Power supply device and power supply system including power supply device

A power supply system comprising:

• a power supply unit including a first power supply unit transmitting standby power to an electronic device and a second power supply unit transmitting main power to the electronic device;
• a cable including a standby power transmission line transmitting the standby power to the electronic device, a main power transmission line transmitting the main power to the electronic device, a first detect line receiving a power-on signal for operating the second power supply unit from the electronic device, and a second detect line electrically connected to the electronic device;
• and
• a power receiving unit of the electronic device configured to receive the standby power and the main power from the power supply unit via the cable and to transmit the power-on signal via the first detect line,
• wherein the power receiving unit does not receive the main power because the second power supply unit does not operate when the power-on signal is not received,
• wherein the first power supply unit includes a blocking circuit including a first switch which is electrically connected to the first detect line and the second detect line,
• wherein voltage applied to the first switch is determined by the second detect line, and
• wherein the first switch blocks the power-on signal received via the first detect line when the second detect line is opened.