JP2017188978A - Electric power supply and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discharge an electric charge charged to a X capacitor with a simple structure.SOLUTION: A zero-cross detection circuit 202 includes: a Y capacitor discharge part 206 that is connected to an output terminal of a live side, a neutral side line, and a bridge diode BD1, and discharges a charging electric charge of a Y capacitor C3; a zero-cross detection resistance R1 in which one end is connected to the Y capacitor discharge part 206, and that is for detecting a zero-cross of an AC voltage to be inputted; and a zero-cross detection part 205 that is connected to the other end of the zero-cross detection resistance R1 and the output terminal of the bridge diode BD1, and detects the zero-cross of the AC voltage by a voltage generated in the zero-cross detection resistance R1. The electric charge charged to a X capacitor C1 is discharged through the Y capacitor discharge part 206, the zero-cross detection resistance R1, the zero-cross detection part 205, and the bridge diode BD1 in a first state, and is discharged through the Y capacitor discharge part 206 and the bridge diode BD1 in a second state.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a power supply apparatus and an image forming apparatus including a zero cross detection circuit suitable for controlling a fixing device mounted on an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer.

  2. Description of the Related Art Image forming apparatuses such as electrophotographic copying machines and printers include a fixing device that heats and presses an unfixed toner image on a recording material to fix it on the recording material. In the power supply device that controls the power supply to the fixing device, the AC voltage supplied from the AC power source is phase-controlled using a bidirectional thyristor (hereinafter referred to as triac) or the like, and the power supply is controlled. Is widely used. In phase control, power supply control is performed based on the timing at which the AC voltage becomes 0 V (hereinafter referred to as zero cross timing), and therefore it is necessary to accurately detect the zero cross timing. On the other hand, in order to remove noise in the power supply line, the power supply apparatus is often provided with an across-the-line capacitor (hereinafter referred to as an X capacitor) between two lines of the AC power supply. In consideration of safety when the user pulls out the power cable from the AC power supply, a discharge means such as a discharge resistor is provided for discharging the charge charged in the X capacitor in a short time. For example, Patent Document 1 discloses a configuration in which a zero-cross detection resistor to which a voltage between two lines of an AC power supply of a zero-cross detection circuit that detects zero-cross timing is applied is also used as a discharge resistor that discharges an X capacitor.

JP 2013-123348 A

  However, in the X capacitor discharge method using the zero cross detection circuit described above, the X capacitor can be discharged by the zero cross detection resistor only when the polarity of the voltage charged to the X capacitor is positive or negative. there were. Therefore, when the polarity of the voltage charged in the X capacitor is a voltage polarity that cannot be discharged by the zero-crossing detection resistor, there is a problem that another discharge means is required to discharge the charge charged in the X capacitor. is there.

  The present invention has been made under such circumstances, and an object of the present invention is to discharge the electric charge charged in the X capacitor with a simple configuration.

  In order to solve the above-described problems, the present invention has the following configuration.

  (1) A first capacitor connected between a first line to which an AC voltage is input from an AC power source and a second line, and the first capacitor and the second line are input. Rectification means for full-wave rectification of the AC voltage, a second capacitor provided between the output terminal of the rectification means and ground, zero-cross detection means for detecting zero-cross of the AC voltage, and detection of the zero-cross And a control unit that controls the zero-crossing detection unit by switching between a first state in which the zero-crossing detection is performed and a second state in which the zero-crossing detection is performed, wherein the zero-crossing detection unit includes: The first line and the second line are connected to the output terminal of the rectifying means, and a discharge part for discharging the charge charged in the second capacitor is connected to the discharge part. A detection resistor for detecting a zero cross of the AC voltage input through the discharge unit, and connected to the other end of the detection resistor and the output terminal of the rectifier, and based on a voltage generated in the detection resistor A detecting unit that detects a zero cross of the AC voltage, and the charge charged in the first capacitor is the discharging unit, the detecting resistor, the detecting unit, and the rectifier in the first state. The power supply device is characterized in that it is discharged through the means and discharged through the discharge section and the rectifying means in the second state.

  (2) An image forming apparatus comprising: an image forming unit that forms an image on a recording material; and the power supply device according to (1).

  According to the present invention, the electric charge charged in the X capacitor can be discharged with a simple configuration.

Schematic configuration diagram of image forming apparatuses according to first and second embodiments The figure which shows the circuit structure of the power supply device of Example 1. FIG. 6 is a flowchart illustrating a control sequence of the power supply device according to the first embodiment. The figure which shows the circuit structure of the power supply device of Example 2. 7 is a flowchart illustrating a control sequence of the power supply device according to the second embodiment.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

[Configuration of Image Forming Apparatus]
FIG. 1 is a cross-sectional view illustrating a schematic configuration of a monochrome printer that forms an image using black toner, which is an example of an electrophotographic image forming apparatus 10. In FIG. 1, recording papers, which are recording materials stacked on the paper feed cassette 11, are fed one by one from the paper feed cassette 11 by the pickup roller 12, and conveyed to the registration roller 14 by the paper feed roller 13. . The recording paper conveyed to the registration roller 14 is further conveyed to the transfer roller 20 at a predetermined timing. The process cartridge 15 as an image forming unit is integrally configured by a charging unit 16, a developing roller 17 as a developing unit, a cleaner 18 as a cleaning unit, and a photosensitive drum 19 as a photosensitive member. Then, an unfixed toner image is formed on the conveyed recording paper by a known series of electrophotographic process processing described below. The surface of the photosensitive drum 19 is uniformly charged by the charging unit 16 and then exposed based on the image signal by the scanner unit 21 which is an exposure unit. Laser light emitted from the laser diode 22 in the scanner unit 21 is deflected by the rotary polygon mirror 23, scans the photosensitive drum 19 through the reflection mirror 24, and a latent image is formed on the photosensitive drum 19. . The latent image formed on the photosensitive drum 19 has toner attached thereto by the developing roller 17 and is visualized as a toner image. Then, the toner image on the photosensitive drum 19 is transferred to the recording paper conveyed from the registration roller 14 by the transfer roller 20. The recording paper on which the toner image has been transferred is conveyed to the fixing device 100, and the unfixed toner image on the recording paper is heated and pressurized by the fixing device 100 and fixed on the recording paper. Then, the recording paper is discharged out of the image forming apparatus 10 by the intermediate paper discharge roller 26 and the paper discharge roller 27, and a series of printing operations is completed.

  A motor 30 (shown as M in the figure) applies a driving force to the driving system of each device such as the fixing device 100. Further, the power supply to the fixing device 100 is controlled by a control method over a plurality of periods including phase control, wave number control, or phase control waveform based on zero cross timing of an AC power supply 201 described later. The power supply apparatus 200 is a power supply apparatus used in the image forming apparatus 10 and is connected to an AC power supply 201 (shown as AC in the figure) such as a commercial power supply via a power cable 50. The image forming apparatus to which the power supply apparatus 200 can be applied is not limited to the one illustrated in FIG. 1, and may be an image forming apparatus such as a color printer including a plurality of image forming units. Further, the image forming apparatus may include a primary transfer unit that transfers the toner image on the photosensitive drum 19 to the intermediate transfer belt and a secondary transfer unit that transfers the toner image on the intermediate transfer belt to the recording paper.

[Configuration of power supply unit]
FIG. 2 is a diagram illustrating a circuit configuration of the power supply device 200 according to the first embodiment. The AC power supply 201 (shown as AC in the figure) is between the live side line (shown as LIVE in the figure) and the neutral line (shown as NEWTRAL in the figure) as the second line. AC voltage is output. The AC voltage input from the AC power supply 201 is full-wave rectified by the bridge diode BD1 and smoothed by the electrolytic capacitor C2. The bridge diode BD1 and the electrolytic capacitor C2 constitute rectifying and smoothing means. Of the DC voltage potential smoothed by the electrolytic capacitor C2, the higher potential side is DCH and the lower potential side is DCL.

  A DC / DC converter 1 (hereinafter referred to as converter 1) which is a first conversion means is an insulated DC / DC converter. Converter 1 converts a DC voltage charged in capacitor C2 (DC voltage applied between DCL to DCH) input to the primary side and outputs DC voltage V1 to the secondary side. Converter 1 outputs power supply voltage Vcc, which is a first DC voltage, to an auxiliary winding (not shown). The capacitor C1, which is the first capacitor, is an X capacitor, and is disposed between two power supply lines, that is, between the live side line and the neutral side line, and is a capacitor for the purpose of noise removal. The resistor R2 is a discharge resistor of the X capacitor used for discharging the capacitor C1 (hereinafter also referred to as X capacitor C1) which is an X capacitor. Also, one end is connected to DCL (the power supply line on the low potential side of the DC voltage smoothed by the electrolytic capacitor C2) which is the output end of the bridge diode BD1, and the other end is connected to the ground (indicated as GND in the figure). The (grounded) capacitor C3 is a Y capacitor. A capacitor C3 (hereinafter also referred to as a Y capacitor C3), which is a second capacitor, is provided as a noise countermeasure.

  The control unit 203 serving as a control unit is a CPU that controls the power supply apparatus 200. Here, the control of the power supply apparatus 200 is performed by the control unit 203, but a controller that is a CPU (not illustrated) of the image forming apparatus 10 described with reference to FIG. Details of the control by the control unit 203 will be described later. The zero-cross detection circuit 202 includes a Y-capacitor discharge unit 206 (to be described later), a zero-cross detection resistor R1 to which a voltage between two power supply lines is applied, and a zero-cross detection unit 205. The zero cross detection circuit 202 detects the zero cross timing of the AC voltage of the AC power supply 201 and outputs a zero cross signal (hereinafter, referred to as Zerox signal) to the control unit 203.

  The above-described fixing device 100 has a heater (not shown) for heating the unfixed toner image on the recording paper. In the image forming apparatus 10, the heater temperature is controlled by supplying power to the heater from the AC power supply 201. In addition, a bidirectional thyristor (triac) or relay, which is a semiconductor switch, is provided in a power supply path from the AC power supply 201 to the fixing device 100 in order to supply and cut off power from the AC power supply 201. A controller (not shown) of the image forming apparatus 10 detects the zero cross timing of the AC voltage of the AC power supply 201 by detecting the rising and falling edges of the Zerox signal. A controller (not shown) controls the power supply from the AC power supply 201 to the heater of the fixing device 100 by turning on and off the triac, for example, using the detected zero cross timing as a trigger. Thereby, the temperature control of the heater of the fixing device 100 is performed.

[X capacitor discharge method]
Next, a method for discharging the electric charge charged in the X capacitor C1 will be described. When the user pulls out the power cable 50 that connects the AC power supply 201 and the power supply device 200 from the power outlet, the X capacitor C1 may be charged. Therefore, in order to prevent the user from touching the terminal of the power cable 50 and receiving an electric shock, means for discharging the charge charged in the X capacitor C1 is required. In this embodiment, the discharge resistor R2 of the X capacitor C1 is used as the first discharge means for discharging the electric charge charged in the X capacitor C1, and the zero-cross detection circuit 202 described later is used as the second discharge means. Thereby, the power supply device 200 has a circuit configuration that can discharge the electric charge of the X capacitor C1 even when one of the first discharging means and the second discharging means fails.

[Power supply voltage of zero cross detection circuit]
Next, the power supply voltage supplied to the zero cross detection circuit 202 of the power supply apparatus 200 will be described with reference to FIG. A voltage Vcc used as the power supply voltage of the zero cross detection circuit 202 is a power supply voltage output from an auxiliary winding (not shown) of the converter 1. The power supply voltage Vcc is supplied to the zero cross detection unit 205 and the Y capacitor discharge unit 206 through the primary phototransistor of the photocoupler PC1. The operation of the photocoupler PC1 which is a switch means is controlled by a Standby signal (standby signal) output from the control unit 203. The control unit 203 sets the standby signal to a high (high level) state at the time of printing or standby in which the image forming apparatus 10 can detect the zero-cross timing, and sets the standby signal to low (low level) when in the energy saving state. Set the state. When the control unit 203 sets the standby signal to the high state, a current flows through the secondary diode of the photocoupler PC1, and the primary phototransistor is turned on. As a result, the power supply voltage Vcc is supplied to the zero cross detection unit 205 and the Y capacitor discharge unit 206 of the zero cross detection circuit 202, and the zero cross timing of the AC voltage input from the AC power supply 201 can be detected. On the other hand, when the control unit 203 sets the Standby state to the Low state, no current flows through the secondary side diode of the photocoupler PC1, and the primary side phototransistor is turned off. As a result, the power supply voltage Vcc is not supplied to the zero cross detection circuit 202, and the zero cross timing of the AC voltage cannot be detected.

  Incidentally, in the same manner as the power supply device disclosed in Patent Document 1 described above, in the power supply device 200 of this embodiment, a Y capacitor is provided in the subsequent stage of the bridge diode BD1 for full-wave rectification of the AC voltage input from the AC power supply 201. C3. In the power supply device 200 having the Y capacitor C3, in order to detect an accurate zero cross timing of the AC voltage of the AC power supply 201, it is necessary to discharge the Y capacitor C3. Therefore, the power supply device 200 is provided with a Y capacitor discharge unit 206 having discharge resistors R3 and R4 for discharging the Y capacitor C3.

[Y capacitor discharge part]
Next, the Y capacitor discharge unit 206 will be described. If the charge (charge voltage) charged in the Y capacitor C3 described above is not discharged well, the zero cross timing detected by the zero cross detection unit 205 is shifted due to the charged charge. Therefore, a Y capacitor discharge unit 206 is provided in order to discharge the electric charge charged in the Y capacitor C3 and accurately detect the zero cross timing. In the Y capacitor discharge unit 206, the live (Live) side line of the power supply device 200 is connected to the anode terminal of the diode D1 constituting the first discharge unit, and the cathode terminal is the Y capacitor C3 constituting the first discharge unit. Is connected to one end of the discharge resistor R3. The other end of the discharge resistor R3 is connected to the collector terminal of the transistor Q1, which is a high voltage switching element, and the emitter terminal of the transistor Q1 is connected to the Y capacitor C3. The base terminal of the transistor Q1 is connected to the power supply voltage Vcc via a pull-up resistor R9 (hereinafter referred to as a resistor R9).

  On the other hand, the neutral side line of the power supply device 200 is connected to the anode terminal of the diode D2 constituting the second discharge part, and the cathode terminal of the diode D2 is connected to the Y capacitor C3 constituting the second discharge part. It is connected to one end of the discharge resistor R4. The other end of the discharge resistor R4 is connected to the collector terminal of the transistor Q1. In the state where the zero-cross timing can be detected, a current flows from the power supply voltage Vcc to the base terminal of the transistor Q1 via the resistor R9, and the transistor Q1 becomes conductive. As a result, a current flows through the discharge resistors R3 and R4 of the Y capacitor C3, and the zero-cross detection circuit 202 can detect the zero-cross timing of the AC power supply 201 with high accuracy. The resistor R9 is a pull-up resistor for driving the transistor Q1, and the resistor R8 is a resistor for protecting the transistor Q1.

  Incidentally, in order for the zero-cross detection circuit 202 to accurately detect the zero-cross timing of the AC power supply 201, it is necessary to make the resistance values of the discharge resistors R3 and R4 sufficiently smaller than the capacitance of the Y capacitor C3. However, if the resistance values of the discharge resistors R3 and R4 are reduced, the AC voltage from the AC power supply 201 is applied to the discharge resistors R3 and R4. Therefore, if the resistance value is small, the power consumption increases. Therefore, in an energy saving state where it is necessary to reduce power consumption, such as when the power supply device 200 is turned off or in sleep, the current flowing through the discharge resistors R3 and R4 is reduced by turning off the high voltage transistor Q1. It is necessary to shut off. In the present embodiment, a high-breakdown-voltage bipolar transistor is used as the transistor Q1, but other switch means such as an FET (field effect transistor) or a relay may be used.

[Circuit operation in the first state]
Next, the circuit operation of the power supply apparatus 200 in the first state, which is an energy saving state in which power consumption is suppressed in a light load state where image formation is not performed such as when the power is turned off or during sleep, will be described. Since the Standby signal is in the low state in the energy saving state, the power supply voltage Vcc is not supplied to the zero cross detection circuit 202 as described above. Therefore, in the zero-cross detection unit 205, no current flows through the pull-up resistor R6 (hereinafter referred to as resistor R6), the primary diode of the photocoupler PC2, and the collector terminal of the transistor Q2, so that power consumption can be suppressed. In the Y capacitor discharge unit 206, since the transistor Q1 is cut off, the current flowing from the live side line via the discharge resistor R3 and the current flowing from the neutral side line via the discharge resistor R4 are cut off, resulting in power consumption. Can be suppressed. In the first state, the secondary phototransistor of the photocoupler PC2 is always cut off (off state), so that the Zerox signal input to the control unit 203 is always in a high (high level) state. As a result, the first state is a state where the zero cross timing cannot be detected.

[Circuit operation in the second state]
Subsequently, the power supply apparatus 200 in the second state in which the image forming apparatus 10 is in a heavy load state where image formation such as standby or printing can be performed or can be performed and the zero cross timing can be detected. The circuit operation will be described. In a state where the zero cross timing can be detected, the Standby signal is set to a high (high level) state, and thus the power supply voltage Vcc is supplied to the zero cross detection unit 205 and the Y capacitor discharge unit 206 as described above. Thereby, the zero cross detection circuit 202 is in a state where the zero cross timing of the AC power supply 201 can be detected.

  When the potential of the live side line supplied from the AC power supply 201 is higher than the potential of the neutral side line, the base current flows to the base terminal of the transistor Q2 of the zero cross detection unit 205 via the diode D1 and the zero cross detection resistor R1. . As a result, when the transistor Q2 is turned on and becomes conductive, the primary diode of the photocoupler PC2 becomes nonconductive because the voltage applied to the anode terminal decreases, and the secondary phototransistor of the photocoupler PC2 becomes nonconductive. Turns off and shuts off. When the secondary side phototransistor of the photocoupler PC2 is cut off, the voltage of the Zerox signal rises through the pull-up resistor R7 by the output V1 of the converter 1, and the control unit 203 has a high (high level) level. A state Zerox signal is input. The resistor R5 and the capacitor C5 connected to the base terminal of the transistor Q2 are provided for adjusting the operation timing of the transistor Q2.

  On the other hand, when the potential of the live side line is lower than the potential of the neutral side line, the current flowing through the diode D2 and the discharge resistor R4 flows to the transistor Q1. At this time, since the potential of the DCL and the potential of the live side line are the same, no voltage is applied to the discharge resistor R3, so that no current flows through the base terminal of the transistor Q2, and the transistor Q2 is in the cut-off state. (OFF state). When the transistor Q2 is cut off, the primary side diode of the photocoupler PC2 is turned on when current flows from the power supply voltage Vcc through the resistor R6, and the secondary side phototransistor of the photocoupler PC2 is also turned on. When the secondary phototransistor of the photocoupler PC2 becomes conductive, a current flows from the output voltage V1 of the converter 1 to the secondary phototransistor of the photocoupler PC2 via the pull-up resistor R7. As a result, the voltage of the Zerox signal decreases, and the Zerox signal in the low (low level) state is input to the control unit 203. Thus, every time the potential of the live side line and the neutral side line is switched, the High (high level) state and the Low (low level) state of the Zerox signal are switched. The control unit 203 can detect the zero cross timing of the AC power supply 201 by detecting the rising of the Zerox signal from the low level to the high level and the falling from the high level to the low level. In the second state where the zero-cross timing can be detected, the resistor R6, the primary diode of the photocoupler PC2, the collector terminal of the transistor Q2, the discharge resistor R3, and the discharge resistor R4 are compared with the first state described above. The power consumption increases due to the flowing current.

[Discharge of X capacitor in the first state and the second state]
A method of discharging the X capacitor C1 in the first state and the second state of the power supply device 200 using the zero cross detection circuit 202 will be described. First, the discharge method in the first state where the power supply apparatus 200 is in the energy saving state will be described. In the first state, when the charge state of the X capacitor C1 is positive (the potential of the live side line is higher than that of the neutral side line), the charge of the X capacitor C1 is the diode D1, the zero-cross detection resistor R1, the bridge diode Discharged via BD1. On the other hand, when the charged state of the X capacitor C1 is negative (the potential of the live side line is lower than that of the neutral side line), the charge of the X capacitor C1 is discharged through the following current path. That is, the electric charge of the X capacitor C1 is discharged through the diode D2, the discharge resistor R4, the discharge resistor R3, the zero cross detection resistor R1, and the bridge diode BD1. In the first state, the current flowing through the zero-cross detection resistor R1 flows to the bridge diode BD1 via the base-emitter diode of the transistor Q2.

  Next, a discharging method in the second state in which the power supply apparatus 200 can detect the zero cross timing will be described. In the second state, when the charge state of the X capacitor C1 is positive (the potential of the live side line is higher than that of the neutral side line), the charge of the X capacitor C1 is the diode D1, the discharge resistor R3, the transistor Q1, It is discharged via the bridge diode BD1. On the other hand, when the charging state of the X capacitor C1 is negative (the potential of the live side line is lower than that of the neutral side line), the charge of the X capacitor C1 passes through the diode D2, the discharge resistor R4, the transistor Q1, and the bridge diode BD1. It is discharged through. Thus, even when the polarity charged in the X capacitor C1 is positive or negative in the first state and the second state of the power supply device 200, the zero cross detection circuit 202 is used to connect the X capacitor C1 to the X capacitor C1. The charged charge can be discharged. In this embodiment, it is assumed that the resistance value of the zero-crossing detection resistor R1 required for discharging the X capacitor C1 is larger than the resistance values of the discharge resistors R3 and R4 of the Y capacitor C3.

  By the way, in order to discharge the charged electric charge when the polarity charged in the X capacitor C1 is both positive and negative in the first state which is an energy saving state, one end of the zero-cross detection resistor R1 is It must be connected to the zero cross detection unit 205. The other end of the zero-cross detection resistor R1 must be connected to the diode D1 of the Y capacitor discharge unit 206 and the rectified portion that has been full-wave rectified by the diode D2. That is, after the live side line is rectified by the diode D1 when the potential of the live side line is higher than the neutral side line, and after the live side line is rectified by the diode D2 when the potential of the live side line is lower than the neutral side line. It must be a place. In the present embodiment, one end of the zero-cross detection resistor R1 is connected to a connection point between the diode D1 and the discharge resistor R3, and the other end is connected to the zero-cross detection unit 205. For example, one end of the zero-cross detection resistor R1 may be connected to a connection point between the diode D2 and the discharge resistor R4, and the other end may be connected to the zero-cross detection unit 205. In addition, when one end of the zero-cross detection resistor R1 is connected to the contact point of the diode D1 and the discharge resistor R3, it is the same even if the diode D2 connected in series and the discharge resistor R4 are replaced from the configuration of the zero-cross detection circuit 202. The effect of can be obtained. Similarly, when one end of the zero-cross detection resistor R1 is connected to the contact point of the diode D2 and the discharge resistor R4, the diode D1 and the discharge resistor R3 connected in series from the configuration of the zero-cross detection circuit 202 are interchanged. An effect can be obtained. The connection method of the zero-crossing detection resistor R1 shown in the zero-crossing detection circuit 202 is an example for discharging the charged charge regardless of whether the polarity charged in the X capacitor C1 is positive or negative. The connection method is not limited.

[Power supply control sequence]
FIG. 3 is a flowchart illustrating a control sequence of the power supply apparatus 200 by the control unit 203 of the present embodiment. The processing in FIG. 3 is started when a request to shift the power supply device 200 to the power ON state is generated by turning on the power switch of the power supply device 200 or connecting the power cable of the power supply device 200 to the AC power supply 201. This is executed by the control unit 203. In step (hereinafter referred to as “S”) 301, the control unit 203 sets the standby signal to the low (low level) state, and cuts off the power supply (supply of the power supply voltage Vcc) to the zero-cross detection circuit 202. . Thereby, the control unit 203 shifts the power supply device 200 to the first state in which no current flows through the discharge resistors R3 and R4 of the Y capacitor C3. In the power supply apparatus 200 according to the present embodiment, in the sleep state, which is an energy saving state, the power supply device 200 is in the first state in order to reduce power consumption.

  In step S302, the control unit 203 determines whether there is a request to shift to a power-off state due to a power switch off operation. If the control unit 203 determines that there is a request to shift to the power-off state, the control unit 203 ends the process, sets the power-off state, and if it determines that there is no request to shift to the power-off state, the processing is performed in step S303. Proceed to In S303, the control unit 203 determines whether there is a request to shift to the standby state. If the control unit 203 determines that there is a request to shift to the standby state, the process proceeds to S304. If the control unit 203 determines that there is no request to shift to the standby state, the control unit 203 holds the first state, The process returns to S302.

  In S304, the control unit 203 sets the Standby (standby) signal to a High (high level) state and supplies power to the zero-cross detection circuit 202 (supply of the power supply voltage Vcc). Thereby, the control part 203 makes the power supply device 200 transfer to the 2nd state into which an electric current flows into discharge resistance R3, R4 of Y capacitor | condenser C3. In the power supply apparatus 200 according to the present embodiment, in a standby state such as during printing, the second state in which the zero cross timing can be detected is set.

  In S305, the control unit 203 detects the zero cross timing of the AC power supply 201 based on the rising and falling timings of the Zerox signal. In S306, the control unit 203 determines whether there is a request for shifting to the sleep state. If the control unit 203 determines that there is a request to shift to the sleep state, the control unit 203 returns the process to S301. If the control unit 203 determines that there is no request to shift to the sleep state, the control unit 203 holds the second state, The process returns to S305.

  As described above, in the power supply device 200 of the present embodiment, the zero cross detection is performed using the zero cross detection resistor R1 having a large resistance value. Furthermore, the high breakdown voltage transistor Q1 switches between a state in which current flows through the discharge resistors R3 and R4 having a resistance value smaller than that of the zero-cross detection resistor R1 and a cutoff state. As a result, switching between a state where the zero-crossing timing can be detected (second state) and a state where the zero-crossing timing cannot be detected but the power consumption can be reduced (first state) by one high-breakdown voltage transistor is switched. Can do.

  Further, in this embodiment, the circuit configuration is such that the current from the X capacitor C1 flows to the zero-cross detection resistor R1 after rectification by the diode D1 that is the rectifier of the discharge resistor R3 and the diode D2 that is the rectifier of the discharge resistor R4. ing. Thereby, in the first state and the second state of the power supply device 200, when the polarity charged in the X capacitor C1 is both positive and negative, the charge charged in the X capacitor C1 is discharged. Can do.

Further, the power consumption of the zero cross detection circuit 202 in the first state in which the power consumption is reduced is substantially equal to the power consumption by the discharge resistor R2 of the X capacitor C1. That is, in this embodiment, the discharge resistor R2 of the X capacitor C1 is used as the first discharge means of the X capacitor C1, and the zero cross detection circuit 202 is replaced as the second discharge means in place of the discharge resistance R2 of the X capacitor. Used. As a result, for example, an increase in power consumption that occurs when a zero-cross detection circuit is newly added can be avoided. As described above, the zero-cross detection circuit 202 of the present embodiment can be discharged regardless of whether the polarity charged in the X capacitor C1 is positive or negative. The state where power is reduced can be switched.
As described above, according to the present embodiment, the electric charge charged in the X capacitor can be discharged with a simple configuration.

[Configuration of power supply unit]
Next, the power supply apparatus 400 of Example 2 is demonstrated with reference to FIG. FIG. 4 is a circuit diagram showing a configuration of the power supply device 400 of the present embodiment. The power supply device 400 shown in FIG. 4 differs from the power supply device 200 of the first embodiment in the following points. The zero cross detection circuit 402 has a configuration in which a circuit for detecting the voltage of the AC power supply 201 is added to the zero cross detection circuit 202 of the first embodiment. In addition to the converter 1, the power supply apparatus 400 includes a DC / DC converter 2 (hereinafter referred to as a converter 2) that is a second conversion unit that outputs a voltage V 2 that is a second DC voltage. Further, the power supply device 400 is added with a voltage dividing circuit (second voltage detecting means) for detecting the voltage V2. In addition, about the structure similar to the power supply device 200 of Example 1, description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  In the power supply device 400, the converter 1 and the converter 2 are connected to the subsequent stage of the bridge diode BD1. The converter 1 described in the first embodiment is an overnight converter that always outputs a DC voltage V1. On the other hand, the converter 2 is an isolated night DC / DC converter that operates only when the power supply apparatus 400 is in the second state, which is in the standby state, and the DC voltage applied between the primary side (DCL to DCH) ) To the secondary side. The converter 2 outputs a DC voltage V2 to the secondary side when the power supply voltage Vcc is supplied from the converter 1 when the standby signal is in a high (high level) state.

  In addition, the Y capacitor discharge unit 406 of the zero cross detection circuit 402 outputs a DC voltage corresponding to the AC voltage of the AC power supply 201 to the voltage detection unit 407. The voltage detection unit 407 serving as the first voltage detection means is a voltage detection means for detecting a state in which the AC voltage of the AC power supply 201 has dropped and the power supply apparatus 400 cannot continue its operation.

[Circuit operation in the second state]
First, the circuit operation of the power supply apparatus 400 in the second state in which the zero cross timing can be detected, such as when the image forming apparatus 10 is on standby or during printing, will be described. In a state where the zero-cross timing can be detected, the Standby signal is set to a high (high level) state, so that the power supply voltage Vcc is supplied to the zero-cross detection unit 205 and the Y capacitor discharge unit 406. As a result, the zero cross detection circuit 402 is in a state in which the zero cross timing of the AC power supply 201 can be detected.

  In the Y capacitor discharge unit 406, the current flowing through the discharge resistors R3 and R4 is charged to the capacitor C6 via the transistor Q1. The resistor R10 is a discharge resistor of the capacitor C6. The DC voltage Vin smoothed by the resistor R <b> 11 and the capacitor C <b> 7 constituting the smoothing circuit is a voltage according to the AC voltage of the AC power supply 201 and is input to the voltage detection unit 407. The voltage detection unit 407 detects the voltage value of the input voltage Vin, and outputs a Vout signal corresponding to the detected voltage value to the converter 2. When the AC voltage of the AC power supply 201 decreases, the charging current to the capacitor C6 decreases, and as a result, the voltage Vin input to the voltage detection unit 407 decreases. The voltage detection unit 407 sets the Vout signal to a low (low level) state when the input voltage Vin is equal to or lower than a predetermined threshold voltage Vth (threshold voltage or lower). On the other hand, when the input voltage Vin is higher than the predetermined threshold voltage Vth, the voltage detection unit 407 sets the Vout signal to a high (high level) state.

  The power supply voltage Vcc and Vout signals are input to the converter 2. The converter 2 is activated when the power supply voltage Vcc is supplied and the Vout signal is in a high state, and outputs a DC voltage V2 to be supplied to the load. On the other hand, the converter 2 stops its operation when the power supply voltage Vcc is not supplied or when the Vout signal is in the Low state, and the DC voltage V2 is not output.

  A signal obtained by dividing the DC voltage V2 output from the converter 2 by the voltage dividing resistors R12 and R13 in order to detect that the AC voltage of the AC power supply 201 has dropped and the converter 2 has stopped outputting the voltage V2. A certain V2sense signal is input to the control unit 203. The control unit 203 can detect that the converter 2 has stopped outputting the DC voltage V2, that is, that the AC voltage input from the AC power supply 201 has decreased, by detecting the voltage value of the V2sense signal. . Note that the detection of the zero-cross timing by the zero-cross detection unit 205 and the discharge of the X capacitor C1 are the same as in the first embodiment, and a description thereof is omitted here.

[Circuit operation in the first state]
Next, the circuit operation of the power supply apparatus 400 in the first state, which is an energy saving state such as when the power is turned off or during sleep, will be described. In the first state, since the standby signal is in the low state, the power supply voltage Vcc is not supplied to the Y capacitor discharge unit 406, the zero cross detection unit 205, and the converter 2. Therefore, in the zero cross detection unit 205, no current flows through the resistor R6, the primary side diode of the photocoupler PC2, and the collector terminal of the transistor Q2, so that power consumption can be suppressed. In addition, since the transistor Q1 is cut off in the Y capacitor discharge unit 406, the current flowing from the live side line via the discharge resistor R3 and the current flowing from the neutral side line via the discharge resistor R4 are cut off to suppress power consumption. be able to. Furthermore, power consumption by the voltage detection unit 407 can be reduced. Converter 2 stops operating because power supply voltage Vcc is not input, and voltage V2 is not output.

[Power supply control sequence]
FIG. 5 is a flowchart illustrating a control sequence of the power supply apparatus 400 by the control unit 203 of this embodiment. The process of FIG. 5 is started when a request to shift the power supply device 400 to the power supply conductive state is generated by turning on the power switch of the power supply device 400, connecting the power cable of the power supply device 400 to the AC power supply 201, or the like. This is executed by the unit 203.

  In step S501, the control unit 203 sets the standby signal to a low (low level) state, and cuts off power supply (supply of the power supply voltage Vcc) to the zero-cross detection circuit 402 and the converter 2. As a result, the control unit 203 shifts the power supply device 400 to the first state in which no current flows through the discharge resistors R3 and R4 of the Y capacitor C3. Further, when supply of power supply voltage Vcc is interrupted, converter 2 also stops operating. S502 and S503 are the same as the processes of S302 and S303 in FIG. 3 of the first embodiment, respectively, and description thereof is omitted here.

  In step S504, the control unit 203 sets the standby signal to a high (high level) state and supplies power to the zero-cross detection circuit 402 and the converter 2 (supply of the power supply voltage Vcc). Thereby, the control part 203 makes the power supply device 400 transfer to the 2nd state into which an electric current flows into discharge resistance R3, R4 of Y capacitor | condenser C3. In this state, a charging current flows through the capacitor C6 of the voltage detection unit 407, and the voltage detection unit 407 can detect the input voltage of the AC power supply 201. The converter 2 is activated when the Vout signal from the voltage detection unit 407 is in a high (high level) state, and outputs the DC voltage V2. Furthermore, a V2sense signal obtained by dividing the DC voltage V2 output from the converter 2 is input to the control unit 203.

  In S505, the control unit 203 determines whether or not the input voltage Vin to the voltage detection unit 407 is higher than the voltage Vth that is a threshold voltage, based on the voltage value of the V2sense signal. As described above, when the input voltage of the AC power supply 201 decreases and the input voltage Vin to the voltage detection unit 407 becomes equal to or lower than the voltage Vth, the voltage detection unit 407 sets the Vout signal to a low (low level) state. Converter 2 stops operating. When the operation of the converter 2 stops, the voltage of the DC voltage V2 output from the converter 2 decreases. Therefore, the voltage of the V2sense signal decreases below a predetermined voltage, and the control unit 203 confirms that the converter 2 has stopped operating. Can be detected. If the control unit 203 determines that the voltage of the V2sense signal is equal to or lower than the predetermined voltage, the control unit 203 proceeds to step S506. If the control unit 203 determines that the voltage of the V2sense signal is higher than the predetermined voltage, the control unit 203 proceeds to step S507. Proceed.

  In step S <b> 506, the control unit 203 notifies the image forming apparatus 10 of an abnormal state in which the input voltage of the AC power supply 201 is decreasing. The image forming apparatus 10 notifies the user of the abnormal state by displaying on the display unit (not shown) that the input voltage has been reduced. Then, the control unit 203 sets the standby signal to the low (low level) state in order to shift the power supply apparatus 400 to the first state that is the energy saving state. As a result, power supply to the zero-cross detection circuit 402 and the converter 2 (supply of the power supply voltage Vcc) is cut off, and the control unit 203 shifts the power supply device 400 to a cut-off state in which no current flows through the discharge resistors R3 and R4. Furthermore, the control unit 203 stops the operation of the converter 2 and ends the process.

  The processing of S507 and S508 is the same as the processing of S305 and S306 of the first embodiment, and a description thereof is omitted here.

As described above, the power supply apparatus 400 of this embodiment is characterized by having means for detecting the voltage of the AC power supply 201 using the current flowing through the discharge resistors R3 and R4 of the Y capacitor C3. In addition, by using the zero-cross detection circuit 402 of the present embodiment, in the first state and the second state, the charge charged in the X capacitor can be obtained regardless of whether the polarity charged in the X capacitor is positive or negative. Can be discharged. Furthermore, the transistor Q1, which is simple switching means, can switch between a state in which zero-crossing timing detection and voltage detection are possible (second state) and a state in which power consumption is reduced (first state).
As described above, according to the present embodiment, the electric charge charged in the X capacitor can be discharged with a simple configuration.

202 Zero Cross Detection Circuit 205 Zero Cross Detection Unit 206 Y Capacitor Discharge Unit BD1 Bridge Diode C1 X Capacitor R1 Zero Cross Detection Resistance

Claims (19)

A first capacitor connected between a first line to which an AC voltage is input from an AC power source and a second line;
Rectifying means for full-wave rectifying the AC voltage input via the first line and the second line;
A second capacitor provided between the output terminal of the rectifying means and the ground;
Zero-cross detection means for detecting zero-cross of the AC voltage;
A control means for controlling the zero-cross detection means by switching between a first state in which the zero-cross detection is not performed and a second state in which the zero-cross detection is performed;
A power supply device comprising:
The zero cross detecting means is connected to the first line and the second line and the output terminal of the rectifying means, and discharges the electric charge charged in the second capacitor; Connected to a detection resistor for detecting a zero crossing of the AC voltage input through the discharge unit, the other end of the detection resistor, and the output end of the rectifying means, and connected to the detection resistor. A detection unit that detects a zero cross of the AC voltage based on a voltage generated;
The charge charged in the first capacitor is discharged through the discharge unit, the detection resistor, the detection unit, and the rectifying means in the first state, and the discharge in the second state. And a power supply device that is discharged through the rectifying means. First conversion means for converting the voltage output from the rectification means into a first DC voltage;
Switch means for supplying and blocking the first DC voltage to the discharge unit and the detection unit;
With
The control means turns off the switch means in the first state to cut off the supply of the first DC voltage, and turns on the switch means in the second state to turn on the first direct current voltage. The power supply device according to claim 1, wherein a voltage is supplied. The discharge unit has one end connected to the first line and discharges the second capacitor, and one end connected to the second line and discharges the second capacitor. A switching element in which one end is connected to the other end of the first discharge unit and the second discharge unit, and the other end is connected to the output end of the rectifier, the second discharge unit;
Have
The switching element is in an on state when in the second state and conducts current from the first discharge part and the second discharge part, and is in an off state when in the first state. The power supply device according to claim 2, wherein currents of one discharge unit and the second discharge unit are interrupted.   When the charge charged in the first capacitor is in the second state and the potential of the first line is higher than the potential of the second line, the first discharge unit, When discharged through the switching element and in the second state, and the potential of the second line is higher than the potential of the first line, the second discharge unit and the switching element The power supply device according to claim 3, wherein the power supply device is discharged. The first discharge part and the second discharge part each have a diode and a resistor connected in series,
The anode terminal of the diode of the first discharge unit is connected to the first line,
The anode terminal of the diode of the second discharge unit is connected to the second line,
5. The power supply device according to claim 3, wherein one end of a resistance of each of the first discharge unit and the second discharge unit is connected to the switching element.   The power supply device according to claim 5, wherein one end of the detection resistor is connected to a connection point between the cathode terminal of the diode of the first discharge unit and the resistor.   The charge charged in the first capacitor is in the first state, and when the potential of the first line is higher than the potential of the second line, the charge of the first discharge unit is A diode, which is discharged through the sensing resistor, in the first state, and when the potential of the second line is higher than the potential of the first line, the diode of the second discharge section The power supply device according to claim 6, wherein the power source device is discharged through the resistance, the resistance of the first discharge unit, and the detection resistance.   The power supply device according to claim 5, wherein one end of the detection resistor is connected to a connection point between a cathode terminal of the diode of the second discharge unit and the resistor.   When the electric charge charged in the first capacitor is in the first state and the electric potential of the second line is higher than the electric potential of the first line, the electric charge of the second discharging unit is A diode, which is discharged through the sensing resistor, in the first state, and when the potential of the first line is higher than the potential of the second line, the diode of the first discharge section The power supply device according to claim 8, wherein the power supply device is discharged through the resistance, the resistance of the second discharge unit, and the detection resistance.   10. The detection unit according to claim 6, wherein the detection unit detects a zero cross based on a voltage generated in the detection resistor, and outputs a zero cross signal corresponding to the detected timing of the zero cross. The power supply device according to item 1. Provided between the switching element of the discharge unit and the output terminal of the rectifying means, comprising a first voltage detection means for detecting the AC voltage input from the AC power supply,
The said 1st voltage detection means detects the said alternating voltage using the electric current which flows into the said resistance of a said 1st discharge part, and the said resistance of a said 2nd discharge part. The power supply described. A second conversion means for converting the first DC voltage output from the first conversion means into a second DC voltage;
The second conversion means outputs the second DC voltage in the second state and when the AC voltage detected by the first voltage detection means is higher than a threshold voltage, 12. The output of the second DC voltage is stopped in the first state or when the AC voltage detected by the first voltage detection means is equal to or lower than the threshold voltage. The power supply device described in 1. Comprising a second voltage detecting means for detecting the second DC voltage;
The second voltage detection means has a voltage dividing resistor for dividing the second DC voltage,
13. The power supply device according to claim 12, wherein the control unit switches to the first state when a voltage divided by the voltage dividing resistor is equal to or lower than a predetermined voltage. Image forming means for forming an image on a recording material;
The power supply device according to any one of claims 1 to 13,
An image forming apparatus comprising: Image forming means for forming an image on a recording material;
The power supply device according to any one of claims 1 to 13,
A controller for controlling the image forming means;
With
The image forming apparatus, wherein the controller is the controller. Image forming means for forming an image on a recording material;
A controller for controlling the image forming means;
An image forming apparatus comprising: the power supply device according to claim 13;
The image forming apparatus according to claim 1, wherein the control unit notifies the controller that the AC voltage of the AC power supply has dropped to the threshold voltage or less. A power supply device according to claim 10;
Image forming means for forming a toner image on a recording material;
A fixing device that heats and pressurizes the toner image and fixes the toner image on a recording material;
A switch for supplying power to and shutting off the fixing device;
A controller for controlling the image forming means, the fixing device, and the switch;
With
The image forming apparatus, wherein the controller controls the switch in accordance with a zero-cross timing of the AC voltage.   The image forming apparatus according to claim 17, wherein the switch is a bidirectional thyristor.   The first state is a state in which the image forming unit does not perform image formation, and the second state is a state in which the image forming unit performs image formation. Item 19. The image forming apparatus according to any one of Items 18 above.

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