A New Series-Parallel Switched Capacitor Configuration of a DC–DC Converter for Variable Voltage  Applications

DC-DC converter is to provide a predetermined and constant output voltage to a load from a poorly specified or fluctuating input voltage source. Switched-capacitor (SC) DC-DC power converters are a subset of DC-DC power converters which efficiently convert one voltage to another with the use of a network of switches and capacitors. Unlike traditional inductor-based DC-DC converters, switched capacitor converters do not depend on magnetic energy storage elements like inductors which increase the complexity of the circuit and also reduce the circuit efficiency. In this chapter, a converter designed to utilize input source to produce multiple output ratios is presented. The proposed converter circuit has a capability to reconfigure its gain using variable circuit structure by selectively activating converter switches by changing the pulses given to the switches which in turn produces both positive and negative voltage ratios. The same switches and capacitors are reused and connected in a predetermined pattern to generate the required output voltage optimizing the usage of the components. The proposed circuit uses four flying capacitors for charging and discharging the voltages, one output capacitor which is ten times of the flying capacitors value used for filtering any ripples in the output voltage, 13 active switches of MOSFETs used to achieve the required output with only one input voltage. It supports various voltage conversion ratios such as 5/1, 4/1, 3/1, 2/1, 1/2, 2/3, 1/5, 1/11, 1/21, 1/31, 1/41, 1/16, 3/43, 2/7, 3/13, 1/6. Out of these conversion ratios, four are of up modes which lift the voltage and 12 are of down ratios. Due to the continuous power supply reduction, positive output ratios of switched-capacitor circuits are widely used in electric vehicle for electronic devices such as audio controller, charging system and LED light and the negative output ratios to find applications in operational amplifiers. While SCs are only capable of a finite number of conversion ratios, SC converters can support a higher power density, smaller size compared with traditional converters for a given conversion ratio. Finally, through simple control methods, regulation over many magnitudes of output power is possible while maintaining high efficiency. The major contribution of the proposed circuit is to obtain maximum voltage conversion ratios with reduced number of switches and capacitors. The working principle, conversion ratios, modeling considerations in different conversion modes, the output waveform results for the voltage ratios and equivalent resistance of the proposed circuit are also explained.