High step-down ratio enables single-stage voltage conversion in 48V systems

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By Christoph Hammerschmidt

To obtain this high voltage ratio, Rohm’s new BD9V100MUF-C uses the semiconductor manufacturer’s proprietary Nano Pulse Control technology, which leverages high-voltage BiDCMOS processes and ultra-high-speed pulse control to realize an unprecedented on time of just 9 nanoseconds. The technology enables single-stage voltage conversion in 48 V systems; at switching frequencies of 2 MHz the number of parts required is halved, reducing application size and simplifying system design, while high-frequency operation also permits the use of smaller external components, e.g. coils and output capacitors.

Energy savings and environmental performance are the driving force behind constant innovation in the auto industry. Through optimized power distribution, mild hybrid vehicles with 48 V systems achieve significantly lower energy and fuel consumption, which in turn reduces CO2 emissions. Active systems for enhanced comfort in automobiles, such as brake-by-wire or electric power steering, increase the electrical power requirements. In traditional 12 V systems, electrical energy must be transported to loads at a low voltage level, causing increased losses in the wiring harness. The need for thicker copper wires also adds weight, with a negative impact on fuel consumption. The use of 48 V technology cuts the amount of electricity transferred by a quarter, so reducing losses in the wiring.

At system level, automobile electronics and sensors typically require a supply voltage of between 1 V and 5 V. This means that the 48 V bus voltage needs to be stepped down to the lower voltages. At the same time, it makes sense to operate the DC/DC converter at 2 MHz, as this will not affect the AM radio band (1.84 MHz max.) and allows the most compact solution.

To date, no power supply IC has achieved both a high conversion ratio and a high switching frequency. A two-stage solution meets these requirements, but has various disadvantages: it takes up more space, needs more components, and is a more complex system.

Nano Pulse Control refers to ultra-fast pulse control technology achieved by combining analogue circuit design, layout and processes utilizing ROHM’s vertically integrated production system. This contributes to greater miniaturization and system simplification in 48 V applications ranging from mild hybrid vehicles and industrial robots to base station sub power supplies.

Samples of the BD9V100MUF-C are available now, OEM quantities from December 2017. 



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