Apparatus for driving electroluminescence panel

• US 4,975,692 A
• Filed: 12/21/1988
• Issued: 12/04/1990
• Est. Priority Date: 12/26/1987
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tateyama, Jiro
• Primary Examiner(s): Brier, Jeffery A.
• Application Number:
  US07/287,010
• Time in Patent Office: 713 Days
• Field of Search: 340/781, 340/811, 340/813, 340/716, 315/169 B, 350/345
• US Class Current: 345/102
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/30 using electroluminescent panels
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336

Abstract

There is provided an apparatus for driving an electroluminescence (EL) panel which is arranged on the back side of the display surface of an LCD and used as a back light thereof. This apparatus comprises: a driver to drive the EL panel of the LCD; a signal generator to generate a plurality of signals having frequencies which are difficult from at least a frequency of a drive signal of the LCD and harmonics of the drive signal; a selector to select one of the signals generated by the generator; a supply circuit to supply an AC voltage having the frequency of the selected signal to the driver as the drive signal of the EL panel; a detector to detect whether the drive signal frequency to the EL panel lies within a frequency range where an interference is exerted on the display surface of the LCD or not; and an adjusting circuit to adjust so that the drive signal frequency is deviated out of the frequency range to exert an influence when the detector detects that the drive signal frequency lies within the frequency range. The driver consists of a self-excited or separately excited inverter. Thus, the luminence deterioration can be minimized and the generation of an interference fringe pattern with the LCD can be suppressed and the EL panel can be driven at a high reliability.

Claims

1. An apparatus for driving an electroluminescence panel which is used as a back light of a liquid crystal display, comprising:

drive means for driving the electroluminescence panel of the liquid crystal display;

signal generating means for generating a plurality of signals which are different in frequency from at least a drive signal of the liquid crystal display and harmonics thereof; and

selecting means for selecting one of the signals generated by said signal generating means,

wherein said drive means generates an AC voltage having the same frequency as the one signal selected by said selecting means and supplies the AC voltage to the electroluminescence panel as a drive signal thereof.

2. An apparatus according to claim 1, wherein said drive means is a self-excited inverter.

3. An apparatus according to claim 1, wherein said drive means is a separately excited inverter.

4. An apparatus according to claim 1, further comprising:

detecting means for detecting whether the drive signal frequency to the electroluminescence panel lies within a frequency range where an interference is exerted on a display surface of said liquid crystal display or not; and

adjusting means for adjusting so that the drive signal frequency is deviated out of said frequency range where an interference is exerted when said detecting means detects that the drive signal frequency lies within said frequency range.

5. An apparatus according to claim 1, wherein said selecting means is switching means which, can manually arbitrarily select one of the signals generated by said signal generating means.

6. An apparatus for driving an electroluminescence panel which is used as a back light of a liquid crystal display, comprising:

a drive power source to supply an AC drive signal to said electroluminescence panel;

detecting means for detecting whether a drive power source frequency to the electroluminescence panel lies within a frequency range where an interference is exerted on a display surface of the liquid crystal display or not; and

adjusting means for adjusting so that the drive power source frequency is deviated out of said frequency range where an interference is exerted when the detecting means detects that the drive power source frequency lies within the frequency range to exert an interference.

7. An apparatus according to claim 6, wherein said electroluminescence panel is driven by a self-excited DC/AC inverter, and said adjusting means adjusts the drive power source frequency by adjusting an input voltage to said self-excited DC/AC inverter.

8. An apparatus for driving an electroluminescence panel which is used as a back light of a liquid crystal display, comprising:

drive means for driving the electroluminescence panel of the liquid crystal display;

signal generating means for generating a plurality of signals which are different in frequency from at least a drive signal of the liquid crystal display and harmonics thereof;

luminance detecting means for detecting a luminance of the electroluminescence panel; and

selecting means for selecting one of the signals generated by said signal generating means in accordance with the luminance of the electroluminescence panel detected by said luminance detecting means,

wherein said drive means generates an AC voltage having the same frequency as the one signal selected by said selecting means and supplies the AC voltage to the electroluminescence panel as a drive signal thereof.

9. An apparatus according to claim 8, wherein said drive means is a self-excited inverter.

10. An apparatus according to claim 8, wherein said drive means is a separately excited inverter.

11. An apparatus according to claim 8, further comprising:

detecting means for detecting whether the drive signal frequency to the electroluminescence panel lies within a frequency range where an interference is exerted on a display surface of the liquid crystal display or not; and

adjusting means for adjusting the drive signal frequency so as to be deviated out of the frequency range to exert an interference when the detecting means detects that the drive signal frequency lies within said frequency range.

12. An apparatus according to claim 11, wherein said adjusting means is switching means which can manually finely adjust the drive signal frequency.