Patent ID: 7923666

Claim:
A phase control method for performing ON/OFF control of a switching unit arranged on a power supply line from an AC power supply to a load by a trigger signal of a phase angle corresponding to an output power command value based on an input power command value, the phase control method comprising: a threshold determination step of, when the input power command value is a command value different from a plurality of selectable command values, rounding up the input power command value and determining the selectable command value closest to the rounded input power command value as a threshold value, and when the input power command value is the same as one of the plurality of selectable command values, determining the command value as a threshold value; a calculation step of calculating a determination value based on the input power command value and an accumulated value of an output error; a selection step of, when the determination value is greater than or equal to the threshold value, selecting the threshold value as an output power command value, and when the determination value is not greater than or equal to the threshold value, selecting the selectable command value lowered from the threshold value by a resolution stage as an output power command value; a control step of performing the ON/OFF control by the trigger signal of a phase angle corresponding to the selected output power command value; and a correction step of correcting the accumulated value of the output error based on the determination value and the selected output power command value.