JP6347118B2 - Electrical equipment and residual charge discharging method - Google Patents

Description

  The present invention relates to an electric device that supplies power to a load via a circuit opening / closing means, and relates to an electric device having means for discharging electric charge remaining in the circuit when the circuit opening / closing means is turned off and a residual electric charge discharging residual charge. The present invention relates to a charge discharging method.

In various types of electrical equipment, when the power is turned off by a relay, switch, etc. that turns on and off the power supply, a residual charge is generated in the capacitive element in the load circuit to which the power was supplied, and then the power is turned on. Inrush current may occur due to residual charges. This inrush current may cause malfunction of a device due to a power supply voltage drop, malfunction of a circuit such as a reset, or damage to circuit elements including a relay.
For this reason, conventionally, a means for removing the residual charge generated in the above situation has been taken.

  For example, in Patent Document 1, when a power supply is shut off in conjunction with opening of a door by a switch that opens and closes a door provided in a paper feeding unit of a copying machine, a residual capacitor connected in parallel with a driving load remains. An arrangement with means for discharging the charge is shown. In addition to this means for discharging the residual charge, this Patent Document 1 is provided with a resistor for suppressing the generation of a large inrush current when the power is turned on in conjunction with the closing of the door. This resistor controls the circuit so that it works only for a predetermined period when the power is turned on.

However, the discharge operation of the residual charge of the capacitor connected in parallel with the driving load in Patent Document 1 is directly dependent on the opening / closing operation of the user's door, and depending on the operation timing, the residual charge is not completely discharged, There arises a problem that an inrush current flows when the door is closed. If a method of starting after discharging all the residual charges is taken, the waiting time is inevitable and convenience is impaired.
Further, since Patent Document 1 does not consider the countermeasure against the residual charges generated on the power supply circuit side, when such residual charges are generated, the generation of the inrush current cannot be prevented.

  An object of the present invention is to prevent an inrush current from being generated when a relay is turned on by an electric charge remaining on each side of the power circuit and the load circuit when the relay is turned off in an electric device that supplies power to the load circuit via a relay that can be turned on and off. Is to do.

The present invention relates to a power source, a load circuit that receives supply of power from the power source, and a circuit that controls on / off of input power from the power source according to a change in the state of the device, and outputs power from the power source to the load circuit when the power is on An electric device having a switching means of the circuit, wherein the potential generated in the power supply line on the input side of the switching means of the circuit is compared with the potential generated in the power supply line on the output side of the switching means of the circuit, and the higher potential side is compared. Connected to the power supply line on the input side of the potential comparison means for instructing and the switching means of the circuit, and the discharge operation can be turned on and off, and connected to the power supply line on the output side of the switching means of the circuit, and the discharge operation Of the first discharge circuit when the input side is instructed by the potential comparison means with the second discharge circuit that can be turned on and off and the open / close means of the circuit turned off. ON control , When said output side by the potential comparison means is indicated to be a higher potential, the by the ON control of the discharging operation of the second discharge circuit, to discharge the charge remaining in the power supply line of the input-side an electrical device having a first and a discharge control circuit you reduce a difference between the potential generated in the power supply line of the resulting potential and the output side.

  According to the present invention, in an electrical device that supplies power to a load circuit via a relay that can be controlled to be turned on and off, when the relay is turned on, generation of an inrush current due to electric charge remaining on each side of the power circuit and the load circuit is prevented. Can do.

1 is a diagram illustrating an outline of a configuration of an image forming apparatus according to an embodiment of an electrical apparatus of the present invention. In the image forming apparatus (FIG. 1), it is a diagram showing a power supply circuit of Embodiment 1 that performs a discharge operation of remaining charges when a relay that turns on and off input power is turned off. FIG. 5 is a diagram illustrating a power supply circuit according to a second embodiment that includes a circuit that performs off control when a relay is turned on, and controls an FET that performs on control of a residual charge discharging operation when the relay is turned off. It is a figure which shows the power supply circuit of Embodiment 3 which has a circuit which performs the operation | movement which discharges the electric charge which remains at the time of a relay off with a constant current.

Embodiments of the present invention will be described with reference to the accompanying drawings.
In the embodiment described below, image forming is performed by using a recording material on a recording medium (paper) by operating a printer engine with output data processed based on original image data in the electric device of the present invention. The example implemented to the apparatus is shown.
In addition, this image forming apparatus has an electrophotographic printer engine capable of high-speed printing and a plurality of paper feed trays on which sheets of different sizes can be stacked, and has a function capable of outputting various types of paper including post-processing in large quantities. Prepare. Therefore, manual maintenance such as replenishment of toner, which is a developing material, to a plurality of paper feed trays is required.

When performing manual maintenance as described above, the user operates the inside of the housing with the door provided on the housing of the device (hereinafter, referred to as an image forming apparatus in this embodiment) opened. There is a risk of contact with a moving part such as a motor or injury due to laser irradiation.
For this reason, a circuit opening / closing means for turning off the power supplied to the load circuit when the inside of the housing is manually operated is provided. This circuit opening / closing means turns off the power supply in conjunction with a change in the state of the device, such as the opening of a door provided in the housing, which triggers the operation inside the housing manually. Further, it is provided as a power control means for turning on the power in conjunction with closing of the door after the operation is completed. In the following description of the embodiment, an example in which a relay is used as the circuit opening / closing means will be described. Therefore, the relay will be described. However, any circuit opening / closing means used for on / off control of the power supply to the circuit may be used. Any means other than the relay may be applied.
In this embodiment, the power is turned off by controlling to turn off the relay as a means for outputting power from the power source to the load circuit according to the opening of the door provided in the housing, and conversely according to the closing of the door The power from the power supply is output to the load circuit by controlling the relay to turn on.

However, when the power supply is cut off by turning off the relays, switches, etc. that connect the power supply to the load circuit, residual charges are generated in the capacitive elements on the power supply circuit side and the load circuit side, and then the power supply is turned on In addition, an inrush current may occur due to the residual charge. This inrush current may cause malfunction of a device due to a power supply voltage drop, malfunction of a circuit such as a reset, or damage to circuit elements including a relay.
Therefore, by providing means for discharging the electric charge remaining on each side of the power supply circuit and the load circuit when the relay is turned off, an inrush current is prevented from occurring when the relay is turned on in order to turn on the power again thereafter.
In order to prevent the inrush current described above, this image forming apparatus discharges the residual charge on the higher potential side so that there is no difference between the potential generated in the power line on the output and input sides of the relay due to the residual charge when the relay is off. Perform the action. The circuit relating to this discharge operation is an element unique to the present embodiment, which is not in the prior art.

The details of the power supply circuit including the circuit relating to the above-described discharge operation will be described later. Before that, the outline of the image forming apparatus of the present embodiment to which the power supply circuit is applied will be described.
FIG. 1 is a diagram illustrating an outline of a configuration of an image forming apparatus according to the present embodiment.
The image forming apparatus requests processing by functions such as a copy, a printer, and a facsimile, receives a job input performed by a user, and performs image output processing such as paper (printing) output in accordance with the job instruction.
As shown in FIG. 1, the image forming apparatus includes an apparatus main body 1, an automatic document feeder 2, a finisher 3 with a stapler and a shift tray, a duplex reversing unit 4, an extended paper feed tray 5, a large capacity paper feed tray LCT 6, Each unit includes a 1-bin discharge tray 7 and an insert feeder 8.

The apparatus main body 1 includes a scanner unit that reads a document, a printer engine that performs print output by an electrophotographic method including elements such as an optical writing unit, a photosensitive member, and a developing unit, a paper feeding unit, and the like.
The device body 1 has a main control unit for controlling the entire device. The main control unit accepts job input and performs paper (printing) output in accordance with job instructions, so as to centrally manage each element unit related to the image output processing system and control its operation. Maintain and manage equipment conditions so that each element operates properly.
The main control unit can be configured by a computer mounted on a controller board provided in the device main body 1. This computer includes a CPU (Central Processing Unit), a ROM (Read Only Memory) that operates under the control of the CPU, a DRAM (Dynamic Random Access Memory), and the like.

The ROM is a memory that controls operations of the printer engine and the paper feed unit, and stores programs, data, and the like used by the CPU when processing image data used for print output. When the CPU of this computer is responsible for data (signal) processing related to the operation of a power supply circuit to be described later, this data processing program and the like are stored in the ROM.
The DRAM is a memory used as a memory for temporarily storing data generated when the CPU drives the program, or a work memory for storing data necessary for driving the program.

Next, a power supply circuit of the image forming apparatus will be described in detail with reference to an embodiment.
As described above, the power supply circuit of the present embodiment supplies power to the load circuit via the relay, and remains on each side of the power circuit and the load circuit when the relay is turned off to turn off the power. A circuit for discharging the residual charge is provided so that the potential difference caused by the charge is eliminated.
In the following, a power supply circuit that controls on / off of input power to the load circuit according to the open / closed state of the front door provided in the housing is used as a drawer circuit of the image forming apparatus that requires power. Each embodiment will be described by way of example.

“Embodiment 1”
This embodiment is a basic form of a power supply circuit having a circuit for discharging residual charges so that a potential difference caused by charges remaining on each side of the power supply circuit and the load circuit is eliminated when the relay is turned off to turn off the power supply. Show.
FIG. 2 is a diagram illustrating a power supply circuit according to the present embodiment that performs a discharge operation of remaining charges when a relay that turns on / off input power is turned off in the image forming apparatus (FIG. 1).
According to the configuration of FIG. 2, the power supply 20 includes a SW converter 201 that includes a switching regulator and outputs DC. The power supply 20 has a capacitive element 210.
The drawer unit 30 is a load circuit to which power is supplied. Note that the circuit of the drawer unit 30 has a capacitive element 310. The substrate 10 of the power supply circuit is provided with a capacitor 110 that is a capacitive element that stabilizes the power supply in parallel with the drawing unit 30 serving as a load circuit.

The power supply circuit for supplying the power of the power supply 20 to the drawer unit 30 as a load circuit incorporates the following elements on the substrate 10.
One of the elements is a relay 101 that controls on / off of input power in accordance with the open / closed state of the front door 21, and an electromagnetic relay is employed here. The relay 101 functions as an interlock relay.
The on / off operation of the relay 101 turns the contact of the relay 101 on and off in conjunction with the opening and closing of the front door 21. The relay 101 is an electromagnetic relay. Here, the contact is turned off by passing a drive current through an electromagnetic coil that turns the contact on and off, and if not, the contact is turned on. For this reason, whether or not the current from the power source 102 for driving the electromagnetic coil flows is controlled by the transistor 103 that performs the switching operation.

When the interlock SW (switch) 21s is opened by closing the front door 21, the voltage from the power source 104 is not applied to the transistor 103, and the switching operation of the transistor 103 is turned off. In this case, the contact of the relay 101 is turned on and power is supplied to the drawer unit 30.
On the other hand, the transistor 103 is turned on (conducting) in response to the voltage applied from the power supply 104 when the interlock SW 21s is closed by opening the front door 21, so that a drive current flows through the electromagnetic coil of the relay 101. Turn off the contact. That is, the relay 101 is turned off in conjunction with the opening of the front door 21. The diode 101d connected between the terminals of the electromagnetic coil of the relay 101 functions as a freewheeling diode.

Another element of the power supply circuit is that when the relay 101 is turned off and the power is turned off, the residual on the higher potential side is eliminated so that there is no difference between the potential generated in the power line on the output and input sides of the relay due to the residual charge. It is a circuit related to the operation of discharging electric charges. That is, a circuit consisting of the first discharge circuit a is the input-side discharge circuit (1) 130 ₁ and the discharge circuit of the output side is a second discharging circuit (2) 130 ₂ like.
A discharge circuit (1) 130 ₁ as an input side discharge circuit is connected to a power line on the input side of the relay 101 and a resistor 130r1, and an output terminal is grounded (GND), and an FET (field effect transistor) 130s1 as a switching element is connected. Configure.
Further, the output-side discharge discharge circuit as a circuit (2) 130 ₂ includes resistors 130r2 on the input side of the power supply line of the relay 101, grounded output terminal (GND) is constructed by connecting a FET130s2 as a switching element.

This configuration discharging circuit (1) 130 _1, at the input of the relay 101 when the power is turned off, for example, to discharge the charges remaining capacitive elements 210 of the power supply 20 through a resistor 130r1 and FET130s1.
In addition, the discharge circuit (2) 130 _2, discharges through the output side of the relay 101 when the power is turned off, for example, the charge remaining in the capacitor element 310 of the capacitor 110 and the pull-out unit 30 resistance 130r2 and FET130s2.
Here, the FETs 130s1 and 130s2 are used as switching elements, but switching elements such as bipolar transistors and IGBTs (Insulated Gate Bipolar Transistors) may be employed.
Switching operation of FET130s1 and FET130s2 performs receives control input from the discharge control circuit for controlling the discharging circuit (1) 130 ₁ and the discharge circuit (2) 130 _2.
The discharge control circuit, the discharge circuit (1) 130 ₁ and the discharge circuit (2) 130 on the _second discharge operation, a circuit for turning off control. In the present embodiment, the comparator 131 and the comparator 132 that perform control input of ON (conduction) and OFF operations in the FETs 130s1 and 130s2 are related. The discharge control circuit (first discharge control circuit) has a different configuration from the discharge control circuit (second discharge control circuit) that forcibly turns off the discharge when the relay is turned on in the second embodiment.

In the discharge circuit (1) 130 ₁ and the discharge circuit (2) 130 _2, whether to perform the discharge, the output of the relay 101, compares the potential generated in the power supply line of each side of the input side of the higher potential Depends on the comparison result obtained as an output indicating
In other words, the output indicating that the side higher potential occurs is the input side of the relay 101 is Rarere obtained as the comparison result, the discharge circuit (1) on the input side of the relay 101 to perform the discharge 130 _1, while , the discharge circuit (2) on the output side to 130 ₂ does not perform the discharge. Conversely, if the output indicating that the side higher potential is occurring on the output side of the relay 101 is Rarere obtained as the comparison result, the discharge circuit (2) on the output side of the relay 101 130 ₂ to perform the discharge, on the other hand, the output side of the discharging circuit (1) in 130 ₁ not to perform the discharge.
Thus, according to the result of comparing the potential generated in the power supply line due to the residual charge on each side of the output and input of the relay when the power is turned off, by controlling the discharge operation for the discharge circuit on the higher potential side, the output, There is no difference in potential generated in the power supply lines on each side of the input. Therefore, it is possible to prevent the occurrence of an inrush current caused by a residual charge when the power is turned on again.

The discharge control circuit of this embodiment (FIG. 2) is provided with a pair of comparators 131 and 132 as a circuit for comparing the potential generated in the power line on each side of the output and input of the relay 101 described above.
In this embodiment, each of the comparators 131 and 132 uses an operational amplifier. However, any means may be used as long as it is a means for comparing potentials, and is not limited to an operational amplifier. For example, the above-described CPU may function as a comparison unit.
The comparator 131 connects the + (plus) input terminal of the operational amplifier to the power supply line on the input side of the relay 101, and connects the − (minus) input terminal to the power supply line on the output side of the relay 101.
The comparator 132 connects the + input terminal of the operational amplifier to the power supply line on the output side of the relay 101, and connects the −input terminal to the power supply line on the input side of the relay 101.
Therefore, a signal indicating that a higher potential is generated from the operational amplifier of the comparator 131 if the potential on the input side is higher than that on the output side, and conversely if the potential on the output side is higher than that on the input side. Output, that is, high output.

Each of the discharge circuit (1) 130 ₁ and the discharge circuit (2) 130 ₂ performs a discharge operation when a high output is applied as a discharge control signal from the corresponding operational amplifier of the comparator 131 and the comparator 132.
Therefore, the input side has a higher potential than the output side, the discharge control signal of the High output from the operational amplifier of the comparator 131, when applied to the discharge circuit (1) 130 ₁ FET130s1 is, FET130s1 is turned on (conductive), the discharge Perform the action. This discharge operation stops when the input side becomes the same potential as the output side.
Conversely, the output side has a higher potential than the input side, the discharge control signal of the High output from the operational amplifier of the comparator 132, when applied to FET130s2 discharge circuit (2) 130 _2, FET130s2 is turned on (conductive), Discharge operation is performed. This discharging operation stops when the output side becomes the same potential as the input side.

Another element of the power supply circuit consumes power wastefully in a series of operations including the discharge of the residual charge that is performed to prevent the inrush current due to the charge remaining on the input and output sides of the relay 101. Rather, it is an element added in order to carry out at an appropriate timing.
The appropriate timing described above is to perform an operation of shutting off the SW / converter 201 of the power source 20 after the power to the drawer unit 30 is turned off by turning off the relay 101. That is, after the cut off SW · converter 201, the output of the relay, so that a difference in potential generated in the power supply line by the residual charge on each side of the input is eliminated, the discharge circuit (1) the residual charge of the high potential side 130 ₁ or It performs operations in the order of discharging by the discharge circuit (2) 130 _2.

In order to perform the operation according to the above-described order, a timing generation circuit 120 that receives the ON output of the interlock SW 21 s of the front door 21 common with the transistor 103 is provided.
The timing generation circuit 120 receives the ON output of the interlock SW 21 s of the front door 21, generates an operation timing according to the above-described order, and outputs a cutoff control to the SW / converter 201 at the generated timing.
When the power to the drawer unit 30 is turned on again by closing the front door 21, the relay 101 is turned on, and then the power from the SW / converter 201 of the power source 20 is restored. That is, the relay 101 is first turned on while the SW converter 201 is cut off, and then the operation is performed in the order in which the power from the SW converter 201 is restored.

Here, a supplementary explanation will be given regarding the discharge operation of the residual charge of the power supply circuit (FIG. 2).
In this power supply circuit, the power supply to the drawer unit 30 is turned on and off by turning the relay 101 off and on in conjunction with opening and closing of the front door 21.
When the power supply is turned off, since the capacitive elements 210 and 310 (capacitor 110) are provided on the input and output sides of the relay 101, residual charges are generated respectively.
In the prior art that does not have the discharge circuit of the present embodiment, an inrush current may be generated if the relay is turned on with residual charges remaining. Problems caused by this inrush current include fusing of a fuse inserted on a power supply line, welding of a relay contact, and reset of operation due to a voltage drop of a supply destination board. The reason why the operation is reset is that a large current flows, so that the GND potential of the supply-side substrate increases by the amount of current applied to the minute resistance of GND, which is equivalent to a voltage drop for the supply-destination substrate. is there. When this voltage drop becomes the monitoring voltage of the reset IC, a reset is caused.

In order to prevent the inrush current that causes the above-described problem, in the present embodiment, the residual charge on the higher potential side is discharged from the discharge circuit so that there is no difference in the potential generated in the power line due to the residual charge on each side of the output and input of the relay 101 (1) Discharge by 130 ₁ or discharge circuit (2) 130 ₂ .
This discharge operation is performed by using the outputs of the pair of comparators 131 and 132 that compare the output of the relay 101 and the potential generated by the residual charge on the power line on each side of the input as the discharge control signal.
That is, the pair of comparators 131 and 132 are connected to the + -input terminals of the comparators on the opposite sides of the power supply lines on the opposite sides, and the output terminals are connected to the discharge circuits on the respective sides. The corresponding discharge circuit is controlled by the high output of the comparator. By controlling the discharge operation, the discharge circuit on the side showing a higher voltage performs the discharge operation and stops the discharge operation when there is no potential difference.

The power supply cut-off performed in relation to the discharge operation is performed according to the following procedure.
After the relay 101 is turned off by opening the front door 21, the SW / converter 201 of the power supply 20 is first shut off according to the output of the timing generation circuit 120. Residual charges generated after the power supply is cut off are discharged by the discharge circuit on the side showing the higher potential among the discharge circuit (1) 130 ₁ and the discharge circuit (2) 130 ₂ .
This is because the procedure of the above-described operation is that if the discharge control operation is performed with the power supply 20 turned on, useless power is lost due to the discharge. That is, when performing the discharge control while power is applied, the potential of the input side is high, the discharging circuit (1) 130 ₁ of the input side is more likely to perform the discharge operation, to introduce until the power-off power This is to avoid such a condition. Further, there are cases where the residual charge on the input side can be suppressed so as not to become the maximum, and as a result, the conditions for preventing the inrush current can be quickly prepared.
As a procedure for the discharge control, when the higher potential side of the discharge circuits (1) 130 ₁ and (2) 130 ₂ discharges the residual charge, the output of the relay 101 and the power line on each side of the input are connected. The potential difference caused by the residual charge is reduced, and the high output of the comparator is not output. Therefore, the discharge circuit that is performing the discharge operation at this time stops this operation.

After the operation related to the opening of the front door 21 is performed, the front door 21 is closed again and the relay 101 is turned on. Then, the SW / converter 201 is released and power is supplied.
The reason for releasing the shut-off of the SW converter 201 after the relay 101 is turned on is that when the SW converter 201 starts power supply first, electric charge is accumulated in the capacitive element 210 on the relay input side, causing the inrush current to the relay 101 Because it becomes.
By performing the residual charge discharging operation at the above-described timing, normal power supply can be performed under conditions that can prevent the inrush current to the relay 101 caused by the charge remaining on the input and output sides of the relay 101. .

As described above, according to the present embodiment, in order to prevent the occurrence of an inrush current to the relay 101, the side showing the higher potential among the potentials generated by the residual charges on the power supply lines on the input and output sides of the relay 101. The discharging circuit performs a discharging operation and eliminates the potential difference on each side.
Since no current flows where there is no potential difference, it is not necessary to completely discharge the residual charges generated in the power supply line in this discharge operation. For this reason, the ON condition of the relay 101 that can prevent the inrush current in a short time can be satisfied. Therefore, even if the front door 21 that is manually opened / closed is opened and then immediately closed, the discharge operation is completed in a short time and the ON condition of the relay 101 is adjusted to prevent an inrush current. be able to.
Also, if there is no difference between the potentials generated on the power supply lines on the input and output sides of the relay 101, the ON condition of the relay 101 can be adjusted in the presence of residual charges, so the rise time of the load extraction unit 30 However, it can be shortened compared with the method in which the residual charge is completely discharged.

“Embodiment 2”
This embodiment adds a new element to the control of the discharge circuit in the power supply circuit (FIG. 2) of the first embodiment shown as the basic form.
Each of the discharge circuits (1) 130 ₁ and (2) 130 ₂ in the power supply circuit of the first embodiment includes resistors 130r1 and 130r2 connected to the power supply lines on the input side and output side of the relay 101, and an output terminal (source). FET is connected to FETs 130s1 and 130s2 that perform a switching operation with GND. Further, the switching operations of the FETs 130s1 and 130s2 are controlled by the high / low outputs of the corresponding comparators 131 and 132, respectively.
Here, the high / low outputs of the comparators 131 and 132 are the output of the relay 101, the higher side of the potential generated by the residual charge on the power line on each side of the input, and the high output is output, and this output is controlled to turn on the FET 130s1 or 130s2. Used for discharging. Accordingly, the potential generated in the power supply line on each side of the output and input by this discharge operation becomes substantially the same potential, and when the high output from the comparator 131 or 132 disappears, the discharge operation is finished.

However, the operation of discharging the charge by the high output from the comparator 131 or 132 is not necessarily performed until the high output disappears and the potential difference becomes zero. For example, the relay 101 may be turned on by closing the front door 21 while the potential difference does not become zero. In this case, the comparator 131 or 132 does not output Low. As described above, when the power is turned on again, the comparators 131 and 132 do not necessarily output a low level, and it may be unclear whether a high level or a low level is output.
When the comparator 131 or 132 outputs High when the relay is on, the discharge operation of the discharge circuit (1) 130 ₁ or (2) 130 ₂ that responds to the High output is turned on. Discharging occurs and consumes power that should not be consumed.

Therefore, in the power supply circuit of the present embodiment, when the relay 101 is turned on and the power supply 20 is turned on again during the above-described discharge operation for preventing an inrush current, the discharge circuit (1) 130 ₁ adds the discharge control circuit shown in the following turning off forcibly discharged any of (2) 130 _2.
The discharge control circuit in the present embodiment, the discharge circuit ₍₁₎ 130 1, form a (2) 130 ₂ FET130s1,130s2 off control output generating circuit for generating a control output for turning off the respective switching operations.
The off control output generation circuit receives a voltage generated when the interlock SW 21s is opened by closing the front door 21, that is, a control output voltage used to turn on the relay, and turns off the switching operation of each of the FETs 130s1, 130s2. Is generated.

FIG. 3 is a diagram showing a power supply circuit of the present embodiment having a circuit for controlling the FETs 130s1 and 130s2 that perform the on-control of the discharge operation of the residual charge when the relay is off, and the off-control when the relay is on.
3, in addition to the discharge control circuit that performs on-control of the FETs 130s1 and 130s2 by the outputs of the pair of comparators 131 and 132 shown in the first embodiment, the above-described off-control output generation circuit is provided as another discharge control circuit. ing.

The off control output generation circuit generates an applied voltage to each gate of the FET in order to turn off the FETs 130 s 1 and 130 s 2 that perform the switching operation in conjunction with the closing of the front door 21.
The off control output generation circuit of this embodiment sets the voltage of the input line so that the voltage of the input line connected from the pair of comparators 131 and 132 to the gates of the FETs 130s1 and 130s2 is equal to or less than the threshold value for turning off the FET. Configure as a voltage setting circuit.
In this voltage setting circuit, FETs 135 ₁ and 135 ₂ that perform switching operations with the output terminals connected to the gates of the FETs 130 s ₁ and 130 s ₂ via the resistors 136 ₁ and 136 ₂ as GND, and resistors 138 ₁ and 138 _{2, respectively.} Power supply 137 ₁ , 137 ₂ connected through the.
In addition, the interlock SW 21s is opened by closing the front door 21 so that the voltage setting circuit works in conjunction with the closing of the front door 21, and the voltage generated at that time is applied to the gate, whereby the FETs 135 ₁ and 135 ₂ are respectively connected. Turn on control. By turning on each of the FETs 135 ₁ and 135 ₂ , the voltage of the input line connected to each gate of the FETs 130 s ₁ and 130 s ₂ is set to the off control voltage. In this way, in conjunction with the closing of the front door 21, it is possible to perform the intended discharge control in which the FETs 130s1 and 130s2 that perform switching operation are turned off.

The above-described off control for the FETs 130s1 and 130s2 added in the present embodiment is performed immediately after each discharge circuit (1) when the power-on relay is turned on during the discharge control shown in the first embodiment for preventing the inrush current. ) 130 ₁ and (2) 130 ₂ are forcibly controlled off. By performing such control, it is possible to eliminate waste of power due to discharge of the input power, which occurs when the discharge circuits (1) 130 ₁ and (2) 130 ₂ are not turned off.
In the power supply circuit (FIG. 3) of the present embodiment, except for the configuration related to the discharge control for forcibly turning off the discharge to each discharge circuit (1) 130 ₁ and (2) 130 ₂ when the relay is on. The configuration is the same as that of the power supply circuit (FIG. 2) of the first embodiment. Therefore, for the configuration common to FIG. 2, the above description is referred to and the description is omitted here.

Here, a supplementary explanation will be given regarding the discharge control operation of the residual charge of the power supply circuit (FIG. 3).
In this power supply circuit, after the relay 101 is turned off, the power supply line having a higher potential among the pair of comparators 131 and 132 that compares the potential generated in the power supply line on each side of the output and input of the relay 101 due to the residual charge is + Set the comparator connected to the input to High output.
The high output of the comparator 131 or 132 performs on-control of the FET 130s1 or 130s2 that responds to this output, and discharges the remaining charges. This discharge operation ends when the difference in potential generated between the output of the relay 101 and the power supply line on each side of the input becomes almost zero. However, while the potential difference still exists and the comparator 131 or 132 is outputting High. The relay 101 may be turned on when the front door 21 is closed.
When the relay is turned on by closing the front door and the power is turned on again, if the discharge operation of the discharge circuit (1) 130 ₁ or (2) 130 ₂ is turned on by the high output of the comparator 131 or 132, the power to be turned on is discharged. End up.

As the such inconvenience does not occur, in the present embodiment, in conjunction with the closing of the front door 21 and discharge circuit (1) is turned off 130 ₁ and (2) 130 ₂ of the discharge operation.
This off operation operates a circuit that generates a voltage to be applied to the gate of the FET 130s1 or 130s2 through the switching operation of the FETs 135 ₁ and 135 ₂ by the voltage generated in response to the closing of the front door 21, and a generated value Is set to turn off the FET.
Therefore, the time required for the off operation can be performed in a considerably short time compared to the time required for the on operation of the relay 101 performed via the electromagnetic coil in conjunction with the closing of the front door 21.
Thus, each discharge circuit ₍₁₎ 130 1 before turning on the relays 101, (2) 130 ₂ it is possible to turn off the power supply to the discharge circuit ₍₁₎ 130 1, (2) 130 ₂ is turned on again There is no wasteful discharge.

“Embodiment 3”
In this embodiment, the discharge circuit is modified in the power supply circuit of the first embodiment shown as the basic form.
In the power supply circuit of the first embodiment (FIG. 2), the potential generated in the power supply lines on the input and output sides of the relay 101 due to the residual charge is compared by the pair of comparators 131 and 132, and is generated in one comparator when there is a potential difference. High output is used for discharge control.
The discharge circuits (1) 130 ₁ and (2) 130 ₂ apply the outputs from the corresponding comparators 131 and 132 to the gates of the FETs 130s1 and 130s2, respectively, turn on (conduct) in response to the High output, and turn off in response to the Low output. The discharge control is performed by this operation.
In this discharge operation, since the sources of the FETs 130s1 and 130s2 connected to the power supply lines on the respective sides of the relay input and output via the resistors 130r1 and 130r are set to GND, the residual charge of the power supply line is changed to GND by the on control of the FETs 130s1 and 130s2. It will be the action to flow.

However, the values of the currents flowing through the FETs 130s1, 130s2 and the resistors 130r1, 130r differ depending on the potential of the power supply line on each side of the relay input and output due to residual charges. The largest current flows when the voltage is maximum. Therefore, as these elements constituting the discharge circuits (1) 130 ₁ and (2) 130 ₂ , a maximum voltage (current) value is assumed and a normal operating state can be maintained with respect to the assumed value. Use things.
For this reason, it is necessary to select FETs 130s1, 130s2 and resistors 130r1, 130r having large ratings. However, elements with a high rating are generally large in size and high in cost.

Therefore, as a component of the discharge circuit of the present embodiment, a circuit having a configuration described below that can use elements having a lower rating than the FETs 130s1 and 130s2 and the resistors 130r1 and 130r constituting the discharge circuit of FIG. Is adopted.
In the present embodiment, a circuit that performs a discharge operation with a constant current is used as the discharge circuit that meets the above-described purpose.
The circuit of this embodiment that performs a discharge operation with a constant current controls the FET on by applying a high output from one of the pair of comparators 131 and 132 to the residual charge of the power supply line on each side of the input and output of the relay 101. In the point of performing the operation of flowing to GND, it is the same as in the first embodiment.
However, the circuit for performing the discharge operation of the present embodiment has an additional element for performing the discharge operation with a constant current. The embodiment of the additional element will be described in detail with reference to FIG.

FIG. 4 is a diagram showing a power supply circuit according to the present embodiment having a circuit for performing an operation for discharging a charge remaining when the relay is turned off with a constant current.
The power supply circuit of FIG. 4 is a constant current circuit (1) 140 as a discharge circuit in which the discharge is controlled by the outputs of the pair of comparators 131 and 132 and the discharge operation is performed with a constant current, instead of the discharge circuit of the first embodiment. having ₁ and (2) 140 _2.

The constant current circuit (1) 140 ₁ includes an FET 140m ₁ and a resistor 140r ₁ as a circuit for discharging the electric charge of the power supply line on the input side of the relay 101. FET140m ₁ is connecting the source to the power supply line and GND via a resistor 130r1 that connects to the drain.
The constant current circuit (1) 140 ₁ has an operational amplifier 140a ₁ for performing a constant current operation. Operational amplifier 140a ₁ is connect the + input terminal to the output terminal of the comparator 131, - connecting the input terminal to the drain of FET140m _1.
Input, compares the output potential of each side of the power supply lines, the comparator 131 is the High output when the input side is higher, FET140m ₁ receives this output that turned on to discharge the input side of the residual charge from the drain. At this time, a voltage corresponding to the current flowing from the drain of FET140m ₁ is comparator 131 - since it is negatively fed back through the input terminal, the current flowing out of the drain is constant.

The constant current circuit (2) 140 _2, as with the constant current circuit (1) 140 _1, constituting a circuit consisting FET140m _2, resistor 140r ₂ and the operational amplifier 140a _2.
Therefore, the input, compares the output potential of each side of the power supply lines, the comparator 132 is the High output when the output side is higher, since FET140m ₂ receives this output is turned on, discharges the output side of the residual charge from the drain To do. At this time, since the voltage corresponding to the current flowing out from the drain of the FET 140m ₂ is negatively fed back through the negative input terminal of the comparator 132, the current flowing out from the drain becomes constant.

In the power supply circuit of this embodiment (FIG. 4), the discharge is controlled by the outputs of the pair of comparators 131 and 132, and constant current circuits (1) 140 ₁ and (2) 140 ₂ that perform a discharge operation with a constant current. Other than the above, the configuration is the same as that of the power supply circuit of the first embodiment (FIG. 2). Therefore, for the configuration common to FIG. 2, the above description is referred to and the description is omitted here.

As described above, in the present embodiment, the higher side of the discharge circuit provided on each of the input and output sides is eliminated so as to eliminate the potential difference between the power lines on the relay input side and the output side due to the residual charge. The second embodiment is the same as the first embodiment in that a discharge control operation is performed to turn on the discharge.
However, since this embodiment is a circuit that performs the discharge operation with a constant current, the current flowing through the FET and the resistor, which are the components of the circuit, can be controlled to be constant regardless of the amount of remaining charge. This is different from the first embodiment in which a current corresponding to a potential generated by the amount of remaining charge flows through the FET and the resistor.

Therefore, according to this embodiment, it is only necessary to select a rated FET or resistor suitable for the operating current determined as the constant current circuit specification, and select a rating smaller than the rating when selected according to the maximum residual charge amount. This gives merit in size and cost.
In addition, since the constant current circuit system of the present embodiment allows a constant current to flow, the time until the discharge is completed is easier to control than the system in which the FET simply performs the switching operation without performing the constant current control in the first embodiment. is there. In this respect, there is an advantage of using a constant current circuit.

10 .... Power supply circuit board, 20 ... Power supply, 21 ... Front door, 21s ... Interlock SW, 30 ... Drawer unit, 101 ... Relay, 103 ... Transistor, 110 ... Capacitor, 120 ... Timing generation circuit, 130 ₁ .. discharge circuit (1), 130 ₂ .. discharge circuit (2), 130 s 1, 130 s ₂ , 135 ₁ , 135 ₂ , 140 m ₁ , 140 m ₂ ... FET, 131, 132. ₁ · constant current circuit (1), 140 ₂ ... constant current circuit _(2), 140a 1, 140a ₂ ... op, 201 ... SW · converter, 210, 310 ... capacitive element.

Japanese Patent Laid-Open No. 2008-9060

Claims (7)

A power supply circuit, a load circuit that receives power supply from the power supply, and on / off control of input power from the power supply according to a change in the state of the device, and circuit opening / closing means that outputs power from the power supply to the load circuit when the power is on An electrical device having
A potential comparing means for comparing a potential generated in the power supply line on the input side of the switching means of the circuit with a potential generated in the power supply line on the output side of the switching means of the circuit, and indicating a higher potential side;
A first discharge circuit connected to a power line on the input side of the circuit opening / closing means and capable of turning on / off a discharge operation;
A second discharge circuit connected to the power supply line on the output side of the circuit opening / closing means and capable of turning on / off the discharge operation;
In a state where the circuit opening / closing means is turned off, when the potential comparison means indicates that the input side is at a higher potential, the discharge operation of the first discharge circuit is controlled to be turned on and output by the potential comparison means When the side is instructed to be at a higher potential, by controlling the discharge operation of the second discharge circuit, the remaining charge is discharged, and the potential generated in the power line on the input side and the output side electrical device having a first discharge control circuit you reduce the difference between the results to the power supply line potential. The electrical device according to claim 1,
Each of the first discharge circuit and the second discharge circuit includes a switching element that operates according to an output of the potential comparison unit, and performs an on / off control of a discharge operation by the operation of the switching element. The electric device according to claim 1 or 2,
An electrical apparatus comprising: a second discharge control circuit that performs off control of a discharge operation of each circuit of the input-side discharge circuit and the output-side discharge circuit in a state where the circuit opening / closing means is turned on. An electric device according to any one of claims 1 to 3,
An electrical device in which each of the first discharge circuit and the second discharge circuit performs a discharge operation with a constant current. The electrical equipment according to any one of claims 1 to 4,
An electrical device in which the state change of the device is an opening of a door provided in a housing of the device. The electrical apparatus according to claim 1, wherein the electrical apparatus is an image forming apparatus having means for forming an image using a recording material on a recording medium. A power supply circuit, a load circuit that receives power supply from the power supply, and on / off control of input power from the power supply according to a change in the state of the device, and circuit opening / closing means that outputs power from the power supply to the load circuit when the power is on A residual charge discharging method in an electrical device having,
Compared to the potential generated in the power supply line on the input side of the switching means of the circuit and the potential generated in the power supply line on the output side of the switching means of the circuit due to the charge remaining in the state where the switching means of the circuit is turned off, the higher A potential comparison step for indicating the potential side;
When the potential comparison process indicates that the potential generated in the power supply line on the input side is higher, the residual charge generated on the input side of the circuit opening / closing means can be turned on / off in the discharge circuit. On the other hand, when it is instructed that the potential generated in the power supply line on the output side is higher in the potential comparison step, the residual charge generated on the output side of the switching means of the circuit is turned on. , is discharged by the oN control of the off can discharge circuit, the input side of the residual charge and a residual charge discharging process reduce a difference between the potential generated in the power supply line and the potential generated in the power supply line of the output-side Discharge method.

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