JPH0557544B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a battery power supply voltage monitor reset circuit for resetting the power supply voltage monitor circuit of an emergency light.

A conventional reset circuit of this type has a circuit configuration as shown by a block surrounded by a broken line in FIG. The transistor _Q1 , which is a switching element, has its emitter connected to the positive side of an emergency power source such as a battery power source 1, its base connected to the output of a power failure detection circuit 2 for detecting a power failure of the AC power supply, and its collector connected to a capacitor. It is grounded via a circuit in which a total of three circuits, a series circuit of C ₁ and resistor R ₂ , resistor R ₁ , and load circuit 3 are connected in parallel. The connection point between the capacitor C ₁ and the resistor R ₂ is connected to the anode of the diode D ₁ and the cathode of the diode D _2. The cathode of the diode D ₁ is connected to the voltage monitor circuit 4, and the anode of the diode D ₂ is connected to the ground. There is. The power failure detection circuit 2 detects a power failure in the AC power supply and turns on the transistor _Q1 . Then, substantially the voltage of the battery power source 1 is applied to the load circuit 3. Here, in the emergency light, an incandescent lamp or an inverter circuit is connected as the load circuit 3, and in the event of a power outage, the output of the inverter circuit will turn on the fluorescent lamp or the incandescent lamp at high frequency. Next, the power outage is over and normal AC power is restored.
When there is AC input, transistor _Q1 turns off,
Load circuit 3 is opened. Note that the resistor _R1 is a load and discharge resistor for the transistor _Q1 . Now, the reset circuit utilizes the charging current flowing through the capacitor _C1 when the transistor _Q1 is turned on by forcibly disconnecting the AC input from the AC power source using the reset switch 5. That is, when the transistor Q ₁ is turned on, the series circuit of the capacitor C ₁ and the resistor R ₂ is biased approximately at the voltage of the battery power supply 1. Due to the charging current flowing through the capacitor _C1 at this time, a positive voltage pulse is generated across the resistor _R2 . This is transmitted to the reset terminal R of the voltage monitor circuit 4 via the diode _D1 , and the voltage monitor circuit 4
This is to reset the . By the way, the voltage monitor circuit 4 has a function of indicating that the voltage of the battery power source 1 has fallen below the specified level by emitting light from a light emitting diode LED, which is a light emitting element, and storing this information even when the voltage of the battery power source 1 is restored. have Therefore, the detection operation of the conventional voltage monitor circuit 4 is provided with hysteresis. In other words, when the comparison input voltage proportional to the voltage +Vcc of the battery power source 1 becomes less than the lower limit setting level, the voltage monitor circuit 4 is set and lights up the light emitting diode LED, and when the comparison input voltage becomes more than the upper limit setting level, it is reset and the light emitting diode
Turn off the LED. That is, as described above, by the function of the reset circuit, a positive voltage pulse is applied superimposed on the comparison input voltage of the voltage monitor circuit 4, and when the value exceeds the upper limit setting level, the voltage monitor circuit 4 is reset. Figure 2 shows the operation of the voltage monitor circuit 4. In the figure, _L1 indicates the upper limit setting level, _L2 indicates the lower limit setting level, and a pulse RP is generated at time _t0 . It will be reset. The horizontal axis represents time, and the vertical axis represents a comparative input voltage proportional to the voltage of the battery power source 1 +Vcc.

Next, release the reset switch 5 and turn off the AC power supply.
When AC is turned on again, transistor _Q1 is turned off and the reset circuit is disconnected from battery power supply 1.
The capacitor C ₁ then starts discharging, but the time constant for discharging at this time is set long by increasing the resistor R ₁ to keep the discharge current low. Also,
The discharge current is blocked by the diode D ₁ so that the discharge does not affect the voltage monitor circuit 4 . In addition,
Diode _D2 is a diode for overcurrent protection. The above is the operating state of the conventional reset circuit. However, in this conventional circuit, since the load circuit 3 is connected in parallel with the reset circuit, there is a drawback that the discharge current of the capacitor _C1 also flows to the load. Now consider the case where an incandescent lamp is directly connected as a load. That is, the lamp is connected to the load circuit 3 in FIG. 1. In this way, when a low impedance load such as an incandescent lamp is connected, the time constant for discharging capacitor _C1 becomes extremely short. Therefore, the discharge current has a very large peak. In the conventional circuit, this discharge current is blocked by diode _D1 , but
A diode has the property of allowing a large reverse current to flow during the storage time. For this reason, a large discharge current is transmitted to the voltage monitor circuit 4, and the comparison input voltage of the voltage monitor circuit 4 changes at time t' ₀ as shown in FIG.
Negative voltage pulses overlap. When the comparison input voltage at this time falls below the lower limit setting level of the voltage monitor circuit 4, that is, _L2 , the circuit is set and the light emitting diode LED is turned on even if the +Vcc voltage of the battery power source 1 is normal. In other words, a malfunction occurs in which the light emitting diode LED, which has been reset once by the reset switch 5, is turned on again when the reset switch 5 is released. Of course, this malfunction does not occur if the load circuit 3 has high impedance.

In this way, in the conventional circuit, the capacitor
Since the structure is such that the discharge current of _C1 also flows to the load circuit 3, when the input impedance of the load circuit 3 is low, the light emitting diode LED that has been reset by the reset switch 5 will be lit again when the reset switch 5 is released. This has the drawback of causing a malfunction in which the reset is not applied. Since the input impedance of the inverter circuit for emergency lights is also usually low, similar malfunctions may occur even when an inverter circuit is connected as the load circuit 3.

The present invention has been made in view of the above problems, and its purpose is to improve the voltage of the battery power supply so that the voltage monitor circuit can be reliably reset while preventing malfunctions due to the influence of the load circuit. To provide a reset circuit for the monitor.

The present invention will be explained below with reference to Examples. FIG. 4 is a circuit configuration diagram of the embodiment of the first invention, and the reset circuit surrounded by a broken line in the figure is different from the conventional example in FIG. 1 in that it includes a transistor Q ₂ and resistors R ₃ and R ₄ . They are different. In other words, the collector of the transistor Q ₁ is connected to the load circuit 3, the series circuit of resistors R ₄ and R ₃ , the transistor Q ₂ , the capacitor C ₁ ,
A series circuit of charging resistor R ₂ is connected to ground through a circuit connected in parallel, a connection point of resistors R ₄ and R ₃ is connected to the base of transistor Q ₂ , and a capacitor is connected to the ground through a circuit connected in parallel.
A discharging resistor R′ ₁ is connected in parallel to the series circuit of C ₁ and resistor R ₂ .

To reset the voltage monitor circuit 4, first turn off the reset switch 5 to cut off the alternating current power supply AC, and turn on the transistor _Q1 with the detection output of the power failure detection circuit ₂ . A current flows through ₃ . This forward biases transistor _Q2 and turns it on. Then capacitor C ₁
A charging current flows through the diode _D1 and is transmitted to the voltage monitor circuit 4 through the diode D1 to generate a positive voltage pulse and reset the state of the light emitting diode LED. That is, when charging the capacitor C ₁ , sufficient charging current flows through the transistors Q ₁ and Q ₂ , so the same operation as the conventional circuit is possible. Next, release the reset switch 5 and reset the transistor.
Turning off _Q1 also turns off transistor _Q2 .
Then, capacitor _C1 starts discharging, but is blocked by the base-emitter junction of transistor _Q2 ,
No discharge current flows into the load circuit 3. The resistor _R'1 is a resistor for discharging the capacitor _C1 , and if this resistor _R'1 is made large, the time constant for discharging the capacitor _C1 can be made sufficiently large. Therefore, the peak of the charging current can be kept low, and if the values of the time constants C ₁ and B 4 are set so that the input voltage does not fall below the lower limit setting level due to the negative pulse applied to the voltage monitor circuit ₄ , Regardless of the input impedance of the load circuit 4, relighting of the light emitting diode LED can be prevented.

As described above, according to the reset circuit of the present invention, even if the impedance of the load circuit 3 is low,
Reset operation is possible and malfunctions can be eliminated. It goes without saying that the present invention can also be applied to load circuits 3 such as motors and relays in addition to emergency lights. Here, the reverse characteristic of the base-emitter junction of transistor Q ₂ is used to block the discharge current of capacitor C ₁ , but the problem in this case is the withstand voltage of the base-emitter junction of transistor Q ₂ . be. If breakdown voltage is a problem, connect the junction of capacitor C ₁ and resistor R′ ₁ and transistor Q ₂
A diode may be connected in series between the emitter and the emitter so that the emitter side becomes the anode. This makes it possible to divide the reverse voltage between the base-emitter junction and the diode and lower it below the withstand voltage. FIG. 5 shows a specific circuit of the above embodiment. The reset circuit surrounded by a broken line is the same as shown in FIG. 4, so a description thereof will be omitted. In FIG. 5, the cathode of the diode _D1 at the reset pulse output end is connected to the base of the transistor _Q6 of the voltage monitor circuit 4, and this connection point is used as the reset terminal R.
Furthermore, the base of transistor Q ₆ is connected to the connection point of resistors R ₅ and R ₆ . The other end of the resistor _R5 is connected to the battery power source 1, and the other end of the resistor _R6 is grounded through the resistor _R7 . Further, the emitter of the transistor _Q6 is connected to the resistor _R8 together with the emitter of the transistor _Q7 , and the other end of the resistor _R8 is grounded. Also, transistor _Q6
the collector of is connected to the collector and base of transistor Q ₄ and to the base of transistor Q ₅ ,
The emitters of transistors Q ₄ and Q ₅ are connected to +Vcc'. Even if this +Vcc' is taken from battery power supply 1,
Alternatively, it may be taken from a rectified power supply. transistor
The collectors of Q ₅ and Q ₇ are shorted and connected to the base of transistor Q ₈ . The base of transistor Q ₇ is connected to the comparison reference voltage Vref, the emitter of transistor Q ₈ is connected to Vcc′, and the collector is connected to resistor R ₉ ,
Grounding through a series circuit consisting of R ₁₀ . Also,
The connection point of resistors R ₉ and R ₁₀ is the transistor Q ₃ and Q ₉
Also connect to the base of. Transistor Q ₃ has its emitter grounded and its collector connected to the connection point of resistors R ₆ and R ₇ . And the transistor Q ₇ has its emitter grounded and its collector connected to the resistor R _{11 .}
The other end is connected to the cathode of the light emitting diode LED, and the anode of the light emitting diode LED is connected to +Vcc'.This voltage monitor circuit 4 is connected to the transistor _Q4 ,
Based on a differential amplifier with an active load consisting of _Q5 ,
The comparison reference voltage Vref and the voltage of battery power supply 1 are connected to resistor R ₅ ,
The voltage of the battery power source 1 is monitored by comparing the comparison input voltage obtained by dividing the voltage with R ₆ and R ₇ .
Also, by shorting and opening resistor _R7 with transistor _Q3 , the voltage division ratio is changed to provide hysteresis.

However, when the voltage of the battery power source 1 drops below the lower limit setting level _L2 as shown in _FIG .
Q ₈ , Q ₉ , Q ₃ are all turned on, and the light emitting diode LED
lights up. At this time, the resistor _R7 is short-circuited, so even if the voltage of the battery power supply 1 is restored to normal by charging or the like, the base voltage of the transistor _Q6 , that is, the comparison input voltage, does not rise to the upper limit setting level _L1 .
Now, when a positive reset pulse is applied to the base of transistor Q ₆ , the comparison input voltage exceeds the upper set level and turns transistor Q ₆ on, which turns off transistors Q ₇ , Q ₈ , Q ₉ , and Q _3. do,
The light emitting diode LED is turned off, and the voltage monitor circuit 4 is reset. At this time, resistor R ₇ is opened, so transistor Q ₆
The base voltage of increases and the light emitting diode LED remains off. Next, when the reset switch 5 is released, even if the negative pulse voltage due to the discharge of the capacitor _C1 is input to the voltage monitor circuit 4 via the diode _D1 , it is suppressed to a small level by the resistor _R'1 . The base voltage of transistor _Q6 is sufficiently higher than the lower limit setting level _L2 , so the circuit will not malfunction and the light emitting diode LED will not light up again.

FIG. 6 shows a circuit configuration diagram of an embodiment of the second invention, and this embodiment circuit uses a transistor Q _{' 2} instead of the discharge current blocking diode D 1 of the capacitor C ₁ in the conventional circuit of FIG. 1. It differs from the conventional example in Fig. 1 in that it uses a transistor Q′ ₂
The base is connected to the connection point between the capacitor _C1 and the resistor _R2 , the emitter is grounded, and the collector is connected to the reset terminal R of the voltage monitor circuit 4.

When the reset switch 5 is turned off to cut off the AC power source AC, the power failure detection output of the power failure detection circuit 2 turns on the transistor _Q1 . This causes a charging current to flow through the capacitor _C1 , and across the resistor _R2 , (voltage of battery power supply 1 - V _CE (sat)
1) voltage is applied. However, V _CE (sat)1 is the saturation voltage of transistor _Q1 . Then, as the capacitor _C1 is charged, the voltage applied across the resistor _R2 decreases exponentially and eventually reaches O [V]. Therefore, transistor _Q'2 is turned on only while the voltage across resistor _R2 exceeds the on-operation voltage of transistor _Q'2 . In this embodiment, this transistor Q′ ₂
The voltage monitor circuit 4 is reset by utilizing the fact that the voltage between the collector and emitter is approximately O [V] during the period when the voltage monitor circuit 4 is on.

Next, release the reset switch 5 and turn on the AC power supply.
When the AC input is reapplied, transistor _Q1 turns off. Then, the reset circuit surrounded by the broken line is opened and capacitor _C1 starts discharging. Although the discharge current at this time biases the base-emitter of transistor _Q'2 in the reverse direction, it does not bias it in the forward direction. Therefore, transistor _Q'2 is always in an off state. Therefore, the collector of transistor _Q'2 is always open and is not affected by the discharging operation of capacitor _C1 . This solves the drawback of the conventional circuit that a reverse pulse occurs. FIG. 7 is a circuit specifically showing the voltage monitor circuit 4 of the above embodiment, and basically has the same configuration as the embodiment circuit shown in FIG. 5, with the reset terminal R connected to a transistor. The circuit is different in that it is connected to the base of _Q3 , and that the PNP type transistor _Q8 in the circuit of FIG. 5 is replaced with an NPN type transistor _Q'8 .

However, this voltage monitor circuit 4 is a transistor.
When the base voltage of Q ₆ is higher than the base voltage of transistor Q ₇ (that is, the reference comparison voltage (Vref)), transistor Q′ ₈ is turned off, which turns off transistors Q ₃ and Q ₉ , and the light-emitting diode LED turns off. . Next, when the voltage of the battery power supply 1 decreases and the base voltage of the transistor _Q8 becomes lower than the base voltage of the transistor _Q7 , the transistor _Q7 is turned on and the transistor _Q6 is turned off. Then, transistors Q ₈ ′, Q ₉ , and Q ₃ turn on, so the light emitting diode LED lights up, warning of a drop in the voltage of battery power supply 1, and at the same time, the voltage across resistor R ₇ is reduced to approximately O [V] by transistor Q ₃ . drop it on If both ends of the resistor R ₇ are short-circuited, the voltage division ratio of the voltage of the battery power supply 1 will change, and the base voltage of the transistor Q ₆ will further decrease, so even if the voltage of the battery power supply 1 is restored later, the voltage monitor circuit 4 memorizes voltage abnormalities.
In the conventional circuit, a reset pulse is applied to the base of transistor _Q6 to turn on transistor _Q6 and reset the light emitting diode LED, but in this embodiment, the collector of transistor _Q'2 is connected to transistors _Q3 and _{Q9. Q3} and _Q6 are forced off only while transistor _Q'2 is on. Transistor Q ₃ ,
Once Q ₆ is turned off, the base potential of transistor Q ₆ rises as resistor R ₇ is released, and the light emitting diode LED becomes stable in the off state. This is a reset operation. Also, AC power supply
When the AC is turned on again, the voltage at the collector of the transistor _Q'2 does not rise due to the discharge current of the capacitor _C1 , which prevents malfunction when the reset switch is released. In this way, this embodiment can perform the same reset operation as the conventional circuit, and can also operate on an AC power supply.
Malfunctions caused by turning on the AC again can be prevented.

FIG. 8 shows another embodiment of the second invention. In this embodiment, a transistor is provided after the transistor _Q'2 .
_Q10 is added to raise the base potential of transistor _Q6 during reset. That is, the collector of transistor Q' ₂ is connected to resistor R ₁₃ , and the other end of resistor R ₁₃ is connected to battery power supply 1 through resistor R ₁₂ .
The base of a transistor _Q10 is connected to the connection point between the resistors _R12 and _R13 , the collector of the transistor _Q10 is connected to the battery power supply 1 through the resistor _R14 , and the emitter is connected to the base of the transistor _Q6 . Normally, however, transistor _Q'2 is off, and no collector current flows through transistor _Q'2 . Transistor _Q10 is therefore off. When reset switch 5 is turned off and transistor _Q1 is turned on, the transistor is turned on for a certain period of time as described above.
Q′ ₂ is turned on. The resistor R ₁₀ is set so that the transistor Q ₁₀ is turned on only when the transistor Q′ ₂ is turned on.
If R ₁₃ is selected, when transistor Q′ ₂ turns on, transistor Q ₁₀ will also turn on, so the base potential of transistor Q ₆ will rise. As a result, the voltage monitor circuit 4 is inverted, and the light emitting diode LED
is turned off. Further, even if the discharge current of the capacitor _C1 flows when the reset switch 5 is released, since the transistor _Q'2 is already turned off, it does not affect the voltage monitor circuit 4 and malfunction can be prevented. In this way, this embodiment also has the effect of preventing malfunctions when the reset switch 5 is released.

As described above, the first invention includes a power outage detection circuit that is connected to an AC power source via a normally closed reset switch to detect a power outage, and an emergency light that is turned on by the power outage detection output of this power outage detection circuit and is powered by a battery. A switching element that supplies power to a load circuit, and a voltage monitor circuit that monitors battery voltage and causes a display element to emit light when the battery voltage drops below a specified voltage, and maintains the light emitting state of this display element. In an emergency lighting device, a reset circuit for a voltage monitor of a battery power source provides a reset signal to the voltage monitor circuit to turn off the display element when the reset switch is turned off, and the reset circuit includes a capacitor connected in parallel to the load circuit via a transistor. and a resistor, a discharging resistor for discharging the charge of the capacitor of the differentiating circuit, a diode for applying the pulse voltage output from the differentiating circuit to the reset terminal of the voltage monitor circuit, and a switching circuit. Since the device is equipped with a bias circuit that turns on the transistor when the device is on and turns off the transistor when the device is off, the capacitor can be charged through the transistor at the time of reset, and a reset operation similar to the conventional one can be achieved. In addition, when the reset switch is released, the path to the load circuit is cut off when the capacitor's charge is discharged by turning off the transistor, so even if a low impedance load is connected as a negative circuit, the capacitor will The discharge current does not flow excessively, and the discharge determined by the discharge resistor occurs, preventing the detection voltage of the voltage monitor circuit from falling below the lower limit setting level when the reset switch is released, and ensuring a reliable reset operation. This effect is achieved. In addition, it is equipped with a transistor that turns on when the switching element is turned on, and a series circuit consisting of a capacitor and a resistor is connected in parallel to the load circuit via this transistor. It is possible to increase the impedance of the capacitor seen from the point through the switching element that is turned on during a power outage, and therefore, at the time when power supply to the load circuit starts, two connections are made to the battery power supply via the switching element. A low impedance circuit, that is, a load circuit, and a capacitor are connected, and this prevents the current that should flow into the load circuit from flowing into the capacitor side, preventing the power supply to the load circuit from becoming unstable. It is possible to stably light the lamp, and when the load circuit is configured using an inverter circuit, it is possible to improve the starting performance of the inverter circuit.

Further, as described above, the second invention includes a power outage detection circuit that is connected to an AC power source via a normally closed reset switch to detect a power outage, and a power outage detection output of the power outage detection circuit that is turned on to turn on the emergency lights from the battery power source. a switching element that supplies power to a load circuit including a voltage monitoring circuit that monitors battery voltage and causes a display element to emit light when the battery voltage falls below a specified voltage, and maintains the light emitting state of the display element; An emergency lighting device comprising: a battery-powered voltage monitor reset circuit that provides a reset signal to the voltage monitor circuit to turn off the display element when the reset switch is turned off, the reset circuit comprising a capacitor and a resistor connected in parallel to the load circuit; a differentiating circuit consisting of a differentiating circuit, a discharging resistor for discharging the charge in a capacitor of the differentiating circuit, and a transistor for inverting the pulse voltage output from the differentiating circuit and applying it to the reset terminal of the voltage monitor circuit. As a result, the voltage monitor circuit can be reliably reset when the transistor is on, and even if the charge in the capacitor is excessively discharged through a low-impedance load circuit after the reset switch is released, the transistor remains Since the base is reverse biased, the operation of the transistor is kept in the off state, and the voltage monitor circuit is not affected by the negative pulse voltage generated when the capacitor is discharged, thus preventing the voltage monitor circuit from malfunctioning. This effect is achieved.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional example, Figs. 2 and 3 are waveform diagrams for explaining the operation of the same as above, Fig. 4 is a circuit configuration diagram of an embodiment of the first invention, and Fig. 5 is a voltage monitor circuit of the same as above. FIG. 6 is a circuit diagram specifically showing the circuit configuration of an embodiment of the second invention, FIG. 7 is a circuit diagram specifically showing the voltage monitor circuit of the same, and FIG. 8 is a circuit diagram specifically showing the voltage monitor circuit of the second invention. 1 is a circuit diagram specifically showing a voltage monitor circuit of another embodiment, in which 1 is a battery power source, 2 is a power failure detection circuit, 3 is a load circuit, 4 is a voltage monitor circuit, 5 is a reset switch, and LED is a light emitting device. Diode, _C1 is a capacitor, _R2 is a charging resistor R1, _R'1 is a discharging resistor _{, Q2} , _Q'2 are transistors, R is a reset terminal, _L1 is an upper limit setting level, _L2 is a This is the lower limit setting level.

Claims (1)

[Claims] 1. A power failure detection circuit that is connected to an AC power source via a normally closed reset switch and detects a power failure, and a load circuit that is turned on by the power failure detection output of this power failure detection circuit and includes an emergency light from a battery power source. A voltage monitoring circuit that monitors the battery voltage and has the function of causing the display element to emit light when the battery voltage drops below the specified voltage and maintaining the light emitting state of the display element. In a lighting device, a reset circuit for a voltage monitor of a battery power source provides a reset signal to a voltage monitor circuit to turn off a display element when the reset switch is turned off, and the reset circuit includes a capacitor and a resistor connected in parallel to a load circuit via a transistor. A differential circuit consisting of,
A discharging resistor that discharges the charge in the capacitor of this differentiating circuit, a diode that applies the pulse voltage output from the differentiating circuit to the reset terminal of the voltage monitor circuit, and a diode that turns on the transistor when the switching element is on. What is claimed is: 1. A reset circuit for a voltage monitor of a battery power source, comprising: a bias circuit for turning off a transistor when the transistor is turned off; 2. A power outage detection circuit that is connected to an AC power source via a normally closed reset switch to detect a power outage, and a switching device that is turned on by the power outage detection output of this power outage detection circuit and supplies power from the battery power source to the load circuit including the emergency lights. In an emergency lighting device consisting of an element and a voltage monitor circuit having a function of monitoring battery voltage and causing a display element to emit light when the battery voltage drops below a specified voltage and maintaining the light emitting state of the display element, the above-mentioned reset This is a reset circuit for a voltage monitor of a battery power source that provides a reset signal to turn off a display element to a voltage monitor circuit when a switch is turned off, and includes a differentiating circuit consisting of a capacitor and a resistor connected in parallel to the load circuit, and a differentiating circuit for this differentiating circuit. A discharging resistor that discharges the charge of the capacitor in the circuit,
A reset circuit for a voltage monitor of a battery power source, comprising a transistor for inverting the pulse voltage output from the differentiating circuit and applying the inverted pulse voltage to the reset terminal of the voltage monitor circuit.