An output self-correcting circuit for a medical electron gun grid power supply

Abstract

The application discloses an output self-correction circuit for a medical electron gun grid power supply, comprising a low-voltage side control unit, an isolation transmission unit, a high-voltage side control unit, a grid power supply and an independent sampling network; the low-voltage side control unit receives a dose rate, an ambient temperature, an external sampling signal and an output voltage feedback signal, generates a corrected reference signal and transmits the corrected reference signal to the high-voltage side control unit through the isolation transmission unit; the high-voltage side control unit outputs a control increment to the grid power supply after F / V conversion of the corrected reference signal, simultaneously receives voltage feedback signals of the grid power supply and the independent sampling network, and transmits the voltage feedback signals to the low-voltage side control unit through the isolation transmission unit; the application provides the grid power supply with output self-correction for a medical electron linear accelerator, realizes long-term stability and parameter consistency of an electron gun emission beam current, does not need manual correction, and greatly improves work efficiency.

Description

Technical Field

[0001] This invention relates to the field of power supply technology, specifically to a gate power supply for an electron gun modulator of a medium-to-high energy medical linear accelerator. Background Technology

[0002] Radiotherapy is an important treatment for malignant tumors, and medical linear accelerators are widely used in clinical radiotherapy. Medium- and high-energy medical linear accelerators can provide two different modes of treatment beams: electron beams and X-rays. Electron beams are used to treat superficial tumors, while X-rays are used to treat deep tumors. Appropriately weighting and combining treatment beams of different modes and energies can make the dose distribution more closely resemble the shape of the lesion, thereby improving treatment efficacy.

[0003] In high-energy medical linear accelerator applications, the grid-controlled electron gun, capable of stably emitting a controllable beam, is a crucial component of the system. To meet the diverse operating modes of the system, the electron gun's emitted beam current requires a wide range of adjustment (1–500 mA), necessitating a matching grid power supply. This is especially critical when using low-energy electron beams where the emitted beam current requirement is lower, making the stability of the grid power supply paramount. Therefore, a self-calibrating circuit for the grid power supply output needs to be designed to generate a highly stable grid power supply, thereby ensuring the dose stability and repeatability of the medical linear accelerator.

[0004] Currently, high-energy medical linear electron accelerators use a switching power supply for their grid power supply, with an output voltage adjustment range of 3V to 300V. The actual output voltage value is determined by the voltage reference V. ref The sampling ratio K is determined. Especially in low-end electronic wire applications, the emission beam current requirement is relatively small, corresponding to a lower gate power supply output value (actual duty cycle D). u The output voltage is relatively low and easily affected by device variability and changes in ambient temperature. Furthermore, the output voltage sampling not only participates in closed-loop voltage regulation but also serves as feedback to the host computer. Due to the op-amp's "virtual short" characteristic (or the negative feedback effect of the control system), the feedback follows the reference. When the actual output voltage changes, the value displayed on the host computer interface may not change. During daily morning checks, the dose rate index of the electron linear accelerator may not meet the clinical needs for radiotherapy. In this case, manual adjustment of the grid power supply is required, and the relevant system also needs to be recalibrated, significantly reducing work efficiency.

[0005] The main drawbacks of existing technical solutions are as follows:

[0006] (1) The electron gun beam (especially under low-power electron wire) cannot be output stably and precisely adjusted for a long time, which cannot meet the requirements of precise radiotherapy;

[0007] (2) Manual calibration is required, which greatly increases the time for morning equipment inspection and is not conducive to improving work efficiency;

[0008] (3) The gate power supply is difficult to measure because it is suspended at a high potential, which places high demands on the operator. Summary of the Invention

[0009] In view of this, the present invention provides an output self-calibration circuit for the gate power supply of a medical electron gun. By reasonably configuring an independent sampling network and combining it with a dual closed-loop control structure, it provides an output self-calibration gate power supply for a medical electron linear accelerator.

[0010] An output self-calibration circuit for the gate power supply of a medical electron gun includes a low-voltage side control unit, an isolation transmission unit, a high-voltage side control unit, a gate power supply, and an independent sampling network connected in series.

[0011] The low-voltage side control unit is used to receive dose rate, ambient temperature, external sampling signal and output voltage feedback signal, generate a corrected reference signal and transmit it to the high-voltage side control unit through the isolation transmission unit.

[0012] The isolation transmission unit is used for data isolation transmission between the low-voltage side control unit and the high-voltage side control unit;

[0013] The high-voltage side control unit outputs the control increment to the gate power supply after the corrected reference signal is converted by F / V, and at the same time receives the voltage feedback signals from the gate power supply and the independent sampling network, and transmits the voltage feedback signals to the low-voltage side control unit through the isolation transmission unit.

[0014] The gate power supply is used to receive the control increment of the high-voltage side control unit and generate a stable gate voltage to be sent to the linear accelerator, while the output voltage feedback signal is sent to the high-voltage side control unit.

[0015] The independent sampling network is used to independently sample the gate power supply and send the sampled output voltage feedback signal to the high-voltage side control unit.

[0016] Furthermore, the low-voltage side control unit includes an auxiliary power supply, a signal interface circuit, a signal isolation circuit, a serial port level conversion circuit, an MCU microprocessor, and a signal preprocessing circuit;

[0017] The signal isolation circuit, the signal interface circuit, and the MCU microprocessor are connected in series. The signal preprocessing circuit is connected to the signal isolation circuit and the MCU microprocessor respectively. The serial port level conversion circuit is connected to the MCU microprocessor.

[0018] The auxiliary power supply is converted from DC to DC to power the circuits of the low-voltage side control unit;

[0019] The signal interface circuit is used to perform V / F conversion of the reference pulse and send it to the signal isolation circuit, and to perform F / V conversion of the voltage signal and send it to the MCU microprocessor.

[0020] The signal isolation circuit is used for signal isolation and level conversion, and the signal interface circuit performs V / F conversion and F / V conversion before outputting to the MCU microprocessor.

[0021] The signal preprocessing circuit preprocesses the external signal and outputs it to the MCU microprocessor.

[0022] The MCU microprocessor performs loop calculations based on the external ambient temperature, reference signal, and voltage feedback signal, and outputs corresponding control increments.

[0023] The serial port level conversion circuit enables communication with an external control system, uploading operating status and real-time data for remote monitoring and control.

[0024] Furthermore, the automatic output voltage correction of the output self-calibration circuit includes the following steps:

[0025] Step 1: The MCU microprocessor receives the external working environment temperature sampled by the temperature sensor, performs temperature compensation on each internal sampled signal (using room temperature of 25℃ as a reference, calculates the current correction factor), and uses the temperature-compensated signal for subsequent processing.

[0026] Step 2: Output voltage feedback signal V of the independent sampling network fb2 The voltage feedback signal V of the gate power supply fb1 The signal is sent to the MCU microprocessor for comparison after preprocessing, and the deviation of the gate voltage reference is obtained through calculation.

[0027] Step 3: The MCU microprocessor sets the initial gate voltage reference V ref The dose rate correction V is obtained by superimposing the gate voltage reference deviation u(k) on P. ref ';

[0028] Step 4: The MCU microprocessor calculates the dose rate correction value V. ref 'With externally input dose rate reference signal J ref The corrected dose rate reference is obtained by superimposing the data with the dose rate feedback signal J. fb The comparison is then fed into a PI controller to generate a corrected gate voltage reference U. ref And it is output to the gate power supply through the isolation transmission unit and the high-voltage side control unit;

[0029] Step 5: The gate power supply will adjust the gate voltage reference U. refThe signal is fed into the PWM signal generation circuit to generate a corresponding PWM drive signal to control the switching transistor to turn on and off, so as to obtain the corrected gate voltage and send it to the linear accelerator.

[0030] Furthermore, the calculation formula in step 2 is as follows:

[0031] u(k)=K p1 ×K×e(k), e(k)=V fb2 (k)-V fb2 (k-1)

[0032] In the formula, Δe=V fb1 (k)-V fb2 (k)

[0033] Where: K: sign function; k: k-th sampling of the independent sampling network; e(k): the difference between the current feedback voltage and the previous feedback voltage of the independent sampling network; Δe: the difference between the feedback voltages of the two sampling networks; ε: the set error range threshold greater than 0.

[0034] Furthermore, the functions performed by the MCU microprocessor include:

[0035] 1: Receive the external ambient temperature through the signal preprocessing circuit and perform corresponding temperature compensation on each internal signal;

[0036] 2: The signal isolation circuit, signal interface circuit, and signal preprocessing circuit receive two voltage feedback signals, a dose rate reference signal, and a dose rate feedback signal. The internal circuit performs corresponding PI loop calculations to obtain the corresponding control increment, thereby achieving the purpose of automatic output voltage correction.

[0037] 3: External serial communication: Communicates with the external control system via a serial port level conversion circuit. The standard RS485 serial port is used to upload the working status and real-time data for remote monitoring and control.

[0038] Beneficial effects:

[0039] 1. Precise and controllable emission beam. This invention, through the rational configuration of independent sampling networks (i.e., adding one or two independent sampling networks) and sharing a V / F conversion circuit, balances the versatility and practicality of the circuit. Combined with a dual closed-loop control structure—closed-loop control of the feedback voltage deviation and the given reference voltage, and closed-loop control of the dose rate detection value and the given dose rate—it provides a self-calibrating grid power supply for medical linear accelerators, achieving long-term stability and parameter consistency of the electron gun emission beam (especially under low-power electron lines), fully meeting the requirements of precise radiotherapy.

[0040] 2. The automatic output voltage correction step 2 of the output self-calibration circuit of the present invention obtains the deviation of the gate voltage reference through a calculation formula. This calculation formula uses an independent sampling network to obtain the deviation and participates in the correction loop, thereby realizing output self-calibration. By comparing and judging the magnitude of ε, the threshold can be reasonably set to avoid the gate power supply output from jumping up and down near the target value and generating oscillation.

[0041] 3. This invention can independently sample the gate power supply and send the sampled output voltage feedback signal to the high-voltage side control unit without manual calibration, which greatly reduces the equipment morning inspection time and significantly improves work efficiency. Attached Figure Description

[0042] Figure 1 This is a block diagram illustrating the principle of an output self-calibration circuit for the gate power supply of a medical electron gun according to the present invention.

[0043] Figure 2 This is a circuit block diagram of the low-voltage side control unit of the present invention.

[0044] Figure 3 This is a schematic diagram of the control of the automatic correction circuit of the present invention.

[0045] Among them, 1-low voltage side control unit, 2-isolation transmission unit, 3-high voltage side control unit, 4-gate power supply, 5-independent sampling network, 11-auxiliary power supply, 12-signal interface circuit, 13-signal isolation circuit, 14-serial port level conversion circuit, 15-MCU microprocessor, 16-signal preprocessing circuit. Detailed Implementation

[0046] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0047] This invention provides an output self-calibration circuit for the gate power supply of a medical electron gun, such as... Figure 1 As shown, it includes a low-voltage side control unit 1, an isolation transmission unit 2, a high-voltage side control unit 3, a gate power supply 4, and an independent sampling network 5, which are connected in series.

[0048] The low-voltage side control unit 1 is used to receive dose rate, ambient temperature, external sampling signal and output voltage feedback signal, generate a corrected reference signal and transmit it to the high-voltage side control unit 3 through the isolation transmission unit 2.

[0049] Isolation transmission unit 2 is used for data isolation transmission between low-voltage side control unit 1 and high-voltage side control unit 3.

[0050] The high-voltage side control unit 3 outputs the control increment to the gate power supply 4 after the corrected reference signal is converted by F / V, and at the same time receives the voltage feedback signals from the gate power supply 4 and the independent sampling network 5, and transmits the voltage feedback signals to the low-voltage side control unit 1 through the isolation transmission unit 2.

[0051] The gate power supply 4 is used to receive the control increment of the high-voltage side control unit 3 and generate a stable gate voltage to be sent to the linear accelerator, while the output voltage feedback signal is sent to the high-voltage side control unit 3.

[0052] The independent sampling network 5 is used to independently sample the gate power supply 4 and send the sampled output voltage feedback signal to the high-voltage side control unit 3.

[0053] like Figure 2 The diagram shown is a circuit block diagram of the low-voltage side control unit of the present invention. The low-voltage side control unit 1 includes an auxiliary power supply 11, a signal interface circuit 12, a signal isolation circuit 13, a serial port level conversion circuit 14, an MCU microprocessor 15, and a signal preprocessing circuit 16; wherein,

[0054] The signal isolation circuit 13, the signal interface circuit 12, and the MCU microprocessor 15 are connected in series. The signal preprocessing circuit 16 is connected to the signal isolation circuit 13 and the MCU microprocessor 15 respectively. The serial port level conversion circuit 14 is connected to the MCU microprocessor 15.

[0055] Working process and principle:

[0056] An external power supply of +24V is input to the auxiliary power supply 11, which, after DC / DC conversion, provides auxiliary power supplies such as D±12V and D+5V to the circuits of the low-voltage side control unit 1.

[0057] Signal isolation circuit 13 is used for isolation and level conversion of the sampled signal and output signal, effectively suppressing strong pulse interference from the linear accelerator. The sampled signal includes V fb1 Voltage feedback signal 1 and V fb2 Voltage feedback signal 2, the output signal includes ΔU control increment, completes signal isolation and is sent to signal interface circuit 12.

[0058] The signal interface circuit 12 is used to perform V / F conversion of the reference pulse and send it to the signal isolation circuit 13, and to perform F / V conversion of the voltage signal and send it to the MCU microprocessor 15.

[0059] The signal preprocessing circuit 16 preprocesses external signals and outputs them to the MCU microprocessor 15, including external ambient temperature and dose rate feedback sampling signals.

[0060] The core of the MCU microprocessor-15 low-voltage side control unit mainly performs the following functions:

[0061] 1) The external ambient temperature is received through the signal preprocessing circuit 16, and corresponding temperature compensation is performed on each internal signal.

[0062] 2) The signal isolation circuit 13, the signal interface circuit 12 and the signal preprocessing circuit 16 receive two voltage feedback signals, a dose rate reference signal and a dose rate feedback signal, and perform corresponding PI and other loop operations internally to obtain the corresponding control increment in order to achieve the purpose of automatic correction of the output voltage.

[0063] 3) External serial communication: Communicates with the external control system via serial port level conversion circuit 14. Uploads working status and real-time data using standard RS485 serial port for remote monitoring and control.

[0064] Preferably, the method for automatic output voltage correction includes the following steps:

[0065] Step 1: The MCU microprocessor receives the external working environment temperature sampled by the temperature sensor, performs temperature compensation on each internal sampled signal (using room temperature of 25℃ as a reference, calculates the current correction factor), and uses the temperature-compensated signal for subsequent processing.

[0066] Step 2: Output voltage feedback signal V of the independent sampling network fb2 The voltage feedback signal V of the gate power supply fb1 The signal is sent to the MCU microprocessor for comparison after being processed by the signal preprocessing circuit. The deviation of the gate voltage reference is obtained by the following calculation formula.

[0067] The mathematical expression for the design deviation u(k) is:

[0068] u(k)=K p1 ×K×e(k), e(k)=V fb2 (k)-V fb2 (k-1)

[0069] In the formula, Δe=V fb1 (k)-V fb2 (k)

[0070] Where: K: sign function; k: k-th sampling of the independent sampling network; e(k): the difference between the current feedback voltage and the previous feedback voltage of the independent sampling network; Δe: the difference between the feedback voltages of the two sampling networks; ε: the set error range threshold greater than 0.

[0071] Step 3: The MCU microprocessor sets the initial gate voltage reference V ref The dose rate correction V is obtained by superimposing the gate voltage reference deviation u(k) on P.ref ';

[0072] Step 4: The MCU microprocessor calculates the dose rate correction value V. ref 'With externally input dose rate reference signal J ref The corrected dose rate reference is obtained by superimposing the data with the dose rate feedback signal J. fb The comparison is then fed into a PI controller to generate a corrected gate voltage reference U. ref And it is output to the gate power supply through the isolation transmission unit and the high-voltage side control unit;

[0073] Step 5: The gate power supply will adjust the gate voltage reference U. ref The signal is fed into the PWM signal generation circuit to generate a corresponding PWM drive signal to control the switching transistor to turn on and off, so as to obtain the corrected gate voltage and send it to the linear accelerator.

[0074] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A self-calibrating circuit for the output of a gate power supply in a medical electron gun, characterized in that, It includes a low-voltage side control unit, an isolation transmission unit, a high-voltage side control unit, a gate power supply, and an independent sampling network connected in series. The low-voltage side control unit is used to receive dose rate, ambient temperature, external sampling signal and output voltage feedback signal, generate a corrected reference signal and transmit it to the high-voltage side control unit through the isolation transmission unit. The isolation transmission unit is used for data isolation transmission between the low-voltage side control unit and the high-voltage side control unit; The high-voltage side control unit outputs the control increment to the gate power supply after the corrected reference signal is converted by F / V, and at the same time receives the voltage feedback signals from the gate power supply and the independent sampling network, and transmits the voltage feedback signals to the low-voltage side control unit through the isolation transmission unit. The gate power supply is used to receive the control increment of the high-voltage side control unit and generate a stable gate voltage to be sent to the linear accelerator, while the output voltage feedback signal is sent to the high-voltage side control unit. The independent sampling network is used to independently sample the gate power supply and send the sampled output voltage feedback signal to the high-voltage side control unit. The automatic output voltage correction of the output self-calibration circuit includes the following steps: Step 1: The MCU microprocessor receives the external working environment temperature sampled by the temperature sensor, performs temperature compensation on each internal sampling signal, calculates the current correction factor with room temperature of 25℃ as the reference, and uses the temperature-compensated signal for subsequent processing. Step 2: Output voltage feedback signal of the independent sampling network Voltage feedback signal of gate power supply The signal is sent to the MCU microprocessor for comparison after preprocessing, and the deviation of the gate voltage reference is obtained through calculation. Step 3: The MCU microprocessor sets the initial gate voltage reference. Deviation from gate voltage reference The dose rate correction is obtained by superimposing the values ​​and performing the P operation. ; Step 4: The MCU microprocessor adjusts the dose rate. Compared with the externally input dose rate reference signal The corrected dose rate reference is obtained by superimposing the data with the dose rate feedback signal. The comparison is then fed into a PI controller to generate a corrected gate voltage reference. And it is output to the gate power supply through the isolation transmission unit and the high-voltage side control unit; Step 5: The gate power supply will adjust the gate voltage reference. The signal is fed into the PWM signal generation circuit to generate a corresponding PWM drive signal to control the switching transistor to turn on and off, so as to obtain the corrected gate voltage and send it to the linear accelerator. The calculation formula in step 2 is as follows: ， In the formula, , in: :Sign function; Independent sampling network Secondary sampling; The difference between the current feedback voltage and the previous feedback voltage of the independent sampling network; The feedback voltage difference between the two sampling networks; ε : The threshold value set for the error range greater than 0.

2. The output self-calibration circuit for the gate power supply of a medical electron gun as described in claim 1, characterized in that, The low-voltage side control unit includes an auxiliary power supply, a signal interface circuit, a signal isolation circuit, a serial port level conversion circuit, an MCU microprocessor, and a signal preprocessing circuit. The signal isolation circuit, the signal interface circuit, and the MCU microprocessor are connected in series. The signal preprocessing circuit is connected to the signal isolation circuit and the MCU microprocessor respectively. The serial port level conversion circuit is connected to the MCU microprocessor. The auxiliary power supply is converted from DC to DC to power the circuits of the low-voltage side control unit; The signal interface circuit is used to perform V / F conversion of the reference pulse and send it to the signal isolation circuit, and to perform F / V conversion of the voltage signal and send it to the MCU microprocessor. The signal isolation circuit is used for signal isolation and level conversion, and the signal interface circuit performs V / F conversion and F / V conversion before outputting to the MCU microprocessor. The signal preprocessing circuit preprocesses the external signal and outputs it to the MCU microprocessor. The MCU microprocessor performs loop calculations based on the external ambient temperature, reference signal, and voltage feedback signal, and outputs corresponding control increments. The serial port level conversion circuit enables communication with an external control system, uploading operating status and real-time data for remote monitoring and control.

3. The output self-calibration circuit for the gate power supply of a medical electron gun as described in claim 2, characterized in that, The functions performed by the MCU microprocessor include: 1: Receive the external ambient temperature through the signal preprocessing circuit and perform corresponding temperature compensation on each internal signal; 2: The signal isolation circuit, signal interface circuit, and signal preprocessing circuit receive two voltage feedback signals, a dose rate reference signal, and a dose rate feedback signal. The internal circuit performs corresponding PI loop calculations to obtain the corresponding control increment, thereby achieving the purpose of automatic output voltage correction. 3: External serial communication: Communicates with the external control system via a serial port level conversion circuit. The standard RS485 serial port is used to upload the working status and real-time data for remote monitoring and control.

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