JPS6124195A - Drive circuit of hot-cathode heavy hydrogen tube - 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] [Field of Application of the Invention] The present invention relates to a drive circuit for a hot cathode type deuterium discharge tube, particularly for use in ultraviolet rays such as spectrophotometers that are easy to light up and require a long life. The present invention relates to a drive circuit for a hot cathode type deuterium discharge tube suitable for use as a light source.

[Background of the invention]

In a hot cathode type deuterium discharge tube, electrons are emitted from the cathode due to the collision of cations, but at the same time, the cathode material itself is also emitted in an atomic state, which scatters or diffuses and attaches to the tube wall. do. The phenomenon in which the cathode material is scattered in all directions by fine external particles due to electric discharge is called the cathode action.

- The amount of cathode material scattered by the cathode action increases in proportion to the discharge time, increases and decreases with the discharge current, increases as the cathode falls, and varies depending on the cathode material and the type of gas.

The life of a discharge tube is often determined by this splash effect. That is, in addition to the cathode collapsing due to this effect, the luminous intensity of the discharge tube is reduced due to the blackening of the tube wall,
Alternatively, when the cathode material adheres to the tube wall, it adsorbs the deposited gas and gradually lowers the atmospheric pressure. These reasons limit the lifespan of the discharge tube.

From the above, it can be said that preventing the cathode material of the discharge tube from scattering is the most important matter for realizing a long-life discharge tube.

Conventionally, two types of discharge tubes have been used, one of which is the 5th discharge tube.
The other one is shown in FIG. 5(a) and FIG. 5(b). The only difference in this structure is whether the cathode and shield are short-circuited or not.

In the discharge tube shown in FIG. 5(a), it was difficult to light up during initial lighting, and failures in lighting continued to occur. The reason for this is that the shield and the cathode are short-circuited, so when the initial lighting is started, a high pulse voltage is momentarily applied to effectively generate positive ions through ionization from the excitation of gas molecules and emit light, but the cathode and the shield are short-circuited. As a result, some of the cations from the anode flow through the shield plate, making it impossible for enough cations to rush into the cathode to cause an arc discharge, resulting in the discharge tube not emitting light and causing a lighting failure. be. Note that this tendency is particularly strong in deteriorated cathodes.

This is because the amount of scattering of the coating on the cathode filament to improve thermionic emission is greatly affected by the discharge time and the increase or decrease of the current.In other words, assuming a constant current, the longer the discharge tube is used, the more There is a drawback that the oxidized coating scatters greatly and the resistance of the filament becomes large and flows bypassing the filament, resulting in no light emission and poor lighting.

As a countermeasure to this problem, the short circuit between the cathode and the shield plate is removed as shown in FIG. 5(b). According to this lighting method, since the shield plate is completely floating, the cathode is the only path through which the anode current flows, so all of the cations rush collectively onto the cathode, making it easy to emit light and light up. However, as mentioned above, this results in increased scattering of the oxide coating on the cathode. In other words, the lighting method shown in FIG. 5 υ) is easy to light up, but has the disadvantage of short life.

To summarize the above, the discharge tube shown in FIG. 5(a) has a long life even though it does not light up. As the discharge tube deteriorates (particularly the oxidized coating applied to the cathode), the lighting becomes more noticeable.

The discharge tube (in Figure 5) is easy to light, but has the disadvantage of a short lifespan.

[Purpose of the invention]

- An object of the present invention is to provide a drive circuit for a hot cathode type deuterium discharge tube that makes it easier to light up a deuterium discharge tube, prevents scattering or diffusion of the oxide coating on the cathode, and has a long life. It is in.

[Summary of the invention]

The amount of oxide coating applied to the cathode of a deuterium discharge tube determines ease of lighting and life. The degree of scattering of this oxidized coating depends on the size of the cations that rush from the anode to the cathode in the deuterium discharge tube. On the other hand, the self-heating of the cathode (before lighting, even if large interfering ions are generated from the anode)
After the application was turned on, the thermionic emission caused by the application of 7.times.) acted as a cushion and did not scatter the oxide coating coated on the cathode. In order to support the above theory, we conducted an experiment to confirm that, as a means to eliminate the scattering of the oxide coating, we opened the cathode and the shield plate only at the start of lighting, and directed large cations toward the cathode. After lighting, that is, while the lighting is being maintained, one end of the cathode and the shield plate are shorted, and the cations are diverted to the shield plate @trap, reducing the amount of cations directed toward the cathode. This creates a deuterium discharge tube that prevents scattering, is easy to light, and has a long life.

[Embodiments of the invention]

FIG. 1 is a configuration diagram showing an embodiment of a drive circuit for a hot cathode type deuterium discharge tube according to the present invention. In the figure, a heating power supply voltage Vt is connected to the cathode filament 3 so that thermoelectrons are always emitted. Before lighting starts, switch S+ applies trigger voltage ■8 to large capacity capacitor C.
3. Charge the cathode filament with a voltage of 3. for 10 seconds or more. After heating the capacitor C, when the capacitor 81 is switched to the contact side, the pulse charge stored in the capacitor C flows between the anodes 10 of the cathode filament 3, and discharge starts. At this time, the inductance L has the role of allowing the charge from the anode 1 to concentrate directly on the cathode filament 3, that is, the property of the inductance does not allow pulse charges to pass through. Therefore, all of the pulsed charges reach the cathode filament 3, making it possible to realize a deuterium discharge tube that is easy to light. The deuterium discharge tube that has started discharging in this way continues to have a constant current flowing into its anode in order to continue stable lighting.

This injected current directly rushes into the cathode filament 3 and passes through the inductance L to the cathode filament 3.
The current flows through one end of the current.

Therefore, since the current flowing through the cathode filament 3 can be reduced, scattering of the oxide coating applied to the filament can be prevented, and a long-life deuterium discharge tube can therefore be realized.

In the hot cathode deuterium discharge tube used in the drive circuit of the hot cathode deuterium discharge tube constructed in this way, the terminal of the shield 2 is provided independently outside the discharge tube, as shown in Figure 2. , an inductance 4 may be provided between this terminal and one of the terminals of the cathode filament 3, and as shown in FIG. An inductance 4 may be provided between the cathode filament 3 and the cathode filament 3.

FIG. 4 is a block diagram showing another embodiment of the driving circuit for a hot cathode type deuterium discharge tube according to the present invention. In the figure, when the switch S1 is turned on, a DC voltage is applied from the power supply Vn to the anode 1 via the high resistance Ro, and at the same time, a voltage -(IOV) is also applied to the cathode filament 3, starting thermionic emission. .

When the cathode filament 3 is heated sufficiently to cause arc discharge, that is, thermionic emission occurs, the anode 1 and the cathode filament 3 become electrically connected, and the high voltage that was previously applied to the anode drops. Instead, a constant current of 300 mA for maintaining discharge is supplied via D+, and stable discharge continues thereafter. In this lighting method, unlike the pulse lighting method of the previous embodiment, it is impossible to use inductance because the lighting is performed at a DC level. Therefore, we tried to achieve the conditions of easy lighting and long life by opening the cathode and the shield plate at the moment of lighting, and shorting the cathode and the shield plate after lighting, by using a circuit including the thyristor 5. There is. That is, the gate G of the thyristor 5 is closed until a high voltage is applied to the anode 1 and discharge occurs, and the cathode filament 3 is sufficiently heated, thermionic emission causes arc discharge, and the deuterium discharge tube starts discharging. After, Thyristor 5
Game) Open G. In other words, after lighting, thyristor 5
The anode A and the cathode K are electrically connected, and as a result, the shield plate 2 and one end of the cathode filament 3 are electrically electrically connected, and even in a DC voltage lighting type, using a thyristor makes lighting easier and has a long life. A deuterium discharge tube can be realized.

The time for opening and closing the thyristor gate G can be set by appropriately selecting the resistor R1 and capacitor C1.

〔Effect of the invention〕

As is clear from the above explanation, according to the drive circuit for a hot cathode type deuterium discharge tube according to the present invention, the discharge tube can be easily lit and can have a long life.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a drive circuit for a hot cathode deuterium discharge tube according to the present invention, and FIGS. 2 and 3 are diagrams showing an example of a hot cathode deuterium discharge tube used in the drive circuit. Fig. 4 is a block diagram showing another embodiment of the drive port/path of the hot cathode type deuterium discharge tube according to the present invention, and Fig. 5 is a block diagram showing another example of the drive port/path of the hot cathode type deuterium discharge tube according to the present invention. FIG. 2 is an explanatory diagram showing an example of a driving method and its configuration. 1... Anode, 2... Shield, 3... Cathode filament, 4... Inductance, 5... Thyristor.

Claims (1)

[Claims] 1. In a drive circuit for a hot cathode type deuterium discharge tube that is equipped with an anode, a cathode, and a shield, and the cathode is made of an oxide or monatomic adhesive material, the shield is opened when applying a voltage between the anode and the cathode. A driving circuit for a hot cathode type deuterium discharge tube, characterized in that a switching mechanism is provided to ground the shield after a predetermined period of time has elapsed.