JP4488556B2 - MEDICAL POWER SUPPLY DEVICE AND X-RAY CT DEVICE USING THE SAME - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a medical power supply apparatus having a function of reducing noise propagating through a power supply line and an X-ray CT apparatus using the medical power supply apparatus.
[0002]
[Prior art]
Conventionally, in a medical device that is supplied with power from an external power source via a power line, in order to prevent the device from malfunctioning due to external noise that has propagated through the power line, noise generated inside the device is In order to prevent propagation and leakage to the outside of the device, the power supply line includes a medical power supply device connected to a line filter (also referred to as a power line filter) that reduces such conduction noise.
[0003]
FIG. 8 is a circuit diagram showing a general configuration of the line filter. Here, as an example, a line filter when a so-called three-phase three-wire system is applied to a power supply method is shown. In the line filter shown in the figure, an AC external power supply (not shown) is connected to input terminals 61, 62, and 63 via three power supply lines corresponding to three phases, and output terminals 64, 65, Similarly, each circuit inside the device (not shown) is connected to 66 via three power lines.
[0004]
This three-phase external power supply is supplied to circuits and electrical parts inside the equipment via input terminals 61 to 63 and output terminals 64 to 66 connected to the power supply line, and further, a DC power supply generated from the AC power supply. Is supplied to a digital circuit for controlling the operation of the device.
[0005]
In addition, external noise that has propagated through the power supply lines connected to the input terminals 61 to 63 is connected between the power supply lines via resistors R1, R2, and R3 connected between the power supply lines. Input to the capacitors C1, C2, C3 is reduced.
[0006]
On the other hand, noise generated inside the apparatus and propagated through the power supply lines connected to the output terminals 64 to 66 is inserted between the inductances L1, L2, and L3 connected to the respective power supply lines and between the power supply lines. This is reduced by a so-called LC low-pass filter composed of capacitors C4, C5 and C6 connected to each other, so that it does not propagate from the input terminals 61 to 63 to the outside of the device through the power line. ing.
[0007]
Furthermore, noises propagated from the inside of the device to the ground line of the line filter are reduced by capacitors C7, C8, and C9 respectively connected between the power supply lines and the ground lines.
[0008]
[Problems to be solved by the invention]
However, in such a conventional line filter, when a very large surge voltage (overvoltage), which is 10 times or more than the normal time, is mixed into the power supply line from the outside of the device due to lightning or the like, A phenomenon occurs in which this surge voltage is amplified by the line filter.
[0009]
In other words, the line filter is originally used to reduce noise, but such an external surge voltage cannot be reduced but is amplified.
[0010]
FIG. 9 is a diagram illustrating an example of the waveform of the surge voltage input to the input terminal of the conventional line filter and the waveform of the output voltage at the output terminal at this time. When a very large transient surge voltage of 2 [kV] is applied to the input terminal during application as shown in FIG. 10A, for example, 3 [kV] as shown in FIG. ] Is amplified from the output terminal.
[0011]
Here, an experiment conducted by the inventors to analyze the mechanism by which the surge voltage is amplified inside the line filter will be described.
[0012]
FIG. 10A is a diagram showing the voltage source 71, and FIG. 10B is a diagram showing an input waveform of a surge voltage of 1 [kV] when applied by the voltage source 71.
[0013]
11B, when the voltage source 71 generates the surge voltage of FIG. 10A and inputs it to the inductance 73, and the output voltage is measured by the voltmeter 72, as shown in FIG. 11A. It is a figure which shows the output waveform. From FIG. 11B, it was observed that the input surge voltage did not change at all and was output as it is in the inductance alone.
[0014]
12B, when the surge voltage of FIG. 10B is generated by the voltage source 71 and input to the capacitor 74, and the output voltage is measured by the voltmeter 72, as shown in FIG. It is a figure which shows the output waveform. From FIG. 12B, it was observed that the surge voltage was amplified about 1.5 times in the capacitor alone, and thereafter the amplitude of the surge voltage was attenuated while oscillating.
[0015]
13 (b), as shown in FIG. 13 (a), the voltage source 71 generates the surge voltage of FIG. 10 (b) and inputs it to an LC low-pass filter composed of an inductance 73 and a capacitor 74. It is a figure which shows an output waveform when the output voltage of the inductance 73 connected in series and the capacitor | condenser 74 is measured with the voltmeter 72. FIG. From FIG. 13B, in the LC low-pass filter, after being amplified by about 1.5 times, the amplitude of the surge voltage is attenuated while oscillating in a state closer to oscillation than in the case of the capacitor alone. Was observed.
[0016]
From the results of this experiment, even if it is a capacitor alone, considering that an inductance component is actually generated in the power supply line, the surge voltage is amplified when the capacitor and the inductance or the inductance component are included. It is considered a thing.
[0017]
As described above, since the amplification factor of the surge voltage in the line filter may be about 1.5 to 2 times, there is a possibility that the amplified surge voltage may cause a problem in a circuit or an electrical part inside the device. It was.
[0018]
Also, if the surge voltage, which is not as high as a transient surge voltage, enters the ground line of the line filter from the outside of the equipment, use this ground line in common with the line filter. May affect the digital circuit. In other words, the digital circuit operates at a low voltage such as 5 [V] or 3.3 [V]. Therefore, when a surge voltage that fluctuates repeatedly is mixed in the ground line, it is a slight fluctuation. Even if there was, there was a risk of malfunction.
[0019]
The present invention has been made in view of the above, and an object of the present invention is to protect each circuit, electrical part, and the like inside a device from a transient surge voltage caused by a lightning strike or a surge voltage that fluctuates repeatedly. An object of the present invention is to provide a medical power supply device that can be used and an X-ray CT apparatus using the same.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, a medical power supply according to the present invention is a medical power supply in which a line filter that prevents leakage of noise generated inside a medical device is inserted and connected to a power supply line that supplies a multiphase power supply from the outside. A first surge absorber that absorbs a surge voltage between the power lines of each phase of the power output stage of the line filter, and connected between the power lines of each phase of the power input stage of the line filter A second surge absorber that absorbs surge voltage is connected to a third surge absorber that absorbs a surge voltage that repeatedly fluctuates between a power line and a ground line of the power output stage of the line filter, A fourth surge absorber that absorbs a surge voltage is connected between the power line and the ground line of the power input stage of the line filter, and the third surge absorber and the fourth surge absorber are connected. Soba is summarized in that connected to the common ground terminal.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments to which the present invention is applied will be described below with reference to the drawings.
[0030]
[First Embodiment]
FIG. 1 is a circuit diagram showing a configuration of a line filter according to the first embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of an X-ray CT apparatus as an example of a medical device to which the line filter is applied. It is.
[0031]
The gantry 1 in FIG. 2 is provided so that an X-ray tube device (not shown) and an X-ray detector (not shown) arranged opposite to each other can be rotated around a subject arranged therebetween. The rotating unit 2 and the fixed unit 3 that supplies the three-phase power supplied from the external power source 8 via the power line 9 to the rotating unit 2 via the power line 10.
[0032]
The fixing unit 3 includes a circuit breaker 4 that cuts off the power supply line 9 when the current supplied from the external power supply 8 becomes excessive, and noise generated inside the device propagates through the power supply line 9 and leaks to the outside. The immunity line filter (Immunity Line Filter, hereinafter referred to as "Immunity LF") 5 that reduces external surge voltage mixed in the power supply line 9 and a three-phase power supply for each circuit and electrical parts inside the equipment, etc. And a power supply circuit 6 for controlling the order of supply to the power supply, and a DC circuit 7 for supplying the DC power generated from the three-phase power supply to each unit (not shown) and a digital circuit for controlling the equipment. is there.
[0033]
The line filter shown in FIG. 1 corresponds to the immunity LF5, and has a configuration in which varistors V4, V5, and V6 are connected between the power supply lines in the power supply output stage of the line filter shown in FIG. . In addition, the same components as those in FIG.
[0034]
First, the imaging operation of the X-ray CT apparatus having such a configuration will be briefly described.
[0035]
The rotating unit 2 maintains the positional relationship between the X-ray tube device and the X-ray detector arranged to face each other in accordance with a control signal transmitted from a control processing device (not shown) via the fixed unit 3. Rotate around the subject. The power for the rotation is supplied from the fixed unit 3 through the power line 10. In the rotating unit 2, power is supplied to the X-ray tube device and the X-ray detector, for example, by a slip ring method. . Such a rotating operation of the rotating unit 2 is one of noise generation sources, but the noise is prevented from leaking through the power supply lines 10 and 9 by the immunity LF5.
[0036]
Next, the X-ray tube device is irradiated with, for example, fan beam-shaped X-rays from a direction of 360 ° at a certain rotation angle, and the X-rays transmitted through the subject at each rotation angle are detected by the X-ray detector. Detect with. The X-ray detector generates a digital signal based on the detected X-ray dose and performs logarithmic conversion to obtain an information signal related to the tomographic plane of the subject, that is, so-called projection data. By using a two-dimensional X-ray detector as the X-ray detector, projection data relating to a plurality of tomographic planes of the subject can be obtained. The X-ray beam shape is not limited to the fan beam shape but may be a parallel beam shape.
[0037]
Subsequently, the projection data obtained by the X-ray detector is transmitted to the control processing device via the fixed unit 3, and the control processing device performs image reconstruction processing by, for example, a filter-corrected back projection method, thereby Obtain an image of the tomographic plane.
[0038]
Next, the operation of the immunity LF5 will be described.
[0039]
Usually, when an overcurrent flows through the power line 9, basically, the circuit breaker 4 operates to cut off the power line 9. However, since current control is more dominant than voltage control in a normal circuit breaker, there are many cases where it is not possible to cope with surge voltage due to lightning strikes.
[0040]
As described above, when the surge voltage is mixed into the power supply line 9 but the current sufficient to operate the circuit breaker 4 does not flow, the surge voltage is reduced by the immunity LF5.
[0041]
In general, a varistor is a semiconductor element whose resistance value decreases non-linearly when the voltage rises, and is particularly excellent in follow-up characteristics against a transient surge voltage.
[0042]
Therefore, as the varistors V4 to V6 connected to the power output stage of the immunity LF5, for example, by using a varistor having a characteristic in which the predetermined value is close to a voltage value assumed due to lightning strike, the varistors are connected via the input terminals 61 to 63. When the supplied power supply voltage is a normal value, the resistance values of the varistors V4 to V6 are kept unchanged, and the resistance value is lowered only when a surge voltage is mixed due to a lightning strike or the like.
[0043]
Therefore, according to the present embodiment, by connecting such varistors V4 to V6 between the power supply lines of the power supply output stage, the external surge voltage mixed through the input terminals 61 to 63 is reduced. Even when the phenomenon of amplification within the immunity LF5 occurs, the amplified surge voltage can be reduced before being output from the output terminals 64 to 66, so that each circuit and electrical equipment in the device can be reduced. Parts can be protected.
[0044]
In the present embodiment, the case where the present invention is applied to an X-ray CT apparatus as an example of a medical device has been described. However, the present invention is not limited to this. For example, an ultrasonic diagnostic apparatus or MRI (Magnetic Resonance Imaging) is used. The present invention can also be applied to other medical devices that receive power supply from an external power source via a power line.
[0045]
In this embodiment, power is supplied by three phases. However, the present invention can be applied even when power is supplied by two phases or four or more phases.
[0046]
Furthermore, in this embodiment, the varistor is used as an example of the surge absorber. However, the present invention is not limited to this, and it is needless to say that the varistor has similar characteristics.
[0047]
[Second Embodiment]
FIG. 3 is a circuit diagram showing a configuration of the immunity LF in the second embodiment of the present invention. The feature is that in the power input stage of the immunity LF shown in FIG. 1, varistors V1, V2, and V3 are connected between the power lines, and the power lines are propagated through the input terminals 61 to 63. The surge voltage is reduced at the power input stage. In addition, the same components as those in FIG.
[0048]
FIG. 4A shows a waveform of the surge voltage input to the input terminal of the immunity LF in which a varistor is connected between each power line in the power input stage and the power output stage as shown in FIG. FIG. 4B is a diagram showing an example of the waveform of the output voltage at the output terminal at this time. FIG. 5B shows that the surge voltage that was about 2 [kV] at the time of application is reduced to about 1 [kV] at the time of output.
[0049]
Therefore, according to the present embodiment, by connecting the varistors V1 to V3 between the power supply lines of the power input stage of the immunity LF, the surge voltage can be reduced at the power input stage, and the immunity LF The internal circuit can be protected from surge voltage.
[0050]
Further, by using the varistors V1 to V3 connected to the power input stage of the immunity LF in combination with the varistors V4 to V6 connected to the power output stage, the surge voltage can be further reduced, so that the inside of the medical device can be reduced. Each circuit and electrical parts can be reliably protected.
[0051]
[Third Embodiment]
FIG. 5 is a circuit diagram showing a configuration of an immunity LF in the third embodiment of the present invention. As a feature thereof, a ground terminal 67 grounded to the immunity LF shown in FIG. 3 is provided, and a varistor V7 is connected between any power supply line of the power input stage of the immunity LF and the ground terminal 67, and the immunity LF A varistor V8 is connected between one of the power supply lines of the power supply output stage and the ground terminal 67 so that a surge voltage can be reduced even when a surge voltage is mixed into the ground line due to a lightning strike or the like. . In addition, the same components as those in FIG.
[0052]
Therefore, according to the present embodiment, the varistors V7 and V8 are connected between the power line of the immunity LF and the ground terminal 67, respectively, so that even when a surge voltage is mixed into the ground line, this is reduced. Therefore, it is possible to protect each circuit and electrical parts inside the medical device from surge voltage.
[0053]
In this embodiment, power is supplied by a three-phase three-wire system. However, even when a single-phase power source is used instead of a three-phase power source, the power source line and the ground terminal are used. By connecting a varistor between the two, an external surge voltage mixed in the power supply line or the ground line can be reduced.
[0054]
[Fourth Embodiment]
FIG. 6 is a circuit diagram showing a configuration of an immunity LF in the fourth embodiment of the present invention. The feature is that between the varistor V7 connected to the power supply line of the power input stage of the immunity LF shown in FIG. 5 and the ground terminal 67, and between the varistor V8 connected to the power supply line of the power output stage and the ground terminal 67. The die surge absorbers DSA1 and DSA2 having excellent absorption characteristics of surge voltage that fluctuates repeatedly during the period are connected to absorb the surge voltage that fluctuates repeatedly that has entered the ground line. In addition, the same components as those in FIG.
[0055]
The die surge absorbers DSA1 and DSA2 have, for example, a maximum value assumed as a repetitively varying surge voltage as a predetermined value, and even if the voltage fluctuates below this predetermined value, the current hardly changes, and the voltage does not change. Use a non-linear voltage-current characteristic in which the resistance value decreases and the current increases when a predetermined value is exceeded, and surge voltage that fluctuates repeatedly below the predetermined value enters the ground line. If this happens, make sure that it can be absorbed.
[0056]
Next, the overall operation of the immunity LF shown in FIG. 6 will be described with reference to FIG.
[0057]
In the immunity LF, the transient surge voltage and the surge voltage (line noise) that fluctuate repeatedly mixed in the power supply line and the ground line (GND) are reduced as follows (blocks 700 and 710).
[0058]
First, the transient surge voltage mixed in the power supply line is reduced by the surge absorber (varistors V1 to V3) connected between the power supply lines in the power input stage (previous stage) of the immunity LF. Are protected (block 720).
[0059]
Subsequently, the surge voltage amplified inside the immunity LF is reduced by the surge absorbers (varistors V4 to V6) connected between the power supply lines in the power output stage (rear stage) of the immunity LF (block 730).
[0060]
In addition, transient surge voltage or repetitively fluctuating surge voltage mixed in the ground line by surge absorbers (varistors V7, V8, die surge absorbers DSA1, DSA2) connected between the power supply line and the ground terminal 67 is generated. The voltage level of the ground line is reduced and the voltage level of the ground line is stabilized, and the malfunction of the digital circuit sharing the immunity LF and the ground line is prevented and other units are protected (block 740).
[0061]
Therefore, according to the present embodiment, by connecting the die surge absorbers DSA1 and DSA2 having excellent absorption characteristics of the surge voltage that repeatedly varies between the power supply line and the ground terminal 67, the surge voltage that repeatedly varies can be obtained. Even when it is mixed in the ground line, the voltage level of the ground line can be stabilized, and the occurrence of malfunction of the digital circuit sharing the immunity LF and the ground line can be prevented.
[0062]
In this embodiment, the die surge absorber having the non-linear voltage-current characteristics as described above is used. However, for example, a non-linear voltage due to a PN junction of silicon (Si) is used. -A silicon surge absorber using current characteristics may be used.
[0063]
【The invention's effect】
According to the medical power supply device of the present invention, a surge absorber is connected between the power supply lines of each phase of the power output stage of the line filter, so that the power line is mixed from the outside of the medical device, The transient surge voltage amplified inside can be reduced, and thus each circuit and electrical parts inside the medical device can be protected from the surge voltage.
[0064]
In addition, by connecting a surge absorber between the power lines of each phase of the power input stage of the line filter, the surge voltage mixed into the power line from the outside of the medical device can be reduced. The circuit can be protected.
[0065]
Furthermore, by connecting a surge absorber between the power line of the line filter and the ground line, it is possible to reduce the surge voltage mixed into the ground line from the outside of the medical device, so that the surge voltage of the medical device can be reduced. Each internal circuit and electrical parts can be protected. Further, even when a single-phase power supply is used instead of the multiphase power supply, an external surge voltage mixed in the power supply line or the ground line can be reduced.
[0066]
In addition, by providing a surge absorber that absorbs a surge voltage that fluctuates repeatedly between the power line and ground line of the line filter, the surge voltage that fluctuates repeatedly that has entered the ground wire from outside the medical device is reduced. Thus, the voltage level of the ground line can be stabilized, and the malfunction of the digital circuit that shares the line filter and the ground line can be prevented.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a configuration of an immunity LF in a first embodiment.
FIG. 2 is a block diagram showing a configuration of an X-ray CT apparatus as an example of a medical device to which immunity LF is applied.
FIG. 3 is a circuit diagram showing a configuration of an immunity LF in the second embodiment.
FIG. 4 is a diagram illustrating an example of a waveform of a surge voltage input to an immunity LF and a waveform of an output voltage.
FIG. 5 is a circuit diagram showing a configuration of an immunity LF in the third embodiment.
FIG. 6 is a circuit diagram showing a configuration of an immunity LF in the fourth embodiment.
FIG. 7 is a block diagram for explaining an operation of an immunity LF in the fourth embodiment.
FIG. 8 is a circuit diagram showing a general configuration of a conventional line filter.
FIG. 9 is a diagram illustrating an example of a surge voltage waveform input to a conventional line filter and an output voltage waveform;
FIG. 10 is a diagram illustrating a voltage source and an input waveform of a surge voltage generated in the voltage source.
FIG. 11 is a diagram showing a circuit configuration for inputting a surge voltage to a single inductance and an output waveform thereof;
FIG. 12 is a diagram illustrating a circuit configuration for inputting a surge voltage to a single capacitor and an output waveform thereof;
FIG. 13 is a diagram showing a circuit configuration for inputting a surge voltage to an LC low-pass filter and an output waveform thereof.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Mount, 2 ... Rotating part, 3 ... Fixed part, 4 ... Circuit breaker, 5 ... Immunity LF, 6 ... Power supply circuit, 7 ... DC supply part, 8 ... External power supply, 9,10 ... Power supply line, L1, L2, L3 ... inductance, C1, C2, C3, C4, C5, C6, C7, C8, C9 ... capacitors, R1, R2, R3 ... resistors, V1, V2, V3, V4, V5, V6, V7, V8 ... Varistor, DSA1, DSA2 ... Die surge absorber, 61, 62, 63 ... Input terminal, 64, 65, 66 ... Output terminal, 67 ... Ground terminal, 71 ... Voltage source, 72 ... Voltmeter, 73 ... Inductance, 74 ... Capacitor

Claims (3)

A medical power supply apparatus in which a line filter that prevents leakage of noise generated inside a medical device is inserted and connected to a power supply line that supplies a polyphase power from outside,
Connecting a first surge absorber that absorbs a surge voltage between the power lines of each phase of the power output stage of the line filter ;
Connecting a second surge absorber for absorbing a surge voltage between the power lines of each phase of the power input stage of the line filter;
Connecting a third surge absorber that absorbs a surge voltage that repeatedly fluctuates between a power line and a ground line of the power output stage of the line filter;
Connecting a fourth surge absorber for absorbing a surge voltage between a power line and a ground line of the power input stage of the line filter;
The medical power supply apparatus, wherein the third surge absorber and the fourth surge absorber are connected to a common ground terminal .   The medical power supply apparatus according to claim 1, wherein the third surge absorber and the fourth surge absorber include a surge absorber that absorbs a surge voltage that fluctuates repeatedly. An X-ray CT apparatus comprising the medical power supply apparatus according to claim 1 .

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