JPS6159462A - High voltage power source for copying machine - Google Patents

Abstract

PURPOSE:To obtain a transfer charge and a bias which differ in falling time by providing a charging circuit which charges a high voltage induced at a secondary coil and a discharging circuit which discharges said charge to a low voltage output between the low voltage output and ground. CONSTITUTION:The primary side of a transformer T3 is switched by a transistor (TR) Q3 to obtain the high voltage at the secondary side, and the voltage is rectified and smoothed by a diode D5 and a capacitor C4 to obtain a DC high voltage. A high voltage output T-OUT is obtained through a protection resistance R9 and connected to the transfer charge. This DC high voltage, on the other hand, is stepped down by a resistance R13, made constant through a Zener diode Z, and further passed through a protection resistance R12 to obtain a low voltage output B-OUT, which is connected to the bias. A current which flows depending upon those outputs is detected by a resistance R14 and fed back to a switching control part A3. The capacitor C5 is charged in the presence of the output T-OUT and the charge is discharged when the output T-OUT is ceased, so that the output B-OUT is lowered.

Description

Detailed Description of the Invention (Technical Field) The present invention provides a method for switching the primary coil of a transformer to
This invention relates to a multi-output high-voltage power supply that rectifies and smoothes the high voltage obtained in the next coil to obtain at least one high-voltage output, and also steps down this high-voltage output to obtain a lower low-voltage output, and in particular relates to a high-voltage power supply for copying machines. It is.

(Prior art) As is well known in copying machines, transfer charge ('l')
The application of a voltage and the application of a real bias (B) voltage are included during the imaging process.

Figure 4 shows the transfer charge (T) and bias (B) of the conventional machine.
), the on and off timings of T and B are different. That is, as long as the main motor M is driven and the developing section is operating, the bias B is turned on almost synchronously with the main motor because it is inconvenient not to apply a bias voltage to the photoreceptor. Since the transfer charge (T) only needs to be turned on at the timing when the transfer paper reaches the transfer section, it is turned on only at the timing shown in the figure. It is natural that the off timing is different.

However, in order to extract outputs with different on and off timings, the circuit has to be large and complicated as shown in FIGS. 5 and 6.

FIG. 5 shows a trigger signal generation circuit 1 for controlling the timing of T and B, which requires ports P3, P1 and two buffer ICs dedicated to T and B respectively.

FIG. 6 shows a high-voltage source circuit for taking out the output, and the transfer charge N, R and bias power supplies are controlled by independent switching control units A1, A2, . Transformers T1 and T2. Transistors Q1 and Q2. and respective peripheral circuits are required.

For this reason, as mentioned above, the number of parts is large, resulting in a high-voltage power supply that is expensive and large.

In FIG. 6, the on/off timings of 13 and T are determined by inputting trigger signals T and B on the input side to switching control units A1 and A2.

In order to improve the high-voltage power supply for copying machines, which had a large number of parts and had no choice but to be larger, we improved the characteristics of the photoreceptor in a copying machine that makes fewer copies, as shown in Figure 8. A multi-output high-voltage power supply was proposed.

That is, the transfer charge trigger and the bias trigger are the same, and one set of (T/B) switching system parts A3.
Transformer T3. Create a transfer charge output (T-(J(J'l")) from the transistor (Current number 3), and connect the resistor R from this.
13. Bias power supply (B-OU
T) is taken out, and compared to the conventional example shown in FIG. 6, the number of parts is smaller, and it is a low-cost, small-sized, still-voltage power source. With this configuration, the transfer charge output and the bias output naturally fall at the same time.

By the way, even though the main motor signal is turned off, the inertia of the main motor causes the urine sleeve to rotate for about 300 milliseconds. Therefore, during this period, the bias output will be 50% of the rated value.
If the above voltage is not applied, toner will stick to the IJ-sphere. On the other hand, even though the characteristics of the photoreceptor have been improved, if a transfer charge is applied while the photoreceptor is rotating at a low speed due to inertia, the photoreceptor will be charged to a level higher than its withstand voltage, causing insulation breakdown. Therefore, it was inevitable that either timing of the T/B trigger signal would cause some kind of problem.

(Purpose) The present invention has been made in view of the drawbacks of the conventional examples, and provides a highly reliable copying machine that is free from defects such as destruction of the photoreceptor and toner sticking to the developing sleeve when using a multi-output cylindrical pressure power source. The purpose of this project is to provide high-voltage power supplies for general use.

(Structure) For this purpose, the present invention is characterized in that outputs with different falling timings are taken out from a multi-output high voltage source consisting of one control circuit and one transformer.

An embodiment of the present invention will be described below based on the drawings.

FIG. 7 is a timing diagram of the main parts of the copying machine using the high-voltage power supply of this embodiment, and the trigger signal of the main motor (Ml) and the trigger signal T/13 of the transfer charge (T) and bias (B) are the same. It has become.

Figure 9 is a circuit diagram of the trigger signal generation circuit 20 showing the port assignments and buffers of the microcomputer at this time.The main motor trigger signal RA and the transfer charge and bias trigger signals 3 are connected to one port and one buffer. It consists of

FIG. 1 is a circuit diagram of a still voltage power supply according to this embodiment. The primary side of the transformer T3 is switched by a transistor Q3 to obtain a high voltage on the secondary side, which is rectified and smoothed by a diode D5 and a capacitor C4 to become a DC high voltage. A high voltage output T-OLl'l'' is obtained via the protective resistor 9 and is connected to the transfer charge.

On the other hand, this DC high voltage is stepped down by a resistor R13, made into a constant voltage by a Zener diode 2, and a low voltage output B-01JT is obtained via a protective resistor R12. This is connected to the bias.

The current flowing through these outputs is connected to the resistor R in the return path.
14 and fed back to the switching control section A3, resulting in a constant current. By the way, the bias current is several μA, which is 1 to 2% of the several hundred μA of the transfer charge current, and a change in the bias current does not affect the constant current property of the transfer charge. While there is an output from T-OUT, the capacitor C5 is charged by the resistor R16 connected to the Zener diode Z. When the trigger signal T/B turns off, the T-OUT output disappears, and the electric charge charged in the capacitor C5 is discharged through the resistor R16 by the action of the diode D6, and 13
- Gradually lower the OUT output. Now resistance a 16
= 47 MΩ Capacitor C5 = 0.02μFf
Io)"D6 = TF'R1 Zener taE200V
When the load resistance of B-OUT is 20MΩ, the rise and fall waveforms of the B-OUT output due to the on and off of the trigger signal T/H are shown in Figure 3 (a) and (b), and the rise is 15. mS The time for the output to drop to 1/2 of the rated output was 300m5.

FIG. 2 shows the main part of the bias output in block form. When the switch S is turned on, the power supply voltage E is applied to B-OUT, and at the same time, the capacitor C5 is charged through the resistor it16. Since this time constant f(,16XC5 is sufficiently smaller than 1 copy/hour, it will be fully charged by the time switch S is turned off.Next, when switch S is turned off, capacitor C5 is discharged by load fl,B through diode D6. .

Here, since C16 takes a long time for one copy, it can be set to a larger value than the load resistance.
5 is discharged with a time constant of approximately RBXC5, and the bias voltage can be continued to be applied for a desired time.

In addition, in the present invention, as is clear from the timing chart of FIG. 7 and the above explanation, the fall of the transfer charge T is steep, but the time constant of the bias B is large.
Since the fall is gentle, while the sleeve is rotating due to the inertia of the main motor, more than 50% of the bias B's low pressure is applied, which prevents toner from sticking to the sleeve. Furthermore, since the transfer charge T does not apply voltage to the photoreceptor, dielectric breakdown does not occur.

In addition, T −0 [J T
Detects the output 'voltage and returns it to the switching control section A3 to limit the maximum voltage applied to the transfer charge, and also adjusts the resistance ratio to prevent high voltage from being applied to the bias when the Zener diode Z becomes open due to a defect. 15 is connected to the output voltage detection section, and similarly limits the maximum voltage applied to the bias.

Although this embodiment is an example in which a transfer charge and a bias are integrated, the same effect can be obtained with the same configuration in other combinations, such as a combination of a charge charge and a bias, or a combination of transfer, charging, and bias. .

Zener Z can be replaced with a resistor if the T-OUT load range is narrow and the voltage change is small. Further, if T-OLIT is a constant voltage power supply, it can be replaced with a resistor in the same way.

(Effects) The present invention is as described above, and the present invention includes]:
In this case, transfer charge and bias with different fall times can be obtained using a high-voltage power supply consisting of one control circuit, one transformer, and one trigger signal, so that dielectric breakdown of the photoreceptor,
It is possible to provide a high-voltage power supply for a copying machine that does not have the problem of toner sticking to a developing sleeve, has a small number of parts, is low cost, and is compact.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a high voltage source according to an embodiment of the present invention, FIG. 2 is an equivalent circuit diagram of the main part thereof, and FIG. 3(a). (b) is a characteristic diagram of the rise and fall of the output, FIG. 4 is an output timing chart of each part of a general copying machine, and FIG. 5 is a trigger signal generation circuit diagram of the first conventional example.
FIG. 6 is a high voltage/NY source circuit diagram according to the first conventional example, and FIG.
The figure is an output timing chart of each part of the copying machine according to the present invention, FIG. 8 is a Takato power supply circuit diagram according to the second conventional example, and FIG.
The figure is a diagram of the trigger signal generation circuit. T3...Trance, D5. C4... Rectifier smoothing circuit. T-OUT...High voltage output, B-0 (JT...
...Low pressure output. R16, C5, D6...Charging/discharging circuit. Misaki ps' Norizo

Claims (1)

[Claims] A multi-output device that switches the primary coil of the transformer to rectify and smooth the high voltage obtained in the secondary coil, extracts at least one high voltage output, and steps down this high voltage output to extract a lower low voltage output. In the power supply,
A copy characterized in that a charging circuit that charges the high voltage obtained in the secondary coil and a discharging circuit that discharges the electric charge charged in the charging circuit to the low voltage output with a time constant are provided between the low voltage output and the ground. High voltage power supply for machines.