JPH05191919A - Power source on/off relay circuit - Google Patents

Abstract

PURPOSE:To attempt space saving and cost reduction by implementing a fuseless disconnection of source supply when an abnormal current is created. CONSTITUTION:A power source relay is arranged on the primary side of a main power source transformer. At the same time, a constant-voltage power source which can be active all the time is arranged. A driving current runs from the constant-voltage power source to the power source relay when the power source is turned on. An excess current detection means (a comparator 50 and a logic unit 56) is provided on the secondary side of the main power source transformer for detecting any excess of a charged current. If required, an excess current period determining means (a time constant circuit 58) may be provided. Thus, the power source relay is automatically turned off when the excess current detection means or excess current period determining means is activated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to power-on / off / power-on of various consumer equipment including audio equipment.
Regarding the relay circuit.

[0002]

2. Description of the Related Art FIG. 4 shows a circuit configuration of a conventional power on / off relay circuit.

A constant voltage power source 10 connected to an outlet 2 via a sub-transformer 4, a rectifying diode 6 and a smoothing capacitor 8, a relay coil of a power source relay 12 and a relay.
A series circuit of drive transistors 14 is connected. The base of the relay drive transistor 14 is connected to the power supply control port of a system microcomputer (not shown). The power relay 12 is a tap changeover switch 1
6, connected to the primary winding of the main power transformer 18 via current fuses F1 to F4. The secondary winding of the main power supply transformer 18 is connected to the full-wave rectification diode 20, and a series circuit of smoothing capacitors C11 and C12 is connected between both ends of the full-wave rectification diode 20.
The common connection point of 11 and C12 is grounded. The positive electrode of one capacitor C11 is a positive DC power source (+ B), and the negative electrode of the other capacitor C12 is a negative DC power source (-B).

When the power switch of the main body of the equipment or the power key of the remote controller is turned on, the system microcomputer outputs an "H" level to the relay drive transistor 14, which turns on the transistor 14 to turn on the constant voltage power supply 10. Power is supplied to the relay coil of the power relay 12 to turn on the power relay 12. As a result, current flows from the outlet 2 to the primary winding of the main power transformer 18 via the power relay 12 and the tap changeover switch 16, and the alternating current induced in the secondary winding causes the full-wave rectifying diode 20 and the smoothing capacitor. DC power is generated by C11 and C12, and DC power supplies (+ B) and (-B) are generated.

Contrary to the above, when the power switch of the main body of the device or the power key of the remote controller is turned off, the power relay 12 is turned off and the DC power (+ B),
(-B) disappears.

In the ON state of the power relay 12, if for some reason an abnormal current exceeding the rating flows,
An overcurrent flows through a current fuse being used among the current fuses F1 to F4, and the current fuse is blown to stop the power supply, thereby protecting each part of the circuit from an abnormal current.

[0007]

In the above-mentioned conventional example, a current fuse is provided on the primary side of the main power supply transformer 18 as a protection circuit for safety measures. The creepage distance must be secured, and the required space becomes large. Further, in a device compatible with multiple power supplies as shown in the drawing, it is necessary to provide current fuses having different ratings for each tap of the primary winding, which is likely to be disadvantageous in terms of cost.

It is conceivable that a current fuse may be inserted at points P and Q on the secondary side of the main power transformer 18 instead of being provided on the primary side, but a DC power source (+ B),
When the voltage of (-B) is high and the capacity of the smoothing capacitors C11 and C12 is large (for example, in the case of a high power amplifier), the smoothing capacitor C1 when the power relay 12 is on.
The inrush current to the C1 and C12 becomes large, and the current fuse may be blown by the inrush current, which is not preferable.

Further, when the current fuse is used as the protection circuit, its arrangement position is restricted due to the necessity of replacement.
That is, it must be arranged in a portion of the device body casing that is exposed to the outside or a portion that can be easily exposed.

The present invention was devised in view of such circumstances, and it is an object of the present invention to realize power supply cutoff when an abnormal current occurs without using a fuse.

[0011]

A first power source ON / OFF relay circuit according to the present invention is provided with a power source relay on the primary side of a main power source transformer and a constant voltage power source which is always active. In a power-on / off-relay circuit configured to flow a drive current from the constant-voltage power supply to the power-supply relay to turn on the power-supply relay by a power-on operation, 2 of the main power-supply transformers are provided.
It is characterized in that an overcurrent detection means for detecting an excessive load current is provided by utilizing a voltage change on the secondary side, and the power relay is automatically turned off when the overcurrent detection means operates. It is what

The second power source on / off relay circuit according to the present invention is provided with a power source relay on the primary side of the main power transformer and a constant voltage power source which is always active to turn on the power source. In a power on / off relay circuit configured to flow a drive current from the constant voltage power supply to the power relay to turn on the power relay, the voltage change on the secondary side of the main power transformer is used. And an overcurrent detection means for detecting an excess of the load current, and an overcurrent time determination means for determining whether or not the overcurrent detection state continues for a predetermined time or longer when the overcurrent detection means operates. The power supply relay is automatically turned off when the overcurrent time determination means determines that it is in the overcurrent detection state for a predetermined time or more. It is characterized in that the.

[0013]

According to the first power on / off relay circuit,
When the overcurrent detection means provided on the secondary side of the main power supply transformer detects the overcurrent, the power supply relay on the primary side is turned off and the power supply is automatically stopped. Since it is configured to also serve as a protection circuit for safety measures, it is not necessary to provide a current fuse on the primary side or the secondary side of the main power transformer.

According to the second power on / off relay circuit, the power relay is turned off when the overcurrent detection state by the overcurrent detection means continues for a predetermined time or longer, but the overcurrent detection state is predetermined. When the time is less than the specified time, the power relay is configured to remain in the ON state.Therefore, it is possible to clearly distinguish between overcurrent detection due to an abnormality and overcurrent detection due to a temporary overload during normal operation, and The power will be shut off only at times.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a power on / off relay circuit according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 and FIG. 2 show the power-on and
It is a circuit diagram which shows the structure of an off-relay circuit. Connection points a to e in FIG. 1 correspond to the connection points a to e in FIG. 2, respectively.

In FIG. 1, 30 is an outlet, 32 is a relay sub-transformer, D1 is a rectifying diode, C1 is a smoothing capacitor, 34 is a constant voltage power supply, 36 is a system microcomputer, 36a is a power supply control port, 38 is a power switch, Tr1 is a relay control transistor, and Tr2 is a relay drive transistor. 40 is a power relay, 4
2 is a tap changeover switch, 44 is a main power transformer,
46 is a full wave rectifier diode, C2 and C3 are smoothing capacitors, (+ B) is a positive DC power source, (-B) is a negative DC power source, R1, R2, R3 and R4 are voltage dividing resistors, 48
Is a full wave rectifier diode, C4 and C5 are smoothing capacitors,
(+ B ₁ ) is a positive DC power source, and (−B ₁ ) is a negative DC power source. DC power supplies (+ B) and (-B) are supplied to a load circuit (not shown) (for example, an audio amplifier circuit). DC power supplies (+ B ₁ ) and (-B ₁ ) are shown in Fig. 2.
Are supplied to the circuit shown in. Main power transformer 44
No current fuse is used on either the primary side or the secondary side.

In FIG. 2, reference numeral 50 is a comparison unit, and 52 and 54.
Is a comparator, 56 is a logic unit, Tr3 and Tr4 are transistors, D2 and D3 are switching diodes, and 58
Is a time constant circuit, D5 is a backflow prevention diode, C6 is a charge / discharge capacitor, R5 is a ground resistance, Tr5 is a transistor, R6 is a base resistance of the transistor Tr5, R7 is an emitter ground resistance, 60 is an inverter circuit, and Tr6 is for inversion. Transistor 62 is a circuit for separating the inverter circuit 60 from the control transistor Tr9 when the power is turned on, Tr
7 is a PNP type transistor, Tr8 is a transistor,
D6, D7 are backflow prevention diodes, R8 is an integration resistance, C
Reference numeral 7 is an integrating capacitor, 64 is a control unit, Tr9 is a control transistor, and Tr10 is a switching transistor.

FIG. 3 shows current-voltage characteristics in a load circuit (not shown) to which DC power supplies (+ B) and (-B) are supplied. The characteristic curve is such that the magnitude (absolute value) of the supplied voltage gradually decreases as the load current increases. A current i ₁ slightly larger than the rated current i ₀ is used as a reference, and a current larger than the reference current i ₁ is used for a predetermined time T.
It is assumed that an abnormal state is when it continues for ₀ or more. That is, it is assumed that the overcurrent has flown into the load circuit.
The voltage corresponding to the reference current i ₁ is V _{1 on} the plus side and V ₂ on the minus side. Their sizes are almost equal,
V ₁ | ≈ | V ₂ |.

The inverting input terminal (-) of the comparator 52 in the comparison section 50 is connected to the connection point of the voltage dividing resistors R1 and R2. The input voltage to the comparator 52 is V _X. Non-inverting input terminal (+) of comparator 52
The comparison reference voltage Vref ₁ given to the reference voltage Vref is defined as follows in relation to the reference voltage V ₁ shown in FIG.

Vref ₁ = {R2 / (R1 + R2)} × V _{1 Further} , the non-inverting input terminal (+) of the comparator 54 in the comparison section 50 is connected to the connection point of the voltage dividing resistors R3 and R4. The input voltage to this comparator 54 is V _Y
Is. Inverting input terminal of the comparator 54 (-) reference voltage Vref ₂ applied to the are determined as follows in relation to the voltage V ₂ of the criteria shown in FIG.

In the Vref ₂ = {R3 / (R3 + R4)} × V ₂ comparator 52, the comparator is provided only when the input voltage V _X is lower than the comparison reference voltage Vref ₁ , that is, when V _X <Vref _1. The output voltage of 52 is "H"
It becomes a level. This corresponds to the hatched portion in FIG. 3 and corresponds to the overcurrent detection state.

In the comparator 54, the input voltage V
When _Y is higher than the comparison reference voltage Vref _2, i.e., only when the V _Y> Vref _2, the output voltage of the comparator 54 is "H"
It becomes a level. This also corresponds to the hatched portion in FIG. 3 and corresponds to the overcurrent detection state.

The logic in the logic unit 56 is as follows. When at least one of the input voltages V _X and V _Y rushes into the hatched portion (overcurrent state) in FIG. 3, that is, when an overcurrent occurs on either the plus side or the minus side in the load circuit, Logic 56
Of the output voltage V _Z is set to the “L” level. Summary, Becomes

Next, the power-on /
The operation of the off relay circuit will be described.

First, the state in which the power relay 40 is off will be described.

The AC voltage supplied from the outlet 30 is stepped down by the relay sub-transformer 32, rectified by the rectifying diode D1, smoothed by the smoothing capacitor C1 and converted into a direct current, which is supplied to the constant voltage power source 34 and fixed. A constant DC power supply V _DD is supplied from the voltage power supply 34 to the system microcomputer 36, a relay coil of the power supply relay 40,
It is supplied to the collector of the relay control transistor Tr1. However, since the "H" level is currently output from the power supply control port 36a of the system microcomputer 36 and the relay control transistor Tr1 is in the conducting state, the relay drive transistor Tr2 is in the non-conducting state. The power relay 40 is off.

When the power switch 38 or the power key of the remote controller (not shown) is pressed once,
The power supply control port 36a of the system microcomputer 36 outputs "L" level, and when the button is pressed again, the power supply control port 36a outputs "H" level. That is, the power control port 36a is "H",
The toggle operation is such that "L" is alternately repeated.

Now, the relay drive transistor Tr
When the power switch 40 or the power key of the remote controller is pressed when the power relay 40 is in the off state and the power supply relay 2 is in the non-conductive state, the power control port 36a of the system microcomputer 36 outputs the "L" level, Since the relay control transistor Tr1 is turned off, the relay drive transistor Tr2 is turned on. Therefore, current flows from the constant voltage power supply 34 to the relay coil of the power supply relay 40, and the power supply relay 40 is turned on.

When the power relay 40 is turned on, the power relay 40 and the tap changeover switch 4 are switched from the outlet 30.
A current flows through the primary winding of the main power transformer 44 via 2 and the alternating current induced in the secondary winding and stepped down is converted into a direct current by the full-wave rectifier diode 46 and the smoothing capacitors C2 and C3, and a direct current power source ( + B), (-B), a full-wave rectifying diode 48 and a smoothing capacitor C
4, converted to DC by C5, DC power supply (+ B ₁ ),
(-B ₁ ) is generated. DC power supplies (+ B) and (-B) are supplied to a load circuit (not shown). DC power supply (+
_{B 1), (- B 1} ) is is supplied as a high potential side power supply and the low potential side power source of the comparator 52 of the comparison unit 50 shown in FIG. 2, a DC power source (+ B ₁₎ is a logical unit 5
6, the time constant circuit 58, the inverter circuit 60, and the separation circuit 62.

When the current flowing through the load circuit is normal,
That is, when the current is smaller than the reference current i ₁ in FIG. 3 (when it is not a hatched portion), the input voltage V _X of the comparator 52 is higher than the comparison reference voltage V ref ₁ and the input voltage V _Y of the comparator 54 is the comparison reference. Since it is lower than the voltage Vref _2, the output voltages of both comparators 52 and 54 are both at "L" level.

At this time, since the transistors Tr3 and Tr4 in the logic section 56 are both non-conducting, the switching diodes D2 and D3 are both non-conducting.

Therefore, the output voltage V _Z of the logic section 56 is at the "H" level, and the charging / discharging capacitor C6 of the time constant circuit 58 is being charged through the backflow prevention diode D5. This charging voltage is applied to the transistor T
Since it is applied to the base of r5, this transistor Tr5 is in a conductive state, the inversion transistor Tr6 in the inverter circuit 60 is also in a conductive state, and its collector is set to the "L" level by grounding via the transistor Tr6. Is becoming Therefore, the separation circuit 6
The transistor Tr7 in 2 is in a non-conducting state, and the control transistor Tr9 in the control unit 64 is in a non-conducting state because its base is at the GND level,
The switching transistor Tr10 is also kept non-conductive.

The transistor Tr8 in the separation circuit 62 is designed to be in a non-conducting state immediately after the power relay 40 is switched from the off state to the on state. That is, the transistor Tr8 is integrated by the integrating circuit including the integrating resistor R8 and the integrating capacitor C7.
This is because the base potential of is slowly raised.

If the transistor Tr8 is instantly turned on when the power relay 40 is turned on, the transistor Tr7 is also turned on, the control transistor Tr9 is turned on, and the switching transistor T is turned on.
Since r10 conducts, the power supply control port 36a of the system microcomputer 36 outputs "H" level by the toggle operation based on the conduction of the switching transistor Tr10 immediately after outputting "L" level to turn on the power supply relay 40. As a result, the power relay 40 cannot be turned on.

In order to surely turn on the power relay 40, a separating circuit 62 having an integrating resistor R8, an integrating capacitor C7 and a transistor Tr8 is inserted between the inverter circuit 60 and the control section 64. .. After the transistor Tr6 of the inverter circuit 60 surely becomes conductive and its collector becomes "L" level,
Even if the transistor Tr8 of the separation circuit 62 changes from the non-conducting state to the conducting state, the transistor Tr7 remains in the non-conducting state, and there is no problem.

Next, the current flowing in the load circuit is shown in FIG.
Of the reference current i ₁ (when entering the hatched portion), that is, the input voltage V _X of the comparator 52 becomes lower than the comparison reference voltage V ref ₁ or the input voltage V of the comparator 54. Consider a case where _Y becomes higher than the comparison reference voltage Vref ₂ .

In this case, one of the output voltages of the two comparators 52 and 54 becomes "H" level and one of the transistors Tr3 and Tr4 in the logic section 56 becomes conductive, so that either one of the switching diodes D2 and D3 is turned on. Becomes conductive. Therefore, the output voltage V _Z of the logic unit 56 becomes the “L” level, and the time constant circuit 58
The charging of the charging / discharging capacitor C6 at is stopped.

Then, the charge charged in the charge / discharge capacitor C6 becomes the ground resistance R5 and the base resistance R6 of the transistor Tr5.
And is discharged via the grounded-emitter resistor R7. The discharge time constant τ is a combined resistance value of these parallel resistances, where R ₅ is the resistance value of the ground resistance R5 and R _in is the total resistance value of the transistor Tr5 side including the base resistance R6 and the grounded emitter resistance R7. Is (R ₅ + R _in ) / (R ₅ · R
_in ), the capacitance of the charging / discharging capacitor C6 is C
₆ , τ = C ₆ · (R ₅ + R _in ) / (R ₅ · R _in ).

If the state of discharge from the charging / discharging capacitor C6 continues for a predetermined time T ₀ or more due to the generation of overcurrent in the load circuit, the charging voltage of the charging / discharging capacitor C6 becomes lower than the conduction voltage of the transistor Tr5. At this time,
This transistor Tr5 is inverted from the conductive state to the non-conductive state. Then, the transistor Tr6 in the inverter circuit 60 is inverted from the conducting state to the non-conducting state, and its collector becomes "H" level by the DC power source (+ B ₁ ). Since the transistor Tr8 of the separation circuit 62 is conductive, when the collector of the transistor Tr6 is inverted to the “H” level, the transistor Tr7 is conductive and the control transistor Tr9 in the control unit 64 is also conductive and the base of the switching transistor Tr10. The potential is GND
In order to fall to the level, the switching transistor Tr10 is switched from the non-conducting state to the conducting state.

Then, the toggle operation of the system microcomputer 36 causes the power supply control port 36a, which has been outputting the "L" level until then, to output the "H" level.
As a result, the relay control transistor Tr1 becomes conductive and the base potential of the relay drive transistor Tr2 drops to the GND level, so that the relay drive transistor Tr2 is switched to the non-conductive state, and the power supply relay 40 is turned off.

That is, when an abnormal state occurs in which an overcurrent continues for a predetermined time T ₀ or more in the load circuit, the power supply relay 40 is automatically turned off and the power supply to the load circuit is automatically cut off. Therefore, each part of the circuit can be protected from the abnormal current. Further, the current fuse is not blown out, and therefore, the troublesome replacement of the current fuse is not necessary.

The output voltage V _Z of the logic section 56 becomes "L" level not only when an abnormal current occurs in the load circuit. For example, even when a loud sound is momentarily output from a music source in an audio device, a large current may flow and the output voltage V _Z may be at “L” level.

However, since it is caused by the music source, the output voltage V _Z becomes "L" level for a moment and returns to "H" level again. Even if the output voltage V _Z goes to the “L” level for a moment and the charging / discharging capacitor C6 in the time constant circuit 58 is discharged, the transistor Tr5 is not switched to the non-conducting state, and the output voltage V _Z is not reached. Returns to "H" level to charge the charging / discharging capacitor C6. By setting R ₅ to be sufficiently larger than R _in , the charging / discharging capacitor C
Charging to 6 can be done quickly.

As described above, even if the output voltage V _Z becomes "L" level momentarily due to the music source,
Due to the presence of the time constant circuit 58, it is possible to avoid a malfunction that unexpectedly switches the power supply relay 40 to the off state.

Some load circuits are always in an abnormal state when the current exceeds the reference current i ₁ . For such a load circuit, the time constant circuit 5
8 is not necessary, and the output voltage V _Z of the logic unit 56 is directly input to the base of the transistor Tr6 of the inverter circuit 60.

Further, the power supply relay 40 may be a contactless relay using a semiconductor element in addition to the electromagnetic relay shown in the figure. The tap changeover switch 42 may not be provided.

[0048]

According to the first power source on / off relay circuit of the present invention, the power source relay is configured to also serve as a protection circuit for safety measures against overcurrent, and the power source when an abnormal current occurs. Since the disconnection is realized without a fuse, the degree of freedom in routing the circuit is increased, and space saving and cost reduction can be achieved.

According to the second power on / off relay circuit of the present invention, in addition to the above effects, overcurrent detection due to an abnormality and temporary overload during normal operation are caused. Since the power supply relay is turned off only when there is an abnormality, it is possible to prevent a malfunction during a temporary overload, by distinctly distinguishing it from the above-described overcurrent detection.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a half of a power on / off relay circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing the other half of the power supply ON / OFF relay circuit of the above embodiment.

FIG. 3 is a current-voltage characteristic curve diagram in the load circuit in the example.

FIG. 4 is a circuit diagram showing a power on / off relay circuit according to a conventional example.

[Explanation of symbols]

32 Relay Sub-transformer 34 Constant Voltage Power Supply 36 System Microcomputer 36a Power Supply Control Port 40 Power Supply Relay 44 Main Power Supply Transformer 46 Full Wave Rectifier Diode 50 Comparing Section 52 Comparator 54 Comparator 56 Logic Section 58 Time Constant Circuit 60 Inverter Circuit 62 Separation Circuit 64 controller Tr1 relay control transistor Tr2 relay drive transistor Tr9 control transistor Tr10 switching transistor C1 smoothing capacitor C2 smoothing capacitor C6 discharge capacitor C7 integrating capacitor R1~R4 dividing resistor R5 ground resistor R7 grounded emitter resistor R8 integrating resistor V _X, V Input voltage to _Y comparison part V _Z Output voltage of logic part

Claims (2)

[Claims] 1. A power supply relay is provided on the primary side of a main power supply transformer, and a constant voltage power supply that is always active is provided, and a drive current is supplied from the constant voltage power supply to the power supply relay by a power-on operation. In a power on / off relay circuit configured to turn on a power relay, an overcurrent detecting means for detecting an excessive load current by utilizing a voltage change on the secondary side of the main power transformer is provided, A power-on / off-relay circuit configured to automatically turn off the power relay when the overcurrent detecting means operates. 2. A power supply relay is provided on the primary side of the main power supply transformer, and a constant voltage power supply that is always active is provided, and a drive current is supplied from the constant voltage power supply to the power supply relay by a power-on operation. In a power on / off relay circuit configured to turn on a power relay, an overcurrent detecting means for detecting an excessive load current by utilizing a voltage change on the secondary side of the main power transformer is provided. An overcurrent time determination means for determining whether the overcurrent detection state continues for a predetermined time or longer when the overcurrent detection means operates, and the overcurrent time determination means extends the overcurrent detection state for a predetermined time or longer. The power-on / off-relay circuit is configured to automatically turn off the power relay when it is determined that