JPS5852729Y2 - protection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protection circuit that can prevent abnormal fluctuations in the output voltage applied to a DC amplifier.

Conventionally, in order to prevent unnecessary low-frequency noise such as motor ground noise applied by a player for playing disc records connected to a DC amplifier from being transmitted to the output side, an animal switch is used to remove low-frequency noise as necessary. It was made so that a filter could be inserted.

However, even if measures are taken to prevent such low-frequency noise from occurring under normal operating conditions, an abnormal DC voltage may be applied immediately after the power is turned on, and in this case, the DC amplifier This causes very large voltage fluctuations on the output side.

Therefore, in order to prevent the output transistor or external circuit from being destroyed even when there is no concern about noise such as motor grounding, conventionally, before turning on the power, the low-pass removal filter is inserted by operating a switch, and then a predetermined period of time has elapsed. After the above-mentioned abnormal voltage is no longer a concern, it is necessary to operate the switch again to stop inserting the low-pass filter, which is a cumbersome operation.

The object of the present invention is to provide a protection circuit which does not have such drawbacks and can automatically prevent abnormal fluctuations in the DC voltage of the battery immediately after power is turned on.

FIG. 1 shows an embodiment of a protection circuit according to the present invention.

In FIG. 1, the output of an abnormal voltage detection circuit 5 that detects fluctuations in the output voltage of the DC intensifier 1 and generates an output is connected to the base of a transistor T1 whose emitter is grounded.

The collector of the transistor T1 is connected to the base of the transistor T2, is connected to a positive voltage source (10B) via a resistor R3, and is further grounded via a capacitor C2.

The terminal of the transistor T2 is grounded, and the collector is connected to the operating coil L2 of the reed relay 2, and is connected to the fixed contact A via the resistor P2 and the operating coil 11 of the reed relay 1, respectively.

It is also connected to contacts A and B of a manual switch S having a movable contact B and a movable contact C, respectively.

Further, the contact C of the manual switch S is connected to a positive voltage source (10B) via a resistor R4.

The input terminal of the DC amplifier 1 is connected to the input terminal 4 via a DC blocking capacitor C1 to form a low-pass filter, and is also grounded via a resistor R1.

A reed relay 1 is connected to both ends of the DC blocking capacitor C1.
normally open contacts IIA and IIB are connected, respectively.

Further, the output terminal of the DC amplifier 1 and the input terminal of the speaker 3 are connected to normally open contacts IIA and I2B of the reed relay 2, respectively.

Now, the case where contacts A and C of the manual switch S are connected will be explained.

Immediately after the power is turned on, the terminal voltage of capacitor C2 is low, so transistor T2 is OFF, so reed relays L1 and Ll do not operate, so the normally open contacts 1A and IIB and I2A and I2B are open. It is a cabinet.

Therefore, since the capacitor C1 is inserted into the input terminal of the DC amplifier 10, abnormal DC fluctuations from the input terminal 4 are prevented.

Similarly, since the speaker 3 is not connected to the output terminal of the DC amplifier 1, it is protected from abnormal voltage immediately after the DC amplifier 1 is powered on.

Thereafter, the capacitor C2 is charged via the resistor R3, so its terminal voltage rises, and after a predetermined period of time, the transistor T2 becomes conductive, so the reed relays 1 and 2 are activated, and each normally open contact L1A is activated. and Ll, B and I2
A and I2B are closed.

Therefore, the input terminal of the DC amplifier 1 is directly connected to the input terminal 4 without passing through the capacitor C1, and the output terminal is connected to the speaker 3.

Furthermore, if the output terminal voltage of the DC amplifier 1 fluctuates abnormally and exceeds the safety limit due to a reason other than the abnormality immediately after the power is turned on, the abnormal voltage detection circuit 5 operates and the transistor T1
becomes conductive.

Therefore, since the discharge transistor T2 of the capacitor C2 becomes non-conductive, the reed relays 1 and 2 do not operate, and each normally open contact opens, so the input terminal 4 is connected to the input terminal of the DC amplifier 1 via the capacitor C1. At the same time, the output terminal is opened, and no abnormal voltage is applied to the DC amplifier 1 and the speaker 3.

Next, when contacts B and C of manual switch S are connected, the above operation is performed only for reed relay 2 & IJ-relay 1 does not operate, so capacitor C1 is always inserted on the input side and DC block ingredients.

As mentioned above, if it is necessary to remove noise caused by motor grounding, etc., turn the manual switch S to the contact H side,
In addition, if this is not necessary, contact A can be turned over to the side, and in either case, the amplifier or external load circuit can be protected without performing troublesome preventive operations against abnormal voltages as in the conventional case.

[Brief explanation of drawings]

The figure shows an embodiment of the invention. 2 and 2 are reed relay operating coils, S is a manual switch, 3 is a speaker, 1 is a DC amplifier, and 5 is an abnormal voltage detection circuit.

Claims (1)

[Scope of utility model registration request] a first switch that supplies the output of the DC amplifier to a load;
a second capacitor connected in parallel to the input capacitor of the DC amplifier;
a switch, a delay means for generating a delayed output after a predetermined time delay after the power is turned on, a means for operating in response to the delayed output to close the first switch, and a manual switch for selecting an operating state or a non-operating state. , means for operating in response to the delayed output and closing the second switch only when an operating state is selected by the manual switch.