JP2009284561A - Power supply protection method, power supply protection circuit, and electric apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply protection circuit that expedites the draw-out of an AC plug from a plug receptacle in an early stage by notifying the severity of overvoltage, and can effectively prevents the breakage of a power supply circuit and the power supply protection circuit. <P>SOLUTION: The power supply protection circuit includes: a means which has a voltage detection circuit 44 for detecting a voltage value related to an alternate current input into the power supply circuit 2 which feeds power to an amplifying circuit 3, and determines whether a voltage value detected in the power supply protection circuit 4 which is constituted so as to block the alternate current input into the power supply circuit 2 is not higher than a first voltage value according to the detected voltage value; a means which determines whether the voltage value is not higher than a second voltage value which is lower than the first voltage value; a relay circuit 47 which blocks the alternate current input into the power supply circuit 2 when it is determined that the voltage value is higher than the second voltage value; and a display part 46 which emits light at higher brightness, or more quickly blinks light compared with the case that the detected voltage value exceeds the second voltage value and is lower than the first voltage value when the detected voltage value is higher than the first voltage value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention includes a power supply protection method for protecting a power supply circuit by cutting off the alternating current input to the power supply circuit when an overvoltage alternating current is input, a power supply protection circuit that implements the power supply protection method, and the power supply circuit. It relates to electrical equipment.

A power protection circuit that protects a power supply circuit when an overvoltage is input has been proposed (for example, Patent Document 1). A power supply protection circuit according to Patent Document 1 includes a relay circuit that cuts off an alternating current input to the power supply circuit, an overvoltage detection unit that detects a voltage value related to the alternating current, and when an overvoltage is detected, the relay circuit is turned off. And a control circuit for controlling. The power supply protection circuit includes a display unit that notifies that an overvoltage has been detected.
According to the power supply protection circuit configured as described above, when an overvoltage alternating current is input to the power supply circuit, the power supply circuit can be protected by turning off the relay circuit. Further, it can be notified that an overvoltage is applied to the power supply circuit.
JP-A-11-69604

  However, the power supply protection circuit according to Patent Document 1 has a problem in that the overvoltage notification method does not change regardless of whether the overvoltage is high or low, and thus the user cannot be notified of the severity of the overvoltage.

If a low overvoltage AC is input, the power protection circuit will not be damaged, but if a high overvoltage AC is input, the power protection circuit itself may also be damaged, smoke, or fire. It is necessary to remove from.
For example, when using an electric device equipped with a power protection circuit in an area where the AC voltage is not stable, a low overvoltage AC is often input. In this case, the user can recognize that the operation of the electric device is stopped due to overvoltage due to light emission of the display unit. In areas where such conditions frequently occur, the user may leave the AC plug unplugged until the AC is stabilized.
However, sometimes a high overvoltage alternating current is input. In this case, it is necessary to remove the AC plug from the outlet at an early stage. However, since the user cannot recognize the severity of overvoltage, leave the AC plug in the outlet, resulting in damage to the power protection circuit. May be invited.

  The present invention has been made in view of such circumstances, and when an overvoltage is input, the alternating current is cut off, and the light emission pattern of the display unit is changed in accordance with the level of the overvoltage to thereby input the overvoltage. A power protection method, a power protection circuit, and an electrical device that can promptly disconnect the AC plug from the outlet at an early stage and can effectively prevent damage to the power circuit and the power protection circuit. The purpose is to provide.

  A power protection method according to the present invention detects a voltage value related to an alternating current input to a power supply circuit that supplies power to a load, and cuts off the alternating current input to the power supply circuit according to the detected voltage value In step (b), it is determined whether or not the detected voltage value is equal to or lower than the first voltage value, and whether or not the detected voltage value is equal to or lower than the second voltage value lower than the first voltage value. When it is determined that the voltage value is higher than two voltage values, AC input to the power supply circuit is interrupted, and when the detected voltage value is higher than the first voltage value, the voltage value exceeds the second voltage value and is equal to or lower than the first voltage value. Compared with the case where it is, it is characterized by making a display part light-emit or blink rapidly at high brightness.

  A power supply protection circuit according to the present invention includes a voltage detection circuit that detects a voltage value related to an alternating current input to a power supply circuit that supplies power to a load, and the power supply circuit includes a voltage detection circuit that detects a voltage value detected by the voltage detection circuit. In the power protection circuit designed to cut off the input alternating current, means for determining whether or not the voltage value detected by the voltage detection circuit is equal to or lower than a first voltage value, and the voltage detected by the voltage detection circuit Means for determining whether or not the value is equal to or lower than a second voltage value lower than the first voltage value, and input to the power supply circuit when it is determined that the voltage value detected by the voltage detection circuit is higher than the second voltage value And a display means for emitting light according to the voltage value detected by the voltage detection circuit, wherein the display means detects the voltage value detected by the voltage detection circuit from the first voltage value. When the voltage is high, the voltage value is Values greater than compared to the case is less than the first voltage value, characterized in that you have to emit light or fast blinking at high luminance.

  A power supply protection circuit according to the present invention includes a transformer that transforms an alternating current input to the power supply circuit, and a rectifier circuit that rectifies the alternating current transformed by the transformer, and the voltage detection circuit includes the rectifier circuit. The DC voltage value rectified in step S1 is detected, and the blocking means includes a relay circuit provided on the input side of the power supply circuit.

  The power source protection circuit according to the present invention includes means for determining whether or not the voltage value detected by the voltage detection circuit is less than a third voltage value lower than the second voltage value, and the voltage value detected by the voltage detection circuit. Is determined to be less than the fourth voltage value lower than the third voltage value, and the blocking means is determined that the voltage value detected by the voltage detection circuit is less than the third voltage value. In the case where the voltage value detected by the voltage detection circuit is less than a fourth voltage value, the display means includes a means for cutting off the alternating current input to the power supply circuit. Compared with the case where the voltage is less than the third voltage value, the light is emitted with high luminance or flashes at high speed.

  An electrical apparatus according to the present invention includes a power supply circuit that supplies power to a load, and the power supply protection circuit according to any one of claims 2 to 4 that protects the power supply circuit. .

In the present invention, the voltage value relating to the alternating current input to the power supply circuit is detected by the voltage detection circuit. The voltage value related to AC is, for example, a DC voltage value obtained by transforming and rectifying AC with a transformer and a rectifier circuit. Then, the power protection circuit determines whether or not the voltage value detected by the voltage detection circuit is equal to or less than a predetermined first voltage value. Further, it is determined whether or not the voltage value detected by the voltage detection circuit is equal to or lower than a second voltage value lower than the first voltage value. When it is determined that the voltage value detected by the voltage detection circuit is higher than the second voltage value, that is, when it is determined that an overvoltage alternating current exceeding the rated voltage is input, the blocking means blocks the alternating current. The blocking means is, for example, a relay circuit. The display means changes the light emission luminance and the flashing speed of light emission according to the voltage value related to the alternating current. Specifically, the display means emits light with higher brightness when the voltage value related to alternating current is higher than the first voltage value, compared to when the voltage value exceeds the second voltage value and is equal to or lower than the first voltage value, Or it flashes at high speed.
Therefore, it is possible to notify the degree of overvoltage on the display device. Therefore, the user of the electric device provided with the overvoltage protection circuit can determine whether or not it is necessary to unplug the AC plug of the electric device from the outlet at an early stage according to the light emission mode of the display device. .
Needless to say, the present invention is not limited to the case where the light emission mode is changed in two stages, but also the power supply protection configured to change the light emission mode in multiple stages according to the magnitude of the voltage value related to AC. Circuits and electrical equipment are included. Further, a power protection circuit and an electric device configured to continuously change the light emission mode as seen from the user are also included. Furthermore, the configuration of the voltage detection circuit is not limited as long as it can detect the degree of alternating overvoltage.

In the present invention, the power protection circuit determines whether or not the voltage value detected by the voltage detection circuit is less than the third voltage value lower than the second voltage value. Further, it is determined whether or not the voltage value detected by the voltage detection circuit is less than a fourth voltage value lower than the third voltage value. When it is determined that the voltage value related to the alternating current input to the power supply circuit is less than the third voltage value, that is, when it is determined that alternating current less than the rated voltage is input, the blocking means blocks the alternating current.
Therefore, it is possible to prevent wasteful power consumption by cutting off the alternating current in which the electric device cannot operate.
Further, the display means changes the light emission luminance and the light emission blinking speed in accordance with the voltage value related to the alternating current. Specifically, the display means emits light with higher brightness when the voltage value related to alternating current is less than the fourth voltage value, compared to when the voltage value is greater than or equal to the fourth voltage value and less than the third voltage value. Or flash at high speed.
Therefore, the degree of the voltage value can be notified on the display device. Therefore, the user of the electric device equipped with the overvoltage protection circuit recognizes that the voltage value is reduced and the electric device is not in a stopped state due to the input of the overvoltage according to the light emission mode of the display device. It is possible to determine that there is no need to remove the AC plug of the electrical device from the outlet.

  According to the present invention, when an overvoltage is input, the alternating current is interrupted, the degree of seriousness of the input alternating current overvoltage is informed, and it is possible to promptly disconnect the AC plug from the outlet. Damage to the power protection circuit can be effectively prevented.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
FIG. 1 is a block diagram illustrating an example of an electrical apparatus according to an embodiment of the present invention. The electric device according to the embodiment of the present invention is, for example, a home theater system, an audio device, a TV, or the like. The AC plug 1 is plugged into a commercial AC power outlet, and the AC input from the AC plug 1 is transformed, rectified, and stabilized. A power supply circuit 2 that supplies power, an amplifier circuit (load) 3 that operates with power supplied from the power supply circuit 2, and a power supply protection circuit 4 that protects the power supply circuit 2.

  The power supply circuit 2 includes a large-capacity transformer 21 that transforms an alternating current input from the AC plug 1, a first rectifying / smoothing circuit 22 that rectifies and smoothes the alternating current transformed by the large-capacity transformer 21, and a first rectifier. And a first stabilized power circuit 23 that stabilizes the direct current rectified and smoothed by the smoothing circuit 22 and outputs the stabilized direct current to the amplifier circuit 3.

  The large-capacity transformer 21 includes a primary winding connected to a power connection terminal of the AC plug 1 via a relay circuit 47 described later, a core, and a secondary winding magnetically coupled to the primary winding.

  The first rectifying / smoothing circuit 22 includes, for example, a full-wave rectifier diode bridge that full-wave rectifies AC power, and the input terminals of the full-wave rectifier diode bridge are respectively connected to both ends of the secondary winding constituting the large-capacity transformer 21. It is connected. One output terminal of the full-wave rectifier diode bridge is grounded, and the other output terminal is connected to the other end of a smoothing capacitor whose one end is grounded.

  The first stabilized power supply circuit 23 is a three-terminal regulator that outputs a DC voltage of 10 V, for example. The other terminal of the full-wave rectifier diode bridge and the other end of the smoothing capacitor are connected to the input terminal of the three-terminal regulator, the ground terminal of the three-terminal regulator is grounded, and the output terminal is connected to the amplifier circuit 3. .

  The power supply protection circuit 4 includes a normally open monostable relay circuit 47 that interrupts the alternating current input to the power supply circuit 2, a display unit 46 that notifies an abnormality in the alternating current, an on / off of the relay circuit 47, and a display unit 46. A control circuit 45 that controls light emission, a small-capacity transformer 41 that transforms an alternating current input from the AC plug 1, and a second rectifying and smoothing circuit 42 that rectifies and smoothes the alternating current transformed by the small-capacitance transformer 41. The second rectifying / smoothing circuit 42 stabilizes the rectified and smoothed direct current and supplies it to the control circuit 45 and the display unit 46, and the second rectifying / smoothing circuit 42 rectifies the direct current. And a voltage detection circuit 44 that detects a detected direct current voltage and outputs a detection signal indicating the detected voltage value V to the control circuit 45.

  The control circuit 45 is a microcomputer including a CPU (Central Processing Unit), for example, and includes a ROM, a RAM, a readable / writable nonvolatile memory, a timer, an input / output port, and the like connected to the CPU via a bus. . The ROM is a nonvolatile storage means, and various computer programs for protecting the power supply circuit 2, a predetermined first voltage value (hereinafter referred to as an upper limit voltage value), and a second voltage value (hereinafter referred to as an upper limit voltage value) lower than the first voltage value. , A semi-upper limit voltage value), a third voltage value lower than the second voltage value (hereinafter referred to as sub-lower limit voltage value), a fourth voltage value lower than the third voltage value (hereinafter referred to as lower limit voltage value), and other data Is remembered. The CPU implements protection of the power supply circuit 2 by reading the computer program and various data stored in the ROM into the temporary storage RAM and executing them.

  The relay circuit 47 includes a movable piece having a movable contact, a fixed contact, and an electromagnetic coil that moves the movable piece by a magnetic force and switches an on / off state of the relay circuit 47. A part of the movable piece constituting the relay circuit 47 is connected to one power connection terminal of the AC plug 1, and the fixed contact is connected to one end of the primary winding constituting the large-capacity transformer 21. The other power connection terminal constituting the AC plug 1 is connected to the other end of the primary winding. On the other hand, one end of the electromagnetic coil is grounded, and the other end is connected to the output port of the control circuit 45. The control circuit 45 switches the relay circuit 47 to the ON state by outputting a high level signal from the input / output port. When a low level signal is output from the input / output port, the relay circuit 47 is turned off.

  The display unit 46 includes, for example, a light emitting diode and a switching element for causing the light emitting diode to blink. The light emission pattern of the light emitting diode is controlled by controlling the switching element by the control circuit 45. In addition, the brightness | luminance of a light emitting diode can also be controlled by controlling on / off of a switching element by PWM (Pulse Width Modulation).

  The small-capacity transformer 41 has a smaller capacity than the large-capacity transformer 21 and includes a primary winding, a core, and a secondary winding connected to the power supply connection terminal of the AC plug 1. Both ends of the primary winding are connected to the respective power connection terminals of the AC plug 1. The capacity of the small-capacity transformer 41 is a capacity that can supply at least power necessary for the control circuit 45 to implement the power protection method.

  The second rectifying / smoothing circuit 42 has the same configuration as that of the first rectifying / smoothing circuit 22, and includes a full-wave rectifying diode bridge. The input terminal of the full-wave rectifying diode bridge is a secondary winding constituting the small-capacity transformer 41. Connected to both ends of the wire. One output terminal of the full-wave rectifier diode bridge is grounded, and the other output terminal is connected to the other end of a smoothing capacitor whose one end is grounded.

  The second stabilized power supply circuit 43 is a three-terminal regulator that outputs a DC voltage of 10 V, for example. The other terminal of the full-wave rectifier diode bridge and the other end of the smoothing capacitor are connected to the input terminal of the three-terminal regulator, the ground terminal of the three-terminal regulator is grounded, and the output terminal is connected to the control circuit 45 and the display unit 46. It is connected.

  The voltage detection circuit 44 is a circuit that detects a DC voltage value output from the first rectification / smoothing circuit 22 or the second rectification / smoothing circuit 42, and the detected voltage value is input to the control circuit 45. The voltage detection circuit 44 includes, for example, a high potential side voltage dividing resistor and a low potential side voltage dividing resistor connected in series to divide the direct current. One end of the high potential side voltage dividing resistor is connected to the other output terminal of the full-wave rectifying diode bridge constituting the first and second rectifying and smoothing circuits 22 and 42. The other end of the high potential side voltage dividing resistor and one end of the low potential side voltage dividing resistor are connected, and the other end of the low potential side voltage dividing resistor is grounded. One end of the low potential side voltage dividing resistor is connected to the input / output port of the control circuit 45, and the divided DC voltage value is input to the control circuit 45. The control circuit 45 acquires the voltage value V related to AC by AD-converting the input analog voltage value into a digital voltage value V.

  The electrical device is interposed between the first rectifying / smoothing circuit 22, the voltage detection circuit 44, and the second stabilized power supply circuit 43. A rectifier diode 5 connected in the forward direction to the power supply circuit 43 and the voltage detection circuit 44 is provided. More specifically, the other output terminal of the full-wave rectifying diode bridge constituting the first rectifying / smoothing circuit 22 and the anode of the rectifying diode 5 are connected, and the full-wave rectifying diode bridge constituting the second rectifying / smoothing circuit 42. Are connected to the cathode of the rectifier diode 5. The other end of the rectifier diode 5 is connected to the one end of the low potential side voltage dividing resistor.

  Next, a processing procedure of the control circuit 45 related to power supply protection will be described. When the AC plug 1 is not plugged into a commercial AC power outlet, the normally open monostable relay circuit 47 is in the off state. Then, when the AC plug 1 is inserted into the outlet, the alternating current is transformed, rectified, stabilized and stabilized through the small-capacity transformer 41, the second rectifying and smoothing circuit 42, and the second stabilizing power supply circuit 43. Direct current is supplied to the control circuit 45. When the direct current necessary for the operation of the control circuit 45 is supplied, the control circuit 45 executes the following processing related to power supply protection. Immediately after the AC plug 1 is plugged into the outlet, the relay circuit 47 is in a disconnected state, so that no alternating current is input to the power supply circuit 2 side.

  FIG. 2 is a flowchart showing a processing procedure of the control circuit 45 related to power supply protection, and FIG. 3 is a chart showing the operation content of the electric equipment. When direct current equal to or higher than the control circuit operable voltage value is supplied to the control circuit 45, the control circuit 45 acquires the voltage value V from the voltage detection circuit 44 (step S11), and the acquired voltage value V is less than the lower limit voltage value. It is determined whether or not (step S12). When it determines with it being less than a lower limit voltage value (step S12: YES), the control circuit 45 makes the display part 46 blink and light-emit with a 1st pattern (step S13), and complete | finishes a process. The blinking speed of the first pattern is set to be faster than the blinking speed of the second pattern described later.

  When it is determined that the acquired voltage value V is greater than or equal to the lower limit voltage value (step S12: NO), the control circuit 45 determines whether or not the acquired voltage value V is less than the quasi lower limit voltage value (step S14). ). When it determines with it being less than a semi-lower limit voltage value (step S14: YES), the control circuit 45 makes the display part 46 blink light emission by a 2nd pattern (step S15), and complete | finishes a process. The blinking speed of the second pattern is set to be slower than the blinking speed of the first pattern.

  When it is determined that the acquired voltage value V is equal to or greater than the quasi lower limit voltage value (step S14: NO), the control circuit 45 determines whether or not the acquired voltage value V is higher than the upper limit voltage value (step S16). . When it determines with it being higher than an upper limit voltage value (step S16: YES), the control circuit 45 makes the display part 46 blink on and off with a 3rd pattern (step S17), and complete | finishes a process. The blinking speed of the third pattern is set to be faster than the blinking speed of the fourth pattern described later.

  When it is determined that the acquired voltage value V is equal to or lower than the upper limit voltage value (step S16: NO), the control circuit 45 determines whether the acquired voltage value V is higher than the quasi upper limit voltage value lower than the upper limit voltage value. (Step S18). If it is determined that the value is higher than the quasi-upper limit voltage value (step S18: YES), the control circuit 45 causes the display unit 46 to flash and emit light in the fourth pattern (step S19), and the process ends. The blink rate of the fourth pattern is set to be slower than the blink rate of the third pattern.

When it is determined that the acquired voltage value V is less than or equal to the quasi-upper limit voltage value (step S18: NO), the control circuit 45 determines whether or not the electrical device is in a standby state (step S20). When it determines with it being in a standby state (step S20: YES), the control circuit 45 finishes the process which concerns on power supply protection. When it is determined that it is not in the standby state (step S20: NO), that is, when a power switch (not shown) for operating the amplifier circuit 3 is in the on state, the relay circuit 47 is controlled to be in the on state (step S21). Finish the protection process.
Note that the control circuit 45 is configured to regularly and periodically execute the above-described processing, and can monitor the overvoltage and protect the power supply circuit 2 both during the operation of the electrical equipment and in the standby state. it can.

  FIG. 4 is a block diagram illustrating an example of an electrical device in which the relay circuit 47 is in an on state. When the voltage value related to AC is in the voltage range not less than the quasi-lower limit voltage value and not more than the quasi-upper limit voltage value and is not in the standby state, the relay circuit 47 is turned on in step S20 as shown in FIG. become. When the relay circuit 47 is turned on, the alternating current input from the AC plug 1 is input to the power supply circuit 2 and the amplifier circuit 3 becomes operable. Further, the direct current smoothed by the first rectifying / smoothing circuit 22 is input to the voltage detection circuit 44 and the second stabilized power supply circuit 43 through the rectifying diode 5, so that the control circuit 45 is supplied through the large-capacity transformer 21. It operates with the direct current.

  When the voltage value V detected by the voltage detection circuit 44 is less than the quasi lower limit voltage value and exceeds the quasi upper limit voltage value even in the standby state or not in the standby state, the relay circuit 47 is in the off state. Therefore, AC is not input to the power supply circuit 2. The control circuit 45 operates based on the direct current supplied through the small capacity transformer 41.

  Further, when the voltage value V detected by the voltage detection circuit 44 exceeds the quasi-upper limit voltage value, it is possible to notify that the overvoltage alternating current is input by the display unit 46 blinking and emitting light. In particular, when the voltage value V exceeds the upper limit voltage value, not only the power supply circuit 2 but also the power supply protection circuit 4 itself may be damaged. Therefore, the display unit 46 is urged to promptly disconnect the AC plug 1 from the outlet. Flashes faster.

  Further, when the voltage value V detected by the voltage detection circuit 44 is less than the sub-lower limit voltage value, the display unit 46 flashes and emits light, indicating that the voltage value V related to the AC voltage is low and the operation is impossible. Can be notified. In particular, when the voltage value V is less than the lower limit voltage value, the display unit 46 flashes and emits light at a higher speed than when the voltage value V is equal to or higher than the lower limit voltage value, thereby informing the degree of AC abnormality. .

  In the electric equipment and the power supply protection circuit 4 configured as described above, when the voltage value V is higher than the quasi-upper limit voltage value, the display unit 46 blinks in the third and fourth patterns according to the voltage value V. As a result, the degree of seriousness of the overvoltage can be notified, prompting the user to disconnect the AC plug 1 from the outlet at an early stage, and damage to the power supply circuit 2 and the power supply protection circuit 4 can be effectively prevented.

  When the voltage value V is less than the sub-lower limit voltage value, the display unit 46 blinks and emits light in the first and second patterns according to the voltage value V, so that the degree of decrease in the voltage value V and the overvoltage are input. It is possible to notify that the electrical device is not in a stopped state. Therefore, it is possible to notify the user that there is no need to remove the AC plug 1 of the electrical device from the outlet.

  In addition, when the relay circuit 47 is in the off state, the direct current is supplied to the control circuit 45 through the small-capacity transformer 41 to protect the power supply circuit 2, so that the standby power in the standby state can be saved. Can be achieved.

  Further, when the relay circuit 47 is in the on state, the direct current is supplied to the control circuit 45 and the display unit 46 through the power supply circuit 2. When the electric device starts to operate, the power-on LED, the backlight of the display unit 46, and the like are lit, and the power consumption increases. However, direct current is supplied to the control circuit 45 and the display unit 46 through the large-capacity transformer 21. Therefore, the electric device can operate without any problem. In other words, the small-capacity transformer 41 does not need to be able to supply the direct current necessary for the control circuit 45 and the display unit 46 when the electric device is operating, and at least the power necessary for the power protection process is supplied to the control circuit 45 and the display unit 46. Since there is no problem if it can be supplied, the small-capacity transformer 41 can be further reduced in size and size.

Next, a modified example of the present invention will be described.
FIG. 5 is a block diagram illustrating an example of an electrical apparatus according to a modification. The electric apparatus according to the modification is different only in the configuration of the power protection circuit 4. The power protection circuit 4 includes a normally closed monostable relay circuit 48 for interrupting the alternating current input to the small-capacity transformer 41. The power protection circuit 4 includes a storage battery 49 that supplies direct current to the control circuit 45 when the relay circuit 48 is turned off.

  The control circuit 45 includes time measuring means (not shown). When the voltage value V detected by the voltage detection circuit 44 is equal to or greater than the quasi-upper limit voltage value or the upper limit voltage value, the control circuit 45 starts measuring time. When the predetermined time elapses while the voltage value V is equal to or greater than the quasi-upper limit voltage value or the upper limit voltage value, the control circuit 45 controls the relay circuit 48 to be in the OFF state. Thereafter, the control circuit 45 periodically turns on the relay circuit 48 to acquire the voltage value V from the voltage detection circuit 44, and the acquired voltage value V is equal to or higher than the quasi lower limit voltage value and equal to or lower than the quasi upper limit value. It is determined whether or not there is. When the voltage value V is not less than the quasi-lower limit voltage value and not more than the quasi-upper limit value, the energization to the relay circuit 48 is stopped and the relay circuit 48 is returned to the on state. When the voltage value V remains at the quasi-upper limit voltage value or the upper limit voltage value, the control circuit 45 controls the relay circuit 48 to the off state.

  In the power supply protection circuit 4 and the electric device according to the modification, when the AC plug 1 is left inserted for a predetermined time or more with the overvoltage alternating current being input, the small capacity transformer 41 AC can be interrupted upstream, and not only the power supply circuit 2 but also the power supply protection circuit 4 itself can be effectively protected.

  In the embodiment, the blinking speed of the display unit is changed according to the voltage value V related to the alternating current. However, the luminance of the display unit may be increased or decreased. The brightness of the display unit may be controlled by increasing or decreasing the effective current flowing through the light emitting diode by PWM control, for example. Further, the display portion may include a plurality of light emitting diodes, and the luminance may be increased or decreased by increasing or decreasing the number of diodes that emit light.

  In addition, although a home theater system or the like has been illustrated as an electric device including an amplifier circuit, the present invention may be applied to other electric devices that require protection of a power supply circuit that supplies power to a load.

  Furthermore, in the present invention, the voltage value is monitored using four threshold voltages, but the number of threshold voltages is not limited to this.

  Furthermore, it should be thought that embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

(Appendix)
In an electrical device including an amplifier circuit, a power supply circuit that supplies power to the amplifier circuit, and a power supply protection circuit that protects the power supply circuit,
The power supply circuit is
A first transformer for transforming alternating current input to the power supply circuit;
A first rectifier circuit for rectifying the alternating current transformed by the first transformer;
A first stabilized power supply circuit that stabilizes the direct current rectified by the first rectifier circuit and supplies the stabilized direct current to the amplifier circuit,
The power protection circuit is
A second transformer that is smaller in capacity than the first transformer and transforms an alternating current input to the power supply circuit;
A second rectifier circuit for rectifying the alternating current transformed by the second transformer;
A voltage detection circuit for detecting a DC voltage rectified by the second rectification circuit;
A relay circuit for cutting off alternating current input to the power supply circuit;
A display unit having a light emitter;
A control circuit for controlling on / off of the relay circuit and light emission of the display unit according to the voltage value detected by the voltage detection circuit;
A second stabilized power supply circuit that stabilizes the direct current rectified by the second rectifier circuit and supplies the stabilized direct current to the control circuit,
And a rectifier diode connected in a forward direction from the first rectifier circuit to the second stabilized power supply circuit and the voltage detection circuit;
The control circuit includes:
Means for determining whether the voltage value detected by the voltage detection circuit is equal to or lower than a first voltage value;
Means for determining whether the voltage value detected by the voltage detection circuit is equal to or lower than a second voltage value lower than the first voltage value;
Means for determining whether the voltage value detected by the voltage detection circuit is less than a third voltage value lower than a second voltage value;
Means for determining whether the voltage value detected by the voltage detection circuit is less than a fourth voltage value lower than a third voltage value;
When it is determined that the voltage value detected by the voltage detection circuit is higher than the second voltage value, or when it is determined that the voltage value detected by the voltage detection circuit is less than the third voltage value, the input to the power supply circuit Blocking means for blocking the alternating current,
When the voltage value detected by the voltage detection circuit is higher than the first voltage value, the display unit emits light with high brightness or is faster than when the voltage value exceeds the second voltage value and is equal to or lower than the first voltage value. Means to blink,
When the voltage value detected by the voltage detection circuit is less than the fourth voltage value, the display unit emits light with higher brightness than when the voltage value is equal to or greater than the fourth voltage value and less than the third voltage value. Or an electrical device comprising a means for flashing at high speed.

It is a block diagram which shows an example of the electric equipment which concerns on embodiment of this invention. It is a flowchart which shows the process sequence of the control circuit which concerns on power supply protection. It is a graph which shows the operation | movement content of an electric equipment. It is a block diagram which shows an example of the electric equipment which has a relay circuit in an ON state. It is a block diagram which shows an example of the electric equipment which concerns on a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC plug 2 Power supply circuit 3 Amplifier circuit 4 Power supply protection circuit 5 Rectifier diode 21 Large capacity transformer 22 1st rectification smoothing circuit 23 1st stabilization power supply circuit 41 Small capacity transformer 42 2nd rectification smoothing circuit 43 2nd stabilization Power supply circuit 44 Voltage detection circuit 45 Control circuit 46 Display unit 47 Relay circuit 48 Relay circuit 49 Storage battery

Claims (5)

In a power protection method for detecting a voltage value related to an alternating current input to a power supply circuit that supplies power to a load and interrupting the alternating current input to the power supply circuit according to the detected voltage value
Determining whether the detected voltage value is less than or equal to the first voltage value and whether or not the detected voltage value is less than or equal to the second voltage value lower than the first voltage value;
When it is determined that the detected voltage value is higher than the second voltage value, the AC input to the power supply circuit is interrupted,
When the detected voltage value is higher than the first voltage value, the display unit emits light with high brightness or blinks rapidly compared to the case where the voltage value exceeds the second voltage value and is equal to or lower than the first voltage value. How to protect the power supply. A voltage detection circuit that detects a voltage value related to an alternating current input to a power supply circuit that supplies power to the load is provided, and the alternating current input to the power supply circuit is blocked according to the voltage value detected by the voltage detection circuit. In the power protection circuit
Means for determining whether the voltage value detected by the voltage detection circuit is equal to or lower than a first voltage value;
Means for determining whether the voltage value detected by the voltage detection circuit is equal to or lower than a second voltage value lower than the first voltage value;
When it is determined that the voltage value detected by the voltage detection circuit is higher than the second voltage value, a blocking unit that blocks AC input to the power supply circuit;
Display means for emitting light according to the voltage value detected by the voltage detection circuit,
The display means includes
When the voltage value detected by the voltage detection circuit is higher than the first voltage value, the voltage value is higher than the second voltage value and less than or equal to the first voltage value. A power protection circuit characterized by that. A transformer for transforming the alternating current input to the power circuit;
A rectifier circuit for rectifying the alternating current transformed by the transformer,
The voltage detection circuit includes:
The DC voltage value rectified by the rectifier circuit is detected,
The blocking means is
The power supply protection circuit according to claim 2, further comprising a relay circuit provided on an input side of the power supply circuit. Means for determining whether the voltage value detected by the voltage detection circuit is less than a third voltage value lower than a second voltage value;
Means for determining whether the voltage value detected by the voltage detection circuit is less than a fourth voltage value lower than a third voltage value;
The blocking means is
When it is determined that the voltage value detected by the voltage detection circuit is less than the third voltage value, the AC voltage input to the power supply circuit is cut off.
The display means includes
When the voltage value detected by the voltage detection circuit is less than the fourth voltage value, light is emitted with high brightness or flashes faster than when the voltage value is greater than or equal to the fourth voltage value and less than the third voltage value. The power protection circuit according to claim 2, wherein the power protection circuit is configured as described above. A power supply circuit for supplying power to the load;
An electrical apparatus comprising: the power supply protection circuit according to any one of claims 2 to 4 that protects the power supply circuit.

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