JP2014079130A - Power source circuit of controller - Google Patents

Abstract

An object of the present invention is to use a low-voltage and low-power-resistant component with an additional configuration for shortening the voltage drop of a secondary-side power supply when an AC power supply during standby is cut off in a power supply circuit of an electric device.
SOLUTION: A rectifying means 2 that generates a primary power source rectified from an AC power source 1, a stable voltage step-down means 3 that consumes power of the primary power source and outputs a secondary power source, and a power interruption detection that detects energization of the AC power source 1. In the configuration including the means 4 and the control means 5 for determining the energized state from the detection signal of the power interruption detection means 4 by supplying the secondary power supply and controlling the device, the power consumption means 6 as a load of the secondary power supply is further provided. The power consumption means 6 is connected to the secondary power supply when the control means 5 is in a standby state and it is determined that the AC power supply is cut off. Since the consumption means 6 can divide into two parts, it is possible to obtain a power supply circuit for an electric device that can use an additional configuration for increasing power consumption with a low withstand voltage and a lower resistance to power consumption.
[Selection] Figure 1

Description

  The present invention relates to a power supply circuit for a control device that reduces power consumption during standby of equipment while supplying a stable voltage drop to the configuration of a control circuit mounted for control in an electrical equipment. .

  In recent years, a power supply circuit of a control device mounted on an electric device is consumed in a so-called standby state in which the main power source such as a commercial power source is energized but is stopped, from the viewpoint of power saving. There is a need for a circuit configuration that reduces as much as possible the power consumed by a main power source, commonly known as standby power.

  In addition, it is very common that the main body of the control device responsible for controlling the equipment mounted on the electrical equipment is configured using a microcomputer that operates using the voltage stabilized and lowered by the circuit configuration of the power supply as the power supply. .

  In this microcomputer, the operation procedure of the device is stored as a program on a memory, and the control operation of the device is sequentially executed based on the stored procedure.

  In such a control device mainly composed of a microcomputer, the number of processes related to the calculation operation and judgment program operation corresponding to the work process required for the control operation is the minimum in the normal state of the device in the standby state of the device, and the control is performed. Since the operation of the target circuit configuration is also stopped, the power consumed by the control device itself is the lowest in the standby state of the device.

  In addition, the microcomputer needs to be supplied with a constant voltage for stable operation, but at the same time the power supply voltage rises when the main power supply is energized to the device, It is necessary to increase the voltage from the voltage value below the specified voltage value for a relatively short time, and it is also specified when the power supply voltage drops when the main power supply to the equipment is cut off. It is indispensable to drop the voltage below the specified voltage value in a relatively short period of time. This specified voltage is generally known as a so-called reset voltage.

  Furthermore, the circuit configuration of the power supply basically includes a capacitor as a component for stabilizing the voltage, and even if the main power supply is momentarily interrupted, the control device can control the normal operation of the device. By supplying the consumed electric power from the electric power held in the provided capacitor, the controller is configured so that the supply of the stably lowered voltage is not interrupted.

  Therefore, when the main power supply is cut off when the device is in the standby state in the control device, the power consumption of the control device itself is the lowest in the standby state, so the supply voltage to the microcomputer responsible for the control is The electric power held in the capacitor provided in the circuit configuration of the power supply is gradually reduced until it is consumed up.

  The speed of the decrease in the supply voltage to the microcomputer becomes slower as the power consumption during standby is further reduced with respect to the control of the normal operation of the device in the control device. Since it is difficult to obtain a change in the power supply voltage in a short time with respect to the reset voltage indispensable for normal operation, there is a tendency that a problem is likely to occur in the stable operation of the control device with respect to intermittent power supply to the main power supply device.

  In addition, if the power consumption during standby is further reduced, the time that the voltage is held in the capacitor provided in the circuit configuration of the power supply also becomes longer, so the repair of the control device performed after the main power supply is shut off There was a tendency for the risk of electric shock failure during maintenance work to increase.

  For this reason, there is a need for a power supply circuit for a control device that can reduce the risk of electric shock failure during maintenance work while stably operating against the intermittent power supply of the main power supply while saving power.

  Conventionally, the power supply circuit of this type of control device is controlled by adding a configuration for detecting the interruption of energization of the main power supply and a configuration for consuming power held by a capacitor provided in the circuit configuration of the power supply. When the device is in the standby state in the apparatus and when the interruption of the main power supply is detected, the power consumption for the power supply circuit configuration is increased in order to reduce the voltage held by the power supply circuit configuration in a shorter time. What was made is known (for example, refer patent document 1).

  Hereinafter, the power supply circuit of the control device will be described with reference to FIG.

  As shown in FIG. 3, a three-phase rectification stack 101 that rectifies a high-voltage AC input power source that is a primary side as a main power supply source, and a smoothing that smoothes a high voltage rectified by the three-phase rectification stack 101. Capacitor 102, an automatic discharge circuit 103 that is connected in parallel to the smoothing capacitor 102 and discharges the electric charge of the smoothing capacitor 102 in response to an external signal input, and the automatic input circuit 103 detects the disconnection of the AC input power source. A power supply control unit 104 for switching discharge of the charge of the smoothing capacitor 102 by the discharge circuit 103, and a parallel power supply connected to the smoothing capacitor 102 so as to supply predetermined DC power to a subsequent load circuit as a DC power supply module. DC-DC converter 105, and when power supply control unit 104 detects the disconnection of AC input power The primary side to become charged electricity of the smoothing capacitor 102 via an automatic discharge circuit 103 has been configured to discharge.

JP-A-62-107678

  In such a power supply circuit of the conventional control device, the power supply control unit 104 converts the electric charge held in the smoothing capacitor 102 based on the high voltage obtained by rectifying the high-voltage AC input power by the three-phase rectification stack 101 into the AC. When the disconnection of the input power supply is detected, the automatic discharge circuit 103 is used for discharging. Therefore, in the configuration of the automatic discharge circuit 103 for increasing the power consumption held in the power supply circuit configuration, smoothing is required. Therefore, it is necessary to have the capability of consuming power held by the capacitor 102 as a circuit configuration of the power source in a single configuration, so that the main configuration responsible for power consumption is required to have high withstand voltage and high resistance to power consumption. Therefore, it is difficult to use general-purpose parts that have low breakdown voltage, low resistance to power consumption, and excellent availability. It has been a problem.

  Therefore, the present invention solves the above-described conventional problems, and has a low breakdown voltage as a configuration for increasing the power consumption of the circuit configuration of the power supply when the device is in a standby state and the main power supply is shut off. Another object of the present invention is to provide a power supply circuit for a control device that can use general-purpose components that have low power consumption tolerance and are more easily available.

  In order to achieve this object, the present invention generates a primary power source by rectifying and smoothing a high-voltage AC power source that constitutes a power source circuit mounted on an electric device having a control function. Rectifying means, and stable voltage step-down means for stepping down and outputting a secondary power source stabilized at a specified voltage while consuming the power of the primary power source from the primary power source, and for energizing the AC power supply device A power-off detection unit that detects a state and outputs a detection result as a voltage value change signal to the secondary power source side; and operates when power is supplied from the secondary power source, and outputs the power-off detection unit The control operation of the device is performed while judging the state of energization to the device of the AC power supply by reading the voltage signal to be performed, and the power consumption of the secondary power supply is the lowest in the standby state where the device is stopped. Control means comprising In the circuit configuration, the control means controls the disconnection of the connection to the secondary power supply, and further includes power load means that becomes a load of power consumption of the secondary power supply when connected to the secondary power supply. In the control means, the power load means is connected to the secondary power supply when it is determined that the energization of the AC power supply equipment is cut off from the voltage signal output from the power interruption detection means which is in the standby state. It is intended to be controlled, thereby achieving the intended purpose.

  According to the present invention, rectifying means for generating a primary power source by rectifying and smoothing a high-voltage AC power source that constitutes a circuit of a power source, which is mounted on an electric device having a control function, and the primary Stable step-down means is provided for stepping down and outputting a secondary power source stabilized at a specified voltage while consuming the power of the power source from the primary power source, and detecting the state of energization of the AC power source device, and detecting the detection result The power cutoff detection means that outputs to the secondary power source side as a voltage value change signal, and operates when there is power supplied from the secondary power supply, and reads the voltage signal output from the power cutoff detection means. A circuit comprising a control means for performing control operation of the device while judging the state of energization of the device of the AC power supply, and in which the power consumption of the secondary power supply is minimized in the standby state where the device is stopped. In the configuration, the control The connection to the secondary power supply is controlled by the stage, and further includes power load means that becomes a load of power consumption of the secondary power supply when connected to the secondary power supply. The power load unit is controlled to be connected to the secondary power source when it is determined that the energization of the AC power supply device is cut off from the voltage signal output from the power cutoff detection unit in the standby state. Thus, when the device is in a standby state and the main power supply is shut off by the control means, the power consumption of the secondary power supply is increased by the power load means. And the power held by the stable voltage-lowering means as a whole are the power consumption required for generating the secondary power source by the stable voltage-lowering means, and the low voltage side 2 by the power-consuming means. Since the power consumption of the power supply can be divided and divided into two elements, the power consumption of the circuit configuration of the power supply is increased when the device is in a standby state and the main power supply is shut off. With this configuration, it is possible to obtain an effect that a general-purpose component having a low breakdown voltage, low power consumption tolerance, and excellent availability can be used.

The circuit diagram which shows the structure of the power supply circuit of the control apparatus of Embodiment 1 of this invention The flowchart figure which showed the control procedure of the power supply circuit of the control apparatus Circuit diagram showing configuration of power supply circuit of conventional control device

A power supply circuit for a control device according to claim 1 of the present invention generates a primary power supply by rectifying and smoothing a high-voltage AC power supply that constitutes a power supply circuit mounted on an electric device having a control function. Rectifying means for performing the operation, and stable voltage step-down means for stepping down and outputting the secondary power source stabilized at a specified voltage while consuming the power of the primary power source from the primary power source, and energizing the device of the AC power source The power shutoff detecting means for detecting the state of the power supply and outputting the detection result as a voltage value change signal to the secondary power supply side, and operating if there is power supply from the secondary power supply, By reading the voltage signal to be output, the control operation of the device is performed while judging the state of energization of the AC power supply device, and the power consumption of the secondary power supply is the lowest in the standby state where the device is stopped. Control means In the circuit configuration, the control means controls the disconnection of the connection to the secondary power supply, and further includes power load means that becomes a load of power consumption of the secondary power supply when connected to the secondary power supply. In the control means, the power load means is connected to the secondary power supply when it is determined that the energization of the AC power supply equipment is cut off from the voltage signal output from the power interruption detection means which is in the standby state. It has a configuration of controlling. Thereby, when the device is in a standby state and the main power supply is shut off by the control means, the power consumption of the secondary power supply is increased by the power load means.
The power held as a whole in the rectifying means and the stable step-down means constituting the circuit of the power supply is the power consumption required for generating the secondary power supply by the stable step-down means, and the secondary power supply on the low voltage side by the power consuming means Power consumption can be divided into two parts and distributed, so that when the device is in a standby state and the main power supply is shut off, the power consumption of the circuit configuration of the power supply is increased. With respect to the configuration, there is an effect that a general-purpose component having low withstand voltage, low power consumption tolerance, and excellent availability can be used.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows an outline of a configuration of a control circuit mounted on an electric device having a control function.

  The AC voltage of the AC power source 1 that is the main power source of the power supply source that is external to the device is first rectified and smoothed by rectifying the AC voltage, and the DC high-voltage primary power source indicated by V1 in the figure. Is drawn into the apparatus by the rectifying means 2 for generating

  In the next stage of the rectifying means 2, a stable voltage-lowering means 3 for lowering the voltage and stabilizing it to a specified voltage while consuming electric power provided for the primary power supply is connected and arranged from the primary power supply. Above, a low-voltage direct current stabilized secondary power source indicated by V2 is generated and output.

  A control means 5 for performing a control operation of a device that operates using a secondary power source as a power source is connected to the next stage of the stable voltage step-down means 3.

  The AC power source 1 is also connected to a power source interruption detection unit 4 that detects the interruption of energization of the AC power source 1 and outputs the detection result to the control unit 5 as a low voltage signal.

  The secondary power supply is connected to a power consuming means 6 configured to be a load of power consumption of the secondary power supply and to control the opening of the connection to the secondary power supply by the voltage signal of the control means 5.

  The secondary power source includes a display device such as an LED, a sounding device such as a buzzer, or a motor that operates using the secondary power source as a power supply source after the arrow shown at the right end of the wiring of the secondary power source in FIG. Although it becomes a control element of apparatuses, such as a power unit, and the apparatus controlled by the control means 5 is connected, since it is not related to the summary of this invention, detailed description shall be abbreviate | omitted.

  Here, the AC power source 1 is, for example, a commercial AC power source, and is AC 100 V (50/60 Hz) in Japan.

  Here, the rectifying unit 2 does not define a specific configuration, and may be any unit that rectifies the AC voltage by using a rectifying element such as a diode.

  Here, although the stable voltage step-down means 3 does not define a specific configuration, it operates by, for example, consuming the power of the input power supply, and intermittently connects the power supply voltage to the primary side of the transformer. By switching, the intermittent voltage that is stepped down to the secondary side of the transformer is generated and the intermittent voltage is rectified by using a rectifier such as a diode, and the voltage value of the rectified voltage is fed back and fed back. When the voltage is different from the reference voltage, it uses a general switching regulator configuration that stabilizes the voltage output to a specified voltage value (for example, DC5V) by changing the period and interval of the intermittent voltage. In this embodiment, one side of the AC power source 1 and the reference potential (GND) side of the secondary power source are shown in a non-insulated schematic configuration.

  Even if the switching regulator configuration is used in the stable voltage step-down means 3, the power conversion operation is performed by consuming the power of the input power supply, and the stepped-down output is generated. The conversion efficiency of the output power is generally about 60% to 90%, and the power of about 10% to 40% becomes a loss and is consumed as heat in the stable voltage step-down means 3.

  Here, since the rectifying means 2 and the stable voltage step-down means 3 are the main components of the circuit configuration of the power supply, as described above, the capacitor 7a for holding the electric power as an electric charge for further stabilizing the rectified voltage, 7b.

  Here, the control means 5 is composed of the above-described microcomputer. For example, a central processing unit that performs calculation and determination processing, an input / output terminal that can capture and output an external voltage change signal, and an analog Built-in A / D input terminal for converting voltage signals into digital values, read-only memory for storing operation procedures as software, and random access memory for temporarily storing calculation and judgment status By doing so, a so-called one-chip microcomputer that can process and execute the control operation independently is used.

  The basic specification is that the input / output terminal of this one-chip microcomputer is in a state where no input / output of current is performed as a high resistance state if the applied power supply is in a stopped state below the normal operating range. In the normal operation after the applied power supply changes to the normal operation range, the terminal state (the positive potential side of the power supply potential, the reference potential (GND) side, or the high resistance) by internal processing based on the software description State input terminal).

  In addition, for the normal operation of this one-chip microcomputer, in the rise and fall of the power supply voltage supplied, the voltage value rises with the reset voltage defined for a relatively short time as a threshold. As described above, the change in the descending direction is indispensable.

  Here, for example, as shown in the figure, the power shutoff detection means 4 divides the AC voltage of the AC power source 1 by a resistor 8a and a resistor 8b having one side connected to the reference potential (GND) side of the secondary power source. As a configuration in which the voltage is applied to the base terminal of the NPN transistor 9a, which is a switching element, with a low-voltage AC voltage generated across the resistor 8b, the collector and emitter terminals of the transistor 9a are intermittently connected. By doing so, a rectangular voltage signal is generated between the both ends of the resistor 8c connected to the secondary power source, with a stable voltage of the secondary power source and synchronized with the AC cycle of the AC power source 1.

  In the power cutoff detection means 4 configured in this way, the state where the voltage across the resistor 8c does not change indicates that the AC power supply 1 is not energized to the device. The interruption of the energization of the AC power supply 1 can be detected as a state in which the voltage value across the resistor 8c is constant.

  Therefore, after the voltage value across the resistor 8c is read by the input / output or A / D input terminal 5a in the one-chip microcomputer constituting the main body of the control means 5, the AC power supply 1 is switched to the AC cycle in the internal processing. If it is determined that there is no change in synchronism, it is possible to determine whether the AC power supply 1 is cut off.

  Here, the power consuming means 6 is, for example, one that consumes the power of the secondary power source by connecting a resistor to the secondary power source and conducting the current, and the resistor 8e is connected to one end of the resistor 8e. By connecting to the positive potential side of the secondary power supply, connecting the other end to the collector terminal of the NPN transistor 9b, and connecting the emitter terminal of the NPN transistor 9b to the reference potential (GND) side of the secondary power supply. If a current is applied to the base terminal of the transistor 9b, the collector and emitter terminals of the transistor 9b become conductive, and the secondary power supply is applied to the resistor 8d, so that the power of the secondary power supply is consumed by the heat generated by the resistor 8d. It is made to let you.

  Further, a resistor 8e is arranged and connected between the base terminal of the transistor 9b and the positive potential side of the secondary power supply, and basically a current based on the voltage of the secondary power supply is supplied to the base terminal via the resistor 8e. As long as the base terminal is not externally connected to the reference potential (GND) side of the secondary power supply, the power of the secondary power supply is consumed by the resistor 8d. .

  Therefore, in the power consuming means 6 configured as described above, if the base terminal of the transistor 9b is connected to the input / output terminal 5b of the one-chip microcomputer constituting the main body of the control means 5, the one-chip microcomputer If the output potential of the input / output terminal 5b is set to the reference potential (GND) of the secondary power supply by internal processing, the connection of the resistor 8d to the secondary power supply is released, and the power consumption of the secondary power supply by the resistor 8d is stopped. If the secondary power supply is set to a positive potential (or a high resistance state), the resistor 8d is connected to the secondary power supply, so that the power consumption of the secondary power supply can be increased.

  Further, as described above, the one-chip microcomputer constituting the main body of the control means 5 controls the input / output terminal 5b in a high resistance state when the applied power source is stopped below the normal operating range. If the means 5 is stopped, the power of the secondary power source is always consumed by the resistor 8d.

  The power consumption of the secondary power source in the power consuming unit 6 is set by the condenser 7a provided in the rectifying unit 2 and the stable voltage step-down unit 3 which are the main components of the power source circuit when the energization of the AC power source 1 is cut off in the standby state. The output voltage value of the secondary power supply is defined by the one-chip microcomputer that is the main component of the control means 5 from the state in which the secondary power supply stably supplies the specified voltage by the electric power held by 7 and 7b. It is set so that the voltage can be lowered below the reset voltage during the specified time. This causes the one-chip microcomputer to stop normally, and the one-chip microcomputer is normal when the secondary power supply voltage next rises. It is set so as to obtain a change in the output voltage of the secondary power supply that can be activated at the same time.

  Therefore, the resistor 8d as the main body of the control means 5 sets a resistance value that enables the power consumption of the secondary power source described above, and selects a resistor having a corresponding power consumption tolerance.

  Next, the procedure of the control process executed when the control unit 5 is in a standby state of the device and the energization of the secondary power supply is cut off will be described with reference to the flowchart shown in FIG.

  Here, as described above, FIG. 2 shows only the routine of the process to be executed in accordance with the determination of the control processing part when the energization of the secondary power supply is cut off in the standby state in the device control processing procedure. .

  Therefore, the main process of device control, the process of changing the apparatus to the standby state, and the process of determining whether to cut off the AC power source 1 are performed as a main routine in a repetitive loop indicated by a dotted line in the figure. Shall.

  In this routine, first, in step S1, it is determined that the device is in a standby state. As a result, when the device is not in a standby state, the routine proceeds to step S2, and the input / output terminal 5b is kept at the reference potential state of the secondary power supply. Return to the main routine.

  When it is determined in step S1 that the device is in a standby state, the process proceeds to step S3.

  In step S3, it is determined whether the energization of the AC power source 1 is cut off. As a result, when the AC power source 1 is not cut off, the process proceeds to step S2, and the input / output terminal 5b is set to the reference potential state of the secondary power source. It will return to the main routine while keeping it.

  When it is determined in step S3 that the AC power supply 1 is in the shut-off state, the process proceeds to step S4.

  In step S4, the input / output terminal 5b is changed to the high resistance state (or the positive potential of the secondary power supply), and the process returns to the main routine.

  As described above, if the state is shifted to step S4, the device is in a standby state and the energization of the AC power source 1 is cut off, so that the power of the secondary power source by the power consuming means 6 is reduced. Consumption will be started.

  According to such a configuration, the rectifying means 2 generates a DC high-voltage primary power supply in a state where the AC voltage of the AC power supply 1 is connected to the device, and the stable voltage-lowering means 3 supplies power provided to the primary power supply. The secondary power source stabilized with the low-voltage direct current is generated while consuming, and the control means 5 executes the control operation of the device in accordance with the procedure defined by operating the secondary power source as a power source. .

  Further, the control means 5 determines the detection of the interruption of energization of the AC power supply 1 by the power supply interruption detection means 4 while executing the control operation of the equipment, so that the AC power supply is in a state where the equipment is controlled in the standby state. When it is determined that the energization interruption of 1 is detected, the power consumption means 6 starts to consume the power of the secondary power source.

  Therefore, when the device is in a standby state and the energization of the AC power supply 1 is cut off, the electric power held in the rectifying means 2 and the stable voltage reducing means 3 constituting the mains of the power supply circuit is the secondary power of the stable voltage reducing means 3. The power required for generating the power source and the power consumption of the secondary power source on the low voltage side by the power consuming means 6 are divided into two elements, the stable voltage step-down means 3 and the power consuming means 6, and are distributed and consumed. Because of the availability, the device has low withstand voltage and low power consumption resistance compared to the configuration for increasing the power consumption of the circuit configuration of the power supply when the device is in standby state and the main power supply is shut off. Excellent general-purpose parts can be used.

  The power consuming means 6 is not limited in its form and principle as long as it can consume the power of the secondary power supply, and may be configured so as not to cause a problem in the product specifications of the device on which the electronic circuit is mounted. For example, it may be a device that consumes electric power such as a display device such as an LED, a sound generation device such as a buzzer, or a power device such as an electric motor.

  Note that the circuit configuration of the target power source is only a configuration in which the stable voltage step-down means 3 for generating a step-down power supply stabilized to a specified voltage is paired with the rectifying means 2 for generating a DC high-voltage power supply. The generation of a plurality of specified voltages is required, and it is necessary to provide a plurality of stable voltage step-down means 3 such as a configuration for stepping down the voltage in multiple stages in series or a configuration for stepping down to individual voltages in parallel. Needless to say, the present invention can be applied to a certain configuration, and there is no difference in operational effects.

  In the present invention, the power shutoff detecting means 4 obtains a rectangular secondary voltage signal synchronized with the alternating current cycle of the AC power supply 1, and shuts off the power supply to the AC power supply 1 when this voltage signal cannot be obtained. Although the configuration to detect is described as an example, a voltage fluctuation component (ripple voltage) mainly composed of the period of the AC power supply 1 superimposed on the DC high-voltage primary power source rectified by the rectifying means 2 is used as a capacitor coupling. It is possible to obtain an AC voltage by passing through and drive a transistor with this AC voltage to obtain a rectangular voltage signal of a secondary voltage, and it goes without saying that there is no difference in operation and effect even if this configuration is used. .

  Although the present invention has been described based on the high-voltage AC power source 1 as the main power source of the power supply source, even if the main power source is a DC high-voltage power source, the specified value of the voltage on the primary voltage side If the power cut-off detection means 4 is configured by a voltage comparison type circuit that changes the voltage signal of the secondary voltage, it is possible to detect the power cut-off state. It goes without saying that there is no difference.

  The power supply circuit of the control device according to the present invention generates a stable low-voltage power supply from a high-voltage power supply and supplies it to the configuration of the control circuit mounted for control in the electric equipment while controlling the equipment during standby. Since the power consumption can be reduced while the circuit is operated more stably, it is useful as a power supply circuit for a control device mounted on an electric device including the control device or an electric device in general.

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Rectification means 3 Stable voltage reduction means 4 Power supply interruption detection means 5 Control means 6 Power consumption means

Claims (1)

Rectifying means for generating a primary power source by rectifying and smoothing a high-voltage AC power source, which is a main part of a power source circuit, mounted on an electrical device having a control function, and consuming power of the primary power source In addition, stable voltage step-down means for stepping down and outputting a secondary power source stabilized at a specified voltage from the primary power source is detected, and the state of energization of the AC power supply device is detected, and the detection result is a signal indicating a change in voltage value. To a device of the AC power source by operating a power supply interruption detection means for outputting to the secondary power supply side and supplying power from the secondary power supply and reading a voltage signal output from the power supply interruption detection means. In a circuit configuration comprising a control means for performing control operation of the device while judging the energization state of the power source and also in a standby state where the device is stopped, the power consumption of the secondary power source is minimized. By means The connection to the secondary power source is controlled to be cut off. In the state where the secondary power source is connected to the secondary power source, the power source further includes a power load unit serving as a load for the power consumption of the secondary power source. A power supply circuit for an electric device that controls the power load means to be connected to a secondary power supply when it is determined that the energization of the AC power supply equipment is cut off from the voltage signal output from the power interruption detection means. .

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