The Research Of Large AC Voltage-Controlled Current Source Based On Power Operational Amplifiers

The large AC current source with adjustable amplitude and frequency has a wide range of applications and market demands in semiconductor power devices and cable conductors' AC equivalent resistance testing.Therefore,the research and development of such power supplies has important engineering value.The large AC current sources using linear power amplifiers have the advantages of high accuracy and stability.However,due to the limitations of research and development level,it is impossible to obtain large AC current with amplitudes greater than 40 A using a single linear power amplifier device.Exploring an appropriate multi-tube parallel circuit topology is an effective way to solve the problem of single linear power amplifier's output limitation.This paper takes linear power amplifier Apex PA50 as the core,puts forward two kinds of parallel design schemes of multi-tube parallel topology,and uses two technical methods of simulation and experiment to study the feasibility of these two topology design schemes.The scheme one of multi-tube parallel circuit topology is power operational amplifiers' primary and secondary parallel mode connection.This scheme belongs to CT sampling VCCS based on primary and secondary parallel mode connection.The advantages of CT sampling and primary-secondary parallel to realize the aim of expanding current.In this paper,we used Multisim to simulate the principle of scheme one.In the process of study,we've analyzed reason of DC bias offset in output current,and designed adjustment circuit to eliminate the DC bias offset,it makes the scheme one has a good ability of large AC current output in simulation.However,the experimental studies have found that the actual output capability of scheme one is not as ideal as the simulation result.The scheme two of multi-tube parallel circuit topology is power operational amplifiers' parallel connection coupled by an isolation transformer.Using the isolation transformer to isolate the parallel operational amplifier,and avoid the back current flow between the two parallel amplifiers.At the same time,the model and the equivalent circuit are derived.Finally,the current source model is constructed basing on this scheme to test the circuit output characteristics.The results of experiments suggest that the multi-tube parallel voltage control current source coupled by isolation transformer has good linearity,reliable stability and low waveform distortion,it proved that the design scheme is feasible,and gives a good idea of large AC current source,has the value of further research.