Current resonance power supply for detecting overcurrent based on an output from a current compensation unit

• US 8,976,545 B2
• Filed: 04/12/2011
• Issued: 03/10/2015
• Est. Priority Date: 04/21/2010
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Samejima, Keisuke, Fukutani, Takayuki
• Primary Examiner(s): Berhane, Adolf
• Assistant Examiner(s): NASH, GARY A
• Application Number:
  US13/084,784
• Publication Number:
  US 20110261592A1
• Time in Patent Office: 1,428 Days
• Field of Search: 363/21.02, 363/21.03, 363/21.16, 363/56.03, 323/284
• US Class Current: 363/21.02
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A current resonance power supply includes a current detecting unit detecting a current flowing through a primary side of a transformer and a current compensating unit compensating the current detected by the current detecting unit in accordance with a variation in voltage input into the primary side of the transformer. The current resonance power supply detects overcurrent on the basis of an output from the current compensating unit.

Claims

1. A current resonance power supply including a transformer including a primary winding, a secondary winding and an auxiliary winding, a first switching element, and a second switching element connected in series with the first switching element, wherein one end of the primary winding of the transformer is connected between the first and the second switching elements, other end of the primary winding of the transformer is connected to the second switching element via a resonance capacitor, the first and second switching elements are alternately operated to resonate the primary winding with the resonance capacitor in order to induce an alternating current voltage at the secondary winding of the transformer, and a voltage is supplied to a control unit through the auxiliary winding, the current resonance power supply comprising:

the control unit configured to control operations of the first and the second switching elements;

a current detecting circuit that is connected between the other end of the primary winding and an input terminal of the control unit and that detects a current flowing through a primary side of the transformer;

a current compensating circuit that is connected between the one end of the primary winding and the current detecting circuit and that compensates the current detected by the current detecting circuit,

wherein the control unit detects overcurrent if a value of the current compensated by the current compensating circuit exceeds a threshold value to stop the operations of the first and second switching elements;

a switch used to turn on or off the voltage input into the primary side of the transformer; and

a voltage supply control unit configured to detect turning-off of the switch, and configured to turn off the supply of the voltage from the auxiliary winding to the control unit.

2. The current resonance power supply according to claim 1,

wherein the current compensating circuit is a circuit in which a diode and a resistor are connected between the one end of the primary winding and the first and second switching elements.

3. An image forming apparatus comprising:

an image forming part configured to form an image;

a controller configured to control an operation of the image forming part; and

a power supply configured to supply a voltage to the controller,

wherein the power supply includes a transformer including a primary winding, a secondary winding and an auxiliary winding, a first switching element, and a second switching element connected in series with the first switching element, wherein one end of a primary winding of the transformer is connected between the first and the second switching elements, other end of the primary winding of the transformer is connected to the second switching element via a resonance capacitor, and the first and second switching elements are alternately operated to resonate the primary winding with the resonance capacitor in order to induce an alternating current voltage at a secondary winding of the transformer and a voltage is supplied to a control unit through the auxiliary winding, the power supply comprising;

the control unit configured to control operations of the first and the second switching elements;

a current detecting circuit that is connected between the other end of the primary winding and an input terminal of the control unit and that detects a current flowing through a primary side of the transformer;

a current compensating circuit that is connected between the one end of the primary winding and the current detecting circuit and that compensates the current detected by the current detecting circuit,

wherein the control unit detects overcurrent if a value of the current compensated by the current compensating circuit exceeds a threshold value to stop the operations of the first and second switching elements,

a switch used to turn on or off the voltage input into the primary side of the transformer; and

a voltage supply control unit configured to detect turning-off of the switch, and configured to turn off the supply of the voltage from the auxiliary winding to the control unit.

4. The image forming apparatus according to claim 3,

wherein the current compensating circuit is a circuit in which a diode and a resistor are connected between the one end of the primary winding and the first and second switching elements.