Design Of Low Noise Operational Amplifier & Application In Conditioning Circuits Of Partial Discharge Detection

The power safety,as an important branch of the application in the Internet of Things,receives more and more attention because of its relationship with national life and property safety.In this field,in order to warn of electrical accidents that may be caused by damage to the insulation material of the wires,partial discharge detection technology is widely used.This technology is currently the main method for assessing the degree of damage to wire insulation materials,but the core analog conditioning circuit that realizes its corresponding functions is still at the board-level implementation stage,and it has the disadvantages of low integration,high cost,and susceptibility to electromagnetic interference.As an indispensable intermediate component in the power safety system,if the analog conditioning circuit is combined with microelectronics technology,the function of fault diagnosis and positioning can be realized on the chip,that can effectively reduce the size of the equipment,reduce the cost,and improve the anti-interference ability in the electromagnetic environment.In order to realize the miniaturization,portability and intelligence of the partial discharge diagnosis and discharge source location circuit,this paper firstly proposes a design scheme to diagnosis faults by using broadband pulse current detection method and to locate faults by using ultrasonic envelope location method,which based on the existing partial discharge diagnosis and discharge source location technology.This scheme uses the frequency band that contains more discharge information,and solves the problem of continuous triggering and attribution recognition of ultrasonic signals.Secondly,combined with the above-mentioned new scheme,an on-chip integrated analog conditioning circuit was designed using 0.18μm CMOS process.The chip includes instrumentation amplifier and active bandpass filter,timing discrimination circuits and time-to-digital conversion circuits,high-speed comparators,and bandgap reference source.Among them,the instrumentation amplifier and the active bandpass filter are used for signal amplification and filtering respectively;the timing discrimination circuit and the time-to-digital conversion circuit are used for time measurement;the band gap reference is used to provide the reference source;the highspeed comparator based on the principle of nesting current mirror is designed to realize the comparison and judgment function.Among the above-mentioned sub-modules,the operational amplifier is the core component and needs to have the characteristics of high speed,low noise,and high power supply rejection ratio.For this reason,this article is based on the current split structure and floating control AB output structure,and makes corresponding optimizations for the speed and noise performance of the operational amplifier.Finally,the simulation verification and layout drawing of the designed signal conditioning circuit are completed.The results show that the voltage temperature coefficient of the bandgap reference source is as low as 1.91ppm/℃,the operational amplifier has a unity gain bandwidth of 65.06 MHz and an equivalent input noise of 3.44 n V/√Hz,and the functions of the entire system are basically realized.The detection and fault location solutions proposed in this paper,as well as the onchip analog signal conditioning circuit,provide a certain reference for the realization of the miniaturization and intelligentization of partial discharge diagnosis and discharge source location equipment.