Hybrid-switching asymmetrical half-bridge flyback DC-DC converter
This paper proposes a hybrid-switching technique for asymmetrical half-bridge flyback converter. In this topology, the duty loss can be minimized because the active switches can achieve zero-voltage-switching (ZVS) and the output diode can be turned off at zero current, which result in higher efficiency, higher power density and universal input voltage range (90-264V). Moreover, this technique doesn't require any addition of components into the original topology and still employ the fixed frequency PWM, therefore the control method is simple and straightforward, while still being highly reliable.
Resonant Asymmetrical Half-Bridge Flyback Converter
The active clamp flyback (ACF) converter is gradually becoming popular in the application field of low or medium output power range due to its advantage of soft switching and high conversion efficiency. An asymmetric half-bridge (AHB) flyback converter has been proposed in previous studies. The main advantages of the AHB flyback are the same number of components as the ACF converter and the soft switching technique. In this paper, an AHB flyback converter with constant off-time (COT) plus pulse frequency modulation (PFM) is proposed, so that the resonant time is not affected by the input voltage and load, and can achieve a wide range of zero voltage switching (ZVS) operating range. Compared to pulse width modulation (PWM), the PFM control with COT can make the system more stable. Finally, a prototype circuit with a specification input of 48 V to an output of 2.5 V/8 A is made for verification.
Characterization of asymmetrical half bridge flyback converter
Flyback derived converters are attractive because of their simple capacitive output filter when compared with other converters used in multiple-output or cost-sensitive applications. This paper analyzes the detailed circuit behavior of the asymmetrical half bridge flyback converter. Several practical issues, including the specific relationships between the duty cycle and the different types of energy in the energy-storage elements, and the zero voltage switching (ZVS) conditions of the power switches have been thoroughly examined. Mathematical equations have also been given. A 5 V/20 A prototype has been built to verify the analytical results.