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Summary: Traditional multiple‐output AC‐DC power supply with power factor correction (PFC) function usually employs a two‐stage cascaded topology that is composed of prestage PFC converter and N independent poststage DC‐DC converters to achieve PFC and voltage or current regulation of N outputs. Hence, the conventional two‐stage cascaded multiple‐output AC‐DC power supply needs N + 1 magnetic components as power inductors or transformers and N + 1 controllers, which increases the cost and size of the multioutput converters. The conventional multiple‐string AC‐DC LED driving circuits usually employ a two‐stage topology to realize PFC and independent current regulation of each LED string. To address the issue of complexity, high cost, and large size of the two‐stage multistring LED driving circuit, a single‐stage triple‐output Cuk PFC converter is proposed by cascading boost converter and single‐inductor triple‐output buck converter with sharing main power switch in this paper. The topology operation principle, control strategy, design consideration, and operation characteristics of the proposed circuit are investigated in detail. With the switch sharing and inductor multiplexing technologies at the same time, the proposed converter utilizes only single‐stage converter to achieve PFC function, independent regulation of triple‐channel output current, and flicker‐free with low twice line frequency LED current ripple. The proposed converter is verified by a 50‐W experimental prototype of LED driver for triple string LEDs. The proposed converter only uses two power inductors and a set of controller to achieve greater than 0.945 PF, up to 90.5% efficiency, low LED current ripple, and independent current regulation for triple LED strings with different forward voltage, which may significantly reduce the cost and size of the traditional AC‐DC multistring LED driving circuit. [ABSTRACT FROM AUTHOR]

Power factor correction (PFC) converters have been frequently employed in various switching power supply devices to reduce input current harmonics. However, the PFC converter suffers from an obvious twice-line-frequency output voltage ripple due to the instantaneous power imbalance between constant output power and variable input power. Suppression of twice-line-frequency ripple usually can be realized by the post-stage DC-DC converter of the two-stage cascade PFC converter; however, the two-stage cascade PFC structure is challenging to realize high efficiency since the energy is transferred twice. To achieve high power factor, high efficiency, and low twice-line-frequency ripple, a hybrid quasi-single-stage (QSS) AC-DC converter is presented in this paper, which consists of a dual output hybrid Boost/Flyback PFC converter and a Buck ripple compensation circuit (RCC). The fundamental principles of the proposed converter and the critical conditions of operation mode transition are discussed in the paper. To confirm that the twice-line-frequency ripple is effectively suppressed, the small signal model of Buck RCC is built and analyzed. Moreover, the main characteristics, including operation mode transition angle, input current, power factor, and switching frequency of the proposed hybrid QSS AC-DC converter, are analyzed. By building a 120 W experimental prototype to validate the feasibility of the proposed hybrid QSS AC-DC converter, the experimental results show that the proposed converter can realize PFC function with high efficiency and extremely low twice-line-frequency output voltage ripple. [ABSTRACT FROM AUTHOR]

When the input inductor operates in discontinuous current mode (DCM), the Cuk converter can automatically achieve power factor correction (PFC) function with only a simple voltage mode control loop. However, the conventional Cuk PFC converter suffers from high intermediate capacitor voltage because of the lack of feedback of the intermediate capacitor voltage and relatively low power factor (PF). In this paper, a Cuk PFC converter using variable inductor which varies with the transient rectified input voltage is proposed to enhance the PF and reduce the intermediate capacitor voltage by injecting a controlled DC bias current into the auxiliary winding of the variable input inductor. The operating principles of the proposed Cuk PFC converter based on variable inductor are analyzed in detail, and the analysis of PF, the voltage of intermediate capacitor, and design considerations are provided. To verify the feasibility of the proposed scheme and compare the characteristics of both the traditional and proposed Cuk PFC converter, a 108W experimental prototype of the proposed converter is built and tested. The experimental results show that the proposed Cuk PFC converter can significantly enhance the PF, decrease the intermediate capacitor voltage, and increase efficiency compared with the traditional Cuk PFC converter. [ABSTRACT FROM AUTHOR]

A variable on‐time (VOT) control strategy for boundary conduction mode (BCM) single‐ended primary inductor converter (SEPIC) power factor correction (PFC) converter with high power factor (PF) and low total harmonic distortion (THD) is proposed. By utilising output voltage and input voltage to modulate the turn‐on time of the switch of BCM SEPIC PFC converter, the unity PF and lower THD can be achieved. The operating principles of the VOT controlled BCM SEPIC PFC converter are analysed. The experimental results based on 100 W prototype demonstrate that the PF and THD of proposed VOT controlled BCM SEPIC PFC converter are better than those of traditional BCM SEPIC PFC converter. [ABSTRACT FROM AUTHOR]

A peak current control technique for a flyback power factor correction (PFC) converter operating in critical conduction mode (CRM) is proposed. By using the square of the line voltage to compensate the peak current envelope of the primary current, the input current distortion of the traditional peak current‐controlled CRM flyback PFC converter can be eliminated, and the unity power factor and low total harmonic distortion (THD) can be obtained. The operating principles and characteristics of the proposed peak current‐controlled CRM flyback PFC converter are analysed. Experimental results of a 30 W prototype show that the power factor and THD of the proposed peak current‐controlled CRM flyback PFC converter are better than those of the traditional peak current‐controlled CRM flyback PFC converter. [ABSTRACT FROM AUTHOR]

A flicker‐free transformerless light emitting diode (LED) driving circuit based on a quadratic buck power factor correction (PFC) converter is proposed. It combines a cascaded input buck PFC converter and an output buck dc–dc converter with a single switch. The proposed LED driving circuit can not only achieve high PFC to comply with the EN61000‐3‐2 standard and low output voltage without a high step‐down transformer, but also reduces second‐order line frequency current ripple flowing through the LED to eliminate light flicker of the LED. Experimental results of a 7 W prototype are presented to verify the analysis results of the proposed converter. [ABSTRACT FROM AUTHOR]