JPH0736370Y2 - High voltage power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a high-voltage power supply device, and in particular, one device,
The present invention relates to a high-voltage power supply device capable of outputting at least two types of levels of each voltage output from a plurality of DC high and medium voltage circuits.

(Prior Art) An example of a conventional high-voltage power supply device will be described with reference to FIG. In the figure, 1 is a reference voltage generating means, 2 and 3 are resistors, 4 is a comparator, 5 is a drive control circuit, 6 is a switching transistor, and 7 is a transformer. Further, 8 is a rectifier circuit of the intermediate pressure generating circuit, 9 is a constant voltage output circuit of the intermediate pressure generating circuit, the intermediate pressure output from the constant voltage output circuit, the developing bias, a chatch up roll. )
Used for voltage, chute bias, etc. Further, 10 is a rectifying circuit of a high voltage generating circuit, 11 is a charging corotron, and the high voltage output from the high voltage rectifying circuit 10 is applied to the charging corotron 11. The high voltage is the monitor resistance 12
Is fed back to the connection point of the resistors 2 and 3 through.

The high-voltage power supply device having the above configuration controls the input of the transformer 7 according to the high-voltage output monitor voltage obtained via the monitor resistor 12, and outputs the high-voltage output and the medium-voltage output from the secondary side of the transformer 7. It is designed to control the output.

FIG. 6 shows a schematic view of the device arranged around the drum. 21 is a drum, 22 is an exposure position, 23 is a developing roll, 24 is a chatchup roll, 25 is a paper conveyance guide, 26 is a transfer corotron, and 27 is a peeling corotron. Further, a is a terminal for the charging corotron to which the high voltage is applied,
Reference numerals b, c and d are terminals for applying the developing bias, the chatchup roll voltage and the tut bias to which the intermediate pressure is applied, respectively.

Now, when a copying or printing operation is executed in a copying machine, a printer or the like including the high voltage circuit having the configuration shown in FIG. 5, for example, the time when the paper is sent out from the registration roll provided on the paper transport path is used as a reference. As the input voltage Vin shown in FIG. 5 is applied at an appropriate timing, the intermediate pressure and the high voltage are generated from the intermediate pressure generating circuit and the high voltage generating circuit. As a result, the medium pressure and the high pressure are applied to the respective devices around the drum, and a predetermined copying or printing operation is advanced.

When the operation proceeds and the last copy or print is completed, the input voltage Vin is turned off at a predetermined timing. Then, the intermediate pressure and the high pressure are reduced, and the series of operations is completed.

(Problems to be solved by the invention) Next, referring to FIG. 7, when n sheets are copied (n
-1) The operation of the first and subsequent sheets will be described.

As shown in (5) of the figure, the on / off signal is kept on until time t7 when the nth copy is completed, and therefore the applied voltage (1) of the charging corotron 11 is also at this time t7. Is being applied up to.

If the (n-1) th copy is completed at time t1,
Since the document information is interrupted until the time t2 when the nth copy starts, the drum charge amount in the exposure unit 22 becomes H (high) level as shown in FIG.
Next, when the nth copy is started, the drum charge amount in the exposure section 22 changes according to the document information in the nth copy period t2 to t5. After the time t5 at which the copying of the nth sheet is completed, the document information does not come, so the drum charge amount in the exposure unit 22 becomes the H level, and this continues until the time t8. Here, times t7 to t8 correspond to the rotation time from the charging corotron position of the drum to the exposure unit position.

Next, the developing bias shown in FIG. 3C will be described. The exposure bias is passed between the (n-1) th copy and the nth copy (time t1 to t2). In order to prevent toner from sticking to the drum surface, that is, when the original information interruption portion comes to a position facing the developing device,
The timing (time of day) when the document information interruption section arrives at the developing device
In accordance with t3 to t4), the developing bias is set to the H level. Also, when the nth copy is finished, similarly,
It is set to the H level from time t6 to t7. When the on / off signal is turned off, the H level changes to the L level at the same time.

Therefore, the toner adhesion amount at the developing portion becomes 0 at the document information interruption portion as shown in FIG. 4 (4), and unnecessary toner does not adhere to the drum.

However, after the copying of the nth sheet is completed, the H level of the developing bias becomes the L level at the same time when the on / off signal is turned off, so that unnecessary toner adheres to the drum during the time t7 to t8. There was a problem.

Also, in order to solve this problem, if the medium voltage generation circuit and the high voltage generation circuit are separately powered, the device becomes large and
There is a problem that the cost of the power supply circuit becomes high.

An object of the present invention is to provide a high-voltage power supply device that can solve the above-mentioned problems of the prior art.

(Means and Actions for Solving the Problem) In order to achieve the above-mentioned object, the present invention provides a high-voltage power supply device having means for comparing a high-voltage output monitor voltage with a reference voltage on the primary side of the high-voltage transformer. It is characterized by the addition of means for changing the voltage.

In the high-voltage power supply device, the first reference voltage of the comparison means is high.
When the voltage is high, the high-voltage output generator outputs a high voltage high enough to discharge the charged corotron, and the medium-voltage output generator outputs a voltage higher than the voltage required by the medium-voltage circuit. On the other hand, when the reference voltage of the comparison means is the second magnitude which is low, the high voltage output generating section outputs a high voltage which is insufficient to discharge the charged corotron, and the medium voltage output generating circuit outputs: It outputs a voltage higher than that required by the medium voltage circuit.

Therefore, the selection of the first and second magnitudes of the reference voltage, that is, the selection of the first and second modes is performed at an appropriate timing, so that the drum is not required after the n-th copy is completed. The problem of toner adhesion can be eliminated.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the high voltage power supply device of the present invention. In the figure, 31 is a transistor, 32 to 34 are resistors, and other symbols are the same as or equivalent to those in FIG. The present embodiment is characterized in that the reference voltage Vx applied to the + terminal of the comparator 4 can be set to two voltage values Vx1 and Vx2 by turning on / off the transistor 31.

The operation when the transistor 31 is turned on and off is
It will be described with reference to the drawings.

Now, when an L level signal is applied to the base of the transistor 31 with the on / off signal being on (first mode), the transistor 31 is turned off and applied to the + terminal of the comparator 4. The applied reference voltage Vx becomes the high reference voltage Vx1 as shown. Then, the comparator 4 outputs an H level signal when a potential lower than the reference voltage Vx1 is input to its negative terminal, and the drive control circuit 5 controls the switching transistor 6 so that its ON period becomes long. As a result, a large amount of energy is stored in the primary winding of the transformer 7, and a large flyback voltage is generated on its secondary side when the switching transistor 6 is turned off. Therefore, the high voltage generation circuit outputs a voltage VH1 larger than the discharge start voltage Vc1 of the charging corotron 11. Further, the medium voltage generation circuit outputs a voltage VM1 larger than the minimum voltage Vc2 required to operate the medium voltage circuit.

Now, at time T1, when the base voltage of the transistor 31 is changed to the H level (second mode), the transistor 31
Is turned on, and the reference voltage Vx becomes the low reference voltage Vx2 as shown. Then, when a voltage higher than the reference voltage Vx2 is input to the negative terminal of the comparator 4, an L level signal is output, and the drive control circuit 5 causes the switching transistor 6 to have an off period longer than that in the above case. To control. As a result, a smaller amount of energy is stored in the primary winding of the transformer 7, and a flyback voltage is generated on its secondary side when the switching transistor 6 is turned off. Therefore, the high voltage generation circuit outputs a voltage VH2 smaller than the discharge start voltage Vc1 of the charging corotron 11. On the other hand, the medium voltage generation circuit outputs a voltage VM2 larger than the minimum voltage Vc2 required to operate the medium voltage circuit.

Further, when the on / off signal is turned off, the input voltage Vin applied to the high voltage power supply device becomes 0, so that the voltage output from the high voltage generating circuit and the intermediate voltage generating circuit also becomes 0.

Next, the operation when copying is performed by using the high-voltage power supply device of this embodiment in a copying machine will be described with reference to FIG. FIG. 3 shows a time chart similar to that of FIG.

The difference between FIG. 3 and FIG. 7 is that the on / off signal is turned off at time t8 and a signal that is at H level is applied to the base of the transistor 31 during the time t7 to t8. Is.

According to this embodiment, since the L-level voltage is applied to the base of the transistor 31 until time t7, the same operation as in the conventional case is performed, and the second high voltage generating circuit and the second intermediate voltage generating circuit operate. The voltage is generated until time T1 in the figure. That is, the high voltage generation circuit generates a voltage VH1 that is higher than the discharge start voltage of the charging corotron 11, and the medium pressure generation circuit generates a voltage VM1 having a magnitude that prevents toner from adhering to the drum 21. As a result, the charging corotron 11 performs a predetermined discharge, and the developing roll 23 operates so that toner does not adhere to the document information interruption portion.

Now, at time t7, when an H-level voltage is applied to the base of the transistor 31, the high voltage generating circuit and the intermediate voltage generating circuit generate the voltage of the magnitude shown at time T1 to T2 in FIG. To do. That is, the high voltage generation circuit generates a voltage VH2 that is smaller than the discharge start voltage of the charging corotron 11, and the medium pressure generation circuit generates a voltage VM2 having a magnitude that prevents toner from adhering to the drum 21. As a result, the charging corotron 11 stops discharging, and the developing roll 23 operates so that the toner does not adhere during the period from time t7 to t8.

As a result of the above-described operation, the toner adhesion amount on the developing portion on the drum 21 becomes 0 after time t7 as shown in FIG. 3 (4), and unnecessary toner is transferred to the drum. Can be prevented.

FIG. 4 shows a second embodiment of the present invention. This embodiment differs from the first embodiment in that a series connection circuit of a transistor 35 and a resistor 36 is connected in parallel with a resistor 32. According to this embodiment, when an L level signal is applied to the base of the transistor 35, the high voltage output and the intermediate voltage output from the high voltage generation circuit and the intermediate pressure generation circuit are the high voltage output and the intermediate voltage output shown at times T1 to T2 in FIG. On the other hand, when an H level signal is applied to the base of the transistor 35, the high voltage generating circuit and the medium voltage generating circuit obtain the high voltage output and the medium voltage output before the time T1 in FIG. That is, the level of the control signal applied to the base of the transistor 35 can be reversed as compared with that in the first embodiment.

Although the reference voltage Vx applied to the + terminal of the comparator 4 is switched by turning on / off the transistors 31 and 35 in the above embodiment, the present invention is not limited to this. You may switch using the switching element of.

(Effects of the Invention) As described above, according to the present invention, in one high-voltage generating device, for example, a high voltage capable of discharging a charging corotron and a first intermediate pressure capable of generating a required amount of pressure can be simultaneously generated.
And the second mode in which the charging corotron can simultaneously generate a high voltage of a magnitude that cannot be discharged and a medium pressure of a required magnitude can be selected. .

Therefore, when the high-voltage generating device is used as a power source for a device arranged around a drum such as a copying machine or a printer, toner adheres to the drum at the end of the copying operation or the printer operation. There is an effect that a defect can be solved by one high-voltage generator.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention, FIG. 2 is a time chart for explaining the operation thereof, and FIG. 3 is a high-voltage power supply device of the embodiment of a device around a drum such as a copying machine. FIG. 4 is a circuit diagram of a second embodiment of the present invention, and FIG. 5 is a circuit of a conventional device when a voltage applied to the device, a drum charge amount, and a toner adhesion amount are used when used as a power source. FIG. 6 and FIG. 6 are schematic views showing the devices arranged around the drum, and FIG. 7 is a time chart showing the voltage applied to the device by the conventional high-voltage power supply device, the drum charge amount, and the toner adhesion amount. 4 ... comparator, 5 ... drive control circuit, 6 ... switching transistor, 31, 35 ... transistor

Claims (1)

[Scope of utility model registration request] 1. A result of comparing a high voltage output monitor voltage with a reference voltage by connecting a high voltage output circuit for supplying an output to a charger and an arbitrary number of medium voltage output circuits to the output side of one high voltage transformer. A high-voltage power supply device configured to control the output voltage of the high-voltage output circuit and the intermediate-voltage output circuit by controlling the input of the high-voltage transformer by means of: And a first output mode in which the intermediate pressure output circuit outputs intermediate pressure, the high voltage output circuit outputs a voltage smaller than the discharge start voltage of the charger, and the intermediate pressure output circuit A high voltage power supply device comprising means for changing the reference voltage in order to selectively obtain a second output mode for outputting a medium voltage.