Drive unit for planar display

• US 5,828,353 A
• Filed: 06/21/1996
• Issued: 10/27/1998
• Est. Priority Date: 05/31/1996
• Status: Expired due to Term

• Current Assignee: Hitachi Maxell Limited (Hitachi, Ltd.)
• Original Assignee: Fujitsu Limited
• Inventors: Kameyama, Shigeki, Yoshikawa, Kazuo, Kishi, Tomokatsu, Otsuka, Akira, Kariya, Kyoji, Hirose, Tadatsugu, Tomio, Shigetoshi, Awata, Yoshimasa
• Primary Examiner(s): Hjerpe, Richard A.
• Assistant Examiner(s): NGUYEN, TRACY
• Application Number:
  US08/667,515
• Time in Patent Office: 858 Days
• Field of Search: 345/55, 345/60, 345/76, 345/87
• US Class Current: 345/55
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/296 Driving circuits for producing the waveforms applied to the driving electrodes
• CPC Class Codes: G09G 3/2965 using inductors for energy recovery
• CPC Class Codes: G09G 3/298 using surface discharge panels

Abstract

A triple-electrode planar display capable of achieving further power saving has been disclosed. A drive unit is dedicated to a planar display having a display panel in which cells being arranged in the form of a matrix and having a memory function and discharge glow function are formed, in which one of each pair of electrodes on the same substrate which are responsible for discharge glow is a common electrode connected in common. The drive unit includes a common electrode drive circuit for applying an alternating voltage to the common electrode, and a power save circuit that when the common electrode is changed from a high potential to a low potential, restores and accumulates power applied to the common electrode, and that when the common electrode is changed from the high potential to the low potential, applies accumulated power to the common electrode. The power save circuit includes a restoration channel that includes a capacitive element and inductance element and that restores power, and an application channel that includes an inductance element and that applies accumulated power to the common electrode.

Claims

1. A drive unit for a planar display having a display panel, in which electrodes are placed between two substrates being arranged with a given space between them, in which a plurality of intersections formed by said electrodes form cells that constitute pixels and that are arranged in the form of a matrix, in which said cell is composed of an electrode formed on one of said two substrates and a pair of electrodes formed on the other substrate, and in which one of the pair of electrodes is a common electrode connected in common, said drive unit for a planar display comprising:

a common electrode drive circuit for changing said common electrode alternately into a high potential and low potential; and

a power save circuit that when said common electrode is changed from the high potential to the low potential, restores and accumulates power applied to said common electrode, and that when said common electrode is changed from the low potential to the high potential, applies accumulated power to said common electrode,

said power save circuit including;

a capacitive element for accumulating restored power;

a restoration channel that includes an inductance element, that is connected between said capacitive element and said common electrode, and that when said common electrode is changed from the high potential to the low potential, restores power applied to said common electrode; and

an application channel that includes an inductance element, that is connected in parallel with said restoration channel between said capacitive element and said common electrode, that when said common electrode is changed from the low potential to the high potential, applies accumulated power to said common electrode.

2. A drive unit for a planar display according to claim 1, said common electrode drive circuit includes:

a third switch that is connected on said restoration channel and interposed between said common electrode and said inductance element, that when power applied to said common electrode is restored, switches over said restoration channel to said low-potential terminal; and

a fourth switch that is connected on said application channel and interposed between said common electrode and said inductance element, and that when accumulated power is applied to said common electrode, switches over said application channel to said high-potential terminal.

3. A drive unit for a planar display according to claim 2, wherein said third switch and fourth switch are field-effect transistors.

4. A drive unit for a planar display according to claim 1, wherein:

on said restoration channel, a first diode for passing a current flowing from said common electrode toward said capacitive element and blocking a current flowing in an opposite direction, and a first switch connected in series with said first diode are interposed between said capacitive element and said inductance element; and

on said application channel, a second diode for passing a current flowing from said capacitive element toward said common electrode and blocking a current flowing in an opposite direction, and a second switch connected in series with said second diode are interposed between said capacitive element and said inductance element.

5. A drive unit for a planar display according to claim 4, wherein said first switch and said second switch are field-effect transistors.

6. A drive unit for a planar display according to claim 4, wherein said first switch and said second switch are insulated-gate bipolar transistors.

7. A drive unit for a planar display according to claim 1, wherein:

on said restoration channel, a first switch formed with an insulated-gate bipolar transistor is interposed between said capacitive element and said inductance element; and

on said application channel, a second switch formed with an insulated-gate bipolar transistor is interposed between said capacitive element and said inductance element.

8. A drive unit for a planar display according to claim 1, wherein said restoration channel and said application channel include reset diodes that are biased inversely and connected to said high-potential terminal and said low-potential terminal.

9. A drive unit for a planar display according to claim 8, wherein said restoration channel and said application channel partly share the same channel, and reset diodes realized by sharing said reset diodes are connected on said common channel.

10. A drive unit for a planar display according to claim 4, wherein:

on said restoration channel, a third diode connected in the same direction as said first diode is interposed between said common electrode and said inductance element; and

on said application channel, a fourth diode connected in the same direction as said second diode is interposed between said common electrode and said inductance element.

11. A drive unit for a planar display according to claim 1, wherein said inductance elements on said restoration channel and said application channel have different inductances.

12. A drive unit for a planar display according to claim 11, the inductance of said inductance element on said restoration channel is larger than that of said inductance element on said application channel.

13. A drive unit for a planar display according to claim 1, further comprising:

a plurality of scan drive circuits each of which drives a scan electrode that is one of said pair of electrodes, and includes a push-pull circuit;

a scan drive power circuit for alternately supplying a high voltage and low voltage to said plurality of scan drive circuits so that said scan electrodes can be changed alternately into a high potential and low potential; and

a power save circuit that when said scan electrodes are changed from the high potential to the low potential, restores and accumulates power applied to said scan electrodes, and that when said scan electrodes are changed from the high potential to the low potential, applies accumulated power to said scan electrodes, said power save circuit including;

a capacitive element for accumulating restored power;

a restoration channel that includes an inductance element, that is connected between said capacitive element and said scan electrodes, that when said scan electrodes are changed from the high potential to the low potential, restores power applied to said scan electrodes; and

a application channel that includes an inductance element, that is connected in parallel with said restoration channel between said capacitive element and said scan electrodes, and that when said scan electrodes are changed from the low potential to the high potential, applies accumulated power to said scan electrodes.

14. A drive unit for a planar display according to claim 13, wherein said scan drive circuits each include:

a first scan diode and first scan switch connected in parallel with each other between said restoration channel and an associated scan electrode; and

a second scan diode and second scan switch connected in parallel with each other between said application channel and said associated scan electrode.

15. A drive unit for a planar display according to claim 13, wherein said scan drive circuits each include:

a first scan diode connected between said restoration channel and an associated scan electrode;

a first scan switch connected between a second high-potential power terminal and said associated scan electrode;

a second scan diode connected between said application channel and said associated scan electrode; and

a second scan switch connected between a second low-potential power terminal and said associated scan electrode.