Filament power supply and radiotherapy equipment

Abstract

This application relates to a filament power supply and a radiotherapy device. The filament power supply includes: an inverter circuit whose input terminal is connected to a DC power supply, and whose output terminal is connected to a magnetron, for converting DC power to AC power and using the AC power to provide power to the magnetron; and an adjustment circuit whose input terminal is connected to the output terminal of the inverter circuit, and whose output terminal is connected to the drive terminal of the inverter circuit, for acquiring the electrical parameters output by the inverter circuit, and generating a drive signal based on the electrical parameters and a given electrical parameter, the drive signal being used to adjust the electrical parameters output by the inverter circuit. By setting the adjustment circuit to acquire the output electrical parameters of the inverter circuit, generating the drive signal, and adjusting the output electrical parameters of the inverter circuit through the drive signal, the electrical parameters output by the inverter circuit can be accurately adjusted to the given electrical parameters required for the current application scenario, ensuring the temperature of the cathode filament in the magnetron, and further improving the service life of the magnetron.

Description

[0001] This application is a divisional application of the invention application with application number 201911375564.2, application date December 27, 2019, entitled "Filament Power Supply and Radiotherapy Equipment". Technical Field

[0002] This application relates to the field of medical device technology, and in particular to a filament power supply and a radiotherapy device. Background Technology

[0003] A medical linear accelerator is a medical device that uses microwave electromagnetic fields to accelerate electrons and create linear motion paths. It is used for radiotherapy of tumors or other lesions in patients. It can produce high-energy X-rays and electron beams, and features high dose rate, short irradiation time, large irradiation field, good dose uniformity and stability, and a small penumbra.

[0004] In current medical linear accelerators, the filament power supply provides energy to the magnetron. The higher the current supplied by the filament power supply to the magnetron, the higher the temperature of the magnetron's cathode filament; conversely, the lower the current supplied, the lower the temperature. The lifespan of the magnetron is closely related to the temperature of the cathode filament. To achieve maximum lifespan, the magnetron's cathode filament must operate at the correct temperature. Too low a temperature leads to reduced X-ray or electron beam emission, causing instability and further damage to the magnetron. Too high a temperature causes rapid cathode degradation, shortening the magnetron's lifespan. Current technology cannot precisely control the current supplied by the filament power supply to the magnetron, thus resulting in a shortened magnetron lifespan. Summary of the Invention

[0005] Therefore, it is necessary to provide a filament power supply and radiotherapy equipment that can improve the service life of the magnetron in order to address the above-mentioned technical problems.

[0006] A filament power supply includes an inverter circuit and an adjustment circuit. The input terminal of the inverter circuit is connected to a DC power supply, and the output terminal of the inverter circuit is connected to a magnetron. The inverter circuit converts DC power into AC power and uses the AC power to provide power to the magnetron. The input terminal of the adjustment circuit is connected to the output terminal of the inverter circuit, and the output terminal of the adjustment circuit is connected to the drive terminal of the inverter circuit. The adjustment circuit acquires the electrical parameters output by the inverter circuit and generates a drive signal based on the electrical parameters and a given electrical parameter. The drive signal is used to adjust the electrical parameters output by the inverter circuit.

[0007] In one embodiment, the inverter circuit further includes an inverter unit and a sampling resistor; the input terminal of the inverter unit is connected to a DC power supply for converting DC power into AC power; the filter unit is disposed at the output terminal of the inverter unit for filtering the AC power; the sampling resistor is disposed at the output terminal of the inverter unit, the input terminal of the adjustment circuit is connected to the sampling resistor, the output terminal of the adjustment circuit is connected to the inverter unit, the adjustment circuit collects the current output by the inverter circuit through the sampling resistor, and generates a drive signal based on the current and a given current, and transmits the drive signal to the inverter unit.

[0008] In one embodiment, the adjustment circuit includes a first analog-to-digital converter (ADC), a first comparison unit, and an adjustment unit. The input terminal of the first ADC is connected to the sampling resistor, and the output terminal of the first ADC is connected to the first input terminal of the first comparison unit. The ADC is used to acquire the current output by the inverter circuit through the sampling resistor and perform analog-to-digital conversion on the current to obtain a digital current signal. The second input terminal of the first comparison unit is connected to a given current signal, and the output terminal of the first comparison unit is connected to the adjustment unit. The comparison unit is used to compare the digital current signal with the given current signal to obtain a first error signal. The output terminal of the adjustment unit is connected to the inverter unit and is used to generate a drive signal based on the first error signal and transmit the drive signal to the inverter unit.

[0009] In one embodiment, the adjustment unit includes a proportional-integral (PI) adjustment unit and a pulse width modulation (PWM) unit; the input terminal of the PI adjustment unit is connected to the output terminal of the first comparison unit, and the output terminal of the PI adjustment unit is connected to the input terminal of the PWM unit, for performing proportional-integral adjustment on the first error signal to obtain an adjustment signal; the output terminal of the PWM unit is connected to the inverter unit, for performing pulse width modulation on the adjustment signal to obtain a drive signal, and transmitting the drive signal to the inverter unit.

[0010] In one embodiment, the adjustment circuit further includes a power calculation unit; the input terminal of the power calculation unit is connected to the input terminal of the magnetron, and the output terminal of the power calculation unit is connected to the second input terminal of the first comparison unit, for obtaining the pulse parameters of the input magnetron, obtaining a given current signal according to the pulse parameters, and transmitting the given current signal to the first comparison unit.

[0011] 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 configured to obtain average power based on the pulse peak voltage, pulse peak current, pulse width, and pulse repetition frequency; and to obtain a given current signal by looking up a power-current mapping table based on the average power.

[0012] In one embodiment, the adjustment circuit further includes a second analog-to-digital converter (ADC) unit and a second comparison unit; the input terminal of the second ADC unit is connected to the output terminal of the inverter circuit, and the output terminal of the second ADC unit is connected to the first input terminal of the second comparison unit; it is used to acquire the voltage output by the inverter circuit and perform analog-to-digital conversion on the voltage to obtain a digital voltage signal; the second input terminal of the second comparison unit is connected to the output terminal of the proportional-integral (PI) adjustment unit, and the output terminal of the second comparison unit is connected to the input terminal of the pulse width modulation (PWM) unit; it is used to compare the adjustment signal with the digital voltage signal to obtain a second error signal, and transmit the second error signal to the PWM unit.

[0013] In one embodiment, the filament power supply further includes a voltage protection circuit; the voltage protection circuit is connected between the inverter circuit and the magnetron and is used to protect the voltage of the filament power supply.

[0014] In one embodiment, the voltage protection circuit includes a first inductor and a second inductor; the positive output of the inverter circuit is connected to the filament of the magnetron through the first inductor; and the negative output of the inverter circuit is connected to the cathode of the magnetron through the second inductor.

[0015] 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 the positive and negative output terminals of the inverter circuit; the second capacitor is connected between the filament input and the cathode input of the magnetron.

[0016] A radiotherapy device, the radiotherapy device comprising any of the above-described filament power supplies.

[0017] The aforementioned filament power supply and radiotherapy equipment include an inverter circuit and an adjustment circuit. The input terminal of the inverter circuit is connected to a DC power supply, and the output terminal is connected to a magnetron. This inverter circuit converts DC power to AC power and uses the AC power to power the magnetron. The input terminal of the adjustment circuit is connected to the output terminal of the inverter circuit, and the output terminal is connected to the drive terminal of the inverter circuit. This drive circuit acquires the electrical parameters output by the inverter circuit and generates a drive signal based on these parameters and a given set of electrical parameters. This drive signal is used to adjust the electrical parameters output by the inverter circuit. The output terminal of the inverter circuit is connected to both the magnetron filament and the magnetron cathode. A voltage protection circuit is installed between the magnetron filament and the magnetron cathode. The inverter circuit includes a filter unit, and the voltage protection circuit and filter unit are used to protect the filament power supply. By setting up the adjustment circuit to acquire the output electrical parameters of the inverter circuit and generating a drive signal based on these parameters, the drive signal is transmitted to the inverter circuit, and the output electrical parameters of the inverter circuit are adjusted using the drive signal. Through feedback adjustment, the electrical parameters output by the inverter circuit can be precisely adjusted to the given electrical parameters required for the current application scenario. In other words, the electrical parameters output by the filament power supply can be precisely controlled to reach the given electrical parameters. The filament power supply provides power to the magnetron through the given electrical parameters, which can ensure the temperature of the cathode filament in the magnetron and further improve the service life of the magnetron. Attached Figure Description

[0018] Figure 1 This is a schematic diagram showing the connection of the pulse modulator, magnetron, and filament power supply in one embodiment;

[0019] Figure 2 This is a schematic diagram showing the current and voltage of the output pulse of the pulse modulator in one embodiment;

[0020] Figure 3 This is a schematic diagram of the pulse width and repetition period of the output pulse of the pulse modulator in one embodiment;

[0021] Figure 4 This is a schematic diagram of the filament power supply in one embodiment;

[0022] Figure 5 This is a schematic diagram of the filament power supply in another embodiment;

[0023] Figure 6 This is a schematic diagram of the filament power supply in another embodiment;

[0024] Figure 7 This is a schematic diagram of the filament power supply in another embodiment;

[0025] Figure 8 Here is a filament heating curve in one embodiment;

[0026] Figure 9 The circuit diagram of the filament power supply in one embodiment;

[0027] Figure 10 The schematic connection diagram of the filament power supply and the magnetron in one embodiment;

[0028] Figure 11a The conduction state diagram of the inverter circuit at t0≤t<t1 in one embodiment;

[0029] Figure 11b The conduction state diagram of the inverter circuit at t1≤t<t2 in one embodiment;

[0030] Figure 11c The conduction state diagram of the inverter circuit at t2≤t<t3 in one embodiment;

[0031] Figure 11d The conduction state diagram of the inverter circuit at t3≤t<t4 in one embodiment;

[0032] Figure 12 The drive signal of the MOS transistor and the waveforms of the output voltage and current in one embodiment;

[0033] Figure 13 The current output waveform in one embodiment. Detailed implementation manners

[0034] For the convenience of understanding the present application, in order to make the above objects, features and advantages of the present application more obvious and understandable, the following will describe the detailed implementation manners of the present application with reference to the accompanying drawings. Many specific details are set forth in the following description in order to fully understand the present application, and the preferred embodiments of the present application are given in the accompanying drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive. The present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0035] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined. In the description of the present application, "several" means at least one, such as one, two, etc., unless otherwise specifically defined.

[0036] Unless otherwise defined, 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 this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0037] like Figure 1 As shown, in a medical linear accelerator, the pulse modulator 300, magnetron 200, and filament power supply 100 are important components of the beam system. The pulse modulator 300 modulates a high-voltage pulse and outputs it to the magnetron 200. Under the influence of an electromagnetic field, the magnetron 200 generates high-frequency electromagnetic waves. These electromagnetic waves are fed into the accelerating tube via a waveguide system, forming an electron accelerating standing wave field that generates X-rays for tumor treatment. The magnetron 200 includes a magnetron anode, a magnetron cathode, and a filament, requiring an external power supply to heat the filament, i.e., the filament power supply 100. During operation, the filament power supply 100 injects current into the magnetron 200, heating the cathode to form an electron cloud in the region where the anode and cathode interact. Depending on the type of magnetron 200, the filament power supply 100 can be a DC power supply 140 or an AC power supply. Figure 2-3 As shown, Figure 2 A schematic diagram showing the current and voltage of the output pulse of the pulse modulator; Figure 3 This diagram illustrates the pulse width and repetition period of the output pulses from the pulse modulator. In actual operation, the voltage and current output by the pulse modulator 300 are typically supplied to the magnetron 200 with a specific pulse width and repetition frequency. For the magnetron 200 to achieve its maximum lifespan, the magnetron cathode must operate at the correct temperature. Too low a cathode temperature leads to reduced emission, resulting in unstable operation of the magnetron 200; too high a cathode temperature causes rapid cathode degradation.

[0038] In one embodiment, such as Figure 4-7 As shown, a filament power supply 100 is provided, which includes an inverter circuit 110 and an adjustment circuit 120. The input terminal of the inverter circuit 110 is connected to a DC power supply 140, and the output terminal of the inverter circuit 110 is connected to a magnetron 200. It is used to convert DC power into AC power and use the AC power to provide power to the magnetron 200. The input terminal of the adjustment circuit 120 is connected to the output terminal of the inverter circuit 110, and the output terminal of the adjustment circuit 120 is connected to the drive terminal of the inverter circuit 110. It is used to acquire the electrical parameters output by the inverter circuit 110, and generate a drive signal based on the electrical parameters and a given electrical parameter. The drive signal is used to adjust the electrical parameters output by the inverter circuit 110.

[0039] Specifically, the inverter circuit 110 controls multiple switching elements to switch alternately under the action of the drive signal, resulting in an alternating voltage waveform on the circuit devices that is related to the period and frequency of the drive signal. The inverter circuit 110 can be either a full-bridge inverter or a half-bridge inverter. The regulating circuit 120 is a feedback circuit that acquires the electrical parameters of the output AC power of the inverter circuit 110. Based on the acquired electrical parameters and the given electrical parameters that the filament power supply 100 needs to output, a drive signal is generated. By feeding the drive signal back to the multiple switching elements in the inverter circuit 110, the electrical parameters of the output AC power of the inverter circuit 110 are controlled to approach the given electrical parameters by controlling the alternating conduction of the switching elements, until the AC power is output with the given electrical parameters. By setting the adjustment circuit 120 to generate a drive signal based on the electrical parameters output by the inverter circuit 110 and the given electrical parameters, the multiple switching elements of the inverter circuit 110 can be driven by the drive signal to precisely control the electrical parameters output by the filament power supply 100 to reach the given electrical parameters. The filament power supply 100 provides power to the magnetron 200 through the given electrical parameters, which can ensure the temperature of the cathode filament in the magnetron 200 and further improve the service life of the magnetron 200.

[0040] In one embodiment, the inverter circuit 110 further includes an inverter unit 111, a filter unit 112, and a sampling resistor 113. The input terminal of the inverter unit 111 is connected to a DC power supply 140 for converting DC power into AC power. The filter unit 112 is disposed at the output terminal of the inverter unit 111 for filtering the AC power. The sampling resistor 113 is disposed at the output terminal of the inverter unit 111. The input terminal of the adjustment circuit 120 is connected to the sampling resistor 113, and the output terminal of the adjustment circuit 120 is connected to the inverter unit 111. The adjustment circuit 120 collects the current output by the inverter circuit 110 through the sampling resistor 113, generates a drive signal based on the current and a given current, and transmits the drive signal to the inverter unit 111.

[0041] Specifically, the inverter unit 111 can be either a full-bridge inverter or a half-bridge inverter. The filter unit 112 can be any one of an inverted L-type filter circuit, an LC filter circuit, an LCπ-type filter circuit, or an RCπ-type filter circuit. The inverter unit 111 converts DC power to AC power, and the filter unit 112 filters the AC power output from the inverter unit 111, transmitting the filtered AC power to the magnetron 200 to provide power. A sampling resistor 113 is provided between the filter unit 112 and the magnetron 200. The adjustment circuit 120 collects the output electrical parameters of the inverter circuit 110 through this sampling resistor 113. These electrical parameters can include any one or a combination of current, voltage, and power. The adjustment circuit 120 compares the collected current with a given current, and after PI regulation, finally generates a drive signal.

[0042] In one embodiment, the adjustment circuit 120 includes a first analog-to-digital converter (ADC) unit 121, a first comparison unit 122, and an adjustment unit 123. The input terminal of the first ADC unit 121 is connected to the sampling resistor 113, and the output terminal of the first ADC unit 121 is connected to the first input terminal of the first comparison unit 122. The first ADC unit 121 is used to acquire 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. The second input terminal of the first comparison unit 122 is connected to a given current signal, and the output terminal of the first comparison unit 122 is connected to the adjustment unit 123. The first comparison unit 122 is used to compare the digital current signal with the given current signal to obtain a first error signal. The output terminal of the adjustment unit 123 is connected to the inverter unit 111 and is used to generate a drive signal based on the first error signal and transmit the drive signal to the inverter unit 111.

[0043] Specifically, the first analog-to-digital converter (A / D converter) 121 is an electronic component that converts analog signals into digital signals. Converting analog signals to digital signals improves the control accuracy of the output current of the inverter circuit 110 and avoids interference caused by signal transmission. The first A / D converter 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 also receives a given current signal. The first comparison unit 122 calculates the difference between the digital current signal and the given current signal to obtain a first error signal. The adjustment unit 123 generates a drive signal based on the first error signal and transmits the drive signal to multiple switching elements of the inverter unit 111. More specifically, the adjustment unit 123 includes a proportional-integral (PI) adjustment unit 1231 and a pulse width modulation (PWM) adjustment unit. The input terminal of the proportional-integral (PI) adjustment unit 1231 is connected to the output terminal of the first comparison unit 122, and the output terminal of the PI adjustment unit 1231 is connected to the input terminal of the pulse width modulation (PWM) unit 1232. It is used to perform proportional-integral adjustment on the first error signal to obtain an adjustment signal. The PI adjustment unit 1231 can be a proportional-integral controller, also called a PI controller. In a PI controller, the integral action refers to the output of the controller being proportional to the integral of the deviation from the input over time. Integral adjustment has two main characteristics: firstly, the output of the adjustment action is related to the duration of the deviation; as long as the deviation exists, the output of the integral controller will increase over time until the deviation is eliminated. The output terminal of the PWM unit 1232 is connected to the inverter unit 111, used to perform pulse width modulation on the adjustment signal to obtain a drive signal, and then transmit the drive signal to the inverter unit 111. The pulse width modulation unit can be a PWM modulator.

[0044] In one embodiment, the adjustment circuit 120 further includes a power calculation unit 124; the input terminal of the power calculation unit 124 is connected to the input terminal of the magnetron 200, and the output terminal of the power calculation unit 124 is connected to the second input terminal of the first comparison unit 122, for obtaining the pulse parameters of the input magnetron 200, obtaining a given current signal according to the pulse parameters, and transmitting the given current signal to the first comparison unit 122.

[0045] Specifically, the power calculation unit 124 can be a microprocessor or other electronic device capable of performing calculations. The power calculation unit 124 acquires the pulse parameters transmitted from the pulse modulator 300 to the magnetron 200, calculates a given current signal based on the pulse parameters, and transmits the given current signal to the first comparison unit 122. The first comparison unit 122 subtracts the given current signal from the digital current signal to obtain a first error signal. The adjustment unit 123 generates a drive signal based on the first error signal and transmits the drive signal to multiple switching elements of the inverter unit 111. The pulse parameters include: pulse peak voltage, pulse peak current, pulse width, and pulse repetition frequency. The power calculation unit 124 calculates the given current signal based on the pulse parameters, specifically: obtaining the average power based on the pulse peak voltage, pulse peak current, pulse width, and pulse repetition frequency; and looking up the power-current mapping table based on the average power to obtain the given current signal. The formula for calculating the average power is:

[0046]

[0047] in, For average power, For pulse peak voltage, For pulse peak current, For pulse width, The average power is calculated using the formula above, given the pulse repetition frequency. For each average power value, the filament power supply 100 corresponds to a given output current and a given voltage. The correspondence between average power and given current and voltage can be stored in a mapping table, such as... Figure 8 As shown, it can also be stored as a graph. This embodiment does not make specific limitations, as long as the corresponding given current and / or given voltage can be found based on the average power.

[0048] In one embodiment, the adjustment circuit 120 further includes a second analog-to-digital converter (ADC) unit 125 and a second comparison unit 126; the input terminal of the second ADC unit 125 is connected to the output terminal of the inverter circuit 110, and the output terminal of the second ADC unit 125 is connected to the first input terminal of the second comparison unit 126; it is used to acquire the voltage output by the inverter circuit 110 and perform analog-to-digital conversion on the voltage to obtain a digital voltage signal; the second input terminal of the second comparison unit 126 is connected to the output terminal of the proportional-integral (PI) adjustment unit 1231, and the output terminal of the second comparison unit 126 is connected to the input terminal of the pulse width modulation (PWM) unit 1232; it is used to compare the adjustment signal with the digital voltage signal to obtain a second error signal, and transmit the second error signal to the PWM unit 1232.

[0049] Specifically, the second analog-to-digital converter (A / D converter) 125 is an electronic component that converts analog signals into digital signals. The second A / D converter 125 acquires the output voltage of the inverter circuit 110 and performs analog-to-digital conversion to obtain a digital voltage signal. Converting the analog signal to a digital signal improves the control accuracy of the output current of the inverter circuit 110 and avoids the influence caused by signal transmission. The second comparison unit 126 calculates the difference between the digital voltage signal and the adjustment signal generated by the proportional-integral adjustment unit 1231 to obtain a second error signal. The second error signal is then pulse-width modulated by the pulse width modulation unit 1232 to generate a drive signal, which is transmitted to multiple switching elements of the inverter unit 111. The first A / D converter 121, the first comparison unit 122, and the adjustment unit 123 constitute a current feedback adjustment unit; the second A / D converter 125, the second comparison unit 126, and the adjustment unit 123 constitute a voltage feedback adjustment unit. In practical use, the filament power supply 100 can be equipped with only a current feedback adjustment unit, or only a voltage feedback adjustment unit, or both a current feedback adjustment unit and a voltage feedback adjustment unit.

[0050] In one embodiment, the 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 to protect the voltage of the filament power supply 100.

[0051] Specifically, a voltage protection circuit 130 is provided to prevent damage to the main power supply circuit caused by excessive voltage. Preferably, the voltage protection circuit 130 includes a first inductor and a second inductor; the positive output of the inverter circuit 110 is connected to the filament of the magnetron 200 through the first inductor; the negative output of the inverter circuit 110 is connected to the cathode of the magnetron 200 through the second inductor. The voltage protection circuit 130 also includes a diode, a first capacitor, and a second capacitor; the diode and the first capacitor are connected in parallel between the positive and negative outputs of the inverter circuit 110; the second capacitor is connected between the filament input and the cathode input of the magnetron 200.

[0052] In the above embodiment, the filament power supply obtains the output electrical parameters of the inverter circuit through an adjustment circuit, generates a drive signal based on the electrical parameters, and transmits the drive signal to the inverter circuit. The drive signal adjusts the output electrical parameters of the inverter circuit. Through feedback adjustment, the output electrical parameters of the inverter circuit can be precisely adjusted to the given electrical parameters required for the current application scenario. In other words, the output electrical parameters of the filament power supply can be precisely controlled to reach the given electrical parameters. The filament power supply provides power to the magnetron through the given electrical parameters, which can ensure the temperature of the cathode filament in the magnetron and further improve the service life of the magnetron.

[0053] In one embodiment, such as Figure 9 As shown, a filament power supply has a full-bridge inverter circuit comprising four MOSFETs connected end-to-end. The connection point of MOSFETs Q1 and Q2 is connected to the positive terminal of the DC power supply, and the connection point of MOSFETs Q3 and Q4 is connected to the negative terminal of the DC power supply. A capacitor C1 is connected between the positive and negative terminals of the DC power supply. The connection point of MOSFETs Q1 and Q3 is output terminal A, and the connection point of MOSFETs Q2 and Q4 is output terminal B. A second-order LC filter circuit is installed at output terminal A, and a second-order LC filter circuit is installed at output terminal B. The connection point of MOSFETs Q1 and Q3 is connected to output terminal A through inductors L1 and L2; one end of capacitor C2 is connected to the connection point of inductors L1 and L2, and the other end is connected to the negative terminal of the power supply; one end of capacitor C3 is connected to output terminal A, and the other end is connected to the negative terminal of the power supply. The connection point of MOSFETs Q2 and Q4 is connected to output terminal B through inductors L3 and L4; one end of capacitor C4 is connected to the connection point of inductors L3 and L4, and the other end is connected to the negative terminal of the power supply; one end of capacitor C5 is connected to output terminal B, and the other end is connected to the negative terminal of the power supply. Inductor L4 is connected to output terminal B through sampling resistor R1. One end of the first analog-to-digital converter unit is connected to sampling resistor R1, and the other end is connected to one input terminal of comparator U1. The other input terminal of comparator U1 is connected to the power calculation unit, the power calculation unit is connected to the output terminal of the pulse modulator, and the output terminal of comparator U1 is connected to the input terminal of the PI modulator. The output terminal of the PI modulator is connected to one input terminal of comparator U2. One end of the first analog-to-digital converter unit is connected to the output terminal of the inverter circuit, and the other end is connected to one input terminal of comparator U2. The output terminal of comparator U2 is connected to the PWM modulator, and the output terminal of the PWM modulator is connected to MOSFETs Q1, Q2, Q3, and Q4 respectively. Figure 10As shown, output terminal A of the inverter circuit is connected to the magnetron cathode through inductor L5, and output terminal B of the inverter circuit is connected to the magnetron filament through inductor L6. A diode D1 and a capacitor C6 are connected in parallel between output terminals A and B. A capacitor C7 is connected between the input terminal of the magnetron filament and the input terminal of the magnetron cathode.

[0054] Specifically, MOSFETs Q1-Q4 are the four switching transistors of the full-bridge circuit, and Vd is the DC input supply voltage. The input voltage Vd must be provided by an insulated switching power supply containing an isolation transformer, and its insulation level should meet the insulation requirements between the cathode voltage of the magnetron and other low-voltage circuits of the modulator. A and B are the output terminals of the full-bridge circuit, i.e., the output terminals of the inverter circuit, connected to the load. The output of each half-bridge circuit contains a second-order LC filter circuit. The output current is sampled through a resistor, and then converted into a digital signal by an analog-to-digital converter, which is fed back to the modulator for closed-loop calculation. The average power is calculated using the peak voltage, peak current, pulse width, and repetition frequency of the high-voltage pulse input from the magnetron, and then the given current is obtained from the average power. The input power calculation unit requires an isolation circuit, such as an optocoupler or optical fiber, to handle the peak voltage, peak current, pulse width, and repetition frequency of the high-voltage pulse. The given current is compared with the sampled current to obtain an error signal, indicating the degree and direction of the output current deviation from the given current value. A positive error indicates that the output current of the inverter circuit is lower than the given current. The PI modulator then adjusts to increase the output current, bringing it back to the given current value. A negative error indicates that the output current of the inverter circuit is higher than the given current. The PI modulator then adjusts to decrease the output current, bringing it back to the given current value. The adjustment result of the PI modulator is compared with the sawtooth wave, and a digital PWM signal is generated by the PWM modulator, which is the drive signal for MOSFETs Q1-Q4. The drive signal controls the on / off state of MOSFETs Q1-Q4, thereby adjusting the current as needed. The entire control system is implemented by a digital signal processor. In this embodiment, output voltage feedforward control is also used. The output voltage of the full-bridge circuit, i.e., the output voltage of the inverter circuit, is detected, converted from analog to digital, and then connected to the output of the PI modulator to generate a compensated PWM signal.

[0055] like Figures 11a-11d As shown, taking a load exhibiting RL characteristics as an example, the working principle of the inverter circuit is explained. The inverter circuit consists of four MOSFETs Q1-Q4, operating in bipolar PWM modulation mode. This means that two diagonally opposite MOSFETs conduct simultaneously, while the upper and lower MOSFETs on the same half-bridge alternately conduct, converting the DC-side voltage Vd into AC current with an amplitude of Vd. Its specific working principle is as follows:

[0056] When \(t_0\leq t < t_1\), MOS transistor Q1 and MOS transistor Q4 are in the conducting state, and the current on the load gradually rises. At this time, the voltage on the load is the DC bus voltage \(V_{AB}=V_d\). When \(t_1\leq t < t_2\), MOS transistor Q1 and MOS transistor Q4 are turned off, and MOS transistor Q2 and MOS transistor Q3 are turned on. At this time, the voltage on the load \(V_{AB}=-V_d\). Because the current flowing through the inductive load cannot change suddenly, the load forces the current to flow through the free-wheeling diodes of MOS transistor Q2 and MOS transistor Q3 for freewheeling. When \(t_2\leq t < t_3\), the current in the load has completed freewheeling. At this time, MOS transistor Q2 and MOS transistor Q3 are in the on state, the voltage on the load \(V_{AB}=-V_d\), and the load current increases in the reverse direction. When \(t_3\leq t < t_4\), MOS transistor Q2 and MOS transistor Q3 are turned off, and MOS transistor Q1 and MOS transistor Q4 are turned on. The load forces the current to flow through the anti-parallel diodes of MOS transistor Q1 and MOS transistor Q4 for freewheeling, and only when the load current has completed freewheeling, MOS transistor Q1 and MOS transistor Q4 are in the normal on state, and then the next cycle of the working process begins.

[0057] According to the above working process, the waveforms of the output voltage and current of the inverter circuit within one cycle and the drive signals of MOS transistors Q1 - Q4 are as Figure 12 shown. It is actually an AC waveform and can be used for the design of the filament power supply for an AC heating magnetron. By controlling the 4 MOS transistors, the positive voltage pulse on the load can be increased in the positive direction to a value, so that the circuit operates in the interval \(t_0 < t < t_2\), and the output current is DC, as Figure 13 shown. By controlling the duty cycle of the conduction of the MOS transistors, the magnitude of the output current can be controlled. By changing the magnitude of the DC side voltage \(V_d\), the maximum value of the output current can be changed.

[0058] In this embodiment, the output terminals of the filament power supply are respectively connected to the cathode and the filament of the magnetron through inductor L5 and inductor L6, which is used to prevent excessive voltage changes from damaging the main circuit of the power supply and at the same time isolate the filament power supply from the high voltage of the magnetron cathode. By setting capacitor C6, capacitor C7 and bias diode D1, etc., it is ensured that no large pulse energy is dissipated in the filament power supply, thereby protecting the filament power supply. Among them, the protection circuit composed of inductor L5, inductor L6, capacitor C6, capacitor C7 and bias diode D1 can be integrated inside the filament power supply or can be used as an independent circuit as an external circuit connecting the filament power supply and the magnetron.

[0059] The filament power supply in the above embodiment is a digital DC power supply that monitors the current and implements feedback control so that the output current of the filament power supply can generate filament current according to the specified heating program. Furthermore, the cathode life is significantly increased. Essentially, it is current control, which is more precise than general voltage control and less susceptible to the influence of pulse transformer parameters, thus exhibiting better performance.

[0060] In one embodiment, a radiotherapy device is also provided, which is a medical linear accelerator including any of the filament power supplies described in the above embodiments. The magnetron of this radiotherapy device has a long service life.

[0061] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A filament power supply, characterized in that, The filament power supply includes an inverter circuit, an adjustment circuit, and a voltage protection circuit; The input terminal of the inverter circuit is connected to a DC power supply, and the output terminal of the inverter circuit is connected to a magnetron. It is used to convert DC power into AC power and use the AC power to provide power to the magnetron. The inverter circuit includes a filter unit and an inverter unit. The filter unit is located at the output terminal of the inverter unit and is used to filter the AC power output by the inverter unit. The input terminal of the adjustment circuit is connected to the output terminal of the inverter circuit, and the output terminal of the adjustment circuit is connected to the drive terminal of the inverter circuit. It is used to obtain the electrical parameters output by the inverter circuit and generate a drive signal based on the electrical parameters and a given electrical parameter. The drive signal is used to adjust the electrical parameters output by the inverter circuit. The voltage protection circuit is connected between the inverter circuit and the magnetron and is used to protect the filament power supply voltage. The inverter circuit further includes a sampling resistor, which is disposed at the output terminal of the inverter unit; the adjustment circuit further includes a power calculation unit, a first analog-to-digital conversion unit, a first comparison unit, and an adjustment unit. The input terminal of the power calculation unit is connected to the input terminal of the magnetron, and the output terminal of the power calculation unit is connected to the second input terminal of the first comparison unit. It is used to obtain the pulse parameters of the input magnetron, obtain a given current signal according to the pulse parameters, and transmit the given current signal to the first comparison unit. The input terminal of the first analog-to-digital converter is connected to the sampling resistor, and the output terminal of the first analog-to-digital converter is connected to the first input terminal of the first comparison unit. It is used to collect the current output by the inverter circuit through the sampling resistor and perform analog-to-digital conversion on the current to obtain a digital current signal. The second input terminal of the first comparison unit is connected to a given current signal, and the output terminal of the first comparison unit is connected to the adjustment unit, which is used to compare the digital current signal with the given current signal to obtain a first error signal. The output of the adjustment unit is connected to the inverter unit and is used to generate a drive signal based on the first error signal and transmit the drive signal to the inverter unit.

2. The filament power supply according to claim 1, characterized in that, The input terminal of the inverter unit is connected to a DC power supply to convert DC power into AC power. The input terminal of the adjustment circuit is connected to the sampling resistor, and the output terminal of the adjustment circuit is connected to the inverter unit. The adjustment circuit collects the current output by the inverter circuit through the sampling resistor, generates a drive signal based on the current and a given current, and transmits the drive signal to the inverter unit.

3. The filament power supply according to claim 1, characterized in that, The adjustment unit includes: a proportional-integral adjustment unit and a pulse width modulation unit; The input terminal of the proportional-integral adjustment unit is connected to the output terminal of the first comparison unit, and the output terminal of the proportional-integral adjustment unit is connected to the input terminal of the pulse width modulation unit, for performing proportional-integral adjustment on the first error signal to obtain an adjustment signal; The output of the pulse width modulation unit is connected to the inverter unit and is used to perform pulse width modulation on the adjustment signal to obtain a drive signal, and then transmit the drive signal to the inverter unit.

4. The filament power supply according to claim 3, characterized in that, The pulse parameters include: pulse peak voltage, pulse peak current, pulse width, and pulse repetition frequency; The power calculation unit is also used to obtain the average power based on the pulse peak voltage, pulse peak current, pulse width, and pulse repetition frequency; and to find the mapping table between power and current based on the average power to obtain a given current signal.

5. The filament power supply according to claim 4, characterized in that, The adjustment circuit further includes a second analog-to-digital conversion unit and a second comparison unit; The input terminal of the second analog-to-digital converter is connected to the output terminal of the inverter circuit, and the output terminal of the second analog-to-digital converter is connected to the first input terminal of the second comparator unit; used to acquire the voltage output by the inverter circuit and perform analog-to-digital conversion on the voltage to obtain a digital voltage signal; The second input terminal of the second comparison unit is connected to the output terminal of the proportional-integral adjustment unit, and the output terminal of the second comparison unit is connected to the input terminal of the pulse width modulation unit. It is used to compare the adjustment signal with the digital voltage signal to obtain a second error signal, and transmit the second error signal to the pulse width modulation unit.

6. The filament power supply according to claim 1, characterized in that, The voltage protection circuit includes a first inductor and a second inductor; The positive output of the inverter circuit is connected to the filament of the magnetron through a first inductor; The negative output terminal of the inverter circuit is connected to the cathode of the magnetron via a second inductor.

7. The filament power supply according to claim 5, characterized in that, The voltage protection circuit also includes a diode, a first capacitor, and a second capacitor; The diode and the first capacitor are connected in parallel between the positive and negative output terminals of the inverter circuit. The second capacitor is connected between the filament input and the cathode input of the magnetron.

8. A radiotherapy device, characterized in that, The radiotherapy device includes a filament power supply as described in any one of claims 1-7.

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