Sampled-Data Modeling for PCM and ZVS Controlled Critical Conduction Mode (CrCM) Active Clamp Flyback (ACF) Converter at Variable Switching Frequency

This paper proposes an AC/DC single-stage structure by integrating a boost topology and an active clamp flyback (ACF) circuit with power-factor-correction (PFC) function. The PFC function can be achieved by controlling a boost PFC topology operated in the discontinuous conduction mode. With the coordination of active clamping components, a resonant technique is obtained and zero-voltage-switching (ZVS) can be achieved. The proposed converter is combined with the advantages of: (1) compared with two-stage circuit, a single stage circuit decreases the component of the main circuit and reduces the complexity of the control circuit; (2) a boost topology with PFC function operated in discontinuous conduction mode can be accomplished without adding any current detecting technique or detecting input signal; (3) by using the inductor from the PFC stage, ZVS function can be achieved without any additional inductor; (4) the increment of switching frequency facilitates the optimization of power density; (5) the conducting loss at the secondary side can be reduced by adding the synchronous rectification; (6) in this proposed scheme, the dual transformers with series-parallel connection are utilized, the current at the secondary side can be shared for lowering the conduction loss of the synchronous transistors. Finally, a prototype converter with AC 110 V input and DC 19 V/6.32 A (120 W) output under 300 kHz switching frequency is implemented. The efficiency of the proposed converter reaches 88.20% and 0.984 power factor in full load condition.

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Comparison of Dc-Dc SEPIC, CUK and Flyback Converters Based LED Drivers

Light & Engineering ◽

10.33383/2018-70 ◽

2020 ◽

pp. 99-107

Author(s):

Erdal Sehirli

Keyword(s):

Integrated Circuit ◽

Closed Loop ◽

Input Voltage ◽

Open Loop ◽

Current Sensor ◽

Switching Frequency ◽

Led Driver ◽

Advantages And Disadvantages ◽

Led Drivers ◽

Conduction Mode

This paper presents the comparison of LED driver topologies that include SEPIC, CUK and FLYBACK DC-DC converters. Both topologies are designed for 8W power and operated in discontinuous conduction mode (DCM) with 88 kHz switching frequency. Furthermore, inductors of SEPIC and CUK converters are wounded as coupled. Applications are realized by using SG3524 integrated circuit for open loop and PIC16F877 microcontroller for closed loop. Besides, ACS712 current sensor used to limit maximum LED current for closed loop applications. Finally, SEPIC, CUK and FLYBACK DC-DC LED drivers are compared with respect to LED current, LED voltage, input voltage and current. Also, advantages and disadvantages of all topologies are concluded.

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Active Clamp Boost Converter with Blanking Time Tuning Considered

Applied Sciences ◽

10.3390/app11020860 ◽

2021 ◽

Vol 11 (2) ◽

pp. 860

Author(s):

Yeu-Torng Yau ◽

Kuo-Ing Hwu ◽

Yu-Kun Tai

Keyword(s):

Boost Converter ◽

Zero Current Switching ◽

Active Clamp ◽

Overall Efficiency ◽

Auto Tuning ◽

Voltage Spike ◽

Resonant Inductor ◽

Off Time ◽

Conduction Mode ◽

Time Point

An active clamp boost converter with blanking time auto-tuned is presented herein, and this is implemented by an additional auxiliary switch, an additional resonant inductor, and an additional active clamp capacitor as compared with the conventional boost converter. In this structure, both the main and auxiliary switches have zero voltage switching (ZVS) turn-on as well as the output diode has zero current switching (ZCS) turn-off, causing the overall efficiency of the converter to be upgraded. Moreover, as the active clamp circuit is adopted, the voltage spike on the main switch can be suppressed to some extent whereas, because of this structure, although the input inductor is designed in the continuous conduction mode (CCM), the output diode can operate with ZCS turn-off, leading to the resonant inductor operating in the discontinuous conduction mode (DCM), hence there is no reverse recovery current during the turn-off period of the output diode. Furthermore, unlike the existing soft switching circuits, the auto-tuning technique based on a given look-up table is added to adjust the cut-off time point of the auxiliary switch to reduce the current flowing through the output diode, so that the overall efficiency is upgraded further. In this paper, basic operating principles, mathematic deductions, potential designs, and some experimental results are given. To sum up, the novelty of this paper is ZCS turn-off of the output diode, DCM operation of the resonant inductor, and auto-tuning of cut-off time point of the auxiliary switch. In addition, the efficiency of the proposed converter can be up to 96.9%.

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Study on a Novel High-Efficiency Bridgeless PFC Converter

Journal of Applied Mathematics ◽

10.1155/2014/514281 ◽

2014 ◽

Vol 2014 ◽

pp. 1-8

Author(s):

Cao Taiqiang ◽

Chen Zhangyong ◽

Wang Jun ◽

Sun Zhang ◽

Luo Qian ◽

...

Keyword(s):

Steady State ◽

High Efficiency ◽

Control Policy ◽

Switching Frequency ◽

Fast Recovery ◽

Zero Current Switching ◽

Zero Current ◽

The One ◽

Gain Characteristic ◽

Conduction Mode

In order to implement a high-efficiency bridgeless power factor correction converter, a new topology and operation principles of continuous conduction mode (CCM) and DC steady-state character of the converter are analyzed, which show that the converter not only has bipolar-gain characteristic but also has the same characteristic as the traditional Boost converter, while the voltage transfer ratio is not related with the resonant branch parameters and switching frequency. Based on the above topology, a novel bridgeless Bipolar-Gain Pseudo-Boost PFC converter is proposed. With this converter, the diode rectifier bridge of traditional AC-DC converter is eliminated, and zero-current switching of fast recovery diode is achieved. Thus, the efficiency is improved. Next, we also propose the one-cycle control policy of this converter. Finally, experiments are provided to verify the accuracy and feasibility of the proposed converter.

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