Power supply apparatus having plurality of piezoelectric transformers

An image forming apparatus comprising:

• an image carrier;
• a charging unit configured to uniformly charge the image carrier based on a charging bias;
• an irradiation unit configured to form an electrostatic latent image by irradiating light onto the image carrier;
• a development unit configured to form a toner image by causing toner to adhere to the electrostatic latent image based on a development bias;
• a transfer unit configured to transfer the toner image to a sheet or an intermediate transfer member based on a transfer bias;
• and
• a power supply apparatus configured to generate any one of the charging bias, the development bias, and the transfer bias,
• wherein the power supply apparatus further comprises:
• a first piezoelectric transformer;
• a first rectification circuit connected to an output side of the first piezoelectric transformer and configured to output a voltage of a first polarity;
• a second piezoelectric transformer;
• a second rectification circuit connected to an output side of the second piezoelectric transformer and configured to output a voltage of a second polarity;
• a frequency adjustment unit connected between the second rectification circuit and an output of the second piezoelectric transformer, and configured to adjust a relationship between an output voltage and a drive frequency of the second piezoelectric transformer;
• and
• a driving circuit configured to supply a drive signal to both the first piezoelectric transformer and the second piezoelectric transformer.