JP5923848B2 - High voltage power supply - Google Patents

Description

  The present invention relates to a high-voltage power supply device, and more particularly to a high-voltage power supply device used in an electrophotographic apparatus.

  In electrophotographic apparatuses such as copying machines and printers, high-voltage power supply apparatuses are used for processes such as charging, exposure, development, separation, and transfer. FIG. 4 is a circuit diagram of a conventional high-voltage power supply device. 4 includes a control unit 102, a drive power source 103, a transformer 104, a rectifier circuit unit 105, a bleeder resistance element 106, a Zener diode 107, and an output current detection unit 108. The control unit 102 converts the voltage of the output current detected by the output current detection unit 108 and monitors it, and controls the power supplied from the drive power supply 103 to the transformer 104. The drive power supply 103 is a DC power supply. The transformer 104 boosts the input voltage input from the drive power supply 103 and supplies the boosted output voltage to a load 109 (for example, a photosensitive drum). The rectifier circuit unit 105 rectifies the output current based on the output voltage before supplying the output voltage boosted by the transformer 104 to the load 109. Specifically, the rectifier circuit unit 105 includes a diode 105a connected in series to the output terminal (HV terminal) of the transformer 104, and a capacitor 105b connected to the diode 105a. The bleeder resistance element 106 is a resistor for discharging the electric charge accumulated in the capacitor 105b when the output voltage of the transformer 104 is stopped.

  The load 109 is, for example, a photosensitive drum, and the surface of the photosensitive layer of the photosensitive drum is charged by the output voltage supplied from the transformer 104, so that a latent image, a toner image, and the like are formed. In FIG. 4, a load 109 is connected in series to a resistance element 109a connected in series to the output terminal (HV terminal) of the transformer 104, a capacitor 109b connected in parallel to the resistance element 109a, a resistance element 109a and a capacitor 109b. The power supply 109c is shown in a pseudo manner. The reason why the load 109 includes the power source 109c is shown in a pseudo manner in order to maintain a state where the surface of the photosensitive layer of the photosensitive drum is charged (a state where charges are accumulated in the load 109). Therefore, even when the transformer 104 stops supplying the boosted output voltage to the load 109, a loop current flows between the transformer 104 and the load 109 by the power source 109c. When a loop current flows between the transformer 104 and the load 109, there is a problem that the circuit constituting the high voltage power supply device 101 is damaged, or the surface of the photosensitive layer of the photosensitive drum is not stable. There is a problem that a desired latent image, toner image, and the like cannot be formed.

  Therefore, in the conventional high-voltage power supply device 101, when the transformer 104 stops supplying the boosted output voltage to the load 109, the transformer 104 and the load are loaded by the power supply 109c (charge accumulated in the load 109) included in the load 109. A zener diode 107 is provided to cut off the loop current flowing between the current and the current 109. Patent Document 1 discloses a configuration of a conventional high-voltage power supply device 101 including a transistor instead of including the Zener diode 107. The output current detection unit 108 detects the amount of load current flowing through the load 109 according to the output voltage supplied from the transformer 104, and transmits a signal based on the detected amount of load current to the control unit 102.

Japanese Patent Laid-Open No. 2003-134721

  When the high-voltage power supply device 101 includes the Zener diode 107, the loop current flowing between the transformer 104 and the load 109 can be cut off, but the Zener diode 107 is connected between the ground terminal and the output terminal (LV terminal) of the transformer 104. Since it is inserted between them, there is a problem that the transformer 104 has to output an excessive voltage by the amount corresponding to the Zener voltage of the Zener diode 107.

  Further, in the case where a transistor is provided instead of the Zener diode 107 as in the conventional high-voltage power supply device 101 disclosed in Patent Document 1, it is necessary to supply a current from the outside in order to drive the transistor. When a current is supplied to the transistor from the outside, since the current supplied from the outside flows to the load 109, the relationship between the amount of current detected by the output current detecting means 108 and the amount of current flowing to the load 109 is affected. There is a problem that the amount of load current flowing through the load 109 cannot be accurately detected in accordance with the output voltage supplied from 104.

  The present invention has been made in view of such circumstances, and the amount of load current flowing through the load can be accurately detected according to the output voltage supplied from the transformer without the transformer outputting excessive voltage. It aims at providing a high voltage power supply device.

In order to achieve the above object, a high-voltage power supply device according to a first invention is a high-voltage power supply device used in an electrophotographic apparatus, wherein an output voltage obtained by boosting an input voltage is connected to a load and an output terminal of the transformer A switching element that cuts off a loop current flowing between the transformer and the load without supplying a current from the outside of the high-voltage power supply device , one to the output terminal of the transformer, and the other to the switching element. Switching control means for switching the switching element from an off state to an on state when the transformer starts supplying the output voltage boosted by the transformer to the load, and the switching control means comprises: between the transformer output terminal and the switching element, integer composed of a diode and a capacitor It is connected to the circuit unit, for driving the switching element by the output voltage supplied to the load from the transformer current flowing through the resistor connected to the output of the rectifier circuit portion.

According to a second aspect of the present invention, in the first aspect , the switching element is a bipolar transistor, and the output of the rectifier circuit section is input to the base terminal of the bipolar transistor via the resistance element. Has been.

In the first invention, since the switching element cuts off the loop current flowing between the transformer and the load, the Zener voltage of the Zener diode is cut as in the case where the Zener diode cuts off the loop current flowing between the transformer and the load. Therefore, there is no problem that the transformer must output an excessive voltage. In addition, when the transformer starts to supply the boosted output voltage to the load, the switching control means for switching the switching element from the OFF state to the ON state does not supply current from the outside of the high-voltage power supply device . Since the switching element is driven by the current flowing through the switching element, it is not necessary to supply an external current to drive the switching element, and the relationship between the amount of current detected by the output current detection means and the amount of current flowing through the load is affected. The amount of load current flowing through the load can be accurately detected according to the output voltage supplied from the transformer.

In the second invention, the switching element is a bipolar transistor, and the output of the rectifier circuit section is input to the base terminal of the bipolar transistor via the resistance element, so that the Zener diode flows between the transformer and the load. As in the case of cutting the loop current, there is no problem that the transformer has to output an excessive voltage by the Zener voltage of the Zener diode.

In the high-voltage power supply device according to the present invention, the switching element cuts the loop current flowing between the transformer and the load. Therefore, the zener diode cuts the loop current flowing between the transformer and the load. There is no problem that the transformer must output an excessive voltage by the amount of the Zener voltage of the diode. In addition, when the transformer starts to supply the boosted output voltage to the load, the switching control means for switching the switching element from the off state to the on state does not supply current from the outside of the high-voltage power supply device. Since the switching element is driven by the current flowing in, there is no need to supply current from the outside to drive the switching element, and the relationship between the amount of current detected by the output current detection means and the amount of current flowing to the load is affected. The amount of load current flowing through the load can be accurately detected according to the output voltage supplied from the transformer without being applied.

1 is a circuit diagram of a high-voltage power supply device according to an embodiment of the present invention. 1 is a schematic diagram illustrating a configuration of an electrophotographic apparatus including a high voltage power supply device according to an embodiment of the present invention. It is a circuit diagram of the high voltage power supply device of another composition concerning an embodiment of the invention. It is a circuit diagram of the conventional high voltage power supply device.

  Hereinafter, a high-voltage power supply device according to an embodiment of the present invention will be described in detail with reference to the drawings. The following embodiments do not limit the invention described in the claims, and all combinations of characteristic items described in the embodiments are essential to the solution. It goes without saying that it is not limited.

  FIG. 1 is a circuit diagram of a high-voltage power supply device according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a configuration of an electrophotographic apparatus including the high voltage power supply device according to the embodiment of the present invention. An electrophotographic apparatus 10 shown in FIG. 2 includes a photosensitive drum 11 including a photosensitive layer 11a made of an inorganic material such as selenium tellurium (Se · Te) or amorphous silicon (a-Si), which has excellent durability and mechanical strength. A corona charger 12 as a charging means for charging the surface of the photosensitive layer 11a of the photosensitive drum 11, and a laser beam as an exposure means for forming a desired latent image (not shown) on the surface of the photosensitive layer 11a of the photosensitive drum 11. 13 is provided. Further, the electrophotographic apparatus 10 is formed by supplying toner 14 on the latent image and toner supply device 15 which is a supply means for supplying toner 14 onto the latent image formed on the surface of the photosensitive layer 11a of the photosensitive drum 11. A transfer unit 17 that is a transfer unit that transfers a toner image (not shown) onto the substrate 16 and the toner 14 of the toner image transferred onto the substrate 16 are fixed, and an image (not shown) is displayed on the substrate 16. A flash lamp 18 which is a fixing means for forming the above.

  A high-voltage power supply device 1 shown in FIG. 1 is a device for supplying a high voltage to the corona charger 12, the transfer device 17, and the like. The high-voltage power supply device 1 supplies a high voltage to the corona charger 12, the transfer device 17, and the like. Is shown as a load 9 including the photosensitive drum 11 and the like in a pseudo manner. 1 includes a control unit 2, a drive power source 3, a transformer 4, a rectifier circuit unit 5, a bleeder resistance element 6 (switching control means), a transistor 7 (switching element), and an output current detection means 8. Prepare. The control unit 2 controls the power supplied from the drive power supply 3 to the transformer 4 based on the signal from the output current detection unit 8. The drive power source 3 is a DC power source. The transformer 4 supplies an output voltage obtained by boosting the input voltage input from the drive power supply 3 to the load 9 (for example, the photosensitive drum 11). The rectifier circuit unit 5 rectifies the output current based on the output voltage before supplying the output voltage boosted by the transformer 4 to the load 9. Specifically, the rectifier circuit unit 5 includes a diode 5a connected in series to the output terminal (HV terminal) of the transformer 4 and a capacitor 5b connected to the diode 5a.

  The bleeder resistance element 6 is a resistor for discharging the charge accumulated in the capacitor 5b when the output voltage is stopped. Further, one of the bleeder resistance elements 6 is connected to the output terminal (HV terminal) of the transformer 4 and the other is connected to the base electrode (control electrode) of the transistor 7, and functions as a switching control means described later.

  The load 9 is, for example, the photosensitive drum 11, and the surface of the photosensitive layer 11 a of the photosensitive drum 11 is charged by the output voltage supplied from the transformer 4, thereby forming a latent image, a toner image, and the like. In FIG. 1, a load 9 is connected in series to a resistance element 9a connected in series to the output terminal (HV terminal) of the transformer 4, a capacitor 9b connected in parallel to the resistance element 9a, a resistance element 9a and a capacitor 9b. The power supply 9c is shown in a pseudo manner. The reason why the load 9 includes the power supply 9c is shown in a pseudo manner in order to maintain a state in which the surface of the photosensitive layer 11a of the photosensitive drum 11 is charged (a state where charges are accumulated in the load 9). . Therefore, even when the transformer 4 stops supplying the boosted output voltage to the load 9, a loop current flows between the transformer 4 and the load 9 by the power source 9c.

  When the high voltage power supply device 1 according to the embodiment of the present invention stops supplying the output voltage boosted by the transformer 4 to the load 9, the power supply 9 c included in the load 9 (charge accumulated in the load 9). In order to cut off the loop current flowing between the transformer 4 and the load 9, an npn transistor 7 is provided. The transistor 7 has an emitter electrode connected to the output terminal (LV terminal) of the transformer 4, a collector electrode connected to one of the output current detection means 8, and a base electrode connected to the other of the bleeder resistance element 6. Therefore, the transistor 7 is driven by a bleeder current flowing in the bleeder resistance element 6 by the output voltage supplied from the transformer 4 to the load 9. Note that the bleeder current is a current that flows in the transformer 4, and it is not necessary to supply a current for driving the transistor 7 from the outside, not a current supplied from the outside. The transistor 7 may be any switching element that cuts off the loop current flowing between the transformer 4 and the load 9, and includes, for example, a bipolar transistor, a MOSFET, and the like.

  The output current detection unit 8 detects the amount of load current flowing through the load 9 according to the output voltage supplied from the transformer 4, and transmits a signal based on the detected amount of load current to the control unit 2. One of the output current detection means 8 is connected to the collector electrode of the transistor 7 and the other is connected to the ground terminal. In the embodiment of the present invention, it is not necessary to supply current from the outside in order to drive the transistor 7, and the base current of the transistor 7 does not flow to the output current detection means 8 and the load 9. The load current amount flowing through the load 9 can be accurately detected according to the output voltage supplied from the transformer 4 without affecting the relationship between the detected current amount and the current amount flowing through the load 9.

  Next, the operation of the high voltage power supply device 1 according to the embodiment of the present invention will be described. First, when the output voltage boosted by the transformer 4 is supplied to the load 9, the output voltage supplied from the transformer 4 to the load 9 is also supplied to the bleeder resistance element 6, and a bleeder current flows through the bleeder resistance element 6. Since the bleeder current flowing through the bleeder resistance element 6 according to the output voltage supplied from the transformer 4 has a current amount equal to or greater than the threshold value of the base current that turns on the transistor 7, the output voltage boosted by the transformer 4 is used as the load 9 , The transistor 7 is turned on, and a loop current flows between the transformer 4 and the load 9 due to the output voltage supplied from the transformer 4 to the load 9.

  On the other hand, when the transformer 4 stops supplying the boosted output voltage to the load 9, the base current is not supplied to turn on the transistor 7, so regardless of the current from the power source 9 c included in the load 9. The transistor 7 is turned off. Therefore, when the transformer 4 stops supplying the boosted output voltage to the load 9, the transistor 7 is switched from the on state to the off state, and flows between the transformer 4 and the load 9 by the power source 9 c included in the load 9. The loop current can be cut off. Since the loop current flowing between the transformer 4 and the load 9 is cut by the power supply 9c provided in the load 9, the circuit constituting the high-voltage power supply device 1 is not affected, and the photosensitive layer 11a of the photosensitive drum 11 is not damaged. The surface is stable in a charged state, and a desired latent image, toner image or the like can be formed.

  As described above, the bleeder resistance element 6 functions as a switching control unit that controls switching of the transistor 7 between the on state and the off state. The high-voltage power supply device 1 according to the embodiment of the present invention is not limited to the case where the bleeder resistance element 6 is used as the switching control means, one is the output terminal (HV terminal) of the transformer 4 and the other is the transistor 7. The switching control means may include a resistance element connected to each base electrode (control electrode). Further, the switching control means is not limited to the bleeder resistance element 6 or the resistance element. When the transformer 4 starts supplying the boosted output voltage to the load 9, the transistor 7 is switched from the OFF state to the ON state. Any circuit configuration can be used as long as the transistor 7 can be driven by the current flowing in the transformer 4.

  As described above, the high-voltage power supply device 1 according to the embodiment of the present invention cuts the loop current flowing between the transformer 4 and the load 9 by the transistor 7, so that a Zener diode is used to connect the transformer 4 and the load 9. There is no problem that the transformer 4 has to output an excessive voltage by the Zener voltage of the Zener diode as in the case of cutting the loop current flowing between them. Further, when the transformer 4 starts to supply the boosted output voltage to the load 9, the switching control means (bleeder resistance element 6) that switches the transistor 7 from the off state to the on state causes the current flowing in the transformer 4. Since the transistor 7 is driven by this, it is not necessary to supply an external current to drive the transistor 7, and the base current of the transistor 7 does not flow to the output current detection means 8 and the load 9, so that the output current detection means 8 The load current amount flowing through the load 9 can be accurately detected according to the output voltage supplied from the transformer 4 without affecting the relationship between the detected current amount and the current amount flowing through the load 9.

  FIG. 3 is a circuit diagram of a high-voltage power supply device 1 having another configuration according to the embodiment of the present invention. In the high-voltage power supply device 1 shown in FIG. 3, the polarity of the output voltage supplied from the transformer 4 to the load 9 is opposite to that of the high-voltage power supply device 1 shown in FIG. In the high-voltage power supply device 1 that supplies an output voltage of reverse polarity to the load 9, the diode 5a of the rectifier circuit unit 5 is connected in series to the output terminal (LV terminal) of the transformer 4, and an anode (anode), a cathode (cathode), Is opposite to the diode 5a shown in FIG. 1, and the transistor 7 is not an npn type but a pnp type. Since the other circuit configuration is the same as that of the high-voltage power supply device 1 shown in FIG. 1, the same components are denoted by the same reference numerals and detailed description thereof is omitted. In the load 9 to which an output voltage having a reverse polarity is supplied from the transformer 4 of the high-voltage power supply device 1, the voltage polarity of the power supply 9c is opposite to the voltage polarity of the power supply 9c shown in FIG.

  Further, the voltage polarity of the output voltage supplied from the transformer 4 to the load 9 is not limited to the circuit configuration of the high-voltage power supply device 1 and the voltage polarity of the output voltage supplied from the transformer 4 to the load 9 is not limited. The circuit configuration of the high-voltage power supply device 1 that can be switched may be used.

DESCRIPTION OF SYMBOLS 1 High voltage power supply device 2 Control part 3 Drive power supply 4 Transformer 5 Rectifier circuit part 5a Diode 5b, 9b Capacitor 6 Bleeder resistance element 7 Transistor 8 Output current detection means 9 Load 9a Resistance element 9c Power supply 10 Electrophotographic apparatus 11 Photosensitive drum 11a Photosensitive layer 12 Corona Charger 13 Laser Light 14 Toner 15 Toner Supply Device 16 Printed Material 17 Transfer Device 18 Flash Lamp

Claims (2)

In a high voltage power supply used for an electrophotographic apparatus,
A transformer for supplying an output voltage obtained by boosting an input voltage to a load;
A switching element that is connected to an output terminal of the transformer and cuts a loop current flowing between the transformer and the load without supplying current from outside the high-voltage power supply device ;
One is connected to the output terminal of the transformer and the other is connected to the switching element. When the transformer starts to supply the boosted output voltage to the load, the switching element is changed from the OFF state to the ON state. Switching control means for switching between
In the switching control means, a rectifier circuit unit composed of a diode and a capacitor is connected between the output terminal of the transformer and the switching element.
The high-voltage power supply apparatus, wherein the switching element is driven by a current flowing through a resistance element connected to an output of the rectifier circuit unit by the output voltage supplied from the transformer to the load . The switching element is a bipolar transistor,
The high-voltage power supply device according to claim 1 , wherein an output of the rectifier circuit unit is input to a base terminal of the bipolar transistor through the resistance element .

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