JPS5952904A - Protecting circuit of amplifying device - Google Patents

Abstract

PURPOSE:To protect an amplifying device and a loudspeaker when a firmamental fault is generated, by providing a transistor (TR) whose electric conduction is controlled by an output of one SEPP amplifying circuit and an output of a pre-driving TR and a TR for detaining an input of a predriving TR of the other SEPP amplifying circuit to a prescribed level at the time of electric conduction of said TR. CONSTITUTION:When the potential of an output terminal 10 rises to Vcc, the potential of a terminal 13 drops contraiwise, therefore, a TR T11, by which the potential V13 of the terminal 13 rises up to a level being nearly Vcc, a TR Q14 becomes an off-state, and the TRs Q14, Q16 are protected. On the other hand, by electric conduction of the TR T11, the base potential of a TR T12 rises, and since it conducts, a terminal 24 is dropped to a ground level forcibly, the collector side potential of TR Q23 rises, TRs Q25, Q27 conduct, and the potential of a terminal 20 becomes nearly Vcc. In this way, a loudspeaker SP is protected, as well.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides protection for an amplifier device 5':! Regarding j times 11'6, in more detail, a 2 channel IC amplifier is 13 T L
, relates to a power-fault protection circuit when used in OCL.

Stereo IC amplifiers having two channels each of a preamplifier section and a power amplifier section are widely used. Since power efficiency is important in devices using dry batteries, a 5EPP (single end push pull) amplifier circuit is used as the power amplifier section. Now, in order to use this kind of IC increaser + 1 yen rI device for high output monaural (13 T L (Balancerl \ransf)
ormer Less), OCL (OutputC
ondenser Less). This connects a yellow speaker between the output midpoints of the 5EPP amplifier circuits of both channels without going through an output capacitor, and sends a non-inverted signal to the preamplifier section of one channel and an inverted signal to the preamplifier section of the other channel. It is realized by connecting to give Shingetsu.

In order to diversify the functions of audio devices, speakers can be attached and detached via appropriate connectors.
If overheating occurs, short-circuit the output midpoint to the power supply to prevent misuse by the user.
There is a risk that the power supply will be short-circuited and the IC amplifier will be destroyed, and in some cases, the speaker will also be destroyed, so it is essential to take countermeasures against this.

The present invention can be added as an external circuit to an IC, has no effect on operating characteristics at all times, and has no effect on the operating characteristics.
It is an object of the present invention to provide a circuit that does not consume much power and can protect the IC itself and a speaker in the event of a short circuit.

The present invention will be described in detail below based on drawings showing embodiments thereof.

Differential amplifier 11 x 4 circuits as preamplifier section 1),,I)
, are roughly two transistors Q111Q, +2, Q2+
+Q22, etc., and the collectors of transistors Q1□ and Q2□ are used as outputs to output 5E as a power amplifier section.
E) ]) Prefix of amplifier circuits P1 and P2, l! i< is applied to the bases of dynamic transistors Q+3 and Q230. Transistor Q+7, (the emitter of N23 is at ground level, and its output collector (f, I of negative output signal amplification) Nl) transistor Q+4,
It is mounted on the Q240 base and connected to the Q250 base and an NPN transistor Q+s for positive output signal amplification via idle link circuits (1) and (2) consisting of two diodes. The collector of the transistor QIl, Q, 25 is connected to the terminal for power supply connection, and the emitter is connected to the output transistor Q+7, Q for amplifying the positive output signal.
, 27 connected to the base of 6, transistor Q+
7. The collector of Q27 is connected to terminal 1 (η゛1-, and the emitter is SEI 1r, 1 circuit ■) 1, ■) 2
It is the output midpoint of , and is connected to the output ☆;1.1 child 10.20. It is connected to terminal 1 via the emitters of transistors Q+4 and Q24, transistors Q+s and Q2R, and the collector is connected to the t1 output signal p and the bases of output transistors Q16 and Q2G for Q width, and the collectors of transistors Q+6 and Q26 The emitter of is at ground level. Also, respective collectors rJ, 5EXJ
P'' is the output midpoint of the width circuit P1, 2) and is connected to the output terminal 10.20. This output midpoint d, via the diode 1) II transistor Q1s, Q28
The base of the feedback resistor 1 is 11'1', while the feedback resistor 1
Also, , , ■Mo, differential amplifier circuit II'111)
It is connected to the bases of transistors Q1° and Q2□ of transistors 1 and 1)2 to apply negative feedback.

The bases of transistors Q+2 and Q2□ are resistors R1□, ■
The external part of the negative feedback circuit is connected to a terminal 11.21 for connecting a capacitor via 12□. The base of the transistor Qss, Q2, is then connected to the input terminal 12.22. In the figure, arrows enclosed in a circle are constants: I
An L flow circuit is shown. Then the front drive transistor Q
The collectors of 13 and Q23 are connected to terminals 13 and 23, respectively.
j: The respective bases are connected to terminals 14 and 24 at h-7'. ) A capacitor for oscillation correction is connected between the 1° 1.1 elements 13 and 14 and between 23 and 24 when the gain is lowered. Between terminals 10-14, 20-24
A capacitor for correcting fH (the upper limit of the operating frequency range where the frequency response drops 3 dB from the peak value) in a similar case is connected between them.

Although not particularly shown, a grounding terminal is also provided.

Above J: When this IC is normally used for stereo equipment, input 1'lbi 12.22
Input left and right audio signals respectively, output ψ11″d 10
．． 4 left and right speakers between each 20 and the ground level.
However, when using in BTL and OCL, input j':! as shown in the figure. An audio signal is given to the a terminal 12, the terminals 11 and 21 are connected to apply the inverse signal to the base of the transistor Q22, and the input terminal 22 is set to the ground level, while the output j': hi terminal 10 Connect the speaker SP between .20 and 20. Terminal 1 is then connected to a power source with voltage vCo. As a result, a little less than four times as much output is output between terminals 10 and 20 as when each channel is used in stereo.

Now, the protection circuit C according to the invention is provided for each of both channels, and has exactly the same ηII\Ib. 1 (11
ぢTo, T2, is a multi-connector type I) N I) l-transistor with two connectors, and each emitter is connected to the output, :, ;i, and H terminals 10 and 20, respectively. , the respective bases υ are connected to one collector of each, and are connected to terminals 13 and 230, respectively. The other connectors are connected to the ground level via resistors R, 3, and 23, respectively.
It is connected to the bases of transistors 'r12 and 'F22. The emitters of these transistors T1□ and T22 are at ground level, and the collectors of each are connected to terminals 24 and 14 on the other channel side, respectively.

Don't let this happen, okay? The operation of the configuration storage circuit is as follows. That is, 11jj is the voltage V at the output terminal 1.320,
o.

V2o and terminal i 3.23 J, lJ prefix J11
4-dynamic transistor Q+3, Q23 (D: J l/
The voltages V13, V23 and C'1.1 γ1 current 1) Vmin B', '/2 are at the same level of VCC, and outside the AC are at the level of 1, in phase, and the transistors T1t, T2
1 I'm off. Therefore the transistor 'jll
The insulator 11Φ circuit of the present invention consisting of 'lll T1□, 'L'21+'
I don't do it.

Now, regarding the conventional case in which the Ox's protection n'h circuit does not exist, and looking at the circuit operation when a short-to-power circuit (shown by a two-dot chain line) occurs, the potential of the output 91M terminal 10 (also ryo 20) is V. 0, and this is negatively fed back to the dynamic amplifier circuit 1 (also (r yo 1) 2). (Increase the negative output of the 4-channel transistor Q, 3 (also 'tj, Q, 23). As a result, the transistor Q1. (or Q24)
is turned on, a current of 114 times flows through Q16 (or Q26), and these are destroyed. On the other hand, there is also a 1.1 V voltage that is applied to the speaker SL) and is broken by the IAVoo's pressure.

On the other hand, book 11i! 11 When the protection circuit according to the invention is provided -1 The potential of the output terminal 10 (or 20) is V. 0
When the voltage rises to 1, the negative feedback circuit fl'+)
3 (or 2:3), about 11L decreases, so the transistors T, , (or T2,) pass through the layer, thereby increasing the potential of terminal 13 (also C-1, 23) 13 (also f', J:V
23) ifc is doubled to a level close to cc, transistors Q, 4 (also Q24) are in the off state f, +J3, and transistors Q14 + Q10 (
Mata V, Q2. , Q,) is 1.・You will be attacked. On the other hand, transistor T1. Due to the conduction of (i, J: T2□), the base 1;
1 child 24 (or 14) in front of other channels
, tj74 dynamic transistor Q2. (or Q10) will be forced to drop to the ground level. Transistor Q23 (or Q1
3) collector side potential rises, transistor Q2□.

Q27 (or CI+5+ Q,,) is 2,? 1, the potential of the terminal 20 (or 10) is approximately V. Set to 0. The positions of the two-dimensional speaker SP:b'+'t1.' are approximately equal, and the speaker SP's position is approximately equal.

As described above, the present invention (/c) is a protection circuit for an amplifier 1't (a differential amplifier circuit of 1 and 2 channels and a S Je I).
It has an amplifier circuit and connects them to 13 'l'' L and O
This is a 1/2" pulse H"J circuit with a 1/2" width device connected to the CL. A transistor whose conduction is controlled by the output 6+1, and 2.7% of the i transistor; Since the transistor is connected to the transistor, when a short circuit occurs, the amplification device, the white of the speaker, etc. will be protected from damage, and the amplification operation will not last 11) at all times.
Increased IK! The present invention (l
J: The second fβ lead effect is produced.

Furthermore, in the embodiment of j-e, multi-collector transistors Bo 1□ and T 21 were used; 4-
Of course, t() number of transistors may also be connected and used so as to have the same effect.

[Brief explanation of the drawing]

The drawing is a circuit diagram showing an embodiment of the present invention. I) 1, D2...Differential increase 11 circuit ■) 1, ■]
2...SEP T-' amplifier circuit Q13, Q23
・・・Prefix Hy<dynamic transistor 'l”llll 'r1
2, i,', + 1 T22-) Runsistor'f,
'1st version of the paper cutter 3r'lden 4. i, 4 stock company? - 1 other agent Ben Misaki tjJ Noboru

Claims (1)

[Claims] 1. This is an amplifier circuit for an amplifier having a 2-channel differential amplifier circuit and a 5EPP amplifier circuit, which are connected by BTL and OCL. and a transistor whose conduction is controlled by the output of the pre-drive transistor, and a transistor which, when the transistor is conductive, restricts the input of the pre-drive transistor of the other S E P l) amplifier circuit to a predetermined level. Amplifier I"'°1 characterized by
<M circuit.