Serial communication apparatus and image forming apparatus including the same

An image forming apparatus comprising:

• a photosensitive member;
• an exposure unit configured to expose the photosensitive member in accordance with an image signal;
• a developing unit configured to develop, using a toner, an electrostatic latent image formed on the photosensitive member exposed by the exposure unit;
• a voltage applying unit configured to apply to the developing unit a voltage;
• a main clock generation unit configured to generate a main clock signal;
• an alternating-current voltage control signal generation unit configured to generate an alternating-current voltage control signal representing a period and a duty ratio of an alternating-current voltage based on the main clock signal;
• a parallel-to-serial conversion unit configured to sample the alternating-current voltage control signal and other control signals input in parallel in synchronization with a sampling signal generated according to the main clock signal, to convert the sampled alternating-current control signal and the sampled other control signals into serial signals, and to output the serial signals and the sampling signal;
• and
• a serial-parallel conversion unit configured to convert the serial signals into parallel signals in synchronization with the sampling signal and to output the sampled alternating-current voltage control signal and the sample control signals in parallel,
• wherein the voltage applying unit uses an alternating-current voltage having a period and a duty ratio represented by the sampled alternating-current voltage control signal output by the serial-to-parallel conversion unit, and
• wherein a frequency of the sampling signal is an integral multiple of a frequency of the alternating-current voltage control signal generated by the alternating-current voltage control signal generation unit.