Power supply apparatus, image forming apparatus, and integrated circuit

Abstract

The power supply apparatus is configured to detect the output voltage of a piezoelectric transformer and controls the frequency of a pulse signal to drive the piezoelectric transformer based on the detected output voltage and a preset target voltage so as to perform feedback control of the output voltage of the piezoelectric transformer, the gain when performing the feedback control is switched in accordance with the target voltage.

What is claimed is: 
     
         1 . A power supply apparatus comprising:
 a piezoelectric transformer;   a signal generation unit configured to generate a signal to drive the piezoelectric transformer;   a detection unit configured to detect an output voltage of the piezoelectric transformer; and   a frequency determination unit configured to determine a frequency of the signal from the signal generation unit by a feed back control based on a feedback signal corresponding to the output voltage detected by the detection unit and a target voltage signal corresponding to a target voltage,   wherein the frequency determination unit is configured to determine the frequency of the signal based on a gain of the feedback signal switched in correspondence with the target voltage signal.   
     
     
         2 . A power supply apparatus according to  claim 1 , wherein the frequency determination unit includes a digital counter circuit configured to generate a pulse signal to drive the piezoelectric transformer. 
     
     
         3 . A power supply apparatus according to  claim 1 , further comprising a memory unit configured to store a table in which gains each associated with each target voltage signal in the feedback control are stored,
 wherein the frequency determination unit is configured to refer to the table stored in the memory unit, and to switch to one gain among the gains each associated with each target voltage.   
     
     
         4 . A power supply apparatus according to  claim 1 , wherein the feedback signal is a converted signal that is digitally converted from the output voltage detected by the detection unit, and the frequency determination unit is configured to perform the feedback control based on a difference between a preset target voltage signal corresponding to a preset target voltage and the converted signal. 
     
     
         5 . A power supply apparatus according to  claim 1 , further comprising an output unit configured to output a difference between the output voltage detected by the detection unit and the preset target voltage,
 wherein the frequency determination unit is configured to perform the feedback control based on a value of a signal obtained by digitally converting the difference output by the output unit.   
     
     
         6 . A power supply apparatus according to  claim 1 , wherein the gain is a setting value of a control parameter used to perform PID control. 
     
     
         7 . An image forming apparatus comprising:
 an image forming unit; and   a power supply apparatus for supplying a high voltage to the image forming unit, the power supply apparatus comprising:   a piezoelectric transformer;   a signal generation unit configured to generate a signal to drive the piezoelectric transformer;   a detection unit configured to detect an output voltage of the piezoelectric transformer; and   a frequency determination unit configured to determine a frequency of the signal from the signal generation unit by a feed back control based on a feedback signal corresponding to the output voltage detected by the detection unit and a target voltage signal corresponding to a target voltage,   wherein the frequency determination unit determines the frequency of the signal based on a gain of the feedback signal switched in correspondence with the target voltage signal.   
     
     
         8 . An image forming apparatus according to  claim 7 , wherein the image forming unit includes a charging unit configured to charge an image bearing member, a developing unit configured to develop a latent image formed on the image bearing member, and a transfer unit configured to transfer an image formed on the image bearing member. 
     
     
         9 . An integrated circuit for controlling an operation of a power supply apparatus including a piezoelectric transformer, comprising:
 a signal generation unit configured to generate a signal to drive the piezoelectric transformer; and   a frequency determination unit configured to determine a frequency of the signal from the signal generation unit by a feed back control based on a feedback signal corresponding to an output voltage of the piezoelectric transformer and a target voltage signal corresponding to a target voltage,   wherein the frequency determination unit is configured to determine the frequency of the signal based on a gain of the feedback signal switched in correspondence with the target voltage signal.   
     
     
         10 . An integrated circuit according to  claim 9 , wherein the frequency determination unit includes a digital counter circuit configured to generate a pulse signal to drive the piezoelectric transformer. 
     
     
         11 . An integrated circuit according to  claim 9 , further comprising a memory unit configured to store a table in which gains each associated with each target voltage signal in the feedback control are stored,
 wherein the frequency determination unit is configured to refer to the table stored in the memory unit, and to switch to one gain among the gains each associated with each target voltage.   
     
     
         12 . An integrated circuit according to  claim 9 , wherein the feedback signal is a converted signal that is digitally converted from the output voltage of the piezoelectric transformer, and the frequency determination unit is configured to perform the feedback control based on a difference between a preset target voltage signal corresponding to a preset target voltage and the converted signal. 
     
     
         13 . An integrated circuit according to  claim 9 , further comprising an output unit configured to output a difference between the output voltage of the piezoelectric transformer and the preset target voltage,
 wherein the frequency determination unit is configured to perform the feedback control based on a value of a signal obtained by digitally converting the difference output by the output unit.   
     
     
         14 . An integrated circuit according to  claim 9 , wherein the gain is a setting value of a control parameter used to perform PID control.