Abstract-In a sensorless predictive current controlled boost converter, parameterizing the inductor plays an important role in controller performance. In this paper, a solution for inductor parameters online identification is investigated. A small signal injection strategy is proposed to create a transient state, and convergence problem of inductance identification in steady state can be avoided. Then a charge balance current observer (CBCO), derived from capacitor current charging balance concept, is adopted to estimate the inductor current for inductance identification. Since inductance is not used in CBCO, current estimation is not affected by inductance identification error. Because of rank-deficient problem, instead of identifying inductor parasitic resistance solely, the inductor equivalent parasitic resistance is derived. By applying it into the conventional current observer for current control loop, the accuracy of current estimation can still be guaranteed since more parasitic effects are included. To improve the accuracy of inductance identification, a load identification method is investigated. Furthermore, the effect of the equivalent series resistance (ESR) of output capacitor on the proposed algorithm is analyzed. Finally, its effectiveness is verified by experimental results.Index Terms-Sensorless, boost converter, inductor parameters, online identification, small signal injection.
In this paper, a linearized discrete charge balance (LDCB) control strategy is proposed for buck converter operating in discontinuous conduction mode (DCM). For DC-DC power converters, discrete charge balance (DCB) control is an attractive approach to improve the output voltage transient response. However, as a non-linear control strategy, the algorithm is complex, which is difficult for implementation. To reduce the complexity, this paper proposes the LDCB control strategy that is derived through linearizing conventional DCB controller. By deriving the differential functions of the DCB control algorithm, the small signal relationship between the input and output of DCB controller is explored. Furthermore, based on the relationship, the LDCB controller is formed through three parallel feed loops to the duty ratio. As a linear control approach, the achieved LDCB controller is greatly simplified for implementation. This not only saves the hardware cost, but also reduces the calculation lag, which provides potential to improve the switching frequency. Besides, since the LDCB controller shares the same small signal model as that of DCB controller, it achieves similar control loop bandwidth and transient performance. Effectiveness of the proposed LDCB control is verified by zero/pole plots, transient analyses and experimental results.
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.
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