JPH0596884U - Fluorescent display filament drive circuit - Google Patents

Abstract

(57) [Summary] [Purpose] The purpose is to shorten the time until the filament reaches the activation temperature so that the display can be performed quickly. In a filament drive circuit of a fluorescent display tube having a filament electrode, a grid electrode and an anode electrode, the filament electrode is connected in series with a DC power source and a switching transistor, and the switching transistor is switched based on a switching operation of a switch. The filament supply that supplies sufficient power to control the temperature and display to supply sufficient power to reach the activation temperature of the filament, and to supply sufficient power to perform residual heat to the extent that the filament does not glow red when not displaying. Power control means is provided.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a filament drive circuit for a fluorescent display tube, and more particularly to a filament drive circuit for a fluorescent display tube with improved responsiveness when displaying with a fluorescent display tube.

[0002]

[Prior Art]

 Examples of conventional fluorescent display devices include those shown in FIGS. 5 and 6. In FIG. 6, a vehicle compartment 51 is provided with an instrument panel 52 forming a front wall, and a front window 53 is arranged above the instrument panel 52. A recess 54 is formed in the instrument panel 52, and a display source 55 is disposed in the recess 54. As the display source 55, the fluorescent display tube 56 shown in FIG. 5 is used, and the fluorescent display tube 56 has a filament 57, a grid 58 and an anode 59.

The filament 57 is connected to the battery 61 via a power supply circuit 60. On the other hand, a driver circuit 62 is connected to the anode 59, and the driver circuit 62 is connected to a switch 64 via a display control circuit 63. Further, between the filament power source of the power supply circuit 60 and the filament 57, a relay 66 which is turned on / off by a relay drive circuit 65 is provided.

This fluorescent display tube display device cuts off the power supply to the filament 57 by a relay 66 when the display is turned off, thereby eliminating the red heat image of the filament 57 projected on the front window 53 at night.

[0005]

[Problems to be solved by the device]

 However, in such a conventional fluorescent display tube display device, the power supply to the filament 57 is cut off by the relay 66 when the display is turned off, and the power is supplied to the filament 57 when the display is performed. Since the filament was re-supplied, the filament 57 was cold when the display was attempted, and it took time for the filament 57 to reach the activation temperature, so that a good display quality could be promptly displayed. There was a problem that I could not do.

The present invention has been made in view of such a conventional problem, and when the display is not performed, the filament is preheated by conducting electricity so that the filament does not turn red. An object of the present invention is to solve the above-mentioned problems by supplying sufficient energy for the filament to reach the activation temperature at the time of displaying, and promptly raising the filament temperature to the activation temperature.

[0007]

[Means for Solving the Problems]

 The filament drive circuit for a fluorescent display tube according to the present invention is a filament drive circuit for a fluorescent display tube having a filament electrode, a grid electrode and an anode electrode, wherein the filament electrode is connected in series with a DC power supply and a switching transistor, The switching transistor is controlled based on the switching operation of the switch, and when the display is performed, sufficient power is supplied to reach the activation temperature of the filament, and when the display is not performed, the residual heat is generated so that the filament does not glow red. A structural feature is that a filament supply power control means for supplying sufficient power to the filament is provided.

[0008]

[Action]

 The filament drive circuit of the fluorescent display tube according to the present invention controls the switching transistor based on the switching operation of the switch, and supplies sufficient electric power to the filament electrode so that the filament reaches the activation temperature when displaying. On the other hand, when the display is not performed, the switching transistor is controlled on the basis of the switching operation of the switch, and the filament is supplied with sufficient power to perform the residual heat to the extent that the filament does not glow red. Therefore, when the display is performed, the filament is in a preheated state and is not cooled, so that the temperature of the filament quickly rises to the activation temperature and the display is performed promptly.

[0009]

【Example】

 The invention will be described below with reference to the drawings. FIG. 1 is an electric circuit diagram showing an embodiment of a filament drive circuit for a fluorescent display tube according to the present invention. In the figure, reference numeral 1 is a battery power source, which is connected to a filament electrode 3a of a fluorescent display tube 3 through a power switch 2 and a switching transistor Q1. The battery power source 1 is also connected to the grid electrode 3b of the fluorescent display tube 3 via a power switch 2.

Reference numeral 4 is a microprocessor unit, 5 is a display switch, and the display switch 5 is connected to an input port of the microprocessor unit 4. The display switch 5 is for inputting an operation signal as to whether or not to display by the fluorescent display tube 3, and an operation signal “0” indicating that no display is made in the ON state, that is, the closed state is the microprocessor. The operation signal “1” is input to the unit 4, and an operation signal “1” for displaying is displayed in the off state.

Reference numeral 6 is an anode drive circuit connected to the output port of the microprocessor unit 4. The output terminal of the anode drive circuit 6 is connected to the anode electrode 3c of the fluorescent display tube 3.

FIG. 2 is a block diagram showing the configuration of the microprocessor unit 4. In the figure, 4a is a central processing unit, 4b is a RAM, and 4c is a ROM, which stores programs for controlling the switching transistor Q1 and the anode drive circuit 6. An output port 4d is connected to the base of the switching transistor Q1 via a buffer circuit 4e.

4 f is also an output port, and is connected to the anode drive circuit 6. 4g is an input port to which the display switch 5 is connected.

Next, the operation will be described with reference to FIG. FIG. 3 is a flowchart showing the operation when controlling the switching transistor Q1 and the anode drive circuit 6.

First, when the display switch 5 is in the closed state, the display switch 5 generates an operation signal “0” indicating that the display shown in FIG. An operation signal indicating that this display is not performed is fetched from the input port 4g, and the flag "0" is set in a predetermined register. Returning to FIG. 3, it is identified based on this flag that the display switch 5 is on, that is, in the closed state (step S1). Next, when the display switch 5 is closed, a pulse signal with a duty ratio of A% is generated (step S2), and the generated pulse signal is output from the output port 4d (step S3). The pulse signal output from the output port 4d is supplied to the base of the switching transistor Q1 via the buffer circuit 4e. Therefore, when the power switch 2 is closed, a pulse signal having a duty ratio A% shown in (b) of FIG. 4 is output to the filament electrode 3a of the fluorescent display tube 3. The duty ratio A% is a preset value for supplying the filament electrode 3a with electric power that does not cause the filament electrode 3a to glow red. Therefore, the filament electrode 3a is supplied with electric power that does not cause red heat and is in a state of being preheated, and the temperature of the filament electrode is maintained at the preheating temperature as shown in FIG. At this residual heat temperature, since the filament electrode 3a is not red-hot, the red-hot image of the filament projected on the front window at night does not appear.

Next, by confirming that the flag set in step S1 is "0", the anode drive circuit control signal of "L" level is output from the output port 4f (step S4). As a result, the anode drive circuit 6 outputs the'L 'level extinguishing signal shown in FIG. 4D to the anode electrode 3c of the fluorescent display tube 3 to turn off the display.

On the other hand, when the display switch 5 is turned off, the display switch 5 generates an operation signal “1” indicating that the display shown in FIG. This operation signal is fetched from the input port 4g and the flag "1" is set in a predetermined register. Based on this flag, it is identified that the display switch 5 is in the off state (step S1), then a pulse signal with a duty ratio B% is generated (step S5), and the generated pulse signal is output. Output from the port 4d (step S3). The pulse signal output from the output port 4d is supplied to the base of the switching transistor Q1 via the buffer circuit 4e, and the filament electrode 3a of the fluorescent display tube 3 has a duty ratio B% shown in (b) of FIG. The pulse signal of is output. The duty ratio B% is a value that is preset as a value that is larger than the duty ratio A% and that corresponds to the electric power required to bring the filament electrode 3a to the activation temperature. Therefore, the filament electrode 3a is supplied with sufficient electric power to reach the activation temperature. As a result, the temperature of the filament electrode 3a rises more quickly from the residual heat temperature as shown by the solid line than in the conventional case shown by the broken line in FIG. 4C. Next, by confirming that the flag set in the step S1 is "1", an "H" level anode drive circuit control signal is output from the output port 4f to the anode drive circuit 6 (step S4). ). As a result, the ‘H’ level lighting signal shown in FIG. 4D is output to the anode electrode 3 c of the fluorescent display tube 3, and the display is performed quickly.

[0018]

[Effect of the device]

 As described above, in the present invention, the switching transistor is controlled based on the switching operation of the switch, and when the display is performed, sufficient electric power is supplied to the filament electrode so that the filament reaches the activation temperature. When the display is not performed, the filament is already overheated when the display is performed because the filament is supplied with enough electric power to control the switching transistor to generate the excess heat so that the filament does not overheat. In this state, the filament temperature rises rapidly from the residual heat temperature to the activation temperature, the display is prompt, and the filament red heat image is not displayed on the front window at night when the display is not performed.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of a filament driving circuit for a fluorescent display tube according to the present invention.

FIG. 2 is a block diagram showing a configuration of a microprocessor unit 4.

FIG. 3 is a flowchart showing an operation when controlling a switching transistor and an Anote drive circuit.

FIG. 4 is a waveform diagram showing an operation signal generated by a display switch, a pulse signal supplied to a filament electrode, a filament temperature, and a lighting or extinguishing signal.

FIG. 5 is a block diagram showing a configuration of a conventional fluorescent display device.

FIG. 6 is an explanatory diagram showing a configuration of a conventional fluorescent display tube display device.

[Explanation of symbols]

Q1 switching transistor 1 battery 3 fluorescent display tube 3a filament electrode 3b grid electrode 3c anode electrode 4 microprocessor unit (filament supply power control means) 5 display switch

Claims (1)

[Scope of utility model registration request] 1. A filament drive circuit for a fluorescent display tube having a filament electrode, a grid electrode, and an anode electrode, wherein the filament electrode is connected in series with a DC power source and a switching transistor, and the filament switching circuit is based on a switching operation of a switch. The switching transistor is controlled to supply enough power to reach the activation temperature of the filament when displaying, and to supply enough power to heat the filament enough to prevent the filament from glowing when not displaying. A filament drive circuit for a fluorescent display tube, comprising filament supply power control means.