SU1073904A1 - X-ray unit - Google Patents

Description

This invention relates to X-ray technique, a. More specifically, X-ray machines with high-frequency conversion in the main circuit. A X-ray machine is known, which contains a series-connected power supply rectifier, high-frequency inverter, high-frequency high-voltage transformer, high-voltage rectifier, filter, measuring unit and x-ray tube, as well as a control unit of the device with controls of the high-voltage inverter fl. In such an apparatus, a high-frequency inverter operates at a frequency of 1-5 kg, which significantly reduces the size and weight of the high-voltage elements of the apparatus. The technical solution closest to the invention is an x-ray apparatus containing a network rectifier, a high-frequency thyristor filter connected to it. an inverter connected to the inverter is a high-voltage transformer, the primary winding of which is included between the medium point of the filter and the midpoint of the inverter thyristors, an X-ray tube, connected to a high-voltage transformer via a high-voltage rectifier, means of controlling an inverter, which generally include a master oscillator and a pulse distributor connected to it, whose outputs are connected to the control electrodes of the inverter thyristors, and a device control unit with switch-on outputs and 2, the advantage of such an apparatus circuit is the possibility of combining various circuit elements with the primary winding of the transformer, which makes it possible to coordinate the apparatus with different Loading the increase the reliability in case of a short circuit, etc. A disadvantage of the known circuits of apparatus of the specified type: is the possibility of interrupting the inversion, when the apparatus is turned on with a push on a given anode voltage, which makes it necessary to constantly increase the anode voltage due to a change in the inverter supply voltage, which increases the output time and does not allow to obtain the required exposure times with sufficient accuracy, especially at short exposures. The purpose of the invention is to improve the accuracy of the exposure time. The goal is achieved by the fact that in the x-ray apparatus, we contain a network rectifier. a smoothing filter connected to it, a high-frequency thyristor inverter, a high-voltage transformer connected to the inverter, an X-ray tube connected to a high-voltage transformer via a high-voltage rectifier, an inverter control device, including a master oscillator, and a pulse distributor connected to it, an apparatus control unit with on and off outputs, an additional thyristor switching circuit is added to the inverter controls, the thyristors of which include the allele thyristors of the inverter and to the control electrodes of which the outputs of the pulse distributor are connected, and the means for switching on the inverter thyristors with a predetermined delay relative to the switching thyristors of the switching circuit and their simultaneous shutdown associated with the outputs of the apparatus 1 and 1. In this case, the means of switching on the inverter thyristors with a given delay relative to the switching circuit thyristors and their simultaneous shutdown include a delay unit, a unit for receiving the signal of the onset of the pulse of the master oscillator, two ZI circuits, circuit 2I and a bistable logic i circuit, and the delay unit and the block receiving the signal of the moment of appearance of the pulse front are connected to the output of the master oscillator, the first inputs of the Zi circuits are connected to the outputs of the pulse distributor, the second inputs to the output of the delay unit the third inputs are connected to the output of a bistable logic circuit, which is connected to one of the turn-on outputs of the control unit of the device, and the other input to the output of the 2I circuit, to one of the inputs of which one of the turn-on outputs of the control unit of the device is connected, and to the other - / ; block output: receiving a signal of the phenomenon of the form of a pulse, and the control electrodes of the inverter thyristors are connected to the outputs of the ZI circuits. In FIG. 1 shows the x-ray chart. 2, time diagrams of signals at the output of various elements of the circuit,. . The X-ray machine contains a power switch 1, a power supply rectifier 2, a smoothing iiC filter 3, a high-frequency thyristor inverter 4 with thyristors T1 and T2, a high-voltage transformer 5, the primary winding of which is connected between the middle points of the filter -3 and inverter 4, a high-voltage rectifier b and x-ray tube 7,. Parallel to the inverter 4, an thyristor switching circuit 8) thyristors TZ and T4, included in the inverter control means 4, and a master oscillator 9, a distributor 10 pulses connected to it, whose outputs are connected to the control switching electrodes of the thyristors of the switching circuit 8, and means 11 for switching on the thyristors of the inverter 4 with a predetermined delay relative to the thyristors of the switching circuit 8 and their simultaneous switching off containing the delay i2, block 13 through. receiving the signal of the moment of appearance of the pulse of the master oscillator 9, two ZIs 14 and 15, circuit 2 and 16, and bistable logic circuit 17. Means 11 are connected to the on and off outputs of the apparatus control unit 18. The blocks 12 and 13 of the means 11 are connected to the output of the master oscillator 9. The first inputs of the ZI 14 and 15 circuits are connected to the outputs of the distributor 10 pulses, the inputs to the output of the delay block 12, the third 4sody to the output cxeNffi 17. The unit 13 output is connected to one input cxeNttJ 2 and 16, to another input one of the turn-on codes of control unit 18 control circuit 2 and 16 is connected to the input of a bistable logic circuit 17, to the other input of which one of the control output switches of control unit 18 is connected, which can be connected to the switching input of the master oscillator and 9, under the control block 1§ in the case under consideration is meant, any known combination tools / steering cheniem On and off of the machine (timing device, the relay ekspozits1 "relay mAs, etc.). The x-ray machine works in the following way. At the initial time, the control unit 18 connects the device to the network via rectifier 1 and switches on the settable generator 9, the output of which appears in rectangular form impulses (Fig. 2a) with a frequency of 2iwHe where 11.1.0 is output frequency of the inverter 4. The signals of the master oscillator 9 are received on. delay circuit 12, distributor 10 pulses and block 13 for receiving a signal at the appearance of a pulse front. The signals at the output of the delay circuit 12, the outputs of the distributor 10 and the output of the switch 13 are shown in FIG. 2. In the present case, it is assumed that the delay circuit 12 is delayed. only the front of the impulse of the generator 9, thus reducing its duration. In principle, the delayed circuit; 12 can be performed in the usual way AND does not change the pulse duration. The delay is realized: It is time for rez - the time required to restore the locking device. The thyristors T1 - T4. The total pulse duration of the generator 9 is chosen equal to the IPPL OZ. YKI.1 where ten is the time required to turn on the thyristors T1 - T4. From the outputs of the distributor 10 pulses, the pulses (Fig. 2b, t) arrive at the control electrodes of the thyristors T 3 and T4 of the switching circuit 8 and at the first inputs of the ZI circuits 14 and 15, to the second inputs of which delayed signals come from the output of the delay circuit 12 ( Fig. 28) After some time after connecting the device to the network, the control unit 18 sends turn-on pulses (Fig. 26) to one input of the circuit, 2 and 16. The duration of this pulse exceeds the pulse duration of the master oscillator 9, but is chosen so that its passage is generated only one pulse from generator 9. The other input of the 2I 16 circuit receives pulses from block 13 (Fig. 29). At the moment of coincidence of pulses from block 13 and block. 18 of circuit 2I16 produces a short pulse (fig. 2 g), which triggers the operation of bistable logic circuit 17, at the output of which a constant voltage appears corresponding to logic 1 (fig. 2). This constant voltage enters the third inputs of the ZI circuits J.4 and 15. At the output of these circuits 14 and 15, pulses with a duration t Bi; / (. At the simultaneous presence of pulses from the distributor Yu block 12 of the delay and constant signal of circuit 1 (Fig. 2i and Fig. 2c). As a result, for example, the thyristor T4 xofmyTauHOHHoro circuit 8 first turns on, then through time tg) the thyristor T2 of inverter 4, then Simultaneously thyristor T4 and T2 turn off, then the thyristor of the circuit 8 of the circuit 8 is turned on, after it through the time of the inverter TgaTyristyrr T1 4, etc. As a result, alternating voltage 1 is supplied to high-voltage transformer 5 (Fig. 2 A is continuous), and rectified high voltage is supplied to tube 7 (schematically shown by the dashed line in Fig. 2 A). When the device is turned off, the control unit 18 sends to the bistable logic circuit a disconnecting ikotulse (Fig. 2mU), which translates it j

a state where there is no voltage at the output (fig., as a result, the supply of pulses to the control electrodes of the thyristors T1 and T2 of the inverter 4 and the disconnection of the high voltage on the tube 7 6 maximum inaccuracy of the picture duration (fig. 2 l) lies within 1/2 T, where T is the period between the fronts of the following each

after another pulse at the output of the distributor 10, i.e. for i = 1000 Hz, it is 0.5 ms. Thus, in the proposed apparatus, it is possible to carry out a reliable pushing operation, thereby reducing the probability of overexposure of patients as a result of inaccuracies in the exposure time exposure.

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Claims (2)

1. X-ray apparatus, / containing a network rectifier, a smoothing filter connected to it, a high-frequency thyristor inverter connected to an inverter A high-voltage transformer, X-ray. a Novaya tube connected to a high-voltage transformer through a high-voltage rectifier, inverter control means, including a master oscillator and a pulse distributor connected to it, a device control unit with on and off outputs, oh In order to increase the accuracy of exposure time exposure, a thyristor switching circuit is additionally introduced into the inverter control means, the thyristors of which are connected in parallel with the inverter thyristors and which control electrodes x sub- keys distributor outputs pulses, and means of thyristors of the inverter to a predetermined delay relative to the thyristor switching unit and simultaneously disable connected to the outputs of switching on and off the machine control unit. 2. The apparatus by π. 1, the fact is that the means for turning on the inverter thyristors with a predetermined delay relative to the thyristors of the switching circuit and their simultaneous shutdown contain a delay unit, a unit for receiving the signal of the moment of appearance of the pulse front of the master oscillator, two § ί ZI circuits , circuit 2I and bistable. , a logic circuit, wherein the delay unit and receiving the signal the onset of the pulse front is connected to the output of the master oscillator, the first input circuit connected to the outputs of the GI pulse distributor, the second input - to the output of the delay unit, the third input - to the output of a bistable logic ^circuit; one input of which is connected to one of the off outputs of the control unit of the device, and the other input to the output of circuit 2I, one of the inputs of which is connected to one of the outputs of the control unit of the device, and to the other is the output of the signal receiving unit of the moment the pulse front appears, and the control electrodes of the inverter thyristors are connected to the outputs of the ZI circuits. > I.