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US 7,599,201 B2Granted
Method of controlling the duty of a PWM signal, PWM signal generating circuit, and image forming apparatus using same
AssigneeKonica Minolta Photo Imaging, Inc.
InventorHiroyuki Okada
Life of this patent
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Abstract
A PWM signal generating circuit that generates a PWM signal having a period controlling portion for slightly fluctuating a period of the PWM signal; and a duty controlling portion for changing a duty of the PWM signal by changing a duty ratio in the period fluctuated by the period controlling portion.
Claims9
A pulse width modulation (PWM) signal generating circuit that generates a PWM signal, comprising:
- a period controlling portion for slightly fluctuating a period, P, of the PWM signal, wherein the period, P, is the amount of time that elapses from a beginning of a low value portion of the PWM signal to the end of a high value portion of the PWM signal that immediately follows the low value portion of the PWM signal;
- and
- a duty controlling portion for changing a duty of the PWM signal by changing a duty ratio in the period fluctuated by the period controlling portion, wherein the duty ratio is defined by Ht/P, wherein Ht is the length of time of the high value portion.
A duty control method of a pulse width modulation (PWM) signal generating apparatus that generates a PWM signal, comprising:
- a period control step of slightly fluctuating a period, P, of the PWM signal, wherein the period, P, is the amount of time that elapses from a beginning of a low value portion of the PWM signal to the end of a high value portion of the PWM signal that immediately follows the low value portion of the PWM signal;
- and
- a duty control step of changing a duty of the PWM signal by changing a duty ratio in the period fluctuated by the period control step, wherein the duty ratio is defined by Ht/P, wherein Ht is the length of time of the high value portion.
An image forming apparatus, comprising:
- a means for forming an image;
- a clock generating portion for generating a clock signal;
- a clock counting portion for receiving the clock signal and counting a clock pulse;
- an instructing portion for outputting an instruction signal specifying a necessary period, P, and duty ratio for a PWM signal, wherein the period, P, is the amount of time that elapses from a beginning of a low value portion of the PWM signal to the end of a high value portion of the PWM signal that immediately follows the low value portion of the PWM signal and wherein the duty ratio is defined by Ht/P, wherein Ht is the length of time of the high value portion;
- a period setting portion for performing setting associated with the slightly fluctuated period based on the instruction signal;
- a duty setting portion for performing setting associated with the duty ratio based on a length of time of the high portion or the low portion of a signal in the period based on the instruction signal;
- a comparison portion for comparing a count value by the clock counting portion with the set values set by the period setting portion and the duty setting portion;
- an output portion for outputting the PWM signal based on a result of the comparison by the comparison portion;
- and
- a piezoelectric actuator that is driven based on the PWM signal by the output portion and in which a driven member is attached to a bar-shaped driving member by frictional coupling and a piezoelectric element is fixed to one end of the driving member.
7 more elements
Dependencies are inferred from the claim text.