Are you working on a grid connected converter where the controller floats with the AC mains or with the negative rail of the DC bus? These converters are common as this design removes the isolation components between the controller and the power switches. Your code is already to go. All you have to do is program and debug it via JTAG. Plug in the JTAG, program and plug it into the mains to test it. Currents flow from the floating ground reference on your board to your earthed PC – via your JTAG pod. Suddenly the magic smoke is emitted from the JTAG! A $300 JTAG pod destroyed.
Loss of an expensive JTAG pod is not the only thing you need to be worried about when connecting to your grid-referenced converter. The mains voltages and high DC voltages are possible sources of shock which may injure or even kill your firmware engineer.
The solution to this is to isolate the JTAG pod. How you may ask? Our solution is the ELMG Universal JTAG Isolator. Designed to have 4000Vrms isolation, this small 70×42 isolation board provides isolation for Xilinx FPGAs and TI and ARM. Completely powered by your board, the isolated JTAG provides isolation for all the necessary JTAG signals as well as providing the necessary voltages for the JTAG pod. Available now the JTAG isolator is a valuable addition to your toolbox and may save your life and your power converter.
“I can just use my laptop unplugged and on battery mode instead”. Using a laptop like this does not mitigate the shock risk as other paths to earth could temporarily exist through paths like the human body. Also running laptops on battery power mean reduced performance and limited time to do what you need before you have to twiddle your thumbs while the battery recharges. And then one day you forget to isolate the laptop and have a small blow up. Finally working with a laptop this way is definitely unsafe and we advise you not to do it – for your own and your workmates’ safety.
Why not just isolate my converter controller and reference it to earth and not have to worry about JTAG isolation? This is a fair enough plan however it can be an expensive strategy. With the cost of decent isolators and the amount of signals that have to be isolated this can add up to a significant cost per board. In the end you may even pay more than the cost of the JTAG isolator per board! With any quantity of boards, this becomes a significant cost which could be reduced by investing in a JTAG isolator or two.
If the JTAG isolator is right for you, you can purchase it now here.
For further information, download the JTAG Isolator Datasheet. If you wish to know more about digital power electronics, sign up to our digital power report or contact ELMG.