Voltage control apparatus, motor unit, image forming apparatus and voltage control method

Abstract

In accordance with one embodiment, a voltage control apparatus comprises a pulse width control section, a pulse width modulation wave generation section, a variable amplifier control section and a variable amplifier. The pulse width control section specifies the pulse width of the pulse width modulation wave. The pulse width modulation wave generation section generates a pulse width modulation wave having the pulse width specified by the pulse width control section. The variable amplifier control section generates a GAIN signal for scaling up/down the pulse width modulation wave generated by the pulse width modulation wave generation section. The variable amplifier scales up/down the pulse width modulation wave generated by the pulse width modulation wave generation section according to the GAIN signal generated by the variable amplifier control section and outputs the scaled up/down the pulse width modulation wave.

What is claimed is: 
     
         1 . A circuit that generates analog control signals of which voltage value is changed, comprising:
 a pulse width control section configured to specify a pulse width of a pulse width modulation wave using an n-bit signal;   a pulse width modulation wave generation section configured to generate a pulse width modulation wave having the pulse width specified by the pulse width control section;   a variable amplifier control section configured to generate a GAIN signal for scaling up/down a voltage of the pulse width modulation wave generated by the pulse width modulation wave generation section;   a variable amplifier configured to scale up/down the voltage of the pulse width modulation wave generated by the pulse width modulation wave generation section according to the GAIN signal generated by the variable amplifier control section and output the pulse width modulation wave that the voltage is scaled up/down, and   a low-pass filter for smoothing the pulse width modulation wave for generating the analog control signals,   wherein the voltage value of the analog control signal is any of a plurality of voltage values, and the plurality of voltage values of the analog control signal are voltage values other than a voltage value of the analog control signal acquired with the pulse width specified using the n-bit signal.   
     
     
         2 . The circuit according to  claim 1 , wherein
 the GAIN signal is a signal for indicating whether or not to amplify the voltage of the pulse width modulation wave; and   the variable amplifier amplifies the voltage of the pulse width modulation wave when the GAIN signal indicates the amplification of the voltage of the pulse width modulation wave.   
     
     
         3 . The circuit according to  claim 2 , wherein
 the GAIN signal is ‘high’ or ‘low’, and   the variable amplifier comprises an operational amplifier configured to amplify the pulse width modulation wave, and   a transistor configured to electrically connect a terminal of the operational amplifier with the ground when the GAIN signal is ‘high’ or to insulate the terminal of the operational amplifier from the ground when the GAIN signal is ‘low’.   
     
     
         4 . A motor unit, comprising:
 the voltage control apparatus according to  claim 1 ;   a motor driver configured to output a current according to a voltage value of the analog control signal; and   a motor driven by the current output from the motor driver.   
     
     
         5 . The motor unit according to  claim 4 , wherein
 the motor is a stepping motor.   
     
     
         6 . An image forming apparatus for forming an image on a paper, comprising:
 the motor unit according to  claim 4 .   
     
     
         7 . A method for generating analog control signals of which voltage value is changed, comprising:
 specifying a pulse width of the pulse width modulation wave using an n-bit signal;   generating a pulse width modulation wave having the specified pulse width;   generating a GAIN signal for scaling up/down a voltage of the generated pulse width modulation wave;   scaling up/down the voltage of the generated pulse width modulation wave according to the generated GAIN signal and outputting the pulse width modulation wave that the voltage is scaled up/down; and   smoothing the pulse width modulation wave for generating the analog control signals,   wherein the voltage value of the analog control signal is any of a plurality of voltage values, and the plurality of voltage values of the analog control signal are voltage values other than a voltage value of the analog control signal acquired with the pulse width specified using the n-bit signal.   
     
     
         8 . The method according to  claim 7 , wherein
 the GAIN signal is a signal indicating whether or not to amplify the voltage of the pulse width modulation wave, and   the GAIN signal indicates the amplification of the voltage of the pulse width modulation wave.