KR20040056225A - Measurement circuit for high vacuum of ion pump - Google Patents

Abstract

PURPOSE: A circuit for measuring a high vacuum in an ion pump is provided to simplify the parts of the electronic circuit by controlling the microprocessor to play the important role related to the calculation, thereby saving the cost of the manufacturing. CONSTITUTION: A circuit for measuring a high vacuum in an ion pump includes a current limiter(16), a high speed switch(20), a current detection and log amplification unit(21), a communication interface(12), a display(25), a display interface(24), a parameter storage memory(14), a microprocessor(10), an output adjusting unit(15) and an input detector(19). The current detection and log amplification unit(21) increases the input voltage if the ion current becomes low, decreases the input voltage if the degree of vacuum is low and converts the ion current detected from the double voltage output unit(18) into a voltage signal in response to the reference value outputted from the DAC(23). The communication interface(12) is coupled to an ADC(22), a DAC(23), a program memory(11) and a PC. The display interface(24) is connected to the display(25). The microprocessor(10) is provided with a display interface(24) connected to the display(25) and a parameter storage memory(14). The output adjusting unit(15) transmits the output voltage value proportional to the degree of microprocessor(10) to the current limiter(16). And, the input detector(19) operates the current limiter(16) by detecting the over input status due to the input voltage rising of the transformer(17).

Description

Measurement circuit for high vacuum of ion pump

The present invention relates to a high vacuum measuring circuit in an ion pump for measuring the degree of vacuum by detecting an ion current at the power supply side when a high voltage is applied between two electrodes of an ion pump to ionize gas in a vacuum vessel.

In general, when a voltage of several thousand volts is applied between an anode and a cathode of an ion pump, electrons emitted from the cathode are accelerated toward the anode and cationized gas is accelerated toward the cathode.

At this time, the total current is determined by the gas molecules, and the pressure of the gas can be measured by measuring the ion current at the power supply side. In addition, the ion current flows through the resistance and is measured by the voltage appearing between both ends of the resistance.

However, in the conventional means, the current is measured, but very high current flows in high vacuum, so the method of using the resistance is accompanied with a lot of errors due to thermal noise.

In particular, in the process of amplifying the measured voltage to an appropriate level of voltage has a problem that it is difficult to measure the economic burden and accurate vacuum degree to use a large number of amplifiers.

The present invention is to solve the above problems of the high-vacuum measuring circuit using the conventional voltage, an object of the present invention is to provide a high voltage of thousands of volts between two electrodes of the ion pump (Ion Pump) to ionize the gas in the vacuum vessel The present invention provides a high-vacuum measuring circuit in an ion pump for converting an ion current on a power supply side into a voltage and measuring a voltage proportional vacuum degree and applying it to the adjustment of an ionization power amount.

1 is a circuit block diagram of the present invention.

2 is a detailed view of the circuit block configuration of the present invention.

※ Explanation of symbols about main part of drawing ※

10: microprocessor 11: program memory

12: communication interface 13: PC

14: Memory for storing parameters 15: Output control unit

16: current limiting unit 17: transformer unit

18: double voltage output unit 19: input detection unit

20: high speed switching unit 21: current detection and log amplifier

22: ADC 23: DAC

24: display interface 25: display

The measuring circuit of the present invention for achieving the above object is to output the voltage of the switching mode in the transformer unit by a high speed switching unit that generates a DC input voltage and a switching pulse through the current limiting unit and the output voltage of the transformer unit is a double voltage output A high voltage output circuit for an ion pump for outputting a high voltage through a section, comprising: a current detection and log amplifier for converting an ion current detected by the double voltage output unit into a voltage signal according to a reference value output from a DAC, and the log A microprocessor which generates four types of voltage selection signals according to the detected voltage signal level of the amplifier and has an ADC, a DAC, a program memory, a communication interface coupled with a PC, a display interface coupled with a display, and a memory for storing parameters; The vacuum proportional output voltage value of the microprocessor is transferred to the current limiting unit. The controller may include an output adjuster and an input detector configured to detect an over-input state caused by an increase in the input voltage of the transformer and operate the current limiter.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram of a circuit of the present invention, in which a transformer 17 is connected to a DC input voltage through a current limiter 16. The transformer 17 is connected to a high speed switching pulse of the high speed switching unit 20 which generates a time pulse output and whose operation is controlled by a microprocessor.

By the high speed switching unit 20 for generating the switching pulse, the transformer unit 17 outputs the switching mode voltage and outputs the high voltage for the ion pump through the double voltage output unit 18. The current detection and log amplifier 21 is connected to the high voltage output terminal to simultaneously detect the output current of the high voltage and log-amplify the input signal of the microprocessor through the DAC 23 as an input.

The output of the current detection and log amplifier 21 is connected to the program memory 11, the communication interface 12 for connecting to the external PC 13 via the ADC 22, the memory 14 for storing parameters and the display ( And input to a microprocessor 10 having a display interface 24 for driving 25.

An input detection unit 19 for connecting the vacuum proportional output voltage value of the microprocessor 10 to be transmitted to the current limiting unit 16 through an output adjusting unit 15 and detecting an over-input state according to an increase in the input voltage of the transformer. ) Is configured to be connected to the current limiting unit 16 to be applied as a power supply limit signal.

FIG. 2 is a detailed circuit diagram of the present invention, wherein the current limiting unit 16 provided between the DC input voltage terminal and the transformer unit 17 is composed of a Darlington circuit by transistors Q1 and Q2. The output adjusting unit 15 to which the output voltage selection signal is applied from the output transistor 15 outputs each transistor Q3-Q6 driven by each output voltage selection signal and a variable resistor VR1-VR4 for determining an output voltage value by the transistor. And an OP amplifier OP1 and an output transistor Q7.

The input detector 19 includes voltage dividing resistors R1 and R2 and an OP amplifier OP2.

The transformer unit 17 includes a transformer T1, and the double voltage output unit 18 includes diodes D1-D6 and capacitors C1-C5.

The current detection and log amplifier 21 is composed of resistors R3 and R4, variable resistor VR3, mirror transistors Q8 and Q9, and OP amplifiers OP3 and OP4.

The high speed switching unit 20 includes a timer IC TM1, inverters I1-I6, and transistors Q10-Q12.

Referring to the operation of the present invention configured as described above is as follows.

First, when an ion high voltage DC input voltage is applied to the input side of the transformer T1 of the transformer unit 17 through the transistors Q1 and Q2 in the current limiting unit 16, the transformer T1 is a high speed switching unit ( The switching pulse of 20) operates in the switching mode to generate a high frequency voltage at its output stage.

The high voltage is rectified by the double voltage output unit 18 including the plurality of high frequency diodes D1-D6 and the plurality of capacitors C1-C5, and the ion chamber is provided with an ionized high voltage.

At this time, the ion current output from the double voltage output unit is detected by the current detection and log amplifier 21 and amplified and then converted into a digital value through the ADC 22 and input to the microprocessor 10. In this case, the current detection and log amplifier 10 converts the digital signal of the ion detection current into a voltage signal and converts the digital reference voltage signal provided from the microprocessor into an analog signal through the DAC 23 to use it as a reference signal.

Parameters, such as various setting values, for the microprocessor 10 to process the input signals are stored in the parameter storage memory 14, and the microprocessor retrieves and processes them as necessary.

The program memory 11 stores basic execution program data of the microprocessor, and initializes the high vacuum measurement circuit by the microprocessor at every reset.

The microprocessor 10 generates an ion current detection value according to the detection voltage signal level of the current detection and log amplifier 21 to generate four types of voltage selection signals proportional to the degree of vacuum.

The four kinds of vacuum proportional voltage selection signals are inputted to the output adjusting unit 15 so that any one of the transistors corresponding to the selection voltage signal, that is, the transistors Q1-Q4 and one of the variable resistors VR1-VR4 coupled thereto, is selected. The OP amplifier OP1 is arithmetic to a value determined by A and this arithmetic output is applied to the transistor Q7.

In this case, when the magnitude of the input voltage of the transformer unit 17 changes rapidly, such an input state change is divided by the resistors R1 and R2, and the arithmetic operation is processed by the OP amplifier OP2, and the operational output of the OP amplifier OP2. According to the logic value, the output transistor Q7 of the output adjuster 15 operates to limit the current limiter 16, so that the input power supply voltage to the transformer 17 is adjusted.

The high speed switching unit 20 is a switching mode pulse generator for applying a high speed operation pulse to the transformer T1 of the transformer unit 17 and is alternated by a timer IC TM1 and a plurality of inverters I1 to I6. The output transistors Q11 and Q12 operate alternately by means of a pulse signal, and these two lines are selectively bypassed to ground by a transistor Q10 controlled by the control signal of the microprocessor.

On the other hand, the operation processing information processed by the microprocessor 10 is output to the display 25 via the display interface 24. In addition, the microprocessor 10 is connected to the PC 13 via the communication interface 12 to be remotely controlled by the PC.

Therefore, the present invention adjusts the overall power supply by increasing the input voltage applied automatically when the ion current is lowered as the degree of vacuum in the ion pump increases, and lowering the applied voltage when the ion current is increased when the degree of vacuum is lowered. In addition, the ion current measuring the vacuum degree converts a current of a certain range (for example, 300 mA to 10 nA) into a voltage using a log amplifier, and the converted voltage signal is converted into an analog-digital converter.

These digitized signal levels can be computed in a microprocessor to provide flexibility in measuring gas pressure.

According to the embodiment of the present invention, the high voltage generator receives a signal of 4 bits from the microprocessor 10 to generate an output of 3300Vdc, 2000Vdc, 1500Vdc, 800Vdc, and receives a signal from the controller in the event of a high voltage output short circuit to cut the output voltage. It has a protective function.

The current limiting unit 16 has a function of blocking an output voltage when a current of 0.3 mA or more is consumed, and adjusts a voltage value introduced into a transformer T1 according to an output voltage selection signal, and converts the voltage value into a transformer and a double voltage output unit 18. The typical SPMS operation of stepping up through the back pressure circuit is shown.

The high-voltage output of the double-voltage output unit is measured by the output current to function as an electrometer through a logarithm amplifier and processed digitally by an analog-to-digital converter coupled to a microprocessor.

The current limit of the current limiter and the output adjuster, which is a high voltage selector circuit, is determined by the feedback signal and the resistance of the transistor. By changing this resistance value, it is possible to enlarge and reduce the current limit region.

In addition, in the high voltage, the output adjuster selects a voltage of 3300V because the current flows weakly in the high vacuum, and 800V is applied in the low vacuum because the current flows a lot. It was made.

For example, when the "H" signal is applied to the output selection terminal, the transistor is turned on, so that the input voltage of the transformer can be adjusted, and the corresponding high voltage is output through the high voltage output terminal.

When no output voltage selection terminal is selected, the maximum voltage is output, so a selection signal must be applied to one terminal, and the selection of this output is determined by the microprocessor.

The reference signal of the log amplifier in the current detection and log amplifier 21 can be set by changing the degree of vacuum in the microprocessor, and it is possible to measure the current from nA level to ㎂ level. At this time, the tilt is adjusted by using a variable resistor, and when the value of the variable resistor is 0, it is set to 1, and when the variable resistor is adjusted, the value is set to 1 or more.

As described above, the present invention changes the applied high voltage according to the degree of vacuum and converts the current into a voltage by using a log amplifier to convert an ion current of several hundred uA to several nA into a voltage. It can measure the vacuum degree widely without the addition of microprocessor, and includes additional functions such as communication and input / output of analog / digital signal, and converts ion current into voltage when adjusting the ionization power supply. By using the voltage value proportional to, accurate high vacuum measurement is possible, and it is possible to reduce the cost of measuring circuit products by simplifying the related electronic circuit part by allowing the microprocessor to take charge of important functions related to operation processing. Bring it.

Claims (1)

The voltage of the switching mode is output from the transformer unit 17 by the high speed switching unit 20 which generates the DC input voltage and the switching pulse through the current limiting unit 16, and the output voltage of the transformer unit is a double voltage output unit ( 18) In the high voltage output circuit for an ion pump that outputs a high voltage by passing it, the higher the degree of vacuum in the ion pump is, the lower the ion current is, the higher the input voltage is automatically applied. A current detection and log amplifier 21 for converting the ion current detected by the double voltage output unit 18 into a voltage signal in accordance with a reference value output from the DAC 23 to lower the input voltage. It generates four kinds of voltage selection signals proportional to the degree of vacuum in accordance with the detected voltage signal level of the log amplification part, and the communication interface 12 coupled with the ADC 22, the DAC 23, the program memory 11, and the PC. A microprocessor 10 having a display interface 24 coupled to the display 25 and a parameter storage memory 14 and a vacuum proportional output voltage value of the microprocessor 10 to the current limiter 16. A high vacuum in the ion pump, characterized in that it comprises an output adjusting unit 15 and an input detecting unit 19 for detecting an over-input state caused by an increase in the input voltage of the transformer to operate the current limiting unit 16. Measuring circuit.