JP2005159635A - Power amplifier circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power amplifier circuit provided with a plurality of amplifiers each being supplied with a power supply voltage via a fuse and each amplifying power of an input signal, which avoids occurrence of an undesirable fuse blowout in the fuse by a current equivalent to the total sum of output currents of the amplifiers. <P>SOLUTION: The power amplifier circuit is provided with: the amplifiers (15), (16) each being supplied with the power supply voltage via the fuse (22) and amplifying power of the input signal; an output current detection section (30) for obtaining a detection output signal as to a sum current equivalent to the sum of currents corresponding to respective output currents of the amplifier sections (15), (16); and output control sections (40, 41) for applying output restriction to the amplifiers (15), (16) in response to the detection output signal obtained from the output current detection section (30) so as to limit the output currents from both the amplifiers (15), (16) and flowing through the fuse (22). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  In the invention described in the claims of the present application, a power supply voltage from a power supply unit is supplied through a fuse, power amplification is performed on an input signal such as an audio signal, and an output signal obtained thereby is output to a speaker or the like. The present invention relates to a power amplifier circuit that supplies a load.

  A vehicle traveling on a road is often equipped with an audio device for providing information to a person (occupant) who gets on the road. An acoustic device (an in-vehicle acoustic device) mounted on such a vehicle usually has a power supply unit as an in-vehicle battery. In other words, in the operating part of the in-vehicle acoustic device, the voltage (battery voltage) from the in-vehicle battery through the main fuse having a relatively large power capacity further has a smaller power capacity than the main fuse. The power supply voltage is supplied through the fuse for the acoustic device.

  Among the operating parts of such an on-vehicle acoustic device, the largest current is generated by power amplification of an input signal such as an audio signal, and the output signal obtained thereby is supplied to a load such as a speaker. Part of the circuit. The power amplifying circuit generates an output current having a relatively large level as a whole in accordance with an input signal, while the battery voltage is supplied as a power supply voltage through a fuse for an acoustic device. The output current of the current occupies most of the current flowing through the fuse for the acoustic device.

  In many cases, the in-vehicle acoustic device takes a so-called multi-channel format including a plurality of audio signal systems such as two systems and four systems, that is, two channels and four channels. In the in-vehicle audio apparatus of the multi-channel format, a power amplification circuit is provided for each channel, and therefore, the number of power amplification circuits corresponding to the number of channels is provided. All of the output currents in the power amplifier circuits corresponding to the number of channels flow through the fuse for the acoustic device that supplies the power voltage to the on-vehicle acoustic device.

  Although the level of the output current of the power amplifier circuit changes according to the input signal, the in-vehicle acoustic device takes a multi-channel format and includes a number of power amplifier circuits corresponding to the number of channels. In some cases, a situation may occur in which the output currents of the plurality of power amplifier circuits are at the maximum level or a level close to the maximum level substantially simultaneously. When such a situation occurs, the current flowing through the fuse for the acoustic device temporarily becomes extremely large, and the power consumed in the fuse for the acoustic device exceeds the power capacity of the fuse. There is a risk that the fuse of this type will blow.

  Of course, the fuse for the acoustic device is arranged so as to avoid the damage of the in-vehicle acoustic device by causing fusing in the initial stage when an abnormal large current continuously flows in the in-vehicle acoustic device. Once the fusing occurs, the fuse does not return, and a new fuse must be provided in place of the fusing in order to operate the on-vehicle acoustic device thereafter. Therefore, for example, as described above, a situation has occurred in which the output currents of the plurality of power amplifier circuits are at the maximum level or a level close to the maximum level, so that the current flowing through the acoustic device fuse temporarily The fusing of a fuse for an audio device that becomes extremely large and results in an undesired blowout that occurs in the fuse for the audio device. Therefore, conventionally, attempts have been made to avoid undesired fusing that occurs in such a fuse for an acoustic device (see, for example, Patent Document 1).

In such an on-vehicle acoustic device (the on-vehicle acoustic device described in Patent Document 1) on which an already proposed attempt has been made, the maximum level at which clipping occurs in the output audio signal from the built-in power amplifier Is applied, the rectangular pulse-shaped clipping detection signal obtained accordingly is supplied to the integrator, and the level of the input audio signal to the power amplifier is reduced according to the integration output signal for the clipping detection signal obtained from the integrator Let In this way, by reducing the level of the input audio signal to the power amplifier, the level of the output audio signal from the power amplifier is reduced, and the output current of the power amplifier is reduced accordingly. The fuse for the acoustic device that supplies the power supply voltage to the device is prevented from being undesirably blown.
JP 2001-309480 A

  In the on-vehicle acoustic apparatus already proposed as described above, when the multi-channel format is adopted and the number of power amplifiers corresponding to the number of channels is provided, the output audio signal causes clipping for each power amplifier. When taking the maximum level, the clipping detection signal in the form of a rectangular pulse obtained accordingly is supplied to the integrator, and the level of the input audio signal is reduced according to the integration output signal for the clipping detection signal obtained from the integrator. Will be. As a result, the level of the output audio signal from each power amplifier is reduced, and accordingly, the output current of each power amplifier is undesired in the fuse for the acoustic device that alone supplies power to the vehicle acoustic device. It is assumed that no fusing occurs.

  However, under such circumstances, a current (sum current) that is the sum of the output currents of the power amplifiers corresponding to the number of channels flows through the fuse for the acoustic device. The current reduction control according to the total current flowing through the fuse for the acoustic device is not performed by the current reduction control according to the integrated output signal for the clipping detection signal from the. Therefore, in the on-vehicle acoustic device that has already been proposed as described above, the total current flowing through the acoustic device fuse causes undesired fusing in the acoustic device fuse that supplies power to the on-vehicle acoustic device. There is a disadvantage that it is not guaranteed that it is not allowed.

  In view of such a point, the invention described in the claims of the present application is that each power supply voltage is supplied through a fuse, and each amplifier is provided with a plurality of amplifiers for performing power amplification on an input signal. There is provided a power amplifier circuit in which a current corresponding to the sum of output currents of the parts is controlled so as not to cause undesired fusing of the fuse by flowing through the fuse.

  In the power amplifier circuit according to any one of claims 1 to 8 in the claims of the present application, the power supply voltage is supplied through the fuse, and the power amplification of the first input signal is performed. A first amplifying unit, a second amplifying unit that is supplied with a power supply voltage through a fuse and performs power amplification on the second input signal, a current corresponding to an output current of the first amplifying unit, and a second amplifying unit In accordance with the detection output signal obtained from the output current detection unit obtained from the output current detection unit, the output current detection unit for obtaining a detection output signal for the sum current corresponding to the sum of the current corresponding to the output current or the current including the sum current, An output control unit that regulates output to both or one of the first and second amplifying units and restricts the output currents of both the first and second amplifying units flowing through the fuses or currents including them. The It is made.

  In particular, in the power amplifier circuit according to the second aspect of the invention, the output current detection unit is configured such that the current corresponding to the output voltage of the first amplifier and the current corresponding to the output voltage of the second amplifier or those And an integration circuit to which a current including is supplied, and a detection output signal is formed by the integration circuit.

  According to the power amplifying circuit according to any one of claims 1 to 8 in the claims of the present application, the first and second amplifying units to which the power supply voltage is supplied to each through the fuse A current corresponding to the sum of the output currents or a current including the sum is detected by the output current detector, and a detection output signal based on the current is formed. Then, the output control unit performs output regulation for both or one of the first and second amplification units according to the detection output signal obtained from the output current detection unit, and the first and second flow through the fuses. The output current of both of the amplifying units or the current including them is limited. As a result, the sum of the output currents of the first and second amplifying units or a current including the sum does not cause undesired fusing of the fuse by flowing through the fuse. The situation where the desired fusing occurs is reliably avoided.

  In addition to the first and second amplification units, when another amplification unit similar to the first and second amplification units is provided, the output current detection unit causes the first and second amplification units to be provided. And a current corresponding to the sum of the output currents of the other amplifying units is detected as a current corresponding to a current including the sum of the output currents of the first and second amplifying units, and a detection output signal based thereon Is formed. Then, the output control unit performs output regulation for all or a part of the first and second amplifying units and the other amplifying units according to the detection output signal obtained from the output current detecting unit, and the fuse All the output currents of the first and second amplifying units and the other amplifying units flowing through the first and second amplifying units are limited as currents including the output currents of both the first and second amplifying units. As a result, all the output currents of the first and second amplifying units and the other amplifying units do not cause undesired fusing of the fuses as they flow through the fuses. The situation that occurs is reliably avoided.

  In particular, according to the power amplifying circuit of the invention described in claim 2, the output current detecting unit corresponds to the current corresponding to the output voltage of the first amplifying unit and the output voltage of the second amplifying unit. Since the detection output signal is formed by the integration circuit to which the current or the current including them is supplied, the first constant is set by appropriately setting the time constant of the integration circuit. In addition, the current corresponding to the sum of the output currents of the second amplifying units or the current including the sum is reliably detected, and an appropriate detection output signal is obtained.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the invention described in any one of claims 1 to 8 in the scope of claims of the present application will be described with examples described below.

  FIG. 1 shows a first embodiment which is an example of a power amplifier circuit according to the invention described in any one of claims 1 to 7 in the claims of the present application.

  The first embodiment shown in FIG. 1 is applied to, for example, an in-vehicle acoustic device mounted on a vehicle. In the first embodiment, for example, the left audio signal SL and the right audio signal SR constituting the stereo audio signal are respectively input to the PWM (pulse width modulation) signal generator 13 and the input terminals 11 and 12, respectively. 14. The PWM signal generator 13 generates a pair of PWM signals PLP and PLN based on the left audio signal SL, as shown in A and B of FIG. Are formed and supplied to the amplifier 15 as an input signal thereto. Further, the PWM signal generation unit 14 is based on the right audio signal SR, and the increase / decrease in the pulse width is opposite to each other, like the pair of PWM signals PLP and PLN shown in FIGS. A pair of PWM signals PRP and PRN are formed and supplied to the amplifying unit 16 as input signals thereto. Regarding the pair of PWM signals PLP and PLN or the pair of PWM signals PRP and PRN, “increase / decrease in the pulse width is opposite to each other” means the level of the left audio signal SL or the right audio signal SR. When the pulse width of the PWM signal PLP or the PWM signal PRP increases according to the change, the pulse width of the PWM signal PLN or the PWM signal PRN decreases according to the level change of the left audio signal SL or the right audio signal SR, and When the pulse width of the PWM signal PLP or the PWM signal PRP decreases according to the level change of the left audio signal SL or the right audio signal SR, the PWM signal PLN or PWM according to the level change of the left audio signal SL or the right audio signal SR. This means that the pulse width of the signal PRN increases.

  The amplifying unit 15 is configured to include a pair of power amplifiers 17 and 18, and each of the power amplifiers 17 and 18 includes a battery voltage VB that is a voltage from the in-vehicle battery 20. The power supply voltage is supplied through a main fuse 21 having a capacity, and further through a fuse 22 for an acoustic device having a power capacity smaller than that of the main fuse 21. The power amplifier 17 is supplied with the PWM signal PLP from the PWM signal generator 13 as an input signal, and the power amplifier 18 is supplied with the PWM signal PLN from the PWM signal generator 13 as an input signal.

  The power amplifier 17 amplifies the power of the PWM signal PLP that is an input signal while the battery voltage VB is supplied as a power supply voltage through the fuse 22, and the amplified PWM signal as shown in A of FIG. An output signal OLP is formed. Further, the power amplifier 18 amplifies the power of the PWM signal PLN that is an input signal while the battery voltage VB is supplied as a power supply voltage through the fuse 22, and is amplified as shown in B of FIG. An output signal OLN which is a PWM signal is formed. As shown in FIGS. 3A and 3B, the output signal OLP and the output signal OLN have a relationship in which the increase and decrease in pulse width are opposite to each other.

  The output signal OLP obtained from the power amplifier 17 and the output signal OLN obtained from the power amplifier 18 are supplied to the speaker 23 through the low-pass filters (LPF) 19a and 19b as output signals of the amplifying unit 15, respectively. As a result, the speaker 23 is driven by a pair of audio signals having opposite polarities based on the output signal OLP and the output signal OLN whose pulse width increases and decreases are opposite to each other. A voice based on is emitted.

  On the other hand, the amplifying unit 16 is configured to include a pair of power amplifiers 24 and 25, and a battery voltage VB that is a voltage from the in-vehicle battery 20 is supplied to the main fuse 21 in each of the power amplifiers 24 and 25. Furthermore, it is supplied as a power supply voltage through a fuse 22 for an acoustic device. The power amplifier 24 is supplied with the PWM signal PRP from the PWM signal generator 14 as an input signal, and the power amplifier 25 is supplied with the PWM signal PRN from the PWM signal generator 14 as an input signal.

  The power amplifier 24 amplifies the power of the PWM signal PRP as an input signal with the battery voltage VB supplied as the power supply voltage through the fuse 22, and is similar to the output signal OLP shown in A of FIG. An output signal ORP which is an amplified PWM signal is formed. Further, the power amplifier 25 performs power amplification on the PWM signal PRN that is an input signal under the condition that the battery voltage VB is supplied as a power supply voltage through the fuse 22, and is similar to the output signal OLN shown in FIG. An output signal ORN which is an amplified PWM signal is formed. The output signal ORP and the output signal ORN have a relationship in which the increase and decrease in pulse width are opposite to each other.

  The output signal ORP obtained from the power amplifier 24 and the output signal ORN obtained from the power amplifier 25 are supplied to the speaker 26 through the LPFs 19c and 19d as output signals of the amplifying unit 16, respectively. As a result, the speaker 26 is driven by a pair of audio signals having opposite polarities based on the output signal ORP and the output signal ORN whose increase and decrease in pulse width are opposite to each other. A voice based on is emitted.

  Under such circumstances, the output current detection unit is connected to the output end from which the output signal OLP in the power amplifier 17 constituting the amplification unit 15 is obtained and the output end from which the output signal ORP in the power amplifier 24 constituting the amplification unit 16 is obtained. 30 is connected. The output current detection unit 30 includes a series connection of a resistance element 31 and a diode 32 having one end connected to the output end of the power amplifier 17, and a resistance element 33 and a diode 34 having one end connected to the output end of the power amplifier 24. The capacitive element 35 and the resistive element 36 arranged between the series connection and the other end of the series connection of the resistive element 31 and the diode 32 and the other end of the serial connection of the resistive element 33 and the diode 34 and the reference potential point. And an integration circuit 37 formed by parallel connection.

  In the integrating circuit 37, a current corresponding to the output signal OLP obtained at the output terminal of the power amplifier 17 flows as a charging current into the capacitive element 35 through the resistance element 31 and the diode 32 and is obtained at the output terminal of the power amplifier 24. A current corresponding to the output signal ORP is supplied as a charging current to the capacitive element 35 through the resistance element 33 and the diode 34. Then, the discharge current from the capacitive element 35 flows from the connection point between the capacitive element 35 and the diodes 32 and 34 to the reference potential point through the resistive element 36. As a result, a voltage obtained across the capacitive element 35 causes a current corresponding to the output signal OLP obtained at the output terminal of the power amplifier 17 and a current corresponding to the output signal ORP obtained at the output terminal of the power amplifier 24. A detection output signal VDI for the sum current corresponding to the sum is formed.

  The current flowing into the capacitive element 35 through the resistance element 31 and the diode 32 in accordance with the output signal OLP obtained at the output terminal of the power amplifier 17 is a current corresponding to the output current of the power amplifier 17, and its level is a resistance. The current flowing into the capacitive element 35 through the resistance element 33 and the diode 34 in accordance with the output signal ORP obtained at the output terminal of the power amplifier 24 is determined by the resistance value of the element 31. The current corresponds to the output current, and its level is determined by the resistance value of the resistance element 33. Further, the output current of the power amplifier 17 is also the output current of the amplifying unit 15, and the output current of the power amplifier 24 is also the output current of the amplifying unit 16. Therefore, the output current detection unit 30 including the integration circuit 37 includes a current corresponding to the output current of the amplification unit 15 including the power amplifier 17 and the amplification unit 16 including the power amplifier 24. The detection output signal for the sum current corresponding to the sum of the current corresponding to the output current is obtained as the detection output signal VDI.

  The detection output signal VDI obtained from the output current detection unit 30 is supplied to one of the pair of input terminals of the voltage comparison unit 40. The reference voltage VR from the reference voltage source 41 is supplied to the other of the pair of input terminals of the voltage comparison unit 40. In the voltage comparison unit 40, when the voltage level of the detection output signal VDI exceeds the predetermined voltage level of the reference voltage VR, the control signal CP is sent out. The control signal CP sent from the voltage comparison unit 40 is supplied to the respective control terminals of the power amplifiers 17 and 18 constituting the amplification unit 15, and the gain of the power amplifiers 17 and 18 is reduced, or the power amplifier 17 And 18 are temporarily stopped to regulate the output of each of the power amplifiers 17 and 18, and the output current of each of the power amplifiers 17 and 18, that is, the output current of the amplifying unit 15 is limited. Further, the control signal CP sent from the voltage comparison unit 40 is also supplied to the control terminals of the power amplifiers 24 and 25 constituting the amplification unit 16 to reduce the gain of the power amplifiers 24 and 25, or The amplification operation of the power amplifiers 24 and 25 is temporarily stopped to regulate the output of each of the power amplifiers 24 and 25, and the output current of each of the power amplifiers 24 and 25, that is, the output current of the amplification unit 16 is changed. Restrict.

  Accordingly, the voltage comparison unit 40 and the reference voltage source 41 are configured to include the power amplifiers 17 and 18 and the power amplifiers 24 and 25 according to the detection output signal VDI obtained from the output current detection unit 30. Thus, an output control unit that restricts the output current of both of the amplification units 15 and 16 is configured.

  By the output restriction control on the power amplifiers 17 and 18 constituting the amplification unit 15 and the power amplifiers 24 and 25 constituting the amplification unit 16 by the control signal CP sent from the voltage comparison unit 40 constituting this output control unit, In accordance with the output signal OLP obtained at the output terminal of the power amplifier 17, the current flowing into the capacitive element 35 through the resistance element 31 and the diode 32, and the resistance according to the output signal ORP obtained at the output terminal of the power amplifier 24. Each of the currents flowing into the capacitive element 35 through the element 33 and the diode 34 is reduced, and as a result, the voltage level of the detection output signal VDI sent from the output current detection unit 30 is equal to the reference voltage VR from the reference voltage source 41. The state is such that the predetermined voltage level is not exceeded.

  Under such circumstances, the output currents of both the amplifying units 15 and 16 substantially occupy most of the current flowing through the fuse 22 that supplies the battery voltage VB to both the amplifying units 15 and 16 as a power source. However, it is limited according to the control signal CP sent from the voltage comparison unit 40 that constitutes the output control unit as described above, so that an undesired blowout of the fuse 22 is not caused. It is said.

  In the first embodiment shown in FIG. 1, one end of the series connection of the resistance element 31 and the diode 32 is the power amplification unit 17 of the power amplification units 17 and 18 constituting the amplification unit 15. In addition, one end of the series connection of the resistance element 33 and the diode 34 is connected to the output end of the power amplifying unit 24 of the power amplifying units 24 and 25 constituting the amplifying unit 16. However, one end of the series connection of the resistance element 31 and the diode 32 may be connected to the output end of the power amplification section 18 of the power amplification sections 17 and 18 constituting the amplification section 15, and the resistance element 33 One end of the series connection of the diode 34 and the diode 34 may also be connected to the output end of the power amplifier 25 of the power amplifiers 24 and 25 constituting the amplifier 16.

  FIG. 4 shows a second embodiment which is an example of a power amplifier circuit according to the invention described in any one of claims 1 to 6 and claim 8 in the claims of the present application.

  The second embodiment shown in FIG. 4 is also applied to, for example, an in-vehicle acoustic device mounted on a vehicle. The second embodiment has a configuration corresponding to that in which the output current detection unit 50 is provided instead of the output current detection unit 30 in the first embodiment shown in FIG. The portions other than the output current detector 50 are the same as those in the first embodiment shown in FIG. Therefore, in FIG. 4, the parts and signals corresponding to the respective parts and signals shown in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and redundant description thereof is omitted.

  The output current detector 50 in the second embodiment shown in FIG. 4 includes a series connection of a resistor 31 and a diode 32, one end of which is connected to the output terminal of the power amplifier 17 constituting the amplifier 15, and the amplifier 15 The resistor element 51 and the diode 52, one end of which is connected to the output terminal of the power amplifier 18 constituting the amplifier, and the diode 52 are connected in series. A series connection of the resistor element 53 and the diode 54, one end of which is connected to the output end of the power amplifier 25 constituting the amplifier unit 16, and the other end of the series connection of the resistor element 31 and the diode 32, The other end of the series connection of the resistance element 51 and the diode 52, the other end of the series connection of the resistance element 33 and the diode 34, and the other end of the series connection of the resistance element 53 and the diode 54. It is configured to include an integrator circuit 55 formed by a parallel connection of a capacitor 35 and a resistor 36 arranged between the reference potential point and.

  In the integrating circuit 55, a current corresponding to the output signal OLP obtained at the output terminal of the power amplifier 17 passes through the resistance element 31 and the diode 32, and a current corresponding to the output signal OLN obtained at the output terminal of the power amplifier 18 is sent to the resistance element. A current corresponding to the output signal ORP obtained at the output terminal of the power amplifier 24 through the resistor 51 and the diode 52 is passed through the resistance element 33 and the diode 34, and further a current according to the output signal ORN obtained at the output terminal of the power amplifier 25 is obtained. The electric current flows into the capacitive element 35 through the resistance element 53 and the diode 54, respectively. Then, the discharge current from the capacitive element 35 flows from the connection point between the capacitive element 35 and the diodes 32, 52, 34 and 54 to the reference potential point through the resistive element 36. Thereby, the voltage obtained across the capacitive element 35 causes the current corresponding to the output signal OLP obtained at the output terminal of the power amplifier 17 and the current and power corresponding to the output signal OLN obtained at the output terminal of the power amplifier 18. A detection output signal VDI for the sum current corresponding to the sum of the current corresponding to the output signal ORP obtained at the output terminal of the amplifier 24 and the current corresponding to the output signal ORN obtained at the output terminal of the power amplifier 25 is formed.

  The current flowing into the capacitive element 35 through the resistance element 31 and the diode 32 in accordance with the output signal OLP obtained at the output terminal of the power amplifier 17 is a current corresponding to the output current of the power amplifier 17, and its level is a resistance. The current flowing into the capacitive element 35 through the resistance element 51 and the diode 52 in accordance with the output signal OLN obtained at the output terminal of the power amplifier 18 is determined by the resistance value of the element 31. , The level of which is determined by the resistance value of the resistive element 51, and the capacitive element 35 through the resistive element 33 and the diode 34 in accordance with the output signal ORP obtained at the output terminal of the power amplifier 24. Is a current corresponding to the output current of the power amplifier 24, and the level of the current flows into the resistor element 33. Further, the current flowing into the capacitive element 35 through the resistance element 53 and the diode 54 in accordance with the output signal ORN obtained at the output terminal of the power amplifier 25 becomes the output current of the power amplifier 25. The corresponding current, the level of which is determined by the resistance value of the resistance element 53. The output current of the power amplifier 17 and the output current of the power amplifier 18 are also the output current of the amplifier 15, and the output current of the power amplifier 24 and the output current of the power amplifier 25 are also the output current of the amplifier 16. is there. Therefore, the output current detection unit 50 configured including the integration circuit 55 includes the current corresponding to the output current of the amplification unit 15 configured including the power amplifiers 17 and 18 and the power amplifiers 24 and 25. The detection output signal for the sum current corresponding to the sum of the current corresponding to the output current of the amplifying unit 16 is obtained as the detection output signal VDI.

  The detection output signal VDI obtained from the output current detection unit 50 is supplied to the voltage comparison unit 40 constituting the output control unit, and the voltage level of the detection output signal VDI reaches a predetermined voltage level of the reference voltage VR from the voltage comparison unit 40. When exceeded, a control signal CP is sent out. The control signal CP sent from the voltage comparison unit 40 is supplied to the respective control terminals of the power amplifiers 17 and 18 constituting the amplification unit 15, and the gain of the power amplifiers 17 and 18 is reduced, or the power amplifier 17 And 18 are temporarily stopped to regulate the output of each of the power amplifiers 17 and 18, and the output current of each of the power amplifiers 17 and 18, that is, the output current of the amplifying unit 15 is limited. Further, the control signal CP sent from the voltage comparison unit 40 is also supplied to the control terminals of the power amplifiers 24 and 25 constituting the amplification unit 16 to reduce the gain of the power amplifiers 24 and 25, or The amplification operation of the power amplifiers 24 and 25 is temporarily stopped to regulate the output of each of the power amplifiers 24 and 25, and the output current of each of the power amplifiers 24 and 25, that is, the output current of the amplification unit 16 is changed. Restrict.

  By the output restriction control on the power amplifiers 17 and 18 constituting the amplification unit 15 and the power amplifiers 24 and 25 constituting the amplification unit 16 by the control signal CP sent from the voltage comparison unit 40 constituting this output control unit, According to the output signal OLP obtained at the output terminal of the amplifier 17, the current flowing into the capacitive element 35 through the resistance element 31 and the diode 32, and the resistance element 51 and the current according to the output signal OLN obtained at the output terminal of the power amplifier 18. In accordance with the current flowing into the capacitive element 35 through the diode 52, the output signal ORP obtained at the output terminal of the power amplifier 24, the current flowing into the capacitive element 35 through the resistance element 33 and the diode 34, and the output terminal of the power amplifier 25. In accordance with the output signal ORN obtained from the capacitor element 35 through the resistor element 53 and the diode 54. Each of the inflowing currents is reduced, and as a result, the voltage level of the detection output signal VDI sent from the output current detection unit 50 does not exceed the predetermined voltage level of the reference voltage VR from the reference voltage source 41 It is said.

  The output currents of both of the amplifying units 15 and 16 substantially occupy most of the current flowing through the fuse 22 that supplies the battery voltage VB to both the amplifying units 15 and 16 as a power source. As described above, the restriction is made according to the control signal CP sent from the voltage comparison unit 40 that constitutes the output control unit, so that an undesired blowout of the fuse 22 is not caused.

  In the second embodiment shown in FIG. 4, the output current detection unit 50 has a capacitance through the resistance element 31 and the diode 32 according to the output signal OLP obtained at the output terminal of the power amplifier 17. Depending on the current flowing into the element 35 and the output signal OLN obtained at the output terminal of the power amplifier 18, the current flowing into the capacitive element 35 through the resistance element 51 and the diode 52 and the output signal ORP obtained at the output terminal of the power amplifier 24 In response to the current flowing into the capacitive element 35 through the resistance element 33 and the diode 34 and the output signal ORN obtained at the output terminal of the power amplifier 25, the current flows into the capacitive element 35 through the resistance element 53 and the diode 54. A sum current corresponding to the sum of the currents is detected, and a detection output signal VDI corresponding to the sum is formed. Therefore, a current corresponding to the output current of the amplifying unit 15 configured to include the power amplifiers 17 and 18, and a current corresponding to the output current of the amplifying unit 16 configured to include the power amplifiers 24 and 25, Detection of the sum current corresponding to the sum is performed in more detail and accurately, and as a result, a more appropriate detection output signal VDI is obtained.

  In the first embodiment shown in FIG. 1 and the second embodiment shown in FIG. 4, the power amplifiers 17 and 18 are included by the control signal CP sent from the voltage comparator 40. The output is restricted for both the amplification unit 15 and the amplification unit 16 including the power amplifiers 24 and 25. Instead of such a configuration, the output by the control signal CP is used. A configuration may be adopted in which the regulation is performed on any one of the amplification units 15 and 16, thereby reducing the current flowing through the fuse 22.

  Further, both the first embodiment shown in FIG. 1 and the second embodiment shown in FIG. 4 are configured to include power amplifiers 17 and 18 in which a power supply voltage is supplied through the fuse 22. The amplifying unit 15 and the amplifying unit 16 including the power amplifiers 24 and 25 are provided, and any one of claims 1 to 8 in the claims of the present application. The power amplifying circuit according to the described invention may be provided with three or more amplifying units each of which is similar to the amplifying unit 15 or the amplifying unit 16. In that case, it is an output current detection unit similar to the output current detection unit 30 shown in FIG. 1 or the output current detection unit 50 shown in FIG. 4, and corresponds to the output currents of three or more amplification units. A device for detecting a sum current corresponding to the sum of the currents to be generated and forming a detection output signal according to the detection result is provided.

  For example, in addition to the amplifiers 15 and 16 in the first embodiment shown in FIG. 1 and the second embodiment shown in FIG. 4, another amplifier similar to the amplifier 15 or the amplifier 16 is provided. In this case, the other amplifying unit also includes, for example, a series connection of the resistance element 31 and the diode 32 connected to the amplification unit 15, or a series connection of the resistance element 31 and the diode 32, and the resistance element 51 and the diode. A series connection of a resistance element and a diode similar to both of the series connection to 52 is connected, and an output current detection unit is configured such that the current through the series connection also flows into the capacitive element 35 as a charging current. . Such an output current detection unit detects a current including a sum current corresponding to the sum of the currents corresponding to the respective output currents of the amplification units 15 and 16, and outputs a detection output signal corresponding to the detection result. Will form.

  Also in such a case, the control signal CP sent from the voltage comparison unit 40 is configured such that output control is performed for all of the amplification units 15 and 16 and another amplification unit, and the control signal sent from the voltage comparison unit 40 One of the configurations in which the output regulation is performed for the amplifying units 15 and 16 and a part of another amplifier is performed by the CP.

  The power amplification circuit according to the invention described in any one of claims 1 to 8 in the claims of the present application as described above is suitable for application to, for example, an in-vehicle acoustic device mounted in a vehicle. In addition, the present invention can be widely applied to electronic devices such as acoustic devices other than on-vehicle acoustic devices.

It is a circuit connection diagram showing an example of a power amplifier circuit according to the invention described in any one of claims 1 to 7 in the claims of the present application. It is a signal waveform diagram with which it uses for operation | movement description of the example shown by FIG. It is a signal waveform diagram with which it uses for operation | movement description of the example shown by FIG. FIG. 10 is a circuit connection diagram showing an example of a power amplifier circuit according to any one of claims 1 to 6 and claim 8 in the claims of the present application.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11, 12, ... Input terminal 13, 14 ... PWM signal generation part 15, 16, ... Amplification part 17, 18, 24, 25 ... Power amplifier, 19a-19d ... LPF , 20 ... vehicle-mounted battery, 21 ... main fuse, 22 ... fuse, 23, 26 ... speaker, 30, 50 ... output current detection unit, 31, 33, 36, 51, 53 ..Resistance element 32, 34, 52, 54 ... Diode, 35 ... Capacitor element, 37, 55 ... Integration circuit, 40 ... Voltage comparison unit, 41 ... Reference voltage source

Claims (8)

A first amplifier that is supplied with a power supply voltage through a fuse and performs power amplification for the first input signal;
A second amplifying unit, wherein the power supply voltage is supplied through the fuse, and performs power amplification on a second input signal;
A detection output signal is obtained for a sum current corresponding to the sum of the current corresponding to the output current of the first amplifying unit and the current corresponding to the output current of the second amplifying unit or a current including the sum current. An output current detector;
In accordance with a detection output signal obtained from the output current detection unit, output restriction is applied to both or one of the first and second amplification units, and both of the first and second amplification units flowing through the fuse are controlled. An output control unit for limiting an output current or a current including the output current;
A power amplifier circuit configured to include:   The output current detection unit has a current corresponding to the output voltage of the first amplifying unit and a current corresponding to the output voltage of the second amplifying unit, or a current corresponding to the output voltage of the first amplifying unit. And an integration circuit to which a current including a current corresponding to an output voltage of the second amplifying unit is supplied, and the detection output signal is formed by the integration circuit. The power amplifier circuit described.   The integrating circuit includes a first resistor element connected to an output terminal of the first amplifying unit, a second resistor element connected to an output terminal of the second amplifying unit, the first and second resistors A capacitor element into which a charging current flows through the resistor element, and a third resistor element through which a discharge current flowing out of the capacitor element flows, and the detection output signal is obtained at one end of the capacitor element. The power amplifier circuit according to claim 2, wherein:   2. The power amplifying circuit according to claim 1, wherein the output control unit reduces the gain of both or one of the first and second amplifying units when the level of the detection output signal exceeds a predetermined value. .   2. The output control unit temporarily stops the amplifying operation of both or one of the first and second amplifying units when the level of the detection output signal exceeds a predetermined value. Power amplifier circuit.   The output control unit includes a voltage comparison unit that generates a comparison output signal by comparing a voltage value of a detection output signal obtained by the integration circuit with a reference voltage value, and the output control unit includes the voltage comparison unit according to the comparison output signal. 3. The power amplifier circuit according to claim 2, wherein output regulation is applied to the first and second amplifying units.   The first amplifying unit includes first and second amplifiers, each of which is supplied with the power supply voltage through the fuse and performs power amplification on the pair of first input signals having opposite polarities. The third and fourth amplifiers are configured to perform power amplification on a pair of the second input signals each having the power supply voltage supplied through the fuse and having opposite polarities to each other. The output current detection unit corresponds to the current corresponding to the output current of the first amplifier or the second amplifier and the output current of the third amplifier or the fourth amplifier. 2. The power amplifier circuit according to claim 1, wherein a detection output signal is obtained for a sum current corresponding to a sum of the sum current and a current including the sum current.   The first amplifying unit includes first and second amplifiers, each of which is supplied with the power supply voltage through the fuse and performs power amplification on the pair of first input signals having opposite polarities. The third and fourth amplifiers are configured to perform power amplification on a pair of the second input signals each having the power supply voltage supplied through the fuse and having opposite polarities to each other. And the output current detection unit includes a current corresponding to the output current of each of the first and second amplifiers and a current corresponding to the output current of each of the third and fourth amplifiers. 2. A power amplifying circuit according to claim 1, wherein a detection output signal is obtained for a sum current corresponding to the sum of and a current including the sum current.

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