Extended Off-Time Control for CRM Boost Converter Based on Piecewise Equivalent Capacitance Model

Abstract

Valley-switching (VS) and zero-voltage switching (ZVS) improves overall efficiency in critical conduction mode (CRM) boost converters. To achieve VS/ZVS, off-time of the main switch is often extended to match the resonance period by circuit inductor and parasitic capacitors of switching components. In this paper, a piecewise equivalent model for parasitic capacitors is proposed to derive analytical solutions of the resonant process, by which the numerical solutions of VS/ZVS time is calculated. To precisely achieve VS/ZVS in a boost converter, corresponding extended off-time based on the numerical solutions is implemented with an extended off-time (EOT) controller. The EOT controller makes the inductor volt-second unbalance in continuous conduction mode (CCM) operation during one switching cycle, leading to the convergence to CRM operation. The analytical and experimental results correct the results derived by conventional equivalent model for parasitic capacitors, which leads to deviated VS/ZVS boundary and wrongly calculated off-time. The proposed model and controller are verified in a nonsynchronous CRM boost converter based on GaN high electron mobility transistor (HEMT) and SiC diode. With the derived extended off-time, a peak efficiency of 99.15% is achieved at output power level of 200W. INDEX TERMS Critical conduction mode, parasitic capacitance, piecewise equivalent capacitance model, extended off-time control, boost converter.

Adaptive Charge-Compensation-Based Variable On-Time Control to Improve Input Current Distortion for CRM Boost PFC Converter

“…Thirdly, the consideration of C eq is simple under ACVOT control. Although the variations of C eq are difficult to solve under different drain-source voltage curves and the piecewise equivalent method in [24] is more precise, using a constant C eq is enough under ACVOT control in most implementations because C eq is not sensitive under ACVOT control.…”

Research on the Optimal Control Timing of ZVS-QSW

“…In applications where both the input/output voltages and converter power levels must vary, the table dimensions grow, increasing storage requirements and complexity. The approach in [7][8][9][10][11][12][13][14]aims to reduce the computational complexity by fixing one parameter, such as peak SR shutdown current, dead time or frequency, etc., and then adjusting the rest of the parameters by on-line calculations with known conditions, which results in the converter to satisfy the ZVS-QSW operation only in specific ranges, and the switching tubes can only be operated in the hard-switched or suboptimal ZVS operation mode in other ranges. Recently, a research method has been proposed in [4] to realize a wide range of minimum conduction ZVS-QSW operation by adjusting the converter switching frequency and enforcing the zero-voltage dead time online.…”