How can I look at my digital signals in my power controller?
One of the big issues when working on digital control of power electronics is being able to look at the digital signals inside your controller. In order to see what is going on inside the control the digital signals need to be brought out so you can look at them.
When a DAC isn’t good enough.
One way to do this is with a digital to analog converter (DAC) where the digital stream is sent out as an analogue signal. These DAC channels are really useful and should be on every digital power electronics controller. However processing power usually limits the logging or data streaming to a DAC to a low number of channels. Each channel requires a scope channel of its own to do measurement. Any measurement is limited in length to the scope’s memory and the scopes sample rate.
Data Collection in the Controller and Detecting Events
There is also the issue that collecting enough data to allow event detection such as;
- single sample errors
- underflow or precision loss and
- bursty instability due to precision loss
can be a very difficult large load on the control processor and memory if the data logging rate is very high or if the rate of the problem is very low.
Control Scope Integrated into Digital Power Controller
To solve this problem we put the data collection and logging into the controller but without loading the controller.
Using the Xlinx Zynq system on a chip (SoC) we use the flexibility of running Linux on one of the two ARM 9 cores to provide the high speed gigabit Ethernet connectivity.
We also use the Linux for secure remote access if required.
Using ELMG Power Core IP blocks and know how we create firmware in the FPGA fabric of the Zynq. This connects to the Linux kernel and then the Linux user space. Data can be logged at full sample rates into SD cards or MMX memory and simultaneously out via the Gigabit Ethernet to the internet.
To be very clear no Linux code is included in the power electronics control function which is all implemented in the FPGA fabric on the Zynq.
Put a scope on the other end of the Ethernet
The video shows the ELMG ControlScope application connected to the ELMG Digital Power Zynq data collection system (named Dlog).
This system implements a fully functional oscilloscope that allows the internal operation of the digital control to be shown and logged.
With gigabit Ethernet logging rates of 25 M bytes per second are possible using Dlog.
This means that logging of your power converter performance and waveforms, scope function or debugging can be done over the internet.