A multimode digital control scheme for boost PFC with higher efficiency and power factor at light load

In this paper, a high power factor and high efficiency PFC circuit for charging electric power to an energy management system in small-sized ship is proposed. In order to achieve high power factor and high efficiency, the continuous conduction mode suitable for a large capacity circuit among active power factor correction methods which can realize power factor correction and power conversion with one converter is adopted. In addition, GaN HEMT MOSFET (Gallium Nitride High Electron Mobility Transistor) and SiC-SBD (Schottky Barrier Diode), which are called as wide band-gap semiconductors, have been applied to a PFC boost converter in order to demonstrate excellent performance such as circuit's efficiency and power factor. To verify the validity of a proposed circuit, a 3kW class circuit was designed and tested for performance. Experiments have shown that the overall efficiency and power factor of the system have been improved when wide band-gap semiconductors have been applied to a proposed circuit than silicon type semiconductors. The results show that efficiency and power factor of a proposed circuit have been verified by achieving a maximum efficiency of 99.2% and a maximum power factor of 0.99.

This paper proposes a leading phase current reduction (LPCR) technique in a continuous conduction mode (CCM) boost power factor correction (PFC) for light load power factor (PF) improvement. The proposed LPCR technique provides the corrected average inductor current reference and the modified duty ratio feed-forward (MDFF) technique which can cancel the effect of the phase lead currents resulting from the EMI filter and input capacitor. Moreover, the proposed LPCR also provides the optimal dead-zone from the corrected current reference and MDFF. Therefore, the proposed LPCR can improve the power quality and efficiency not only in high AC line voltage range but also in extreme light load conditions. The principle and analysis of the proposed LPCR are presented, and the performance and feasibility are verified by experimental results from 230Vrms input and 750W–400V output laboratory prototype.

The paper proposes a digital based control method which can be used on power factor correction (PFC) circuit to improve converter power factor (P.F.) at light load conditions. A major contributor to a non-unity P.F. is the need of input capacitor to alleviate differential mode electromagnetic interference (EMI) conducted back to the AC source. At light load, the overall system impedance (EMI filter and PFC circuit) becomes more capacitive which leads to large phase difference between voltage and current and results in a low power factor. A digital phase locked loop base vector cancellation (DPLLVC) technique is proposed in this digest to improve the light load P.F. This technique improves upon the previously proposed Phase Leading Filter Current Compensation (PLFCC) technique as it no longer requires a derivative of the input voltage, which can add noise. In addition to DPLLVC technique, a tracking error compensation scheme is added to further improve the PF under light loads. The scheme is tested and results reported on a 3.3KW Gallium-Nitride (GaN) based Totem Pole bridgeless PFC (TTPL PFC) design. With DPLLVC and tracking error compensation techniques, over 37% P.F. improvement is observed when compared to the results with PLFCC technique at 2% load.

Single-phase grid-tied microinverters are required to operate over a wide power range in photovoltaic applications. It is desirable to improve the efficiency over the entire power range without extra cost. This article proposes a variable switching frequency (VSF) multimode control scheme to optimize the device losses at each operating point for a single-phase T-type hybrid-bridge inverter. The proposed optimal control scheme is devised based on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V–I</i> plane analysis and can therefore be applied in both unity power factor (PF) and nonunity PF operations. With reasonable simplifications and curve fitting, neither a multidimensional lookup table nor excessive computational burden is required for the controller. A 1-kW prototype is built to verify the proposed optimal VSF scheme and compare it with the conventional constant switching frequency (CSF) scheme. The experimental results show that the proposed optimal VSF scheme can achieve higher efficiency than the CSF scheme over a wide power range. The weighted average efficiency of the proposed scheme is improved by a maximum of 1.3% in unity PF operation and 0.63% in nonunity PF operation.

In this paper, a series-capacitor-based interleaving buck power factor correction (PFC) converter is proposed, the intermediate energy storage capacitance of which is operated at discontinuous capacitor voltage mode (DCVM), and automatic power factor (PF) correction for this converter is obtained. Moreover, the voltage across the series capacitor of the proposed PFC converter is clamped at the input voltage, and thus peak voltage stress existed in the traditional DCVM buck PFC could be relieved. By effectively regulating the charge/discharge time for the series capacitor, ultrahigh step-down conversion ratio of the proposed converter is achieved, the conversion ratio of which is independent of the duty cycle and only related to the switching frequency and circuit parameters. Therefore, high PF can be obtained due to very narrow deadtime of the input current. Meanwhile, the proposed PFC converter can realize the soft turn- on of part power switch and soft turn- off of part power diodes. In addition, comparing with the traditional discontinuous inductor current mode PFC, the input current of the proposed PFC converter is continuous so that the peak value and root-mean-square value of input current can be reduced. The operational principle, performance analysis, and parameter design principle are given in this paper. The analysis results show that the PF and total harmonic distortion are also independent of the duty cycle. Finally, a 220-Vac input, 60 W/15 V output experimental prototype is built to verify the validity of the theoretical analysis.

Nowadays in an electrical power system various DC-to-DC converters are widely used due to their variable range in output and efficient power conversion, but they draw current in form of pulses making the power factor of the system poor and Total Harmonic Distortion(THD) very high. For linear load, the correction of power factor can be done via passive load but with non-linear load, the distorted current line needs to be corrected with various control schemes. In this paper popular topology for Active Power Factor Correction(APFC) i.e boost converter has been studied in a power system under distorted main supply voltage, needing higher current compensation. A method for elimination of harmonic distortion from the input supply voltage is done with the means of SOGI-PLL, providing an inexpensive solution. This paper discusses all the steps for the straightforward control design of the PFC+PLL along with design criteria and calculations. The design and simulation of the boost converter with power factor correction in continuous conduction mode are modelled using MATLAB/SIMULINK software.

In this paper, a coupled-inductor Sepic-type power factor corrector (PFC) with soft-switching is proposed to drive high brightness LED panel. The two inductors in the Sepic-type PFC are magnetically coupled to lower volume. A soft-switching cell composed of an active switch, a resonant inductor and a resonant capacitor is embedded into the PFC to obtain zero-voltage switching (ZVS) feature so as to promote converter efficiency. The proposed PFC is suitable for universal-line input 85Vac ~ 265 Vac for low output voltage applications. Over the input voltage range, it can achieve high efficiency and high power factor. To drive LED panel, a digitalized feedback control loop is adopted to accomplish current sharing, voltage regulating, and dimming feature. A prototype is designed, analyzed and implemented to demonstrate the feasibility of the Sepic-type PFC. Simulation results and hardware measurements have illustrated that the proposed PFC driving LED panel can achieve high power factor, improve efficiency, and accomplish current sharing and dimming feature.

Power factor correction (PFC) is an effective method to reduce harmonic current in power grid. A novel boost high power factor rectifier with UCC28019 is proposed. The UCC28019 8-pin active Power Factor Correction controller uses the boost topology operating in continuous conduction mode (CCM). It does not need multipliers. The use of the IC will make the PFC circuit design easily and the volume of the rectifier small. The fundamental principle of the proposed rectifier is introduced. Its sections such as current loop and over-current protection, voltage loop and over-voltage protection, and so on, are analyzed and designed respectively in detail. Experimental results of the designed 350W prototype prove that the boost high power factor rectifier is rational and reliable, its power factor can reach 0.992, and its application prospect is wide.

Based on the power circuit topology structure of the four-phase interleaved power factor corrector (PFC) that works in continuous conduction mode (CCM), this paper establishes its EL (Euler-Lagrange) mathematical model. The passivity of the four-phase interleaved PFC is proved and the passivity-based controller using the state variables feedback and damping injection method is designed. The proposed control scheme which is easy to control without proportion integral controller has strong robustness on disturbance of input voltage, load and parameters of system components. Especially in wide-range load condition applications, the dynamic response of input current is fast and the output voltage almost has no changes, therefore, the power factor correction and constant DC output functions of PFC are realized. Meanwhile, multi-phase interleaved PFC employing passivity-based controller has a good effect on current sharing. Simulation results prove that the passivity-based controller has a superior performance and the method is feasible.

Wireless power transfer (WPT) technology has been a research and industrial hotspot with applications in many areas, such as wireless electric vehicle charging system that requires high power, high efficiency, and high power factor (PF). Usually, the power is drawn from a 50/60 Hz single-phase or three-phase ac power source. For a high power application, a three-phase ac source is commonly used. In this paper, a three-phase single-stage WPT resonant converter with PF correction (PFC) and bus voltage control is proposed to improve efficiency and power quality of three-phase input and reduce production cost and complexity for a high power WPT system. A T-type topology is applied as the common part to perform both the PFC and dc–dc WPT functionalities simultaneously. The proposed converter is much more advantageous than a conventional three-phase two-stage WPT converter with individual PF corrector. In addition, three-phase single-stage topologies have better power quality than single-phase single-stage topologies because zero-sequence components can be naturally eliminated.

When the on-time is constant during a line cycle, the input power factor (PF) of critical conduction mode buck-buck/boost power factor correction converter is low. A variable on-time control (VOTC) scheme is put forward in this paper to realize high PF. By utilizing the input and output voltage to modulate the on-time of buck and buck/boost switch, we can realize high-input PF with low-total harmonic distortion within the universal input voltage range. The operating principles and the comparative analysis of the converter with conventional constant on-time control (COTC) and VOTC are analyzed. The proposed control scheme achieves high PF and efficiency as compared with the COTC. A 100-W prototype was built up to verify the effectiveness of the proposed control strategy.

This paper proposes an improved modulated carrier control method for a continuous conduction mode (CCM) power factor correction (PFC) boost converter. The proposed method allows precise sinusoidal line current shaping for a boost PFC converter operating in CCM. This is accomplished by simply comparing the compensated modulated carrier signal with the switch current information, such that the current loop compensation is eliminated and multiplier is not required. Also, the proposed control method overcomes the instability problem of conventional modulated carrier control around the zero crossings of the line voltage at light load. The performance of the proposed control method is experimentally verified on a 300 W PFC converter.

Improving of power factor and reducing harmonic distortion in electrical instruments are needed. An interleave boost converter is used for an active PFC (Power Factor Correction). In the interleave PFC boost converter, if a duty ratio, a load resistance and an input voltage are changed, the dynamic characteristics are varied greatly. This is the prime reason of difficulty of controlling the interleave PFC boost converter. In this paper, the robust digital controller using an A2DOF (Approximate 2-Degree-Of-Freedom) method for suppressing the variation of output voltage at a load sudden change with high power factor and low harmonic is proposed. Experimental studies using a micro-processor for controller demonstrate that this type of digital controller is effective to improve power factor and to suppress output voltage variation.

In this paper, we design and develop a high power factor, high efficiency two-stage AC - DC power converter. This paper proposes a two-stage AC - DC power converter. The first stage is boost active power factor correction circuit. The latter stage is near constant frequency LLC resonant converter. In addition to traditional LLC high efficiency advantages, light-load conversion efficiency of this power converter can be improved. And it possesses high power factor and near constant frequency operating characteristics, can significantly reduce the electromagnetic interference. This paper first discusses the main structure and control manner of power factor correction circuit. And then by the LLC resonant converter equivalent model proceed to circuit analysis to determine the important parameters of the converter circuit elements. Then design a variable frequency resonant tank. The resonant frequency can change automatically on the basis of the load to reach near constant frequency operation and a purpose of high efficiency. Finally, actually design and produce an AC – DC power converter with output of 190W to verify the characteristics and feasibility of this converter. The experimental results show that in a very light load (9.5 W) the efficiency is as high as 81%, the highest efficiency of 88% (90 W). Full load efficiency is 87%. At 19 W ~ 190 W power changes, the operating frequency change is only 0.4 kHz (AC 110 V) and 0.3 kHz (AC 220 V).

To reduce total harmonic distortion (THD) and improve the power factor (PF) of a boost power factor correction (PFC) converter, here, the authors propose a non‐linear control algorithm that includes the feedforward correction (FC) algorithm in the continuous conduction mode (CCM) and the non‐linear frequency variation (FV) algorithm in the mixed conduction mode (MCM). The proposed FC algorithm achieves current out of distortion through zero crossing with a lower current loop bandwidth. The proposed non‐linear FV algorithm achieves high PF and low THD under minimal load conditions. The non‐linear FV algorithm comprises a third harmonic extraction algorithm, a harmonic control loop for reducing THD and a frequency production algorithm. By using this non‐linear FV algorithm, the inductor size is reduced, which leads to lower cost and also achieves better THD and PF. The proposed algorithms are verified experimentally in terms of current tracking, current THD, PF, heating and loss on a 2000‐W boost PFC converter hardware prototype.