JPS5929374Y2 - Vacuum tube abnormal heat generation prevention circuit - Google Patents

Description

[Detailed explanation of the invention] This invention is to prevent abnormal heat generation caused by vacuum tubes.
It concerns a simple and practical protection circuit.

Conventional abnormal heat generation prevention circuits install switching circuits and relays in parallel with vacuum tubes (refers to vacuum tubes that may generate abnormal heat; all "vacuum tubes" mentioned below refer to the same thing), and prevent abnormalities in the bias circuit. Bias, zero bias) was detected, and the high voltage applied to the vacuum tube was turned off to prevent abnormal heat generation.

However, this conventional circuit is configured to detect an abnormality in the bias circuit as the cause of abnormal heat generation, so there are difficulties in setting the circuit constants, and if other reasons (cooling water cutoff, fan stoppage, and control grid bias gradually increase) It was difficult to detect abnormal heat generation in vacuum tubes caused by misalignment, etc.

Furthermore, since the protection circuit itself uses a large number of parts, the reliability of the protection circuit is poor.

The present invention aims to eliminate the above-mentioned conventional drawbacks and completely prevent secondary disasters (device fires) caused by abnormal heat generation of vacuum tubes.

The present invention inserts a temperature-sensitive switching element into the line connected to the control grid of the vacuum tube, and directly detects abnormal heat generation due to any cause by the temperature-sensitive switching element, opens the control grid, and increases the anode current. It is characterized by forcibly blowing out a fuse inserted into the anode line to prevent abnormal heat generation.

FIG. 1 shows an example of the mounting positional relationship of the main components related to the present invention.

1 is a thermostat provided according to the present invention, 2 is a vacuum tube that may generate abnormal heat, 3 is a combustible wire, and 4 is a heat insulating material that prevents heat from the vacuum tube 2 from being transferred to the wire 3. is fixed.

The heat insulating material 4 is a material that maintains its heat insulating effect at least until the thermostat 1 senses the temperature and operates.

FIG. 2 shows an embodiment of the circuit according to the invention.

1 is a contact of the thermostat, 2 is a vacuum tube, 5 is a protection fuse, and 6 is an excitation tube.

In Figure 2, if point A of the bias circuit (same potential as the control grid) is grounded or open, the plate current increases momentarily, causing fuse 5 to melt and causing an abnormality in vacuum tube 2. Prevent fever.

In addition, if the bias voltage at point A gradually increases due to deterioration of the excitation tube 6, or if the vacuum tube 2 generates abnormal heat due to a failure of the cooling device, the thermostat 1 senses the temperature and raises the bias voltage at point A of the bias circuit. By leaving it open,
A large plate current momentarily flows, blowing out the fuse 5 and preventing abnormal heat generation.

Note that instead of using the temperature-sensitive switching element of the present invention, it is also possible to use an element such as a thermistor as the temperature-sensitive element, but this requires an additional amplifier circuit and power supply, making the circuit complicated.

It is also possible to install a fuse inserted in the anode line as a temperature fuse at a place that generates abnormal heat, but current temperature fuses have problems in terms of reliability (operating temperature error is about ±5°C), and the location where they are used is is a high voltage, so
There is a safety problem in attaching the temperature fuse itself externally and using it for temperature detection as well.

As mentioned above, in this invention, the abnormal heat generated in the vacuum tube is directly detected and controlled using a temperature-sensitive switching element, so compared to the conventional vacuum tube bias detection circuit, it is possible to detect and control the abnormal heat generated in the vacuum tube. It is also possible to prevent abnormal heat generation of the vacuum tube due to water cutoff, fan stoppage, etc.).

Further, since the only parts added by the present invention are the temperature-sensitive switching element and the fuse, the number of parts is reduced and the reliability of the protection circuit is improved.

In addition, as the anode circuit insertion fuse, it is possible to select a fuse that blows even when an instantaneous increase in anode current that does not reach abnormal heat generation can be selected, so that the function of protecting the circuit can be further improved.

[Brief explanation of drawings]

FIG. 1 is a layout diagram showing an example of the positional relationship in which parts are attached according to the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. 1... Temperature-sensitive switch element, 2... Vacuum tube, 3... Fuse.

Claims (1)

[Scope of utility model registration request] In a vacuum tube where there is a possibility of abnormal heat generation, a temperature-sensitive switch element is inserted into the line connected to the control grid, and a fuse is inserted into the anode line, and the temperature-sensitive switch element opens the control grid in the event of abnormal heat generation. A circuit for preventing abnormal heat generation of a vacuum tube, characterized in that the circuit is configured to prevent abnormal heat generation of a vacuum tube by blowing out the fuse.