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This paper aims to solve the problems of large hard switching loss and unclear resonant parameter design in the existing inverter power supply topology.

This paper proposes a simple and reliable two-stage isolated inverter composed of series quasi-resonant push-pull and external freewheeling diode full-bridge inverter. The power supply topology is analyzed, the topology mode is analyzed, the mathematical model of the converter is established and the DC gain of the converter is deduced. The relationship between the load and the output gain of the resonant tank is presented, a new resonant parameter design method is proposed, and the parameter design of the resonant element of the converter is clarified.

The resonant components of the converter are designed according to the proposed resonant parameter design method, and the correctness of the method is verified by simulation and the development and testing of a 500 W experimental prototype. After experimental tests, the peak efficiency of the experimental prototype can reach 94%. Because the experimental prototype achieves soft switching, the heat generation of the switch is greatly reduced, so the heavy heat sink is removed, and the volume is reduced by about 30% compared with the traditional power supply, and the total harmonic distortion of the output voltage is about 2%.

The feasibility of the scheme is verified by experiments, which is of great significance for improving the efficiency of the inverter power supply and parameter optimization.

Strategic change is integral to the survival and development of firms. The purpose of this paper is to analyze the impact of environmental uncertainty on a firm’s strategic change and further demonstrates the moderating role of political connection and family ownership on the relationship between environmental uncertainty and a firm’s strategic change.

This paper uses the population sample of Chinese firms listed on the Shenzhen Stock Exchange and the Shanghai Stock Exchange from 2008 to 2014 and quantitatively tests hypotheses through correlation analysis, regression analysis and other methods.

Environmental uncertainty has a positive effect on the degree of strategic changes made. Political connection and family ownership negatively moderate the impact of the two dimensions of environmental uncertainty (environmental dynamism and environmental munificence) on strategic changes.

Conclusions enrich the research of other studies on firms’ strategic changes. From an open systems perspective, this paper reveals the influences of external environmental factors on firms’ strategic changes. In addition to this, in analyzing the ways in which environmental uncertainty affects a firm’s strategic change, the research expands the application scope of information processing theory and resource-based view. This paper also provides significant practical observations on firms’ strategic decision making in this area.