Power supply switching apparatus

A power supply switching apparatus for switching a power supply for supplying power to a load between a first power supply and a second power supply, the power supply switching apparatus comprising:

• a controller including an adjusting unit connected to one of the first power supply and the second power supply and configured to adjust a level of a signal input from the power supply being connected thereto,
• an integrating unit configured to integrate a signal output from the adjusting unit, and
• a third comparator configured to output a binary signal having a level corresponding to a magnitude of a single output from the integrating unit;
• and
• a switch including
• a mechanical relay having an input side connected to the first power supply and the second power supply and configured to switch an outputting current between a current supplied from the first power supply and a current supplied from the second power supply in accordance with an input control signal, and
• a relay driver configured to output the input control signal to the mechanical relay, the input control signal instructing the mechanical relay to switch the outputting current in accordance with the binary signal from the third comparator
• wherein the controller further includes a fourth comparator disposed before the integrating unit and configured to output a binary signal having a level corresponding to a magnitude of an input signal,
• wherein the first power supply or the second power supply connected to the controller is an alternating-current power supply, the controller further includes a rectifying unit configured to rectify an input signal, and a high-pass filter configured to reduce a frequency component at or below a specific frequency in the signal rectified by the rectifying unit, the rectifying unit and the high-pass filter being disposed after the adjusting unit, and the fourth comparator receives an output from the high-pass filter.