Primary Side Sensing techniques
Primary Side Sensing (PSS) is an emerging approach designed to cut components, save cost and improve isolation and safety within flyback SMPS designs.
Several companies have introduced PSS controllers to monitor waveform changes in the auxiliary winding to the control IC – which is located on the primary, high voltage side - and to use those measurements to regulate the voltage and current outputs. This approach removes the need for expensive optocouplers and all secondary-side feedback components but also delivers supplies with poor voltage regulation and virtually no current regulation.
CamSemi’s PSS controllers offer a breakthrough in current regulation. They combine sophisticated proprietary algorithms with novel digital techniques to sense the output voltage much more accurately than has previously been possible.
Advantages include:
- delivering ‘best in class’ current and voltage regulation of just +/- 5%. No need for voltage reference circuits for measurement and tight control.
- enabling quasi-zero voltage switching to reduce EMI and increase the operating efficiency of designs. Making EMI and efficiency compliance faster, easier and lower cost.
- using emitter drive topology to deliver fast, optimised switching of low cost bipolar switches and to reduce system costs. Whereas some competitive approaches typically demand costly MOSFETs.
Below is a CamSemi basic PSS schematic - eliminating 10 or more components compared with a flyback design.
