Increasing Reliability and Efficiency in Power Converter Designs Part 3 – Hardware Design & Debug

By Keysight Technologies

Introduction

The need to reduce energy consumption as well as CO2 emissions is driving the growth of power electronics and power converters. These needs are driven by growth in the vehicle electrification and home energy management systems where renewable energy usage is becoming more prevalent. Two of the main power converter design drivers are increased conversion efficiency and better reliability. In green energy applications such as solar power, Levelized Cost of Energy (LCOE) is the main decider for what solar inverter a customer chooses for their solar installation. Both efficiency and reliability are two of the main variables in the LCOE algorithm that determines whether your inverter company gets the sale or not. In hybrid electric (HEV) and electric vehicles (EV) reliability is tied to an automotive manufacturer’s reputation and is also linked to safety and the preservation of human life. Hence comprehensive EV test for the various vehicle electrical subsystems at the design and test stages is vital.

The ceiling or limits of these design drivers was getting close for many power converter applications that used power devices based on silicon. The emergence of wide band gap (WBG) power devices based on silicon carbide (SiC) and gallium nitride (GaN) hold promises of raising the ceiling of these design drivers. With the ability to switch faster, handle higher voltages, and larger temperature ranges WBG devices can increase efficiency and reliability as well as reduce form factor in next generation power converter designs. But before power converter designs based on WBG power devices can become main stream there are design and test challenges that must be understood and overcome to utilize them to their full potential.

This is part three in a four part series that takes a look at each stage of the power converter design cycle. At each stage we will look at design and test challenges of next generation power converters and discuss hardware and software tools to help you overcome them. We will put an emphasis on improving the design drivers previously mentioned: increasing efficiency, improving reliability, and reducing form factor. We also consider the design and test challenges that WBG devices introduce into the power converter design cycle. Each of the four parts of this series will cover one of the following design cycles:

  1. Power device and component evaluation
  2. Design software simulation
  3. Hardware design and debugging
  4. Design validation and certification

Hardware Design and Debug

Once you have fully optimized your design in software simulation, it is time to build hardware prototypes of the design and begin testing them ensure they match the expected results of the simulation and the overall requirements of the project. If something is not right, for instance you are not getting the output stability you expected, you need the right tools to get the insight into your design to track down the root cause of the of the issue so you can correct it. Also as the design is coming together EMC levels need to be checked to avoid time consuming and costly design rework. Keysight’s large benchtop hardware and software portfolio, spanning from DC to RF, can help you do just that with differentiated capabilities targeted at power electronic designers to help them get the most efficient and reliable product to market fast. In the following sections we will discuss some common test challenges power electronics engineers face and how Keysight’s hardware and software can help you overcome them.

Optimizing your design and speeding up the design process:

When integrating and testing the prototype hardware of your power converter design, you need an instrument that gives you quick and easy insight into each stage of your power converter design so that you can spot problems right away to ensure optimization of the design. Depending on the stage of the power converter you are developing and testing, you may need to verify the harmonic content of your output current or the switching losses of your H-Bridge or even the overall efficiency of the design. Keysight’s InfiniiVision X-Series Oscilloscopes with the power measurements option gives you an easy-to-use and highly versatile all-in-one power circuit simulator tool that delivers measurement insight into every stage of your power converter design.

When we discussed dynamic measurements of power devices in part one, we introduced the InfiniiVision X-Series oscilloscope. Here we want to discuss in more detail its power measurements option and how it can give you quick insight into the performance of your power converter designs. The power measurements option is a turn-key embedded application available on any InfiniiVision 3000, 4000, or 6000 X-Series oscilloscope. This licensed option essentially turns the oscilloscope into a complete power analysis tool by providing:

  • 14 power-related measurements
  • Connections diagrams
  • Automatic de-skew
  • Automatic setups

Figure 1 is a screen capture from an InfiniiVision oscilloscope that provides an overview of the 14 power-related measurements that the option delivers.

Figure 1

Figure 1. 14 power related measurements that the option provides

Figure 2 shows an example of a switching device power and energy loss measurement of a step-down Buck switch mode power supply (SMPS). With the power measurements option, the scope automatically optimizes vertically scaling of the voltage and current waveforms, turns on the power waveform (V x I), and then continuously measures the power and energy loss across one switching cycle. The scope also provides a precision offset calibration so that losses during the conduction phase (when voltage is very low) can be performed in the presence of large switching voltages with maximum accuracy. Oscilloscope and/or probe offset error, even if it’s within the scope’s specifications; can contribute to significant measurement errors during the conduction phase of switching…

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