JP2010074967A - Power supply device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply device in which responsiveness to polarity switching is enhanced without via a bias resistor in the power supply device that executes the polarity switching. <P>SOLUTION: The power supply device includes: a first power supply circuit (10) and a second power supply circuit (20) that output the output voltages having different polarities from a common output terminal; a first switch (30) for making the output of the first power supply circuit conductive/non-conductive; a second switch (40) for making the output of the second power supply circuit conductive/non-conductive; each first control means (11, 21) for executing control to drive a transistor by switching each output of the first/second power supply circuits on the basis of an input switching signal; and each second control means (31, 41) that executes control to make the first switch conductive while making the second switch non-conductive during the output of the first power supply circuit, and executes control to make the first switch non-conductive while making the second switch conductive during the output of the second power supply circuit. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power supply device and an image forming apparatus.

  In an image forming apparatus such as a printer or a copying machine, a photosensitive member is uniformly charged by a charging device, an electrostatic latent image is formed by an exposure device, a toner image is formed by a developing device, and a toner image is formed by a transfer device. Transcript to. Further, after the transfer to the paper, the paper is peeled off from the photoconductor or the transfer device by a peeling device and an image is output.

  For example, in a color printing apparatus, a so-called image forming unit of a photoreceptor, a charging device, a developing device, and a transfer device is configured for each color of yellow (Y), magenta (M), cyan (C), and black (K). Each of these is operated to perform color printing.

  An electrophotographic printer / copier has a high voltage power source for applying a specified voltage or current to a load such as a charging device, a developing device, or a transfer device. The voltage or current is supplied for processing such as charging, development, transfer, peeling, and cleaning. Recent printers, copiers, etc. are being colorized and speeded up against the background of demand for high functionality in the market. In order to meet the demand, a tandem engine that prepares a photoreceptor and blocks including charging, developing, and transfer functions for each color (for example, YMCK color) and prints paper in one pass is becoming mainstream. The advantage of the tandem type is that multiple colors (for example, four colors of YMCK) can be printed at a time, so that the same speed performance as that of a monochrome machine can be realized.

  As a transfer device, for example, in a secondary transfer device that transfers a toner image from an intermediate transfer belt on which a negative polarity toner image is formed onto a sheet, a backup roll that faces a secondary transfer roll that is grounded with the intermediate transfer belt interposed therebetween A bias is applied by a power supply device as a high voltage power source. -In the case of bias, the negative polarity toner repels and is transferred to the transfer roll side, that is, to the paper. In the case of + bias, it becomes a cleaning (CLN) bias. This cleaning bias is applied to leave a batch on the intermediate transfer belt so that the secondary transfer roll is not soiled by a density control patch formed between toner images.

  In such a power supply device that applies voltages of different polarities, two converters (power supply circuit) for positive / negative output are connected in series and two converters (power supply circuit) for positive / negative output are connected in parallel. There is something to connect through.

  For example, the output of the first power supply circuit for positive and negative outputs and the output of the second power supply circuit are connected in series by providing a bypass resistor, and the first and second power supply circuits having different polarities are selected and output. There are those disclosed in Patent Document 1 and Patent Document 2.

  The above-described transfer device is a tandem-type image forming device that particularly requires high-speed polarity switching responsiveness. For example, as shown in FIG. 2, a toner image such as an image on an intermediate transfer member formed by a primary transfer device. Is used as a secondary transfer device for transferring the image to a sheet-like recording medium such as paper.

  In such a transfer device, when a bias is applied to the backup roll, a transfer bias (−) for transferring toner to a sheet-like recording medium such as paper, and a density control patch as a secondary transfer device at the time of non-transfer are used. Select the first and second power supply circuits that have outputs with different polarities by providing a bypass resistor in series with the two power supply circuit outputs with cleaning (CLN) bias (+) so that they do not adhere to the transfer roll. By switching, it is supplied to the backup roll as a load.

  With the increase in speed, the requirement for the polarity switching time has become strict, and it has been found that it is difficult to satisfy the requirement with the prior art apparatus. When the polarity switching from -output to + output is delayed, toner that forms a patch adheres to the transfer roll and the back side of the paper becomes dirty. Although the transfer roll has a cleaning device, it cannot be cleaned when the density of the attached patch is high. In other words, with such a series connection configuration, when switching from minus output to plus output, especially when the impedance on the output side is large, it takes time to discharge the minus output and start up the plus output until it switches to plus output. Switching the polarity takes time. Especially in the case of a machine with a high process speed, there was a possibility that the toner on the patch would adhere to the transfer roll due to the delay in the rise of the positive output and the stain would become serious, and the back side of the copy paper would become dirty, changing the roll impedance and causing a transfer failure. . If the polarity switching from the + output to the-output is delayed, an image quality defect due to a transfer failure to the paper is caused.

  On the other hand, Patent Document 3 discloses a power supply device configured to connect positive and negative converters in parallel via a switch. In this power supply device, a negative separation bias for separating the transfer material from the photosensitive member and a positive transfer bias are applied to the transfer means via a switch. In such a parallel connection type, noise is generated when the output is switched by the switch, and measures for the device and peripheral devices are required. Further, the switching device and the noise countermeasure are increased in size, and the switching speed is limited.

JP 2000-232729 A Japanese Examined Patent Publication No. 02-016659 JP 05-224541 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a power supply apparatus that performs polarity switching without increasing the response of polarity switching in a power supply apparatus that performs polarity switching, and an image forming apparatus to which the power supply apparatus is applied.

  In order to achieve this object, the invention according to claim 1 is provided in parallel with each other, and outputs first and second power supply circuits that output output voltages of different polarities from a common output terminal, and A first switch provided on the output side of the first power supply circuit and conducting / non-conducting the output of the first power supply circuit; and an output of the second power supply circuit provided on the output side of the second power supply circuit. A second switch for conducting / non-conducting, first control means for performing control by switching the outputs of the first and second power supply circuits based on an input switching signal, and the first power supply circuit The first switch is turned on and the second switch is turned off at the time of output of the second power supply, and the first switch is turned off and the second switch is turned on at the time of output of the second power supply circuit. The second control hand that performs the control When, those having a.

  According to a second aspect of the present invention, in the first aspect of the present invention, at least one of the first and second switches includes a plurality of switches connected in series, and the second control means includes the plurality of switches. The switch is controlled to be on / off at the same timing.

  According to a third aspect of the present invention, in the second aspect of the present invention, as the driving means for the plurality of switches, switching means driven based on an output signal of the second control means, and the switching means being a primary One or more transformers connected to the side windings and driven at the same timing; and a rectifying / smoothing circuit provided corresponding to the plurality of switches and connected to the secondary side windings of the transformers; The plurality of switches are driven by the output of the circuit.

  According to a fourth aspect of the invention, in the second aspect of the invention, the plurality of switches are transistors.

  According to a fifth aspect of the invention, in the fourth aspect of the invention, the transistor is a field effect transistor.

  According to a sixth aspect of the present invention, in the second aspect of the present invention, one of the first and second switches comprises the plurality of switches connected in series, and the other is on the low voltage side of the output of the power supply circuit. Provided.

  The invention according to claim 7 is provided in parallel with each other, and outputs a first power supply circuit and a second power supply circuit that output output voltages of different polarities from a common output terminal, and an output side of the first power supply circuit. A first switch provided to conduct / non-conduct an output of the first power supply circuit; and a second switch provided on an output side of the second power supply circuit to conduct / non-conduct an output of the second power supply circuit. , A first control means for performing control to switch and drive the outputs of the first and second power supply circuits based on an input switching signal, and the first power supply circuit at the time of output of the first power supply circuit A second control for making the switch conductive and making the second switch non-conductive, and making the first switch non-conductive and making the second switch conductive when the second power supply circuit outputs. Control means and image forming image And forming means, based on the power supply output that is outputted from the first and second power supply circuit, in which includes a transfer unit that transfers the image that is the image forming unit formed on the recording medium.

  According to an eighth aspect of the invention, in the seventh aspect of the invention, the image forming means is an image forming means for forming an image on an intermediate transfer member, and the transfer means is an image formed on the intermediate transfer member. Is a secondary transfer means for transferring the image to the recording medium.

  According to the first aspect of the present invention, the responsiveness at the time of polarity switching can be improved as compared with the case where this configuration is not provided.

  According to the second aspect of the present invention, the high-speed polarity switching responsiveness is improved as compared with the case where the present configuration is not provided, and the output of the power supply circuit is made conductive / non-conductive with the withstand voltage corresponding to the total of a plurality of switches. can do.

  According to the third aspect of the present invention, the high-speed polarity switching responsiveness can be improved as compared with the case where this configuration is not provided, and a high-breakdown-voltage switch can be driven with a low voltage input.

  According to the fourth aspect of the present invention, the high-speed polarity switching responsiveness can be improved as compared with the case where the present configuration is not provided, and a high-withstand-voltage and small-sized switch can be provided at the output of the power supply circuit.

  According to the fifth aspect of the present invention, the high-speed polarity switching response is improved as compared with the case where the present configuration is not provided, and a high-breakdown-voltage and small-sized switch can be provided at the output of the power supply circuit.

  According to the sixth aspect of the present invention, compared with the case where the present configuration is not provided, the high-speed polarity switching response is improved, and a small switch having a high withstand voltage and a simple circuit configuration becomes possible.

  According to the sixth aspect of the invention, compared with the case where this configuration is not provided, the high-speed polarity switching response can be improved, the switch can be driven with a low voltage input, and the circuit configuration can be simplified. is there.

  According to the seventh aspect of the present invention, the responsiveness at the time of polarity switching can be improved as compared with the case where this configuration is not provided. Even in the case of image formation that requires high-speed polarity switching responsiveness, it is possible to reduce recording medium contamination and image quality defects.

    According to the eighth aspect of the present invention, the response at the time of polarity switching can be improved as compared with the case where the present configuration is not provided. Even in the case of image formation that requires high-speed polarity switching responsiveness and strict density management, it is possible to reduce dirt on the recording medium and image quality defects.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the drawings.

  FIG. 1 is a circuit diagram showing a configuration example of a power supply device 100 according to the first embodiment of the present invention. FIG. 2 is a block diagram of an image forming apparatus according to an embodiment of the present invention including the power supply device 100 of FIG.

  The image forming apparatus in FIG. 2 shows a configuration example of a tandem printer. In this embodiment, the high-voltage power supply is set to correspond to each image forming unit of each color YMCK. However, the high-voltage power supply may be provided in common to each image forming unit.

  The configuration and operation of the tandem printer in FIG. 2 will be described. Around each photosensitive drum 2101, a charger 2102 having a charging roll is provided. After the photosensitive drum 2101 is uniformly charged by the charger 2102, the photosensitive drum 2101 is exposed on the photosensitive drum 2101 by an exposure device (not shown). Exposure is performed to form an electrostatic latent image. The electrostatic latent image is developed by the developing device 2103, and the toner image on the photosensitive drum 2101 is transferred onto the intermediate transfer member (for example, intermediate transfer belt) 2107 by the primary transfer device 2104. After these processes are successively performed for YMCK, the image is transferred onto a sheet-like recording medium such as paper by a secondary transfer device 2106, and the paper is peeled off by a peeling device 2105 and output.

  Here, the secondary transfer unit 2106 includes a transfer roll 2106 a that is grounded and a backup roll 2106 b that is opposed to the intermediate transfer body 2107. A bias is applied to the backup roll 2106b as a load. Although omitted in FIG. 2, the transfer roll 2106a of the secondary transfer device 2106 is provided with a cleaning device for collecting the toner adhering to the transfer roll 2106a, and an intermediate transfer body downstream from the secondary transfer position. A cleaning device for collecting the toner attached to 2107 is provided.

  Next, a basic configuration of the power supply apparatus 100 as a high-voltage power supply provided corresponding to the secondary transfer device 2106 of such a tandem type image forming apparatus will be described with reference to FIG.

  As shown in FIG. 1, the power supply apparatus 100 according to the present embodiment includes a negative output first power supply circuit 10 that applies a transfer bias to a load, and a non-transfer bias, that is, a cleaning (CLN) bias, to the load. A positive output second power supply circuit 20 is provided. An input power supply voltage Vcc (for example, 24 V) is commonly supplied to the power supply circuits 10 and 20.

  The negative output first power supply circuit 10 includes a control unit 11, a transistor 12, a transformer 13, and a rectifying / smoothing circuit 14. A switch (1) 30 is inserted in the output line between the rectifying / smoothing circuit 14 and the common output terminal 50.

  The positive output second power supply circuit 20 is provided in parallel to the first power supply circuit 10, and includes a control unit 21, a transistor 22, a transformer 23, and a rectifying and smoothing circuit 24. A switch (2) 40 is inserted in the output line between the rectifying / smoothing circuit 24 and the common output terminal 50. The common output terminal 50 is connected to a load, and the outputs of the first and second power supply circuits are selectively supplied to the load by switching the switch (1) 30 and the switch (2) 40.

  The control unit 11 of the first power supply circuit 10 switches and drives the transistor 12 and performs constant voltage control based on the −output voltage detected by the −output voltage detection circuit (not shown). Further, the constant current control is performed by the -output current detected by the -output current detection circuit (not shown). These controls are selected by a constant voltage / constant current selection input signal (not shown) input from the external control unit.

  The transistor 12 is a field effect transistor, and its drain is connected in series to the input power supply Vcc via the primary winding of the transformer 13 and its source is grounded. Furthermore, the output of the control part 11 is connected to the gate. The transistor 12 may be a bipolar transistor.

  The rectifying / smoothing circuit 14 has a capacitor 14a connected in parallel with the secondary winding of the transformer 13, a cathode connected to one end (high voltage side) of the secondary winding, and an anode connected to the output point of the rectifying / smoothing circuit 14. And a resistor 14c having one end connected to the anode of the diode and the other end connected to the other end (low voltage side) of the secondary winding.

  The control unit 21 of the second power supply circuit 20 switches and drives the transistor 22 and performs constant voltage control using a + output voltage detected by a + output voltage detection circuit (not shown). For example, the + output voltage detection circuit may detect the output from the rectifying / smoothing circuit 24, or may detect the voltage excited in the detection winding (not shown) of the transformer 23 as a voltage corresponding to the + output voltage. Also good.

  The transistor 22 is a field effect transistor, and its drain is connected in series to the input power supply Vcc via the primary winding of the transformer 23, and its source is grounded. Further, the output of the control unit 21 is connected to the gate. The transistor 22 may be a bipolar transistor.

  The rectifying / smoothing circuit 24 has a capacitor 24a connected in parallel with the secondary winding of the transformer 23, an anode connected to one end (high voltage side) of the secondary winding, and a cathode connected to the output point of the rectifying / smoothing circuit 24. And a resistor 24c having one end connected to the anode and the other end connected to the secondary winding of the transformer 23.

  In the present embodiment, the switch (1) 30 and the switch (2) 40 are constituted by transistors in order to reduce the size. As the transistor, for example, a field effect transistor that can easily obtain a high breakdown voltage is used. However, a bipolar transistor may be used.

  The switch (1) 30 has a source connected to the output point side of the rectifying and smoothing circuit 14 and a drain connected to the output end 50 side. The switch (2) 40 is connected to the output point side of the rectifying and smoothing circuit 24 and connected to the drain output end 50 side. The source is connected.

  The switch on / off control units 31 and 41 perform on / off (also referred to as conduction / non-conduction) control of the switch (1) 30 and the switch (2) 40. On / off control is performed based on detection of operating states of the first and second power supply circuits 10 and 20. As long as the operating states of the first and second power supply circuits 10 and 20 can be detected, they may be detected anywhere. For example, it may be controlled based on an input switching signal from an external control unit for switching the output operation of the first and second power supply circuits 10 and 20, or an output voltage detection circuit, an output current detection circuit, And may be detected and controlled by a + output voltage detection circuit or the like.

  Next, the operation of the power supply device according to this embodiment configured as described above will be described.

  First, the operation at the time of transfer giving the transfer bias (−) will be described. At the time of transfer, as shown in FIG. 3, the image section is a section in which a transfer bias (-) is applied and the image is transferred onto a sheet-like recording medium such as paper. At the time of transfer, a selection signal for selecting a transfer signal (−output selection signal) is input from an external control unit to a − + output switching control unit (not shown). The − + output switching control unit that has received the transfer signal selection signal inputs a drive signal to the control unit 11 of the first power supply circuit 10 based on a constant voltage / constant current selection signal (not shown). The control unit 11 controls either one of constant voltage control and constant current control. For example, in the case of constant voltage control, at this time, a negative output PWM signal input from the external control unit is input to the control unit 11. The control unit 11 drives the transistor 12 by monitoring the voltage detected by the −output voltage detection circuit so that the output voltage corresponds to the duty indicated by the input −output PWM signal. As a result, the negative output is generated on the secondary side via the transformer 13 and the rectifying / smoothing circuit 14 by performing the constant voltage control so that the −output voltage becomes the target value indicated by the duty value.

  On the other hand, at the time of transfer, the − + output switching control unit invalidates the drive signal for the control unit 21 of the second power supply circuit 20 and controls the second power supply circuit 20 to be non-operating. .

  At this time, the first power supply circuit 10 operates, the output thereof is in the on state, the second power supply circuit 20 is stopped, and a signal indicating that the output is in the off state is sent to the switch on / off control unit 31. 41, the switch on / off control unit 31 controls the switch (1) 30 to be in an on (conduction) state, and the switch on / off control unit 41 sets the switch (2) 40 to an off (non-conduction) state. Be controlled. As a result, the negative output of the first power supply circuit 10 is supplied to the load via the switch (1) 30.

  Next, an operation during non-transfer (during cleaning) for applying a cleaning (CLN) bias will be described. As shown in FIG. 3, roughly speaking, a section in which a density adjustment patch between images is formed is a non-transfer time (cleaning time) in which a cleaning (CLN) bias is applied. Strictly speaking, it is a switching section where switching from −output to + output should be completed between the end of the image and the tip of the patch, and the patch section is a period during which the cleaning (CLN) bias should be reliably supplied. The period from the end of the patch to the next image is a switching section where switching from + output to −output should be finished. At the time of non-transfer, a non-transfer (cleaning signal) selection signal is input to a − + output switching control unit (not shown) so that a cleaning signal (+ output selection signal) is output. As a result, the − + output switching control unit inputs a drive signal as a cleaning signal to the control unit 21 of the second power supply circuit 20. In this case, the − + output switching control unit does not output a drive signal to the control unit 11 of the first power supply circuit 10. Therefore, the control unit 11 does not drive the first power supply circuit 10 and puts it into a stopped state. On the other hand, the control unit 21 to which the cleaning signal is input starts constant voltage control. At this time, a + output PWM signal is input to the control unit 21 from the external control unit. The control unit 21 monitors the voltage detected by the + output voltage detection circuit (not shown) so as to obtain a + output voltage corresponding to the duty value indicated by the input + output PWM signal, and drives the transistor 22. To do. Thereby, the transformer 23 and the rectifying / smoothing circuit 24 generate a positive output on the secondary side.

  On the other hand, at the time of transfer, the − + output switching control unit invalidates the drive signal for the control unit 11 of the first power supply circuit 10 and controls it to be non-driven, and the first power supply circuit 10 is not operated. .

  At this time, the second power supply circuit 20 operates, the output thereof is in the on state, the first power supply circuit 10 is stopped, and a signal indicating that the output is in the off state is sent to the switch on / off control unit 31. 41, the switch on / off control unit 31 controls the switch (1) 30 to the off (non-conducting) state, and the switch on / off control unit 41 switches the switch (2) 40 to the on (conducting) state. Be controlled. As a result, the + output of the second power supply circuit 20 is supplied to the load via the switch (2) 40.

  Next, a case where the switch (2) 40 side is insufficient for the breakdown voltage of one transistor will be described. As a plurality of transistors according to the present invention, a plurality of insulating transformers are provided to turn on / off a plurality of charge effect transistors (FETs) at the same timing. An output is generated on the next side and each transistor (FET) is driven simultaneously by rectifying the output. FIG. 4 shows a detailed configuration of the power supply apparatus 101 provided with such a switch 2 (high withstand voltage switch circuit).

  As shown in FIG. 4, the switch (2) 40 includes a switch on / off control unit 41a, a transistor 42, a transformer 43, a drive circuit 44, a plurality of transistors 45 connected in series, a balance resistor 46, and a constant voltage element. 47 is comprised.

  In addition to the function of the switch on / off control unit 41 in FIG. 1, the switch on / off control unit 41 a has a function of switching at a predetermined frequency in order to drive the transformer 43 via the transistor 42. The switch on / off control unit 41a only needs to drive the transformer by controlling switching through the transistor 42 to drive the plurality of transistors 45 on and off. As in a switching control unit in a normal power supply, for example, as a target value, the secondary side output may be accurately controlled by detecting the PWM signal and output, or the secondary side output is predetermined without giving the PWM signal. It may be fixedly controlled within the range.

  As shown in FIG. 4, the transistor 42 has its gate connected to the switch on / off control unit 41, and its drain connected to the input power supply voltage (for example, 24V) via the primary winding of one or more transformers 43. And its source is grounded.

  The transformer 43 is composed of one or more for driving the plurality of transistors 45. In the example of FIG. 4, two secondary windings are provided to drive two transistors 45 per transformer. In the figure, a circuit for driving four or more switches 45 using two or more transformers 43 is shown. That is, as the transformer 43, transformers 43a, 43b... Are shown, and as the plurality of transistors 45, four or more secondary windings 431 corresponding to four or more transistors 451, 452, 453, 454. , 432, 433, 434... Are provided as the drive circuits 44 corresponding to the secondary windings 431, 432, 433, 434..., Secondary drive circuits 441, 442, 443, 444,.・ ・ Is provided.

  The drive circuits 441, 442, 443, 444... Have the same circuit configuration and include a diode 44a, a capacitor 44b, a resistor 44c, a gate resistor 44d, and a bias resistor 44e. The diode 44a has an anode connected to one end of the secondary winding and a cathode connected to one end of the gate resistor 44d. One end of the capacitor 44b is connected to the cathode of the diode 44a, the other end is connected to the other end of the secondary winding, and both ends of the resistor 44c are connected in parallel to both ends of the capacitor 44b. The other end of the gate resistor 44d is connected to the gate of the transistor 45 (451, 452, 453, 454...). The bias resistor 44e is connected between the gate and source of the transistor 45.

  The transistors 45 (451, 452, 453, 454...) Are connected in series between the + side terminal, that is, the output point of the second power supply circuit 20, and the − terminal side, that is, the common output terminal 50. The

  The balance resistor 46 (461, 462, 463, 464...) Is connected between the drain and source of the transistor 45 (451, 452, 453, 454...) Between the + side terminal and the − side terminal. Such a voltage is applied to each transistor evenly.

  The constant voltage element 47 (471, 472, 473, 474...) Controls the drain-source voltage to a constant voltage below the breakdown voltage so that a voltage higher than the breakdown voltage of each transistor is applied.

  The internal operation of the switch (2) 40a in this case is as follows. When the switch (2) is turned on, the switch on / off control unit 41a switches the transistor 42 at a predetermined frequency, drives the transformer 43 (43a, 43b,...), And boosts the primary side input voltage. Thus, a voltage is generated on the secondary side (secondary winding). This voltage is rectified and smoothed by each drive circuit and applied to the gate of the transistor 45 (451, 452, 453, 454...), And each transistor is turned on at the same timing.

  On the other hand, when the switch (2) is turned off, a signal for turning off the transistor 42 is output from the switch on / off control unit 41a, so that the transistor 42 is turned off and is not output to the secondary winding of the transformer 43. Accordingly, since no voltage appears on the secondary side, the drive circuit 44 turns off the plurality of transistors 45 at the same timing.

  Thus, the low voltage trigger signal (detection signal) that detects the on / off state (operating state) of the first and second power supply circuits 10 and 20 exceeds the maximum output voltage of the first power supply circuit 10. It is possible to control on / off of the output. That is, with such a switch configuration, even when an output voltage higher than the breakdown voltage of one transistor (FET) is applied to both ends of the switch 2, the output can be controlled on / off without any problem.

  Next, in the same way as the switch 2, the switch 1 is provided with a plurality of insulating transformers in order to turn on / off a plurality of transistors (FETs) at the same timing, and the transformer is switched by a switching means on the primary side. Accordingly, a case will be described in which outputs are generated on the secondary side and the transistors (FETs) are simultaneously driven by rectifying the output. FIG. 5 shows a detailed configuration diagram of the power supply apparatus 102 in which both the switches 1 and 2 are configured by a high voltage switch circuit.

  As shown in FIG. 5, the switch (1) 30a includes a switch on / off control unit 31a, a transistor 32, a transformer 33, a drive circuit 34, and a plurality of transistors 35 connected in series, like the switch (2) 40a. , A balance resistor 36, and a constant voltage element 37.

  As in the transistor 42, the transistor 32 has a gate connected to the switch on / off control unit 31a and a drain connected to the input power supply voltage (for example, 24V) as the primary of the transformer 33, as shown in FIG. Connected via a winding, its source is grounded.

  Similarly to the transformer 43, the transformer 33 is composed of one or more for driving the plurality of transistors 35. In the example of FIG. 5, two secondary windings are provided to drive two transistors 35 per transformer. In the figure, a circuit for driving four or more switches 35 using two or more transformers 33 is shown. That is, transformers 33a, 33b... Are shown as the transformer 33, and as the plurality of transistors 35, four or more secondary windings 331 corresponding to four or more transistors 351, 352, 353, 354. 332, 333, 334... Are provided as the drive circuit 34 corresponding to the secondary windings 331, 332, 333, 334..., And the secondary side drive circuits 341, 342, 343, 344,.・ ・ Is provided.

  The drive circuit 34 (341, 342, 343, 344...) Has the same circuit configuration as the drive circuit 44, and includes a diode 34a, a capacitor 34b, a resistor 34c, a gate resistor 34d, and a bias resistor 34e. Consists of. The diode 34a has an anode connected to one end of the secondary winding and a cathode connected to one end of the gate resistor 34d. One end of the capacitor 34b is connected to the cathode of the diode 34a, the other end is connected to the other end of the secondary winding, and both ends of the resistor 34c are connected in parallel to both ends of the capacitor 34b. The other end of the gate resistor 34d is connected to the gate of the transistor 35 (351, 352, 353, 354...). The bias resistor 34e is connected between the gate and source of the transistor 35.

  The transistor 35 (351, 352, 353, 354...) Has a negative output, unlike the case of the transistor 45, because the first power supply circuit 10 has a negative output. The output terminal 50 is connected in series between the negative terminal side (source side), that is, the output point of the first power supply circuit 10.

  Like the balance resistor 46, the balance resistor 36 (361, 362, 363, 364...) Is connected between the drain and the source of the transistor 35 (351, 352, 353, 354...). The voltage applied between the negative terminal and the negative terminal is equally divided across the transistors.

  Like the constant voltage element 47, the constant voltage element 37 (371, 372, 373, 374...) Has a voltage between the drain and the source that is equal to or lower than the breakdown voltage so that a voltage higher than the breakdown voltage of each transistor is applied. The constant voltage is controlled.

  The internal operation of the switch (1) 30a in this case is as follows. When the switch (1) is turned on, the switch on / off control unit 31a switches the transistor 32 at a predetermined frequency, drives the transformer 33 (33a, 33b...), And boosts the primary side input voltage. Thus, a voltage is generated on the secondary side (secondary winding). This voltage is rectified and smoothed by each drive circuit and applied to the gate of the transistor 35 (351, 352, 353, 354...), And each transistor is turned on at the same timing.

  On the other hand, when the switch (1) 30a is turned off, a signal for turning off the transistor 32 is output from the switch on / off control unit 31a, so that the transistor 32 is turned off and is output to the secondary winding of the transformer 33. Since no voltage appears, the drive circuit 34 turns off the plurality of transistors 35 at the same timing.

  Thus, since both switches 1 and 2 are high withstand voltage switch circuits, a low voltage trigger signal (detection signal) that detects the on / off state (operating state) of the first and second power supply circuits 10 and 20 is used. Thus, it becomes possible to turn on / off the output of the first and second power supply circuits 10 and 20 that is equal to or higher than the maximum output voltage. In other words, by adopting such a switch configuration, even when an output voltage exceeding the breakdown voltage of one transistor (FET) is applied to both ends of the switches 1 and 2, the output can be controlled on and off without any problem. . With such a configuration, on / off control is possible even when the output voltage of the first power supply circuit 10 and the output voltage of the second power supply circuit 20 become high voltages.

Next, a second embodiment is shown in FIG. When the output voltage of the second power supply circuit 20 is low and on / off control of the switch is possible with one transistor (FET), the first power supply circuit 20
A power supply device 103 provided with the switch 1 on the low voltage side of the output stage of the power supply circuit 10 will be described with reference to FIG.

  As shown in FIG. 6, the switch (1) 30 has an output point where the diode 14b of the secondary winding of the transformer 13 in the first power supply circuit 10 is inserted as shown in FIG. It is provided not on the side (high voltage side) but on the low voltage side that is the ground side. Others are the same as those of the power supply apparatus 101 of FIG.

  If comprised in this way, the low voltage trigger signal (detection signal) which detected the ON / OFF state (operation state) of the 1st and 2nd power supply circuits 10 and 20 will be input into switch 1 as it is, and will be turned ON / OFF Since it can be controlled, the circuit configuration is simple and the operation can be performed quickly.

  FIG. 7 shows the configuration of the high-breakdown-voltage switch circuit described in the switches 1 and 2 and is an example in the case where ten transistors 85 are connected in series. The transformer 83 that is switched by the transistor 82 includes five transformers 83 a to 83 e, and each primary winding is connected in series between the input power supply voltage (for example, 24 V) and the output point of the transistor 82. The secondary winding of the transformer 83 has two for each transformer corresponding to the ten transistors 85 (850 to 859), and includes secondary windings 830 to 839. The drive circuit 84 (840 to 849) corresponding to each transistor is the balance resistor 86 (860 to 869), and the constant voltage element 87 (870 to 879) is the same as the corresponding element described in the first and second embodiments. Substantially the same. The constant voltage elements 87 (870 to 879) are realized by four constant voltage elements connected in series per one transistor 85.

  If the withstand voltage of one transistor is 1500 V, a withstand voltage of 15 KV is logically obtained between the + side terminal and the − side terminal. The withstand voltage between the primary and secondary windings of each transformer 83 (83a to 83e) shown in FIG. 8 is about 3 KV for A, about 5 KV for B, and about 7 KV for C, D Then, a breakdown voltage structure of about 9 KV and E of about 11 KV are required.

  As described above, according to this embodiment, when switching from a negative output to a positive output, even if the impedance on the output side is large, there is no need to go through a bypass resistor, so the charge discharge of the negative output and the rise of the positive output can be performed quickly. Therefore, the polarity switching response time until switching to the positive output is greatly improved. Conversely, when switching from a positive output to a negative output, the polarity switching response time for switching to a negative output is also greatly improved. As a result, even a machine with a high process speed can prevent the toner from adhering to the transfer roll, so that it is possible to prevent the copy paper as a sheet-like recording medium from being soiled or to prevent a transfer failure.

  In the embodiment described above, the switch on / off control unit has been described as being divided into two switches. However, the switch on / off control unit may be configured by one to control the on / off of the two switches. .

  In the embodiments of the present invention described above, the high voltage power source used in the tandem type image forming apparatus for forming a color image such as electrophotography and the image forming apparatus have been described. However, the present invention is not limited to the color tandem type. In addition, the black-and-white image forming apparatus can be effectively used in a high-voltage power supply used in an image forming apparatus that requires high-speed polarity switching responsiveness, such an image forming apparatus, and the like. Further, the present invention is not limited to the number of engines such as a tandem engine, and the present invention can be effectively applied to writing a density control patch between images to be transferred on an intermediate transfer member, such as a black and white machine or a four-cycle machine.

  The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention. For example, the present invention can be used in a high-voltage power supply used in an image forming apparatus that requires high-speed polarity switching responsiveness such as electrophotography, and such an image forming apparatus.

1 is a circuit diagram illustrating a basic configuration example of a power supply apparatus 100 according to a first embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration example of an image forming apparatus according to the present embodiment to which the power supply device of FIG. 1 is applied. FIG. 6 is an explanatory diagram showing a switching relationship between a transfer bias and a cleaning bias for an image and a patch formed on an intermediate transfer member. It is a circuit diagram which shows the structural example of the power supply device 101 which used one switch as the high voltage | pressure-resistant switch circuit. It is a circuit diagram which shows the structural example of the power supply device 102 which used two switches as the high voltage | pressure-resistant switch circuit. It is a circuit diagram which shows the structural example of the power supply device 103 which concerns on the 2nd Example of this invention. It is a circuit diagram which shows the structural example of the high voltage | pressure-resistant switch circuit in the Example which concerns on this invention.

Explanation of symbols

10, 10a: first power supply circuit 20, 20a: second power supply circuit 11, 21: control unit 12, 22, 32, 35, 42, 45, 82, 85: transistor 13, 23, 33, 43, 83 : Transformer 14, 14-1, 24, 24-1: Rectification smoothing circuit 11, 21: Control unit 30, 30a: Switch 1
31, 31a, 41, 41a: switch on / off control unit 40, 40a: switch 2
34, 44, 84: drive circuit 50: output terminal 51:-+ output switching control unit

Claims (8)

A first power supply circuit and a second power supply circuit that are provided in parallel with each other and output output voltages of different polarities from a common output terminal;
A first switch provided on the output side of the first power supply circuit and conducting / non-conducting the output of the first power supply circuit;
A second switch provided on the output side of the second power supply circuit and conducting / non-conducting the output of the second power supply circuit;
First control means for performing control to switch and drive the outputs of the first and second power supply circuits based on an input switching signal;
The first switch is turned on at the time of output of the first power supply circuit and the second switch is turned off. The output of the second power supply circuit is turned off and the first switch is turned off. Second control means for controlling the second switch to be conductive;
A power supply device comprising:   At least one of the first and second switches is composed of a plurality of switches connected in series, and the second control unit controls conduction / non-conduction of the plurality of switches at the same timing. The power supply device according to claim 1.   As the driving means for the plurality of switches, switching means driven based on an output signal of the second control means, and one or more transformers connected to the primary winding and driven at the same timing And a rectifying / smoothing circuit provided corresponding to the plurality of switches and connected to a secondary winding of the transformer, wherein the plurality of switches are driven by the output of the rectifying / smoothing circuit. The power supply device according to claim 2.   The power supply apparatus according to claim 2, wherein the plurality of switches are transistors.   The power supply device according to claim 4, wherein the transistor is a field effect transistor.   3. The power supply device according to claim 2, wherein one of the first and second switches includes the plurality of switches connected in series, and the other is provided on a low voltage side of an output of the power supply circuit. A first power supply circuit and a second power supply circuit that are provided in parallel with each other and output output voltages of different polarities from a common output terminal;
A first switch provided on the output side of the first power supply circuit and conducting / non-conducting the output of the first power supply circuit;
A second switch provided on the output side of the second power supply circuit and conducting / non-conducting the output of the second power supply circuit;
First control means for controlling to drive by switching the outputs of the first and second power supply circuits based on an input switching signal;
The first switch is turned on at the time of output of the first power supply circuit and the second switch is turned off. The output of the second power supply circuit is turned off and the first switch is turned off. Second control means for controlling the second switch to be conductive;
An image forming means for forming an image;
Transfer means for transferring an image formed on the image forming means to a recording medium based on power output output from the first and second power supply circuits;
An image forming apparatus comprising:   The image forming unit is an image forming unit that forms an image on an intermediate transfer member, and the transfer unit is a secondary transfer unit that transfers an image formed on the intermediate transfer member to a recording medium. The image forming apparatus according to claim 7.

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