Power supply system and image forming apparatus having power supply system

• US 8,958,713 B2
• Filed: 03/26/2014
• Issued: 02/17/2015
• Est. Priority Date: 03/27/2013
• Status: Active Grant

• Current Assignee: Brother Kogyo Kabushiki Kaisha
• Original Assignee: Brother Kogyo Kabushiki Kaisha
• Inventors: Inukai, Katsumi
• Primary Examiner(s): TRAN, DUNG D
• Application Number:
  US14/225,907
• Publication Number:
  US 20140293358A1
• Time in Patent Office: 328 Days
• Field of Search: None
• US Class Current: 399/88
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 1/083 for the ignition at the zero crossing of the voltage or the current
• CPC Class Codes: H02M 7/05 Capacitor coupled rectifiers
• CPC Class Codes: H02M 7/217 using semiconductor devices only
• CPC Class Codes: H04N 1/00888 Control thereof
• 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 power supply system includes: a switching power supply generating a voltage from an alternating current power supply; capacitors connected to the alternating current power supply; a rectification circuit configured to rectify an alternating current voltage applied to the capacitors; a backflow regulation regulating backflow of current from the switching power supply; a signal generation circuit generating a detection signal corresponding to a zero cross point of the alternating current power supply; a power supply line connected to the switching power supply and the rectification circuit; an electricity storage unit connected to the power supply line; a voltage limit element configured to limit a voltage of the output line of the rectification circuit, and a control unit, power being fed to the control unit through the power supply line. The control unit is configured to detect a zero cross point based on the detection signal.

Claims

1. A power supply system comprising:

a switching power supply configured to rectify and smooth an alternating current voltage of an alternating current power supply and generate a predetermined direct current voltage;

a first capacitor including a first electrode and a second electrode, the first electrode being connected to one end of the alternating current power supply;

a second capacitor including a third electrode and a fourth electrode, the third electrode being connected to the other end of the alternating current power supply;

a rectification circuit configured to rectify an alternating current voltage applied to the first and second capacitors, the rectification circuit including an output line connected with an output line of the switching power supply;

a backflow regulation element that is provided on the output line of the rectification circuit and is configured to regulate backflow of current from the switching power supply towards the rectification circuit;

a signal generation circuit connected to the output line of the rectification circuit, the signal generation circuit configured to generate a detection signal corresponding to a zero cross point of the alternating current power supply based on an output of the rectification circuit;

a power supply line positioned at a more downstream side than the backflow regulation element and connected to the output line of the switching power supply and the output line of the rectification circuit;

an electricity storage unit connected to the power supply line;

a voltage limit element configured to limit a voltage of the output line of the rectification circuit to be lower than a voltage of the power supply line, and

a control unit that is positioned at a more downstream side than the electricity storage unit, power being fed to the control unit through the power supply line,

wherein the control unit is configured to detect a zero cross point based on the detection signal.

2. The power supply system according to claim 1, wherein the backflow regulation element is a diode.

3. The power supply system according to claim 1, wherein the signal generation circuit includes a switching device configured to be turned on and off based on the output of the rectification circuit and generate the detection signal corresponding to the zero cross point of the alternating current power supply.

4. The power supply system according to claim 3 further comprising a reverse voltage applying circuit configured to turn off the switching device by applying, to a control terminal of the switching device, a voltage having a reverse polarity to a voltage turning on the switching device.

5. The power supply system according to claim 4, wherein

the switching device is a transistor having an emitter connected to a reference potential-side and a collector connected to the output line of the rectification circuit, and

the reverse voltage applying circuit includes:

a capacitor provided between a base of the transistor and the output line of the rectification circuit,

a first discharge resistance connected between the output line of the rectification circuit and the reference potential, and

a second discharge resistance connected between the emitter and base of the transistor.

6. The power supply system according to claim 1, wherein the electricity storage unit includes a dedicated charging path having impedance lower than a charging path passing through the power supply line.

7. The power supply system according to claim 6, further comprising:

a constant voltage element configured to make a voltage of the power supply line be a constant voltage that is a voltage lower than the output voltage of the switching power supply; and

a current limit element that is provided on the power supply line and is configured to limit current flowing from the switching power supply towards the constant voltage element.

8. The power supply system according to claim 1, further comprising a switching circuit configured to switch an output state where the switching power supply generates the direct current voltage and a stop state where the switching power supply stops an output,

wherein the electricity storage unit stores electricity by output current of the rectification circuit or output current of the switching power supply, and

wherein the stored electricity becomes power for the switching circuit.

9. An image forming apparatus comprising:

a power supply system comprising;

a switching power supply configured to rectify and smooth an alternating current voltage of an alternating current power supply and generate a predetermined direct current voltage;

a first capacitor including a first electrode and a second electrode, the first electrode being connected to one end of the alternating current power supply;

a second capacitor including a third electrode and a fourth electrode, the third electrode being connected to the other end of the alternating current power supply;

a rectification circuit configured to rectify an alternating current voltage applied to the first and second capacitors, the rectification circuit including an output line connected with an output line of the switching power supply;

a backflow regulation element that is provided on the output line of the rectification circuit and is configured to regulate backflow of current from the switching power supply towards the rectification circuit;

a signal generation circuit connected to the output line of the rectification circuit, the signal generation circuit configured to generate a detection signal corresponding to a zero cross point of the alternating current power supply based on an output of the rectification circuit;

a power supply line positioned at a more downstream side than the backflow regulation element and connected to the output line of the switching power supply and the output line of the rectification circuit;

an electricity storage unit connected to the power supply line;

a voltage limit element configured to limit a voltage of the output line of the rectification circuit to be lower than a voltage of the power supply line, and

a control unit that is positioned at a more downstream side than the electricity storage unit, power being fed to the control unit through the power supply line; and

an image forming unit that forms an image,

wherein the control unit is configured to detect a zero cross point based on the detection signal, and control the image forming unit by using the detection of the zero cross point.

10. The image forming apparatus according to claim 9, wherein

the image forming apparatus includes a communication unit transmitting and receiving FAX data and having a FAX function, and

the control unit includes an RTC circuit configured to measure current time.