JP3358326B2 - High voltage power supply and image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-voltage power supply having an AC component and a DC component, and more particularly, to a high-voltage power supply in which the output DC component is unipolar constant current control and the output DC component voltage ranges between positive and negative. Power supply.

[0002]

2. Description of the Related Art Generally, an image forming apparatus such as an electrophotographic copying machine scans a uniformly charged photosensitive member (drum or belt) with a laser beam or the like modulated by an image signal to form an electrostatic latent image. After formation, a copy is obtained through a process of transferring the toner-developed product to transfer paper and fixing it.

FIG. 5 shows an image forming apparatus 1 to which the present invention is applied.
FIG. 1 is an explanatory diagram of a configuration of an example full-color copying machine. A full-color copying machine generally designated by reference numeral 1 optically reads a document on a platen of the copying machine, separates the document into color components, and sends the color components to a laser writing device 10 (not shown).
Is provided.

The laser writing device 10 includes a laser light source 11, a polygon mirror 12, a lens 13, and a mirror 14.
And the like. The laser light modulated with the image information is
To form the image information on the photosensitive drum 20 as an electrostatic latent image. The charger (corotron) 22 disposed opposite to the photosensitive drum 20 is provided with a photosensitive drum 2 in advance.
0 is uniformly charged, for example, if the supplied image information is a yellow component, the photosensitive drum 20 exposes an area not corresponding to yellow, and the electrostatic latent image corresponds to yellow of a color image. Becomes

A rotary developing unit 40 provided corresponding to the photosensitive drum 20 includes a yellow developing unit 45y, a magenta developing unit 45m, a cyan developing unit 45c, (Less than,
(Also referred to as black). The developing unit 45 is driven to rotate so that a developing device corresponding to a color component of an electrostatic latent image formed on the photosensitive drum 20 is set at a developing position facing the photosensitive drum 20. The toner image is formed by the container.

Here, first, the black developing unit 45k is set at the developing position, and a black toner image is formed on the photosensitive drum 20 as a visible image. On the other hand, the transfer paper 5 is supplied from a transfer medium tray or a manual feed tray in the direction of arrow A, and is passed through a registration (hereinafter, also simply referred to as a “register”) roll 63, a registration pinch roll 62, and a suction opposing roll (deflector roll) 64. Transfer drum 60
Sent to

[0007] The transfer drum 60 is formed by forming a dielectric sheet into a cylindrical shape, and a plurality of chargers (corotrons) are provided inside and outside the transfer drum 60. The attraction corotron 66, which is disposed inside the transfer drum 60 so as to face the deflector roll 64, moves the transfer paper 5 to a predetermined position on the dielectric sheet of the transfer drum 60 by electrostatic attraction generated by the discharge. Is adsorbed.

In this way, the transfer paper 5 held on the transfer drum 60 is sent to a position facing the photosensitive drum 20, that is, to a transfer device section, and is discharged from the photosensitive drum 20 by the discharge of the transfer corotron 70. The black toner image is transferred. Next, the photosensitive drum 20 is attached to the transfer paper 5.
After the residual toner not contributing to the transfer to the photosensitive drum 20 is removed by the cleaning device 24, the toner is uniformly charged again by the charger 22, and the yellow toner image is formed on the photosensitive drum 20 through the same process as the black toner image. Formed.

At this time, the transfer drum 60 continues to rotate while holding the transfer material paper on which the black toner image has been transferred, and is superimposed on the black toner image on the transfer paper 5 sent again to the transfer section. The yellow toner image is transferred. Then, by repeating the same process for the remaining colors, a color image in which the toner images of the four colors are multiplex-transferred onto the transfer paper 5 is completed.

Transfer paper 5 on which transfer of the cyan toner image has been completed
Is removed from the transfer drum 60 by the peeling claw 74 and the inner pressing roll 76 interlocking with the peeling claw 74, by removing the electrostatic attraction acting between the transfer drum 60 and the transfer drum 60. The transfer drum 60 from which the transfer paper 5 has been peeled is subjected to static elimination of the dielectric sheet by the static elimination corotron 80, and cleaning of paper dust and the like by the brush cleaner 82, so that the next recording sheet (transfer material) is adsorbed. Is prepared.

The released transfer paper 5 is fixed on a toner image by a fixing device 90 and is discharged onto a discharge tray 95 by discharge rollers 92 and 94. This completes a series of recording processes for forming a color image. As described above, in this type of electrophotographic process, charging of the photoreceptor, pre-transfer charging, transfer paper adsorption, transfer, transfer paper peeling,
Alternatively, a corona discharger called a so-called corotron is used for static elimination of the photoreceptor or the like, and a high-voltage power supply for applying a high voltage to the corona discharger is provided.

FIG. 6 is a circuit configuration diagram and a current-voltage characteristic diagram illustrating an example of a conventional high voltage power supply device, wherein 2 is a DC power supply, 2a is a DC converter circuit, 2b is a capacitor, and 3 is an AC power supply. Reference numeral 3a denotes an AC converter circuit, 8 denotes a DC power supply, and 7 denotes a load. In FIG. 1A, a high-voltage power supply for applying an AC component and a DC component in which the voltage of a DC component ranges between positive and negative to a load 7 (corona discharger) is connected to a DC converter circuit 2a which is a DC power supply by an AC power supply Has a circuit configuration in which the AC converter circuit 3a and the DC power supply 8 are connected in series.

As shown in FIG. 1B, the AC component and D
The high-voltage power supply in which the DC component of the output Vc having the C bias component crosses positive and negative is an AC converter circuit 3 which is an AC power supply.
In addition to the DC power supply a, two DC power supplies indicated by the DC converter circuit 2a and the DC power supply 8 are required. Therefore, the circuit configuration becomes complicated. FIG. 7 is a circuit configuration diagram and a current-voltage characteristic diagram for explaining another example of the high-voltage power supply device according to the prior art. AC converter circuit, 6 is a DC current detection circuit, 6a is a resistor, 6b
Is a capacitor, 7 is a load, 9 is a rectifier circuit, 9a is a resistor,
9b is a diode.

FIG. 1 shows an AC power supply as an AC power supply.
A converter circuit 3a and a DC converter circuit 2 as a DC power supply
a rectifier circuit 9 is connected in series between
It is obtained by rectifying the flow. Thereby, compared to the configuration of FIG.
The advantage is that the configuration is simplified because the DC power supply is reduced.
is there. However, in this circuit configuration, the AC current is rectified and
Average value V of DC component obtained _RIs the resistance of the resistor 9a.
R, average of AC current is I_ACmeanThen, V_R≒ 1/2 × R × I_ACmean Therefore, the shift voltage by the rectifier circuit, that is, V_RIs
Average value I of AC current_{ACme an}Fluctuates depending on

In the corona discharger, which is the load 7, the I _ACmean fluctuates greatly due to the adhesion of dust and changes in the atmospheric pressure, temperature, humidity, etc., so that the obtained shift voltage also fluctuates, and as a result, the DC power supply becomes stable. The voltage range in which the control operation has to be performed is widened. Also, the average power loss P _R of the resistor R, when the effective value of I _AC was I _{AC rms,}
P _R = 1/2 × R × I _ACrms ²

Here, suppose that I _AC is 1 mA _rms and 50
To obtain a DC component of 0 V, R _{を 得} (2 × 500) / I _ACmean = (2 × 500) / (10 ⁻³ × √2 × 2 / π) = 1.11 × 10 ⁶ [Ω] P _R ≒ 1/2 × R × (1 × 10 ⁻³ ) ² = 0.555 [W], and the power loss is large.

As a disclosure of the above-mentioned prior art, for example, Japanese Patent Application Laid-Open No. 63-146058 is known.

[0018]

As described above, in the prior art for applying a high voltage to a corona discharger, the circuit configuration is complicated and the voltage range in which a stable control operation must be performed is wide. However, there is a problem that the power loss is large. SUMMARY OF THE INVENTION An object of the present invention is to provide a high-voltage power supply device that has a simple circuit configuration and solves the above-mentioned problems of the related art.

[0019]

In order to achieve the above object, a high voltage power supply according to a first aspect of the present invention, as shown in FIG. 1, is a high voltage power supply for outputting a high voltage including an AC component and a DC bias component. In the power supply device, A that generates the AC component
C power source and D which generates the DC component by constant current control
And a constant voltage element connected in series with the DC power supply with a polarity that generates a constant voltage by an output current of the DC power supply.

In the high-voltage power supply according to the first invention, a capacitor can be connected in parallel with the constant voltage element. Further, in the high-voltage power supply device according to the first aspect of the invention, the constant voltage element has at least the DC voltage value when the DC voltage at the output terminal changes to a voltage of the opposite polarity of the DC power supply as a constant voltage value. Can be configured. Further, in the high-voltage power supply according to the first aspect of the invention, the constant voltage element may be constituted by a Zener diode.
In that case, the constant voltage value is a clamp voltage. Also,
An image forming apparatus according to a second aspect of the invention includes a corona discharger to which a high voltage is applied by the high-voltage power supply of the first aspect.

[0021]

The high-voltage power supply according to the first aspect of the present invention comprises an AC power supply 3
And a DC power supply 2 for constant current control are connected in series, and a constant voltage element is connected in series to the DC power supply, thereby generating an AC component in which a positive or negative constant current controlled DC component is superimposed. Let it. In the configuration of the high-voltage power supply device according to the first invention, the AC power supply 3 can be constituted by an AC converter 3a for an AC component.
Can be configured by a DC component converter 2a for positive or negative constant current control by detecting the DC component of the output current. In this case, the high-voltage power supply according to the first aspect of the invention includes an independent converter 3a for the AC component, a constant voltage element 4, and a positive or negative independent constant current control DC that detects the DC component of the output current. The component converter 2a is connected in series. The high-voltage power supply device having this configuration generates an AC component in which a DC component subjected to positive or negative constant current control is superimposed.

The constant voltage element is connected with a polarity that generates a constant voltage by the output current of the DC converter, and generates a stable constant voltage opposite to the voltage generated by the DC converter at the output terminal of the series connection circuit. It is possible to obtain a high-voltage power supply device of DC constant current control in which the output DC voltage ranges between positive and negative polarities. Further, in the configuration of the second aspect, the power loss is further reduced by connecting the capacitor in parallel with the constant voltage element.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a circuit diagram illustrating a high-voltage power supply according to a first embodiment of the present invention, wherein 2 is a DC power supply, 2a is a DC converter circuit, 2b is a capacitor,
Is an AC power supply, 3a is an AC converter circuit, 4 is a Zener diode (ZD), 6 is a DC current detection circuit, 6a is a resistor ( _RL ), 6b is a capacitor, and 7 is a load.

In FIG. 1, a DC power supply 2, an AC power supply 3, and a DC current detection circuit 6 are connected in series.
A zener diode 4 is inserted between the power supply 2 and the AC power supply 3 as a constant voltage element. Since the Zener diode 4 is connected to the DC converter circuit 2a so as to have a reverse voltage polarity, the Zener diode 4 also has a DC voltage _{corresponding to the} clamp voltage V _ZDdc even when the polarity is reverse to the AC converter circuit 3a constituting the AC power supply.
The voltage shifts, and only one DC converter circuit is required, so that one DC converter circuit is not required as compared with the conventional example, and the configuration is simplified.

The clamp voltage V _ZDdc at the Zener diode 4 is V _ZDdc ≒ 1/2 × V _ZD , and is always a substantially constant value. FIG. 3 is an explanatory diagram of a constant current operation characteristic of a DC voltage in the first embodiment of the high-voltage power supply device according to the present invention. When the clamp voltage V _ZDdc becomes a constant value, the voltage shift of the DC component is constant. There does not depend on the AC current I _{ACME an,} as described in FIG. 7, can narrow the output voltage range of the DC power supply. Further, since the maximum value is reduced, the power of the DC power supply is reduced, and the DC power supply configuration is simplified.

FIG. 4 is a circuit diagram illustrating a second embodiment of the high-voltage power supply according to the present invention. The same reference numerals as in FIG. 2 denote the same parts, and 4b denotes a capacitor. In the figure, a capacitor 4b is connected in parallel with the Zener diode 4 in the circuit configuration shown in FIG. The clamp voltage V _ZDdc at the Zener diode 4 in this configuration is V _ZDdc ≒ V _ZD .

Also in this embodiment, since the output shift voltage does not depend on the effective value I _{ACrms of the AC} current I _AC ,
As in the previous embodiment, the clamp voltage is almost constant and the power of the DC power supply is small. In the circuit configuration of this embodiment, the effective value I _{ACrms of the AC} current I _AC bypasses the capacitor 4 b connected in parallel with the Zener diode 4. only I _DC flows in.

Therefore, this Zener diode 4
The loss at is P_ZD= I_DC× V_ZD And, for example, I_DCIs 50 μA, V_ZDTo 500V
If I_ACP regardless of the value of _ZDIs 25 mW, and the effective value I is
_ACrmsIndependent of the value of_DCLoss only
Thus, a low-voltage high-voltage power supply is configured.

The high-voltage power supply according to the present invention can be applied to a power supply of a paper peeling charger and a pre-transfer charger, which constitute an image forming apparatus, and can obtain favorable effects. However, the present invention is not limited to this. It can be applied to other devices as a high voltage power supply having a DC component and a DC component.

[0030]

As described above, according to the present invention,
An AC power supply, a DC power supply of positive or negative independent constant current control by detecting a DC component of the output current, and a DC component of positive or negative constant current control superposed by connecting a constant voltage element in series An AC component is generated, a constant voltage element is connected with a polarity that generates a constant voltage by the output current of the DC power supply, and a stable constant voltage opposite to the voltage generated by the DC power supply is connected to the output terminal of the series connection circuit. Generate voltage and output DC
Obtaining a high-voltage power supply with reduced power loss by adopting a configuration to obtain a DC constant-current controlled high-voltage power supply in which the voltage crosses both positive and negative polarities and by connecting a capacitor in parallel with the constant-voltage element Can be.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a basic configuration of a high-voltage power supply device according to the present invention.

FIG. 2 is a circuit diagram illustrating a high-voltage power supply device according to a first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a constant current operation characteristic of a DC voltage in the first embodiment of the high-voltage power supply device according to the present invention.

FIG. 4 is a circuit diagram illustrating a high-voltage power supply device according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating the configuration of a full-color copying machine as an example of an image forming apparatus to which the present invention is applied.

FIG. 6 is a circuit configuration diagram and a current-voltage characteristic diagram illustrating an example of a conventional high-voltage power supply device.

FIG. 7 is a circuit configuration diagram and a current-voltage characteristic diagram illustrating another example of the high-voltage power supply device according to the related art.

[Explanation of symbols]

2. DC power supply, 2a DC converter circuit, 2b capacitor, 3 AC power supply, 3
a AC converter circuit, 4 Zener diode (ZD), 6 DC current detection circuit, 6a
..... resistor ( _RL ), 6b ... capacitor, 7
····load.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) G05F 1/00 G03G 15/00 G03G 15/02 H02J 1/00

Claims (5)

(57) [Claims] 1. A high-voltage power supply device for outputting a high voltage in which an AC component is biased with a DC component, comprising: an AC power supply for generating the AC component; and an AC power supply connected in series to the AC power supply and controlling the DC component by constant current control. A high-voltage power supply device comprising: a DC power supply to be generated; and a constant-voltage element connected in series with the DC power supply with a polarity that generates a constant voltage by an output current of the DC power supply. 2. The high-voltage power supply according to claim 1, wherein
A high-voltage power supply device comprising a capacitor provided in parallel with the constant voltage element. 3. The high-voltage power supply device according to claim 1, wherein the constant voltage element converts at least the DC voltage value when the DC voltage at the output terminal changes to a voltage of the opposite polarity of the DC power supply. A high-voltage power supply device having a constant voltage value. 4. The high-voltage power supply device according to claim 3, wherein the constant voltage element is a Zener diode, and the constant voltage value is a clamp voltage. 5. An image forming apparatus comprising a corona discharger to which a high voltage is applied by the high voltage power supply according to claim 1.