LLC resonant converter with lossless primary-side current feedback

摘要

An LLC resonant converter implements a primary-side current feedback scheme. The LLC resonant converter includes an isolation transformer having a primary winding and at least one secondary winding and is controlled by a control circuit to operate at a switching frequency. The LLC resonant converter includes a first capacitor connected to the primary winding through AC coupling to sense a first voltage indicative of a current flowing through the primary winding of the isolation transformer, and a current sense circuit configured to receive the first voltage and to generate a feedback signal. The feedback signal is coupled to the control circuit to regulate the switching frequency in response to the current at the primary winding. In another embodiment, the current sense circuit is a current and voltage sense circuit configured to sense a voltage at the primary winding.