JPH11187168A - Compound machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the loss of functions in the case of occurrence of an abnormality by maintaining functions of high priority. SOLUTION: By rectifying an input from an AC power source through a rectifier circuit DB 1 and switching a rectified voltage, a current flows through a primary winding wire N1 of a transformer T1 and a voltage is induced at a secondary winding wire N. The secondary rectifying and smoothing of one of induced voltages is performed and an output voltage V1 (25 V) for a load 1 is stabilized by photocouplers PC 1a and PC 1b. The output of this voltage V1 is stabilized by voltage drop chopper circuits 3 and 5, and at least one of second DC output V2 (5 V) and third DC output V2 (5 V) is prepared. When abnormality such as over voltage is detected by the second DC output circuit, the second DC output is stopped and power is supplied from the third DC output circuit to the load connected to this second DC output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a multifunction machine, for example, an F
The present invention relates to a digital copying machine having an additional function such as an AX, and more particularly to a multi-output switching regulator suitable for use in the multifunction peripheral.

[0002]

2. Description of the Related Art A switching regulator including a DC-DC converter having a small size, light weight, low cost, high efficiency and excellent constant voltage characteristics is widely used as a DC power supply for OA equipment such as a copying machine and a laser printer. . These O
With the remarkable development of the A equipment, the output capacity and the number of output systems of the switching power supply have been remarkably increased with the increase in the number of functions and the speed. In particular, due to the increase in the number of functions, a multifunction peripheral in which one device has a plurality of functions such as copying, printing, and faxing has appeared. In such a multifunction device, it is necessary to control each function, so one device has a large number of CPUs and control boards, and a switching power supply has a large capacity and a large number of outputs.
Switching power supplies having a plurality of outputs of the same voltage level have also been used.

In the invention described in Japanese Patent Application Laid-Open No. 2-68570, an image recording apparatus in which a sequence is controlled by a CPU is provided with a current detection circuit and a means for shutting off a power supply path to a load. Over current occurrence is detected in chronological order and the power supply path is cut off.
Try to prevent danger.

In the invention described in Japanese Patent Application Laid-Open No. Hei 5-333636, a switching element is provided at a power output terminal of a power supply circuit to supply power to a load in order to further reduce power consumption during standby. It is disclosed to shut off only the power supply (however, in this case, the power supply is always operating and the loss in the power supply is not reduced).

[0005]

According to a first aspect of the present invention, in an image forming apparatus switching power supply having a plurality of outputs of the same voltage level, an overvoltage (second output) is supplied to an output (second output) for supplying power to a main control unit. If an abnormality such as
Stopping the second output, enabling power to be supplied to the main control unit from another output of the same voltage level (third output), and stopping from a low-priority load (function). Therefore, it is an object to maintain a high priority function. A second object of the present invention is to provide a multifunction device having a facsimile function to prioritize a facsimile reception function. A third object of the present invention is to enable a user to set the priority of a function.

[0006]

According to a first aspect of the present invention, there is provided a rectifier circuit for rectifying an input from an AC power supply, a first switching element for switching a current rectified by the rectifier circuit, and A control circuit for controlling on / off of a switching element, a transformer having a secondary winding for flowing a current to a secondary winding by flowing a current switched by the first switching element to the primary winding, One of the powers induced in the winding is subjected to secondary rectification and smoothing, the output voltage is detected and compared with a predetermined reference voltage to obtain a control signal, and the control signal is used to determine the first switching element. And a first DC output circuit for driving the first DC output to stabilize the output voltage, and a step-down chopper circuit including a second switching element, a choke coil, a capacitor and the like for stabilizing the output of the first DC output. A second DC output circuit, and at least one of a third DC output voltage having the same voltage level as the second DC output voltage, and detecting an abnormality such as an overvoltage in the second DC output circuit. Is a multi-function device that stops the second DC output and controls the load (main control circuit) connected to the second DC output to supply power from the third DC output circuit. In the above, when the second DC output circuit is stopped and power is supplied from the third DC output to a load connected to the second DC output circuit, the load is connected to the third DC output circuit. If power is supplied to both the load and the load connected to the second DC output circuit, and if the output specification of the third DC output circuit is exceeded, the power is connected to the third DC output circuit. Machines with lower priority according to load priority Power supply is cut off from the load and the adjustment is made so as to satisfy the output specifications, so that the high-priority function is maintained by stopping from the low-priority load (function). In this way, the stoppage of the function when an abnormality occurs is minimized.

A second aspect of the present invention is characterized in that, in the first aspect of the present invention, when the apparatus has a facsimile function, the function of receiving a facsimile is given the highest priority. However, by prioritizing the FAX reception function for which the failure cannot be confirmed, the influence of the failure of the user is minimized.

According to a third aspect of the present invention, in the first aspect of the present invention, the function priority can be set by a user. There is something to suppress the effects of.

[0009]

FIG. 1 is an electric circuit diagram for explaining an embodiment of a multifunction peripheral according to the present invention. More specifically, FIG. 1 shows an embodiment of a three-output switching power supply according to the present invention. It is a circuit diagram. In FIG. 1, when a power switch (not shown) is turned on, AC power input from an AC power supply is rectified by a diode bridge DB1 via an input fuse F1, a noise filter circuit 1, and a choke coil L1, and is primary rectified and smoothed. Charge capacitor C0. The primary DC power charged in the capacitor C0 is supplied to the PWM control circuit 2
Is turned on and off by the switching element Q1 which is turned on / off by the driving pulse output from the output terminal OUT of the transformer T1, and is composed of the primary winding N1 of the transformer T1, the switching element Q1, and the primary current detecting resistor R3. The current flows through the circuit and induces power in the secondary windings N2, N3, and N4 for external output and internal output of the transformer T1.

The secondary winding N3 for internal output is a diode D
3. PW through the rectifying and smoothing circuit composed of the capacitor C3
Power is supplied to the power input terminal VCC of the M control circuit 2 and is not output to the outside. Note that a series circuit of a resistor R2 and a diode D1 connected to the positive terminal of the capacitor C0 is also connected to VCC, which supplies power to the PWM control circuit 2 when the switching power supply is started. When power is supplied from the winding N3, the PWM control circuit 2 becomes irrelevant.

The secondary winding N4 for internal output is for supplying electric power to the gate of the triac TRI. When electric power is induced in N4, a current flows to the gate of the triac TRI via the resistor R4. Since the current flows, the TRI becomes conductive, and the current flowing through the inrush current suppressing resistor R1 is bypassed.

The series-parallel circuit of the resistor R5, the capacitor C5, and the diode D2 connected in parallel to the primary winding N1 is a svaner circuit, and is a transient generated when the primary current flowing through the primary winding N1 is turned on and off. It functions to protect the switching element Q1 by absorbing a voltage, especially a flyback voltage generated when the switching element is off.

When the primary current is turned on and off, the electric power induced in the secondary winding N2 for external output becomes a current passing through the diode D4 and the choke coil L3 when the primary current is turned on, and charges the capacitor C11. The power stored as magnetic energy in the core of the choke coil L3 for smoothing the secondary current is converted back to a current when the primary current is turned off, passes through the commutation diode D5, and the capacitor C1.
Charge 1 further.

A series circuit of a resistor R10, a capacitor C7, a resistor R11 and a capacitor C8 connected in parallel to the diodes D4 and D5, respectively, is a svaner circuit for suppressing a spike voltage due to a reverse recovery current of the diodes D4 and D5. The power rectified and smoothed in this way and charged in the capacitor C11 is supplied to the first output voltage V1 (here, the driving voltage 24).
V) is output through the fuse F2, and the "load 1"
Supply power.

The first output voltage V1 is connected to resistors R22, R2
The voltage is divided by 3 and is output to a shunt regulator ZD1 connected between output terminals by forming a series circuit with the resistor 21 and the light emitting element PC1a of the photocoupler PC1. The shunt regulator ZD1 causes the PC1a to emit light in accordance with the difference between the input divided voltage signal and the internal reference voltage, and the optical signal is fed back to the F / B terminal of the PWM control circuit 2 via the light receiving element PC1b of the PC1. You.

The PWM control circuit 2 controls the pulse width of the drive pulse in accordance with the signal fed back and changes the output voltage V1 of the first DC output to a predetermined value (24
V). Therefore, the output voltage V1 of the first output is stabilized with respect to input fluctuations and load fluctuations.

When the voltage value of the first output exceeds a predetermined value, the Zener ZD2 conducts, causing the light emitting element PC2a of the photocoupler PC2 to emit light, and setting the OVP terminal of the PWM control circuit 2 to Hi via PC2b. This turns off the output of the OUT terminal and stops all outputs of the switching power supply.

A part of the first output voltage charges a capacitor C12 for switching noise cutoff via a backflow preventing diode D5 and also inputs the chopper circuit 3 as a step-down stabilizing circuit. The chopper circuit 3 includes a capacitor C12 and a transistor Q2 for turning on / off an input current.
, A commutation diode D7, a smoothing circuit including a choke coil L5, and a capacitor C13, a resistor R14 for detecting an output current, and a transistor Q2 for outputting a drive pulse.
And a second PWM control circuit 4 for controlling ON / OFF of the second PWM control circuit.

When the transistor Q3 is turned on, the capacitor C
12 flows through the choke L5 to the capacitor C1.
Charge 3 Power stored as magnetic energy in the core of the choke L5 during that time is converted back to current when the primary current is turned off, and passes through the commutation diode D7 to the capacitor C1.
Charge 3 further. The voltage between the terminals of the capacitor C13 is smoothed, passes through the output current detection resistor R14, is output as the second output (here, 5 V for main control), and supplies power to the “load 2”.

The output terminal voltage of the resistor R14 is fed back to the F / B terminal of the PWM control circuit 4 as an output voltage signal of the second output voltage V2, and the voltage between the terminals is output as an output current signal. The PWM control circuit 4 outputs a drive pulse of which the pulse width is controlled to the base of the transistor Q2 according to the signal fed back, and
By controlling ON / OFF of the second DC output 2, the output voltage V2 of the second DC output is controlled so as to have a preset value (5V), and the output voltage V2 is stabilized against input fluctuations and load fluctuations.

Similarly, a part of the first output charges the switching noise blocking capacitor C18 via the backflow prevention diode D10 and is also input to the chopper circuit 5 which is a step-down stabilizing circuit. Then, after control by the same circuit, it is output as a third output voltage (here, 5 V for sub-control) and supplies power to "load 3" (details of the control are the same as those of the second output, so description is omitted).

When an overcurrent flows due to a short circuit at the output terminal of the second output or the like, the voltage across R14 increases, and the transistor Q3 changes from the cut-off state to the conductive state. When the / L terminal exceeds a predetermined value, the output from the OUT terminal is turned off and PW
The output of the M control circuit 4 stops. Therefore, the power supply from the second output to “load 2” is cut off.

When it is detected that the C / L terminal has exceeded a predetermined value at "load 2" (when the power supply voltage monitoring IC detects that the power supply voltage of load 2 has dropped), Q6 is turned on. Power is supplied to the load 2 from the third output. If the cause of the overcurrent of the second output is the load 2, the voltage across the resistor R16 increases, and the third output also stops. When both the second and third outputs stop and the voltage supplied to the load 2 falls below a certain value, the light emitting element PC2 of the photocoupler PC2
a is emitted, and all outputs are stopped.

When power is supplied from the third output to "load 2", the overcurrent detection section operates to stop the output even if "load 2" has no abnormality depending on the load capacity of "load 3". It is possible to get rid of it. To prevent this, when power is supplied from the third output to “load 2”, power supply to a part (or all) of “load 3” is cut off. When an overcurrent flows due to an abnormality of the “load 3”, only the third output voltage is stopped. At this time, the first and second outputs are continued.

FIG. 2 is a block diagram showing a control system of the digital copying machine according to the present invention. In FIG. 2, reference numeral 100 denotes a switching power supply for supplying power to each unit of the apparatus. 5V (2 systems) is output. Reference numeral 101 denotes a drive system load such as a motor, which operates according to a signal from the main control unit 102. The main control unit 102 controls the entire copying operation based on signals from the sensor 103 and the like, and when the main control unit 102 stops, all functions including additional functions stop. Reference numerals 104 to 106 denote control boards for a facsimile, a printer, and a scanner, which are additional functions of the digital copying machine, and are detachable by the system.

When an abnormality occurs in the output 2 of the switching power supply 100 and the output is stopped, the switching (SW) is performed.
The relay switch 107a of the circuit 107 is turned on, and the output 3
Power is supplied from to maintain the function. At this time, depending on the connection state of the additional function, the output capacity of the output 3 may be exceeded and the output may be stopped due to an overcurrent or the like. To prevent this, the main control unit 102 detects the presence or absence of connection of each additional function, turns on the switch 107a, and outputs
When it is determined that the output capacity of the output 3 is exceeded when the power is supplied to the main control unit 102 from the switches 107b to 107b,
One of the switches 107d is turned on. When the switch is turned off, some additional functions are disabled, but the copying function and some additional functions are enabled. In addition, only the FAX function can supply power from the output 2 so that the function can be maintained to the maximum. In addition, by setting the priority and switching the function to be stopped from the operation unit 108 or the like, the influence on each user can be minimized even in the event of a failure.

[0027]

According to the first aspect of the present invention, there is provided a rectifier circuit for rectifying an input from an AC power supply, a first switching element for switching a current rectified by the rectifier circuit, and turning on and off the first switching element. A control circuit for controlling;
A transformer having a secondary winding that causes a current to flow through the secondary winding when the current switched by the first switching element flows through the primary winding; One of them is subjected to secondary rectification and smoothing, the output voltage is detected and compared with a predetermined reference voltage to obtain a control signal, and the control signal drives the first switching element to stabilize the output voltage. DC output circuit, a second DC output circuit for stabilizing the output of the first DC output by a step-down chopper circuit including a second switching element, a choke coil, a capacitor, and the like, and a voltage level equal to that of the second DC output. Having at least one of the third DC outputs of
If the DC output circuit detects an abnormality such as an overvoltage, the second DC output is stopped, and power is supplied from the third DC output circuit to the load (main control circuit) connected to the second DC output. In the multifunction peripheral, the second DC output circuit is stopped and power is supplied from a third DC output to a load connected to the second DC output circuit. When power is supplied to both the load connected to the third DC output circuit and the load connected to the second DC output circuit, and the output specification of the third DC output circuit is exceeded. Is adapted to cut off power supply from a load having a lower priority function according to the priority of the load connected to the third DC output circuit and adjust the load so as to satisfy the output specification. Stop from low load (function) By going, higher priority function that can be maintained, it is possible to minimize the outage at the time of occurrence of an abnormality.

According to a second aspect of the present invention, in the first aspect of the present invention, when a facsimile function is provided, the facsimile receiving function is given the highest priority. By giving priority to the reception function of the FAX which cannot confirm the failure, the influence of the failure of the user can be minimized.

According to a third aspect of the present invention, in the first aspect of the present invention, the function priority can be set by the user. Can be held down.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram for explaining an example of a three-output switching power supply according to the present invention.

FIG. 2 is a block diagram showing a control system of the digital copying machine according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Noise filter circuit, 2 ... PWM control circuit, 3 ... Chopper circuit, 4 ... PWM control circuit, 5 ... Chopper circuit.

Claims (3)

[Claims] A rectifier circuit for rectifying an input from an AC power supply, a first switching element for switching a current rectified by the rectifier circuit, a control circuit for on / off controlling the first switching element; A transformer having a secondary winding that causes a current to flow through the secondary winding when a current switched by the first switching element flows through the primary winding; and one of powers induced in the secondary winding. And a second rectifier / smoothing, which detects the output voltage and compares it with a predetermined reference voltage to obtain a control signal. The control signal drives the first switching element to stabilize the output voltage. A DC output circuit for stabilizing an output voltage of the first DC output by a step-down chopper circuit including a second switching element, a choke coil, a capacitor, and the like; And at least one third DC output voltage having the same voltage level as the DC output voltage of the second DC output voltage.
If the DC output circuit detects an abnormality such as an overvoltage, the second DC output is stopped, and power is supplied from the third DC output circuit to the load connected to the second DC output. In the multifunction peripheral, when the second DC output circuit is stopped and power is supplied from a third DC output to a load connected to the second DC output circuit, When power is supplied to both the load connected to the DC output circuit and the load connected to the second DC output circuit, if the output specification of the third DC output circuit is exceeded, the third A multi-function peripheral according to which priority is given to a load connected to a DC output circuit to cut off power supply from a load having a low-priority function and adjust the load so as to satisfy output specifications. 2. The multifunction peripheral according to claim 1, wherein when the multifunction peripheral has a facsimile function, the facsimile reception function is given the highest priority. 3. The multifunction peripheral according to claim 1, wherein a user can set the priority of the function.