The design process involves working through calculations and making tradeoffs to arrive at suitable power supply component selection. Getting components specified correctly is certainly a solid foundation to build the design on. Where designs often go awry, however, is in the layout phase. From an EMI perspective, there are certain nets that must get special care in the layout phase to insure low RF emissions. These are the high di/dt or dv/dt nets. They must be treated in such a way to reduce parasitic inductance, capacitive coupling, and radiating loop size. They must also be designed in such a way to avoid general reference plane contamination with the RF currents. There are also sensitive nets (feedback, compensation, etc.) which must be protected from noiser nets.
To complete the power supply design, custom filters are added for controlling EMI. CE filters are differential-mode type and can be analytically designed for particular attenuation as required. RE filters are primarily common-mode type and are needed where controlling common mode current at the source is insufficient to meet requirements.
Power supply architectures we have executed for past projects:
- Flyback (AC-DC)
- Inverter (DC-AC)
We have a Keysight 1 GHz bandwidth oscilloscope with high-voltage differential probe, high-bandwidth current probe, and Power Analysis Software. We also have a frequency response analyzer for power supply stability analysis. A 1.5 Ghz bandwidth spectrum analyzer with CISPR EMI filter option facilitates conducted emissions measurement. A Fluke thermal imager is used to troubelshoot, assess thermal design, and component stresses. With these tools we can analyze and tune any power supply topology.