JP2005073339A - Backup power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backup power supply capable of assuring maximum backup time for a load with a requisite minimum of discharge current (backup current), by supplying a discharge current required only for the load by preventing the discharge current (backup current) to a charging circuit when a momentary blackout occurs with the power supply. <P>SOLUTION: The backup power supply comprises a charging circuit 2, an electrolytic capacitor C, a discharge circuit 3, and a discharge detecting means 4. The counter flow of the current from a power supply 5 to the discharge circuit 3 is prevented. When a power supply voltage VCC drops at momentary blackout, a discharge current (backup current IB) is naturally made to flow in a free balance method. A discharge state is detected with less power loss based on the discharge current (backup current IB), and the charging circuit 2 is prevented from being charged with the discharge current (backup current IB). So, the backup current IB equal to a load current IL required by a load 6 is supplied to backup driving of the load 6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a backup power supply apparatus that supplies DC power to a load and backs up when an instantaneous power failure occurs in the power supply apparatus, and more particularly to a backup power supply apparatus that can stably detect discharge current with little power loss.

  A power supply that generates DC power from a commercial power supply (50Hz / 60Hz, 100V AC power) and supplies it to the load is affected by surge voltages such as lightning and induced lightning. May occur.

  In general, the time of instantaneous power failure is almost 70 ms to 300 ms, but it is a short time, but the equipment (for example, production line equipment) that becomes a load is temporarily down or the memory is abnormal. It may cause a line stop.

  A backup power supply device is employed to back up such an instantaneous power failure of the power supply device and guarantee the operation of the load device.

  A conventional backup power supply device is connected in parallel with a power supply device that supplies DC power to a load, and when the power supply device is normal (a state in which no instantaneous power failure occurs), a charging circuit that takes in charging current from the power supply device and charges it , Equipped with an electrolytic capacitor that accumulates electric energy boosted by the charging circuit, and a discharge circuit that accumulates and discharges the electric energy accumulated in the electrolytic capacitor as discharge energy, and accumulates when an instantaneous power failure occurs in the power supply device The discharge energy is discharged and supplied to the load, and the power supply to the load is backed up.

  FIG. 5 shows a block diagram of an embodiment of a conventional backup power supply apparatus. In FIG. 5, a backup power supply device 50 includes a charging circuit 51, an electrolytic capacitor C, a discharge circuit 52, a voltage detection unit 53, a switch drive unit 54, and a MOSFET-Q, and is supplied from a power supply device 55 (power supply voltage VCC). The charging current 51 is taken in from the power supply current IP and boosted by the charging circuit 51, the boosted electrical energy is stored in the electrolytic capacitor C, and the stored electrical energy is stepped down by the discharge circuit 52 to generate the discharge voltage VD.

  On the other hand, the load 56 is driven by the load current IL (= power supply current IP−charge current IC) supplied from the power supply device 55 (power supply voltage VCC).

  When an instantaneous power failure occurs in the AC power supply VAC of the commercial power supply line due to the influence of a surge voltage such as a lightning strike or induced lightning, the power supply 55 also instantaneously interrupts the supply of the DC power supply and the power supply voltage VCC decreases.

  The voltage detection unit 53 monitors the decrease in the power supply voltage VCC, and when the power supply voltage VCC detects a decrease in the predetermined voltage ΔV, supplies the stop signal ST to the charging circuit 51 to stop the operation of the charging circuit 51 (the charging current IC In addition, the switch driver 54 supplies the drive signal SD to the MOSFET-Q to drive the MOSFET-Q on.

  When MOSFET-Q is turned on, a backup current IB that is a discharge current flows from the discharge circuit 52. The discharge voltage VD output from the discharge circuit 52 becomes the backup voltage VB due to the voltage drop of the on-resistance of the MOSFET-Q. The backup voltage VB is set to be equal to or lower than the detection voltage of the voltage detection unit 53 (= power supply voltage VCC−predetermined voltage ΔV). To be supplied.

  Further, during the instantaneous power failure of the power supply device 55, the stop signal ST is supplied from the voltage detection unit 53 to stop the operation of the charging circuit 51, so that the backup current IB supplied from the discharging circuit 52 is all supplied to the load 56. (Backup current IB = load current IL).

  On the other hand, when the instantaneous power failure of the power supply 55 is restored and the power supply voltage VCC is generated, the operation of the voltage detection unit 53 is stopped, the MOSFET-Q is turned off, the backup operation is stopped, and the charging circuit 51 is operated. Then, the charging current IC is taken from the power supply current IP and charging is started again.

  FIG. 7 shows a switching characteristic diagram from the power supply voltage to the backup voltage in FIG. In FIG. 7, when an instantaneous power failure occurs, the power supply voltage VCC decreases, and at time t1, the voltage detector 53 detects an instantaneous power failure from the voltage drop of the power supply voltage VCC. It takes time (= t2-t1) to turn on.

  Further, at time t2, the power supply voltage VCC further decreases, and after the MOSFET-Q is turned on, the backup voltage VB is reached at time (= t3-t2) and backup is started.

  In this way, the backup power supply 50 detects a drop in the power supply voltage VCC during an instantaneous power failure, stops the operation of the charging circuit 51, turns on the MOSFET-Q, and supplies the backup current IB ( = Load current IL) is supplied for backup, so that the finite electric energy charged can be used effectively.

  FIG. 6 shows a block diagram of another embodiment of a conventional backup power supply apparatus. 6, the backup power supply device 57 is different in that it includes a voltage comparison unit 58 and a resistor R instead of the voltage detection unit 53, the switch drive unit 54, and the MOSFET-Q shown in FIG.

  When the backup power supply 57 is charged and an instantaneous power failure occurs in the power supply 55 and the power supply voltage VCC decreases and falls below the discharge voltage VD, the backup current IB is passed from the discharge circuit 52 via the resistor R. Flowing.

  A backup current IB flows and changes across the resistor R from the discharge voltage VD and the power supply voltage VCC (VCC> VD) to the discharge voltage VD and the backup voltage VB (VD> VB). The discharge voltage VD and the backup voltage VB are When the voltage comparison unit 58 compares and the discharge voltage VD exceeds the backup voltage VB (VD> VB), the stop signal ST is supplied to the charging circuit 51, the operation of the charging circuit 51 is stopped, and the charging current IC flows in. Stop.

  By this operation, the load 56 is driven by the backup voltage VB, and the backup current IB is supplied to the load 56.

  By connecting the discharge circuit 52 and the power supply device 55 via the resistor R, when the power supply voltage VCC drops below the discharge voltage VD, the backup current IB naturally flows from the backup power supply device 57 to the load 56, so-called free balance. A scheme is formed.

  FIG. 8 is a switching characteristic diagram from the power supply voltage to the backup voltage in FIG. In FIG. 8, when an instantaneous power failure occurs, the power supply voltage VCC decreases at time t0, reaches the backup voltage VB at time ta, and the backup current IB flows naturally in a free balance to start backup.

  When the backup current IB flows, the voltage comparison unit 58 compares the discharge voltage VD across the resistor R with the backup voltage VB, supplies the stop signal ST to the discharge circuit 51, stops the discharge circuit 51, and sets the charge current IC. Stop inflow.

  As described above, when the power supply voltage VCC decreases during the instantaneous power failure, the backup power supply 57 naturally flows the backup current IB through the resistor R, stops the operation of the discharge circuit 51, and the charge current IC The inflow is stopped and the backup current IB (= load current IL) is supplied to the load 56 with the backup voltage VB for backup, so that the finite electric energy charged can be used effectively.

In addition, as disclosed in “Patent Document 1”, the conventional power supply device uses the output of the DC / DC converter as a DC power supply output in a normal state and charges the battery with charging means, It is known that a battery is quickly switched to a DC power source output when an instantaneous interruption is detected. In addition, although the literature relevant to the backup power supply apparatus was searched, since there is no corresponding literature, “Patent Literature 1” is described as a reference.
JP 10-42488 A

  The conventional backup power supply device shown in FIG. 5 determines that the instantaneous power failure has been restored when the backup voltage VB is generated when the backup voltage VB is set to a value lower than the backup voltage VB. There is a problem that chattering occurs in the backup voltage VB by repeatedly starting the backup when the backup voltage VB decreases and the backup voltage VB decreases, and a highly accurate voltage detection unit is required.

  Further, as shown in FIG. 7, it takes time to turn on the MOSFET-Q after the voltage detector detects a drop in the power supply voltage VCC, and there is a problem that the DC voltage drops during backup.

  Since the conventional backup power supply device shown in FIG. 6 is configured to perform a backup in a free balance manner through a resistor, the problem of the DC voltage drop and the setting problem of detecting the drop of the power supply voltage VCC during the backup are solved. However, since the backup current IB flows through the resistance value R, when the backup current IB is large, the voltage drop of the resistor increases, the power loss due to the resistor increases, and the backup voltage VB decreases. There is.

  In addition, if the value of the resistor is decreased to suppress the voltage drop and the decrease in the backup voltage VB is to be eliminated, when the backup current IB is small, the difference between the discharge voltage VD and the backup voltage VB is small, and the voltage comparison unit Since the backup state cannot be determined, the charging circuit cannot be stopped, the charging current IC cannot be stopped, and the backup current IB becomes large, and the back time required for the load cannot be secured.

  Explaining this phenomenon: Instantaneous power outage → Backup current IB flows in free balance → Backup state cannot be detected → Charging circuit operates → Large backup current IB including charging current IC occurs → Backup state detected → Charging circuit → Backup current IB decreases → Backup state cannot be detected and charging circuit operates → Repeated phenomenon that large backup current IB including charging current IC occurs, and the electrical energy of the backup power supply is rapidly discharged Backup time cannot be secured.

  Further, when the power supply device is normal (a state where no instantaneous power failure occurs), the power supply voltage VCC appears in the discharge circuit through the resistor, and the discharge circuit monitors the power supply voltage VCC and accumulates in the electrolytic capacitor. When oscillating to step down the electric energy to the discharge voltage VD, the output of the discharge circuit is at the power supply voltage VCC, so the discharge circuit has stopped oscillating, and an instantaneous power failure occurs at this point There is a problem that a time lag occurs from the oscillation until the discharge voltage VD is generated, and the backup is delayed.

  The present invention has been made to solve such a problem, and its purpose is to prevent a discharge current (backup current) to a charging circuit when a power failure occurs in a power supply device, and a discharge current necessary for a load. It is an object of the present invention to provide a backup power supply device that can supply only a large amount of power, and can ensure the maximum backup time of a load by minimizing the discharge current (backup current).

  In order to solve the above problems, a backup power supply device according to the present invention is connected in parallel to a power supply device that supplies a DC power supply to a load, and a charging circuit that charges a charging current from the power supply device, and electrical energy charged in the charging circuit A backup power supply that stores discharge energy based on the power supply circuit and supplies a backup current by supplying a discharge current to the load when an instantaneous power failure occurs in the power supply circuit. Discharge detection means for preventing discharge current from being charged in the charging circuit by blocking the discharge current through the free balance method and detecting the discharge state with low power loss based on the discharge current. Features.

  The backup power supply device according to the present invention prevents backflow from the power supply device to the discharge circuit, allows a discharge current (backup current) to flow in a free-balance manner, and detects a discharge state based on the discharge current with low power loss. Since the charging circuit is equipped with discharge detection means to prevent the discharge current from being charged, even if an instantaneous power failure occurs in the power supply, the power supply to the load is continuously supplied without interruption, and the charging circuit Only the discharge current necessary for the load can be supplied.

  In addition, the discharge detection means according to the present invention is a diode connected in the forward direction from the output of the discharge circuit, a comparator that compares the anode voltage and the cathode voltage of the diode, and the comparator determines that the anode voltage is greater than the cathode voltage Is provided with a charge stopping means for stopping the operation of the charging circuit.

  The discharge detection means according to the present invention includes a diode connected in the forward direction from the output of the discharge circuit, a comparator that compares the anode voltage and the cathode voltage of the diode, and the comparator that determines that the anode voltage is greater than the cathode voltage. Is equipped with a charging stop means for stopping the operation of the charging circuit, so that if an instantaneous power failure occurs in the power supply device and the cathode voltage of the diode becomes lower than the anode voltage, a discharge current (backup current) flows immediately. Since the backup of the load is started and the operation of the charging circuit is stopped, the backup time can be secured with the minimum discharge current.

  Furthermore, the diode according to the present invention is characterized in that it operates as a current blocking diode that blocks current flowing from the power supply device to the discharge circuit.

  Since the diode according to the present invention operates as a current blocking diode that blocks current flowing from the power supply device to the discharge circuit, it can be used for both reverse flow blocking and discharge current detection with a simple configuration.

  The backup power supply apparatus according to the present invention prevents backflow from the power supply apparatus to the discharge circuit, allows a discharge current to flow in a free balance manner, detects the discharge state based on the discharge current with low power loss, and discharges to the charging circuit. Discharge detection means to prevent the current from being charged, so that even if an instantaneous power failure occurs in the power supply, the power supply to the load is continuously supplied without interruption and the discharge current to the charging circuit Thus, only the discharge current required for the load can be supplied, and the discharge current can be minimized to ensure the maximum load backup time.

  The discharge detection means according to the present invention determines a diode connected in the forward direction from the output of the discharge circuit, a comparator that compares the anode voltage and the cathode voltage of the diode, and the comparator determines that the anode voltage is greater than the cathode voltage. In this case, since the charging circuit is provided with a charging stop means for stopping the operation of the charging circuit, when an instantaneous power failure occurs in the power supply device and the cathode voltage of the diode becomes lower than the anode voltage, the discharging current is immediately supplied to the load circuit. Since the backup is started and the operation of the charging circuit is stopped, the backup time can be secured with the minimum discharge current, and the efficient backup can be realized.

  Furthermore, since the diode according to the present invention operates as a current blocking diode that blocks current flowing from the power supply device to the discharge circuit, it can be used for both reverse flow blocking and discharge current detection with a simple configuration. It can be configured by a free balance method.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a basic block diagram of an embodiment of a backup power supply apparatus according to the present invention. In FIG. 1, the backup power supply device 1 includes a charging circuit 2, an electrolytic capacitor C, a discharging circuit 3, and a discharge detecting means 4.

  The backup power supply device 1 is connected in parallel with the power supply device 5, is charged with electric energy by being supplied with a charging current IC that is a part of the power supply current IP from the power supply device 5, and is discharged based on the charged electric energy. Accumulate energy.

  Further, the backup power supply 1 backs up by supplying a discharge current (backup current IB) to the load 6 when an instantaneous power failure occurs in the power supply circuit 5.

  The charging circuit 2 is composed of a booster circuit such as a DC / DC converter, takes in the charging current IC supplied from the power supply device 5, boosts the power supply voltage VCC, and supplies a high frequency pulse to the electrolytic capacitor C.

  The charging circuit 2 includes a switching element and a control circuit that captures or stops the capturing of the charging current IC supplied from the power supply device 5, and the charging current is based on the control signal SC supplied from the discharge detecting means 4. An operation of capturing IC or stopping capturing of charging current IC is executed.

  The electrolytic capacitor C smoothes high-frequency pulses supplied from the charging circuit 2 to accumulate (charge) the electric energy of the charging voltage VC, and supplies the accumulated electric energy to the discharging circuit 3. The electrical energy charged in the electrolytic capacitor C is used as backup discharge energy.

  The discharge circuit 3 includes a step-down circuit, a discharge control circuit, etc., and steps down the electric energy of the charging voltage VC stored (charged) in the electrolytic capacitor C to generate discharge energy of the discharging voltage VD.

  In addition, the discharge circuit 3 monitors the power supply voltage VCC appearing at the output terminal of the discharge detection means 4 and adjusts the discharge voltage VD to be lower than the power supply voltage VCC (VCC> VD), thereby generating an instantaneous power failure. Even if not, the discharge voltage VD is always generated to be in a standby state.

  The discharge detection means 4 prevents the backflow of current from the power supply device 5 to the discharge circuit 3, and when the power supply voltage VCC decreases during an instantaneous power failure, it naturally causes the backup current IB (discharge current) to flow in a free balance manner. The load required for the load 6 by detecting the discharge state with low power loss based on the backup current IB (discharge current) and preventing the backup circuit IB (discharge current) from being charged in the charging circuit 2 A backup current IB (= IL) equal to the current IL is supplied, and the drive of the load 6 is backed up. Note that the backup voltage VB is lower than the discharge voltage VD by the voltage drop of the discharge detection means 4.

  As described above, the backup power supply device 1 according to the present invention prevents the backflow from the power supply device 5 to the discharge circuit 3 and allows a discharge current (backup current IB) to flow in a free balance manner. Is detected with low power loss, and the discharge detection means 4 for preventing the charging circuit 2 from being charged with the discharge current (backup current IB) is provided. The power supply to the battery is continuously supplied without interruption, and the discharge current (backup current IB) to the charging circuit 2 is prevented and only the necessary discharge current IB (= load current IL) is supplied to the load 6. It is possible to minimize the discharge current (backup current IB) and to secure the maximum backup time of the load 6.

  FIG. 2 is a block diagram showing the principal part of one embodiment of the discharge detecting means according to the present invention. In FIG. 2, the discharge detection means 4 includes a diode D, a comparator 7 and a buffer 8. The buffer 8 constitutes a charging stop unit.

  The diode D is composed of a silicon diode, and has an anode connected to the output of the discharge circuit 3 and a cathode connected to the positive polarity (+ side) of the charging circuit 2. That is, the diode D is connected in the forward direction from the output of the discharge circuit 3.

  When an instantaneous power failure does not occur in the power supply device 5, the discharge voltage VD is applied to the anode side of the diode D, and the power supply voltage VCC is applied to the cathode side. Since the power supply voltage VCC is set to a voltage (VCC> VD) higher than the discharge voltage VD, the diode D operates as a reverse current blocking diode that blocks current from the power supply device 5 to the discharge circuit 3.

  When an instantaneous power failure occurs in the power supply device 5, the power supply voltage VCC decreases and becomes a backup voltage VB that is lower than the discharge voltage VD by the forward voltage VF (≈0.6V) of the diode D. Therefore, the backup current IB flows naturally due to the free balance.

  Since the forward voltage VF (≈0.6 V) of the diode D is less fluctuated due to the value of the flowing backup current IB, the backup voltage VB is kept substantially constant (VB = VD−VF).

  Since the power consumption of the diode D is the product of the forward voltage VF (≈0.6 V) and the backup current IB (= VF × IB), it can be suppressed to a relatively small power loss. For example, when the backup current IB flows through 2 A (ampere), the power loss of the diode D is 1.2 W (watts), and the power loss is 4 W (watts) when the resistor R shown in FIG. 6 is 1 Ω (ohms). It becomes smaller compared to.

  When the backup current IB is as small as 10 mA (milliampere), the potential difference between the diodes D is several hundred mV depending on the type of the diode, and the potential difference can be easily detected, but the resistor R shown in FIG. The potential difference between the resistors R when the resistance is 1 Ω (ohms) is as small as 10 mV (millivolt), and it is difficult to detect the potential difference, which may cause a false detection, and a highly accurate detector is required.

  The diode D may be a Schottky barrier diode and the forward voltage VF can be set lower than about 0.6V.

  FIG. 3 is a switching characteristic diagram from the power supply voltage (VCC) to the backup voltage (VB) according to the present invention. In FIG. 3, when an instantaneous power failure occurs at time t0, the power supply voltage VCC decreases, reaches the backup voltage VB (= discharge voltage VD−forward voltage VF) at time tb, maintains a constant value, and backs up with free balance. A current IB is supplied.

  The comparator 7 connects the anode side of the diode D to one input (for example, the + side), and connects the cathode side of the diode D to the other input (for example, the-side), whereby the discharge voltage VD on the anode side is connected. Is compared with the power supply voltage VCC on the cathode side or the backup voltage VB, and a comparison signal HO corresponding to the comparison result is supplied to the buffer 8 (charging stop means).

  When the power supply device 5 has no instantaneous power failure and is normal, the power supply voltage VCC is compared with the discharge voltage VD, and the power supply voltage VCC is set higher than the discharge voltage VD (VCC> VD). 7 outputs an L level determination signal HO.

  When an instantaneous power failure occurs in the power supply device 5, the discharge voltage VD is compared with the backup voltage VB, and the discharge voltage VD is higher than the backup voltage VB by the forward voltage VF (≈0.6V). The comparator 7 outputs a determination signal HO at H level.

  The buffer 8 (charging stop means) charges the determination signal HO supplied from the comparator 7 at the same level (H level or L level) and provides the charging circuit 2 with the control signal SC having an increased current capacity. The operation of the circuit 2 is stopped, and the backup current IB (corresponding to the charging current IC) flowing into the charging circuit 2 at the time of backup is stopped.

  FIG. 4 is an explanatory view of an embodiment of the charging circuit stop according to the present invention. In FIG. 4, the charging circuit 2 includes a transformer T, a primary side in which a MOSFET-Q1 and a resistor R1 are connected in series with the primary winding of the transformer T, and a secondary side of the secondary winding of the transformer T. A DC converter is configured.

  The path L of the charging current IC flowing in the charging circuit 2 is formed by P1 → primary winding → MOSFET-Q1 → resistor R1 → P2. By driving the gate P of the MOSFET-Q1 with a high-frequency pulse drive signal from a control circuit (not shown), a high frequency oscillates and a charging current IC flows through the path L.

  In order to stop the charging current IC of the charging circuit 2 by the control signal SC of the discharge detecting means 4 shown in FIG. 2, the path L is turned off by a switching element (not shown) or the gate P is driven off from the control circuit (not shown). Can be realized.

  The reason why the backup circuit IB (charging current IC) does not flow by stopping the charging circuit 2 is that the backup current IB is a load required for the load 6 in order to effectively use the electric energy accumulated at the time of backup. Only current IL flows (load current IL = backup current IB). Thereby, the backup time of the load 6 can be ensured to the maximum.

  As described above, the discharge detecting means 4 according to the present invention includes the diode D connected in the forward direction from the output of the discharge circuit 3, the comparator 7 that compares the anode voltage and the cathode voltage of the diode D, and the anode voltage by the comparator 7. Is determined to be greater than the cathode voltage, charging stop means 8 for stopping the operation of the charging circuit 2 is provided, so that an instantaneous power failure occurs in the power supply device 5 and the cathode voltage of the diode D (backup voltage VB). ) Becomes lower than the anode voltage (discharge voltage VD), the discharge current (backup current IB) is immediately supplied to start backup of the load 6 and the operation of the charging circuit 2 is stopped. Therefore, the minimum discharge current (backup current) The backup time can be secured by IB), and efficient backup can be realized.

  Further, the diode D according to the present invention operates as a current blocking diode that blocks the current flowing from the power supply device 5 to the discharge circuit 3, so that it can be used for both reverse flow blocking and detection of the discharge current (backup current IB) with a simple configuration. The backup power supply device 1 can be configured in a free balance method.

  The backup power supply device according to the present invention can supply only the backup current necessary for the load at the time of an instantaneous power failure of the power supply device, and can minimize the backup current IB to ensure the maximum backup time of the load. Therefore, it can be applied to a power source of a load that requires a long backup time.

Basic block configuration diagram of a backup power supply device according to an embodiment of the present invention Block diagram of essential parts of an embodiment of discharge detecting means according to the present invention Switching characteristic diagram from power supply voltage (VCC) to backup voltage (VB) according to the present invention Explanatory drawing of one Embodiment of the charging circuit stop which concerns on this invention Block diagram of an embodiment of a conventional backup power supply device Block diagram of another embodiment of a conventional backup power supply Switching characteristics from power supply voltage to backup voltage in Fig. 5 Switching characteristics from power supply voltage to backup voltage in Fig. 6

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Backup power supply device 2 Charging circuit 3 Discharge circuit 4 Discharge detection means 5 Power supply device 6 Load 7 Comparator 8 Buffer (charging stop means)
C Electrolytic capacitor D Diode Q1 MOSFET
T transformer R1 resistor VAC AC power supply VCC power supply voltage VC charge voltage VD discharge voltage VB backup voltage VF forward voltage (≒ 0.6V)
IP power supply current IL load current IC charge current IB backup current (discharge current)
SC control signal HO judgment signal

Claims (3)

A charging circuit that is connected in parallel with a power supply device that supplies a DC power supply to a load and charges a charging current from the power supply device; and a discharge circuit that accumulates discharge energy based on electrical energy charged in the charging circuit; A backup power supply that backs up by supplying a discharge current to the load when an instantaneous power failure occurs in the power supply circuit,
In addition to preventing backflow from the power supply device to the discharge circuit, a discharge current is allowed to flow in a free balance manner, and a discharge state is detected with a low power loss based on the discharge current so that the charging circuit is charged with the discharge current. A backup power supply device comprising a discharge detection means for preventing the discharge. When the discharge detection means determines that the diode connected in the forward direction from the output of the discharge circuit, a comparator for comparing the anode voltage and the cathode voltage of the diode, and the anode voltage is higher than the cathode voltage by the comparator The backup power supply device according to claim 1, further comprising: charge stopping means for stopping the operation of the charging circuit. 3. The backup power supply apparatus according to claim 2, wherein the diode operates as a current blocking diode that blocks a current flowing from the power supply apparatus to the discharge circuit.

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