POWER SUPPLY APPARATUS AND IMAGE FORMING APPARATUS

• US 20130329469A1
• Filed: 05/30/2013
• Published: 12/12/2013
• Est. Priority Date: 06/08/2012
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Kubota, Junichi
• Granted Patent: US 9,160,235 B2
• Time in Patent Office: Days
• US Class Current: 363/21.16
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence

Abstract

The power supply apparatus includes the feedback winding of a transformer having a first winding, and a second winding whose number of turns is larger than that of the first winding. A voltage output from the transformer is detected. Based on the detected voltage, connection between a switch element and the first winding or the second winding is switched.

Claims

1. A power supply apparatus comprising:

a transformer including a primary winding, a secondary winding, and a feedback winding, the feedback winding including a first winding and a second winding whose number of turns is larger than a number of turns of the first winding;

a switch element connected to the primary winding in series and turns on/off a power supply line to the transformer by a voltage applied to a control terminal, the switch element continuously turned on/off when the transformer outputs a predetermined voltage and intermittently turned on/off when a voltage lower than the predetermined voltage is output;

a detection unit that detects the voltage output from the transformer; and

a switching unit that switches to connect the first winding to the control terminal of the switch element when the voltage detected by the detection unit is at least the predetermined voltage and connect the second winding to the control terminal when the voltage detected by the detection unit is the voltage lower than the predetermined voltage.

2. An apparatus according to claim 1, wherein the detection unit includes a Zener diode connected with a terminal of the second winding in series, and a capacitor connected with the Zener diode in series.

3. A power supply apparatus comprising:

a transformer including a primary winding, a secondary winding, and a feedback winding, the feedback winding including a center tap portion;

a switch element that is connected in series with the primary winding and turns on/off power supply to the transformer by a voltage applied to a control terminal, the switch element continuously turned on/off when the transformer outputs a predetermined voltage, and intermittently turned on/off when a voltage lower than the predetermined voltage is output, and

a detection unit that detects the voltage output from the transformer; and

a switching unit that switches to connect the center tap portion to the control terminal of the switch element when the voltage detected by the detection unit is at least the predetermined voltage and connect a terminal of the feedback winding to the control terminal when the voltage detected by the detection unit is lower than the predetermined voltage.

4. An apparatus according to claim 3, wherein the detection unit includes a Zener diode connected with the terminal of the feedback winding in series, and a capacitor connected with the Zener diode in series.

5. An image forming apparatus comprising:

a control unit that controls an operation of the image forming apparatus; and

a power supply that supplies power to the control unit,

the power supply comprising;

a transformer including a primary winding, a secondary winding, and a feedback winding, the feedback winding including a first winding and a second winding whose number of turns is larger than a number of turns of the first winding;

a switch element that is connected in series with the primary winding and turns on/off a power supply line to the transformer by a voltage applied to a control terminal, the switch element continuously turned on/off when the transformer outputs a predetermined voltage, and intermittently turned on/off when a voltage lower than the predetermined voltage is output;

a detection unit that detects the voltage output from the transformer; and

a switching unit that switches to connect the first winding to the control terminal of the switch element when the voltage detected by the detection unit is the predetermined voltage and connect the second winding to the control terminal when the voltage detected by the detection unit is the voltage lower than the predetermined voltage.

6. An apparatus according to claim 5, wherein the detection unit includes a Zener diode connected with a terminal of the second winding in series, and a capacitor connected with the Zener diode in series.

7. An image forming apparatus comprising:

a control unit that controls an operation of the image forming apparatus; and

a power supply that supplies power to the control unit,

the power supply comprising;

a transformer including a primary winding, a secondary winding, and a feedback winding, the feedback winding including a center tap portion;

a switch element that connected with the primary winding in series and turns on/off power supply to the transformer by a voltage applied to a control terminal, the switch element continuously turned on/off when the transformer outputs a predetermined voltage, and intermittently turned on/off when a voltage lower than the predetermined voltage is output, and

a detection unit that detects the voltage output from the transformer; and

a switching unit that switches to connect the center tap portion to the control terminal of the switch element when the voltage detected by the detection unit is at least the predetermined voltage and connect a terminal of the feedback winding to the control terminal when the voltage detected by the detection unit is the voltage lower than the predetermined voltage.

8. An apparatus according to claim 7, wherein the detection unit includes a Zener diode connected with the terminal of the feedback winding in series, and a capacitor connected with the Zener diode in series.