Figure 2-9 Simplified Application Circuit Diagram

The UCC28056 device drives PFC boost stages based on a mixed mode method that operates in TM and discontinuous conduction mode (DCM) at reduced load, automatically reducing switching frequency. This device incorporates burst mode operation to further improve light load performance, enabling systems to meet challenging energy standards while eliminating the need to switch off the PFC. UCC28056 can drive a PFC power stage up to 300W, providing a sinusoidal line input current with low distortion, close to unity power factor. These features along with FET drain valley turn-on with a simple boost inductor allows the lowest component count and reduced system cost.

• Excellent light load efficiency and high efficiency over a wide range of load due to multi-mode TM and DCM control
• Enables low system cost through FET drain valley synchronized turn-on which eliminates the need for a second winding on the boost inductor
• Burst mode with soft-entry and soft-exit periods enables ultra-low audible noise output
• Low start-up current consumption (< 46μA)
• Wide V_CC range 8.5V to 34V
• Cycle-by-cycle current limit
• Second independent OVP
• Integrated OTP