JP2004328998A - Power supply unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply circuit by which accuracy of a power interruption detecting level is improved without being affected by load fluctuation and the power interruption is momentarily discriminated. <P>SOLUTION: The power supply circuit comprises a comparator COMP1 which compares a voltage V1 and a reference voltage Vref1 to output, a capacitor C2 charged by a constant-current source 3, a comparator COMP2 which compares voltages Vc2 across ends of the capacitor C2 and a reference voltage Verf to output, a switching device Q1 controlled by a power interruption signal S1, a switching element Q2 controlled by an output signal S2 of the comparator COMP1, a switching element Q3 which controls a charging current flowing toward a secondary battery BATT, and a switching element Q4 which controls the switching element Q3 via resistors R5, R6 and is controlled by the output signal S2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a power supply device, and more particularly, to a power supply device including a secondary battery that supplies power to a load when an AC power supply is shut off.

2. Description of the Related Art Conventionally, in a power supply device having a secondary battery and supplying power even when an AC power supply is cut off, that is, at a power failure, as one of means for detecting the presence or absence of an AC power supply, a DC voltage obtained by smoothing a DC output of a rectifier is used. Some are compared with a reference voltage, and an example of the circuit is shown in FIG. (First conventional example)
This circuit includes a charging device that obtains a pulsating voltage VDB by full-wave rectifying an AC power supply Vac via a current transformer T1 and a rectifier DB, and charges a secondary battery BATT via a charging circuit 1; And a power failure detection circuit for determining the presence or absence. The power failure detection circuit detects the presence or absence of an AC power supply by comparing the reference voltage Vref with a voltage Vc1 obtained by smoothing the pulsating voltage VDB via the diode D1 and the capacitor C1.

  However, the first conventional example has the following first problem. When the current transformer T1 is not an ideal transformer, if the output voltage of the current transformer T1 fluctuates due to a load fluctuation due to charging of the secondary battery BATT or the like, the voltage Vc1 also fluctuates as shown in FIG. Depending on the degree of the load fluctuation, there may be a case where the power failure detection is not performed correctly, that is, it is difficult to perform the power failure detection with high accuracy. Further, the capacitor C1 is a relatively large-capacity capacitor. After the AC power is cut off, the voltage Vc1 gradually decreases as shown in FIG. Would.

In order to solve the first problem, there is a method of detecting a peak value of a pulsating voltage VDB obtained by rectifying an AC power supply Vac instead of detecting a voltage Vc1 smoothed by a capacitor C1. 7 is shown in FIG. 7, and the operation waveform diagram is shown in FIG. (Second conventional example)
This circuit includes a comparator COMP1 for comparing and outputting a voltage V1 obtained by dividing a pulsating voltage VDB by resistors R1 to R3 and a reference voltage Vref1, a capacitor C2 charged by a constant current source 3, and both ends of the capacitor C2. A comparator COMP2 that compares and outputs a voltage (hereinafter, referred to as a voltage) Vc2 and a reference voltage Verf, and is controlled by an output signal (hereinafter, referred to as a power failure signal) S1 of the comparator COMP2 and is connected to both ends of a resistor R3. Switching element Q1, a switching element Q2 connected to both ends of a capacitor C2 via a resistor R4 and controlled by an output signal (hereinafter, referred to as an output signal) S2 of a comparator COMP1, and an output of a rectifier DB. A switching element Q for controlling a charging current flowing from the end to the secondary battery BATT via the diode D2 and the resistor R7. A switching element Q4 for controlling the switching element Q3 via the resistors R5 and R6; an output signal S2 via the NOT gate N1; a power failure signal S1; and a charging current detection signal S3 for the secondary battery BATT detected by the resistor R7. And a charging current control circuit 4 that receives the three signals to control the switching element Q4.

  Next, the operation will be briefly described with reference to FIG. The reference voltage Vref1 has two levels VrH1 and VrL1 (VrH1> VrL1) by being controlled by the output signal S2, and the reference voltage Vref2 has two levels VrH2 and VrL2 (VrH2> VrL2) by being controlled by the power failure signal S1. Take). As shown in FIG. 8A, when the voltage V1 is equal to or lower than VrL1, the comparator COMP1 outputs an L-level output signal S2 to turn off the switching element Q2, and as shown in FIG. Vc2 gradually rises, and the reference voltage Vref1 rises from VrL1 to VrH1 in response to the L-level output signal S2. When the pulsating voltage VDB rises and the voltage V1 becomes equal to or higher than VrH1, the comparator COMP1 outputs an H-level output signal S2 to turn on the switching element Q2, and as shown in FIG. The reference voltage Vref1 gradually decreases from VrH1 to VrL1 in response to the H-level output signal S2 while gradually decreasing via the resistor R4 and the switching element Q2. By setting the voltage V1 so as to exceed VrH1 during normal operation, the voltage Vc2 is not charged to a certain value or more. By setting the voltage Vc2 at this time to be lower than VrH2, The comparator COMP2 outputs the L-level power failure signal S1.

  When the L-level output signal S2 and the L-level power failure signal S1 are input to the charging current control circuit 4, the charging current control circuit 4 turns on the switching element Q4 to turn on the switching element Q3. A charging current IB of the secondary battery BATT having a constant current as shown in d) is obtained. Here, the phase of the charging current IB is controlled by switching of the switching element Q3, that is, the switching of the switching element Q4, and constant current charging can be performed by detecting the charging current IB with the resistor R7.

  When the AC power supply Vac is cut off, that is, at the time of a power failure, the voltage V1 does not exceed VrH1 as shown in FIG. 8A, so that the comparator COMP1 keeps outputting the L level output signal S2 and turns off the switching element Q2. However, the voltage Vc2 continues to rise as shown in FIG. When the voltage Vc2 exceeds VrH2, as shown in FIG. 8C, the comparator COMP1 outputs an H-level power failure signal S1, which can determine a power failure. That is, the power failure is determined when the voltage V1 does not exceed VrH1 and the voltage Vc2 reaches VrH2.

In the present circuit, if control is performed so as to maintain the phase angle of the charging current IB at 90 degrees or less, a load fluctuation occurs in the phase of 0 to 90 degrees depending on whether the secondary battery BATT is charged, and the pulsating voltage VDB Is changed, that is, as the secondary battery BATT is charged, the value of the voltage V1 is reduced as shown in FIG. 8 (a). Since the value of the voltage VDB becomes substantially constant, that is, since the secondary battery BATT is not charged, the value of the voltage V1 becomes substantially constant as shown in FIG. 8A, and it is possible to always determine the power failure under the same condition. The accuracy of the power failure detection level can be improved.
JP-A-7-31070

  However, the second conventional example has the following second problem.

  In the circuit shown in FIG. 7, since the charging phase is 90 degrees to 180 degrees, when the pulsating voltage VDB is a high voltage, the switching element Q4 is turned off to stop charging. Due to the load fluctuation, the current flowing through the current transformer T1 sharply decreases to generate a back electromotive force, and as shown in FIG. 8A, a surge occurs in the voltage V1, that is, the pulsating voltage VDB. This surge can be absorbed by connecting a capacitor C3 for absorbing surge to the positive input terminal of the comparator COMP1, but the waveform of the pulsating voltage VDB will be distorted unless an appropriate capacitor C3 is selected. However, since it becomes difficult to secure the accuracy of the power failure detection level, the waveform of the pulsating voltage VDB changes due to a load change due to the turning on and off of the switching element Q4, that is, the waveform of the voltage V1 changes. As a result, the accuracy of the power failure detection level deteriorates.

  The present invention has been made in view of all of the above problems, and its object is to improve the accuracy of a power failure detection level without being affected by load fluctuations, and to enable instantaneous power failure determination. It is to provide a power supply circuit.

  In order to solve the above problems, according to the first aspect of the present invention, a secondary battery that is charged when an AC power supply is normal and supplies power to a load when the AC power supply is cut off, In a power supply device comprising: a power failure detection circuit that detects interruption; and a charging circuit that charges the secondary battery in each cycle of a pulsating output that rectifies the AC power, wherein the power failure detection circuit includes the pulsating voltage. After detecting that the voltage exceeds a predetermined voltage in the process of rising from zero volt, the charging of the secondary battery is started, and the charging circuit limits the charging current of the secondary battery. At the same time, when the charging current value reaches a predetermined value, a quasi-constant current charging for stopping charging of the secondary battery is performed.

  According to the invention described in claim 2, a secondary battery that is charged at the time of normal operation of the AC power supply and supplies power to the load when the AC power supply is cut off, and a power failure detection circuit that detects the cut off of the AC power supply, A charging circuit for charging the secondary battery in each cycle of pulsating output in which the AC power is rectified, wherein the power failure detection circuit causes the pulsating voltage to rise from zero volts. After detecting that the predetermined voltage has been exceeded, the charging of the secondary battery is started, and the charging circuit detects a charging current value of the secondary battery, and the charging current value reaches a predetermined value. It is characterized by performing constant-current charging in which charging of the secondary battery is stopped at the time of reaching the current.

  According to the first or second aspect of the present invention, a power supply capable of improving the accuracy of a power failure detection level without being affected by a load fluctuation, and of being able to instantaneously determine a power failure and being downsized. Circuit can be provided.

(Embodiment 1)
FIG. 1 is a circuit diagram of the first embodiment according to the present invention, and FIG. 2 is an operation waveform diagram thereof.

  The difference from the second conventional example shown in FIG. 7 is that the charging current control circuit 4 is omitted and the switching element Q4 is controlled only by the output signal S2, so that the quasi-constant current type charging circuit and the power failure detection circuit can be separated. This is a combined configuration, and the same components as those of the second conventional example are denoted by the same reference numerals, and description thereof is omitted. That is, in the second conventional example, the pulsating voltage VDB is detected after the charging of the secondary battery BATT is stopped, but in the present embodiment, the presence or absence of the AC power supply Vac is determined by detecting the pulsating voltage VDB. It has a configuration for charging the secondary battery BATT later.

  Next, the operation will be briefly described with reference to FIG. While the pulsating voltage VDB is increasing from zero volts, the comparator COMP1 outputs the output signal S2 at the L level to turn off the switching element Q4 and stop charging the secondary battery BATT. The power failure detection is determined based on whether the voltage V1 reaches VrH1. When the voltage V1 has reached VrH1, it is determined that "AC power is present", and the comparator COMP1 outputs an H-level output signal S2, turns on the switching element Q2, and discharges the charge of the capacitor C2. At the same time, the switching element Q4 is turned on to charge the secondary battery BATT, and a charging current IB flows as shown in FIG. On the other hand, when the voltage V1 has not reached VrH1, the comparator COMP1 outputs the L-level output signal S2 and turns off the switching element Q2 to charge the capacitor C2. Then, the voltage Vc2 gradually increases, and when the voltage Vc2 reaches VrH2, it is determined that a "power failure" has occurred.

  Further, when the pulsating voltage VDB, that is, the voltage V1 decreases past the peak and reaches VrL1, the switching element Q4 is turned off by the L-level output signal S2 to stop charging the secondary battery BATT, and at the same time, The capacitor C2 is charged as described above. The value of the charging current IB can be arbitrarily set by changing the values of the resistor R7 and the reference voltage VrL1.

  When it is determined that “AC power is present” and the charging of the secondary battery BATT is started, the pulsating voltage decreases due to a change in the load of the current transformer T1 when charging the secondary battery BATT. As shown, the voltage V1 decreases, but since the power failure detection has already been performed before charging the secondary battery BATT, the accuracy of the power failure detection does not deteriorate due to the load fluctuation of the current transformer T1. Further, since the presence or absence of the AC power supply Vac is determined when the charging of the secondary battery BATT is stopped, the power failure can be reliably detected regardless of the presence or absence of the charging current IB to the secondary battery BATT. It is possible to improve the level of accuracy. Further, as described above, when the charging of the secondary battery BATT is stopped, a surge due to the back electromotive force occurs. At this time, the presence or absence of the AC power supply Vac is not determined, so that the accuracy level of the power failure detection is not affected. Has no effect. Even if such a surge voltage exceeds VrH1, only the charging of the capacitor C2 is reset by the H-level output signal S2, and does not affect the accuracy level of the power failure detection. Therefore, the capacity of the capacitor C3 is small enough to remove noise.

  Furthermore, in the second conventional example, since the peak voltage at the phase of the pulsating voltage VDB of 90 to 180 degrees is detected, the point at which the voltage Vc2 reaches VrH2 is at the point where the phase of the pulsating voltage VDB is 90 to 180 degrees. It was necessary to set it after the temperature and after the pulsating voltage VDB rose. However, in the present embodiment, since the peak voltage is detected at the rising portion of the pulsating voltage VDB, the detection point can be set at a phase of the pulsating voltage VDB of 0 to 90 degrees, and the time T required for power failure detection is reduced. It is possible to do.

(Embodiment 2)
FIG. 3 is a circuit diagram of the second embodiment according to the present invention, and FIG. 4 is an operation waveform diagram thereof.

  The difference from the second conventional example shown in FIG. 7 is that the NOT gate N1 is omitted, so that the charging circuit of the constant current charging system and the power failure detection circuit are combined. The same components as in the example are denoted by the same reference numerals, and description thereof will be omitted.

  Next, the operation will be briefly described with reference to FIG. When the voltage V1 reaches VrH1, the switching element Q4 is turned on by the charging current control circuit 4, and charging of the secondary battery BATT is started as shown in FIG. 4B. Since a voltage is generated in the resistor R7 by the charging current IB, this voltage is detected, and when the charging current IB reaches a predetermined value, the switching element Q4 is turned off by the charging current control circuit 4 to charge the secondary battery BATT. Stop. After the charging is stopped, when the voltage V1 reaches VrL1, the switching element Q2 is turned off, and charging of the power failure detection capacitor C2 is started. VrL1 is set to a value that is sufficiently low so that the voltage V1 does not fall below VrL1 when charging the secondary battery BATT, and that the voltage V1 falls below VrL1 near the valley of the pulsating voltage VDB. At the time of a power failure, charging of the secondary battery BATT is not performed. That is, when the power failure signal S1 is at the H level, the switching element Q4 is turned off.

  With this configuration, it is possible to improve the level of accuracy of the power failure detection, shorten the time T required for the power failure detection, and perform the secondary operation at the time when the pulsating voltage VDB is in a high phase. In order to start and stop charging of the battery BATT, that is, to shorten the phase width of the charging current IB as shown in FIG. 4B, the secondary battery BATT can be charged efficiently. If the phase width of the charging current IB is increased to a level substantially equal to the phase width of the charging current IB described in the first embodiment, the first embodiment can be performed even if the output voltage of the current transformer T1 is lowered. Since the charging current IB as shown in the embodiment can be obtained, it is possible to reduce the size of components. In the first embodiment as well, by setting VrL1 to a higher value, it is possible to reduce the size of the power transformer.

FIG. 2 is a circuit diagram showing a first embodiment according to the present invention. FIG. 4 shows an operation waveform diagram according to the embodiment. FIG. 4 is a circuit diagram showing a second embodiment according to the present invention. FIG. 4 shows an operation waveform diagram according to the embodiment. FIG. 2 is a circuit diagram showing a first conventional example according to the present invention. FIG. 4 shows an operation waveform diagram according to the conventional example. FIG. 4 is a circuit diagram showing a second conventional example according to the present invention. FIG. 4 shows an operation waveform diagram according to the conventional example.

Explanation of reference numerals

BATT rechargeable battery Vac AC power supply

Claims (2)

A secondary battery that is charged during normal operation of the AC power supply and supplies power to the load when the AC power supply is cut off, a power failure detection circuit that detects the cut off of the AC power supply, and a pulsating output of the AC power supply that is rectified. And a charging circuit for charging the secondary battery for each cycle, wherein the power failure detection circuit detects that the pulsating voltage has exceeded a predetermined voltage in a process of rising from zero volts. After the detection, the charging of the secondary battery is started, and the charging circuit limits the charging current of the secondary battery and charges the secondary battery when the charging current value reaches a predetermined value. Characterized in that it performs quasi-constant current charging for stopping the power supply. A secondary battery that is charged during normal operation of the AC power supply and supplies power to the load when the AC power supply is cut off, a power failure detection circuit that detects the cut off of the AC power supply, and a pulsating output of the AC power supply that is rectified. And a charging circuit for charging the secondary battery for each cycle, wherein the power failure detection circuit detects that the pulsating voltage has exceeded a predetermined voltage in a process of rising from zero volts. After the detection, the charging of the secondary battery is started, and the charging circuit detects a charging current value of the secondary battery, and charges the secondary battery when the charging current value reaches a predetermined value. A power supply device for performing constant current charging to stop the power supply.

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