DISCHARGING CIRCUIT AND POWER SUPPLY

• US 20120207505A1
• Filed: 02/13/2012
• Published: 08/16/2012
• Est. Priority Date: 02/16/2011
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Hayasaki, Minoru, Kobayashi, Junya
• Granted Patent: US 8,937,471 B2
• Time in Patent Office: Days
• US Class Current: 399/88
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 1/322 Means for rapidly discharging a capacitor of the converter for protecting electrical components or for preventing electrical shock

Abstract

A discharging circuit includes a filter unit connected between the input lines of a commercial AC power supply, a switch whose operations are controlled by the filter unit; and a discharging unit which discharges voltage of the capacitance element when the switch unit is turned on.

Claims

1. A discharging circuit which discharges voltage of a capacitance element for noise reduction connected between input lines for AC voltage to be input from a commercial AC power supply, the discharging circuit comprising:

a filter unit connected between the input lines;

a switching unit whose operations are controlled by the filter unit; and

a discharging unit which discharges voltage of the capacitance element when the switching unit is turned on.

2. The discharging circuit according to claim 1, wherein the filter unit has a resistance and a capacitor connected in series between the lines;

and

the time constant of the filter unit is longer than the cycle of the input AC voltage.

3. The discharging circuit according to claim 2, wherein

the switching unit and the discharging unit are connected in series between the lines;

and

the switching unit is connected between the resistance of the filter unit and the capacitor.

4. The discharging circuit according to claim 2, wherein

the discharging unit is a resistance element, and

the resistance value of the resistance element of the filter unit is higher than the resistance value of the resistance element of the discharging unit.

5. The discharging circuit according to claim 1, wherein the switching unit is a bidirectional thyristor capable of feeding current bidirectionally.

6. The discharging circuit according to claim 1, wherein the switching unit has a first transistor which feeds current in one direction and a second transistor which feeds current in the opposite direction from that of the first transistor.

7. The discharging circuit according to claim 6, wherein the switching unit has a first filter unit connected to the first transistor, and a second filter unit connected to the second transistor.

12. The discharging circuit according to claim 1, further comprising a control unit which turns on the switching unit if detects an output from the rectifying unit.

8. A discharging circuit which discharges voltage of a capacitance element for noise reduction connected between input lines for AC voltage to be input from a commercial AC power supply, the discharging circuit comprising:

a rectifying unit connected between the input lines;

a discharging unit connected to the rectifying unit;

a filter unit connected to the discharging unit; and

a switching unit whose operations are controlled by the filter unit, wherein

the discharging unit discharges voltage of the capacitance element when the switching unit is turned on.

9. The discharging circuit according to claim 8, wherein the rectifying unit includes two diodes connected in series between the input lines, and the discharging unit is connected between the two diodes.

10. The discharging circuit according to claim 8 wherein the switching unit includes an FET.

11. The discharging circuit according to claim 8, further comprising:

a comparing unit which compares an output from the filter unit and a reference value; and

a transmitting unit which transmits an output of the comparing unit.

13. A power supply which rectifies and smoothes AC voltage input from a commercial AC power supply and outputs voltage, the power supply comprising:

a rectifying unit which rectifies the input AC voltage;

a capacitance element for noise reduction connected between the rectifying unit and an input unit for the AC voltage; and

a discharging circuit provided between the capacitance element and the rectifying unit, wherein

the discharging circuit has

a filter unit connected between the input lines;

a switching unit whose operations are controlled by the filter unit; and

a discharging unit which discharges voltage of the capacitance element when the switching unit is turned on.

14. An image forming apparatus having the power supply according to claim 13, comprising a control unit which controls an image forming operation, wherein voltage is supplied from the power supply to the control unit.

15. A power supply which rectifies and smoothes AC voltage input from a commercial AC power supply and outputs voltage, the power supply comprising:

a rectifying unit which rectifies the input AC voltage;

a capacitance element for noise reduction connected between the rectifying unit and an input unit for the AC voltage; and

a discharging circuit provided between the capacitance element and the rectifying unit, wherein the discharging circuit has

a rectifying unit connected between the input lines;

a discharging unit connected to the rectifying unit;

a filter unit connected to the discharging unit; and

a switching unit whose operations are controlled by the filter unit; and

the discharging unit discharges voltage of the capacitance element when the switching unit is turned on.

16. An image forming apparatus having the power supply according to claim 15, comprising a control unit which controls an image forming operation, wherein voltage is supplied from the power supply to the control unit.