JPH05176479A - Battery separation control circuit for preventing overdischarge of battery - Google Patents

Abstract

PURPOSE:To quicken the operation of a comparator for providing hysteresis and prevent the simultaneous operation of both comparators by a method wherein the operating voltages of the comparators are considered in a battery separation control circuit for separating the battery from a power supplying line when the voltage of a backup battery provided in the power supplying line has become lower than a predetermined value. CONSTITUTION:The entitled circuit is provided with a hysteresis providing circuit 1 and a second comparator 2. When a battery voltage has become lower than a predetermined value, the second comparator is brought into operating condition after the first comparator 1-1 of the hysteresis providing circuit 1 has been operated while the value of a resistor R1 is set so as to increase a detecting voltage for the second comparator 2 by a required value and a first reference voltage as wall as a second reference voltage are set at different values so that the first comparator 1-1 and the second comparator 2 are brought into operating conditions together.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery disconnection control circuit which outputs a control signal for disconnecting a backup battery attached to a power supply line from a power supply line when the voltage of the backup battery is below a predetermined value. For example, as a power source for a private branch exchange (PBX), there is one as shown in FIG. That is, the rectifier circuit 1 is connected to the AC power supply 100.
01 is further connected, a power conversion transformer 103 with a switching control element 102 is further connected, and a smoothing circuit 104 is connected to the secondary side of the power conversion transformer 103.
The output of the smoothing circuit 104 is supplied to the private branch exchange. The output of the smoothing circuit 104 is the power conversion transformer 10 with another switching control element 102 '.
2'of the power conversion transformer 103 'supplied to the 3'
Smoothing circuits 104 'and 104 "are connected to the secondary side and the tertiary side, and the outputs of the smoothing circuits 104' and 104" are also supplied to the private branch exchange.

Further, a battery 105 is connected to the output side of the smoothing circuit 104.
When the power source is normal, it is in a charging state, and when the power source is out of power, it is in a discharging state and functions as a standby power source. Also, this battery 105
When the voltage becomes equal to or lower than a predetermined voltage value, the battery disconnection control circuit 106 for preventing battery over-discharging disconnects the power supply line.

[0003]

2. Description of the Related Art FIGS. 6 and 7 are electrical circuit diagrams showing a main part of a conventional battery disconnection control battery disconnection control circuit for battery overdischarge prevention. , A battery voltage detecting comparator 22, a switch circuit 23 and the like.

Here, the hysteresis applying circuit 21 is a circuit for preventing a chattering phenomenon from occurring when the battery is disconnected from the power supply line. Therefore, the hysteresis applying circuit 21 has a reference voltage and a battery voltage. And a resistor R1 'connected to the output side of the comparator 21-1. That is, the comparator 21-1 in this case is DC
It is used together with the resistor R1 'as an IC for the purpose of providing a hysteresis in order to suppress the influence of the change in the battery voltage due to the ON / OFF of the operating power supply of the DC converter.

The battery voltage detecting comparator 22 is
It is for detecting the battery voltage for comparing the reference voltage with the battery voltage affected by the hysteresis providing circuit 21. That is, the comparator 22 compares the detected voltage proportional to the battery voltage with the reference voltage, and the output turns on and off the switch circuit 23 to send the power-down signal [POWER DOWN (PD)] signal to the outside. Of.

The reference voltages of the hysteresis applying circuit 21 and the battery voltage detecting comparator 22 are resistors R
2, Zener diode ZD, diode D1 and the like. That is, as the reference voltage in this case, the voltage of the Zener diode ZD is Vdz, and the forward drop voltage of the diodes D1 to D3 is Vf.
And the power supply voltage is Vo, Vo- (Vdz-V
f).

The switch circuit 23 connects and disconnects the battery by receiving a signal from the comparator 22 and turning it on and off, and includes a switching transistor Tr1 and a photocoupler PC including a light emitting element PC1 and a light receiving element (not shown). It is configured with.
In the figure, R3 to R9 are resistors (however, the resistor R9 is a variable resistor), D2 and D3 are diodes, and C1 to C3 are capacitors.

With such a configuration, when the voltage of the backup battery attached to the power supply line becomes equal to or lower than a predetermined value, the battery voltage detection comparator 22 cooperates with the hysteresis adding circuit 21 to detect it and switch it. Circuit 23 provides a control signal to disconnect the battery from the power supply line. That is, when the commercial input power fails, the battery voltage shifts to the battery input, the operating battery voltage drops, and when the discharge end voltage is reached, the power supply sends a power-down signal (PD) signal to disconnect the battery, Is disconnected from the power supply line to prevent over discharge of the battery.

By the way, FIG. 12 is a diagram for explaining the input relationship of the comparator 22. Considering the input relationship of the comparator 22 from this figure, the reference potential is the output E in this circuit. I understand. Further, the reference potential for comparison in the comparator is the −24 volt line of the battery to which the ground line of the IC is connected, and this point will be described below with attention.

First, as shown in FIG. 12, the reference voltage of the output monitor circuit is the sum (Vdz + V) of the voltage of the Zener diode DZ of FIG. 6 and FIG. 7 and the forward drop of the diode D1.
f), which is, for example, a median value of about 5.9.
It becomes a bolt. Since the voltage applied to the comparator as an input voltage is considered to be 0 volt with the -24 volt line (0 volt line of the battery) as the reference, the IC input of the reference voltage is [Vo- (Vdz + V
f)]. Then, as for the voltage of the battery and the output of −24 V, the line on the + side is fixed to E (ground), so that the line on the − side changes.

In other words, the reference voltage of the monitoring circuit is fixed, but the input voltage to the IC as the reference voltage fluctuates due to changes in the battery voltage. Further, the detection voltage corresponding to the output is divided by the voltage dividing resistor to obtain ((Vo−Vf) × R9) / (R9 + R8 + R
Represented by 7). The negative line also fluctuates like the standard.

However, when the hysteresis applying circuit 21 operates and the resistor R1 'is connected in parallel with the resistor R9, the combined resistance value is RX = (R1' * R9) / (R1 '+ R9).
Therefore, this resistance value is used in place of the above R9. Then, as shown in FIG. 12, at the time of starting the circuit, the one in which the input corresponding to the detected voltage is higher than the reference voltage is started at the same level and the comparator 21- 1 is also inverted and the input to the comparator 22 on the detection side changes as shown by the arrow.

Next, during normal operation, the detection input is at a low level, and when the final discharge voltage is reached, the hysteresis applying circuit 21 connects the resistor R9 in parallel with the resistor R1 '. What has been done is resistance R1 '
Operates to force the sense input high as shown by the arrow. This prevents erroneous operations due to voltage fluctuations such as the operation of the DC-DC converter or the voltage drop when shifting to battery operation.

[0014]

In the process of performing the above operation, if the input relationship of the comparator 22 is reversed and the output is inverted, and the operation of the comparator 21-1 is also performed synchronously, the operation shift occurs. The problem of will disappear. In other words, in normal use in which the amount of change in voltage corresponding to the change in time is large (operation in which a large voltage value fluctuates in a short time), it is not necessary to consider the occurrence of abnormality. This is because, for example, even if the operations of a plurality of comparators are deviated, no problem will occur if the voltage changes during the time when the effects of the operation deviate from their outputs.

The operation of the comparison circuit has been briefly described above, but the reason why the operation shift occurs will be briefly described. In other words, the quad type IC used this time
Even if voltages of the same numerical value are applied to the inputs of the two comparators 21-1 and 22 inside, the operating point is deviated due to variations in the internal components of the IC, such as variations in the voltage to the transistors. It can be easily guessed that this will occur when the equivalent circuit of the comparator is considered. For this reason, when the battery is discharged (particularly, a battery having a large battery capacity can be clearly seen), if the voltage change is a slight decrease (change) in mV unit, the operation of the comparator 22 alone causes a deviation. Even if the output is inverted, the comparator 21-1
Therefore, the state in which the output of the comparator 21-1 is not inverted continues because the above operation cannot be performed. If the battery voltage fluctuates while this state continues, the output corresponding to the input of the comparator 22 also changes, so the PD signal also changes, and if the detection input changes with a certain amplitude, the output changes. Performs operations that appear to cause chattering.

This will be briefly described below with reference to FIGS. 8, 9 and 11. That is, when the operation of the comparators 22 and 21-1 is deviated (the operating voltage of the comparator 22 is higher) while the battery voltage is low, the output of the comparator 22 is inverted first, but the output of the comparator 22 is reversed. When the battery voltage rises due to the effect of the inversion of the above, the output of the comparator 22 is also inverted, and the voltage decreases conversely. As an output, the on / off operation is performed, and it looks like a chattering phenomenon. That is, as shown in FIGS. 8 and 11, the detection comparator 22 performs the chattering operation before the comparator 21-1 is inverted. The output of the comparator 22 for ideal detection operation when the battery is disconnected is as shown in FIG.

In this way, at the time of power failure of the commercial input power, the battery voltage is lowered during operation by shifting to battery input,
When the discharge end voltage is reached, the quad-type IC is used when the power supply sends out a PD signal and disconnects the battery.
Since the outputs of the comparators are not inverted at the same time because the comparators are out of operation, the hysteresis operation does not work and a slight change in the input affects the PD signal, which causes the PD signal to be repeatedly turned on and off so as to chatter. Of.

The present invention was devised in view of the above problems. By considering the operating voltage (reference voltage) of the comparators, the operation of the hysteresis giving comparators can be accelerated, and the operations of both comparators can be performed simultaneously. It is an object of the present invention to provide a battery disconnection control circuit for preventing battery over-discharge, which is designed to prevent such a situation.

[0019]

FIG. 1 is an electric circuit diagram for explaining the principle of the present invention. In the circuit shown in FIG. 1 as well, the voltage of the backup battery attached to the power supply line has a predetermined value. In the following, it relates to a battery disconnection control circuit that issues a control signal for disconnecting the battery from the power supply line. This battery disconnection prevention battery disconnection control circuit is, as shown in FIG. 1, a first reference voltage Vref1. And a battery voltage are compared with a first comparator 1-1 and a resistor R1 connected to the output side of the first comparator 1-1, and a second reference voltage Vref2 and a hysteresis adding circuit. The second comparator 2 for comparing with the battery voltage affected by 1.

The value of the resistor R1 is set so as to increase the detection voltage to the second comparator 2 by a required value, and the first reference voltage Vref1 and the second reference voltage Vre are set.
f2 is set to a different value. The reference voltages Vref1 and Vref2 of the hysteresis applying circuit 1 and the battery voltage detecting comparator 2 are the resistors R10 and R1.
1, R12, Zener diode ZD, diode D1
Etc., but in this case,
The resistors R11 to R12 are added to the conventional one, and the presence of the resistors R10 to R12 sets the reference voltages Vref1 and Vref2 to different values.

In the figure, R3, R7 to R9 are resistors and D
3 is a diode.

[0022]

In the battery disconnection control circuit for preventing battery over-discharge of the present invention described above, the value of the resistor R1 is set so as to increase the detection voltage to the second comparator 2 by a required value, and the first reference voltage Vref1 and Second reference voltage Vre
Since f2 is set to a different value, when the battery voltage becomes equal to or lower than a predetermined value, the first comparator 1-1 operates and then the second comparator 2 enters the operating state, and thereafter the first comparator 1 operates. -1 and the second comparator 2 are both in the operating state.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. 2 and 3 are electrical circuit diagrams showing a main part of a battery disconnection control circuit for preventing battery overdischarge according to one embodiment of the present invention. The battery disconnection control circuit for preventing battery overdischarge is a hysteresis applying circuit. 1, a battery voltage detection comparator 2, a switch circuit 3 and the like.

Here, the hysteresis applying circuit 1 is a circuit for preventing a chattering phenomenon from occurring when the battery is disconnected from the power supply line. Therefore, the hysteresis applying circuit 1 has the first reference voltage Vref1 and the reference voltage Vref1. It comprises a comparator (first comparator) 1-1 for comparing with the battery voltage, and a resistor R1 'connected to the output side of the comparator 1-1. That is, the comparator 1-1 in this case is also used together with the resistor R1 as an IC for the purpose of providing a hysteresis in order to suppress the influence of the change of the battery voltage due to the ON / OFF of the operating power supply of the DC-DC converter. The value of the resistor R1 is set so that the detection voltage to the comparator 2 is increased by a required value.

The battery voltage detection comparator (second comparator) 2 detects the battery voltage by comparing the second reference voltage Vref2 with the battery voltage affected by the hysteresis applying circuit 1. .. That is, the comparator 2 compares the detected voltage proportional to the battery voltage with the second reference voltage Vref2,
By turning on and off the switch circuit 23 with the output,
The power down signal (PD) signal is transmitted to the outside.

Here, the first reference voltage Vref1 and the second reference voltage Vref2 are set to different values. Then, the hysteresis applying circuit 1 and the reference voltages Vref1 and Vref of the battery voltage detecting comparator 2
2 is given by the resistors R10, R11, R12, the Zener diode ZD, the diode D1 and the like. In this case, the resistors R11 to R12 are added to the conventional one, and the resistors R10 to R10 are added. Due to the presence of R12, both reference voltages Vref1 and Vref2 are set to different values.

In this case, the first reference voltage Vref1 is equal to the second reference voltage Vref1.
It is smaller than the reference voltage Vref2, for example, Vref1 =-
6 volts, set Vref2 = -5 volts. When set in this way, the hysteresis comparator 1-
1 has an inversion voltage of -21.6 volts, and the voltage detection comparator 2 has an inversion voltage of -21.4 volts.
become that way. That is, since the comparators 1-1 and 2 are connected to the same place, when the comparator 1-1 is inverted, the comparator 2 is also inverted with a difference of 0.3 volt. The state at this time is schematically shown in FIG.

The switch circuit 3 connects and disconnects the battery by receiving a signal from the comparator 2 and turning it on and off.
r1 and a photocoupler PC including a light emitting element PC1 and a light receiving element (not shown). In the figure, R3 to R9 are resistors (resistor R9 is a variable resistor),
D2 and D3 are diodes, and C1 to C3 are capacitors.

Here, the fact that the chattering phenomenon can be improved by using this circuit as compared with the conventional one will be described a little. First, as mentioned above, in the conventional case, 2
A problem occurred due to the operation of the individual comparators being misaligned, but as a countermeasure against this, this circuit is designed to correct the operation misalignment between the comparators, so the above problems are improved. Will be done. That is, the comparator 2 for comparison and detection and the comparator 1-1 for hysteresis need to be operated at the same time to eliminate the operation deviation. Therefore, as the operation, the output of the hysteresis giving circuit 1 is first when the battery is disconnected. When the operation of reversing the input signal is performed, the PD signal is transmitted at that time, as shown in FIG. 5, because the input voltage for detection is forcibly pulled high by the hysteresis.

In the hysteresis applying circuit 1,
Since the detection resistance value changes by several volts at the battery voltage, the output does not change even if the voltage changes slightly. Conversely speaking, it is sufficient to set the hysteresis width so that there is no influence of voltage fluctuation due to ON / OFF of the DC-DC converter. Therefore, if the value of the resistor R1 is set so that the detection voltage to the comparator 2 is increased by a required value, and the reference voltage is also divided by resistance to set both reference voltages to different values, a countermeasure for the conventional circuit can be obtained. It will be possible.

With such a configuration, when the voltage of the backup battery attached to the power supply line becomes equal to or lower than a predetermined value, the battery voltage detection comparator 2 cooperates with the hysteresis applying circuit 1 to detect this, and the comparator 1
The output of -1 becomes low, the output of the comparator 2 becomes high, the base of the switching transistor Tr1 becomes high, and the photocoupler PC is turned off, whereby the switch circuit 3 disconnects the battery from the power supply line. Issue a control signal for. That is, at the time of a power failure of the commercial input power, when the voltage shifts to the battery input and the operating battery voltage drops and reaches the discharge end voltage, the power source sends a power down signal [POWER DOWN (PD)] signal to disconnect the battery. As a result, the battery is disconnected from the power supply line. This prevents over-discharge of the battery.

At this time, the value of the resistor R1 is set so as to increase the detection voltage to the comparator 2 by a required value, and the first reference voltage Vref1 and the second reference voltage Vref are set.
Since 2 is set to a different value, when the battery voltage becomes equal to or lower than a predetermined value, the first comparator 1-1 operates and then the second comparator 2 enters the operating state, and thereafter the first comparator 1 operates. -1 and the second comparator 2 are both in the operating state. This can prevent the chattering phenomenon from occurring in the comparator 2.

When the battery voltage is normal, the output of the comparator 1-1 is high, and as a result, the output of the comparator 2 is also low, which causes the base of the switching transistor Tr1 to go low. And the photocoupler PC is in the ON state. As a result, the battery voltage is supplied to the power supply line without disconnecting the battery from the power supply line.

[0034]

As described in detail above, according to the battery disconnection control circuit for preventing battery over-discharge of the present invention, when the voltage of the backup battery attached to the power supply line becomes a predetermined value or less, In a battery disconnection control circuit that outputs a control signal for disconnecting from a power supply line, a hysteresis adding circuit including a first comparator that compares a first reference voltage with a battery voltage, and a resistor connected to an output side of the first comparator. , A second comparator for comparing the second reference voltage with the battery voltage affected by the hysteresis applying circuit,
Since the value of the resistance of the hysteresis providing circuit is set so as to increase the detection voltage to the second comparator by a required value, and the first reference voltage and the second reference voltage are set to different values, the battery voltage Is less than a predetermined value,
After the first comparator operates, the second comparator enters the operating state, and the first comparator and the second comparator both enter the operating state, whereby it is possible to reliably prevent the chattering phenomenon from occurring in the first comparator. There are advantages.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram for explaining the principle of the present invention.

FIG. 2 is an electric circuit diagram showing an embodiment of the present invention.

FIG. 3 is an electric circuit diagram showing an embodiment of the present invention.

FIG. 4 is a diagram for explaining the operation of one embodiment of the present invention.

FIG. 5 is a diagram illustrating the operation of the embodiment of the present invention.

FIG. 6 is an electric circuit diagram showing a conventional example.

FIG. 7 is an electric circuit diagram showing a conventional example.

FIG. 8 is a diagram illustrating an operation of a conventional example.

9 is an enlarged view showing an IX portion of FIG.

FIG. 10 is a diagram illustrating an operation of a conventional example.

FIG. 11 is a diagram for explaining the operation of the conventional example.

FIG. 12 is a diagram illustrating an input relationship of a voltage detection comparator.

FIG. 13 is a diagram for explaining an arrangement position of a battery disconnection control circuit for preventing battery overdischarge.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hysteresis providing circuit 1-1 1st comparator 2 2nd comparator 3 Switch circuit 21 Hysteresis providing circuit 21-1 1st comparator 22 2nd comparator 23 Switch circuit 100 AC power supply 101 Rectifier circuit 102, 102 'Switching control element 103, 103 ′ Power conversion transformer 104, 104 ′, 104 ″ Smoothing circuit 105 Battery 106 Battery overdischarge prevention battery disconnection control circuit C1 to C3 Capacitors D1 to D3 Diodes PC Photocoupler PC-1 Light emitting element R1 to R12 Resistance Tr1 Switching Transistor ZD Zener diode

Claims (1)

[Claims] 1. A battery disconnection control circuit that outputs a control signal for disconnecting the battery from the power supply line when the voltage of a backup battery attached to the power supply line falls below a predetermined value. A first comparator (1-1) for comparing with a first comparator (1-1) and a resistor (R1) connected to the output side of the first comparator (1-1), and a second reference voltage. A second comparator (2) for comparing the battery voltage affected by the hysteresis applying circuit (1), and when the battery voltage becomes a predetermined value or less, the first comparator (1-1) ) Is activated, the second comparator (2) is activated and the first comparator (1-
The value of the resistor (R1) is set so that the detection voltage to the second comparator (2) is increased by a required value so that both 1) and the second comparator (2) are in an operating state. A battery disconnection control circuit for preventing battery over-discharge, wherein the first reference voltage and the second reference voltage are set to different values.