JPH08315741A - Vacuum microswitch - Google Patents

Abstract

PURPOSE: To enhance reliability by enclosing an overvoltage protective part in the same element by dividing a gate, and bypassing overvoltage by automatically turning it on when the overvoltage is detected. CONSTITUTION: A gate is divided into two parts of G0 and G1, and a main switch part 10 and an overvoltage protective part 11 are arranged in the same element. When voltage between A and K is not more than an overvoltage protective level, the protective part 11 does not operate, and the switch part 10 operates by an ON signal of a driving device 12. When it is not less than the overvoltage protective level, an overvoltage detecting circuit 13 detects this, and operates a gate pulse generator 14, and turns the protective part 11 on, and bypasses the voltage between A and K. When it reduces to the overvoltage protective level or less, the generator 14 is stopped, and the protective part 11 is turned off. In this way, the protective part 11 is automatically turned on, and since overvoltage is bypassed and restrained, reliability can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum micro switch having an overvoltage protection function.

[0002]

2. Description of the Related Art A vacuum micro device is a device that uses a micron-sized field emission cold cathode, and is a semiconductor device in various aspects such as high-speed electron traveling property, high dielectric strength, temperature resistance and radiation resistance. It has much better characteristics than Therefore, ultra-high-speed microwave devices, power devices,
It is expected to be applied to a very wide range of fields such as electron beam devices and flat panel image display devices.

FIG. 5 shows the basic structure of a vacuum micro device. The vacuum micro-element is a field emission cold cathode, which is arranged in a vacuum container and includes a cathode K having a plurality of conical emitters and a gate G arranged around the emitters.
It is composed of an anode A facing it. Next, the operating principle of this element will be described.

Turn-on is performed by applying a positive voltage to the gate G, and a very high electric field is applied to the emitter E.
It occurs at the apex of the conical part of. Due to this high electric field, electrons are extracted by the tunnel effect at the apex of the conical portion of the emitter E, and the electrons emitted from the emitter E reach the anode A through the orbits as shown in FIG. It becomes a state. Turn-off is performed by releasing the voltage of the gate G.

[0005]

In the vacuum micro device, when a voltage higher than the breakdown voltage is applied between the anode and the cathode (hereinafter referred to as AK), vacuum breakdown occurs and a breakdown current flows. Since this breakdown current concentrates on the local area of the emitter, it causes melting of the conical emitter, short circuit between the gate electrode and the emitter, etc., resulting in deterioration or destruction of the characteristics of the device. Therefore, in the vacuum micro device, it is important to prevent the vacuum dielectric breakdown and protect the device.

As a commonly used overvoltage protection method, there is a method of connecting a non-linear resistor in parallel between A and K of the element. However, since the vacuum micro device has a high-speed switching ability, it is considered that the vacuum micro device is mainly used in the MHz to GHz range. Therefore, it is necessary that the overvoltage protection also has a high-speed response characteristic. The time is slow and not sufficient for overvoltage protection of vacuum micro devices.

Further, since it is necessary to provide a circuit for absorbing the overvoltage outside the element, there is a problem that the switch becomes large. Therefore, an object of the present invention is to provide a vacuum microswitch having a high-speed response characteristic and an overvoltage protection function.

[0008]

In order to achieve the above object, a vacuum microswitch according to claim 1 of the present invention comprises a cathode having an emitter and a gate for controlling a flow of electrons emitted from the emitter. In a vacuum microswitch for driving a vacuum microdevice having a field emission cold cathode and an anode arranged to face the field emission cold cathode by a drive signal from a driving means, a gate of the vacuum microdevice is A drive means that is divided into a plurality of parts and is provided with a main switch part for supplying a main current to the vacuum micro device and an overvoltage protection part for supplying a current when an overvoltage occurs, and a drive means for supplying a drive signal for controlling the main current to the gate of the main switch part. An overvoltage detecting means for detecting an overvoltage between the anode and the cathode of the vacuum microelement, and an overvoltage from the overvoltage detecting means Receiving a detection signal, characterized in that a gate pulse generating means for providing a drive signal to the gate of the overvoltage protection unit.

According to a second aspect of the present invention, in the vacuum microswitch according to the first aspect, a resistance layer for limiting current is provided below the emitter of the overvoltage protection portion.

According to a third aspect of the present invention, in the vacuum microswitch according to the second aspect, the resistance value of the resistance layer of the overvoltage protection portion is R ≥ Vpro / Iomax Vpro: Overvoltage protection of the vacuum microelement. Level Iomax: Characterized by the maximum allowable current of the overvoltage protection unit.

In the vacuum microswitch according to claim 4 of the present invention, a field emission cold cathode comprising a cathode having an emitter and a gate for controlling a flow of electrons emitted from the emitter, and the field emission cold cathode are provided. In a vacuum micro switch for driving a vacuum micro element having an anode and an anode arranged opposite to each other by a signal from a driving means, a gate of the vacuum micro element is divided into a plurality of parts, and a main current is supplied to the vacuum micro element. A switch unit and an overvoltage protection unit that allows a current to flow when an overvoltage occurs are provided, drive means for applying a drive signal for controlling the main current to the gate of the main switch unit, and overvoltage between the anode and cathode of the vacuum micro element are detected. An overvoltage detecting means and the current flowing between the gate and the cathode of the overvoltage protection unit of the vacuum micro device are detected. A flow detecting means, a discriminating means for comparing the above-mentioned detection signal detection signal with a predetermined reference voltage from the current detection means to determine whether larger or smaller than the reference voltage,
Based on the overvoltage detection signal from the overvoltage detection means and the discrimination signal from the discrimination means, there is an overvoltage between the anode and the cathode of the vacuum micro element, and between the gate and the cathode of the overvoltage protection unit of the vacuum micro element. There is provided start command means for outputting a start command when the flowing current is smaller than a predetermined reference voltage, and gate pulse generation means for receiving a start command from the start command means and giving a drive signal to the gate of the overvoltage protection unit. It is characterized by having done.

In a vacuum microswitch according to a fifth aspect of the present invention, there are provided a field emission cold cathode comprising a cathode having an emitter and a gate controlling an electron flow emitted from the emitter, and the field emission cold cathode. In a vacuum micro switch for driving a vacuum micro element having an anode and an anode arranged opposite to each other by a signal from a driving means, a gate of the vacuum micro element is divided into a plurality of parts, and a main current is supplied to the vacuum micro element. A switch unit and an overvoltage protection unit that allows a current to flow when an overvoltage occurs are provided, drive means for applying a drive signal for controlling the main current to the gate of the main switch unit, and overvoltage between the anode and cathode of the vacuum micro element are detected. Driving the overvoltage detection means and the gate of the overvoltage protection unit by receiving the overvoltage detection signal from the overvoltage detection means Wherein the gate pulse generating means for providing, that had a inserted resistor between the gate of the gate pulse generating means and the overvoltage protection unit No..

According to a sixth aspect of the present invention, in the vacuum microswitch according to the fifth aspect, the resistance value of the resistor inserted between the gate pulse generating means and the gate of the overvoltage protection unit is R = (Vgo-Vth) / (nIomax) Vgo: Output voltage of the gate pulse generating means Vth: Threshold voltage of the vacuum micro element Iomax: Maximum allowable current of the overvoltage protection part n: Gate-cathode current and anode-cathode of the overvoltage protection part It is characterized by the ratio of the inter-current.

[0014]

In the vacuum microswitch according to the first aspect of the present invention, the main switch section and the overvoltage protection section are formed in the same element by dividing the gate of the vacuum microelement. When operating normally, the main current is controlled by the main switch unit, but the overvoltage protection unit does not operate. When a voltage higher than the protection level is applied between the A and K of the vacuum micro device, the overvoltage detection means outputs an abnormality detection signal, and in response to this, the gate pulse generation means generates an ON signal to the gate to turn on the overvoltage protection part. . When the voltage becomes lower than the protection level, the output of the overvoltage detection means is stopped and the overvoltage protection unit is turned off again.

In the vacuum microswitch according to the second and third aspects of the present invention, the main switch section and the overvoltage protection section are formed in the same element by dividing the gate of the vacuum microelement. When operating normally, the main current is controlled by the main switch unit, but the overvoltage protection unit does not operate.
When a voltage higher than the protection level is applied between the A and K of the vacuum micro device, the overvoltage detection means outputs an abnormality detection signal, and in response to this, the gate pulse generation means generates an ON signal to the gate to turn on the overvoltage protection part. . At this time, a current limited by the resistance layer provided in the emitter flows through the overvoltage protection unit. When the voltage becomes lower than the protection level, the output of the overvoltage detection means is stopped and the overvoltage protection unit is turned off again.

A vacuum microswitch according to a fourth aspect of the present invention has a characteristic peculiar to a vacuum microdevice, that is, A-
Constant ratio n to the current between K (usually about n = 0.2)
This utilizes the characteristic that the current of (3) flows between the gate and the cathode.

In the vacuum microswitch according to the fourth aspect of the present invention, the main switch section and the overvoltage protection section are formed in the same element by dividing the gate of the vacuum microelement.
When operating normally, the main current is controlled by the main switch unit, but the overvoltage protection unit does not operate. When a voltage higher than the protection level is applied between the A and K of the vacuum micro device, the overvoltage detecting means outputs an abnormality detection signal. On the other hand, the current detection unit detects the gate-cathode current of the overvoltage protection unit, and the determination unit determines whether the detection signal is an overcurrent. The start-up command means is based on the overvoltage detection signal from the overvoltage detection means and the discrimination signal from the discrimination means, and the anode-cathode of the vacuum micro element is overvoltage, and the gate-cathode of the overvoltage protection unit of the vacuum microelement is When the current flowing in the gate is smaller than a predetermined reference voltage, a start command is output, and in response to this, the gate pulse generation means generates an ON signal to the gate, and the overvoltage protection unit is turned on.

According to the fifth and sixth aspects of the present invention, the main switch section and the overvoltage protection section are formed in the same element by dividing the gate of the vacuum micro element. When operating normally, the main current is controlled by the main switch unit, but the overvoltage protection unit does not operate.
When a voltage higher than the protection level is applied between A and K of the vacuum micro device, the overvoltage detection circuit outputs an abnormality detection signal, and in response to this, the gate pulse generator generates an ON signal to the gate and the overvoltage protection unit is turned ON. . When a current over the allowable current Iomax flows into the overvoltage protection unit, nI is generated between the gate and the cathode.
Since the current of omax flows, the gate voltage becomes lower than the threshold voltage due to the voltage drop generated in the resistor R, and the current of the overvoltage protection unit is limited. When the current is below the allowable current, the gate voltage is above the threshold voltage,
The overvoltage protection unit is turned on again.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram of a vacuum micro device according to a first embodiment of the present invention.

In FIG. 1, a vacuum micro device (hereinafter,
In VMD), the gate is divided into two gates G0 and G1, whereby a main switch section 10 and an overvoltage protection section 11 are formed in the same element.

The main switch section 10 comprises a cathode K having a plurality of conical emitters, a gate G0 arranged around the emitters, and an anode A facing the gate G0. In order to turn on / off the main current to the gate G0. The drive device 12 which supplies the drive signal of is connected.

The overvoltage protection unit 11 comprises a cathode K having a plurality of conical emitters, a gate G1 arranged around the emitters, and an anode A facing the gate G1.
A protection circuit including an overvoltage detection circuit 13 for detecting an overvoltage applied between A and K of MD, and a gate pulse generator 14 for applying a positive voltage to a gate G1 based on an overvoltage detection signal from the overvoltage detection circuit 13. 15 are connected. .

The overvoltage detection circuit 13 sets the overvoltage protection level at a voltage below the breakdown voltage at which vacuum insulation breakdown occurs,
When the AK voltage of VMD exceeds the overvoltage protection level, it is determined as an overvoltage.

Next, the operation of the first embodiment will be described. When the AK voltage of VMD is equal to or lower than the overvoltage protection level, the overvoltage protection unit 11 does not operate, and the main switch unit 10 operates by the ON signal of the driving device 12.

When the AK voltage of VMD is equal to or higher than the overvoltage protection level, the overvoltage detection circuit 13 detects the overvoltage and operates the gate pulse generator 14 to turn on the overvoltage protection unit 11. This action causes V
The AK voltage of MD is bypassed.

When the voltage between A and K of VMD decreases below the overvoltage protection level, the operation of the gate pulse generator 14 is stopped and the overvoltage protection unit 11 is turned off. In this way, the gate is divided and the overvoltage protection unit is built in the same element, and when the overvoltage is detected, the overvoltage protection unit is automatically turned on to bypass and suppress the overvoltage. A reliable vacuum microswitch is obtained.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a schematic view of a vacuum micro device according to a second embodiment of the present invention. In FIG. 2, VMD is
The gate is divided into two, G0 and G1, so that the main switch section 20 and the overvoltage protection section 21 are formed in the same element.

The main switch section 20 is composed of a cathode K having a plurality of conical emitters, a gate G0 arranged around the emitters, and an anode A facing the gate G0. The gate G0 turns on / off the main current. The drive device 12 which supplies the drive signal of is connected.

The overvoltage protection portion 21 comprises a cathode K having a plurality of conical emitters, a gate G1 arranged around the emitter, an anode A facing the gate G1, and a resistance layer 22 formed under the emitter. VMK AK
Overvoltage detection circuit 13 for detecting overvoltage applied between
And a gate pulse generator 14 for applying a positive voltage to the gate G1 based on the overvoltage detection signal from the overvoltage detection circuit 13.
The protection circuit 15 including is connected. Overvoltage protection unit 2
The resistance value R of the resistance layer 22 formed under the emitter of No. 1 is given by the following equation.

[0030]

[Formula 1] R ≥ Vpro / Iomax, where Vpro: VMD overvoltage protection level Iomax: Maximum allowable current (breakdown current) of the overvoltage protection unit The overvoltage detection circuit 13 has a protection level at a voltage below the breakdown voltage at which vacuum insulation breakdown occurs. Is set, and it is determined that the voltage is overvoltage when the voltage between the AK of VMD exceeds the overvoltage protection level.

Next, the operation of the second embodiment will be described. When the AK voltage of VMD is equal to or lower than the overvoltage protection level, the overvoltage protection unit 21 does not operate, and the main switch unit 20 operates by the ON signal of the drive device 12.

When the AK voltage of VMD is equal to or higher than the overvoltage protection level, the overvoltage detection circuit 13 detects the overvoltage and operates the gate pulse generator 14 to turn on the overvoltage protection unit 21. This action causes V
Although the voltage between A and K of MD is bypassed, the current flowing in the overvoltage protection unit 21 at this time is limited to the maximum allowable current Iomax or less by the resistance layer 22 formed in the emitter.

When the voltage between the A and K of VMD decreases below the overvoltage protection level, the operation of the gate pulse generator 14 is stopped and the overvoltage protection unit 21 is turned off. In this way, the gate is divided and the overvoltage protection unit is built in the same element, and when an overvoltage is detected, the overvoltage protection unit is automatically turned on to bypass and suppress the overvoltage. A highly reliable vacuum microswitch can be obtained by providing a function of preventing damage and characteristic deterioration of the protective part due to overcurrent.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a schematic view of a vacuum micro device according to a third embodiment of the present invention. In FIG. 3, VMD is
The gate is divided into two, G0 and G1, whereby a main switch section 30 and an overvoltage protection section 31 are formed in the same element.

The main switch section 30 is composed of a cathode K having a plurality of conical emitters, a gate G0 arranged around the emitters, and an anode A facing the gate G0, for turning on and off the main current to the gate G0. The drive device 12 which supplies the drive signal of is connected.

The overvoltage protection unit 31 is composed of a cathode K having a plurality of conical emitters, a gate G1 arranged around the emitters, and an anode A facing the gate G1.
An overvoltage detection circuit 13 for detecting an overvoltage applied between A and K of MD, a gate pulse generator 14 for applying a positive voltage to a gate G1, and a current transformer for detecting a current between G1 and K of an overvoltage protection unit 31. Circuit 32, a comparator 33 that compares the detection signal of the current transformer 32 with a reference voltage, and a protection circuit 35 that includes an AND circuit 34 that performs a logical product of the output of the comparator 33 and the output of the overvoltage detection circuit 13 are connected. To be done.

The overvoltage detection circuit 13 sets the protection level at a voltage equal to or lower than the breakdown voltage at which vacuum insulation breakdown occurs, and VMD
When the voltage between A and K becomes higher than the overvoltage protection level, it is judged as an overvoltage, and a high level signal is output, and when it is lower than the overvoltage protection level, a low level signal is output.

The reference voltage of the comparator 33 is set to the output voltage of the current transformer 32 when nIomax flows between G1 and K, where Imax is the maximum allowable current of the overvoltage protection unit 31. Here, n is the ratio of the current between G1 and K and the current between A and K. Then, the comparator 33 includes the current transformer 3
When the output of 2 is smaller than the reference voltage, a high level signal is output, and when the output of the current transformer 32 is larger than the reference voltage, a low level signal is output.

Next, the operation of the third embodiment will be described. When the AK voltage of VMD is equal to or lower than the overvoltage protection level, the overvoltage protection unit 31 does not operate, and the main switch unit 30 operates by the ON signal of the drive device 12.

When the AK voltage of VMD is equal to or higher than the overvoltage protection level, the output of the overvoltage detection circuit 13 becomes high level. At this time, when the AK current of the overvoltage protection unit 31 is less than or equal to the allowable current Iomax, the output of the comparator is at a high level, and the logical product of the outputs of the AND circuits 34 is true. It operates and the overvoltage protection unit 31 is turned on. By this operation, VMD A
The -K voltage is bypassed.

When the current of the overvoltage protection unit 31 exceeds Iomax, the current between G1 and K becomes nIomax or more and the output of the current transformer 32 exceeds the reference voltage.
Output goes low. As a result, the comparator 33
And the output of the overvoltage detection circuit 13 is AN
Since the output of the D circuit 34 is false, the gate pulse generator 14 does not operate and the overvoltage protection unit 31 starts to turn off. This operation limits the current of the overvoltage protection unit 31.

Then, the current of the overvoltage protection unit 31 becomes Iomax.
When it is reduced to below, the comparator output becomes high level again, and the logical product of the outputs of the AND circuits 34 becomes true, so that the gate pulse generator 14 operates and the overvoltage protection unit 3 operates.
1 is turned on. By this operation, VMD AK
Voltage is bypassed.

Further, when the voltage between VM and AK of VMD decreases below the overvoltage protection level, the gate pulse generator 14
Is stopped, and the overvoltage protection unit 31 is turned off.
In this way, the gate is divided and the overvoltage protection unit is built in the same element. When the overvoltage is detected, the overvoltage protection unit is automatically turned on to bypass and suppress the overvoltage. -K current is used as an overcurrent monitor, and when an overcurrent is detected, it cuts off the ON signal to the overvoltage protection unit to prevent destruction and characteristic deterioration due to overcurrent in the overvoltage protection unit. A vacuum microswitch designed to be realized is obtained.

In this embodiment, the current is detected by using the current transformer, but a shunt or the like may be applied. Next, a fourth embodiment of the present invention will be described with reference to FIG.

FIG. 4 is a schematic view of a vacuum micro device according to the fourth embodiment of the present invention. In FIG. 4, the VMD has a gate divided into two gates G0 and G1, whereby a main switch section 40 and an overvoltage protection section 41 are formed in the same element.

The main switch section 40 is composed of a cathode K having a plurality of conical emitters, a gate G0 disposed around the emitters, and an anode A facing the gate G0, for turning on / off the main current to the gate G0. The drive device 12 which supplies the drive signal of is connected.

The overvoltage protection section 41 comprises a cathode K having a plurality of conical emitters, a gate G1 arranged around the emitters, and an anode A facing the gate G1.
An overvoltage detection circuit 13 for detecting an overvoltage applied between AK of MD, a gate pulse generator 14 for applying a positive voltage to a gate G1 based on an overvoltage detection signal of the overvoltage detection circuit 13, and a gate pulse generator A protection circuit 43 consisting of 14 and a resistor 42 inserted between the gate G1 is connected.

The overvoltage detection circuit 13 sets the protection level at a voltage equal to or lower than the breakdown voltage at which vacuum insulation breakdown occurs, and VMD
When the voltage between A and K becomes higher than the overvoltage protection level, it is judged as an overvoltage. The resistance value R of the resistor 42 is given by the following equation.

[0049]

## EQU00002 ## R = (Vgo-Vth) / (nIomax) where Vgo: output voltage of the gate pulse generator Vth: threshold voltage (minimum turn-on voltage) of the vacuum micro element Iomax: maximum allowable current of the overvoltage protection part n: Ratio of G1-K Current and AK Current Next, the operation of the fourth embodiment will be described.

When the voltage between the AK of VMD is below the overvoltage protection level, the overvoltage protection unit 41 does not operate, and the main switch unit 40 operates by the ON signal of the drive unit 12.
When the AK voltage of VMD is equal to or higher than the overvoltage protection level, the overvoltage detection circuit 13 detects the overvoltage and operates the gate pulse generator 14.

At this time, if a current of Iomax or less, that is, a current of (Iomax-ΔIo) is flowing between A and K of the overvoltage protection unit 41, the voltage drop due to the resistor 42 is R ·
n (Iomax-.DELTA.Io), and the voltage Vg applied to the gate G1 is given by the following equation.

[0052]

## EQU3 ## Vg = Vgo-R.n (Iomax-.DELTA.Io) = Vth + (Vgo-Vth) .DELTA.Io / Iomax> Vth Therefore, the voltage Vg applied to the gate G1 becomes equal to or higher than the threshold voltage Vth. The overvoltage protection unit 21 is turned on. This operation bypasses the AK voltage of VMD.

If the AK current of the overvoltage protection unit 41 is Iomax or more, that is, a current of (Iomax + ΔIo) is flowing, the voltage drop across the resistor 42 is R · n (I
omax-ΔIo) and the voltage V applied to the gate G1
g becomes as follows.

[0054]

Vg = Vgo−R · n (Iomax + ΔIo) = Vth− (Vgo−Vth) ΔIo / Iomax <Vth Therefore, the voltage Vg applied to the gate G1 becomes equal to or lower than the threshold voltage Vth. The protection unit 41 starts to turn off. This operation limits the current of the overvoltage protection unit 1.

As described above, the gate is divided and the overvoltage protection unit is built in the same element. When the overvoltage is detected, the overvoltage protection unit is automatically turned on to bypass and suppress the overvoltage. In addition, when the applied voltage of the gate G1 is automatically increased / decreased due to the increase / decrease of the current between G1 and K, and the overcurrent flows, the gate voltage of the overvoltage protection unit is set below the threshold voltage, and the overvoltage protection unit is destroyed due to the overcurrent and the characteristics are deteriorated. A vacuum micro switch with high reliability can be obtained by providing a function of preventing the above.

[0056]

As described above, in the vacuum microswitch according to claim 1 of the present invention, the gate is divided and the overvoltage protection unit is built in the same element, and the overvoltage protection unit is automatically activated when an overvoltage is detected. A highly reliable vacuum microswitch can be obtained by having a function of bypassing overvoltage by turning on the switch.

In the vacuum microswitch according to the second aspect of the present invention, the gate is divided and the overvoltage protection unit is built in the same element. When the overvoltage is detected, the overvoltage protection unit is automatically turned on to prevent the overvoltage. A highly reliable vacuum microswitch can be obtained by providing a function of bypassing and further providing a function of preventing destruction and characteristic deterioration due to overcurrent of the overvoltage protection unit.

In the vacuum microswitch according to the third aspect of the present invention, the gate is divided and the overvoltage protection unit is built in the same element. When the overvoltage is detected, the overvoltage protection unit is automatically turned on to prevent the overvoltage. A highly reliable vacuum microswitch can be obtained by providing a function of bypassing and further providing a function of preventing destruction and characteristic deterioration due to overcurrent of the overvoltage protection unit.

In the vacuum microswitch according to claim 4 of the present invention, the gate is divided and the overvoltage protection unit is built in the same element, and when the overvoltage is detected, the overvoltage protection unit is automatically turned on to prevent the overvoltage. By providing a bypass function, the current between G1 and K is used as an overcurrent monitor, and when an overcurrent is detected, the ON signal to the overvoltage protection unit is shut off to prevent damage and characteristics deterioration of the overvoltage protection unit due to overcurrent. A vacuum micro switch with high reliability can be obtained by adding functions.

In the vacuum microswitch according to claim 5 of the present invention, the gate is divided and the overvoltage protection unit is built in the same element, and when the overvoltage is detected, the overvoltage protection unit is automatically turned on to prevent the overvoltage. When the overcurrent protection circuit has a bypass function and the applied voltage of the gate G1 is automatically increased or decreased by the increase or decrease of the current between G1 and K, the gate voltage of the overvoltage protection unit is set below the threshold voltage and the overvoltage protection unit A vacuum micro switch with high reliability can be obtained by providing a function of preventing destruction and characteristic deterioration due to electric current.

In the vacuum microswitch according to the sixth aspect of the present invention, the gate is divided and the overvoltage protection unit is built in the same element. When the overvoltage is detected, the overvoltage protection unit is automatically turned on to prevent the overvoltage. When the overcurrent protection circuit has a bypass function and the applied voltage of the gate G1 is automatically increased or decreased by the increase or decrease of the current between G1 and K, the gate voltage of the overvoltage protection unit is set below the threshold voltage and the overvoltage protection unit A vacuum micro switch with high reliability can be obtained by providing a function of preventing destruction and characteristic deterioration due to electric current.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of the present invention.

FIG. 4 is a configuration diagram showing a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a basic structure of a vacuum micro device.

[Explanation of symbols]

 10, 20, 30, 40 ... Main switch unit 11, 21, 31, 41 ... Overvoltage protection unit 12 ... Driving device 13 ... Overvoltage detection circuit 14 ... Gate pulse generator 32 ...・ Current transformer 33 ・ ・ ・ Comparator 34 ・ ・ ・ AND circuit 42 ・ ・ ・ Resistance

Claims (6)

[Claims] 1. A vacuum having a field emission cold cathode comprising a cathode having an emitter and a gate for controlling a flow of electrons emitted from the emitter, and an anode arranged so as to face the field emission cold cathode. In a vacuum micro switch for driving a micro device by a drive signal from a driving means, a gate of the vacuum micro device is divided into a plurality of parts, a main switch part for supplying a main current to the vacuum micro device and an overvoltage for supplying a current when an overvoltage occurs. A protection unit is provided, drive means for applying a drive signal for controlling a main current to the gate of the main switch section, and an anode of the vacuum micro element.
A vacuum micro, comprising: an overvoltage detecting means for detecting an overvoltage between the cathodes; and a gate pulse generating means for receiving an overvoltage detection signal from the overvoltage detecting means and giving a drive signal to a gate of the overvoltage protection part. switch. 2. The vacuum microswitch according to claim 1, wherein a resistance layer for limiting a current is provided below the emitter of the overvoltage protection unit. 3. The resistance value of the resistance layer of the overvoltage protection unit is R ≧ Vpro / Iomax Vpro: overvoltage protection level of the vacuum micro device Iomax: maximum allowable current of the overvoltage protection unit. Vacuum micro switch. 4. A vacuum having a field emission cold cathode comprising a cathode having an emitter and a gate for controlling a flow of electrons emitted from the emitter, and an anode arranged so as to face the field emission cold cathode. In a vacuum micro switch for driving a micro element by a signal from a driving means, the gate of the vacuum micro element is divided into a plurality of parts,
A drive means for providing a drive signal for controlling the main current to the gate of the main switch portion, wherein a main switch portion for supplying a main current to the vacuum micro element and an overvoltage protection portion for supplying a current when an overvoltage is generated are provided, and the vacuum micro element. Of overvoltage detecting means for detecting an overvoltage between the anode and the cathode, a current detecting means for detecting a current flowing between the gate and the cathode of the overvoltage protection part of the vacuum microelement, a detection signal from the current detecting means and a predetermined signal. Discriminating means for comparing reference voltages to discriminate whether the detection signal is larger or smaller than the reference voltage, and an anode of the vacuum micro element based on the overvoltage detection signal from the overvoltage detection means and the discrimination signal from the discrimination means. -The cathode has an overvoltage, and the current flowing between the gate and the cathode of the overvoltage protection unit of the vacuum micro device is a predetermined reference voltage. A vacuum comprising: a start command means for outputting a start command when it is smaller, and a gate pulse generation means for receiving a start command from the start command means and giving a drive signal to the gate of the overvoltage protection unit. Microswitch. 5. A vacuum having a field emission cold cathode comprising a cathode having an emitter and a gate for controlling a flow of electrons emitted from the emitter, and an anode arranged so as to face the field emission cold cathode. In a vacuum micro switch for driving a micro element by a signal from a driving means, the gate of the vacuum micro element is divided into a plurality of parts,
A drive means for providing a drive signal for controlling the main current to the gate of the main switch portion, wherein a main switch portion for supplying a main current to the vacuum micro element and an overvoltage protection portion for supplying a current when an overvoltage is generated are provided, and the vacuum micro element. An overvoltage detecting means for detecting an overvoltage between the anode and the cathode, a gate pulse generating means for receiving a overvoltage detection signal from the overvoltage detecting means and giving a drive signal to the gate of the overvoltage protection part, and the gate pulse generating means. And a resistor inserted between the gates of the overvoltage protection unit. 6. The resistance value of a resistor inserted between the gate pulse generating means and the gate of the overvoltage protection unit is R = (Vgo-Vth) / (nIomax) Vgo: output voltage Vth of the gate pulse generating means: vacuum 6. The vacuum microswitch according to claim 5, wherein the threshold voltage Iomax of the micro device is the maximum allowable current of the overvoltage protection unit, and n is the ratio of the gate-cathode current and the anode-cathode current of the overvoltage protection unit.