JPH01124897A - Driving of fluorescent indicator tube - Google Patents

Abstract

PURPOSE: To prolong the service life by detecting the change of the anode current and controlling the cathode voltage so that the anode current may be kept at a prescribed vale. CONSTITUTION: A driving voltage is given to anodes P1 to Pn of individual display segments of a fluorescent display tube 1 from a driver 4, to which a data input signal is inputted through a decoder 5, to make them emit light. An anode current detection part 2 always monitors the change of anode currents of segments and detects their variation to control a cathode power source 6 by an anode current control part 3 so that anode currents are kept constant. Thus, the degradation in emission capability of an oxide cathode, which is caused by sulfur generated by a decomposition phenomenon of phosphors during the operation of the fluorescent display tube, is automatically restored to extend the life.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a driving direction of a fluorescent display tube.

[Conventional technology]

A fluorescent display tube is a type of display tube that uses a low-speed electron beam to make a phosphor emit light.The driving voltage is 30V or less, and it can display multiple colors using various low-speed electron beam-excited light-emitting phosphors. It has unique characteristics and is used in a wide range of fields.

A conventional method for driving a fluorescent display tube is performed using a driving circuit having a configuration as shown in FIG. That is, a predetermined cathode voltage Et is applied to both ends of the cathode F of the fluorescent display tube 1, a voltage E is applied between the cathode F and the grid electrode 0, and data and input are applied to the anodes P1 to P of each display segment. A driving voltage is applied from a driver 4 according to the result of decoding the signal by a decoder 5, and a light emitting display is performed.

[Current problems that the invention attempts to solve]

The above-mentioned conventional method for driving a fluorescent display tube uses Zns, especially when high brightness is required and the anode current density is large, such as when used in automobile dash boards.
(Zn,Cd)S-based phosphors decompose, and the generated sulfur (S) rapidly reduces the emission ability of the oxide cathode, resulting in a very short service life of the fluorescent display tube. There is a problem.

[Means for solving problems]

The method for driving a fluorescent display tube of the present invention detects a change in the anode current of the fluorescent display tube, and in response to the detection result, maintains the anode current at a predetermined level within a range having a predetermined upper limit value. The method further includes a control process for automatically varying the cathode voltage of the fluorescent display tube so as to achieve the desired effect.

〔Example〕

Next, the present invention will be explained with reference to examples.

FIG. 1 is a block diagram showing one embodiment of the present invention. In the circuit shown in the figure, a variable voltage cathode power supply 6 is connected in place of the constant voltage cathode voltage Er in the drive circuit of Fig. 2, and the voltage of the cathode power supply 6 is variably controlled in accordance with changes in the anode current. The anode current detection section 2 has a configuration in which an anode current detection section 2 and an anode current control section 3 are additionally connected. If this occurs, the amount of change is detected and the information is transmitted to the anode current controller 3, and the voltage of the cathode power source 6 is varied so as to bring the anode current closer to the initial state.

By adding the anode current detection section 2 and the anode current control section 3 to the conventional drive circuit to variably control the cathode voltage, the anode current can be kept constant, greatly improving the service life of the fluorescent display tube. It is possible. The upper limit of the variable voltage range of the cathode power source 6 is preset to a value that does not overheat the cathode F.

〔Effect of the invention〕

As explained above, in the present invention, it is possible to automatically recover from the reduction in the emission ability of the oxide cathode caused by sulfur generated by the decomposition phenomenon of the phosphor during the operation of the fluorescent display tube. This has the effect of greatly improving the service life of the fluorescent display tube.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional method for driving a fluorescent display tube. 1... Fluorescent display tube, 2... Anode current detection section, 3...
・Anode current control section, 4...driver, 5...decoder, 6...cathode power supply, P1-P0...anode, G.
... Grid electrode, F... cathode. Agent Patent Attorney Susumu Uchihara T51 Figure Day?・Sufu Wakiki Tsuki 22]

Claims (1)

[Claims] A change in the anode current of the fluorescent display tube is detected, and in response to the detection result, the cathode voltage of the fluorescent display tube is automatically adjusted to maintain the anode current at a predetermined value within a range having a predetermined upper limit value. A method for driving a fluorescent display tube having a control process that is variable.