JPH0477681A - High voltage fuse fusing meltdown circuit - Google Patents

Abstract

PURPOSE:To surely detect and inform the presence of meltdown of many high voltage fuses by comparing the output voltage of inductance with specified threshold voltage. CONSTITUTION:When the short-circuit accident of CRT 13 occurs, short-circuit current flows in CRT 13 from a high voltage power source 1 through inductance 3 to melt down a high voltage fuse 2 and, since the current allowed to flow in the inductance 3 is changed remarkably before and after the meltdown of the high voltage fuse, the voltage proportional to its current change generates between both sides of the inductances 3. And the voltage is divided by resistances R1, R2 to give to the input terminal of the positive side of an operation amplifier 15. Thereby the input voltage VH the positive side of the operation amplifier 15 is more than negative side input voltage Vr, the output of the operation amplifier 15 is changed to a high level, a thyristor 16 is in an ON condition, LED 17 is put on and it is informed that meltdown of the high voltage fuse 2 occurred.

Description

[Detailed Description of the Invention] [Summary] Regarding a blowout detection circuit for a high-voltage fuse inserted into a high-voltage power supply, the present invention aims to detect and notify the blowout of a high-voltage fuse inserted into a high-voltage power supply with a simple circuit configuration. , in a circuit in which a plurality of high voltage fuses are connected to the output side of a high voltage power supply, an inductance connected in series to the input or output of the high voltage power supply, and voltage comparison means for comparing the output voltage of the inductance with a predetermined threshold voltage. and a notification means for notifying that the high voltage fuse has blown when the output voltage of the inductance is equal to or higher than a predetermined threshold voltage as a result of the comparison by the voltage comparison means.

[Industrial Application Field] The present invention relates to a blowout detection circuit for a high voltage fuse inserted into a high voltage power supply.

[Conventional technology]

2. Description of the Related Art A display device is known that displays characters, pictures, etc. by controlling the lighting and extinguishing of a large number of CRTs arranged in a matrix.

In this type of device, high voltage is supplied to the anodes of multiple CRTs from the same high voltage power supply. And those CRTs
In order to prevent other normal CRTs from being unable to light up when a short-circuit failure occurs in one of the CRTs, a high-voltage fuse is inserted in each one or several CRTs.

As a result, one or several fused C of the high pressure fuse
Although the RT turns off, the lighting of other CRTs can be controlled.

[Problem to be solved by the invention]

By the way, in a display device that mainly displays numerical values, if the above-mentioned high-voltage fuse blows out and some CRTs are turned off, some of the numerical values will be missing and other parts will be displayed. There is a risk that it may be mistakenly recognized as a numerical value.

Therefore, in such cases, it has been desired to be able to notify that the high-pressure fuse has blown in order to prevent erroneous indications.

However, even if it is possible to detect the blowout of a high-voltage fuse by providing a voltage detection circuit or a current detection circuit for each high-voltage fuse, it is difficult to provide such a detection circuit for all high-voltage fuses due to the cost. It was unrealistic from all aspects.

An object of the present invention is to detect and notify the blowout of a high-voltage fuse inserted into a high-voltage power supply with a simple circuit configuration.

(Means for solving problems) FIG. 1 is a diagram explaining the principle of the present invention.

In the present invention, in a circuit in which a plurality of high voltage fuses 2 are connected to the output side of the high voltage power source 1, an inductance 3 is connected in series to the input or output of the high voltage power source 10.

The voltage comparison means 4 compares the output voltage of the inductance 3 with a predetermined threshold voltage.

Then, as a result of the comparison by the voltage comparison means 4, when the output voltage of the inductance 3 is equal to or higher than a predetermined threshold voltage, the notification means 5 performs a notification operation assuming that the high voltage fuse 2 has blown.

[For production]

Based on the above configuration, if one of the loads connected to the high voltage fuse 2, such as a CRT, is short-circuited and an overcurrent flows, the high voltage fuse 2 connected to that CRT will melt.

When the high voltage fuse 2 blows out, the current flowing through the inductance 3 suddenly changes, and a voltage proportional to the current change is generated across the inductance 3.

This voltage is compared with a predetermined threshold voltage by a voltage comparison means 4, such as a comparator, and if it is equal to or higher than the threshold voltage, the comparison result is output to the notification means 5.

Based on the comparison result, the notifying means 5 notifies the user that the high-voltage fuse 2 has blown out by means of a display or an alarm sound.

Therefore, one blowout detection circuit provided on the high voltage power supply 1 side can detect whether or not a plurality of high voltage fuses 2 are blowing out, and notify the result.

〔Example〕

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

FIG. 2 is a configuration diagram of a display device incorporating a high voltage fuse blowout detection circuit according to an embodiment of the present invention.

In this embodiment, 8×8 CRTs 3 are used as one display unit 11, and a plurality of these display units 11 are assembled to form a display device.

Furthermore, 8×8 CRTl of one display unit 11
For example, a high voltage fuse 2 is inserted for every four CRTs.

As shown in the figure, the display device includes a 24V power supply 12 that generates 24V DC, and a l0 supply to the anode of the CRT l3.
The high voltage power supply 1 that creates the high voltage of KV is the common power supply section 1.
It is set as 8.

From this common power supply section 18, a voltage of 24 V DC is directly outputted to each display unit ll, and a high voltage of IOK■ is outputted via the inductance 3.

The 24V voltage is output to the drive circuit (not shown) of the CRTI 3 of each display unit 11, and is also output to the DC/DC
The DC converter 14 converts the voltage into DC 5V and outputs it as a power supply voltage for the control system.

Similarly, the high voltage output from the high voltage power supply 1 via the inductance 3 is supplied to the anodes P of the plurality of CRTIs 3 via the high voltage fuse 2 in each display unit 11.

Resistors R1 and R2 are connected in series between the output side of the inductance 3 connected to the output of the high voltage power supply 1 and ground.

The above-mentioned resistor R1 is connected to the positive input terminal of the operational amplifier 15.
, R2 are inputted, and a voltage (2) obtained by dividing the power supply voltage of (5) by resistors R3 and R4 is inputted to the negative input terminal as a reference threshold voltage.

During normal operation, that is, when no short-circuit failure or the like occurs in the CRT 13, the voltage V is obtained by dividing the output side voltage of the inductance 3 by the resistors R1 and R2.

is lower than the threshold voltage ■1 applied to the positive input terminal, so the output of the operational amplifier 15 is always at a low level.

The output of this operational amplifier 15 is output to the gate of the thyristor 16, and when the high voltage fuse 2 is not blown, the thyristor 16 is in an off state.

A resistor 5 and an LED 17 are connected to the cathode side of the thyristor 16.
are connected in series. The LED 17 is an element that indicates whether or not the high voltage fuse 2 is blown, and when the output of the operational amplifier 15 is at a low level, the LED I 7 is in an off state.

Although not shown, each display unit 11 has a C
A drive circuit for controlling the grid G of the RT 13 is built in, and the display of the CRT 13 is controlled in accordance with signals output from a control section (not shown) that control lighting, turning off, brightness, and the like.

Next, the operation of the blowout detection circuit when a short circuit failure occurs in the CRT 13 in the display unit 11 and the high voltage fuse 2 blows out will be described.

When the CRT 13 is operating normally, the current output from the high voltage power supply 1 through the inductance 3 is 100
μ8 or less. However, when a short-circuit failure occurs in the CRT 13, a current of about 15 mA flows from the high-voltage power supply 1 through the inductance 3 to the short-circuited CRT 13.

This short circuit current blows out the high voltage fuse 2 connected to the failed CRT 13, and the current flowing through the inductance 3 becomes about 100/7A again.

At this time, the current flowing through the inductance 3 changes greatly between before and after the high-voltage fuse 2 blows out, so a voltage proportional to the current change is generated across the inductance 3.

This voltage is then divided by the resistors R1 and R2 mentioned above and applied to the positive input terminal of the operational amplifier 15. As a result, the positive input voltage VW of the operational amplifier 15 becomes larger than the negative input voltage 2, and the output of the operational amplifier 15 changes to a high level.

This high-level signal turns the thyristor 16 on, and the LED 17 lights up to notify that the high-pressure fuse 2 has blown out.

In addition, when a certain period of time passes after the high-pressure fuse 2 is blown,
The output voltage of the inductance 3 returns to its original steady value, and the output of the operational amplifier I5 becomes low level again.

However, since the thyristor 16 remains on at this time, the LED 17 remains lit. The SIRISK 16 functions as a circuit that latches the detection result of the operational amplifier 15 as to whether or not the high voltage fuse 2 is blown.

As described above, by comparing the output voltage of the inductance 3 inserted in series with the high voltage power supply 1 with a predetermined threshold voltage, the high voltage fuse 2 connected to the high voltage power supply 1 is
It is possible to reliably detect and notify the melting of the fuse.

Therefore, it is possible to quickly take measures such as stopping the display in the event of a failure on display devices such as some CRTs where the display may be erroneously recognized due to a failure, thereby improving the reliability of the display device. It can be further improved.

Moreover, since it is sufficient to provide, for example, one comparison circuit and latch circuit for one high-voltage power supply 1, the circuit configuration is simple.

In the above embodiment, the inductance 3 is inserted on the output side of the high voltage power supply 1, but it may be inserted on the input side to detect current changes on the input side.

Also, what about the high voltage fuse? The 8-off notification may be made by driving a buzzer or the like and making a sound.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention, and FIG. 2 is a configuration diagram of a display device according to an embodiment of the present invention. High voltage power supply, high voltage fuse, inductance, voltage comparison means, notification means. (Effects of the Invention) According to the present invention, it is possible to reliably detect and notify the presence or absence of melting of a large number of high-voltage fuses used in display devices, etc. Moreover, this can be achieved without adding complicated circuits. can do.

Claims (1)

[Claims] In a circuit in which a plurality of high voltage fuses (2) are connected to the output side of a high voltage power source (1), an inductance (3) connected in series to the input or output of the high voltage power source (1); voltage comparison means (4) for comparing the output voltage of the inductance (3) with a predetermined threshold voltage;
), when the output voltage of the inductance (3) is equal to or higher than a predetermined threshold voltage as a result of the comparison, the high-voltage fuse (2) is blown. High voltage fuse blowout detection circuit.