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JPS5140961

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DESCRIPTION JPS5140961
■ Speaker protection circuit ■ Akira 46-40184 [Fa] Application Akira 46 (1971) June 9
released field 48-7730 @ Akira 48 (1973) January 31 0 inventor Nishimoto Ruri Tokyo
Metropolitan Tokyo Izumi 2 Izumi 2 14 1 1 Sansui Electric Co., Ltd. @ applicant Sansui Electric
Co., Ltd. Tokyo 14 1 14 [phase] Agent patent attorney Takeshi Suzue 3 persons outside of the
detailed description of the invention Detailed description of the invention The present invention
is a stereo receiver etc. The present invention relates to a speaker protection circuit that protects
a speaker from abnormal DC voltage in a circuit that is used for audio equipment and does not
use an output capacitor and a coupling capacitor between the speaker and a single-ended pushpull amplifier. In audio equipment such as stereo receivers, so-called direct connection circuits
that do not use an output capacitor and a coupling capacitor between the power increase corner
[111111] unit and the speaker generate an abnormally high DC voltage due to destruction of the
elements of the output amplifier. Can cause damage to the speaker. An object of the present
invention is to provide a speaker protection circuit which protects a speaker of a direct
connection circuit from an abnormal DC voltage. An embodiment of the present invention will be
described below with reference to the drawings. FIG. 1 is a block diagram of this embodiment,
showing a 2-channel direct connection circuit in a 2-channel stereo receiver. Usually, the
speakers 1 and 2 are connected to the amplifiers 3 and 4 in the previous stage by the switches 5
and 6 respectively, and the output signals of the amplifiers 3 and 4 are applied through the
switches 5 and 6 and driven. The DC voltage appearing at the output terminal is below the
specified value. When the DC voltage appearing at the output terminals of the amplifiers 3 and 4
exceeds the specified value due to the breakdown of the elements of the amplifiers 3 and 4 etc., it
is detected by the detection circuit 7 and the switches 5 and 6 are operated by the control circuit
8 1.2 is separated from the amplifiers 3 and 4 and protected from abnormal DC voltage. FIG. 2
shows the detection circuit T. The terminals 10.11 and 10 are connected to the output terminals
of the amplifiers 3 and 4 and the terminal 10 is grounded. The terminals 9 and 11 are grounded
via the resistors R1 and R2 and the capacitors CI and C2, and the resistors R1 and R2 and the
capacitors CI and C2 form a low pass P wave device, and the cut-off frequencies thereof are the
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speakers 1 and 2 Is set below the minimum setting frequency of the audio to be reproduced. The
anode of diode D1 and the cathode of diode D2 are commonly connected to the ground terminal
of capacitors CI and C2, the anode of diode D3 and the cathode of diode D4 are connected to the
other terminal of capacitor C1, and the other terminal of capacitor C2 is diode D5. And the
cathode of the diode D6 are connected.
ダイオードDI、D3. The negative [111111] EndPage: 1 pole of D5 is commonly connected
to the terminal 12, and the diode D2 ° D4. The anode of D6 is commonly connected to terminal
13. ダイオードD1∼D4はダイオードD1. D2 common arm and diode D3. A bridge
rectification circuit is constituted by the channel-specific arm consisting of D4, and a diode D1.
D2. D6. D6 is also the common arm and the diode D5. A bridge rectifier circuit is
constituted by the D6 and D6 channel-specific arms, and the terminals 12 and 13 are connected
to the I1m circuit 8. Then, the output signal of the amplifier 3 is applied between the terminals 9
and 10, and a low-pass filter consisting of a resistor R1 and a capacitor C1 takes out a DC
component below the lowest set frequency of the audio signal and a bridge rectification
consisting of diodes D1 to D4. The switches 5 and 6 are opened when they are led through the
circuit between the output terminals 12.degree. 13 and added to the control circuit 8 and
become equal to or more than the rejection value. Similarly, the output signal of the amplifier 4 is
applied between the terminals 11.degree. 10, and a low pass filter consisting of a resistor R2 and
a capacitor C2 takes out a DC component below the lowest frequency and the diodes DI, D2.
D5. The switches 5 and 6 are opened when they are led out between the output terminals
12.degree. 13 through the bridge rectifier circuit D6 and added to the control circuit 8 to reach a
specified value or more. FIG. 3 shows a detection circuit in an embodiment for a 3-channel direct
connection circuit. In FIG. 2, a terminal 14 is connected to a common grounding point of
capacitors CI and C2 via a resistor R3 and a capacitor C3 in series. The low pass filter is
constituted by the capacitor C3 and the anode of the diode DI and the cathode of the diode D8
are connected to the connection point of the resistor R3 and the capacitor C3 and the cathode of
the diode D7 is connected to the terminal 12 and the anode of the diode D8 to the terminal 13
Connected to the diode DI, D2. D7. The common arm and the diode D7. A bridge rectification
circuit is constituted by the channel-specific arms consisting of D8, and a detection circuit of the
third channel is constituted by these low pass filters and the bridge rectification circuit. Then, the
output signal of the amplifier of the third channel is applied between the terminals 14 and 10 to
operate in the same manner as the detection circuit of the first and second channels. In this case,
the control circuit receives the outputs of the output terminals 12 and 13 and simultaneously
controls the switch provided between the 3-channel speaker and the amplifier in the previous
stage [1111111].
Also in the direct connection circuit of four or more channels, the low pass filter and two diodes
are added for each channel in the detection circuit, and the control circuit simultaneously
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controls the switch between the speaker and the amplifier of each channel. can do. FIG. 4 shows
a detection circuit and a control circuit according to a modification of the present invention,
which is an embodiment for a 4-channel direct connection circuit. Terminals 15 to 18 are applied
with the output signal of the amplifier of each channel between the ground terminal 19 and the
input resistors R4 to R7 connected between the ground terminal 19 and the ground terminal 19.
The terminals 15 and 16 are commonly connected to the ground terminal 19 via a capacitor C4
via resistors R8 and R9, and the terminals 17.18 are connected to the ground terminal 19 via a
capacitor C5 via resistors R10 and R11. . The resistors R8, R9 and the capacitor C4 constitute a
low pass filter, and the capacitor C4 operates on the output signal of the 2-channel amplifier
applied to the terminal 15.16. The resistors R10 and R11 and the capacitor C5 likewise
constitute a low pass filter. The anode of the diode D9 and the cathode of the diode D10 are
connected to the connection point of the resistors R8 and R9 and the capacitor C4, the anode of
the diode D11 and the cathode of the diode D12 are connected to the ground terminal 19, and
the resistor R10 and R11 and the capacitor C5 are connected The anode of the diode D13 and
the cathode of the diode D14 are connected to the point. ダイオードD9. The cathodes of Dll
and Di3 are connected to the terminal 20 and the diodes DiO and Di2. The anode of D14 is
connected to the terminal 21 and connected to the ground terminal 19 through the capacitor C6,
and the diodes D9 to D12 constitute a bridge rectification circuit and the diode D11. A bridge
rectification circuit is constituted by diodes D11 to D14 with D12 as a common arm, and a
detection circuit is constituted by these bridge rectification circuits and the low-pass filter. The
terminal 2 ONPN type transistor TR1 is connected to the base, the emitter of the transistor TR1 is
connected to the terminal 21 via the resistor R12, and the capacitor CI is connected between the
terminals 20 and 21. The collector of the transistor TRI is connected to the cathode of the diode
D15 via a resistor R13, and a capacitor C8 is connected between the terminal 21 and the same.
The collector and emitter of transistor TR1 are connected to NPN type Tositran 11111] EndPage:
2 raster TR20 base and emitter, the collector of transistor TR2 is connected to the anode of diode
D16 and the cathode of diode J 16 is connected to the cathode of diode D15 Ru.
A capacitor C9 is connected between the cathode of the diode J) 15 and the terminal 21 and an
AC power supply is connected to the anode of the diode D15 and the terminal 21 via the
terminals 22 and 23. The transistors TRI and TR2 constitute a Schmitt circuit to be a control
circuit. The output of the AC power supply is rectified by a diode D15, smoothed by a capacitor
C9, and given a Schmitt circuit (C). Also, an output terminal 24.25 is led out from both ends of
the diode D160, a relay is connected, and its contact point is connected between the speaker of
each channel and the amplifier, respectively. Thus, for example, if a positive DC voltage is applied
between the terminals 15 and 19, current flows to the resistor R8, the diode D9, the transistor
TRI, the resistor R12, the diode D12, the ground terminal 19, and a negative DC voltage is
applied. Then, current flows through the ground terminal 19, the diode D11, the transistor TR1,
the resistor R1λ diode D10, and the resistor R8. Therefore, a current flows in which the
transistor TR1 is biased in the forward direction, and when the current exceeds a predetermined
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value, the collector and the emitter of the transistor TRI conduct and a current flows in the relay
connected between the tiger [111111] terminals 24.25. And the speaker is disconnected from
the amplifier. The same operation is performed when a DC voltage is applied between terminals
16, 19. 17. 19 and 18. 19. As described above, according to the speaker protection circuit
according to the present invention, the speaker can be protected from an abnormal voltage in a
single-ended push-pull direct coupling circuit of a plurality of channels, and in particular, one
arm of each full-wave rectifier circuit is commonly used. The configuration is extremely simple
because of the configuration, and furthermore, each full-wave rectifier circuit operates
independently of each other so that the sensitivity is good.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a
speaker protection circuit according to the present invention, FIG. 2 is a circuit diagram showing
a detection circuit in the embodiment, and FIG. 3 is another embodiment of the present invention.
FIG. 4 is a circuit diagram showing a main part of a modification of the present invention. 1.2 · · ·
· · · · Speaker, 3, 4, · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · detection circuit, 8 · · · Control
circuit. [Phase] cited reference 50-4'0534 [111111] EndPage: 3
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