JP2021061682A - Power supply device, image formation device and input overvoltage protection method of power supply device - Google Patents

Abstract

To suppress development of degradation in a smoothing capacitor.SOLUTION: The power supply device includes: a rectifier circuit for rectifying an alternating current; a smoothing capacitor for smoothing the voltage rectified by the rectifier circuit; and an inrush current prevention circuit for preventing an inrush current from invading into the smoothing capacitor. The power supply device further includes a detection circuit for detecting a voltage applied to a resistor provided between the rectifier circuit and the smoothing capacitor. The power supply device further includes a cutoff circuit which, when a voltage detected by the detection circuit is less than a voltage determination value, connects the smoothing capacitor with the rectifier circuit and when the voltage detected by the detection circuit is the voltage determination value or higher, releases the connection of the smoothing capacitor to the rectifier circuit with the detection circuit as a drive source to cut off invasion of an electric current into the smoothing capacitor. The power supply device includes a cutoff hold circuit which, after the cutoff circuit releases the connection of the smoothing capacitor with the rectifier circuit, maintains a cutoff state with the cutoff circuit by applying a voltage for operating the detection circuit to the detection circuit as the drive source.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power supply device, an image forming device, and an input overvoltage protection method for the power supply device.

Patent Document 1 describes a rectifying unit that rectifies AC, a smoothing unit that smoothes the voltage output from the rectifying unit (hereinafter referred to as "smoothing capacitor"), and a rectifying unit and a smoothing capacitor for the purpose of protecting the smoothing capacitor from overvoltage. A switching unit that switches between connection and disconnection, an overvoltage detection unit that detects the overvoltage of the voltage applied to the smoothing capacitor, and a connection state between the rectifier unit and the smoothing capacitor when the overvoltage detection unit detects an overvoltage. A power supply device having a switching control unit for opening a capacitor is disclosed. The power supply device disclosed in Patent Document 1 employs a configuration in which the connection state between the rectifying unit and the smoothing capacitor is opened when an overvoltage applied to the smoothing capacitor is detected.

However, in the power supply device disclosed in Patent Document 1, it takes a certain period of time from the start of application of the voltage to the smoothing capacitor until the voltage reaches a value determined to be an overvoltage. Therefore, even if a voltage exceeding the withstand voltage of the smoothing capacitor is momentarily applied during the time, the connection state between the rectifying unit and the smoothing capacitor cannot be opened until the time elapses, and the smoothing capacitor deteriorates. There was a problem that there was a possibility that

In view of the above problems, the present invention can suppress the progress of deterioration of the smoothing capacitor.

In view of the above problems, the power supply device according to the present invention includes a rectifier circuit that rectifies alternating current, a smoothing capacitor that smoothes the voltage rectified by the rectifier circuit, and an inrush current that prevents inrush current from flowing into the smoothing capacitor. It is equipped with a prevention circuit. The power supply device includes a detection circuit that detects a voltage applied to a resistor provided between the rectifier circuit and the smoothing capacitor. The power supply device connects the smoothing capacitor to the rectifier circuit when the voltage detected by the detection circuit is less than the voltage determination value, and when the voltage detected by the detection circuit is equal to or more than the voltage determination value, the detection A cutoff circuit is provided which uses the circuit as a drive source to open the connection of the smoothing capacitor to the rectifier circuit and cut off the inflow of current into the smoothing capacitor. In the power supply device, after the cutoff circuit opens the connection of the smoothing capacitor to the rectifier circuit, a voltage for operating the detection circuit is applied to the detection circuit as a drive source to cut off by the cutoff circuit. It is provided with a cutoff holding circuit for holding the state.

According to the present invention, there is an effect that the progress of deterioration of the smoothing capacitor can be suppressed.

It is a figure which shows the structural example of the power-source device which concerns on Embodiment 1 of this invention. It is a figure which shows the structural example of the detection circuit and the inrush current prevention circuit shown in FIG. It is a timing chart for demonstrating the operation of the power-source device which concerns on Embodiment 1 of this invention. It is a flowchart for demonstrating operation of the power-source device which concerns on Embodiment 1 of this invention. It is a figure which shows the path of the current which flows when the cutoff holding circuit is closed. It is a figure which shows the structural example of the power-source device which concerns on a comparative example. It is a timing chart for demonstrating the operation of the power-source device which concerns on a comparative example. It is a figure which shows the structural example of the power-source device which concerns on Embodiment 2 of this invention. It is a timing chart for demonstrating the operation of the power-source device which concerns on Embodiment 2 of this invention. It is a flowchart for demonstrating operation of the power-source device which concerns on Embodiment 2 of this invention. It is a figure which shows the structural example of the power-source device which concerns on Embodiment 3 of this invention. It is a figure which shows the structural example of the detection circuit and the inrush current prevention circuit shown in FIG. It is a flowchart for demonstrating operation of the power-source device which concerns on Embodiment 3 of this invention. It is a figure which shows the structural example of the power-source device which concerns on 1st modification of Embodiments 1-3 of this invention. It is a figure which shows the structural example of the power-source device which concerns on 2nd modification of Embodiments 1-3 of this invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a configuration example of a power supply device, an image forming device, and an input overvoltage protection method for the power supply device according to the first embodiment of the present invention. FIG. 2 is a diagram showing a configuration example of the detection circuit and the inrush current prevention circuit shown in FIG.

The power supply device 100-1 is, for example, a power conversion device that converts a single-phase alternating current supplied from a commercial power source into a direct current and inputs it to a load. The load is, for example, an inverter 8 that converts a DC voltage into an AC voltage. The load may be a device or a machine that inputs a DC voltage, and may be, for example, a DC / DC converter that converts a DC voltage into a DC voltage having a desired voltage value and outputs the load, in addition to the inverter 8.

The power supply device 100-1 includes a power plug 2, a rectifier circuit 9, a positive electrode side DC bus P, a negative electrode side DC bus N, and a smoothing capacitor 3 as functions for converting a DC voltage into an AC voltage.

Further, the power supply device 100-1 includes an inrush current prevention circuit 6 and an overvoltage suppression unit 20. The overvoltage is a voltage having an abnormal value that exceeds the withstand voltage of the smoothing capacitor 3, and when an overvoltage is applied to the smoothing capacitor 3, deterioration of the smoothing capacitor 3 may progress.

The power plug 2 is, for example, a plug plug that is inserted into an outlet 1 to which a single-phase AC voltage from a commercial power source is supplied. The power plug 2 includes, for example, a housing gripped by the user's hand, two metal flat plug blades protruding from the housing, and first AC wiring 2a and 2 connected to one of the two flat plug blades. It is provided with a second AC wiring 2b connected to the other of the two flat plug blades.

The rectifier circuit 9 is, for example, a single-phase full-wave rectifier circuit configured by combining four diodes. The rectifying circuit 9 is not limited to a configuration in which four diodes are combined, and may be configured in combination with a MOSFET (Metal Oxide Semiconductor-Field Effect Transistor) which is a metal oxide semiconductor field effect transistor.

The rectifier circuit 9 includes a first input terminal 9a to which the first AC wiring 2a is connected, a second input terminal 9b to which the second AC wiring 2b is connected, and a first output terminal to which the positive DC bus P is connected. 9c and a second output terminal 9d connected to the inrush current prevention circuit 6 and the detection circuit 4 are provided. The first input terminal 9a and the second input terminal 9b are electrically connected to the outlet 1 via the first AC wiring 2a and the second AC wiring 2b. The first output terminal 9c is connected to one end 7a of the cutoff holding circuit 7 and one end of the smoothing capacitor 3 via the positive electrode side DC bus P.

The inrush current prevention circuit 6 is a circuit that prevents the inrush current from flowing into the smoothing capacitor 3. As shown in FIG. 2, the inrush current prevention circuit 6 is connected in parallel to, for example, a resistor 6a that attenuates the inrush current that flows into the smoothing capacitor 3 immediately after the power plug 2 is inserted into the outlet 1, and a resistor 6a. The relay unit 6b is provided. For example, since the relay unit 6b is in the open state until a certain time (for example, several tens of ms to several hundreds ms) elapses from the time when the power plug 2 is inserted into the outlet 1, a current flows through the resistor 6a. As a result, the inrush current is suppressed. Then, when the time elapses and the inrush current is suppressed, the relay unit 6b is closed. As a result, a current path having an impedance lower than that of the resistor 6a is formed. Therefore, it is possible to suppress the power loss due to the current flowing through the resistor 6a during the steady operation of the load.

Since a specific configuration example of the inrush current prevention circuit 6 is known as disclosed in, for example, Japanese Patent No. 5933038 and Japanese Patent No. 6081039, detailed description thereof will be omitted below.

The overvoltage suppression unit 20 is a function for suppressing the voltage applied to the smoothing capacitor 3 due to the inrush current. The overvoltage suppression unit 20 includes a cutoff circuit 5, a cutoff holding circuit 7, and a detection circuit 4.

The cutoff circuit 5 is an opening / closing mechanism for cutting off the inflow of the inrush current into the smoothing capacitor 3. The cutoff circuit 5 is provided, for example, on the negative electrode side DC bus N.

One end 5a of the cutoff circuit 5 is connected to one end of the smoothing capacitor 3 and the inverter 8 via the negative electrode side DC bus N. The other end 5b of the cutoff circuit 5 is connected to the inrush current prevention circuit 6 via the negative electrode side DC bus N. The other end 5b of the cutoff circuit 5 is connected to the detection circuit 4 via the wiring 30. The cutoff circuit 5 includes, for example, a switch 5c and a solenoid 5d that drives the switch 5c. The switch 5c is a normally closed switch that is in a closed state when, for example, a drive signal from the detection circuit 4 is not input, and is in an open state when the drive signal is input.

When the voltage detected by the detection circuit 4 is less than the voltage determination value, the cutoff circuit 5 configured in this way maintains the electrical connection of the smoothing capacitor 3 to the rectifier circuit 9 without driving the switch 5c. To do. The voltage determination value is, for example, 200V in the case of a 100V system power supply and 418V in the case of a 200V system power supply.

When the voltage detected by the detection circuit 4 is equal to or higher than the voltage determination value, the cutoff circuit 5 sets the switch 5c to an open state, that is, a cutoff state by inputting a drive signal using the detection circuit 4 as a drive source. As a result, the electrical connection state of the smoothing capacitor 3 to the rectifier circuit 9 is opened, and the inflow of current to the smoothing capacitor 3 is cut off.

The time for the break circuit 5 to hold the open state is the time until the inrush current is suppressed (for example, about several tens of ms to several hundred ms). After the time has elapsed, the output of the drive signal from the detection circuit 4 is stopped, so that the switch 5c returns to the closed state. The cutoff circuit 5 is not limited to the solenoid type switching mechanism as long as it can cut off the inflow of the inrush current into the smoothing capacitor 3, and may be composed of a semiconductor switching element.

The cutoff holding circuit 7 is an opening / closing mechanism that supplies power for holding the open state in the cutoff circuit 5, that is, the cutoff state, to the detection circuit 4. One end 7a of the cutoff holding circuit 7 is connected to a DC bus (for example, a positive electrode side DC bus P). The other end 7b of the cutoff holding circuit 7 is connected to the detection circuit 4.

The cutoff holding circuit 7 has, for example, a switch 7c and a solenoid 7d for driving the switch 7c. The switch 7c is a normally open switch that is in an open state when, for example, a drive signal from the detection circuit 4 is not input, and is in a closed state when the drive signal is input. The solenoid 7d includes, for example, a coil that generates an electromagnetic force when a drive signal from the detection circuit 4 is input, and a plunger that drives the switch 7c by the electromagnetic force of the coil.

When the voltage detected by the detection circuit 4 is less than the voltage determination value, the cutoff holding circuit 7 configured in this way does not input the drive signal from the detection circuit 4, so the switch 7c is held in the open state and detected. No power is supplied to the circuit 4.

Further, when the voltage detected by the detection circuit 4 is equal to or higher than the voltage determination value, the cutoff holding circuit 7 controls the switch 7c to the closed state by inputting the drive signal from the detection circuit 4. As a result, even if power is not supplied to the detection circuit 4 via the cutoff circuit 5 and the wiring 30, power is supplied to the detection circuit 4 via the cutoff holding circuit 7.

The detection circuit 4 is a drive source for controlling the operation of the cutoff holding circuit 7, and is also a drive source for holding the open state of the switch 5c of the cutoff circuit 5. The detection circuit 4 includes, for example, a voltage detection unit 4a, a storage unit 4d, a power supply unit 4b, and a calculation unit 4c.

The voltage detection unit 4a detects the voltage applied to both ends of the resistor 6a of the inrush current prevention circuit 6, and inputs the voltage information indicating the value of the voltage to the calculation unit 4c.

The storage unit 4d is a memory composed of a RAM (Random Access Memory), a ROM (Read Only Memory), and the like. In the storage unit 4d, in addition to the voltage determination value used by the determination unit 4c1 of the calculation unit 4c, a program for realizing functions such as the determination unit 4c1 and the drive signal generation unit 4c2 of the calculation unit 4c is stored. There is. When the calculation unit 4c reads and executes the program, functions such as the determination unit 4c1 and the drive signal generation unit 4c2 are realized. Details of the determination unit 4c1 and the drive signal generation unit 4c2 will be described later.

The power supply unit 4b is connected to one end of the wiring 30. The other end of the wiring 30 is connected to the negative electrode side DC bus N. As a result, the power supply unit 4b is electrically connected to the negative electrode side DC bus N via the wiring 30. Further, the power supply unit 4b is connected to the other end 7b of the cutoff holding circuit 7. As a result, the power supply unit 4b is electrically connected to the positive electrode side DC bus P via the cutoff holding circuit 7. Therefore, power is supplied to the power supply unit 4b via the wiring 30 or the cutoff holding circuit 7. The power supply unit 4b is connected to one end of the wiring 30 and to the other end 7b of the cutoff holding circuit 7. As a result, the power supply unit 4b is electrically connected to the positive electrode side DC bus P via the cutoff holding circuit 7. Therefore, power is supplied to the power supply unit 4b via the cutoff holding circuit 7.

Since the cutoff circuit 5 and the cutoff holding circuit 7 are controlled by the drive signal generation unit 4c2 of the detection circuit 4 so as to operate complementarily to each other, for example, when the switch 5c of the cutoff circuit 5 is in the closed state, the wiring 30 Power is supplied to the power supply unit 4b via the power supply unit 4b. Further, when the switch 5c of the cutoff circuit 5 is in the open state, power is supplied to the power supply unit 4b via the cutoff holding circuit 7. The power supply unit 4b uses these electric powers to generate electric power for driving the voltage detection unit 4a and the calculation unit 4c.

The calculation unit 4c includes a determination unit 4c1 and a drive signal generation unit 4c2.

The determination unit 4c1 inputs, for example, the voltage determination value stored in the storage unit 4d and the voltage information from the voltage detection unit 4a. The determination unit 4c1 holds, for example, a voltage table in which the voltage information and the voltage value estimated from the voltage information are associated with each other, and when the voltage information is input, the determination unit 4c1 refers to the voltage table and obtains the voltage value corresponding to the voltage information. Ask. Then, the determination unit 4c1 compares the voltage value with the voltage determination value stored in the storage unit 4d to determine whether the voltage value is less than the voltage determination value or the voltage value is greater than or equal to the voltage determination value. To judge.

As a result of the determination, the determination unit 4c1 does not input the determination information to the drive signal generation unit 4c2 when the voltage value is less than the voltage determination value, and outputs the determination information when the voltage value is equal to or more than the voltage determination value. Input to the generation unit 4c2. The determination information is information indicating that the voltage applied to the smoothing capacitor 3 has reached an abnormal value.

When the determination information is input, the drive signal generation unit 4c2 generates a drive signal by using the electric power supplied from the power supply unit 4b. The drive signal is a DC voltage for exciting the coils of the solenoid 5d of the cutoff circuit 5 and the solenoid 7d of the cutoff holding circuit 7.

Next, the operation of the power supply device 100-1 will be described with reference to FIGS. 3 to 5.

FIG. 3 is a timing chart for explaining the operation of the power supply device according to the first embodiment of the present invention. The horizontal axis of FIG. 3 is time. In FIG. 3, in order from the top, the waveform of the voltage applied to the outlet 1, the state before and after the power plug 2 is inserted into the outlet 1, the voltage applied to the smoothing capacitor 3, and the inrush current prevention circuit 6 are applied. The voltage to be generated, the voltage detected by the detection circuit 4, the level of the drive signal, the state of the switch 5c of the cutoff circuit 5, and the state of the switch 7c of the cutoff holding circuit 7 are shown.

The voltage of the broken line applied to the outlet 1 represents a normal voltage value, that is, a value of a normal voltage generated from the outlet 1. The solid line voltage represents the voltage value at the time of abnormality, that is, the value of the abnormal voltage generated from the outlet 1.

The state before the power plug 2 is plugged into the outlet 1 is "OFF", and the state after the power plug 2 is plugged into the outlet 1 is "ON".

The drive signal “Low” represents the output level of the drive signal generation unit 4c2 when the drive signal is not generated, or a state in which the drive signal is not output. The drive signal "High" represents the output level of the drive signal generation unit 4c2 when the drive signal is generated, or a state in which the drive signal is being output.

The time t1 is the timing when the power plug 2 is plugged into the outlet 1. The time t2 represents the timing when the voltage applied to the inrush current prevention circuit 6 reaches the voltage determination value. The timing is equal to the timing at which the level of the drive signal changes from low level to high level. Further, the timing is equal to the time when the switch 5c of the cutoff circuit 5 changes from closed to open, and is equal to the time when the switch 7c of the cutoff holding circuit 7 changes from open to closed.

FIG. 4 is a flowchart for explaining the operation of the power supply device according to the first embodiment of the present invention. The timing at which step S1 shown in FIG. 4 is executed is, for example, when no voltage is applied to the DC bus, the switch 5c of the cutoff circuit 5 is closed, and the switch 7c of the cutoff holding circuit 7 is open. ..

When the power plug 2 is inserted into the outlet 1 at time t1 (step S1), the detection circuit 4 detects the voltage due to the inrush current (step S2). Further, in the detection circuit 4, it is determined whether or not the detected voltage is equal to or higher than the voltage determination value (step S3).

When the detected voltage is less than the voltage determination value (step S3, No), that is, in the period from the time t1 to the time t2 shown in FIG. 3, the detection circuit 4 closes the switch 5c of the cutoff circuit 5. Since the switch 7c of the cutoff holding circuit 7 is held in the open state while being held, the drive signal is not generated (step S31).

When the detected voltage is equal to or higher than the voltage determination value (steps S3, Yes), that is, when the time t2 shown in FIG. 3 is reached, the detection circuit 4 opens the switch 5c of the cutoff circuit 5 and holds the cutoff. A drive signal is generated to close the switch 7c of the circuit 7 (step S4).

The path of the current flowing through the power supply device 100-1 by the process of step S4 is shown in FIG. FIG. 5 is a diagram showing a path of a current flowing when the cutoff holding circuit is in the closed state.

When the switch 5c of the cutoff circuit 5 is in the open state and the switch 7c of the cutoff holding circuit 7 is in the closed state, the current A rectified by the rectifier circuit 9 is cut off and held as shown by the thick solid line in FIG. It flows to the detection circuit 4 via the circuit 7. As a result, after time t2, it is possible to prevent the smoothing capacitor 3 from being applied with a high voltage that exceeds the withstand voltage of the smoothing capacitor 3.

Returning to FIG. 4, for example, when a user who notices that the switch 5c is in the open state connects and disconnects the outlet 1, the processes after step S2 are repeated (step S5).

Next, the configuration and operation of the comparative example of the power supply device 100-1 will be described with reference to FIGS. 6 and 7. In the following, the same parts as those in the first embodiment are designated by the same reference numerals, the description thereof will be omitted, and different parts will be described.

FIG. 6 is a diagram showing a configuration example of a power supply device according to a comparative example. The power supply device 100A according to the comparative example includes a detection circuit 4A instead of the detection circuit 4, the cutoff holding circuit 7, and the wiring 30 of the power supply device 100-1.

The detection circuit 4A is connected in parallel to the smoothing capacitor 3 and detects the voltage applied to the smoothing capacitor 3. The detection circuit 4A determines whether the voltage applied to the smoothing capacitor 3 is less than the voltage determination value or greater than or equal to the voltage determination value. That is, the detection circuit 4A determines whether or not the voltage caused by the inrush current is equal to or higher than the voltage determination value based on the voltage applied to the smoothing capacitor 3 instead of the voltage applied to the inrush current prevention circuit 6. judge.

The detection circuit 4A has the same function as the drive signal generation unit 4c2 shown in FIG.
Specifically, when the detection circuit 4A determines that the voltage applied to the smoothing capacitor 3 is equal to or higher than the voltage determination value, the detection circuit 4A generates a drive signal for opening the switch 5c of the cutoff circuit 5.

FIG. 7 is a timing chart for explaining the operation of the power supply device according to the comparative example. The horizontal axis of FIG. 7 is time. In FIG. 7, in order from the top, the waveform of the voltage applied to the outlet 1, the state before and after the power plug 2 is inserted into the outlet 1, the voltage applied to the smoothing capacitor 3, and the inrush current prevention circuit 6 are applied. The voltage to be generated, the voltage detected by the detection circuit 4A, the level of the drive signal, and the state of the switch 5c of the cutoff circuit 5 are shown.

The voltage Vc of the smoothing capacitor 3 is expressed by the following equation (1). C is the capacitance of the smoothing capacitor 3, and i is the current flowing through the smoothing capacitor 3.

Vc (t) = (1 / C) × ∫i (t) ・ dt ・ ・ ・ (1)

As can be seen from the equation (1), the voltage Vc of the smoothing capacitor 3 increases in proportion to the integrated value of the current flowing through the smoothing capacitor 3. Therefore, as shown in FIG. 7, the voltage Vc of the smoothing capacitor 3 gradually rises from the time t1 when the charging of the smoothing capacitor 3 is started, and becomes the voltage determination value at the time t2 after a certain time elapses from the time t1. Reach the equivalent value. Therefore, even if an overvoltage that exceeds the withstand voltage of the smoothing capacitor 3 is momentarily applied between the time t1 and the time t2, it takes a certain period of time for the voltage Vc of the smoothing capacitor 3 to reach the voltage determination value. Needs.

Therefore, in the power supply device 100A according to the comparative example, even if an overvoltage is momentarily applied during this fixed time, the connection state between the rectifier circuit 9 and the smoothing capacitor 3 cannot be immediately opened, and the smoothing capacitor 3 Deterioration may progress.

On the other hand, the power supply device 100-1 according to the first embodiment can control the cutoff circuit 5 and the like by using the voltage applied to the inrush current prevention circuit 6. Therefore, when a voltage exceeding the withstand voltage of the smoothing capacitor 3 is momentarily applied, the cutoff circuit 5 or the like can be controlled to cut off the current flowing into the smoothing capacitor 3. Therefore, the progress of deterioration of the smoothing capacitor 3 can be suppressed.

As a result, the reliability of the power supply device 100-1 is improved, the high-quality power supply device 100-1 can be provided to the user, and the maintenance cost can be significantly reduced. Further, since the voltage fluctuation caused by the deterioration of the smoothing capacitor 3 is suppressed, stable operation of the load can be guaranteed.

The power supply device 100-1 uses the voltage applied to the resistor 6a of the inrush current prevention circuit 6, but a shunt resistor is provided on the DC bus and the voltage generated across the shunt resistor is used. You may. In this case, since a shunt resistor for voltage detection can be provided at an arbitrary position on the DC bus, the design conditions of the power supply device 100-1 can be given a degree of freedom.

Further, the power supply device 100-1 is provided with a shunt resistor separately by using a resistor 6a (a resistor provided in the inrush current prevention circuit 6) of the inrush current prevention circuit 6 instead of the shunt resistance. A resistor 6a for suppressing the inrush current can be used without this. Therefore, the configuration of the power supply device 100-1 can be simplified, the reliability of the power supply device 100-1 can be improved, and an increase in the manufacturing cost of the power supply device 100-1 can be suppressed.

Embodiment 2
FIG. 8 is a diagram showing a configuration example of the power supply device according to the second embodiment of the present invention. In the following, the same parts as those in the first embodiment are designated by the same reference numerals, the description thereof will be omitted, and different parts will be described.

The power supply device 100-2 according to the second embodiment includes a resistor 10 connected in parallel to the smoothing capacitor 3 in addition to the configuration of the power supply device 100-1. One end of the resistor 10 is connected to one end of the smoothing capacitor 3 and the positive electrode side DC bus P, and the other end of the resistor 10 is connected to the other end of the smoothing capacitor 3 and the negative electrode side DC bus N.

Next, the operation of the power supply device 100-2 will be described with reference to FIGS. 9 and 10.

FIG. 9 is a timing chart for explaining the operation of the power supply device according to the second embodiment of the present invention. The horizontal axis of FIG. 9 is time. In FIG. 9, in order from the top, the waveform of the voltage applied to the outlet 1, the state before and after the power plug 2 is inserted into the outlet 1, the voltage applied to the smoothing capacitor 3, and the inrush current prevention circuit 6 are applied. The voltage to be generated, the voltage detected by the detection circuit 4, the level of the drive signal, the state of the switch 7c of the cutoff holding circuit 7, and the state of the switch 5c of the cutoff circuit 5 are shown.

FIG. 10 is a flowchart for explaining the operation of the power supply device according to the second embodiment of the present invention. In the flowchart of FIG. 10, step S41 is added between steps S4 and S5. Since the processing of the other steps is the same as the operation described in the first embodiment, the description thereof will be omitted.

When the drive signal is generated based on the determination information in step S4, the switch 5c is opened. As a result, charging of the smoothing capacitor 3 is stopped, and the smoothing capacitor 3 is discharged by the resistor 10 (step S41). That is, the electric charge stored in the smoothing capacitor 3 is consumed by the resistor 10.

As a result, the voltage of the smoothing capacitor 3 gradually decreases as shown by the arrow indicated by the reference numeral A in FIG.

The voltage change rate dVc / dt of the voltage Vc when the smoothing capacitor 3 is charged is expressed by Eq. (2). Ic is the discharge current and C is the capacitance of the smoothing capacitor 3.

dVc / dt = Ic / C ... (2)

Then, when a certain time elapses from the time t2, all the charges of the smoothing capacitor 3 are discharged, so that the voltage of the smoothing capacitor 3 becomes a value equivalent to the voltage value before the time t1.

When the user notices an abnormality in the power supply device 100-2 when the voltage of the smoothing capacitor 3 drops in this way and pulls out the power plug 2 from the outlet 1 at time t3, the smoothing capacitor 3 is discharged by the resistor 10. , The voltage detected by the detection circuit 4 drops below the voltage determination value. Then, when the power plug 2 is plugged into the outlet 1 again at time t4, the voltage of the smoothing capacitor 3 drops, so that the inrush current flows again. Therefore, the voltage of the smoothing capacitor 3 rises again. At this time, since the voltage of the smoothing capacitor 3 is sufficiently lowered between the time t2 and the time t3, it is not added to the voltage value at the time t2. After that, when the voltage of the smoothing capacitor 3 rises and reaches the voltage determination value at time t5, the drive signal changes from Low to High, so that the switch 5c is opened.

According to the power supply device 100-2 according to the second embodiment, even if the user notices an abnormality in the power supply device 100-2 and the power plug 2 is inserted or removed, the resistor 10 discharges the charge of the smoothing capacitor 3. Since the power is turned on again after the power is turned on, it is possible to suppress the application of a high voltage exceeding the withstand voltage of the smoothing capacitor 3. Therefore, in addition to the effect of the first embodiment, a structure robust to the user's operation of inserting and removing the power plug 2 can be obtained.

Embodiment 3
FIG. 11 is a diagram showing a configuration example of the power supply device according to the third embodiment of the present invention. In the following, the same parts as those in the first embodiment are designated by the same reference numerals, the description thereof will be omitted, and different parts will be described. The configuration of the third embodiment can be combined with the second embodiment.

The overvoltage suppression unit 20 of the power supply device 100-3 according to the third embodiment includes a detection circuit 4B instead of the detection circuit 4. Further, the power supply device 100-3 according to the third embodiment includes a display means 11.

The display means 11 is, for example, an LCD (Liquid Crystal Display), an organic EL (Electroluminescence) display, or the like that displays information set in the power supply device 100-3, operating state information of the power supply device 100-3, and the like.

Next, the configuration of the detection circuit 4B and the like will be described with reference to FIG.

FIG. 12 is a diagram showing a configuration example of the detection circuit and the inrush current prevention circuit shown in FIG. The difference from the detection circuit 4 of FIG. 2 is that the detection circuit 4B includes a display control unit 4e in addition to the configuration of the detection circuit 4.

Next, the operation of the power supply device 100-3 will be described with reference to FIG.

FIG. 13 is a flowchart for explaining the operation of the power supply device according to the third embodiment of the present invention. In the flowchart of FIG. 13, step S42 is added between steps S4 and S5. Since the processing of the other steps is the same as the operation described in the first embodiment, the description thereof will be omitted.

When the drive signal is generated based on the determination information in step S4, in step S42, the display control unit 4e of the calculation unit 4c determines that an abnormal value voltage has been applied to the smoothing capacitor 3 based on the determination information. The indicated notification information is generated and input to the display means 11. The display means 11 displays that a voltage having an abnormal value is applied to the smoothing capacitor 3 based on the notification information from the display control unit 4e. The display is performed, for example, by lighting an icon notifying the abnormality on the screen of the display means 11.

According to the power supply device 100-3 of the third embodiment, the display means 11 can display that an abnormal value voltage has been applied to the smoothing capacitor 3, so that the display means 11 indicates that the abnormal voltage has been applied. It can notify the user. Therefore, the user can know that an abnormal value voltage has been applied to the smoothing capacitor 3. Therefore, for example, the user records the number of occurrences of an abnormal value voltage in the past, and the smoothing capacitor which may be deteriorated at the next periodic inspection of the power supply device 100-3. By taking measures such as replacing 3 as soon as possible, it is possible to prevent the power supply device 100-3 from being stopped due to a failure.

FIG. 14 is a diagram showing a configuration example of a power supply device according to the first modification of the first to third embodiments of the present invention. In the power supply device 100B according to the first modification, the inrush current prevention circuit 6 is provided in the second AC wiring 2b of the power supply plug 2.

The power supply device 100B according to the first modification includes an overvoltage suppression unit 20A instead of the overvoltage suppression unit 20 of the first to third embodiments. The overvoltage suppression unit 20A includes a rectifier circuit 12 for the detection circuit 4 in addition to the configuration of the overvoltage suppression unit 20.

The rectifier circuit 12 is, for example, a single-phase full-wave rectifier circuit configured by combining four diodes. The rectifier circuit 9 is not limited to a configuration in which four diodes are combined, and may be configured by combining MOSFETs.

The first input terminal 12a of the rectifier circuit 12 is connected between the inrush current prevention circuit 6 and the second input terminal 9b of the rectifier circuit 9. The second input terminal 12b of the rectifier circuit 12 is connected to the second AC wiring 2b. The first output terminal 12c of the rectifier circuit 12 is connected to the detection circuit 4 and the other end 7b of the cutoff holding circuit 7. The second output terminal 12d of the rectifier circuit 12 is connected to the detection circuit 4, the solenoid 7d of the cutoff holding circuit 7, and 5d of the cutoff circuit 5. The current rectified by the rectifier circuit 12 flows through the detection circuit 4.

According to the power supply device 100B, the inrush current prevention circuit 6 is arranged between the power supply plug 2 and the rectifier circuit 9, so that the rectifier circuit 12 is required. That is, when the inrush current prevention circuit 6 is arranged between the power plug 2 and the rectifier circuit 9, the inrush current is not rectified, so that a separate rectifier circuit 12 is required for voltage detection.

On the other hand, as in the power supply devices 100-1 to 100-3 according to the first to third embodiments, the inrush current is rectified by providing the inrush current prevention circuit 6 between the rectifier circuit 9 and the smoothing capacitor 3. Since it is rectified by the circuit 9, the rectifier circuit 12 becomes unnecessary. Therefore, the configuration of the power supply devices 100-1 to 100-3 is simplified, the reliability of the power supply devices 100-1 to 100-3 is improved, and the high-quality power supply devices 100-1 to 100-3 are provided to the user. At the same time, maintenance costs can be significantly reduced.

FIG. 15 is a diagram showing a configuration example of a power supply device according to a second modification of the first to third embodiments of the present invention. The power supply device 100C according to the second modification includes a detection circuit 4C. The detection circuit 4C includes a detection determination unit 40 and a power supply unit 41. The detection determination unit 40 includes a series connector formed by directly connecting two resistors R1 and R2. One end of the series connector is connected to the cutoff holding circuit 7 and the wiring 30. The other end of the series connection is connected to the rectifier circuit 9, the solenoid 5d, and the solenoid 7d.

A predetermined voltage value (voltage determination value) is set by the voltage division ratio between the resistor R1 and the resistor R2. Specifically, for example, the voltage applied to both ends of the series connector is E, the voltage applied to the resistor R1 is V1, the voltage applied to the resistor R2 is V2, and the resistance value of the resistor R1 is r1. When the resistance value of the resistor R2 is r2, the value of V2 is expressed by the equation (3).

V2 = E ・ R2 / (R1 + R2) ・ ・ ・ (3)

The voltage V2 applied to the resistor R2 is applied to the switch 5c and the switch 7c. Therefore, a voltage determination value is set by the voltage division ratio between the resistor R1 and the resistor R2, and when a voltage V2 equal to or greater than this voltage determination value is generated, the switch 5c and the switch 7c can be operated. That is, the switch 5c and the switch 7c are changed from the open state to the closed state, or from the closed state to the open state.

One end of the power supply unit 41 is connected to the connection point 40a of the two resistors R1 and R2, and the other end is connected to the rectifier circuit 9. The power supply unit 41 is connected in parallel with the resistor R, and the solenoid 5d and the solenoid 7d are further connected in parallel. When an abnormal inrush current flows, power is supplied to the power supply unit 41 via the wiring 30, and after the switch 5c is operated, power is supplied to the power supply unit 41 via the switch 7c.

According to the power supply device 100C according to the second modification, since the detection circuit 4C can be manufactured by using a general-purpose circuit component such as a resistor, the calculation unit 4c and the storage unit 4d shown in FIG. 2 are not required. The structure can be simplified. Therefore, the reliability of the power supply device 100C is improved, and a high quality power supply device 100C can be provided to the user.

The power supply devices 100-1 to 100-3 according to the first to third embodiments can be provided in the image forming apparatus.

In the input overvoltage protection method of the power supply devices 100-1 to 100-3 according to the first to third embodiments, the power supply device is rectified by a rectifier circuit that rectifies alternating current and the rectifier circuit when the power plug is inserted into the outlet. The step of detecting the voltage applied to the resistor provided between the smoothing capacitor for smoothing the voltage, and the smoothing capacitor to the rectifier circuit when the detected voltage becomes equal to or higher than the voltage determination value. Includes a step of opening the connection of the above and putting a breaking circuit that cuts off the inflow of current into the smoothing capacitor into a breaking state. As a result, the existing inrush current prevention circuit 6 can be used to cut off the current flowing into the smoothing capacitor 3, and the progress of deterioration of the smoothing capacitor 3 can be suppressed.

1: Outlet 2: Power plug 2a: 1st AC wiring 2b: 2nd AC wiring 3: Smoothing capacitors 4, 4A, 4B, 4C: Detection circuit 4a: Voltage detection unit 4b: Power supply unit 4c: Calculation unit 4c1: Judgment unit 4c2: Drive signal generation unit 4d: Storage unit 4e: Display control unit 5: Breaking circuit 5a: One end 5b: Other end 5c: Switch 5d: Solvent 6: Inrush current prevention circuit 6a: Resistor 6b: Relay part 7: Breaking hold Circuit 7a: One end 7b: Other end 7c: Switch 7d: Solvent 8: Inverter 9: Rectifier circuit 9a: First input terminal 9b: Second input terminal 9c: First output terminal 9d: Second output terminal 10: Resistor 11 : Display means 12: Rectifier circuit 12a: First input terminal 12b: Second input terminal 12c: First output terminal 12d: Second output terminal 20, 20A: Overvoltage suppression unit 30: Wiring 40: Detection determination unit 40a: Connection point 41: Power supply unit 100-1, 100-2, 100-3, 100A, 100B: Power supply device N: DC bus P on the negative side: DC bus R1, R2 resistors on the positive side

Japanese Unexamined Patent Publication No. 2016-163537

Claims (7)

A rectifier circuit that rectifies alternating current and
A smoothing capacitor that smoothes the voltage rectified by the rectifier circuit,
An inrush current prevention circuit that prevents the inrush current from flowing into the smoothing capacitor,
A detection circuit that detects the voltage applied to the resistor provided between the rectifier circuit and the smoothing capacitor, and
When the voltage detected by the detection circuit is less than the voltage determination value, the smoothing capacitor is connected to the rectifier circuit, and when the voltage detected by the detection circuit is equal to or more than the voltage determination value, the detection circuit is used as a drive source. As a result, a cutoff circuit that opens the connection of the smoothing capacitor to the rectifying circuit to cut off the inflow of current into the smoothing capacitor.
After the cutoff circuit opens the connection of the smoothing capacitor to the rectifier circuit, a voltage for operating the detection circuit is applied to the detection circuit as a drive source to maintain the cutoff state by the cutoff circuit. Break-and-hold circuit and
Power supply with. The power supply device according to claim 1, wherein the resistor is a resistor provided in the inrush current prevention circuit. The power supply device according to claim 1 or 2, further comprising a resistor connected in parallel to the smoothing capacitor and discharging the electric charge of the smoothing capacitor. According to any one of claims 1 to 3, when the voltage detected by the detection circuit is equal to or higher than the voltage determination value, a display means for notifying that a voltage having an abnormal value is applied to the smoothing capacitor is provided. The power supply described. The power supply device according to any one of claims 1 to 4, wherein the inrush current prevention circuit is provided between the rectifier circuit and the smoothing capacitor. An image forming apparatus including the power supply device according to any one of claims 1 to 5. The power supply is
When the power plug is inserted into the outlet, the step of detecting the voltage applied to the resistor provided between the rectifier circuit that rectifies the alternating current and the smoothing capacitor that smoothes the voltage rectified by the rectifier circuit, and
When the detected voltage becomes equal to or higher than the voltage determination value, the step of opening the connection of the smoothing capacitor to the rectifier circuit and putting the cutoff circuit that cuts off the inflow of current into the smoothing capacitor into a cutoff state.
Power supply input overvoltage protection methods, including.

Images