JP4921191B2 - Digital amplifier and television receiver - Google Patents

Description

  The present invention relates to a digital amplifier and a digital television receiver using the digital amplifier.

  A digital amplifier generally has a configuration for converting amplitude information of an analog speech waveform into time information for switching on / off of an output switching unit. As the switching frequency is higher, the amount of information per unit time is increased, and the influence of image noise on the audible band is reduced, and it is possible to reproduce sound faithfully up to a high frequency.

  However, every time the switching unit is switched on and off, current consumption occurs due to a through current, a charging / discharging current of a parasitic capacitance, and so on, so that the power consumption increases as the switching frequency increases.

  As a method for reducing power consumption, Patent Document 1 discloses that the frequency of a drive pulse supplied to a switching element is lowered when it is detected that there is no input signal or according to the average level of the input signal. Are listed.

Patent Document 2 describes that the delay time of the timing adjustment circuit that suppresses the through current is controlled, and the delay time is switched between the high sound quality mode and the low power consumption mode.
JP 2004-72707 A JP 2004-363699 A

  However, in the method described in Patent Document 1, regardless of whether the input signal is a music signal that is easily affected by image noise or a serif signal that is not easily affected, the switching frequency is used when the signal level is equal to or higher than a certain level. However, there is a problem that reproduction is performed in a state where power consumption is high, that is, power consumption is large.

  In the method described in Patent Document 2, the delay time of the timing adjustment circuit that suppresses the through current is controlled in response to the required signal quality and power consumption. The delay time of the timing adjustment circuit is the switching element. Absorbs response time variations. Therefore, there is a problem that if the delay time is reduced so as to perform reproduction with high fidelity, the power consumption greatly varies depending on the response time of the switching element.

Therefore, the present invention solves the above problems,
A digital amplifier and a television receiver using a digital amplifier that realizes power saving by detecting the characteristics of the input signal and controlling the frequency of the clock signal based on the characteristics without losing the fidelity of audio playback. The purpose is to provide.

The digital amplifier of the present invention includes a receiving unit that receives a television broadcast wave, a program information decoding unit that decodes program-related information superimposed on the television broadcast wave, and a decoder that decodes audio data output from the receiving unit. Based on the genre information included in the program related information and the audio decoding unit that outputs the audio input signal, weighting is performed for each genre so that “music genre”> “movie genre”> “news genre”. Arranged in a television receiver having a weighting unit for outputting a genre signal,
A clock generator for outputting a clock signal;
A pulse width modulation unit that performs pulse width modulation on the clock signal based on the audio input signal;
A conversion unit that includes at least two switching elements, a drive unit that drives the switching element, and a temperature detection unit that detects a temperature of the switching element, and converts an output of the pulse width modulation unit;
Analyzing the characteristics of the audio input signal and outputting a parameter according to the degree of amplitude change per fixed time of the stereo sum signal ;
And have groups Dzu the output of the analyzing portion and a control unit for controlling the frequency of said clock signal,
Wherein,
And have groups Dzu the output of the temperature detecting unit, so that the frequency of the clock signal and the temperature rises lowered, controls the clock generator,
Based on the genre signal output from the weighting unit , “frequency of clock signal in case of music genre >> frequency of clock signal in case of movie genre >> frequency of clock signal in case of news genre” Controlling the clock generator ,
Furthermore, based on the parameters output from the analysis unit, when the amplitude change per fixed time of the stereo sum signal is gradual, compared to the case where the amplitude change per fixed time of the stereo sum signal is severe, The clock generator is controlled so that the frequency of the clock signal is lowered .

  The television receiver of the present invention is characterized in that the digital amplifier according to the present invention is used as an audio amplifier.

  According to the present invention, since the switching frequency of the digital amplifier is set to an optimum value according to the characteristics of the input signal, the power consumption can be reduced without affecting the characteristics of the audio output. Specifically, the outputs of the input signal analysis unit, temperature detection unit, and decoding unit are comprehensively judged, and the digital amplifier is operated at the optimum frequency, so that the faithful reproducibility of audio and low power consumption are achieved. In addition, miniaturization and safety can be improved.

  Embodiments of the present invention will be described below.

The digital amplifier of the present invention
The present invention is applied to audio amplifiers for audio equipment, audio amplifiers for video equipment, audio amplifiers for television receivers, and the like.

  In particular, the audio amplifying apparatus for a television receiver is widely applied from a low-frequency information center such as a news program to a high-frequency information source such as a music program. This is a preferred embodiment to which the present invention is applied in that low power consumption can be realized without deterioration in sound quality by changing the operating frequency of the digital amplifier according to the program content.

  When the input signal is a line, etc., there is little information in the high frequency range, and the influence of image noise on the audible frequency range is small. Can be

  Whether the input signal is a speech system such as an announcement or a music system is determined, and in the case of the speech system, the power consumption can be reduced without affecting the characteristics of the audio output.

  An embodiment of the present invention will be described by taking an audio amplifying apparatus for a television receiver as an example.

(Embodiment 1)
FIG. 1 is a block diagram of a television receiver equipped with a digital amplifier according to Embodiment 1 of the present invention.

  The frequency band received by the antenna unit 1 is selectively received by the receiving unit 2 only for the desired broadcast and demodulated into multiplexed signals such as video, audio, and program information. The demodulated multiplexed signal is decoded by the video decoding unit 8, the audio decoding unit 3, and the program information decoding unit 13, respectively.

  The video data obtained by decoding by the video decoding unit 8 is adjusted to a desired characteristic by the video signal processing unit 9, and the video is displayed on the display unit 11 after the timing and amplitude of the signal are adjusted by the display driving unit 10. Is done.

  The audio data obtained by decoding by the audio decoding unit 3 is converted into a stereo analog audio signal by the D / A converter unit 4. As shown in FIG. 6, the pulse width modulation unit 17 outputs a PWM signal obtained by modulating the pulse width of the clock signal in accordance with the amplitude change of the analog audio signal.

  The pulse frequency of the PWM signal is determined by the output frequency of the variable frequency clock generator 16.

  The PWM signal is converted into two converted PWM signals having opposite polarities by the buffer amplifier 24 and the inverting buffer amplifier 25 of the drive unit 20. The first switching unit 18 and the second switching unit 19 are alternately turned on and off by the two converted PWM signals, and a PWM switching signal amplified to an amplitude between the power supply and the ground potential is generated.

  The PWM switching signal passes through the low-pass filtering unit 5 and is converted into an analog audio signal. The speaker unit 6 converts the PWM switching signal into an audible sound and outputs the audible sound.

  The drive unit 20, the first and second switching units 18 and 19, and the low-pass filtering unit 5 constitute a conversion unit that converts the PWM signal into an amplitude modulation signal again.

  Here, a half-bridge output configuration is shown, but a full-bridge output configuration is also possible.

  The genre type decoded by the program information decoding unit 13 is converted by the weighting unit 14 into a genre signal set for each genre type of the program so that the voltage value of the signal is, for example, music> movie> variety> news. The That is, a genre signal is generated based on the genre information of the program.

  The genre information for each program is superimposed on the EPG in the current broadcast and the metadata in the server type broadcast. For example, if the program genre is “news”, the program is mainly a speech, and if it is “music”. It can be determined that the program is mainly music.

  The stereo analog audio signal output from the D / A converter unit 4 is converted into a stereo sum signal L + R and a stereo difference signal LR and input to the input signal analysis unit 12.

  In the input signal analysis unit 12, signal processing of an analog audio signal is performed in each component as follows.

  As shown in FIG. 2, the level of the stereo sum signal L + R and the stereo difference signal LR input to the stereo difference component detector 21 is detected by the level detector 32, and the stereo sum signal level and the stereo difference signal are detected. The level is input to the level comparator 33. The level comparator 33 outputs a stereo comparison signal corresponding to the input level to the control unit 15.

  That is, in the stereo difference component comparison unit 21, a stereo comparison signal that is a difference in volume between the left and right is output as a control element in the control unit 15 so as to be one parameter indicating the signal characteristics of the input signal.

  Announcements such as news programs are generally recorded in monaural. Also in the movie, the line is assumed to be output from the center speaker, so when it is downmixed to stereo, it becomes a monaural signal in the left and right phase.

  On the other hand, since many music signals are recorded in stereo, if the left / right difference component in the stereo signal is small, it can be detected as a serif signal.

  As shown in FIG. 3, the stereo sum signal L + R input to the frequency feature detection unit 22 is input to the two level detectors 32 through the low pass filter 34, the high pass filter 36, and the band pass filter 35.

  The high and low frequency levels and the mid frequency level that are the outputs of the level detectors 32 are input to the level comparator 33. The level comparator 33 outputs a band signal corresponding to the input level to the control unit 15. That is, in the frequency feature detection unit 22, the stereo sum signal is divided into three frequency bands, a high frequency, a mid frequency, and a low frequency. Then, the frequency feature detection unit 22 outputs a band signal as a control element in the control unit 15 so that the difference between the high and low frequency levels and the mid frequency level becomes one parameter indicating the signal characteristics of the input signal.

  Human voices are mainly composed of mid-range components, but instrument sounds contain a lot of bass and treble components. It can be detected.

  Further, as shown in FIG. 4, the stereo sum signal L + R input to the rhythm detector 23 is input to the level detector 32 through the envelope detector 37 and the differentiator 38.

  The level detector 32 outputs a rhythm signal corresponding to the input level to the control unit 15.

  That is, the rhythm detection unit 23 detects the steepness of the amplitude change of the stereo sum signal so that the rhythm signal representing the rhythm of the sound becomes one parameter indicating the signal characteristics of the input signal. Is output as a control element.

  The time change of the amplitude of the serif sound is random and the change is gentle, but the music signal sharply changes the amplitude every certain time to form a rhythm, and if the time change of the amplitude is slow and there is no continuity, It can be detected as a system signal.

  The genre signal, stereo comparison signal, band signal, and rhythm signal are input to the control unit 15. The control unit 15 performs arithmetic processing such as addition processing on each input signal, and outputs a control signal based on the arithmetic processing to the variable frequency clock generation unit 16.

  For example, when the output of the input signal analysis unit is multi-stage or linear, when the input signal is determined to be a “music program” based on the genre signal, weighting such as making it close to high-frequency operation becomes possible. .

  That is, the control unit 15 dynamically changes the frequency of the clock signal output from the variable frequency clock generation unit 16 by the control signal.

  Since the variable frequency clock generator 16 outputs a higher frequency clock as the signal voltage value of the control signal is higher, the PWM switching frequency of the digital amplifier becomes higher. In the category type, high frequency switching is performed in the order of music> movie> variety> news. In other words, when a program with the genre type “music” is received, fidelity is given priority, and when a “news” program is received, playback with lower power consumption is given priority. In addition, even when a program whose genre type is “music” is received, playback with priority on low power consumption is performed, for example, in a dialogue-oriented scene such as commentary by a host. At this time, the stereo difference component detection unit 21 has a smaller stereo difference signal than the stereo sum signal, and the frequency feature detection unit 22 has a lower level of the high frequency and low frequency than the level of the mid frequency. This is because the rhythm detection unit 23 detects that the amplitude change level is smaller than the amplitude change time. As a result, even when playing music programs, low power consumption is prioritized according to the audio signal each time, so the overall power consumption during the playback time is reduced and the line However, since there is little high frequency information in the audio signal, the user does not recognize the sound quality degradation. Even when a program whose genre type is “News” is received, for example, in a music concert announcement, reproduction with priority on fidelity is performed. At this time, the stereo difference component detection unit 21 has a larger stereo difference signal than the stereo sum signal, and the frequency feature detection unit 22 has higher and lower frequency levels than the mid-frequency level. This is because the rhythm detection unit 23 detects that the amplitude change level is larger than the amplitude change time. As a result, even when a news program is being played back, since fidelity is given priority in accordance with the audio signal each time in a music scene, the user is not dissatisfied with sound quality.

  According to the television receiver of the present invention, a high-frequency switching operation that emphasizes fidelity is performed during playback of a music scene, and a low-frequency switching operation that emphasizes low current consumption is performed during playback of a speech-oriented scene. Can reduce current consumption without degradation of sound quality that can be recognized.

(Embodiment 2)
FIG. 7 is a block diagram of a television receiver equipped with a digital amplifier device according to the second embodiment of the present invention.

  The temperature of the first switching unit 18 and the second switching unit 19 is detected by the thermally coupled temperature detection unit 26, and is output as a lower voltage value as the temperature is higher.

  When the genre type obtained by decoding by the program information decoding unit 13 is a music program, and the analysis result by the input signal analysis unit 12 also outputs a high voltage signal representing music, the variable frequency clock generation unit The clock frequency output by 16 is a high frequency. At this time, since the first switching unit 18 and the second switching unit 19 perform a high frequency switching operation, the number of through currents flowing in a unit time increases and the power consumption increases. The temperature rises as the high-frequency switching operation state continues. When the temperature detection unit 26 detects that the temperature is high, the control unit 15 outputs a low voltage signal as a control signal and controls the clock frequency output from the variable frequency clock generation unit to be a low frequency. .

  By forming such a feedback system, the temperature rise can be suppressed within a certain range, and the heat dissipation mechanism can be miniaturized and a highly safe digital amplifier can be realized.

  Further, since the same operation is performed when the ambient temperature of the digital amplifier rises, a digital amplifier that can operate safely in a wide temperature range can be realized.

(Embodiment 3)
FIG. 8 is a block diagram of a television receiver equipped with a digital amplifier device according to the third embodiment of the present invention.

  The audio data obtained by decoding by the audio decoding unit 3 is input to an input signal analysis unit 12 configured by a DSP (Digital Signal Processor) that operates as a digital signal. At the same time, the audio data is converted into a PCM digital signal synchronized with the variable frequency clock generator 16 by the sampling rate converter SRC27, and further converted into a pulse modulation signal synchronized with the sampling frequency of the PCM digital signal by the PCM / PWM converter 28. Is done.

  In this embodiment, an audio signal is converted into a pulse modulation signal without being converted into an analog signal, and a digital amplifier device that realizes faithful and low current consumption without being affected by external noise can be realized.

(Embodiment 4)
FIG. 9 is a block diagram of a television receiver equipped with a digital amplifier device according to the third embodiment of the present invention.

  The voice input to the external analog voice input unit 29 is converted into voice data by the A / D converter 30, and the voice data from the voice decoding unit 3 and the voice data from the A / D converter unit are converted by the input switching unit 31. Either one is selected. When the two switches operate in conjunction with each other and audio data from the A / D converter unit is selected, the input switching unit 31 is switched so as not to refer to the output of the weighting unit 14 by genre type. According to the present embodiment, it is possible to realize a digital amplifier device in which the clock frequency is optimally set by the input signal analysis unit 12 even for audio input from the external analog input unit, and a faithful and low current consumption is realized.

1 is a block diagram of a television receiver equipped with a digital amplifier device according to a first embodiment of the present invention. It is a block diagram of the stereo difference detection part of the input analysis part in this invention. It is a block diagram of the frequency feature detection part of the input analysis part in this invention. It is a block diagram of the rhythm detection part of the input analysis part in this invention. It is a block diagram of the input / output signal of a pulse modulation part. It is explanatory drawing of the waveform of the input-output signal of a pulse modulation part. It is a block diagram of the television receiver carrying the digital amplifier device in the 2nd Embodiment of this invention. It is a block diagram of the television receiver carrying the digital amplifier device in the 3rd Embodiment of this invention. It is a block diagram of the television receiver carrying the digital amplifier device in the 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna part 2 Receiving part 3 Audio | voice decoding part 4 D / A converter part 5 Low-pass filter part 6 Speaker part 7 Digital amplifier 8 Video decoding part 9 Video signal processing part 10 Display drive part 11 Display part 12 Input signal analysis part 13 Program Information decoding unit 14 Weighting unit 15 Control unit 16 Variable frequency clock generation unit 17 Pulse modulation unit 18 First switching unit 19 Second switching unit 20 Drive unit 21 Stereo difference component detection unit 22 Frequency feature detection unit 23 Rhythm detection unit 24 Buffer Amplifier 25 Inverting Buffer Amplifier 26 Temperature Detector 27 Sampling Rate Converter 28 PCM / PWM Converter 29 External Analog Audio Input Unit 30 A / D Converter 31 Input Switching Unit 32 Level Detector 33 Level Comparator 34 Low-pass filter 35 Middle-pass filter 36 High-pass filter 3 Envelope detector 38 differentiator

Claims (1)

In digital amplifiers that amplify audio input signals,
The digital amplifier is
A receiver for receiving television broadcast waves;
A program information decoding unit for decoding the program related information superimposed on the television broadcast wave;
An audio decoding unit that decodes audio data output from the receiving unit and outputs the audio input signal;
A television receiver having a weighting unit that outputs a genre signal weighted for each genre so that “music genre”> “movie genre”> “news genre” based on genre information included in the program-related information Placed inside
A clock generator for outputting a clock signal;
A pulse width modulation unit that performs pulse width modulation on the clock signal based on the audio input signal;
A conversion unit that includes at least two switching elements, a drive unit that drives the switching element, and a temperature detection unit that detects a temperature of the switching element, and converts an output of the pulse width modulation unit;
Analyzing the signal characteristics of the audio input signal and outputting a parameter corresponding to the degree of amplitude change per fixed time of the stereo sum signal ;
And have groups Dzu the output of the analyzing portion and a control unit for controlling the frequency of said clock signal,
Wherein,
And have groups Dzu the output of the temperature detecting unit, so that the frequency of the clock signal and the temperature rises lowered, controls the clock generator,
Based on the genre signal output from the weighting unit , “frequency of clock signal in case of music genre >> frequency of clock signal in case of movie genre >> frequency of clock signal in case of news genre” Controlling the clock generator ,
Furthermore, based on the parameters output from the analysis unit, when the amplitude change per fixed time of the stereo sum signal is gradual, compared to the case where the amplitude change per fixed time of the stereo sum signal is severe, A digital amplifier , wherein the clock generator is controlled so that the frequency of the clock signal is lowered .

Images