JPS6177093A - Fluorescent indicator tube driving circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is applied to CRT display devices and other devices that display information using a fluorescent display tube.

The present invention relates to a drive circuit for a fluorescent display tube. In particular, the invention relates to a circuit that controls the input of a driver that sequentially switches each digit of a fluorescent display tube to turn on the light, and turns off the light when the scan signal stops for a predetermined period of time.

[Conventional technology]

FIG. 2 is a block diagram of a conventional fluorescent display tube drive circuit. As shown in FIG. 2, a conventional fluorescent display tube drive circuit inputs commands from a host computer system and analyzes them.The scan signal SI and the first digit designation signal S2 of the control circuit 1 are sent to the shift register 2. , and the shift register 2 selects the digit to be lit. The output signal of the shift register 2 is input to the driver 5 and converted into a voltage for driving the control grid of the digit to be lit on the fluorescent display tube 6. Display data S4 is also output from the control circuit 1 and input to the character generator graph, where it is converted into a display pattern. The output signal of the character generator turf is input to the driver 8 and converted into a voltage for driving the segment anodes corresponding to the display pattern of the fluorescent display tube 6.

The output voltages of the driver 5 and the driver 8 are
is input, and display data S4 is displayed.

[Problem that the invention seeks to solve]

However, in such conventional fluorescent display tube drive circuits, if the control circuit stops outputting the scan signal for some reason, the lit digits cannot be switched and one digit remains lit for a long time. Become.

As a result, in the worst case, the interior of the fluorescent display tube may be damaged.

The present invention solves the above-mentioned drawbacks, and aims to provide a fluorescent display tube drive circuit that can avoid internal damage to the fluorescent display tube when the scan signal from the control circuit stops. purpose.

[Means for solving problems]

The present invention provides a drive circuit for a fluorescent display tube that generates an electric signal and a scan signal containing information to be displayed. and circuit means for prohibiting display on the optical display tube.

[For production]

The present invention monitors the scan signal with a monitoring circuit, and when the scan signal stops for a predetermined period of time, outputs a detection signal to a circuit means that prohibits the display of the fluorescent display tube, thereby preventing internal damage to the fluorescent display tube. can be avoided.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a driving circuit for a fluorescent display tube according to an embodiment of the present invention. In FIG. 1, a scan signal Sl and a first target designation signal S2 are connected from a control circuit 1 to a shift register 2, and a digit to be lit is selected.

Here, the feature of the present invention is the driver output cut portion surrounded by a dashed line. That is, the scan signal S from the control circuit 1 and the first digit designation signal S2 are branched and connected to the scan signal monitoring circuit 3, and the scan signal S1 and the first digit designation signal S2 are monitored. When the scan signal Sl and the first digit designation signal S2 are normal, the scan signal monitoring circuit 3 outputs scan signal monitoring data S3 at the rHJ level, and the first digit designation signal S2 is outputted from the scan signal monitoring circuit 3.
2 and the scan signal S are stopped for a predetermined period of time, the scan signal monitoring data S3 at the "L" level is output. The output signal of the shift register 2 and the scan signal monitoring data S3 from the scan signal monitoring circuit 3 are connected to the inputs of an AND circuit 4, respectively. When the scan signal monitoring data S2 is at the rLJ level, the AND circuit 4 is at the rL level.
Output J level signal and scan signal monitoring data S3
When is at the rHJ level, the AND circuit 4 outputs a signal at the rHJ level. The output signal of the AND circuit 4 is connected to the driver 5, and when the output signal is at the rHJ level, the drive voltage converted from the driver 5 is connected to the control grid of the digit to be lit on the fluorescent display tube 6. From the control circuit l,
Display data S4 is also connected to the character generator graph. The display pattern converted from the character generator 7 is connected to the driver 8. The driving voltage converted from the driver 8 is connected to the segment anode of the fluorescent display tube 6, and the display data S4 is displayed. When the output signal of the AND circuit 4 is at the rLJ level, the display data S4 is not displayed.

The operation of the drive circuit for the fluorescent display tube having such a configuration will be explained. In FIG. 1, display data S4 from the control circuit 1 is converted into a display pattern by a character generator 7. According to this display pattern, the driver 8 applies voltage to the segment anodes of the fluorescent display tube 6 corresponding to the display pattern. Scan signal SI and first digit designation signal S2 from control circuit 1 are input to shift register 2. The shift register 2 selects the digit to be lit. The output signal of the shift register 2 is input to an AND circuit 4, and the output signal of the AND circuit 4 is input to a driver 5.

The driver 5 sequentially applies voltage to the control grid of each digit of the fluorescent display tube 6, and the display data S4 is displayed.

Here, the features of the present invention will be explained. Now, when the input of the driver 5 is at rHJ level, the fluorescent display tube 6
It is assumed that the light is turned on and the light is turned off at the "L" level. In this case, the scan signal monitoring circuit 3 first monitors the scan signal S1 when the first digit designated symbol S2 is at the "L" level, and when the scan signal S1 stops for a predetermined time or more, the scan signal monitoring circuit 3 detects the scan signal monitoring circuit 3. S3 is set to "L" level.

Further, when the first digit I determination signal S2 is at the "II" level, the scan signal monitoring data S3 is set at the "L" level regardless of the scan signal S1. Therefore, the AND circuit 4 connected to this output sets all the outputs of the driver 5 to rLJ level and turns off the light.

As explained above, when the scan signal S or the first digit designation code S2 stops, all the lights are turned off, so that the inside of the fluorescent display tube 6 is Damage can be avoided.

〔Effect of the invention〕

As explained above, the present invention provides a scan signal monitoring circuit and an AND circuit, and turns off the light when the scan signal or the first digit designation signal stops, thereby preventing damage to the inside of the fluorescent display tube. There are great effects that can be avoided.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a drive circuit for a fluorescent display tube according to an embodiment of the present invention. FIG. 2 is a block diagram of a conventional fluorescent display tube drive circuit. ■...Control circuit, 2...Shift register, 3...
Scan signal monitoring circuit, 4...AND circuit, 5.8.
... Driver, 6... Fluorescent display tube, 7... Character generator, Sl... Scan signal, S2... 1
Digit designation signal, S...Scan signal monitoring data, S
4...Display data.

Claims (1)

[Claims] (1) In the fluorescent display tube drive circuit that generates electrical signals and scan signals containing information to be displayed, there is a monitoring circuit that detects when the scan signal is interrupted for a predetermined time; 1. A drive circuit for a fluorescent display tube, comprising circuit means for inhibiting display on the display tube.