Battery Chargers Get Faster and Smaller with Diode Technology

PH_PR_BAL-CC25-01D3STMicroelectronics’ family of Field-Effect Rectifier diodes (FERD) offers a 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 percent less than a synchronous rectification kit.

Available in the ranges from 15 A to 2×30 A and from 45 V to 60 V, 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 30 A device using FERD technology features a forward voltage drop reduced by about 140 mV compared to a conventional 30 A 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.

The FERD technology is also well suited for applications and systems in other segments, such as freewheeling or reverse battery protection in automotive applications; OR-ing in telecom power supplies; or rectification in industrial systems, and could be offered in FERD devices with various voltage and current ratings to support the needs of the different markets.

12 FERD devices are currently available, housed in TO-220AB, D²PAK, and PowerFLAT  5 by 6, with prices starting at $0.51 for the FERD15S50DJF-TR (15A, 50V) in quantities of 1,000 units.