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Optimizing efficiency in UPS systems: The power of A-SRB

UPS Architectures: Challenges and solutions

Uninterruptible Power Supply (UPS) systems are key to protecting the data that we rely on so heavily in the modern world. While the data centers that store our information have layers of redundancy to protect information in the event of failure of a server or storage media (such as a drive), if the power disappears suddenly then data is at risk of corruption or loss.

To protect equipment from mains-borne transients, most UPS equipment are ‘online’ types that convert the incoming mains from AC to DC, pass it through a battery and then invert if from DC back to AC again for the load. Inherent in this type of UPS is mains conditioning, which protects the server from the mains-borne spikes that can lead to damage and / or premature failure.

However, as the mains input is converted twice (online UPS are often termed ‘double conversion’) then efficiency is a critical consideration. With rising energy costs, not only are data center operators paying for the cost of any wasted energy, the costs associated with cooling also increase.

Among the biggest contributions to overall losses in a UPS are losses caused by the switching activity of bridge circuits. These switching losses increase as operating frequency increases – and raising operating frequency is an approach that is used to reduce the overall size of the UPS. Toshiba has developed techniques that can significantly reduce these losses in power converters built up by Super Junction MOSFET’s.

The first technique, Synchronous Reverse Blocking (SRB) addresses the reverse recovery charge associated with the freewheeling diode commonly found in half-bridge topologies. By adding a second synchronously controlled switch and a Silicon Carbide (SiC) diode, this contribution to switching losses can be eliminated almost completely.

Recharging the output capacitance of SJ MOSFET’s during every switching cycle is another major source of switching losses. Here, Toshiba’s patented Advanced-SRB (A-SRB) utilizes a charge pump voltage source within a dedicated driver IC to pre-charge MOSFET output capacitance Coss during the deadtime prior to a switching transition, reducing associated losses dramatically.

Toshiba has produced a detailed white paper on improving efficiency in half-bridge based UPS systems covering the theory behind the advances as well as practical realization using Toshiba’s driver modules. To get your free copy of this white paper, please click here:

Click here to download the whitepaper

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