Battery chargers get faster and smaller

SWITZERLAND: STMicroelectronics' new family of Field-Effect Rectifier diodes (FERD) offers a unique trade-off between low forward voltage drop (VF) and low leakage current (IR) that allows designers of equipment such as battery chargers and notebook adaptors to meet the most stringent energy-efficiency standard requirements without the expense of using synchronous rectification techniques.

Standards such as Energy Star 6.0 test the limit of what can be achieved with conventional Schottky diodes in battery chargers and notebook adaptors. Synchronous rectification provides superior performance but at significantly greater cost. The ST FERD family provides an attractive alternative as it meets the efficiency levels required by the energy-savings standards applicable to off-line Switch Mode Power Supplies while costing about 30% less than a synchronous rectification kit.

Available in the ranges from 15A to 2x30A and from 45V to 60V, the FERD diodes are based on a patented ST technology that achieves the best-in-class VF/IR for a given silicon surface area. For example, a 30A device using FERD technology features a forward voltage drop reduced by about 140mV compared to a conventional 30A Schottky diode, without increasing the leakage current.

With its lower forward voltage drop and better managed leakage current, the ST technology increases the current that can flow for a given package power-dissipation capability. Benefits include faster charging of smart phones and tablets, reduced notebook-charger size and weight, and increased lifetime of the equipment as the FERD diodes operate at lower temperature