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This brief presents a switched-capacitor dc-dc converter that offers features of voltage step-down, voltage step-up, and bidirectional power flow. Concept of energy transfer is achieved by using two current-controlled bidirectional converter cells, which are operating in antiphase. Good regulation capability and continuous input current waveform are other substantial advantages that facilitate practical realization and reduce electromagnetic interference with other circuits and supply networks. State-space averaging technique is applied to study the static and dynamic characteristics. A 20-W, 5-V-9-V prototype has been built and has an overall efficiency of over 80% in all operations.

A two-stage, two-wire TRIAC dimmable electronic ballast for fluorescent lamps is presented in this paper. It is constructed by using a flyback converter as the input power factor corrector to supply a half-bridge series-resonant parallel-loaded inverter to ballast the lamp. The flyback converter is operated in discontinuous conduction mode so that the filtered input current profile is the same as the TRIAC-controlled voltage waveform. The switches in the inverter are switched at a constant frequency slightly higher than the resonant frequency of the resonant tank. Based on the constant average input current characteristics of the inverter, the dimming operation is simply achieved by pulsewidth modulation control of the magnitude of the flyback converter output voltage. No synchronization network is required between the input and output stages. In addition, a linear power equalization scheme is developed so that the dc-link voltage (and hence the lamp power) is in a linear relationship with the firing angle of the TRIAC. The average output voltage of the dimmer controls the equalized flyback converter output voltage. Modeling, analysis, and design of the ballast will be described. A prototype was implemented to verify the experimental measurements with the theoretical predictions.Index Terms-Electronic ballasts, fluorescent lamps.