JPH04233821A - High voltage switch and switching method for the same switch - Google Patents

Abstract

PURPOSE:To attain high speed and to improve the dielectric strength and the reliability of the high voltage switch. CONSTITUTION:The high voltage switch is configurated, which consists of semiconductor switch groups 11, 12 each comprising plural sets of series connection of semiconductor switches 10 being a combination of a p-channel semiconductor layer and an n-channel semiconductor layer, and the high voltage switch is switched by using an ignition circuit or a break-over means so as to turn on part of semiconductor switches of the said semiconductor switch groups 11, 12 thereby breaking over and resulting in a turning on state the remaining semiconductor switches.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a high-voltage switch for discharging high voltage, and for suppressing spark discharge that occurs when a grounded article to be coated approaches a high-voltage electrode in an electrostatic coating device, for example. , relates to a high voltage switch interposed between a high voltage power supply and ground, and a switching method for the high voltage switch.

0002

2. Description of the Related Art A high voltage switch conventionally used in an electrostatic coating apparatus will be explained. As shown in FIG. 3, the electrostatic coating device for the cup-type electrostatic coating method includes a DC high-voltage power supply device 1 comprising a variable DC high-voltage generator E, etc., a bowl-shaped cup 2 serving as a high-voltage electrode, It includes a high voltage switch 3 connected between the high voltage electrode side and the low voltage terminal (ground). The high voltage switch 3 includes a plurality of reverse blocking three-terminal thyristors (hereinafter simply referred to as thyristors) S (
Several tens of thyristors) are connected in series, and the gate of thyristor S
An ignition device 4 is connected to G. In the figure, each resistor R is a current limiting resistor. Then, while applying a high voltage from the DC high voltage power supply device 1 to the cup 2,
When the cup 2 is rotated at high speed and paint flows out from the center of the cup 2, the paint is sprayed from around the cup as charged paint particles due to centrifugal force, and the paint particles are grounded to the object 5 to be painted. is sorbed by Coulomb force.

As the ignition device 4 for the high voltage switch 3, a method has been proposed in which simultaneous ignition is performed by magnetic coupling, as shown in FIG. 4, for example. A rod-shaped ferrite core 40 is used as a magnetic core for transmitting ignition energy, and a trigger winding 41 is wound around one end of this ferrite core 40, while a gate G of each thyristor S is wound around the other end. An ignition winding 42 that connects the cathode K side is wound thereon. When a pulse is applied to the trigger winding 41, each ignition winding 42
The ignition energy is magnetically transmitted to the thyristors S, and the entire high voltage switch 3 can be turned on by turning on each thyristor S.

That is, during painting, when the spark discharge occurrence prediction circuit 12 provided in the DC high voltage power supply device 1 generates a spark discharge occurrence prediction signal based on the detection signal from the current detection circuit 11, the drive circuit 13 causes the spark discharge occurrence prediction signal to be generated. A pulse is applied to the trigger winding 41 of the ignition device 4, closing the high voltage switch 3. When the high voltage switch 3 is closed, the ground capacity C1 of the high voltage cable 6 connecting between the output terminal O of the DC high voltage power supply 1 and the input terminal I of the electrostatic painting gun is
The charges charged in the cup 2 and the object to be coated, and the charges charged in the capacitor C2 formed between the cup 2 and the ground are discharged via the high voltage switch 3. According to the above-mentioned ignition device having the structure of a high voltage switch, compared to a method in which a pulse is applied to each gate G of each thyristor S,
It has the advantage that multiple thyristors can be activated simultaneously with a simple structure.

[Problem to be solved by the invention]

However, according to the high voltage switch having the above structure, since the ferrite core 40 is used as the ignition device 4, the ignition energy is transmitted to the ignition winding 42 by the pulse applied to the trigger winding 41. is trigger winding 4
The farther the distance from 1, the more delay there will be. Therefore, in a high voltage switch with a withstand voltage of about 100 kV in which about 120 thyristors S are connected, the delay in transmission does not affect the operating speed of the switch, but there are the following problems.

That is, the thyristor S has a cross-sectional structure as shown in FIG.
It is constructed by stacking a type semiconductor layer and an n-type semiconductor layer, and providing a gate G in the p-type semiconductor layer on the center side. Immediately after a voltage is applied to the gate G, electrons do not move over the entire interface between the p-type semiconductor layer and the n-type semiconductor layer, but the part close to the gate G becomes a channel, and then The area is expanding. Therefore, immediately after the high voltage switch is turned on, the channel area of the thyristor S whose ignition winding 42, which is far from the trigger winding 41, is connected to the gate G is equal to the channel area of the other thyristor S. Since the area is small compared to the area, a large current tends to flow through this area, creating a so-called hot spot, which leads to deterioration.

The present invention has been made in view of the above-mentioned circumstances, and aims to provide a high-voltage switch and a switching method therefor that can achieve high withstand voltage and high speed, and also have high reliability and a simple structure. The purpose is

[0008]

[Means for Solving the Problems] In order to solve the problems of the above-mentioned conventional example, a high voltage switch according to claim 1 includes a plurality of semiconductor switches each consisting of a combination of a p-type semiconductor layer and an n-type semiconductor layer connected in series. It is characterized by comprising a group of connected semiconductor switches and a voltage applying means for applying a voltage to appropriate locations where the semiconductor switches are connected.

A high voltage switch according to a second aspect of the present invention includes: a first semiconductor switch group in which a plurality of semiconductor switches formed by combining a p-type semiconductor layer and an n-type semiconductor layer are connected in series; a second semiconductor switch group connected to the first semiconductor switch group, which is formed by connecting a plurality of semiconductor switches in series, which are formed by combining a semiconductor layer with a semiconductor layer and forming a gate part; It is characterized by comprising an ignition circuit that applies a voltage to the gate portion of each semiconductor switch constituting the semiconductor switch group.

[0010] The high voltage switch switching method according to claim 3 turns on some of the semiconductor switches of a semiconductor switch group formed by connecting a plurality of semiconductor switches in series, each of which is a combination of a p-type semiconductor layer and an n-type semiconductor layer. The feature is that by setting the switch to the state, the remaining semiconductor switches are caused to break over and are turned on.

[0011]

According to the high voltage switch according to claim 1, when a voltage is applied to the point where the semiconductor switches are connected, the semiconductor switch connected between the voltage application point and the ground becomes a breaker. The semiconductor switch connected between the voltage application point and the high voltage side then breaks over and becomes a short circuit state, making the entire high voltage switch conductive.

0012
According to the high voltage switch according to claim 2, when a voltage is applied from the ignition circuit to each gate portion of the second semiconductor switch group, the second semiconductor switch group is turned on, and then the second semiconductor switch group is turned on. The first group of semiconductor switches breaks over and becomes short-circuited, making the entire high-voltage switch conductive.

According to the high voltage switch switching method according to claim 3, by turning on some of the semiconductor switches in the semiconductor switch group in which a plurality of semiconductor switches are connected in series, this is used as a trigger to switch on the remaining semiconductor switches. It is possible to cause the semiconductor switches in the semiconductor switch to break over and make the entire semiconductor switch group conductive.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an equivalent circuit of a high voltage switch, which is used for high voltage short-circuiting in the electrostatic coating apparatus shown in FIG. 3, for example.

The high voltage switch includes a first semiconductor switch group 11 in which 90 semiconductor switches 10 are connected in series, a second semiconductor switch group 12 in which 30 semiconductor switches 10 are connected in series, and a first semiconductor switch group 11 in which 90 semiconductor switches 10 are connected in series. semiconductor switch group 11
and a voltage applying means 13 for applying a voltage to the connection portion (point C) with the second semiconductor switch group 12. The terminal A at the end of the first semiconductor switch group 11 is connected to the high voltage side (-
90 kV), and terminal B at the end of the second semiconductor switch group 12 is grounded.

Each semiconductor switch 10 has a forward direction thyristor S on the terminal A side and a gate G of the thyristor S.
and a gate resistor RGK connected between the cathode K and the gate resistor RGK. Gate resistor RGK is provided to maximize the withstand voltage value of thyristor S. Since the withstand voltage value of each thyristor S is about 900V, the entire switch including 120 thyristors S connected in series can have a withstand voltage of about 108 kV. In addition, each semiconductor switch 10
A current limiting resistor R1 that protects the thyristor S by limiting the current value when a short-circuit current flows is connected to each of them. In addition, a voltage dividing resistor R2 is connected in parallel to each semiconductor switch 10 and current limiting resistor R1 to keep the voltage applied to each thyristor S constant. Due to its nature, the breakover voltage of the thyristor S varies depending on the individual thyristors S. Therefore, by connecting the voltage dividing resistor R2, the voltage applied to each thyristor S is set to a constant voltage that is lower than the voltage that causes any of the thyristors S to break over, and each thyristor S is stabilized. ing.

The voltage applying means 13 includes a pulse transformer 14
, a DC power supply 15 that supplies voltage to the primary side of the pulse transformer 14 , and a switching element 16 . One end of the secondary side of the pulse transformer 14 is connected to point C, which is the connecting portion between the first semiconductor switch group 11 and the second semiconductor switch group 12. pulse transformer 1
The other end of the secondary side of 4 is connected to point D, which is obtained by dividing the high voltage applied between terminals A and B by resistor R3 and resistor R4. Resistance R3 and resistance R4 are R3:R4
By setting the value of 3:1, the potentials at points C and D are at the same potential (-22.5V), so that in normal cases, no potential difference will occur between both ends of the secondary side of the pulse transformer 14. It has become.

FIG. 3 shows a high voltage switch having the above structure.
When applied to the electrostatic coating device shown in FIG. A current is applied to the primary side of 14 and flows. Then, a voltage of about -10 kV is generated on the secondary side of the pulse transformer 14 by magnetic coupling.

As a result, the potential at point C becomes about -30 kV, which exceeds the withstand voltage of 27 kV (-900 V x 30) of the second semiconductor switch group 12, so that each thyristor S of the second semiconductor switch group 12 breaks over and becomes short-circuited.

When the second semiconductor switch group 12 is short-circuited, the voltage at point C becomes 0V, so -90 kV is applied to both ends of the first semiconductor switch group 11. This voltage is the first
The withstand voltage of the semiconductor switch group 11 is -81kV
(-900V x 90), each thyristor S of the first semiconductor switch group 11 breaks over and becomes short-circuited, and the entire switch becomes conductive.

In the above embodiment, the thyristor S was used as the semiconductor switch 10, but a two-way two-terminal thyristor (SSS) may also be used. In this case, a two-way two-terminal thyristor is connected to the thyristor S in FIG. 1, and since the two-way two-terminal thyristor does not have a gate terminal, the gate resistor RGK in this embodiment can be omitted. can.

Further, in the above embodiment, the same potential as the point C is applied to the point D on the secondary side of the pulse transformer 14, which is obtained by dividing the high voltage applied to the high voltage switch. A configuration in which an external DC power supply that provides the same potential as point C may be directly connected may be used. Alternatively, the voltage may be obtained by transforming the DC high voltage power supply 1 (FIG. 1) which is the power source of the electrostatic coating apparatus.

FIG. 2 shows another embodiment of the present invention.
The second semiconductor switch 12 in FIG. 1 is turned on using a conventional ignition method. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals.

That is, the semiconductor switches 10 constituting the first semiconductor switch group 11 are composed of two-way two-terminal thyristors (SSS). Further, the semiconductor switches 10 constituting the second group of semiconductor switches 12 are composed of thyristors, and the gate G of each thyristor is connected to the ignition circuit 17.
It is connected to the. The ignition circuit 17 is one that gives a pulse to each gate G based on the signal from the drive circuit 13 (Fig. 3) of the electrostatic coating device, and a ferrite core is used as shown in the conventional example shown in Fig. 5. A simultaneous firing method using magnetic coupling may also be used. According to this embodiment, since the number of semiconductor switches 10 constituting the second group of semiconductor switches 12 is small, the problems described in the conventional example do not occur even if the simultaneous firing method using magnetic coupling is used. .

Further, in FIG. 2, the semiconductor switches 10 constituting the second group of semiconductor switches 12 are composed of optical thyristors that apply optical signals to their gates, and the ignition circuit 17 is used as an optical signal generator. For example, the switching operation of the second group of semiconductor switches 12 can be performed at extremely high speed, and the switching speed of the entire high voltage switch can be improved. Furthermore, since an optical signal is used as the gate signal, the insulation from the high voltage device in the ignition circuit 17 can be improved.

As described above, according to this embodiment, since a plurality of semiconductor switches are connected in series to form a high voltage switch, it is possible to increase the withstand voltage and speed up the switch operation. In addition, by turning on a part of the semiconductor switches in a semiconductor switch group in which multiple semiconductor switches are connected in series, this triggers the remaining semiconductor switches to break over, causing the entire semiconductor switch group to turn on. is in a conductive state. In conduction due to breakover, electrons try to flow instantaneously across the entire interface between the p-type semiconductor and the n-type semiconductor, so hot spots as described in the conventional example do not occur. It is possible to improve the reliability of a high voltage switch in which a plurality of semiconductor switches are connected in series.

Furthermore, in the above embodiment, a high voltage switch used in an electrostatic coating device was explained as an example, but it is not limited to an electrostatic coating device, but can be used in any device that uses a high voltage power source where a short circuit is required. Can be applied.

[0028]

According to the present invention, a high voltage switch is constructed by connecting a plurality of semiconductor switches in series, and this is triggered by turning on some of the semiconductor switches of the high voltage switches. As a result, the remaining semiconductor switches are brought into breakover, and the entire high-voltage switch is brought into conduction, thereby achieving high withstand voltage and high speed.
A highly reliable high voltage switch can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an equivalent circuit diagram showing an embodiment of a high voltage switch of the present invention.

FIG. 2 is an equivalent circuit diagram showing another embodiment of the high voltage switch of the present invention.

FIG. 3 is an equivalent circuit diagram showing the entire electrostatic coating device.

FIG. 4 is an explanatory diagram showing the structure of a conventional high voltage switch.

FIG. 5 is an explanatory diagram showing the structure of a thyristor.

[Explanation of symbols]

10　Semiconductor switch 11 First semiconductor switch group 12 Second semiconductor switch group 13 Voltage application means 14 Pulse transformer 15 DC power supply 16 Switching element S Thyristor

Claims (3)

[Claims] [Claim 1] A semiconductor switch group in which a plurality of semiconductor switches formed by combining a p-type semiconductor layer and an n-type semiconductor layer are connected in series, and a voltage is applied to appropriate locations where the semiconductor switches are connected. A high voltage switch comprising: voltage application means. 2. A first semiconductor switch group in which a plurality of semiconductor switches each having a combination of a p-type semiconductor layer and an n-type semiconductor layer are connected in series; - a second semiconductor switch group connected to the first semiconductor switch group, which is formed by connecting a plurality of semiconductor switches formed by forming a second semiconductor switch group in series;
A high voltage switch comprising: an ignition circuit that applies a voltage to the gate portion of each semiconductor switch constituting the second semiconductor switch group. 3. By turning on some of the semiconductor switches in a semiconductor switch group formed by connecting a plurality of semiconductor switches in series, each of which is a combination of a p-type semiconductor layer and an n-type semiconductor layer, the remaining semiconductor switches are turned on. breakover
1. A method for switching a high voltage switch, which is characterized in that the high voltage switch is turned on.