JPS58159668A - Power source for copying machine - Google Patents

Abstract

PURPOSE:To reduce the number of transformers of a power source to one set by winding coils for inducing low and high voltages on the same transformer. CONSTITUTION:The collector current of a transistor Q1 is increased when the transistor is conducted, and when the magnetic flux of a transformer 5 is saturated, the polarity of the voltage induced at the primary coil is inverted. Thus, when the transistor Q1 is interrupted, the energy stored during the ON period of the transistor Q1 is discharged to the secondary circuit. Accordingly, the polarity of the induced voltage of the coils is inverted again, and the transistor Q1 is turned ON. Thus, the transistor Q1 continues to self-oscillate and DC output voltages are continuously generated from high and low output voltage circuits 6-1, 6-2 and 7 respectively.

Description

[Detailed description of the invention] The present invention relates to a power supply device for a copying machine.

The power supply circuit of an electronic copying machine includes a sequence control circuit, a low voltage constant voltage circuit for supplying a lamp, a lenoid, a clutch, etc., and a high voltage circuit for charging a reservoir.

For this reason, conventionally, a commercial frequency power source is stepped down with a line frequency transformer and then rectified to form a DC power source of approximately 24V, and a DC-DCC converter is used to convert the voltage of the DC power source into a high-voltage DC source for charging. Convert to voltage. Therefore, since the number of transformers increases, a large number of drive circuits are also required. Therefore, the weight of the copying machine increases.

This was one of the causes of increased costs, increased dimensions, and low reliability.

The present invention has been proposed in view of these problems in the prior art, and its purpose is to provide a low voltage source and a high voltage source required for copying machines with a single lightweight transformer. Our goal is to provide a power supply unit for electronic copying machines that can.

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a partial block diagram of an embodiment of a copying apparatus using a power supply device according to the present invention. In FIG. 1, when the power supply switch 1 is closed, power is supplied to the drum motor 11 and the rectifier circuit 3 via the filter circuit 2. Therefore, when the photosensitive tram 12 starts rotating, the switching circuit 4 receives the output of the rectifier circuit 3 and performs a switching operation. Due to the operation of the switching circuit 4, the high voltage induced through the converter transformer 5 is extracted as a DC voltage of 5 to 8 kV from the high voltage output circuit 6-1. In addition, the voltage generated in the low-voltage power supply circuit 7 is supplied to a sequence control circuit (not shown), a clutch, a lamp, etc. (not shown) through an output terminal 8. The sequence controller operates and lights up the pre-static discharge lamp 19 and the blank exposure lamp 18. After that, the drum 12 rotates several times until the cleaning is completed and the fuser is ready for fusing, and then copying is accepted. When this becomes possible, the optical system and paper feed roller 17 (not shown) operate, and the document is irradiated with the scanning light 15. Also, the document is fed from the paper feed cassette 16, and the developing device 13 and the development roller 14 are fed. Development is performed and the copying is completed.After a predetermined period of time has elapsed after the copying is completed, the power supply switch 1 is shut off in response to a command from the sequence controller.

FIG. 2 shows a specific circuit example of the portion indicated by a block in the first IN. That is, the output of a rectifier circuit 3 consisting of a diode fringe circuit is switched by a switching circuit 4 consisting of an automatic slotted parter. Transistor Q1 in this switching circuit 4-
is turned on by closing the power-on switch l. When the transistor Q1 turns on, the stop voltage induced in the primary IjS line of the conharc transformer 5 is applied to the base of the transistor Q1. Therefore, the collector current of the transistor Q1 increases linearly. . Thereafter, when the magnetic flux of the converter transformer 5 is saturated, the polarity of the voltage induced in the primary winding is reversed. Therefore, transistor Q1
is turned off, and 1! due to diode D1! ! Since the polarity of the induced voltage on the primary side is short-circuited, the energy stored during the on-period of the transistor Ql is released to the secondary side circuit. Once the energy is released, the polarity of the induced voltage in each winding is reversed again, turning on transistor Q1. Since the transistor Ql continues to self-oscillate in this manner, a DC output voltage is continuously generated from the high voltage output circuit 6-1, 6-2 and the low voltage power supply circuit 7, respectively.

FIG. 3 is an example of a circuit for stabilizing the seven-source circuit shown in FIG. 2 without requiring the addition of one auxiliary power source and without increasing the gravitational loss. In the circuit shown in FIG. 3, the output of the low voltage power supply circuit 7-2 is connected to the resistors R148 and R15.
After being voltage-divided by the operational amplifier ○At, it is compared with a reference voltage by the Zener diode ZDI. operational amplifier OA
When the issuing element of the photocoupler Pct issues electricity at the comparison output of I, the impedance between the terminals of the resistor R8 becomes low. It becomes a negative potential. Therefore, transistor Tr3 is turned on, and transistor Tr2 is also turned on, so transistor T
The base of ri is negatively biased and transistor Tri is also turned off. That is, in the negative half cycle of the winding of the converter transformer 5, the parallel circuit of the resistor R8 and the output side element of the photocoupler and the guiot D4 are
A negative potential is applied to the timing capacitor C4i, and a positive potential is applied to the resistor R9 and the tie motor D5 in the positive cycle. At this time, if the output voltage of the low voltage cold source circuit 7-2 is high, the photocoupler P
Due to the reduction in the impedance/s of the output side element of CI, a negative potential sufficient to make the transistor Tr3 conductive is applied to the capacitor C4. When the transistor Tr2 becomes conductive due to the conduction of the transistor Tr3, the transistor Trl is turned off, so that a back electromotive force is generated in each winding. resistor R4
Since the polarity of the back electromotive force applied to one end of the transistor Tri is negative, the transistor Tri is cut off until the energy stored in the collector winding is exhausted. During this time, the positive potential induced in the winding is applied to resistor R9 and guiot D5.
The timing capacitor C4i is passed through the transistors Tr3 and Tr2, and the transistors Tr3 and Tr2 are turned off. In this way, the larger the output of the operational amplifier OAI is, the more rapidly the timing capacitor C4 is charged with a negative potential.
The conduction time of the transistor Tri becomes shorter in accordance with the time constant during charging. Therefore, the DC output voltage obtained by rectifying and smoothing the voltage induced in the secondary winding of the converter transformer 5 is kept constant. In this way, the output voltage can be stabilized by controlling the output voltage. By the way, since the converter transformer 5 has sufficiently small leakage reactance and winding resistance, the output type r of one winding among the plurality of secondary windings is
By detecting the eMA and returning it, fluctuations in the pressure of other eMAs can be suppressed to within 51%. Therefore, regardless of load fluctuations and input voltage fluctuations, the output characteristics of all windings are stabilized. Incidentally, since the charger has eight circuits that supply a constant current, a high voltage is introduced to terminals 8-3 and 8-4 through high resistances R16 and R17.

Figure 4 shows another embodiment of the present invention, and the difference from the circuit shown in Figure 3 is that a dedicated detection winding is provided for constant voltage control to eliminate the influence of the load number, and the detection winding is grounded. By separating it from the line, feedback is provided to the primary circuit without the use of an odocoupler. That is, the voltage divided by resistors R23 and R24 and the Zener diode ZD3
The reference voltage is compared and amplified by a comparison amplifier composed of transistors Tr5 and Tr6, and the output voltage is stabilized by feedback to the primary circuit by controlling the conduction of transistor Tr7.

FIG. 5 shows a wiring diagram of an embodiment in which the circuit shown in FIG. 3 is provided with a short circuit protection circuit. In the example shown in Figure 5, the low voltage power supply circuit No. 7-2 fuse or circulator, throat breaker F1
When the resistors R18 and R19 are inserted into the high voltage output circuit 6-1 and 6-2, voltage is applied to the base of the transistor Tr4 through the Zener diodes ZDI and ZD2 in the event of a short circuit or overload. By being conductive, one input terminal of the operational amplifier OAI is brought close to the ground potential, and the output voltage of the operational amplifier OAI is raised to a sufficiently high level.
The output side impedance of the photocoupler Pct (FIG. 3) is sufficiently lowered to sufficiently reduce the output voltage. Note that resistors R16 and R17 are approximately 10% of the equivalent load resistance of the charger.
It has a resistance value of ~50% and is provided for stabilizing the band'i [u property.

FIG. 6 shows an example in which the voltage between the terminals of the resistor R14 of the high voltage output circuit 6-2 is detected and fed back to the primary circuit. In this case, the magnitude of the load current in the high voltage output circuit 6-2 is detected as the voltage between the terminals of the resistor R14, so the voltage supplied to the terminal 8-4 is controlled to a value that supplies a constant current to the load. Ru. When constant current control is performed, low voltage power supply circuit 7-1.7-2
Since the output voltage of regulator 31-1.31 also changes,
Insert -2. However, in cases where the current change in the charger is small, it is possible to remove the reculators 31-1 and 31-2.

FIG. 7 is a wiring diagram of an embodiment in which the circuit shown in FIG. 6 is provided with a short circuit protection circuit. That is, in the circuit shown in FIG. 6, a resistor R15 for short circuit current detection is installed in the high voltage output circuit 6-1.
is inserted, and the voltage between the terminals of this resistor R15 is used to make the transistor Tr4 conductive to bring the potential of the one side input terminal of the operational amplifier OAI close to the ground potential, thereby increasing the output of the operational amplifier ○Al, and increasing the output of the photocoupler ○Al. PCI(
The output voltage is lowered by lowering the output side impedance (FIG. 6) to a sufficiently low F. Note that a Zener diode is connected between the base of the transistor Tr4 and the detection side terminal of the resistor R15.
A direct voltage q circuit consisting of Z D 2 and resistor R16 is inserted to detect an excessive voltage across the terminals of resistor R15 in the event of a short circuit, and to protect the pace of transistor Tr4.

As described above, the present invention provides 11'! obtained by rectifying a commercial power supply.
The current pressure is switched to connect the low voltage winding for sequence control and the winding of the torso 7' wound with the high voltage @ wire for charging, and the Since a part of the voltage is fed back to the primary circuit, there is the effect that the low voltage source and high voltage source required for the copying machine can be stably obtained.

[Brief explanation of the drawing]

FIG. 1 is a partial block diagram of an embodiment of a copying apparatus using a power supply device according to the present invention, and FIG. 2 is a circuit diagram showing an example of blocks 1 to 7 in FIG. FIG. 3 is a circuit diagram showing an example of a power supply device according to the present invention equipped with a return circuit, and FIG. 4 is a circuit diagram showing another embodiment of a power supply device according to the present invention provided with a winding for feedback. Circuit diagram, FIG. 5 is a short circuit protection circuit suitable for the power supply device according to the present invention, FIG. 6 is a circuit diagram of a '4i power source device according to the present invention having constant current characteristics, and FIG. 7 is a circuit diagram according to the present invention. This is a short circuit protection circuit suitable for power supplies. Here, 2... filter circuit, 3... rectifier circuit,
4... Switching circuit, 5... Converter transformer, 8-1.6-2... High voltage output circuit, 7... Low voltage power supply circuit. Patent applicant Can27 Co., Ltd. Figure 2-326- Figure 5

Claims (1)

[Claims] 1. Sequence control circuit that operates at low voltage and crystal type Ji
- a power supply device for a copying machine equipped with a charging device that operates at 100 nm, wherein the windings for inducing the low voltage and the high voltage are included in the same transformer. power supply. 2. The power supply for a copying machine according to claim 1, wherein the charger is connected to a high voltage circuit via a high resistance corresponding to approximately 10 to 50% of the equivalent load resistance of the charger. Device. 3. Copy 4 of Claim 1, characterized in that the DC power obtained by rectifying the commercial power source is switched and supplied to the primary winding of the transformer, The load current of the high-voltage power supply obtained by rectifying the converted voltage is detected and fed back to a switching circuit coupled to the primary winding of the transformer, thereby maintaining the load current of the high-voltage power supply constant. A power supply device for a multi-machine according to claim 3. 5. The - part of the low voltage output voltage obtained by rectifying the voltage induced in the secondary @ line of the transformer is converted to the - part of the low voltage output voltage obtained by rectifying the voltage induced in the secondary @ line of the transformer. ! 8. The copying machine according to claim 3, characterized in that the voltage fed back to the switching circuit coupled to the line and stabilized by the voltage induced in the secondary winding is switched on the DC power source. 4. The power supply device for a copying machine as claimed in claim 3, wherein the circuit for oscillating the copying machine is an automatic oscillation circuit. 7. Copied to claim 6, characterized in that the voltage induced in the secondary S line is stabilized by changing the conduction time of the switching circuit coupled to the primary winding of the transformer. Machine power supply.