| Electron irradiation technology is widely used in the areas of production and living, such as modification of organic materials, sterilization of food and medical and health supplies, delaying germinating of agricultural production and so on. Comparing industrial radiation electron linear accelerator with cobalt -60,the former has some advantages in irradiation processing, for example, the safety performance is better, the irradiation dose is online adjustable and uniform, the follow-up harmless processing is unnecessary and so on. Therefore, the electron accelerator has the basic conditions to replace cobalt -60, and it has become the preferred equipment in current radiation processing industry.Klystron is a vacuum microwave amplifier, it is widely used in industry with the advantages of high power and efficiency, and it is the core component to amplify the microwave excitation source in industrial radiation electron linear accelerator. Klystron requires two power supplies to work: focusing power supply and filament power supply. Focusing power supply focuses on the electron beam to ensure the pass rate in klystron cavity, filament power supply give heat to the filament in klystron, in order to make it launch e-beam.According to the working state of adjusted tube, power supplies have two kinds, one is linear, the other one is switching. When the adjusted tube is working in linear amplified state, it is linear power supply, when the tube is working in switching state, then it is switching power supply. Linear regulator circuit has many advantages, such as the circuit structure is simple, the adjustment is convenient, and the failure rate is low, the output voltage has a strong stability, the ripple voltage is small, without high-frequency interference and so on. However, the efficiency of power supply is very low, and in order to solve the heat problem of adjusted tube, it is needed to install the radiator. Besides, there is heavy frequency transformer. Switching power supply has low power consumption, high efficiency, small size, light weight, and wide voltage range, but it also has serious interference and complex circuit. Focusing power is of DC steady with high power and stability in Electron accelerated klystron power supply, and it is appropriate to choose switching power to design. Filament power is of AC sine wave which power is not so high, so it is more cost-effective to select the linear power to design.Focusing power has big current output, and it is required to have high power stability (stability <0.1%), it's difficult to satisfy the requirements by using the conventional method of designing switching power. For this reason, we start from the control structure of stabilized power, through the analysis of it, we can find the factor that affect the stability of the current power supply, then aiming at these factors, proposing the corresponding measures, so we can increase the stability of the power supply. The DC stabilized power of high stability is composed by benchmark, regulator, power converter, filter, load and current sampling devices, and it is a negative feedback closed loop regulating system. In the DC stabilized power supply, the steady-state errors can be divided into two categories: one is static error, including the given error and the disturbance error, and it is related to the type of the power system and the input signals, static error can be overcomed through the self-regulation of the system. The other one is systematic error, it is mainly caused by current sample, regulators and benchmark, it is the error that the power system can not overcome, they are the benchmark bias dUref, sampling bias dHd, regulator introduced bias dUd.Through the comparison of several common circuit topologies in circuit design, choosing a full-bridge converter as the circuit structure of focusing power, which is the most suitable for the condition of high power, using IGBT as the switch tube of the main power circuit, and using the hybrid integrated driver EXB841 as the driver of IGBT. The theory of each unit circuit is described, and the selection of each component, transformer and the calculation of parameters are given in detail. According to the requirements of high stability, the corresponding methods of improving reference voltage, sampling, and the precision of regulator are given. A method of protecting the switch when debugging the power supply is proposed. Finally, the output of experiment is given.Filament power supply requires AC output of low voltage and high current, it's belong to AC / AC transformation in power conversion circuits. Using the indirect conversion method, that is making the AC voltage from the power grid pass through the rectifier and filter circuit, then it is transformed into the DC, and making it pass through the inverter circuit so that it is transformed into a stable low-voltage and high-current AC. The whole idea of designing this power supply is the theory that negative feedback has a stable output. According to the principle of introducing negative feedback in amplifier, the current series negative feedback is introduced in this design. In order to amplify the sine wave current, it is common to use two tubes, which have the same parameter and symmetrical features (NPN type and PNP type), and they can constitute a complementary output, which can conduct alternately in positive half cycle and negative half cycle of the signal, thereby, we can amplify the AC signals. However, the filament power supply requires a larger current output, and only one transistor can not meet the requirement, thus, we make multiple tubes work in parallel ways to amplify current. At the same time, in order to reduce the complexity of the system, we put the power supply of the amplifier and the adjusted tube together, but this increased the supply voltage of the amplifier, so we use the high-voltage amplifier OPA445 as the error amplifier of the power supply. In addition, using the high-power NPN-type transistor 2SC5200 and the high-power PNP-type transistor 2SA1943 as adjusted tube, they give out high output, so they can meet the requirements better. Through the debugging of the prototype, it shows the output waveform is fine, and it's meet the requirements of the klystron filament completely. |
PDF Full Text Request