JPH11143553A - Power supply device and current detection method in power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a current control accuracy in a desired area and also to improve an output accuracy at a desired point as necessary by performing a selective switching between a means which detects a load current in a desired control range and a detection means having high sensitivity. SOLUTION: A 1st error amplifier 14 which is selected via the input of an external signal compares a detected signal of a 1st current detection means 12 with an output control signal(CONTROL) inputted from the outside and outputs a signal obtained by amplifying the difference between the above detected and control signals. The output sent from a high voltage output means 11 is controller at a desired level in response to the level of the external output control signal and by the control of a control means 17, etc., through a switch 16. A 2nd error amplifier 15 which is selected by an external switch sign 1 (SELECT) amplifies the difference between two signals sent from a 2nd current detection means 13 and inputs the amplified error to the means 17. Thus, the output sent from the means 11 is controlled so that two detection signals sent from the means 13 are equal to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device and a method for detecting a current in the power supply device, and more particularly, to a method for generating a high voltage output in an image forming apparatus such as an electrophotographic copying machine or a printer. The present invention relates to a suitable power supply device and a current detection method in the power supply device.

[0002]

2. Description of the Related Art Recent electrophotographic copiers and printers, particularly image forming apparatuses that form one image by superimposing a single color or a plurality of colors, adsorb a toner image formed on a photosensitive member to a transfer member. Then, the image is transferred onto the copied copy paper and the process is repeated a plurality of times to superimpose a plurality of images on one image.

In an electrophotographic image forming apparatus having the above-described transfer member, a high voltage of a constant current output is applied when a toner image is transferred to copy paper. Is repeated a plurality of times, the charge potential of the transfer body increases, and in some cases, a high voltage exceeding several tens [KV] is required. However, applying such a high voltage to the device and charging the device requires a sufficient creepage with a ground housing such as a chassis in consideration of preventing leakage in the device. There is a problem that the device itself becomes large.

On the other hand, in order to solve the above-mentioned problem, the potential of the transfer body is first charged to the negative side,
A technique has been put into practical use in which the absolute value of the charged potential of the transfer body is suppressed by sequentially increasing the potential in the transfer step.
However, in this method, the potential of the portion of the transfer body on which the copy paper does not ride may damage the photoreceptor. To avoid this, the portion of the transfer body on which the copy paper does not ride is always set to 0. It was necessary to control the transfer high voltage output to 0 [μA] so as not to perform the charging on the minus side so as to reach the potential and not to perform the charging in the transfer step.

In addition, when the above-mentioned 0 [μA] control is performed, it is necessary to apply a high transfer voltage when the copy paper passes, but the transfer high voltage must be applied before the leading edge of the copy paper passes. When the voltage is applied, the attraction force between the copy paper and the transfer body is reduced, and in some cases, the copy paper may be peeled off from the transfer body. Therefore, 0 [μA] control is performed until the leading end of the copy paper passes. Continuous control was performed.

[0006]

However, the above prior art has the following problems. That is, in the conventional constant current type high voltage output device as described above,
The output of 0 to several hundred [μA] or − several hundred [μA] to + several hundred [μA] is converted to a minus number [KV] to a plus number [K
V] according to a voltage level signal supplied externally. However, in this case, it is difficult to secure the accuracy of the control of 0 [μA], and the error of the voltage level signal, the error of the control circuit of the high-voltage output device, or the wide control range, There was a problem that the displacement was large.

Further, when the conventional high-voltage output device as described above is used in an electrophotographic image forming apparatus or the like, a desired 0 [μA] output accuracy cannot be obtained, so that a desired electrophotographic process can be performed. However, there is a problem in that the paper cannot be obtained, causing problems such as peeling of the copy paper from the transfer body.

The present invention has been made in view of the above points, and realizes a high accuracy of 0 [μA] control while enabling a wide range of current control, and also improves the accuracy of current control in a desired region. It is an object of the present invention to provide a power supply device and a current detection method in the power supply device, which can improve the output accuracy at a required point as required regardless of 0 [μA] and enable a good electrophotographic process. And

[0009]

In order to achieve the above object, the present invention provides a power supply device having a high voltage output means for generating a high voltage, wherein the power supply device detects a load current in a desired control range. One current detecting means, a second current detecting means having a high detection sensitivity for detecting a load current, and a switching means for selectively switching an output of the first and second current detecting means. I do.

In order to achieve the above object, the invention according to claim 2 is characterized in that the first current detecting means is connected between two output terminals of the high-voltage output means and generates a load current generated between the two output terminals. A voltage corresponding to the value is output, and the second current detection means is a current detection resistor connected between both output terminals of the high voltage output means and detecting a load current based on a potential difference between both ends. .

In order to achieve the above object, the invention according to claim 3 includes a first amplifying means for comparing an output signal of the first current detecting means with an externally input control signal and amplifying a difference therebetween; A second amplifying unit that compares the potentials at both ends of the second current detecting unit and amplifies the difference, and a control unit that controls the high-voltage output unit based on the output of the first or second amplifying unit. Wherein the switching means selectively switches the outputs of the first and second amplifying means based on a switching signal input externally.

According to a fourth aspect of the present invention, there is provided a power supply device having high voltage output means for generating a high voltage, wherein a load current in a desired control range is detected and detection sensitivity can be switched. It has a characteristic current detecting means.

In order to achieve the above object, the invention according to claim 5 is characterized in that the current detecting means is connected between two output terminals of the high voltage output means and responds to a load current value generated between the two output terminals. Output the output voltage.

In order to achieve the above object, a sixth aspect of the present invention is characterized in that the current detection means has a plurality of current detection characteristics that can be switched based on a switching signal input externally.

According to a seventh aspect of the present invention, the current detecting means has a current detection characteristic having a relatively wide detection range and low detection sensitivity, and a current detection characteristic having a relatively narrow detection range and high detection sensitivity. It is characterized by having.

According to another aspect of the present invention, there is provided an amplifier for comparing an output signal of the current detector with an externally input control signal and amplifying a difference between the output signal and an output of the amplifier. Control means for controlling the high-pressure output means based on the control signal.

To achieve the above object, the invention of claim 9 is characterized in that it can be applied to an image forming apparatus such as an electrophotographic copying machine or a printer.

To achieve the above object, a tenth aspect of the present invention is a current detecting method in a power supply device having a high voltage output means for generating a high voltage, wherein the first method detects a load current in a desired control range. It is characterized by comprising a current detection step, a second current detection step having a high detection sensitivity for detecting a load current, and a switching step for selectively switching the outputs of the first and second current detection steps.

In order to achieve the above object, the invention according to claim 11 is that, in the first current detecting step, a voltage corresponding to a load current value generated between two output terminals of the high voltage output means is output. In the second current detecting step, a load current is detected based on a potential difference between both ends of a current detecting resistor connected between both output terminals of the high voltage output means.

In order to achieve the above object, a twelfth aspect of the present invention provides a first amplification step of comparing an output signal of the first current detection step with an externally input control signal and amplifying a difference therebetween, A second amplification step of comparing the two potentials in the second current detection step and amplifying the difference, and a control step of controlling the high voltage output means based on the output of the first or second amplification step. Have
In the switching step, an output of the first and second amplification steps is selectively switched based on a switching signal input from the outside.

In order to achieve the above object, a thirteenth aspect of the present invention is a current detecting method in a power supply device having a high voltage output means for generating a high voltage. And a current detection step capable of switching the current.

In order to achieve the above object, the invention of claim 14 is characterized in that, in the current detecting step, a voltage corresponding to a load current value generated between two output terminals of the high voltage output means is output. And

In order to achieve the above object, the invention of claim 15 is characterized in that the current detection step has a plurality of current detection characteristics that can be switched based on a switching signal input externally.

In order to achieve the above object, the invention according to claim 16 is characterized in that the current detection step comprises a current detection characteristic having a relatively wide detection range and a low detection sensitivity, and a current detection characteristic having a relatively narrow detection range and a high detection sensitivity. It is characterized by having.

In order to achieve the above object, an invention according to a seventeenth aspect provides an amplification step for comparing an output signal of the current detection step with an externally input control signal and amplifying a difference between the output signal and an output of the amplification step. And a control step of controlling the high-voltage output means based on the control signal.

To achieve the above object, the invention of claim 18 is characterized in that it can be applied to an image forming apparatus such as an electrophotographic copying machine or a printer.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

[1] First Embodiment FIG. 1 is a block diagram showing a configuration of a high-voltage power supply according to a first embodiment of the present invention. The high-voltage power supply according to the first embodiment includes a high-voltage output unit 11, a first current detection unit 12, a second current detection unit 13, a first error amplification unit 14, The configuration includes an amplifying unit 15, a switching unit 16, a control unit 17, and a driving unit 18. In the figure, L indicates a load, and A indicates an output terminal.

The high-voltage output means 11 amplifies and rectifies the AC signal on the input side to generate a DC high voltage. The first current detection means 12 is connected to the low voltage output side of the high voltage output means 11, detects an output current and outputs a level signal. The second current detecting means 13 is connected to the low voltage output side of the high voltage output means 11 and has two output terminals, and detects an output current based on a potential difference between the two output terminals. The first error amplifier 14 compares the detection signal from the first current detector 12 with an output control signal (CONTROL) input from the outside, and amplifies the difference.

The second error amplifier 15 receives the two outputs from the second current detector 13 and amplifies the difference. The switching means 16 receives signals from the first error amplifying means 14 and the second error amplifying means 15 and selects and outputs the two inputs according to a switching signal (SELECT) input from outside. I do. The control unit 17 receives the signal from the switching unit 16 and generates a voltage level signal or a PWM (pulse width modulation) signal. The driving unit 18 drives the high voltage output unit 11 in response to a signal from the control unit 17.

Next, the operation of the high-voltage power supply according to the first embodiment configured as described above will be described.
When the output from the first error amplifying means 14 is selected by the input of the external signal, the high voltage output from the high voltage output means 11 is detected by the first current detecting means 12 as its current value, and the detection signal is The signal is input to the first error amplifier 14. At this time, the first error amplifier 14 compares the input current detection signal with the output control signal (CONTROL) input from the outside, and outputs a signal obtained by amplifying the difference.

The output signal is input to the control means 17 through the switching means 16. The control unit 17 outputs a level signal or a PWM signal corresponding to the level of the output signal to the driving unit 18. The driving means 18 generates a driving signal according to the input level signal or PWM signal,
The high voltage output means 11 is driven. By the above control, the output from the high voltage output means 11 is controlled to a desired current value according to the level of the output control signal from the outside.

On the other hand, an external switching signal (SELE)
When the output of the second error amplifying means 15 is selected by CT), the second error amplifying means 15 amplifies the difference between the two signals from the second current detecting means 13 and Input the amplified signal. As a result, the output from the high voltage output means 11 is controlled so that the two detection signals from the second current detection means 13 become equal. As a result, the current is controlled so as not to flow through the second current detecting means 13, and the output of the high voltage output means 11 is controlled to 0 [μA].

FIG. 2 is a circuit diagram showing a detailed configuration of the current detecting means (current detecting circuit) of the high-voltage power supply according to the first embodiment shown in FIG. In FIG. 2, R1, R
2, R3 is a resistor, and Vs is a DC reference voltage. The current detecting means outputs a voltage Vd, and its output terminal is connected to the low voltage output side of the high voltage output means 11 described above.

In the current detection by the current detecting means (current detecting circuit), the output current IL from the high voltage output means 11
Flows through the load L to the ground, flows from the ground to the resistor R2 of the current detecting means, passes through the resistor R3, and flows to the low voltage output side of the high voltage output means 11. Therefore, the detection output Vd of the current detecting means is represented by the following equation.

Vd = {R2 × Vs− (R1 × R2 + R2 × R3 + R3 × R1) × IL} / (R1 + R2) (1) On the other hand, a resistor R3 surrounded by a broken line in the drawing is a second current detection. Means for outputting Vt and Vg as detection outputs. In this circuit, if the high voltage output means 11 is controlled so that Vt = Vg, the current flowing through the resistor R3 becomes 0, that is, the output current of the high voltage output means 11 becomes 0 [μA].

FIG. 3 is a circuit diagram showing a detailed configuration of the switching means 16 (switching circuit) of the high-voltage power supply according to the first embodiment shown in FIG. In FIG. 3, D
1 and D2 are diodes, Tr1, Tr2 and Tr3 are transistors with built-in resistors, V1 and V2 are outputs of the second error amplifier 15 and the output of the first error amplifier 14, respectively, VSL
CT is the selected output voltage.

In this circuit, when the switching signal (SELECT) inputted from the outside becomes a high level signal of about 5 [V], the transistors Tr2 and Tr
3 is turned on, and the anode side of the diode D2 and the base end of the transistor Tr1 are at the ground level. Thereby, the transistor Tr1, the diode D
2 is in the OFF state, and the diode D1 is in the ON state. As a result, the output voltage V1 of the second error amplifying means 15 is selectively output to the output VSLCT of the switching means 16.

On the other hand, when the switching signal (SELECT) becomes a low level near the ground level, the transistors Tr2 and Tr3 are turned off, the transistor Tr1 is turned on, and the diode D1 is turned off.
F, the diode D2 is turned on, and the output VSLCT of the switching means 16 outputs the output V2 of the first error amplifying means 14.

As described above, the first and second current detecting means 12 and 13 and the switching means 16 are provided in a high-voltage power supply device which can be mounted on an image forming apparatus such as an electrophotographic copying machine or a printer. As a result, external control of the constant current output of the high voltage power supply device and high precision of the 0 [μA] output become possible, and the electrophotographic process in the image forming apparatus due to a control error of the 0 [μA] output, which has been a conventional problem. Can be solved.

As described above, according to the first embodiment of the present invention, the high voltage power supply is connected between the high voltage output means 11 for generating a high voltage and the two output terminals of the high voltage output means 11. A first current detecting means for outputting a voltage corresponding to a load current value generated between both output terminals, and a load current connected between both output terminals of the high voltage output means for detecting a load current based on a potential difference between the two outputs; Second current detecting means 13
And a first error amplifying means 14 for comparing an output signal of the first current detecting means 12 with an externally input control signal and amplifying the difference, and a potential of two outputs of the second current detecting means 13. Error amplification means 1 for comparing the
5, a switching means 16 for selectively switching the outputs of the first and second error amplifying means 14 and 15 based on a switching signal inputted from the outside, and generating a voltage level signal or a PWM signal based on the output of the switching means 16. Control means 1
7 and the driving means 18 for driving the high voltage output means 11, the following effects can be obtained.

In the high-voltage power supply unit, apart from the first current detecting means 12 for detecting a load current in a desired control range, a second current detecting means 13 having a high detection sensitivity for detecting a load current is provided. , First and second current detecting means 1
Switching means 16 for selectively enabling either one of 2 and 13
Is provided, current control over a wide range can be realized, and at the same time, highly accurate 0 [μA] control can be performed.

That is, since the outputs of the first and second current detecting means 12 and 13 for detecting a wide range of current and for detecting a current with high sensitivity are switched, the current can be controlled over a wide range. [ΜA] Higher control accuracy can be realized. Thereby, a favorable electrophotographic process can be performed in an image forming apparatus such as an electrophotographic copying machine or a printer equipped with the high-voltage power supply according to the first embodiment of the present invention.

[2] Second Embodiment FIG. 4 is a block diagram showing a configuration of a high-voltage power supply according to a second embodiment of the present invention. The high-voltage power supply according to the second embodiment includes a high-voltage output unit 41 and a current detection unit 4.
9, an error amplifying unit 44, a control unit 47, and a driving unit 48. In the figure, L indicates a load, and A indicates an output terminal.

The high voltage output means 41 amplifies and rectifies an AC signal on the input side to generate a DC high voltage. The current detecting means 49 is connected to the high voltage output means 4.
1 is connected to the low-voltage output side, and changes the detection gain by a switching signal (nSELECT) input from the outside.

The error amplifying means 44 includes a detection signal from the current detecting means 49 and an output control signal (CO
NTROL) and amplifies the difference. The control means 47 receives the signal from the error amplification means 44 and generates a voltage level signal or a PWM (pulse width modulation) signal. The driving means 48 receives the signal from the control means 47 and drives the high voltage output means 41.

Next, the operation of the high-voltage power supply according to the second embodiment configured as described above will be described.
When the current detection means 49 changes the detection gain based on a switching signal (nSELECT) input from the outside, the error amplifying means 44 outputs the signal between the detection signal of the current detection means 49 and the output control signal (CONTROL) input from the outside. The difference is amplified based on the comparison. Along with this, the control means 47 generates a voltage level signal or a PWM signal based on the output signal of the error amplification means 44, and the driving means 48 drives the high voltage output means 41 based on the output signal of the control means 47.

As described above, by providing the current detecting means 49 with the function of the switching means for switching the detection sensitivity, the control gain at the time of 0 [μA] control is changed.
[ΜA] Control accuracy at the time of control can be improved.
That is, at the time of 0 [μA] control, the detection value fluctuates greatly due to a slight current change, so that the sensitivity is high, and 0 [μA] with higher precision
A] Control can be realized.

FIG. 5 is a circuit diagram showing a detailed configuration of the current detecting means 49 (current detecting circuit) of the high-voltage power supply according to the second embodiment shown in FIG. In FIG. 5, R
a, Rb, Rc, Rd, Re are resistances, and Tra, T
rb and Trc are transistors, Va is a current detection output, and Vb is an output terminal connected to the low voltage output side of the high voltage output means 41.

In this circuit, when the external switching signal (nSELECT) is at a low level near the ground level, the transistor Tra, the transistor Trb, and the transistor Trc are in the OFF state.
Is expressed by the following equation using the load current IL.

Va = (Rb + Rc) × Vs / (Ra + Rb + Rc) −Ra × Rc × IL / (Ra + Rb + Rc) (2) If the gain at this time is selected as (II) in FIG.
The sensitivity of the detection current can be increased.

On the other hand, when the switching signal (nSELECT) becomes a high level of about 5 [V], the transistor Tr
a, the transistor Trb, and the transistor Trc are turned on, and a resistor Rd is connected in parallel with the resistor Ra, and a resistor Re is connected in parallel with the resistor Rc.
a and Rc are reduced. As a result, the load current I
The sensitivity to the change in L is low, and the characteristics at this time are shown in FIG.
If (III) is selected, the current range from 0 to Ih can be controlled in the range of the detection voltages Vd1 to Vd2.

On the other hand, (I) in FIG. 6 shows the characteristics of current detection by the conventional current detecting means, and the second embodiment comprises the characteristics (II) and (III) in FIG. In the switching method according to the above, it is clear that high sensitivity detection is realized in the low current control range where high accuracy is required while securing the same current detection range as compared with the conventional characteristic (I).

As described above, the current detecting means 49 for detecting the load current of the high-current power supply of constant current which can be mounted on an image forming apparatus such as an electrophotographic copying machine or a printer has a relatively wide detection range. The function of switching means for switching between low-sensitivity current detection and current detection with a relatively narrow detection range and high detection sensitivity has been added, so the accuracy in the required area is improved while securing the desired current control range. Can be done. Thus, the conventional problem of 0
The problem of the electrophotographic process in the image forming apparatus due to the control error of [μA] output can be solved.

As described above, according to the second embodiment of the present invention, the high voltage power supply is connected between the high voltage output means 41 for generating a high voltage and the two output terminals of the high voltage output means 41. A current detecting means 49 for outputting a voltage corresponding to a load current value generated between the two output terminals;
9 and an externally input control signal, and amplifies the difference.
Has a control means 47 for generating a voltage level signal or a PWM signal on the basis of the output of the control signal and a drive means 48 for driving the high-voltage output means 41.

The high-voltage power supply device is provided with current detecting means 49 for detecting a load current in a desired control range. Further, the current detecting means 49 detects the detection sensitivity of the current detecting means 49 based on a switching signal inputted from the outside. By having a switching function, it is possible to realize a wide range of current control, and at the same time, it is possible to perform 0 [μA] control with high accuracy.

That is, a relatively wide range of current detection is performed by combining a relatively low-sensitivity current detection and a high-sensitivity current detection. Accuracy can be improved, and output accuracy at a required point can be improved as required regardless of 0 [μA]. This allows
An excellent electrophotographic process in an image forming apparatus such as an electrophotographic copying machine or a printer equipped with the high-voltage power supply according to the second embodiment of the present invention can be realized.

The high-voltage power supply according to the first and second embodiments of the present invention is limited to the generation of high-voltage output in an image forming apparatus such as an electrophotographic copying machine or a printer. Instead, the present invention can be applied to another device that performs a predetermined operation based on generation of a high-voltage output.
Further, the present invention may be applied to a system including a plurality of devices or to an apparatus including a single device.

[0059]

As described above, according to the first aspect of the present invention, there is provided a power supply device provided with a high voltage output means for generating a high voltage, wherein a first current for detecting a load current in a desired control range is provided. It has a detecting means, a second current detecting means having a high detection sensitivity for detecting a load current, and a switching means for selectively switching the outputs of the first and second current detecting means. That is, since two current detecting means are switched between a wide range of current detection and a high-sensitivity current detection, it is possible to perform a wide range of current control and improve the accuracy of 0 [μA] control at high voltage output. Can be realized. Thereby, a favorable electrophotographic process can be performed in an image forming apparatus such as an electrophotographic copying machine or a printer equipped with the power supply device of the present invention.

According to the second aspect of the present invention, the first current detecting means of the power supply device is connected between two output terminals of the high voltage output means and detects a load current value generated between the two output terminals. The second current detection means is a current detection resistor connected between both output terminals of the high voltage output means and detecting a load current based on a potential difference between both ends thereof. Therefore, by switching between the two current detecting means for detecting the current in a wide range and for detecting the current with high sensitivity, it is possible to perform a wide range of current control as described above and to improve the 0 [μA] control in the high voltage output. Accuracy can be realized,
A favorable electrophotographic process in an image forming apparatus equipped with the power supply device of the present invention can be realized.

According to the third aspect of the present invention, the power supply device comprises: a first amplifying means for comparing an output signal of the first current detecting means with an externally input control signal and amplifying a difference therebetween;
A second amplifying means for comparing the potentials of two output terminals of the second current detecting means and amplifying the difference, and a control for controlling the high-voltage output means based on an output of the first or second amplifying means Means for selectively switching the outputs of the first and second amplifying means based on a switching signal input from the outside. Therefore, by selectively switching the outputs of the first and second amplifying means and controlling the high-voltage output means by the control means, a wide range of current control is enabled as described above, [Μ
A) It is possible to realize high-precision control, and it is possible to enable a favorable electrophotographic process in an image forming apparatus equipped with the power supply device of the present invention.

According to the fourth aspect of the present invention, there is provided a power supply device having high voltage output means for generating a high voltage, wherein the current detection means capable of detecting a load current in a desired control range and switching detection sensitivity is provided. Have. That is, by switching the detection sensitivity of the current detection means and performing a wide range of current detection by combining a relatively low-sensitivity current detection and a high-sensitivity current detection, a wide range of current control can be performed. In addition, the accuracy of current control in a desired region can be improved, and the output accuracy at a required point can be improved as necessary regardless of 0 [μA]. This allows
A favorable electrophotographic process can be realized in an image forming apparatus such as an electrophotographic copying machine or a printer equipped with the power supply device of the present invention.

According to the fifth aspect of the present invention, the current detecting means of the power supply device is connected between two output terminals of the high voltage output means and has a voltage corresponding to a load current value generated between the two output terminals. Is output. Therefore, by switching the detection sensitivity of the current detection means and performing a wide range of current detection by combining a relatively low-sensitivity current detection and a high-sensitivity current detection, a wide It is possible to improve the accuracy of current control in a desired region while enabling the control, and it is possible to improve the output accuracy at a necessary point as necessary regardless of 0 [μA]. A good electrophotographic process in an image forming apparatus equipped with a power supply device can be enabled.

According to the invention of claim 6, the current detecting means of the power supply device has a plurality of current detecting characteristics which can be switched based on a switching signal input from the outside. Therefore,
By combining a relatively low-sensitivity current detection and a high-sensitivity current detection to perform a wide range of current detection, as described above, a wide range of current control is possible, and a current control in a desired region is performed. Accuracy can be improved,
Regardless of 0 [μA], the output accuracy at a required point can be improved as required, and a good electrophotographic process in an image forming apparatus equipped with the power supply device of the present invention can be realized.

According to the present invention, the current detecting means of the power supply device has a current detecting characteristic having a relatively wide detection range and a low detection sensitivity, and a current detection characteristic having a relatively narrow detection range and a high detection sensitivity. . Therefore, current detection over a wide range can be performed by combining current detection with a relatively wide detection range and low detection sensitivity, and current detection with a relatively narrow detection range and high detection sensitivity. In addition, the accuracy of current control in a desired region can be improved, and the output accuracy at a required point can be improved as necessary regardless of 0 [μA]. A good electrophotographic process in the image forming apparatus.

According to the invention of claim 8, the power supply device compares the output signal of the current detection means with an externally input control signal and amplifies the difference between the output signal and the output signal of the amplification means. Control means for controlling the high voltage output means. Accordingly, by controlling the high-voltage output means by the control means, it is possible to improve the accuracy of current control in a desired region while enabling a wide range of current control as described above, and to reduce the current to 0 [μA]. Regardless, the output accuracy at necessary points can be improved as required, and a favorable electrophotographic process in an image forming apparatus equipped with the power supply device of the present invention can be realized.

According to the ninth aspect, the power supply device is applicable to an image forming apparatus such as an electrophotographic copying machine or a printer. Therefore, a favorable electrophotographic process can be realized in an image forming apparatus such as an electrophotographic copying machine or a printer equipped with the power supply device of the present invention.

According to a tenth aspect of the present invention, there is provided a current detecting method in a power supply device provided with a high voltage output means for generating a high voltage, comprising: a first current detecting step of detecting a load current in a desired control range; The method includes a second current detection step having a high detection sensitivity for detecting a load current, and a switching step of selectively switching outputs of the first and second current detection steps. That is, since two current detection steps are switched between current detection for a wide range and current detection for a high sensitivity, high accuracy of 0 [μA] control at high voltage output can be achieved while wide range current control is possible. Can be realized. Thereby, a favorable electrophotographic process can be performed in an image forming apparatus such as an electrophotographic copying machine or a printer equipped with the power supply device of the present invention.

According to the eleventh aspect, in the first current detecting step of the current detecting method in the power supply device,
A voltage corresponding to a load current value generated between two output terminals of the high-voltage output means is output, and in the second current detection step, a current detection resistor connected between both output terminals of the high-voltage output means is provided. The load current is detected based on the potential difference between both ends of the switch. Therefore, by switching between the two current detection steps for wide-area current detection and high-sensitivity current detection, similar to the above, it is possible to perform wide-area current control and to increase the 0 [μA] control at high voltage output. Accuracy can be realized, and a favorable electrophotographic process can be performed in an image forming apparatus equipped with the power supply device of the present invention.

According to a twelfth aspect of the present invention, in the current detection method in the power supply device, the first amplification step of comparing the output signal of the first current detection step with an externally input control signal and amplifying the difference is performed. Step, a second amplification step of comparing two potentials in the second current detection step and amplifying the difference, and controlling the high voltage output means based on an output of the first or second amplification step. And the switching step selectively switches the outputs of the first and second amplification steps based on a switching signal input externally. Therefore, by selectively switching the outputs of the first and second amplification steps and controlling the high voltage output means in the control step, a wide range of current control can be performed as described above, and the high voltage output can be controlled. [ΜA] Higher control accuracy can be realized,
A favorable electrophotographic process in an image forming apparatus equipped with the power supply device of the present invention can be realized.

According to the thirteenth aspect of the present invention, there is provided a current detecting method for a power supply device having a high voltage output means for generating a high voltage, wherein a load current in a desired control range is detected and detection sensitivity can be switched. It has a current detection step. That is, the detection sensitivity of the current detection step is switched,
By performing a wide range of current detection by combining a relatively low-sensitivity current detection and a high-sensitivity current detection, the accuracy of the current control in a desired region is improved while enabling a wide range of current control. In addition to this, the output accuracy at a required point can be improved as required regardless of 0 [μA]. Thereby, a favorable electrophotographic process can be performed in an image forming apparatus such as an electrophotographic copying machine or a printer equipped with the power supply device of the present invention.

According to the fourteenth aspect, in the current detecting step of the current detecting method in the power supply device, a voltage corresponding to a load current value generated between two output terminals of the high voltage output means is output. Therefore, by switching the detection sensitivity of the current detection step and performing a wide range of current detection by combining a relatively low-sensitivity current detection and a high-sensitivity current detection, a wide current It is possible to improve the accuracy of current control in a desired region while enabling the control, and it is possible to improve the output accuracy at a necessary point as necessary regardless of 0 [μA]. A good electrophotographic process in an image forming apparatus equipped with a power supply device can be enabled.

According to a fifteenth aspect of the present invention, the current detection step of the current detection method in the power supply device has a plurality of current detection characteristics that can be switched based on a switching signal input externally. Therefore, by performing a wide range of current detection by combining the relatively low-sensitivity current detection and the high-sensitivity current detection, a wide range of current control can be performed in the same manner as described above, and in a desired region. The accuracy of the current control can be improved, and the output accuracy at a required point can be improved as required regardless of 0 [μA]. A simple electrophotographic process.

According to the sixteenth aspect of the present invention, the current detecting step of the current detecting method in the power supply device includes a current detecting characteristic having a relatively wide detection range and a low detection sensitivity, and a current detection characteristic having a relatively narrow detection range and a high detection sensitivity. Has detection characteristics. Therefore, current detection with a relatively wide detection range and low detection sensitivity,
Since a wide range of current detection can be performed in combination with current detection having a relatively narrow detection range and high detection sensitivity, it is possible to improve the accuracy of current control in a desired region while enabling wide current control. At the same time, it is possible to improve the output accuracy at a necessary point as required regardless of 0 [μA], thereby enabling a favorable electrophotographic process in an image forming apparatus equipped with the power supply device of the present invention. it can.

According to a seventeenth aspect of the present invention, the current detecting method in the power supply device comprises: an amplifying step of comparing an output signal of the current detecting step with a control signal inputted from the outside, and amplifying a difference therebetween; Controlling the high-voltage output means based on the output of the control unit. Therefore, by controlling the high voltage output means in the control step, a wide range of current control can be performed as described above,
It is possible to improve the accuracy of current control in a desired region, and to improve the output accuracy at a necessary point as necessary regardless of 0 [μA]. A good electrophotographic process in the forming apparatus can be enabled.

According to the eighteenth aspect, the current detection method in the power supply device is applicable to an image forming apparatus such as an electrophotographic copying machine or a printer. Therefore, a favorable electrophotographic process can be realized in an image forming apparatus such as an electrophotographic copying machine or a printer equipped with the power supply device of the present invention.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a high-voltage power supply according to a first embodiment of the present invention.

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

FIG. 3 is a circuit diagram illustrating an example of a switching circuit of the high-voltage power supply device according to the first embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a high-voltage power supply according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing an example of a current detection circuit of a high-voltage power supply according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram of current control in a high-voltage power supply according to a second embodiment of the present invention.

[Explanation of symbols]

 11, 41 High voltage output means 12 First current detection means 13 Second current detection means 14 First error amplification means 15 Second error amplification means 16 Switching means 17, 47 Control means 18, 48 Driving means 44 Error amplification Means 49 Current detection means L Load

Claims (18)

[Claims] 1. A power supply device comprising high-voltage output means for generating a high voltage, comprising: first current detection means for detecting a load current in a desired control range; and second detection means for detecting a load current having a high detection sensitivity. And a switching means for selectively switching the outputs of the first and second current detecting means. 2. The first current detecting means is connected between two output terminals of the high-voltage output means and outputs a voltage corresponding to a load current value generated between the two output terminals, 2. The power supply device according to claim 1, wherein said current detecting means is a current detecting resistor connected between both output terminals of said high voltage output means and detecting a load current based on a potential difference between both ends. 3. A first amplifying means for comparing an output signal of the first current detecting means with a control signal inputted from the outside and amplifying a difference between the output signal and a potential at both ends of the second current detecting means. A second amplifying unit for comparing and amplifying the difference, and a control unit for controlling the high voltage output unit based on an output of the first or second amplifying unit, wherein the switching unit is externally input. 3. The power supply device according to claim 1, wherein an output of the first and second amplifying means is selectively switched based on a switching signal. 4. A power supply device provided with high-voltage output means for generating a high voltage, comprising a current detection means capable of detecting a load current in a desired control range and switching detection sensitivity. apparatus. 5. The current detection means is connected between two output terminals of the high-voltage output means and outputs a voltage corresponding to a load current value generated between the two output terminals. 4. The power supply device according to 4. 6. The power supply device according to claim 4, wherein said current detection means has a plurality of current detection characteristics that can be switched based on a switching signal input externally. 7. The current detection means according to claim 6, wherein said current detection means has a current detection characteristic having a relatively wide detection range and a low detection sensitivity, and a current detection characteristic having a relatively narrow detection range and a high detection sensitivity. Power supply. 8. An amplifying means for comparing an output signal of the current detecting means with a control signal inputted from the outside and amplifying the difference, and a control means for controlling the high voltage output means based on an output of the amplifying means. The power supply device according to any one of claims 4 to 7, further comprising: 9. The power supply device according to claim 1, wherein the power supply device is applicable to an image forming apparatus such as an electrophotographic copying machine or a printer. 10. A current detection method in a power supply device provided with high-voltage output means for generating a high voltage, comprising: a first current detection step of detecting a load current in a desired control range; and a detection sensitivity of detecting a load current. And a switching step for selectively switching the outputs of the first and second current detection steps. 11. In the first current detecting step, a voltage corresponding to a load current value generated between two output terminals of the high voltage output means is output, and in the second current detecting step, the high voltage The method according to claim 10, wherein the load current is detected based on a potential difference between both ends of a current detection resistor connected between both output terminals of the output means. 12. A first amplification step of comparing an output signal of the first current detection step with an externally input control signal and amplifying a difference between the output signal and two potentials in the second current detection step. A second amplification step of comparing and amplifying the difference, and a control step of controlling the high-voltage output means based on an output of the first or second amplification step, wherein the switching step includes an external input. The output of the first and second amplification steps is selectively switched based on a switching signal.
12. A method for detecting a current in a power supply device according to claim 11. 13. A current detecting method in a power supply device provided with a high voltage output means for generating a high voltage, comprising a current detecting step capable of detecting a load current in a desired control range and switching a detection sensitivity. A current detection method in a power supply device. 14. The method according to claim 13, wherein in the current detecting step, a voltage corresponding to a load current value generated between two output terminals of the high-voltage output means is output.
A method for detecting a current in the power supply device according to claim 1. 15. The current detection method according to claim 13, wherein the current detection step has a plurality of current detection characteristics that can be switched based on a switching signal input externally. 16. The current detection step according to claim 15, wherein the current detection step has a current detection characteristic having a relatively wide detection range and low detection sensitivity, and a current detection characteristic having a relatively narrow detection range and high detection sensitivity. Current detection method in power supply device. 17. An amplifying step of comparing an output signal of the current detecting step with a control signal input from the outside and amplifying a difference between the output signal and a control step of controlling the high voltage output means based on an output of the amplifying step. The method for detecting a current in a power supply device according to claim 13, further comprising: 18. The method according to claim 10, wherein said method is applicable to an image forming apparatus such as an electrophotographic copying machine or a printer.