Abstract. With the development of science, technology and production, there is an increasing demand for high-current power supply, which is widely applied in research of high-speed railways, subways, electric cars, DC transmission and electromagnetic measurement science. The commercial high-current power supply basically uses the form of switching power supply and its ripple wave is generally greater than 1%, with the peak-peak value up to the pulse ripple shortcomings of a few volts (with a constant amplitude), and the ripple wave basically has nothing to do with the amplitude of the output current. Therefore, it is very difficult for switching power to be applied in high-current AC power supply. In this paper, we have researched and designed a kind of AC/DC linear high-current power supply based on the linear theory. In this paper, we have researched and designed a kind of AC/DC high-current power supply based on the linear theory, with the AC current frequency kept from 50Hz to 1 kHz. Moreover, a plan has been designed to test the AC/DC high-current performance and assess the accuracy, ripple wave (harmonic wave) and short-term drift performance of the power supply.
System Principle and designThe linear current supply means that the power supply has no break variable or pulse superposition in the process of current output. DC current supply has better stability and a small ripple coefficient, while AC current supply has smaller distortion and better stability.Commonly, a high-current DC power supply above 1kA usually adopts direct mains supply rectification and the low output voltage will result in a larger ripple wave (above 2%) and poor stability (about 0.2% / 3 minutes), because the output current will change with the circuit resistance of the power grid and power supply. Therefore, the solution of the above-mentioned problems requires an adjustable and stable AC supply featuring a higher frequency (above 1 kHz) and free of power frequency modulation by means of rectification and filtration. AC current supply is even more demanding.To sum up, the high power amplifier (HPA) should be the core component for research and design of AC/DC linear high-current supply, requiring that the power amplifier amplitude can be adjusted (in an intelligent manner) and have a higher common mode rejection ratio. Moreover, DC current supply is provided with an efficient rectification and filtration assembly. The short-term stability of AC/DC current supply depends on the simulative closed-loop system while the long-term stability depends on the SCM (single chip microcomputer) digital closed-loop system subject to automatic tracking.See Fig.1 for the schematic block diagram of the power supply for research and design: After filtration, the grid 220V (50Hz) current goes through the isolation transformer, the rectification and filtration circuits as well as a power amplification circuit. Then, an AC or DC high-power current will be output through current boosting, filtration and current sampling feedback control.
