Power supply apparatus

A power supply apparatus includes a boosting converter, an inrush current limiting element, a detection circuit, a switch element, and a control circuit. The inrush current limiting element is configured to limit an inrush current to the boosting converter. The detection circuit is configured to detect whether an output voltage of the boosting converter has reached a set voltage. The switch element is configured to short-circuit the inrush current limiting element. The control circuit is configured to operate the switch element according to the detection to short-circuit the inrush current limiting element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2016-159355, filed on Aug. 15, 2016, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.

BACKGROUND

Technical Field

The present disclosure relates to a power supply apparatus.

Related Art

A power supply apparatus includes a current limiting element to suppress an inrush current that occurs at power-on. Since the current limiting element consumes power, it is desirable to short-circuit the current limiting element except when the inrush current occurs. Therefore, there is known a power supply apparatus including a switch element that short-circuits both ends of a current limiting element at the time other than the time of power-on.

In a case where an “instantaneous interruption” or an “instantaneous drop” occurs in the state where the current limiting element as described above is short-circuited, an inrush current that occurs when the power supply apparatus returns from the instantaneous interruption or the instantaneous drop cannot be suppressed by using the current limiting element. Herein, the “instantaneous interruption” is a phenomenon in which an input voltage becomes zero instantaneously. In addition, the “instantaneous drop” is a phenomenon in which the input voltage decreases instantaneously.

In addition, the above-described power supply apparatus cannot suppress inrush currents to a capacitor provided in an input stage or a direct current to direct current (DCDC) converter input stage. In order to suppress the inrush currents, a current limiting circuit is provided for each capacitor. In addition, since the current limiting element is short-circuited while a current is flowing through the current limiting element, a secondary inrush current cannot be suppressed.

SUMMARY

In an aspect of the present disclosure, there is provided a power supply apparatus that includes a boosting converter, an inrush current limiting element, a detection circuit, a switch element, and a control circuit. The inrush current limiting element is configured to limit an inrush current to the boosting converter. The detection circuit is configured to detect whether an output voltage of the boosting converter has reached a set voltage. The switch element is configured to short-circuit the inrush current limiting element. The control circuit is configured to operate the switch element according to the detection to short-circuit the inrush current limiting element.

DETAILED DESCRIPTION

The present disclosure relates to a power supply apparatus. In the power supply apparatus according to an embodiment of the present disclosure, with one inrush current prevention circuit, it is possible to suppress an inrush current and a secondary inrush current that occur when the power supply apparatus is turned on and an inrush current that may occur at the time of return from the instantaneous interruption or the instantaneous drop.

In the inrush current prevention circuit included in the power supply apparatus according to the embodiment of the present disclosure, an inrush current limiting element is inserted into a main line. As a result, with one circuit, it is possible to limit various inrush currents (inrush current at power-on, and inrush current at the time of return from the instantaneous interruption or the instantaneous drop) that occur due to inflow of a current to a plurality of capacitors.

Specifically, when no current flows in the inrush current limiting element, the power supply apparatus according to the embodiment of the present disclosure short-circuits the inrush current limiting element, and suppresses the secondary inrush current first. Furthermore, the power supply apparatus according to the embodiment of the present disclosure detects the inrush current that occurs at the time of return from the instantaneous interruption or the instantaneous drop, and suppresses the inrush current and the secondary inrush current by the same sequence as a sequence performed at power-on.

Furthermore, the power supply apparatus according to the embodiment of the present disclosure short-circuits the switch element and turns on the DCDC converter after a smoothing capacitor is charged and a voltage difference in the inrush current element disappears following the power-on. By using such a sequence, it is possible to perform control such that no secondary inrush current occurs.

In addition, the power supply apparatus according to the embodiment of the present disclosure detects a decrease in a potential across a rectifying smoothing capacitor to detect an instantaneous interruption or an instantaneous drop and then open the switch element. By using such a sequence, it is possible to suppress the inrush current that can occur at the time of return from the instantaneous interruption or the instantaneous drop.

Furthermore, the power supply apparatus according to the embodiment of the present disclosure turns off the DCDC converter when the switch element is opened, as described above. Then, even after return from the instantaneous interruption or the instantaneous drop, the power supply apparatus short-circuits the switch element and turns on the DCDC converter after a potential difference across the inrush current limiting element disappears. By using such a sequence, the secondary inrush current that can occur after return from the instantaneous interruption or the instantaneous drop is suppressed. That is, with the power supply apparatus according to the embodiment of the present disclosure, it is possible to suppress various inrush currents exemplified above using one inrush current limiting circuit.

Referring to the drawings, embodiments according to the above features will be described.FIG. 1is a circuit diagram illustrating a power supply apparatus according to a first embodiment of the present disclosure. In addition,FIG. 2is a timing chart for describing an operation sequence of the power supply apparatus100according to the first embodiment.

<Circuit Configuration in First Embodiment>

As illustrated inFIG. 1, the power supply apparatus100according to the present embodiment is configured as a boosting converter circuit. The power supply apparatus100includes an input terminal101, an inrush current limiting element102, and a switch element103that short-circuits the inrush current limiting element102. In addition, the power supply apparatus100includes a boosting converter120. The power supply apparatus100also includes a first output voltage dividing resistor111and a second output voltage dividing resistor112that divide an output voltage (VA) of the boosting converter120to output a divided voltage (VB), a comparator113, and a reference voltage source114.

In addition, the power supply apparatus100includes a DCDC converter115, and a load116is coupled to the DCDC converter115. Note that the switch element103is of a normally open type (A contact).

The boosting converter120includes an input capacitor121, a coil122, a switching element123, a diode124for rectification, an output smoothing capacitor125, a first voltage dividing resistor126, a second voltage dividing resistor127, and a controller128.

The input capacitor121is used for reducing input noise. The voltage divided by a resistance ratio between the first voltage dividing resistor126and the second voltage dividing resistor127is input to the controller128. The controller128performs feedback control in which a switching operation of the switching element123is controlled on the basis of an input voltage to boost the output voltage (VA) of the boosting converter120so that the output voltage (VA) reaches a set voltage (VSET) that is set in advance. Note that the set voltage (VSET) is appropriately set using a voltage value defined in advance.

In the power supply apparatus100, a voltage dividing circuit includes the first output voltage dividing resistor111and the second output voltage dividing resistor112. A detection circuit that detects whether the output voltage (VA) has reached the set voltage (VSET) includes this voltage dividing circuit, the comparator113, and the reference voltage source114.

In addition, a control circuit in the power supply apparatus100includes the comparator113and a circuit that inputs the output voltage (signal) of the comparator113to the switch element103.

<Circuit Operation in First Embodiment>

Next, the operation and effects of the power supply apparatus100according to the present embodiment will be described. InFIG. 2, the horizontal axis represents passage of time. The vertical axis represents fluctuation of each voltage or each current described later. Note that a predetermined position on the vertical axis does not represent a specific concrete numerical value (voltage value or current value). A plurality of waveforms arranged along the vertical axis corresponds to voltages or currents corresponding to reference signs specified inFIG. 1.

Herein, referring toFIG. 1, reference signs used for respective waveforms illustrated inFIG. 2will be described. VINrepresents a power supply voltage applied to the input terminal101of the power supply apparatus100. VArepresents an output voltage of the boosting converter120. VBrepresents the divided voltage of VA.

VREFrepresents a reference voltage to compare with the output divided voltage VBof the boosting converter120and, by the comparison, to detect that the voltage VAhas reached the set voltage VSET. IRrepresents a current flowing through the inrush current limiting element102.

ISWrepresents a current flowing through the switch element103that short-circuits the inrush current limiting element102. IINis an input current and corresponds to a current obtained by combining IRand ISW. VSWrepresents a voltage that controls ON/OFF of the switch element103and the DCDC converter115.

Next, each timing used inFIG. 2will be described. Time point a1 corresponds to the moment of power-on. Time point b1 corresponds to the moment when the boosting converter120reaches the set voltage (VSET). Time point c1 represents the moment when an instantaneous interruption or an instantaneous drop occurs in the power supply apparatus100. Time point d1 corresponds to the moment when the power supply apparatus100returns from the instantaneous interruption or the instantaneous drop. Time point e1 corresponds to the moment when the boosting converter120reaches the set voltage after return from the instantaneous interruption or the instantaneous drop.

<Operation at Time Point a1 to Time Point b1>

Time from time point a1 to time point b1 corresponds to time from when the power supply apparatus100is turned on until the output voltage (VA) of the boosting converter120reaches the set voltage (VSET). In the power supply apparatus100, the output voltage (VA) of the boosting converter120is zero just before the power is turned on (before time point a1). Therefore, the divided voltage (VB) of VAis also zero. When the divided voltage (VB) is zero, the comparator113does not operate because there is no input to be compared, and a comparison output (VSW) corresponding to the output of the comparator113becomes zero. When the comparison output (VSW) is zero, the switch element103does not operate. Therefore, a contact of the switch element103remains open. In addition, the DCDC converter115is also off.

Since the switch element103remains off at power-on (time point a1), the input current (IIN) passes through the inrush current limiting element102from the input terminal101and charges the input capacitor121of the boosting converter120. In addition, the input current (IIN) passes through the inrush current limiting element102, the coil122, and the diode124, and charges the output smoothing capacitor125of the boosting converter120.

The inrush current that occurs at the time of this current application (time point a1) is suppressed by the inrush current limiting element102. From time point a1 to time point b1, the output voltage (VA) of the boosting converter120increases while the input current (IIN) decreases. When time reaches time point b1, the output voltage (VA) reaches the set voltage (VSET) and becomes a constant value. At the same time, charging of the output smoothing capacitor125is completed and the input current (IIN) becomes zero.

<Operation at Time Point b1 to Time Point c1>

Time from time point b1 to time point c1 corresponds to time from when the output voltage (VA) of the boosting converter120of the power supply apparatus100reaches the set voltage (VSET) until the power supply apparatus100goes into steady operation. The values of the first output voltage dividing resistor111, the second output voltage dividing resistor112, and the reference voltage source114are set in advance such that when the output voltage (VA) of the boosting converter120reaches the set voltage (VSET), the divided voltage (VB) becomes equal to the reference voltage (VREF) supplied by the reference voltage source114. As a result, it is possible, by the comparison output (VSW) that is an output of the comparator113, to detect that the output voltage (VA) of the boosting converter120has reached the set voltage (VSET).

When the divided voltage (VB) exceeds the reference voltage (VREF), the comparison output (VSW) that is the output of the comparator113becomes a Hi level. When the comparison output (VSW) becomes the Hi level, the switch element103and the DCDC converter115are turned on. That is, when the output voltage (VA) of the boosting converter120reaches the set voltage (VSET), the reaching can be detected by the level of the comparison output (VSW) that is the output of the comparator113.

When the comparison output (VSW) becomes the Hi level, the switch element103operates to close the contact. In addition, the DCDC converter115is turned on, and power supply to the load116is started.

Since the output voltage (VA) of the boosting converter120has reached the set voltage (VSET) when the switch element103operates, the boosting converter120stops operating, and the DCDC converter115is off just before time point b1. Therefore, the current (IR) flowing through the inrush current limiting element102is zero. Therefore, even if the switch element103is short-circuited, no secondary inrush current occurs in the power supply apparatus100.

In addition, when the DCDC converter115is turned on, the DCDC converter115starts drawing a current. As a result, the input current (IIN) gradually increases and the power supply apparatus100goes into steady operation. Since the switch element103is on (the contact is closed and the inrush current limiting element102is short-circuited) in steady operation, the input current (IIN) is equal to the current (ISW) flowing through the switch element103(IIN=ISW). In addition, the current (IR) flowing through the inrush current limiting element102is zero (IR=0). Therefore, in steady operation, the inrush current limiting element102does not consume power in the power supply apparatus100.

<Operation at Time Point c1 to Time Point d1>

Time from time point c1 to time point d1 corresponds to time from the occurrence of an instantaneous interruption or an instantaneous drop in the power supply apparatus100until the power supply apparatus100returns from the instantaneous interruption or the instantaneous drop. Note that the “instantaneous interruption” is a phenomenon in which the power supply voltage (VIN) that is the input voltage becomes zero instantaneously. In addition, the “instantaneous drop” is a phenomenon in which the power supply voltage (VIN) that is the input voltage decreases instantaneously.

Even if the instantaneous interruption or the instantaneous drop occurs, the DCDC converter115draws a current for supplying power to the load116. Therefore, the boosting converter120supplies power to the DCDC converter115while power supply from the input terminal101is insufficient. At this time, since the output voltage (VA) of the boosting converter120has decreased, the divided voltage (VB) is naturally lower than the reference voltage (VREF). As a result, the comparison output (VSW) from the comparator113becomes a Low level. When the comparison output (VSW) becomes the Low level, the switch element103and the DCDC converter115are turned off. As a result, the contact of the switch element103is opened and therefore the inrush current limiting element102is no longer in a short-circuit state.

<Operation at Time Point d1 to Time Point e1>

Time from time point d1 to time point e1 corresponds to time from when the power supply apparatus100returns from the instantaneous interruption or the instantaneous drop that has occurred until the output voltage (VA) of the boosting converter120returns to the set voltage (VSET). The divided voltage (VB) with respect to the output voltage (VA) of the boosting converter120remains lower than the reference voltage (VREF) at the time of return from the instantaneous interruption or the instantaneous drop (time point d1). Therefore, the comparison output (VSW) from the comparator113is at the Low level, and the switch element103remains off.

The input current (IIN) when the switch element103is off charges the input capacitor121from the input terminal101via the inrush current limiting element102. In addition, the input current (IIN) charges the output smoothing capacitor125via the inrush current limiting element102, the coil122, and the diode124. At this time, the inrush current limiting element102suppresses the inrush current that occurs at the time of return from the instantaneous interruption and the instantaneous drop. Thereafter, when the output voltage (VA) of the boosting converter120reaches the set voltage (VSET), charging of the output smoothing capacitor125is completed. This cycle is the same operation as the operation when the power supply apparatus100is turned on (time point a1).

<Operation after Time Point e1>

Time after time point e1 corresponds to time from when the output voltage (VA) of the boosting converter120reaches the set voltage (VSET) until the power supply apparatus100goes into the steady operation after the instantaneous interruption or the instantaneous drop occurs.

The comparator113compares the divided voltage (VB) obtained by dividing the output voltage (VA) of the boosting converter120by the first output voltage dividing resistor111and the second output voltage dividing resistor112with the reference voltage (VREF). As described above, each circuit element of the power supply apparatus100is set such that the divided voltage (VB) when the output voltage (VA) reaches the set voltage (VSET) is equal to the reference voltage (VREF). Therefore, when the divided voltage (VB) of the boosting converter120exceeds the reference voltage (VREF), the exceedance means that the output voltage (VA) is the set voltage (VSET).

Since the comparison output (VSW) of the comparator113at this time is at the Hi level, the switch element103and the DCDC converter115are turned on. When the switch element103is turned on, the inrush current limiting element102is short-circuited.

At this time, a charging current of the output smoothing capacitor125is zero and the DCDC converter115is also off. Therefore, the current (IR) flowing through the inrush current limiting element102is zero. Therefore, a secondary inrush current that occurs when the switch element103is short-circuited does not occur at all.

After this, the DCDC converter115is turned on and starts drawing a current. As a result, the input current (IIN) gradually increases and the power supply apparatus100goes into the steady operation. Since the switch element103is on in steady operation, the input current (IIN) is equal to the current (ISW) flowing through the switch element103(IIN=ISW). In addition, the current (IR) flowing through the inrush current limiting element102becomes zero (IR=0). Therefore, there is no power consumption in the inrush current limiting element102, and power loss by the inrush current limiting element102does not occur in steady operation.

As described above, in order to suppress various types of inrush currents, the power supply apparatus100according to the present embodiment short-circuits the inrush current limiting element102when no current flows in the inrush current limiting element102, and suppresses a secondary inrush current while reducing unnecessary power consumption. Furthermore, the power supply apparatus100detects the inrush current that occurs at the time of return from the instantaneous interruption or the instantaneous drop, and suppresses the inrush current and the secondary inrush current by the same sequence as a sequence performed at power-on. That is, the power supply apparatus100includes one inrush current limiting circuit that includes the first output voltage dividing resistor111, the second output voltage dividing resistor112, the comparator113, the reference voltage source114, and the switch element103. With this inrush current limiting circuit, various inrush currents can be suppressed.

<Circuit Configuration in Second Embodiment>

Next, a power supply apparatus according to another embodiment of the present disclosure will be described with reference toFIGS. 3 and 4.FIG. 3is a circuit diagram illustrating the power supply apparatus according to the second embodiment of the present disclosure. In addition,FIG. 4is a timing chart for describing an operation sequence of the power supply apparatus200according to the second embodiment.

Note that in the following description, the same configurations as the configurations described in the first embodiment are denoted by the same reference signs, and detailed description of some of the configurations will be omitted. The power supply apparatus200according to the present embodiment includes the following configurations similarly to the power supply apparatus100according to the first embodiment.

That is, the power supply apparatus200includes an input terminal101, an inrush current limiting element102, a switch element103, a boosting converter120, a first output voltage dividing resistor111and a second output voltage dividing resistor112, a comparator113, a reference voltage source114, and a DCDC converter115.

In addition to the above configuration, the power supply apparatus200further includes a delay circuit220that controls an output timing of a signal output when an increase and a decrease in an output voltage (VA) of the boosting converter120are detected, a second reference voltage source206, and a second comparator207.

The delay circuit220is a circuit that generates a delay after detecting an increase in the output voltage (VA) to output a signal, and then outputs a signal without giving a delay after detecting a decrease in the output voltage (VA). The delay circuit220includes a time constant resistor204, a time constant capacitor205, and a capacitor discharging diode203.

According to the power supply apparatus100according to the first embodiment, the comparator113compares the reference voltage (VREF) with the divided voltage (VB), and by the comparison, detects that the output voltage (VA) of the boosting converter120has reached the set voltage (VSET). In view of an actual circuit, an error may occur because of the setting accuracy of the set voltage (VSET) due to a variation in characteristics of the circuit elements (the first output voltage dividing resistor111and the second output voltage dividing resistor112) and the accuracy of the reference voltage (VREF).

Therefore, as illustrated inFIG. 7, with the configuration of the power supply apparatus100according to the first embodiment alone, there is a case where detection is performed before the set voltage (VSET) is reached or a case where detection is not performed even when the set voltage (VSET) is reached. There is room for contrivance to further improve the accuracy of operation.

Accordingly, in the power supply apparatus200, the first output voltage dividing resistor111, the second output voltage dividing resistor112, and the reference voltage source114are set such that an increase in the output voltage (VA) of the boosting converter120is detected before the output voltage (VA) reaches the set voltage (VSET).

Furthermore, in the power supply apparatus200, after the increase in the output voltage (VA) is detected, a delay taking into consideration real time until the output voltage (VA) reaches the set voltage (VSET) is given. After the output voltage (VA) reaches the set voltage (VSET), the switch element103and the DCDC converter115are turned on. Control is performed such that such operation is performed.

In the power supply apparatus200, a voltage dividing circuit includes the first output voltage dividing resistor111and the second output voltage dividing resistor112. A detection circuit that detects whether the output voltage (VA) has reached the set voltage (VSET) includes the voltage dividing circuit, the comparator113, the delay circuit220, the reference voltage source114, the second comparator207, and the second reference voltage source206.

In addition, a control circuit in the power supply apparatus200includes the delay circuit220, the second comparator207, and the circuit that inputs the output voltage (signal) of the second comparator207to the switch element103.

<Circuit Operation in Second Embodiment>

Next, the operation and effects of the power supply apparatus200according to the present embodiment will be described. InFIG. 4, the horizontal axis represents passage of time. The vertical axis represents fluctuation of each voltage or each current described later. InFIG. 4, as inFIG. 2, a predetermined position on the vertical axis does not represent a specific concrete numerical value (voltage value or current value). A plurality of waveforms arranged along the vertical axis corresponds to voltages or currents corresponding to reference signs specified inFIG. 3.

InFIG. 4, the present embodiment is similar to the first embodiment with respect to a power supply voltage (VIN), the output voltage (VA) of the boosting converter120, the divided voltage (VB), a current (IR) flowing through the inrush current limiting element102, an input current (IIN), a composite current of IRand IIN(ISW), and a comparison output (VSW).

In the present embodiment, a reference voltage input to the comparator113is a first reference voltage (VREF1). The comparator113outputs a signal, obtained by detecting that the output voltage (VA) of the boosting converter120has reached the set voltage (VSET), on the basis of a comparison with the first reference voltage (VREF1).

As for reference signs of the voltages and the currents according to the present embodiment, VCAPrepresents a voltage across the time constant capacitor205. VREF2represents a second reference voltage to detect the increase in the output voltage (VA) by comparison with VCAP.

Next, each timing used inFIG. 4will be described. Time point a2 corresponds to the moment of power-on. Time point b2 corresponds to the moment when the boosting converter120reaches the first reference voltage (VREF1). Time point c2 corresponds to the moment when the voltage across the time constant capacitor205(VCAP) reaches the second reference voltage (VREF2). Time point d2 corresponds to the moment when an instantaneous interruption or an instantaneous drop occurs in the power supply apparatus200.

Time point e2 corresponds to the moment when the divided voltage (VB) of the output voltage (VA) of the boosting converter120falls below the first reference voltage (VREF1). Time point f2 corresponds to the moment when the power supply apparatus200returns from the instantaneous interruption or the instantaneous drop. Time point g2 corresponds to the moment when the voltage across the time constant capacitor205(VCAP) reaches the second reference voltage (VREF2) after return from the instantaneous interruption or the instantaneous drop.

<Operation at Time Point a2 to Time Point b2>

Time from time point a2 to time point b2 corresponds to time from when the power supply apparatus200is turned on until the output voltage (VA) of the boosting converter120reaches the set voltage (VSET). In the power supply apparatus200, the output voltage (VA) of the boosting converter120is zero just before the power is turned on (before time point a2). Therefore, the divided voltage (VB) of VAis also zero. When the divided voltage (VB) is zero, the comparator113does not operate because there is no input to be compared, and an output of the comparator113becomes zero. In this case, since the comparison output (VSW) that is an output of the second comparator207also becomes zero, the switch element103does not operate. Therefore, a contact of the switch element103remains open. In addition, the DCDC converter115is also off.

Since the switch element103remains off at power-on (time point a2), the input current (IIN) passes through the inrush current limiting element102from the input terminal101and charges the input capacitor121of the boosting converter120. In addition, the input current (IIN) passes through the inrush current limiting element102, the coil122, and the diode124, and charges the output smoothing capacitor125of the boosting converter120.

The inrush current that occurs at the time of this current application (time point a2) is suppressed by the inrush current limiting element102. From time point a2 to Time point b2, the output voltage (VA) of the boosting converter120increases while the input current (IIN) decreases. When time reaches time point b2, the output voltage (VA) reaches the set voltage (VSET) and the divided voltage (VB) reaches the first reference voltage (VREF1). At the same time, charging of the output smoothing capacitor125is completed and the input current (IIN) becomes zero.

<Operation at Time Point b2 to Time Point c2>

Time from time point b2 to time point c2 corresponds to a period for giving a constant delay after the divided voltage (VB) of the output voltage (VA) of the boosting converter120reaches the first reference voltage (VREF1). When the divided voltage (VB) exceeds the first reference voltage (VREF1), the output of the comparator113becomes the Hi level. An output current from the comparator113passes through the time constant resistor204and charges the time constant capacitor205over time. When the voltage across the charged time constant capacitor205(VCAP) exceeds the second reference voltage (VREF2), the output of the second comparator207becomes the Hi level.

By ensuring this period sufficiently in accordance with the actual circuit operation, it is possible to operate the second comparator207after the output voltage (VA) of the boosting converter120has reached the set voltage (VSET), that is, after the charging of the output smoothing capacitor125is completed.

<Operation at Time Point c2 to Time Point d2>

Time from time point c2 to time point d2 corresponds to time from the operation of the second comparator207until the power supply apparatus200goes into steady operation as described above. By sufficiently taking the delay period already described, the comparison output (VSW) that is the output of the second comparator207is set to Hi level after the output voltage (VA) reaches the set voltage (VSET). When the comparison output (VSW) becomes the Hi level, the switch element103and the DCDC converter115are turned on.

At this time, since the output voltage (VA) of the boosting converter120has reached the set voltage (VSET), a charging current of the output smoothing capacitor125is zero. In addition, since the DCDC converter115is off until just before, the current flowing through the inrush current limiting element102is zero. Therefore, a secondary inrush current that occurs when the inrush current limiting element102is short-circuited by the switch element103does not occur at all.

After the above, the DCDC converter115gradually starts drawing a current. Therefore, the input current (IIN) gradually increases and the power supply apparatus200goes into steady operation. Since the switch element103is on (the contact is closed and the inrush current limiting element102is short-circuited) in steady operation, the input current (IIN) is equal to the current (ISW) flowing through the switch element103(IIN=ISW). In addition, the current (IR) flowing through the inrush current limiting element102is zero (IR=0). Therefore, in steady operation, the inrush current limiting element102does not consume power in the power supply apparatus200.

<Operation at Time Point d2 to Time Point e2>

Time from time point d2 to time point e2 is a period from when the instantaneous interruption or the instantaneous drop occurs in the power supply apparatus200until the output voltage (VA) of the boosting converter120decreases and the divided voltage (VB) falls below the first reference voltage (VREF1). Even if the instantaneous interruption or the instantaneous drop occurs, the DCDC converter115draws a current for supplying power to the load116. Therefore, the boosting converter120supplies power to the DCDC converter115while power supply from the input terminal101is insufficient. At this time, since the output voltage (VA) of the boosting converter120has decreased, the divided voltage (VB) naturally becomes lower than the first reference voltage (VREF1).

<Operation at Time Point e2 to Time Point f2>

Time from time point e2 to time point f2 corresponds to time from when the divided voltage (VB) falls below the first reference voltage (VREF1) until the power supply apparatus200returns from the instantaneous interruption or the instantaneous drop. In the power supply apparatus200, when the divided voltage (VB) falls below the first reference voltage (VREF1), the comparator113stops outputting. When the output of the comparator113stops, the time constant capacitor205is instantaneously discharged via the capacitor discharging diode203. Then, since the voltage across the time constant capacitor205(VCAP) becomes zero, the comparison output (VSW) that is the output of the second comparator207becomes the Low level. When the comparison output (VSW) becomes the Low level, the switch element103and the DCDC converter115are turned off. As a result, the contact of the switch element103is opened and therefore the inrush current limiting element102is no longer in a short-circuit state.

<Operation at Time Point f2 to Time Point g2>

Time from time point f2 to time point g2 is a period for giving a constant delay after return from the instantaneous interruption/instantaneous drop. After return from the instantaneous interruption/instantaneous drop, the divided voltage (VB) exceeds the first reference voltage (VREF1). Therefore, the output of the comparator113becomes the Hi level. At this time, the output current of the comparator113charges the time constant capacitor205over time via the time constant resistor204. As a result, when the voltage across the time constant capacitor205(VCAP) exceeds the second reference voltage (VREF2), the comparison output (VSW) that is the output of the second comparator207becomes the Hi level. By taking this period sufficiently, it is possible to operate the second comparator207after charging of the output smoothing capacitor125is completed.

<Operation after Time Point g2>

Time after time point g2 corresponds to time from the operation of the second comparator207until the power supply apparatus200goes into steady operation. In the power supply apparatus200, by taking the delay period sufficiently, the comparison output (VSW) of the second comparator207is set to the Hi level after the output voltage (VA) of the boosting converter120reaches the set voltage (VSET) and the charging current of the output smoothing capacitor125becomes zero. As a result, the switch element103and the DCDC converter115are turned on.

At this time, since the output voltage (VA) of the boosting converter120has reached the set voltage (VSET), the charging current of the output smoothing capacitor125is zero. In addition, since the DCDC converter115is also off, the current flowing through the inrush current limiting element102is zero. Therefore, a secondary inrush current that occurs when the switch element103is short-circuited does not occur at all.

Since the DCDC converter115gradually starts drawing a current after the above, the input current IINgradually increases, and the power supply apparatus200goes into the steady operation. Since the switch element103is on in steady operation, the input current (IIN) is equal to the current (ISW) flowing through the switch element103(IIN=ISW). In addition, the current (IR) flowing through the inrush current limiting element102becomes zero (IR=0). Therefore, there is no power consumption in the inrush current limiting element102, and power loss by the inrush current limiting element102does not occur in steady operation.

As described above, in order to suppress various types of inrush currents, the power supply apparatus200according to the present embodiment short-circuits the inrush current limiting element102when no current flows in the inrush current limiting element102, and suppresses a secondary inrush current while reducing unnecessary power consumption. Furthermore, the power supply apparatus200detects the inrush current that occurs at the time of return from the instantaneous interruption or the instantaneous drop, and suppresses the inrush current and the secondary inrush current by the same sequence as a sequence performed at power-on. In addition, in consideration of a variation in circuit elements that realize suppression of inrush currents as described above, a configuration that allows accurate control of the detection timing is employed. The configuration can suppress various inrush currents at higher accuracy.

<Circuit Configuration in Third Embodiment>

Next, a power supply apparatus according to still another embodiment of the present disclosure will be described with reference toFIGS. 5 and 6.FIG. 5is a circuit diagram illustrating the power supply apparatus according to the third embodiment of the present disclosure. In addition,FIG. 6is a timing chart for describing an operation sequence of the power supply apparatus300according to the third embodiment.

Note that in the following description, the same configurations as the configurations described in the first embodiment and the second embodiment are denoted by the same reference signs, and detailed description of some of the configurations will be omitted. The power supply apparatus300according to the present embodiment includes the following configurations similarly to the power supply apparatus100according to the first embodiment.

That is, similarly to the power supply apparatus100, the power supply apparatus300includes an input terminal101, an inrush current limiting element102, a switch element103, a boosting converter120, a first output voltage dividing resistor111, a second output voltage dividing resistor112, a comparator113, a reference voltage source114, and a DCDC converter115.

Similarly to the power supply apparatus200, the power supply apparatus300further includes a delay circuit220that controls an output timing of a signal output when an increase and a decrease in an output voltage (VA) of the boosting converter120are detected, a second reference voltage source206, and a second comparator207.

Note that the delay circuit220is a circuit that generates a delay after detecting an increase in the output voltage (VA) to output a signal, and then outputs a signal without giving a delay after detecting a decrease in the output voltage (VA). The delay circuit220includes a time constant resistor204, a time constant capacitor205, and a capacitor discharging diode203.

In addition to the above configuration, the power supply apparatus300further includes a second switch element301that gives a hysteresis characteristic to the detection of the output voltage (VA) of the boosting converter120, and a third reference voltage source302. That is, the power supply apparatus300has a plurality of reference voltages.

In the power supply apparatus300, a ripple (pulsating flow) occurs in the output voltage (VA) of the boosting converter120, depending on the load116coupled to the DCDC converter115. In the power supply apparatus200described as the second embodiment, control is performed such that the increase in the output voltage (VA) of the boosting converter120is detected, and the DCDC converter115and the switch element103are turned on with a delay. In such control, a ripple in the output voltage (VA) may be detected. If the ripple is detected, a malfunction may be caused.

Accordingly, the power supply apparatus300according to the present embodiment is configured to switch between the reference voltage source114and the third reference voltage source302that detect an output of the boosting converter120and, by the switching, to give a hysteresis characteristic to a detection voltage and prevent a malfunction. Note that the second switch element301is of a switching contact type (C contact).

In the power supply apparatus300, a voltage dividing circuit includes the first output voltage dividing resistor111and the second output voltage dividing resistor112. A detection circuit that detects whether the output voltage (VA) has reached the set voltage (VSET) includes the voltage dividing circuit, the comparator113, the delay circuit220, the reference voltage source114or the third reference voltage source302, the second comparator207, and the second reference voltage source206.

In addition, a control circuit in the power supply apparatus300includes the delay circuit220, the second comparator207, and the circuit that inputs the output voltage (signal) of the second comparator207to the switch element103.

Note that in the detection circuit, switching of the reference voltage source114or the third reference voltage source302is performed in the second switch element301.

<Circuit Operation in Third Embodiment>

Next, the operation and effects of the power supply apparatus300according to the present embodiment will be described. InFIG. 6, the horizontal axis represents passage of time. The vertical axis represents fluctuation of each voltage or each current described later. InFIG. 6, as inFIGS. 2 and 4, a predetermined position on the vertical axis does not represent a specific concrete numerical value (voltage value or current value). A plurality of waveforms arranged along the vertical axis corresponds to voltages or currents corresponding to reference signs specified inFIG. 5.

InFIG. 6, the present embodiment is similar to the first embodiment and the second embodiment with respect to a power supply voltage (VIN), the output voltage (VA) of the boosting converter120, a divided voltage (VB), a current (IR) flowing through the inrush current limiting element102, an input current (IIN), a composite current of IRand IIN(ISW), and a comparison output (VSW).

InFIG. 6, the present embodiment is similar to the second embodiment with respect to the voltage across the time constant capacitor205(VCAP) and the second reference voltage (VREF2).

InFIG. 6, VREF3represents a third reference voltage to compare with the divided voltage (VB) and, by the comparison, to detect a decrease in the output voltage (VA) of the boosting converter120.

Next, each timing used inFIG. 6will be described. Time point a3 corresponds to the moment of power-on. Time point b3 corresponds to the moment when the boosting converter120reaches the first reference voltage (VREF1). Time point c3 corresponds to the moment when the voltage across the time constant capacitor205(VCAP) reaches the second reference voltage (VREF2). Time point d3 corresponds to the moment when an instantaneous interruption or an instantaneous drop occurs in the power supply apparatus300.

Time point e3 corresponds to the moment when the divided voltage (VB) of the output voltage (VA) of the boosting converter120falls below the first reference voltage (VREF1) because of the instantaneous interruption or the instantaneous drop. Time point f3 corresponds to the moment when the power supply apparatus300returns from the instantaneous interruption or the instantaneous drop. Time point g4 corresponds to the moment when the voltage across the time constant capacitor205(VCAP) reaches the second reference voltage (VREF2) after return from the instantaneous interruption or the instantaneous drop.

<Operation at Time Point a3 to Time Point b3>

Time from time point a3 to time point b3 corresponds to time from when the power supply apparatus300is turned on until the output voltage (VA) of the boosting converter120reaches the set voltage (VSET). In the power supply apparatus300, the output voltage (VA) of the boosting converter120is zero just before the power is turned on (before time point a3). Therefore, the divided voltage (VB) Of VAis also zero. When the divided voltage (VB) is zero, the comparator113does not operate because there is no input to be compared, and the output of the comparator113becomes zero. In this case, the comparison output (VSW) that is the output of the second comparator207also becomes zero. When the comparison output (VSW) is zero, the switch element103does not operate. Therefore, a contact of the switch element103remains open. In addition, the DCDC converter115is also off.

Since the switch element103remains off at power-on (time point a3), the input current (IIN) passes through the inrush current limiting element102from the input terminal101and charges the input capacitor121of the boosting converter120. In addition, the input current (IIN) passes through the inrush current limiting element102, the coil122, and the diode124, and charges the output smoothing capacitor125of the boosting converter120.

The inrush current that occurs at the time of this current application (time point a3) is suppressed by the inrush current limiting element102. From time point a3 to time point b3, the output voltage (VA) of the boosting converter120increases while the input current (IIN) decreases. When time reaches time point b3, the output voltage (VA) reaches the set voltage (VSET) and the divided voltage (VB) reaches the first reference voltage (VREF1). At the same time, charging of the output smoothing capacitor125is completed and the input current (IIN) becomes zero.

<Operation at Time Point b3 to Time Point c3>

Time from time point b3 to time point c3 corresponds to a period for giving a constant delay after the divided voltage (VB) of the output voltage (VA) of the boosting converter120reaches the first reference voltage VREF1. When the divided voltage (VB) exceeds the first reference voltage (VREF1), the output of the comparator113becomes the Hi level. An output current from the comparator113passes through the time constant resistor204and charges the time constant capacitor205over time. When the voltage across the charged time constant capacitor205(VCAP) exceeds the second reference voltage (VREF2), the output of the second comparator207becomes the Hi level.

By ensuring this period sufficiently in accordance with the actual circuit operation, it is possible to operate the second comparator207after the output voltage (VA) of the boosting converter120has reached the set voltage (VSET), that is, after the charging of the output smoothing capacitor125is completed.

<Operation at Time Point c3 to Time Point d3>

Time from time point c3 to time point d3 corresponds to time from the operation of the second comparator207as described above until the power supply apparatus300goes into steady operation. By sufficiently taking the delay period already described, the comparison output (VSW) that is the output of the second comparator207is set to Hi level after the output voltage (VA) reaches the set voltage (VSET). When the comparison output (VSW) becomes the Hi level, the switch element103and the DCDC converter115are turned on.

At this time, since the output voltage (VA) of the boosting converter120has reached the set voltage (VSET), a charging current of the output smoothing capacitor125is zero. In addition, since the DCDC converter115is off until just before, the current flowing through the inrush current limiting element102is zero. Therefore, a secondary inrush current that occurs when the inrush current limiting element102is short-circuited by the switch element103does not occur at all.

At the same time, the second switch element301is operated to switch the reference voltage input to the comparator113to the third reference voltage (VREF3). Note that the third reference voltage (VREF3) is a voltage lower than the first reference voltage (VREF1). As a result, a hysteresis characteristic can be given to the detection voltage that detects the output voltage (VA) of the boosting converter120, and a malfunction caused by detecting an output ripple voltage can be prevented.

After the above, the DCDC converter115gradually starts drawing a current. Therefore, the input current IINgradually increases and the power supply apparatus300goes into steady operation. Since the switch element103is on (the contact is closed and the inrush current limiting element102is short-circuited) in steady operation, the input current (IIN) is equal to the current (ISW) flowing through the switch element103(IIN=ISW). In addition, the current (IR) flowing through the inrush current limiting element102is zero (IR=0). Therefore, in steady operation, the inrush current limiting element102does not consume power in the power supply apparatus300.

<Operation at Time Point d3 to Time Point e3>

Time from time point d3 to time point e3 is a period from when an instantaneous interruption or an instantaneous drop occurs in the power supply apparatus300until the output voltage (VA) of the boosting converter120decreases and the divided voltage (VB) falls below the third reference voltage (VREF3). Even if the instantaneous interruption or the instantaneous drop occurs, the DCDC converter115draws a current for supplying power to the load116. Therefore, the boosting converter120supplies power to the DCDC converter115while power supply from the input terminal101is insufficient. At this time, since the output voltage (VA) of the boosting converter120has decreased, the divided voltage (VB) naturally becomes lower than the third reference voltage (VREF3).

<Operation at Time Point e3 to Time Point f3>

Time from time point e3 to time point f3 corresponds to time from when the divided voltage (VB) falls below the third reference voltage (VREF3) until the power supply apparatus300returns from the instantaneous interruption or the instantaneous drop. In the power supply apparatus300, when the divided voltage (VB) falls below the third reference voltage (VREF3), the comparator113stops outputting. When the output of the comparator113stops, the time constant capacitor205is instantaneously discharged via the capacitor discharging diode203. Then, since the voltage across the time constant capacitor205(VCAP) becomes zero, the comparison output (VSW) that is the output of the second comparator207becomes the Low level. When the comparison output (VSW) becomes the Low level, the switch element103and the DCDC converter115are turned off. At this point, since the second switch element301is also turned off, the reference input to the comparator113is switched from the third reference voltage (VREF3) to the first reference voltage (VREF1).

<Operation at Time Point f3 to Time Point g3>

Time from time point f3 to time point g3 is a period for giving a constant delay after return from the instantaneous interruption/instantaneous drop. After return from the instantaneous interruption/instantaneous drop, the divided voltage (VB) exceeds the first reference voltage (VREF1). Therefore, the output of the comparator113becomes the Hi level. At this time, the output current of the comparator113charges the time constant capacitor205over time via the time constant resistor204. As a result, when the voltage across the time constant capacitor205(VCAP) exceeds the second reference voltage (VREF2), the comparison output (VSW) that is the output of the second comparator207becomes the Hi level. By taking this period sufficiently, it is possible to operate the second comparator207after charging of the output smoothing capacitor125is completed.

<Operation after Time Point g3>

Time after time point g3 corresponds to time from the operation of the second comparator207until the power supply apparatus300goes into steady operation. In the power supply apparatus300, by taking the delay period sufficiently, the comparison output (VSW) of the second comparator207is set to the Hi level after the output voltage (VA) of the boosting converter120reaches the set voltage (VSET) and the charging current of the output smoothing capacitor125becomes zero. As a result, the switch element103and the DCDC converter115are turned on.

At this time, since the output voltage (VA) of the boosting converter120has reached the set voltage (VSET), the charging current of the output smoothing capacitor125is zero. Since the DCDC converter115is also off, the current flowing through the inrush current limiting element102is zero. Therefore, a secondary inrush current that occurs when the switch element103is short-circuited does not occur at all.

At the same time, the second switch element301is operated to switch the input reference voltage to the third reference voltage (VREF3) lower than the first reference voltage (VREF1). As a result, a hysteresis characteristic can be given to the detection voltage of the boosting converter120, and a malfunction caused by detecting the output ripple voltage is prevented.

Since the DCDC converter115gradually starts drawing a current after the above, the input current IINgradually increases, and the power supply apparatus300goes into the steady operation. Since the switch element103is on in steady operation, the input current (IIN) is equal to the current (ISW) flowing through the switch element103(IIN=ISW). In addition, the current (IR) flowing through the inrush current limiting element102becomes zero (IR=0). Therefore, there is no power consumption in the inrush current limiting element102, and power loss by the inrush current limiting element102does not occur in steady operation.

As described above, in order to suppress various types of inrush currents, the power supply apparatus300according to the present embodiment short-circuits the inrush current limiting element102when no current flows in the inrush current limiting element102, and suppresses a secondary inrush current while reducing unnecessary power consumption. Furthermore, the power supply apparatus300detects the inrush current that occurs at the time of return from the instantaneous interruption or the instantaneous drop, and suppresses the inrush current and the secondary inrush current by the same sequence as a sequence performed at power-on. In addition, as described above, two different reference voltages are used to detect the ripple of the output voltage (VA) of the boosting converter120. As a result, it is possible to reliably and stably suppress various inrush currents.