Power supply apparatus and magnetic resonance imaging system

A power supply apparatus comprising:

• a power supply unit having an input terminal connected to a load power-feed terminal, said power supply unit being designed to supply power to a load;
• a voltage comparator having an input terminal connected to the load power-feed terminal, said voltage comparator comparing a nominal voltage and an actual voltage of the load power-feed terminal;
• a reference voltage pull-down unit comprising a counter, a digital-to-analog converter, and a phase inverter;
• said voltage comparator being connected to said counter and, when the voltage comparator determines that the actual voltage is lower than the nominal voltage, the voltage comparator causes said counter to begin counting, and said digital-to-analog converter converts a digital signal from the counter, representing the count thereof, to a corresponding analog voltage;
• and
• said phase inverter inverting a phase of the analog voltage so as to produce a phase-inverted analog voltage that is supplied to an output voltage reference terminal of the power supply unit.