JPS5929370Y2 - Muting relay drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive circuit for a muting relay inserted into an amplifier circuit that drives a speaker.

Conventionally, drive circuits for such muting relays operate using DC voltage, but such drive circuits have the following drawbacks.

That is, since the voltage supplied to the base of the transistor for driving the relay is gradually increased, the operation of the relay becomes slow and the contacts may not make sufficient contact.

Additionally, when using a power amplifier B class stage DC power supply as the relay's 1-drive DC power supply, the relay drive voltage may fluctuate greatly due to insufficient capacity of the power supply, resulting in unstable relay operation. there were.

Accordingly, an object of the present invention is to provide a relay drive circuit that quickly restores the operation of the relay and has less mutual influence with other circuits.

The present invention will be explained below with reference to the drawings.

FIG. 1 shows one embodiment of the present invention.

The example circuit has a transformer T1 having a primary winding that receives AC power via a power switch S1.

A capacitor C1 is connected in parallel to the coil of the muting relay RL, and a gate-controlled rectifier SCR for driving the relay is connected in series to this parallel circuit.

Relay RL continues to be energized while the trigger voltage from the trigger voltage supply circuit is supplied to the gate terminal of gate-controlled rectifier SCR.

The trigger voltage supply circuit includes a diode D1. D2, capacitors C2 to C4, resistors R1 to R8, transistors Q0. Q2 There is.

The output terminal of power amplifier PA is the normally open contact γL of relay RL.
It is connected to one end of the power speaker SP via a filter circuit including a resistor R0 and a capacitor C5.

When a DC voltage is generated at the output end of the power amplifier PA,
The DC voltage is supplied to a connection point J1 between the base of the transistor Q1 and the resistor R6.

Diode D3, resistor R1, light emitting diode LD, and capacitor C6 switch the relay non-operating state to light emitting diode LD.
This constitutes a display circuit that displays information by emitting light.

The operation of the above circuit will be explained below.

First, when the switch S1 is closed, a positive voltage is generated across the capacitor C2 and a negative voltage is generated across the capacitor C3 during the first cycle of the AC voltage, and the transistor Q2 is turned off.

Therefore, when a positive voltage is applied to the molding capacitor C4 via the resistor R6 and the voltage across the capacitor C4 rises to the set value with the time constant of T=R6XC4, the resistors R7,
The voltage divider circuit of R8 supplies the voltage across capacitor C4 as a trigger voltage to the gate terminal of gate-controlled rectifier SCR, causing SCR to fire and relay RL to switch S1 [
It will operate after a delay time T from .

The switch S1 is interlocked with the power supply switch of the audio output supply circuit to the speaker including the power amplifier PA,
A muting time of time T is obtained.

Note that it is clear that the insertion position of the contact γL can be arbitrarily selected.

The rise time of the gated rectifier SCR is much faster than that of the relay due to the nature of the device, ensuring rapid operation of the relay RL.

Next, when DC power is supplied to the speaker SP for some reason, a DC voltage is generated across the speaker SP.

When this DC voltage is positive, this DC voltage is supplied to the base of transistor Q2 via resistor R5, turning on transistor Q2 and discharging capacitor C4.

Then, the voltage disappears and the SCR is turned off, and the relay RL is restored and prevents DC voltage from being supplied to the speaker SP.

On the other hand, when the DC voltage is negative, transistor Q1 is turned on, the potential at connection point J2 rises, and transistor Q2
The base potential of the transistor Q2 rises, turning on the transistor Q2, and the relay RL is also restored to protect the speaker SP.

Next, when switch S1 is opened, capacitor C3×
The time constant of resistor R1 is made sufficiently small so that transistor Q
The base potential of transistor Q2 immediately rises, turning on transistor Q2 and discharging capacitor C4.

Therefore, even when the switch is immediately turned on again, T=
A delay time of R6×C4 is obtained.

Note that the light emitting diode of the display circuit is excited and emits light only when the SCR is off, indicating the non-operating state of the relay.

FIG. 2 shows another embodiment of the invention.

This embodiment circuit is completely the same as the circuit shown in FIG. 1, except that the voltage generated in the capacitor C4 is applied to the resistor R7 as the emitter current of the transistor Q3, and the corresponding elements are shown in FIG. The same reference numerals are given.

With such a configuration, the SCR trigger current can be set independently of the resistor R6, so the value of the resistor R6 can be determined mainly with the aim of obtaining the desired delay time.
This is preferable because there is more room for selecting the delay time.

From the above explanation, it is clear that according to the relay drive circuit according to the present invention, the operation of the relay can be restored quickly and reliably, and since AC power is used, there is less mutual interference with other circuits that require DC power, which is very effective. preferable.

Further, since a gate-controlled rectifier is used, the circuit configuration can be simplified because control can be performed using a control signal unrelated to the operating current of the relay.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams showing an embodiment of the present invention. Explanation of main symbols, RL...muting relay, SCR...gate control rectifier, PA...
...Power amplifier, SP...Speaker, γ
L...Relay RL contact, T1...Transformer.

Claims (1)

[Scope of utility model registration request] A muting relay drive circuit that drives a muting switch connected to the input side or output side of a power amplifier that drives a speaker, the slow recovery circuit being connected in parallel to the coil of the muting relay; an SCR connected in series to the coil, and a power supply circuit that supplies an AC voltage to a series circuit of the coil and the SCR;
A trigger for supplying a trigger voltage to the gate of the SCR when a predetermined period of time has elapsed from the start of voltage supply from the power supply circuit is configured to stop supplying the trigger voltage when DC voltage is supplied to the voltage supply circuit and the speaker. and a speaker protection circuit configured to provide electrical current to the charged capacitor. the first connected to discharge the
a circuit for smoothing the negative voltage of the alternating current voltage and supplying it to the base of the first transistor to make the first transistor non-conductive, and applying a voltage across the capacitor to the gate of the SCR. The speaker protection circuit includes a circuit that makes the first transistor conductive due to the positive voltage generated at the output side of the power amplifier, and a circuit that makes the first transistor conductive due to the negative voltage generated at the output side of the power amplifier. A muting relay drive circuit comprising: a second transistor that makes the transistor conductive;