Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2001-05-04
2003-06-24
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C345S102000
Reexamination Certificate
active
06583579
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a backlight for illuminating a display section including a liquid crystal display element and an operation section including button switches. More particularly, the invention relates to a backlight device and a backlighting element, which are constructed with an EL panel, LEDs, lamps and others.
There is known a device equipped with a liquid crystal display panel (referred to as an LCD panel) having a liquid crystal display element (LCD) and an operation panel including panel switches associated with operation buttons. Recently, this type of device has been equipped with a backlighting function to illuminate the reverse side of the display section and the operation section in order to render display characters and characters on switches to be legible even in a dark place. In this type of communication device, those characters must be legible in every use condition. Therefore, the backlighting function is indispensable in particular for mobile communication devices, such as portable phones and pagers.
An electrical arrangement of a device with a conventional backlight device is shown in FIG.
12
. As shown, the device is made up of a display unit
101
, a backlighting element
102
, a backlight driver
103
, a control unit
104
, a switch
105
, and a power supply
106
. The display unit
101
includes a LCD for displaying characters, for example. The backlighting element
102
includes an EL (electroluminescence) panel for illuminating the back of the display unit
101
. The backlight driver
103
drives and controls the backlighting element
102
. The control unit
104
controls the display unit
101
and the backlight driver
103
. The switch
105
is provided for backlighting. The power supply
106
is used for supplying electric power to the whole device.
FIGS. 13 and 14
cooperate to show a structural arrangement including a display unit and a backlighting element.
FIG. 13
shows a side view of a structure including the display unit and the backlighting element.
FIG. 14
shows a plan view of the backlighting element. An LCD panel
101
a
forms a display unit
101
. An EL panel
102
a
forms a backlighting element
102
. The EL panel
102
a
is disposed on the rear side of the LCD panel
101
a
. Light emitted from the EL panel
102
a
passes through the LCD panel
101
a
, and is irradiated from the front broad side thereof. Thus, a structure in which a light is irradiated from the back of the LCD panel
101
a
is employed. A light emitting section
107
is formed in the EL panel
102
a
, while covering the entire viewing area of the LCD panel
101
a.
Characters and/or images are displayed in the display unit
101
under control by the control unit
104
. In this case, the backlighting element
102
is lit in order to secure a satisfactory viewing in a dark place. To light the backlighting element
102
, the switch
105
is operated. In response to this, the control unit
104
sends an operation instruction to the backlight driver
103
. In turn the backlight driver
103
applies a drive signal having an AC waveform (e.g., a sinusoidal waveform, a triangle waveform, or a rectangular waveform) at the amplitude of, for example, 50 to 100 Vpp, to the backlighting element
102
. Then, light emitting elements within the backlighting element
102
is excited to emit light and illuminate the display unit
101
. Electric power consumed by the backlight driver
103
and the backlighting element
102
, when those operate, depends on the area of and luminance brightness on the light emitting section of the backlighting element
102
. The power consumed is generally 10 to 50 mA for the size of approximately 60 mm×30 mm. After the backlighting element is lit, the backlighting element
102
automatically lights off under control by the control unit
104
when the following condition is satisfied; viz., the user intentionally lights off the backlighting element or the device is not operated for a predetermined time (several tens seconds to several minutes).
In the conventional backlight device thus constructed, power consumption is large when the backlighting element is lit. When it is applied to the mobile communication devices designed placing emphasis on the portability, such as pagers, portable telephones, PHS terminals, and PDA terminals, reduction of the communication device entails a restriction on the power capacity of the power supply (e.g., a battery) Therefore, the lighting of the backlighting element will greatly influence the battery lifetime. In case where a battery used for such a communication device as an air zinc battery is small in capacity, when the backlighting element is lit to consume large power, the battery voltage will drop. A conventional measure, generally taken for this, is to reduce the power consumption by reducing the luminance brightness of the backlighting element.
Where the EL panel is used, a signal of an AC waveform, e.g., a triangle waveform, needs to be generated for a drive signal during the lighting of the backlighting element, and its power is large. Because of this, the drive signal will cause power source voltage to vary and produce unwanted spurious radiations. Those voltage variation spurious radiations will cause noise and deteriorate radio and acoustic performances of the backlight device. For this reason, additional components are required for noise shielding. Device complication and production cost increase result.
The enhancement of the device function increases the areas that are required for the display section and the operation section of the backlight device, and increases the backlight emitting area. With this, more electric power is consumed for securing a required backlight brightness. Therefore, the power consumption problem is more serious.
SUMMARY OF THE INVENTION
Accordingly, a first object of the present invention is to provide a backlight device and a backlighting element, which effectively suppress power consumption when the backlighting element is lit while keeping luminance brightness at a required level. A second object of the present invention is to provide a backlight device and a backlighting element, which makes the device free from the noise generated when the backlighting element is lit.
Aspect 1 defines a backlight device comprising: a backlighting element for illuminating the back of visually presenting means of a device; and drive control means for intermittently driving the backlighting element at appropriate timings when the backlighting element is lit.
In the backlight device of aspect 1, the drive control means lights on the backlighting element at appropriate timings, for example, at such time intervals as to make the user visually insensitive to flickering of the backlighting element or to make the user visually sensitive to its flicker but to allow the user to decipher characters, for example, on the visually presenting means. The result is reduction of the drive time of the whole device during the backlighting, and reduction of device power consumption.
Aspect 2 defines a backlight device defined comprising: a backlighting element for illuminating the back of visually presenting means of a device; and drive control means for temporarily stopping the driving of the backlighting element when a device portion being adversely affected by noise generated by operation of the backlighting element is operated, in synchronism with operation timings of the device portion.
In the backlight device of aspect 2, the drive control means temporarily stops the driving of the backlighting element when the device portion being adversely affected by noise generated by operation of the backlighting element, for example, the radio processing unit of a communication device, is operated, in synchronism with the device portion. With this, there is no chance that the noise by the backlighting adversely affects the device.
Aspect 3 defines a backlighting element with an EL panel for illuminating the back of visually presenting means of a device, the backlighting
Matsushita Electric - Industrial Co., Ltd.
Pearne & Gordon LLP
Vu David
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