Field of the Invention
The present invention relates to a printing apparatus and a control method therefor, and in particular to a power control technique for a printing apparatus having a plurality of power states.
Description of the Related Art
Conventionally, image forming apparatuses have a power state called a “low-power (power-saving) state” different from a job executing state and a job executable state so as to reduce power consumption while they are not operating. To return from the low-power state to the job executable state, initialization of each device is required, but it takes long to initialize some devices. For this reason, there is conventionally known an image forming apparatus which has some different low-power states and sets a state suitable for a processing time period required to initialize devices.
Specifically, in the low-power state, the power to devices of which initialization takes a long time is not turned off, and only the power to devices that can be quickly returned to the job executable state turned off. This speeds up the return to the job executable state although a greater amount of power is consumed than in a normal low-power state. As a result, a user is allowed to quickly obtain an output result of printing or the like from the image forming apparatus in the low-power state.
Japanese Laid-Open Patent Publication (Kokai) No. 2001-201986 describes a technique to turn off the power to devices even in the job executable state so as to reduce power consumption. In this case, when a user issues an instruction to execute a job, the power to a device required for the job is turned on.
However, according to Japanese Laid-Open Patent Publication (Kokai) No. 2001-201986, a device is initialized when a job is to be executed, and hence it takes a long time before execution of the job. Namely, according to Japanese Laid-Open Patent Publication (Kokai) No. 2001-201986, greater importance is placed on saving of power in the job executable state than on shortening of the time period that elapses before execution of a job. On the other hand, the above described technique by which the power to devices of which initialization takes a long time is kept on, and the power to devices that can be initialized within a short time is turned off in the low-power state places greater importance on shortening of the time period before execution of a job than on saving of power in the low-power state.
Therefore, using both of these techniques for an image forming apparatus will bring about a situation in which two purposes, i.e. shortening of the time period before execution of a job in the low-power state and saving of power in the job executable state are mutually contradictory, and power may not be controlled in an appropriate manner as intended by a user.