KR100228419B1 - Filament heating apparatus for x-ray tube of high frequency wave type - Google Patents

Abstract

TECHNICAL FIELD The present invention relates to a filament heating apparatus for an X-ray tube of a high frequency type, comprising: a chopper 100 for converting a commercial power source into a necessary DC power source and keeping it constant; A high frequency inverter (200) for converting the direct current power into a high frequency alternating current voltage; A current controller 300 for comparing a current flowing through a primary side of the transformer with a target value and outputting a signal for adjusting a width of a voltage intermittent pulse output from the high frequency inverter 200; A signal synchronizing unit 400 for changing a target current value set in synchronization with the X-ray imaging step; A voltage adjuster 500 for comparing the DC voltage with a predetermined reference value and applying an error value between the DC voltage and the chopper 100 to the chopper 100; An initial voltage control unit (600) for controlling the chopper (100) so that the DC voltage gradually increases at the start of the apparatus; And an over-current limiter (700) for shutting off the output voltage of the high-frequency inverter (200) when an over-current flows in the primary side of the transformers (T1, T2), thereby reducing the size of the heat- It is possible to cope with the rating of filaments of the type and to perform the X-ray photographing more easily, and also to be able to take a quick and precise X-ray photographing.

Description

Filament heating device for high-frequency X-ray tube

The present invention relates to a filament heating apparatus for an X-ray tube of a high frequency type, comprising a step-down type chopper and a high frequency inverter using a pulse width modulation method, The size of the transformer or the like is largely reduced by making the driving frequency high and the current / voltage is appropriately applied to the rating of the transformer for inducing the required current and voltage, and the current flowing in the filament is precisely controlled to a minute amount To a filament heating apparatus for an X-ray tube of a high-frequency type as far as possible.

Generally, an X-ray tube having a voltage-current characteristic of a twin-tube is used to heat a filament of a negative electrode to generate a hot electron. To heat the filament, a heating transformer is used. The filament increases or decreases the amount of thermoelectrons emitted by the secondary side heating current supplied from the transformer, and the amount of current flowing through the x-ray tube is determined by the amount of thermoelectrons emitted. Since the generation intensity of the X-rays is dependent on the current flowing through the X-ray tube, the heating variation of the filament of the X-ray tube greatly affects the output of the X-rays. Therefore, a filament heating current controller for stabilizing the fluctuation of the filament heating amount becomes necessary.

The conventional filament includes a simple ballast 10 at a commercial frequency (60 Hz) power source and a variable resistor 20 for determining the amount of current flowing to the primary side of the transformer T, as shown in FIG. 8 Respectively.

In the conventional filament heating apparatus configured as described above, the stabilizer 10 outputs an AC voltage which is constantly maintained within a predetermined allowable range even when the fluctuation of the commercial AC voltage (60 Hz, 110 to 220 V) This voltage is supplied to the primary side of the transformer T by the resistance value of the variable resistor 20 set by the operator, and the current is induced to the secondary side to be applied to the filament of the x- 30 are heated.

However, the conventional filament heating apparatus configured as described above can not precisely control the current flowing through the x-ray tube, can not operate in response to various types of x-rays and wide load conditions, It had a problem that it was slow.

Accordingly, it is an object of the present invention to overcome the above-mentioned problems, and it is an object of the present invention to provide a transformer that can operate in response to various kinds of X-ray types and wide load conditions, Another object of the present invention is to provide a high frequency filament heating apparatus for an X-ray tube capable of precisely controlling a current flowing through a filament, It is still another object of the present invention to provide a high frequency filament heating apparatus for an x-ray tube which is easy to use by automatically outputting a control signal for controlling filament heating and other elements required for radiography by simple operation of an operator, Another object of the present invention is to provide a method for controlling a plurality of X- Frequency filament heating apparatus capable of providing a steady power without fluctuation in spite of the fact that a sudden increase in current / voltage is prevented from being introduced at the time of initial start-up The present invention also provides a high frequency heating apparatus for an X-ray filament that protects a device to be used and can extend its service life. Another object of the present invention is to provide an efficient high frequency And a filament heating device for an X-ray tube.

FIG. 1 is a configuration diagram of a preferred embodiment of a filament heating apparatus for a high frequency type x-ray tube according to the present invention,

FIG. 2 is a control operation waveform diagram for pulse width modulation of the high-frequency inverter of FIG. 1,

3 is a detailed configuration diagram of the signal synchronization unit of FIG. 1,

FIG. 4 is a detailed configuration diagram showing a part of the current control unit in FIG. 1 in more detail,

FIG. 5 is a detailed configuration diagram of the current calculation unit of FIG. 4 in more detail,

FIG. 6 is a detailed diagram showing the proportional integral controller of FIG. 4 in more detail,

FIG. 7 is a detailed configuration diagram of the pulse width modulator of FIG. 1,

FIG. 8 shows a configuration of a conventional filament heating apparatus for an X-ray tube.

DESCRIPTION OF THE REFERENCE NUMERALS

A: small focus filament B: large focus filament

C1, ..., Cm: capacitors C101 and C102: capacitor

C201, C202: Divisional capacitor C203: Impedance matching capacitor

D214-1, D214-2: Signal delay element L101: Inductor

R1, ..., Rn: Resistors R501 and R502: Voltage detecting resistors

S101: Chopper switch S201, S202: Inverter switch

SW321, SW322: opening / closing switch SW: filament selection switch

T, T1, T2: Heating transformer VR1, ..., VRk: Variable resistance

ZD1: Zener diode 10: Ballast

20: variable resistor 30: filament

100: Step-down type chopper 101: Bridge diode

110: Pulse width modulator 200: High frequency inverter

210: pulse width modulator 211:

212: Triangle wave generator 213:

213-1: first comparator 213-2: second comparator

214: Dead time compensation unit 214-1, 214-2: Logic multiplication element

215, 216: Logical multiplication element 300:

310: current detector 311: current sensor

312: current calculation unit 312-1: gain adjustment unit

312-2: filter 312-3: rms converter

320: target value variation setter 321: proportional integral controller

321-1: Error amplifier 321-2: Proportional controller

321-3: Integral controller 400: Signal synchronizer

401: rising edge trigger 402, 403: falling edge trigger

404: Logical negative element 420: Timer

431: an OR circuit element 432, 433:

500: voltage adjuster 510: voltage compensator

600: initial voltage control unit 700: overcurrent limiter

800: LED indicator

According to another aspect of the present invention, there is provided a filament heating apparatus for an X-ray tube including a transformer, wherein the filament heating device for an X- Variable rectifying means for converting and holding an arbitrary DC voltage suitable for being supplied with a voltage and a current according to the rated voltage; DC / AC converting means for intermittently interrupting the converted DC voltage with a high frequency control signal to output a high frequency AC voltage to the transformer; A control signal for detecting or calculating an alternating current flowing in a primary side of the transformer, comparing the value with a set target current value, and increasing or decreasing an effective value of the alternating voltage output from the direct current / To the DC / AC conversion means for outputting the current; A signal synchronizing means for synchronizing with the X-ray imaging step to change a set target current value which is a comparison reference of the current control means, and to output synchronized control signals for thermoelectronic emission; And initial voltage control means for controlling the variable rectifying means so that the DC voltage output from the variable rectifying means gradually increases and reaches a set value by operating only at the start of the apparatus, The apparatus is characterized in that the detected value is converted to an effective value which is an actual amount of energy transferred and then a control operation is performed in accordance with the value. The filament heating apparatus for an X-ray tube of high frequency type according to the present invention comprises: And a voltage regulating means for regulating a time period during which the voltage is transferred from the input to the output of the variable rectifying means in order to maintain a constant DC voltage outputted from the variable rectifying means. Wherein said DC / AC converting means comprises an output terminal As further comprising a capacitor for impedance matching seongsoja will have a second characteristic.

The filament heating device for a high frequency type x-ray tube according to the present invention configured as described above applies a current suitable for the rating of the filament for an X-ray tube to the filament within a precise range as follows.

First, the variable rectifying means outputs a DC voltage of a reference value arbitrarily set to generate a voltage / current matching the rating of the filament heating transformer (or the rating of the filament) from the inputted commercial AC voltage. And the voltage output from the variable rectifying means is converted back to a high frequency AC voltage by the DC / AC converting means. The converted AC voltage of the high frequency induces a large amount of energy to the secondary side through the transformer in a short time, thereby rapidly heating the filament, and the number of turns of the transformer for generating a constant inductance component, So that it is possible to reduce the size of the used heat transformer.

The current control means detects the alternating current flowing in the primary side of the transformer and converts the value into a value of the effective value to which the actual energy is transferred, AC converting means is controlled to reduce the amount of energy delivered by reducing the time of voltage application to the transformer, and if the effective value is smaller than the effective value, the DC / AC converting means controls the voltage to the transformer side By increasing the applied time to increase the amount of energy delivered, the current for replenishing the thermoelectrons emitted from the filament is kept constant. On the other hand, the voltage regulating means detects the DC voltage outputted from the variable rectifying means and compares the value with a DC voltage of a reference value required for applying a voltage / current matching the rating of the heating transformer to the transformer, The output voltage of the variable rectifying unit is always maintained at a required DC voltage by slightly increasing or decreasing the energy delivered to the output terminal of the variable rectifying unit according to the result.

The signal synchronizing means senses the signal when the operator presses the operation switch for radiographing the X-ray, calculates the current required for the operation, and changes the target current value to the current control means. The control signal for rotating the X-ray tube and the control signal for applying the high voltage between the anode and the cathode of the X-ray tube are synchronously generated at the time of the X-ray emission operation so that the entire process is automatically performed by the simple operation of the operator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the configuration and operation of a preferred embodiment of a filament heating apparatus for a high frequency type x-ray tube according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of a preferred embodiment of a filament heating apparatus for a high frequency type x-ray tube according to the present invention, which comprises a step-down type chopper 100 for converting a commercial power source into a necessary DC power source and keeping it constant; A high frequency inverter 200 for interrupting a voltage transmitted to the output terminal by using the converted DC power as a high frequency control signal and outputting a high frequency AC voltage to the transformers T1 and T2; In order to keep the current flowing in the primary side of the transformers T1 and T2 constant, the current is detected from the primary side, and the current is compared with the target current set as the target value, and the high- A current controller 300 for adjusting the width of the voltage intermittent pulse; A signal synchronizing unit 400 for synchronizing with an operator's X-ray imaging step to change a target current value set in the current control unit 300 and outputting control signals for thermoelectron emission or the like; A voltage regulator 500 for detecting an output voltage of the step-down chopper 100 and comparing the output voltage with a reference value set to match the rating of the transformers T1 and T2 and applying the error value to the chopper 100, ; An initial voltage control unit (600) for operating the chopper (100) so that the DC voltage output from the chopper (100) gradually increases to a predetermined value when the apparatus is started; An overcurrent limiter 700 for controlling the high frequency inverter 200 to prevent a voltage from being applied to the transformers T1 and T2 when the current flowing through the primary side of the transformers T1 and T2 exceeds a limited value; And an LED indicator 800 for displaying an operating state and an overcurrent state of the device. In FIG. 1, a small focus filament A, a large focus, A filament B and a switch SW for selecting a focusing filament heating transformer T1 and a focusing filament heating transformer T2 as well as a filament A and B to be heated by the operator are also shown.

Among the above components, the step-down type chopper 100 includes a bridge diode 101 for converting a commercial AC power source to a constant DC power source, a capacitor C101, A switch S101 for interrupting transmission of the converted DC power to the output terminal; A pulse width modulator (110) for adjusting a duty cycle at which the switch (S101) is interrupted to adjust a value of a DC power supplied to an output terminal; And a capacitor C102 which is a filter element for smoothing the voltage output from the switch S101 and an inductor L101, and the high frequency inverter 200 converts the applied direct current voltage Capacitors C201 and C202 respectively for partial pressure; Switches (S201, S202) for interrupting transmission of the divided voltage to the output; A pulse width modulator 210 for alternately opening and closing the switches S201 and S202 at a constant rate; And a capacitor C203 for matching the input impedance of the transformer T1 and the transformer T2. The current controller 300 includes a current detector 310 for detecting a current on the primary side; And a target value variation setter 320 for applying a signal for controlling a duty ratio of the pulse width modulator 210 according to a control signal of the signal synchronizing unit 400 and a detected current value, The voltage adjusting unit 500 includes: Resistors R501 and R502 for dividing and detecting the output voltage of the chopper 100; And a voltage compensator 510 for comparing the detected voltage with a voltage of a reference value and outputting a signal for adjusting the duty ratio of the pulse width modulator 110 according to the comparison result.

Hereinafter, the operation of the preferred embodiment of the filament heating apparatus for a high frequency type x-ray tube according to the present invention will be described in detail.

First, when power is applied, a DC voltage is applied to the input terminal of the switch S101 by the bridge diode 101 and the capacitor C101. The pulse width modulator 110 outputs an intermittent signal of about 40 kHz for interrupting the switch S101 to transmit the voltage at the input terminal of the switch S101 to the output terminal. The output voltage is increased by increasing the energy delivered to the output stage and the output voltage is decreased when the duty ratio is decreased. Therefore, it is necessary to set the application rate that can correspond to the rating of the heating transformer T1 or T2 or the rating of the cathode filament, So that various ratings can be satisfied.

In the initial stage of starting, the intermittent signal is controlled by the initial voltage control unit 600 and gradually increases the duty ratio of the output pulse. As the duty ratio of the output pulse increases, the voltage of the output terminal gradually rises, so that an excessive voltage application phenomenon due to the initial applied voltage does not occur. After a certain period of time elapses after the initial start, the pulse width modulator 110 adjusts the duty ratio according to the error value applied by the voltage compensator 510 without the duty ratio being controlled by the initial voltage controller 600 . The output voltage of the switch S101 is smoothed by the capacitor C102 and the inductor L101 and the smoothed output voltage is detected by the resistors R501 and R502. The voltage compensator 510 compares the detected voltage with a reference value and applies an error value according to the comparison result to the pulse width modulator 110. If the detected voltage value is smaller than the reference voltage, And outputs an error value for finely decreasing the duty ratio of the pulse if the detected value is larger. Accordingly, the pulse width modulator 110 may be controlled by increasing the current consumed or by changing the input voltage while interrupting the switch S101 according to the duty ratio of the pulse set to match the output voltage of the chopper 100 When the output DC voltage fluctuates, the output voltage is finely compensated to maintain the DC voltage always matching the reference value set to meet the electrical rating.

The DC voltage which is kept constant is divided by the capacitors C201 and C202 and divided by the switches S201 and S202 to be selected by the switch SW of the transformers T1 and T2 The output of the transformer is such that the pulse width modulator 210 intermittently switches the switches S201 and S202 to a high frequency signal of about 20 kHz to generate high frequency alternating current. If a high frequency alternating current is applied to the transformers T1 and T2, the impedance of the circuit increases and thus the high speed filament heating is interrupted. The capacitor C203 controls the input impedance of the transformers T1 and T2 So that energy can be smoothly transmitted to the secondary side even when driven by the high frequency AC as described above. In order to reduce the loss due to the eddy current in the transformer when the high-frequency system is used, it is preferable to fabricate the transformers T1 and T2 using a ferrite core.

The current detector 310 detects a current flowing in the primary side of the transformers T1 and T2 and transmits the detected current to the target value variation setter 320. [ The target value variation setter 320 compares the current value of the currently set target value with the detected current value when a specific control signal from the signal synchronizer 400 is applied and outputs the detected current value to the pulse width modulator 210 This procedure will be described in detail with reference to the pulse waveform modulation control operation waveform diagram of the high-frequency inverter 200 of FIG. 2.

First, for convenience of explanation, it is assumed that the adjustment signal PI + output from the target value variation setter 320 is a value shown in FIG. 2, the negative signal PI- is a signal generated by inverting the input adjustment signal PI + in the pulse width modulator 210. The pulse width modulator 210 compares the triangular wave generated by the pulse width modulator 210 with the adjustment signal PI +, PI-, and if the signal value of the triangular wave is greater than the value of the positive signal PI + The switch 202 is turned on by applying the signal GS20 shown in FIG. 2 to the gate of the control signal S202 and the signal value of the triangle wave is set to the value of the negative signal PI- The switch S201 is turned on. When the switches S201 and S202 are operated to open and close, the output voltage Vout of the high frequency inverter 200 outputs an AC voltage similar to the second voltage. A current flows from the output voltage to the primary side of the transformers T1 and T2. The current is detected by the current detector 310 and compared with the target value by the target value variation setter 320 And amplifies the adjustment signal PI + when the value is larger than the target value. When the adjustment signal PI + is finely amplified, the inverted adjustment signal PI- is also minutely amplified together with a negative value. Therefore, as shown in FIG. 2, the switches S201, The pulse widths of the turn-on signals GS201 and GS202 applied to the gates of the transformers T1 and T2 are reduced so that the width of the output voltage Vout is reduced, The current is reduced. On the contrary, when the current flowing in the primary side decreases and the adjustment signal PI + is slightly decreased by the target value variation setter 320, the width of the output voltage Vout increases to finely increase the current flowing in the primary side . The current controller 300 applies a signal to the pulse width modulator 210 to adjust the duty ratio of the control signal applied to the switches S201 and S202 so that the primary side of the transformers T1 and T2 So that the current flowing through the resistor is always maintained at the current value of the predetermined target value.

Hereinafter, the operation of the preferred embodiment of the heating apparatus for a high-frequency type x-ray tube according to the present invention will be described in detail with reference to the constitution diagrams showing the respective components in more detail.

FIG. 3 is a detailed block diagram of the signal synchronizer 400, which includes a rising edge trigger 401; Two falling edge triggers 402 and 403; Flip flop 410; And a timer 420; 4 shows the current control unit 300 in more detail. The current control unit 300 controls the operation of the signal synchronizing unit 400, Switches SW321 and SW322 for controlling that control signals ('preheating', 'ready') are applied to the pulse width modulator 210; A current sensor 311 for sensing a primary current of the transformers T1 and T2; A current calculator 312 for converting the sensed current into an effective value; And a proportional-plus-integral controller (321) for comparing the calculated value of the effective value with the current value of the target value and outputting an adjustment signal (PI +) to the input terminal of the switch (SW322).

3, when the operator presses the 'Ready' switch, the rising edge trigger 401 recognizes the push signal and sets the output value Q of the flip-flop 410 until that time It makes the 'ready' signal HIGH while resetting the 'preheat' signal which kept HIGH state. When the 'ready' signal becomes HIGH, this signal is applied to the target value variation setter 320 to short-circuit the switch SW322 so that the output of the proportional-plus-integral controller 321 is input to the pulse width modulator 210 . The current sensor 311 senses the primary current of the transformers T1 and T2 and inputs the sensed value to the current calculator 312. The current calculator 312 calculates the alternating current Is converted into a value of an effective value indicating a value to which energy is transferred, and the value is applied to the proportional-plus-integral controller 321. The proportional-plus-integral controller 321 compares the current value If ^{* with the} current value If ^* set as the target value and outputs the adjustment signal PI + according to the result as described above. The adjustment signal PI + Signal to the pulse width modulator 210 so that the effective value of the current flowing in the primary side of the selected transformer of the transformers T1 and T2 reaches the target value and becomes equal to the target value By keeping the value constant, the filament (A or B) of the selected secondary side is rapidly heated by the 'ready' signal. The signal synchronizing unit 400 outputs the 'Rotor' signal together with the 'ready' signal in a HIGH state. When the 'Rotor' signal becomes HIGH, the anode (not shown) of the x-ray tube starts to rotate After this, the hot electrons emitted from the cathode are hit evenly.

If the operator presses the 'Shoot' switch while the 'Ready' switch is pressed, the user is notified of the time of the launching time set by the timer 420 because the user has a normal rotation speed when about 0.4 to 0.8 seconds have elapsed since the anode started to rotate. A signal is generated. When the output of the timer 420 becomes HIGH, the signal outputs 'Kvp' control signal HIGH through the AND gates 432 and 433 to apply a very high voltage to the positive and negative electrodes of the x-ray tube, So that the hot electrons are emitted. When the thermoelectrons begin to emit, the current flowing in the secondary side begins to decrease. The primary current of the transformer is detected from the primary side of the transformer, and the primary current is kept constant by compensating the current according to the current control procedure described above , Thereby continuously compensating for the released hot electrons.

The falling edge triggers 402 and 403 reset the flip flop 410 so that all signals other than the 'preheat' signal are LOW State. The 'preheat' signal in the HIGH state and the 'ready' signal in the LOW state are input to the target value variation setter 320 and supplied to the proportional-plus-integral controller 321 ) Is replaced with a constant current which is a 'preheating reference current' in the adjustment signal PI +. Therefore, in the preheating state, the pulse width modulator 210 is a signal having a constant pulse width so that the current corresponding to the preheating reference current always flows to the primary side of the transforming voltages T1 and T2. The switches S201 and S202 ) Are alternately interrupted. In this case, the control process by the current feedback is not performed.

5 to 7 are diagrams showing the current calculator 312, the proportional integral controller 321 and the pulse width modulator 210 among the constituent elements of FIG. 4 in more detail. The internal operation of each of the components 312, 321, and 210 will be described in more detail.

5, first, the current sensor 311 senses a current from the primary side of the transformers T1 and T2, and the sensed fine current component is passed through the gain adjuster 312-1 The amplified signal is filtered using a 20-kHz band filter 312-2 to detect only the current component on the primary side of the amplified signal. When only the sensed current component is extracted, the current value is inputted to the effective value converter 312-3 and the effective value If of the sensed current is outputted. The proportional integral controller 321 shown in FIG. 6 converts the filament heating target current value If ^* into an actual value converted into an effective value The proportional controller 321-2 and the integral controller 321-3 amplify the difference between the heating current value If by the error amplifier 321-1 and use the amplified error signal as a reference, ). At this time, when the adjustment signal PI + rises above a certain level, the Zener diode ZD1 bypasses the current of the output stage, thereby causing the pulse width modulator 210 to excessively increase the energy To the primary side of the transformers T1, T2. The control signal PI + obtained as described above is input to a pulse width modulator 210 configured as shown in FIG. 7. In the pulse width modulator 210 of FIG. 7, And generates an inverted signal PI- of the input adjustment signal PI +. The adjustment signal PI + and the inverted signal PI- are respectively compared with the triangular wave output from the triangle wave generator 212 in the comparator 213. The first comparator 213-1 compares the inverted signal PI- The second comparator 213-2 outputs a HIGH state only in a section where the triangular wave signal is larger than the adjustment signal PI +. (See FIG. 2). The delay of the switching element The output signal of the comparator 213 passes through the dead time compensator 214 to insert a dead time into the logic signal output as described above. The signal input to the dead-time compensator 214 is input to the direct AND gates 214-1 and 214-2 and is simultaneously input to the delay elements D214-1 and D214-2. The delay elements D214- 1 and D214-2 are delayed by a predetermined time and input to the logical multiplication devices 214-1 and 214-2 as they are as a raw signal, so that a logical multiplication operation is performed with a signal not delayed. Therefore, the HIGH state signal output from one of the comparators 213 is removed from the signal front end portion in the HIGH state by the time delayed by the delay elements D214-1 and D214-2, that is, Time is inserted to completely prevent the short-circuit between the switch arms (S201 and S202) of the high-frequency inverter (200). As described above, the signal having the dead time inserted is input to the gates of the switches S201 and S202 in the high frequency inverter 200 through the AND gates 215 and 216, respectively.

A current limit signal, which is a control signal output from the overcurrent limiter 700 shown in FIG. 4, is input to one input terminal of the AND gates 215 and 216, Current limit signal 'to a LOW state when it is determined that the current detected from the current sensor 311 is higher than a predetermined level. When the 'current limit signal' is simultaneously input to the logic multipliers 215 and 216 in a LOW state, the signal applied to the gates of the switches S201 and S202 is LOW Energy is not transferred to the transformers T1 and T2, and the current of the primary side, over which the overcurrent flows, is reduced.

The filament heating device for a high frequency type x-ray tube according to the present invention operates as described above. Since the signal for transmitting energy to the transformer is a high frequency, the size of the heating transformer can be miniaturized. Therefore, It is possible to reduce the size of the transformer enclosure including the insulating oil provided with the filament heating transformer. Actually, according to the embodiment of the present invention, a high frequency signal of 20 kHz is used as a heating signal and a ferrite core is used as a material of the transformer to reduce the size of the heat transformer to 64 mm x 59 mm x 32 mm and the weight to 210 g .

Further, by adjusting the input voltage of the high-frequency inverter using a chopper which can freely change the magnitude of the output DC voltage, it is possible to adjust the input voltage of the high- It is convenient, and the control signal necessary for radiography is automatically synchronized and output by a simple switch operation of the operator, thereby making it easier to take an X-ray and to reduce operational errors that may occur.

The filament heating apparatus for a high frequency type x-ray tube according to the present invention comprises a controller for maintaining a current for heating the filament and a DC voltage provided for outputting a current to a constant level regardless of any external load, Is a very useful and convenient invention that can make the X-ray imaging more precise by keeping the number of thermoelectrons emitted from the cathode of the X-ray tube constant.

Claims (4)

A filament heating apparatus for an X-ray tube comprising a transformer, comprising: a variable rectifying unit for converting an input AC voltage into an arbitrary DC voltage suitable for supplying a voltage and a current suitable for rating of a cathode filament, Way; DC / AC converting means for intermittently interrupting the converted DC voltage with a high frequency control signal to output a high frequency AC voltage to the transformer; A control signal for detecting or calculating an alternating current flowing in a primary side of the transformer, comparing the value with a set target current value, and increasing or decreasing an effective value of the alternating voltage output from the direct current / To the DC / AC conversion means for outputting the current; A signal synchronizing means for synchronizing with the X-ray imaging step to change a set target current value which is a comparison reference of the current control means, and to output synchronized control signals for thermoelectronic emission; And an initial voltage control means for controlling the variable rectifying means so that the DC voltage output from the variable rectifying means is gradually increased to reach a set value while operating only at startup of the apparatus. . The apparatus for heating filament of claim 1, wherein the calculation is to obtain an effective value from the detected AC value. The variable rectifying device according to claim 1, further comprising: a rectifying device for rectifying the direct-current voltage outputted from the variable rectifying device to an output from the variable rectifying device in order to detect a DC voltage output from the variable rectifying device and compare the detected DC voltage with a set value, Further comprising a voltage adjusting means for adjusting a time to which the filament is to be delivered. The filament heating apparatus of claim 1, wherein the DC / AC conversion means further comprises a capacitive element for matching an impedance to an output terminal in order to increase energy transmitted to the transformer.