Abstract
Due to their high power density and appropriateness for small circuits integration, switched-capacitor (SC) converters have gotten more interests. Applying the soft-charging technique effectively eliminates the current transient that results in a higher power density and a higher fundamental efficiency. Achieving the complete soft-charging operation is impossible by using the conventional control diagram for any SC converter topology. In this paper, we proposed a split-phase control to achieve the complete soft-charging operation in a power switched-capacitor (PSC) converter. The proposed control diagram was designed for a 1-to-4 PSC converter (two-level of the PSC converter). The implemented split-phase diagram successfully controls eight switches to exhibit eight modes of operation. In addition to the current transient elimination, the complete soft-charging allows us to reduce capacitor sizes. However, reducing capacitor size negatively increases the output voltage ripple; hence, an output LC filter is needed. The complete soft-charging achievement accomplishes a 96% efficiency due to the lower output impedance and the dead time switching. LT-Spice software has been used to verify the proposed control and the results were compared with hard-charging and incomplete soft-charging operations.
Highlights
DC-to-DC converters are commonly designed with magnetic elements for energy storing purposes
A control diagram has been proposed to achieve a complete soft-charging in a 1-to-4 power switched-capacitor (PSC) converter
It can be clearly seen that the output impedance eventually decreases at a higher switching frequency selection
Summary
DC-to-DC converters are commonly designed with magnetic elements for energy storing purposes. Eliminating the current transient to increase the fundamental efficiency and the power density are the major functions of the soft-charging technique. In conventional operation (hard-charging), there are two ways to reduce the current transient, either by large capacitors selection or a higher fsw These two implementations reduce the power density and the fundamental efficiency respectively. The complete soft-charging operation has been applied to the proposed PSC converter in [7]. A control diagram has been proposed to achieve a complete soft-charging in a 1-to-4 PSC converter. Achieving the complete soft-charging shows an output impedance reduction and a superior efficiency achievement to the 1-to-4 PSC converter.
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