JPS6123850Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a protection device for a changeover switch to prevent damage to the changeover switch due to inrush current during load switching.

[Summary of the idea]

The present invention provides a protection device for a switch that prevents damage to the switch due to an inrush current that flows during the switching operation of a first switch for load switching. By opening the contacts of the load protection relay means with the switch, it is possible to use a switch with a small current capacity, and an increase in switching noise is prevented.

[Conventional technology]

As is well known, recent audio equipment, especially amplifiers, are designed to respond to this versatility by allowing selective switching between multiple modes using one or more switches. Not only are there different types of mode switching, such as switching between a record player and a tape recorder, but also devices that selectively connect three tape recorders connected at the same time to an amplifier one by one, or that selectively connect many speakers connected at the same time to an amplifier one by one, are widely used, responding to the diversification of users' audio preferences.

By the way, in such mode switching, etc., when the contacts of the switch are opened and closed by the switching operation, an abnormally large surge current flows in the current path, and the above-mentioned switch connected to the current path exceeds the current capacity. It may be destroyed by twisting. For this reason, it is necessary to use a switch with a large current capacity, and since expensive and large structural members are used, there are disadvantages such as an unavoidable increase in the price of the switch.

In order to solve this problem, a device constructed as shown in FIG. 1 has been proposed as an earlier example of the present invention.

In the example shown in FIG. 1, a second switch, which is turned on immediately before the first switch is turned on or off, and which is turned off when the switch is in steady state, is associated with the first switch, and the second switch is turned on immediately before the first switch is turned on or off. Either the input level or the output level of the amplifier that supplies the current is controlled to be reduced by the above switch, thereby preventing it from being destroyed by the rush current generated when the first switch is switched. This is a protection device for the switch.

That is, the switch protection device shown in FIG.
For example, it is used in a speaker switching circuit, 1 is a signal source of an audio signal, an amplifier 2 for amplifying the audio signal is connected to this signal source 1, and a protection circuit 3 for the speaker against direct current is connected to this amplifier 2. has been done. Further, a switch 6 is connected to the output side of the protection circuit 3 for selectively connecting a plurality of speakers 4 and 5 to the protection circuit 3. This switch 6 consists of four fixed contacts 6a, 6b, 6c, 6d and one movable contact piece 6e, and by sliding the movable contact piece 6e, the fixed contact 6d is connected to each other via the movable contact piece 6e. It is connected to fixed contacts 6a, 6b and 6c. By means of such a mechanism, audio signals are supplied to the speakers 4 and 5, or the supply of audio signals to both speakers 4 and 5 is cut off.

On the other hand, on the input side of the amplifier 2, a protection switch 7 is interposed between this and ground. This protection switch 7 has four fixed contacts 7a, 7b,
7c, 7d and one movable contact piece 7e, the fixed contacts 7a, 7b, 7c are mutually connected, and by sliding the movable contact piece 7e, the movable contact piece 7e
The fixed contact 7d is connected to the fixed contact 7 via e.
selectively connected to a, 7b and 7c. In this connected state, the audio signal on the input side of the amplifier 2 is grounded, and what is important here is that the switch 6 and protection switch 7 are interlocked. Immediately before each of the fixed contacts 6a to 6d and the movable contact piece 6e of the switch 6 are disconnected (transient state)
In this case, the movable contact piece 7e of the switch 7 is
The fixed contact 7d can be switched to be connected to other fixed contacts 7a to 7d.

Therefore, in the above circuit, when listening to the sound from the sound source 1 through the speaker 5 and switching the sound to the speaker 4 as needed, the movable contact piece 6e of the switch 6 is moved upward. Move in the direction of the arrow and connect the fixed contact 6d to the fixed contact 6.
b to the fixed contact 6a. At this time, at the moment when the movable contact piece 6e leaves the fixed contact 6d and at the moment when it comes into contact with the fixed contact 6a, an inrush current flows through these contacts 6e, 6b,
6a and the speakers 4 and 5, but in reality, at these moments, that is, during the transient period, one of the fixed contacts 7a to 7c is connected to the fixed contact 7d via the movable contact piece 7e. Since the input of the amplifier 2 is grounded,
The output decreases or becomes zero, and the inrush current no longer appears.

[Problem that the invention attempts to solve]

However, in the example that precedes the present invention as described above, the switch 7 is connected to the input side of the amplifier 2, so when the switch 7 operates on and off in conjunction with the switch 6, the switching The resulting noise is amplified by the amplifier 2 and supplied to the speaker, which is not only harsh on the ears, but may also have an adverse effect on the speaker, such as damage or destruction. Furthermore, since the switch 7 is connected to the audio signal line through which the audio signal current flows, the switch 7 also requires a certain amount of current capacity.

In addition, when installing a load changeover switch with a large current capacity on the output side, as mentioned above, a switch with a large current capacity is not only expensive and expensive, but also has difficulty in contacting at low output. However, there are drawbacks such as the switch itself being large and requiring extra space.

In view of the above-mentioned problems, the present invention has been devised to provide a protection device for the switch that can prevent damage to the switch due to inrush current when using a switch with a small current capacity, and that does not have adverse effects such as amplification of noise or an increase in the number of parts. The purpose is to provide

[Means for solving problems]

The present invention consists of a relay switch and a first switch for load switching connected in series to the output terminal of an amplifier, a low-pass filter connected to the output terminal of the amplifier, and a low-pass filter connected to the output of the low-pass filter. a switching element that is turned on when the DC output exceeds a predetermined value; a load protection relay that opens the relay switch when the switching element is turned on; and a load protection relay that is turned on immediately before the first switch is turned on or off. and a second switch that is turned off during normal operation, and when the second switch is turned on, the switching element is turned on to prevent the load switching switch from being destroyed by high current. This switch protection device solves the above problems.

[Effect]

The switch protection device of the present invention utilizes an existing load protection circuit, for example, a speaker protection circuit, and uses a relay switch provided in the speaker protection circuit for inrush current cutoff operation to protect a load switching switch. Use as is. In other words, by associating the relay means such as the existing speaker protection circuit with the first switch and the second switch, it is possible to effectively eliminate adverse effects such as switching noise without increasing the number of parts. It has the effect of

〔Example〕

A preferred embodiment of the present invention will be described with reference to FIG. In FIG. 2, the same reference numerals are given to the same parts as those shown in FIG. 1, and the explanation thereof will be omitted.

FIG. 2 shows a switch protection circuit showing an embodiment of the present invention, in which the first switch 6 and the second switch 7 are connected in the conventional speaker protection circuit 3 as shown in FIG. , is connected to the output side of the amplifier 2 from the viewpoint of noise prevention.

In FIG. 2, reference numeral 8 is a switching contact of a relay to be described later, which is interposed between the amplifier 2 and the switch 6, and is opened when an ultra-low frequency component as shown in waveform a appears. The current to the load to the speakers 4 and 5 is cut off. Further, the base of a transistor 11 is connected to the output side of the amplifier 2 via a low-pass filter consisting of a resistor 9 and a capacitor 10.
Its collector is connected to the base of another control transistor 13 via a resistor 12, and its emitter is directly connected. The collector of the transistor 11 is connected to the collector of a detection transistor 14, the base of the transistor 11 is connected to the emitter of the transistor 14, and the base of the transistor 14 is grounded. Furthermore, the emitter of the transistor 13 is connected to a resistor 15.
The emitter is connected to the supply voltage source terminal 16 via the collector, and the collector is connected to the base of a transistor 18 that drives a relay coil 17. The switch 7 and the capacitor 19 are connected in parallel between the emitter and collector of the transistor 13, and the parallel resistor 20 is connected between the terminal 16 and the base of the transistor 18. Furthermore, the emitters of the transistors 13 and 18 are connected to each other. 21 is the above relay coil 1
This is a spark killer connected in parallel to 7.

First, the operation of the speaker protection circuit will be briefly described. When an audio current of a positive predetermined level or higher is obtained from the output side of the amplifier 2 through the low-pass filter, the transistor 11 is turned on, and the voltage across the resistor 12 decreases, so the transistor 13 is turned on. becomes.
Therefore, the base potential of the transistor 18 rises and is kept in the off state, and the relay coil 17 connected in series therewith is kept in the deenergized state and is therefore controlled by it. Since the relay contact 8 is open, the supply of signals to the speakers 4 and 5 is cut off. Similarly, when an audio current of less than a predetermined negative level is obtained on the output side of the amplifier 2, the transistor 14 is turned on, and the same operation as described above causes a large amount of noise to be applied to the speakers 4 and 5. The supply of audio current is cut off, and both speakers 4 and 5
will be protected.

On the other hand, as mentioned above, when selectively switching and connecting the speakers 4 and 5 to the amplifier 2, the movable contact piece 6e of the switch 6 is slid.
When the fixed contacts 6a to 6c are selectively connected to the fixed contact 6d, the movable contact piece 7e of the switch 7 connects to the fixed contact 7d immediately before the connection.
By connecting the transistor 13 to one of the fixed contacts 7a to 7c, the emitter and collector of the transistor 13 are short-circuited, and the charge stored in the capacitor 19 is discharged.
This will now be applied to the base of the transistor 18, so the transistor 18 will be off and the relay coil 17 will not be energized.
The relay contact 8 is opened and the supply of high level current to the switch 6 is cut off, thereby preventing the switch 6 from being destroyed.

The switch protection device of this embodiment having such a configuration first has a relay switch 8 connected in series to the output terminal of the amplifier 2.
This structure protects the switch 6. Therefore, when the second switch is connected to the input side of the amplifier 2, the disadvantage of amplification of switching noise by the amplifier 2 is prevented. Furthermore, since the relay of the existing speaker protection circuit is also used to protect the switch, the structure can be constructed without increasing the number of parts. Furthermore, if the second switch is used directly as a current path for grounding the audio signal line, a certain amount of current capacity is required, but the switch 7 of this embodiment turns on the transistor 18, There is also the advantage that a device with an extremely small current capacity that can be turned off can be used.

[Effect of idea]

The switch protection device of the present invention is configured to protect the switch using a relay switch connected in series to the output side of the amplifier. Therefore, the disadvantage of amplification of switching noise caused by the amplifier is prevented. In addition, since the load protection circuit normally installed in audio equipment, such as the relay of the speaker protection circuit, is also used to protect the switch, the protection device for the switch can be configured without increasing the number of parts. . Furthermore, if the second switch is used as a current path for grounding directly,
Although a certain amount of current capacity is required, in the case of the present invention, a switch with a very small current capacity can be used as the second switch.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a switch protection device prior to the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the switch protection device of the present invention. 2... Amplifier, 4, 5... Speaker, 6... First switch, 7... Second switch, 8... Relay contact, 11, 13, 14, 18... Transistor, 17... Relay coil .

Claims (1)

[Claims for Utility Model Registration] A relay switch and a first switch for switching loads connected in series to the output terminal of an amplifier, a low-pass filter connected to the output terminal of the amplifier, and a low-pass filter connected to the output of the low-pass filter. a switching element that is turned on when the first switch is turned on and its DC output exceeds a predetermined value; a load protection relay means that opens the relay switch when the switching element is turned on; and immediately before the first switch is turned on or off. and a second switch that is turned on and turned off during normal operation, and when the second switch is turned on, the switching element is turned on to prevent the load switching switch from being destroyed by a large current. A switch protection device characterized by: