Power circuit and method for controlling drive and control voltages of an image formation apparatus
First Claim
1. A power circuit that supplies a power voltage to an image formation apparatus, comprising:
- a transformer having a primary winding, a plurality of secondary windings, and a first switching element connected to the primary winding, the transformer configured to input a primary voltage of the primary winding and to output respective secondary voltages from each of the secondary windings;
a synchronous rectifying unit including a second switching element the synchronous first rectifying unit connected to one of the secondary windings, the synchronous first rectifying unit configured to rectify the secondary voltage of the one of the secondary windings and to output a driving voltage;
a second rectifying unit connected to another of the secondary windings, the second rectifying unit configured to rectify the secondary voltage of the another of the secondary windings and to output a control voltage;
a pulse-width modulation control unit configured to control the primary winding based on a difference between the control voltage and a reference voltage, such that the driving voltage and the control voltage attain respective predetermined voltage levels; and
a synchronous rectification control unit configured to control the second switching element according to an operation mode, wherein, when the operation mode is a normal operation mode in which the image formation apparatus carries out image formation, the synchronous rectification control unit switches the second switching element to set the first synchronous rectifying unit to an electrically conducting state whereby the driving voltage is output, and when the operation mode is an energy saving mode in which the image formation apparatus is in a waiting state, the synchronous rectification control unit switches the second switching element to set the synchronous first rectifying unit to an electrically non-conducting state whereby the driving voltage is not output.
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Abstract
Synchronous rectifier circuits are provided for each secondary windings of a transformer. Field-effect transistors of which ON voltage is lower than the forward voltage of a diode are provided in each of the synchronous rectifier circuits. In an energy saving mode, the field-effect transistors in the synchronous rectifier circuit that outputs a diving voltage are turned OFF. A comparator circuit outputs a signal corresponding to a difference between a control voltage output from one of the synchronous rectifier circuits and a reference voltage. Based on this signal, a pulse-width modulation control circuit ON/OFF controls a field-effect transistor provided corresponding to a primary winding of a transformer in such a manner that the control voltage the reference control voltage attain predetermined levels.
44 Citations
13 Claims
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1. A power circuit that supplies a power voltage to an image formation apparatus, comprising:
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a transformer having a primary winding, a plurality of secondary windings, and a first switching element connected to the primary winding, the transformer configured to input a primary voltage of the primary winding and to output respective secondary voltages from each of the secondary windings;
a synchronous rectifying unit including a second switching element the synchronous first rectifying unit connected to one of the secondary windings, the synchronous first rectifying unit configured to rectify the secondary voltage of the one of the secondary windings and to output a driving voltage;
a second rectifying unit connected to another of the secondary windings, the second rectifying unit configured to rectify the secondary voltage of the another of the secondary windings and to output a control voltage;
a pulse-width modulation control unit configured to control the primary winding based on a difference between the control voltage and a reference voltage, such that the driving voltage and the control voltage attain respective predetermined voltage levels; and
a synchronous rectification control unit configured to control the second switching element according to an operation mode, wherein, when the operation mode is a normal operation mode in which the image formation apparatus carries out image formation, the synchronous rectification control unit switches the second switching element to set the first synchronous rectifying unit to an electrically conducting state whereby the driving voltage is output, and when the operation mode is an energy saving mode in which the image formation apparatus is in a waiting state, the synchronous rectification control unit switches the second switching element to set the synchronous first rectifying unit to an electrically non-conducting state whereby the driving voltage is not output. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of supplying a power voltage to an image formation apparatus, comprising:
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converting a primary voltage of a primary winding to respective secondary voltages of secondary windings;
rectifying the secondary voltage of one of the secondary windings and outputting a driving voltage;
rectifying the secondary voltage of another of the secondary windings and outputting a control voltage;
controlling the primary winding based on a difference between the control voltage and a variable reference voltage, such that the driving voltage and the control voltage attain respective predetermined voltage levels; and
switching, based on an operation mode, a second switching element connected to the one of the secondary windings.
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9. A power circuit that supplies a power voltage to an image formation apparatus, comprising:
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a transformer including a primary winding, a plurality of secondary windings, and a first switching element connected to the primary winding, the transformer configured to input a primary voltage of the primary winding and to output respective secondary voltages from each of the secondary windings;
a synchronous first rectifying unit including a second switching element, the synchronous first rectifying unit connected to one of the secondary windings, the synchronous first rectifying unit configured to rectify the secondary voltage of the one of the secondary windings and to output a driving voltage;
a second rectifying unit connected to another of the secondary windings, the second rectifying unit configured to rectify the secondary voltage of the another of the secondary windings and to output a control voltage;
a pulse-width modulation control unit configured to control the primary winding based on a difference between the control voltage and a variable reference voltage, such that the driving voltage and the control voltage attain respective predetermined voltage levels; and
a synchronous rectification control unit configured to control the second switching element according to an operation mode. - View Dependent Claims (10)
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11. A method of supplying a power voltage to an image formation apparatus, comprising:
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converting a primary voltage of a primary winding to respective secondary voltages of secondary windings;
rectifying the secondary voltage of one of the secondary windings and outputting a driving voltage;
rectifying the secondary voltage of another of the secondary windings and outputting a control voltage;
controlling the primary winding based on a difference between the control voltage and a reference voltage, such that the driving voltage and the control voltage attain respective predetermined voltage levels; and
switching a second switching element connected to the one of the secondary windings, such that (1) during a normal operation mode in which the image formation apparatus carries out image formation, the driving voltage is output, and (2) during an energy saving mode in which the image formation apparatus is in a waiting state, the driving voltage is not output. - View Dependent Claims (12, 13)
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Specification