This paper introduces a new high step-down converter that achieves zero voltage switching in both primary and auxiliary switches without relying on coupled inductors, thus ensuring low RIPPLE in input and output CURRENTs. The auxiliary circuit is optimized with the fewest possible components, facilitating zero voltage switching for the main and auxiliary switches and solving the reverse recovery issue of freewheeling diodes through zero CURRENT switching conditions. Additionally, this design reduces voltage stress on the switches, allowing the use of MOSFETs with lower drain-source resistance. A key advantage of this converter is that it avoids using coupled inductors, which eliminates issues related to leakage inductance and potential increases in the converter's size and weight. This enhances the converter's efficiency and practicality. The auxiliary circuit design can also be extended to multiple phases, making it adaptable for various applications. The control mechanism is simple because the auxiliary switch operates in complementary with the main switch, simplifying the overall circuit design and integration. The proposed converter's design and operational principles have been validated through PSpice simulations, and a 90W prototype has been constructed. Experimental results demonstrate an impressive 95 percent efficiency at full load.

The low-frequency CURRENT RIPPLE decreases the lifetime of the DC voltage sources such as fuel cells and chemical batteries. In this paper, based on series and parallel feedback theory, a nonlinear PI Controller is designed. This controller reduces the low-frequency CURRENT RIPPLE of two stages converter by increasing the output impedance of the boost section. Since the designed controller corrupts dynamic response of the boost converter, a large output voltage overshoot or undershoot is appeared in step load conditions.We will show that this problem can be overcome by applying a nonlinear gain in forward path. In this proposed method, the output overshoot and undershoot voltages stay in an acceptable range. Therefore, both the low frequency input CURRENT RIPPLE and DC bus over/under shoot problems are disappeared simultaneously without employing any additional equipment, especially bulky DC capacitor. Simulation and experimental results for a 2.5 kW prototype confirm the performance of the proposed idea.

In this paper, a new bidirectional buck-boost dc-dc converter with capability of soft switching and zero input CURRENT RIPPLE is proposed. The coupled inductor is used in the proposed converter to eliminate the input CURRENT RIPPLE. In the proposed converter, zero voltage switching (ZVS) and zero CURRENT switching (ZCS) can be obtained for the main and auxiliary switches, respectively. In addition, the proposed topology is analyzed in all operating modes and all equations of voltage and CURRENT for components are obtained.Moreover, the required conditions for soft switching operation and also achieving zero input CURRENT RIPPLE are calculated. Finally, the acuracy performance of the proposed converter is reconfirmed through simulation results in EMTDC/PSCAD software program.