JP3862307B2 - Power supply - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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.
[0002]
[Prior art]
Conventionally, in a power supply device that has a secondary battery and supplies power even when the AC power supply is cut off, that is, when a power failure occurs, a DC voltage obtained by smoothing the DC output of the rectifier is used as one of means for detecting the presence or absence of the AC power supply. There is a comparison with a reference voltage, and an example of the circuit is shown in FIG. (First conventional example)
In this circuit, the AC power supply Vac is full-wave rectified via the current transformer T1 and the rectifier DB to obtain the pulsating voltage VDB, and the charging device 1 charges the secondary battery BATT, and the AC power supply Vac It is comprised from the power failure detection circuit which judges the presence or absence. The power failure detection circuit detects the presence or absence of an AC power source by comparing the voltage Vc1 obtained by smoothing the pulsating voltage VDB through the diode D1 and the capacitor C1 with the reference voltage Vref by the comparator COMPo.
[0003]
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 load fluctuation due to charging of the secondary battery BATT, etc., the voltage Vc1 also fluctuates as shown in FIG. Depending on the degree of load fluctuation, there is a possibility that the power failure detection is not correctly performed, that is, it is difficult to detect the power failure with high accuracy. The capacitor C1 is a relatively large capacitor, and after the AC power supply is cut off, the voltage Vc1 gradually decreases as shown in FIG. 6 (a). End up.
[0004]
In order to solve the first problem, there is a circuit that detects the peak value of the pulsating voltage VDB obtained by rectifying the AC power supply Vac instead of detecting the voltage Vc1 smoothed by the capacitor C1. FIG. 7 shows an operation waveform diagram thereof. (Second conventional example)
This circuit includes a comparator COMP1 that compares and outputs a voltage V1 obtained by dividing the pulsating voltage VDB with resistors R1 to R3 and a reference voltage Vref1, a capacitor C2 that is charged by the constant current source 3, and both ends of the capacitor C2. A comparator COMP2 that compares and outputs the voltage (hereinafter referred to as voltage) Vc2 and the reference voltage Verf, and an output signal (hereinafter referred to as a power failure signal) S1 of the comparator COMP2, and is connected to both ends of the resistor R3. Switching element Q1, the switching element Q2 connected to both ends of the capacitor C2 via the resistor R4 and controlled by the output signal (hereinafter referred to as an output signal) S2 of the comparator COMP1, and the output of the rectifier DB Switching element Q for controlling the charging current flowing from the end to secondary battery BATT via diode D2 and resistor R7 A switching element Q4 for controlling the switching element Q3 via the resistors R5 and R6, an output signal S2, a power failure signal S1 via the NOT gate N1, and a charging current detection signal S3 for the secondary battery BATT detected by the resistor R7. And a charging current control circuit 4 for controlling the switching element Q4 in response to the three signals.
[0005]
Next, the operation will be briefly described with reference to FIG.
The reference voltage Vref1 takes two levels VrH1, VrL1 (VrH1> VrL1) by being controlled by the output signal S2, and the reference voltage Vref2 has two levels VrH2, VrL2 (VrH2> VrL2 by being controlled by the power failure signal S1. ). As shown in FIG. 8A, if 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. 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. As shown in FIG. 8B, the voltage Vc2 is While gradually decreasing through the resistor R4 and the switching element Q2, the reference voltage Vref1 decreases from VrH1 to VrL1 in response to the H level output signal S2. By setting the voltage V1 to exceed VrH1 at normal time, the voltage Vc2 is not charged above a certain value, and by setting the voltage Vc2 at this time to be smaller than VrH2, it is normal The comparator COMP2 at the time outputs an L level power failure signal S1.
[0006]
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 Q3 by turning on the switching element Q4. A charging current IB of the secondary battery BATT having a constant current as shown in d) is obtained. The charging current IB is phase-controlled by switching of the switching element Q3, that is, the switching element Q4, and constant current charging can be performed by detecting the charging current IB with the resistor R7.
[0007]
When the AC power supply Vac is cut off, that is, when a power failure occurs, the voltage V1 does not exceed VrH1 as shown in FIG. 8A. Therefore, the comparator COMP1 continues to output the L level output signal S2 and turns off the switching element Q2. As shown in FIG. 8B, the voltage Vc2 continues to rise. When the voltage Vc2 exceeds VrH2, as shown in FIG. 8 (c), the comparator COMP1 outputs an H level power failure signal S1, so that a power failure can be determined. That is, a power failure is determined when the voltage V1 does not exceed VrH1 and the voltage Vc2 reaches VrH2.
[0008]
In this circuit, if the control is performed so that the phase angle of the charging current IB is maintained at 90 degrees or less, the load fluctuation occurs depending on whether or not the secondary battery BATT is charged at the phase of 0 to 90 degrees, and the pulsating voltage VDB. Although the value of the voltage V1 decreases as shown in FIG. 8A by charging the secondary battery BATT, there is no load fluctuation at the phase of 90 to 180 degrees. Since the value of the voltage VDB is substantially constant, that is, the secondary battery BATT is not charged, the value of the voltage V1 is substantially constant as shown in FIG. 8A, and it is always possible to determine the power failure under the same conditions. The accuracy of the power failure detection level can be improved.
[0009]
[Problems to be solved by the invention]
However, the second conventional example has the following second problem.
[0010]
In the circuit shown in FIG. 7, since the phase for charging is 0 to 90 degrees, when the pulsating voltage VDB is high, the switching element Q4 is turned off to stop charging, and the load due to the switching element Q4 being turned off Due to the fluctuation, the current flowing through the current transformer T1 rapidly decreases and a back electromotive force is generated, 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 the surge absorbing capacitor C3 to the positive input terminal of the comparator COMP1, but if the capacitor C3 having an appropriate capacity is not selected, the waveform of the pulsating voltage VDB is distorted. Since it becomes difficult to ensure the accuracy of the power failure detection level, the waveform of the pulsating voltage VDB changes due to the load fluctuation due to the on / off of the switching element Q4, that is, the waveform of the voltage V1 changes. Therefore, the accuracy of the power failure detection level is deteriorated.
[0011]
The present invention has been made in view of all the above-mentioned problems. The object of the present invention is to improve the accuracy of the power failure detection level without being affected by the load fluctuation and to determine the power failure instantly. A power supply circuit is provided.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, according to the invention described in claim 1, a secondary battery that is charged during normal operation of the AC power source and supplies power to a load when the AC power source is shut off, and the AC power source a power failure detection circuit for detecting a cutoff, in the power supply device and a charging circuit configured to charge the secondary battery with the AC power supply and a current transformer rectifier for each cycle of the pulse current output obtained by rectifying through the charging The circuit starts charging the secondary battery after detecting that the pulsating voltage has exceeded a first predetermined voltage in the process of rising from zero volts, and the pulsating voltage is rather smaller than the predetermined voltage, and stops the charging of the secondary battery when the pulsating voltage passed the peak of the ripple voltage has reached the second predetermined voltage in the process of lowered while, the power failure detection circuit is the pulsating voltage is first When the from the time when reaching the predetermined voltage has elapsed a predetermined time, wherein the pulsating voltage is judged to power failure if not exceeds the first predetermined voltage.
[0018]
Embodiment
(Embodiment 1)
A circuit diagram of a first embodiment according to the present invention is shown in FIG. 1, and an operation waveform diagram thereof is shown in FIG.
[0019]
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 a quasi-constant current charging circuit and a power failure detection circuit are provided. This is a combined configuration, and the same components as those of the second conventional example are denoted by the same reference numerals, and the 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. The secondary battery BATT is charged later.
[0020]
Next, the operation will be briefly described with reference to FIG. In the process in which the pulsating voltage VDB rises from zero volts, the comparator COMP1 outputs an L level output signal S2, turns off the switching element Q4, and stops the charging of the secondary battery BATT . When the voltage V1 reaches 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 as shown in FIG. 2 (d) flows. On the other hand, when the voltage V1 does not reach VrH1, the comparator COMP1 outputs the L level output signal S2 and turns off the switching element Q2, thereby charging the capacitor C2. Therefore, as shown in FIG. At this time, the voltage Vc2 gradually rises, and when the voltage Vc2 reaches VrH2, it is determined that a power failure has occurred.
[0021]
In addition, when the pulsating voltage VDB, that is, the voltage V1 decreases after reaching a peak and reaches VrL1, the switching element Q4 is turned off by the L level output signal S2 to stop the charging of the secondary battery BATT, and at the same time, Similarly, the capacitor C2 is charged. The value of the charging current IB can be arbitrarily set by changing the values of the resistor R7 and the reference voltage VrL1.
[0022]
When it is determined that “AC power is present” and charging of the secondary battery BATT is started, the load of the current transformer T1 fluctuates when the secondary battery BATT is charged, so that the pulsating voltage decreases, that is, as shown in FIG. As shown, the voltage V1 decreases, but the power failure detection has already been performed before the secondary battery BATT is charged. Therefore, the accuracy of the power failure detection due to the load variation of the current transformer T1 does not occur. In addition, 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 detection can be reliably performed regardless of the presence or absence of the charging current IB to the secondary battery BATT. It becomes possible to improve the level of accuracy. Furthermore, as described above, a surge due to the counter electromotive force occurs when charging to the secondary battery BATT is stopped, but at this point in time, the presence or absence of the AC power supply Vac is not judged, so the level of power failure detection accuracy is affected. Does not reach. Even if such a surge voltage exceeds VrH1, charging of the capacitor C2 is only reset by the H level output signal S2, and the level of power failure detection accuracy is not affected. For this reason, it is sufficient that the capacitance of the capacitor C3 is small enough to remove noise.
[0023]
Furthermore, in the second conventional example, since the peak voltage when the phase of the pulsating voltage VDB is 0 degree to 90 degrees is detected, the point where the voltage Vc2 reaches VrH2 is the phase of the pulsating voltage VDB being 0 degree to 90 degrees. It was necessary to set after the lapse of time and after the pulsating voltage VDB rose. However, in this embodiment, since the peak voltage is detected at the rising portion of the pulsating voltage VDB, the phase of the pulsating voltage VDB can be set to 0 degree to 90 degrees , and the time T required for detecting a power failure is shortened. Is possible.
[0024]
(Embodiment 2)
A circuit diagram of a second embodiment according to the present invention is shown in FIG. 3, and an operation waveform diagram thereof is shown in FIG.
[0025]
7 differs from the second conventional example shown in FIG. 7 in that the NOT gate N1 is omitted, and a constant current charging type charging circuit and a power failure detection circuit are combined. The same components as those in the example are denoted by the same reference numerals and the description thereof is omitted.
[0026]
Next, the operation will be briefly described with reference to FIG.
When the voltage V1 reaches VrH1, the charging current control circuit 4 turns on the switching element Q4, and charging of the secondary battery BATT is started as shown in FIG. 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 the secondary battery BATT is charged, and that the voltage V1 falls below VrL1 near the valley of the pulsating voltage VDB. Further, the secondary battery BATT is not charged during a power failure, that is, the switching element Q4 is turned off when the power failure signal S1 is at the H level.
[0027]
By configuring in this way, it is possible to improve the level of accuracy of power failure detection, reduce the time T required for power failure detection, and at the same time secondary when the pulsating voltage VDB is at a high phase. In order to start and stop the charging of the battery BATT, that is, the phase width of the charging current IB is short as shown in FIG. 4B, the secondary battery BATT can be charged efficiently. Further, 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 shown in the first embodiment, the first embodiment can be achieved 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 the components. In the first embodiment as well, it is possible to reduce the size of the power transformer by setting VrL1 higher.
[0028]
【The invention's effect】
According to the first aspect of the present invention, it is possible to provide a power supply circuit that can improve the accuracy of the power failure detection level without being affected by the load fluctuation, can determine the power failure instantaneously, and can be downsized. .
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a first embodiment according to the present invention.
FIG. 2 shows an operation waveform diagram according to the embodiment.
FIG. 3 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. 5 is a circuit diagram showing a first conventional example according to the present invention.
FIG. 6 shows an operation waveform diagram according to the conventional example.
FIG. 7 is a circuit diagram showing a second conventional example according to the present invention.
FIG. 8 shows an operation waveform diagram according to the conventional example.
[Explanation of symbols]
BATT Secondary battery Vac AC power supply

Claims (1)

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 shut off, a power failure detection circuit that detects the interruption of the AC power supply, and the AC power supply via a current transformer and a rectifier And a charging circuit that charges the secondary battery every cycle of rectified pulsating output, wherein the charging circuit is a first in the process in which the pulsating voltage rises from zero volts. after it is detected that exceeds a predetermined voltage, starts charging of the secondary battery, the pulsating voltage is rather smaller than the first predetermined voltage, and passes a peak of the ripple voltage When the second predetermined voltage in the process of decreasing the pulsating voltage is reached, the charging of the secondary battery is stopped, and the power failure detection circuit detects that the pulsating voltage is the second predetermined voltage. when the from the time it reaches after the elapse of a predetermined time Power supply, characterized in that it is determined that a power failure when the pulsating voltage has not exceeded the first predetermined voltage.

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