Improving the Light Load Efficiency of a Bus Converter Array

October 5, 2015

The Vicor Bus Converter Modules (BCMs) can easily be paralleled to create an array that delivers higher current than can be supplied by a single component. Many of these applications, however, do not require the maximum load current to be delivered all the time, requiring the array to operate in a light load or no load condition.

Improve light load efficiency of Bus Converter ArraysContinuing to operate all BCMs in the array, however, will reduce efficiency as each active component will consume a small, but measurable, current, even when there is no load. This new application note describes a technique to reduce the number of active bus converters as the load decreases, and add bus converters as the load increases, maximizing efficiency.

The technique (described in an application note) deduces the output current of each BCM from a sense resistor on the input of the bus converter and uses set threshold levels to enable and disable each of the converters in the array using the primary-referenced PC pin, eliminating the need for isolation, and so simplifying the control circuit design.

There are several advantages of this approach that are outlined in the application note:

  • The design of the control circuits for each BCM is simpler due to commonality in the circuits
  • The sense resistors consume less power as the currents are lower on the primary side, allowing the designer to select smaller, less expensive components
  • The configuration offers more flexibility

The application note includes a worked example showing how to calculate the component values for the current sensing and control circuits for an Eco Array of six 384 V to 48 V BCMs, producing a saving of 31 W in a no load condition.


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