Design of Power Switched-Capacitor Converters and Their Performance Analysis in a Soft-Charging Operation
Date of Award
Mohammad Matin, Ph.D.
Amin Khodaei, Ph.D.
Shimelis Assefa, Ph.D.
Switched-capacitor converters, Power switched-capacitor converter, Small circuit integration
Switched-capacitor (SC) converters have gained more interest due to their high power density and appropriateness for small circuit integration. Building a SC DC-to-DC converter with only capacitors and switches is the main reason to seek a higher power density achievement. However, the SC converters suffer dominant losses related to their capacitors and switches. These losses can be determined and optimized by calculating the converter's output impedance in its two asymptotic limits.
We proposed a high voltage gain and a very low output impedance power switched-capacitor converter (PSC) with a lower number of components compared to other step-up switched-capacitor topologies. The high output efficiency and the higher power density are two fundamental aspects of the PSC converter.
We can eliminate the current transient by applying the soft-charging technique that results a higher power density and a higher efficiency in PSC. The soft-charging operation is more preferable to the soft-switching technique (resonant operation) since it does not require any auxiliary components. Furthermore, soft-charging helps to resize capacitors and reduce the switching frequency of the PSC converter.
Furthermore, a split-phase control design is proposed to achieve the complete soft-charging operation in a PSC. The control diagram was designed for a 1-to-4 PSC (two levels of the PSC) which controls eight switches to exhibit eight modes of operation. The complete soft-charging 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.
In this research, we also proposed a two-level power switched-capacitor boost converter (PSC-boost) for a high voltage gain application by integrating a PSC converter and a conventional boost converter. The PSC switched-capacitors and the conventional boost converter are respectively cascaded as a primary and a secondary side of the proposed converter. Without alerting of the secondary side (conventional boost), the conversion ratio can be increased by adding more switched-capacitors cells. The proposed converter similarly acts as an MBC; however, it can maintain the rated voltage gain at a higher duty cycle. Unlike the MBC converter, the simulated voltage gain is closer to the calculated voltage gain for PSC-boost converter. In addition to the switched-capacitors insertion, a switched inductor model is used instead of the single inductor in the traditional boost converter. Five switches, five capacitors, seven diodes, and three inductors are used to build a PSC-boost switched-inductor converter. The PSC-boost converter accomplishes 94% efficiency which a higher rated power.
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Alateeq, Ayoob, "Design of Power Switched-Capacitor Converters and Their Performance Analysis in a Soft-Charging Operation" (2018). Electronic Theses and Dissertations. 1531.
Received from ProQuest