Research On Current-mode And Programmable Scanning Magnet Power Supply

Radiation processing technology, which has been widely used in materialmodification, food sterilization, Cable irradiation, and so on, is to make use of thechemical, physical and biological effects, caused by the interaction between the raysand matter, to process the Irradiation objects. Compared with the cobalt, Electronirradiation accelerator has many advantages, such as online adjustable, high-usagesafe, beam orientation and so on.The stability of output waveform is one of the important indicators to measureelectron irradiation accelerator performance. When the power grid voltage or theoutput load changed, electron irradiation accelerator still want to output and maintainthe stable current, and this puts forward higher requirements for the scanning magnetpower supply. In addition, the problem of domestic scanning magnet power supply isthat Scanning dose reached the maximum in titanium window edge, which can causelocal damage easily. So it is necessary to develop new type current scanning magnetpower supply, to enhance the level of domestic electronic irradiation acceleratorperformance.According to the technical indicators of the new type current scanning powersupply, the corresponding hardware circuit was designed. A current mode scanningmagnet power supply, whose working frequency can continuous adjustable from5Hzto50Hz and the peak current is7A, was developed. The whole hardware circuitdesign adopted feedback closed-loop control scheme based on pulse width modulation.The sensor sampled electric current of the output load, converted into voltage signal,as the feedback signal, then to make a comparison with the reference signal. Throughthe error amplifier，the amplifying error signal was transported into pulse widthmodulation controller，then generate PWM pulse, to drive H-bridge inverter circuit, tomake sure that the output current waveform can track reference waveform with highprecision and real-time.Firstly, the present development of industrial irradiation accelerator and relevantswitch power technology were introduced; secondly, the main circuit and parameters of the power supply were designed; thirdly, the article analysis the closed loop controlstrategy, at the same time, the design method of reference waveform generator and PIregulation circuit were given. Programmable reference waveform was outputted bysingle chip microcomputer, whose frequency is easy to control and has high precisionand stability, to realize the best match between scanning current and accelerator.Through debugging the prototype, we can acquire stable output waveform,whose linearity is good. The new type current scanning power supply has beensuccessfully used in the electron irradiation accelerator, which can implement to trackwith reference waveform and inhibit the influence caused by the changed load onoutput current.