Non-Isolated High-Gain DC-DC Converter Using Charge Pump and Coupling Inductor

Abstract

As generally acknowledged, the high-gain DC-DC converter is widely used in the sustainable energy system as the front-stage of the DC-AC converter. Therefore, it is indispensable for low voltage to be boosted to high voltage. In general, the boost converter or the buck-boost converter is widely used in such applications. However, it is not easy for such converters to achieve high voltage ratio. In theory, the voltage ratios of these two converters can reach infinity, but in actuality about three or four, limited by parasitic component effect and controller capability. Consequently, if the voltage ratio of the converter is desired to be over five, then two-stage converter based on the boost converter or the buck-boost converter is utilized, or different converter topologies [1-18] are created. In [1-10], the Luo converter and its derivatives are presented, whose voltage lift technique is similar to that of the Cuk converter or the SEPIC converter, based on the energy transfer from one inductor via the intermediate capacitor then to the other inductor. Therefore, the transferred energy is mainly determined by the capacitance, thus causing the current stress on the capacitor to be serious. In [11][12], the voltage-boosting converter with very high voltage ratio also uses a capacitor as an energy-transferring medium, similar to the behavior of the Cuk converter or the SEPIC converter, and hence the current stress on the capacitor is also serious. In [13], the voltage-boosting converter, specified with input voltage, output voltage and rated output current being 24V, 200V and 2A, respectively, is presented. Such a converter combines the characteristics of the boost converter and the characteristics of the bootstrap scheme to achieve voltage boosting. The higher the voltage ratio is, the more the number of bootstraps and hence the more the number of diodes and capacitors. However, the surge current occurs as the energy is transferred via large capacitance, and hence the value of the capacitor can not be too large and the corresponding equivalent series resistance (ESR) is relatively large. In [14], the voltage-boosting converter has the voltage ratio of 1/(12D) in the continuous conduction mode (CCM), where D is the duty cycle of the main switch. And as compared with the boost converter, this converter is complicated due to four switches required. In [15], the KY converter is presented, but the maximum voltage ratio of such a converter is only two. As for [16-18], the coupled-boost converter is presented, which uses a coupling inductor as an energy-transferring medium. In [18], this converter has the voltage ratio of 1+nD/(1-D). However, in this converter, suppressing the voltage spike created due to the leakage inductance of the coupling inductor is taken into account by