Brian T. Irving

Open-Loop Control Methods for Interleaved DCM/CCM Boundary Boost PFC Converters

Open-loop interleaving methods for PFC boost converters operating at the boundary of discontinuous-conduction mode and continuous-conduction mode with a master-slave relationship are analyzed. It is shown that the only method that results in stable operation is the synchronization of the slave converter to the turn-on instant of the master converter, where each converter operates with current-mode control. Effects of mismatched inductances, phase-shift error, switching-frequency limit, and valley switching on the quality of the input current are discussed in detail.

Analysis, design, and performance evaluation of droop current-sharing method

The droop current sharing method is analyzed, and a general design procedure is proposed. It is shown that the current-sharing accuracy of N+1 power supplies is a function of the output-voltage set-point accuracy, the slope of the output-voltage droop, and gains of the control loop. It was found that to achieve a current sharing accuracy of 10% the output voltage of the paralleled power supplies needs to be set within 0.35%. The accuracy of the design procedure was compared against measured results of three power supplies operating in parallel.

Effect of Valley Switching and Switching-Frequency Limitation on Line-Current Distortions of DCM/CCM Boundary Boost PFC Converters

A systematic analysis of line-current distortions of the discontinuous-conduction-mode and the continuous-conduction-mode boundary boost power factor correction converter due to valley switching (VS) and switching-frequency limitation, where VS is either maintained or lost after the onset of switching-frequency limitation, is provided. Closed-form expressions for the line current are derived. It is shown that if the switching frequency is limited and VS is not maintained, the line current is more distorted with voltage-mode control than with current-mode control. The effects of line-current distortions are demonstrated with both simulation and experimental results.

Review and Stability Analysis of PLL-Based Interleaving Control of DCM/CCM Boundary Boost PFC Converters

In this paper, a systematic review of phase-locked loop (PLL)-based closed-loop control methods for interleaved discontinuous conduction mode/continuous conduction mode (DCM/CCM) boundary boost power factor correction (PFC) converters is presented. A detailed analysis of the stability of the PLL with instant averaging filter is performed and verified by simulation. The stability of the PLL with instant averaging filter and with RC filter is compared by simulation. Based on the simulation results, it is concluded that the PLL-based closed-loop methods always provide stable operation, unlike the open-loop control methods, where the only method that results in stable operation is the slave synchronization to the turn- on instant of the master with current-mode control. It is also shown that the dynamic response of the PLL-based closed-loop methods with master-slave approach and democratic approach is almost identical. Experimental results obtained on a 300-W, universal input, 400-V output, interleaved DCM/CCM boundary boost PFC prototype circuit with a dedicated controller IC utilizing a democratic, PLL-based closed-loop method are also provided.

A comparative study of soft-switched CCM boost rectifiers and interleaved variable-frequency DCM boost rectifier

In this paper, three single-phase, high-power-factor rectifier implementations were evaluated on a comparative basis. Specifically, a zero-voltage-switching continuous-conduction-mode boost rectifier, a zero-current-zero-voltage-switching continuous-conduction-mode boost rectifier, and an interleaved variable-frequency discontinuous-conduction-mode boost rectifier were compared with respect to their efficiencies, compliance with the EN61000-3-2 specifications, complexity, and costs. The comparisons were done for the single-phase input voltage of 90 V/sub RMS/-264 V/sub RMS/ and for 0-1.2 kW output-power range.

Analysis, design, and performance evaluation of flying-capacitor passive lossless snubber applied to PFC boost converter

A boost converter which employs a flying-capacitor passive lossless snubber to reduce the losses caused by the reverse-recovery characteristic of the boost rectifier is described. The passive snubber consists of a snubber inductor, two snubber rectifiers, and a snubber capacitor. The losses are reduced by inserting a snubber inductor in the series path of the boost switch and the rectifier to control the di/dt rate of the rectifier during its turn-off. The snubber is analyzed and design guidelines are offered to achieve optimum performance. The proposed snubber is applied to a 500-W power factor corrected (PFC) boost converter which is designed to operate in the universal line range (90-264 V/sub RMS/). Performance evaluations of the proposed snubber are made and compared to the conventional boost converter with respect to efficiency and device temperature.

Analysis and design of self-oscillating flyback converter

The self-oscillating flyback converter is a popular circuit for cost-sensitive applications due to its simplicity and low component count. It is widely employed in mobile phone chargers and as the stand-by power source in off-line power supplies for data-processing equipment. However, the optimization of this circuit is almost exclusively performed by a cut-and-dry approach since its operation is generally not well understood. This paper presents a detailed steady-state analysis of the self-oscillating flyback converter along with its small-signal model. Design guidelines of the control circuit and loop compensation are presented and verified on an offline, stand-by, 5 V/2 A power supply.

Line current distortions of DCM/CCM boundary boost PFC converter

A systematic analysis of line current distortions of the DCM/CCM boundary boost PFC converter due to valley switching and switching-frequency limitation is provided. Closed form expressions for the line current are derived. It is shown that if the switching frequency is limited and valley switching is not maintained, the line current is more distorted with voltage mode control than with current mode control. The effects of line current distortions are demonstrated with both simulation and experimental results.

Digital implementation of a unity-power-factor constant-frequency DCM boost converter

A DSP implementation of digital control for constant-frequency, unity-power-factor, and discontinuous-conduction-mode boost rectifier is described. By employing variable-duty-cycle control, the power factor of over 0.99 is achieved in the entire universal line-voltage range (90-264 V). In addition, the transient response of the rectifier is optimized by utilizing a nonlinear PI-controller with anti windup that is independently optimized for U.S. line-voltage range (90-132 V) and for European line-voltage range (180-264 V) and by temporarily increasing the bandwidth of the control loop during transients. The performance of the proposed DSP control was verified on a 100-kHz, 400-W unity-power-factor rectifier prototype

On-the-Fly Topology-Morphing Control—Efficiency Optimization Method for LLC Resonant Converters Operating in Wide Input- and/or Output-Voltage Range

This paper presents a control method for efficiency improvement of the LLC resonant converter operating with a wide input-voltage and/or output-voltage range by means of topology morphing, i.e., changing of power converters topology to that which is the most optimal for given input-voltage and/or output-voltage conditions. The proposed on-the-fly topology-morphing control maintains a tight regulation of the output during the topology transitions so that topology transitions are made without noticeable output-voltage transients. The performance of the proposed topology morphing method is verified experimentally on an 800-W LLC dc/dc converter prototype designed for a 100-V to 400-V input-voltage range.