Monolithic Power Systems, Inc.

Zhaoqi Mao

Yuancheng Ren

Junming Zhang

Lei Miao

Disclosed is a light load control circuit and the method accordingly where the synchronous rectification is latched off when the light load condition is detected for several successive cycles.

Latch-off of synchronous rectification for light load control

The present invention discloses a light load control circuit and the method accordingly where the synchronous rectification is latched off selectively according to the gate voltage of the synchronous rectifier.

Latch-off of real time synchronous rectification for light load control

The present invention discloses a smart driving method for a secondary synchronous rectifier of an isolated converter and its apparatus thereof. The apparatus comprises: a main circuit having a secondary synchronous rectifier Q; a differentiation filter circuit, filtering the drain-source voltage Vds of the secondary synchronous rectifier, comprising a capacitor and at least one resistor connected in series and outputting a filtered voltage Vf from either between said capacitor and said at least one resistor or between said at least one resistor; a smart driver, receiving Vf and Vds and putting out a driving signal to the gate of the secondary synchronous rectifier. The control approach is fulfilled by comparing Vds to a reference voltage Vthrand comparing the absolute value of Vf to another reference voltage Vthr. When Vds&#x3c;Vthrand |Vf|&#x3e;Vthr, Qis turned on. When Vds&#x3e;Vthr, Qis turned off, where Vthris a predetermined reference voltage. The driving is reliable with an additional differentiation filter circuit to eliminate error trigger.

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Hangzhou, China

Zhaoqi Mao