Full-wave Type Research Articles

High Power Full-Bridge DC-DC Converter using a Center-Tapped Transformer and a Full-Wave Type Rectifier

This paper proposes a high power full-bridge DC-DC converter, using a center-tapped transformer and a full-wave type rectifier. The proposed converter realizes unipolar primary voltage switching, using the unipolar pulse-width modulation (PWM) technique. Also, the proposed converter reduces the freewheeling conduction loss, using the unipolar PWM technique and a resonant circuit, composed of a clamp capacitor and resonant inductor in the primary, and thus achieves high efficiency. However, because the proposed converter uses only a full-bridge circuit, center-tapped transformer, and full-wave type rectifier, the structure of the proposed converter is simple. In this paper, the operational principle of the proposed converter is described in detail, and a design example of a proposed converter prototype is shown. Finally, experimental results of the prototype are shown, to verify the feasibility of the proposed converter.

Low Drift Push-Pull Self-Saturating Magnetic Amplifier Using a Single Core

Push-pull magnetic amplifiers using a single core are known for circumventing the problem of core matching, but these amplifiers have the following drawbacks: the extreme reduction of gain with the decrease of input resistance, low output power, etc. These problems can be solved by using two magnetic circuits of a stacked four-legged core structure as twin cores in the full-wave type of self-saturating magnetic amplifier. Experiments show that it is possible to obtain twin cores sufficiently well matched, because each leg is from the same sheet, and to decrease the thermal resistance between the twin cores by the yoke connecting between them. As a result it is evident that the use of a four-legged core can improve the zero drift caused mainly by the change of ambient temperature. With this four-legged core structure, the input magnetomotive force equivalent to the zero drift caused by the change of ambient temperature can be decreased by at least one order of magnitude, as compared with spiral core pairs.

Low drift push-pull self-saturating magnetic amplifier using a single core

Push-pull magnetic amplifiers using a single core are known for circumventing the problem of core matching, but these amplifiers have the following drawbacks: the extreme reduction of gain with the decrease of input resistance, low output power, etc. These problems can be solved by using two magnetic circuits of a stacked four-legged core structure as twin cores in the full-wave type of self-saturating magnetic amplifier. Experiments show that it is possible to obtain twin cores sufficiently well matched, because each leg is from the same sheet, and to decrease the thermal resistance between the twin cores by the yoke connecting between them. As a result it is evident that the use of a four-legged core can improve the zero drift caused mainly by the change of ambient temperature. With this four-legged core structure, the input magnetomotive force equivalent to the zero drift caused by the change of ambient temperature can be decreased by at least one order of magnitude, as compared with spiral core pairs.

The minimum detectable change in the mean noise-input power to a radio receiver

Exact expressions are given for the minimum detectable fractional change in the mean noise-input power to a radio receiver. These expressions involve only the pre-detector and post-detector filter responses and have been derived for receivers using either a vth-power instantaneous detector (half- or full-wave type) or an ideal vth-power envelope detector. Using these expressions an example, in which the pre-detector filter is a single tuned circuit and the post-detector filter is a simple rc integrator, is worked out in detail. By the use of some well justified approximations in treating this example the results are presented in simple form and show clearly the effect of pre- and post-detector-filter bandwidths, as well as the detector law, on the sensitivity of the receiver to changes in noise-input power. The results for this example are presented graphically.