Patent ID: 8374003

Claim:
An isolated switching power supply apparatus comprising: a direct-current input power supply; a power transmission transformer including a primary winding and a secondary winding; at least one main switching element arranged to perform switching control on a direct-current voltage applied to the primary winding of the power transmission transformer; a rectification circuit including at least one rectification switching element and being connected to the secondary winding of the power transmission transformer; a smoothing circuit connected to the secondary winding of the power transmission transformer; and a control circuit including a primary control unit arranged to control the at least one main switching element, a secondary control unit arranged to control the at least one rectification switching element, and an isolated signal bidirectional transmission element connected between the primary control unit and the secondary control unit; wherein an input/output conversion ratio is controlled in accordance with a duty ratio of the at least one main switching element; the isolated signal bidirectional transmission element defines a signal transmission path via which a timing signal corresponding to a turn-on time or a turn-off time of the at least one main switching element can be transmitted between a primary side and a secondary side; the primary control unit includes at least one primary drive switch arranged to drive the isolated signal bidirectional transmission element, a primary digital control unit arranged to control a time of driving of the at least one primary drive switch, and a primary detection unit arranged to detect an output of the isolated signal bidirectional transmission element; the secondary control unit includes at least one secondary drive switch arranged to drive the isolated signal bidirectional transmission element, a secondary digital control unit arranged to control a time of driving of the at least one secondary drive switch, and a secondary detection unit arranged to detect an output of the isolated signal bidirectional transmission element; and the primary detection unit and the secondary detection unit are arranged to turn on or turn off the at least one main switching element and the at least one rectification switching element, respectively, when detecting the timing signal, and the at least one main switching element or the at least one rectification switching element is turned on or turned off in response to the timing signal that has been transmitted earlier from the primary control unit or the secondary control unit.