JPS6141157A - High voltage source for sopying machine - Google Patents

Abstract

PURPOSE:To obtain a small-size high voltage source in a single power source structure, with no deterioration of a photosensitive medium, free from the generation of a large amount of ozone and excellent in reliability, by taking out a bias voltage with application of a voltage below a discharge start voltage even if a transfer charge trigger signal is ''off''. CONSTITUTION:A transistor Q2 is driven at an oscillation frequency, which is determined by an external resistor R14 and a capacitor C5 for a switching regulator IC. A high voltage pulse which is generated on the secondary side of a transformer TR3 is smoothed by a diode D5 and a capacitor 6 to obtain a high DC voltage. A load current between output terminals T and B is detected by a variable resistor VR3 and compared in a comparator with the reference voltage. The pulse width varied according to the result of the comparison, whereby the output current is controlled to a constant level. When a transfer charge trigger input or a bias trigger signal goes to a normal level, a photocoupler P1 or P2 is turned on, the reference voltage in the IC and a reference voltage as a division voltage from a voltage divider consisting of resistors R4 and R5 or resistors R6 and R7 are fed as inverted inputs to the comparator, which provides a current according to the values of the inputs.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a high-voltage power supply for a transfer charger and a developing bias of a photographing machine.

(Prior Art) The transfer charger and developing bias of a copying machine have different application timings. If this is controlled at one timing to cover both on-times, the on-time state will occur even when the transfer charger is off, which will cause problems such as accelerated deterioration of the photoreceptor and generation of large amounts of ozone. In the past, even though they were housed in the same unit, they were configured as two completely independent power supplies.

FIG. 2 shows a circuit diagram of a conventional multi-output high-voltage power supply.

T% source B power supply independent control circuits HIC1 and HIC
It consists of two completely independent power supplies with transformers TRI and TR2.

To explain this circuit diagram in more detail, HIc
1 is a hybrid IC for constant current high voltage power supply control, and this output turns on and off the switching transistor Q1, and the high voltage induced on the secondary side of the transformer TRI is voltage-doubled and rectified by diodes DI and D2 and capacitors C1 and C2. T
Output. Then, the output current is detected by the polyimum V'iL1 and the hybrid IC (HICI)tc
This stabilizes the T output. This T
The output is output when the trigger input t is at the X level.

Next & CHIC2 is a no-brid IC for controlling a constant voltage high voltage power supply. It has a built-in switching transistor and a transistor, and directly drives the transformer TR2 to generate high voltage on the secondary side. It is rectified by the diode D3 and capacitor C3, and outputs B5. shall be. Then, the output voltage is detected by the resistor R1 and the volume V)12, and the output voltage is detected by the hybrid IC (i(IC2)).
K feedback stabilizes.

This B output is output when the trigger input is at P level.

As described above, in the conventional (multi-output) high-voltage power supply for copying machines, the Tt source for the transfer charger and the 8% source for the actual bias require a large number of parts, a large space, and are expensive. Therefore, it had the disadvantage that it could not be used as a high-voltage source for low-cost copying machines.

(Purpose) The present invention eliminates the drawbacks of the conventional example, and while it is possible to obtain outputs for a transfer charger and an edge bias with a single power supply configuration, it also avoids problems such as deterioration of the photoreceptor and generation of a large amount of ozone. The aim is to provide a compact high-voltage power supply with excellent reliability.

(Structure) For this purpose, the present invention focuses on the fact that the bias voltage is one or less of the voltage for the transfer charger, and extracts the power source for the developing bias from the output of the power source for the transfer O charger, and also extracts the power source for the transfer charger. Even when there is no trigger signal 1 to turn on/off, the voltage is below the corona discharge voltage.
It is characterized in that a voltage is applied.

Hereinafter, one embodiment of the present invention will be described based on FIG. 1iK.
Before that, the timing chart portion related to the present invention will be explained based on FIG.

When the print key is pressed, bias B is turned on and the main starter is activated at the same time. Then, the pulses generated in synchronization with the rotation of the main motor are counted, the charging charge C is energized at a predetermined timing, and after further counting, the transfer charge T is energized at the next predetermined timing.

Similarly, the charge transfer charge is turned on and off at a predetermined count. When image formation is completed, the main motor stops and the transfer charge is turned off after a certain period of time, completing the copying operation.

The bias voltage is less than one of the transfer charge voltage,
If it is taken out from the transfer charge power supply by resistor voltage division, a bias power supply circuit is not required, and the size and cost can be reduced. However, as mentioned above, there is a timing when the transfer charge is off when the bias is being output. As described in the conventional example section, if the transfer charge is output during the period when the bias is output, the fatigue of the photoreceptor increases and the amount of ozone generated increases. Therefore, even when the trigger of the transfer charge power source is off, the transfer charge has a low voltage that does not cause discharge and is sufficient to obtain a bias voltage of 1 to 2.
By outputting a voltage of KV, a bias voltage is obtained from this transfer power source.

A concrete example will be explained with reference to FIG.

The basic configuration of the power supply is a pulse width controlled switching regulator. The external device of the switching regulator IC is a transistor Q, which is driven at an oscillation frequency determined by a resistor R14 and a capacitor C5.
A high voltage pulse is generated on the secondary side of 3, which is passed through diode D.
5 Rectification and smoothing is performed using capacitor C6 to obtain high voltage DC.

The current flowing through the load connected to the output terminals T and B is detected by a variable resistor VR3 and compared with a reference voltage by a comparator. Then, change the switching pulse width depending on the magnitude and output 1.
Constant current control is performed so that the current c is constant. This reference voltage is normally at the p level, but when the trigger input t or b reaches the ρ level, the photocoupler P1 or P2 is turned on, connecting the reference power supply in the IC to the resistor hole 4.几5 or resistance R
The respective reference voltages divided by voltages 6 and 87 are input to the inverting input of the comparator, and an output current corresponding to this value is output.

Here, t is the transfer charge +lD) trigger input, and when this is at the ρ level, the resistor R+4. R6, is set and output terminal T is set to 5.
~7KV (D) At the same time as obtaining DC high voltage, step down with resistor R15 and create a constant voltage of 300V with varistor 2 to obtain bias voltage. b is the bias trigger, so that when this is at the ρ level, the output current will be around lθμ Resistors R2 and kL3 are set, and at this time, the output is actually 1 to 2 KV, and there is no discharge from the transfer charge, but from now on, it is dropped at resistor FL15, and a constant voltage of 300 V is obtained at varistor Z, which becomes bias voltage B. The state and the state of each output voltage are as shown in Figure 4, and a constant bias voltage can be obtained even if the transfer charge cage pressure T changes to below the discharge starting voltage and to the predetermined output voltage by turning on and off the trigger t. Another comparator has a non-inverting input input with a reference voltage from resistors R6 and R7,
The bias voltage from the resistor 10° 11 is fed back from the varistor 2 to the inverting input to prevent an abnormal increase in the bias voltage due to failure of the varistor to open.

Resistor 12 is a current limiting resistor, R14 is a base resistor, R1
6. R17 is an output cough resistance resistor, diode D4 is an operation stabilizing diode, and capacitor C4 is a control stabilizing capacitor.

Exactly the same effect can be obtained by attaching the resistor 1t15 and the varistor 2 to an external unit and applying the transfer charging voltage T to the pig carrying unit.

(Effects) The present invention is as described above, and is configured to apply a voltage below the discharge starting voltage without generating ozone or affecting the photoreceptor even when the transfer charge trigger is off, and extracting the bias voltage from this. By doing so, a transfer charge power source and a bias power source can be obtained with one control circuit and one transformer without problems such as deterioration of the photoreceptor or generation of large amounts of ozone, providing a low temperature, low cost, high Ef power source for copying machines. can.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a high-voltage power supply for a copying machine according to the second embodiment of the present invention, Fig. 2 is a circuit diagram of the same according to a conventional example, Fig. 3 is a timing chart of the charger and bias, and Fig. 4 is the main 5 is a timing chart of bias, transfer trigger, and output according to the invention. T: Transfer charger output, B: Current bias output. Figure 1

Claims (1)

[Claims] The power supply for developing bias is taken out from the output side of the high voltage power supply that applies corona discharge voltage to the transfer charger, and when there is no trigger signal of the transfer charger, a voltage lower than the corona discharge voltage is output, and when there is a trigger signal, a predetermined corona discharge is performed. A high-voltage power supply for copying machines characterized by outputting voltage.