CN116406069A - Filament power supply and radiotherapy equipment - Google Patents
Filament power supply and radiotherapy equipment Download PDFInfo
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- H—ELECTRICITY
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- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- H05H7/00—Details of devices of the types covered by groups H05H9/00, H05H11/00, H05H13/00
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- H—ELECTRICITY
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- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
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- H05H2277/00—Applications of particle accelerators
- H05H2277/10—Medical devices
Abstract
The application relates to a filament power and radiotherapy equipment. The filament power supply includes: the input end of the inverter circuit is connected with a direct current power supply, the output end of the inverter circuit is connected with a magnetron and is used for converting direct current into alternating current and providing electric energy for the magnetron by utilizing the alternating current; the input end of the adjusting circuit is connected with the output end of the inverter circuit, the output end of the adjusting circuit is connected with the driving end of the inverter circuit, and the adjusting circuit is used for acquiring the electric parameters output by the inverter circuit, generating driving signals according to the electric parameters and given electric parameters, and adjusting the electric parameters output by the inverter circuit by the driving signals; the output end of the inverter circuit is respectively connected with a magnetron filament and a magnetron cathode, a voltage protection circuit is arranged between the magnetron filament and the magnetron cathode, and the inverter circuit comprises a filtering unit which is used for protecting a filament power supply. The magnetron filament temperature control device can ensure the temperature of the magnetron filament to prolong the service life and improve the safety of a filament power supply.
Description
The application is "the application number is: 201911375564.2, filing date: 12 months and 27 days in 2019, the name is: the invention of filament power supply and radiotherapy equipment is applied separately.
Technical Field
The application relates to the technical field of medical equipment, in particular to a filament power supply and radiotherapy equipment.
Background
The medical electron linear accelerator is an accelerating device which accelerates electrons by utilizing a microwave electromagnetic field and has a linear motion orbit, and is used for the radiotherapy of tumors or other focus of a patient. It can generate high-energy X-ray and electron beam, and has the features of high dosage rate, short irradiation time, large irradiation field, high dosage uniformity and stability, small penumbra area, etc.
In the current medical electron linear accelerator in the prior art, a filament power supply supplies power to a magnetron. The larger the current provided by the filament power supply to the magnetron, the higher the temperature of the magnetron cathode filament; the smaller the current supplied by the filament power supply to the magnetron, the lower the temperature of the magnetron cathode filament. And the lifetime of the magnetron is closely related to the temperature of the cathode filament. To achieve maximum lifetime, the cathode filament of the magnetron must be operated at the correct temperature. Too low a temperature results in unstable operation of the magnetron due to reduction of emission of X-rays or electron rays, further damage of the magnetron, and too high a temperature results in rapid deterioration of the cathode, resulting in shortened life of the magnetron. The prior art cannot precisely control the current supplied from the filament power supply to the magnetron, thereby shortening the life of the magnetron.
Disclosure of Invention
In view of the foregoing, it is desirable to provide a filament power supply and a radiotherapy apparatus that can improve the service life of a magnetron.
A filament power supply including an inverter circuit and a conditioning circuit; the input end of the inverter circuit is connected with a direct current power supply, the output end of the inverter circuit is connected with a magnetron and is used for converting direct current into alternating current and providing electric energy for the magnetron by utilizing the alternating current; the input end of the adjusting circuit is connected with the output end of the inverter circuit, the output end of the adjusting circuit is connected with the driving end of the inverter circuit and is used for acquiring the electric parameters output by the inverter circuit and generating driving signals according to the electric parameters and given electric parameters, and the driving signals are used for adjusting the electric parameters output by the inverter circuit; the output end of the inverter circuit is respectively connected with a magnetron filament and a magnetron cathode, a voltage protection circuit is arranged between the magnetron filament and the magnetron cathode, the inverter circuit comprises a filter unit, and the voltage protection circuit and the filter unit are used for protecting a filament power supply.
In one embodiment, the inverter circuit further comprises an inverter unit and a sampling resistor; the input end of the inversion unit is connected with a direct current power supply and is used for converting direct current into alternating current; the filtering unit is arranged at the output end of the inversion unit and is used for filtering the alternating current; the sampling resistor is arranged at the output end of the inversion unit, the input end of the regulating circuit is connected with the sampling resistor, the output end of the regulating circuit is connected with the inversion unit, the regulating circuit collects the current output by the inversion circuit through the sampling resistor, generates a driving signal according to the current and a given current, and transmits the driving signal to the inversion unit.
In one embodiment, the adjusting circuit comprises a first analog-to-digital conversion unit, a first comparison unit and an adjusting unit; the input end of the first analog-to-digital conversion unit is connected with the sampling resistor, the output end of the first analog-to-digital conversion unit is connected with the first input end of the first comparison unit, and the first analog-to-digital conversion unit is used for collecting the current output by the inverter circuit through the sampling resistor and performing analog-to-digital conversion on the current to obtain a digital current signal; the second input end of the first comparison unit is connected with a given current signal, and the output end of the first comparison unit is connected with the adjusting unit and is used for comparing the digital current signal with the given current signal to obtain a first error signal; the output end of the adjusting unit is connected with the inversion unit and is used for generating a driving signal according to the first error signal and transmitting the driving signal to the inversion unit.
In one embodiment, the adjusting unit comprises: a proportional integral adjusting unit and a pulse width modulating unit; the input end of the proportional-integral regulating unit is connected with the output end of the first comparing unit, and the output end of the proportional-integral regulating unit is connected with the input end of the pulse width modulating unit and is used for carrying out proportional-integral regulation on the first error signal to obtain a regulating signal; the output end of the pulse width modulation unit is connected with the inversion unit and is used for carrying out pulse width modulation on the adjusting signal to obtain a driving signal and transmitting the driving signal to the inversion unit.
In one embodiment, the regulating circuit further comprises a power calculation unit; the input end of the power calculation unit is connected with the input end of the magnetron, the output end of the power calculation unit is connected with the second input end of the first comparison unit, and the power calculation unit is used for acquiring pulse parameters input into the magnetron, obtaining a given current signal according to the pulse parameters and transmitting the given current signal to the first comparison unit.
In one embodiment, the pulse parameters include: pulse peak voltage, pulse peak current, pulse width, and pulse repetition frequency; the power calculation unit is further used for obtaining average power according to the pulse peak voltage, the pulse peak current, the pulse width and the pulse repetition frequency; and searching a mapping table of power and current according to the average power to obtain a given current signal.
In one embodiment, the adjusting circuit further includes a second analog-to-digital conversion unit and a second comparison unit; the input end of the second analog-to-digital conversion unit is connected with the output end of the inverter circuit, and the output end of the second analog-to-digital conversion unit is connected with the first input end of the second comparison unit; the inverter circuit is used for acquiring the voltage output by the inverter circuit and performing analog-to-digital conversion on the voltage to obtain a digital voltage signal; the second input end of the second comparison unit is connected with the output end of the proportional-integral regulating unit, and the output end of the second comparison unit is connected with the input end of the pulse width modulation unit; and the pulse width modulation unit is used for comparing the regulating signal with the digital voltage signal to obtain a second error signal and transmitting the second error signal to the pulse width modulation unit.
In one embodiment, the voltage protection circuit includes a first inductor and a second inductor; the output positive electrode of the inverter circuit is connected with the filament of the magnetron through a first inductor; and the output negative electrode of the inverter circuit is connected with the cathode of the magnetron through a second inductor.
In one embodiment, the voltage protection circuit further includes a diode, a first capacitor, and a second capacitor; the diode and the first capacitor are connected in parallel between an output positive electrode and an output negative electrode of the inverter circuit; the second capacitor is connected between a filament input and a cathode input of the magnetron.
A radiotherapy apparatus comprising any one of the filament power supplies described above.
The filament power supply comprises an inverter circuit and an adjusting circuit, wherein the input end of the inverter circuit is connected with a direct current power supply, the output end of the inverter circuit is connected with a magnetron and used for converting direct current into alternating current and providing electric energy for the magnetron by utilizing the alternating current; the input end of the adjusting circuit is connected with the output end of the inverter circuit, the output end of the adjusting circuit is connected with the driving end of the inverter circuit, and the adjusting circuit is used for acquiring the electric parameters output by the inverter circuit and generating driving signals according to the electric parameters and given electric parameters, and the driving signals are used for adjusting the electric parameters output by the inverter circuit; the output end of the inverter circuit is respectively connected with a magnetron filament and a magnetron cathode, a voltage protection circuit is arranged between the magnetron filament and the magnetron cathode, and the inverter circuit comprises a filtering unit which is used for protecting a filament power supply. The method comprises the steps of obtaining output electric parameters of an inverter circuit through a setting adjusting circuit, generating a driving signal according to the electric parameters, transmitting the driving signal to the inverter circuit, and adjusting the electric parameters output by the inverter circuit through the driving signal. Through feedback adjustment, the electric parameters output by the inverter circuit can be accurately adjusted to given electric parameters required by the current use scene, namely, the electric parameters output by the filament power supply can be accurately controlled to reach the given electric parameters, the filament power supply supplies electric energy to the magnetron through the given electric parameters, the temperature of a cathode filament in the magnetron can be ensured, and the service life of the magnetron can be further prolonged. Meanwhile, the voltage protection circuit and the filtering unit are used for jointly carrying out voltage isolation and protection on the filament power supply, so that the safety of the filament power supply is improved.
Drawings
FIG. 1 is a schematic diagram of the connections of a pulse modulator, magnetron and filament power supply in one embodiment;
FIG. 2 is a schematic diagram of the current and voltage of the output pulse of the pulse modulator according to one embodiment;
FIG. 3 is a schematic diagram of pulse width and repetition period of a pulse modulator output pulse in one embodiment;
FIG. 4 is a schematic diagram of a filament power supply in one embodiment;
FIG. 5 is a schematic diagram of another embodiment of a filament power supply;
FIG. 6 is a schematic diagram of another embodiment of a filament power supply;
FIG. 7 is a schematic diagram of another embodiment of a filament power supply;
FIG. 8 is a filament heating profile in one embodiment;
FIG. 9 is a circuit diagram of a filament power supply in one embodiment;
FIG. 10 is a schematic diagram of the connection of a filament power supply to a magnetron in one embodiment;
FIG. 11a is a diagram illustrating the on state of the inverter circuit at time t 0. Ltoreq.t < t1 according to one embodiment;
FIG. 11b is a diagram illustrating the on state of the inverter circuit at time t 1. Ltoreq.t < t2 in one embodiment;
FIG. 11c is a diagram illustrating the on state of the inverter circuit at time t 2. Ltoreq.t < t3 in one embodiment;
FIG. 11d is a diagram illustrating the on state of the inverter circuit at time t 3. Ltoreq.t < t4 in one embodiment;
FIG. 12 is a diagram showing waveforms of driving signals and output voltage and current of a MOS transistor according to an embodiment;
fig. 13 is a waveform of current output in one embodiment.
Detailed Description
In order to facilitate understanding of the present application, the following detailed description of the specific embodiments of the present application will be described in connection with the accompanying drawings, so that the foregoing objects, features, and advantages of the present application will be more readily understood. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, the preferred embodiments of which are shown in the accompanying drawings. This application may, however, be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. This application is intended to be limited to the details of the particular embodiments disclosed herein since it is to be understood that modifications may be made by those skilled in the art without departing from the spirit of the present application.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "plurality" is at least two, such as two, three, etc., unless explicitly defined otherwise. In the description of the present application, the meaning of "several" means at least one, such as one, two, etc., unless explicitly defined otherwise.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
As shown in fig. 1, in the medical electron linear accelerator, the pulse modulator 300, the magnetron 200, and the filament power supply 100 are important components of the beam current system in the medical electron linear accelerator. The pulse modulator 300 modulates a high-voltage pulse to be output to the magnetron 200, and the magnetron 200 generates a high-frequency electromagnetic wave under the action of an electromagnetic field. The electromagnetic wave is fed into the accelerating tube through the waveguide system to form an electron accelerating standing wave field, and X rays are generated for treating tumors. The magnetron 200 includes a magnetron anode, a magnetron cathode, and a filament, and an external power supply for heating the filament, that is, the filament power supply 100 is required. During operation, the filament power supply 100 injects a current into the magnetron 200, heating the cathode for forming an electron cloud in the region of interaction between the anode and the cathode. Depending on the type of magnetron 200, the filament power supply 100 may be a dc power supply 140 or an ac power supply. As shown in fig. 2-3, fig. 2 is a schematic diagram of the current and voltage of the output pulse of the pulse modulator; fig. 3 is a schematic diagram of pulse width and repetition period of the output pulse of the pulse modulator. During actual operation, the voltage and current output by the pulse modulator 300 are typically provided to the magnetron 200 at a pulse width and repetition rate. To achieve maximum lifetime of the magnetron 200, the magnetron cathode must be operated at the correct temperature. Too low a magnetron cathode temperature can lead to reduced emissions and thus unstable operation of the magnetron 200; too high a magnetron cathode temperature can lead to rapid degradation of the cathode.
In one embodiment, as shown in fig. 4-7, a filament power supply 100 is provided, the filament power supply 100 including an inverter circuit 110 and a conditioning circuit 120; the input end of the inverter circuit 110 is connected with the direct current power supply 140, and the output end of the inverter circuit 110 is connected with the magnetron 200 and is used for converting direct current into alternating current and providing electric energy for the magnetron 200 by utilizing the alternating current; the input end of the adjusting circuit 120 is connected with the output end of the inverter circuit 110, the output end of the adjusting circuit 120 is connected with the driving end of the inverter circuit 110, and is used for obtaining the electrical parameter output by the inverter circuit 110, and generating a driving signal according to the electrical parameter and a given electrical parameter, wherein the driving signal is used for adjusting the electrical parameter output by the inverter circuit 110; the output end of the inverter circuit 110 is respectively connected with a magnetron filament and a magnetron cathode, a voltage protection circuit 130 is arranged between the magnetron filament and the magnetron cathode, the inverter circuit 110 comprises a filter unit 112, and the voltage protection circuit 130 and the filter unit 112 are used for protecting a filament power supply.
Specifically, the inverter circuit 110 controls the plurality of switching elements to alternately switch under the action of the driving signal, and an alternating voltage waveform associated with the period and frequency of the driving signal is obtained on the circuit device. The inverter circuit 110 may adopt full-bridge inversion or half-bridge inversion. The adjusting circuit 120 is a feedback circuit, obtains an electrical parameter of the output ac power of the inverter circuit 110, generates a driving signal according to the obtained electrical parameter and a given electrical parameter to be output by the filament power supply 100, and controls the electrical parameter of the output ac power of the inverter circuit 110 to approach the given electrical parameter by controlling the alternating conduction of the switching elements by feeding back the driving signal to the switching elements in the inverter circuit 110 until the ac power is output at the given electrical parameter. By setting the adjusting circuit 120 to generate a driving signal according to the electrical parameter output by the inverter circuit 110 and the given electrical parameter, the electrical parameter output by the filament power supply 100 can be precisely controlled to reach the given electrical parameter by driving the plurality of switching elements of the inverter circuit 110 by the driving signal, and the filament power supply 100 provides the magnetron 200 with electric energy through the given electrical parameter, so that the temperature of the cathode filament in the magnetron 200 can be ensured, and the service life of the magnetron 200 can be further prolonged.
Specifically, the magnetron 200 in this embodiment includes a magnetron anode, a magnetron cathode, and a magnetron filament, the inverter circuit 110 includes two output ports respectively connected to the magnetron filament and the magnetron cathode, and a voltage protection circuit 130 is disposed between the magnetron filament and the magnetron cathode. The inverter circuit 110 is further provided with a filtering unit 112, and the filtering unit 112 is disposed between the dc power supply and the magnetron.
Specifically, the voltage protection circuit 130 in this embodiment is configured to absorb the high-voltage pulse signal of the magnetron cathode, so as to avoid pulse energy entering the magnetron filament and the filament power supply 100; further, in this embodiment, a filtering unit 112 is further provided to filter the high-voltage pulse signal escaping into the filament power supply, so as to avoid damage to circuit devices such as the dc power supply 140 and the inverter circuit 110. The voltage protection circuit 130 and the filtering unit 112 jointly perform voltage isolation and protection on the filament power supply 100, so that the safety of the filament power supply 100 is improved.
In one embodiment, the inverter circuit 110 further includes an inverter unit 111 and a sampling resistor 113; the input end of the inverter unit 111 is connected to a dc power supply 140, for converting dc power into ac power; the filtering unit 112 is disposed at an output end of the inverter unit 111, and is configured to perform filtering processing on the alternating current; the sampling resistor 113 is disposed at an output end of the inverter unit 111, an input end of the adjusting circuit 120 is connected with the sampling resistor 113, an output end of the adjusting circuit 120 is connected with the inverter unit 111, the adjusting circuit 120 collects current output by the inverter circuit 110 through the sampling resistor 113, generates a driving signal according to the current and a given current, and transmits the driving signal to the inverter unit 111.
Specifically, the inverter unit 111 may adopt either full-bridge or half-bridge inversion. The filter unit 112 may employ any one of an inverted-L filter circuit, an LC pi filter circuit, and an RC pi filter circuit. The dc power is converted into ac power by the inverter unit 111, the ac power outputted from the inverter unit 111 is filtered by the filter unit 112, and the filtered ac power is transmitted to the magnetron 200 to supply power to the magnetron 200. A sampling resistor 113 is provided between the filter unit 112 and the magnetron 200, and the adjustment circuit 120 collects the output electric parameters of the inverter circuit 110 through the sampling resistor 113. Wherein the electrical parameter may comprise any one or a combination of several of current, voltage and electrical power. The adjusting circuit 120 compares the collected current with a predetermined current, and finally generates a driving signal after PI adjustment.
In one embodiment, the adjusting circuit 120 includes a first analog-to-digital conversion unit 121, a first comparing unit 122, and an adjusting unit 123; the input end of the first analog-to-digital conversion unit 121 is connected with the sampling resistor 113, and the output end of the first analog-to-digital conversion unit 121 is connected with the first input end of the first comparison unit 122, so as to collect the current output by the inverter circuit 110 through the sampling resistor 113 and perform analog-to-digital conversion on the current to obtain a digital current signal; a second input end of the first comparing unit 122 is connected to a given current signal, and an output end of the first comparing unit 122 is connected to the adjusting unit 123, for comparing the digital current signal with the given current signal to obtain a first error signal; an output end of the adjusting unit 123 is connected to the inverting unit 111, and is configured to generate a driving signal according to the first error signal, and transmit the driving signal to the inverting unit 111.
Specifically, the first analog-to-digital conversion unit 121 is an analog-to-digital converter, i.e., an a/D converter, and is an electronic component for converting an analog signal into a digital signal. By converting the analog signal into the digital signal, the control accuracy of the output current of the inverter circuit 110 can be improved, and the influence of the signal in the transmission process can be avoided. The first analog-to-digital conversion unit 121 obtains the output current of the inverter circuit 110 through the sampling resistor 113, performs analog-to-digital conversion on the current to obtain a digital current signal, and transmits the digital current signal to the first comparison unit 122, the first comparison unit 122 is further connected with a given current signal, the first comparison unit 122 performs a difference between the digital current signal and the given current signal to obtain a first error signal, and the adjustment unit 123 generates a driving signal according to the first error signal and transmits the driving signal to the plurality of switching elements of the inverter unit 111. More specifically, the adjusting unit 123 includes: a proportional integral adjustment unit 1231 and a pulse width adjustment unit. The input end of the proportional-integral adjusting unit 1231 is connected to the output end of the first comparing unit 122, and the output end of the proportional-integral adjusting unit 1231 is connected to the input end of the pulse width modulating unit 1232, so as to perform proportional-integral adjustment on the first error signal, and obtain an adjustment signal. The proportional-integral adjusting unit 1231 may be a proportional-integral adjuster, also called PI adjuster. The integral action in PI regulators refers to the action of the output of the regulator proportional to the deviation of the input with respect to the integration of time. The integral regulation has two main characteristics, one is that the output of the regulation is related to the time when the deviation exists, and the output of the integral regulator increases with time until the deviation is eliminated as long as the deviation exists. The output end of the pulse width modulation unit 1232 is connected to the inversion unit 111, and is configured to perform pulse width modulation on the adjustment signal to obtain a driving signal, and transmit the driving signal to the inversion unit 111. The pulse width modulation unit may be a PWM modulator.
In one embodiment, the conditioning circuit 120 further includes a power calculation unit 124; an input end of the power calculating unit 124 is connected to an input end of the magnetron 200, and an output end of the power calculating unit 124 is connected to a second input end of the first comparing unit 122, so as to obtain a pulse parameter input to the magnetron 200, obtain a given current signal according to the pulse parameter, and transmit the given current signal to the first comparing unit 122.
Specifically, the power calculation unit 124 may be a microprocessor or the like, and an electronic device capable of performing a calculation function. The power calculation unit 124 obtains the pulse parameters transmitted to the magnetron 200 by the pulse modulator 300, calculates a given current signal according to the pulse parameters, transmits the given current signal to the first comparison unit 122, and makes a difference between the digital current signal and the given current signal by the first comparison unit 122 to obtain a first error signal, and the adjustment unit 123 generates a driving signal according to the first error signal and transmits the driving signal to the plurality of switching elements of the inversion unit 111. Wherein the pulse parameters include: pulse peak voltage, pulse peak current, pulse width, and pulse repetition frequency. The power calculation unit 124 calculates a given current signal according to the pulse parameters, specifically: obtaining average power according to the pulse peak voltage, the pulse peak current, the pulse width and the pulse repetition frequency; and searching a mapping table of power and current according to the average power to obtain a given current signal. Wherein, the calculation formula for calculating the average power is:
P av ＝V peak *I peak *τ*f
wherein P is av Is average power, V peak Is pulse peak voltage, I peak The average power is calculated by the above formula for the pulse peak current, τ for the pulse width, and f for the pulse repetition frequency. Each value of average power, filament power supply 100 corresponds to a given current and a given voltage output, averageThe correspondence between the power and the given current and the given voltage may be stored in a mapping table, as shown in fig. 8, or may be stored in a graph, which is not limited in this embodiment, and only needs to find the corresponding given current and/or given voltage according to the average power.
In one embodiment, the adjusting circuit 120 further includes a second analog-to-digital conversion unit 125 and a second comparison unit 126; an input end of the second analog-to-digital conversion unit 125 is connected to an output end of the inverter circuit 110, and an output end of the second analog-to-digital conversion unit 125 is connected to a first input end of the second comparison unit 126; the voltage output by the inverter circuit 110 is obtained, and the voltage is subjected to analog-to-digital conversion to obtain a digital voltage signal; a second input end of the second comparing unit 126 is connected to an output end of the proportional integral adjusting unit 1231, and an output end of the second comparing unit 126 is connected to an input end of the pulse width modulating unit 1232; for comparing the adjustment signal with the digital voltage signal to obtain a second error signal and transmitting the second error signal to the pulse width modulation unit 1232.
Specifically, the second analog-to-digital conversion unit 125 is an analog-to-digital converter, i.e., an a/D converter, which is an electronic component for converting an analog signal into a digital signal. The second analog-to-digital conversion unit 125 obtains the output voltage of the inverter circuit 110, and performs analog-to-digital conversion on the voltage to obtain a digital voltage signal. By converting the analog signal into the digital signal, the control accuracy of the output current of the inverter circuit 110 can be improved, and the influence of the signal in the transmission process can be avoided. The second comparing unit 126 performs a difference between the digital voltage signal and the adjustment signal generated by the proportional integral adjusting unit 1231 to obtain a second error signal, and performs pulse width modulation on the second error signal by the pulse width modulating unit 1232 to generate a driving signal, and transmits the driving signal to the plurality of switching elements of the inverter unit 111. The first analog-to-digital conversion unit 121, the first comparison unit 122 and the adjusting unit 123 form a current feedback adjusting unit; the second analog-to-digital conversion unit 125, the second comparison unit 126 and the adjustment unit 123 constitute a voltage feedback adjustment unit. In the actual use process, the filament power supply 100 may only be provided with a current feedback adjustment unit, the filament power supply 100 may also only be provided with a voltage feedback adjustment unit, and the filament power supply 100 may also be provided with both a current feedback adjustment unit and a voltage feedback adjustment unit.
In one embodiment, filament power supply 100 further includes a voltage protection circuit 130; the voltage protection circuit 130 is connected between the inverter circuit 110 and the magnetron 200, and is used for protecting the filament power supply 100.
Specifically, by providing the voltage protection circuit 130, damage to the power supply main circuit due to an excessive voltage is prevented. Preferably, the voltage protection circuit 130 includes a first inductor and a second inductor; the output anode of the inverter circuit 110 is connected with the filament of the magnetron 200 through a first inductor; the output cathode of the inverter circuit 110 is connected to the cathode of the magnetron 200 through a second inductor. The voltage protection circuit 130 further includes a diode, a first capacitor, and a second capacitor; the diode and the first capacitor are connected in parallel between the output anode and the output cathode of the inverter circuit 110; the second capacitance is connected between the filament input and the cathode input of the magnetron 200.
In the filament power supply in the embodiment, the output electrical parameters of the inverter circuit are obtained through the setting and adjusting circuit, the driving signals are generated according to the electrical parameters, the driving signals are transmitted to the inverter circuit, and the electrical parameters output by the inverter circuit are adjusted through the driving signals. Through feedback adjustment, the electric parameters output by the inverter circuit can be accurately adjusted to given electric parameters required by the current use scene, namely, the electric parameters output by the filament power supply can be accurately controlled to reach the given electric parameters, the filament power supply supplies electric energy to the magnetron through the given electric parameters, the temperature of a cathode filament in the magnetron can be ensured, and the service life of the magnetron can be further prolonged.
In one embodiment, as shown in fig. 9, the filament power supply and the inverter circuit are in a full-bridge topology, and the filament power supply comprises four MOS transistors, the four MOS transistors are connected end to end, the connection point of the MOS transistor Q1 and the MOS transistor Q2 is connected with the positive electrode of the direct current power supply, and the connection point of the MOS transistor Q3 and the MOS transistor Q4 is connected with the negative electrode of the direct current power supply. A capacitor C1 is connected between the positive electrode and the negative electrode of the direct current power supply. The connection point of the MOS tube Q1 and the MOS tube Q3 is an output end A, and the connection point of the MOS tube Q2 and the MOS tube Q4 is an output end B. The output end A is provided with a 2-order LC filter circuit, and the output end B is provided with a 2-order LC filter circuit. The connection point of the MOS tube Q1 and the MOS tube Q3 is connected to the output end A through an inductor L1 and an inductor L2; one end of the capacitor C2 is connected to a connection point of the inductor L1 and the inductor L2, and the other end of the capacitor C is connected to a negative electrode of a power supply; one end of the capacitor C3 is connected to the output end A, and the other end is connected to the negative electrode of the power supply. The connection point of the MOS tube Q2 and the MOS tube Q4 is connected to the output end B through an inductor L3 and an inductor L4; one end of the capacitor C4 is connected to a connection point of the inductor L3 and the inductor L4, and the other end of the capacitor C is connected to a negative electrode of a power supply; one end of the capacitor C5 is connected to the output end B, and the other end is connected to the negative electrode of the power supply. The inductor L4 is connected with the output end B through a sampling resistor R1. One end of the first analog-to-digital conversion unit is connected with the sampling resistor R1, the other end of the first analog-to-digital conversion unit is connected with one input end of the comparator U1, the other input end of the comparator U1 is connected with the power calculation unit, the power calculation unit is connected with the output end of the pulse modulator, and the output end of the comparator U1 is connected with the input end of the PI modulator. The output end of the PI modulator is connected with one input end of the comparator U2, one end of the first analog-to-digital conversion unit is connected with the output end of the inverter circuit, the other end of the first analog-to-digital conversion unit is connected with one input end of the comparator U2, the output end of the comparator U2 is connected with the PWM modulator, and the output end of the PWM modulator is respectively connected with the MOS tube Q1, the MOS tube Q2, the MOS tube Q3 and the MOS tube Q4. As shown in fig. 10, the output terminal a of the inverter circuit is connected to the magnetron cathode through an inductance L5, and the output terminal B of the inverter circuit is connected to the magnetron filament through an inductance L6. A diode D1 and a capacitor C6 are connected in parallel between the output terminal a and the output terminal B. A capacitor C7 is connected between the input end of the magnetron filament and the input end of the magnetron cathode.
Specifically, the MOS transistors Q1-Q4 are 4 switching transistors of the full bridge circuit, vd is a dc input supply voltage, where the input voltage Vd must be provided by an insulating switching power supply including an isolation transformer, and the insulation level of the input voltage Vd should meet the insulation requirement between the cathode voltage of the magnetron and other weak circuits of the modulator. A. And B is the output end of the full-bridge circuit, namely the output end of the inverter circuit, and is connected with a load. The electrical output of each half-bridge contains a 2-stage LC filter circuit. The output samples the current through a resistor, and converts the sampled signal into a digital signal through an analog-to-digital converter, and the digital signal is fed back to the modulator for closed loop operation. The average power is calculated by the high-voltage pulse peak voltage, the high-voltage pulse peak current, the pulse width and the repetition frequency input by the magnetron, and then the given current is obtained by the average power. When the high-voltage pulse peak voltage, the high-voltage pulse peak current, the pulse width and the repetition frequency are input into the power calculation unit, the high-voltage pulse peak voltage, the high-voltage pulse peak current, the pulse width and the repetition frequency are required to pass through an isolation circuit, for example, through an optical coupler or an optical fiber. The given current is compared with the sampled current to obtain an error signal indicating the extent and direction of the output current from the given current value. The error is positive, which indicates that the output current of the inverter circuit is lower than the given current, and the PI modulator adjusts and improves the output current to return to the given current value; the error is negative, indicating that the output current of the inverter circuit is higher than the given current, the PI modulator adjusts the reduced output current back to the given current value. The adjustment result of the PI modulator is compared with the sawtooth wave, a digital PWM signal is generated through the PWM modulator, namely a driving signal of the MOS transistors Q1-Q4, and the MOS transistors Q1-Q4 are controlled to be turned on and off through the driving signal, so that current is adjusted according to requirements. The whole control system is completed by a digital signal processor, and in the embodiment, output voltage feedforward control is also adopted, and the output voltage of the full-bridge circuit, namely the output voltage of the inverter circuit, is detected, and is connected with the output end of the PI modulator after analog-digital conversion to generate a compensated PWM signal.
As shown in fig. 11a to 11d, the operation principle of the inverter circuit will be described by taking a load exhibiting RL characteristics as an example. The inverse circuit consists of 4 MOS tubes Q1-Q4, and works in a bipolar PWM modulation mode, namely, two MOS tubes which are opposite angles of each other are conducted simultaneously, and the upper MOS tube and the lower MOS tube of the half bridge on the same side are conducted alternately, so that the voltage Vd on the direct current side is changed into alternating current with the amplitude Vd. The specific working principle is as follows:
when t0 is less than or equal to t < t1, the MOS tube Q1 and the MOS tube Q4 are in a conducting state, the current on the load gradually rises, and the voltage on the load is the direct current bus voltage VAB=Vd; when t1 is less than or equal to t < t2, the MOS transistor Q1 and the MOS transistor Q4 are turned off, the MOS transistor Q2 and the MOS transistor Q3 are turned on, and at the moment, the voltage VAB= -Vd on the load, because the current flowing through the inductive load cannot be suddenly changed, the load forces the current to flow through the freewheeling diodes of the MOS transistor Q2 and the MOS transistor Q3; when t2 is less than or equal to t < t3, the current in the load is already freewheeling, at the moment, the MOS tube Q2 and the MOS tube Q3 are in an on state, the voltage VAB= -Vd on the load, and the load current is increased along the opposite direction; when t3 is less than or equal to t < t4, the MOS transistor Q2 and the MOS transistor Q3 are turned off, the MOS transistor Q1 and the MOS transistor Q4 are turned on, the load forces current to follow current through the anti-parallel diodes of the MOS transistor Q1 and the MOS transistor Q4, and the MOS transistor Q1 and the MOS transistor Q4 are in a normal on state only when the follow current of the load is completed, and then the working process of the next period is started.
According to the above operation, waveforms of the output voltage and current of the inverter circuit and driving signals of the MOS transistors Q1 to Q4 in one cycle are as shown in fig. 12. It is actually an ac waveform that can be used for filament power designs using ac heated magnetrons. By controlling the 4 MOS tubes, positive voltage pulse on the load can be increased to a value in the positive direction, so that the circuit works in the interval of t0< t < t2, the output current is direct current, and as shown in fig. 13, the magnitude of the output current can be controlled by controlling the duty ratio of the conduction of the MOS tubes. By changing the magnitude of the dc side voltage Vd, the maximum current value to be output can be changed.
In this embodiment, the output end of the filament power supply is connected to the cathode of the magnetron and the filament through the inductor L5 and the inductor L6, respectively, for preventing the power supply main circuit from being damaged due to too high voltage variation, and isolating the filament power supply from the magnetron cathode. By arranging the capacitor C6, the capacitor C7, the bias diode D1 and the like, it is ensured that no large pulse energy is dissipated in the filament power supply, and therefore the filament power supply is protected. The protection circuit composed of the inductor L5, the inductor L6, the capacitor C7 and the bias diode D1 may be integrated inside the filament power supply, or may be used as an independent circuit as an external circuit connected to the magnetron as the filament power supply.
The filament power supply in the above embodiment is a digital dc power supply, and the current is monitored and feedback control is implemented so that the output current of the filament power supply can generate the filament current according to a prescribed heating program, and further the cathode lifetime is greatly increased. The method is characterized by current control in nature, is more accurate than general voltage control, is not easily influenced by parameters of a pulse transformer, and has better performance.
In one embodiment, there is also provided a radiotherapy apparatus which is a medical electron linac, comprising any of the filament power supplies of the embodiments described above. The magnetron of the radiotherapy equipment has long service life.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples merely represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the invention. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application is to be determined by the claims appended hereto.
Claims (10)
1. A filament power supply, characterized in that the filament power supply comprises an inverter circuit and a regulating circuit;
the input end of the inverter circuit is connected with a direct current power supply, the output end of the inverter circuit is connected with a magnetron and is used for converting direct current into alternating current and providing electric energy for the magnetron by utilizing the alternating current;
the input end of the adjusting circuit is connected with the output end of the inverter circuit, the output end of the adjusting circuit is connected with the driving end of the inverter circuit and is used for acquiring the electric parameters output by the inverter circuit and generating driving signals according to the electric parameters and given electric parameters, and the driving signals are used for adjusting the electric parameters output by the inverter circuit;
the output end of the inverter circuit is respectively connected with a magnetron filament and a magnetron cathode, a voltage protection circuit is arranged between the magnetron filament and the magnetron cathode, the inverter circuit comprises a filter unit, and the voltage protection circuit and the filter unit are used for protecting a filament power supply.
2. The filament power supply of claim 1, wherein the inverter circuit further comprises an inverter unit and a sampling resistor;
the input end of the inversion unit is connected with a direct current power supply and is used for converting direct current into alternating current;
the filtering unit is arranged at the output end of the inversion unit and is used for filtering the alternating current;
the sampling resistor is arranged at the output end of the inversion unit, the input end of the regulating circuit is connected with the sampling resistor, the output end of the regulating circuit is connected with the inversion unit, the regulating circuit collects the current output by the inversion circuit through the sampling resistor, generates a driving signal according to the current and a given current, and transmits the driving signal to the inversion unit.
3. The filament power supply of claim 2, wherein the conditioning circuit comprises a first analog-to-digital conversion unit, a first comparison unit, and a conditioning unit;
the input end of the first analog-to-digital conversion unit is connected with the sampling resistor, the output end of the first analog-to-digital conversion unit is connected with the first input end of the first comparison unit, and the first analog-to-digital conversion unit is used for collecting the current output by the inverter circuit through the sampling resistor and performing analog-to-digital conversion on the current to obtain a digital current signal;
the second input end of the first comparison unit is connected with a given current signal, and the output end of the first comparison unit is connected with the adjusting unit and is used for comparing the digital current signal with the given current signal to obtain a first error signal;
the output end of the adjusting unit is connected with the inversion unit and is used for generating a driving signal according to the first error signal and transmitting the driving signal to the inversion unit.
4. A filament power supply according to claim 3, characterized in that the adjusting unit comprises: a proportional integral adjusting unit and a pulse width modulating unit;
the input end of the proportional-integral regulating unit is connected with the output end of the first comparing unit, and the output end of the proportional-integral regulating unit is connected with the input end of the pulse width modulating unit and is used for carrying out proportional-integral regulation on the first error signal to obtain a regulating signal;
the output end of the pulse width modulation unit is connected with the inversion unit and is used for carrying out pulse width modulation on the adjusting signal to obtain a driving signal and transmitting the driving signal to the inversion unit.
5. The filament power supply of claim 4, wherein the conditioning circuit further comprises a power calculation unit;
the input end of the power calculation unit is connected with the input end of the magnetron, the output end of the power calculation unit is connected with the second input end of the first comparison unit, and the power calculation unit is used for acquiring pulse parameters input into the magnetron, obtaining a given current signal according to the pulse parameters and transmitting the given current signal to the first comparison unit.
6. The filament power supply of claim 5, wherein the pulse parameters comprise: pulse peak voltage, pulse peak current, pulse width, and pulse repetition frequency;
the power calculation unit is further used for obtaining average power according to the pulse peak voltage, the pulse peak current, the pulse width and the pulse repetition frequency; and searching a mapping table of power and current according to the average power to obtain a given current signal.
7. The filament power supply of claim 6, wherein the conditioning circuit further comprises a second analog-to-digital conversion unit and a second comparison unit;
the input end of the second analog-to-digital conversion unit is connected with the output end of the inverter circuit, and the output end of the second analog-to-digital conversion unit is connected with the first input end of the second comparison unit; the inverter circuit is used for acquiring the voltage output by the inverter circuit and performing analog-to-digital conversion on the voltage to obtain a digital voltage signal;
the second input end of the second comparison unit is connected with the output end of the proportional-integral regulating unit, and the output end of the second comparison unit is connected with the input end of the pulse width modulation unit; and the pulse width modulation unit is used for comparing the regulating signal with the digital voltage signal to obtain a second error signal and transmitting the second error signal to the pulse width modulation unit.
8. The filament power supply of claim 1, wherein the voltage protection circuit comprises a first inductance and a second inductance;
the output positive electrode of the inverter circuit is connected with the filament of the magnetron through a first inductor;
and the output negative electrode of the inverter circuit is connected with the cathode of the magnetron through a second inductor.
9. The filament power supply of claim 8, wherein the voltage protection circuit further comprises a diode, a first capacitor, and a second capacitor;
the diode and the first capacitor are connected in parallel between an output positive electrode and an output negative electrode of the inverter circuit;
the second capacitor is connected between a filament input and a cathode input of the magnetron.
10. A radiotherapy apparatus comprising the filament power supply of any one of claims 1 to 9.
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| CN201911375564.2A CN111050454B (en) | 2019-12-27 | 2019-12-27 | Filament power supply and radiotherapy equipment |
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| US5920155A (en) * | 1996-10-28 | 1999-07-06 | Matsushita Electric Works, Ltd. | Electronic ballast for discharge lamps |
| EP2216893A4 (en) * | 2007-10-24 | 2014-07-09 | Univ Nagasaki | Load control device, and lighting device |
| CN103458593A (en) * | 2013-08-14 | 2013-12-18 | 中国电子科技集团公司第十六研究所 | Closed-loop controllable light-dimming electrodeless lamp electronic ballast and method thereof for adjusting luminance of electrodeless lamp |
| CN203537642U (en) * | 2013-08-14 | 2014-04-09 | 中国电子科技集团公司第十六研究所 | Light-adjusting electrodeless lamp electronic ballast with closed-loop controllable |
| CN104616950B (en) * | 2014-12-27 | 2017-01-04 | 芜湖国睿兆伏电子有限公司 | A kind of pre-heater circuit of magnetron heater |
| CN105392259B (en) * | 2015-12-10 | 2019-01-18 | 广州萃智信息科技有限公司 | A kind of the light decay control device and its method of CDM lamp |
| CN105682316A (en) * | 2016-01-06 | 2016-06-15 | 瑞昌市佳佳机电设备有限公司 | UV lamp, UV lamp starting device and UV lamp power control device |
| CN105915070B (en) * | 2016-05-10 | 2018-04-17 | 东华大学 | A kind of superaudio induction heating power device and its digitalization control method |
| CN209627777U (en) * | 2018-12-25 | 2019-11-12 | 洪国慧 | A kind of filament current control circuit |
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