Current basic light-emitting diode ( LED ) driver lighting applications are relatively simple to design, but if other functions such as phase-controlled dimming and power factor correction (PFC) are required, the design becomes complicated. Non-dimming LED drivers without power factor correction typically include an off-line switching power supply for regulating the output at a constant current.
This is not the same as the standard off-line switching power supplies, such as those commonly used in AC-to-DC (AC/DC) adapters. This type of design is based on standard switched power supply (SMPS) circuit topologies such as buck, boost, and flyback converters.
New standard drives LED dimming technology breakthrough
On December 3, 2009, the US Department of Energy (DOE) released the final version of the "Integrated LED Light Energy Star Certification" that requires a household LED driver with a power factor greater than 0.7. Industrial application requirements are expected to be above 0.9. At present, many products on the market cannot meet these requirements, so the future must be more advanced design. There are two basic power factor correction methods: low cost passive power factor correction (passive PFC) and active power factor correction (active PFC). The former is simpler and the latter is more complicated, but both methods require other circuits to be installed at the front end of the converter.
Before delving into these methods, it should be mentioned that in order to meet ENERGY STAR standards, LED drivers must also have dimming capabilities.
This usually means that dimming can be done with existing wall dimmers based on the phase control principle of operation, which was originally designed for purely resistive incandescent lamps. While other dimming methods such as linear 0 to 10 volt dimming, or digitally addressed lighting interface (DALI) may also meet the requirements, they are likely to be limited to high-end industrial LED drivers. Phase-controlled dimmers are by far the most widely used dimmers, and this is clearly an important advantage for using them to achieve dimming for LEDs. Since there are a large number of low-cost dimmers based on triacs on the market, LED drivers are not guaranteed to be compatible with all types of dimmers, especially in many dimmers. Design and limited performance. To this end, the ENERGY STAR program requires LED driver manufacturers to clearly indicate on their website which dimmers are compatible with the product.
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