Make the Right Design Choices in Load Switching and Simulation

Derek ONG, LOK Teng Kee & CHUAH Rhun Chia
Keysight Technologies,
Penang, Malaysia

In a typical mechatronic manufacturing functional test setup, actual load simulations are usually done by connecting the DUT outputs to power or ground in order to establish either a high or low side driver. Each output is connected with different load and the test will either be sequential or concurrent. At lower power levels, these can usually be managed with general purpose switches. However, when it comes to higher power levels of currents more than 5 amps, such switching and loading might pose a greater challenge. Furthermore, critically in the manufacturing line, the tradeoff between cost and test time would have a great influence on the test strategy.

This paper will present some key points to design a cost effective high power switching and load management solution. Firstly, we will discuss the selection process for the types of relays to be used in the switch methodology. Next, for automotive testing where high current measurements are typically done at the output channels, we will look into how this measurement is done; with or without loads and by instantaneous or continuous measurements. Then, we will discuss single load or multi load connections and explore different approaches.

These connections provide simulation at different loading conditions. A typical example would be to emulate the steering wheel audio control button with different resistive loads. Subsequently, we will also discuss voltage protection and temperature cooling which are essential in such high power applications. Finally, we will give a bird eye's view on the complete high level architecture of the combination of switch and load box, where usually the right solution is more than the sum of the parts.

By providing the reader with guidance and tips on which design and methodology to adopt for the high power switch and load solutions, a cost effective while robust solution that promotes reusability of the test system in high mix test environment would be at your fingertips.

In summary, the complete design of a switch load unit involves a thorough study of many design aspects such as the ones presented here. The right relays and the suitable current measurement techniques are only a portion of the complexity of the design. High side and low side drivers, multi-load requirements and bridge loads are also key in switch load unit design. From a safety point of view, Flyback protection should always be included into the design if there are inductive loads. On the mechanical side, the ventilation of the complete design must evaluated and tested. Finally, understanding the production test scenario and choosing the right switch paradigm is most vital in achieving the lowest cost of test.