JP2009055530A - Power amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove a power supply ripple components, or the like, when selecting single end driving, when the same amplifier body is applied in selecting BTL (bridged transformer-less) drive and also in selecting single-end drive. <P>SOLUTION: A power amplifier applies at least one of processing systems which serve as a hot side and a cold side in selecting BTL drive, as a processing system in the single end driving when selecting the single-end driving. The power amplifier includes an unwanted component removing signal generating means for generating an unwanted component removing signal from the output of a known unwanted component source; and an unwanted component removing means for removing an unwanted component, in a signal to be amplified by superimposing the unwanted component removing signal generated by the unwanted component removing signal generating means on an input signal to or an output signal from the amplifier body in the processing system in the single-end driving, when at least the single end driving is selected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power amplifier, and can be applied to, for example, a switchable application as a BTL (Bridged Transless) drive PWM (Pulse Width Modulation) amplifier and a single-end drive PWM amplifier.

  In recent years, digitization of power amplifiers has been rapidly progressing. In particular, audio amplifiers are remarkable for their full-scale adoption. Devices equipped with digital power amplifiers (so-called switching amplifiers) include headphones, DVD players, minicomponents, television receivers, personal computers, mobile phones and the like.

  In Patent Documents 1 to 3, the same amplifier unit is used as an element of a BTL drive amplifier as shown in FIG. 2A or as an element of a single-end drive amplifier as shown in FIG. Is also applicable.

It can be used as both a BTL drive amplifier and a single-end drive amplifier. For example, in a BTL configuration, a high-power speaker output is obtained, and in a single-end configuration, a 4-channel speaker output (2 channels out of them) is obtained. Since it is possible to obtain a headphone output having a GND common terminal, an audio product configuration having various variations is possible even if the same circuit configuration is used.
Japanese Patent Laid-Open No. 08-162863 JP 2006-174997 A JP 2005-509347 A

  However, when the BTL drive amplifier is used as a single-ended drive amplifier, a ripple component or noise component of the power supply that did not appear during BTL drive may appear in the output.

  In the BTL drive amplifier, since the output is obtained as a difference between the HOT output and the COLD output, the ripple component and noise component of the power source superimposed as the in-phase component of the HOT output and the COLD output are canceled by the output and do not appear in the output ( (See FIG. 3A). On the other hand, when the amplifier output is obtained between one side (for example, HOT output) of the output of the BTL drive amplifier and the GND, and the single-end configuration is used, the noise component and the ripple component that have been canceled during the BTL drive are canceled. It appears in the output as it is (see FIG. 3B). For this reason, when an amplifier having a BTL configuration is intended to be used as a single-end configuration amplifier, there are practical and performance problems.

  In particular, when a single power supply PWM amplifier is applied to the amplification unit, the problem of power supply ripple is significant. As shown in FIG. 3B, when the PWM amplifier of the single power supply Vcc is applied, the operation reference point potential of the output signal becomes Vcc / 2, and therefore the single power supply Vcc has a ripple. Then, the output signal (for example, audio signal) to the load as viewed from the ground (GND) potential is swayed by ripples. On the other hand, when a PWM amplifier with positive and negative power supplies ± Vcc is applied, since the operation reference point potential of the output signal is the ground (GND) potential, even if ripples are on the power supply, there is no significant influence. That is, when a single power supply PWM amplifier is applied to the amplifier, the problem of power supply ripple is significant.

  Therefore, there is a demand for a power amplifier that can remove unnecessary components such as a power supply ripple component from the amplifier output even when switched between a BTL drive amplifier and a single-end drive amplifier.

  The present invention is a power amplifier that applies at least one of a processing system that becomes a hot side and a cold side when a BTL drive is selected as a processing system for a single-end drive when a single-end drive is selected. An unnecessary component removal signal generating means for generating an unnecessary component removal signal from the output of the unnecessary component source, and (2) at least when selecting the single-end drive, the unnecessary component removal signal generated by the unnecessary component removal signal generating means And an unnecessary component removing unit that removes an unnecessary component in the signal to be amplified by superimposing the input signal or the output signal to the amplifier main body in the processing system using the single-end drive.

  According to the present invention, the same amplifier body can be applied when selecting BTL drive, when selecting single-ended drive, and even when selecting single-ended drive, power ripple components and the like are removed. be able to.

(A) First Embodiment Hereinafter, a first embodiment in which a power amplifier according to the present invention is applied to a switching amplifier (digital power amplifier) for an audio amplifier will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a main configuration of the switching amplifier 100 according to the first embodiment.

  In FIG. 1, the switching amplifier 100 is capable of BTL output (BTL driving) with respect to one load (for example, a single speaker) LD, and a pair of loads (for example, R) by switching the output method. Channel and L channel speakers) LDR and LDL are capable of single-end output (single-end drive).

  The switching amplifier 100 of the first embodiment includes an audio signal selection circuit 101, a pair of switching amplifier units 102H and 102C, a pair of low-pass filters 103H and 103C, a pair of changeover switches 104H and 104C, a pair of DC coupling capacitors 105R, 105L, and a pair of power supply ripple removal signal generators 106R and 106L.

  The audio signal selection circuit 101 is supplied with an output mode selection signal indicating the BTL output mode or the single end output mode.

  When the output mode selection signal indicates the BTL output mode, the audio signal selection circuit 101 supplies the input audio signal to the first (hot side) switching amplifier unit 102H as it is and also inputs the input audio signal. The signal is inverted and supplied to the second (cold side) switching amplifier 102C.

  Also, the audio signal selection circuit 101 provides substantially the same audio signal to the first and second switching amplifier units 102H and 102C when the output mode selection signal indicates the single end output mode. For example, if the R channel and L channel audio signals are input separately, the R channel audio signal is supplied to the first switching amplifier unit 102H and the L channel audio signal is supplied to the second switching amplifier unit 102C. give. In the single-ended output mode, when one audio signal is input, the audio signal selection circuit 101 divides the audio signal into two and supplies it to the first and second switching amplifier units 102H and 102C. Alternatively, after the audio signal is branched into two, R channel and L channel audio signals are formed by sound image localization processing, the R channel audio signal is supplied to the first switching amplifier unit 102H, and the L channel audio signal is supplied to the second channel. To the switching amplifier section 102C.

  Each of the first and second switching amplifier units 102H and 102C is, for example, a single power supply PWM amplifier including a PWM control circuit and a switching circuit. The PWM control circuit forms and outputs a switching control signal for the corresponding switching circuit based on the input audio signal, and the switching circuit is a switching circuit that operates with a single power source, and the corresponding PWM control. PWM corresponding to an input audio signal to the switching amplifier unit, which has a dynamic range corresponding to a power supply voltage Vcc of a single power source, turning on and off a plurality of built-in switching elements according to a switching control signal given from the circuit A signal is formed and output. In the case of a PWM amplifier with a single power supply Vcc, as described above, an output with Vcc / 2 as the operation reference point potential can be obtained.

  The first and second low-pass filters 103H and 103C integrate the PWM signals output from the corresponding switching circuits 102H and 102C and convert them into analog signals. FIG. 1 shows a ladder connection of inductors and capacitors, but it goes without saying that the specific configurations of the low-pass filters 103H and 103C are not limited to those shown in FIG.

  Each of the first and second changeover switches 104H and 104C is a switch having a 1-input / 2-output configuration, and the output signals of the corresponding low-pass filters 103H and 103C are input to the input terminal c. The output mode selection signal described above is input to the first and second changeover switches 104H and 104C, and the first and second changeover switches 104H and 104C perform a linked switching operation.

  When the output mode selection signal indicates the BTL output mode, each of the first and second changeover switches 104H and 104C selects the BTL drive output terminal a, and for each load LD, BTL The output ends of the first and second low-pass filters 103H and 103C are connected so that output (BTL drive) is possible.

  On the other hand, when the output mode selection signal indicates the single end output mode, the first and second changeover switches 104H and 104C each select the output terminal b for single end driving. Accordingly, the first changeover switch 104H connects the output terminal of the first low-pass filter 103H to the first load LDR via the first DC coupling capacitor 105R and the second changeover switch 104C. Connects the output terminal of the second low-pass filter 103C to the second load LDL via the second DC coupling capacitor 105L.

  The first and second DC coupling capacitors 105R and 105L remove the direct current component of the input signal and supply a signal consisting only of the alternating current component to the corresponding loads LDR and LDL.

  Here, the output mode selection signal indicates, for example, that the detection configuration for monitoring the insertion / removal of the headphone jack detects the removal of the headphone jack by instructing the single end output mode when the insertion of the headphone jack is detected. It may be automatically formed so that the BTL output mode is instructed during the operation. Further, for example, the output mode selection signal may indicate a single end output mode or a BTL output mode in accordance with a user's operation such as a dip switch or a toggle switch.

  The first and second power supply ripple removal signal generation units 106R and 106L respectively extract the power supply voltage (Vcc) from the power supply 108 to the switching amplifier units 102H and 102C, which is the source of the power supply ripple, as a signal representing the power supply ripple. The power ripple elimination signal (which is adjusted so that the gain is equal to the power ripple component and the phase is reversed) can be canceled. For example, when the power supply voltage Vcc fluctuates, outputs from the first and second switching amplifier units 102H and 102C using a switching circuit that operates with a single power supply Vcc are centered on the operation reference point potential Vcc / 2. It has a component (power ripple component) that accompanies the power fluctuation. Therefore, the first and second power supply ripple removal signal generators 106R and 106L invert the power supply voltage from the power supply 108 and form a power supply ripple removal signal whose gain is adjusted, and the corresponding first and second switching amplifiers. If the signals are input to the units 102H and 102C, the power supply ripple component appearing at the outputs of the first and second switching amplifier units 102H and 102C can be removed.

  Although FIG. 1 shows that there is a power supply 108 for each processing system, the same power supply is generally used. In FIG. 1, the power supply ripple removal signal generation units 106R and 106L are provided for each processing system. However, a common power supply ripple removal signal generation unit is provided so as not to affect both processing systems. And may be input to the switching amplifier units 102H and 102C of each processing system.

  In the switching amplifier 100 according to the first embodiment, when the BTL output mode is selected, the audio signal selection circuit 101 supplies the input audio signal to the first switching amplifier unit 102H as it is and also inverts the input audio signal. The audio signal is supplied to the second switching amplifier unit 102C.

  At this time, the power supply ripple removal signal generated by the first power supply ripple removal signal generation unit 106R is also superimposed on the audio signal and input to the first switching amplifier unit 102H. Here, in the output of the first switching amplifier unit 102H, the power supply ripple component that is to be mixed in the switching amplifier operation is canceled by the power supply ripple removal signal superimposed on the audio signal.

  Further, the power supply ripple removal signal generated by the second power supply ripple removal signal generation unit 106L is also input to the second switching amplifier unit 102C while being superimposed on the audio signal. Here, in the output of the second switching amplifier unit 102C, the power supply ripple component which is to be mixed in the switching amplifier operation is canceled by the power supply ripple removal signal superimposed on the audio signal.

  The PWM signal from the first switching amplifier unit 102H is converted into an analog signal via the first low-pass filter 103H, and then becomes a hot-side input to the load LD via the first changeover switch 104H. The PWM signal from the second switching amplifier unit 102C is converted into an analog signal through the second low-pass filter 103C, and then becomes a cold-side input to the load LD through the second changeover switch 104C. As a result, the load LD is BTL driven.

  As described with reference to FIG. 3A, even if there are power source ripple components in the outputs of the hot side processing system and the cold side processing system, they are offset and do not cause a problem when the load is driven. . However, in the first embodiment, even when the BTL output mode is selected, there is no power source ripple component in the output of the hot side processing system and the cold side processing system.

  Next, the operation when the single-ended output mode is selected in the switching amplifier 100 of the first embodiment will be described.

  In the single-ended output mode, an audio signal intended for the first load LDR is supplied from the audio signal selection circuit 101 to the first switching amplifier unit 102H, and an audio signal intended for the second load LDL is second. Is supplied to the switching amplifier section 102H.

  Even in the single-ended output mode, the first switching amplifier unit 102H is supplied with the power supply ripple removal signal generated by the first power supply ripple removal signal generation unit 106R, and thereby the first switching amplifier unit 102H. In the output signal, the power supply ripple component is also removed.

  The PWM signal from the first switching amplifier unit 102H is converted into an analog signal through the first low-pass filter 103H, then through the first changeover switch 104H, and further through the operation of removing the power supply ripple component. Even if it is shifted (same when DC shift is caused by factors other than the removal operation), the DC component is removed through the first DC coupling capacitor 105R and applied to the load LDR, and the load LDR is single-ended driven. Is done.

  Similarly, even in the single end output mode, the second switching amplifier unit 102C is supplied with the power supply ripple removal signal generated by the second power supply ripple removal signal generation unit 106L. The output signal of the amplifier section 102C is also removed from the power supply ripple component.

  The PWM signal from the second switching amplifier unit 102C is converted into an analog signal through the second low-pass filter 103C, and then DC-shifted through the second changeover switch 104C and further through the operation of removing the power supply ripple component. Even when the direct current is shifted due to a factor other than the removal operation, the direct current component is removed through the second DC coupling capacitor 105L and applied to the load LDL, and the load LDL is single-ended driven. The

  According to the first embodiment, it is possible to obtain an output from which the power source ripple component can be removed not only in the BTL output mode but also in the single-ended output mode. As a result, good output quality can be achieved in any mode even if the same amplifier unit is used to switch between single-end driving and BTL driving.

  Such an effect is obtained by replacing a single power supply PWM amplifier in which the operation reference point potential of the output signal to the load is half the power supply voltage (Vcc / 2) in the switching amplifier units 102H and 102C in the single end output mode. Especially when applying.

(B) Second Embodiment Next, a second embodiment in which the power amplifier according to the present invention is applied to a switching amplifier (digital power amplifier) for an audio amplifier will be described in detail with reference to the drawings.

  FIG. 4 is a block diagram showing a main configuration of the switching amplifier 100A according to the second embodiment. The same reference numerals are given to the same and corresponding parts as those in FIG. 1 according to the first embodiment. Yes.

  In FIG. 4, the switching amplifier 100A of the second embodiment includes a pair of noise removal signal generation units 107R and 107L in addition to the configuration of the switching amplifier 100 of the first embodiment.

  In some cases, the noise source 109 is known as well as the power source 108 that is the source of the power source ripple. For example, when the signal line is long, the signal line captures the high-frequency signal or spike-like pulse that is radiated from the circuit that handles the high-frequency signal or spike-like pulse of the device. It may become. Each of the first and second noise removal signal generation units 107R and 107L forms a noise removal signal capable of canceling the known noise based on the output from the known noise source 109, and the corresponding first and second switching. This is input to the amplifier units 102H and 102C.

  In FIG. 4, it is described that there is a noise source 109 for each processing system, but in general, the same noise source 109 is used. In FIG. 4, the noise removal signal generation units 107R and 107L are provided for each processing system. However, a common noise removal signal generation unit is provided and distributed so as not to affect both processing systems. Then, the signals may be input to the switching amplifier units 102H and 102C of each processing system.

  The principle of operation that can remove the common-mode noise from the known noise source 109 is the same as the power supply ripple removal described above.

  According to the second embodiment, the same effect as that of the first embodiment can be obtained. According to the second embodiment, in the single-ended output mode, not only the power supply ripple component but also the common-mode noise component can be removed when the noise source is known.

(C) Other Embodiments In the description of each of the above-described embodiments, various modified embodiments have been referred to. However, modified embodiments as exemplified below can be given.

  In each of the above embodiments, in the single-ended output mode, both the hot side in the BTL output mode and the processing system on the cold side function to drive separate loads, but the hot side in the BTL output mode or The present invention can also be applied to the case where only one processing system on the cold side is single-ended driven.

  FIG. 5 shows a switching amplifier in which an input level adjuster 110 made of a variable resistor or the like is provided on the input path from the power supply 108 to the power supply ripple removal signal generation unit 106 (106R or 106L). Providing such an input level adjuster 110 can easily cope with product variations (power ripple level differs depending on the product). Note that an input level adjuster may be provided on the input path from the noise source 109 in FIG. 4 to the noise removal signal generation unit 107 (107R or 107L).

  The unnecessary components to be removed by the present invention are only required to be (1) that the source is known and (2) that the waveform and level at the same time in the source and amplifier output are correlated. Therefore, for example, the waveform may be deformed over time, and periodicity or the like is not required.

  In each of the embodiments described above, the amplifier body is a PWM amplifier. However, the amplifiers in each system are not limited to PWM amplifiers, and may be other switching amplifiers or analog amplifiers. good. Also, the PWM amplifier is not limited to a single power supply PWM amplifier, and although the effect is somewhat inferior to that of a single power supply PWM amplifier, a dual power supply PWM amplifier may be used. Depending on the type of amplifier applied, the removal and cancellation of power supply ripple components and noise components can be replaced with a method of inputting (superimposing) a noise removal signal on the input side of the amplifier. This method may be realized by applying the method.

  In each of the above embodiments, the power ripple removal signal and the noise removal signal are removed even when the BTL output mode is selected. However, when the BTL output mode is selected, the power ripple removal signal and the noise removal signal are selected. The removal by may not be executed.

  In each of the above-described embodiments, the case where the load is a speaker has been described.

1 is a block diagram illustrating an overall configuration of a switching amplifier according to a first embodiment. It is explanatory drawing of BTL drive and single end drive. It is explanatory drawing of the subject of the possible prior art corresponding to both BTL drive and single end drive. It is a block diagram which shows the whole structure of the switching amplifier which concerns on 2nd Embodiment. It is a block diagram which shows the modification of 1st Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100, 100A ... Switching amplifier, 101 ... Audio signal selection circuit, 102H, 102C ... Switching amplifier part, 103H, 103C ... Low pass filter, 104H, 104C ... Changeover switch, 105R, 105L ... DC coupling capacitor, 106R, 106L ... Power supply Ripple removal signal generators 107R, 107L: Noise removal signal generators 108: Power supplies for switching amplifiers.

Claims (5)

A power amplifier that applies at least one of a processing system that becomes a hot side and a cold side when selecting a BTL drive as a processing system with a single end drive when selecting a single end drive,
An unnecessary component removal signal generating means for generating an unnecessary component removal signal from an output of a known unnecessary component source;
At least when selecting single-ended drive, the unnecessary component removal signal generated by the unnecessary component removal signal generation means is superimposed on the input signal or output signal to the amplifier body in the processing system in the single-end drive, and the signal to be amplified An unnecessary component removing means for removing an unnecessary component in the power amplifier. The amplifier body is a single power supply PWM amplifier,
2. The power amplifier according to claim 1, wherein the unnecessary component removal signal generating means generates an unnecessary component removal signal for removing a power supply ripple component of the single power source for the amplifier body.   3. The power amplifier according to claim 1, wherein the unnecessary component removal signal generating means generates an unnecessary component removal signal for removing a noise component contained in an input signal to the amplifier body.   4. Either of the processing systems that are on the hot side and the cold side when selecting the BTL drive are applied as separate processing systems for the single end drive when selecting the single end drive, respectively. A power amplifier according to claim 1.   5. The power amplifier according to claim 4, wherein the unnecessary component removal signal generating means and the unnecessary component removal means are operated even when BTL drive is selected.

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