Single-stage flyback AC-DC converters of high energy efficiency for commercial LED dimming systems

Light-emitting diodes (LEDs) have largely replaced conventional light circuits, and have been applied in household lighting, smart lighting, and commercial lighting systems. LED driver structures can be divided into single-stage or double-stage power management structures. Previously, systems with a single-stage power management structure, which featured a fixed-frequency structure, were commonly used for low-power systems, whereas those with a double-stage power management structure were regularly used for high-power commercial dimming systems. However, the use of two-stage power management structures is generally not recommended because they have several drawbacks, including poor power factors (PFs) under the all kinds of load condition, larger output power range, more expensive component costs, requiring extensive circuit sizes, and complex dimming systems. To solve these problems, this study proposed a single-stage flyback AC-DC converter for commercial LED dimming systems; this system structure replaces both single-stage and double-stage power management structures and ameliorates load efficiencies under light and heavy loads, enhances power factors, lowers total harmonic distortion, has a simple structure, and is cheap and easy to commercialize. To verify the feasibility of this structure in replacing existing structures, simulations and experiments were performed in commercial areas that required T8-LED 16.8 W converters per ping. Measured data showed a dimming range from of 6.5% load to 100% full load, a load efficiency of 88.51% at full load, a maximum power factor of 99.67%, and an overall system efficiency that satisfied Energy Star standards. Therefore, the converter proposed in this study can be used for LED lighting.