Nano Power Inverter - Roll Your Own Style

Author	Message
wiseguy Guru Joined: 21/06/2018 Location: Australia Posts: 1156	Posted: 10:06am 16 May 2019         Warpspeed said   This all looks very good Mike. I originally used pulse transformers for generating the isolated gate driver voltages the same way you are doing. I found it difficult to control the final dc voltage on the isolated side. Overshoot or ringing on the secondaries of the transformer would sometimes produce some worryingly high dc voltages. I managed to fix all that by using full wave rectification, and a suitable zener. It then all ended up working much more predictably. I went and fired up the circuit and took some scope shots. The first shot is with no load, the nominal 12V was 18.1V. Loaded with a 220K it became 13.3V, 33K was 12.9V, 470R was 12.02 and 150R 10.9V This shot was loaded with 470R note the leading ringing was gone. Conclusion there is some ringing unloaded at the front edge this has enough energy to raise the voltage by a few volts unloaded. With a 1mA load voltage is less than 13V and with 80mA ~ 11V. I am comfortable that the 2.5mA minimum of the FOD3182 opto will keep it well under control and around 12.5V. The UCC3080 driver seems well suited in this app. If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike