JPS5921598Y2 - speaker protection circuit - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a speaker protection circuit used in audio amplifiers and the like.

<Background Art> There is a midpoint drift detection circuit in the speaker protection circuit of an audio amplifier, and the amplifier and speaker are not connected for several seconds after the power is turned on, when the drift is relatively large, in order to protect the speaker.

After a few seconds, when the midpoint drift stabilizes, the amplifier and speaker are connected.

In such a state, there is a protection circuit that turns off a relay connected between the speaker and the amplifier when an abnormality occurs in the amplifier and a drift occurs at the midpoint of the amplifier.

<Purpose> The present invention relates to such a circuit, especially when the relay that is located between the speaker and the amplifier and protects the speaker is OFF, for example, when a drift occurs at the midpoint several seconds after the power is turned on. This is a speaker protection circuit that indicates that the speaker and amplifier are not connected.When the relay is OFF, the light emitting diode blinks, and when the relay is ON, that is, when there is no drift at the midpoint of the amplifier, it blinks. The light emitting diode stops blinking and continues to light up to indicate to the user that there is no abnormality, giving a sense of security.In addition, in the event of an abnormality in the amplifier, the light emitting diode blinks to give a sense of urgency and to alert the user to an abnormality in the amplifier. This circuit detects the problem early, protects the speaker, and also serves as a pilot lamp to indicate when the power is on if there is no abnormality.

<Structure of the present invention> Further, the present invention will be explained in detail using the drawings.

Figure 1 shows the circuit of the present invention as a block diagram. In the figure, 1 is a detection circuit that detects the midpoint drift of the amplifier, and 2 is a Schmitt trigger circuit. A drive circuit operates the relay, 3 is a control circuit, and 4 is a multivibrator that blinks the light emitting diode.

The multivibrator 4 has a resistance R in FIG.
2. It is an astable multivibrator that oscillates at a set low frequency depending on the values of capacitor C1, resistor R4, and capacitor C2.

<Operation of the present invention> In Fig. 2, when power is turned on to power terminal B,
At the same time that the multivibrator 4 operates and starts oscillating, the transistor Q6. Q7, resistance R1□, R1゜,
Condenser C4 of the Schmitt trigger circuit, which is composed of R13, R14, R1, R16, capacitor C4, and RLY■, starts charging and when the power is turned on, transistor Q6 is ON and Q7 is OFF, but capacitor C
When transistor Q6.4 is charged to a predetermined value, it is no longer possible to maintain a steady state, and transistor Q6. The ON and OFF states of Q7 are switched, the relay operates, and relay terminals 1 (connected to the amplifier) and 3 (connected to the speaker)
is connected, and the amplifier and speaker are connected.

By doing this, the drift when the power is turned on is not applied to the speaker, and the speaker and amplifier are connected only when the power is stabilized.

When the power is turned on, Q6 is turned on until capacitor C4 reaches a predetermined value, so the collector current of transistor Q6 flows through R13, the potential across R13 becomes high, and the transistor of the control circuit in FIG. A voltage is applied to the base of Q3 via resistors R6 and R7, and Q3
turns on, the multivibrator starts oscillating,
Light emitting diode D1. D2 starts blinking.

Next, when capacitor C4 is charged to a predetermined value, Q6 and Q7 are switched between ON and OFF, and Q6 is OFF and Q7 is
turns on, and the potential across the resistor R13 becomes low because only the base current of the transistor Q7 that is turned on flows through R13, and the transistor Q3 of the control circuit turns off, so the multivibrator oscillation stops and the multivibrator transistor Q2 is OFF and Ql is ON, so that the light emitting diode D1 continues to light up and the light emitting diode D2 goes out.

At this time, the relay operates and the amplifier and speaker are connected.

On the other hand, if a drift occurs at the midpoint of the amplifier, if the drift is applied to the base of transistor Q4 of the donoft detection device or the emitter of transistor Q5 from terminal ■ through R5, Q4 or Q5 turns ON and collector current flows. , Rlo occurs, and the base potential of Q6 drops.Q6 turns ON, and the multivibrator starts oscillating in the same manner as described above, warning of an abnormality in the amplifier.

When there is no abnormality, the light emitting diode D1 continues to shine as described above and serves as an indication that the power is on.

<Effects of the present invention> As described above, according to the configuration of the present invention, by flashing the light emitting diode when there is an abnormality in the amplifier, etc., it gives a sense of urgency, detects the abnormality in the amplifier early, protects the speaker, and always The effect is great, as it also doubles as a power-on display.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the circuit of the present invention, and FIG. 2 is a specific circuit diagram thereof.

Claims (1)

[Scope of utility model registration request] a multivibrator; a light emitting diode driven by the multivibrator; and when the power is turned on and the multivibrator is turned on while a power supply voltage is applied to the multivibrator, the multivibrator is oscillated and the light emitting diode is blinked; A switching transistor that stops the oscillation of the multivibrator and keeps the light emitting diode lit by turning it off, a midpoint drift detection circuit that detects the midpoint drift of the speaker amplifier, and a midpoint drift detection circuit that detects the midpoint drift of the speaker amplifier by operating a relay. The relay terminal between the relay terminal and the speaker is turned ON and OFF.
The Schmitt trigger circuit is more powerful than a Schmitt trigger circuit which takes a state and outputs an output to turn on the switching transistor, and after a predetermined time has elapsed, takes a second state to operate the relay and turn on one terminal of the relay. When the midpoint drift detection circuit detects the midpoint drift in the second state, the circuit switches to the first state, operates the relay, and turns the relay terminal off.
A speaker protection circuit that outputs F and outputs to the switching transistor.