Patent ID: 8433211

Claim:
A developing device comprising: a toner carrying member having plural electrodes; a toner supply unit configured to supply toner on a surface of the toner carrying member; and a hopping electric field generator unit configured to generate, when the toner is carried in a developing region facing a latent image carrying member, an electric field to cause the toner to perform hopping on the surface of the toner carrying member by applying a pulse voltage to the plural electrodes carried thereon to attach the toner to a latent image on the latent image carrying member, wherein the hopping electric field generator unit includes: a pulse voltage generator circuit configured to generate the pulse voltage; a first direct-current power source electrically floating from a ground and configured to supply bias to regulate a peak value of the pulse voltage to the pulse voltage generator circuit; and a second direct-current power source provided between a low level side of the first direct-current power source and the ground and having a same polarity as a charging polarity of the toner, and configured to output a variable voltage level, wherein the hopping electric field generator unit controls the peak value of the pulse voltage by changing an output level of the first power source, and controls a mean of the pulse voltage by changing an output level of the second power source.