JPH0543129U - Flat fluorescent lamp - Google Patents

Abstract

(57) [Abstract] [Purpose] The brightness of a flat fluorescent lamp having a wide operating temperature range used as a backlight of a liquid crystal display device is controlled to be constant. [Configuration] A flat fluorescent device in which a liquid crystal panel 6 is brought into contact with the front surface of the light emitting portion 5, a printed circuit board for a drive circuit is arranged on the rear surface of the light emitting portion 5, and a light receiving element PC1 is arranged on the side surface of the light emitting portion 5. In the lamp, a flat fluorescent lamp in which the drive circuit of the light emitting section 5 is controlled by the output signal of the light receiving element PC1 to adjust the brightness.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a flat fluorescent lamp, and more particularly to a flat fluorescent lamp which is a backlight unit of a liquid crystal display such as a liquid crystal viewfinder used in a video camcorder.

[0002]

[Prior Art]

 Conventionally, as a drive circuit for adjusting the brightness change of a flat fluorescent lamp, for example, there is JP-A-3-170910 (G02F 1/133). This is because the flat fluorescent lamp utilizes the characteristic that the brightness changes greatly when the temperature of the lamp changes, and the circuit diagram of the main part is shown in FIG. A synchronization signal from the outside is received at terminal a, resistor R1, and a second monostable multivibrator integrated circuit is provided via a delay circuit composed of the first monostable multivibrator integrated circuit IC1, resistor R2, and capacitor C2. The circuit IC2 operates to drive a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) Q1. The ON period of the MOSFET Q1 that influences the brightness of the flat fluorescent lamp FL1 is determined by the resistors R3 and R4, the impedance of the temperature sensitive element Th1 and the time constant of the capacitor C3. Here, the temperature sensitive element Th1 plays a role of adjusting the ON period of the MOSFET Q1 so as to keep the brightness of the flat fluorescent lamp FL1 constant. In addition, T1 is a transformer and C1 is a capacitor.

[0003]

[Problems to be solved by the device]

 As described above, when the brightness is kept constant by utilizing the temperature change of the flat fluorescent lamp, there are the following problems.

(1) There are variations in the relationship between the temperature and the brightness of the flat fluorescent lamp.

(2) There is variation in the state of heat conduction from the flat fluorescent lamp to the temperature sensitive element.

(3) Parts other than the flat fluorescent lamp generate heat, which affects the temperature-sensitive element.

(4) When used as a backlight for a liquid crystal display device such as a camcorder or a vehicle, the temperature range is severe because the operating temperature range of the device is wide, and it is difficult to adjust the brightness only with the temperature sensitive element. Could be.

Therefore, in order to perform the brightness adjustment with higher accuracy, the light from the fluorescent lamp is received, converted into an electric signal, and the brightness is controlled using this signal.

The present invention solves the above-mentioned problems by taking into account that the structure of the fluorescent lamp is a flat type, and controlling the brightness by using a light receiving element.

[0010]

[Means for Solving the Problems]

 The present invention relates to a flat fluorescent lamp used as a backlight of a liquid crystal display device, in which a liquid crystal panel is in contact with the front surface and a light emitting portion having a proximity conductor on the rear surface, and a rear surface side of the light emitting portion. A printed circuit board for a drive circuit, and a light receiving element arranged on a side surface of the light emitting section, and controlling the drive circuit of the light emitting section by the output signal of the light receiving element to adjust the brightness. It is a flat fluorescent lamp.

[0011]

[Action]

 Since the present invention is configured as described above, it is possible to directly detect the light quantity of the flat fluorescent lamp and maintain the brightness constant with high accuracy.

Further, since the temperature sensitive element is not used, there is no inconvenience that the control becomes impossible depending on the operating temperature.

[0013]

【Example】

 First, FIG. 4 shows an embodiment of a drive circuit for a flat fluorescent lamp. The same parts as those in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted.

In the present drive circuit example, a light receiving element PC1 such as a CdS cell or a phototransistor is used instead of the temperature sensitive element shown in FIG. The light receiving element PC1 detects the light amount of the flat fluorescent lamp FL1 and converts it into an electric signal. Therefore, it plays a role of adjusting the ON period of the MOSFET Q1 so as to keep the brightness of the flat fluorescent lamp constant.

Example 1 FIG. 1 is a cross-sectional view of a main part of Example 1 of a flat fluorescent lamp including the drive circuit as described above. Reference numeral 1 is a printed circuit board, 2 is a case, and 3 is an electronic component mounted on the printed circuit board. Further, the copper foil 4 is attached to the rear surface side of the light emitting portion 5 as a proximity conductor for facilitating the start of discharge of the light emitting portion 5 which is a fluorescent lamp unit. In the present embodiment, the rear surface of the light emitting portion 5 is shielded by the copper foil 4, and the liquid crystal panel 6 is also mounted on the front surface of the light emitting portion 5, so that the light receiving element PC1 is attached to the side surface.

Example 2 FIG. 2 shows a sectional view of the essential parts of Example 2. In this embodiment, a transparent electrode 7 is provided as a conductor near the light emitting section 5. Therefore, the printed circuit board 1 is provided with the opening 8, and the light receiving element PC1 is arranged in the opening 8 to receive light from the rear surface side of the light emitting portion.

Third Embodiment FIG. 3 shows a sectional view of the essential parts of the third embodiment. In this embodiment, the transparent electrode 7 is provided on the rear surface of the light emitting portion 5 having the recess 9 on the rear surface. The light receiving element PC1 is arranged on the printed circuit board 3 in the recess 9.

[0018]

[Effect of the device]

 According to the present invention, the brightness of the flat fluorescent lamp can be accurately adjusted and kept constant over a wide operating temperature range.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a first embodiment.

FIG. 2 is a sectional view of a main part of a second embodiment.

FIG. 3 is a cross-sectional view of a main part of the third embodiment.

FIG. 4 is a drive circuit diagram using a light receiving element.

FIG. 5 is a conventional drive circuit diagram using a temperature sensitive element.

[Explanation of symbols]

 1 Printed circuit board 4 Copper foil 5 Light emitting part 6 Liquid crystal panel 7 Transparent electrode 8 Opening 9 Recessed PC1 Light receiving element

Claims (4)

[Scope of utility model registration request] 1. A flat fluorescent lamp used as a backlight of a liquid crystal display device, wherein a liquid crystal panel 6 is in contact with a front surface and a light emitting portion 5 is provided with a proximity conductor 4 on a rear surface, and a rear surface side of the light emitting portion 5. And a light receiving element PC1 arranged on the side surface of the light emitting section 5, and the light emitting section 5 is driven by an output signal of the light receiving element PC1.
A flat fluorescent lamp characterized in that the brightness is adjusted by controlling the driving circuit of the. 2. A flat type fluorescent lamp used as a backlight of a liquid crystal display device, wherein a liquid crystal panel 6 is in contact with a front surface and a substantially transparent proximity conductor 7 is provided on a rear surface, and the light emitting section 5. The printed circuit board 1 for a drive circuit, which is arranged on the rear surface side of the printed circuit board 1 and has an opening 8, and a light receiving element PC1 arranged in the opening 8 of the printed board 1.
And, the light emitting unit 5 is provided according to the output signal of the light receiving element PC1.
A flat fluorescent lamp characterized in that the brightness is adjusted by controlling the driving circuit of the. 3. A flat fluorescent lamp used as a backlight of a liquid crystal display device, wherein a liquid crystal panel 6 is in contact with the front surface, a substantially transparent proximity conductor 7 is provided on the rear surface, and a recess 9 is provided on the rear surface. 5
A drive circuit printed circuit board 1 disposed on the rear surface side of the light emitting portion 5; and a light receiving element PC1 disposed in the recess 9 of the light emitting portion 5. Light emitting part 5
A flat fluorescent lamp characterized in that the brightness is adjusted by controlling the driving circuit of the. 4. The driving circuit of the flat fluorescent lamp is a pulse drive, and the pulse width of the driving pulse is changed by an output signal of the light receiving element PC1. Flat fluorescent lamp.