October 11, 2010

Power Supply Efficiency and Power Factor: Regulations Update

The U.S. Environmental Protection Agency (EPA) has recently announced that effective December 31, 2010, external adapters will no longer be eligible for the Energy Star label. The main reason for this move is in 2008 a mandatory federal minimum efficiency standard went into effect for adapters, mandating basically the same Energy Star performance level.

Last month the ENERGY STAR also published its Draft 3 revision to the proposed criteria for LED lamps, which can be screw into standard lamp sockets to replace incandescent bulbs. To earn the ENERGY STAR logo the LED lamp should have power factor ≥ 0.70. Of course, Energy Star is a voluntary program. However, chances are their requirements will be eventually incorporated in a federal standard. Also, Europe already requires lighting PF>0.9. These developments will certainly cause LED lamps manufacturers to use active power factor correction (PFC) circuits for LED drive. Given the efficiency and size requirements, it's likely that the SMPS designers would also have to use other techniques such as bridgeless PFC rectifiers and synchronous rectification.