Accurate mode boundary detection in digitally controlled boost power factor correction rectifiers

Abstract

This paper presents an accurate mode boundary detection technique for digitally controlled boost power factor correction (PFC) rectifiers. Auto-tuning of the current and voltage control loops as well as estimation of power-stage parameters L and C are accomplished using sinusoidal perturbations injected into the control loops. The estimated L value acquired by this perturbation based tuning process is used to improve the detection of the boundary between continuous conduction mode (CCM) and discontinuous conduction mode (DCM) in the presence of inductance tolerance, thereby minimizing the mode transition effects and reducing the input current harmonic distortion. The proposed approach is verified by experimental results on a 300 W digitally controlled boost PFC rectifier prototype.

Autotuning of Digitally Controlled Boost Power Factor Correction Rectifiers

“…Furthermore, when the system operates at intermediate loads, the actual duty cycle command changes smoothly across the CCM/DCM boundary, without undesirable transients. In CCM and DCM, the ideal duty cycle commands can be represented as [18] …”

“…The estimated L value, acquired by the current loop tuning process, is used for the accurate mode boundary detection in combination with the duty ratio command feedforward technique [17] such that the two-mode current loop compensator, which is designed separately for CCM and DCM to maintain the desired stability margins in both modes, switches its parameters according to the operating mode (CCM/DCM) determined by the boundary detection, as depicted in Fig. 1(b) [18]. Since this approach is based on the perturbation injection method, tuning can be activated at start-up or on command to avoid any undesirable effects of the perturbation signal in normal operation.…”

Modeling and Control of the Distributed Power Converters in a Standalone DC Microgrid

“…Whereas, the outer loop T v (s) is compensated using the same G co (s). The detection of the conduction mode is implemented using the method in [20]. It is a common practice to assume a resistive load in the control design of switching regulators.…”