Analysis of the noise and efficiency characteristics in a quasi-resonant converter
A quasi-resonant converter using flyback topology can realize soft switching with relatively simple circuit. However, a switching device with high withstand voltage is necessary to achieve complete zero voltage switching when the input voltage is high and it causes decrease of efficiency because a switching device with high withstand voltage has relatively high on voltage. Therefore, we analyzed efficiency and noise of a quasi-resonant converter with a low breakdown voltage and low on voltage switching device under the condition of non-zero voltage switching. As a result of the analysis, it is found that high efficiency and low noise are achieved with non-zero voltage switching.
Analysis of surge and noise generation mechanism in a forward DC‐to‐DC‐converter
The surge and noise generation in a switching converter depends heavily on the switching speed of the transistor, the recovery characteristics of the diode, the leakage inductances of the transformer and other parasitic inductances, and capacitances. Therefore its mechanism is so complicated that to obtain a complete understanding of the mechanism of surge and noise generation, it is definitely necessary to introduce the analytical procedure through which the quantitative discussions are made. This paper clarifies the mechanism of surge and noise generation in a forward dc-to-dc converter which is one of the most popular types of converter. The analysis is performed by partitioning the switching time into several states and deriving a high-frequency equivalent circuit for each state. The equivalent circuits include not only inductive and capacitive parasitic parameters, but also the parameters related to the switching speed of the transistor and the recovery characteristics of the diode. As a result, the effects of these various parameters on the surge and noise generation are clarified quantitatively.
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.