Backup power supply

Abstract

To provide a backup power supply device and a control method thereof that can adaptively step down the voltage of a power storage unit while suppressing a significant increase in the number of components.SOLUTION: A backup power supply device that supplies power to a power supply target device that operates by supplying power from an external power supply at the time of emergency of the power supply state of the external power supply includes a power storage unit, a series regulator arranged on a path connecting the power storage unit and the power supply target device, and a control circuit that changes the output voltage of the series regulator in multiple stages according to changes in the power supply state of the external power supply and changes in the voltage of the power storage unit.SELECTED DRAWING: Figure 1

Description

Technical Field

[0005] , , , , , , , ,

[0006]

[0001] The present invention relates to a backup power supply Place .

Background Art

[0002] Conventionally, in an emergency such as a power outage when power supply from an external power source to a power supply target device becomes impossible, a backup power supply device having a storage battery may be connected to the power supply target device. The backup power supply device supplies power to the power supply target device instead of the external power source, for example, during a power outage.

[0003] As a conventional power supply device having a power storage unit including a storage battery, there is known one that does not directly output the voltage of the power storage unit to the power supply target device. For example, in the power supply device described in Patent Document 1, a battery voltage is boosted or bucked by a regulator to generate a target voltage.

[0004] In the case of a backup power supply device, for example, during non-power outage, the voltage of the power storage unit (hereinafter referred to as "power storage unit voltage") is bucked to a voltage lower than the voltage of the external power source (hereinafter, distinguished from the power storage unit voltage and referred to as "power supply voltage"). In this way, during non-power outage, the output voltage output from the backup power supply device is kept lower than the power supply voltage, the usage frequency of the storage battery during non-power outage is reduced, and deterioration of the storage battery is suppressed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Furthermore, as the voltage of the energy storage unit increases, the difference between the energy storage unit voltage and the rated voltage of the powered device also increases. As a result, the amount of voltage reduction required during a power outage, i.e., the amount of voltage reduction from the energy storage unit voltage to the rated voltage, may increase.

[0008] In other words, it is necessary to adaptively step down the voltage from the energy storage unit to the output voltage in response to changes in the situation.

[0009] The purpose of this disclosure is to provide a backup power supply that can adaptively reduce the voltage of the energy storage unit while suppressing a significant increase in the number of components. Place It is about providing. [Means for solving the problem]

[0010] The backup power supply device of this disclosure is a backup power supply device that supplies power to a powered device that operates by power supply from an external power source in the event of an emergency in the power supply state of the external power source, and comprises: a power storage unit; a series regulator arranged on a path connecting the power storage unit and the powered device; and a control circuit that changes the output voltage of the series regulator in multiple stages in response to changes in the power supply state of the external power source and changes in the voltage of the power storage unit. The series regulator comprises a p-type field-effect transistor arranged on the path and a gate voltage adjustment circuit that gradually reduces the gate voltage of the p-type field-effect transistor. The gate voltage adjustment circuit performs a first step of reducing the gate voltage in an emergency, and after the first step, performs a second step of reducing the gate voltage when the voltage of the energy storage unit drops to the rated voltage of the power supply device. . [Effects of the Invention]

[0012] According to this disclosure, a backup power supply device can adaptively reduce the voltage of the energy storage unit while suppressing a significant increase in the number of components. Place It can be provided. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a circuit diagram showing a backup power supply according to an embodiment. [Figure 2] Figure 2 is a timing chart illustrating an example of voltage control by a backup power supply according to this embodiment. [Figure 3] Figure 3 is a flowchart showing an example of the voltage control operation of the backup power supply according to the embodiment. [Figure 4] Figure 4 is a circuit diagram showing a backup power supply device according to Modification 1. [Figure 5] Figure 5 is a circuit diagram showing a backup power supply device according to Modification 2. [Modes for carrying out the invention]

[0014] Hereinafter, a backup power supply device according to the embodiment of this disclosure will be described with reference to the drawings.

[0015] (Circuit configuration) Figure 1 is a circuit diagram showing a backup power supply unit 100 according to an embodiment. The backup power supply unit 100 is electrically connected to an external power supply unit 1 and a power supply target device 2 via input / output terminals 191 and 192. The external power supply unit 1 is, for example, a device that converts commercial AC power to DC power and outputs it. The external power supply unit 1 supplies power to the power supply target device. The power supply target device 2 is a device that operates by receiving power. The power supply target device 2 may be, for example, a server device.

[0016] The backup power supply unit 100 is a power supply unit that supplies power to the powered device 2 in the event of an emergency, typically a power outage, when the external power supply unit 1 is not functioning properly.

[0017] The backup power supply device 100 includes a power storage unit 110, a series regulator 130, and a control circuit 140. The control circuit 140 controls the output voltage of the series regulator 130 in multiple steps based on the voltage of the power storage unit 110 and the change in the power supply state of the external power supply 1.

[0018] The power storage unit 110 is connected to input / output terminals 191 and 192 via a power supply path PL. The power supply path PL is a supply path that supplies the power stored in the power storage unit 110 to the power supply target device 2.

[0019] The power storage unit 110 includes a storage battery 111. In the present embodiment, as illustrated in FIG. 1, the power storage unit 110 includes one storage battery 111. Therefore, in the present embodiment, the power storage unit voltage is equivalent to the voltage of the storage battery 111. Note that the power storage unit 110 may include a plurality of storage batteries 111. For example, the power storage unit 110 may include 10 storage batteries 111 connected in series. When the power storage unit 110 includes a plurality of storage batteries 111, the power storage unit voltage corresponds to the combined voltage of the plurality of storage batteries 111.

[0020] The storage battery 111 is, for example, a secondary battery such as a nickel-hydrogen storage battery and a lithium-ion storage battery.

[0021] The backup power supply device 100 includes a current detection circuit 120. The current detection circuit 120 detects the output current of the backup power supply device 100 by measuring the current flowing through the power supply path PL, and outputs the detection result to the control circuit 140.

[0022] The current detection circuit 120 includes, for example, a resistance element 121 and an operational amplifier 122. The resistance element 121 is disposed on the power supply path PL. When the voltages at both ends of the resistance element 121 are input to the two input terminals of the operational amplifier 122, respectively, the operational amplifier 122 outputs a signal based on the voltage difference to the control circuit 140.

[0023] The series regulator 130 is located on the power supply path PL and receives the voltage input from the energy storage unit. Under the control of the control circuit 140, it outputs a predetermined voltage as the output voltage. In this embodiment, the output voltage of the series regulator 130 is output to the powered device 2, and therefore refers to the same value as the output voltage of the backup power supply unit 100.

[0024] The series regulator 130 includes a drive element 131 and a gate voltage adjustment circuit 132.

[0025] The driving element 131 is a transistor. Figure 1 shows that the driving element 131 is a p-type field-effect transistor (FET). The driving element 131 is located on the power supply path PL, and its output voltage changes depending on its on-resistance.

[0026] The gate voltage adjustment circuit 132, under the control of the control circuit 140, changes the gate voltage of the drive element 131 in multiple stages. This change in gate voltage changes the on-resistance of the drive element 131.

[0027] The gate voltage adjustment circuit 132 includes a voltage divider circuit 133, a reference power supply 137, a switching element 150, an operational amplifier 160, and a switching element 170.

[0028] The voltage divider circuit 133 is a circuit that divides the output voltage fed back from the drain side of the driving element 131 and inputs it to the operational amplifier 160, and is equipped with resistor elements 134 to 136.

[0029] The resistor 134 is located on the feedback path from the drain side of the drive element 131 to the non-inverting input terminal of the operational amplifier 160. In this embodiment, one resistor 134 constitutes the first resistor section.

[0030] Resistor 135 is connected in series with resistor 134 and is connected to the non-inverting input terminal and ground of the operational amplifier 160. The middle section of resistors 134 and 135 is connected to the non-inverting input terminal of the operational amplifier 160.

[0031] Resistor element 136 is connected in parallel with resistor element 135. Resistor element 136 is also connected to ground via switching element 150 and to the non-inverting input terminal of operational amplifier 160. In this embodiment, resistor elements 135 and 136 constitute a second resistance section.

[0032] The reference power supply 137 is a power supply that outputs a reference voltage for controlling the output voltage to the inverting input terminal of the operational amplifier 160. The reference voltage is determined according to the rated voltage of the powered device 2 and the voltage of the external power supply 1, etc.

[0033] In this embodiment, as illustrated in Figure 1, the switching element 150 is an n-type field-effect transistor (FET). The source of the switching element 150 is connected to the resistor 136, the drain to ground, and the gate to the control circuit 140. When a voltage is applied to the gate of the switching element 150, the switching element 150 changes from a non-conductive state to a conductive state due to the resulting gate-drain voltage Vgd.

[0034] When the switching element 150 is switched between a non-conductive state and a conductive state, the combined resistance value of the resistor element 135 and the resistor element 136 (hereinafter sometimes simply referred to as the "combined resistance value") changes. As the combined resistance value changes, the voltage division ratio of the voltage divider circuit 133 changes. As a result, the voltage input to the non-inverting input terminal of the operational amplifier 160 changes.

[0035] The operational amplifier 160 outputs a voltage based on the voltage difference between the voltages input to the inverting input terminal and the non-inverting input terminal. The output terminal of the operational amplifier 160 is connected to the gate of the driver element 131. A resistor 184 may be placed between the output terminal of the operational amplifier 160 and the gate of the driver element 131.

[0036] In this embodiment, as illustrated in Figure 1, the switching element 170 is an n-type field-effect transistor. The source of the switching element 170 is connected to the gate of the driving element 131, the drain to ground, and the gate to the control circuit 140. When a voltage is applied to the gate of the switching element 170, the switching element 170 changes from a non-conductive state to a conductive state due to the resulting gate-drain voltage Vgd.

[0037] When the switching element 170 switches between a non-conductive state and a conductive state, the gate of the drive element 131 switches between being disconnected from and connected to ground. When the gate of the drive element 131 is connected to ground, the gate-source voltage Vgs of the drive element 131 becomes extremely large, and as a result, the on-resistance of the drive element 131 becomes extremely small.

[0038] A resistive element 185 may be placed between the source and gate of the drive element 131.

[0039] The control circuit 140 determines the power supply status of the external power supply 1 based on the signal from the current detection circuit 120. The control circuit 140 also detects the voltage of the energy storage unit. Based on the change in the power supply status of the external power supply 1 and the voltage of the energy storage unit, the control circuit 140 switches the switching elements 150 and 170 between a conductive state and a non-conductive state.

[0040] (Output voltage control) The output voltage control of the backup power supply unit 100 will be described below. Here, as an example, we will assume that the power supply voltage Vd is 12V, the rated voltage Vs of the powered device 2 is 14V, and the maximum value VM of the storage unit voltage Vu when the backup power supply unit 100 is 100% charged is 14.5V. Note that 12V, given as an example of the power supply voltage Vd, is a fixed value based on the specifications of the external power supply 1. Needless to say, in the event of a power outage, the voltage output from the external power supply 1 will be almost 0V or will drop significantly from 12V.

[0041] Figure 2 is a timing chart illustrating the voltage control by the backup power supply unit 100. The solid line shows the change in the energy storage unit voltage Vu, the dashed line (thick line) shows the change in the gate voltage Vg of the drive element 131, and the dashed line (thick line) shows the change in the output voltage Vout.

[0042] Under normal conditions, i.e., when there is no power outage, the external power supply 1 supplies power to the device 2 at the power supply voltage Vd. When the backup power supply 100 is at 100% charge, the storage voltage Vu is 14.5V (maximum value VM), which is higher than the power supply voltage Vd (12V). Therefore, the control circuit 140 controls the output voltage Vout to be less than the power supply voltage Vd. Since the output voltage Vout is less than the power supply voltage Vd, no current is output from the backup power supply 100. In other words, when there is no power outage, the output current Iout is approximately 0A.

[0043] Specifically, the control circuit 140, for example, puts the switching element 150 into a non-conducting state. The non-inverting input terminal and the inverting input terminal of the operational amplifier 160 are input to the voltage based on the voltage division ratio of the voltage divider circuit 133 and the reference voltage from the reference power supply 137, respectively. The operational amplifier 160 then outputs a voltage based on the difference between the voltage based on the voltage division ratio of the voltage divider circuit 133 and the reference voltage. The output voltage of the operational amplifier 160 is input to the gate of the driving element 131 through the resistor element 184. Incidentally, when there is no power outage, the control circuit 140 keeps the switching element 170 in a non-conducting state at all times. This is because if the switching element 170 becomes conductive, the gate voltage will no longer be applied from the operational amplifier 160 to the driving element 131.

[0044] This gate voltage controls the conduction state of the drive element 131. In the example of output voltage control described here, the output voltage Vout is controlled to a constant voltage value V1 (for example, 11V) that is less than the power supply voltage Vd (see Figure 2).

[0045] Subsequently, at time T1, if a power outage occurs in external power supply 1, the output voltage from external power supply 1 will become approximately 0V or drop significantly from 12V, reversing the relationship between the output voltage Vout and the output voltage. As a result, the output current Iout will begin to flow through the power supply path PL. Furthermore, as the output current Iout begins to increase, the storage voltage Vu will begin to decrease from its maximum value VM. In addition, the gate voltage Vg will decrease along with the decrease in the storage voltage Vu.

[0046] Then, at time T2, the output current Iout reaches the threshold Ith, and the control circuit 140 determines that the power supply state of the external power supply 1 is an emergency state, that is, a power outage state. The threshold Ith is, for example, less than the maximum current value when power is supplied from the backup power supply 100 to the powered device 2, and higher than 0A. At this time, in order to supply power from the energy storage unit 110 to the powered device 2, the control circuit 140 increases the output voltage Vout to an extent that does not exceed the rated voltage Vs.

[0047] Specifically, the control circuit 140 switches the switching element 150 from a non-conductive state to a conductive state. When the switching element 150 switches from a non-conductive state to a conductive state, the combined resistance value of the resistors 135 and 136 changes. Consequently, the voltage division ratio in the voltage divider circuit 133 changes, and the voltage input to the non-inverting input terminal of the operational amplifier 160 changes. As a result, the voltage output from the operational amplifier 160 changes, and the gate voltage Vg of the drive element 131 decreases in steps.

[0048] As the gate voltage Vg decreases, the conduction state of the drive element 131 changes. Specifically, the on-resistance of the drive element 131 decreases. As a result, the output voltage Vout increases to a constant voltage value V2 (for example, 13.6V) that is less than or equal to the rated voltage Vs and is maintained thereafter. Note that the constant voltage value V2 only needs to be less than or equal to the rated voltage Vs and higher than the constant voltage value V1, for example, it may be the same value as the rated voltage Vs (14V).

[0049] As a result, the voltage is controlled to a constant voltage that does not exceed the rated voltage Vs, and power is supplied from the backup power supply unit 100 to the powered device 2.

[0050] At time T2, the control circuit 140 may change the on-resistance of the switching element 150 by a method other than switching the switching element 150 between a non-conductive state and a conductive state. When the on-resistance of the switching element 150 changes, the combined resistance value of the resistors 135 and 136 changes, and the voltage division ratio of the voltage divider circuit 133 changes. As a result, the voltage input to the non-inverting input terminal of the operational amplifier 160 changes.

[0051] From time T2 onward, as power is supplied to the powered device 2, the energy storage voltage Vu gradually decreases. Furthermore, as the energy storage voltage Vu decreases, the gate voltage Vg of the drive element 131 also gradually decreases.

[0052] At time T3, the energy storage voltage Vu becomes the rated voltage Vs. In other words, even if the energy storage voltage Vu is output as the output voltage Vout, the output voltage Vout will not exceed the rated voltage Vs. At this time, the control circuit 140 controls the switching element 170 so that the energy storage voltage Vu is directly output as the output voltage Vout.

[0053] Specifically, the control circuit 140 switches the switching element 170 from a non-conductive state to a conductive state. As a result, the gate of the drive element 131 becomes connected to ground. That is, the gate voltage Vg of the drive element 131 becomes 0V. Therefore, the gate-source voltage Vgs of the drive element 131 matches the energy storage voltage Vu.

[0054] The larger the gate-source voltage Vgs, the smaller the on-resistance of the drive element 131. Therefore, when the gate voltage Vg of the drive element 131 becomes 0V, the on-resistance of the drive element 131 becomes extremely small. In other words, the current conducting between the source and drain of the drive element 131 increases. Consequently, the energy storage voltage Vu is directly output as the output voltage Vout from the series regulator 130.

[0055] Figure 3 is an example of a flowchart showing the output voltage control operation of the backup power supply unit 100.

[0056] First, in step S1, the control circuit 140 determines whether the backup power supply 100 is connected to the external power supply 1 and the powered device 2. If the backup power supply 100 is not connected to the external power supply 1 and the powered device 2 ("NO" in step S1), the output voltage control operation ends. If the backup power supply 100 is connected to the external power supply 1 and the powered device 2 ("YES" in step S1), the process proceeds to step S2.

[0057] In step S2, the control circuit 140 determines whether the power supply state of the external power supply 1 is critical based on the signal from the current detection circuit 120. For example, the current detection circuit 120 converts the signal from the current detection circuit 120 into an output current Iout and compares the output current Iout with a threshold Ith. The control circuit 140 then determines that the power supply state is normal if the output current Iout is less than or equal to the threshold Ith, and determines that the power supply state is critical if the output current Iout exceeds the threshold Ith.

[0058] If the power supply is normal ("NO" in step S2), the process transitions to step S7, where the control circuit 140 controls the output voltage Vout to less than the power supply voltage Vd. Specifically, the control circuit 140 puts the switching element 150 into a non-conducting state. More specifically, the control circuit 140 switches the switching element 150 to a non-conducting state if it was originally in a conducting state, and maintains that non-conducting state if it was originally in a non-conducting state. Therefore, a voltage based on the voltage division ratio between the combined resistance value when the switching element 150 is in a non-conducting state and the resistor element 134 is input to the non-inverting input terminal of the operational amplifier 160. The operational amplifier 160 outputs a voltage based on the difference between the voltage based on the voltage division ratio and the reference voltage. This voltage is input to the gate of the driving element 131 through the resistor element 184. Based on the voltage input to the gate, the on-resistance of the driving element 131 is determined, and consequently, the output voltage of the series regulator 130 is determined. For example, the output voltage is controlled to a constant voltage value V1 (before time T1 in Figure 2).

[0059] Furthermore, if the power supply condition is normal ("NO" in step S2), the control circuit 140 keeps the switching element 170 in a non-conducting state at all times. However, the control circuit 140 may switch the switching element 170 from a non-conducting state to a conducting state and connect the gate of the drive element 131 to ground only when it detects that the power supply condition is normal and that the energy storage voltage Vu is less than the power supply voltage Vd. In other words, the control circuit 140 may output the energy storage voltage Vu as the output voltage Vout.

[0060] Subsequently, in step S8, the control circuit 140 determines whether the connection between the backup power supply 100 and the external power supply 1 and the powered device 2 has been disconnected. If the connection between the backup power supply 100 and the external power supply 1 and the powered device 2 has been disconnected ("YES" in step S8), the output voltage control operation ends. If the backup power supply 100 and the external power supply 1 and the powered device 2 are still connected ("NO" in step S8), the process proceeds to step S2.

[0061] If the power supply condition is critical ("YES" in step S2), in step S3, the control circuit 140 determines whether the energy storage voltage Vu exceeds a predetermined value. Here, the predetermined value is the rated voltage Vs of the power supply target device 2.

[0062] If the energy storage voltage Vu exceeds a predetermined value ("YES" in step S3), the process transitions to step S4, where the control circuit 140 performs constant voltage control to keep the output voltage Vout at a constant voltage value V2 that is less than or equal to the predetermined value. Specifically, the control circuit 140 changes the switching element 150 from a non-conductive state to a conductive state, thereby changing the combined resistance value (control at time T2 in Figure 2). If the switching element 150 was originally in a conductive state, the control circuit 140 maintains that conductive state.

[0063] Next, in step S5, the control circuit 140 determines whether the connection between the backup power supply 100 and the external power supply 1 and the powered device 2 has been disconnected. If the connection between the backup power supply 100 and the external power supply 1 and the powered device 2 has been disconnected ("YES" in step S5), the output voltage control operation ends. If the backup power supply 100 and the external power supply 1 and the powered device 2 are still connected ("NO" in step S5), the process proceeds to step S2.

[0064] If the energy storage voltage Vu does not exceed a predetermined value ("NO" in step S3), the process proceeds to step S6, and the control circuit 140 outputs the energy storage voltage Vu as the output voltage Vout.

[0065] In step S6, the control circuit 140 switches the switching element 170 from a non-conductive state to a conductive state, connecting the gate of the drive element 131 to ground (similar to the control at time T3 in Figure 2). Subsequently, the process of step S5 is executed. If the switching element 170 was originally in a conductive state, the control circuit 140 maintains that conductive state.

[0066] As described above, the backup power supply device 100 according to this embodiment includes a power storage unit 110, a series regulator 130 arranged in a power supply path PL connecting the power storage unit 110 and the power supply target device 2, and a control circuit 140 that changes the output voltage Vout of the series regulator 130 in multiple stages in response to changes in the power supply state of the external power supply 1 and changes in the voltage Vu of the power storage unit.

[0067] The control method for the backup power supply device 100 according to this embodiment involves changing the output voltage Vout of the series regulator 130 on the power supply path PL connecting the energy storage unit 110 and the power supply target device 2 in multiple stages in accordance with changes in the power supply state of the external power supply 1 and changes in the energy storage unit voltage Vu.

[0068] According to this embodiment, by placing a series regulator 130 on the power supply path PL and changing the output voltage of this series regulator 130 in multiple stages, the voltage Vu of the energy storage unit can be adaptively reduced according to various conditions. Furthermore, since a configuration such as connecting a large number of diodes in series is not adopted to reduce the voltage Vu of the energy storage unit, a significant increase in the number of components required to reduce the voltage Vu of the energy storage unit can be suppressed, and power loss and an increase in the size of the device can also be suppressed.

[0069] The series regulator 130 has a drive element 131 located in the power supply path PL. The control circuit 140 controls the drive element 131 to output a first constant voltage (constant voltage value V1) that is lower than the power supply voltage Vd under normal conditions, a second constant voltage (constant voltage value V2) that is lower than or equal to the predetermined value and higher than the constant voltage value V1 when the energy storage voltage Vu exceeds a predetermined value (rated voltage Vs of the external power supply 1) in an emergency, and the energy storage voltage Vu does not exceed the rated voltage Vs when the energy storage voltage Vu is output.

[0070] According to this embodiment, by simply placing the drive element 131 on the power supply path PL, the output voltage Vout can be controlled in multiple stages according to various conditions.

[0071] For example, even if the backup power supply unit 100 has a relatively large battery capacity and the difference between the rated voltage Vs and the storage unit voltage Vu is relatively large, the output voltage can be controlled with a small number of components to reduce the frequency of battery use during normal operation when there is no power outage, thereby suppressing battery degradation, and to reduce the burden on the powered device 2 during emergencies.

[0072] The series regulator 130 includes a transistor (driving element 131) arranged on the power supply path PL, and a gate voltage adjustment circuit 132 that changes the gate voltage of the transistor (driving element 131) in multiple stages in response to changes in the power supply state of the external power supply 1 and changes in the voltage of the energy storage unit.

[0073] In other words, by placing a simple and inexpensive transistor on the power supply path PL and changing its gate voltage in response to changes in the power supply state and the voltage of the energy storage unit, the output voltage Vout can be controlled in multiple stages according to various conditions.

[0074] The more components placed on the power supply path PL, such as diodes and transistors for stepping down the voltage of the energy storage unit, the greater the power loss of the backup power supply unit during power supply. According to this embodiment, by simply placing transistors on the power supply path PL and controlling their gate voltages, the output voltage Vout can be controlled in multiple stages, thereby reducing the power loss of the backup power supply unit 100 during power supply. Furthermore, while a large number of diodes and transistors for stepping down the voltage of the energy storage unit may increase the size of the backup power supply unit, this is not the case with this embodiment.

[0075] The gate voltage adjustment circuit 132 includes an operational amplifier 160 connected to the gate of the transistor (driving element 131) on the output side to control the gate voltage Vg, and a voltage divider circuit 133 that divides the output voltage Vout and inputs it to the operational amplifier 160. The control circuit 140 changes the voltage division ratio of the voltage divider circuit 133 in accordance with changes in the power supply state of the external power supply 1.

[0076] Therefore, under normal circumstances, the output voltage Vout can be maintained below the power supply voltage Vd, and in emergencies, it can be maintained below the rated voltage Vs of the powered device 2, through analog control.

[0077] More specifically, the voltage divider circuit 133 includes a pair of resistors 134 and 135 connected in series with an operational amplifier 160 connected in the middle, and a resistor 136 connected in parallel to resistor 135. The gate voltage adjustment circuit 132 includes a switching element 150 that switches the connection state between resistor 136 and ground between a conducting state and a non-conducting state, thereby changing the combined resistance value of resistors 135 and 136. Furthermore, the control circuit 140 controls the switching element 150 so that the connection state between resistor 136 and ground is non-conducting under normal circumstances and conducting in emergencies.

[0078] In other words, by simply controlling the switching element 150 between a conductive state and a non-conductive state, the gate voltage of the transistor (driving element 131) can be changed, thereby allowing the output voltage Vout to be changed in multiple stages.

[0079] The backup power supply unit 100 has a current detection circuit 120 that detects the output current using a resistive element 121 placed in the power supply path PL. The control circuit 140 also determines whether the power supply status of the external power supply 1 is normal or abnormal based on the detection result of the current detection circuit 120.

[0080] Therefore, a simple and inexpensive circuit configuration can be used to detect changes in the power supply status of external power supply 1.

[0081] The gate voltage adjustment circuit 132 has a switching element 170 that switches the connection state between the gate of the transistor (driving element 131) and ground between a conducting state and a non-conducting state, thereby changing the on-resistance of the transistor (driving element 131). The control circuit 140 controls the switching element 170 so that the connection state between the gate and ground is normally non-conducting, and in emergencies, it is either non-conducting or conducting depending on the energy storage voltage Vu.

[0082] By making the switching element 170 conductive, the gate of the transistor (driving element 131) is connected to ground, making the gate-source voltage extremely large. As a result, the on-resistance of the transistor (driving element 131) becomes extremely small, so that power loss in the transistor (driving element 131) can be minimized when power is supplied from the backup power supply unit 100 to the powered device 2.

[0083] The transistor (driving element 131) is a p-type field-effect transistor. The control circuit 140 conducts the gate to ground when it is an emergency and the storage voltage Vu does not exceed a predetermined value (rated voltage Vs).

[0084] Therefore, compared to using an n-type field-effect transistor as the transistor (driving element 131), the power loss in the transistor (driving element 131) during power supply by the backup power supply device 100 can be minimized with a simpler circuit configuration.

[0085] (Variation 1) The following describes the differences between Modification 1 and the embodiment. Figure 4 is a circuit diagram showing the backup power supply device 100 according to Modification 1.

[0086] As shown in Figure 4, the voltage divider circuit 133 comprises multiple sets of resistor elements 136 and switching elements 150, and these sets are connected in parallel between the non-inverting input terminal of the operational amplifier 160 and ground. Therefore, in the modified example 1, the second resistance section is formed by the resistor element 135 and multiple resistor elements 136. Although Figure 4 shows that the voltage divider circuit 133 is provided with two sets of resistor elements 136 and switching elements 150, it may be provided with three or more sets.

[0087] According to Modification 1, the control circuit 140 can individually control the switching between energized and de-energized states of the multiple switching elements 150, thereby enabling it to set a larger combined resistance value between the resistor element 135 and the multiple resistor elements 136. Therefore, it is possible to set a larger voltage division ratio in the voltage divider circuit 133.

[0088] (Modification 2) The following describes the differences between Modification 2 and the embodiment. Figure 5 is a circuit diagram showing the backup power supply device 100 according to Modification 2.

[0089] As shown in Figure 5, the voltage divider circuit 133 may include a resistor 139 connected in parallel with the resistor 134 and a switching element 180, instead of the resistor 136 and the switching element 150. The switching element 180 is a field-effect transistor or the like. Therefore, in the modified example 2, the first resistance section is formed by the resistor 134 and the resistor 139.

[0090] In the modified example 2, the control circuit 140 controls the switching element 180 to be in a conducting state under normal circumstances and in a non-conducting state in emergencies. This allows the combined resistance value of the resistors 134 and 139 on the feedback path to be changed, thereby changing the voltage division ratio of the voltage divider circuit 133.

[0091] (Other variations) In the embodiments and the above-described modifications, the output current was detected using a resistor 121, but it may also be detected using a Hall element. When using a Hall element, it generates less heat compared to the resistor 121, so the temperature rise of the backup power supply 100 can be suppressed.

[0092] In the embodiments and the modifications described above, the threshold Ith is used to determine the power supply state. The threshold Ith may be set to a small value. That is, the control circuit 140 may determine that the external power supply 1 is in an emergency state, i.e., a power outage state, if even a small output current Iout flows. The control circuit 140 may also change the threshold Ith according to user settings.

[0093] Furthermore, the control circuit 140 may determine that the external power supply 1 is in a power outage state when it receives a signal indicating a power outage from a predetermined communication device.

[0094] The control circuit 140 may not only control the switching between the non-conductive and conductive states of the switching element 150, but may also accept the settings of the voltage Vd of the external power supply 1 and the rated voltage Vs of the powered device 2, and determine the above-mentioned voltage values ​​V1 and V2 based on the accepted information. That is, the control circuit 140 may determine the target value of the normal output voltage Vout (the above-mentioned voltage value V1) and the target value of the emergency output voltage Vout (the above-mentioned voltage value V2) according to the voltage Vd of the external power supply 1 to which the backup power supply 100 is connected and the rated voltage Vs of the powered device 2.

[0095] In this case, the resistive element 136 may be a variable resistor. The control circuit 140 may also change the above-mentioned voltage values ​​V1 and V2 according to the power supply voltage Vd and the rated voltage Vs of the powered device 2 by controlling the resistance value of the variable resistor.

[0096] Furthermore, the driving element 131 may be a variable resistor. More specifically, the driving element 131 may be an n-type field-effect transistor. In the case of an n-type field-effect transistor, the gate voltage adjustment circuit 132 is configured to apply a gate voltage that is higher than the source voltage of the driving element 131. In contrast, in the case of a p-type field-effect transistor, the on-resistance can be reduced by making the gate voltage smaller than the source voltage and increasing the gate-source voltage. Here, the configuration that reduces the gate voltage is easier to realize with a relatively simple circuit configuration compared to the configuration that increases the gate voltage. In particular, in this embodiment, there are cases where the storage voltage Vu is not stepped down but output directly as the output voltage Vout. In this case, the gate voltage can be easily minimized by simply grounding the gate. In this respect, the configuration in which a p-type field-effect transistor is used as the driving element 131 placed on the power supply path PL, as in this embodiment, is advantageous. [Industrial applicability]

[0097] This disclosure is suitably used in a backup power supply device and a control method for a backup power supply device that provides power to a power supply target device that operates using power supplied from an external power source in the event of an emergency in the power supply state of the external power source. [Explanation of symbols]

[0098] 1 External power supply 2. Devices to be powered 100 Backup power supply 110 Energy Storage Unit 111 Storage Battery 120 Current detection circuit 121 Resistor element 122 Op-amps 130 Series Regulators 131 Driving element 132 Gate Voltage Regulating Circuit 133 Voltage divider circuit 134-136, 139 Resistor elements 137 Reference power supply 140 Control circuits 150, 170, 180 switching element 160 Op-amps 184, 185 Resistor elements 191, 192 input / output terminals PL Power Supply Path

Claims

1. A backup power supply device that provides power to a power supply target device that operates using power supplied from an external power source in the event of an emergency in the power supply state of the external power source, The energy storage unit, A series regulator is arranged on the path connecting the power storage unit and the power supply target device, A control circuit that changes the output voltage of the series regulator in multiple stages in response to changes in the power supply state of the external power supply and changes in the voltage of the energy storage unit, Equipped with, The series regulator comprises a p-type field-effect transistor arranged on the path and a gate voltage adjustment circuit that gradually reduces the gate voltage of the p-type field-effect transistor. The gate voltage adjustment circuit performs a first step of reducing the gate voltage in an emergency, and after the first step, performs a second step of reducing the gate voltage when the voltage of the energy storage unit drops to the rated voltage of the power supply device. Backup power supply.

2. The control circuit is During normal operation, prior to the execution of the first step, a first constant voltage lower than the voltage of the external power supply is output. After the execution of the first stage and before the execution of the second stage, a second constant voltage is output that is less than or equal to the rated voltage and higher than the first constant voltage. After the execution of the second step, the voltage of the energy storage unit is output. Controlling the aforementioned p-type field-effect transistor, The backup power supply device according to claim 1.

3. The gate voltage adjustment circuit comprises an operational amplifier connected to the gate of the p-type field-effect transistor on the output side to control the gate voltage, and a voltage divider circuit that divides the output voltage and inputs it to the operational amplifier. The control circuit changes the voltage division ratio of the voltage divider circuit in accordance with the change in the power supply state of the external power supply. The backup power supply device according to claim 1.

4. The voltage divider circuit has a first resistor section and a second resistor section connected in series with the operational amplifier connected in the middle section. At least one of the first resistor and the second resistor includes a plurality of resistor elements and a voltage divider resistor control switching element, The control circuit controls the voltage divider resistor control switching element according to whether the power supply state of the external power supply is normal or abnormal, thereby changing the combined resistance value of the plurality of resistor elements. The backup power supply device according to claim 3.

5. The system further includes a current detection circuit that detects the output current using elements arranged along the aforementioned path. The control circuit determines whether the power supply state of the external power supply is normal or abnormal based on the detection result of the current detection circuit. The backup power supply device according to claim 4.

6. The gate voltage adjustment circuit includes an on-resistance control switching element that switches the connection state between the gate and ground of the p-type field-effect transistor between a conducting state and a non-conducting state, thereby changing the on-resistance of the p-type field-effect transistor. The control circuit controls the on-resistance control switching element such that the connection state between the gate and ground is normally non-conductive and in an emergency, it is either non-conductive or conductive depending on the voltage of the energy storage unit. The backup power supply device according to claim 1.

7. The control circuit shall maintain a conductive state between the gate and ground in an emergency and when the voltage of the energy storage unit does not exceed a predetermined value. The backup power supply device according to claim 6.

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