阅读说明：本技术 一种空间电子束焊接聚焦电源系统 (Space electron beam welding focusing power supply system ) 是由 曲延滨 白凤强 张秉刚 王厚勤 宋蕙慧 侯睿 于 2019-11-13 设计创作，主要内容包括：本发明涉及一种数字控制高精度高功率密度空间电子束焊接聚焦电源系统,属于焊接电源领域,特别是应用于空间环境中电子束聚焦的情况。空间电子束焊接聚焦电源系统主要包括：高频半桥逆变、LLC谐振网络、高频变压器、全波整流滤波、电压电流采样电路、辅助供电电路、隔离驱动电路和DSP控制板。整个电源由于采用高频DC-DC变换器技术和数字化控制技术,具有高功率密度和高精度的特点。(The invention relates to a digital control high-precision high-power-density space electron beam welding focusing power supply system, belongs to the field of welding power supplies, and particularly relates to the situation of electron beam focusing in a space environment. The space electron beam welding focusing power supply system mainly comprises: the device comprises a high-frequency half-bridge inverter, an LLC resonance network, a high-frequency transformer, a full-wave rectification filter, a voltage and current sampling circuit, an auxiliary power supply circuit, an isolation drive circuit and a DSP control board. The whole power supply has the characteristics of high power density and high precision due to the adoption of a high-frequency DC-DC converter technology and a digital control technology.)

1. A space electron beam welding focusing power supply system is characterized in that the whole system has the characteristics of light weight, small size, high precision, high power density and digital control, and mainly comprises a high-frequency half-bridge inverter, an LLC resonant network, a high-frequency transformer, a full-wave rectification filter, a voltage and current sampling circuit, an auxiliary power supply circuit, an isolation drive circuit and a DSP control board.

2. The spatial electron beam welding focusing power supply system of claim 1, wherein the power density of the power supply can be effectively improved by adopting a high-frequency DC-DC converter technology, the main circuit adopts a high-frequency half-bridge inverter, an LLC resonant network, a high-frequency transformer and full-wave rectification filtering, and the loss can be effectively reduced by utilizing the soft switching characteristic of the LLC resonant converter.

3. The power system of claim 1, wherein the power system is digitally controlled to improve the power accuracy and response speed, and the control circuit mainly comprises a voltage/current sampling circuit, an auxiliary power supply circuit, an isolation driving circuit, and a DSP control board.

4. The system of claim 1, wherein the entire power supply has high power density and high precision due to the high frequency DC-DC converter technology and the digital control technology.

Technical Field

The invention relates to a space electron beam welding focusing power supply system, belongs to the field of welding power supplies, and particularly relates to a space electron beam welding focusing power supply system applied to the condition of electron beam welding focusing in a space environment.

Background

Space assembly, maintenance and repair tasks do not leave the connection technology, the current space connection technology is limited to mechanical connection and glue joint, and in comparison, space welding has the advantages of high connection strength and rigidity, good sealing performance, simple joint structure, light weight, high reliability and the like, and development of the space welding technology is helpful for improving the capacity of space construction, maintenance and repair. The space welding technology is steadily developed in the past half century, and a reliable technical foundation is laid for the application of the space welding technology in the assembly of large space structures and the repair and maintenance of space vehicles. Electron beam welding is the most fully demonstrated space welding method at present, and the electron beam welding technology has wide application prospects in space construction.

One of the core technologies of space electron beam welding is the design of a power supply system, wherein a focusing and bundling power supply can be divided into a magnetic focusing power supply and an electric focusing power supply, the principle that electrons are subjected to Lorentz force in a magnetic field and the principle that electrons are subjected to electric field force in an electric field are respectively utilized, scholars at home and abroad carry out deep research on a magnetic focusing mode theoretically and practically, and the magnetic lens as a main lens has the advantages of convenience in processing, easiness in ensuring precision, small aberration, safety, easiness in adjustment, large field section diameter, easiness in meeting paraxial conditions and the like of electrons entering the lens, and in addition, the control mode of the magnetic lens is simpler, and the high-precision adjustable constant current source can meet requirements. The electric focusing method generally adopts an equal-diameter three-circle single lens, and although the size and the weight are small, the control method is complex and needs negative high voltage of about 5 kV. After considering the factors in multiple aspects, a focusing power supply is designed by adopting a magnetic focusing mode.

The existing magnetic focusing power supply technology mainly comprises three types, namely: 1. the linear control type current-stabilizing DC power supply works by using the amplification characteristic of a high-power transistor connected in series in a power supply output loop, and the transistor plays the role of a variable resistor. The power supply has good stability and high response speed, but because the high-power transistor works in an amplification region in an output loop, the loss is high, the heat productivity is high, the efficiency is low, and the requirement on heat dissipation design is high. 2. The switch control mode current stabilizing DC power supply realizes the stabilization of current or voltage by controlling the on-off of the switch tube, and the power supply has the characteristics of high efficiency, high power density and high precision. 3. The switch control and linear control combined steady-current DC power supply: the problem of big ripple of switching control mode is solved, but the inefficiency of linear control mode can not be subducted, and the circuit is more complicated moreover.

In the article, the IGBT is adopted as a power switch tube in the research of the high-stability klystron focusing magnetic field power supply, the working frequency is lower, the volume of the whole power supply device is larger, and the power density is lower. An energy-saving electron beam focusing magnetic field pulse power supply special for an electron linear accelerator (application number 201710598910.8) is disclosed, which is used in the occasion of a high-energy pulse output mode of a linear electron accelerator, the power supply works in a pulse state, not only can energy consumption be saved, but also the service life of a focusing coil can be prolonged, but the power supply is a special power supply of a pulse electron beam accelerating device and cannot be suitable for the occasion of continuous output of electron beams. An ultra-high-speed large-current pulse constant current source (application number 201610908411X) discloses a method for realizing pulse constant current by using a capacitor pulse control depth negative feedback method, wherein a large capacitor is connected in parallel with a power supply, so that the energy stored by the capacitor is mainly supplied to a load at the initial working stage, and a pulse with a microsecond-level rising edge is supplied to the load; meanwhile, a high-power Darlington tube is connected with the load in series, so that the load can pass pulse current of hundreds of amperes. Although the method realizes pulse constant current and improves the efficiency, the method only adapts to the resistor with smaller load change, when the load change is larger, the power supply voltage needs to be improved, and the heating of the tube is serious and the tube is easy to damage due to the increase of the voltage VCE when the power Darlington tube works in a linear area; the focusing coil is an inductive load, the rising time is prolonged, and the depth negative feedback is easy to self-excite to cause the instability of the circuit.

Therefore, the power supply system of the electron beam welding machine currently in China has the following defects.

1. The lower operating frequency results in a larger volume and weight of the magnetic element and a lower power density.

2. The application of the pulse type electron beam focusing power supply is limited, and the pulse type electron beam focusing power supply cannot be applied to the occasions of continuous output of electron beams.

3. The control method is simple, the constant current output precision is low, the control mode cannot be switched under the light load mode, and the loss is reduced.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a digital control high-precision high-power density space electron beam welding focusing power supply system. The control circuit comprises a voltage and current sampling circuit, a digital microcontroller and a driving circuit. Has digital control and high precision. The invention adopts the technical scheme that the device has the characteristic of high power density and aims to achieve the purpose.

The space electron beam welding focusing power supply system mainly comprises: the device comprises a high-frequency half-bridge inverter, an LLC resonance network, a high-frequency transformer, a full-wave rectification filter, a voltage and current sampling circuit, an auxiliary power supply circuit, an isolation drive circuit and a DSP control board.

Due to the adoption of the technical scheme, compared with the prior art, the invention has the following beneficial effects.

The focusing power supply system of the space electron beam welding machine has the characteristics of light weight and small volume, the switching frequency of the whole power supply system is about 100KHz, the driving circuit is simple, the influence of interference signals on the driving level can be effectively inhibited by the RC filtering additionally driven by the primary side, and the triode additionally driven by the secondary side ensures that an MOS (metal oxide semiconductor) tube is quickly turned off, so that the loss is reduced, and the whole efficiency of the power supply is improved.

The focusing power supply system of the space electron beam welding machine has the characteristics of high precision and good stability, the whole power supply system adopts elements with digital closed-loop control and high stability, a protection circuit monitors abnormal conditions in real time, the whole system can be rapidly and effectively protected in case of faults, and the whole system can be ensured to stably and reliably work in an extreme space environment.

The focusing power supply system of the space electron beam welding machine has the characteristics of high precision, high efficiency and convenience in maintenance. The whole system adopts a high-precision DSP main control chip with the working frequency of 60MHz, the focusing power supply can realize the continuous adjustment of 0-1.5A when stably working, the output voltage ripple is less than 200mV, the minimum adjustment step length is 0.5%, the working efficiency of the whole system is higher than 87%, the power supply adopts the modularized design, the maintenance and the replacement of easily damaged elements are convenient, and the high-precision control, the high-efficiency effect and the maintenance requirement are realized.

Drawings

Fig. 1 is an overall schematic block diagram of a power supply.

Fig. 2 is a schematic block diagram of a main circuit.

Fig. 3 is a schematic block diagram of a driving circuit.

Fig. 4 is a schematic block diagram of output voltage current sampling.

Fig. 5 is a schematic block diagram of an auxiliary power supply.

Fig. 6 is a functional block diagram of the controller.

FIG. 7 is a diagram illustrating an interrupt structure of the controller.

FIG. 8 is a diagram of a controller state machine.

FIG. 9 is a schematic diagram of voltage-current dual closed loop control of the controller.

Fig. 10 is a current loop control flow chart.

Detailed Description

In order to better understand the technical solution of the present invention, the following further describes the working principle and the implementation mode of the present invention with reference to the attached drawings.

As shown in fig. 1, the overall power supply schematic block diagram is shown, and the entire power supply system mainly includes a high-frequency half-bridge inverter, an LLC resonant network, a high-frequency transformer, a full-wave rectification filter, a voltage-current sampling circuit, an auxiliary power supply circuit, an isolation drive circuit, and a DSP control board.

As shown in fig. 2, which is a schematic block diagram of a main circuit, the input side of the power supply is a dc input, and the LLC half-bridge generates a high-frequency ripple at the dc terminal at the moment of high-frequency switching. In order to prevent the input high voltage sudden-adding from damaging the post-stage circuit and filter the current ripple generated by the post-stage circuit, 4 capacitors of 10nF are added at the direct current input end. The highest input voltage of the power supply is direct current 120V, the LLC is soft on during operation, the instantaneous peak voltage higher than the input voltage cannot appear on the power tube, 1.25 times of margin is taken, and an MOS tube with the withstand voltage level of 150V is selected.

The circuit input of the whole system is a 110V direct-current power supply, the transformer is a secondary single-winding transformer, the secondary turn ratio of the transformer is 3: the winding of 1 reduces the voltage to 30V and is connected to a half-wave rectifying circuit, and the direct-current voltage of 30V is output. Each path of rectification of the secondary side adopts 3 2A/200V patch fast recovery diodes for rectification, so that the loss and the heat productivity of each diode are reduced while the current and voltage margin is ensured.

As shown in fig. 3, a schematic block diagram of a driving circuit IS shown, a high-order MOS transistor exists in a half-bridge LLC, and a driving potential needs to be increased to ensure reliable driving, and the design adopts a 5kV isolation driving IC SI8233BD-D-IS driving IC with a Boost-Strap function to simultaneously drive a high-order MOS and a low-order MOS and ensure isolation of a control signal from a primary side MOS. The RC filter with smaller cut-off frequency is added on the driving primary side, so that the influence of interference signals on the driving level can be effectively inhibited; the triode is additionally arranged at the secondary side driving end to be pulled down quickly, so that the MOS tube is guaranteed to be turned off quickly, the turn-off loss of the power MOS tube is reduced, and the overall efficiency of the power supply is improved.

As shown in fig. 4, a schematic block diagram of output voltage and current sampling is shown, where a power supply operates in a high-frequency switching mode, a large interference signal exists, and in order to ensure accurate sampling of output voltage and current and to realize accurate control of output by a loop, the design uses an operational amplifier differential sampling mode for sampling output voltage and current. For voltage differential sampling, RC filtering is added at a feedback end to filter out high-frequency voltage components; for current differential sampling, C filtering is added at a feedback end to filter out high-frequency current components. Meanwhile, RC filtering is added to a voltage and current sampling port of the DSP, and clutter signals are filtered secondarily.

As shown in fig. 5, a schematic block diagram of the controller is shown, a conventional flyback circuit is used to generate a power supply 12V for driving the IC and a 9V, 9V for supplying power to the DSP, and the linear LEO conversion is performed on the 9V to obtain a stable power supply voltage of 3.3V for the controller. In order to simplify the design and effectively reduce the board volume, a flyback IC chip NCP1014AP065G with an MOS is selected as a flyback circuit master controller. And a patch capacitor is selected to replace 12V and 9V filter capacitors at the output end of the flyback circuit under the volume of guaranteed capacity.

As shown in FIG. 6, the controller schematic block diagram is that two complementary channels of 12-bit PWM0 (A/B) of DSP drive LLC half bridge MOS; the 12-bit analog-to-digital conversion ADCB0 collects output voltage signals, and the ADCB1 collects output current signals, so that the accurate control of the output voltage and the output current is realized; the 12-bit analog-to-digital conversion ADCA0 collects voltage signals of other adjustable resistors to realize the adjustment of the change of output voltage and current.

As shown in FIG. 7, the controller interrupt structure is schematic, and the program run has two interrupts, including 50kHz interrupt and 200Hz interrupt. With the 50KHz interrupt priority being highest. The module samples output voltage and output current parameters in 20us interruption, operates a current loop and a voltage loop to obtain the PWM working frequency of the module, updates a PWM period register and uses Burst control under the condition of light load; and the priority of the 5ms interrupt program is second, the operation level is lower, a current reference value signal o of the slide rheostat is obtained, and the LLC operation state machine is operated.

Fig. 8 is a schematic diagram of a controller state machine, where the LLC program main body adopts a state machine mechanism for idle waiting state, output ascending soft start state, normal running state, recoverable fault state, and non-recoverable fault shutdown, and the running period is 5 mS. The method comprises an initialization state and a null state, wherein the state transition conditions are as follows:

initialization state to idle waiting state: the module is powered on, the program enters an initialization state, and jumps to an idle waiting state after the initialization of the program operation related parameters is completed; idle wait state to output ramp soft start state: the module has no fault, and the program jumps to an output ascending soft start state; outputting a rising soft start state to a normal operation state: the module is normally started, the output current reaches a current reference value, and no fault occurs; outputting a rising soft start state to a recoverable fault state: a restorability fault occurs in the module starting process; outputting a rising soft start state to an unrecoverable fault state: an unrecoverable fault occurs in the module starting process; normal operating state to recoverable fault state: a restorability fault occurs in the normal operation process of the module; normal operating state to unrecoverable fault state: an unrecoverable fault occurs during normal operation of the module. Recoverable failure state to idle waiting state: when a module generates a restorability fault, jumping to an idle waiting state after the fault is eliminated, and waiting for self-recovery starting; recoverable to non-recoverable fault states: (ii) an occurrence of an unrecoverable failure;

non-recoverable failure state: and 3, the module is reset manually and repeatedly powered down without any jump.

As shown in fig. 9, which is a schematic diagram of voltage and current dual closed loop control of a controller, the LLC is designed in a loop structure with current as an inner loop (fast loop) and voltage as an outer loop (slow loop), and a current reference of the current loop is given by a sliding rheostat adjustment amount.

As shown in fig. 10, which is a flow chart of current loop control, the LLC employs current inner loop control to make the output current quickly track a given current reference. The design of the traditional PI loop is adopted, the working principle is that actual output obtained by sampling is compared with given input and then is sent to a PI controller, the PI controller carries out error limitation after adjustment and calculation, whether gain changes or not is judged, a compensation coefficient is corrected, loop compensation is calculated, and the amplitude limit of loop output is carried out.