Rohm adds 24 power supply ICs for AC/DC converters

August 29, 2013 // By Graham Prophet
Rohm Semiconductor has announced power supply ICs for AC/DC converters in primary power supplies for home appliances and AC adapters; integrated power MOSFETs result in high efficiency and small form factor.

The BM2xxx/F series consists of 24 models that use a proprietary low ON-resistance SJ MOSFET and feature circuit optimisation, resulting in industry-leading efficiency and low noise. In addition, a surface mount type is available in the SOP8 package that contributes to miniaturisation. Rohm is working on expanding its lineup to achieve high efficiency in a wide range of home electronics, including appliances, TVs, and monitors.

There is a strong demand for power supply ICs in AC/DC converters to be Energy Star compliant and provide high efficiency operation that includes standby power. Also, the increased number of components leads to a larger mounting area, presenting additional challenges regarding design complexity and time.

Rohm adapted power supply technology from developing LDOs, DC/DC converters, and the like along with discrete transistor analogue power technology to develop the BM2Pxxx/F series, optimised for AC adapters, home electronics, and office equipment up to 25W that require high efficiency operation in a compact form factor.

To improve efficiency a proprietary high performance super junction MOSFET is used, while exhaustive optimisation of the driver circuitry enabled the company to maximise MOSFET performance. Products pass the 86.35% efficiency rating required by Energy Star 6.0. Efficiency over 87% is possible by simply replacing conventional products with Rohm ICs (100 VAC, 25W applications), while greater than 90% can be achieved through optimisation of peripheral components.

The internal super junction MOSFET features a voltage resistance of 650V, low ON resistance (just 4.0Ω even with the SOP8 package), low gate charge Qg, and high-speed switching capability. Standby power consumption is less than 20 mW (at 100 VAC) for a 25W adapter and only 30 mW at 230 VAC – significantly less than the 100 mW required by the Version 6.0 Energy Star. And even lower consumption is possible by adjusting the peripheral circuitry.

AC/DC systems typically use a planar-type MOSFET, which is difficult to miniaturise due to problems associated with heat dissipation. In