SUMMARYA novel isolated high voltage-boosting converter, derived from the traditional forward converter, is presented in this paper. As compared with the traditional forward converter, the demagnetizing winding of the transformer in the proposed converter is used not only to demagnetize but also to improve the voltage conversion ratio. Therefore, the duty cycle is not limited, and the utilization of the transformer, also called coupled inductor, can be increased also. Furthermore, the proposed converter maintains the advantage of possessing a non-pulsating output current, leading to a small output voltage ripple. Moreover, by applying one additional voltage-boosting winding to the transformer, the voltage conversion ratio can be significantly improved. In addition, an active clamp circuit is employed in the proposed converter to reduce the voltage stress of the main switch, caused by the leakage inductance in the transformer, and the switches can achieve zero-voltage switching. Finally, the analysis of operating principles, choice of the turns, turns ratio, core size, and each wire size of the coupled inductor are described in detail, and the experimental results with a prototype with 12-V input voltage, 100-V output voltage, and 100-W output power are provided to verify the feasibility and effectiveness of the proposed converter.
Photoreflectance ͑PR͒ of surface-intrinsic-n ϩ type doped GaAs has been measured for various power densities of pump laser. The spectra exhibited many Franz-Keldysh oscillations, whereby the strength of electric field F in the undoped layer can be determined. The thus obtained Fs are subject to photovoltaic effect and are less than built-in field F bi. In the previous work we have obtained the relation FϷF bi Ϫ␦F/2 when ␦FӶF bi by using electroreflectance to simulate PR, where ␦F is the modulating field of the pump beam. In this work a method was devised to evaluate ␦F by using photoinduced voltages V s and, hence, the relation can be verified by PR itself. The ␦Fs obtained by V s are also consistent with those of using imaginary part of fast Fourier transform of PR spectra.
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