Output circuit and related apparatus and method for electrically detecting whether cable is connected to output port of output circuit

A method for detecting whether an output port of a circuit is electrically connected to an output cable, the method comprising:

• (a) receiving a signal from the output port;
• (b) determining whether the output port is electrically connected to the output cable according to a signal voltage of output port;
• (c) operating the circuit in a normal mode when it is determined that the output port is electrically connected to the output cable;
• (d) operating the circuit in a power-saving mode and providing a low power detecting signal to the output port when it is determined that the output port is not electrically connected to the output cable;
• and
• (e) amplifying the signal voltage of the output port when the circuit is operating in the power-saving mode, and comparing whether the amplified signal voltage of the output port is larger than a predetermined detecting threshold, then determining whether the output port is electrically connected to the output cable according to the comparison result.

An output circuit comprising:

• an output port for electrically connecting to an output cable in a detachable manner;
• a signal circuit for providing a signal current to the output port;
• and
• a decision module for electrically connecting to the output port and determining whether the output port is electrically connected to the output cable according to a signal voltage of the output port, the decision module comprising:
• a control circuit for operating the signal circuit in a normal mode when it is determined that the output port is electrically connected to the output cable, and for operating the signal circuit in a power-saving mode when it is determined that the output port is not electrically connected to the output cable;
• a comparator for comparing whether the signal voltage of the output port is larger than a predetermined detecting threshold when the signal circuit is operating in the power-saving mode, the decision module determining whether the output port is re-connected to an output cable according to the comparison result of the comparator;
• and
• an amplifier electrically connected between the output port and the comparator, wherein when the signal circuit is operating in the power-saving mode, the amplifier amplifies the signal voltage of the output port, and the comparator compares whether the amplified signal voltage of the output port is larger than the detecting threshold.