Synchronous rectifier driving device and synchronous rectifier driving method

摘要

PROBLEM TO BE SOLVED: To provide a synchronous rectification element drive unit and a synchronous rectification element driving method capable of realizing a satisfactory synchronous rectification operation irrespective of an operating state of a switching power supply device.SOLUTION: A synchronous rectification element Q2 drive unit drives a synchronous rectification element Q2 for rectifying voltage of a secondary coil Ns of a transformer T in a switching power supply device 1, and is provided with: a first comparator CP1 which detects on-timing of the synchronous rectification element Q2 based on both end voltages of the synchronous rectification element Q2; a second comparator CP2 which detects reference timing of voltage fluctuation of the secondary coil Ns; a pulse generator 11 which causes the synchronous rectification element Q2 to be turned on in the on-timing detected by the first comparator CP1 on condition that timing is within a preset determination period from the reference timing detected by the second comparator CP2; and a drive circuit 12.SELECTED DRAWING: Figure 2