1428 IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 24, NO. 5, MAY2009 Letters Phase Feedforward Control for Single-Phase Boost-Type SMR Hung-Chi Chen, Member, IEEE, Heng-Yi Li, and Ru-Shiuan Yang Abstract—In this letter, a phase feedforward control (PFFC) for a single-phase boost-type switching-mode rectifier is addressed. In the conventional input voltage feedforward loop, the feedforward signal is fixed regardless of the load level. The proposed phase feedforward signal adjusts according to the load level without sens- ing the load current. The simulated and experimental results also demonstrate the effectiveness of proposed PFFC. Compared to a conventional feedforward signal, relatively small proportional gain can be used in the proposed PFFC without loss of current tracking performance, which would also increase the overall system immu- nity against noise. Index Terms—AC–DC power conversion. I. INTRODUCTION T HE USE of switching-mode rectifier (SMR) with power factor correction (PFC) function is an effective mean to perform the qualified ac/dc conversion. In general, the PFC function includes the input current waveform shaping and the output dc voltage regulation. The boost-type SMRs are the most popular circuit topology among all the others for their continuous current in the front-end inductors [1]. In a boost-type SMR, large-scale input voltage variation can be seen as a disturbance. It follows that input voltage feedforward loops [2]–[6] for boost-type SMRs can be found often in the literature. The concept of the input voltage feedforward loop is to gen- erate a “nominal duty ratio pattern” from the rectified input voltage. This nominal duty ratio pattern effectively produces an average voltage across the switch equal to the instantaneous rectified input voltage. However, it is noted that this nominal duty ratio pattern is fixed regardless of load condition [3]–[5], i.e., the conventional input feedforward signal at heavy load is the same as that at light load. It implies that the performance of current shaping function would be degraded at heavy load. To overcome it, several load feedforward loops without sensing load current had been proposed in [6], [7] where the load condi- tion is estimated from the reference current. The proposed phase feedforward control (PFFC) can be regarded as a combination of input voltage feedforward control and load feedforward control. In PFFC, the original phase feedforward signal is also gener- ated from the rectified input voltage and then delayed through Manuscript received August 3, 2008; revised November 11, 2008, and January 6, 2009. Current version published May 15, 2009. This work was supported by the National Science Council in Taiwan under Grant NSC97-2221-E-009-184. Recommended for publication by Associate Editor J. Jatskevich. The authors are with the Department of Electrical and Control Engineer- ing (ECE), National Chiao Tung University (NCTU), Hsinchu 30010, Taiwan (e-mail: hcchen@cn.nctu.edu.tw; hyli@iner.gov.tw; rushiuan@gmail.com). Digital Object Identifier 10.1109/TPEL.2009.2013953 Fig. 1. Power circuit of the boost-type SMR. phase shifter according to the current reference magnitude. The larger the current magnitude is, the more the shifting phase of phase feedforward signal can be found. Compared to the conven- tional input voltage feedforward control, the proposed PFFC is able to adjust the feedforward signal according to the load level and relatively small proportional gain can be used to yield the desired current tracking performances and increase the overall system immunity against noise. From the viewpoint of implementation, the proposed PFFC can also be seen as a combination of a phase shifter with varying phase and two “fixed gain” blocks. It is well-known that imple- menting a phase shifter with varying phase in analog circuit is significantly harder than that in a digital system [like DSP/field- programmable gate array (FPGA)]. Therefore, there is near-zero complexity added to the digital implementation of PFFC. After the development of PFFC, we also find that the proposed PFFC can be seen as various implementations of the “full feedforward control,” and therefore, the performance improvement of PFFC is limited compared to [7]. However, implementing “full feedforward control” in analog circuits is easier than that in a digital system due to its calculation load of current loop, such as the PI current controller and derivative of the reference current. Therefore, “full feedforward control” is preferred in an analog circuit and the proposed PFFC is suitable for a digital PFC controller. II. CONVENTIONAL FEEDFORWARD CONTROL Power circuit configuration of a boost-type SMR is shown in Fig. 1. The circuit mainly consists of a diode bridge rectifier and a boost-type dc/dc converter. The input voltage v s can be ex- pressed by ˆ V s sin(2πf in t), where f in is the input line frequency. To simplify the analysis, some assumptions are made. 1) The circuit components are lossless and the circuit in- cludes a reasonable bulk capacitor C d . 2) The switching frequency f tri is significantly higher than the line frequency f in . 0885-8993/$25.00 © 2009 IEEE