JP4673653B2 - Abnormal discharge prevention method and vacuum apparatus in vacuum apparatus - Google Patents

Description

  The present invention relates to a method for preventing abnormal discharge in a vacuum apparatus such as a PVD apparatus, a CVD apparatus, a sputtering apparatus, or an electron beam evaporation apparatus using plasma generated in a vacuum, and a vacuum apparatus.

  Conventionally, a vacuum such as a PVD apparatus, a CVD apparatus, a sputtering apparatus, an etching apparatus, or an electron beam vapor deposition apparatus that includes a vacuum load that uses plasma generated in a vacuum and a power supply device that supplies power to the vacuum load. In the apparatus, the interelectrode impedance of the electrodes of the vacuum load may decrease, or foreign substances such as conductive dust may short-circuit between the electrodes. In such a case, the plasma generated in the vacuum of the vacuum load temporarily shifts to abnormal discharge such as abnormal discharge, or in the electron beam vapor deposition apparatus, a high potential filament and surrounding electrodes An abnormal discharge may occur between the two. In particular, when an abnormal discharge occurs in the sputtering apparatus, there is a problem that the target melts and gives a defect to a substrate material such as a liquid crystal panel during the sputtering, thereby reducing the product yield. In addition, in the electron beam evaporation apparatus, the filament is broken by the discharge energy.

  Therefore, the occurrence of such abnormal discharge must be prevented, and an abnormal discharge prevention technique has already been proposed (see, for example, Patent Documents 1 and 2). An outline will be described with reference to FIG. 5 showing a circuit configuration of a typical vacuum apparatus for realizing the abnormal discharge preventing method according to Patent Document 1. In FIG. 5, an inductor 3 is connected in series between the negative electrode of the DC input power source 1 and the vacuum load 2, and a reverse voltage pulse generation circuit 4 that applies a reverse voltage to the vacuum load 2 is provided. The reverse voltage pulse generation circuit 4 is a gate signal that selectively drives the reverse voltage source 6 and the semiconductor switch element 5 having a polarity opposite to that of the voltage of the semiconductor switch element 5 and the DC input power source 1 such as IGBT or MOSFET. And generating circuit 7. In the vacuum apparatus having such a configuration, even when no abnormal discharge occurs, the semiconductor switch element 5 is repeatedly turned on and off continuously at a repetition frequency of several tens of kHz, so that the number shown in FIG. A reverse voltage pulse having a repetition frequency of 10 kHz is generated. This reverse voltage pulse neutralizes the charging of a target (not shown) that causes the occurrence of abnormal discharge in the vacuum load 2 and prevents the occurrence of abnormal discharge.

  In such a vacuum apparatus, if the current that has been flowing to the inductor 3 is Io, the DC voltage output from the DC input power supply 1 is V, the width of the reverse voltage pulse is T, and the inductance of the inductor 3 is L. When a reverse voltage pulse is generated, a current of (Io + V × T / L) must be supplied from the reverse voltage source 6, and the reverse voltage source 6 requires more power as the repetition frequency of the reverse voltage pulse increases. And This method of constantly generating a reverse voltage pulse and repeatedly applying the reverse voltage pulse to the vacuum load 2 is superior in terms of preventing abnormal discharge in advance, but since it always generates a reverse voltage pulse, the semiconductor There is a problem that the power loss due to high-frequency switching of the switch element 5 and the power loss of the snubber circuit that protects the semiconductor switch element 5 from an overvoltage increase, although not shown.

In order to reduce such power loss, although not shown in FIG. 5, an abnormal discharge detection circuit for detecting abnormal discharge is provided, and as shown in FIG. 6 (B), the semiconductor switch element only when abnormal discharge is detected. A method has been proposed in which 5 is turned on for several microseconds to several tens of microseconds and a reverse voltage pulse is applied to the vacuum load 2 from the reverse voltage source 6 to extinguish the abnormal discharge (for example, Patent Documents). 2 and 3). However, this method detects abnormal discharge when it occurs and extinguishes abnormal discharge.Therefore, there is no effect to prevent abnormal discharge, and every time abnormal discharge occurs, the minimum abnormal discharge current is applied to the vacuum load. As a result, the negative effect is generated in the vacuum load 2.
JP-T 8-510504 JP-A-8-31647 JP 2004-48903 A

  In order to solve such problems of the conventional method, in the present invention, a sign of occurrence of abnormal discharge is detected by a change in voltage, and when a sign of occurrence of abnormal discharge is detected, the reverse voltage source 6 applies a reverse voltage. By applying a pulse to a vacuum load, it is an object to reduce power loss and prevent the occurrence of abnormal discharge.

In order to solve the above problems, a first invention provides a vacuum load, a DC input power supply for supplying power to the vacuum load, and an inductor connected in series between the DC input power supply and the vacuum load. And detecting a precursor of abnormal discharge generated in a vacuum apparatus including a reverse polarity pulse generation circuit that applies a pulse voltage having a polarity opposite to that of the output voltage of the DC input power source to the vacuum load. a method for preventing the change rate (that voltage change rate) with respect to time of said vacuum load or voltage of the inductor, or the rate of change of the rate of change with time of the current flowing through them (referred to secondary rate of change of current ) detecting the secondary rate of change of the rate of change or the current of the voltage, the secondary rate of change of the rate of change or the current of the voltage is actually abnormal discharge occurrence of the minimum rate of voltage change or current Secondary change Smaller than the value corresponding to the ratio, when and at higher set value or more than the second-order rate of change of the rate of change or the current of the minute discharge voltage does not reach the abnormal discharge, applies a reverse polarity pulses to the vacuum load Thus, there is provided a method for preventing the occurrence of abnormal discharge in a vacuum apparatus, characterized by preventing the occurrence of abnormal discharge such as arc discharge.

A second invention includes a vacuum load, a DC input power supply for supplying power to the vacuum load, an inductor connected in series between the DC input power supply and the vacuum load, and an output of the DC input power supply in a vacuum apparatus and a reverse polarity pulse generating circuit for applying a pulse voltage of the voltage polarity opposite to the vacuum load, the rate of change with time of the vacuum load or voltage of the inductor (that the change rate of the voltage), or their A rate-of-change detection circuit that detects a rate of change of the rate of change of current with respect to time (referred to as a secondary rate of change of current ), and the rate of change of the voltage or the rate of secondary change of the current detected by the rate-of-change detector There determines whether larger or smaller than the set value, the output signal to the opposite polarity pulse generating circuit when the secondary rate of change of the rate of change or the current of the voltage is above the set value And a voltage determination circuit that generates, secondary rate of change of the rate of change or the current of the voltage, a change in the minimum voltage at the secondary change rate of the actual occurrence of abnormal discharge rate of change or the current of the voltage smaller than the value corresponding to the secondary rate of change of rate or current to and when it is abnormal rate of change of the discharge micro discharge voltage does not reach or current secondary change rate larger set value or more than of the reverse There is provided a vacuum apparatus characterized in that an abnormal discharge such as arc discharge is prevented in advance by applying a reverse polarity pulse to the vacuum load by a polarity pulse generating circuit.

According to a third invention, in the second invention, the change rate detection circuit for detecting the change rate of the voltage of the vacuum load or the inductor includes a capacitor connected in parallel to the vacuum load or the inductor and the capacitor And a current detecting means connected in series to each other.

According to a fourth invention, in the second or third invention, the determination circuit includes a capacitor that charges a detection amount that indicates a change rate of the voltage, and a reference voltage source that supplies a reference voltage corresponding to the set value. And a comparison circuit that compares the voltage of the capacitor with the reference voltage of the reference voltage source and outputs an output signal that changes when the voltage of the capacitor becomes equal to or higher than the reference voltage. A vacuum device is provided.

According to a fifth invention, in any one of the second to fourth inventions, the voltage determination circuit includes a capacitor that charges a detection amount indicating a rate of change of the voltage, and a first reference voltage. A first reference voltage source, a first comparison circuit that compares the first reference voltage and a charging voltage of the capacitor and generates an output signal when the latter exceeds the former, and the first reference voltage A second reference voltage source having a second reference voltage having a greater value than the second reference voltage, and comparing the second reference voltage and the charging voltage of the capacitor to generate an output signal when the latter exceeds the former. And a comparison circuit.

According to a sixth aspect of the invention, in any one of the second to fifth aspects, the reverse voltage pulse having a wider pulse width is generated when the abnormal discharge occurs than when the minute discharge that does not lead to the abnormal discharge occurs. A vacuum apparatus is provided that is applied to the vacuum load.

According to the first and second inventions, power loss can be reduced and the occurrence of abnormal discharge can be greatly reduced. In addition, the number of times the reverse voltage is applied to the vacuum load can be greatly reduced, and the influence can be reduced.

According to the third aspect of the invention, in addition to the effects obtained by the second aspect of the invention, a voltage change rate detection circuit having a simple circuit configuration is proposed.

According to the fourth invention, in addition to the effects obtained by the second invention, power loss due to application of a reverse voltage pulse can be reduced.

According to the fifth aspect of the invention, in addition to the effects obtained by the second aspect of the invention, a voltage determination circuit having a simple circuit configuration capable of distinguishing between occurrence of minute discharge and occurrence of abnormal discharge is proposed.

According to the sixth aspect of the invention, it is possible to further reduce power loss and to prevent occurrence of abnormal discharge. In addition, since the number of times of applying the reverse voltage to the vacuum load can be greatly reduced and the application time can be further shortened, the influence can be further reduced.

[Embodiment 1]
First, the vacuum apparatus of Embodiment 1 for implementing this invention using FIG. 1 and FIG. 2 is demonstrated. FIG. 1 is a diagram showing a vacuum apparatus 100 according to the first embodiment of the present invention. FIG. 2A is a diagram for explaining the voltage state of the vacuum apparatus when the discharge prevention function of the present invention is not provided, and FIG. 2B is the voltage state of the vacuum apparatus having the discharge prevention function of the present invention. It is a figure for demonstrating. In FIG. 1, a DC input power supply 1 is a general DC power supply comprising a rectifier that rectifies a single-phase or three-phase commercial AC voltage and converts it into DC power, and a smoothing circuit that smoothes the rectified voltage. . An inductor 3 is connected in series between the DC input power source 1 and the vacuum load 2. The DC input power source 1 may be a so-called switching regulator power source using a MOSFET or the like.

  The vacuum load 2 is a vacuum unit that generates plasma in vacuum in a vacuum apparatus such as a PVD apparatus, a CVD apparatus, a sputtering apparatus, an etching apparatus, or an electron beam evaporation apparatus. It functions to suppress a sudden increase in current when an abnormal discharge such as a discharge (hereinafter referred to as an abnormal discharge) occurs. As in the prior art, a reverse voltage pulse generation circuit 4 is connected across the vacuum load 2. The reverse voltage pulse generation circuit 4 includes a semiconductor switch element 5 such as an IGBT or a MOSFET connected in series to each other, a reverse voltage source 6 having a polarity opposite to that of the DC input power supply 1, and a gate signal for driving the semiconductor switch element 5 on and off. And a gate signal generating circuit 7 for outputting. Each time the semiconductor switch element 5 is turned on, the reverse voltage pulse generation circuit 4 applies a reverse voltage pulse to the vacuum load 2.

  In the first embodiment, a voltage drop rate detection circuit 8 that detects the voltage drop rate of the vacuum load 2 is connected across the vacuum load 2. The voltage drop rate detection circuit 8 includes a capacitor 9 connected in series with each other, a current limiting resistor 10, a detection resistor 11, and a constant voltage element 12 connected in parallel to the detection resistor 11 to limit the voltage at both ends thereof. It consists of. In the second embodiment to be described later, a voltage increase rate detection circuit that detects an increase rate of the voltage of the inductor is provided, but when referring to both the voltage drop rate detection circuit and the voltage increase rate detection circuit, it is referred to as a voltage change rate detection circuit. The detection voltage indicating the voltage drop rate of the vacuum load 2 is charged to the capacitor 15 of the voltage determination circuit 14 through the discharge preventing diode 13. In addition to the capacitor 15, the voltage determination circuit 14 compares the reference voltage source 16, the voltage of the capacitor 15 with the reference voltage of the reference voltage source 16, and outputs an output signal when the former exceeds the latter. And a discharging resistor 18 connected in parallel to the capacitor 15. The time constant formed by the capacitor 15 and the discharging resistor 18 in the first embodiment is preferably the minimum time during which the comparison circuit 17 can stably perform the comparison operation, and is, for example, about 5 μs. For example, the discharging resistor 18 may be replaced with a semiconductor element such as an FET that is turned on at a predetermined time after the comparison circuit 17 is operated to discharge the charge of the capacitor 15 and a driving circuit that drives the semiconductor element.

  Next, the operation of the vacuum apparatus 100 will be described. When the vacuum load 2 is magnetron sputtering, the voltage Vo of the vacuum load 2, that is, the plasma voltage, only has a gradual voltage fluctuation accompanying the movement of the magnet in a stable state in which abnormal discharge hardly occurs during plasma operation. . Accordingly, the rate of change of the voltage of the vacuum load 2 detected by the voltage drop rate detection circuit 8, in this case, the drop rate is small and does not reach the reference voltage of the reference voltage source 16. An output signal that can drive the signal is not generated. As long as this state continues, the gate signal generation circuit 7 does not apply a drive signal to the semiconductor switch element 5, and therefore no reverse voltage pulse is applied to the vacuum load 2. Therefore, in a stable state in which abnormal discharge is unlikely to occur, the semiconductor switch element 5 does not switch, so that switching loss does not occur and unnecessary reverse power is not consumed even in the vacuum load 2.

However, when the target of the vacuum load 2 is easily charged and abnormal discharge is likely to occur, a small discharge that does not shift to the abnormal discharge occurs. If the current is increased by this small discharge, the inductor 3 is present. In order to do so, the increase in current causes the voltage Vo of the vacuum load 2 to drop for a short time. As shown by A1, A2, and A3 in FIG. 2A, the voltage Vo of the vacuum load 2 drops for a short time when a minute discharge occurs. The state in which the voltage drop of the vacuum load 2 is caused by such a minute discharge is an unstable state in which the vacuum load 2 easily shifts from the plasma state to the abnormal discharge state. If the inductor 3 does not exist, abnormal discharge occurs. Often migrated.
In FIG. 2, −Vo is displayed because the output polarity of the sputtering power source is negative.

  In the present invention, an unstable state that easily shifts to an abnormal discharge state is regarded as a precursor phenomenon of occurrence of abnormal discharge. In the first embodiment, the voltage drop rate detection circuit 8 uses the precursor phenomenon as a voltage drop rate of the vacuum load 2. If the detected voltage indicating the voltage drop rate is higher than a reference value, that is, a set value, the voltage determination circuit 14 determines that the risk of shifting to abnormal discharge is high, and operates the reverse voltage pulse generation circuit 4 The reverse voltage pulse is applied to the vacuum load 2. The target (not shown) of the vacuum apparatus 2 is neutralized by the reverse voltage pulse and does not shift to abnormal discharge. In addition, even when the abnormal discharge has occurred, the voltage drop rate of the vacuum load 2 is maximized, so that the reverse voltage pulse generation circuit 4 operates and the reverse voltage pulse is applied to the vacuum load 2 by Disappear abnormal discharge.

  Detailed operation for preventing the occurrence of abnormal discharge will be described. As shown in FIG. 2 (A), when the voltage Vo of the vacuum load 2 drops for a short time due to the occurrence of minute discharges indicated by A1, A2 and A3, the capacitor charged with the polarity shown in the figure by the voltage of the DC input power supply 1 The voltage 9 is discharged through the current limiting resistor 10, the detection resistor 11 and the vacuum load 2. The peak value of this discharge current is proportional to the voltage drop rate of the voltage Vo of the vacuum load 2. In the minute discharges A1 and A3 in FIG. 2A, the voltage drop rate of the voltage Vo of the vacuum load 2 is large, and the peak value of the discharge current of the capacitor 9 is accordingly large. When the charging voltage becomes higher than the reference voltage of the reference voltage source 16 and the comparison circuit 17 gives an output signal to the gate signal generation circuit 7 of the reverse voltage pulse generation circuit 4, the semiconductor switch element 5 is turned on for a predetermined time. A reverse voltage pulse P as shown in 2 (B) is applied to the vacuum load 2.

  However, in the minute discharge A2 in FIG. 2A, the voltage drop rate of the voltage Vo of the vacuum load 2 is small, and accordingly, the peak value of the discharge current of the capacitor 9 is smaller than that of the minute discharges A1 and A3. Since the charging voltage of the capacitor 15 of the circuit 14 does not reach the reference voltage of the reference voltage source 16, the comparison circuit 17 does not give an output signal to the gate signal generation circuit 7 of the reverse voltage pulse generation circuit 4. Therefore, the semiconductor switch element 5 is not turned on and no reverse voltage pulse is generated as shown in FIG. 2B, so that the reverse voltage pulse is not applied to the vacuum load 2. The reference voltage of the reference voltage source 16, that is, the set value, is a value obtained from various experimental results, and is set to a voltage value smaller than the voltage value corresponding to the minimum voltage drop rate when an actual abnormal discharge occurs. ing.

  Next, a specific example will be described. In FIG. 1, it is assumed that the capacitance C of the capacitor 9 of the voltage drop rate detection circuit 8 is 1 nF, the resistance value of the detection resistor 11 is 100Ω, and the voltage of the vacuum load 2 is 500 V to 5 μs in the case of minute discharges A1 and A3. Assuming that the voltage drops to 400 V during the period t, the detected current i due to the voltage drop rate is 0.02 A from the equation i = C (V1−V2) / t. If the current limiting resistor 10 is 1 kΩ, the maximum discharge current determined by the current limiting resistor 10 is 0.5 A when the voltage of the vacuum load 2 is 500 V, which is 25 times the current of 0.02 A. Therefore, the presence of the current limiting resistor 10 can be ignored when considering the detection voltage. The detection voltage Vs of the detection resistor 11 by the detection current i is 2V from Vs = 0.02 × 100. The detected voltage peaks charge the capacitor 15 of the voltage determination circuit 14 through the discharge preventing diode 13. For simplicity, if the forward voltage drop of the diode 13 is ignored, the charging voltage is 2V. The charging voltage is held for a time of about several μs (for example, 5 μs) with a time constant determined by the capacitor 15 and the discharging resistor 18. The comparison circuit 17 compares the held detection voltage with the reference voltage of the reference voltage source 16. Here, as described above, the reference voltage of the reference voltage source 16 is set to a value smaller than the voltage value corresponding to the minimum voltage drop rate when the actual abnormal discharge occurs.

  If the reference voltage of the reference voltage source 16 is set to 1.9V, for example, the detection voltage (2V) exceeds the reference voltage (1.9V), so the comparison circuit 17 generates the reverse voltage pulse as the output signal. The signal is supplied to the gate signal generation circuit 7 of the circuit 4. That is, the voltage determination circuit 14 determines that it is a precursor of the occurrence of abnormal discharge, and provides a signal for operating the reverse voltage pulse generation circuit 4. In this case, the gate signal generation circuit 7 turns on the semiconductor switch element 5 for 10 μs, for example. Therefore, a reverse voltage pulse having a pulse width of 10 μs is applied to the vacuum load 2. The voltage of the capacitor 15 of the voltage determination circuit 14 is discharged by the discharging resistor 18 to prepare for detection of the next voltage drop rate.

  Next, in the case of the minute discharge A2, if the voltage of the vacuum load 2 drops from 450V to 450V in a period t of 500 μs, the detected current i is obtained from the equation i = C (V1−V2) / t: 0.01A. The detection voltage Vs of the detection resistor 11 by the detection current i is 1 V from Vs = 0.01 × 100. Accordingly, the peak value of the charging voltage of the capacitor 15 of the voltage determination circuit 14 is approximately 1 V, and this voltage is lower than the reference voltage (1.9 V) of the reference voltage source 16, so that the comparison circuit 17 converts the output signal to a reverse voltage. It is not given to the gate signal generation circuit 7 of the pulse generation circuit 4. That is, the voltage determination circuit 14 determines that there is no risk of occurrence of abnormal discharge, and does not operate the reverse voltage pulse generation circuit 4. Therefore, the reverse voltage pulse is not applied to the vacuum load 2 when the minute discharge A2 is generated.

  Even if the occurrence of abnormal discharge is prevented as described above, the reference voltage of the reference voltage source 16 is determined by the balance between the occurrence of abnormal discharge and the shift to abnormal discharge. obtain. In FIG. 2A, the occurrence of abnormal discharge is indicated by A4. When abnormal discharge occurs, the abnormal discharge can be regarded as a short circuit, so the voltage drop rate is steeper than that in the case of minute discharge. In this case, the discharge current i of the capacitor 9 of the voltage drop rate detection circuit 8 is determined by the current limiting resistor 10. When the abnormal discharge A4 occurs, assuming that the initial voltage (V1) of the vacuum load 2 drops from 500V to a voltage (V2) of approximately 0V at time t of 1 μs, the resistance value (R1) of the current limiting resistor 10 is as described above. ) Is 1 kΩ, the detection current i is 0.5A from V1 / R1. When calculated by the voltage drop rate, the detected current i is 0.5 A from the equation i = C (V1−V2) / t. Therefore, the detection voltage Vs is Vs = 0.5 × 100, and is 50 V from this equation.

  When the abnormal discharge A4 is generated, the detection voltage is set to a constant voltage because the detection voltage is significantly larger than that of the minute discharge indicating the occurrence of the abnormal discharge or a high detection voltage around this. For example, the voltage is limited to about 15 V by the element 12. As described above, since the reference voltage of the reference voltage source 16 is set to 1.9V, the limited detection voltage 15V is naturally higher than the reference voltage 1.9V, so that the comparison circuit 17 outputs the output signal. This is applied to the gate signal generation circuit 7 of the reverse voltage pulse generation circuit 4. Accordingly, even when the abnormal discharge A4 occurs, the semiconductor switch element 5 is turned on and the reverse voltage pulse P is applied to the vacuum load 2 to extinguish the abnormal discharge A4, similarly to the minute discharges A1 and A3. As is clear from the foregoing, in the first embodiment, the reverse voltage pulse is generated only when a minute discharge that may shift to an abnormal discharge occurs and when an abnormal discharge occurs. Therefore, the generation of the reverse voltage pulse can be suppressed to the minimum, and the power loss can be reduced.

[Embodiment 2]
A second embodiment according to the present invention will be described with reference to FIGS. FIG. 3 shows a circuit diagram of the second vacuum apparatus 200. In FIG. 3, the same symbols as those shown in FIG. 1 indicate members having the same names. The vacuum device 200 of the second embodiment is different from the first vacuum device 100 in that a voltage increase rate detection circuit 8 ′ having substantially the same circuit configuration as the voltage drop rate detection circuit 8 is provided at both ends of the inductor 3. The rest of the configuration is the same as the configuration of the vacuum apparatus 1 and the operation is also the same. Therefore, differences from the vacuum apparatus 100 will be mainly described.

  As shown in FIG. 2A, the occurrence of the minute discharges indicated by A1, A2, and A3 increases the current flowing through the inductor 3 in accordance with the magnitudes of the minute discharges A1, A2, and A3. As the current flowing through the inductor 3 increases, the voltage increase rate of the inductor 3 also increases. Along with this, the increasing rate of the current flowing through the capacitor 9, the current limiting resistor 10, and the detecting resistor 11 of the voltage increase rate detecting circuit 8 ′ also increases, and the increasing rate of the current flowing through the inductor 3 at both ends of the detecting resistor 11 is increased. A voltage rising at a corresponding increase rate is detected. The detected voltage is charged in the capacitor 15 of the voltage determination circuit 14 through the discharge preventing diode 13.

  Thereafter, as in the case of the vacuum device 100 described above, the comparison circuit 17 outputs the output signal to the gate signal generation circuit of the reverse voltage pulse generation circuit 4 only when the charging voltage of the capacitor 15 becomes equal to or higher than the reference voltage of the reference voltage source 16. 7, the semiconductor switch element 5 is turned on for a predetermined time, and a reverse voltage pulse P as shown in FIG. 2B is applied to the vacuum load 2. Since the operation similar to that of the vacuum apparatus 100 is performed even when the abnormal discharge is started, the description is omitted. Even in this embodiment, since a reverse voltage pulse is generated only when a minute discharge that may shift to an abnormal discharge occurs and when an abnormal discharge occurs, the possibility of causing an abnormal discharge is minimized. Further, the generation of the reverse voltage pulse can be suppressed to the minimum, and the power loss can be reduced. The gate signal generation circuit 7 according to the second embodiment has an insulating means such as a pulse transformer or a photocoupler (not shown) because the potential is floating.

[Embodiment 3]
A third embodiment according to the present invention will be described with reference to FIGS. FIG. 4 shows a circuit diagram of the third vacuum apparatus 300. In FIG. 4, the same symbols as those shown in FIGS. 1 and 3 indicate members having the same names. The feature of the vacuum device 300 of the third embodiment is that the minute discharge is distinguished from the abnormal discharge, and in the case of the minute discharge, a reverse voltage pulse having a smaller pulse width than that of the abnormal discharge is applied to the vacuum load, This is to prevent the transition to abnormal discharge with a small reverse power.

  The voltage drop rate detection circuit 8 is the same as that described with reference to FIG. The main difference between the vacuum apparatus 300 of the third embodiment and the vacuum apparatus 100 is in the voltage determination circuit 14 and the reverse voltage pulse generation circuit 4. The voltage determination circuit 14 determines whether the voltage change rate detected by the voltage drop rate detection circuit 8 is due to minute discharge or abnormal discharge. The reverse voltage pulse generation circuit 4 generates a reverse voltage pulse with a narrow pulse width when the voltage change rate detected by the voltage drop rate detection circuit 8 is due to a minute discharge, and the voltage drop rate detection circuit 8 detects the reverse voltage pulse. When the applied voltage change rate is due to abnormal discharge, a reverse voltage pulse having a wider pulse width than that in the case of minute discharge is generated.

  The voltage determination circuit 14 includes a first reference voltage source 16A, a first comparison circuit 17A, a second reference voltage source 16B, and a second comparison, in addition to the capacitor 15 and the discharge resistor 18 similar to those in the above-described embodiment. It consists of a circuit 17B. The first reference voltage source 16A has a reference voltage V1 set in the same manner as the reference voltage source 16 of the vacuum apparatus 100. The reference voltage V1 is based on a voltage value corresponding to a voltage drop rate when an actual abnormal discharge occurs. Even a small voltage is set. The second reference voltage source 16B has a reference voltage V2 that is a voltage value corresponding to the minimum voltage drop rate when an actual arc voltage is generated or a value smaller than the voltage value and larger than the reference voltage V1. As mentioned before, when an abnormal discharge occurs, it presents a significantly larger detection voltage or a higher detection voltage around this compared to the case of a minute discharge indicating a sign of the occurrence of an abnormal discharge. When a micro discharge indicating a sign of occurrence of abnormal discharge occurs, only a significantly smaller detection voltage is exhibited than when abnormal discharge occurs, so an abnormality is present between the reference voltage V2 and the reference voltage V1. A sufficient voltage difference can be provided to distinguish between discharge and microdischarge. In this embodiment, for example, it is assumed that the reference voltage V1 is 1.9V and the reference voltage V2 is 10V.

  The reverse voltage pulse generation circuit 4 includes, in addition to the semiconductor switch element 5 and the reverse voltage source 6, a first gate signal generation circuit 7A for receiving a signal output from the first comparison circuit 17A and generating a drive signal. The second gate signal generation circuit 7B that generates a drive signal in response to the output signal from the second comparison circuit 17B, and ORs the output signals of the first gate signal generation circuit 7A and the second gate signal generation circuit 7B. The OR gate circuit 19 logically applies one drive signal to the semiconductor switch element 5. However, the OR gate circuit 19 may be omitted.

  Next, the operation of the vacuum apparatus 300 will be described. Since the operation of the voltage drop rate detection circuit 8 is the same as that of the vacuum apparatus 100, description thereof is omitted. As shown in FIG. 2, if the small discharges A1 and A3 indicating the precursor of abnormal discharge occur and the charging voltage of the capacitor 15 indicating the voltage drop rate of the vacuum load 2 rises to 2V, the charging voltage 2V Exceeds the reference voltage V1 (for example, 1.9 V) of the first reference voltage source 16A, the first comparison circuit 17A provides an output signal to the first gate signal generation circuit 7A. Accordingly, the first gate signal generation circuit 7A generates a drive signal having a predetermined pulse width. The pulse width of the drive signal generated by the first gate signal generation circuit 7A is set to be narrower than the pulse width of the drive signal generated by the gate signal generation circuit 7 of the vacuum apparatus 100 in the first embodiment. The semiconductor switch element 5 is turned on by the pulse width drive signal generated by the first gate signal generation circuit 7A, and a reverse voltage pulse having a narrow pulse width is applied to the vacuum load 2 as shown by a chain line in FIG. Apply. This reverse voltage pulse only needs to have a reverse power that can be extinguished at the stage of the micro discharge so that the micro discharge does not shift to the abnormal discharge, so compared with the reverse voltage pulse that extinguishes the generated abnormal discharge. The pulse width may be narrow.

  On the other hand, when the micro discharges A1 and A3 indicating the occurrence of abnormal discharge are generated, the charging voltage of the capacitor 15 indicating the voltage drop rate of the vacuum load 2 only rises to 2 V, for example, and this voltage is the second reference. Since the reference voltage V2 (for example, 10V) of the voltage source 16B is not reached, the second comparison circuit 17B does not generate an output signal, and therefore the second gate signal generation circuit 7B does not generate a drive signal.

  Next, as shown in FIG. 2A, when the abnormal discharge (A4) occurs, the abnormal discharge can be regarded as a short circuit as described above, and thus the voltage drop rate becomes steeper than that in the case of the minute discharge. In this case, the discharge current i of the capacitor 9 of the voltage drop rate detection circuit 8 is determined by the current limiting resistor 10, and when the example of the vacuum device 100 is applied, when the abnormal discharge A4 occurs, the discharge current i is present at both ends of the detection resistor 11. The detection voltage Vs to be output is about 50V. Although this voltage is limited to about 15V by the constant voltage element 12, since the capacitor 15 of the voltage determination circuit 14 is peak-charged, the charging voltage of the capacitor 15 rises to about 15V. Therefore, first, when the charging voltage of the capacitor 15 exceeds the reference voltage V1 (for example, 1.9 V) of the first reference voltage source 16A, the first comparison circuit 17A outputs the output signal to the first gate signal generation circuit. 7A, and then when the charging voltage of the capacitor 15 exceeds the reference voltage V2 (for example, 10V) of the second reference voltage source 16B, the second comparison circuit 17B outputs the output signal to the second gate signal generation circuit. Give to 7B.

  Although not shown, the second gate signal generation circuit 7B generates a drive signal having a pulse width larger than the pulse width of the drive signal generated by the first gate signal generation circuit 7A. The pulse width of this drive signal corresponds to the pulse width of the reverse voltage pulse indicated by the solid line in FIG. 2B, and is equal to or greater than a value that can provide reverse power that can reliably extinguish an abnormal discharge. The OR gate circuit 19 first passes the drive signal from the first gate signal generation circuit 7A, and passes the drive signal from the second gate signal generation circuit 7B with a slight delay. For example, even if the OR gate circuit 19 is an OR circuit composed of two diodes, the voltage level of the drive signal from the second gate signal generation circuit 7B is set to be higher than that of the drive signal from the first gate signal generation circuit 7A. If set high, the drive signal from the second gate signal generation circuit 7B is applied to the gate of the semiconductor switch 5 with priority over the drive signal from the first gate signal generation circuit 7A.

  In the third embodiment, a reverse voltage pulse having a small pulse width is applied to the vacuum load 2 for the occurrence of a micro discharge having a magnitude that is a precursor of the abnormal discharge, and when the abnormal discharge occurs, the abnormal discharge is generated. When the charging voltage of the capacitor 15 exceeds the reference voltage V1 (for example, 1.9 V) of the first reference voltage source 16A before the determination is made, the first comparison circuit 17A outputs the output signal to the first gate. The first gate signal generation circuit 7A applies the drive signal to the semiconductor switch element 5 to start driving at that time, and then the drive signal from the second gate signal generation circuit 7B is applied to the semiconductor. Since it is applied to the switch element 5, it is possible to instantly cope with the occurrence of abnormal discharge and extinguish the abnormal discharge at the shortest point. In the vacuum apparatus 300, power loss can be further reduced as compared with the vacuum apparatuses 100 and 200.

  In the above embodiment, the voltage change rate detection circuit such as the voltage drop rate detection circuit 8 or the voltage increase rate detection circuit 8 ′ is exemplified as a simple circuit configuration, but the voltage change rate detection circuit is a vacuum load. 2 voltage or inductor 3 voltage is sampled at a certain time width, for example, every 5 μs, the difference between the immediately preceding sampling voltage and the immediately following sampling voltage is taken, and the difference voltage is divided by the sampling time (5 μs). By doing so, you may obtain | require the voltage change rate per microsecond. Further, the difference between the voltage change rate obtained by the immediately preceding sampling and the voltage change rate obtained by the immediately following sampling is obtained, and a voltage corresponding to the secondary change rate obtained by dividing by the sampling time is detected. With this value, it is possible to extinguish a minute discharge and extinguish an abnormal discharge at a higher speed. The current limiting resistor 10 is not always necessary.

  Further, since the potentials between the control electrodes of the switching circuits 17, 17A, 17B and the switch 5 are different, signal insulation means such as a pulse transformer and a photocoupler are provided in the gate signal generation circuit 7, 7A, 7B or the OR gate circuit 19. Needless to say, you need it.

[Embodiment 4]
Next, although not illustrated, an example will be described in which a current flowing through a vacuum load and an inductor is detected to detect a precursor of abnormal discharge. In the circuit shown in FIG. 1, the voltage of the inductor 3 is changed by the change of the current flowing through the inductor 3, and the voltage of the vacuum load 2 is changed as described above. Therefore, when the inductance of the inductor 3 is L, the voltage of the inductor 3 is v, and the flowing current is i, v = L · di / dt, and the rate of change of the voltage v of the inductor 3 is dv / dt = L · (Di / dt) ² As is apparent from this equation, the rate of change of the voltage v of the inductor 3 is the rate of change of the rate of change of the current flowing through the inductor 3, that is, the secondary rate of change (secondary differentiation). In the embodiment described above, detection of a precursor of abnormal discharge using the rate of change of current is not preferable because detection of the precursor is delayed. However, if a secondary change rate (secondary derivative) of current is used, It is possible to perform detection at the same speed as when detecting a precursor of abnormal discharge with the rate of change.

  The secondary change rate (secondary differential) of the current can be easily obtained by processing the detected current value using a microcomputer having a simple configuration (not shown). The current detection value is sampled at a certain time width, for example, every 5 μs, and the difference between the immediately preceding sampling current detection value and the immediately following sampling current detection value is taken, and the difference current detection value is determined by the sampling time (5 μs). By dividing, the current change rate per unit time can be obtained, and by dividing by the sampling time (5 μs), the secondary change rate (secondary derivative) of the current per unit time can be obtained. Alternatively, the secondary change rate (secondary differentiation) can also be obtained by a secondary differentiation circuit comprising a differentiation circuit and a differentiation circuit that differentiates the differential output signal. When the secondary change rate of the current is obtained, the secondary change rate of the current is compared with a reference value by the comparison means, and when the secondary change rate of the current exceeds a predetermined set value, By operating the reverse voltage pulse generation circuit 4 and applying the reverse voltage pulse to the vacuum load 2, the occurrence of abnormal discharge can be prevented. Here, the set value is smaller than the value corresponding to the minimum secondary change rate when the actual abnormal discharge occurs, and is smaller than the secondary change rate of the minute discharge that does not lead to the abnormal discharge. It is set to be large. By using a microcomputer, a preset value can be programmed in advance in response to a change in the state of the vacuum load after the start of the apparatus, so that even more preferable abnormal discharge can be prevented. It is possible.

It is a figure which shows the vacuum apparatus 100 which is one Embodiment of this invention. It is a wave form diagram for demonstrating the vacuum apparatus of this invention. It is a figure which shows the power supply device 200 for discharge which is other one Embodiment of this invention. It is a figure which shows the power supply device 300 for discharge which is other one Embodiment of this invention. It is a figure which shows an example of the conventional vacuum apparatus. It is a figure for demonstrating an example of the conventional vacuum apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Input DC power source 2 ... Vacuum load 3 ... Inductor 4 ... Reverse voltage pulse generation circuit 5 ... Semiconductor switch element 6 ... Reverse voltage source 7 ... Gate signal generation circuit 8 ... Voltage drop rate detection circuit (voltage change rate detection circuit)
8 '... voltage increase rate detection circuit (voltage change rate detection circuit)
DESCRIPTION OF SYMBOLS 9 ... Voltage change rate detection capacitor 10 ... Current limiting resistor 11 ... Detection resistor (detection means)
DESCRIPTION OF SYMBOLS 12 ... Constant voltage element 13 ... Discharge prevention diode 14 ... Voltage judgment circuit 15 ... Capacitor 16 ... Reference voltage source 17 ... Comparison circuit 18 ... Discharge resistance 19 ...・ OR gate circuit

Claims (6)

A vacuum load; a DC input power supply for supplying power to the vacuum load; an inductor connected in series between the DC input power supply and the vacuum load; and a pulse having a polarity opposite to the output voltage of the DC input power supply A method for detecting a precursor of abnormal discharge generated in a vacuum device including a reverse polarity pulse generation circuit for applying a voltage to the vacuum load and preventing the occurrence of the abnormal discharge in advance,
The vacuum load or the rate of change with time of the voltage of the inductor (that the change rate of the voltage), or to detect the rate of change of the rate of change (that secondary rate of change of current) with respect to time of the current flowing through them,
The rate of change of voltage or the rate of secondary change of current is the rate of change of voltage or the rate of secondary change of current becomes the minimum rate of change of voltage or the rate of secondary change of current when an actual abnormal discharge occurs. Apply a reverse polarity pulse to the vacuum load when it is greater than a set value that is less than the corresponding value and greater than the rate of change of voltage or current secondary change of minute discharge that does not lead to abnormal discharge A method for preventing the occurrence of abnormal discharge in a vacuum apparatus, wherein the occurrence of abnormal discharge such as arc discharge is prevented in advance. A vacuum load; a DC input power supply for supplying power to the vacuum load; an inductor connected in series between the DC input power supply and the vacuum load; and a pulse having a polarity opposite to the output voltage of the DC input power supply In a vacuum apparatus comprising a reverse polarity pulse generation circuit for applying a voltage to the vacuum load,
Change rate detection circuit for detecting a rate of change with time of the vacuum load or voltage of the inductor (voltage of rate of change), or rate of change of the rate of change with time of the current flowing through them (referred to secondary rate of change of current) When,
Determining whether the secondary rate of change of the rate of change or the current of the voltage detected by said change rate detecting circuit is greater than the set value smaller, secondary rate of change of the rate of change or the current of the voltage the A voltage determination circuit that generates an output signal to the reverse polarity pulse generation circuit when the value is equal to or greater than a set value;
With
The voltage change rate or the current secondary change rate is changed to the voltage change rate or the current secondary change rate which is the minimum voltage change rate or current secondary change rate when an actual abnormal discharge occurs. When the voltage change rate or the secondary change rate of the current of the minute discharge that is smaller than the corresponding value and does not lead to abnormal discharge is equal to or greater than the set value , the reverse polarity pulse generation circuit is connected to the vacuum load. A vacuum apparatus characterized by preventing occurrence of abnormal discharge such as arc discharge by applying a reverse polarity pulse. In claim 2 ,
The rate-of-change detection circuit for detecting the rate of change of the voltage of the vacuum load or the inductor comprises a capacitor connected in parallel to the vacuum load or the inductor and a current detecting means connected in series to the capacitor. Features vacuum equipment. In claim 2 or claim 3 ,
The determination circuit includes:
A capacitor for charging a detection amount indicating the rate of change of the voltage ;
A reference voltage source for providing a reference voltage corresponding to the set value;
A comparison circuit that compares the voltage of the capacitor with the reference voltage of the reference voltage source and outputs an output signal that changes when the voltage of the capacitor becomes equal to or higher than the reference voltage;
A vacuum apparatus comprising: In any one of Claims 2-4 ,
The voltage determination circuit includes:
A capacitor for charging a detection amount indicating the rate of change of the voltage ;
A first reference voltage source having a first reference voltage;
A first comparison circuit that compares the first reference voltage with the charging voltage of the capacitor and produces an output signal when the latter exceeds the former;
A second reference voltage source having a second reference voltage having a value greater than the first reference voltage;
A second comparison circuit that compares the second reference voltage with the charging voltage of the capacitor and produces an output signal when the latter exceeds the former;
A vacuum apparatus comprising: In any one of Claims 2-5,
A vacuum apparatus, wherein the reverse voltage pulse having a wider pulse width is applied to the vacuum load when the abnormal discharge occurs than when the minute discharge that does not lead to the abnormal discharge occurs.

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