JPH0697813B2 - Switching circuit - Google Patents

Description

TECHNICAL FIELD The present invention illuminates a lamp with an AC power supply when a commercial AC power supply is energized, charges a storage battery, and is driven by the storage battery when the AC power supply fails. The present invention relates to a switching circuit in which an inverter circuit lights a lamp.

(Background Art) FIG. 5 is a circuit diagram of a conventional switching circuit (Japanese Patent Application No. 61-94215), and FIG. 6 is an operation explanatory diagram thereof. AC power supply AC
Is applied to the primary side of the isolation transformer T ₁ . On the secondary side of the isolation transformer T ₁ , an AC voltage that is a reduced commercial power supply voltage is generated. This AC voltage is full-wave rectified by the diode bridge DB and charged in the capacitor C ₁ .
The charging voltage of the capacitor C ₁ is determined by the diode D ₁
And a resistor R _{1 for current} limiting and a collector-emitter of a transistor T ₂ for controlling charging start, and is supplied to the storage battery BT.

When the AC power supply AC is energized, the charging voltage of the capacitor C ₁
It is supplied to the IC chip (IC) through the diode D ₂ for blocking the reverse current. Here, the IC chip (IC) is NOT circuit (A), N
AND circuit (B), NOT circuit (C) and NOT circuit (D) 1
An IC chip included in the package. When the AC power supply AC fails, the power supply terminal and ground terminal of the IC chip (IC)
The charging voltage of the storage battery BT is applied via the backflow prevention diodes DBD ₃ and D ₄ . Figure 6 (a) shows an IC chip (IC)
2 shows an IC drive voltage V _IC applied between the power supply terminal and the ground terminal of FIG.

At both ends of the capacitor C _1, resistors R ₂ for the charge and discharge of the capacitor C ₁ is connected in parallel. Now, assuming that the AC power supply AC is energized, the terminal voltage V _{C1 of the} capacitor C ₁
Since (Fig. 6 (b)) is at H level, the output V _A of the NOT circuit (A) (Fig. 6 (c)) is at L level, and the output V _D of the NOT circuit (D) (D 6 (g)) is at the H level. When the output V _D of the NOT circuit (D) becomes H level, the base current flows through the resistor R ₆ to the transistor Q _1, the transistor Q ₁ is turned on for the relay drive. The charging voltage of the capacitor C ₁ is supplied to the relay coil L ₁ of the power failure detection relay via the transistor Q ₁ for relay drive. A diode D ₅ for preventing back electromotive force is connected in parallel to both ends of the relay coil L ₁ . When the transistor Q ₁ is turned on, an exciting current flows in the relay coil L ₁ and the contact switch of the power failure detection relay
₁ , SW ₂ , SW ₃ are switched 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.

By the way, when the output V _A of the NOT circuit (A) becomes L level, the output V _B of the NAND circuit (B) (FIG. 6 (d))
It is because the H level, via the capacitor C _2, resistors R ₃
The both-end voltage V _CR (Fig. 6 (e)) becomes H level. Therefore, the output V _C of the NOT circuit (C) (Fig. 6 (f)) is L
Level and the base potential of the transistor Q ₂ is lowered, the transistor Q ₂ is turned off. Therefore, even if the AC power supply AC is turned on, the charging of the storage battery BT does not start immediately, and the relay coil L ₁
The initial applied voltage can be increased. When the predetermined delay time determined by the time constant between the capacitor C ₂ and the resistor R ₃ elapses, the voltage V _CR across the resistor R ₃ decreases, and when this voltage becomes lower than the threshold voltage of the NOT circuit (C). Then, the output V _C of the NOT circuit (C) is inverted to the H level. Thus, base current flows through the resistor R ₅ to the transistor Q _2, the transistor Q ₂ is turned on.

When the transistor Q ₂ is turned on, 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 the insulation transformer T ₁ drops slightly, and the voltage V _CI across the capacitor C ₁ drops accordingly, and the voltage applied to the relay coil L ₁ also drops, but a power failure occurs. Since the detection relay has already completed the moving operation, it is sufficient to supply only the holding voltage, and there is no problem in holding the relay. 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 AC power supply AC loses power, the charge charged in the capacitor C ₁ is discharged by the resistor R ₂ , so that the voltage V _C1 across the capacitor C ₁ drops rapidly. At this time, IC chip (IC)
From the storage battery BT via the diodes D ₃ and D ₄
V _IC is supplied. The output V _A of the NOT circuit (A) becomes H level because the voltage V _C1 across the capacitor C ₁ decreases. Therefore, the inputs of the NAND circuit (B) are both at the H level, and the output V _B thereof is at the L level. Also NOT
When the output V _A of the circuit (A) becomes H level, NOT
The output V _D of the 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
Since it also decreases, the exciting current to the relay coil L ₁ of the power failure detection relay is cut off in any case. Therefore, the contacts SW ₁ , SW ₂ , and SW ₃ of the power failure detection relay are switched to the NC side (normally closed side).
The INV operates and the lamp FL lights up in an emergency.

As described above, only when the AC power supply AC is turned on, the transistor Q ₂ for charge start control is turned off for a predetermined time to open the charging circuit, and the load current is reduced to increase the output voltage of the insulating transformer T _1. Then, the transistor Q ₂ is turned on and charging is started after the relay is positively operated. In addition, the holding voltage of the relay driven by DC voltage is generally about 10% of the rating.
When the relay turns on, it keeps the voltage even if it drops considerably.

Next, the lighting circuit of the lamp FL will be described. AC source
As described above, when the AC is energized, the contacts SW ₁ and SW ₂ of the power failure detection relay are switched to the NO side (normally open side), so that one end of each filament of the lamp FL such as a fluorescent lamp is switched. Is connected to an AC power source AC via a ballast L ₂ which is a current limiting element. Also, at each other end of the filament of the lamp FL,
The glow lamp GL and the noise prevention capacitor C _a are connected in parallel. Therefore, the lamp FL is started and lit like a normal fluorescent lamp lighting circuit. At this time,
In the inverter circuit INV, the contact SW ₃ that serves as a start switch is switched to the NO side (normally open side), so that the oscillation is stopped.

On the other hand, when the AC power supply AC fails, as described above,
Since the contact SW ₃ of the power failure detection relay is switched to the NC side (normally closed side), the base bias current flows to the inverter driving transistors Q _a and Q _b via the bias resistors R _a and R _b . The bases of the transistors Q _a and Q _b are connected to the base drive winding of the oscillation transformer T ₂ , and the charging voltage of the storage battery BT is connected to the primary winding of the oscillation transformer T ₂ via the inductance L ₃ between the emitter and collector. A well-known push-pull type inverter circuit, which is connected so as to be applied with opposite polarities alternately.
Configures INV. During a power failure of the AC power supply AC, the contacts SW ₁ and SW ₂ of the power failure detection relay are switched to the NC side (normally closed side). Therefore, the oscillation transformer T ₂ is connected to both ends of the lamp FL via capacitors C _b and C _c. Secondary winding voltage is applied. A preheating current is supplied to one of the preheating filaments from a part of the secondary winding of the oscillation transformer T ₂ . by this,
The lamp FL is emergency lit by the inverter circuit INV.

However, in this conventional example, since the voltage T _c shown in FIG. 6 (f) is at the “High” level during emergency lighting, the transistor Q ₂ is in the on state, and during emergency lighting. Also in, the charging circuit is not disconnected from the output side of the isolation transformer T ₁ . Therefore, if the voltage of the AC power supply AC is gradually increased from this state, the insulation transformer T ₁
The current supplied from the storage battery BT and the inverter circuit IN
Flow into V respectively. The isolation transformer T ₁ has a characteristic that the output voltage decreases as the load current increases. Therefore, when the battery voltage decreases, the isolation transformer T ₁
Load current increases, the output voltage of the isolation transformer T ₁ also decreases, and the commercial voltage level when switching to the AC lighting side of the power failure detection circuit increases. Moreover, even when the operating state of the inverter circuit INV is different from the normal state, such as when the lamp FL is unloaded, the output voltage of the insulating transformer T ₁ changes. As a result, there is a problem in that the switching voltage varies when the commercial power source AC is restored, and the switching operation becomes uncertain.

Japanese Utility Model Laid-Open No. 57-41438 discloses a circuit in which an inverter circuit is driven by a storage battery to light a lamp during a power failure detection period. Since it is connected to the input side of the transformer, it lacks the premise that the power failure detection circuit and the charging circuit are connected to the output side of the same isolation transformer.
It does not suggest the problem to be solved by the present invention. Further, JP-A-51-93343 discloses a charging circuit that charges a storage battery via a switch element that is opened during a power failure detection period, but an insulation transformer to which the power failure detection circuit is connected, The isolation transformer with which the accumulator is charged is another transformer and therefore does not suggest the problem to be solved by the present invention.

(Object of the Invention) The present invention has been made in view of the above points,
The purpose is to disconnect the charging circuit from the output side of the isolation transformer during emergency lighting,
Another object of the present invention is to provide a switching circuit in which the output voltage of the insulation transformer is kept constant regardless of the battery voltage and the operating state of the inverter circuit.

DISCLOSURE OF THE INVENTION In the switching circuit according to the present invention, as shown in FIGS. 1 to 4, an insulating transformer T connected to an AC power supply AC is provided.
_1, and connected to the output side of the isolation transformer T ₁ detects the power failure of the AC power supply AC by stopping the energization, during the power failure detection period, the inverter circuit INV is driven by the storage battery BT to turn on the lamp FL, A power failure detection circuit 1 that switches the power of the lamp FL so that the lamp FL is lit by the AC power supply AC during the non-power failure detection period, a switch element 2 that is opened during the power failure detection period by the power failure detection circuit 1, and the switch The charging circuit 3 is connected to the output side of the insulating transformer T ₁ through the element 2 and charges the storage battery BT.

As described above, in the present invention, the charging circuit 3 for charging the storage battery BT is provided with the insulating transformer via the switch element 2 that is opened during the power failure detection period of the power failure detection circuit 1.
Since it is connected to the output side of T ₁ , the power failure detection circuit 1
During the power failure detection period due to, the charging circuit 3 for charging the storage battery BT, the inverter circuit INV fed from the storage battery BT, and the like are disconnected from the output side of the isolation transformer T ₁ , and therefore the AC power supply is used. The output voltage of the isolation transformer T ₁ when the AC power is restored is determined independently of the battery voltage of the storage battery BT and the operating state of the inverter circuit INV, and therefore the switching voltage of the power failure detection circuit 1 becomes constant. .

Examples of the present invention will be described below.

Embodiment 1 FIG. 1 is a circuit diagram of a switching circuit according to an embodiment of the present invention, and FIG. 2 is an operation explanatory diagram thereof. In this embodiment, the same elements as those of the conventional example of FIG. When the AC power supply AC is energized, the charging voltage of the capacitor C ₁ is supplied to the capacitor C ₃ for obtaining the operating power supply of the logic circuit via the backflow blocking diode D ₂ . During a power failure of the AC power supply AC, the battery voltage of the storage battery BT is supplied to the capacitor C ₃ via the reverse current blocking diode D ₃ . A series circuit of a resistor r ₁ and a Zener diode ZD ₁ is connected to both ends of the capacitor C ₃ . The constant voltage generated at the cathode of the Zener diode ZD ₁ is supplied to the base of the transistor Q ₅ . The capacitor C ₇ is charged to a constant voltage from the capacitor C ₃ via the transistor Q ₅ , and the charging voltage is the IC chip (I
C). This IC chip (IC) shows only the power supply parts of the logic gate circuits (G ₁ ) to (G ₉ ).

On the secondary side of the insulating transformer T ₁ , the anodes of the diodes D ₇ and D ₈ are grounded. The cathodes of both diodes D ₇ and D ₈ are commonly connected, and are grounded via a series circuit of resistors R ₇ and R ₈ . A capacitor C ₄ is connected to both ends of the resistor R ₈ via a resistor R ₉ and a diode D ₁₀ . When a voltage is generated on the secondary side of the isolation transformer T ₁ , the capacitor C ₄ is charged. The anode of diode D ₁₀ is
Since it is connected to the non-grounded terminal of the capacitor C ₇ via the diode D ₉ , the upper limit value of the voltage of the capacitor C ₄ is regulated by the voltage of the capacitor C ₇ . A discharge resistor R ₁₀ is connected in parallel to both ends of the capacitor C ₁ . NOT circuits (G ₁ ) and (G ₂ ) form a buffer circuit. NOT
The output of the circuit (G ₂₎ is positively fed back to the input of the NOT circuit via a resistor R ₁₁ (G _1), whereby, it said buffer circuit has a hysteresis characteristic. The output of this buffer circuit is inverted by the NOT circuit (G ₃ ) and connected to one input of the NOR circuit (G ₇ ). The output of the NOT circuit (G ₃ ) is inverted by the NOT circuit (G ₄ ) at the next stage and input to the integrating circuit including the resistor R ₁₂ and the capacitor C ₅ . The output of the integrating circuit, while being applied to one input of the NOR circuit (G ₅₎ via a resistor R _13, is inputted to the NOT circuit (G _6), NOT output NOR circuit of the circuit (G ₆₎ Connected to the other input of (G ₇ ). The output of the NOT circuit (G ₄ ) is connected to the other input of the NOR circuit (G ₅ ).

The output of the NOR circuit (G ₅ ) goes through the resistor R ₁₆ to the transistor Q ₆
Connected to the base of. When the transistor Q ₆ is turned on, the base of the transistor Q ₃ is grounded through a resistor R _14, so that the transistor Q ₃ is turned on.
The output of the NOR circuit (G ₇ ) is connected to transistor Q via resistor R _6.
It is connected to the base of ₁ and the output of NOR circuit (G ₇ ) is H
At the level, transistor Q ₁ is turned on. NOR circuit (G ₇ ) outputs NOT circuit (G ₈ ),
(G ₉ ) buffer circuit also functioning as a delay circuit and resistor R
It is connected to the base of the transistor Q ₄ via ₁₅ and. When the transistor Q ₄ is turned on, the base of the transistor Q ₂ is grounded via a resistor R _5, so that the transistor Q ₂ is turned on.

2 (a) to (i) are (a) to (i) in the circuit of FIG.
The operation waveforms of the parts denoted by the reference symbol (i) are shown. First, when the AC power supply AC is energized, as shown in FIG. 2 (a), the charging voltage of the capacitor C ₄ is at the H level, so the buffer circuit composed of the NOT circuits (G ₁ ) and (G ₂ ) Output becomes H level as shown in FIG. At this time, the outputs of the NOT circuits (G ₃ ) and (G ₄ ) are
As shown in (d), it becomes L level and H level, respectively. Since the output of the NOT circuit (G ₅ ) is at the H level, the voltage of the capacitor C ₅ becomes the H level as shown in the same figure (e) in the steady state, and the output of the NOT circuit (G ₆ ) becomes the same figure. It is at the L level as shown in (f). Therefore, NO
Since the output of the R circuit (G ₇ ) becomes H level as shown in the figure (g), the transistor Q ₁ turns on and the relay coil L ₁
Is excited, relay contacts SW ₁ and SW ₂ are switched to the normally open (NO) side, and lamp FL is turned on for commercial use. At this time, the output of the NOT circuit (G ₉ ) is also at H level, so
Q _4, G ₂ are ON, the storage battery BT is charged by the commercial power source AC. On the other hand, since the output of the NOR circuit (G ₅ ) is at H level, the transistors Q ₆ and Q ₃ are in the off state, and the inverter circuit INV is not operating.

Next, when the AC power supply AC fails, the NOT circuit (G ₃ )
The output of the NOR circuit is inverted to the H level, the output of the NOR circuit (G ₇ ) becomes the L level, the transistor Q ₁ is turned off, and the relay contacts SW ₁ and SW ₂ are switched to the normally closed (NC) side. At this time, since the output of the NOT circuit (G ₉ ) is at L level,
Transistor Q _4, Q ₂ is turned off. The output of the NOR circuit (G ₅ ) becomes H level with a delay from the above operation by the time required for discharging the capacitor C ₅ , and the output of the transistor Q ₆ ,
Q ₃ turns on, the inverter circuit INV starts oscillating, and the lamp FL lights up in an emergency.

Thus, in the present embodiment, when the voltage is gradually increased when the AC power supply AC is restored, the output voltage of the insulating transformer T ₁ also rises.
Since Q ₂ is off, the output voltage of the insulating transformer T ₁ does not fluctuate even if the battery voltage of the storage battery BT fluctuates, and the switching voltage can be set to a constant value. In the present embodiment, as described above, the switching operation is performed more reliably by applying the positive feedback to the buffer circuit including the NOT circuits (G ₁ ) and (G ₂ ) with the resistor R ₁₁ . I am trying to get it.

Second Embodiment FIG. 3 is a circuit diagram of an essential part of another embodiment of the present invention,
FIG. 3 is a diagram showing operation waveforms of respective parts of the circuit shown in FIG. In this embodiment, the structure of the portion surrounded by the broken line in FIG. 3 is different from that of the previous embodiment. That is, the output of the NOR circuit (G ₇ ) is input to the NOT circuit (G ₈ ) and
It is input to the integrator circuit consisting of resistor R ₁₉ and capacitor C ₈ . The output of the NOT circuit (G ₈ ) is the output of the NOR circuit (G
It is connected to one input of ₁₀ ) and (T ₁₁ ). The other input of the NOR circuit (G ₁₀ ) is connected to the resistor R ₁₉ and capacitor C ₈
The integrating output of the integrating circuit is applied via a resistor R ₂₀ . In addition, the other input of the NOR circuit (G ₁₁ )
The output of the R circuit (G ₁₀ ) is connected. NOR circuit (G ₁₁ )
Is applied to the base of transistor Q ₄ via resistor R ₁₅ . According to this embodiment, the configuration described above delays the time until the transistor Q ₂ turns on after the AC power source AC is restored by the time t ₁ determined by the resistor R ₁₉ and the capacitor C _8. Then, the relay R _y is moved by impressing movement within this time t ₁ . That is,
In this embodiment, when the output of the NOR circuit (G ₇ ) (Fig. 4 (g)) becomes H level, the output of the NOT circuit (G ₈ ) (Fig. 4 (l)) becomes L level. Since the terminal voltage of the capacitor C ₈ (Fig. 4 (nu)) gradually rises from the L level to the H level, the NOR circuit (G ₁₀ ) of the NOR circuit (G ₁₀ ) waits until the capacitor C ₈ is charged. The output (Fig. 4 (o)) becomes H level, and the output of the NOR circuit (G ₁₁ ) (Fig. 4 (w)) becomes L level. The voltage of the capacitor C ₈ is NOR circuit (G ₁₀₎
When the threshold voltage rises to, the output of the NOR circuit (G ₁₀ ) becomes L level and the output of the NOR circuit (G ₁₁ ) becomes H level. Therefore, in this embodiment, t ₁ is turned on after the transistor Q ₁ is turned on and before the transistor Q ₄ is turned on.
Is caused by the delay time. By doing so, the switching voltage of the relay can be made constant, and the relay can be driven by cutting off the charging circuit. Therefore, a high voltage can be obtained as the output voltage of the insulating transformer T ₁ , and the switching of the relay can be performed. The operation can be surely performed.

(Effect of the invention) In the present invention, as described above, the charging circuit for charging the storage battery is provided with the output side of the isolation transformer via the switch element that is opened during the power failure detection period by the charge detection circuit. Therefore, during the power failure detection period by the power failure detection circuit, the charging circuit for charging the storage battery and the inverter circuit fed from the storage battery are disconnected from the output side of the insulation transformer. Therefore, the output voltage of the insulation transformer when the AC power is restored is determined regardless of the battery voltage of the storage battery and the operating state of the inverter circuit, and therefore the switching voltage of the power failure detection circuit is constant. There is. Further, during emergency lighting in which power is being supplied from the storage battery to the inverter circuit, charging current does not flow from the commercial power source to the storage battery, so the storage battery does not enter into a floating charging state and deterioration of the storage battery can be prevented. There is.

In the case of using a circuit configuration in which charging is displayed when a charging current is flowing in the storage battery, in the conventional example, when the commercial AC power supply voltage is low, that is, the power is not completely restored. There is a possibility that a small amount of charging current may flow and a charging display may be made, but in the present invention, such an erroneous charging display may not occur.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is an operation explanatory diagram of the same as above, and FIG. 3 is a main part circuit diagram of another embodiment of the present invention.
FIG. 4 is an operation explanatory view of the above, FIG. 5 is a circuit diagram of a conventional example,
FIG. 6 is a diagram for explaining the operation of the above. 1 is a power failure detection circuit, 2 is a switch element, 3 is a charging circuit,
AC is an AC power supply, T ₁ is an insulation transformer, FL is a lamp, BT is a storage battery, and INV is an inverter circuit.

Claims (1)

[Claims] 1. An insulation transformer connected to an AC power supply, and a power failure connected to the output side of this insulation transformer to detect a power failure of the AC power supply by stopping energization, and an inverter circuit is driven by a storage battery during the power failure detection period. Then, the lamp is turned on, and a power failure detection circuit that switches the power supply of the lamp so that the lamp is turned on by the AC power supply during the non-power failure detection period, and a switch element that is opened during the power failure detection period by the power failure detection circuit, A switching circuit comprising: a charging circuit connected to the output side of the insulation transformer via a switch element to charge the storage battery.