The device is a current-mode PFC controller operating in Transition Mode (TM). Based on the core of a standard TM PFC controller, it offers improved performance and additional functions.
The highly linear multiplier, along with a special correction circuit that reduces crossover distortion of the mains current, allows wide-range-mains operation with an extremely low THD even over a large load range.
The output voltage is controlled by means of a voltage-mode error amplifier and a precise (1.5% @TJ = 25°C) internal voltage reference. The stability of the loop and the transient response to sudden mains voltage changes are improved by the voltage feedforward function (1/V2 correction).
Additionally, the IC provides the option for tracking boost operation (where the output voltage is changed tracking the mains voltage). The device features extremely low consumption (≤ 90 µA before start-up and ≤ 5 mA running).
In addition to an effective two-step OVP that handles normal operation overvoltages, the IC provides also a protection against feedback loop failures or erroneous output voltage setting.
In the L6563 a protection is added to stop the PFC stage in case the boost inductor saturates. This function is not included in the L6563A. This is the only difference between the two part numbers.
An interface with the PWM controller of the DC-DC converter supplied by the PFC preregulator is provided: the purpose is to stop the operation of the converter in case of anomalous conditions for the PFC stage (feedback loop failure, boost inductor's core saturation) in the L6563 only and to disable the PFC stage in case of light load for the DC-DC converter, so as to make it easier to comply with energy saving norms (Blue Angel, EnergyStar, Energy2000, etc.). The device includes disable functions suitable for remote ON/OFF control both in systems where the PFC pre-regulator works as a master and in those where it works as a slave.
The totem-pole output stage, capable of 600 mA source and 800 mA sink current, is suitable to drive high current MOSFETs or IGBTs. This, combined with the other features and the possibility to operate with the proprietary Fixed-Off-Time control, makes the device an excellent low-cost solution for EN61000-3-2 compliant SMPS in excess of 350W.