Discharge protection circuit structure for an x-ray tube

Abstract

The application discloses a kind of discharging protection circuit of X-ray tube, the discharging protection circuit includes high voltage control unit, sampling unit and high voltage transformer component;Control program in high voltage control unit in the application, for controlling the KV and MA value output by high voltage generating device;Double-sided copper-clad plate large-area grounding process and impulse current absorption loop are used in sampling unit, and cooperate with the discharge protection resistance in high voltage transformer component Limiting discharge impulse current, for inhibiting the impact caused by X-ray tube discharge on X-ray generating device.Using this circuit structure, the damage caused by X-ray tube discharge on X-ray generating device is eliminated, the working stability of the product is improved, and at the same time, the use requirements for X-ray tube are reduced.Because the price of X-ray tube accounts for a large proportion of the entire X-ray generating device, selecting a lower-priced domestic X-ray tube can reduce the cost of X-ray generating device, and facilitate the popularization of the product to primary hospitals.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of medical devices, in particular to a discharge protection circuit structure of an X-ray tube. The resistance, high-voltage transformer assembly and circuit of the X-ray tube discharge protection can be installed in an X-ray generating device. BACKGROUND

[0002] With the improvement of medical staff's requirements for the medical image quality of the X-ray machine, the requirements for the X-ray quality of the X-ray machine output are also increasingly high, which promotes the high-frequency X-ray machine to gradually replace the traditional power-frequency X-ray machine. With the improvement of people's living standards, more and more obese patients are increasing, and the output KV and MA of the X-ray machine required when shooting X-ray images are also gradually increasing. At present, the X-ray tube used by the X-ray machine will gradually decrease in vacuum degree after being placed for a period of time, and the high-frequency X-ray machine is prone to discharge between the anode and the cathode of the X-ray tube when emitting X-rays at high KV when it is restarted, especially the domestic X-ray tube. Since the discharge current of the MA loop is very large when the X-ray tube discharges, it is easy to cause damage to the MA sampling circuit in the MA loop, and in severe cases, it can even cause damage to the entire MA control circuit. Due to the above reasons, there is an urgent need for a discharge protection circuit for X-ray tube discharge in high-frequency X-ray generating devices.

[0003] At present, domestic high-frequency X-ray machines generally warn users in a prominent position or in the instruction manual that after the equipment is placed for a period of time, the X-ray tube needs to be trained before it is restarted to improve the vacuum degree of the X-ray tube and reduce the probability of X-ray tube discharge. Another method is to use high-quality X-ray tubes from well-known foreign X-ray tube manufacturers to reduce the probability of X-ray tube discharge. The first method: due to the cumbersome operation, the X-ray tube discharge problem cannot be completely avoided, which makes it difficult to reduce the failure rate of the high-frequency X-ray machine. The second method: will increase the cost of the X-ray generating device, which is not convenient for the product to be popularized to primary hospitals, and cannot completely avoid the X-ray tube discharge problem, which makes it difficult to reduce the failure rate of the high-frequency X-ray machine.

[0004] At present, foreign high-frequency X-ray machines generally use a specially designed high-voltage large-heat-capacity discharge protection resistor connected in series at the high-voltage anode output end and the high-voltage cathode output end to limit the discharge current, and cooperate with the use of high-quality X-ray tubes from well-known foreign X-ray tube manufacturers to prevent X-ray tube discharge from damaging the X-ray generating device, but this method has a high production cost and is not convenient for popularization to primary hospitals. SUMMARY

[0005] The present application aims at providing a discharge protection circuit structure of an X-ray tube to solve the problem that the MA sampling loop is damaged easily and even the whole MA control circuit is damaged in serious cases due to the strong discharge impact current of the MA sampling loop when the X-ray tube discharges, and the problems of complicated operation, high production cost and unstable work of the domestic high-frequency X-ray machine, and the problem of high price of the foreign high-frequency X-ray machine.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A discharge protection circuit structure of an X-ray tube, comprising a high-voltage control unit, a sampling unit and a high-voltage transformer assembly.

[0008] The high-voltage control unit comprises a high-voltage inverter and a CPU control unit.

[0009] A voltage drop compensation circuit is arranged in the CPU control unit, and a pulse width modulation voltage containing a voltage drop compensation amount is connected to the input terminals IV1 and IV2 of the high-voltage transformer assembly through the output terminals IV1 and IV2 of the high-voltage inverter, and the voltage drop compensation circuit compensates the high-voltage output value of the X-ray tube according to the voltage drop generated on the high-voltage anode output protection resistor and the high-voltage cathode output protection resistor in the high-voltage transformer assembly.

[0010] The sampling unit comprises a sampling circuit board, a ceramic gas discharge tube absorption circuit, a transient voltage stabilizing diode absorption circuit, an MA sampling circuit and a KV sampling circuit.

[0011] The sampling circuit board comprises a sampling circuit board substrate and copper foil layers for conduction on the top layer and the bottom layer of the sampling circuit board substrate, and the copper foil layers on the top layer and the bottom layer of the sampling circuit board are designed with large-area grounding to ensure that the ceramic gas discharge tube absorption circuit and the transient voltage stabilizing diode absorption circuit effectively absorb the impact current generated by the discharge of the X-ray tube.

[0012] The ceramic gas discharge tube absorption circuit and the transient voltage stabilizing diode absorption circuit are both arranged on the sampling circuit board; wherein the ceramic gas discharge tube absorption circuit comprises an MA+ absorption circuit and an MA- absorption circuit, and one end of the MA+ absorption circuit and the MA- absorption circuit is connected to the MA+ in input terminal and the MA-in input terminal of the sampling circuit board respectively, and the other end is directly connected to the large-area grounded copper foil on the top layer and the bottom layer of the sampling circuit board, cooperating with the current limiting of the high-voltage large heat capacity protection resistor to perform primary absorption on the discharge of the X-ray tube.

[0013] The transient voltage stabilizing diode absorption circuit includes a MA+ transient voltage stabilizing diode absorption circuit and a MA- transient voltage stabilizing diode absorption circuit, and the signal after the primary absorption of the X-ray tube discharge impact current by the ceramic gas discharge tube absorption circuit is sent to the transient voltage stabilizing diode absorption circuit, and then the signal after the secondary absorption of the X-ray tube discharge impact current by the transient voltage stabilizing diode absorption circuit is sent to the MA sampling circuit. The transient voltage stabilizing diode absorption circuit is used for absorbing the impact current generated by the X-ray tube discharge before the breakdown of the ceramic gas discharge tube and the remaining part of the X-ray tube discharge current after the breakdown of the ceramic gas discharge tube;

[0014] The MA sampling circuit and the KV sampling circuit convert the high-impedance signal input by the high-voltage transformer assembly into a low-impedance signal and transmit the low-impedance signal to the CPU control unit, so as to improve the anti-interference performance in the signal transmission process.

[0015] The high-voltage transformer assembly includes an anode voltage doubling rectifier circuit, a cathode voltage doubling rectifier circuit, a high-voltage anode output protection resistor and a high-voltage cathode output protection resistor. One end of the high-voltage anode output protection resistor is connected to the output end of the anode voltage doubling rectifier circuit, and the other end is connected to the anode of the X-ray tube. One end of the high-voltage cathode output protection resistor is connected to the output end of the cathode voltage doubling rectifier circuit, and the other end is connected to the cathode of the X-ray tube, which is used to limit the strong impact current generated during the discharge of the X-ray tube.

[0016] The resistance is composed of a resistance skeleton, resistance pins, a resistance body and cable paper. The resistance body is wound on the resistance skeleton, and the resistance body is wrapped with insulating cable paper. The resistance pins are fixed on the resistance skeleton and located at both ends of the resistance body. The resistance pins are brass columns.

[0017] The high-voltage control unit includes a voltage drop compensation circuit. The voltage drop compensation circuit includes CPU central processor D1, D / A converter D13, D / A conversion rate adjustment potentiometer RP1, operational amplifiers N1A and N1B connected in sequence. The voltage drop generated on the high-voltage anode output protection resistor and the high-voltage cathode output protection resistor in the high-voltage transformer assembly is compensated by the operation program in the CPU central processor D1, so as to ensure the accuracy of the KV value output by the high-voltage generator.

[0018] Preferably, the sampling circuit board further includes a sampling circuit board substrate and copper foil layers on the top layer and the bottom layer of the sampling circuit board substrate for conduction. The copper foil layers on the top layer and the bottom layer of the sampling circuit board are designed with a large area of grounding, so that the copper foil on the double-sided copper-clad printed circuit board except for the connection circuit is designed as ground, which is used to reduce the potential of the impact current at each grounding point of the sampling unit during the discharge of the X-ray tube, and ensure that the ceramic gas discharge tube absorption circuit and the transient voltage stabilizing diode absorption circuit effectively absorb the impact current generated by the X-ray tube discharge.

[0019] Preferably, the ceramic gas discharge tube absorption circuit is composed of the ceramic gas discharge tube F2, F3, voltage doubling rectifier circuit capacitors C1, C2, C3, C4, C5, C6, C7, C8, self-developed high-voltage large heat capacity discharge protection resistors R1, R2 and the X-ray tube, the high-voltage large heat capacity discharge protection resistor is used to limit the discharge current of the X-ray tube, and the overvoltage breakdown characteristic of the gas discharge tube is used to limit the voltage amplitude of the current sampling signal to 70V, which is the rated breakdown voltage.

[0020] Preferably, the transient voltage stabilizing diode absorption circuit includes current limiting resistors R7, R8, transient voltage stabilizing diodes V3, V4, filter capacitors C9, C10, C23, C24, the current limiting resistors R7, R8 are used to limit the current flowing through the transient voltage stabilizing diode after the breakdown of the gas discharge tube when the X-ray tube discharges, the overvoltage breakdown characteristic of the transient voltage stabilizing diode is used to limit the amplitude of the impact voltage output to the sampling circuit when the X-ray tube discharges, and the filter capacitors are used to limit the amplitude of the peak voltage output to the sampling circuit when the X-ray tube discharges.

[0021] In summary, due to the adoption of the technical solutions, the present application has the following advantages:

[0022] 1. In the present application, the self-developed high-voltage large heat capacity discharge protection resistor is used to limit the strong impact current generated when the X-ray tube discharges, and the impact current absorption circuit is used to suppress the impact of the X-ray tube discharge on the X-ray generating device; the circuit structure eliminates the damage of the X-ray tube discharge to the X-ray generating device, reduces the requirements on the X-ray tube, and since the price of the X-ray tube accounts for a large proportion of the entire X-ray generating device, the use of a domestic X-ray tube with a lower price can reduce the cost of the X-ray generating device and facilitate the popularization of the product to primary hospitals.

[0023] 2. The high-voltage large heat capacity discharge protection resistor is added in the high-voltage transformer assembly, the ceramic gas discharge tube absorption circuit and the transient voltage stabilizing diode absorption circuit are arranged in front of the sampling circuit, and the application of the double-sided copper-clad large-area grounding process of the sampling circuit board; the damage of the X-ray tube discharge to the MA+ and MA- sampling circuits and the X-ray generating device control circuit is eliminated; the technical requirements of the X-ray generating device on the X-ray tube are reduced, the cost of the X-ray generating device is reduced after the domestic X-ray tube is configured, the product is facilitated to be popularized to primary hospitals, and the disease diagnosis capability of primary hospitals is improved; since the working reliability of the X-ray generating device is improved, the failure rate of the equipment is reduced, the product maintenance cost of the company is reduced, and the utilization rate of the equipment is improved. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The discharge protection circuit principle block diagram of the present application;

[0025] Figure 2 The circuit diagram of the voltage drop compensation circuit in the present application;

[0026] Figure 3 The circuit diagram of the ceramic gas discharge tube absorption circuit in the present application;

[0027] Figure 4 The circuit diagram of the transient voltage stabilizing diode absorption circuit in the present application;

[0028] Figure 5 The structural diagram of the self-developed high-voltage large heat capacity discharge protection resistor in the present application;

[0029] Figure 6 The curve diagram of the damage rate of the X-ray tube discharge to the X-ray generating device in the present application.

[0030] In the figure:

[0031] M1, high-voltage control unit; M11, CPU control unit;

[0032] M111, KV control circuit; M112, voltage drop compensation circuit

[0033] M12, high-voltage inverter;

[0034] M2, sampling unit; M21, sampling circuit board;

[0035] M22, ceramic gas discharge tube absorption circuit; M23, transient voltage stabilizing diode absorption circuit;

[0036] M24, MA sampling circuit; M25, KV sampling circuit;

[0037] M3, high-voltage transformer assembly; M31, voltage doubling rectifier circuit;

[0038] M311, anode voltage doubling rectifier circuit; M312, cathode voltage doubling rectifier circuit;

[0039] M32, high-voltage anode output protection resistor; M33, high-voltage cathode output protection resistor;

[0040] M321, the skeleton of the high-voltage output protection resistor; M322, the wiring brass column of the high-voltage output protection resistor;

[0041] M323, the resistor body 6J22 cardamas of the high-voltage output protection resistor; M324, the insulating cable paper of the high-voltage output protection resistor;

[0042] M4, X-ray tube. DETAILED DESCRIPTION

[0043] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0044] With reference to Figure 1 A discharge protection circuit structure of an X-ray tube in an X-ray generating device, comprising a high-voltage control unit M1, a sampling unit M2 and a high-voltage transformer assembly M3.

[0045] The input end of the high-voltage control unit M1 is connected with the sampling output end of the sampling unit M2, the input end of the sampling unit M2 is connected with the sampling output end of the high-voltage transformer assembly M3, the input end of the high-voltage transformer assembly M3 is connected with the output end of the high-voltage control unit M1, the high-voltage output of the high-voltage transformer assembly M3 is connected with the X-ray tube M4 assembly, and the sampling output of the high-voltage transformer assembly M3 is connected with the sampling unit M2.

[0046] The high-voltage control unit M1 is used to generate a pulse width modulation voltage for driving the high-voltage transformer assembly M3, wherein a voltage drop compensation circuit M112 is used to compensate for the voltage drop generated on the high-voltage anode output protection resistor M32 and the high-voltage cathode output protection resistor M33 in the high-voltage transformer assembly M3, the sampling unit M2 is used to send the MA, KV sampling signals output by the high-voltage transformer assembly M3 to the high-voltage control unit M1 after X-ray tube discharge interference absorption and output impedance reduction processing, wherein a gas discharge tube absorption circuit M22 and a transient voltage stabilizing diode absorption circuit M23 are used to absorb the impact current generated during X-ray tube discharge, the high-voltage transformer assembly M3 is used to send the pulse width modulation voltage output by the high-voltage control unit M1 to the X-ray tube M4 after voltage doubling and rectification, and the X-ray generated by the X-ray tube M4 is used for image diagnosis, wherein the high-voltage anode output discharge protection resistor M32 and the high-voltage cathode output discharge protection resistor M33 are used to limit the impact current generated during X-ray tube M4 discharge, and the protection of the X-ray generating device during X-ray tube M4 discharge is realized through the application of the above voltage drop compensation circuit M112, gas discharge tube absorption circuit M22, transient voltage stabilizing diode absorption circuit M23 and anode discharge protection resistor M32, cathode discharge protection resistor M33. The discharge protection function of the X-ray tube will be further described below.

[0047] The high voltage control unit M1 includes a CPU control unit M11 and a high voltage inverter M12, the CPU control unit M11 further includes a KV control circuit M111 and a voltage drop compensation circuit M112; the input end of the high voltage control unit M1 is connected with two groups of X-ray tube sampling output signals of MA+, MA- and KV+, KV- of the sampling unit M2, the pulse width modulation inverter voltage output by the high voltage control unit M1 is connected to the IV1, IV2 input end of the high voltage transformer assembly M3; the high voltage control unit M1 is used for controlling the KV value and the MA value output by the X-ray tube.

[0048] The KV control circuit M111 in the CPU control unit M11 is composed of a TL594 pulse width modulator; the KV set voltage value KV-SET of the KV control circuit M111 is input by the voltage drop compensation circuit M112, the KV closed loop feedback signal voltage value in the KV control circuit M111 is input by the sampling unit M2, and the pulse width modulation signal output by the KV control circuit M111 is connected to the input end of the high voltage inverter M12. The KV control circuit M111 compares the KV feedback signal with the KV set voltage, adjusts the pulse width of the modulation signal output to the high voltage inverter M12, controls the output power of the high voltage inverter M12, and makes the KV value output by the high voltage generating device (i.e. the high voltage generator) reach the requirement of the set value.

[0049] With reference to Figure 2, voltage drop compensation circuit M112 in CPU control unit M11; current-voltage conversion operational amplifier circuit consisting of CPU central processor D1: AT89C55, D / A converter D13: AD7524, D / A conversion rate adjustment potentiometer RP1, N1A: TL084, and potential shift circuit consisting of N1B: TL084; output signal of the voltage drop compensation circuit is input to input terminal of KV control circuit M111 as set value of KV control. Control program in the CPU central processor D1 increases KV output set value in the form of digital output with the increase of high voltage output current, operational amplifier circuit consisting of D / A converter D13, D / A conversion rate adjustment potentiometer RP1, and operational amplifier N1A converts digital signal into analog signal, and potential shift circuit consisting of operational amplifier N1B shifts KV output set value downward by 0.4V and outputs to input terminal of KV control circuit M111, so that set value of the KV control circuit M111 is kept at -0.4V in standby state, ensuring that high voltage generating device will not have high voltage output in standby state. Voltage drop compensation circuit M112 increases digital voltage value output by CPU central processor D1 with the increase of output current through software programming, and then converts digital voltage signal into analog voltage signal through D / A conversion circuit as KV set value of KV control circuit M111, and takes KV sampling value of the voltage doubler rectifier circuit in high voltage transformer assembly M3 as feedback value of KV control circuit M111, so that pulse width output by pulse width modulator of the KV control circuit M111 is increased correspondingly through KV closed loop control circuit in high voltage generating device, and output power of high voltage inverter is increased correspondingly, so that output voltage of the voltage doubler rectifier circuit in high voltage transformer assembly M3 is increased correspondingly, offsetting voltage drop of the discharge protection resistor, and ensuring the accuracy of KV value output by the high voltage generating device.

[0050] Discharge protection resistor R1, R2 voltage drop compensation program design in high voltage transformer assembly M3:

[0051] MA increment corresponding to each 1kV compensation value:

[0052] U ÷ R

[0053] = U ÷ (R1 + R2 + R7 + R8 + R11 + R12)

[0054] = 1 × 10 3 ÷ (4.2 × 10 3 + 4.2 × 10 3 + 51 + 51 + 10 + 10)

[0055] = 0.117A

[0056] Considering the loss of other lines in the high voltage loop and the MA output grading, the MA grading is: 32mA, 40mA, 50mA, 63mA, 80mA, 100mA, 125mA, 160mA, 200mA, 250mA, 320mA; it is determined that for every 100mA current increase, 1kV high voltage inverter output compensation is performed, so that the high voltage value output to the X-ray tube after compensation reaches the set value;

[0057] Assembly language compensation program:

[0058] MOV A, DAMA

[0059] MOV B, #50

[0060] DIV AB

[0061] MOV B, A

[0062] MOV A, DAKV

[0063] ADD A, B

[0064] Wherein: "#1" is 2mA, "#50" is 100mA.

[0065] According to the GB9706.3 national standard, the deviation of X-ray tube voltage output should be not more than 10%, and the enterprise internal control standard requires that the deviation of X-ray tube voltage output should be not more than 5%, the resistance voltage drop compensation circuit is used to control the deviation caused by inserting the protection resistance within 1KV, which realizes the purpose of protecting the X-ray generating device and not affecting the normal work of the X-ray generating device.

[0066] The high voltage inverter M12 in the high voltage control unit M1 is composed of a bridge inverter circuit composed of two groups of intelligent IGBT modules; the input end of the high voltage inverter is connected with the output end of the KV control circuit in the CPU control unit, the output end of the high voltage inverter is connected with the input end of the high voltage transformer assembly M3, the pulse width modulation signal output by the KV control circuit drives the high voltage inverter to generate an AC 420V pulse width modulation voltage, which is output to the high voltage transformer assembly M3 to generate the DC high voltage required by the X-ray tube assembly M4.

[0067] The sampling unit M2 includes a sampling circuit board M21, a gas discharge tube absorption circuit M22, a transient voltage stabilizing diode absorption circuit M23, an MA sampling circuit M24 and a KV sampling circuit M25; the gas discharge tube absorption circuit M22 is a ceramic gas discharge tube absorption circuit.

[0068] The ceramic gas discharge tube absorption circuit M22, the transient voltage stabilizing diode absorption circuit M23, the MA sampling circuit M24 and the KV sampling circuit M25 are welded on the sampling circuit board M21, the input end of the ceramic gas discharge tube absorption circuit M22 is connected to the MA+ and MA- sampling output end of the high voltage transformer assembly M3, the output end of the ceramic gas discharge tube absorption circuit M22 is connected to the input end of the transient voltage stabilizing diode absorption circuit M23, the output end of the transient voltage stabilizing diode absorption circuit M23 is connected to the input end of the MA sampling circuit M24, the output end of the MA sampling circuit M24 is connected to the MA+ and MA- input end of the CPU control unit M11, the input end of the KV sampling circuit M25 is connected to the KV+ and KV- sampling output end of the high voltage transformer assembly M3, and the output end of the KV sampling circuit M25 is connected to the KV+ and KV- input end of the CPU control unit. The ceramic gas discharge tube absorption circuit M22 and the transient voltage stabilizing diode absorption circuit M23 are arranged in front of the sampling unit M2 input stage, and the application of the double-sided copper-clad plate large-area grounding process of the sampling circuit board M21 eliminates the impact of the X-ray tube M4 discharge on the MA sampling circuit, and the MA sampling circuit M24 and the KV sampling circuit M25 convert the high-impedance signal input by the high voltage transformer assembly M3 into a low-impedance signal and transmit it to the CPU control unit M11, so as to improve the anti-interference performance in the signal transmission process.

[0069] The application of the double-sided copper-clad plate large-area grounding process of the sampling circuit board 21: in the circuit board design, the copper foils on the top layer and the bottom layer of the circuit board are designed as grounding surfaces except the circuit connection lines, and the impact current generated during the discharge of the X-ray tube 4 is guided to the grounding surface of the high voltage transformer assembly 3 through the top layer and the bottom layer of the circuit board when flowing through the grounding points of the ceramic gas discharge tube absorption circuit 22 and the transient voltage stabilizing diode absorption circuit 23, and is guided from the three grounding screws to the grounding surface of the high voltage transformer assembly 3 through the top layer and the bottom layer of the circuit board, which effectively reduces the ground potential of each grounding point of the ceramic gas discharge tube absorption circuit 22 and the transient voltage stabilizing diode absorption circuit 23, and makes the potential change of the impact current generated during the discharge of the X-ray tube 4 not affect the working safety of the MA sampling circuit.

[0070] Reference Figure 3 The ceramic gas discharge tube absorption circuit M22 is composed of an MA+ discharge absorption loop and an MA- discharge absorption loop, wherein the MA+ discharge absorption loop is connected in sequence to the cathode of the X-ray tube, a cathode discharge protection resistor R2, cathode voltage doubling rectification capacitors C5, C6, C7 and C8, and a ceramic gas discharge tube F2 to ground, and the MA- discharge absorption loop is connected in sequence to the anode of the X-ray tube M4, an anode discharge protection resistor R1, anode voltage doubling rectification capacitors C1, C2, C3 and C4, and a ceramic gas discharge tube F3 to ground.

[0071] In this circuit, F2 and F3 use 2R70TC type ceramic gas discharge tubes with a rated DC breakdown voltage of 70V, an impulse breakdown voltage of less than 600V, and an impulse current of 50Hz, 20A, and 1s. When the output voltage of the high-voltage generator reaches a maximum of 125kV, the strongest discharge occurs between the anode and cathode of X-ray tube M4 (short circuit between anode and cathode). The working process of the ceramic gas discharge tube absorption circuit M22 is as follows: the discharge current flows from the anode of X-ray tube M4 → the cathode of X-ray tube M4 → the CATH of the high-voltage transformer assembly M3. →R2→C5→C6→C7→C8→MA+→MA+in of sampling unit M2→F2→GND→F3→MA-in→MA-in of high voltage transformer assembly M3→C4→C3→C2→C1→R1→ANODE→Returning to the anode of X-ray tube M4, when X-ray tube M4 discharges, F2 and F3 clamp the leading edge impulse voltage of the signal sent to the transient voltage regulator diode absorption circuit to below 600V (breakdown delay time less than 1μs), and clamp the impulse voltage after the ceramic gas discharge tube breaks down to 70V;

[0072] Maximum discharge current I of X-ray tube:

[0073] I = (Um - Ut) ÷ R1

[0074] = (62.5 × 10 3 -70)÷(4.2×10 3 )

[0075] =14.87A

[0076] Where: Um: Maximum anode output voltage = 0.5 × 125 × 10 3 =62.5×10 3 Ut: Voltage after the ceramic gas discharge tube breaks down;

[0077] The current Is in the transient Zener diode absorption circuit after the ceramic gas discharge tube breaks down:

[0078] Is=(Ut-Us)R7

[0079] = (70-12)÷51

[0080] =1.47A

[0081] Where: Ut is the voltage after the ceramic gas discharge tube breaks down; Us is the operating voltage of the transient voltage regulator diode; and R7 is the current-limiting resistor of the transient voltage regulator diode absorption circuit.

[0082] The maximum impulse current It that the ceramic gas discharge tube can withstand:

[0083] It = I - Is

[0084] =14.87-1.47

[0085] = 13.4A

[0086] Wherein: I is the maximum discharge current of the X-ray tube; Is is the current absorbed by the transient voltage protection diode circuit after the breakdown of the ceramic gas discharge tube.

[0087] When the X-ray tube discharges at the highest voltage, the MA+ ceramic gas discharge tube F2 and the MA- ceramic gas discharge tube F3 bear an impact current of 13.4A, and the impact time is ≤2ms (the action time of the X-ray tube discharge protection), which is less than the rated value of the impact current of the ceramic gas discharge tube, 20A, 1s, and meets the requirements of the ceramic gas discharge tube absorption circuit.

[0088] Reference Figure 4 The transient voltage protection diode absorption circuit M23 includes 51Ω / 8W current limiting resistor R7, R8, TVP1504 transient voltage protection diode V3, V4, 1μF filter capacitor C9, C10, 0.047μF filter capacitor C23, C24, and 10Ω / 2W sampling resistor R11, R12;

[0089] The working process of the transient voltage protection diode absorption circuit is: MA+A output by the ceramic gas discharge tube absorption circuit → R7 → V3-, C9, C23, R11 → ground → V4-, C10, C24, R12 → R8 → back to MA-A of the ceramic gas discharge tube absorption circuit;

[0090] Wherein the current limiting resistor R7, the transient voltage protection diode V3, and the filter capacitors C9, C23 constitute the MA+ absorption circuit;

[0091] The current limiting resistor R8, the transient voltage protection diode V4, and the filter capacitors C10, C24 constitute the MA- absorption circuit;

[0092] The current limiting resistors R7, R8 are used to limit the current flowing through the transient voltage protection diode absorbing circuit after the breakdown of the ceramic gas discharge tube. The transient voltage protection diodes V3 and V4 are used to clamp the impact voltage of 600V before the breakdown of the gas discharge tube of the MA+ and MA- sampling circuit and the impact voltage of 70V after the breakdown to 12V when the X-ray tube discharges. The filter capacitors C9, C23, C10 and C24 are used to filter out the spike voltage generated by the MA+ and MA- sampling circuit when the X-ray tube discharges. The current limiting resistors R7, R8 (51Ω / 8W) are made of 0.12mm diameter "6J40" constantan wire wound on a porcelain tube with a diameter of 7.5mm and a length of 22mm, with a total of 51 turns. The constantan wire is 1.201m long (constantan wire resistance: 42.5Ω / m), the unit mass of the 0.12mm diameter constantan wire is 0.0997g / m, the specific heat c of the constantan wire is 0.380J / g.℃, and the maximum allowable operating temperature is 275℃. The transient voltage protection diode TVP1504 has a rated operating voltage of 12V and a maximum operating pulse current Ippm of 89.8A.

[0093] When the X-ray tube discharges without considering the existence of the ceramic gas discharge tube, the voltage at the position of the ceramic gas discharge tube is:

[0094] I x R7 + Us

[0095] = 14.87 x 51 + 12

[0096] = 770.4V

[0097] Where I is the maximum discharge current of the X-ray tube, 14.87A, and Us is the clamping voltage of the transient voltage protection diode, 12V.

[0098] Since the voltage at the position of the ceramic gas discharge tube is 770.4V when the X-ray tube discharges without considering the existence of the ceramic gas discharge tube, which is greater than its impact breakdown voltage of 600V, the voltage of the ceramic gas discharge tube is clamped at 600V when the X-ray tube discharges.

[0099] The maximum impact current (impact time 1μs) of the current limiting resistors R7, R8 when the ceramic gas discharge tube is not broken when the X-ray tube discharges:

[0100] (Um - Us) ÷ R7

[0101] = (600 - 12) ÷ 51

[0102] = 11.53A

[0103] Where Um is the clamping voltage of the ceramic gas discharge tube when it is not broken when the X-ray tube discharges, 600V, and Us is the clamping voltage of the transient voltage protection diode, 12V.

[0104] Without considering the existence of V3, the voltage divided on R11 is 11.5A x 10Ω = 115V, which is greater than 12V, and V3 appears overvoltage breakdown phenomenon, clamping the voltage to 12V;

[0105] The energy W1 absorbed by R7, R8 current-limiting resistors when the ceramic gas discharge tube does not overvoltage breakdown during X-ray tube discharge:

[0106] W1 = P x t

[0107] = I 2 x R x t -6

[0108] = 11.5 2 x 51 x 1 x 10 -6

[0109] = 6.74 x 10 -3 J

[0110] Wherein: P is the power on R7, R8 resistors when the ceramic gas discharge tube does not overvoltage breakdown during X-ray tube discharge; I is the current of R7, R8 resistors when the ceramic gas discharge tube does not overvoltage breakdown during X-ray tube discharge; R is the resistance value of R7, R8; t is the breakdown time of the ceramic gas discharge tube 1μs = 10 -6 s.

[0111] The working current of R7, R8 current-limiting resistors after the breakdown of the ceramic gas discharge tube during X-ray tube discharge:

[0112] U F2 ÷ (R7 + R11)

[0113] = 70 ÷ (51 + 10)

[0114] = 1.15A

[0115] V R11 = I R11 x R11

[0116] = 1.15 x 10

[0117] = 11.5V

[0118] Wherein: U F2 is the breakdown voltage of the ceramic gas discharge tube; V R11 is the voltage on R11; I R11 is the current on R11;

[0119] Since the voltage divided on R11 is 11.5V, V3 is not turned on.

[0120] The energy W2 absorbed by R7, R8 current-limiting resistors after the breakdown of the ceramic gas discharge tube during X-ray tube discharge:

[0121] W2 = P x t

[0122] = I 2 × R × t

[0123] = 1.15 2 × 51 × 2 × 10 -3

[0124] = 0.135 J

[0125] Wherein: P is the power on the R7, R8 current-limiting resistor after the ceramic gas discharge tube is broken down when the X-ray tube is discharged; t is the X-ray tube discharge protection action time 2ms = 2 x 10 -3 ; I is the working current of the R7, R8 current-limiting resistor after the ceramic gas discharge tube is broken down when the X-ray tube is discharged; R is the resistance value of R7, R8.

[0126] The total energy W absorbed by the R7, R8 current-limiting resistor when the X-ray tube is discharged:

[0127] W = W1 + W2

[0128] = 0.00674 + 0.135

[0129] = 0.1417 J

[0130] The temperature rise Δt of the R7, R8 current-limiting resistor when the X-ray tube is discharged:

[0131] Q = cmΔt

[0132] Δt = Q ÷ cm

[0133] = 0.1417 ÷ (0.380 x 1.201 x 0.0997)

[0134] = 3.11℃

[0135] Wherein: Q = cmΔt; Q is the total energy absorbed by the R7, R8 current-limiting resistor when the X-ray tube is discharged, which is equal to W; c is the specific heat of constantan wire c = 0.380 J / g.℃; m is the mass of constantan wire = constantan wire length 1.201 m x unit mass of constantan wire 0.0997 g / m.

[0136] The temperature rise of the R7, R8 current-limiting resistor is 3.11℃ when the X-ray tube is discharged, which is much smaller than the maximum allowed temperature rise of 235℃ (the maximum working temperature is 275℃, and the maximum use environment temperature is 40℃), meeting the use requirements.

[0137] According to the maximum pulse current curve of the transient voltage protection diode TVP1504, it can be seen that the maximum working current corresponding to the 2ms pulse of the transient voltage protection diode is 30% of the maximum pulse current of the transient voltage protection diode, that is, 26.94A which is 30% of 89.8A.

[0138] The maximum working current of the transient voltage stabilizing diode, i.e. the transient voltage stabilizing diode current when the ceramic gas discharge tube has not been overvoltage breakdown:

[0139] I R7 -I R11

[0140] = I R7 -U R11 ÷ R11

[0141] = 11.53-12÷10

[0142] = 10.33A;

[0143] Wherein: I R7 is the maximum impact current of the current limiting resistor R7, R8 when the ceramic gas discharge tube has not been breakdown during the X-ray tube discharge, which is 11.53; I R11 is the current of R11 when the ceramic gas discharge tube has not been breakdown during the X-ray tube discharge; U R11 is the voltage of R11 when the ceramic gas discharge tube has not been breakdown during the X-ray tube discharge; I R7 -I R11 ; I R7 -U R11 ÷ R11.

[0144] The maximum working current of the transient voltage stabilizing diode is 11.53A when the X-ray tube discharges, which is less than the limit current 26.94A corresponding to the 2ms pulse of the transient voltage stabilizing diode (the X-ray tube discharge protection action time is less than or equal to 2ms), so that the transient voltage stabilizing diode can meet the needs of the X-ray tube discharge absorption circuit.

[0145] The high-voltage transformer assembly M3 comprises an anode voltage doubling rectifier circuit M311, a cathode voltage doubling rectifier circuit M312, a high-voltage anode output protection resistor M32 and a high-voltage cathode output protection resistor M33; and is used for outputting the high-voltage voltage required by the X-ray tube; wherein one end of the high-voltage anode output protection resistor M32 is connected to the output end of the anode voltage doubling rectifier circuit M311, and the other end is connected to the anode of the X-ray tube M4; one end of the high-voltage cathode output protection resistor M33 is connected to the output end of the cathode voltage doubling rectifier circuit M312, and the other end is connected to the cathode of the X-ray tube M4, and is used for limiting the strong impact current generated when the X-ray tube discharges.

[0146] The high-voltage anode output protection resistor and the high-voltage cathode output protection resistor in the application are high-voltage large heat capacity discharge protection resistors independently developed, which limit the strong impact current generated when the X-ray tube discharges, cooperate with the impact current absorption circuit, and inhibit the impact of the X-ray tube discharge on the X-ray generating device; by adopting the circuit structure, the damage of the X-ray tube discharge to the X-ray generating device is eliminated, and the use requirement of the X-ray tube is reduced.

[0147] Reference Figure 5 , the high-voltage high-heat capacity output protection resistor M32 and M33 structure: by having excellent electrical insulation, solvent resistance of polyformaldehyde rod as the skeleton of the resistor M321, by 6J22 cardamom silk as the resistor body M323, which has a high resistivity, long-term stability of the resistor with the characteristics of small size, resistance value stability; 8 layers of 0.12mm thick cable paper as the outer insulation M324, when immersed in transformer oil, to enhance the insulation of the resistor, so that it can withstand the impact of the 62.5kV high voltage and 14.87A current applied by the X-ray tube discharge; When the X-ray tube discharges, the worst case is that the voltage between the anode and the cathode of the X-ray tube is zero volt, the maximum high voltage output is 125kV, and the anode protection resistor and the cathode protection resistor each bear 50% of the high voltage output voltage.

[0148] The insulation voltage of the 6J22 cardamom silk of the first grade insulation paint is 1400V, the unit mass of the 6J22 cardamom silk with a diameter of 0.12mm is 0.092g / m, and the specific heat c of the 6J22 cardamom silk is 0.46J / g.℃; The high-voltage transformer assembly energy storage capacitor is composed of 8 3.3nF capacitors in series, the highest working temperature of the high-voltage transformer assembly is 65℃, the X-ray tube discharge protection action time of the X-ray generating device is 2ms, the maximum output power of the X-ray generating device is 25kW, and the energy released in the X-ray tube discharge protection action time is the output energy of the high-voltage capacitor in the high-voltage transformer assembly plus the output energy of the high-voltage generating device in the X-ray tube discharge protection action time.

[0149] The maximum voltage U 匝 :

[0150] U 匝 = U ÷ n

[0151] = 62.5 × 10 3 ÷ 758

[0152] = 82.5V

[0153] Where: U is the maximum voltage that the resistor can withstand; n is the number of turns of the resistor; U 匝 = U ÷ n.

[0154] As can be seen from the above calculation, the voltage between the turns of the anode resistor and the cathode resistor is 82.5V, which is much smaller than the insulation voltage of the 6J22 cardamom silk of the first grade insulation paint, which is 1400V, and the turn-to-turn withstand voltage meets the requirements;

[0155] According to the "Electrical Engineer's Handbook (Third Edition: Chief Editor Wang Jianhua)" "The maximum voltage between the turns of the resistor is equal to the maximum voltage that the resistor can withstand divided by the number of turns of the resistor." Figure 31-2" DC discharge curve diagram, it can be seen that the DC discharge voltage of transformer oil is about 230 kV at a distance of 20 mm, and the distance between the high-voltage large heat capacity discharge protection resistor is 108 mm, which is greater than the above-mentioned insulation width of 20 mm, so the minimum withstand voltage value is greater than 230 kV, which meets the withstand voltage requirement of 62.5 kV of the resistance 62.5 kV when the X-ray tube discharges.

[0156] The total energy storage W1 of the high-voltage capacitor in the high-voltage transformer assembly:

[0157] W1 = 1 / 2CU 2

[0158] = 0.5 x (3.3 x 10 -9 ÷ 8) x 125000 2

[0159] = 3.22 J

[0160] Wherein: the voltage of the voltage doubling capacitor is 3.3 nF = 3.3 x 10 -9 , the voltage doubling number is 8, the capacitor value C after series connection is 3.3 x 10 -9 ÷ 8; U is the total voltage of the high-voltage capacitor in the high-voltage transformer assembly.

[0161] The output energy W2 of the high-voltage device in the X-ray tube discharge protection action time (the protection action time is less than or equal to 2 ms):

[0162] W2 = P x t

[0163] = 25000 x 0.002

[0164] = 50 J

[0165] Wherein: the maximum output power P of the high-voltage device is 25 kW, and the maximum duration t of the X-ray tube discharge is 2 ms.

[0166] The total output energy in the X-ray tube discharge process is the energy storage W1 of the high-voltage capacitor in the high-voltage transformer assembly plus the output energy W2 of the high-voltage device in the X-ray tube discharge protection action time;

[0167] Wtotal = W1 + W2

[0168] = 3.22 + 50

[0169] = 53.22 J

[0170] The total weight m of the anode current limiting protection resistor and the cathode current limiting protection resistor:

[0171] m = 2 x 0.092 x n x pi x Phi

[0172] = 2 x 0.092 x 758 x 3.14 x 0.015

[0173] = 6.57 g

[0174] Wherein: n is the number of turns 758; Φ is the resistance diameter Φ = 0.015 m; the unit mass of the resistance wire 0.092 g / m.

[0175] The energy released during the discharge of the X-ray tube is mainly absorbed by the current-limiting protection resistor, and the temperature rise Δt of the resistor within the action time of the X-ray tube discharge protection is:

[0176] Qabsorption = cmΔt

[0177] Δt = Q ÷ cm

[0178] = 53.22 ÷ (0.46 × 6.57)

[0179] = 17.6℃

[0180] Wherein: Qabsorption is the total absorbed energy of the anode current-limiting protection resistor and the cathode current-limiting protection resistor during the discharge of the X-ray tube; c is the specific heat of 6J22 carbon mica c: 0.46 J / g.℃; m is the total weight of the anode current-limiting protection resistor and the cathode current-limiting protection resistor; Qabsorption = cmΔt.

[0181] The temperature rise of the resistor during discharge is 17.6℃, plus the maximum working temperature of the oil tank 65℃, which is 82.6℃, less than the flash point of 25# transformer oil 140°, meeting the requirements of the heat capacity of the anode current-limiting protection resistor and the cathode current-limiting protection resistor during discharge.

[0182] Reference Figure 6 , the damage rate curve of the X-ray tube discharge to the X-ray generating device, without the discharge protection circuit, see curve 1 in the figure, when the discharge voltage exceeds 85KV, the damage rate of the X-ray tube discharge to the X-ray generating device increases exponentially with the increase of the discharge voltage, and when the discharge voltage reaches 125KV, the damage rate of the X-ray tube discharge to the X-ray generating device reaches 25%, which seriously affects the working stability of the X-ray generating device. In the case of adding the protection resistor of the X-ray tube discharge, the high-voltage transformer assembly and the circuit, see curve 2 in the figure, the discharge voltage does not cause damage to the X-ray generating device within the range of 80KV to 125KV, which confirms the working effectiveness of the protection resistor of the X-ray tube discharge, the high-voltage transformer assembly and the circuit.

[0183] Although the embodiments of the present application have been shown and described above, it should be understood that the above-mentioned embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and modifications to the above-mentioned embodiments within the scope of the present application, which should be included in the protection scope of the present application.

Claims

1. A discharge protection circuit arrangement for an X-ray tube, the circuit comprising: The high-voltage control unit, the sampling unit and the high-voltage transformer assembly are characterized in that: The high-voltage control unit comprises a CPU control unit and a high-voltage inverter, wherein the CPU control unit further comprises a KV control circuit and a voltage drop compensation circuit; the input end of the high-voltage control unit is connected with the KV and MA sampling signals output by the sampling unit, and the output end of the high-voltage control unit is connected with the high-voltage transformer assembly; the voltage value output by the voltage drop compensation circuit is compared with the KV sampling voltage value output by the sampling unit, the pulse width of the pulse width modulation signal output by the KV control circuit is adjusted, the pulse width modulation signal is used as the input control signal of the high-voltage inverter, the output power of the high-voltage inverter is controlled, and the KV and MA values output by the high-voltage generator meet the requirement of the output set value, The high-voltage inverter in the high-voltage control unit is composed of a bridge inverter circuit formed by two groups of intelligent IGBT modules; The sampling unit comprises a sampling circuit board, a ceramic gas discharge tube absorption circuit, a transient voltage stabilizing diode absorption circuit, an MA sampling circuit and a KV sampling circuit; the input end of the sampling unit is connected with the KV and MA sampling signals output by the high-voltage transformer assembly, the output end of the sampling unit is connected with the CPU control unit, the impact current generated when the X-ray tube discharges is sent to the sampling unit through the MA sampling output end of the high-voltage transformer assembly, the impact current is sent to the MA sampling circuit after passing through the ceramic gas discharge tube absorption circuit and the transient voltage stabilizing diode absorption circuit, the copper foil layer grounding part of the sampling circuit board is designed in a large area, the copper foils of the top layer and the bottom layer of the double-sided copper-clad printed circuit board except the connection circuit are all designed as ground, and the MA sampling circuit and the KV sampling circuit convert the high-impedance signals input by the high-voltage transformer assembly into low-impedance signals and transmit the low-impedance signals to the CPU control unit; The high-voltage transformer assembly comprises two resistors, one of which is an anode high-voltage large heat capacity discharge protection resistor, one end of which is connected to the output end of the anode voltage doubling rectifier circuit and the other end of which is connected to the anode of the X-ray tube, and the other resistor is a cathode high-voltage large heat capacity discharge protection resistor, one end of which is connected to the output end of the cathode voltage doubling rectifier circuit and the other end of which is connected to the cathode of the X-ray tube; The input end of the high-voltage transformer assembly is connected with the output end of the high-voltage control unit, one group of output ends of the high-voltage transformer assembly is connected with the X-ray tube, and the other group of KV and MA sampling signal output ends of the high-voltage transformer assembly are output to the sampling unit, wherein the voltage doubling rectifier circuit provides stable direct-current high voltage for the X-ray tube; The resistor is composed of a resistor framework, resistor pins, a resistor body and cable paper, the resistor body is wound on the resistor framework, the resistor body is wrapped with insulating cable paper, and the resistor pins are fixed on the resistor framework and located at both ends of the resistor body, and the resistor pins are brass columns.

2. The circuit structure for X-ray tube discharge protection according to claim 1, characterized in that: The high-voltage control unit comprises a voltage drop compensation circuit. The voltage drop compensation circuit comprises a CPU (Central Processing Unit) D1, a D / A (Digital / Analog) converter D13, a D / A conversion rate adjusting potentiometer RP1, and an operational amplifier N1.

3. The discharge protection circuit structure of an X-ray tube according to claim 1, characterized in that: The sampling unit comprises a sampling circuit board; The sampling circuit board further comprises a sampling circuit board substrate and copper foil layers on the top and bottom layers of the sampling circuit board substrate for electrical conduction.

4. The discharge protection circuit structure of an X-ray tube according to claim 1, characterized in that: The sampling unit further comprises a ceramic gas discharge tube absorption circuit. The ceramic gas discharge tube absorption circuit comprises ceramic gas discharge tubes F2 and F3, voltage doubling rectifier circuits C1, C2, C3, C4, C5, C6, C7, and C8, high-voltage large-heat-capacity discharge protection resistors R1 and R2, and an X-ray tube.

5. The discharge protection circuit structure of an X-ray tube according to claim 1, characterized in that: The sampling unit further comprises a transient voltage stabilizing diode absorption circuit. The transient voltage stabilizing diode absorption circuit comprises current limiting resistors R7 and R8, transient voltage stabilizing diodes V3 and V4, filter capacitors C9, C10, C23, and C24, input terminals of MA+ and MA- transient voltage stabilizing diode absorption circuits, output terminals of the ceramic gas discharge tube absorption circuit, and input terminals of MA+ and MA- sampling circuits.

6. The discharge protection circuit structure of the X-ray tube according to claim 1, characterized in that: The resistance skeleton is a polyformaldehyde rod.

7. The discharge protection circuit structure of an X-ray tube according to claim 1, characterized in that: The resistance body is a 6J22 cardamom silk.

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