A novel hybrid low cost controller for maintaining low input current harmonic over wide range of load conditions for power factor corrected boost AC to DC converter

With growing usage of switching power supplies, there has been excessive injection of current harmonics on AC power supply networks. Various agencies world-wide have framed benchmark for maintaining current harmonic distortion. Boost power factor corrected (PFC) converter is the most popular front end converter in power supplies. For medium to high power applications, average current mode control technique is used for controlling boost PFC converter. This technique works very well at near rated load conditions; however, if load drops down to a fraction of rated load, input current harmonic distortion increases considerably. A novel hybrid controller is proposed here which maintains low input current harmonic distortion over wide range of load conditions. The proposed hybrid controller dynamically switches between average current mode and transition or critical mode control (CRM) depending upon load conditions. The proposed hybrid controller provides a cost effective solution for applications having space and weight constraints, using low cost commercial off the shelf (COTS) integrated circuits (IC). Implementation of the proposed hybrid controller is illustrated here and experimental test results are recorded.