Image forming apparatus

An image forming apparatus comprising:

• a photosensitive member on which an electrostatic latent image is formed;
• a developing roller configured to develop the electrostatic latent image by supplying toner to the photosensitive member;
• a contacting member configured to contact a surface of the developing roller;
• and
• an electronic power source configured to output a first voltage,
• wherein a second voltage generated by using the first voltage is applied to the developing roller,
• wherein a third voltage generated by using the second voltage is applied to the contacting member,
• wherein the electric power source includes
• a control portion provided with an output terminal for outputting a signal to switch a potential difference between the second voltage and the third voltage,
• a first coupling portion connected in series to the output terminal and configured to allow only the signal with a first frequency or higher to pass through,
• a second coupling portion connected in series to the output terminal and configured to allow only the signal with a second frequency, lower than the first frequency, or higher to pass through,
• a first switching circuit connected in series to the first coupling portion and configured to switch the potential difference by receiving the signal which has passed through the first coupling portion, and
• a second switching circuit connected in series to the second coupling portion and configured to switch the potential difference by receiving the signal passed through the second coupling portion,
• wherein the control portion switches the potential difference to any of three or more kinds of values by changing a frequency of the signal outputted to the first coupling portion and the second coupling portion.