A secondary-side protection and sense circuit for a power converter has a sensing component, an adder amplifying circuit, an electronic switch, and a charge/discharge circuit. The sensing component is connected to an output connecting terminal of the power converter. The adder amplifying circuit has an operational amplifier, a first resistor, and a second resistor. The operational amplifier has an input terminal connected to the sensing component, an output terminal connected to a primary-side control component, and a power terminal. The first resistor and the second resistor are connected in series and between the input terminal and the power terminal of the operational amplifier. The electronic switch is connected between a ground terminal and a connection node between the first resistor and the second resistor. The charge/discharge circuit is connected to the electronic switch and the power terminal of the operational amplifier.