JP2002283661A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device which is capable of accurately detecting a drop in the power supply voltage following the shut-off of an AC power supply and securely storing data which need to be retained even when the power supply is shut off. SOLUTION: An output voltage is detected by a voltage detecting means (step 10) and is loaded as a digital value from an A/D converter. Further, it is judged whether the detected value falls within a specified value range (step 11). When the judgement results are abnormal, the lowest duty is selected and is reflected on a PWM signal, which is, in turn, outputted to the converter (step 17). When the judgement results are normal, the duty reflected on the PWM signal stands above a predetermined upper limit value (step 12; Y). When the detected value of the output voltage is less than a target value (step 13; Y), the AC power supply is shut off and the input DC voltage of the converter drops and the PWM limit signal is asserted (step 14) on the judgement that the output voltage drops soon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus for surely storing necessary data when AC power is turned off.

[0002]

2. Description of the Related Art In an image forming apparatus, various studies have been made on how to protect necessary data when AC power is cut off. For example, in the invention described in Japanese Patent Application Laid-Open No. 10-185965, the interruption of the AC power is detected by detecting no zero-cross signal, and necessary data is stored in a nonvolatile memory. By the way, in the conventional device, when the main power supply SW is turned off or the AC power supply is cut off due to the occurrence of a power failure, the DC power supply voltage of the control board is monitored, and when it is detected that the voltage has dropped below a certain voltage, a detection signal is generated. This occurred, and the fact was notified to the CPU of the control board. Before receiving the notification, the CPU of the control board does not save data that needs to be retained even when the power is shut off to the FlashROM or perform new writing to the hard disk before the DC power supply voltage falls below the operable range. I was If the DC power supply voltage falls below the operable range while writing to the hard disk, not only will the data being written be lost, but if the document management information on the hard disk is being rewritten, This is because other documents cannot be called. If the hard disk is writing, the writing is interrupted.

[0003]

However, since the above operation is started after the DC power supply voltage drops below a certain voltage, the time that can be secured from the start of operation until the DC power supply voltage falls below the operable range is short. There is a problem to say. Since it is short, the time-consuming data storage in the FlashROM needs to be limited to a small amount of data. In addition, since writing to the hard disk is performed by a series of operations on continuous data, there is a case where even if it is detected and then controlled to interrupt the writing, the writing cannot be interrupted. On the other hand, if the voltage to be detected is increased, there is a risk that erroneous detection may occur due to a decrease in the DC power supply voltage due to a change in current consumption during normal operation even when the AC power supply is not cut off. Also, if the capacity of the capacitor for smoothing the AC power after rectification is increased and the rate of decrease of the DC power supply voltage when the AC power is cut off is slowed down, it is necessary to increase the capacity of the smoothing capacitor, resulting in high cost and power factor. There is a danger that the power supply harmonic current will increase and the same AC power supply will malfunction. Further, there is a conventional device that monitors the AC power supply voltage and detects that the AC power supply has been cut off. However, in this case, the DC power is supplied by the power stored in the smoothing capacitor, and the DC power supply voltage does not decrease. Even in the case of such a short interruption (hereinafter, referred to as an instantaneous interruption), it is detected, and an unnecessary save operation to the non-volatile memory or an unnecessary interruption to the writing to the hard disk is performed. There was a problem that could not be performed.

Therefore, a first object of the present invention is to accurately detect that the AC power supply is cut off and the DC power supply voltage starts to decrease, and to reliably store data that needs to be retained even during the power cutoff. It is an object of the present invention to provide an image forming apparatus capable of performing the above. A second object of the present invention is to accurately detect that the AC power supply is cut off and the DC power supply voltage starts to decrease,
It is an object of the present invention to provide an image forming apparatus capable of preventing a writing operation from being disabled during writing to a hard disk and losing data. Further, a third object of the present invention is to accurately detect that the DC power supply voltage starts to decrease even in the case of a non-volatile memory such as a hard disk which operates with a power supply of a plurality of voltages, and to prevent data loss. It is an object of the present invention to provide an information processing apparatus capable of performing the above.

[0005]

According to the first aspect of the present invention, a rectifying / smoothing means connected to an AC power supply, a DC / DC converter to which DC power is supplied by an output of the rectifying / smoothing means, and a DC / DC converter. Power supply control means for generating a control signal (PWM signal) for raising and lowering the output voltage of the DC converter, image formation control means for supplying DC power from the output of the DC / DC converter, and storing data by inputting a storage request Thereafter, in an image forming apparatus provided with a nonvolatile memory capable of retaining data even after power is turned off, a voltage detecting means for detecting a DC power supply voltage supplied to the image forming control means, and a DC / DC output from the power control means. It is detected by the voltage detecting means that the state of the control signal of the DC converter is in a state of increasing the output voltage beyond a preset state. , Upper limit detection signal (PWMlimi
a signal generating means for generating t), and when the generation of the upper limit detection signal is detected, the data is stored in the non-volatile memory, thereby achieving the first object.

According to the second aspect of the present invention, a rectifying / smoothing means connected to an AC power supply, a DC / DC converter to which a DC power is supplied by an output of the rectifying / smoothing means,
Power supply control means for generating a control signal for raising and lowering the output voltage of the C / DC converter, image forming control means to which DC power is supplied by the output of the DC / DC converter, and which can hold written data even after power is turned off In an image forming apparatus including a non-volatile memory (hard disk), a voltage detection unit for detecting a DC power supply voltage supplied to the image formation control unit, and a control signal of a DC / DC converter output from the power supply control unit. Signal generation means for generating an upper limit detection signal when the voltage detection means detects that the state is in a state of increasing the output voltage beyond a preset state, and detects occurrence of the upper limit detection signal Then, the second object is achieved by not writing new data to the nonvolatile memory.

According to the third aspect of the present invention, there is provided a rectifying / smoothing means connected to an AC power supply, and a plurality of DC / DC converters to which DC power is supplied by an output of the rectifying / smoothing means.
Power supply control means for generating control signals for independently raising and lowering the output voltages of the plurality of DC / DC converters;
Image forming control means to which a plurality of DC power supplies are supplied by the output of a C / DC converter, and voltage detection for detecting a plurality of DC power supply voltages to be supplied to the image forming control means in an image forming apparatus having a nonvolatile memory Means, wherein at least one of the control signals of the plurality of DC / DC converters output by the power supply control means is in a state of increasing the output voltage to a predetermined state or more. The third object is achieved by providing a signal generating means for generating an upper limit detection signal when detected by the following.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to FIGS.
FIG. 1 is a diagram showing a control block diagram of a multifunction copying machine according to this embodiment. Power is supplied from the AC power supply AC to the switching power supply SWP via input current detection means and the main power switch SW1. Main power switch SW
1 is input to a rectifying / smoothing circuit including a diode bridge DB1 and a capacitor C1, and a DC voltage is applied to a first DC / DC converter (hereinafter referred to as a converter) DC / DC1 and a second converter DC / DC2. Is being entered. The output of the diode bridge DB1 is connected to a resistor R1 and a relay RA2 which constitute a starting circuit of the switching power supply SWP.

A first converter DC / DC1 generates a DC power supply (specifically, 12V) for the power system of the hard disk, and a second converter DC / DC2 generates a DC power supply (specifically, 5V) for the control system. Has been generated. The power input to the first converter DC / DC1 is one of the transformers T11.
It is input to the next coil and is further connected to the primary side ground via the switch element FET11. Switch element FE
A transformer drive circuit is constituted by T11 and the drive circuit DRIV11. The drive circuit DRIV11 includes a port PWM for outputting a PWM signal of the power control unit CONT.
Connected to 1. The secondary coil of the transformer T11 is connected to the first output terminal Vout1 of the switching power supply SWP via a rectifying and smoothing circuit composed of diodes D11 and D12 and choke coil CH11 and capacitor C11, and the low voltage side is grounded in the secondary circuit Connected to GND. A voltage detection means VSEN11 for detecting an output voltage is connected to this output, and a detection signal is connected to Vf1, which is an input port of an A / D converter built in the power supply control means CONT.

In the second converter DC / DC2, parts having the same function are denoted by the same reference numerals in the 20's, and the description of the configuration is omitted. The second converter DC / DC2 is provided with a power supply circuit of the power supply control means CONT.
It comprises a diode D31 and a capacitor C31 connected to the tertiary coil of No. 21, a constant voltage circuit CV31 and a diode D32 for preventing backflow. Power supply control means CONT
A battery B1, a diode D1, and a contact driven by a relay RA2 of a starting circuit are connected in series between the power supply terminal VCC and GND.

The power control means CONT uses a microcomputer (not shown) and a digital signal processor (DSP) having an A / D (analog / digital) converter, a PWM timer and the like. In addition to the above-described signals, the power supply control means CONT also includes a communication port S1 and a PWM limit which is an upper limit detection signal.
Is connected to a control plate of an image control unit that controls the entire image forming apparatus. Further, a switch SW2 for selecting or canceling the energy saving mode for reducing the power consumption of the image forming apparatus during standby is connected to the port P1. The starting operation of each converter will be described. When the main power switch SW1 of the image forming apparatus is turned on, the switching power supply S
A current flows from the WP diode bridge DB1 to the relay RA2 of the starting circuit via the resistor R1 to turn on the contact. Thereby, the power supply terminal VCC of the power supply control means CONT
Is supplied from the battery B1 via the diode D1, and the power supply control means CONT is activated. When the power control means CONT starts, the power control means starts control for starting the converter DC / DC2. When the converter DC / DC2 starts, DC power is supplied from the output terminal Vout2 to the engine control means, and the engine control means starts. Next, the power supply control means CONT includes a converter DC / DC generating a power-system DC power supply.
1 is started, and a series of start processing is completed.

Next, an outline of a control loop of the converter shown in FIG. 3 will be described. The rectifying / smoothing 1 of FIG. 3 is commonly used by the first converter and the second converter. The first and second converters DC / DC1 and DC / DC2, which supply DC power to the control system or power system load, perform substantially the same control by the power control means CONT. A DC voltage obtained by rectifying and smoothing a commercial power supply is obtained as an input, and this is switched at about 100 KHz to drive a transformer. The output of the transformer is rectified and smoothed again and supplied to the load.
The output voltage is detected and fed back to the power supply control means CONT, and the duty of the PWM signal for switching is controlled so that these become a predetermined value. This control loop stabilizes the converter output.

Next, the waveform of the PWM signal shown in FIG. 4 will be described. In the PWM signal, the period T0 is fixed, and the pulse width T1 is controlled according to the feedback. Period T0
Is referred to as a duty.

The PWM characteristic 1, which is the relationship between the duty of the PWM signal and the output power of the converter, will be described with reference to FIG.
This is the case when the input DC voltage is constant. The output power of the converter is proportional to the duty.
That is, when the load current increases and the output power needs to be increased, the duty of the PWM signal is increased.

The PWM characteristic 2, which is the relationship between the duty of the PWM signal and the DC input voltage of the converter, will be described with reference to FIG. This is the case when the output power is constant. The duty is inversely proportional to the input DC voltage of the converter. That is, when the input DC voltage decreases, the duty of the PWM signal is increased. When the AC power supply is cut off, the charging current to the smoothing capacitor is not supplied, so that the input DC voltage of the converter decreases. Then, the DC output voltage of the converter also decreases, so that the power supply control means increases the duty of the PWM signal and controls the output voltage to maintain the target value. However, due to the problem of transformer magnetic saturation, the duty of the PWM signal has a maximum value, which is around 50%. Since the duty cannot be increased any more, if the input DC voltage continues to decrease and the duty reaches the maximum value, the output voltage can no longer be maintained at the target value, and the output voltage will decrease thereafter. To go.

The procedure for detecting the output voltage control and the PWM upper limit shown in FIG. 7 will be described with reference to a flowchart. First, the output voltage control of the converter will be described. First and second converters DC / DC1, DC / DC
The output 2 performs constant voltage control. The constant voltage control is processed in a software manner in the power supply control means CONT, and is executed at a predetermined cycle (specifically, every 1 ms). First, the output voltage is detected by the voltage detecting means (step 1).
0), as a digital value from the A / D converter. It is determined whether or not the detected value is within a predetermined value (Step 11). If the detected value is abnormal (Step 11; N), the minimum duty is selected and reflected in the PWM signal and output to the converter (Step 17). On the other hand, if it is normal (step 1
1; Y), when the duty of the PWM signal is equal to or greater than the predetermined upper limit value (step 12; Y) and the detected value of the output voltage is less than the target value (step 13; Y), AC The power supply is cut off, the input DC voltage of the converter decreases, and it is determined that the output voltage will soon decrease, and the PWM limit signal is asserted (step 14).

The upper limit value of the PWM duty is set to the same value as the maximum value or a value smaller by about 5%. When the same value as the maximum value is set, the output voltage decreases at the same time as the assertion of the PWM limit signal. If the value is smaller than the maximum value,
A little time can be gained from the assertion of the PWM limit signal to the start of the output voltage drop. In the normal case, when the duty of the PWM signal is not equal to or higher than the upper limit value (Step 12; N), or when the detected voltage is equal to or higher than the target value even when the duty ratio of the PWM signal is equal to or higher than the upper limit value (Step 13; N), PWMli is used.
Do not assert the mit signal.

Regardless of whether the PWM limit signal is asserted or not, a proportional operation is performed next and the PWM
Determine a new duty for the M signal (step 1
5). In the proportional operation, the output set value (specifically, 5 V or 12 V) is set as a target value, and the duty is increased or decreased according to the difference between the target value and the current output value. It is determined whether the result of the duty calculation is within the above maximum value (step 1).
6) If exceeding (step 16; N), the maximum value is set as a new duty (step 18). If the result is normal, the calculation result is reflected on the PWM signal and output to the converter (step 19). Two converters DC / DC
1 and DC / DC2 independently perform the control shown in FIG. 7, but the PWM limit is commonly used. Therefore, if either condition of the two converters is satisfied, the PWM limit signal is asserted.

Next, a control block diagram of another multifunction copying machine shown in FIG. 2 will be described. The image forming control means includes a control plate 1
0 and a hard disk: HDD 20, and the control board 10 has a switching power supply: SWP output Vout as a power supply.
2 are supplied. Two outputs Vout1 and Vout2 of a switching power supply are supplied as power to the hard disk. The control board 10 includes a CPU (Central Processing Unit) 12, a ROM (Read Only Memory) 13 in which a program is written, and a Fl for writing stored data.
AshROM 19, NVRA for storing control parameters
M (non-volatile random access memory) 17, an HDD controller 11 for controlling reading and writing to a hard disk, a serial interface for communicating with a switching power supply: SIO15, and a CPU that detects assertion of a PWM limit signal from the switching power supply
An interrupt controller 16 for interrupting the system is mounted.

In writing data to the hard disk, when the CPU writes a command to the hard disk controller, predetermined data is continuously written into blocks. It takes time to write image data, and it takes about 500 ms for A4 sheets. If the interruption command is received during the writing, the writing is interrupted at the point where the writing of the block being written is completed. The time required to write one block is about 10 ms when the block size is maximized. When writing data to the FlashROM, it is necessary to erase the data in advance. Depending on the size of the block to be erased, it takes several hundred milliseconds to several seconds, depending on the size of the block to be erased. Then, writing is performed before the AC power supply is cut off and the output Vout2 of the switching power supply decreases.

FIG. 8 shows an internal block diagram of the NVRAM. Commands can be written by the CPU sequentially accessing specific addresses. When a save command is detected, the contents of the SRAM are written to the EEPROM, and when a call command is detected, the contents of the EEPROM are written to the SRAM. During normal operation, normal SRAM
Before the AC power supply is cut off and the output Vout2 of the switching power supply decreases, the CPU writes a save command and writes data in the SRAM to the EEPROM.

The PWM limit shown in the flowchart of FIG.
The processing procedure when the signal is asserted is shown. When detecting the assertion of the PWMlimi signal, the interrupt controller interrupts the CPU. When the CPU is interrupted, the CPU interrupts the processing and shifts to the interrupt processing of FIG. In the interrupt processing, first, it is confirmed whether or not the hard disk controller is performing the writing (step 20). When writing (step 20;
Y), a write suspend command is written to the hard disk controller (step 21), and the write is interrupted when the writing to the block currently being written is completed. Next, a hard disk write prohibition flag of the hard disk controller is set so that writing to the new hard disk is not performed (step 22).
Subsequently, a save command is written to the NVRAM (step 23), and the contents of the SRAM in the NVRAM are written to the EEPROM.
Write to M. Next, the storage data is written to the FlashROM (step 24).

FIG. 10 shows the timing from the interruption of the AC input to the generation of the PWM limit signal when the upper limit value of the PWM signal duty is set to 95% of the maximum value of the PWM signal. Before the output voltage of the converter drops, it is possible to detect that the drop has occurred.

[0024]

According to the first aspect of the present invention, since the duty of the PWM signal of the converter reaches the upper limit, the AC
It accurately detects that the power supply is cut off and the DC power supply voltage starts to decrease, and writes a save command to NVRAM or data to FlahROM. Before the power falls below the operable range, the writing operation to the memory that can hold data even when the power is turned off can be terminated, and the data can be reliably stored.

According to the invention of claim 2, the converter P
When the duty of the WM signal reaches the upper limit, it is accurately detected that the AC power supply is cut off and the DC power supply voltage starts to decrease, and no new writing to the hard disk is performed. In this case, it is possible to prevent the DC power supply voltage from falling below the operable range during the writing, thereby preventing the writing operation from being disabled and losing data.

According to the third aspect of the present invention, when the duty of the PWM signal of one of the DC / DC1 and DC / DC2 converters reaches the upper limit, the AC power supply is cut off and the DC power supply voltage starts to decrease. Accurately detect that
Since new writing to the hard disk is not performed, even when operating with a two-voltage power supply like a hard disk, either DC power supply voltage falls below the operable range during writing to the hard disk and writing It is possible to prevent the operation from being disabled and the data from being lost.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating control blocks of a multifunction copying machine according to an embodiment.

FIG. 2 is a diagram illustrating control blocks of the multi-function copying machine according to the embodiment.

FIG. 3 is a diagram illustrating a control loop of a SWP (switching power supply) according to the present embodiment.

FIG. 4 is a diagram showing a PWM signal waveform which is a control signal of a power control unit.

FIG. 5 is a diagram showing a relationship between a duty of a PWM signal waveform and output power.

FIG. 6 is a diagram illustrating a relationship between a duty of a PWM signal and an input DC voltage.

FIG. 7 is a flowchart illustrating a processing procedure of a power control unit.

FIG. 8 is a block diagram of NVRAM which is a nonvolatile memory.

FIG. 9 is a flowchart illustrating a processing procedure of an image forming control unit.

FIG. 10 is a timing chart showing a timing from an AC input disconnection to a generation of a PWM limit signal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Control board 11 HDD controller 12 CPU 13 ROM 14 RAM 16 Interrupt controller 20 HDD

Claims (3)

[Claims] A rectifying / smoothing means connected to an AC power supply;
DC power is supplied by the output of the rectifying and smoothing means.
C / DC converter, power supply control means for generating a control signal (PWM signal) for raising and lowering the output voltage of the DC / DC converter, image forming control means for supplying DC power by the output of the DC / DC converter, In an image forming apparatus including a nonvolatile memory capable of retaining data even after power is turned off after data is stored by inputting a storage request, voltage detection means for detecting a DC power supply voltage supplied to the image formation control means, When the voltage detector detects that the state of the control signal of the DC / DC converter output by the power supply controller is higher than a preset state, the upper limit detection signal (PWMlimit) is output. Signal generating means for generating, and when the generation of the upper limit detection signal is detected, data is stored in the nonvolatile memory. An image forming apparatus comprising Rukoto. 2. A rectifying and smoothing means connected to an AC power supply;
DC power is supplied by the output of the rectifying and smoothing means.
A C / DC converter, and power supply control means for generating a control signal for raising and lowering the output voltage of the DC / DC converter;
An image forming apparatus comprising: an image forming control unit to which DC power is supplied by an output of the DC / DC converter; and a non-volatile memory (hard disk) capable of holding written data even after power is turned off. Voltage detecting means for detecting a DC power supply voltage supplied to the DC / DC converter, and a state of a control signal of the DC / DC converter output by the power supply controlling means being in a state of increasing the output voltage beyond a preset state. Signal generation means for generating an upper limit detection signal when detected by the detection means, wherein when the occurrence of the upper limit detection signal is detected, writing of new data to the nonvolatile memory is not performed. Image forming device. 3. A rectifying / smoothing means connected to an AC power supply.
A plurality of DC / DC converters to which DC power is supplied by an output of the rectifying / smoothing means;
Power supply control means for generating a control signal for independently raising and lowering the output voltage of a converter, image formation control means for supplying a plurality of DC power supplies by a plurality of DC / DC converter outputs, and an image forming apparatus comprising a nonvolatile memory And a voltage detecting means for detecting a plurality of DC power supply voltages supplied to the image forming control means, wherein at least one state of the plurality of DC / DC converter control signals output by the power control means is provided. An image forming apparatus comprising: a signal generation unit that generates an upper limit detection signal when the voltage detection unit detects that the output voltage is higher than a preset state.