JPH05224503A - High-voltage power source circuit - Google Patents

Abstract

PURPOSE:To form and output plural different power at an arbitrary time with a single high-voltage transformer by at least, controlling output with a PWM signal, on the secondary side of a high-voltage transformer. CONSTITUTION:When a transfer unit and a photosensitive body are cleaned, the relay switch 32 of an output part for an electrostatic charging device 29, and the relay switch 37 of an output part for the transfer unit 35, are turned on, and moreover, a relay switch 36 is turned off. Further, the relay switches 35, 36, and 37 are changed over, and simultaneously, a voltage detecting circuit 27 is stopped, and a current detecting circuit 28 is operated. Then, the current detecting circuit 28 detects the output of the current of the output part for the transfer unit 35, obtained via a secondary side coil 25C and the relay switch 37, and controls the pulse width of a PWM signal on a PWM output circuit 26, to control the output of the current to a constant current output for a transfer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high voltage power supply circuit which is provided in an electrophotographic apparatus or the like and which forms and outputs a plurality of different voltage outputs and current outputs by voltage conversion by a high voltage transformer and output control by a PWM signal. More specifically, the present invention relates to a high-voltage power supply circuit capable of forming each of the above outputs at a desired time with a single high-voltage transformer.

[0002]

2. Description of the Related Art Generally, an electrophotographic apparatus is adapted to obtain a copied image by combining a copying operation and a cleaning operation. In the above copying operation, the original image is exposed on the photoconductor charged by the charger to form an electrostatic latent image, toner is attached to the electrostatic latent image to form a toner image, and then the toner image is formed. The cleaning operation is an operation of transferring to a transfer sheet by using a transfer device, and the cleaning operation is an operation of moving toner adhering to the transfer device to a photoconductor and removing unnecessary toner on the photoconductor by the cleaning device.

The charger used in the above copying operation is
For example, the photosensitive member is charged with a charging voltage of -1.26 KV. Further, the transfer device is adapted to transfer the toner image by a transfer current of -4 μA (voltage of -1 to -3 KV) during the copying operation, and
During the cleaning operation, the toner attached to the transfer device is moved to the photoconductor by a cleaning voltage of, for example, + 500V. Therefore, the electrophotographic apparatus is provided with a high-voltage power supply circuit capable of forming and outputting a plurality of different outputs at arbitrary times in order to perform a copying operation and a cleaning operation.

As shown in FIGS. 5 and 6, the conventional high-voltage power supply circuit has PWM output circuits 81, 84, 85 for converting a DC voltage into a switching pulse by a PWM signal.
And a high-voltage transformer 80, 82, 83 for converting each of these switching pulses into a voltage for charging, transferring, and cleaning. When charging the photoconductor, a constant voltage equal to the charging voltage is used. So that the output
While detecting the voltage output by the PWM output circuit 81, P
The output width is controlled by controlling the pulse width of the WM signal.

When the toner image is transferred, the PWM output circuit 84 detects the current output and controls the pulse width of the PWM signal to perform output control so that a constant current output equal to the transfer current is output. Like this,
When the toner attached to the transfer device is moved to the photoconductor, the PWM output circuit 85 detects the voltage output so that the constant voltage output equal to the cleaning voltage is output, and the pulse width of the PWM signal is controlled to control the output. To do.

Since the conventional high-voltage power supply circuit is provided with the PWM output circuits 81, 84, 85 and the high-voltage transformers 80, 82, 83 for each output, each output is formed and output at an arbitrary time. You can do it.

[0007]

However, in the above-mentioned conventional high-voltage power supply circuit, the most expensive high-voltage transformers 80, 82, 83 among the constituent parts are provided for each output, and a plurality of these high-voltage transformers 80, 82, 83 are provided. The existence of 82 and 83 is an obstacle to cost reduction. Further, as shown in FIG. 5, even if only a single high-voltage transformer 80 is used, P
By changing the pulse width of the WM signal, charging, transfer,
However, in such a high-voltage power supply circuit, since the control by the PWM signal is performed only on the primary side of the high-voltage transformer 80, each output becomes a time-divided output and is different at the same time. It cannot be used in applications such as electrophotographic devices that require output.

Therefore, an object of the present invention is to provide a high-voltage power supply circuit capable of forming and outputting a plurality of different outputs by a single high-voltage transformer at arbitrary times.

[0009]

In order to solve the above problems, a high voltage power supply circuit of the present invention forms a plurality of different outputs at arbitrary times by voltage conversion by a high voltage transformer and output control by a PWM signal. It is output and has the following features.

That is, the high-voltage power supply circuit is characterized in that the output control by the PWM signal is performed at least on the secondary side of the high-voltage transformer.

[0011]

According to the above configuration, since the output control by the PWM signal is performed on the secondary side of the high voltage transformer, when increasing the separate outputs that need to be formed at the same time, even if a single high voltage transformer is used, This can be dealt with by increasing the number of output controls on the secondary side. Therefore, the high voltage power supply circuit is
Significant cost reduction is possible.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

As shown in FIG. 3, the high-voltage power supply circuit according to this embodiment is built in an electrophotographic apparatus having a copying apparatus main body 1. The high-voltage power supply circuit is not limited to the electrophotographic device, and may be used in other devices.
An original placing table 2 is provided on the upper surface of the copying apparatus main body 1, and the original placing table 2 is, as shown in FIG.
It is adapted to be reciprocally moved in the left-right direction by the mounting table moving device 20.

The mounting table moving device 20 described above has a loop-shaped endless gear 22 having rack gear portions 22a and 22b at the top and bottom, and the rack gear portion 2 of the endless gear 22.
It has a planetary gear 24 and a drive output gear 23 disposed between 2a and 22b. The endless gear 22 and the planetary gear 24 allow the document placing table 2 to be moved at two different speeds during feeding and returning. It is designed to be moved.

As shown in FIG. 3, at one end of the document placing table 2 is a document cover 3 which moves together with the document placing table 2.
Is openable and closable. A document 6 is placed on the upper surface of the document placing table 2, and an irradiation lamp 15 for irradiating the placed document 6 with light is provided below the document placing table 2. It is arranged at a substantially central portion of the main body 1.

The reflected light from the original 6 illuminated by the illumination lamp 15 is the rod lens array 4
The photoconductor 13 rotatably arranged is exposed through the photoconductor 13. A roller-shaped charger 14 is provided on the photoconductor 13 between the exposure portion 13a of the photoconductor 13 and the irradiation lamp 15. They are arranged in contact with each other. The charger 14 is configured to form an electrostatic latent image on the photoconductor 13 by exposure by charging the photoconductor 13 with a charging voltage of -1.26 KV, for example.

In addition to the above-mentioned charger 14, a developing device 10 for adhering toner to an electrostatic latent image to form a toner image around the photoconductor 13 is used, for example, -4 μA during copying operation.
While the toner image is transferred to the transfer paper by the transfer current of, a roller-shaped transfer device 12 that moves the toner adhering to the transfer device to the photoconductor by a cleaning voltage of, for example, + 500V during cleaning operation A cleaning device 17 for removing the toner and a toner storage portion 18 for storing the toner removed by the cleaning device 17 are provided.

Further, on the paper feed side for supplying the transfer paper between the transfer device 12 and the photoconductor 13, the registration roller 8 for adjusting the paper feed timing of the transfer paper and the manual feed for accommodating the transfer paper are provided. While the paper section 5 is arranged in this order,
A fixing device 19 including an upper heat roller 19a and a lower heat roller 19b for heating and melting the toner of the transfer paper is disposed on the paper discharge side.

The charging voltage, the transfer current, and the cleaning voltage supplied to the charging device 14 and the transfer device 12 are formed by a high voltage power supply circuit. As shown in FIG. 1, this high-voltage power supply circuit includes one primary coil 25a and two secondary coils 25b and 25c.
And a PWM output circuit 26 is provided on the primary side coil 25a of the high voltage transformer 25.
The switching pulse converted from the DC voltage by the PWM signal of is input. The high-voltage transformer 25 converts the switching pulse input to the primary coil 25a into a voltage and converts the switching pulse into a voltage of the secondary coil 25a.
The output is from b.25c.

One of the secondary coils 25b of the high voltage transformer 25 is connected to a charger output unit 29 for outputting a voltage output equal to the charging voltage to the charger 14 of FIG. The other secondary coil 25c of
3 is connected to the transfer unit output unit 35 that outputs a current output equal to the transfer current or a voltage output equal to the cleaning voltage to the transfer unit 12 of FIG.

The charger output section 29 includes a diode 30 having a cathode connected to one terminal of the secondary coil 25b, a transistor 31 having an emitter terminal connected to the anode of the diode 30, and a transistor 31.
One end is connected to the collector terminal of the
Relay switch 32 that is in a state, and relay switch 32
A booster circuit 33 including a capacitor 33a and a diode 33b connected to the other end of the
PW which outputs the PWM signal connected to the base terminal of 1
And an M output circuit 34.

The booster circuit 33 is the relay switch 3
The voltage input via 2 is boosted four times, and the ON-OFF operation of the transistor 31 is controlled by 60 times.
The voltage is set to 0 V or less. The charger output unit 29 having the booster circuit 33 is
The voltage output output from the booster circuit 33 via the output terminal 29a is detected by the PWM output circuit 34, and the ON-O of the transistor 31 is controlled by controlling the pulse width of the PWM signal.
By controlling the FF time, a constant voltage output equal to the charging voltage is formed and output.

The transfer device output section 35 has a relay switch 36 that is turned on during the cleaning operation and a relay switch 37 that is turned on during the copying operation. One end of both relay switches 36 and 37 is provided. Is connected to the other secondary coil 25c. The anode side of the diode 38 is connected to the other end of the relay switch 36 that is turned on during the cleaning operation, and the cathode side of the diode 38 is connected to the output terminal 35a connected to the transfer unit 12 in FIG. There is. A voltage detection circuit 27 is connected to the output terminal 35a via a resistor 43, and the voltage detection circuit 27 detects the voltage output during the cleaning operation so that a constant voltage output equal to the cleaning voltage is obtained. , PW for the PWM output circuit 26
The pulse width of the M signal is controlled.

On the other hand, the cathode side of the diodes 39 and 40 connected in series is connected to the other end of the relay switch 37 which is turned on during the copying operation, and a capacitor 41 is connected in parallel to these diodes 39 and 40. It is connected. One end of a capacitor 42 is connected between the diodes 39 and 40.
The other end is connected to GND via the resistor 44, and the secondary coil 25c and the current detection circuit 28 are connected.
The current detection circuit 28 detects the current output during the copying operation and controls the PWM output circuit 26 to control the pulse width of the PWM signal so as to obtain a constant current output equal to the transfer current. It has become.

The electrophotographic apparatus having the structure described above is shown in FIG.
The operation of the high-voltage power supply circuit will be described based on the output time chart of FIG.

First, when the copy start switch is pressed, the cleaning operation is executed. That is, as shown in FIG. 1, the relay switch 32 of the charger output unit 29 and the relay switch 37 of the transfer device output unit 35 are turned off, while the relay switch 36 of the transfer device output unit 35 is turned on. Will be put in a state. Then, the switching pulse converted from the DC voltage by the PWM signal of the PWM output circuit 26 is input to the primary coil 25a of the high voltage transformer 25, and the voltage detection circuit 27 is activated.

The operated voltage detection circuit 27 detects the voltage output of the transfer device output section 35 formed via the secondary coil 25c and the relay switch 36, and the PWM output circuit 26 is detected. By controlling the pulse width of the PWM signal in accordance with the above, the voltage output is controlled to be a constant voltage output equal to the cleaning voltage.

The above constant voltage output is as shown in FIG.
Since the toner is supplied to the transfer device 12, the toner attached to the transfer device 12 is moved to the photoconductor 13.
Then, the toner attached to the photoconductor 13 is
Cleaning device 17 together with the toner remaining in No. 3
The toner is scraped off and stored in the toner storage unit 18. After this, the relay switch 36 of FIG.
When the F state is set, the transfer unit 12 is set to 0V and the toner of the opposite polarity is cleaned.

By the above cleaning operation, the transfer device 1
2 and the photoconductor 13 are cleaned, then,
When the copy operation is executed and the document table 2 is moved to the start position, as shown in FIG.
While the relay switch 32 of the charger output unit 29 and the relay switch 37 of the transfer unit output unit 35 are turned on, the relay switch 36 of the transfer unit output unit 35 is turned off.

Further, the relay switches 35 and 36 described above are used.
Simultaneously with the switching of 37, the voltage detection circuit 27 is stopped and the current detection circuit 28 is operated. Then, the current detection circuit 28 detects the current output of the transfer unit output section 35 formed via the secondary coil 25c and the relay switch 37,
By controlling the pulse width of the PWM signal by the PWM output circuit 26, the current output is controlled so as to become the constant current output for transfer.

When the relay switch 32 of the charger output unit 29 is turned on to form a voltage output through the secondary coil 25b, the relay switch 32, and the booster circuit 33, this voltage is generated. Output is PWM
By controlling the pulse width of the PWM signal detected by the output circuit 34, the output is controlled to be the constant voltage output for charging.

As for the constant voltage output of the charger output unit 29 and the constant current output of the transfer unit output unit 35, first, the constant voltage output of the charger output unit 29 is supplied to the charger 14, and the charger 14 exposes it. The body 13 will be charged.
An electrostatic latent image is formed on the charged photoconductor 13 by exposure, and thereafter, toner is attached to the electrostatic latent image by the developing device 10 to form a toner image. .. Then, when the toner image is moved to the vicinity of the transfer device 12, the constant current output of the transfer device output unit 35 is supplied to the transfer device 12, so that the photoconductor 1
The toner image of No. 3 is transferred to the transfer paper.

When the above transfer is completed, the copying operation is stopped, and all the relay switches 32 and 36 shown in FIG.
When 37 is turned off, the output states of the charger output unit 29 and the transfer unit output unit 35 are set to 0V. Then, the cleaning operation described above is performed again, so that the toner remaining on the transfer unit 12 and the photoconductor 13 is removed.

In this way, the high voltage power supply circuit of this embodiment is
Output control by the PWM signal is performed not only on the primary side of the high voltage transformer 25 but also on the secondary side. The output control by the PWM signal on the secondary side can be dealt with by increasing the number of output controls on the secondary side even with a single high-voltage transformer 25 when increasing the separate outputs that need to be formed at the same time. I have to. Therefore, this high-voltage power supply circuit can form and output a plurality of different outputs by a single high-voltage transformer 25 at an arbitrary time, and by unifying the high-voltage transformer 25, a significant cost reduction can be achieved. ing.

[0035]

As described above, the high voltage power supply circuit of the present invention forms and outputs a plurality of different outputs at arbitrary times by voltage conversion by the high voltage transformer and output control by the PWM signal. This is a configuration in which output control by signals is performed at least on the secondary side of the high-voltage transformer.

As a result, since the output control by the PWM signal is performed on the secondary side of the high voltage transformer, even with a single high voltage transformer, by increasing the number of output controls on the secondary side, separate outputs can be output at arbitrary times. Can be formed into. Therefore, by unifying the high-voltage transformer, it is possible to significantly reduce the cost.

[0037]

[Brief description of drawings]

FIG. 1 is a circuit diagram of a high voltage power supply circuit of the present invention.

FIG. 2 is an output time chart of the electrophotographic apparatus.

FIG. 3 is a schematic configuration diagram of an electrophotographic apparatus.

FIG. 4 is a perspective view of a mounting table moving device.

FIG. 5 is a circuit diagram showing a portion that forms a charging voltage of a conventional high-voltage power supply circuit.

FIG. 6 is a circuit diagram showing a portion that forms a cleaning voltage and a transfer voltage of a conventional high voltage power supply circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copying device main body 2 Original mounting table 10 Developing device 12 Transfer device 13 Photoconductor 14 Charger 15 Irradiation lamp 17 Cleaning device 19 Fixing device 20 Mounting table moving device 25 High voltage transformer 26 PWM output circuit 27 Voltage detection circuit 28 Current detection circuit 29 Charger output part 31 Transistor 32 Relay switch 33 Booster circuit 35 Transfer device output part 36 Relay switch 37 Relay switch

Claims (1)

[Claims] 1. Voltage conversion and PWM by a high voltage transformer
In a high-voltage power supply circuit that forms and outputs a plurality of different outputs at arbitrary times by output control by signals, the output control by the PWM signal is performed at least on the secondary side of the high-voltage transformer. High voltage power circuit.