JPS5956865A - High voltage power source circuit for electrostatic copying machine - Google Patents

Abstract

PURPOSE:To prevent the overshoot of a high voltage output at the rising time by providing control means connected to a power source voltage circuit of an error amplifier which inputs the output corresponding to the photoreceptor of a photocoupler for gradually increasing the voltage from the prescribed value. CONSTITUTION:The power source voltage of an error amplifier 35 is controlled at the rising time of the output voltage to correct the delay of the feedback action of a detection signal, thereby suppressing the overshoot. When an REM terminal is set to a low level in the state that the amplifier 35 stands by at V<+>, a transistor TR45 is turned OFF, and a condenser 46 starts charging. On the other hand, a high voltage system becomes operating state, and the voltage V<+> of the amplifier 35 is gradually increased at the speed determined by the time constant of the capacitor C of the condenser 46. Accordingly, the output of the amplifier 35 gradually varies, and when the oscillator is shifted to the oscillated state, the output of the high voltage rectifier is prevented from becoming overshooting.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a high-voltage power supply circuit for an electrostatic copying apparatus, in particular a high-voltage power supply circuit configured to supply a constant current to an electrostatic charge application section in an electrostatic copying apparatus. A high-voltage power supply circuit for an electrostatic copying device that prevents an undesirably high DC voltage from being applied to the device, and also suppresses overshoot from occurring at the rise point of the output voltage when starting the high-voltage generator. It is related to.

An electrostatic copying apparatus generally has a configuration as shown in FIG. In the figure, reference numeral 1 indicates a rotating drum plate 1 and 2 are electrostatic latent image forming surfaces, which are composed of, for example, a selenium layer.
3 is a direct current high voltage applying device corresponding to the electrostatic charge applying section according to the present invention; 4 is an input source; 5 is a lens; 6 is an electrostatic latent image;
7 is a toner (jl-supply part), 8 is a copy paper, 9 is a pressure application part for copy paper, 8' is a copy paper to which the toner is transferred, 10 is a toner fixed part, 11 is an electrostatic lfv image an AC voltage applying section comprising an image-forming charge erasing section;
12 is an erasing light applying section constituting an electrostatic image forming surface charge erasing section, which applies an alternating current voltage of about 10F-f; 13 represents a brush for removing residual toner.

The electrostatic copying apparatus has the above-mentioned configuration, and (1) the electrostatic latent image generated by the previous copy is transferred to the charge erasing section 11.1.
2 and the brush 13, (11) Then, the electrostatic latent image forming surface 2 is supplied with an electrostatic charge by the electrostatic charge applying section 3 in the manner shown in FIG. is irradiated onto the electrostatic latent image forming surface 2, (Iv
) An electrostatic latent image 6 is formed on the electrostatic latent image forming surface 2, and (V
) L-toner l (Toner is deposited on the latent image 6 by the supply unit 7, (VD rotating drum 1 and copy paper 8
During the movement of the copy paper 8', the toner is transferred onto the copy paper 8' in a form corresponding to the recorded figure, and (vl
The toner on the il-copy 8' is fixed onto the paper by the toner fixing section 10.

However, if the electrostatic charge applied to the electrostatic latent image forming surface 2 by the DC high voltage applying device 3 is supplied to the forming surface 2 deeper than a predetermined depth, the electrostatic latent image forming surface charges Erasing sections 11 and 12. Furthermore, the remaining electrostatic linked image cannot be removed correctly with only the erasing mechanism using BL/13, so to speak.
Duplicate copies will occur in an undesirable manner. Conventionally, the above 2
In order to prevent duplicate copying, care has been taken to maintain the voltage level of the DC high voltage supplied to the DC high voltage applying device 3 at a predetermined level. However, recently, it has been found that keeping the current level of the DC current flowing from the DC high voltage application device 3 to the electrostatic latent image forming surface 2 constant is effective in preventing the above two types of copying. It is required to maintain the current level supplied to the application device 3 at, for example, 400 [μA] ±1%, while applying a DC voltage exceeding, for example, 'lK'l while controlling to supply a constant current. It became necessary to ban it.

The present invention prevents the application of undesired high voltage while performing highly accurate constant current control on the DC high voltage application device 3 that supplies high voltage and minute current as described above, and also prevents the generation of high voltage. It is an object of the present invention to provide a high-voltage power supply circuit for an electrostatic copying apparatus that suppresses occurrence of overshoot at the rise point of the output voltage during startup.

Figure 2 shows the overall configuration of an embodiment of the high voltage power supply circuit of the present invention, Figure 3 (α) shows the circuit configuration of the main parts of Figure 2, and Figure 3 (h) shows the overshoot of the high voltage output. An explanatory diagram showing the state is shown.

In FIG. 2, 14 is a low voltage DC voltage source, for example 22 [V:] + 30% tanned 22 [V] -
It has a voltage fluctuation of about 20%. Reference numeral 15 denotes a chopper type switch regulator, which changes the DC voltage to an oscillation circuit, which will be described later, to change the voltage level of the alternating voltage generated by the nuclear search circuit. Reference numeral 16 denotes a two-oscillation circuit, which is constituted by two inverter circuits, for example, equivalent to a Royer circuit. 1'7id voltage transformer, 1
B is the primary winding.

19 represents a secondary winding, and 20 represents a tertiary winding.

21 is a high voltage rectifier circuit that rectifies the AC high voltage induced in the secondary winding 19 and applies the voltage to the DC high voltage applying device 3 shown in FIG.

Reference numeral 22 denotes a current level extraction unit that extracts the current level flowing into the DC high voltage application device 3.

Reference numeral 23 denotes an auxiliary power supply circuit which controls the light emitting section of a photocoupler, which will be described later, even when the output of the high voltage rectifier circuit 21 is short-circuited, and supplies a current of a predetermined level, for example, about 5 mA, to the light emitting section of the photocoupler. Work to get it. 24
is a high voltage circuit DC current level amplification circuit, 25 is an amplifier, 2
Reference numeral 6 denotes a linearity correction circuit for correcting the linearity of a photocoupler, which will be described later.

Reference numeral 27 represents a light emitting section of the photocoupler according to the present invention, which constantly maintains a light emitting state, and when the current level extracted by the above-mentioned current level extracting section 22 increases, the output of the amplifier 25 increases, and the output of the amplifier 25 increases. The light emitting section 27 emits larger light. 281-t, a high voltage short circuit detection unit,
A comparator 29 is provided (8), and the comparator 29 detects ``if the current level extracted by the current level extraction section 22 increases undesirably with respect to a so-called reference voltage made up of a diode 57 and a resistor 30,'' The light emitting section 27 of the photocoupler is caused to emit light with sufficient intensity via the diode 31.

32 is a three-terminal regulator that operates to maintain the output voltage (voltage at point A) at a constant voltage regardless of voltage fluctuations of the low-voltage DC voltage source 14.

Reference numeral 33 denotes a light receiving section of a photocoupler according to the present invention, which supplies a current corresponding to the light end from the above-mentioned light emitting section 27 to the resistor 34. 35 is an error amplifier with a resistor 58.3
6.37 is compared with the rlj pressure generated in the resistor 34, and the error thereof is amplified. 59.6
0 represents a resistor, 38 represents a Zener diode,
These constitute a voltage limiting circuit 419 according to the present invention, which prohibits the output voltage of the error amplification unit 35 from exceeding a predetermined voltage level of, for example, 15 [V]. 39 is a switch regulator control comparator.

The output side voltage level of the above-mentioned illustrated resistor 60 is compared with the output voltage of the above-mentioned chopper type switch regulator 15, and the 9 illustrated resistor 40. Through the transistor 41° chopper type switch regulator 15.

Control is performed so that the voltage at point B is equal to the voltage at point C. In other words, the DC power supply voltage to the oscillator circuit 16 is controlled, and the current level extracted by the current level extraction unit 22 is 4ooCtiA].

The illustrated terminal REM is a terminal that controls the illustrated circuit in FIG. The circuit 16 is controlled to enable oscillation. When the output of the comparator 43 becomes low level, the transistor 45 is turned off via the resistor 44, and charging of the capacitor 46 is started via the resistors 47 and 48, gradually reducing the potential at point 1). The power supply voltage to the error amplifier 35 is gradually increased through the transistor 49. This prevents the output of the high voltage rectifier circuit 21 from overshooting when the single oscillation circuit 16 shifts to the oscillation state. In other words, the potential at point B shown in FIG. 9 is gradually increased, and the potential at point C is increased in accordance with i1 to prevent the above-mentioned autoshoot.

In the configuration shown in FIG. 2, that is, in the configuration of one embodiment of the present invention, the extracted signal level from the current level extractor 22 existing on the high voltage circuit is guided to the circuit having the voltage level of the low voltage DC voltage source. Hit me.

For example, a photocoupler (2'7, 33) capable of providing an insulation level of 100 CMΩ or more is used. And then, this ε亥 ho]...cuff'u (2"7.
33) is configured to be used not as an on/off control as is generally used, but as a so-called ratio 11 control. That is, when employing men-off control to perform the operation shown in FIG.
Although it uses an Lm path, etc., compared to such a circuit, it uses a photocoupler in the form of proportional control, making it cheaper and simpler.

Furthermore, as mentioned above, when using a photocoupler (27, 33), it is possible to extract the necessary current response, and even if the high voltage circuit is short-circuited, the photocoupler (27, 33) can be used.
, 33) in order to put it into operation.

A tertiary winding 20 is provided and an auxiliary power supply circuit 23 is used. Furthermore, as mentioned above, 1 illustration 44°45.46.
Using the configuration of 47.48.49.

Considerations are taken to prevent the output of the high-voltage rectifier circuit 21 from undesirably overshooting or shooting.

Although the above considerations have been taken, Fig. 3(a)(h)
The two characteristic configurations of the present invention will be explained in more detail with reference to the following.

FIG. 3(a) is an extraction of the circuit configuration shown in FIG. 2, focusing on the circuit portion that enables output and suppresses pressure overshoot, so the reference numbers used are 2
It is the same as the one shown in the figure.

In the above-mentioned constant N1 flow high-voltage power supply, the detection signal from the high-voltage side is reflected in the control at high speed while the high-voltage side circuit and the low-voltage side circuit are electrically isolated by using a photocoupler. However, there is a limit to this response speed, especially when the voltage transformer's secondary winding is turned on when the power is turned on.
An overshoot as shown in 6(h) occurs, and due to the overshoot, a charged state is generated at a deep position on the electrostatic latent image forming surface 2, and the charged state cannot be erased by the erasing section 11. state. In the present invention, as outlined above, when the output voltage rises, the error amplifier 3
The power supply voltage (reference voltage) No. 5 is controlled to correct the delay in the feedback action of the detection signal, thereby suppressing the overshoot.

That is, in FIG. 3(a), the REV terminal is set to low.
When the oscillation circuit 16 (see Figure 2) is maintained in the operating state, the output of the comparator 43 (21st step) is at low level, and the output of the comparator 43 (21st step) is at the low level,
is off, the capacitor 46 is exposed to light, and the transistor 49 is turned on to apply 1 voltage to the amplifier 35. Immediately before the power is turned on, the REM terminal is at a high level, the output of the resistor 43 is at a high level, and the output of the transistor 45 is at a high level.
is on and the capacitor 46 is in a discharge state. Further, the high voltage system is also in an inactive state, and the emitter potential of the light receiving section 33 of the photocoupler is also 0 volts. Therefore, the error amplifier 35 constituting the operational amplifier becomes an oven circuit, and at that time, the power supply voltage V+ applied to the amplifier 35 is
Outputs a voltage close to .

Therefore, the collector-emitter voltage of the transistor 45 is set to Vca, and the transistor Tr1. The base-emitter voltages of T7-2 are VBgl and VB+!, respectively. ! z
, terminal 14c7) voltage f Vi , resistance 4'7.48 (
7) Value kR,.

■ If <, 2.

That's what I mean. ? c If Vcp << 1, Vsml key\'RFt2 06V, the above amplifier: 35
The power supply voltage V is as follows. Therefore, high voltage output is turned off (0
state) in i-t,.

The error intensifier 35 is on standby (idling) at the above-mentioned V.sub.2.

In this state, when the FIM terminal is brought to a low level, the transistor 45 is turned off.

Charging of the capacitor 46 begins. On the other hand, the high voltage system also enters the operating state, but the power supply voltage V of the error amplifier 35
is the time constant of civil resistor R, R2, and capacitor 46 C
It increases at a rate determined by R10R2)'C. Therefore, the output of the error amplifier 35 also changes gradually, and when the first oscillation circuit 16 (FIG. 2) shifts to the first oscillation state, the output of the high voltage rectifier circuit 21 changes as shown in FIG.
Overshoot (solid line in the figure) as shown in the figure is suppressed.

As described above, in the second aspect of the present invention, overshoot at the rise of the high voltage output can be prevented by configuring the circuit to gradually increase the power supply voltage for the error amplifier on the low voltage side.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram for explaining the structure of an electrostatic copying apparatus, FIG. 2 shows the overall structure of an embodiment of the high-voltage power supply circuit of the present invention, and FIG. 3(a) shows the main parts of FIG. Lottery 7Js L
FIG. 3(h) is a diagram showing an overshoot state of the high voltage output. In the figure, 1 is a rotating drum, and 2 is an electrostatic latent image forming surface. 3 is a DC high voltage application device corresponding to the electrostatic charge application section. 6 is an electrostatic latent image, 7 is a toner co-feeding section, 8 is copy paper, 1
4 is a low voltage DC voltage source, 15 is a chopper type switch regulator, 16 is an oscillation circuit, 17 is a voltage transformer, 18,
19. 20 are windings, 21 is a high voltage rectifier circuit, 22 is a current level extraction section, 23 is an auxiliary power supply circuit, 24 is a high voltage circuit DC current level amplification circuit, 27 is a photocoupler light emitting section,
32 is a three-terminal regulator, and 33 is a photocoupler light receiving section. 35 is an error amplifier, 59, 60.38 is a voltage limiting circuit,
39 represents a switch regulator control comparator. Patent Applicant Sawa #Denki Co., Ltd. Representative Patent Attorney Mori 1B Hiroshi (3 others) 1 year old
m

Claims (1)

[Scope of Claims] An electrostatic latent image forming surface is provided, and an electrostatic charge applying section that applies an electrostatic charge to the electrostatic latent image forming surface is provided, and the electrostatic charge applied by the electrostatic charge applying section is utilized. In an electrostatic copying apparatus that records by forming an electrostatic latent image on the electrostatic latent image forming surface, a chopper-type switch regulator connected to a low-voltage DC voltage source, and a DC output voltage of the switch regulator are provided. An oscillator circuit that generates the corresponding alternating voltage. A voltage transformer to which the alternating output voltage of the oscillation circuit is supplied to the primary winding; a high voltage rectifier circuit connected to the secondary winding of the voltage transformer to apply a DC high voltage to the electrostatic charge applying section; A current level extraction unit that extracts the current level of the DC current supplied from the high voltage rectifier circuit to the electrostatic charge application unit, an auxiliary power supply circuit connected to the tertiary winding of the voltage transformer, and an output from the auxiliary power supply circuit. a current level amplifier that is energized by a voltage and amplifies the current level extracted by the current level extraction section; a photocoupler that is excited by the current level amplifier and is always placed in a light emitting state to change the light emission level depending on the current level. a light emitting section, a voltage regulator connected to the low voltage DC voltage source to generate a low voltage reference voltage, a light receiving section of the photocoupler connected to the output of the voltage regulator, and an error in which the output corresponding to the photocoupler is input. An amplifier, a control means connected to the voltage circuit and gradually increasing the power supply voltage of the error amplifier from a predetermined value, and controlling the power supply voltage of the error amplifier when the oscillation circuit shifts to the oscillation state. 1. A high-voltage power supply circuit for an electrostatic copying apparatus, characterized in that an undesired overshoot occurring in the secondary winding of the upper Ri2' FIt pressure transformer d is prevented by incremental control.