal, so no voltage, the switch 18 is opened and the Switch 19 is closed by a digital signal W0. Thus, according to the above ( dimensioned) switches 18 and 19 a for a VFD and LED element appropriate signal can be generated. The information whether a voltage U ' place of 30V or purely 2V use (according to the control a VFD or LED display), the respective driver element 11.1 to 11:16 are obtained directly from the level shifter 10 or by the control logic 5 (See Figure 1).

For controlling an LCD element, the switches 19, 20, 21 and 22 are used. By closing the respective switch means of the associated, the control block 7 coming digital signal W0, W1, W2 or W3, the A voltage at the output to 0, 1/3 U, 2/3 U or U will be adjusted, where U typically 3.3 volts.

In this manner, by activating the appropriate switch of 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 driven.

The control logic 5, the storage member 6 and the control blocks 7 and 8 of Circuitry 1 are digitally carried out while the driver block 11 is carried out in analogy with the driver elements 11.1 to 11:16. The whole A 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.