Efficiency is often the key factor in power converters, where efficiencies above 90% are required. This is true for battery operated IoT devices to get the most out of the battery, and it is also true for small DCDC converters supplied by a DC rail. Highly accurate power measurements are necessary to optimize the converter.
Highly accurate power measurements
Designers need the capability of highly accurate power measurements to be able to improve converter efficiency during the design process. Improved efficiency results in a smaller battery, which means the converter size and overall system cost can be reduced. This allows developing a highly efficient converter design that can be released to production. To measure the efficiency of the converter, it is necessary to measure the input and output power with high accuracy.
Design process requires equipment with highest accuracy
A designer can follow an incremental process to increase the efficiency of the design. This incremental process consists of several small steps where the designer has to evaluate the improvement in efficiency after each design modification. The evaluation of the efficiency value is a challenging task because the improvement of the efficiency is the sum of several relatively small changes in the design. That is the reason why it is essential to have equipment with highest accuracy for power measurements. Rohde and Schwarz offers specialty power supplies that are perfect for challenging small power converter applications.
Measurement setup
The R&S
NGM202 and R&SNGL202 provide great functionality and performance to measure, evaluate and optimize the important DCDC converter efficiency with just one instrument. The two-quadrant architecture allows them to function both, as a source and sink to provide highest flexibility. The highly precise read-back measurement capability for voltages and currents at the input and output offers the designer a very simple solution where only one device is required to measure the efficiency. The efficiency measurement setup of a DC-DC switching converter hence only consists of the power supply and the DUT connected to the two channels. Optional remote sensing connections increase the accuracy at higher currents.
Channel 1 is configured to work as a constant voltage source that supplies the converter with the required voltage and current (source). Channel 2 is configured to operate as a load in constant current mode (sink) to load the converter with a valid operational current based on the converter specification. A reasonable overcurrent protection level of the source as well as the prevention of the DUT’s overcurrent detection need to be considered in the configuration of the device. The voltage and current at the input and output are measured internally, and therefore the input and output power can be calculated and displayed on the screen.
Efficiency measurement at different load settings
The efficiency measurements at different load conditions shown in the table below indicate that the converter is already an efficiency-optimized converter. The R&SNGM202 or R&SNGL202 let you determine the efficiency of your individual circuitries and layouts. This means that in addition to going through the discussed optimization process to improve efficiency, the designer has to perform multiple measurements to validate the efficiency under all circumstances. This effort can be reduced tremendously by using the remote control functionality that allows to automatically create efficiency traces with an external script and a piece of software.
