Patent ID: 7504780

Claim:
A power supply unit capable of varying power supplied to a light source at timings determined by synchronization signals, the power supply unit comprising: an interface that receives a plurality of types of synchronization signals with different pulse widths; and a control unit that changes a setting of output power supplied by the power supply unit in accordance with the pulse widths of the plurality of types of synchronization signals that have been received; wherein the control unit includes: obtaining a standard time interval from a cycle of a standard type of synchronization signal that has a longest pulse width out of the plurality of types of synchronization signals received; determining type of each synchronization signal included in the plurality of types of synchronization signals received from ratio of pulse width of each synchronization signal to the standard time interval; obtaining intervals of respective synchronization signals received; redefining, when any of the standard time interval, combination of types of synchronization signals included in the standard time interval, and intervals between the respective synchronization signals changes, supply power values corresponding to respective types of synchronization signals included in the plurality of types of synchronization signals received; and changing, after a first delay time from a leading edge of a synchronization signal received, the setting of output power of the power supply unit to a supply power value corresponding to a type of the synchronization signal.