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.
Noise Generation in a Forward DC-to-DC Converter
The mechanism of switching-noise generation is examined for the most popular power converter, i.e. the forward dc-to-dc converter. Particularly the output noise voltage generated during the transistor's turnoff is analyzed by dividing the turnoff time into four sequent states and deriving the corresponding high-frequency equivalent circuits. In these circuits the parameter of transistor's fall time is also introduced. As the result, not only the influence of the inductive or capacitive parasitic elements on the noise generation but also the relationship between the transistor's switching speed and the noise voltage are quantitatively clarified.