JP3141435B2 - High voltage power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

2. Description of the Related Art Generally, an electrophotographic apparatus such as a copying machine is
A charging station for uniformly charging a photosensitive member (photosensitive material) as an intermediate recording medium; an exposure station for forming an electrostatic latent image on the charged photosensitive member; and a developing station for visualizing the electrostatic latent image with toner. , A transfer station for transferring a visual image formed by toner onto transfer paper, and a fixing station for fixing the toner image on the transfer paper. Information such as characters and images is reproduced by a series of processes passing through these stations. .

In the above process, a plurality of types of corona dischargers (hereinafter referred to as "chargers") are used. In particular, a main transfer charger in a transfer station for transferring a toner image formed on a photoreceptor to transfer paper is used. A pre-transfer charger is provided at the former stage, and a transfer paper peeling charger for peeling the transfer paper from the photoreceptor after the transfer process is provided. As a power supply for these pre-transfer chargers and transfer paper peeling chargers,
A DC superimposed AC high voltage power supply in which a DC voltage is superimposed on an AC voltage is used.

The purpose of superimposing the DC component on the AC high voltage applied to the pre-transfer charger is to set the center value of the AC voltage between the potential of the image area on the photoconductor and the potential of the image area other than the image area. Is to shift the potential other than the image portion to the side where the image is easily transferred and to the side where the transfer is difficult, to increase the density of the image portion and prevent the toner other than the image portion from being transferred to the recording paper. Further, after transferring the toner image of the photoconductor to the transfer paper, the electric field applied at the time of transfer is removed by an AC electric field applied to the peeling charger to reduce the electrostatic coupling force between the photoconductor and the transfer paper. However, the peeling force may be insufficient at the time of peeling, or the peeling electric field may be too strong, and the toner image may remain on the photoconductor side. The purpose of superimposing the DC component on the AC high voltage applied to the peeling charger is to adjust the potential of the transfer paper with the DC component so that the transfer paper can be easily peeled from the photoconductor.

A conventional high-voltage power supply of this type is disclosed, for example, in Japanese Patent Publication No. 27422/1990 or Japanese Patent Application Laid-Open No. 2-27708.
As disclosed in Japanese Patent Application Publication No. 1 (1999) -1995, a waveform shaping capacitor is connected in parallel with a high-voltage winding of a step-up transformer connected to a DC power supply. DC converters can be connected in series, and Japanese Patent Publication No. 1-56637 and Japanese Utility Model Application Laid-Open No. 63-923.
As disclosed in Japanese Patent Application Publication No. 62-62, a configuration is generally used in which another winding (tertiary winding) is added to a step-up transformer, and a DC output is obtained by rectifying an induced current of the other winding.

FIG. 5 shows a DC-D converter for generating a DC component.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of a configuration of a conventional AC superimposed high-voltage DC power supply device using a C converter.
2, 43 are switching elements, 5 is a waveform shaping capacitor, 6 is a rectifier diode, 7 is a smoothing capacitor, 11 is a control circuit, and 12 is a DC-DC converter.

In the configuration shown in FIG. 1, the DC supplied from the DC power supply 1 to the primary winding (low-voltage side winding) 21 of the step-up transformer 2 is switched on / off by the control circuit 11 alternately. 42 is chopped. As a result, a boosted high-voltage AC is induced in the secondary winding 22 of the step-up transformer 2. Waveform shaping capacitor 5
Suppresses the vibration term that occurs in this high-voltage AC at light load,
Waveform shaping.

On the other hand, the DC-DC converter 12 chops the DC from the DC power supply 11 flowing through the primary winding 31 of the step-up transformer 3 by the switching element 43 which is turned on / off by the control circuit 121 in the same manner as described above. A substantially rectangular high-voltage alternating current is induced in the secondary winding 32. The high-voltage AC induced in the secondary winding 32 is rectified to DC by a rectifier circuit including a rectifier diode 6 and a smoothing capacitor 7.

The DC-DC converter 12 is connected in series with the parallel circuit of the secondary winding 22 of the step-up transformer 2 and the waveform shaping capacitor 5, so that the output is a DC-DC converter.
A DC superimposed AC high voltage in which the AC obtained from the secondary winding 22 of the step-up transformer 2 is superimposed on the DC obtained by the DC converter 12 is output. FIG. 6 is a diagram for explaining the configuration of a conventional DC superimposed AC high-voltage power supply device in which a tertiary winding is provided in an AC step-up transformer to obtain a DC component. Is a step-up transformer for AC, 21 is the primary winding of the step-up transformer, 22 is the secondary winding, 33 is the tertiary winding, 41 and 42 are switching elements, 5 is a capacitor for waveform shaping, 6 is a rectifying diode, 7 Is a smoothing capacitor, 8 is a rectifier resistor, and 11 is a control circuit.

In the configuration shown in FIG. 1, the DC supplied from the DC power supply 1 to the primary winding (low-voltage side winding) 21 of the step-up transformer 2 is switched on and off alternately by the control circuit 11 by the switching elements 41, 42 is chopped. As a result, a boosted high-voltage AC is induced in the secondary winding 22 of the step-up transformer 2. Waveform shaping capacitor 5
Suppresses the vibration term generated in the high-voltage AC at light load and shapes the waveform.

On the other hand, a rectifier diode 6, a smoothing capacitor 7, and a smoothing resistor 8
The DC output of this rectifier circuit is connected in series to a parallel circuit of the secondary winding 22 of the step-up transformer 2 and the shaping capacitor 5. Therefore, a DC superimposed AC high voltage in which the AC high voltage obtained in the secondary winding 22 of the step-up transformer 2 is superimposed on the DC high voltage obtained in the tertiary winding 33 is output.

[0011]

In the above prior art, the configuration is complicated by providing a tertiary winding in a DC-DC converter or a step-up transformer in order to create a DC component, and the occupied space in the applied equipment is increased. There is a problem that the cost increases. An object of the present invention is to provide a DC superimposed AC high-voltage power supply that generates a DC component with a simple configuration by solving the above-described problems of the related art, and a DC output that is different from an AC high-voltage output.

[0012]

In order to achieve the above object, the present invention utilizes a part of a reactive current flowing through a waveform shaping capacitor (5) to form a waveform of the waveform shaping capacitor (5). A step-up transformer (2) connected to a DC power supply (1), and switching elements (41, 42) connected to a low-voltage side winding of the step-up transformer (2). A control circuit (11) for controlling on / off of the switching elements (41, 42); and a high-voltage side winding (2) of the step-up transformer (2).
A waveform shaping capacitor (5) connected in parallel to 2);
And a rectifier circuit (60) inserted in series with the waveform shaping capacitor (5).

According to the present invention, a step-up transformer (2) such as a leakage transformer connected to a DC power supply (1) and a low-voltage side winding (primary winding 21) of the step-up transformer (2) are alternately connected. Switching elements (41, 42) to be turned on / off, and the switching elements (41, 4);
A control circuit (11) for controlling ON / OFF of 2); a waveform shaping capacitor (5) having one end connected to one terminal of a high-voltage side winding (secondary winding 22) of the step-up transformer (2); ,
A first rectifier diode (61) having one electrode connected to the other end of the waveform shaping capacitor (5), the waveform shaping capacitor (5) and the first rectifier diode (6);
A second rectifier diode (62) having one electrode connected to the connection point of (1) in the forward direction with respect to the first diode;
And a parallel circuit of a resistor (8) and a smoothing capacitor (7) connected between the other electrode of the second rectifier diode (62) and the terminal of the other electrode of the first rectifier diode (61). It is possible to configure.

The present invention can also be configured to take out a required DC output from the rectifier circuit (60). A plurality of parallel capacitors (51, 52) are used as waveform shaping capacitors. It is also possible to provide a smoothing circuit (60, 60 ') for each capacitor to obtain one or more DC outputs.

[0015]

The waveform shaping capacitor (5) connected in parallel to the secondary winding (high-voltage side winding) (22) is a step-up transformer (2).
The AC high voltage induced in the secondary winding (22) by turning on / off the DC current flowing through the primary winding (low-voltage side winding 21) is shaped.

A rectifier circuit (60) connected to the waveform shaping capacitor (5) rectifies an AC current flowing through the waveform shaping capacitor (5), smoothes the current, and generates a DC component.
This rectifier circuit generates a DC component in a range sufficiently smaller than the peak-to-peak value of the AC output, and does not affect the reactive current flowing through the waveform shaping capacitor, thus impairing the waveform shaping function. Therefore, a DC component can be obtained with a simple configuration, and a required DC output can be obtained from the rectifier circuit.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a circuit diagram illustrating an embodiment of a high-voltage power supply device according to the present invention, wherein 1 is a DC power supply, 2 is an AC boosting transformer, and 21 is a primary winding (low-voltage side winding) of an AC boosting transformer. ), 22 are the same secondary windings (high-voltage windings), 41 and 42 are switching transistors as switching elements, 5 is a capacitor for waveform shaping, 6
1, 62 are rectifier diodes, 7 is a smoothing capacitor, 8
Is a rectifier resistor, 11 is a switching transistor on /
This is a control circuit for performing off control.

In the configuration shown in FIG. 1, the DC supplied from the DC power supply 1 to the primary winding 21 of the AC step-up transformer 2 is:
The switching elements 41 and 42, which are alternately turned on / off by the control circuit 11, alternately perform chopping at a predetermined cycle. As a result, a boosted alternating high voltage is induced in the secondary winding 22 of the AC step-up transformer 2. The waveform shaping capacitor 5 functions as a low-pass filter, and suppresses a vibration term generated in the high-voltage AC at a light load,
Waveform shaping.

A rectifier circuit composed of rectifier diodes 61 and 62, a smoothing capacitor 7, and a resistor 8 is connected between the secondary winding 22 and the waveform shaping capacitor 5, and an alternating current flowing through the waveform shaping capacitor 5 is provided. One of the currents flows through a series circuit of the rectifier diode 61, the secondary winding 22, and the waveform shaping capacitor 5. The other of the alternating current flowing through the waveform shaping capacitor 5 flows through the secondary winding 22, the waveform shaping capacitor 5, the rectifier diode 62 of the smoothing circuit 60, and the parallel circuit of the smoothing capacitor 7 and the rectifier resistor 8.

FIG. 2 is a waveform chart for explaining the operation of FIG. 1, and the reference numerals of the respective waveforms correspond to the waveforms of the same reference numerals in FIG. The waveforms A and A in FIG. 2 indicate ON / OFF of the switching transistors 41 and 42 controlled by the control circuit 11.
A voltage waveform applied to each half of the primary winding 21 of the step-up transformer 2 when the primary winding 2 is turned off.
An alternating current is induced in the secondary winding 22 in accordance with a change in the current flowing through the first winding. FIG. 3C shows a high-voltage AC voltage waveform shaped by the rectifying capacitor 5.

The rectifier circuit 60 rectifies and smoothes the current, and generates a voltage change having the waveform shown at d at both ends of the rectifier diode 62. Therefore, the current causing the voltage change of the waveform d is smoothed by the smoothing circuit including the smoothing capacitor 7 and the resistor 8, and a DC component as shown in the waveform E at the point A in FIG. 1 is generated.

As a result, the voltage appearing at the output becomes the DC superimposed AC voltage shown in waveform f in which the DC voltage component shown in waveform e is superimposed on waveform c, as shown in waveform f in FIG. In FIG. 1, the DC component at point A is (average current)
× (resistance value of the rectifier resistor 8), the peak-to-peak voltage of the waveform c in FIG. 2 is V _PP (V), and the frequency is f (H
z), the capacitance of the waveform shaping capacitor 5 is C
(F), the average voltage between terminals of the smoothing capacitor 7 is V
_{Assuming 0} (V), the average current I ₀ (A) is as follows: I ₀ = f × C × (V _PP −V ₀ ) (Equation 1)

In this case, the average voltage V ₀ between the terminals of the smoothing capacitor 7 is given by: V ₀ = f × C × R × V _PP ｆ (f × C × R -1) (2) In the present embodiment, sufficient (in (Equation 1), V ₀ = 0 equivalent) of a conventional no smoothing circuit 60 is close to the state, i.e., V ₀ of the equation (1) is against the V _PP By generating a DC output within a small range, the reactive current flowing through the waveform shaping capacitor 5 is not affected, so that the function of waveform shaping is not impaired.

If a DC output such as V ₀ ≒ V _PP is generated, I ₀ = 0 in (Equation 1), no reactive current flows through the waveform shaping capacitor, and the waveform shaping capacitor has a waveform shaping function. Will not work. FIG. 3 is a circuit diagram for explaining another embodiment of the high-voltage power supply device according to the present invention, wherein the same reference numerals as those in FIG.
Is a rectifier resistor, and 9 is a constant voltage control transistor for stably controlling the DC voltage of the output 2.

In this embodiment, the output 1 is used as the AC high voltage output.
And a DC voltage obtained by the rectifier circuit 60 is taken out as an output 2 of another output. According to this embodiment, a stabilized predetermined DC output can be obtained from the DC superimposed AC high voltage power supply. FIG. 4 is a circuit diagram illustrating still another embodiment of the high-voltage power supply device according to the present invention, wherein the same reference numerals as those in FIG.
1, 52 are waveform shaping capacitors, 60, 60 'are rectifying and smoothing circuits, 63, 64 are rectifying diodes, 71, 7
2 is a smoothing capacitor, and 10 and 101 are Zener diodes as constant voltage elements.

In this embodiment, the waveform shaping capacitor 5 shown in FIG. 1 or 3 is divided into a parallel circuit of a capacitor 51 and a capacitor 52, and a rectifier circuit 60 and a rectifier circuit 60 'are provided. Rectifier circuit 60,
The configuration is such that a required DC output is extracted from 60 ′. As described above, according to the present embodiment, it is possible to extract a plurality of DC outputs from the AC high-voltage power supply.

The present invention is not limited to the configuration of each embodiment described above, and the polarity of the DC output, the configuration of the generation circuit (rectifying / smoothing circuit) and specific elements are arbitrary.

[0028]

As described above, according to the present invention,
By utilizing a part of the reactive current flowing through the waveform shaping capacitor of the AC high-voltage power supply, a DC component can be obtained with a simple configuration without impairing the original waveform shaping function of the waveform shaping capacitor.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating an embodiment of a high-voltage power supply device according to the present invention.

FIG. 2 is a waveform chart for explaining the operation of the embodiment of the present invention shown in FIG.

FIG. 3 is a circuit configuration diagram illustrating another embodiment of the high-voltage power supply device according to the present invention.

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

FIG. 5 is an explanatory diagram of a configuration of a conventional AC superimposed high-voltage DC power supply device using a DC-DC converter.

FIG. 6 is a diagram illustrating the configuration of a conventional AC superimposed DC high voltage power supply in which a third winding is provided in an AC step-up transformer to obtain a DC component.

[Explanation of symbols]

1 ... DC power supply, 2 ... AC step-up transformer,
21 ··· Primary winding of AC step-up transformer (low-voltage side winding), 22 ··· Secondary winding (high-voltage winding), 41,
42... A switching transistor which is a switching element, 5... A waveform shaping capacitor, 60.
..Smoothing circuits, 61, 62,.
.... smoothing capacitor, 8 .... resistor, 11 ...
..A control circuit that controls on / off of the switching transistor.

Claims (1)

(57) [Claims] 1. A step-up transformer connected to a DC power supply, a switching element connected to a low-voltage side winding of the step-up transformer to turn on / off the supply of the DC power, and control for controlling on / off of the switching element. A circuit and a waveform shaping capacitor connected in parallel to the high-voltage winding of the step-up transformer to shape an alternating high-voltage induced in the high-voltage winding;
And a rectifier circuit for rectifying and smoothing the AC current flowing through the waveform shaping capacitor to generate a DC component.