JP2012005234A - Power supply circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply circuit where a primary circuit is isolated from a secondary circuit without using an insulating component that transmits abnormal signals, which are detection results of abnormalities in an input voltage being input to the primary circuit, to the secondary circuit with the primary circuit being isolated from the secondary circuit.SOLUTION: The power supply circuit 1 comprises the primary circuit powered from a power supply and the secondary circuit that converts a power to supply it to a load and is isolated from the primary circuit. In the power supply circuit 1, a controller section 70 generates a duty cycle indicating a ratio of an on-time per a predetermined cycle for turning a switch circuit section 10 on and off repeatedly in response to an output voltage value detected by an output voltage detection circuit section 60. Then the controller section 70 controls a drive circuit section 80 based on the generated duty cycle, and determines whether the input voltage being input to the primary circuit is abnormal or not based on the detected output voltage value and the duty cycle.

Description

  The present invention relates to a power supply circuit.

  A conventional power supply circuit may be configured as an insulation type in which a primary circuit and a secondary circuit are insulated by an insulation transformer. In such a conventional power supply circuit, the control unit that controls the operation state is often provided in either the primary side circuit or the secondary side circuit (see, for example, Patent Document 1). Therefore, the monitoring control information for controlling the power supply circuit is transmitted across the primary side circuit and the secondary side circuit. For example, the power supply circuit shown in FIG. 6 transmits an abnormality signal of the input voltage detected by the voltage detection circuit included in the primary side circuit to the control unit included in the secondary side circuit, and the control unit determines abnormality. .

JP 2009-17754 A

  However, in the power supply circuit shown in FIG. 6, it is necessary to insulate the primary side circuit and the secondary side circuit from the input voltage detection circuit unit included in the primary side circuit to the control unit included in the secondary side circuit. In order to transmit the detected abnormal signal, it is necessary to use an insulating component such as a photocoupler, a pulse transformer (insulating transformer), or an insulating voltage detecting IC (Integrated Circuit). For this reason, there was a problem that the number of parts constituting the circuit increased.

  The present invention has been made to solve the above problems, and its purpose is to detect an abnormality in the input voltage input to the primary circuit in a state where the primary circuit and the secondary circuit are insulated. It is an object of the present invention to provide a power supply circuit in which a primary side circuit and a secondary side circuit are insulated without using an insulating component that transmits a signal to a secondary side circuit.

  In order to solve the above problem, the present invention is a power supply circuit configured to insulate a primary circuit supplied with power from a power supply and a secondary circuit that converts the power and supplies the load to a load, An insulating transformer that insulates between the primary circuit and the secondary circuit, an output voltage detection circuit that detects an output voltage output from the secondary circuit to the load, and the primary circuit from the power source A switch circuit portion that is turned on or off to supply power to the drive circuit; a drive circuit portion that generates a drive signal that turns on or off the switch circuit portion; and a value of the output voltage detected by the output voltage detection circuit portion In response to this, a time ratio indicating a ratio of a predetermined conduction time per cycle in which the switch circuit unit is repeatedly turned on and off is generated, and the drive circuit is generated based on the generated time ratio. And a control unit that determines whether or not the input voltage input to the primary circuit is an abnormal voltage based on the detected value of the output voltage and the time ratio. It is.

  In the present invention, the control unit stores first information indicating that the input voltage is in a low-voltage abnormal state in which the input voltage is lower than a predetermined fluctuation range allowed as the input voltage. A first storage unit, wherein the detected output voltage value is equal to or less than a predetermined first threshold value, and the duty ratio is a maximum value within a settable range; It is determined that the input voltage is in the low voltage abnormal state, the first information is stored in the first storage unit, and the detected output voltage value is equal to or greater than a predetermined second threshold value. If the input voltage is normal, the input voltage is determined to be normal, the first information is erased from the first storage unit, and the first threshold value is predetermined as the output voltage. A value less than or equal to the lower limit indicated by the specified fluctuation range There, the second threshold value, characterized in that the a first threshold value or more.

  Further, the present invention is the above invention, wherein the control unit stores second information indicating that the input voltage is in an abnormal overvoltage state in which the input voltage is higher than a predetermined fluctuation range allowed as the input voltage. 2 when the value of the detected output voltage is equal to or greater than a predetermined third threshold value and the time ratio is a minimum value within a settable range. It is determined that the voltage is in the overvoltage abnormal state, the second information is stored in the second storage unit, and the value of the detected output voltage is equal to or less than a predetermined fourth threshold value. And determining that the input voltage is normal, erasing the second information from the second storage unit, and the third threshold value is a predetermined value allowed as the output voltage. A value greater than or equal to the upper limit indicated by the fluctuation range There, the fourth threshold value, wherein said a third following values threshold.

  According to the present invention, in the power supply circuit configured to insulate the primary side circuit supplied with power from the power supply and the secondary side circuit that converts power and supplies the load to the load, the output voltage detection circuit unit includes the secondary circuit The output voltage output from the side circuit to the load is detected. In addition, the control unit indicates a predetermined ratio of conduction time per cycle in which the switch circuit unit is repeatedly turned on and off according to the value of the output voltage detected by the output voltage detection circuit unit. Generate a ratio. The control unit controls the drive circuit unit based on the generated duty ratio. In addition, the control unit determines whether or not the input voltage input to the primary side circuit is an abnormal voltage based on the value of the output voltage detected by the output voltage detection circuit unit and the duty ratio. The output voltage output from the secondary side circuit to the load is correlated with both the input voltage input to the primary side circuit and the duty ratio. Therefore, based on the value of the output voltage output from the secondary circuit to the load detected by the output voltage detection circuit unit and the generated time ratio, the control unit detects an abnormality in the input voltage input to the primary circuit. Can be detected. As a result, in the present invention, the primary side circuit and the secondary side circuit are insulated from each other without using an insulating component that transmits an abnormal signal that detects an abnormality of the input voltage input to the primary side circuit to the secondary side circuit. A power supply circuit can be provided.

It is a block diagram which shows the power supply circuit by this embodiment. It is a graph which shows the operation | movement of the input low voltage detection of the power supply circuit in the embodiment. 4 is a flowchart showing an operation of detecting an input low voltage of the power supply circuit in the embodiment. It is a graph which shows the operation | movement of the input overvoltage detection of the power supply circuit in the embodiment. 4 is a flowchart showing an operation of detecting an input overvoltage of the power supply circuit in the same embodiment. It is a block diagram which shows the power supply circuit of a prior art.

Hereinafter, a power supply circuit according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic block diagram showing the power supply circuit 1 according to the present embodiment.
The power supply circuit 1 shown in FIG. 1 includes a switch circuit unit 10, an insulating transformer unit 20, a rectifier circuit unit 30, a coil 40, a capacitor 50, an output voltage detection circuit unit 60, a control unit 70, and a drive circuit unit 80. The power source 90 is a DC power source and is connected to the switch circuit unit 10. The power source 90 supplies power to the primary side circuit. The power supply circuit 1 is configured by insulating a primary side circuit to which power is supplied from the power source 90 and a secondary side circuit that converts the power and supplies it to a load (not shown).

The switch circuit unit 10 is disposed between the power supply 90 and the insulating transformer unit 20. The switch circuit unit 10 conducts or cuts off the power supply 90 and the primary coil of the insulating transformer unit 20 based on the drive signal supplied from the drive circuit unit 80.
The insulating transformer unit 20 is disposed between the primary side circuit and the secondary side circuit. The insulating transformer unit 20 includes a primary side coil and a secondary side coil which are insulated from each other, and insulates the primary side circuit and the secondary side circuit. The insulating transformer unit 20 converts the AC signal supplied as power from the power supply 90 to the primary coil via the switch circuit unit 10 and supplies the converted AC signal to the rectifier circuit unit 30 from the secondary coil. .
The rectifier circuit unit 30 rectifies the AC signal supplied from the insulating transformer unit 20 into a signal based on the ground terminal of the secondary circuit. The rectifier circuit unit 30 supplies a rectified signal (rectified signal) to the coil 40.

The coil 40 supplies a voltage (output voltage) according to the cycle of the rectified signal supplied from the rectifier circuit unit 30 and a duty (duty) to an unillustrated load.
The capacitor 50 is connected to the ground terminal of the secondary side circuit and the output line, and smoothes and stabilizes the output voltage supplied to the load by the coil 40.
The output voltage detection circuit unit 60 includes, for example, an analog / digital converter (ADC). The output voltage detection circuit unit 60 detects the output voltage of the secondary circuit as an analog signal, and supplies the output voltage information of the digital signal including the detected output voltage value to the control unit 70.
The drive circuit unit 80 is disposed between the control unit 70 and the switch circuit unit 10. The drive circuit unit 80 generates a drive signal corresponding to the duty supplied from the control unit 70 and supplies the drive signal to the switch circuit unit 10.

  The control unit 70 generates a duty corresponding to the value of the output voltage detected by the output voltage detection circuit unit 60 and supplies it to the drive circuit unit 80. Here, the duty is a time ratio indicating a ratio of a predetermined conduction time per cycle in which the switch circuit unit 10 is repeatedly turned on and off. Further, the control unit 70 determines whether or not the input voltage (voltage of the power supply 90) of the primary side circuit is an abnormal voltage based on the value of the output voltage supplied from the output voltage detection circuit unit 60 and the duty. . Here, the abnormal voltage is, for example, a voltage that falls outside a predetermined fluctuation range in which the input voltage of the primary circuit is allowed as the input voltage. In addition, when the control unit 70 determines that the voltage of the power supply 90 is an abnormal voltage, the control unit 70 performs a protection operation. The protection operation includes, for example, control for outputting an alarm to an alarm output unit (not shown), control for stopping the operation of the primary side circuit, and the like.

The control unit 70 includes an OnDuty (on duty) generation unit 71, an abnormality determination unit 72, and a storage unit 73.
The OnDuty generation unit 71 generates a Duty corresponding to the value of the output voltage detected by the output voltage detection circuit unit 60. The OnDuty generation unit 71 supplies the generated Duty to the drive circuit unit 80.
The abnormality determination unit 72 determines whether or not the voltage of the power supply 90 is an abnormal voltage based on the value of the output voltage detected by the output voltage detection circuit unit 60 and the duty generated by the OnDuty generation unit 71. judge. Based on the determination as to whether or not the voltage of the power supply 90 is an abnormal voltage, the abnormality determination unit 72 stores information indicating that the input voltage of the primary side circuit is an abnormal voltage in the storage unit 73 (for example, a logic state). “1”) is stored or information is deleted.
The storage unit 73 includes an input undervoltage flag 731 and an input overvoltage flag 732, and stores information indicating that the input voltage of the primary side circuit is an abnormal voltage that is outside a predetermined fluctuation range that is allowed. . The input low voltage flag 731 stores information (first information) indicating that the input voltage of the primary side circuit is in a low voltage abnormal state that is lower than a predetermined fluctuation range allowed as the input voltage. Further, the input overvoltage flag 732 stores information (second information) indicating an overvoltage abnormality state in which the input voltage of the primary side circuit has risen above a predetermined fluctuation range that is allowed.

Next, the operation of this embodiment will be described.
First, an operation in which the power supply circuit 1 shown in FIG. 1 generates an output voltage will be described.
Based on the drive signal supplied from the drive circuit unit 80, the switch circuit unit 10 repeatedly conducts and shuts off between the power supply 90 and the primary coil of the insulating transformer unit 20. The insulating transformer unit 20 converts the AC signal supplied as power from the power supply 90 to the primary coil via the switch circuit unit 10 and supplies the converted AC signal to the rectifier circuit unit 30 from the secondary coil. . The rectifier circuit unit 30 generates a rectified signal obtained by rectifying the converted AC signal, and supplies the rectified signal to the coil 40. The coil 40 outputs a voltage corresponding to the period of the rectified signal supplied from the rectifier circuit unit 30 and the duty as an output voltage. The output voltage is smoothed by the capacitor 50 and output as a desired voltage.

  The OnDuty generation unit 71 of the control unit 70 generates a Duty corresponding to the value of the output voltage detected by the output voltage detection circuit unit 60. The OnDuty generation unit 71 supplies a control signal indicating the generated Duty to the drive circuit unit 80. The drive circuit unit 80 generates a drive signal corresponding to the duty based on the control signal supplied from the on-duty generation unit 71 and supplies the drive signal to the switch circuit unit 10. Here, the output voltage of the power supply circuit 1 is determined by the cycle of the drive signal generated by the drive circuit unit 80 and the duty. Therefore, the OnDuty generation unit 71 controls the drive circuit unit 80 so that the output voltage of the power supply circuit 1 is within a predetermined fluctuation range allowed as the output voltage of the power supply circuit 1.

  For example, when the OnDuty generation unit 71 determines that the value of the output voltage detected by the output voltage detection circuit unit 60 is higher than a predetermined reference voltage value (rated value), the OnDuty generation unit 71 sets the duty to Control to lower. Thereby, the conduction | electrical_connection period of the switch circuit part 10 becomes short, and the output voltage of the power supply circuit 1 falls. In addition, when the OnDuty generation unit 71 determines that the value of the output voltage detected by the output voltage detection circuit unit 60 is lower than a predetermined reference voltage value (rated value), the OnDuty generation unit 71 determines the duty. Control to increase. Thereby, the conduction | electrical_connection period of the switch circuit part 10 becomes long, and the output voltage of the power supply circuit 1 rises. By repeating the duty control by the on-duty generation unit 71, the output voltage of the power supply circuit 1 is maintained at a predetermined reference voltage value (rated value).

Next, the determination operation when the power supply circuit 1 shown in FIG. 1 is in an abnormal state of the input voltage of the primary circuit will be described.
First, the operation when the input voltage of the primary side circuit is in the low voltage abnormal state will be described.
FIG. 2 is a graph showing the operation of detecting the input low voltage of the power supply circuit 1 in the same embodiment.
In the graph of FIG. 2A, the horizontal axis indicates the input voltage input to the primary circuit, and the left vertical axis indicates the output voltage output from the secondary circuit. The right vertical axis indicates Duty. Here, the waveform 401 indicates the value of the output voltage detected by the output voltage detection circuit unit 60 with respect to the input voltage input to the primary side circuit. A waveform 711 indicates the duty generated by the on-duty generation unit 71 with respect to the input voltage input to the primary side circuit.
In the graph (waveform 721) of FIG. 2B, the horizontal axis indicates the input voltage input to the primary circuit, and the vertical axis indicates the logic state of the input low voltage flag 731.

In FIG. 2, the OnDuty generator 71 performs control to increase the duty so that the output voltage output to the secondary circuit does not decrease when the input voltage input to the primary circuit decreases. As a result, the duty of the waveform 711 is increased, but the output voltage of the waveform 401 is kept constant (region higher than the input voltage V1). However, when the input voltage input to the primary circuit further decreases, the duty is fixed to the maximum value (Duty MAX), and the output voltage indicated by the waveform 401 decreases (region from the input voltage V0 to V1). .
In the waveform 401, when the value of the output voltage detected by the output voltage detection circuit unit 60 becomes smaller than a predetermined first threshold value, the abnormality determination unit 72 determines that the low voltage abnormality state is present. . Here, the low voltage abnormal state indicates an abnormal state in which the input voltage input to the primary circuit is low. In this case, the abnormality determination unit 72 stores the logic information “1” in the input low voltage flag 731 of the storage unit 73 and sets the input low voltage flag 731. That is, the abnormality determination unit 72 sets the logical information “1” as a flag indicating an abnormal state, and stores it in the input low voltage flag 731 of the storage unit 73. As a result, the waveform 721 shifts to “1” at the input voltage at the point P1.
In addition, when the output voltage detected by the output voltage detection circuit unit 60 of the waveform 401 increases and becomes larger than a predetermined second threshold value, the abnormality determination unit 72 determines that the input voltage is a normal value. It is determined that In this case, the abnormality determination unit 72 stores the logic information “0” in the input low voltage flag 731 of the storage unit 73 and cancels the input low voltage flag 731. That is, the abnormality determination unit 72 cancels the logical information “1” as a flag indicating an abnormal state and erases it from the input low voltage flag 731 of the storage unit 73. As a result, the waveform 721 shifts to “0” at the input voltage at the point P2.

  The first threshold value is, for example, a value equal to or lower than a lower limit value indicated by a predetermined variation range allowed as an output voltage output from the secondary side circuit. Further, the second threshold value is set to a value equal to or higher than the first threshold value, for example. The first threshold value and the second threshold value are information stored in advance in an area (not shown) of the storage unit 73, for example.

FIG. 3 is a flowchart showing the operation of detecting the input low voltage of the power supply circuit 1 in the same embodiment.
In FIG. 3, first, the abnormality determination unit 72 acquires the value of the output voltage detected by the output voltage detection circuit unit 60 (step S701). Next, the abnormality determination unit 72 acquires the duty generated by the on duty generation unit 71 (step S702).
Next, the abnormality determination unit 72 determines whether or not the acquired value of the output voltage is equal to or less than a predetermined first threshold value (step S703). If it is determined in step S703 that the acquired output voltage value is equal to or less than a predetermined first threshold value, the process proceeds to step S704. If it is determined in step S703 that the acquired output voltage value is smaller than the predetermined first threshold value, the process proceeds to step S706.

  In step S704, the abnormality determination unit 72 determines whether or not the acquired duty is the maximum value within a settable range. If the abnormality determination unit 72 determines that the acquired duty is the maximum value within a settable range, the abnormality determination unit 72 determines that the input voltage input to the primary circuit is in a low-voltage abnormality state. In this case, the abnormality determination unit 72 stores the logical information “1” in the input low voltage flag 731 of the storage unit 73 (stores the first information), and sets the input low voltage flag 731 (step S705). ). In step S704, when the abnormality determination unit 72 determines that the acquired duty is not the maximum value in the settable range, the process returns to step S701.

  In step S706, the abnormality determination unit 72 determines whether or not the acquired output voltage value is equal to or greater than a predetermined second threshold value. The abnormality determination unit 72 determines that the input voltage input to the primary circuit is in a normal state when it is determined that the acquired output voltage value is equal to or greater than a predetermined second threshold value. To do. In this case, the abnormality determination unit 72 stores the logic information “0” in the input low voltage flag 731 of the storage unit 73 (deletes the first information), and cancels the input low voltage flag 731 (step S707). ). In step S706, when the abnormality determination unit 72 determines that the acquired output voltage value is smaller than a predetermined second threshold value, the process returns to step S701.

Next, the operation when the input voltage of the primary side circuit is in an overvoltage abnormal state will be described.
FIG. 4 is a graph showing the operation of input overvoltage detection of the power supply circuit 1 in the same embodiment.
In the graph of FIG. 4A, the horizontal axis indicates the input voltage input to the primary circuit, and the left vertical axis indicates the output voltage output from the secondary circuit. The right vertical axis indicates Duty. Here, the waveform 402 indicates the value of the output voltage detected by the output voltage detection circuit unit 60 with respect to the input voltage input to the primary circuit. A waveform 712 indicates the duty generated by the on-duty generation unit 71 with respect to the input voltage input to the primary side circuit.
In the graph (waveform 722) of FIG. 4B, the horizontal axis indicates the input voltage input to the primary circuit, and the vertical axis indicates the logic state of the input overvoltage flag 732.

In FIG. 4, the OnDuty generation unit 71 performs control to reduce the Duty so that the output voltage output to the secondary circuit does not increase when the input voltage input to the primary circuit increases. As a result, the duty of the waveform 712 is reduced, but the output voltage of the waveform 402 is kept constant (region lower than the input voltage V2). However, when the input voltage input to the primary circuit further increases, the Duty is fixed to a minimum value (Duty MIN), and the output voltage indicated by the waveform 402 increases (region higher than the input voltage V2).
In the waveform 402, when the value of the output voltage detected by the output voltage detection circuit unit 60 becomes larger than a predetermined third threshold value, the abnormality determination unit 72 determines that the overvoltage abnormality state is present. Here, the overvoltage abnormal state indicates an abnormal state where the input voltage input to the primary circuit is high. In this case, the abnormality determination unit 72 stores the logic information “1” in the input overvoltage flag 732 of the storage unit 73 and sets the input overvoltage flag 732. That is, the abnormality determination unit 72 sets the logical information “1” as a flag indicating an abnormal state, and stores it in the input overvoltage flag 732 of the storage unit 73. As a result, the waveform 722 shifts to “1” at the input voltage at the point P3.
In addition, when the output voltage detected by the output voltage detection circuit unit 60 of the waveform 402 decreases and becomes smaller than a predetermined fourth threshold value, the abnormality determination unit 72 determines that the input voltage is a normal value. It is determined that In this case, the abnormality determination unit 72 stores the logic information “0” in the input overvoltage flag 732 of the storage unit 73 and cancels the input overvoltage flag 732. That is, the abnormality determination unit 72 cancels the logical information “1” as a flag indicating an abnormal state and erases it from the input overvoltage flag 732 of the storage unit 73. As a result, the waveform 722 shifts to “0” at the input voltage at the point P4.

  The third threshold value is, for example, a value equal to or higher than an upper limit value indicated by a predetermined fluctuation range allowed as an output voltage output from the secondary side circuit. Further, the fourth threshold value is set to a value equal to or smaller than the third threshold value, for example. Further, the second threshold value and the fourth threshold value are information stored in advance in an area (not shown) of the storage unit 73, for example.

FIG. 5 is a flowchart showing the operation of detecting the input overvoltage of the power supply circuit 1 in the same embodiment.
In FIG. 5, first, the abnormality determination unit 72 acquires the value of the output voltage detected by the output voltage detection circuit unit 60 (step S711). Next, the abnormality determination unit 72 acquires the duty generated by the on duty generation unit 71 (step S712).
Next, the abnormality determination unit 72 determines whether or not the acquired output voltage value is equal to or greater than a predetermined third threshold value (step S713). If it is determined in step S713 that the acquired output voltage value is greater than or equal to a predetermined third threshold value, the process proceeds to step S714. If it is determined in step S713 that the acquired output voltage value is greater than the predetermined third threshold value, the process proceeds to step S716.

  In step S714, the abnormality determination unit 72 determines whether or not the acquired duty is the minimum value in a settable range. If the abnormality determination unit 72 determines that the acquired duty is the minimum value within the settable range, the abnormality determination unit 72 determines that the input voltage input to the primary circuit is in an overvoltage abnormality state. In this case, the abnormality determination unit 72 stores the logical information “1” in the input overvoltage flag 732 of the storage unit 73 (stores the second information), and sets the input overvoltage flag 732 (step S715). In step S714, when the abnormality determination unit 72 determines that the acquired duty is not the minimum value in the settable range, the process returns to step S711.

  In step S716, the abnormality determination unit 72 determines whether or not the acquired value of the output voltage is equal to or less than a predetermined fourth threshold value. The abnormality determination unit 72 determines that the input voltage input to the primary circuit is in a normal state when it is determined that the acquired output voltage value is equal to or less than a predetermined fourth threshold value. To do. In this case, the abnormality determination unit 72 stores the logical information “0” in the input overvoltage flag 732 of the storage unit 73 (deletes the second information), and cancels the input overvoltage flag 732 (step S717). In Step S716, when it is determined that the value of the acquired output voltage is greater than a predetermined fourth threshold value, the abnormality determining unit 72 returns to the process of Step S711.

  As described above, in the power supply circuit 1, the OnDuty generation unit 71 of the control unit 70 generates a Duty corresponding to the value of the output voltage detected by the output voltage detection circuit unit 60. Further, the abnormality determination unit 72 of the control unit 70 is input based on the duty generated by the on-duty generation unit 71 and the value of the output voltage detected by the output voltage detection circuit unit 60. It is determined whether the voltage is an abnormal voltage. The output voltage output from the secondary side circuit is correlated to both the input voltage input to the primary side circuit and the duty. Therefore, based on the value of the output voltage output from the secondary side circuit detected by the output voltage detection circuit unit 60 and the duty generated by the OnDuty generation unit 71, the abnormality determination unit 72 is connected to the primary side circuit. It is possible to detect an abnormality in the input voltage (undervoltage abnormal state and overvoltage abnormal state). Thereby, in the power supply circuit 1, it is not necessary to use insulation components, such as a photocoupler, a pulse transformer (insulation transformer), and an insulation type voltage detection IC (Integrated Circuit), and the components constituting the circuit can be reduced. In addition, the power supply circuit 1 is insulated between the primary side circuit and the secondary side circuit without using an insulating component that transmits an abnormal signal that detects an abnormality of the input voltage input to the primary side circuit to the secondary side circuit. A power supply circuit can be provided.

According to the embodiment of the present invention, the power supply circuit 1 configured to insulate the primary side circuit supplied with power from the power source 90 and the secondary side circuit that converts the power and supplies the load to the load includes: In order to supply power from the power supply 90 to the primary side circuit, the isolation transformer unit 20 that insulates the secondary side circuit, the output voltage detection circuit unit 60 that detects the output voltage output from the secondary side circuit to the load, and Corresponding to the value of the output voltage detected by the output voltage detection circuit unit 60, the switch circuit unit 10 that is conducted or cut off, the drive circuit unit 80 that generates a drive signal that conducts or cuts off the switch circuit unit 10, The drive circuit is generated based on the generated time ratio (Duty) by generating a time ratio (Duty) indicating a ratio of a predetermined conduction time per cycle in which the switch circuit unit 10 is repeatedly turned on and off. 80 controls, based on the value and the duty ratio of the detected output voltage (Duty), and a control unit 70 judges whether an input voltage inputted to a primary side circuit is abnormal voltage.
As a result, the power supply circuit 1 is input to the primary side circuit based on the value of the output voltage output from the secondary side circuit detected by the output voltage detection circuit unit 60 and the duty generated by the OnDuty generation unit 71. It is possible to detect abnormal input voltage (undervoltage abnormal state and overvoltage abnormal state). Therefore, the power supply circuit 1 is insulated between the primary side circuit and the secondary side circuit without using an insulating component that transmits an abnormal signal that detects an abnormality of the input voltage input to the primary side circuit to the secondary side circuit. A power supply circuit can be provided.

In addition, the control unit 70 stores first information (logic information “1”) indicating that the input voltage is in a low-voltage abnormal state in which the input voltage is lower than a predetermined fluctuation range allowed as the input voltage. Storage unit (input low voltage flag 731), the detected output voltage value is equal to or smaller than a predetermined first threshold value, and the maximum value is within a range in which the duty ratio (Duty) can be set. If the input voltage is low, it is determined that the input voltage is in a low voltage abnormal state, the first information (logic information “1”) is stored in the first storage unit (input low voltage flag 731), and the detected output is detected. When the voltage value is equal to or greater than a predetermined second threshold value, it is determined that the input voltage is normal, and the first information (logic information “1”) is stored in the first storage unit (input low Erase from voltage flag 731). Further, the first threshold value is a value equal to or lower than a lower limit value indicated by a predetermined fluctuation range allowed as the output voltage. Further, the second threshold value is a value equal to or greater than the first threshold value.
Thereby, the power supply circuit 1 can respond to the low voltage abnormal state which shows the abnormal state where the input voltage input to the primary circuit is low.

In addition, the control unit 70 stores second information (logic information “1”) indicating that the input voltage is in an overvoltage abnormal state in which the input voltage has risen above a predetermined fluctuation range allowed as the input voltage. A storage unit (input overvoltage flag 732) is provided, the detected output voltage value is equal to or greater than a predetermined third threshold value, and is the minimum value within a range in which the duty ratio (Duty) can be set. In this case, it is determined that the input voltage is in an overvoltage abnormal state, the second information (logic information “1”) is stored in the second storage unit (input overvoltage flag 732), and the detected output voltage value is When it is equal to or lower than a predetermined fourth threshold value, it is determined that the input voltage is normal, and the second information (logic information “1”) is stored from the second storage unit (input overvoltage flag 732). to erase. The third threshold value is a value equal to or higher than an upper limit value indicated by a predetermined fluctuation range allowed as an output voltage, and the fourth threshold value is a value equal to or lower than the third threshold value. .
Thereby, the power supply circuit 1 can respond to the overvoltage abnormal state which shows the abnormal state where the input voltage input into the primary side circuit is high.

In addition, this invention is not limited to said embodiment, It can change in the range which does not deviate from the meaning of this invention. In the present invention, the primary side circuit supplied with power from the power source 90 and the secondary side circuit that converts power and supplies it to the load are insulated from each other, and the value of the output voltage output to the secondary side circuit is obtained. Any other form may be used as long as the power supply circuit generates the duty based on the duty and controls the output voltage based on the duty.
In the above embodiment, the first threshold value has a different value form from the second threshold value. However, the first threshold value has the same value as the second threshold value. But it ’s okay. Further, although the first threshold value has been described as being below the lower limit value indicated by the predetermined fluctuation range allowed as the output voltage of the power supply circuit 1, it may be a value less than the lower limit value.
In the above embodiment, the third threshold value has a different value form from the fourth threshold value. However, the third threshold value has the same value as the fourth threshold value. But it ’s okay. Further, the third threshold value has been described as being above the upper limit value indicated by the predetermined fluctuation range allowed as the output voltage, but may be a value exceeding the upper limit value.

In the above embodiment, the input undervoltage flag 731 and the input overvoltage flag 732 have been described as storage areas of the storage unit 73, but other forms may be used. For example, the control unit 70 may include two storage units, and the input undervoltage flag 731 and the input overvoltage flag 732 may be included in different storage units. In addition, although the mode in which the input undervoltage flag 731 and the input overvoltage flag 732 are different from each other has been described, for example, a mode in which one flag is shared as an input abnormality flag may be used. In addition, the abnormality determination unit 72 may be configured to determine either a low voltage abnormal state or an overvoltage abnormal state. Further, the first to fourth threshold values have been described as being stored in the storage unit 73, but may be stored in other storage units. Moreover, although the control part 70 demonstrated the form provided with the memory | storage part 73, the form provided with a memory | storage part in addition to the control part 70 may be sufficient.
Further, in the two flowcharts shown in FIGS. 3 and 5, the processing in steps S701 and S711 and the processing in steps S702 and S712 have been described as being processed individually, but they may be processed in common.

Moreover, in said embodiment, although the output voltage detection part 60 demonstrated the form provided with ADC, it is not limited to this. For example, a plurality of comparators may be provided to output a comparison result with several voltage values such as a reference voltage value (rated value) and first to fourth threshold values.
In the above embodiment, the processing of each unit of the control unit 70 may be realized by dedicated hardware such as an IC (Integrated Circuit) or may be realized by software processing.

  The power supply circuit 1 described above has a computer system therein. The process of the control unit 70 described above is stored in a computer-readable recording medium in the form of a program, and the above process is performed by the computer reading and executing this program. Here, the computer-readable recording medium means a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Alternatively, the computer program may be distributed to the computer via a communication line, and the computer that has received the distribution may execute the program.

DESCRIPTION OF SYMBOLS 1 Power supply circuit 10 Switch circuit part 20 Isolation transformer part 30 Rectifier circuit part 40 Coil 50 Capacitor 60 Output voltage detection circuit part 70 Control part 71 OnDuty generation part 72 Abnormality judgment part 73 Storage part 80 Drive circuit part 90 Power supply 731 Input low voltage flag 732 Input overvoltage flag

Claims (3)

A power circuit configured to insulate a primary side circuit supplied with power from a power source and a secondary side circuit that converts the power and supplies it to a load;
An insulating transformer that insulates between the primary circuit and the secondary circuit;
An output voltage detection circuit unit for detecting an output voltage output from the secondary circuit to the load;
A switch circuit portion that is turned on or off to supply power from the power source to the primary circuit;
A drive circuit unit for generating a drive signal for conducting or blocking the switch circuit unit;
In correspondence with the value of the output voltage detected by the output voltage detection circuit unit, a time ratio is generated that indicates a ratio of a predetermined conduction time per cycle in which the switch circuit unit is repeatedly turned on and off. And controlling the drive circuit unit based on the generated time ratio,
A power supply circuit comprising: a control unit that determines whether or not an input voltage input to the primary side circuit is an abnormal voltage based on the value of the detected output voltage and the time ratio. . The controller is
A first storage unit that stores first information indicating that the input voltage is in a low-voltage abnormal state that is lower than a predetermined fluctuation range allowed as the input voltage;
When the detected output voltage value is equal to or less than a predetermined first threshold value and the time ratio is a maximum value within a settable range, the input voltage is in the low-voltage abnormal state. And determine that the first information is stored in the first storage unit,
When the detected output voltage value is equal to or greater than a predetermined second threshold value, it is determined that the input voltage is normal, and the first information is erased from the first storage unit. And
The first threshold value is a value equal to or lower than a lower limit value indicated by a predetermined fluctuation range allowed as the output voltage,
The power supply circuit according to claim 1, wherein the second threshold value is equal to or greater than the first threshold value. The controller is
A second storage unit that stores second information indicating that the input voltage is in an overvoltage abnormal state in which the input voltage is higher than a predetermined fluctuation range allowed as the input voltage;
When the detected output voltage value is equal to or greater than a predetermined third threshold value and the time ratio is a minimum value within a settable range, the input voltage is in the overvoltage abnormal state. Determining that there is, storing the second information in the second storage unit,
When the detected output voltage value is less than or equal to a predetermined fourth threshold value, it is determined that the input voltage is normal, and the second information is erased from the second storage unit And
The third threshold value is a value equal to or higher than an upper limit value indicated by a predetermined fluctuation range allowed as the output voltage,
The power supply circuit according to claim 1, wherein the fourth threshold value is a value equal to or less than the third threshold value.

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