JPH04365208A - Amplifier - Google Patents

Abstract

PURPOSE:To prevent sound interruption with the operations of a heat detection circuit and an over voltage detection circuit in the amplifier equipped with these circuits. CONSTITUTION:When a junction temperature Tj of a variable gain amplifier 1 or 2 is changed and increased to a Tj1, the output voltage of a heat detection circuit 5 is changed from a low level to a high level, and a control voltage 103 of a control circuit 7 is changed from Vc2 to Vc1 and turned to a fixed level (Vc1). In respect to the change of the control voltage 103, the output level of the variable gain amplifier 1 and 2 is gradually decreased and fixed. Next, when the junction temperature, Tj of the variable gain amplifier 1 or 2 is lowered from Tj1 to Tj2, the output voltage of the heat detection circuit 5 is changed from the high level to the low level. The level of the control voltage 103 is increased from the Vc1 to the Vc2 and fixed (Vc2). The output level of the variable gain amplifiers 1 and 2 is gradually increased and returned to the former output level state.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplifier, and more particularly to an amplifier constructed from a semiconductor integrated circuit.

0002

[Prior Art] The configuration of a conventional amplifying device of this type is shown in FIG.
Shown below. As shown in FIG. 6, this amplifier device includes a variable gain amplifier 1 that amplifies signals input from an L channel signal source 19 and an R channel signal source 20, respectively.
2 and 13 and these variable gain amplifiers 11 and 1
2, a heat detection circuit 16, an overvoltage detection circuit 17, a protection circuit 18,
It is configured to include power supplies 21 and 22.

In FIG. 6, a temperature rise generated depending on the operating state of variable gain amplifiers 12 and 13 that amplify signals input from an L channel signal source 19 and an R channel signal source 20 is detected by a heat detection circuit 16. detected by
Further, the potential levels at power supplies 21 and 22 are detected by overvoltage detection circuit 17 and both are input to protection circuit 18 . The protection circuit 18 acts to cut off the outputs of the variable gain amplifiers 12 and 13 through the protective action of the protection circuit when heating occurs due to temperature rise or when the power supply voltage rises abnormally, and the output of the variable gain amplifiers 12 and 13 is cut off. The circuit is protected.

0004

[Problem to be Solved by the Invention] In the conventional amplifier device described above, when the junction temperature Tj of the amplifier rises for some reason, the heat detection circuit 16 is activated and the protective action by the protection circuit 18 is activated. think of. Now, the variable gain amplifiers 12 and 13 operate, the junction temperature Tj rises, and when the temperature detected by the heat detection circuit 16 reaches Tj1 at time t0 shown in the operating state diagram of FIG. In operation, outputs 104 and 105 of variable gain amplifiers 12 and 13 are cut off, as shown in FIG. Therefore, speaker 1
The outputs of 4 and 15 are also stopped. And time t1
In, when the junction temperature Tj of variable gain amplifiers 12 and 13 decreases to a temperature lower than Tj1,
Outputs 104 and 1 from variable amplifiers 12 and 13 again
05 is output. Thereafter, as shown in FIG.
The state in which the signal is output and the state in which it is cut off are repeated.

However, in this case, the time period (t0 to t
1), (t2 to t3) and (t4 to t5)
Since the times of , respectively, are short, the outputs 104 and 105 of the variable gain amplifiers 12 and 13 are in a state where they repeatedly operate and do not operate intermittently, giving the illusion that oscillation is continuing. Therefore, in order to avoid such problems, conventionally, in the heat detection circuit 16, as shown in FIG.
The circuit is configured such that once the temperature rises above Tj1 and the protection circuit 18 is activated, the protection circuit 18 will not cause an output cutoff action unless the junction temperature becomes below Tj2 shown in FIG.

However, by providing a hysteresis characteristic accompanying the operation of the thermal detection circuit 18, the junction temperature Tj of the variable gain amplifier changes from Tj1 to Tj2.
The time (t0 to t1) until the temperature decreases becomes longer,
During this period, the variable gain amplifiers 12 and 13 are in a cut-off state, so there is a disadvantage that a relatively long sound break occurs in the output sound output from the speakers 14 and 15.

[0007]

[Means for Solving the Problems] The amplifier circuit of the present invention has a variable gain amplifier that amplifies and outputs a predetermined input signal, and a function of detecting a junction temperature of the variable gain amplifier, and has a function of detecting a junction temperature of the variable gain amplifier. It has a heat detection means that outputs a predetermined level signal at a point in time when a predetermined temperature is exceeded, and a function to detect a power supply voltage supplied to the variable gain amplifier, and at a point in time when the power supply voltage exceeds a predetermined voltage level. , a control voltage for suppressing and controlling the gain of the variable gain amplifier between the overvoltage detection means that outputs a predetermined level signal and the level signal output from the heat detection circuit or the overvoltage detection circuit is input. and a control means for outputting.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. As shown in FIG. 1, in this embodiment, variable gain amplifiers 1 and 2 amplify signals input from an L channel signal source 8 and an R channel signal source 9, respectively.
, speakers 3 and 4 driven by these variable gain amplifiers 1 and 2, a heat detection circuit 5, an overvoltage detection circuit 6, a control circuit 7, and power supplies 10 and 11.

In FIG. 1, for some reason, the junction temperature Tj of variable gain amplifier 1 or 2 becomes
When it changes as shown in Figure 2 and increases to Tj1,
The output voltage of the heat detection circuit 5 changes from low level to high level at time t0. When the output of the heat detection circuit 5 changes from low level to high level, the control voltage 103 output from the control circuit 7 accordingly changes from VC2 to VC1 between time t0 and a certain time t10, and then At a certain level (V
C1).

On the other hand, with respect to changes in control voltage 103, variable gain amplifiers 1 and 2 have control voltage/gain characteristics as shown in FIG. As shown in FIG.
0, it gradually decreases as time (t0 +
After time t10), it becomes a constant level.

Next, the junction temperature Tj of variable gain amplifier 1 or 2 decreases as shown in FIG. 2, and when the junction temperature Tj of both amplifiers decreases from Tj1 to Tj2 at time t11, at that time The output voltage of the heat detection circuit 5 changes from high level to low level. As a result, the level of the control voltage 103 output from the control circuit 7 rises from VC1 to VC2, as shown in FIG. 2, and thereafter remains at a constant level (VC2). Along with this, the levels of the outputs 101 and 102 of the variable gain amplifiers 1 and 2 gradually increase and return to the output level state before the time t0.

[0013] In the above, the operation of the heat detection circuit and control circuit 7 due to changes in the junction temperature of the variable gain amplifier has been explained, but this also applies to the overvoltage detection circuit and control circuit 7 when an abnormal voltage occurs. The same applies to the effect of .

[0014]

[Effects of the Invention] As explained above, the present invention has the advantage that when a variable gain amplifier overheats due to an increase in junction temperature,
In addition, by providing a function to control and suppress the gain of the variable gain amplifier in response to an abnormal rise in the power supply voltage, the output of the variable gain amplifier is not cut off, thereby eliminating sound output from the speaker. The effect is that it can be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing an example of operation in this embodiment.

FIG. 3 is a diagram showing the gain characteristics of the variable gain amplifier in this example.

FIG. 4 is a block diagram showing a conventional example.

FIG. 5 is a diagram showing an example of operation in a conventional example.

FIG. 6 is a diagram showing an example of operation in a conventional example.

[Explanation of symbols]

1, 2, 12, 13 variable gain amplifier 3, 4, 1
4, 15 Speakers 5, 16 Heat detection circuit 6, 17 Overvoltage detection circuit 7 Control circuit 8, 9, 19, 20 Signal source 10, 11, 21, 22 Power supply 18 Protection circuit

Claims (1)

[Claims] 1. A variable gain amplifier that amplifies and outputs a predetermined input signal, and a function of detecting a junction temperature of the variable gain amplifier, and when the junction temperature exceeds a predetermined temperature, a predetermined level is detected. Heat detection means for outputting a signal; and overvoltage detection means for detecting a power supply voltage supplied to the variable gain amplifier, and outputting a predetermined level signal when the power supply voltage exceeds a predetermined voltage level. and a control means for outputting a control voltage for suppressing and controlling the gain of the variable gain amplifier while the level signal output from the heat detection circuit or the overvoltage detection circuit is input. An amplifying device characterized by: