5 Conclusion

Instead of controlling the input current directly, charge mode controls how much electric charge to deliver to the PFC output in each switching cycle. This algorithm works for all PFC topologies, but it is especially useful for totem-pole bridgeless PFC, which has traditionally required a sensor such as Hall-effect sensor to sense the bidirectional inductor current. The problem is that Hall-effect sensors are not only expensive, but also have limitations such as limited bandwidth, sensitive to magnetic field and DC offset shifting with temperature, etc. Because charge-mode control eliminates the need to sense inductor current, there is no need for an expensive bidirectional current sensor. Instead, you can use a current-sense resistor along with a low-bandwidth op amp or a CT, which are much less expensive.

Because of its high efficiency, totem-pole bridgeless PFC is attractive for applications that require high efficiency. Its high cost was always a barrier for its broader adoption, but this new control algorithm is now an option in applications that require both high efficiency and low cost. It is possible to implement charge-mode control with existing digital controllers such as Texas Instruments C2000™ microcontrollers and the UCD3138 controller, or you can employ it in the development of a new analog PFC controller.