JP2011130585A - Power transmitting circuit, and power supply device and electric apparatus with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power transmitting circuit that prevents a flow of excessively large rush current by an insufficient state of charge and easily cancels the insufficient state of charge. <P>SOLUTION: The power transmitting circuit transmits an input power through a power transmission line to a power transmission target. The power transmitting circuit includes a conduction switch which switches on and off to make the power transmission line conductive and nonconductive, a smoothing capacitor which has one electrode connected to the downstream side of the conductive switch and smoothes a power transmitted through the power transmission line, a power detecting circuit which detects whether the power is within an allowable range on the upstream side of the conduction switch, a charge detecting circuit which detects whether a charge volume of the smoothing capacitor reaches a reference volume, and a switch control circuit which controls the conduction switch. The switch control circuit controls the conduction switch based on the results of detection by the power detecting circuit until the charge volume of the smoothing capacitor reaches the reference volume. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power transmission circuit that transmits input power to a power supply target, and a power supply device and an electrical apparatus including the same.

  2. Description of the Related Art Conventionally, there has been used a power transmission circuit that sends input power to a power transmission target by adding processing such as rectification and smoothing to the input power. The power transmission circuit is used by being connected between an AC power supply and a power transmission target, for example, so that power in a more manageable state is supplied to the power transmission target. A configuration example of such a power transmission circuit will be briefly described.

  FIG. 6 is a configuration diagram of the power transmission circuit. In this power transmission circuit, an AC power source 111 is connected to the front side, and a power transmission target (for example, a switching power source) 112 is connected to the rear side. The AC power supply 111 and the power transmission target 112 are connected by a power transmission line in which a filter 113, a relay switch 121, a bridge diode rectifier circuit D11, and a PFC [Power Factor Correction] circuit 114 are sequentially interposed. The power transmission line is provided with a smoothing capacitor 115 that smoothes the power.

  The power transmission line is also connected to the microcomputer MC via the bridge diode rectifier circuit D12 and the switching power supply 120, and the microcomputer MC is supplied with driving power from the AC power supply 111. Further, the microcomputer MC can switch the state of the relay switch 121.

  This power delivery circuit operates as follows. When the power transmission circuit is in the standby mode (the relay switch 121 is opened, the power transmission line is non-conductive, and the power is not transmitted), the microcomputer MC instructs the operation start from the outside. Accept. When an instruction to start the operation is given, the microcomputer MC closes the relay switch 121 and turns on the power transmission line. As a result, the power transmission circuit enters a state (steady operation mode) in which power input from the AC power supply 111 is transmitted to the power transmission target 112 via the power transmission line. In the steady operation mode, the input power is rectified and smoothed by the action of the bridge diode rectifier circuit D12 and the smoothing capacitor 115.

JP 2008-160996 A JP 2007-215300 A JP 2005-073405 A JP 2004-364484 A

  Here, attention is paid to the state of charge of the smoothing capacitor 115 in the power transmission circuit described above. In the standby mode, the smoothing capacitor 115 is in a state where it is not charged, or is in a state where the amount of charge is smaller (undercharged state) than in the steady operation mode. The undercharged state is eliminated by the current flowing through the power transmission line and the current being gradually charged, so that the smoothing capacitor 115 is finally fully charged.

  However, when the smoothing capacitor 115 is in an undercharged state, if a relatively large amount of power is input to the power transmission circuit when the power transmission line is in a conductive state, an excessive rush current flows through the power transmission line. This tendency becomes more prominent as the capacity of the smoothing capacitor 115 increases. When such an excessive rush current flows, there is a concern that the power transmission circuit and the power transmission target may be damaged or damaged.

  In view of the above-described problems, an object of the present invention is to provide a power transmission circuit that can easily eliminate an undercharged state while preventing an excessive rush current from flowing due to an undercharged state as much as possible. .

  In order to achieve the above object, a power transmission circuit according to the present invention is a power transmission circuit that includes a power transmission line and transmits input power that has been input to a power transmission target through the power transmission line. A conduction switch provided on the power transmission line for switching between conduction / non-conduction of the power transmission line and one electrode connected to the downstream side of the conduction switch on the power transmission line. A smoothing capacitor for smoothing the power in the power transmission line and whether the power upstream of the conduction switch on the power transmission line is within a predetermined allowable range. A power detection circuit that detects whether or not a charge amount of the smoothing capacitor has reached a predetermined reference amount, and a switch that controls the conduction switch. And a control circuit, and the switch control circuit, until the amount of charge of the smoothing capacitor reaches the reference amount, based on a detection result of the power detection circuit is configured to control the conduction switch.

  According to this configuration, the conduction switch is controlled based on the detection result of the power detection circuit until the undercharged state of the smoothing capacitor is eliminated (until the charge amount reaches the reference amount), and the conduction / non-conduction of the power transmission line is controlled. It becomes possible to switch conduction. Therefore, it becomes easy to eliminate the undercharged state while preventing the excessive rush current from flowing due to the undercharged state as much as possible.

  In the above configuration, the switch control circuit is configured such that when the power upstream of the conduction switch on the power transmission line is within the allowable range, the power transmission line is in a conduction state. When the power upstream of the conduction switch on the power transmission line is not within the allowable range, the conduction switch may be controlled so that the power transmission line is in a non-conduction state. .

  According to this configuration, by setting the allowable range to a level that does not allow excessive rush current to flow even in an undercharged state, it is possible to prevent excessive rush current from flowing due to an excessively charged state. It is possible to eliminate the undercharged state while preventing it.

  More specifically, in the configuration described above, the switch control circuit is configured such that after the amount of charge of the smoothing capacitor reaches the reference amount, the power transmission line is turned on regardless of the detection result of the power detection circuit. The conduction switch may be controlled so as to be maintained in a state. According to this configuration, it is possible to suppress unnecessary switching of the conduction switch.

  Further, in the above configuration, AC power may be input as the input power, and a rectifier circuit that rectifies the AC power may be provided in front of the conduction switch on the power transmission line. Good.

  According to this configuration, for example, it is possible to connect an AC power supply to the front side and transmit the power obtained from the AC power supply to the power transmission target through the power transmission line.

  A power supply apparatus according to the present invention includes a power transmission circuit according to the above configuration and a switching power supply as the power transmission target, and the switching power supply indicates a state of power transmitted from the power transmission circuit. It is set as the structure which converts and outputs the electric power after conversion. Moreover, the electrical equipment according to the present invention is configured to include the power supply device having the above configuration. According to the power supply device and the electric apparatus, it is possible to enjoy the advantages related to the power transmission circuit having the above configuration.

  As described above, according to the power transmission circuit of the present invention, the conduction switch is controlled based on the detection result of the power detection circuit until the undercharged state of the smoothing capacitor is resolved (until the charge amount reaches the reference amount). Thus, it is possible to switch between conduction / non-conduction of the power transmission line. Therefore, it becomes easy to eliminate the undercharged state while preventing the excessive rush current from flowing due to the undercharged state as much as possible.

It is a block diagram showing the structure of the electric power transmission circuit which concerns on embodiment of this invention. It is a flowchart in connection with starting operation which concerns on embodiment of this invention. It is an example of the timing chart regarding the state of a conduction switch. It is another example of the timing chart regarding the state of a conduction switch. It is explanatory drawing showing the circuit structural example of the electric power transmission circuit which concerns on embodiment of this invention. It is explanatory drawing showing the circuit structural example of the conventional power transmission circuit.

  The embodiment of the present invention will be described below with an example of a power transmission circuit.

  FIG. 1 is a block diagram showing the configuration of the power transmission circuit. As shown in the figure, the power transmission circuit 1 includes a power transmission line 10, a rectifier circuit 11, a conduction switch 12, a smoothing capacitor 13, a switch control circuit 14, a power detection circuit 15, a charge detection circuit 16, and the like. The power transmission circuit 1 is used by connecting an AC power source on the front side and a power transmission target (for example, a switching power source) on the rear side.

  The power transmission line 10 connects an AC power source and a power transmission target, and AC power is input from the AC power source. And the electric power transmission line 10 transmits the input alternating current power toward the back | latter stage side, and sends it out to electric power sending object.

  However, the power transmission line 10 is switched between conduction and non-conduction by a conduction switch 12. The power transmission line 10 transmits power from the front stage side to the rear stage side only when it is in a conductive state. The power transmission line 10 may be provided with some circuit or device such as a PFC circuit.

  The rectifier circuit 11 is provided in the middle of the power transmission line 10 and plays the role of rectifying the input AC power. The conduction switch 12 is provided in the middle of the power transmission line 10 and on the downstream side of the rectifier circuit 11, and switches the conduction / non-conduction of the power transmission line 10 by switching the presence / absence of disconnection of the portion. It is.

  The conduction switch 12 is formed of, for example, a transistor, and when in the “ON” state, the power transmission line 10 is in a conduction state, and when in the “OFF” state, the power transmission line 10 is in a non-conduction state. . Switching of the conduction switch 12 is controlled by the switch control circuit 14.

  The smoothing capacitor 13 is a capacitor that smoothes the power in the power transmission line 10. The smoothing capacitor 13 has a configuration in which one electrode is connected to a location downstream of the conduction switch 12 in the power transmission line 10 and the other electrode is grounded.

  The switch control circuit 14 is formed of, for example, various logic circuits and the like, and controls switching between the ON state and the OFF state of the conduction switch 12 based on various information. The switch control circuit 14 receives an instruction to start or stop the operation from the outside, and operates according to the instruction. How the switch control circuit 14 controls the conduction switch 12 will be described again.

  The power detection circuit 15 monitors the power (hereinafter sometimes referred to as “detection power” for convenience) in the power transmission line 10 at a location upstream of the conduction switch 12 and the magnitude of the detection power is determined. It is continuously detected whether or not it is within a predetermined allowable range. The detection power may be current or voltage at the predetermined location. Information on the detection result by the power detection circuit 15 is transmitted to the switch control circuit 14. As a result, information indicating whether or not the magnitude of the detection power is currently within the allowable range is transmitted to the switch control circuit 14 in real time.

  The charge detection circuit 16 monitors the charge amount of the smoothing capacitor 13 and continuously detects whether or not the charge amount has reached a predetermined reference amount. The charge amount can be monitored, for example, by monitoring the voltage of one electrode in the smoothing capacitor. Information on the detection result by the charge detection circuit 16 is transmitted to the switch control circuit 14. As a result, information indicating whether or not the current charge amount has reached the reference amount is transmitted to the switch control circuit 14 in real time.

  In addition, as the operation state of the power transmission circuit 1, “standby mode”, “start-up mode”, and “steady operation mode” are prepared. The standby mode is a mode in which the operation start instruction is received (standby) while the conduction switch 12 is maintained in the OFF state (that is, without transmitting power). When receiving the instruction to start the operation, the power transmission circuit 1 in the standby mode shifts to the steady operation mode through the activation mode.

  The start-up mode is a state in which a start-up operation is performed to shift its own state from the standby mode to the steady operation mode. The start-up operation is performed when the smoothing capacitor 13 is in an undercharged state (a state in which charging is not performed or a state in which the amount of charge is small compared to the steady operation mode) while preventing an excessive rush current from flowing. The main purpose is to charge 13 and eliminate the undercharged state.

  The steady operation mode is a state in which the conduction switch 12 is maintained in the ON state and power is transmitted. The power transmission circuit 1 in the steady operation mode transmits the power input from the previous stage side to the power transmission target while smoothing the power using the action of the smoothing capacitor 13. Thereby, the smoothed power can be supplied to the power transmission target. The power transmission circuit 1 in the steady operation mode shifts to the standby mode when receiving an instruction to stop the operation.

  Next, the specific contents of this starting operation will be described with reference to the flowchart shown in FIG.

  When the start-up operation is started (that is, when an operation start instruction is received), the switch control circuit 14 has the detection power within the allowable range based on the detection result information from the power detection circuit 15. It is monitored whether it is (step S1). When the charge amount of the smoothing capacitor 13 has already reached the reference amount at the start of the start operation, the start operation is immediately terminated and the power transmission circuit 1 enters the steady operation mode. In the following description, it is assumed that the charge amount has not reached the reference amount at the start of the start-up operation.

  When the magnitude of the detection power is within the allowable range (Y in step S1), the switch control circuit 14 turns on the conduction switch 12 (step S2). Thereafter, the switch control circuit 14 monitors whether or not the charge amount of the smoothing capacitor 13 has reached the reference amount based on the information of the detection result by the charge detection circuit 16 (step S3). In parallel with this, the switch control circuit 14 monitors whether or not the magnitude of the detection voltage is out of the allowable range based on the information of the detection result by the power detection circuit 15 (step S4).

  During such monitoring (steps S3 and S4), since the power transmission line 10 is in a conductive state, the smoothing capacitor 13 is gradually charged. Further, although the power transmission line 10 is in a conductive state, the power input from the AC power supply is relatively small (the level of the detection power is within an allowable range), and therefore smooth. Even if the charge amount of the capacitor 13 is small, an excessive rush current does not flow.

  When the charge amount reaches the reference amount (Y in step S3), that is, when the undercharge state is resolved, the start-up operation is terminated and the power transmission circuit 1 enters the steady operation mode. If the magnitude of the detection power is outside the allowable range (Y in step S4), the switch control circuit 14 turns off the conduction switch 12 (step S5). Thereafter, the switch control circuit 14 repeats the operation of step S1.

  Here, FIG. 3 shows an example of a timing chart regarding the state of the conduction switch 12 when the start-up operation is performed. Note that the graph (A) in FIG. 3 shows the state of detection power (here, the power before the rectifier circuit 11) (here, the voltage waveform), and the graph (B) is The state of the continuity switch 12 (a state where ON / OFF is switched) is shown. Further, in this example, the voltage range from −Va to Va (that is, a range in which the magnitude of the voltage is equal to or less than Va) is set as an allowable range. It is assumed that an AC voltage that exceeds the value is input.

  As shown in FIG. 3, according to the start-up operation, even when such an AC voltage is input, the conduction switch 12 is in an OFF state during a period in which the magnitude exceeds the allowable range. Become. Therefore, it is possible to prevent an excessive rush current from flowing to the power transmission circuit 1 and the power transmission target.

  On the other hand, during the period in which the AC voltage is within the allowable range, the conduction switch 12 is in an ON state, and the smoothing capacitor 13 is gradually charged as described above. Finally, the amount of charge of the smoothing capacitor 13 reaches the reference amount, and the main purpose of the starting operation is fulfilled.

  The detection power may be power on the front side of the rectifier circuit 11 or power on the rear side of the rectifier circuit 11. FIG. 4 similarly shows an example of a timing chart related to the state of the conduction switch 12 when the startup operation is performed when the detection power is power on the rear stage side of the rectifier circuit 11. In this figure, the voltage range from 0 to Va is set to an allowable range. Thus, in any case, during the period when the detection power exceeds the allowable range, the conduction switch 12 is in the OFF state, and the main purpose of the starting operation can be achieved.

  The reference amount described above is set to such an amount that an excessive rush current does not flow even when the conduction switch 12 is maintained in the ON state. Usually, since the magnitude of power input to the power transmission circuit 1 (such as the magnitude of power supplied by the AC power supply) is known, this setting is also made in consideration of the circuit characteristics of the power transmission circuit 1 and the like. It is possible to do.

  Further, the allowable range described above is set to a range in which an excessive rush current does not flow even when the charge amount of the smoothing capacitor 13 does not reach the reference amount. Since the reference amount and the allowable range are set in this way, the power transmission circuit 1 can prevent an excessive rush current from flowing in the startup mode.

  Next, a more specific configuration of the power transmission circuit 1 will be described with an example.

  FIG. 5 shows a more specific configuration of the power transmission circuit 1. As shown in the figure, the power transmission circuit 1 includes a filter 23, a PFC circuit 24, an electrolytic capacitor (25, 26, 30), a Zener diode 27, a comparator (28, 29), a switching power supply 31, a photocoupler 33, a resistor ( R1 to R16), diode bridge rectifier circuits (D1, D2), diodes (D3, D4), transistors (Q1 to Q5), a microcomputer MC, and the like.

  Note that the microcomputer MC can accept an instruction to start an operation from the outside (for example, an instruction by a user). The diode bridge rectifier circuit D1 corresponds to the rectifier circuit 11 described above, the transistor Q1 corresponds to the conduction switch 12, and the electrolytic capacitor 25 corresponds to the smoothing capacitor 13.

  An AC power supply 21 is connected to the front side of the power transmission circuit 1 and a power transmission target 22 is connected to the rear side. The power transmission circuit 1 is a line (corresponding to the power transmission line 10) in which the filter 23, the bridge diode rectifier circuit D1, the drain and source of the transistor (MOSFET) Q1, and the PFC circuit 24 are interposed in this order from the front side. Thus, the AC power source 21 and the power transmission target 22 are connected.

  Between the filter 23 and the bridge diode rectifier circuit D1, an anode of a diode D3 and an anode of a diode D4 are connected. The cathode of the diode D3 is grounded through the resistor R1 and the resistor R2 in this order. The cathode of the diode D4 is grounded through the resistor R3 and the electrolytic capacitor 26 in this order. The resistor R1 and the resistor R2 are connected to the inverting input terminal of the comparator 28.

  The resistor R3 and the electrolytic capacitor 26 are connected to the base of the transistor Q2 via the resistor R6. The preceding stage of the resistor R6 is grounded through the resistor R4 and the Zener diode 27 in order, and the resistor R4 and the Zener diode 27 are connected to the non-inverting input terminal of the comparator 28 and the inverting input terminal of the comparator 29. . The output terminal of the comparator 28 is connected to the base of the transistor Q3 via the resistor R5. The resistor R5 and the base of the transistor Q3 are connected to the collector of the transistor Q2 and grounded through the resistor R7. The emitter of the transistor Q2 is grounded.

  The diode bridge rectifier circuit D1 and the transistor Q1 are connected to the gate of the transistor Q1 through a resistor R8. The gate of the transistor Q1 is connected to the collector of the transistor Q3 via the resistor R9, and the emitter of the transistor Q3 is grounded. The resistor R9 and the collector of the transistor Q3 are connected to the collector of the transistor Q4.

  The output terminal of the comparator 29 is connected to the base of the transistor Q4 via the resistor R10, and the emitter of the transistor Q4 is grounded. The output terminal of the comparator 29 and the resistor R10 are grounded via a resistor R11. The PFC circuit 24 and the power transmission target 12 are grounded via an electrolytic capacitor 25 and grounded via a resistor R12 and a resistor R13 in this order. The resistor R12 and the resistor R13 are connected to the non-inverting input terminal of the comparator 29.

  The filter 23 and the bridge diode rectifier circuit D1 are connected to the preceding stage of the switching power supply 31 via another bridge diode rectifier circuit D2. In addition, an electrolytic capacitor 30 for smoothing the power is provided in front of the switching power supply 31. The subsequent stage of the switching power supply 31 is connected to one end of the microcomputer MC and the resistor R14. The other end of the resistor R14 is connected to the anode of the light emitting diode in the photocoupler 33, and the cathode of the light emitting diode is connected to the collector of the transistor Q5. The emitter of the transistor Q5 is grounded.

  The microcomputer MC is connected to the base of the transistor Q5 via the resistor R15. The resistor R15 and the base of the transistor Q5 are grounded via a resistor R16. The collector of the transistor in the photocoupler 33 is connected between the resistor R6 and the base of the transistor Q2, and the emitter of the transistor is grounded.

  In addition, about the mounting of each part in the electric power transmission circuit 1, it can be set as a various aspect. For example, the comparators (28, 29) may be integrated into one IC chip. Further, the microcomputer MC is supplied with driving power from the switching power supply 31, and can control ON / OFF of the transistor Q5 (conduction between the collector and the emitter).

  Next, the operation content of the power transmission circuit 1 having the configuration shown in FIG. 5 will be described.

  In the standby mode, the microcomputer MC turns off the transistor Q5, and the transistor Q1 is maintained in the off state. When the microcomputer MC receives an operation start instruction, the start operation is started. At this time, the microcomputer MC turns on the transistor Q2, turns on the photocoupler 33, and turns off the transistor Q2.

  In this state, the input to the inverting input terminal of the comparator 28 (the voltage between the AC power supply 21 and the transistor Q1 divided by the resistors R1 and R2 via the diode D3) is not applied to the comparator 28. When it is smaller than the input to the inverting input terminal (voltage determined by the characteristics of the Zener diode 27 and the like), the output of the comparator 28 is ON, and otherwise it is OFF.

  That is, the magnitude of the voltage (corresponding to the detection power) at a position before the transistor Q1 is in a range smaller than a predetermined voltage (determined by the characteristics of the resistors R1 and R2, etc., and corresponds to an allowable range) Whether or not the output of the comparator 28 is determined. This operation corresponds to the operation of step S1 described above. The allowable range can be adjusted by changing the characteristics of the resistor R1 and the resistor R2.

  When the output of the comparator 28 is ON, the transistor Q3 is turned ON, and as a result, the transistor Q1 is also turned ON. This operation corresponds to the operation in step S2 described above. As will be described later, when the voltage input from the AC power supply 21 increases and the output of the comparator 28 is turned off, the transistor Q3 is turned off. If the transistor Q4 is also turned off, the transistor Q1 is turned off. Become.

  When the transistor Q1 is turned on, a current corresponding to the power supplied from the AC power source flows through the line connecting the AC power source 21 and the power transmission target 22, and the electrolytic capacitor 25 is gradually charged. On the other hand, a voltage corresponding to the amount of charge of the electrolytic capacitor 25 (the voltage at the electrolytic capacitor 25 divided by the resistors R12 and R13) is input to the non-inverting input terminal of the comparator 29. When this input is larger than the input to the inverting input terminal of the comparator 29 (voltage determined by the Zener diode 27), the output of the comparator 28 is turned on, and otherwise it is turned off.

  That is, the output of the comparator 29 is determined depending on whether or not the charge amount of the electrolytic capacitor 25 has reached a predetermined amount (determined by the characteristics of the resistor R12 and the resistor R13 and corresponding to the reference amount). This operation corresponds to the operation in step S3 described above. The reference amount can be adjusted by changing the characteristics of the resistor R12 and the resistor R13.

  When the output of the comparator 29 is turned on, the transistor Q4 is turned on. The state where the transistor Q4 is ON is maintained as long as the charge amount of the electrolytic capacitor 25 reaches the reference amount. In this state, the transistor Q1 is turned on regardless of the ON / OFF state of the transistor Q3. That is, the power transmission circuit 1 is in a state where the transistor Q1 is maintained in the ON state (the above-described steady operation mode) regardless of the magnitude of the voltage input from the AC power supply 21, and the startup operation is terminated.

  Further, even after the transistor Q1 is turned on due to the output of the comparator 28 being turned on, whether or not the magnitude of the voltage at the front stage side of the transistor Q1 is within the allowable range. The output of the comparator 28 is determined. This operation corresponds to the operation in step S4 described above. As a result of the increase in the voltage input from the AC power supply 21, the output of the comparator 28 is turned off when the voltage level at the location upstream of the transistor Q1 exceeds the allowable range.

  When the output of the comparator 28 is turned off, the transistor Q3 is turned off. At this time, if the transistor Q4 is also OFF (that is, if the charge amount of the electrolytic capacitor 25 has not reached the reference amount), the transistor Q1 is turned OFF. This operation corresponds to the operation of step S5 described above. Thereafter, the operation immediately after the transistor Q2 is turned off (corresponding to the operation in step S1 described above) is repeated.

  As described above, the power transmission circuit 1 of the circuit shown in FIG. 5 realizes the starting operation. The power transmission circuit 1 is provided with a functional unit (not shown) that receives an operation stop instruction after completing the start-up operation and shifts to the standby mode when the instruction is given. Note that the specific circuit configuration of the power transmission circuit 1 is not limited to that shown in FIG. 5, and various configurations can be adopted as long as the functions have the same purpose. According to the power transmission circuit 1, since a situation in which an excessive rush current is generated at the time of startup is suppressed, it is easy to maintain safety.

  Moreover, according to the power transmission circuit 1, it is not necessary to set it as an excessive specification supposing such a situation. For example, it is not necessary to increase the peak current rating value (rated current) or the like in each component (fuse, bridge diode, PFC circuit diode, etc.) used in the power transmission circuit 1 higher than necessary. Therefore, according to the power transmission circuit 1, it is easy to realize a reduction in product cost.

  As is clear from the above description, in the circuit configuration shown in FIG. 5, the portion formed of the microcomputer MC, the photocoupler 33, the transistors (Q2 to Q4), and the like is added to the switch control circuit 14 described above. Equivalent to. Further, a portion formed from the comparator 28 or the like corresponds to the power detection circuit 15 described above, and a portion formed from the comparator 29 or the like corresponds to the charge detection circuit 16 described above.

  In the power transmission circuit 1 shown in FIG. 5, an FET having a quick response compared to a relay switch or the like is applied as the conduction switch 12. Therefore, it is possible to switch between conduction / non-conduction of the power transmission line with high accuracy according to the output of the comparator 28 (corresponding to the detection result of the power detection circuit 15).

  Further, the power transmission circuit 1 can form a power supply device as a whole by connecting a switching power supply as the power transmission target 22. Since the switching power supply itself is known as a kind of a stabilized power supply that performs a switching operation (usually ON / OFF of a semiconductor switch), detailed description thereof is omitted. Moreover, the power supply device formed in this way can be provided in various electric devices. In this case, the electric device can be supplied with driving power or the like through the power supply device.

  As described above, the power transmission circuit 1 of this embodiment includes the power transmission line 10 and transmits the input power that has been input to the power transmission target by transmitting the power transmission line 10. Further, the power transmission circuit 1 is provided on the power transmission line 10, and a conduction switch 12 that switches between conduction / non-conduction of the power transmission line 10, and a downstream side of the conduction switch 12 on the power transmission line 10, One electrode is provided in a connected state, and the smoothing capacitor 13 for smoothing the power in the power transmission line 10 and the power upstream of the conduction switch 12 on the power transmission line 10 are within an allowable range. A power detection circuit 15 that detects whether or not the charge amount of the smoothing capacitor 13 reaches a reference amount, a charge detection circuit 16 that detects whether or not the charge amount of the smoothing capacitor 13 has reached a reference amount, a switch control circuit 14 that controls the conduction switch 12, It has.

  The switch control circuit 14 controls the conduction switch 12 based on the detection result of the power detection circuit 15 until the charge amount of the smoothing capacitor 13 reaches the reference amount.

  As a result, according to the power transmission circuit 1, the conduction switch 12 is controlled based on the detection result of the power detection circuit 15 until the undercharged state of the smoothing capacitor 13 is resolved (until the charge amount reaches the reference amount). The conduction / non-conduction of the power transmission line 10 can be switched. Therefore, it is easy to eliminate the undercharged state while preventing the excessive rush current from flowing due to the undercharged state as much as possible.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this content. The present invention can be implemented with various modifications without departing from the spirit of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be used for a circuit for reducing a rush current used in various electric devices.

DESCRIPTION OF SYMBOLS 1 Power transmission circuit 10 Power transmission line 11 Rectifier circuit 12 Conduction switch 13 Smoothing capacitor 14 Switch control circuit 15 Power detection circuit 16 Charge detection circuit 21 AC power supply 22 Power transmission object 23 Filter 24 PFC circuit 25 Electrolytic capacitor (smoothing capacitor)
26, 30 Electrolytic capacitor 27 Zener diode 28, 29 Comparator 31 Switching power supply 33 Photocoupler R1 to R16 Resistor D1 Diode bridge rectifier circuit (rectifier circuit)
D2 Diode bridge rectifier circuit D3, D4 Diode Q1 Transistor (conduction switch)
Q2 to Q5 Transistor MC Microcomputer

Claims (6)

A power transmission circuit comprising a power transmission line and transmitting the input power input to the power transmission target by transmitting the power transmission line,
A conduction switch that is provided on the power transmission line and switches between conduction / non-conduction of the power transmission line;
A smoothing capacitor that is provided in a mode in which one electrode is connected to the downstream side of the conduction switch on the power transmission line, and smoothes the power in the power transmission line;
A power detection circuit that detects whether or not the power upstream of the conduction switch on the power transmission line is within a predetermined allowable range;
A charge detection circuit for detecting whether or not a charge amount of the smoothing capacitor has reached a predetermined reference amount;
A switch control circuit for controlling the conduction switch,
The switch control circuit
The power transmission circuit controls the conduction switch based on a detection result of the power detection circuit until a charge amount of the smoothing capacitor reaches the reference amount. The switch control circuit includes:
When the power upstream of the conduction switch on the power transmission line is within the allowable range, so that the power transmission line is in a conduction state,
When the power upstream of the conduction switch on the power transmission line is not within the allowable range, so that the power transmission line is in a non-conduction state,
The power transmission circuit according to claim 1, wherein the conduction switch is controlled. The switch control circuit includes:
After the amount of charge of the smoothing capacitor reaches the reference amount, the conduction switch is controlled so that the power transmission line is maintained in the conduction state regardless of the detection result of the power detection circuit. The power transmission circuit according to claim 2, wherein AC power is input as the input power,
4. The power transmission circuit according to claim 3, wherein a rectification circuit for rectifying the AC power is provided in a stage preceding the conduction switch on the power transmission line. 5. A power transmission circuit according to any one of claims 1 to 4,
A switching power supply as the power transmission target;
With
The switching power supply converts a state of power transmitted from the power transmission circuit and outputs the converted power.   An electric device comprising the power supply device according to claim 5.

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