JP2021108433A - Audio amplifier ic, and on-vehicle audio system and electronic apparatus using the audio amplifier ic - Google Patents

Abstract

To provide an audio amplifier IC capable of detecting abnormalities in a load or a peripheral circuit by a method different from the conventional methods.SOLUTION: In an audio amplifier IC, when a load diagnostic mode is set while a load 201 is mounted, a switch SW1 is turned on. During an open detection period, a first threshold voltage VTH1 is set to a first level VOPEN, and a first current ITEST1 generated by a first current source CS1 is gradually increased to a first current amount IOPEN. During a short detection period following the open detection period, the first threshold voltage VTH1 is set to a second level SHORT larger than the first level VOPEN, and the first current ITEST1 is gradually increased to a second current amount ISHORT. When a first comparison signal S1 transits to the second level during the open detection period, the load 201 is determined as open abnormality. When the first comparison signal S1 is at the first level during the short detection period, the load 201 is determined as short abnormality.SELECTED DRAWING: Figure 2

Description

The present invention relates to an amplifier that drives a speaker or headphones.

An audio amplifier (also called a power amplifier) is used to amplify an audio signal and drive an electroacoustic conversion element such as a speaker or headphones. FIG. 1 is a circuit diagram of an audio system 200R including a BTL (Bridged Tied Load) type audio amplifier 100R. The positive electrode terminal + and the negative electrode terminal-of the electroacoustic conversion element 202, which is a load, are connected to the outputs OUTP and OUTN of the audio amplifier 100R. The audio amplifier 100R includes a first amplifier 102P and a second amplifier 102N that output _{opposite-phase drive voltages V OUTP} and V _OUTN.

The audio amplifier 100R further includes a load connection state detection circuit 106 that detects an abnormality such as an opening of the electroacoustic conversion element 202. For example, the load connection state detection circuit disclosed in Patent Document 1 flows a predetermined amount of current toward one output terminal, and is normal, open, or short-circuited based on the voltage or current appearing in the one output terminal. Which state is detected.

Japanese Unexamined Patent Publication No. 2011-182263 JP-A-2017-112428

The present invention has been made in such a situation, and one of the exemplary purposes of the embodiment is to provide an audio amplifier IC capable of detecting an abnormality in a load or a peripheral circuit by a method different from the conventional method.

One aspect of the present invention relates to a BTL (Bridged Tied Load) type audio amplifier IC (Integrated Circuit). The audio amplifier IC is connected to the first amplifier, the second amplifier, the first output pin connected to the output of the first amplifier, the second output pin connected to the output of the second amplifier, and the first output pin. A first current source that sources a first current whose amount of current can be controlled to the first output pin, a switch provided between the second output pin and the fixed voltage line (ground), and the first output pin and the second output pin. A first comparator that compares the potential difference with a controllable first threshold voltage and generates a first comparison signal that is the first level when the potential difference is lower than the first threshold voltage and the second level when the potential difference is higher. A controller for controlling a first current source and a switch is provided. The controller turns the switch on when set to load diagnostic mode with the load mounted, and (i) sets the first threshold voltage to the first level during the open detection period and sets the first current source. The first current generated by is gradually increased to the first current amount, and (ii) in the short detection period following the open detection period, the first threshold voltage is set to the second level larger than the first level, and the second level is set. The first current generated by the 1 current source is gradually increased from the first current amount to the second current amount, and (iii-1) the first comparison signal is the first level in the open detection period and the second in the short detection period. When the load is at the level, it is determined that the load is normal, and (iii-2) when the first comparison signal transitions to the second level during the open detection period, the load is determined to be open abnormality, and (iii-3) the first comparison signal. Is the first level in the short circuit detection period, the load is determined to be a short circuit abnormality.

According to this aspect, it is possible to detect a load short-circuit abnormality or an open abnormality in one sequence without generating pop noise. Moreover, since a short circuit abnormality and an open abnormality can be detected by a single comparator, the circuit area can be reduced.

The switch may have a variable impedance in the on state. The controller may set the impedance of the switch relatively high during the open detection period and the impedance of the switch relatively low during the short detection period. Thereby, the input voltage range of the first comparator in the open detection period and the short detection period can be appropriately set individually.

The switch may include first and second NMOS transistors that are connected in parallel and are of different sizes. By selectively turning on the two NMOS transistors, the impedance in the turned-on state can be changed.

The audio amplifier IC compares the first detection voltage obtained by dividing the voltage of the first output pin with the controllable second threshold voltage, and when the first detection voltage is lower than the second threshold voltage, the first detection voltage is obtained. A second comparator may be further provided to generate a second comparison signal that becomes the second level when it is one level higher. When the controller is set to the ground fault detection mode, the second threshold voltage and the third threshold voltage are set to the third level, and the first current generated by the first current source is up to the third current amount. When it is gradually increased and the second comparison signal maintains the first level, it may be determined that the ground fault is abnormal outside the first output pin or the second output pin.

The audio amplifier IC is connected to the second output pin, and the second current source whose current amount can be controlled is sourced to the second output pin, and the voltage of the second output pin is defined as the second threshold voltage. A third comparator that generates a third comparison signal that becomes the first level when the voltage of the second output pin is lower than the third threshold voltage and the second level when the voltage of the second output pin is higher than the interlocking third threshold voltage. And may be further provided. In (iv) ground fault detection mode, the controller gradually increases the second current generated by the second current source to the third current amount, and when the third comparison signal maintains the first level, the first output pin. Alternatively, it may be determined that the ground fault is abnormal outside the second output pin.

When set to the skyscraper detection mode, the controller sets the second and third threshold voltages to a fourth value higher than the third level and turns off the first and second current sources. When the state is set and at least one of the second comparison signal or the third comparison signal transitions to the second level, it may be determined that there is a tentacle abnormality outside the first output pin or the second output pin.

Any combination of the above components, and conversion of the expression of the present invention between methods, devices, and the like are also effective as aspects of the present invention.

According to the present invention, an abnormality in a load or a peripheral circuit can be detected by a method different from the conventional method.

It is a circuit diagram of an audio system including an audio amplifier of BTL (Bridged Tied Load) type. It is a circuit diagram of the audio system including the audio amplifier IC which concerns on Embodiment 1. FIG. It is an equivalent circuit diagram of an audio amplifier IC in a load diagnosis mode. 4 (a) to 4 (c) are operation waveform diagrams of the audio amplifier IC of FIG. It is a circuit diagram of the 1st comparator and its surroundings. It is a circuit diagram of the audio amplifier IC which concerns on Embodiment 2. FIG. It is an equivalent circuit diagram of the audio amplifier IC in the ground fault detection mode. It is an equivalent circuit diagram of the audio amplifier IC in the heavenly interference detection mode. 9 (a) to 9 (c) are external views of the electronic device. It is a figure which shows the in-vehicle audio system.

Hereinafter, the present invention will be described with reference to the drawings based on preferred embodiments. The same or equivalent components, members, and processes shown in the drawings shall be designated by the same reference numerals, and redundant description will be omitted as appropriate. Further, the embodiment is not limited to the invention but is an example, and all the features and combinations thereof described in the embodiment are not necessarily essential to the invention.

In the present specification, the "state in which the member A is connected to the member B" means that the member A and the member B are physically directly connected, or the member A and the member B are electrically connected. It also includes cases of being indirectly connected via other members that do not affect the state or interfere with the function.

Similarly, "a state in which the member C is provided between the member A and the member B" means that the member A and the member C, or the member B and the member C are directly connected, and also electrically. It also includes the case of being indirectly connected via another member that does not affect the connection state or interfere with the function.

The vertical and horizontal axes of the waveform charts and time charts referred to in the present specification are appropriately enlarged or reduced for ease of understanding, and each waveform shown is also simplified for ease of understanding. Or exaggerated or emphasized.

(Embodiment 1)
FIG. 2 is a circuit diagram of an audio system 200 including the audio amplifier IC 100 according to the first embodiment. The audio system 200 includes an electroacoustic conversion element 202, filters 204P and 204N, and an audio amplifier IC100.

The electroacoustic conversion element 202 is a speaker, headphones, or the like, and the electroacoustic conversion element 202 and the filters 204P and 204N are connected to the audio amplifier IC100 in a BTL (Bridged Tied Load) format. The audio amplifier IC100 and the filters 204P and 204N are mounted on the circuit board 210.

The audio amplifier IC 100 amplifies the audio signal in the positive phase and the negative phase, and applies the audio signal in the positive phase to one end of the electroacoustic conversion element 202 and the opposite phase to the other end.

The audio amplifier IC100C mainly includes a first amplifier 102P, a second amplifier 102N, a first output pin OUTP, and a second output pin OUTN, and is integrally integrated on one semiconductor substrate. "Integrated integration" includes cases where all the components of a circuit are formed on a semiconductor substrate or cases where the main components of a circuit are integrated integrally, and some of them are used for adjusting circuit constants. A resistor, a capacitor, or the like may be provided outside the semiconductor substrate. By integrating the circuit on one chip, the circuit area can be reduced and the characteristics of the circuit element can be kept uniform.

The first amplifier 102P outputs a positive phase audio signal, and the second amplifier 102N outputs a negative phase audio signal. The first amplifier 102P and the second amplifier 102N are, for example, class D amplifiers (switching amplifiers), and may include an inverter. The first amplifier 102P and the second amplifier 102N may be class A or class AB linear amplifiers.

The audio amplifier IC 100 is provided with a first current source CS1, a first comparator COMP1, and a controller 110 in order to detect an abnormality in the load 201 including the electroacoustic conversion element 202 and the filters 204P and 204N.

The first current source CS1 is connected to the first output pin OUTP, and is configured to source _{the first current I TEST1 whose current amount can be controlled to the first output pin OUTP.}

The switch SW1 is provided between the second output pin OUTN and the fixed voltage line (that is, ground).

The first comparator COMP1 compares the potential difference ΔV between the first output pin OUTP and the second output pin OUTN with the controllable first threshold voltage V _TH1, and the potential difference ΔV is lower than _{the first threshold voltage V TH1.} When the first level (for example, low) is generated, the first comparison signal S1 which becomes the second level (for example, high) when the value is high is generated. The input of the first comparator COMP1 is provided with switches SWp and SWn for disconnecting the first comparator COMP1 from the output pins OUTP and OUTN during normal audio reproduction. If the input of the first comparator COMP1 has a sufficiently high impedance, the switches SWp and SWn may be omitted.

The controller 110 controls the first current source CS1 and the switch SW1, and determines whether or not there is an abnormality in the electroacoustic conversion element 202 based on the first comparison signal S1 generated by the first comparator COMP1.

The above is the configuration of the audio amplifier IC100. Next, the operation will be described. FIG. 3 is an equivalent circuit diagram of the audio amplifier IC100 in the load diagnosis mode. When the controller 110 is set to the load diagnosis mode in a state where the electroacoustic conversion element 202, which is a load, is mounted, the outputs of the first amplifier 102P and the second amplifier 102N are set to the high impedance state, and the switch SW1 is set to the ON state. do.

Then, (i) in the open detection period _{T OPEN_DET,} the first threshold voltage _{V TH1} is set to a first level _{V OPEN,} the first current _{I TEST1} the first current source CS1 is generated first current amount _{I OPEN} Gradually increase until.

(Ii) in the open detection period _{T OPEN_DET} subsequent short detection period _{T SHORT_DET,} the first threshold voltage _{V TH1} is set to a first level _{V OPEN} greater than the second level _{V SHORT,} the first current source CS1 is generated The first current I _TEST1 is gradually increased from the first current amount I _OPEN to the second current amount I _SHORT.

4 (a) to 4 (c) are operation waveform diagrams of the audio amplifier IC 100 of FIG. FIG. 4A shows a waveform when the load 201 is normal. When the load 201 is normal, the potential difference ΔV between the two output pins OUTP and OUTN is expressed by the equation (1).
ΔV = R _{LOAD (NORM)} × I _TEST1
R _{LOAD (NORM)} is the combined impedance of the series resistance of the inductance of the electroacoustic conversion element 202 and the filter 204, and is typically about 4 to 32 Ω, for example.

The maximum value of the potential difference ΔV in the open detection period _{TOPEN_DET is}
ΔV = I _OPEN × R _{LOAD (NORM)}
Will be. In this state, when ΔV <V _OPEN , the load 201 is not open.

The maximum value of the potential difference ΔV in the short detection period _{TSHORT_DET is}
ΔV = I _SHORT × R _{LOAD (NORM)}
Will be. In this state, when ΔV> V _SHORT , the load 201 is not short-circuited.

That controller 110, a first comparison signal S1 is the first level in the open detection period _{T OPEN_DET} (low), when the short detection period _{T SHORT_DET} a second level (high), the load 201 including an electro-acoustic transducer 202 Is determined to be normal.

FIG. 4B shows a waveform when the load 201 has an open abnormality. When the open abnormality occurs, _{the capacitor of the filter 204P is charged by the current I TEST1} and the potential of the first output pin OUTP rises, whereby the potential difference ΔV exceeds the first threshold voltage V _OPEN .

Therefore, the controller 110 determines that the load 201 is an open abnormality when _{the first comparison signal S1 transitions to the second level (high) in the open detection period TOPN_DET.}

FIG. 4C shows a waveform when the electroacoustic conversion element 202 has a short circuit abnormality. When a short-circuit abnormality occurs in the electroacoustic conversion element 202, R _LOAD ≈ 0, the potential difference ΔV becomes small, and the threshold voltage V _SHORT is not exceeded.

Therefore, when the first comparison signal S1 is _{the first level (low) in the short detection period TSHORT_DET} , the controller 110 determines that the electroacoustic conversion element 202 has a short abnormality.

The above is the operation of the load diagnosis by the audio amplifier IC100.

According to this audio amplifier IC100, a short-circuit abnormality or an open abnormality of the load 201 (electroacoustic conversion element 202) can be detected in one sequence. In this load diagnosis, by gradually changing the current I _TEST1, from electroacoustic transducer 202 of pop noise is generated can be prevented.

Further, since a short circuit abnormality and an open abnormality can be detected by a single comparator COMP1, the circuit area can be reduced.

Subsequently, a specific configuration example of the audio amplifier IC100 will be described. FIG. 5 is a circuit diagram of the first comparator COMP1 and its surroundings. The comparator COMP1 includes a tail current source 120, a differential pair 122, a current mirror load 124, and an offset resistor 126. The offset resistor 126 is inserted on one source side of the transistor of the differential pair 122. The first comparator COMP1 has an input offset voltage V _OFS1 corresponding to the resistance value of the offset resistor 126, and the first comparison signal S1 has a first level (low) when _{Vp <Vn + V OFS1 and Vp> Vn + V OFS1} . When it becomes the second level (high). Vp is the voltage of the non-inverting input terminal, and Vn is the voltage of the inverting input terminal. Since ΔV = Vp−Vn, this offset voltage V _OFS1 corresponds to the first threshold voltage _VTH1 in FIG.

The offset resistor 126 is a variable resistor and is _controlled to have a relatively small value in the open detection period TOPEN_DET and a relatively large value in the short detection period _{TSHORT_DET} .

A logic inverting circuit 130 may be added after the first comparator COMP1. The logic inverting circuit 130 includes an inverter 132 and a selector 134. The inverter 132 inverts the first comparison signal S1. The first comparison signal S1 before inversion and the first comparison signal S1X after inversion are input to the selector 134. The selector 134 receives the control signal CONT_SDET asserted (1) in the short detection mode and negated (0) in the open detection mode, and selects one of the two inputs S1 and S1X according to the value of the control signal CONT_SDET. .. As a result, the output ERR_DET of the selector 134 transitions to low when the load 201 is normal and high when an abnormality occurs.

The impedance (on resistance) of the switch SW1 in the on state can be switched. The controller 110 _{sets the impedance of the switch SW1 relatively high in the open detection period TOPN_DET} , and sets the impedance of the switch SW1 relatively low in the short detection period _{TSHORT_DET} . Thereby, the input voltage range of the first comparator COMP1 in the open detection period _{TOPEN_DET} and the short detection period _{TSHORT_DET can be appropriately set individually.}

The switch SW1 includes a plurality of (two in this example) MOS transistors M11 and M12 connected in parallel. MOS transistors M11, M12 have different on-resistance _{(R ON1>} R _ON2). The potential Vn of the inverting input terminal (−) of the first comparator COMP1 is Vn = R _{ON (SW1)} × I _TEST1 . In the open detection period _{TOPEN_DET} in which the first current I _TEST1 is small, the transistor M11 is turned on and M12 is turned off, and the on resistance of the switch SW1 is _{set large (R ON1} ). In the short detection period _{TSHORT_DET} where the first current I _TEST1 is large, the transistor M11 is turned off and the transistor M12 is turned on (or both are turned on, and the on resistance of the switch SW1 is made small (R _ON2 ), so that the open detection period is set. in T _{OPEN_DET} the short detection period _{T SHORT_DET, .R ON1} that the input voltage range of the first comparator COMP1 can be appropriately _set, may be about ten times _{R ON2.}

(Embodiment 2)
FIG. 6 is a circuit diagram of the audio amplifier IC100A according to the second embodiment. In addition to the load diagnosis mode, the audio amplifier IC100A supports a ground fault detection mode and a ceiling fault detection mode of the output pins OUTP and OUTN.

The audio amplifier IC 100A includes a second comparator COMP2, a voltage source VS2, a third comparator COMP3, a voltage source VS3, and a second current source CS2 in addition to the audio amplifier IC100 of FIG.

The voltage Vp of the first output pin OUTP is divided by resistance. The second comparator COMP2 compares the first detected voltage Vp'after voltage division with the controllable second threshold voltage _VTH2, and the first detected voltage Vp'is lower than _{the second threshold voltage VTH2.} A second comparison signal S2 is generated, which sometimes becomes the first level (for example, low) and sometimes becomes the second level (for example, high).

The voltage Vn of the second output pin OUTN is also divided by resistance. The third comparator COMP3 compares the second detected voltage Vn'after voltage division with the controllable third threshold voltage V _TH3, and the second detected voltage Vn'is lower than _{the third threshold voltage V TH3.} A third comparison signal S3 is generated, which sometimes becomes the first level (for example, low) and sometimes becomes the second level (for example, high).

Switches SW21 and SW22 are provided to disconnect the comparators COMP2 and COMP3 from the output pins OUTP and OUTN during normal audio reproduction. If the inputs of the comparators COMP2 and COMP3 have sufficiently high impedance, the switches SW21 and SW22 may be omitted.

The second threshold voltage V _TH2 and the third threshold voltage V _TH3 are generated by the voltage sources VS2 and VS3, respectively. The controller 110A changes the third threshold voltage _VTH3 in conjunction with the second threshold voltage _VTH2. One of the voltage sources VS2 and VS3 may be omitted, and the threshold voltage generated by the remaining one may be supplied to the second comparator COMP2 and the third comparator COMP3.

The second current source CS2 is connected to the second output pin OUTN, and the second current I _TEST2 whose current amount can be controlled is sourced to the second output pin OUTN.

The controller 110A controls the first current source CS1 and the second current source CS2, and based on the second comparison signal S2 and the third comparison signal S3 generated by the second comparator COMP2 and the third comparator COMP3, the output pin OUTP, Determine if there is an OUTN abnormality.

The above is the configuration of the audio amplifier IC100A. Next, the operation will be described.
(Ground fault detection mode)
FIG. 7 is an equivalent circuit diagram of the audio amplifier IC100A in the ground fault detection mode. When the controller 110A is set to the ground fault detection mode, the outputs of the first amplifier 102P and the second amplifier 102N are brought into a high impedance state.

When the controller 110A is set to the ground fault _{detection mode, the second threshold voltage V TH2} is set to the third level V _{GND_DET, and the first current I TEST1} generated by the first current source CS1 is set to the third current. Gradually increase to quantity I _{GND_DET.} When the second comparison signal S2 maintains the first level (low), the controller 110A determines that the ground fault is abnormal outside the first output pin OUTP or the second output pin OUTN.

Further, in the ground fault detection mode, the controller 110A _{gradually increases the second current I TEST2} generated by the second current source CS2 to the third current amount I _{GND_DET} , and the third comparison signal S3 sets the first level (low). When maintaining, it is determined that the ground fault is abnormal outside the first output pin OUTP or the second output pin OUTN.

When both the second comparison signal S2 and the third comparison signal S3 transition to high, the controller 110A determines that no ground fault has occurred at any of the output pins OUTP and OUTN.

(Temple detection mode)
FIG. 8 is an equivalent circuit diagram of the audio amplifier IC100A in the skyscraper detection mode. When the controller 110A is set to the crown detection mode, the outputs of the first amplifier 102P and the second amplifier 102N are set to a high impedance state.

The controller 110A, when set on the top fault detection mode, the second threshold voltage _{V TH2} is set to higher than the third level _{V GND_DET} fourth value _{V DD_DET,} the first current source CS1 and the second current source CS2 Is turned off.

When at least one of the second comparison signal S2 and the third comparison signal S3 transitions to the second level (high), the controller 110A determines that the sky fault is abnormal outside the first output pin OUTP or the second output pin OUTN. .. When both the second comparison signal S2 and the third comparison signal S3 maintain a low position, the controller 110A determines that no ceiling fault has occurred at any of the output pins OUTP and OUTN.

If the ground fault detection mode or the top fault detection mode is executed before mounting the electroacoustic conversion element 202 (before connection), the top faults and ground faults of the two output pins OUTP and OUTN should be detected separately. Can be done.

The present invention has been described above based on the embodiments. This embodiment is an example, and it is understood by those skilled in the art that various modifications are possible for each of these components and combinations of each processing process, and that such modifications are also within the scope of the present invention. be. Hereinafter, such a modification will be described.

(Use)
Finally, the application of the audio amplifier IC100 will be described. 9 (a) to 9 (c) are external views of the electronic device 1. FIG. 9A is a display device 600 which is an example of the electronic device 1. The display device 600 includes a housing 602 and a speaker 2. The audio amplifier IC 100 is built in the housing and drives the speaker 2. The speaker 2 corresponds to the electroacoustic conversion element 202.

FIG. 9B is an audio component 700 which is an example of the electronic device 1. The audio component 700 includes a housing 702 and a speaker 2. The audio amplifier IC 100 is built in the housing 702 and drives the speaker 2.

FIG. 9C is a small information terminal 800 which is an example of the electronic device 1. The small information terminal 800 is a smartphone, a tablet computer, an audio player, a digital camera, a digital video camera, or the like. The small information terminal 800 includes a housing 802, a speaker 2, and a display 804. The audio amplifier IC 100 is built in the housing 802 and drives the speaker 2.

FIG. 10 is a diagram showing an in-vehicle audio system 500. The in-vehicle audio system 500 includes four speakers 502 _FL , 502 _FR , 502 _RL , 502 _RR , four filters 504 _FL , 504 _FR , 504 _RL , 504 _RR , a sound source 506, and an audio amplifier IC 300.

The sound source 106 outputs a left-right (LR) two-channel or multi-channel digital signal. The audio amplifier IC 300 includes a 4-channel power amplifier 310 and an audio interface circuit 302 for the sound source 106. The format of the audio interface circuit 302 is not limited.

The D / A converters 400L and 400R convert L-channel and R-channel digital audio signals into differential analog audio signals. Although it is indicated by the symbol of the single-ended amplifier in FIG. 10, one power amplifier 310 corresponds to the set of the power amplifiers 102P and 102N in FIG. 2, and drives the corresponding speaker 502 by BTL. The power amplifier 310 may be a class D amplifier or a class AB amplifier.

The filter 504, the sound source 506, and the audio amplifier IC 300 are built in the audio head unit and the car navigation device. Alternatively, the audio amplifier IC 300 may be a product independent of the sound source 106.

Although the present invention has been described using specific terms and phrases based on the embodiments, the embodiments show only one aspect of the principles and applications of the present invention, and the embodiments are claimed. Many modifications and arrangement changes are permitted within the range not departing from the idea of the present invention defined in the scope.

200 Audio system 201 Load 202 Electroacoustic conversion element 204 Filter 210 Circuit board 100 Audio amplifier IC
102P 1st amplifier 102N 2nd amplifier OUTP 1st output pin OUTN 2nd output pin CS1 1st current source CS2 2nd current source SW1 switch COMP1 1st comparator COMP2 2nd comparator COMP3 3rd comparator S1 1st comparison signal S2 2nd Comparison signal S3 Third comparison signal 110 Controller

Claims (8)

BTL (Bridged Tied Load) type audio amplifier IC (Integrated Circuit)
With the first amplifier
With the second amplifier
The first output pin connected to the output of the first amplifier,
The second output pin connected to the output of the second amplifier,
A first current source that is connected to the first output pin and has a controllable amount of current to be sourced to the first output pin.
A switch provided between the second output pin and the fixed voltage line,
The potential difference between the first output pin and the second output pin is compared with a controllable first threshold voltage, and when the potential difference is lower than the first threshold voltage, it is the first level, and when it is higher, it is the second level. The first comparator that generates the first comparison signal, and
A controller that controls the first current source and the switch,
With
The controller
When the load diagnostic mode is set while the load is mounted, the switch is turned on and the switch is turned on.
(I) In the open detection period, the first threshold voltage is set to the first level, and the first current generated by the first current source is gradually increased to the first current amount.
(Ii) In the short detection period following the open detection period, the first threshold voltage is set to a second level larger than the first level, and the first current generated by the first current source is set to the first level. Gradually increase from the first current amount to the second current amount,
(Iii-1) When the first comparison signal is the first level in the open detection period and the second level in the short detection period, it is determined that the load is normal.
(Iii-2) When the first comparison signal transitions to the second level during the open detection period, the load is determined to be an open abnormality, and the load is determined to be an open abnormality.
(Iii-3) An audio amplifier IC characterized in that when the first comparison signal is at the first level in the short detection period, the load is determined to be a short abnormality. The switch has a variable impedance in the on state and has a variable impedance.
The controller according to claim 1, wherein the controller sets the impedance of the switch relatively high during the open detection period, and sets the impedance of the switch relatively low during the short detection period. Audio amplifier IC. The audio amplifier IC according to claim 2, wherein the switch includes a first NMOS transistor and a second NMOS transistor which are connected in parallel and have different sizes. The first detection voltage obtained by dividing the voltage of the first output pin is compared with the controllable second threshold voltage, and when the first detection voltage is lower than the second threshold voltage, the first level is obtained. Further equipped with a second comparator that produces a second comparison signal that becomes the second level when high.
When the controller is set to the ground fault detection mode, the switch is turned off, the second threshold voltage is set to the third level, and the first current generated by the first current source is set to the third level. The claim is characterized in that when the amount of current is gradually increased and the second comparison signal maintains the first level, it is determined that the ground fault is abnormal outside the first output pin or the second output pin. The audio amplifier IC according to any one of 1 to 3. A second current source, which is connected to the second output pin and whose current amount can be controlled, is sourced to the second output pin.
The second detection voltage obtained by dividing the voltage of the second output pin is compared with the third threshold voltage linked with the second threshold voltage, and the second detection voltage is the third threshold voltage. A third comparator that generates a third comparison signal that is the first level when it is lower and the second level when it is higher.
With more
The controller (iv) gradually increases the second current generated by the second current source to the third current amount in the ground fault detection mode, and the third comparison signal maintains the first level. The audio amplifier IC according to claim 4, wherein the first output pin or a ground fault abnormality outside the second output pin is determined. When the controller is set to the skyscraper detection mode, it turns off the switch, sets the second threshold voltage to a fourth value higher than the third level, and sets the first current source and the second. When the current source is turned off and at least one of the second comparison signal or the third comparison signal transitions to the second level, it is determined that the first output pin or the second output pin is external to the ceiling fault. The audio amplifier IC according to claim 5, wherein the audio amplifier IC is characterized by the above. Electro-acoustic conversion element and
The audio amplifier IC according to any one of claims 1 to 6 for driving the electroacoustic conversion element.
An in-vehicle audio system characterized by being equipped with. Electro-acoustic conversion element and
The audio amplifier IC according to any one of claims 1 to 6 for driving an electroacoustic conversion element.
An electronic device characterized by being equipped with.

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