Patent ID: 6917190

Claim:
A power supply apparatus, comprising: an input terminal having an input voltage applied thereto from a direct current power source; an output voltage generator configured to generate a constant output voltage based on said input voltage; an output terminal of said output voltage generator outputting said constant output voltage; a reference voltage generator configured to generate a reference voltage; a voltage divider having an output point, said voltage divider configured to accept said constant output voltage from said output terminal of said output voltage generator and further configured to divide said constant output voltage into a divided voltage in accordance with a voltage dividing ratio which is variable in response to an externally-input control signal and to output said divided voltage to said output point of said voltage divider, wherein said voltage divider comprises a first resistance circuit including a plurality of resistors connectable in series, and a second resistance circuit connected in series with said first resistance circuit, said second resistance circuit including a plurality of resistors connectable in parallel including at least one switchably controllable resistor; and a voltage control circuit configured to control said output voltage generator to regulate said constant output voltage such that said divided voltage from said voltage divider is equalized to said reference voltage.