Abstract
This paper presents an Optimized Sensorless Charge Balance (OSCB) controller based on a damped current model for flyback converter operating in Discontinuous Conduction Mode (DCM). By solving total differential equations of non-ideal transformer currents, the damped current model is derived with consideration of parasitics, leakage inductance of transformer, and the Resistor-Capacitor-Diode (RCD) snubber circuit. Based on the proposed model, current observation and control algorithms of the Sensorless Charge Balance (SCB) controller are optimized, which forms the OSCB control strategy. The average current damping is considered in the equivalent discrete-time small signal model. Furthermore, frequency analyses show that OSCB controller achieves higher closed-loop bandwidth and lower overshoot than a SCB controller, which indicates an improved transient performance. Finally, both OSCB and conventional SCB controllers are experimentally evaluated on a flyback converter prototype.
Highlights
Flyback converters are widely used in industrial applications, since they make it possible to reduce the component count, provide isolation, and achieve good control performance [1,2,3]
Since a flyback converter operating in Discontinuous Conduction Mode (DCM) can be considered as a current source that is easy to control, it is widely used in PV-AC module and Power Factor Correction (PFC)
An Optimized Sensorless Charge Balance (OSCB) controller based on a damped current model is proposed for flyback converter operating in DCM
Summary
Flyback converters are widely used in industrial applications, since they make it possible to reduce the component count, provide isolation, and achieve good control performance [1,2,3]. Sensorless Charge Balance (SCB) controllers are applied to different converters operating in DCM This strategy regulates the output voltage by controlling charge current of output capacitor, and it can achieve a fast transient response without current sensing [20,21]. An Optimized Sensorless Charge Balance (OSCB) controller based on a damped current model is proposed for flyback converter operating in DCM. Analyses of the small signal models indicate that OSCB controller achieves higher closed-loop bandwidth and lower overshoot than that of SCB controller. Both accuracy of the damped current model and the effectiveness of the OSCB controller are experimentally verified on a flyback converter prototype.
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