Quick coupler circuit of construction machine with automatic pressurization system

A quick coupler circuit of a construction machine with an automatic pressurization system, the quick coupler circuit comprising:

• a quick coupler cylinder configured to attach and/or detach an attachment to and/or from the construction machine by expansion and/or contraction;
• a flow pump configured to supply fluid to the quick coupler cylinder;
• a quick coupler valve through which fluid for operating the quick coupler cylinder passes;
• a spool valve which includes a spool, configured to move along an axial direction, and to form a pressure at a node of the flow pump according to movement of the spool;
• an electronic proportional pressure reducing valve configured to control the spool valve;
• a quick coupler switch configured to perform an ON/OFF operation;
• and
• a controller configured to output a control current to the electronic proportional pressure reducing valve in response to the operation of the quick coupler switch,
• wherein the controller is further configured to output a decreasing control current, which is reduced until the value reaches a predetermined limit control current value, during a predetermined period of time after the quick coupler switch's OFF operation.