JPH04112497A - Filament power source device for x-ray tube - Google Patents

Abstract

PURPOSE:To shorten a preliminary overheating time by detecting a difference between an actual value and a target value of a filament temperature suitable for obtaining a desired tube current, and performing over-drive at a frequency according to a magnitude of a difference signal during a preliminary heating period of the filament temperature. CONSTITUTION:When a detection voltage Vd is lower than a set value of an undervoltage setter 21 at the time of pre-heating start, a comparator 22 determines an undervoltage to output an undervoltage signal S1 of an H level. A set signal S2 of a flip-flop 25 is output at a time t1 on the basis of an AND condition between the signal S1 and a signal S6 of an H level applied from an on-delay timer 28 to an AND gate 24. When the flip-flop 25 is latched by the signal S2 and a signal S3 of an H level is output to the output side thereof, a (b) contact of an analog switch 29 is closed and an over-drive signal is added from a signal source 30 to the input side of a current regulator 13. Therefore, an energizing time of a switching element 3A of a step-down chopper is increased, thus performing over-drive.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a filament power supply device for an X-ray tube used in an X-ray imaging device, and in particular to an electric power supply device for reducing the filament's reserve power and heating time. This invention relates to a power supply device equipped with a complete dry-life circuit.

[Conventional technology]

FIG. 8 is a schematic configuration diagram showing a conventional filament power supply device for an X-ray tube. As shown in the figure, the filament power supply device is composed of a power supply section 1 and a control circuit 15 thereof. The power supply section 1 includes a first-current power supply 2, a switching element 3A, a diode 3B, a reactor 6C2, a smoothing capacitor 3D, and a chip drive circuit 12 that supplies a driving pulse for the switching element 3AK. Step-down chopper 3 output t'' - I received by next side center tap
l! ! Green transformer 5. A pair of switching elements 4A.

4B, and a center-tap circuit type 180 conduction type input 4 comprising a drive circuit 11 and a drive circuit 11 thereof. Further, the secondary side of the insulating transformer 50 is connected to the filament 6F of the X-ray tube 6, and the heating power supplied to the filament, that is, the filament current If and the filament voltage Vf, is supplied to the X-ray tube 6 from the high-voltage power supply device 7. voltage vp.

Since K is controlled to a predetermined value in correspondence with the tube current p, the X-ray tube 6 generates all X-rays of desired intensity.

On the other hand, the control circuit 15 includes a current setter 14 that outputs a control target value f8 of the filament current f in accordance with the set values of the tube voltage setter 18 and the tube flow film regulator 19, and a current detector 8. The output current of the step-down chipper 3, in other words, the output current of the isolation transformer 5, is Constant current control of primary current. In addition, the current flowing into the center tap of the secondary winding is transferred to the secondary winding by alternately turning on and off a pair of switching elements t-180° of the 180" conduction type input/coupler 4. A square wave AC voltage Vf is generated,
The filament of the X-ray tube B is supplied as a filament electric current f.

FIG. 9 is a characteristic diagram showing an example of the wave characteristics and filament characteristics of the Xa tube, where 'MIi flow p is the tube voltage V
p and filament current f (related to filament m degree).

Therefore, by storing the target value of If corresponding to the set values of the tube voltage and tube IE flow as an arbitrary function in the setter 14 of the target current factor f in the control circuit 15, the target value factor f8 is output. be able to. Incidentally, since the filament current flow f and the voltage Vf are in a proportional relationship, the control circuit may be changed to a voltage control type, or a running power control type may be used for both. Also, reactor 6
Since the current flowing through C is proportional to the filament current f, if the current detector 8 detects the output 'IE current of the collar 3, t is applied to the secondary side of the isolation transformer, which has a high potential.
The disadvantages of placing a flow detector can be avoided.

[Problem to be solved by the invention]

In the conventional device described above, it takes some time after the heating of the filament is started until the filament temperature becomes constant and the desired tube current p determined by the optical characteristics flows stably through the tube in FIG. This time is called the preheating time in XN & photographing equipment.

If this preheating is insufficient, the exposure conditions for X-ray photography will become unstable, and if preheating takes too long, the subject may move or become deformed during that time, making it difficult to accurately image the desired area. The problem arises that it cannot be done. Therefore, a method has been proposed in which a thick filament voltage or current is supplied at the beginning of the preheating period (referred to as overdrive) to accelerate the heating of the filament, thereby shortening the preheating period (Japanese Patent Application Laid-Open No. 55-124998. According to the reference table, in this method, the time width of preheating is changed in anticipation, so the increase in filament a degree due to the history of repeated preheating and imaging, and the target Because it is not possible to detect a difference of 1 degree between filament I and finely correct the control amount, the overdrive amount tends to be over or under, and this causes the time required to reach the target temperature and stabilize the overdrive. A problem arises that is almost the same as if it were not performed.

An object of the present invention is to obtain a filament power supply device equipped with an overdrive circuit that can reliably and stably shorten preheating time.

[Means to solve the problem]

In order to solve the above-mentioned problems, 1. According to the present invention, a t-source which is composed of an inverter of a step-down tube and a center-tap transformer circuit type and supplies filament heating power to the X1@ tube determined based on the tube voltage and tube current. a control circuit comprising: a setter for the output target value of the power supply unit; and a regulator for controlling the drive circuit of the step-down chip 5 based on the output target value and the actual value. A detection circuit detects that there is a difference exceeding a predetermined level between the actual value and the output target value, and the control circuit receives the detection signal through a t-AND gate and receives a signal to overdrive the power supply section for a predetermined time. an overdrive circuit that outputs an output to the circuit, and is configured to alternately repeat detection of the difference and overdrive by the detection circuit until the filament temperature reaches the target value, and the detection circuit The overdrive circuit that receives the signal 1 via the AND gate is composed of a drive circuit consisting of a slip-flop circuit and a monostable multi-circuit, a main circuit section that closes the circuit according to the output signal of the drive circuit, and emits an overdrive signal, and a plurality of on-delay timers. It shall consist of a timing control section. Also, specifically,
If the control circuit does not consist of a target current setter and a current regulator,
An undervoltage setting device that outputs a set voltage lower than the output target value based on the tube voltage setting value and tube current setting value, and an undervoltage signal by comparing the output with a detection voltage that is proportional to the filament voltage. A detection circuit consisting of a detection circuit consisting of a comparator that generates a signal, a detection circuit consisting of a combination of an underimpedance setting device and a comparator that compares the set value with the output of an impedance calculation device, and a control circuit comprising a target voltage setting device and A device consisting of a combination of voltage regulators and a detection circuit consisting of an overcurrent setting device and a comparator, and a detection circuit comprising an underimpedance setting device and a comparator that compares the set value with the output of an impedance calculator. The control circuit consists of a combination of a power setting device and a power regulator that calculates an error between the output of the power setting device and the output of the power generator, and also includes an undervoltage setting device and the output of the power setting device. The detection circuit is equipped with a detection circuit that compares the detected voltage with a proportional relationship to the current voltage, and the detection circuit is a combination of an underimpedance setter, an impedance calculator, and a comparator that compares the outputs of both. shall be included.

[Effect]

In this invention, during the preheating period, as the filament temperature increases, its impedance increases.
This method is designed to take into consideration the fact that a difference occurs between the target value and the actual value of i, and the overdrive signal t- is sent to the overdrive signal t- for a predetermined period of time by a detection circuit for this difference and its output signal received via an AND gate. By installing an overdrive circuit that outputs output to the control circuit, and by repeatedly detecting the difference and performing the overdrive operation to bring the filament a degree closer to the target value button, it is possible to detect the large difference between the target value and the actual value. It is possible to finely control the overdrive amount in proportion to the temperature, and the time required for preheating can be reliably shortened.

In addition, the overdrive circuit sets a flip-flop according to the detection signal, generates a drive pulse with a desired time width in a monostable multi-circuit, and closes the switch of the overdrive power supply. In addition, detection and overdrive can be performed alternately at predetermined timing by setting and resetting the 7-lip frog and AND gate using a plurality of on-delay timers.

If the control circuit is a current control system consisting of a target current setter and a regulator, the impedance of the filament is low during the preheating period, so by configuring it with a comparator that compares it with the output voltage of the zipper, The difference between the actual value and the target value of filament temperature can be easily detected.

Furthermore, even if the detection circuit is configured with an underimpedance setter and a converter that compares its output with the output of an impedance calculator (a dividing circuit that divides by the voltage tt current), the actual value of the filament temperature and the target Differences in values can be detected equivalently.

If the control circuit is a constant voltage control system consisting of a target voltage setter and regulator, a filament current larger than the target current flows during the preheating period, so the detection circuit iAtAt
By using a combination of a constant setting device and a controller, or a combination of an underimpedance setting device and a comparator that compares its output with the output of an impedance calculator, the same effect as in the case of current control can be obtained. is obtained.

If the control circuit is a constant power control system consisting of a single-power setting device and a regulator, the detection circuit can be a combination of an undervoltage setting device and a comparator that compares its output with the detection voltage, or an underimpedance setting device. , in combination with a comparator that compares its output with the output of an impedance calculator, and also in combination with an overcurrent setting device and a comparator, to equivalently detect the difference between the actual value and the target value of the Q2 ment saturation. and can control overdrive.

〔Example〕

The present invention will be explained below based on examples.

FIG. 1 is a block diagram showing a filament power supply device for an X-ray tube according to an embodiment of the present invention. Hereinafter, the same reference numerals will be used for the same parts as in the conventional device, and detailed explanations will be omitted. The control circuit 15 includes a target current setter 14, and a current regulator 16 that calculates an error between the set value f8 and the detected value 1d of the current detector 8 and issues a control signal to the chimney collar drive circuit. Correspondingly, the detection circuit 2o is composed of a constant voltage control system consisting of:
It is comprised of an undervoltage setter 21 and a comparator 22 that compares the set value with the voltage detection value Vd on the output side of the reactor 3C. In addition, the overdrive circuit 31 receives the operation command via the on-time delay timer 23 and becomes set, and the AND gate 24 and the output S of the AND gate.
The clip 70 knob element 25.7 is reset by
A monostable multi-circuit 26 that outputs a drive ff1M54 of a predetermined time width from the set signals S and K of the lip 70 block elements. A main circuit consisting of an analog switch 29 that is closed by the drive signal S4, and a signal source 30 that outputs an overdrive signal to the current regulator 16 when the switch 29 is closed, and the reset of the flip-flop 25 and the AND gate 24. It is composed of on-delay timers 27 and 28 that control timing.

In the embodiment circuit configured as described above, the current setting device 14 is equipped with a storage element such as a ROM, and is configured to set a target value at the tube voltage vp in the tube current characteristics of the X-ray tube 6 already explained in FIG. A target value Ifs of the filament current f required to produce the full output of the tube is stored so that it can be retrieved in accordance with the setting values of the tube voltage and tube current setters 18 and 19. In addition, the undervoltage setter 21 stores a filament voltage setting value corresponding to a current level lower than the target ti value set in the flow film regulator 14 as an undervoltage threshold, and is detected by the comparator 22. When the detected voltage Vd is lower than the threshold value, the comparator 22Fi determines this as an undervoltage and outputs the signal SX'.
f! :Output.

Figure 82 #: is a time chart showing the operation of the overdrive circuit in the embodiment, in which the detection voltage Vd is set at the undervoltage setter 21 [[!] at the start of preheating. very lowly,
The comparator 22 determines that there is an undervoltage and outputs an H level undervoltage signal S1, and the on-delay timer 28 outputs an A signal.
1. by the AND condition with the H level signal S6 applied to the ND gate 24. At this point, the set signal S of the 7 lip-flops.

is output, the free-lag flop 25 is latched by the signal S, and at the same time, the H level signal S is output to its output side, and at the same time, the monostable multi-circuit 26 to 3
From point 1 to 1. A signal S4 that goes to L level up to one point is output, the b contact of the analog switch 29 is closed, and the overdrive store name (not shown) from the 冲音源 30 is added to the input side of the current regulator 13. In particular, the conduction time of the switching element 3A of the step-down transistor increases, and overdrive is performed.

Next, the flip 70 knob 24 is the on-delay timer 2.
7 detects the rising edge of the signal S4 and is reset by the reset signal SI which is issued with a delay until time t3, and the signal S1 changes to L level, resulting in a situation where it waits for the input of the set signal S2. Note that the signal S6 goes to the L level at time 31 when the signal S4 changes to the L level, and remains at the L level until the on-delay timer 28 detects the rise of the signal S4 and changes it to the H level with a delay until the time 34, that is, 1.
The period from time point to time point t4 is the overdrive possible period. In addition, the period when the signal S is at H level becomes the undervoltage detection period, and during the preheating period of the filament, undervoltage detection and overdrive are automatically repeated alternately. The process is repeated until a value suitable for obtaining the tube current value is reached, but at the start of preheating, the range of undervoltage is large and the number of repetitions of overdrive becomes large, so the time required for molecular preheating can be shortened. At the same time, the frequency of overdrive decreases as the target temperature approaches, so it is possible to avoid the filament temperature from rising too high, and the detection circuit automatically detects increases and fluctuations in the filament temperature due to the history as changes in undervoltage. Since the overdrive amount is controlled based on the detection, the control accuracy of the filament temperature can be significantly improved.

FIG. 3 is a block diagram showing a modified example of the above-mentioned actual M example, in which the detection port wr40t-insufficient impedance setter 21C
1 missing impedance calculator 41. It differs from the actual IIpA example described above in that it is configured in combination with a comparator 22 that compares the outputs of both. In this case, the ninth
Dividing the filament voltage Vff by the filament current in the figure gives the filament impedance, and dividing the detected voltage V'd by the detected current d gives the actual value Zd, which is proportional to the filament impedance, and the filament temperature reaches the target value. Up to this point, the filament impedance (mainly the resistance component) shows a value lower than the target value, so by comparing the set value of the insufficient impedance with the output of the insufficient impedance calculator, the overdrive circuit 310 is set as in the previous embodiment. Since an input signal can be obtained and control can be performed based on the overdrive f: filament voltage ta characteristic (referred to as filament characteristic), there is an advantage that more accurate control can be achieved with respect to fluctuations in filament characteristic.

FIG. 4 is a block diagram showing a different embodiment of the present invention, in which a control circuit 55 includes a target voltage setter 14B for the filament voltage Vf, and a voltage regulator 12E for calculating an error between the set value and the detected voltage. In addition to being composed of a constant voltage control system, one detection circuit 50 is composed of an overcurrent setter 21B, and a comparator 22 that compares its output current with the detected current d and generates an input signal for the overdrive circuit. The point is mentioned above! j! It is different from the example. In this case, the current flowing through the button that controls the constant voltage of the bladder collar increases by the amount of the decrease in filament impedance, so by detecting this with the detection circuit and using it as an input signal to the overdrive circuit, the above-mentioned implementation can be performed. The same functions as in the example can be obtained, and the advantage is that it can be easily applied to existing filament power supply devices having a constant voltage control system.

FIG. 5 is a block diagram showing a modification of the different embodiments described above, in which the detection circuit 60 is connected to the underimpedance setter 2.
1C and an underimpedance calculator 4 consisting of a divider circuit.
1 and the output of both? In comparison, this embodiment differs from the previous embodiments in that it is constructed with a comparator that generates an input signal for the overdrive circuit, and has the advantage that highly accurate preheating can be performed based on the filament characteristics of the C1 X-ray tube itself.

6 is a block diagram showing another embodiment of the present invention, in which the control circuit 65 consists of a power setter 14C determined by the product of the filament voltage and current, and a multiplication circuit for the detected current d and the detected voltage Vd. It is constituted by a constant power control system consisting of a power calculator 16 and a power regulator 12C that calculates an error between the outputs of both, and a detection circuit 70 that compares the output with the undervoltage setting device 21 and the detected voltage Vd. It differs from the previous embodiments in that it is constructed with a comparator 22 that emits a signal when the filament is heated. This BAk8 has the advantage of being easily applicable to filament power supplies requiring a power control system.

In addition, in FIG. 6, the detection circuit is the overcurrent setting device 21B.
and a comparator 22 that compares its output with the detected current value d, the same function as in the other embodiments described above can be obtained.

FIG. 7 is a block diagram showing a modification of the other embodiment described above, in which the detection circuit 80 is connected to the underimpedance setter 21C.
This embodiment is different from the other embodiments described above in that it is composed of an impedance calculator 41, and a comparator 22 that compares the outputs of both and outputs an insufficient impedance signal to the overdrive circuit. Even if the configuration is configured as shown in FIG.

〔Effect of the invention〕

As described above, this invention includes a filament power supply device consisting of a step-down chipper and a center-tap transformer type inverter, a t-end section that supplies heating power to the X@ tube, and a control circuit for the step-down chipper. a detection circuit that calculates the difference between a control target value and an actual value; and an overdrive circuit that generates overdrive No. 1 for a predetermined time based on the difference signal and controls to alternately repeat detection of the difference signal and overdrive. It was configured to have the following. As a result, during the preheating period of the filament temperature, the detection circuit detects that the filament temperature is lower than the salinity suitable for obtaining the desired tube charge i as a difference between the target 1 shift and the actual value, and the difference signal is Since the overdrive is performed at a frequency according to the size of , the preheating time can be reliably shortened compared to the conventional method.

In addition, the overdrive circuit includes a main circuit and an on-delay timer for timing control, and controls to alternately repeat monitoring of filament salinity and overdrive. It is possible to perform preheating while monitoring the filament a degree'fc. Therefore, the influence of fluctuations in the filament m degree due to the operating history and operating conditions, which was a problem with the conventional method of overdriving in anticipation, is eliminated. It is possible to provide an X@tube filament power supply device that can accurately and stably maintain filament salinity to quickly reach and maintain a target hot water temperature.

Furthermore, the present invention can be applied to a filament power supply device having any of the control circuits of a constant current control system, a constant voltage control system, and a constant power control system, without changing the configuration of the overdrive circuit. Voltage detection system, iAt
By combining it with any of the flow measurement detection and insufficient impedance detection systems, it is possible to configure a power supply with excellent performance in controlling filament temperature, so it can be widely applied to a variety of filament power supplies, both existing and new. This provides the advantage of improving preliminary cutting edge thermal performance.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a filament power supply device for an X-ray tube according to an embodiment of the present invention together with a power supply section, Fig. 2 is a time chart showing the operation of an overdrive circuit in the embodiment, and Fig. 3 is a block diagram showing the operation of an overdrive circuit in the embodiment. A block diagram showing a modified example,
FIG. 4 is a block diagram showing a different embodiment of the invention, FIG. 5 is a block diagram showing a modification of the different embodiment, FIG. 6 is a block diagram showing another embodiment of the invention, and FIG. FIG. 8 is a block diagram showing a modification of another embodiment, FIG. 8 is a configuration diagram showing a conventional filament power supply device, and FIG. 9 is a characteristic diagram showing an example of tube current characteristics and filament characteristics of an X-ray tube. 1...Power supply section, 3...Step-down converter 4...Inverter, 5...Insulation transformer/s (with center tap),
6... X-ray tube, 8... flow detector, 13... current regulator, 14... current setting device, 15, 55. (55・
...Control circuit, 21...Undervoltage setting device, 22...
Comparator, 2o, 40, 50, 60, 70.80・
...Detection circuit, 21B...Overcurrent setting device, 21C...
- Underimpedance setting device, 41... Impedance calculator, 12B... Voltage regulator, 12C... Power regulator, 14B... Voltage setting device, 14C... Power setting device, 16... Power calculator, 31... Overdrive circuit, 25... Flip-flop element, 26...
・Monostable multi-circuit, 23.27,28...
On-delay timer, 29...analog switch, 3
0...Signal source.

Claims (1)

[Scope of Claims] 1) A power supply section comprising a step-down chopper and a center-tap transformer circuit type inverter and supplying filament heating power to the X-ray tube determined based on tube voltage and tube current;
A control circuit comprising a setter for the output target value of the power supply unit and a regulator for controlling the drive circuit of the step-down chopper based on the output target value and the actual value,
a detection circuit that detects that there is a difference exceeding a predetermined level between the actual value and the output target value; and a control circuit that receives the detection signal via an AND gate and sends a signal to overdrive the power supply section for a predetermined time. and an overdrive circuit that outputs an output toward the filament, and is configured to alternately repeat detection of the difference and overdrive by the detection circuit until the filament temperature reaches a target value. Wire tube filament power supply. 2) An overdrive circuit that receives the detection signal of the detection circuit via an AND gate includes a drive circuit consisting of a flip-flop circuit and a monostable multi-circuit, and a main circuit section that closes the circuit based on the output signal of the drive circuit and generates an overdrive signal; X according to claim 1, further comprising a timing control section comprising a plurality of on-delay timers.
Wire tube filament power supply. 3) an undervoltage setter whose control circuit is composed of a target current setter and a current regulator, and which outputs a set voltage lower than the output target value based on the tube voltage set value and the tube current set value;
and a detection circuit comprising a comparator that compares its output with a detection voltage proportional to the filament voltage and generates an undervoltage signal.
Or a filament power supply device for an X-ray tube according to claim 2. 4) The filament power supply device for an X-ray tube according to claim 3, wherein the detection circuit comprises a combination of an underimpedance setter and a coinparator that compares the set value with the output of the impedance calculator. 5) Claim 1, wherein the control circuit comprises a combination of a target voltage setter and a voltage regulator, and further comprises a detection circuit comprising an overcurrent setter and a comparator.
Or a filament power supply device for an X-ray tube according to claim 2. 6) The filament power supply device for an X-ray tube according to claim 5, wherein the detection circuit comprises a combination of an underimpedance setter and a comparator that compares the set value with the output of the impedance calculator. 7) The control circuit consists of a combination of a target power setter and a power regulator that calculates an error between the output of the target power setter and the output of the power calculator, and also includes an undervoltage setter and its output in a proportional relationship with the filament voltage. 3. The filament power supply device for an X-ray tube according to claim 1, further comprising a detection circuit comprising a comparator for comparing the detection voltage with the detection voltage. 8) The filament power supply device for an X-ray tube according to claim 7, wherein the detection circuit comprises a combination of an underimpedance setter, an impedance calculator, and a comparator for comparing the outputs of both.