Patent ID: 8929756
Filing Date: 2015-01-06
Classification: G03G

Abstract:
1. A developing device including: a developing roller facing a photosensitive drum and configured to carry toner thereon; a magnetic roller facing the developing roller and configured to, using a magnetic brush technique, supply the toner to the developing roller and detach the toner from the developing roller; a capacitor; a transformer connected on a primary side thereof to the capacitor and configured to output from a secondary side thereof an AC voltage to be applied to the developing roller; a switching section connected to the capacitor and including a switching element capable of switching between energization and de-energization of a series circuit, the series circuit including the capacitor and the transformer; a control section configured to generate a control signal for controlling the switching of the switching section and control the duty ratio of the control signal; a single or a plurality of temperature detecting sections configured to detect the surrounding temperature around the capacitor and the transformer or the respective temperatures of the capacitor and the transformer; and a storage section storing, in association with temperatures detected by the temperature detecting section or sections, pieces of temperature characteristic data for determining the resonance period of the series circuit, wherein the control section changes the duty ratio of the control signal in multiple sequential steps to a desired duty ratio, and when changing the duty ratio in the multiple sequential steps, the control section determines the resonance period of the series circuit based on the temperature detected with the temperature detecting section and the piece of temperature characteristic data associated with the detected temperature and changes the duty ratio of the control signal to the next step during a changing time slot which is one of the first and second halves of a period of voltage fluctuation of the capacitor based on the determined resonance period, the one half in which the current flowing through the switching section is smaller than in the other half of the period.