JPH0442889B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention drives a load such as an emergency light or guide light with an AC power source when a commercial AC power source is energized, and also charges a rechargeable power source. This invention relates to a switching circuit that drives a load using a rechargeable power source during a power outage.

(Background Art) FIG. 5 is a circuit diagram showing a conventional emergency light switching circuit. In this circuit, first, when AC current is applied, the output from the isolation transformer _T1 is used as a power source to charge the storage battery BT, and at the same time, the relay coil _L1 of the power failure detection relay is excited. The contacts of this relay
When SW ₁ and SW ₂ switch to the NO side, the lamp
FL is turned on for commercial purposes, and contact SW ₃ is opened, so that the inverter circuit INV stops oscillating.
Next, during a power outage, each contact is connected to the NC side because the driving power for the relay coil _L1 is lost. When the contact SW ₃ becomes NC side, the inverter circuit INV starts oscillating. Also the contact
By switching SW ₁ and SW ₂ to the NC side, the inverter circuit INV boosted by the oscillation transformer T ₂
A high frequency high voltage of is applied to the lamp FL, and the lamp
FL lights up in an emergency.

In this conventional example, after the lamp FL is turned on in an emergency and the storage battery BT is completely discharged, the AC power supply is turned off.
When the AC power is restored, the alternating current of the battery increases significantly, so the output voltage of the isolation transformer _T1 becomes low. FIGS. 6 and 7 are explanatory diagrams for explaining this. Figure 6 shows an isolation transformer
FIG. 2 is a diagram showing the relationship between the output voltage V _T of T ₁ and the load current I _T , and shows that as the load current I _T increases, the output voltage V _T decreases. FIG. 7 is a diagram showing changes in charging current Ib and battery voltage Vb of storage battery BT when charging a completely discharged storage battery BT,
It can be seen that at the initial stage of charging, the battery voltage Vb is low and the charging current Ib is large. In this way, at the beginning of charging, if the battery voltage is low (including 0), even if the AC power supply AC is restored, the isolation transformer T ₁
Because the output voltage is low, the voltage applied to the relay coil _L1 of the power failure detection relay is below the relay's sensing voltage, and the lamp FL will not turn on for commercial purposes until the battery voltage of the storage battery BT recovers. This will cause inconvenience.

In order to avoid this, it is best to increase the output voltage of the isolation transformer _T1 so that even when the battery voltage drops, the voltage applied to the relay coil _L1 remains below the relay's impression voltage, but the output voltage of the transformer If the voltage is increased, there is a problem that the transformer becomes larger, and it is also necessary to increase the resistance value of the charging current limiting resistor _R1 , resulting in the problem of extra power consumption.

On the other hand, in order to solve these problems,
As shown in the circuit shown in the figure, it is conceivable to use an AC-driven type relay and connect its relay coil L ₁ ' to the AC power line, but in this case, various surge voltages may be present on the AC power line. This surge voltage may cause dielectric breakdown between the contacts and the coil, and in the worst case, there is a problem of short-circuiting of the power supply.
Therefore, it is better to provide the relay coil on the secondary side of the isolation transformer.

(Object of the Invention) The present invention has been made in view of the above-mentioned points, and its purpose is to quickly reduce the load when the AC power supply is restored, regardless of the voltage of the rechargeable power supply. An object of the present invention is to provide a switching circuit that can be driven by an AC power source.

(Disclosure of the Invention) To explain the switching circuit according to the present invention with reference to illustrated embodiments, as shown in FIGS. 1 to 4,
It is connected to the isolation transformer T ₁ connected to the AC power source AC and to the output side of the isolation transformer T ₁ , so that when the power is on, the AC power source AC drives the lamp FL, and when the power is off, the storage battery BT drives the lamp FL. a relay circuit 1 for switching the power source for driving the lamp FL;
A switch element 2 is opened for at least a predetermined period of time from the start of energization to the relay circuit 1 when the AC power source AC is turned on until the switching operation is completed, and the relay is connected to the output side of the isolation transformer T1 via the switch element ₂ . It has a charging circuit 3 that is connected in parallel with the circuit 1 and charges the storage battery BT.

In the present invention, as described above, the AC power source AC
The storage battery
Since the BT charging circuit 3 is connected in parallel with the relay circuit 1, when the AC power source AC is turned on, the initial voltage applied to the relay circuit 1 is increased regardless of the battery voltage of the storage battery BT. Therefore, the relay circuit 1 can be reliably switched and a load such as the lamp FL can be quickly driven with alternating current. Also,
After the switching operation of relay circuit 1 is completed, switch element 2
is closed and charging of the storage battery BT starts, the voltage applied to the relay circuit 1 decreases due to the increase in the load current of the isolation transformer _T1 , but if the applied voltage is equal to or higher than the holding voltage, the relay circuit 1 The switched state can be maintained, and the current consumption of the relay circuit 1 can be reduced by lowering the applied voltage.

Embodiment 1 Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a circuit diagram of a switching circuit according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of its operation. The power supply voltage of the alternating current power supply AC is applied to the primary side of the isolation transformer _T1 . isolation transformer
On the secondary side of _T1 , an alternating current voltage that is a step-down version of the commercial power supply voltage is generated. This AC voltage is full-wave rectified by diode bridge DB and charged to capacitor _C1 . The charging voltage of the capacitor C ₁ is determined by a diode D ₁ for blocking reverse current, a resistor R ₁ for current limiting, and
Collector of transistor _Q2 for charge start control
It is supplied to the storage battery BT via the emitter. Storage battery BT, diode bridge DB,
Capacitor C ₁ , diode D ₁ and resistor R ₁ are
It constitutes the charging circuit 3 described above.

When the AC power source AC is energized, the charging voltage of capacitor C ₁ is passed through diode D ₂ for blocking reverse current.
Supplied to the IC chip. Here, IC chip IC
is an IC chip that includes NOT circuit A, NAND circuit B, NOT circuit C, and NOT circuit D in one package. In the event of an AC power outage, the IC chip
The charging voltage of the storage battery BT is applied to the power supply terminal and the ground terminal of the battery BT via reverse current blocking diodes D ₃ and D ₄ . Figure 2 a shows the IC driving voltage applied between the power supply terminal and ground terminal of the IC chip.
V _IC is shown.

A resistor R ₂ for discharging the charge of the capacitor C ₁ is connected in parallel to both ends of the capacitor C ₁ . now,
Assuming that the AC power supply AC is energized, the terminal voltage V _C1 of the capacitor C ₁ (Figure 2 b) becomes H level, so the output V _A of the NOT circuit A (Figure 2 c)
becomes L level, and the output V _D of NOT circuit D
(Fig. 2g) is at H level. When the output V _D of the NOT circuit D becomes H level, a base current flows through the transistor Q ₁ via the resistor R ₆ and the relay drive transistor Q ₁ is turned on. The charging voltage of the capacitor _C1 is supplied to the relay coil _L1 of the power failure detection relay via the relay drive transistor _Q1 . A diode _D5 for preventing back electromotive force is connected in parallel to both ends of the relay coil _L1 . Transistor Q ₁
is turned on, an excitation current flows through the relay coil L ₁ , and the contacts SW ₁ ,
SW ₂ and SW ₃ switch to the NO side (normally open side). At this time, the lamp FL is turned on for commercial use and the inverter circuit
INV is in the oscillation stopped state. Here, the relay coil L ₁ and its relay contacts SW ₁ , SW ₂ ,
SW ₃ , relay drive transistor Q ₁ , diode D ₅ , resistor R ₆ , NOT circuits A and D, etc. constitute the above-mentioned relay circuit 1 .

By the way, since the output V A of NOT circuit _A becomes L level, the output V _B of NAND circuit B (Fig. 2 d) becomes H level, so capacitor C ₂
The voltage V _CR (FIG. 2e) across the resistor R ₃ becomes H level through the resistor R 3 . Therefore, the output of NOT circuit C
V _C (Fig. 2 f) becomes L level, and the transistor
The base potential of Q ₂ becomes low and transistor Q ₂ is turned off. Therefore, even if the AC power source AC is turned on, charging of the storage battery BT does not start immediately, and as a result, the relay coil
This allows the initial applied voltage of _L1 to be increased. After a predetermined delay time determined by the time constant of capacitor C ₂ and resistor R ₃ , resistor R ₃
The voltage across V _CR decreases, and when this voltage becomes lower than the threshold voltage of NOT circuit C,
The output V _C of the NOT circuit C is inverted to H level. As a result, a base current flows through the transistor Q ₂ via the resistor R ₅ , and the transistor Q ₂ is turned on. The above-mentioned switch element 2 is constituted by this transistor _Q2 , the NOT circuits A and C, the NAND circuit B, the resistors _R3 , _R4 , _R5 , and the capacitor _C2 .

By turning on transistor _Q2 ,
A charging current flows from the capacitor C ₁ to the storage battery BT via the diode D ₁ and the resistor R ₁ . As the load current increases, the output voltage of isolation transformer T ₁ decreases slightly, and accordingly, capacitor C ₁
The voltage across _L1 decreases, and the voltage applied to the relay coil _L1 also decreases, but since the power failure detection relay has already finished its operation, it is only necessary to supply the holding voltage, and the voltage applied to the relay coil L1 decreases. There is no problem. In addition,
When the output V _C of the NOT circuit C becomes H level, the other input of the NAND circuit B also becomes H level.

Next, when the alternating current power supply AC fails, the capacitor
Since the charge on C ₁ is discharged by resistor R ₂ ,
The voltage V _C1 across capacitor C ₁ drops rapidly.
At this time, the driving voltage V _IC is supplied to the IC chip IC from the storage battery BT via the diodes D ₃ and D ₄ . As the voltage V _C1 across the capacitor C ₁ decreases, the output V _A of the NOT circuit A becomes H level. Therefore, both inputs of NAND circuit B are high.
level, so its output V _B becomes L level. Furthermore, as the output V _A of the NOT circuit A becomes H level, the output V _D of the NOT circuit D becomes L level, and the transistor Q ₁ is turned off. At this time, the voltage V _C1 of the capacitor C ₁ has also decreased, so in any case, the power failure detection relay coil L ₁
The excitation current to is cut off. Therefore, contacts SW ₁ , SW ₂ , and SW ₃ of the power failure detection relay switch to the NC side (normally closed side), and at this time, the inverter circuit INV operates and the lamp FL lights up in an emergency. be.

In this way, only when the AC power source AC is turned on, the transistor Q ₂ for charge start control is turned off for a predetermined period of time, leaving the charging circuit in an open state, and by reducing the load current, the output voltage of the isolation transformer T ₁ is increased. After the relay is operated reliably, transistor _Q2 is turned on and charging begins. Note that the holding voltage of relays driven by DC voltage is generally about 10% of the rated voltage, and once the relay is turned on, it is designed to hold the voltage even if the voltage drops considerably.

Next, the lighting circuit for the lamp FL will be explained.
When the AC power supply AC is energized, the contacts SW ₁ and SW ₂ of the power failure detection relay are NO as described above.
side (normally open side), each end of the filament of the lamp FL, such as a fluorescent lamp, is connected to the alternating current power supply AC via the ballast _L2 , which is a current limiting element. Furthermore, a glow lamp GL and a noise prevention capacitor Ca are connected in parallel to each other end of the filament of the lamp FL. Therefore, the lamp FL is started and lit in the same way as a normal fluorescent lamp lighting circuit. At this time, the inverter circuit
INV is in a stopped oscillation state because contact SW ₃ , which is the starting switch, has been switched to the NO side (normally open side).

On the other hand, when the AC power supply AC fails, as mentioned above, contact SW ₃ of the power failure detection relay switches to the NC side (normally closed side), so the bias resistor
A base bias current flows through Ra and Rb to the inverter driving transistors Qa and Qb. The bases of the transistors Qa and Qb are connected to the base drive winding of the oscillation transformer _T2 , and the charging voltage of the storage battery BT is connected to the inductance _L3 between the emitter and collector.
are connected to the primary winding of the oscillation transformer _T2 so that the voltage is applied alternately with opposite polarity, thereby forming a well-known push-pull type inverter circuit INV. In the event of a power outage of the AC power source AC, contacts SW ₁ and SW ₂ of the power outage detection relay switch to the NC side (normally closed side), so capacitors Cb and Cb are connected to both ends of the lamp FL.
The secondary winding voltage of the oscillation transformer _T2 is applied via Cc. Further, a preheating current is supplied to one of the preheating filaments from a part of the secondary winding of the oscillation transformer _T2 . This allows the lamp to
FL is turned on in an emergency by the inverter circuit INV.

Embodiment 2 FIG. 3 is a circuit diagram of another embodiment of the present invention,
FIG. 4 is an explanatory diagram of the operation. Elements that are the same as those in the previous embodiment are given the same reference numerals and redundant explanations will be omitted. In this embodiment, the inverter circuit
INV starting switch is transistor Q ₃ , Q ₄
When the AC power supply AC is out of power, the start of oscillation of the inverter circuit INV is delayed compared to the recovery operation of the relay, and when the AC power supply AC is restored, the relay operation is delayed longer than the oscillation stop of the inverter circuit INV. The difference is that the delay prevents the high frequency, high voltage of the inverter circuit INV from being applied to the contacts when the relay contacts open and close, thereby improving the contact life. In this embodiment, as in the previous embodiment, the output voltage of the isolation transformer _T1 is increased by opening the charging circuit 3 for a predetermined period of time from the time when the AC power source AC is turned on.
We ensure that the relay's moving action is carried out reliably.

The operation of the circuit shown in FIG. 3 will be explained below with reference to FIG. When AC power source AC is turned on, the terminal voltage of capacitor _C1 increases. capacitor
The terminal voltage of C ₁ is input to a buffer consisting of NOT circuits E and F, and as the terminal voltage of capacitor C ₁ increases, the output of NOT circuit F V _F
(FIG. 4b) is at H level. By this,
The output V _K (Fig. 4 h) of the NOR circuit K becomes L level, transistors Q ₃ and Q ₄ turn off,
First, the oscillation of the inverter circuit INV is stopped.
As a result, the emergency lighting of lamp FL is stopped.
Until the next commercial lighting, the lamp FL stops emitting light.

Furthermore, as the output V _F of the NOT circuit F becomes H level, the output voltage V _CR1 (Fig. 4 d) of the time constant circuit consisting of the series circuit of the resistor R ₉ and the capacitor C ₃ gradually increases. do. When the terminal voltage V _CR1 of capacitor C ₃ becomes higher than the threshold level of NOT circuit H, the output V H of NOT circuit _H (Fig. 4 e) becomes L level, and one input of NOR circuit J becomes L level. level. The other input of this NOR circuit J is that the output V _G of the NOT circuit G (Fig. 4C) is L.
level, so it is L level. Therefore, the output V _J (Fig. 4 f) of the NOR circuit J becomes H level, the transistor Q ₁ is turned on, and the excitation current flows through the relay coil L ₁ of the power failure detection relay.
Each relay contact SW ₁ and SW ₂ switches to the NO side (normally open side). As a result, the lamp FL is lit for commercial use.

By switching the output V _H of NOT circuit H from H level to L level, the output V ₁ of NOT circuit I
(Fig. 4g) is switched from L level to H level, so the input of NOT circuit L is switched from L level to H level via capacitor _C4 . Therefore, at the moment when the relay coil _L1 of the power failure detection relay starts being energized, the output V _L of the NOT circuit L
(FIG. 4j) is switched from the H level to the L level, and the transistor _Q2 is turned off. For this reason,
The charging current to the storage battery BT is cut off and the capacitor
The terminal voltage of _C1 rises, and the relay operates at this high voltage. The output voltage V _CR2 (Fig. 4i) of the time constant circuit consisting of capacitor C ₄ and resistor R ₁₃ gradually drops, and when this voltage V _CR2 becomes lower than the threshold level of NOT circuit L,
The output V _L of the NOT circuit L switches from L level to H level, and transistor Q ₂ is turned on. As a result, charging of the storage battery BT is started, and the voltage of the capacitor _C1 drops slightly, but since the relay has already finished the touching operation, it is sufficient if a holding voltage lower than the touching voltage is supplied. , there is no effect on the holding operation of the relay.

Next, when the alternating current power supply AC fails, the capacitor
Since the terminal voltage of _C1 decreases, the output V _F of NOT circuit F becomes L level. As a result, the output V _G of the NOT circuit G goes from the L level to the H level, so the output V _J of the NOR circuit J goes to the L level, and the transistor Q ₁ is turned off. At this time, the voltage of capacitor C ₁ has also decreased, so in any case, the relay coil L ₁ of the power failure detection relay is de-energized and the contacts SW ₁ and SW ₂ are switched to the NC side (normally closed side). Switching occurs, and commercial lighting of the lamp FL is stopped. After this, the lamp FL stops emitting light until the oscillation operation of the inverter circuit INV is started.

As the output of the NOT circuit F becomes L level, the terminal voltage V _CR1 of the capacitor _C3 gradually decreases. When this voltage V _CR1 becomes lower than the threshold level of NOT circuit H, the output of NOT circuit H
V _H becomes H level, and the output V ₁ of NOT circuit I becomes L
level. Therefore, the output of NOR circuit K
Since V _K becomes H level and transistors Q ₃ and Q ₄ are turned on, inverter circuit INV starts oscillating operation. As a result, the lamp FL is turned on in an emergency by the high frequency and high voltage from the inverter circuit INV. Note that the output V ₁ of NOT circuit I
Even if switches from H level to L level, NOT
Since the input of circuit L never goes to H level,
The output V _L of NOT circuit L remains at H level,
Transistor _Q2 is in the on state. That is,
Transistor Q ₂ is turned off only during the period in which the power failure detection relay performs a sensitive operation after the alternating current power source AC is turned on.

(Effects of the Invention) As described above, in the present invention, the switch element is opened for a predetermined period of time from the start of energization to the relay circuit by turning on the AC power until the switching operation of the relay circuit is completed. The charging circuit of the rechargeable power supply is connected to the output side of the isolation transformer in parallel with the relay circuit, so when the AC power is turned on, the power is connected to the relay circuit regardless of the voltage of the rechargeable power supply. This has the effect that the initial applied voltage can be increased, and therefore the relay circuit can be reliably switched and the load can be quickly driven with alternating current. In addition, when the switch element is closed and charging of the rechargeable power source starts after the switching operation of the relay circuit is completed, the voltage applied to the relay circuit decreases due to the increase in the load current of the isolation transformer. If the holding voltage is higher than the holding voltage, the relay circuit can maintain its switched state, and by reducing the applied voltage, the current consumption of the relay circuit can be reduced, making it possible to use a small isolation transformer. The effect is that it can be done.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention, FIG. 2 is an explanatory diagram of the same operation as above, FIG. 3 is a circuit diagram of another embodiment of the present invention, FIG. 4 is an explanatory diagram of the same as above, FIG. 5 is a circuit diagram of a conventional example, FIGS. 6 and 7 are operation explanatory diagrams of the same, and FIG. 8 is a circuit diagram of another conventional example. AC is an alternating current power supply, _T1 is an isolation transformer, FL is a lamp, BT is a storage battery, 1 is a relay circuit, 2 is a switch element, and 3 is a charging circuit.

Claims (1)

[Claims] 1 An isolation transformer connected to an AC power source and a load drive device that is connected to the output side of the isolation transformer and drives the load with the AC power source when energized, and drives the load with a rechargeable power source when not energized. A relay circuit that switches the power supply, a switch element that is open for at least a predetermined period of time from the start of energization to the relay circuit when AC power is turned on until the switching operation is completed, and a switch element that is connected to the output side of the isolation transformer via the switch element. A switching circuit comprising: a charging circuit connected in parallel with the relay circuit to charge the rechargeable power source.