JP2008125325A - Dc high-voltage generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove ripples contained in a DC high voltage which is supplied to a load over an entire frequency band. <P>SOLUTION: This high-voltage generator is provided with resonance transformers 6, 7; a Cockcroft-Walton circuit 8 for boosting and rectifying high-frequency voltages induced at secondary sides of the resonance transformers 6, 7; a filter circuit 9 for removing the ripples contained in the DC high voltage from the Cockcroft-Walton circuit 8; a feedback circuit 13 for supplying a DC high voltage so that the DC high voltage from the filter circuit 9 becomes equal to reference DC voltages to primary sides of the resonance transformers 6, 7; a fluctuation detection circuit 14 for detecting the amount of fluctuation in the DC high voltage from the filter circuit 9; a band-pass filter 15 for allowing a signal of a prescribed frequency band among signal of fluctuation amounts detected by the fluctuation-portion detection circuit 14 to pass through; and an inversion amplifier 16 for inverting the polarity of the signal that has passed through the band-pass filter 15 and supplying the polarity to each of the secondary sides of the resonance transformers 6, 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

   The present invention relates to a direct current high voltage generator provided with a Cockcroft-Walton circuit.

DC high-voltage generators such as high-voltage electron microscopes and focused ion beam devices that ionize atoms, take them out and use them as a beam, and irradiate the material with this ion beam to change the shape and properties of the material As the step-up rectifier circuit, since a high stability is required, a Cockcroft-Walton circuit (CWC) is generally used.
FIG. 1 shows an outline of a DC high voltage generator using a balanced cockcroft-Walton circuit.

  In the figure, reference numeral 1 denotes a power amplifier. A DC voltage from the power amplifier is switched by switching elements 3 and 4 which are complementarily turned on and off by a pulse output from an oscillator 2. Reference numeral 5 denotes a polarity inverter (inverter).

  As a result of the switching, a resonant transformer (a transformer that excites at a resonant frequency determined by the impedance of itself and the Cockcroft-Walton circuit) 6, 7 has a current whose polarity is inverted at a constant cycle, that is, an alternating current flows. Therefore, a high frequency voltage is induced on the secondary side of the transformers 6 and 7.

  The high frequency voltage is composed of two pairs of capacitors and diodes (a first column composed of a plurality of stages of capacitors C1 and D1 and a second column composed of a pair of capacitors C2 and a diode D2). The voltage is boosted and rectified by the Walton circuit 8. The cockcroft-Walton circuit 8 forms a balanced cockcroft-Walton circuit, and balance resistors R1, R2 are provided on the top thereof.

  The high voltage from the connection middle point of these balance resistors R1 and R2 is removed by the filter circuit (ripple removal circuit) 9 including the filter resistor Rf and the filter capacitor Cf.

  The DC voltage generated in this way is supplied to the load 10 as the DC high voltage from the filter circuit 9.

JP 2004-023913 A JP 09-191649 A JP 08-116673 A JP 09-149645 A

  In the DC high voltage generator having such a configuration, the DC high voltage supplied to the load 10 is affected by the temperature drift of the components. Therefore, in order to remove such fluctuations due to the influence of temperature drift or the like, an error amplifier 11 is provided, and the DC high voltage Vo to the load 7 is supplied to the reference DC voltage Vref from the reference power supply 12 via the resistor Ra. Is input to the error amplifier 11 via the resistor Rb, and a DC high voltage is applied from the power amplifier 1 to the resonant transformers 6 and 7 so that the DC high voltage to the load 10 becomes equal to the reference DC voltage. A feedback circuit 13 is provided so as to be supplied to the primary side.

  If the gain of the error amplifier 11 is sufficiently large in all frequency bands, the feedback circuit 13 can ensure high stability in all frequency bands. However, in practice, the error amplifier 8 oscillates with a phase delay in a high frequency band, and the gain cannot be increased in the high frequency band. Therefore, the feedback circuit 13 can sufficiently ensure high stability. Is the low frequency band.

  On the other hand, the filter circuit 9 removes the DC high voltage ripple (variation) from the Cockcroft-Walton circuit 8 but cannot sufficiently remove the ripple (variation) in the low frequency band. It is a ripple (variation) in the frequency band.

  Accordingly, in such a DC high voltage generator, the filter circuit 9 is sufficiently active (variation removal) and the feedback circuit 13 is sufficiently effective (variation removal) between the low frequency band. Noise (variation) in the frequency band could not be removed sufficiently, and the stability in this intermediate frequency band was not good.

  The present invention has been made to solve the problem as described above, and an object thereof is to provide a novel DC high voltage generator.

  The direct current high voltage generator of the present invention includes a transformer that induces a high frequency voltage on the secondary side when an alternating current flows on the primary side, a cockcroft that boosts and rectifies the high frequency voltage induced on the secondary side of the transformer. A Walton circuit, a ripple removal circuit for removing ripples included in the DC high voltage from the Cockcroft-Walton circuit, and a DC high voltage such that the DC high voltage from the ripple removal circuit is equal to a reference DC voltage. In a high voltage generator comprising a feedback circuit configured to remove a fluctuation of a DC high voltage from the ripple removal circuit with respect to a reference DC voltage by supplying to the primary side of the DC high voltage, the DC high voltage from the ripple removal circuit is A fluctuation detection circuit for detecting a fluctuation in voltage, and a signal in a predetermined frequency band among the fluctuation signals detected by the fluctuation detection circuit Band filter that passes, inverts the polarity of the signal passed through the band-filters, characterized in that a supply inverting amplifier on the secondary side of the excitation transformer.

  According to the present invention, fluctuations in the entire frequency band of the DC high voltage to the load can be removed, so that a stable DC high voltage in the entire frequency band can be supplied to the load.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 shows a schematic example of a DC high voltage generator according to the present invention. In the figure, the same reference numerals as those used in FIG. 1 denote the same components.

  The difference between the DC high voltage generator shown in FIG. 2 and the DC high voltage generator shown in FIG. 1 is as follows.

  In the DC high voltage generator shown in FIG. 2, in order to detect only the fluctuation component of the DC high voltage supplied to the load 10, a detection circuit 14 composed of a series circuit of a detection capacitor Cd and a detection resistor Rd is used as a feedback circuit 13. A band-pass filter 15 provided between the load 10 and passing only a fluctuation signal of a frequency band to be removed between the detection circuit and the intermediate point of the secondary side of the resonant transformer 6 and the secondary side of the resonance transformer 6; An inverting amplifier 16 that inverts and amplifies the polarity of the fluctuation signal that has passed through the bandpass filter is inserted.

  In the DC high voltage generator having such a configuration, the DC voltage from the power amplifier 11 is switched by the switching elements 3 and 4 that are complementarily turned on and off by the pulse output from the oscillator 2.

  By the switching, an alternating current flows on the primary side of the resonant transformers 6 and 7, thereby inducing a high-frequency voltage on the secondary side of the transformers 6 and 7.

  The high-frequency voltage is boosted and rectified by the Cockcroft-Walton circuit 8, and a DC high voltage is obtained at the midpoint between the two balance resistors R1, R2 of the Cockcroft-Walton circuit. A high-frequency ripple component included in the DC high voltage is reduced by the filter circuit 9 and supplied to the load 10.

  This high DC voltage is sent from the reference power supply 12 via the resistor Ra to the error amplifier 11 to which the reference DC voltage is supplied via the resistor Rb. The error amplifier has a DC voltage such that the DC high voltage Vo / Ra via the resistor Ra becomes equal to the reference voltage Vref / Rb from the reference power source 12 via the resistor Rb from the power amplifier 1 to each of the resonant transformers 6 and 6. 7 to be supplied to the primary side. As a result, the low frequency fluctuation component with respect to the reference DC voltage of the DC high voltage sent to the load 10 is removed.

  Further, the fluctuation of the DC high voltage is detected by the detection circuit 14 and sent to the band filter 15.

  The band-pass filter passes only the fluctuation signal of the frequency band to be removed among the fluctuations of the DC high voltage, that is, the fluctuation signal of the intermediate frequency band between the low frequency band and the high frequency band. Send to.

  The inverting amplifier inverts and amplifies the polarity of the DC high voltage fluctuation signal in the intermediate frequency band, and supplies it to the intermediate point between the secondary side and the secondary side of the resonant transformer 6, and the Cockcroft-Walton circuit 8 is changed. As a result, fluctuations in the intermediate frequency band of the DC high voltage sent to the load 10 are removed.

As a result, the DC high voltage from the Cockcroft-Walton circuit 8 supplied to the load 10 through the filter circuit 9, the feedback circuit 13, and the detection circuit 14 is obtained by removing fluctuations in the entire frequency band.
In the above example, the present invention is applied to a DC high voltage generator using a balanced cockcroft-Walton circuit as a cockcroft-Walton circuit. However, the present invention is not limited to other types. Needless to say, the present invention can also be applied to a DC high voltage generator using the Cockcroft-Walton circuit.

1 shows a schematic example of a conventional DC high voltage generator. 1 shows an example of a DC high voltage generator according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Power amplifier 2 ... Oscillator 3, 4 ... Switching element 5 ... Polarity inverter 6, 7 ... Resonance transformer 8 ... Cockcroft-Walton circuit 9 ... Filter circuit Rf ... Filter resistance Cf ... Filter capacitor
DESCRIPTION OF SYMBOLS 10 ... Load 11 ... Error amplifier 12 ... Reference power supply 13 ... Feedback circuit 14 ... Detection circuit 15 ... Band filter

Claims (4)

  When an alternating current flows on the primary side, a transformer that induces a high-frequency voltage on the secondary side, a Cockcroft-Walton circuit that boosts and rectifies the high-frequency voltage induced on the secondary side of the transformer, from the Cockcroft-Walton circuit A ripple removing circuit for removing ripples included in the DC high voltage, and supplying the DC high voltage to the primary side of the transformer so that the DC high voltage from the ripple removing circuit is equal to the reference DC voltage. Fluctuation detection for detecting fluctuations of DC high voltage from the ripple removal circuit in a high voltage generator having a feedback circuit configured to remove fluctuations of the DC high voltage from the removal circuit with respect to the reference DC voltage Circuit, a bandpass filter for passing a signal of a predetermined frequency band among signals of fluctuation detected by the fluctuation detection circuit, Inverts the polarity of the signal passed through the filter, the DC high voltage generator, characterized in that a supply inverting amplifier on the secondary side of the excitation transformer.   The DC high voltage generator according to claim 1, wherein the fluctuation detection circuit includes a capacitor that passes an AC component included in the DC high voltage from the ripple removal circuit.   2. The bandpass filter is configured to pass a signal in a frequency band intermediate between a high frequency band of a ripple removed by the ripple removal circuit and a low frequency band corresponding to a fluctuation removed by the feedback circuit. DC high voltage generator.   2. The feedback circuit includes an error amplifier to which a DC high voltage and a reference DC voltage from the ripple removal circuit are input, and a power amplifier that amplifies an output of the error amplifier and supplies the amplified output to the primary side of the transformer. The DC high-voltage generator as described.

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