The invention discloses a synchronous rectification
control circuit, and the circuit comprises a primary side circuit and an auxiliary side circuit. The primary side circuit comprises a primary side
inductor, a primary side switching tube, and a primary side sampling
resistor. The auxiliary side circuit comprises an auxiliary side
inductor, an auxiliary switching tube, an auxiliary side first sampling
resistor, an auxiliary side second sampling
resistor, an auxiliary side
capacitor, an auxiliary side load resistor, and a synchronous rectification control
chip. The circuit detects the
voltage Vd of a leakage end, connected with an auxiliary switching tube SR_
MOSFET, of the auxiliary side
inductor in a mode of cycle-by-cycle analogy, can enable an IC in a DCM /
CCM mode to precisely control the time point of discharging finishing, effectively judges the switching-off point, achieves an advanced switching-off function, and solves a difficult problem that the precise switching-off cannot be achieved at the DCM / CCM
modes at the same time in the prior art. The circuit can simplify the
peripheral application circuits, and reduces application devices.