EP0277254A1 - Treiberschaltung für eine Elektrolumineszenzanzeigetafel - Google Patents

Treiberschaltung für eine Elektrolumineszenzanzeigetafel Download PDF

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Publication number
EP0277254A1
EP0277254A1 EP87101375A EP87101375A EP0277254A1 EP 0277254 A1 EP0277254 A1 EP 0277254A1 EP 87101375 A EP87101375 A EP 87101375A EP 87101375 A EP87101375 A EP 87101375A EP 0277254 A1 EP0277254 A1 EP 0277254A1
Authority
EP
European Patent Office
Prior art keywords
electroluminescent display
transistor
display panel
signal
drive circuit
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP87101375A
Other languages
English (en)
French (fr)
Inventor
Ronald F. Hormel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Old Carco LLC
Original Assignee
Chrysler Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Chrysler Corp filed Critical Chrysler Corp
Priority to EP87101375A priority Critical patent/EP0277254A1/de
Publication of EP0277254A1 publication Critical patent/EP0277254A1/de
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/02—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes by tracing or scanning a light beam on a screen
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00—Command of the display device
    • G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
    • G09G2310/0264—Details of driving circuits
    • G09G2310/0267—Details of drivers for scan electrodes, other than drivers for liquid crystal, plasma or OLED displays
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00—Command of the display device
    • G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
    • G09G2310/0264—Details of driving circuits
    • G09G2310/0275—Details of drivers for data electrodes, other than drivers for liquid crystal, plasma or OLED displays, not related to handling digital grey scale data or to communication of data to the pixels by means of a current
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/04—Maintaining the quality of display appearance
    • G09G2320/043—Preventing or counteracting the effects of ageing

Definitions

  • Electroluminescent display drive circuits are traditionally driven by transformers.
  • the transformer driven excitation of the electroluminescent display panel is inherently inefficient due to the capacitive load from the panel being reflected back into the transformer. This causes an efficiency drop due to a power factor loss created by the existence of the inductance of the transformer and the capacitance of the electroluminescent panel
  • electroluminescent display devices have traditionally been driven by high power devices, usually transformers. Although transformers may be necessary to generate high voltage, they are not necessary to drive the electroluminescent displays.
  • the electroluminescent display can be designed to operate at a frequency which will minimize the EMI effects.
  • the electroluminescent display panel is shown connected to a high voltage supply via two resistors R127 and R128.
  • the circuit is completed by way of two transistors Q105 and Q106, each connected to one of the resistors R127 and R128.
  • the collectors of each of these transistors is connected to the electroluminescent display panel, one to each side.
  • the electroluminescent display panel is depicted as a capacitor connected between the collectors of the two transistors.
  • each transistor, Q105 and Q106 are then connected to ground.
  • each transistor, Q105 and Q106 are connected to signal source.
  • This signal source can be an individual oscillating circuit or it can be an output from a microprocessor.
  • input A to Q105 is 180 degrees out of phase with input B to Q106.
  • Both inputs are to the base of the transistors and are both square wave signals.
  • the frequency of each input signal can be the same, just 180 degrees out of phase.
  • varying the frequency of the input signal to increase the dead zone can be used to dim the output of the display.
  • the subject invention will drive the electroluminescent display without the use of a traditional transformer.
  • the emphasis of traditional designs is toward power and the use of power transistors.
  • the subject invention utilizes transistors that operate at a much lower power and emit very little heat.
  • the design lends itself nicely to surface mounted devices and allows for a design which lets the designer select the resistor values for specific applications.
  • the resistor will correspond to the capacitance of the individual electroluminescent display panel used and the frequency that it is driven at.
  • EMI electro-magnetic interference
  • FIG. 2 another embodiment of the electroluminescent display drive circuitry is shown.
  • the particular design calls for the inputs A and B as in Fig. 1. Both inputs A and B are fed to the base of an NPN transistor, in this case input A fed to the base of NPN transistor Q109 and input B fed to the base of NPN transistor Q110. Both transistors Q109 and Q110 are connected to ground via the emitter.
  • each transistor is connected to one end of the electroluminescent display through resistors R135 and R136.
  • the electroluminescent display panel is depicted as a capacitance; this is done even though the display has inherent resistive losses.
  • the electroluminescent display is connected to the high voltage through two NPN transistors Q107 and Q108.
  • the emitters of the drive transistors Q107 and Q108 are tied to the high voltage and each collector is tied to the electroluminescent display panel through a time constant resistor R133 for Q107 and R134 for Q108.
  • Driving each transistor Q107 and Q108 is a connection between the base of each transistor and a resistor.
  • the resistor R131 being connected to the base of Q107; and resistor R132 being connected to the base of Q108.
  • Each resistor R131 and R132 is connected to the collector of the PNP transistors, Q108 and Q107, respectively, on the opposite side of the electroluminescent display.
  • Each emitter of transistors Q107 and Q108 are connected to the high voltage supply and the base of each transistor is further biased by resistor R129 and R130 being connected between the bases of each transistor and the high voltage supply.
  • FIG. 3 another embodiment shown in cut-away format illustrates the use of capacitor C112 hooked in parallel across the electroluminescent display, still depicted as a capacitor.
  • the cut-away view of Fig. 3 is otherwise the same as shown in Fig. 2.
  • Figs. 1, 2 and 3 All of the circuits shown in Figs. 1, 2 and 3 generate an A/C voltage across the electroluminescent display panel.
  • the peak-to-peak voltage across the electroluminescent display will be approximately twice the amount of the high voltage input. This amount might be less in Figs. 2 and 3 where the high voltage across the electroluminescent display will be slightly lower due to effect of an RC network.
  • the RC network is made up of the series combination of resistors R133 and R134 in series with the electroluminescent display panel shown in Fig. 2.
  • the RC network is Fig. 3 comprises the resistors R133 and R134 in series with the parallel combination of the electroluminescent display, along with the capacitor C112.
  • Electroluminescent displays are generally discussed in an article "D.C. Electroluminescence for Automobile Instruments" published by the Institute of Electrical Engineers on July 6-9, 1976, and written by B. Shepherd, R. N. Thomas and P. J. Smith. This article is hereby incorporated by reference.
  • FIG. 5 shown is a typical excitation circuit for an electroluminescent display. Notice that a transformer is utilized such that the secondary of the transformer is connected directly across electroluminescent display. A power factor other than 1 is created due to the interactin between the inductance of the transformer and the capacitance of the electroluminescent display. In addition, the bulk and weight of a transformer is eliminated.
  • FIG. 5 This is shown in Fig. 5 with a +V voltage supplied to the primary of transformer T.
  • the collector of transistor Q is connected to the primary of T; the emitter to ground; the base to an input signal I.
  • the electroluminescent display panel is depicted as a capacitor connected across the secondary of transformer Q.
  • circuits described in the subject invention run at high frequencies and create a voltage without a power to contend with.
  • Fig. 6 Examples of waveforms in prior art power supplies and in the subject invention are shown in Fig. 6. Examples of waveforms for the power supplies of the present invention are shown in Fig. 7. Both Fig. 6 and Fig. 7 graph voltage and current as a function of time. It can be seen that the power factor is not an issue in Fig. 7 as the current through the electroluminescent display is in phase with the voltage across it.
  • the subject circuit does not introduce a transformer to the direct excitation of the display and, therefore, reduces the size and weight of the design.
  • the subject invention eliminates or reduces the effect of the power factor as no inductance is present in the direct excitation of the electroluminescent display drive circuit; this is because current and voltage are in phase.
  • capacitor C112 is shown connected in parallel across the capacitive electroluminescent display panel.
  • the capacitor C112 is used to mask or reduce the effect of capacitance changes of the electroluminescent display panel.
  • the electroluminescent display panel Over a period of time, the electroluminescent display panel will change in its inherent capacitance due to age. In general, the electroluminescent display will decrease in capacitance over a period of time.
  • the capacitance of the electroluminescent display panel changes, the voltage across the panel increases due to the new and shorter RC time constant created by the changed capacitance; i.e., the RC charging time effects of resistors R133, R134 in series with the parallel combination of the electroluminescent display and capacitor C112.
  • This shorter RC time constant provides for a constant output from the electroluminescent display panel. Therefore, the panel can be used for a longer period of time since the affects of aging are masked by the high voltage input.
  • capacitor C112 is chosen to be approximately equal to the capacitance of the electroluminescent display when new, the above-­described increases in the voltage across the electroluminescent display will increase the peaks of the electroluminescent voltage waveform shown in Fig. 7.
  • capacitor C112 is chosen to be much larger than the electroluminescent capacitance, i.e., such that the capacitance of C112 is ten times or more greater than the capacitance of the electroluminescent display, then the effect of the capacitance change in the electroluminescent display will be felt as the voltage across the panel will remain relatively constant due to the lack of change in the RC time constant.
  • capacitor C112 is much smaller than the capacitance of the electroluminescent display, then the aging effects of the electroluminescent display on its inherent capacitance will be exaggerated.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Electroluminescent Light Sources (AREA)
EP87101375A 1987-02-02 1987-02-02 Treiberschaltung für eine Elektrolumineszenzanzeigetafel Withdrawn EP0277254A1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP87101375A EP0277254A1 (de) 1987-02-02 1987-02-02 Treiberschaltung für eine Elektrolumineszenzanzeigetafel

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP87101375A EP0277254A1 (de) 1987-02-02 1987-02-02 Treiberschaltung für eine Elektrolumineszenzanzeigetafel

Publications (1)

Publication Number Publication Date
EP0277254A1 true EP0277254A1 (de) 1988-08-10

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP87101375A Withdrawn EP0277254A1 (de) 1987-02-02 1987-02-02 Treiberschaltung für eine Elektrolumineszenzanzeigetafel

Country Status (1)

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EP (1) EP0277254A1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU648693B2 (en) * 1991-10-02 1994-04-28 Nec Corporation Driver circuit for long luminescence life display device and method of driving such device

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3343128A (en) * 1963-06-27 1967-09-19 Gen Dynamics Corp Electroluminescent panel driver circuits
FR2473207A1 (fr) * 1980-01-07 1981-07-10 Gte Laboratories Inc Dispositif de commande d'ecrans electroluminescents
GB2105085A (en) * 1981-08-31 1983-03-16 Sharp Kk Drive for thin-film electroluminescent display panel

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3343128A (en) * 1963-06-27 1967-09-19 Gen Dynamics Corp Electroluminescent panel driver circuits
FR2473207A1 (fr) * 1980-01-07 1981-07-10 Gte Laboratories Inc Dispositif de commande d'ecrans electroluminescents
GB2105085A (en) * 1981-08-31 1983-03-16 Sharp Kk Drive for thin-film electroluminescent display panel

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PROCEEDING OF THE SOCIETY FOR INFORMATION DISPLAY, vol. 18, no. 2, second quarter 1977, pages 125-133, K.O. FUGATE: "High display viewability provided by thin-film EL, black layer, and TFT drive" *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU648693B2 (en) * 1991-10-02 1994-04-28 Nec Corporation Driver circuit for long luminescence life display device and method of driving such device

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Inventor name: HORMEL, RONALD F.