JPS61133600A - X-ray apparatus - Google Patents

Abstract

PURPOSE:To provide a highly stable X-ray apparatus by preventing simultaneous turning on of both of the first and second thyristors. CONSTITUTION:The first shot of the driver pulse generated by the beginning signal of the X-ray radiation is amplified by a driver circuit 37 to be applied on a thyristor 12. Then the thyristor 12 is turned on to give current to a primary winding 6a during a half period, and subsequently, determined by a resonant circuit condenser 5 and the primary winding 6a an attenuating oscillation of the primary current occurs. This primary current is detected by a detecting means 16 and voltage-converted by an I/V conversion means 17. Afterwards the voltage converted primary current is detected as to its zero phase by a zero phase detecting circuit 30 consisting of a comparison circuit. The timing after this zero phase detection determines the operating frequency of the driver pulses, and the second and subsequent serial shots of the driver pulse depending on this frequency are applied to the thyristors 12, 14, which prevents the simultaneous conduction of the two thyristors.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a series resonant bridge inverter type X-ray apparatus.

[Technical fungi of the invention and their problems] Generally, in a series resonant bridge inverter type X-ray apparatus, an AC input voltage from an AC power source is rectified and smoothed to obtain a DC voltage, and this is converted into a DC voltage using a large-capacity capacitor. A predetermined alternating current voltage is generated via a series resonant bridge inverter, and based on this, a dual current voltage necessary for irradiation of the X-ray tube is generated.

・By the way, in this J:Una X-ray device,
The value of the DC voltage, that is, the X-ray tube voltage, required for the X-ray tube to emit radiation is determined by the first voltage that forms the resonant circuit. It can be varied by changing the firing period of the second sirisk. However, the first. By changing the firing period of the second thyristor
When the tube voltage is varied, the following problems arise.

That is, 1st. The second thyristor is configured to alternately switch in response to driver pulses output at predetermined ignition cycles. At this time, the first thyristor turns on and current flows through the thyristor to the primary winding for half a period, and then due to damped vibration caused by the resonant circuit, the first thyristor, which had been in the off state until then, turns off.
The next half cycle of current flows through the rectifier. When the first thyristor is in the automatic state, when the second thyristor is turned on, a primary current in the opposite direction to the current of the first thyristor flows in the primary winding in a mesh pattern for half a cycle. In this way, when one thyristor is in the off state, the other thyristor is turned on and alternating current can be obtained by alternately taking out half-cycle currents with different polarities.

And the first. Shorten the firing period of the second thyristor,
If the other thyristor is turned on immediately after one thyristor is turned off, the primary current flowing through the transformer continues and the X-ray tube voltage can be increased.

However, when the firing period of the driver pulse is short<(F large firing frequency) 1, both thyristors may turn on simultaneously due to noise or the like while switching is repeated many times. Conversely, if the ignition period is lengthened, problems such as an increase in ripples included in the X-ray tube voltage occur.

[Object of the Invention] The present invention has been made in view of the above circumstances, and the present invention has been made in view of the above circumstances.
The object of this invention is to prevent the second thyristor from turning on at the same time and provide an extremely stable X-ray apparatus.

[11/11 Summary of the Invention] The present invention for achieving the above object is summarized as follows: Consists of a resonant circuit including a secondary winding, a bridge section that applies a predetermined voltage to the resonant circuit, and a control means that sends a driver pulse to the bridge section and controls the timing of supplying DC voltage from the bridge section to the resonant circuit. X with series resonant bridge inverter
In the wire device, the control means includes a zero phase detection circuit that detects the zero phase of the primary current flowing through the primary winding by the nth driver pulse, and a zero phase detection circuit that detects the zero phase of the primary current flowing through the primary winding based on the nth driver pulse.
It is characterized by having a decouple control circuit that determines the period of the first and subsequent driver pulses, and a driver pulse generation circuit that generates the driver pulse at the period determined by the duty control circuit. It is something.

[Embodiment 1 of the Invention Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The X-ray apparatus shown in FIG.
rectifying means 2 and + in which b, 2c, and 2d are bridge-connected;
a first rectifying and smoothing means 22 consisting of a smoothing means 3 configured by series connection of capacitors 3a and 3b; and a primary winding 68.
．． A transformer 6 having a secondary winding 6b, and a resonant transformer 6 connected between the primary winding 6a of the transformer 6 and the connection point of the capacitors 3a and 3b to form a resonant circuit together with the primary winding 6a. 5. A bridge section 20.A diode 13.15 and a thyristor 12.14 are bridge-connected and supply the output of the rectification and smoothing means 22 to the resonant circuit at a predetermined period. A control means 19 that sends driver pulses to the thyristors 12 and 14 of this bridge section 20. A detection means (for example, a current transformer) 16 that detects the current flowing in the primary winding 6a and converts the detected current of the detection means 16 into a voltage signal. a series resonant bridge inverter 21 configured with I/V (current/voltage) conversion means 17, and a bridge type rectifier circuit 7 that rectifies the voltage induced in the secondary winding 6b of the transformer 6. and smoothing the output of this rectifying circuit 7] and the DC output voltage (X
ray tube voltage) to the anode 9a and filament 9b of the X-ray tube 9.
The apparatus includes high voltage cables 10a and 10b for applying voltage to the X-ray tube L1, and a second detection means 11 for detecting the X-ray tube L1.

The second detection means 11 is connected to the second rectification and smoothing means 23.
Resistor 118.11 connected in series between the output terminal of and ground
b, the X-ray tube voltage is divided and detected by these resistors 11a and 11b, and based on this detection result, the control means 19
is designed to be controlled.

Next, the configuration of the control means 19 will be explained with reference to FIG. The control means 19 includes a detection means 16 for detecting the current flowing through the primary winding 6a and an I/■ conversion means 17 for converting the detected current of the detection means 16 into a voltage signal. means 30, a duty control circuit 31 including a timer circuit for outputting a driver pulse after an arbitrary time elapses from this zero phase, and a divided voltage signal of the Xl1I tube 1F from the second detection means 11 as a reference. a feedback circuit 32 that compares the voltage with the voltage and can vary the timer circuit in the duty control circuit 31; a timer circuit 34 that operates according to a signal from the hand-held switch 33; and the duty control circuit 31. a driver pulse generating circuit 35 that generates driver pulses for the second valve port and subsequent ones from the X* exposure timer circuit 34; and a first firing circuit that generates driver pulses for the first valve port in response to a signal from the hand-held switch 33. The driver pulse generation circuit 36 and the first
It consists of a valve port and a drive circuit 37 that amplifies driver pulses from the second shot until the end of the exposure time. The driver pulse output from the drive circuit 37 is applied to the thyristor 12.14.

The operation of the apparatus having the above configuration will be explained next.

The AC input voltage supplied from the AC power supply 1 is converted into a DC voltage by the first rectifying and smoothing means 22 and the bridge unit 20
is applied to At this time, in the bridge section 20, the thyristors 12 and 14 alternately perform switching operations in response to driver pulses outputted from the control means 19 at a predetermined frequency.

The details of the driver pulses output from the control means 19 will be described later with reference to FIGS. 2 and 3.

When the thyristor 12 turns on, first the capacitor 3
The current due to the DC voltage of a flows through the thyristor 12 to the primary winding 6a for half a cycle (forward direction), and then the resonance capacitor 5 and the primary winding 6a (strictly speaking, the secondary side of the transformer 60 is also affected). The damped oscillation determined by the thyristor 12, which was previously on, turns off and flows through the rectifier 13 in the next half cycle (in the opposite direction). Therefore, when the thyristor 12 turns on by -q, one period of primary current flows through the primary winding 6a.

Similarly, when the thyristor 14 is turned on, one period of 1
Although the secondary current flows through the primary winding 6a, the current direction is opposite to that when the thyristor 12 is turned on, as described above.

In this way, when the primary current flows through the primary winding 6a, a voltage is induced in the secondary winding 6b. This induced voltage is rectified by the rectifying and smoothing means 7 and smoothed by the capacitor 8, and then applied as an X-ray tube voltage to the anode 9a of the X-ray tube 9 and the filament 9b.

In this way, X-ray [1) J is performed by the X-ray tube 9, but generally the X-ray tube voltage is several + kV and the X-ray tube current is several hundred mAPi! Since the temperature is 60 degrees, when using X-ray
The primary winding 6a instantaneously increases to several hundred (peak value) as large as 1.
Next current flows.

Next, the operation of the control means 1B will be explained in detail with reference to FIGS. 2 and 3.

First, when the hand-held switch 33 is operated at the time of starting X-ray @ emission, the xmta start signal is output to the first outlet driver pulse generation circuit 36, and the first valve driver pulse P
1 is amplified by the drive circuit 37 and applied to the thyristor 12. Then, as shown above, the thyristor 12 is turned on and the current first flows through the primary winding 6a for half a cycle, and then the resonance capacitor 5 and the primary winding 6a are determined by J: and the primary current is attenuated. Vibrate. This primary current is detected via the detection means 16 and converted into voltage by the I/V conversion means 17. The zero phase of this voltage-converted primary current is detected by a zero phase detection circuit 30 consisting of a comparison circuit. Two thyristors 12 and 14 are turned on at the same time (
In order to prevent this from occurring, it is necessary to turn off the thyristor 12 and issue the second chain of driver pulses P2 to the thyristor 14. Therefore, after detecting the zero phase of the primary current, the second driver pulse [1]
2 to the thyristor 14, the duty control roll circuit 31 has a timer circuit that can be set for an arbitrary time longer than the turn-off time of the thyristor 12.
The time set by this timer circuit determines the shortest output point of the second chain of driver pulses P2. In other words, the shortest output point of the driver pulse is automatically determined to ensure that one thyristor is turned off before the other thyristor is turned on. Furthermore, the X-ray +1=tube voltage signal from the second detection means 11 is input to the duty control circuit 31 via the feedback circuit 32. And based on this signal,
If the X-ray tube voltage becomes lower than a predetermined value, the cycle of the driver pulse train is shortened to increase the X-ray tube voltage, and conversely, if the voltage becomes higher than the predetermined value, the cycle of the driver pulse train is lengthened. By having a periodic control circuit that lowers the X-ray tube voltage, the operating frequency (radius frequency) is controlled.

Next, the driver pulse generation circuit 3 uses the operating frequency determined by the duty control circuit 31.
5 generates the second and subsequent driver pulses after the hand-held switch 33 is operated. This driver pulse P
2. During the period when P3... is displayed, the X-ray m+)1 start signal from the handheld switch 33 to XIi! This is determined by the one hour timer of the X-ray irradiation timer circuit 34, which operates for an arbitrarily set time until the distance reaches 1 m.

In this way, the driver pulses from the first valve port and the second valve port until the end of the exposure time after the XS*+W injection start signal is input are transmitted to the thyristor 1 through the drive circuit 37.
2.14.

As shown in]-, the driver pulse P1 of the first valve port turns on the thyristor 12, and then the zero phase when the primary current undergoes damped oscillation is detected, and the driver pulse operates at the timing after this zero phase is detected. Since the frequency is determined and the second and subsequent driver pulses based on this frequency are applied to the thyristor 12.14, simultaneous conduction of the two thyristors is prevented. In addition, after zero phase detection, the X-ray tube voltage division signal from the feedback circuit 32 causes
Since the timer circuit in the duty control circuit 21 can be set to one hour, the X-ray tube voltage can be controlled.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist.

[Effects of the Invention] As detailed above, according to the present invention, after detecting the zero phase from the damped oscillation of the primary current generated by the n-th driver pulse, , n+1 and subsequent driver pulses are generated, so simultaneous conduction of the two thyristors is prevented, and an extremely stable X-ray apparatus can be provided.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an X-ray apparatus according to the present invention, FIG. 2 is a block diagram showing an embodiment of the control means according to the present invention, and FIG. It is 1 sheet. DESCRIPTION OF SYMBOLS 1... AC power supply, 5... ] power supply, 6... Transformer, 6a... Primary winding, 6b... Secondary winding, 9...
... X-ray tube, 19... Control means, 20... Bridge section, 21... Series resonant bridge inverter, 22.
...First rectifying and smoothing means, 23...Second rectifying and smoothing means 30...Zero phase detection circuit, 31...Duty control circuit, 32...Feedback circuit, 33...Hand-held switch , 34...X-ray III timer circuit, 35...driver pulse generation circuit, 36...nth driver pulse generation circuit, 37...drive circuit.

Claims (2)

[Claims] (1) A transformer in which a DC input voltage is applied to the primary winding and obtains the X-ray tube driving output from the secondary winding, a resonant circuit including the primary winding, and a predetermined voltage is applied to the resonant circuit. In the X-ray apparatus, the X-ray apparatus is equipped with a series resonant bridge inverter configured to include a bridge section and a control means for sending a driver pulse to the bridge section and controlling the timing of supplying DC voltage from the bridge section to the resonant circuit. The means includes a zero phase detection circuit that detects the zero phase of the primary current flowing through the primary winding due to the nth driver pulse, and a duty control that determines the period of the n+1th and subsequent driver pulses based on this zero phase. An X-ray apparatus comprising: a circuit; and a driver pulse generation circuit that generates driver pulses at a cycle determined by the duty control circuit. (2) The duty control circuit includes a period control circuit that can vary the frequency of the driver pulse according to the amount of feedback of the X-ray tube voltage division signal. The X-ray device described.