Image forming apparatus and method of starting up modules in the image forming apparatus

An image forming apparatus, comprising:

• an electric power supply;
• a plurality of modules including a plurality of direct current (DC) modules and at least one alternating current (AC) module, to be driven by an electric power supplied from the electric power supply;
• a startup time calculator to calculate a startup time of each of the modules;
• and
• a fastest startup pattern determiner to determine a fastest startup pattern based on the startup time of each of the modules calculated by the startup time calculator, and to start up the modules in accordance with the determined fastest startup pattern, the fastest startup pattern determined based on a longest startup time among the startup times of the DC and AC modules,
• the fastest startup pattern determined by the fastest startup pattern determiner satisfying one of the following conditions:
• (1) When TDC>TAC, all the modules start a startup processing at the time of turning on the electric power supply;
• (2) When TAC>TDC, the DC modules start a startup processing in an order which minimizes power consumption in the DC modules while keeping the startup time of the DC modules within the range of the startup time of the AC module;
• and
• (3) When TAC≈TDC, all the modules start a startup processing at the time of turning on the electric power supply and complete the startup processing at the same time, wherein TDC represents the startup time of the DC modules and TAC represents the startup time of the AC module.