JPH10295086A - High-voltage power supply equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a compact, lightweight, low-cost equipment by comparing an input signal waveform to a high-voltage AC output waveform, performing the power amplification based on the result of the comparison, applying it to a contact charging device to stably maintain a charged potential, and achieving a high-quality image. SOLUTION: A result of voltage division of an AC high-voltage output waveform is directly compared to an input waveform signal 6 by comparing a means 4. Then, based on the result, an error is amplified by a comparator U3, and an AC high-voltage output is generated through a power amplifier 1 and a booster transformer T1. Because of this, by the current waveform of a distorted waveform occurred in a rectifying circuit, the distortion of an AC high-voltage output waveform occurring in a leakage inductance of the booster transformer T1 is corrected by the error-amplifying operation, and the AC high-voltage output waveform which is always synchronous with the input waveform signal can be obtained. Thus, by applying it to the contact charging device, high-quality images with a charged voltage which is maintained stable can be achieved realizing compactness, light-weight and low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a high-voltage power supply having at least an AC output, which is used in an electrophotographic apparatus such as a laser beam printer, a copying machine or a facsimile.

[0002]

2. Description of the Related Art In recent years, electrophotographic application apparatuses such as a laser beam printer, a copying machine, and a facsimile having an electrophotographic process such as charging, exposure, development, and transfer have adopted a small-diameter photosensitive member, a BCR (Bias Charge).
Roll) and BTR (BiasTransfer Ro)
With the adoption of a small contact charging device, transfer device, or the like referred to as II), miniaturization is progressing.

Various proposals have also been made for the high-voltage power supply device required for each of the above-mentioned processes to reduce the size, weight, and cost.
No. 7, JP-A-1-308129 and the like. The high-voltage power supply devices according to these proposals are configured to supply a plurality of high-voltage outputs necessary for each process from the output of one boosting transformer, thereby simplifying the transformer driving circuit, reducing the number of components, and reducing the number of transformers. ,
It is intended to achieve a reduction in size, weight, and cost.

In Japanese Patent Application Laid-Open No. 64-59267, FIG.
As shown in FIG.
1 generates an AC high voltage on the transformer secondary side, and superimposes the AC high voltage of the secondary windings 103a and 103b on the DC output of the rectifying and smoothing circuit 102a provided on the secondary side,
A DC superimposed AC high voltage output for a charger and a developing device is obtained.

[0005] In Japanese Patent Application Laid-Open No. Hei 1-308129, FIG.
As shown in FIG.
A high-voltage AC voltage is generated on the secondary side of the transformer by a drive circuit including the power amplifier circuit 105 and the like.
2, Q3 and Q4 generate stabilized or variably controlled DC outputs, which are combined to obtain a plurality of stabilized or variable DC outputs and a DC superimposed AC high voltage output.

[0006]

However, the above-mentioned prior art has the following problems.

(Problem 1) The surface potential of the photoreceptor produced by the BCR is a basic quantity directly related to the density and contrast of an output image.
It is roughly determined by the high-voltage DC component applied to the signal, but is affected by the waveform of the AC component. However, in the high-voltage power supply according to the prior art, the BCR is required
It generates multiple DC and AC outputs including output, and generates a distorted current to obtain a DC output in the rectifier circuit,
Since this current is supplied from the drive circuit on the primary side of the step-up transformer, an impedance drop occurs due to leakage inductance between the primary and secondary of the step-up transformer due to the distorted current,
Distortion occurs in the secondary AC high-voltage waveform with respect to the primary voltage waveform of the step-up transformer. The amount of this distortion is determined by the leakage inductance of the step-up transformer and the distorted wave current flowing through the rectifier circuit, but these vary among the power supply units, so that the amount of distortion also varies, and the surface potential of the photoconductor also varies between the units. However, there is a problem that the output image quality is adversely affected.

The above problems will be described below with reference to the conventional example shown in FIG. In the operation explanatory diagram of FIG. 8, w21 indicates that the output AC high voltage waveform is a sine wave, and the rectifier circuit 10 of FIG.
This is an AC high-voltage output waveform when 2a and 102b do not exist, and w22 is the current of the step-up transformer T1. When the rectifier circuits 102a and 102b exist, the rectified current w23
Occurs, and the current of the step-up transformer T1 is distorted like w24.
Then, the output AC high-voltage waveform is distorted like w25 due to the impedance drop of the leakage inductance Ls shown by the equivalent circuit of the step-up transformer T1 in FIG. Rectification circuit 1
Depending on the DC load currents 02a and 102b and the leakage inductance Ls, if these change, the distortion amount also changes. Similarly, in the conventional example of FIG.
, W41 is the rectifier circuit 10 of FIG.
This is an output AC high-voltage waveform in the case where 6, 107 and 108 do not exist, and w42 is the current of the step-up transformer T1. When the rectifier circuits 106, 107, and 108 exist, the rectified current w
43 occurs, and the current of the step-up transformer T1 is distorted like w44. Then, the impedance drop of the leakage inductance Ls shown by the equivalent circuit of the step-up transformer T1 in FIG.
The output AC high voltage waveform is distorted like w45. The amount of distortion depends on the DC load current of the rectifier circuits 106, 107 and 108 and the leakage inductance Ls, and if these change, the amount of distortion also changes.

Further, as is apparent from the above description,
If the leakage inductance Ls of the step-up transformer T1 changes or the specification of the DC output changes, the amount of influence on the photoconductor surface potential due to the distortion of the AC high-voltage waveform is empirically re-established even if other conditions are the same. It is necessary to grasp and to determine the value of the DC component again, and there is a problem that the design of the charging device including the high-voltage power supply is complicated.

When the DC output is changed or turned on / off, for example, when the DC output is used as a developing bias, the DC output for adjusting the image density or the DC output between sheets is changed. On / off is often required. In this case, the output current of the rectifier circuits 106, 107, and 108 changes with the change or on / off of the DC output, and the distorted current flowing through the rectifier circuits 106, 107, and 108 also changes. There is a problem that the potential changes on the time axis, and particularly the image density of the halftone density changes.

(Problem 2) In a contact charging device or a developing device such as a BCR, a roll portion to which a high-voltage power output is applied has a structural spread and is arranged close to the surface of the photoconductor. A distributed capacitance is formed for the space. When an AC high voltage is applied, a capacitive current is supplied to this distributed capacitance. However, although the supplied power is reactive power, power is supplied to the power amplifier 105 on the primary side of the step-up transformer T1 with supply. There is a problem that loss occurs.

The above problems will be described below with reference to FIG. 12 which is an explanatory diagram of power loss of a conventional circuit and FIG. 13 is a conceptual diagram of a power amplifier. For convenience of explanation, the AC high-voltage output is a sine wave, the effects of the exciting inductance and leakage inductance of the step-up transformer T1 are ignored, and the current of the rectifier circuit is ignored. FIG.
In w2, w62 indicates an AC component waveform of the AC high-voltage output waveform, and w61 indicates a current waveform flowing through the entire capacity including the capacitive load connected to the AC high-voltage output and the distributed capacity of the step-up transformer. Since the current w61 is a capacitance current, the voltage w62
In the section indicated by w63, that is, the section of w62 and w61 having the same polarity, power is supplied to the entire capacity, and the section indicated by the section of w64, that is, w62 and w6
In the section where 1 is of opposite polarity, the power supplied in the section of w63 is fed back to the high voltage power supply side, and no power loss occurs in the entire capacity. However, as an example, as shown in FIG. 13, in a normal power amplifier having no ability to regenerate the feedback power from the above-mentioned capacity to the power supply side, power consumption occurs even if the average supply power is 0. I do. In FIG. 13, the source current from the power amplifier is supplied by the active operation of Q1, and the sink current from the power amplifier is supplied by the active operation of Q2. In FIG. 12, W65 is the output voltage of the power amplifier, W68 is the output current, and the section of W66 is shown in FIG.
In the section of W67, power is amplified by the operation of Q2 in FIG.
There is a problem that power loss as shown by W69 occurs.

(Problem 3) A contact charging device such as a BCR has a large impedance dependency on the environment, and particularly a large humidity dependency. The charging characteristics are maintained by, for example, changing the amount of high AC voltage applied in accordance with the conditions. Therefore, the AC high voltage on the secondary side of the step-up transformer T1 greatly changes, and the input voltage of the rectifier circuit also greatly changes. In order to obtain a stable DC output against this change, it is necessary to design a DC stabilization circuit so that the stabilization ability can be secured under the condition of the minimum rectifier circuit input voltage.
The power loss of the DC stabilization circuit under the condition of the highest input voltage of the rectifier circuit was large. In addition, the components used in the rectifier circuit and DC stabilization circuit must use those with a large withstand voltage under the conditions of the highest rectifier circuit input voltage.
This has led to increased costs.

Further, in the developing device, a high-quality AC high-voltage waveform such as a sine wave, a rectangular wave, or a sawtooth waveform is required from the viewpoint of developing performance, but even if the primary side waveform of the step-up transformer is maintained at a high quality. In addition, there is a problem that it is difficult to maintain a high quality AC high voltage output due to ringing and rounding of the output waveform due to the influence of the leakage inductance of the step-up transformer T1.

The present invention has been made in order to solve these problems.
It can be applied to a contact charging device such as the one described above to achieve high image quality by stably maintaining the charging potential, to easily design a charging device including a high-voltage power supply, to reduce power loss, and to use a power amplifier with a low current capacity. Components, and the rectifier circuit and DC stabilization circuit can be composed of low-voltage components.
An object of the present invention is to provide a low-cost high-voltage power supply. Also,
Another object of the present invention is to provide a high-voltage power supply capable of outputting a high-quality AC high-voltage waveform to a developing device or the like.

[Means for Solving the Problems]

To achieve the above object, the present invention comprises the following means. In order to provide a compact, lightweight, low-cost high-voltage power supply that can be applied to a contact charging device such as a BCR and maintain a stable charging potential to achieve high image quality, the power of an input waveform signal is amplified, In a high-voltage power supply device that boosts the amplification result with a step-up transformer and obtains a high-voltage AC output and a DC output obtained by rectifying the AC output, a comparing unit that compares the input waveform signal with the high-voltage AC output waveform, And a power amplifying means for performing the power amplification based on the comparison result of the comparing means.

Further, in order to reduce the power loss, the power amplifying means comprises switching means which operates at a higher frequency than the frequency f0 of the high-voltage AC output. Inductance Lf, part or all of which consists of leakage inductance Ls of the step-up transformer, and a capacitance component Cs of a load part or all of which is connected to a high-voltage AC output
And a means configured to regenerate the reactive power generated by the capacitance component of the load connected to the high-voltage AC output, while removing the low-pass filter by the capacitance Cf.

Further, in order to reduce the power loss and make the drive circuit composed of low-current-capacity components, a parallel resonance circuit composed of an exciting inductance L0 of the step-up transformer and a total capacitance component Cf including the capacitance Cs. Is the high frequency AC output frequency f0
Is provided.

Further, the rectifier circuit and the DC stabilizing circuit can be constituted by low-voltage components, so that power loss can be reduced.
The DC output obtained by rectifying the AC output is a rectifier circuit composed of a Cockcroft-Walton circuit that rectifies the AC output via the capacitance Cin, and a variable impedance element provided between the output of the rectifier circuit and the ground of the rectifier circuit. And means configured to determine an output value from the impedance of the variable impedance element and the impedance of the Cin.

Further, in order to provide a high-quality AC high-voltage waveform to the developing device, the high-voltage power supply device for amplifying the input waveform signal with power and boosting the amplification result with a boosting transformer to obtain a high-voltage AC output. Comparing means for comparing an input waveform signal with the high-voltage AC output waveform, and power amplifying means for performing the power amplification based on a comparison result of the comparing means.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 A high-voltage power supply device according to one embodiment of the present invention amplifies an input waveform signal, boosts the amplification result with a boosting transformer,
In a high-voltage power supply device that obtains a high-voltage AC output and a DC output obtained by rectifying the AC output, a comparison unit that compares an input waveform signal with the high-voltage AC output waveform, and the power amplification based on a comparison result of the comparison unit. And a power amplifying means for performing the following.

In FIG. 1, reference numeral 1 denotes a power amplifier. The electrode amplifier 1 is composed of an npn-type transistor Q1 and a pnp-type transistor Q2, and these npn-type transistors Q1 and pnp. In the transistor Q2, the bases are connected to each other, and the emitter of the npn transistor Q1 and the emitter of the pnp transistor Q2 are connected to each other. The collector of npn transistor Q1 is connected to power supply Vcc, and the collector of npn transistor Q1 is connected to ground terminal Vss. Further, npn-type transistors Q1 and pn
The emitter of the p-type transistor Q2 is a step-up transformer T
1 primary winding. In addition, the step-up transformer T
A first rectifier circuit 2 and a second rectifier circuit 3 for rectifying an AC high voltage output to obtain a DC output are connected to one secondary winding. The first rectifier circuit 2 includes capacitors C4, C5
And diodes D3 and D4. The DC output of the first rectifier circuit 2 is a DC output control circuit Q3
And superimposed on the AC high voltage output of P1. On the other hand, the second rectifier circuit 3 is composed of capacitors C6 and C7 and diodes D5 and D6, and the DC output of the second rectifier circuit 3 is controlled by the DC output control circuit Q4 to P2. DC output. Reference numeral 4 denotes comparison means for comparing the input waveform signal with the AC high-voltage output waveform. This comparison means includes an error amplifier U3 and a resistor R2. Reference numeral 5 denotes output AC waveform detecting means comprising a voltage divider for detecting an AC high voltage output waveform on the secondary side of the step-up transformer T1 and comparing the output waveform with an input waveform signal. It is constituted by capacitors C11 and C12 connected in series. The capacitor C11 is connected to a secondary winding of the step-up transformer T1. The result of the voltage division by the output AC waveform detecting means 5 is as follows:
It is input to one input terminal of the error amplifier U3 of the comparison means 4. The input waveform signal 6 has its DC component cut off via the capacitor C13, and the error amplifier U3
Is input to the other input terminal. In FIG. 1, 7
Indicates a capacitive load, but may be another type of load.

With the above configuration, the voltage division result of the AC high voltage output waveform is directly compared with the input waveform signal 6. The comparison result is error-amplified by the comparator U3, and generates an AC high-voltage output generated via the power amplifier 1 and the step-up transformer T1. Therefore, for example, the step-up transformer T is generated by the distorted current waveform generated by the rectifier circuit as indicated by w23 in FIG.
The distortion of the AC high-voltage output waveform as shown by w25 in FIG. 8 caused by the leakage inductance of 1 is corrected by the above-described error amplifying operation, and an AC high-voltage output waveform always consistent with the input waveform signal can be obtained.

In the above configuration, the input waveform signal 6 may be any waveform other than a sine wave, for example, a rectangular wave, a sawtooth wave, or the like. Obtainable. Further, the voltage divider constituted by the capacitors C1 and C2 may be constituted by, for example, a resistor other than the capacitor, and operates similarly. Also, instead of dividing the capacitors C2 of the voltage dividers C1 and C2 with resistors and dividing the output waveform into analogous shapes, the capacitors C1
Current, ie, the differential waveform of the output voltage waveform may be compared with the input waveform signal. In this case, the operation is performed so that the time-integrated waveform of the input waveform signal always coincides with the AC high-voltage output waveform. As in the case of dividing the voltage into a similar form, it is possible to obtain an AC high voltage output waveform in which the AC high voltage output waveform always coincides with the integral waveform of the input waveform signal. Further, in the above configuration, the rectifier circuits 2 and 3 have two systems, but may have more or less systems.
It is clear that it works as well. Further, in the above-described configuration, the AC high-voltage output is one system, but may be multiple systems, and the same operation is performed. In the above configuration, the rectifier circuit is a one-stage Cockcroft-Walton circuit.
It may be a half-wave rectifier circuit or a multi-stage voltage doubler rectifier circuit,
Acts similarly. Further, in the above configuration, the DC output control circuit is a shunt regulator type control circuit. However, it is apparent that the DC output control circuit may be of a series regulator type, or may be uncontrolled, and operate similarly. It is. Further, the AC high-voltage output current is detected, and for a period sufficiently longer than the output cycle of the AC high-voltage output, the result of comparison between the detection result of the AC high-voltage output current and a predetermined reference value indicates that the power amplifier 1 The AC high-voltage output is configured to be controlled at a constant current by manipulating the amplitude of the input signal waveform, and the AC high-voltage output waveform that matches the input waveform signal as described above is applied to a short time region that is shorter than the cycle of the AC high-voltage output. With such a configuration, it is possible to use the present invention to apply an AC high voltage with a constant current characteristic to the BCR impedance change described in (Problem 3).

Second Embodiment Next, a high-voltage power supply according to a second embodiment of the present invention will be described. The high-voltage power supply according to the second embodiment includes:
The power amplifying means comprises switching means which operates at a higher frequency than the frequency f0 of the high-voltage AC output, and a part or all of the high-frequency component included in the output of the switching means comprises the leakage inductance Ls of the step-up transformer. It is removed by a low-pass filter composed of an inductance Lf and a capacitance Cf composed of a load capacitance component Cs connected to a high-voltage AC output partly or entirely, and is connected to the high-voltage AC output. This is configured to regenerate the reactive power supplied to the capacitance of the load. Further, in the high-voltage power supply device according to Embodiment 2, the parallel resonance frequency of the parallel resonance circuit including the excitation inductance L0 of the step-up transformer and the capacitance Cf approximately matches the frequency f0 of the high-voltage AC output. The configuration is as follows.

In FIG. 2, Q1 and Q2 are switching means operating at a high frequency with respect to the output frequency f0 of the AC high voltage output, and D1 and D2 are capacitors C3, C5,
C6, a regenerative diode for regenerating the feedback power from the total capacity including the capacitive component of the load connected to the AC high-voltage output to the power supply system Vcc;
A high frequency switching power amplifier 1 for performing power amplification by Q2 and regenerative diodes D1 and D2 is constructed. T1 is a step-up transformer. The inductance L1 and the leakage inductance Ls of the step-up transformer T1 (not shown)
Lf for removing high frequency components of the output of the high frequency switching power amplifier 1;
Is configured. The total capacitance component including the capacitors C3, C5, C6 and the capacitance component of the load connected to the AC high-voltage output is:
The capacitance Cf of the Lf and Cf filters for removing the high frequency component of the output of the high frequency switching power amplifier 1
Is configured. C5, D3, D4 and C4 are rectifier circuits 2 for obtaining a DC output obtained by rectifying the AC high voltage output, and this DC output is superimposed on the AC high voltage output of P1 under the control of the DC output control circuit Q3. C6, D5, D6, and C7 are rectifier circuits 3 that rectify the AC high-voltage output and obtain another DC output.
This DC output is controlled by the DC output control circuit Q4 and DC output to P2. Reference numeral 4 denotes comparison means for comparing the input waveform signal and the AC high-voltage output waveform, and operates as a comparator to drive the switching means Q1 and Q2 constituting the high-frequency switching power amplifier 1.
The capacitors C11 and C12 are voltage dividers for detecting the AC high-voltage output waveform and comparing it with the input waveform signal. The voltage division result is input to one input terminal of the comparator U3 of the comparison means 4. . The input waveform signal is cut off the DC component via the capacitor C13, and is supplied to the comparator U3 of the comparing means U3.
3 is input to the other input terminal.

In the above configuration, C5, D3, D4, C
4 and a rectifier circuit 2 composed of C6, D5, D6 and C7,
3, a DC output control circuit comprising Q3 and Q4, C11
The configuration and operation of the voltage divider composed of
Therefore, the power amplifier 1 is composed of switching means that operates at a higher frequency than the high-frequency AC output frequency f0, and the high-frequency component included in the output of the switching means is Inductance Lf, part or all of which consists of leakage inductance Ls of step-up transformer T1, and capacitance component C of a load part or all of which is connected to a high-voltage AC output
The operation of a part configured to regenerate the reactive power supplied to the capacitance of the load connected to the high-voltage AC output while removing the low-pass filter composed of the capacitance Cf made up of s and s will be described. FIG. 3 shows a circuit subsequent to the power amplifier in FIG. 2 as an equivalent circuit, ignoring the presence of a rectifier circuit for convenience of explanation. FIG. 4 is a diagram for explaining the operation waveforms of the respective parts in FIG. 3. Vac in FIG. 3 is represented by the Vac waveform in FIG. 4, and Iac in FIG. 3 is represented by the Iac waveform in FIG. . In the section indicated by w111 in FIG. 4, power is supplied from the power supply to the load side, and in the section indicated by w112, power is fed back from the load side to the power supply.

The operation in the vicinity of time t = t0 in FIG. 4 will be described in detail below as an example. W113 to w119 in FIG. 4 show the operation of each part in the vicinity of time t0 in an enlarged manner in time, w113 is a period during which the switching means Q1 of FIG. 3 is on, and W114 is a diode D1 of FIG. A conduction period, w115 is a period during which the switching means Q2 in FIG. 3 is on, and W116 is a conduction period of the diode D2 in FIG. W117 is the V1 waveform in FIG. 3, and corresponds to Vcc / 2 and -Vcc corresponding to the ON period of the switching means Q1 and the ON period of the switching means Q2.
/ 2 value. W118 is the I1 waveform of FIG.
If the effects of the excitation inductance L0 and the distributed capacitance C0 of the step-up transformer T1 are ignored, Iac (t
0) is the average value, and its slope is a waveform defined by Lf and the voltage difference between V1 and Vac, corresponding to the ON periods of the switching means Q1 and Q2 in FIG. In the illustrated waveform, the amplitude is drawn extremely large for convenience of explanation. The solid line of w119 is Vac in FIG.
The dashed-dotted line 119 is a waveform exaggerating a small change in Vac for explaining the switching operation of the comparator U3 and the power amplifier 1.

In the description, it is assumed that the voltage division result of the Vac by the capacitors C11 and C12 is low with respect to the input waveform signal. In this state, the comparator U3 turns on the switching means Q1, and gradually increases Vac (AC high-voltage output) via the Lf and Cf filters. When Vac rises and the result of voltage division of Vac with respect to the input waveform signal at time t01 increases, comparator U
3 turns on the switching means Q2 by inverting the output.
Since the direction of I1 at the time of the inversion is the Vac rising direction, at the time t0
Up to 2, the diode D2
Then, the power is regenerated to the power supply Vcc, and then the voltage Vac falls and the switching means Q2 is maintained on until time t03 when the result of the Vac voltage division with respect to the input waveform signal is reduced. Then, at time t03 when the voltage division result of Vac becomes lower than the input waveform signal, the output of the comparator U3 is inverted and the switching means Q1 is turned on. I1 at the time of inversion
Is the Vac descending direction, and therefore, Va until the time t04.
Vc via the diode D1 while decreasing the descending speed of c
The power is regenerated to c, the Vac rises, and the switching means Q1 is kept on until time t05 when the result of the Vac voltage division with respect to the input waveform signal increases, and the operation shifts to the above. Then, the above operation is repeated. By repeating the above operation at high speed in a period sufficiently small with respect to the AC high voltage output cycle, the AC high voltage output waveform contains a minute high frequency component.
The effect of the voltage drop due to the impedance of f is compensated, and the waveform becomes the same as the input waveform signal. Power amplifier 1
The switching means Q1 and Q2 that constitute the above-described embodiment perform the regeneration of the reactive power through the diodes D1 and D2 by the above-described switching operation, so that the loss of the power amplifier 1 does not occur in principle, and the lossless operation is performed. .

In the above configuration, Lf and Lf of the Cf filter are constituted by L1 and the leakage inductance Ls of the step-up transformer T1 shown in FIG. 11, but may be constituted only by Ls. Since it is attached to the transformer T1, there is no cost loss due to the addition of the inductance L1. Further, in the above configuration, the Lf and Cf of the Cf filter are constituted by the total capacitance component composed of C3, C5, C6 and the capacitance component of the load connected to the AC high-voltage output. Capacitor C5 only with the capacitance component or this
A configuration in which C6 is added may be adopted, and in this case, cost loss due to the addition of the capacitor C3 does not occur.

In the above configuration, the step-up transformer T
1 by designing the gap of the exciting inductance L0 and the capacitance of the capacitance Cf so that the parallel resonance frequency of the parallel resonance circuit composed of L0 and Cf substantially matches the frequency f0 of the high-voltage AC output. Then, due to the parallel resonance operation of L0 and Cf, the frequency f of the AC output in the output current of the power amplifier 1 indicated by I1 in FIG.
0 component can be canceled and the switching means Q
1, Q2, diodes D1, D2 and step-up transformer T
1, the current capacity and power loss of the primary coil can be reduced, the ripple current and power loss of the capacitors C1 and C2 can be reduced, and low ripple current capacity products can be used for the capacitors C1 and C2. Further, the power loss of the power supply device as a whole can be reduced, the means for radiating the power loss can be reduced, and the size can be reduced.

In the above configuration, there is no operational problem even if the rectifier circuit is omitted and the AC high voltage output is not a sine wave. In this case, power loss is improved and an AC high-voltage output waveform that faithfully reproduces the input waveform signal is obtained.In particular, when applied to a developing bias, an arbitrary waveform such as a rectangular waveform or a sawtooth waveform can be obtained with high accuracy. , High-quality developing performance can be obtained.

The above-mentioned configuration is modified. For example, the output of the comparator U3 is switched between three modes of switching means Q1 on and switching means Q2 off, switching means Q2 on and switching means Q1 off, switching means Q1 off and switching means Q2 off. The same effect can be obtained even if a drive is used. Further, the primary windings of the power amplifier 1 and the step-up transformer T1 may be changed to be configured and operated by a push-pull circuit equivalent to the above configuration. In the above configuration, the high-frequency operating frequency of the power amplifier 1 is a self-excited operation determined by the circuit state. However, an oscillation circuit that determines the high-frequency operating frequency may be provided and operated. Although Q1 and Q2 use bipolar transistors, field effect transistors may be used. In this case, power regeneration diodes D1 and D2 are connected to Q1 and Q2.
1. A parasitic diode in Q2 can be substituted.

Third Embodiment Next, a high voltage power supply according to a third embodiment of the present invention will be described. In the high-voltage power supply device according to the third embodiment, the rectified DC output of the AC output is converted into a rectifier circuit composed of a Cockcroft-Walton circuit that rectifies the AC high-voltage output via a capacitance Cin; A variable impedance element provided between the circuit and the ground, and the output value is determined by the impedance of the variable impedance element and the impedance of Cin.

FIG. 5 has the same contents as the rectifier circuit and the DC output control circuit in FIGS.
rectifying ac through a capacitance Cin, a capacitor Cin, diodes Da and Db and a capacitor C
And a variable impedance element Q provided between the output of the rectifier circuit and the ground of the rectifier circuit.

The operation of the above configuration will be described with reference to FIG. In the configuration of FIG. 5, the peak-to-peak voltage of the AC high-voltage output Vac is Vpp, the frequency of Vac is f0, the rectifier circuit output current is Idc, and the rectifier circuit output voltage is Vd.
Assuming that the ripple voltage of Vdcout is negligibly small, the output characteristic of the rectifier circuit due to the impedance drop of the capacitor Cin is expressed by the following relationship: Idc = f0 × Cin × (Vpp−Vdcout). When this relationship is plotted in FIG.
The rectifier circuit output shown in the figure, where Idc = 0 and Vdcout = Vpp (max) as the starting point when Vpp is the maximum, and Idc = 0 and Vdcout = Vpp (min) when the Vpp is the minimum. It becomes a characteristic straight line. Since the sum of the supply current Idcount to the load and the control current Icont of the variable impedance element Q is Idc, the intersection of the straight line of the parallel impedance of the load and the variable impedance element Q and the output characteristic straight line of the rectifier circuit is the output voltage Vd.
c, and by controlling the current Icont by Q,
As shown in the figure, Vdc can be arbitrarily controlled from 0V.

According to the above configuration, for example, in the operating state at the point b in FIG. 6, the maximum voltage of the rectifier circuit Da, Db, C is V
dcout, and the total power loss including the loss at the load is equal to Idc × Vdc. On the other hand, for example, the impedance of Cin is selected to be sufficiently low, a resistor is arranged between the variable impedance element Q and the output of the rectifier circuit, and the output voltage is controlled by the voltage dividing ratio between the resistor and Q. In the case of a normal shunt regulator configuration, the voltage of the capacitor C becomes Vpp (max) at the operation at the point b.
And the maximum voltage of Da, Db, C of the rectifier circuit is Vpp
(Max), and the total power loss including the loss at the load is Idc × Vpp (max). Therefore, from the above,
The rectifier circuit and the DC stabilization circuit can be configured with low-voltage components and power loss can be reduced as compared with the related art.

[0038]

According to the present invention, there is provided a high-voltage power supply apparatus which amplifies an input waveform signal by power, boosts the amplified result with a boosting transformer, and obtains a high-voltage AC output and a rectified DC output of the AC output. It is provided with a comparing means for comparing a waveform signal with the high-voltage AC output waveform, and a power amplifying means for performing the power amplification based on a comparison result of the comparing means, so that the present invention is applied to a contact charging device such as a BCR. Small, lightweight, which can achieve high image quality while maintaining stable charging potential.
A low-cost high-voltage power supply can be provided.

Further, the power amplifying means comprises switching means which operates at a higher frequency than the high-frequency AC output frequency f0. An inductance Lf composed of an inductance Ls, and a capacitance Cf composed of a capacitance component Cs of a load part or all of which is connected to a high-voltage AC output;
And means for regenerating the reactive power generated by the capacitance component of the load connected to the high-voltage AC output, thereby reducing power loss and miniaturization. .

Further, the parallel resonance frequency of the parallel resonance circuit constituted by the exciting inductance L0 of the step-up transformer and the total capacitance component Call including the capacitance Cf substantially matches the frequency f0 of the high-voltage AC output. By providing the means, the power loss can be reduced, the power amplifier component can be composed of low current capacity components, the primary coil current capacity of the step-up transformer is reduced,
Power ripple is reduced.

The DC output obtained by rectifying the AC output is provided between a rectifier circuit composed of a Cockcroft-Walton circuit for rectifying the AC output via a capacitance Cin and an output of the rectifier circuit and the ground of the rectifier circuit. A variable impedance element, and the impedance of the variable impedance element and the impedance of the Cin,
By providing the means configured to determine the output value, the rectifier circuit and the DC stabilization circuit can be configured with low-voltage components, and power loss can be reduced.

Further, in a high-voltage power supply device which amplifies the input waveform signal by power and boosts the amplification result by a step-up transformer to obtain a high-voltage AC output, the input waveform signal is compared with the high-voltage AC output waveform. Since the power supply device includes the comparing means and the power amplifying means for performing the power amplification based on the comparison result of the comparing means, a high-quality AC high-voltage waveform can be obtained, and this is applied to a developing bias to develop characteristics. Can be maintained stably and high image quality can be achieved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a high-voltage power supply according to Embodiment 1 of the present invention.

FIG. 2 is a circuit diagram showing a high-voltage power supply according to Embodiment 2 of the present invention.

3 is an equivalent circuit diagram of the high-voltage power supply device shown in FIG.

FIG. 4 is an operation explanatory diagram of the high-voltage power supply device shown in FIG. 2;

FIG. 5 is a circuit diagram showing a high-voltage power supply according to Embodiment 3 of the present invention.

FIG. 6 is an operation explanatory diagram of the high-voltage power supply device shown in FIG. 5;

FIG. 7 is a circuit diagram showing a conventional high-voltage power supply device.

FIG. 8 is an operation explanatory diagram of the high-voltage power supply device shown in FIG. 7;

FIG. 9 is a circuit diagram showing a conventional high-voltage power supply device.

FIG. 10 is an operation explanatory diagram of the high-voltage power supply device shown in FIG. 10;

FIG. 11 is an equivalent circuit diagram of a step-up transformer.

FIG. 12 is an explanatory diagram illustrating power loss of a conventional high-voltage power supply device.

FIG. 13 is a conceptual diagram of a conventional power amplifier.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Power amplifier, 2 1st rectifier circuit, 3 2nd rectifier circuit, 4 Comparison means, 5 Output AC waveform detection means, 6
Input waveform signal, 7 loads, T1 step-up transformer.

Claims (5)

[Claims] 1. A high-voltage power supply apparatus for power-amplifying an input waveform signal, boosting the amplification result with a boosting transformer, and obtaining a high-voltage AC output and a rectified DC output of the AC output. A high-voltage power supply device comprising: a comparison unit that compares a high-voltage AC output waveform; and a power amplification unit that performs the power amplification based on a comparison result of the comparison unit. 2. A high-voltage power supply device for amplifying an input waveform signal with power and boosting the amplification result with a step-up transformer to obtain a high-voltage AC output, wherein a comparison is made between the input waveform signal and the high-voltage AC output waveform. Means, and a power amplifying means for performing the power amplification based on a comparison result of the comparing means. 3. The high-voltage power supply device according to claim 1, wherein the power amplifying unit operates at a frequency f0 of the high-voltage AC output.
A switching means that operates at a high frequency compared to the high frequency component included in the output of the switching means,
Part or all of the inductance Lf includes the leakage inductance Ls of the step-up transformer, and part or all of the capacitance Cs includes the capacitance component Cs of a load connected to the high-voltage AC output.
and f) removing the reactive power supplied to the capacitance of the load connected to the high-voltage AC output by removing the low-pass filter configured by the low-pass filter. 4. The high-voltage power supply device according to claim 1, wherein a parallel resonance frequency of a parallel resonance circuit including an exciting inductance L0 of the step-up transformer and the capacitance Cf is the high-voltage high voltage. A high-voltage power supply device characterized in that it is configured to substantially match the frequency f0 of the AC output. 5. The high-voltage power supply device according to claim 1, wherein the DC output obtained by rectifying the AC output is a Cockcroft-Walton circuit that rectifies the AC output via a capacitance Cin. Rectifier circuit, and a variable impedance element provided between the output of the rectifier circuit and the ground of the rectifier circuit, and the output value is determined by the impedance of the variable impedance element and the impedance of the Cin. A high-voltage power supply device comprising: