Design And Implementation Of High Power Current Pulse Generator Based On FPGA

The technique of generating current pulse is widely used in the nuclear physics industry,military industry,medical industry and metrology industry.Various applications that requiring different current amplitude and pulse width make many difference on the working principles and performance of a current pulse generator.Therefore,there is no such standardized current pulse generator which will just meets a certain application.A specialized current pulse generator has to be developed from scratch in most of the case.The current amplitude or pulse width of most of the existing current pulse generators hardly can be adjusted,and its load is fixed as well.An adjustable current pulse generator proposed in this thesis solved these problems to some extent,which means the current amplitude and pulse width can be easily tuned while the load is different.The current pulse generator uses FPGA as a controller,all of the control signals are optically coupled to high voltage side of the circuit,which will then control a constant current source to generate current pulse.The adjustable current pulse has short rise time and fall time.In order to ensure the rise/fall time of different current pulses are about the same when their amplitude differs,a new method which combines several constant current sources together is proposed,this method solves above problem and reduces power dissipation requirement for MOSFET.Meanwhile,this kind of current pulse generator can be easily modified to other high power applications.The generated current pulse can be sensed by a precision low inductance resistor,this signal then will be sampled and quantified by a high speed high resolution ADC,the FPGA processes these data to get amplitude value and width value of the measured current pulse,further data processing is required to reduce measuring error.This current pulse generator can detect overload or under-voltage situation,it will alert user when this situation occurs and the output will be shut off.Besides,it can give a clear indication whether the test passes or not.Many approaches are used to achieve high performance,including theoretical analysis,circuit simulation and parameter optimization.The amplitude of current pulse can be digitally adjusted from 0.10 A to 9.99 A with a minimum step of 10 mA,the pulse width can be digitally adjusted from 0.01 ms to 99.99 ms with a minimum step of 10 us.Both the rise and fall time of generated current pulse is less than 10 us,and the maximum overshoot of current pulse is 5%.Measurement accuracy of pulse amplitude and pulse width are ±1%,and the measurement repeatability is good as well.Through the analysis of experiment data,it shows that the proposed current pulse generator achieved its expected design goal when under different test conditions.