Analysis, design and implementation of a zero voltage switching two‐switch CCM flyback converter

Abstract

This study presents a two-switch continuous conduction mode pulse width modulation flyback converter that employs an LC snubber circuit. The snubber circuit is used to achieve zero voltage switching (ZVS) operation for the main switches during the turn-off transition and soft switching for power diodes. With the proposed LC snubber, the magnetic energy in the transformer leakage inductance can be fully recycled and transferred to the input side. The resonant circuit consists of a resonant inductor, a resonant capacitor and two diodes. The operating principles, theoretical analysis and the design methodology of ZVS two-switch continuous conduction mode (CCM) flyback converter are presented. A 200 W (50 V/4 A) laboratory prototype of the proposed converter, operating at a switching frequency of 300 kHz is built to verify the theoretical analysis. At full load the efficiency is 94%. 1 Introduction Low element count, isolated, design simplicity and simple control circuit are advantages of the flyback converter. However the main drawbacks of the single switch flyback converter are: † The high voltage spike on switch at turn-off state due to resonance of the transformer leakage inductance and the switch output capacitance that causes losses and electromagnetic interference (EMI) noise. † The high voltage stress on switch at turn off, that is the sum of input voltage, reflected output voltage and voltage spike that cause selecting the high voltage switch, increases conduction losses. † The switch is operated at hard switching. † The rectifier diode is operated at hard switching and the reverse recovery loss is high.

Analysis and design of two‐switch flyback converter with double passive lossless snubber

“…To have transformer optimal design, the Mn-Zn PC47-EI33/29/13 ferrite core from TDK is selected based on the area product technique in [33]. Based on (20), the L m (min) = 332 μH is calculated. To have CCM operation in 10% to full loads, the L m = 500 μH is selected.…”

“…From the results in Table 3, it can be noticed that the proposed converter has higher efficiency. The converter used in [20] has lower auxiliary component counts than the proposed converter, but it works under hard switching at light load. The other topologies make it a more complicated auxiliary circuit than the TSFC‐DPLS.…”

“…However, the circuit implementation is complex, and the ZCS condition for the auxiliary switch is poor at light load. In [20], a simple lossless snubber is introduced to prepare the ZVS turn off for power switches. However, the TSFC upper switch is operated under hard switching at light load.…”

Performance‐recovery proportional‐type output‐voltage tracking algorithm of three‐phase inverter for uninterruptible power supply applications

“…Power converters such as AC/DC, DC/AC, and DC/DC converters have various industrial applications that require efficient, highquality power [1][2][3][4][5]. In particular, a three-phase uninterruptible power supply (UPS) plays a pivotal role in securing safety in case of a sudden power failure.…”

Impact of Transformer Design on Flyback Converter Voltage Spikes

“…It causes increase of voltage spikes generated during the switch commutation. The energy consumed for generation of voltage spikes lowers the efficiency of flyback converter [1]- [8]. The overvoltage clamp circuits have to be employed for spike suppression to avoid the breakdown of switch transistors [3], [5]- [6].…”