WO2014208042A1

WO2014208042A1 - Vehicular voice output control device

Info

Publication number: WO2014208042A1
Application number: PCT/JP2014/003218
Authority: WO
Inventors: 剛塩見
Original assignee: 株式会社デンソー
Priority date: 2013-06-26
Filing date: 2014-06-17
Publication date: 2014-12-31
Also published as: JP2015012309A

Abstract

A vehicular voice output control device is provided with: a signal processing means (3) that limits a frequency passband of a voice signal; a reference clock output means (7) that outputs a reference clock; a pulse width modulation means (4) that pulse-width modulates the voice signal input from the signal processing means by tracking the frequency of the reference clock input from the reference clock output means, so as to generate a pulse width modulation signal, and that outputs the generated pulse width modulation signal; an amplification means (5) that amplifies the pulse width modulation signal input from the pulse width modulation means using a switching element (12, 13); a temperature detection means (8) that detects a detection temperature reflecting the temperature of at least the amplification means; and a control means (7) that sets the frequency passband of the voice signal in the signal processing means and the frequency of the reference clock output from the reference clock output means in accordance with the detection temperature detected by the temperature detection means.

Description

Audio output control device for vehicle

Cross-reference of related applications

This disclosure is based on Japanese Application No. 2013-133740 filed on June 26, 2013, the contents of which are incorporated herein.

The present disclosure relates to a vehicular audio output control apparatus that generates a pulse width modulation signal by following a frequency of a reference clock to generate a pulse width modulation signal and amplifies and outputs the generated pulse width modulation signal.

The digital amplifier follows the frequency of the reference clock to convert the audio signal into PWM (Pulse Width Modulation) and generates a PWM signal. The PWM signal input from the PWM converter is amplified by the switching element and output. And an amplifying unit. If the temperature of the amplifier section is likely to exceed the guaranteed operating temperature due to a temperature increase due to switching loss of the switching element in a high temperature environment, conventionally, a simple on / off operation is performed to stop the output of the audio signal for the purpose of component protection. It was off control. In this case, there is no particular problem even if the output is stopped as long as the audio signal does not affect the safety and safety of driving such as music. However, if it is an audio signal that can affect driving safety and safety, such as a warning sound to the driver, it may not be possible to properly secure driving safety and safety if the output is stopped. Yes, it is not preferable to stop outputting the audio signal. Under such circumstances, it is necessary to achieve both the protection of parts in a high temperature environment and the ensuring of driving safety and safety.

It is known that switching loss can be reduced in order to suppress the temperature rise of the amplification section. As a technique for suppressing the temperature rise of the amplifying unit, for example, in Patent Document 1, in a device that receives a television broadcast wave, a switching frequency is variable according to a broadcast genre, and a frequency band of an audio signal is narrow like news. In some cases, a technique for reducing unnecessary switching loss is disclosed.

JP 2007-251928 A

However, the technique disclosed in Patent Document 1 can only suppress the temperature rise of the amplification section by reducing the switching loss, and can protect the parts in a high temperature environment and ensure the safety and safety of operation. It does not lead to coexistence with.

The present disclosure has been made in view of the above-described circumstances, and an object of the present disclosure is to provide a vehicle audio output control device capable of achieving both protection of components in a high temperature environment and ensuring of driving safety and safety. Is to provide.

According to the vehicle audio output control apparatus according to an aspect of the present disclosure, the signal processing means limits the pass frequency band of the audio signal. The reference clock output means outputs a reference clock. When the audio signal is input from the signal processing unit, the pulse width modulation unit generates a pulse width modulation signal by performing pulse width modulation on the input audio signal following the frequency of the reference clock input from the reference clock output unit. The generated pulse width modulation signal is output. The amplifying means having the switching element amplifies the pulse width modulation signal input from the pulse width modulating means by the switching element. The temperature detection means detects a detection temperature that reflects at least the temperature of the amplification means. The control means sets the pass frequency band of the audio signal in the signal processing means and the frequency of the reference clock output from the reference clock output means in accordance with the detected temperature detected by the temperature detection means.

That is, since the frequency of the reference clock is set according to the detection temperature reflecting the temperature of the amplification means, the frequency of the reference clock is decreased at the time of high-temperature operation in a high temperature environment compared with the time of normal operation. The switching frequency can be reduced as compared with the normal operation. Since the switching loss is proportional to the switching frequency, the switching loss can be reduced more than that during normal operation by lowering the switching frequency than during normal operation. As a result, the temperature rise of the amplifying means can be suppressed as compared with the normal operation, and the parts can be protected.

Also, if the frequency of the reference clock is lowered than during normal operation, there is a risk that the high frequency band cannot be pulse width modulated and distortion components are generated. In order to avoid the generation of distortion components, it is necessary to set the pass frequency band of the audio signal so as to prohibit the high band side pass, but the frequency band of the warning sound etc. to the driver is pulse width modulated. By assigning while avoiding the high band side that may not be obtained, it is possible to appropriately output a warning sound to the driver. With this configuration, unlike conventional systems that perform simple on / off control to stop the output of audio signals, it is possible to achieve both protection of parts in a high-temperature environment and ensuring driving safety and safety. it can.

The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings. The drawing
Functional block diagram showing the first embodiment of the present disclosure Circuit diagram of amplifier and integrator Flow chart of temperature detection routine Figure showing the transition of detected temperature Diagram showing pass frequency band and normal clock frequency during normal operation Diagram showing pass frequency band and reference clock frequency during high temperature operation Functional block diagram showing a second embodiment of the present disclosure

(First embodiment)
Hereinafter, a first embodiment of the present disclosure will be described with reference to FIGS. 1 to 6. The vehicular audio output control device 1 controls output of audio signals such as music in the passenger compartment and a warning sound to the driver while being mounted on the vehicle. The warning sound informs the driver of cautions when driving such as the possibility that the own vehicle may collide with the vehicle ahead and that there is a traffic jam on the route on which the own vehicle travels. It is voice. The vehicle audio output control device 1 controls the output of a warning sound in cooperation with an ECU (Electronic Control Unit) having a navigation function and an ECU having a collision prevention function.

The vehicle audio output control device 1 includes an audio generation unit 2, a signal processing unit 3 (corresponding to a signal processing unit), a PWM (Pulse Width Modulation) conversion unit 4 (corresponding to a pulse width modulation unit), and an amplification unit 5 (Corresponding to amplification means), integrator section 6, control section 7 (reference clock output means, corresponding to control means), and temperature detection section 8 (corresponding to temperature detection means). The PWM converter 4, the amplifier 5, and the integrator 6 constitute a digital amplifier 9. Note that the vehicle audio output control device 1 switches between an activated state and a stopped state in conjunction with, for example, turning on / off an accessory switch.

The sound generation unit 2 functions as a sound source, generates music, a warning sound for the driver, and the like as a sound signal, and outputs the generated sound signal to the signal processing unit 3. In the present embodiment, the configuration in which the audio generation unit 2 is incorporated in the vehicle audio output control device 1 is described. However, the audio generation unit 2 is provided outside the vehicle audio output control device 1. It may be a configuration (externally attached).

The signal processing unit 3 is a low-pass filter (LPF: Low-pass filter) that cuts (does not pass) a frequency component higher than the cutoff frequency, and determines the cutoff frequency based on an on signal or an off signal input from the control unit 7. Switching, the pass frequency band of the audio signal is selectively switched between the first frequency band and the second frequency band. That is, when the off signal is input from the control unit 7, the signal processing unit 3 sets the pass frequency band of the audio signal to the first frequency band. When the audio signal is input from the audio generation unit 2 in a state where the pass frequency band of the audio signal is set to the first frequency band, the signal processing unit 3 sets the pass frequency band of the input audio signal to the first frequency. The output is limited to the band and output to the PWM converter 4. On the other hand, when the signal processing unit 3 receives the ON signal from the control unit 7, the signal processing unit 3 shifts the cutoff frequency to the low band side and prohibits the passage of the audio signal on the high frequency side of the first frequency band. 2 frequency band. When the audio signal is input from the audio generation unit 2 in a state where the pass frequency band of the audio signal is set to the second frequency band, the signal processing unit 3 sets the pass frequency band of the input audio signal to the second frequency. The output is limited to the band and output to the PWM converter 4. The first frequency band is a frequency band including at least a frequency band of music (music band) and a warning sound frequency band (warning sound band). The second frequency band is narrower than the first frequency band and does not include the high frequency side of the music frequency band, but includes at least the warning sound frequency band.

When an audio signal is input from the signal processing unit 3, the PWM conversion unit 4 performs PWM conversion by causing the amplitude change of the input audio signal to correspond to the pulse width of the reference clock input from the control unit 7, thereby generating a square wave. A PWM signal is generated, and the generated PWM signal is output to the amplifying unit 5. In this case, the control unit 7 switches the frequency of the reference clock between the first frequency (f1) and the second frequency (f2) lower than the first frequency, as will be described later, and the PWM conversion unit 4 Output to. In other words, when the audio signal is input from the signal processing unit 3 while the reference clock is input from the control unit 7 at the first frequency, the PWM conversion unit 4 converts the input audio signal into the reference clock having the first frequency. PWM conversion to generate a PWM signal. On the other hand, when the PWM conversion unit 4 inputs an audio signal from the signal processing unit 3 while the reference clock is input from the control unit 7 at the second frequency, the input audio signal is converted to the reference clock of the second frequency. PWM conversion to generate a PWM signal.

As shown in FIG. 2, the amplifying unit 5 includes a negative logic circuit 11, N-type MOSFETs (Metal-Oxide-Semiconductor-Field-Effect-Transistors) 12, 13 that are half-bridge connected as two switching elements, And an FET driver 14 for driving the two

FETs

12 and 13. When the amplification unit 5 receives the PWM signal from the PWM conversion unit 4, the amplification unit 5 generates two PWM signals having opposite polarities from the input PWM signal, and alternately turns on / off the two

FETs

12 and 13 to thereby change the amplitude. Is generated (voltage and current amplification) and is output to the integrator unit 6. In this case, the switching loss due to the two

FETs

12 and 13 being alternately turned on / off is proportional to the switching frequency. That is, the switching loss is relatively large when the PWM conversion unit 4 is inputting the reference clock from the control unit 7 at the first frequency, while the PWM conversion unit 4 receives the second reference clock from the control unit 7. It is relatively small when input at a frequency of.

The integrator unit 6 includes a coil 15 and a capacitor 16 as shown in FIG. When the integrator unit 6 receives the PWM signal from the amplification unit 5, the integrator unit 6 converts the input PWM signal into an audio signal and outputs it to the speaker 10. The speaker 10 is disposed at a predetermined part of the vehicle. When an audio signal is input from the integrator unit 6 (digital amplifier 9), the speaker 10 converts the audio signal into vibration and outputs audio.

The temperature detection unit 8 is disposed inside a housing (not shown) that houses the signal processing unit 3 and the digital amplifier 9 described above, and reflects the ambient temperature inside the housing (the temperature of the amplification unit 5 is reflected). Temperature) can be detected. The temperature detection unit 8 outputs the detected ambient temperature inside the housing to the control unit 7 as a detection temperature. The control unit 7 includes a known microcomputer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an I / O (Input / Output) bus, and the like. The control unit 7 switches and controls the frequency of the reference clock output to the PWM conversion unit 4 according to the detected temperature input from the temperature detection unit 8 in accordance with a computer program stored in a ROM or the like, and a signal processing unit. The output of the on signal or the off signal to 3 is switched.

Next, the operation of the above configuration will be described with reference to FIGS. When the vehicle audio output control device 1 is in the activated state, the control unit 7 periodically executes the temperature detection routine shown in FIG. When the vehicle audio output control device 1 is activated, the control unit 7 sets the frequency of the reference clock to the first frequency and outputs (resets) the off signal to the signal processing unit 3. When starting the temperature detection routine, the control unit 7 determines the detection temperature input from the temperature detection unit 8, and determines whether or not the detection temperature is equal to or higher than the first set temperature (S1). The first set temperature is a temperature slightly lower than the operation guarantee temperature for component protection, and is written in the computer program at the stage when the vehicle audio output control device 1 is manufactured, for example.

If the detected temperature is not equal to or higher than the first set temperature immediately after the vehicle audio output control device 1 is activated, the control unit 7 determines that the detected temperature is not equal to or higher than the first set temperature (S1: NO). The detection routine is terminated and the next temperature detection routine is awaited.

Here, when the vehicular audio output control device 1 executes a process of outputting music or a warning sound, when the two

FETs

12 and 13 are alternately turned on / off repeatedly in the amplifier 5, the temperature rises due to switching loss. To do. When the control unit 7 determines that the temperature of the amplification unit 5 has risen to the first set temperature and the detected temperature has become equal to or higher than the first set temperature (S1: YES, refer to “t1” in FIG. 4), the ON signal To the signal processing unit 3, and the setting of the passing frequency band of the audio signal in the signal processing unit 3 is changed from the first frequency band to the second frequency band (S2). Next, the control unit 7 changes the setting of the frequency of the reference clock output to the PWM conversion unit 4 from the first frequency to the second frequency (S3).

That is, the control unit 7 changes the setting of the reference clock frequency from the first frequency to the second frequency when the detected temperature has shifted from less than the first set temperature to above the first set temperature. The switching loss in the amplifying unit 5 is reduced, and the temperature rise of the amplifying unit 5 thereafter is suppressed. Further, when the frequency of the reference clock is changed from the first frequency to the second frequency in this way, there is a possibility that the high frequency band cannot be PWM-converted and a distortion component may be generated. The signal passing frequency band is changed from the first frequency band to the second frequency band (passing on the high band side is prohibited) to avoid the possibility of distortion components.

In this case, music etc. has information up to the high band side, so prohibiting the passage on the high band side will lead to sound quality degradation. However, the warning sound to the driver is generally around 1 [kHz] where human sensitivity is high, and is sufficiently lower than 20 [kHz] which is the upper limit of the human audible band. Even if passage on the high band side is prohibited, sound quality degradation does not occur. In other words, even when the detected temperature is equal to or higher than the first set temperature, the warning sound can be appropriately output by not restricting the passage of the frequency band such as the warning sound to the driver. Can be appropriately provided to the driver.

Next, after the detected temperature becomes equal to or higher than the first set temperature, the control unit 7 determines whether or not the detected temperature is lower than the second set temperature (S4). The second set temperature is a temperature for giving a hysteresis characteristic, and is a temperature lower than the first set temperature. The second set temperature is also written in the computer program at the stage where the vehicle audio output control device 1 is manufactured, for example.

As described above, the control unit 7 changes the setting of the reference clock frequency from the first frequency to the second frequency to suppress the temperature increase of the amplification unit 5, so that the temperature of the amplification unit 5 is set to the second setting. If it is determined that the detected temperature is lower than the second set temperature (S4: YES, refer to “t2” in FIG. 4), the reference clock frequency is changed from the second frequency to the first frequency. (S5). Next, the control unit 7 outputs an off signal to the signal processing unit 3, changes the setting of the pass frequency band of the audio signal in the signal processing unit 3 from the second frequency band to the first frequency band (S6), and temperature The detection routine is terminated and the next temperature detection routine is awaited.

That is, the control unit 7 changes the setting of the frequency of the reference clock from the second frequency to the first frequency when the detected temperature shifts from the second set temperature or more to less than the second set temperature. Before changing the setting of the passing frequency band of the audio signal in the signal processing unit 3 from the second frequency band to the first frequency band (allowing high-frequency band passing), the detected temperature becomes equal to or higher than the first set temperature. Return to the state. In this case, by allowing the passage of the first frequency band on the high band side, not only the warning sound or the like is appropriately output as before the passage of the first frequency band on the high band side is prohibited. Also, music and the like can be output appropriately. The control unit 7 repeatedly performs the above-described process during a period in which the vehicle audio output control device 1 is in the activated state.

Thus, as shown in FIG. 4, the vehicle audio output control device 1 is a period from when it is activated or until the detected temperature first becomes equal to or higher than the first set temperature after being lower than the second set temperature. Then, as shown in FIG. 5, the operation is performed with the frequency of the reference clock as the first frequency and the pass frequency band of the audio signal as the first frequency band (normal operation). On the other hand, during the period from when the detected temperature becomes equal to or higher than the first set temperature to when the detected temperature first falls below the second set temperature, the vehicular audio output control device 1 performs the frequency of the reference clock as shown in FIG. Is set as the second frequency and the pass frequency band of the audio signal is set as the second frequency band (high temperature operation).

As described above, according to the first embodiment, in the vehicle audio output control device 1, the detected temperature of the amplifying unit 5 that amplifies the PWM signal is less than the first set temperature to the first set temperature or higher. When the transition is made, the pass frequency band of the audio signal in the signal processing unit 3 is changed from the first frequency band to the second frequency band, and the reference clock frequency is changed from the first frequency to the second frequency. I made it. Thereby, by reducing the frequency of the reference clock, the switching loss in the amplifying unit 5 can be reduced, and the subsequent temperature rise of the amplifying unit 5 can be suppressed. Further, if the frequency of the reference clock is lowered, the high band side cannot be PWM-converted and a distortion component may be generated. In order to avoid the generation of the distortion component, it is necessary to prohibit the passage on the high band side. However, it is possible to appropriately output the warning sound to the driver by allocating the frequency band of the warning sound while avoiding the high band side where the PWM conversion may not be possible. Unlike conventional systems that perform simple on / off control to stop the output of audio signals, it is possible to achieve both protection of parts in a high temperature environment and ensuring driving safety and safety.

In this case, the setting of the passing frequency band of the audio signal in the signal processing unit 3 is first changed from the first frequency band to the second frequency band, and then the frequency of the reference clock is changed from the first frequency to the second frequency. The setting was changed. As a result, if the frequency of the reference clock is lowered before the high-band side is prohibited, a distorted audio signal may be output, but after the high-band side is prohibited, the reference clock is output. By reducing the frequency, the possibility can be eliminated and the reliability of the product can be ensured.

When the detected temperature of the amplifying unit 5 shifts from the second set temperature or more to less than the second set temperature, the frequency of the reference clock is changed from the second frequency to the first frequency, and the signal processing unit 3 The passing frequency band of the audio signal is changed from the second frequency band to the first frequency band. Thereby, it is possible to quickly return to a state before the detected temperature becomes equal to or higher than the first set temperature, and not only a warning sound or the like but also music or the like can be output appropriately.

In this case, the frequency of the reference clock is first changed from the second frequency to the first frequency, and then the audio signal passing frequency band in the signal processing unit 3 is changed from the second frequency band to the first frequency band. The setting was changed. As a result, if the high frequency band is allowed to pass before the reference clock frequency is increased (returned), a distorted audio signal may be output in this case as well. By allowing the passage on the high band side after increasing the value, the possibility can be eliminated and the reliability of the product can be ensured. Moreover, since the temperature lower than the first set temperature is set as the second set temperature, the hysteresis characteristic can be provided, and the frequency of the reference clock and the passing frequency band of the audio signal are frequently switched by a subtle temperature change. Can be avoided in advance.

(Second Embodiment)
Hereinafter, a second embodiment of the present disclosure will be described with reference to FIG. In addition, description is abbreviate | omitted about the same part as above-mentioned 1st Embodiment, and a different part is demonstrated. In the first embodiment, the configuration in which the frequency band of the audio signal and the frequency of the reference clock are set in two stages in the signal processing unit 3 has been described. In contrast, the second embodiment is configured to set the pass frequency band of the audio signal and the frequency of the reference clock in the signal processing unit 3 in three or more stages.

That is, the control unit 7 outputs a coefficient setting signal to the signal processing unit 3. When the signal processing unit 3 receives the coefficient setting signal from the control unit 7, the signal processing unit 3 switches the cut-off frequency to three or more levels based on the coefficient included in the input coefficient setting signal, and sets the pass frequency band of the audio signal to three or more levels. Selectively in frequency band. The control unit 7 switches and controls the frequency of the reference clock output to the PWM conversion unit 4 in three or more steps according to the detected temperature input from the temperature detection unit 8. Also in the second embodiment, it is possible to achieve both the protection of parts under a high temperature environment and the ensuring of driving safety and safety. For example, even in a configuration in which the level of component protection is required in three or more steps, the switching loss in the amplifying unit 5 is gradually reduced in three or more steps according to the detected temperature, thereby increasing the temperature of the amplifying unit 5 by three or more steps. Can be suppressed in stages.

(Modification)
The present disclosure is not limited to the above-described embodiment, and can be modified or expanded as follows. A plurality of modified examples may be combined.

The configuration in which the control unit combines the means for outputting the reference clock and the means for setting the pass frequency band of the audio signal and setting the frequency of the reference clock has been exemplified. However, these means are configured by separate functional blocks. May be.

Although the configuration in which the first set temperature and the second set temperature are different is illustrated, the first set temperature and the second set temperature may be configured to be the same, that is, to have a hysteresis characteristic. It is not necessary.

Claims

Signal processing means (3) for limiting the pass frequency band of the audio signal;
A reference clock output means (7) for outputting a reference clock;
The audio signal input from the signal processing means is pulse width modulated following the frequency of the reference clock input from the reference clock output means to generate a pulse width modulated signal, and the generated pulse width modulated signal is output. Pulse width modulation means (4);
Amplifying means (5) having switching elements (12, 13) and amplifying the pulse width modulation signal input from the pulse width modulation means by the switching elements;
Temperature detection means (8) for detecting a detection temperature reflecting at least the temperature of the amplification means;
Control means for setting the pass frequency band of the audio signal in the signal processing means and setting the frequency of the reference clock output from the reference clock output means in accordance with the detected temperature detected by the temperature detecting means. (7), The audio | voice output control apparatus for vehicles provided with.
In the vehicle audio output control device according to claim 1,
The signal processing means can set at least a first frequency band and a second frequency band that prohibits passage on the high frequency side of the first frequency band as a passing frequency band of the audio signal,
The reference clock output means can set at least a first frequency and a second frequency lower than the first frequency as the frequency of the reference clock,
The control means is triggered by the fact that the detected temperature detected by the temperature detecting means has shifted from less than a first set temperature to above the first set temperature, and the pass frequency band of the audio signal is changed to the first set temperature. While changing the setting from the frequency band to the second frequency band, changing the setting of the frequency of the reference clock from the first frequency to the second frequency, the detected temperature detected by the temperature detecting means is the second. The frequency of the reference clock is changed from the second frequency to the first frequency, and the frequency band of the audio signal is passed, triggered by the transition from the set temperature to less than the second set temperature. Is changed from the second frequency band to the first frequency band.
In the vehicle audio output control device according to claim 2,
When the detected temperature detected by the temperature detecting unit shifts from less than a first set temperature to more than the first set temperature, the control unit first sets the pass frequency band of the audio signal to the first An audio output control device for a vehicle that changes a setting from a frequency band to the second frequency band, and thereafter changes a setting of the frequency of the reference clock from the first frequency to the second frequency.
In the vehicle audio output control device according to claim 2 or 3,
The control means first sets the frequency of the reference clock to the second frequency when the detected temperature detected by the temperature detection means shifts from the second set temperature or more to less than the second set temperature. The vehicular audio output control apparatus that changes the setting from the second frequency band to the first frequency band after changing the setting from the second frequency band to the first frequency.
In the vehicle audio output control device according to any one of claims 2 to 4,
The vehicle sound output control device, wherein the control means uses a temperature lower than the first set temperature as the second set temperature.