JPH0832184B2 - Power supply for sputter ion pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a sputtering ion pump (hereinafter referred to as an ion pump) for evacuation of various apparatuses using ultra-high vacuum such as a surface analysis apparatus, a molecular beam epitaxial growth apparatus, and an accelerator. Abbreviated)
The present invention relates to an improvement of a power supply for driving a vehicle.

(Prior Art and Problems Thereof) FIG. 3 is a diagram showing a circuit configuration of Japanese Patent Publication No. 58-54465, “Ion Pump Power Supply” which is an example of a conventional inverter type ion pump power supply.

In this conventional power supply, an alternating current of 50 or 60 Hz is rectified by the rectifier circuit 20 and then smoothed by the capacitor C ₃ to be a direct current. This direct current is input to the DC / AC inverter 30. This inverter 30 incorporates a switching transistor, and converts a DC input into an AC output having a pulse width corresponding to the driving time width of the switching transistor. The output of the inverter 30 is input to the small high frequency transformer T ₂ . The output of the transformer T ₂ is rectified by the diodes D ₁ and D ₂ and further smoothed by the capacitors C ₁ and C ₂ . This D ₁ , D ₂ , C ₁ and C ₂
The DC output of the rectifying / smoothing circuit consisting of is supplied to the ion pump 10.

In addition, the transformer T ₂ corresponding to the discharge current of the ion pump 10
A detection circuit 40 for detecting the peak value of the current on the primary side of, and a control circuit 50 for controlling the drive time width of the switching transistor in the inverter 30 corresponding to the detection value of the detection circuit 40. A voltage corresponding to the discharge current value of the pump 10 can be applied to the ion pump 10.

The circuit of FIG. 3 is not shown in Japanese Patent Publication No. 58-54465, “Power Supply for Ion Pump” (however,
An overcurrent detection relay 101 (which is also a conventional technique) is additionally shown, but this overcurrent detection relay 101 is a self-holding type, and as described later, the pressure inside the ion pump 10 is high and the glow discharge region is high. If the ion pump is operated for a long time, there is a risk of causing an accident due to overheating of the ion pump.Therefore, when the internal pressure of the ion pump rises to the glow discharge area and the discharge current increases, relay
It is added for the purpose of operating 101 and opening the AC input at its contact 102 as shown.

However, when starting the ion pump, this relay for overcurrent detection
101 needs to be immobilized. Therefore, it is considered that the switch 100 connected in parallel to the relay 101 is closed at the time of startup so that the ion pump power supply can operate even in the glow discharge region. The switch 100 is opened when the ion pump is turned on during steady operation.

Another reason for installing the overcurrent detection relay 101 will be described in detail here. In the conventional ion pump power source, when spark discharge occurs in the output ion pump 10, FIG.
As shown in (b), the output voltage instantly becomes 0 V, and a steep pulsed current flows. Then, when the spark discharge disappears and the output current becomes 0, the output voltage rises again. When the output voltage rises to the spark discharge start voltage, spark discharge is generated again, and this is repeated to become continuous spark discharge.

In the case of the inverter type ion pump power supply, the step-up transformer and output smoothing capacitor can be made smaller than the commercial frequency ion pump power supply, and the output voltage after spark discharge rises from 0V to the spark discharge start voltage. There is a feature that the time required for is short. Therefore, the discharge power consumed between the output resistance R ₁ of the ion pump power supply and the ion pump electrode (r ₁ ) by _one spark discharge, and the capacity of the output smoothing capacitor is smaller than that of the commercial frequency ion pump power supply. However, the continuous spark discharge shortens the spark discharge cycle, and therefore the number of times of spark discharge per second is larger than that of the commercial frequency ion pump power source.

For this reason, when continuous spark discharge occurs, even in the case of the inverter system, excessive power may be consumed by the output resistance R ₁ and the spark discharge equivalent resistance r ₁ between the ion pump electrodes, and the power supply for the ion pump may be damaged. .

The above phenomenon also occurs when the ion pump, which is the load of the ion pump power supply, is driven with the internal pressure close to the atmospheric pressure, the ion pump power supply is damaged, and the electrode inside the ion pump is also damaged. Risk of melting.

In the conventional inverter type ion pump power supply, no special consideration was given to this continuous spark discharge, but in the circuit of FIG. 3, the above-mentioned overcurrent protection function is provided as a protection function against an abnormal rise in ion pump internal pressure. The current detection relay 101 is provided, and its response is made sufficiently fast to detect continuous spark discharge to operate the relay, thereby protecting the power supply.

However, in this case, even if a single or several spark discharges occur, the overcurrent detection relay 101 turns off the contact 102 and holds it by itself. There is a problem that the driving will stop.

Further, the overcurrent detection relay 101 is designed to kill the ion pump when it is started and to operate it only after the internal pressure of the ion pump is sufficiently lowered and the output current is reduced, so that the continuous spark discharge is started at the time of starting. There is also a problem that the power source for the ion pump and the ion pump cannot be protected when the above occurs.

(Object of the Invention) The present invention solves the above-mentioned problems of the conventional ion pump power supply, protects the ion pump power supply and the ion pump from continuous spark discharge at the time of startup, and causes spark discharge during continuous operation. The purpose is to effectively prevent operation stoppage.

(Structure of the Invention) The present invention relates to an inverter type high voltage generation circuit, a detection circuit for detecting a spark discharge generated in an ion pump connected to an output thereof, and an oscillation of the inverter based on the detection of the detection circuit. And a slow start circuit that starts oscillation of the inverter and gradually increases its output after the stop circuit stops the oscillation of the inverter. After the start, the time until the output voltage of the high-voltage generating circuit reaches a predetermined steady value is set longer than the spark discharge generation period. Is.

(Example) FIG. 1 is a diagram of an example of the present invention. The same reference numerals are given to the same or similar members as in FIG.
The rectifier circuit 20, the inverter 30, the transformer shown in FIG.
An inverter type high voltage generating circuit is configured by T _{2 and the} like.

Unlike the conventional ion pump power supply shown in FIG. 3, in this embodiment, a spark discharge detection circuit 200 (described in detail later) is newly added and its detection output signal is sent to the one-shot circuit 210 as a stop circuit, and the one The output of the shot circuit 210 is sent to the AND circuit 220, and the one-shot circuit 210
The output of the conventional inverter control circuit 50 is stopped from being sent to the inverter 30 for a fixed time determined by, and the inverter operation is stopped for the fixed time t ₁ . The output of the one-shot circuit 210 is also sent to the slow start circuit 230. In the slow start circuit 230, after the oscillation stop time t ₁ , the inverter control circuit gradually increases the switching transistor drive pulse width in the inverter. The output voltage so that the output voltage
It is configured to rise over t ₂ and return to the normal value.

Now, the spark discharge detection circuit 200 described above can be configured as follows.

That is, the output current is almost DC during glow discharge or Penning discharge, which are normal discharges in the ion pump, whereas during spark discharge, the output current becomes a pulsed current as shown in Fig. 4B. It is also possible to use a transformer or the like to extract and detect only this pulsed current.

Alternatively, by utilizing the fact that the maximum output current during normal discharge is less than a fraction of the peak value of the pulsed current during spark discharge, a current detector with a response speed of tens of microseconds or less is used to detect the current threshold value. Can also be configured by setting the output current value to several times the maximum output current value during normal discharge.

In the circuit configuration of FIG. 1, when a spark discharge is generated at a high voltage output, as shown in FIGS. 2A and 2B, after the spark discharge is generated, a fixed time t determined by the one-shot circuit 210.
_{During 1} , the inverter oscillation is stopped and the output voltage is 0V.
After the stop time t ₁ has elapsed, the output voltage gradually rises over the time t ₂ determined by the slow start circuit 230 and returns to the steady value.

Since the output voltage rise is not as steep as that of the conventional power supply, the recurrence of the spark discharge can be suppressed also by this. Even if the spark discharge occurs again, the spark discharge cycle is t ₁ + t ₂ as shown in FIG. ₂ , which should be set sufficiently longer than the spark discharge cycle t _θ of the conventional power supply. There is.

This prevents excessive power consumption by the output resistance R ₁ of the ion pump power source and the equivalent resistance r ₁ between the ion pump electrodes during continuous spark discharge, and prevents the accident of melting of the internal electrode of the ion pump. Even if spark discharge occurs during continuous operation, the high-voltage output temporarily becomes 0 V, but since the output voltage gradually rises over time t ₂ after the time t ₁ after the spark discharge, the spark discharge Recurrence is suppressed. Furthermore, the output voltage rises to the original value after a lapse of time t ₁ + t ₂ after the spark discharge, so that it is possible to prevent the ion pump operation during continuous operation from being stopped by the spark discharge.

(Effects of the Invention) According to the present invention, it is possible to protect the power source for the ion pump and the ion pump from continuous spark discharge at the time of startup, and also to prevent operation stop due to spark discharge during continuous operation.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an ion pump power supply according to an embodiment of the present invention. FIG. 2 is a diagram showing changes in output voltage and current during output spark discharge in the ion pump power supply of the embodiment of FIG. FIG. 3 is a circuit diagram of a conventional inverter type ion pump power supply. FIG. 4 is a diagram showing changes in output voltage and current during output spark discharge in a conventional ion pump power supply. T ₂ …… High frequency transformer, C ₃ …… Smoothing capacitor, 20
...... Low frequency rectifier circuit, 30 ...... DC / AC inverter, D ₁ , D ₂
…… Diode, C ₁ , C ₂ …… Capacitor, R ₁ …… Output resistance, r ₁ …… Ion pump electrode equivalent resistance, 10 …… Ion pump, 100 …… Switch, 101 …… Overcurrent detection relay , 102 …… contacts, 200 …… spark discharge detection circuit, 210 ……
One shot circuit, 220 …… AND circuit, 230 …… Slow start circuit.

Claims (1)

[Claims] 1. An inverter type high voltage generating circuit, a detection circuit for detecting a spark discharge generated in a sputter ion pump connected to its output, and the oscillation of the inverter is temporarily stopped based on the detection of the detection circuit. A stop circuit to
A slow start circuit for starting the oscillation of the inverter and gradually increasing the output thereof after the stop circuit stops, the stop circuit and the slow start circuit stop the oscillation of the inverter and then start the high voltage. A power supply for a sputter ion pump, wherein the time until the output voltage of the voltage generation circuit reaches a predetermined steady value is set longer than the spark discharge generation cycle.