‘Fast start’ controllers for 8 and 10W chargers

March 25, 2014 // By Graham Prophet
CamSemi has two new ‘fast start’ Primary Side Sensing (PSS) controllers to extend the target applications for the company’s latest generation C2170 family into higher powers. The C2173 and C2174 controllers target low cost MoU-compliant, USB smartphone charger and other universal input applications typically rated at 8W and 10W respectively.

These PSS controllers offer, at this power level, manufacturers the combination of three significant cost and performance benefits within the same device: more efficient switching of bipolar transistors (BJT) to deliver the higher operating efficiencies required by US Department of Energy level 6 efficiency regulations and tier two of Europe’s Code of Conduct version five (effective 1 January 2016); five star (less than 30 mW) no-load power performance (NLP); and fast-start charging without needing an active start-up switch. Both devices feature integrated output transient detection (TD) to enable manufacturers to further reduce NLP while maintaining fast transient response.

The controllers offer programmable dynamic response allowing one part to be easily configured in multiple designs by specifying one of four resistor values. This approach provides manufacturers with greater design flexibility and easier inventory management.

The C2173 and C2174 use the company’s BJT drive scheme, as well as a further improvement in IC power consumption enabling BJTs to be more easily used at higher powers. C2174 is also the first PSS controller to use CamSemi’s supplementary base drive scheme to further reduce IC power dissipation and junction temperature and to enable the performance advantages of combined base and emitter switching at higher powers. Both controllers offer class-leading load transient response with passive start-up speeds well below 0.5 second, whereas competitive approaches require an additional active start-up switch to ensure fast start of charging cycles.

C2173 and C2174 offer the same performance benefits as existing C2170 controllers targeting lower power applications including: an increased Reverse Bias Safe Operating Area (RBSOA) margin to accommodate a wide range of low cost BJTs; voltage regulation of ±2% and current regulation of ±3% offering more margin for thermal design; and full featured protection.

C2173 is packaged in SOT23-6, C2174 in SOP8.

Cambridge Semiconductor (CamSemi); www.camsemi.com