JPH0213003A - Temperature compensating circuit - Google Patents

Abstract

PURPOSE:To rationally realize the temperature compensation in a driving condition by composing a current detecting means of a thermal member to execute approximately the same temperature rise as the voice coil material of a loudspeaker and controlling the feedback quantity of a positive feedback with an electric change quantity corresponding to the temperature of the member. CONSTITUTION:In order to execute a negative impedance drive to equivalently nullify or reduce the direct current resistance components of the voice coil of the loudspeaker, a detecting element RS is connected as a current detecting element 3 in series to the loudspeaker which is a load 2. Further, a thermosensible resistance element RX thermal-coupled to a detecting resistance RS is provided, and it is connected to a feedback circuit 4. The radiant resistance and thermal time constant of the detecting resistance RS are set so that the temperature rise of the voice coil of the loudspeaker 2 and the temperature rise of the detecting resistance RS can be made approximately equal. Thus, since a feedback ratio beta of the feedback circuit 4 is controlled according to the temperature rise of the detecting resistance RS, the temperature compensation can be suitably executed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a temperature compensation circuit used in an amplifier circuit for driving a negative impedance, and in particular, to a temperature compensation circuit that rationally realizes temperature compensation in the driving state. used for.

[Conventional technology]

Generally, a speaker has a voice coil disposed in a magnetic gap of a magnetic circuit, and drives a diaphragm or the like by passing a driving current through the voice coil. Here, the voice coil has a unique internal impedance that includes a DC resistance component, and this determines the resonance Q value and the highest and lowest resonance frequencies f of the sound pressure reproduction characteristics of the speaker system in which the speaker is installed. has an important influence on

The present applicant focused on this fact and filed a patent application for a sound reproduction device that equivalently nullifies or reduces the direct current resistance component of this voice coil (Japanese Patent Application No. 62-334).
262.334263, etc...unpublished). Figure 5 (
An equivalent circuit diagram conceptually representing this is shown in a). In the figure, CM and LH are the capacitance and inductance of the motional impedance ZM of the electromagnetic transducer (speaker), respectively, and Rv is the internal resistance of the voice coil that is the load. This internal resistance Rv is reduced by a negative resistance -RA equivalently formed on the drive side, and the apparent drive impedance ZA is 28''''Rv -Rt.

becomes. However, if ZA becomes negative, the operation of the circuit becomes unstable, so Rv≧RA.

According to this sound reproduction device, the resonance Q value of the unit vibration system including the speaker is ideally zero, and the lowest resonance frequency f. The concept of will also disappear.

Furthermore, when driving the above-mentioned resonator, the resonance Q value is not lowered, so strong resonant acoustic radiation can be achieved.

In order to perform such negative impedance drive,
It is necessary to equivalently generate negative impedance, and for this purpose a detection cord R is connected as a current detection element 3 in series with the speaker, which is the load 2. FIG. 5(b) shows a circuit diagram of the negative impedance generating circuit.

As shown in the figure, a detection resistor R is connected to the load 2 (internal resistance R), and the detection output is given to an adder 5 via a feedback circuit 4 with a feedback factor β, and then sent to an amplifier 1 with an amplification factor A. will be returned. Therefore, the equivalent output impedance R8 for the load 2 is Ro-R8(1-A-β).

[Problem to be Solved by the Invention] However, in this negative impedance drive, if appropriate temperature compensation is not performed for changes in the direct current resistance Rv of the voice coil of the speaker due to temperature changes in the voice coil, This results in larger fluctuations in the driving state than in the case of constant voltage driving. Considering that the voice coil is made of copper wire, an increase in temperature is unavoidable. However, the idea of actively compensating for temperature changes in internal resistance R is
This has not been done in the past.

SUMMARY OF THE INVENTION An object of the present invention is to provide a temperature compensation circuit that can compensate for the temperature of a load with a simple configuration.

[Means to solve the problem]

The temperature compensation circuit according to the present invention positively feeds back the detection output of the current detection means inserted in series with the speaker serving as a load to the input terminal to generate a negative resistance component in the output impedance, and generates a negative resistance component in the voice coil of the speaker. In a speaker drive amplifier circuit designed to equivalently reduce or nullify the direct current resistance of the speaker, the current detection means is made of a member having a heat dissipation resistance and a thermal time constant that has a temperature rise approximately equal to that of the voice coil material of the speaker. The present invention is characterized in that a temperature sensing means having a predetermined resistance temperature coefficient is thermally coupled to the current detection means, and the feedback amount of the positive feedback is controlled by an electrical change amount corresponding to the temperature of the temperature sensing means. .

Here, instead of the above-mentioned temperature sensing means, a temperature detecting means thermally coupled to the current detecting means may be provided, and a multiplying means for multiplying the detection signal of the temperature detecting means by the feedback rate of the positive feedback may be provided. good.

[Effect]

According to the configuration of the present invention, the drive current flowing through the voice coil of the speaker flows directly to the current detection element, so that as the temperature of the voice coil rises, the temperature of the current detection element also increases in almost the same way. . Here, the current detection element and the temperature sensing means or temperature detection means are thermally coupled, thereby controlling positive feedback. Therefore, the temperature compensation described above will be performed.

〔Example〕

Hereinafter, the present invention will be described in detail based on FIGS. 1 to 4 of the accompanying drawings. In addition, in the description of the drawings, the same elements are given the same reference numerals, and redundant description will be omitted.

FIG. 1 is a circuit diagram of a negative impedance drive circuit according to a first embodiment. The difference between this circuit and the circuit shown in FIG. 5(b) is that a temperature-sensitive resistance element (for example, a thermistor) R is provided which is thermally coupled to the detection resistor R as the current detection means 3, and this is connected to the feedback circuit 4. It is that you are.

Here, the heat dissipation resistance and thermal time constant of the detection resistor R in FIG.
It is set so that the temperature rise between the two roads becomes -. According to the first embodiment, since the feedback factor β of the feedback circuit 4 is controlled in accordance with the temperature rise of the detection resistor R6, temperature compensation can be suitably performed.

This will be explained using a specific example shown in FIG. Here, the temperature coefficient of the same polarity as the voice coil R of speaker 2 (voice coil R is v

When the resistor R has a positive temperature coefficient, such as copper, the detection resistor R also has a positive temperature coefficient. In this case, since the feedback factor β is β-1+R/R1, the driving impedance of the equivalent motional impedance ZH is R+R+1+A (1+R/R1)1 v S
x...(1) becomes. Here, voice coil R has a temperature coefficient.
Since there is only the temperature-sensitive resistance R, this can be expressed as v
When x is extracted, equation (1) becomes R-RA(R/R1)...(2)v
S x, and if this is zero, temperature compensation has been ideally performed, so we set R=RA(R/R1) v S x. Here, for the voice coil R1 temperature-sensitive resistor ■R, R-R(1+K-T) v vo Tv v R-R(1+K-T) K: Temperature coefficient of R, Tv v Tv: Temperature of R, ■ R: Value of R at 0℃, xOx K: Temperature coefficient of R, Tx x T,: Temperature of R.) Therefore, Equation (2) is R(1+K −T ) vo Tv v −RA−R(1+K −T )/R1s x
o Tx X. Here, since we set TV:=fT due to the thermal coupling mentioned above, (1+K ◆T )/(1+K −T )Tv
v Tx x? (R-A-R)/
By using a temperature-sensitive resistor Rx that has a temperature coefficient KTx such that (R-R) s xo vo t, it is possible to almost eliminate the influence of temperature. Note that the temperature-sensitive resistor R has a temperature coefficient of opposite polarity to that of the voice coil R.
When using X, the circuit configuration shown in FIG. 3 may be used.

Next, a second embodiment of the present invention will be described with reference to FIG.

FIG. 4 is its circuit diagram. Here, a temperature detection element 11 thermally coupled to the detection resistor R is provided, and this detection signal (
(parameters that change due to temperature) are given to the conversion circuit 12 and converted into a voltage signal (Y). This voltage signal (Y) is then applied to a multiplier 13, multiplied by a feedback signal (X) from a feedback circuit 4, and applied to an adder 5.

In this circuit, the driving impedance of the equivalent motional impedance ZH is R+R(1-AβY) (3
) v S . Here, the voice coil resistance R at 0°C is R
Then, v vO (1+K −T )R...(4) Tv V
It can be set as VO. Therefore, equation (3) is (1+K
-T ) R Tv v v.

+R(1-AβY) (5). Here, in equation (5), the temperature parameter is KT
Since v and Y, RvOKTVTV-RSAβY-0 is sufficient, so RvoKTvTv -Rs AβY...
(6), and the formula (6) is Y/T - (R,.K,v)/RSAβ...(7
)■ becomes. Here, since T'xT is set by the thermal coupling described above, the temperature/voltage conversion characteristic Y/T from the temperature S of the detection resistor R to the voltage signal (Y)
The temperature detection element 11 and the conversion circuit 12 may be set so that ζ(RvOKlx)/(RsAβ).

In the second embodiment, various types of temperature detection elements can be used as the temperature detection element 11. For example, a resistor having a temperature coefficient, a semiconductor such as a thermistor or a posistor, a thermocouple, or the like can be used.

Alternatively, a configuration may be adopted in which a junction voltage of an element such as a transistor or a diode is used.

Furthermore, the multiplier 13 may be a multiplier circuit (vCA) configured based on the VBE (base-emitter voltage) characteristics of a transistor, a circuit using a variable resistance region such as an FET, or a circuit using a variable resistance region such as a FET. A circuit combining S cells or an analog switch circuit may also be used.

〔Effect of the invention〕

As explained above, in this invention, the drive current flowing through the voice coil of the speaker flows directly to the current detection element, so as the temperature of the voice coil rises, the temperature of the current detection element also increases almost in the same way. This current detecting element and the temperature sensing means or temperature detecting means are thermally coupled. Therefore, the temperature of the voice coil and the temperature sensing means or temperature detecting means rises in the same way, and positive feedback comes to be controlled thereby, making it possible to perform the above-mentioned temperature compensation.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a first embodiment of the present invention, FIGS. 2 and 3 are diagrams showing the configuration of a specific example of the circuit of FIG. 1,
FIG. 4 is a diagram showing the circuit configuration of the second embodiment of the present invention, and FIG. 5 is an equivalent circuit diagram of the electrodynamic electroacoustic transducer of the prior application and a circuit diagram of the negative impedance generating circuit. . 1... Amplifier (amplification factor A) 2... Load (speaker), 3... Current detection means (detection resistor R), 4...
Feedback circuit (feedback rate β), 5... Adder, R... Temperature sensitive resistor.

Claims (1)

[Claims] 1. The detection output of the current detection means inserted in series with the speaker serving as a load is positively fed back to the input side to generate a negative resistance component in the output impedance, and the voice coil of the speaker is In the speaker driving amplifier circuit, the current detecting means has a heat dissipation resistance and a thermal time constant that cause a temperature rise approximately equal to that of the voice coil material of the speaker. A temperature sensing means having a predetermined temperature coefficient of resistance is provided and is thermally coupled to the current detection means, and the amount of feedback of the positive feedback is controlled by an electrical change amount corresponding to the temperature of the temperature sensing means. A temperature compensation circuit featuring: 2. The detection output of the current detection means inserted in series with the speaker serving as the load is positively fed back to the input side to generate a negative resistance component in the output impedance, which is equivalent to the DC resistance of the voice coil of the speaker. In the speaker driving amplifier circuit, the current detecting means is composed of a heat dissipation resistor and a member having a thermal time constant that has a temperature rise approximately equal to that of the voice coil material of the speaker, and A temperature compensation circuit characterized in that a temperature detection means thermally coupled to the current detection means is provided, and a multiplication means is provided for multiplying the detection signal of the temperature detection means by the feedback rate of the positive feedback.