JP2007336424A - Power amplifier device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power amplifier device capable of performing efficient amplification and efficiently reducing high-frequency noise of an output signal with simple constitution. <P>SOLUTION: Signals which are efficiently amplified by amplifier circuits 120A and 120B by using a switching system are passed through LPFs 130A and 130B to generate a positive-phase signal S3A wherein high-frequency noise including positive-phase switching noise remains and an opposite-phase signal S3B wherein high-frequency noise including opposite-phase switching noise remains. The positive-phase signal S3A is put together with opposite-phase switching noise, having a frequency nearby a switching frequency which is extracted from the opposite-phase signal S3B, by a composite filter 140A, and also has its high-frequency noise reduced. The opposite-phase signal S3B is put together with positive-phase noise, having a frequency nearby the switching frequency which is extracted from the positive-phase signal S3A, by a composite filter 140B, and also has the high-frequency noise reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power amplification device.

  2. Description of the Related Art Conventionally, as a power amplifying apparatus for audio or the like, a power amplifying apparatus that connects a load to a BTL (Balanced Transformerless) is known. As such a power amplifying device, one having the circuit configuration shown in FIG. 1 is known (hereinafter referred to as “conventional example 1”: see Patent Document 1).

  The power amplifying apparatus 700 of the conventional example 1 amplifies the audio signal S0 output from the signal source 910, and includes a PWM (Pulse-Width Modulation) circuit 710, amplifier circuits 720A and 720B, and a low-pass filter (LPF). 730 and a CMR filter 740.

  In this power amplifying apparatus 700, the PWM circuit 710 performs pulse width modulation on the audio signal S0 to generate PWM signals S71A and S71B having opposite phases to each other. The PWM signals S71A and S71B generated in this way are amplified by the amplification circuits 720A and 720B using a switching method, and are output as signals S72A and S72B.

  The signal S72A is integrated in a low-pass filter (LPF) 730 according to a time constant determined by the inductance value of the inductor LA and the capacitance value of the capacitance C. As a result, the high frequency component including the switching noise included in the signal S72A is efficiently attenuated, and the positive phase signal S73A corresponding to the original audio signal S0 is output from the LPF 730.

  On the other hand, the signal S72B is integrated in the LPF 730 according to a time constant determined by the inductance value of the inductor LB and the capacitance value of the capacitance C. As a result, the high frequency component including the switching noise included in the signal S72B is efficiently attenuated, and a negative phase signal S73B having a phase opposite to that of the positive phase signal S73A corresponds to the original audio signal S0 from the LPF 730. Is output.

  Thereafter, common mode noise in the positive phase signal S73A and the negative phase signal S73B output from the LPF 730 is removed by the CMR filter 740. Then, the signals S74A and S74B output from the CMR filter 740 are supplied to the speaker 920 that is a load.

  Patent Document 1 also discloses a circuit configuration of a power amplifying device that can realize the functions of the LPF 730 and the CMR filter 750 in the power amplifying device 700 of Conventional Example 1 while reducing the number of components. .

  Further, a power amplifying apparatus having a circuit configuration shown in FIG. 2 is proposed as a power amplifying apparatus connected to a load by BTL (hereinafter referred to as “conventional example 2”: see Patent Document 2). In FIG. 2, the same or equivalent elements as those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

  Similar to the power amplification device 700 described above, the power amplification device 800 of Conventional Example 2 amplifies the audio signal S0 output from the signal source 910, and includes a PWM circuit 710, amplification circuits 720A and 720B, and an LPF 830A. , 830B, noise component extraction means 840A, 840B, and noise component synthesis means 850A, 850B.

  In this power amplification device 800, as in the case of the power amplification device 700 described above, the PWM circuit 710 performs pulse width modulation on the audio signal S0 and generates PWM signals S71A and S71B having opposite phases to each other. The PWM signals S71A and S71B generated in this way are amplified by the amplification circuits 720A and 720B using a switching method, and are output as signals S72A and S72B.

  Subsequently, in the LPF 830A, high frequency components including switching noise in the signal S72A are efficiently attenuated. Then, a positive phase signal S83A corresponding to the original audio signal S0 is output from the LPF 830A. Further, in the LPF 830B, high frequency components including switching noise in the signal S72B are efficiently attenuated. Then, in response to the original audio signal S0, a negative phase signal S83B having an opposite phase to the positive phase signal S83A is output from the LPF 830B.

  Next, in the noise component extraction unit 840A configured by a band pass filter (BPF) or the like, the positive phase high frequency noise S85A superimposed on the positive phase signal S83A is extracted, and the positive phase signal S84A and the positive phase high frequency noise S85A are extracted. Is output. Further, in the noise component extraction unit 840B configured similarly to the noise component extraction unit 840A, the negative phase high frequency noise S85B superimposed on the negative phase signal S83B is extracted, and the negative phase signal S84B and the negative phase high frequency noise are extracted. S85B is output.

  Next, in the noise component synthesizing unit 850A, the normal phase signal S84A and the negative phase high frequency noise S85B are combined to cancel the positive phase high frequency noise remaining in the positive phase signal S84A and the negative phase high frequency noise S85B. The Further, in the noise component synthesizing unit 850B, the reverse phase signal S84B and the normal phase high frequency noise S85A are combined to cancel the negative phase high frequency noise remaining in the negative phase signal S84B and the normal phase high frequency noise S85A. The

  Thus, a normal phase signal S86A and a negative phase signal S86B from which high frequency noise including switching noise is effectively removed are generated. Then, the normal phase signal S86A and the negative phase signal S86B are supplied to the speaker 920 which is a load.

  Note that Patent Document 2 also includes a configuration example of a power amplifying device further including a CMR filter 740 that removes common mode noise in the normal phase signal S86A and the negative phase signal S86B generated in the power amplifying device 800 of Conventional Example 2. It is disclosed.

JP 2003-46345 A WO 2006/049154 A1

  In the power amplifying apparatus 700 of Conventional Example 1 described above, switching noise resulting from the switching operation of the amplifier circuits 720A and 720B is generated along with the class D amplification operation. For example, when the original signal S0 is an audio signal, such switching noise often has a frequency that overlaps or is very close to a radio broadcast wave.

  In the power amplifying apparatus 700, the LPF 730 prevents such switching noise from remaining in the output signal. However, from the viewpoint of eliminating switching noise by the LPF having a simple configuration, it is difficult to say that the frequency band of the audio signal is far away from the frequency band of the radio broadcast wave. Therefore, for example, when the wiring from the power amplifying device to the speaker is close to the radio broadcast wave receiving antenna as in an in-vehicle audio device, in the single-stage configuration of the LPF with only the LPF 730, the switching noise is reduced. The removal cannot be performed sufficiently, and noise of a non-negligible magnitude radiated from the wiring from the power amplification device to the speaker is mixed into the radio broadcast wave. The power amplifying apparatus 700 includes the CMR filter 740 subsequent to the LPF 730. However, since the switching noises superimposed on the signals S73A and S73B output from the LPF 730 are in opposite phases to each other, the CMR filter 740 is provided. In some cases, switching noise cannot be reduced.

  On the other hand, in the power amplifying apparatus 800, the switching noise on the positive phase side and the reverse phase side is first removed by the LPF 830A and the LPF 830B with the same performance as the high frequency noise removal by the LPF 730 in the power amplifying apparatus 700. Then, switching noise is further removed by signal synthesis by the noise component synthesis means 850A and 850B. As a result, the switching noise, which is the main component of the high frequency noise, can be removed with the same high frequency noise as when two stages of LPFs are connected.

  However, in the case of the on-vehicle audio device described above, removal of high frequency noise including switching noise in the output signal may not be sufficient even with high frequency noise removal in the power amplification device 800. According to the knowledge obtained from the results of research and development by the inventor, in the case of an in-vehicle audio device, the switching noise, which is the main component of high-frequency noise, is about the case where three stages of LPFs are connected. It is preferable to perform the above noise removal.

  The present invention has been made in view of the above circumstances, and provides a power amplifying apparatus that can efficiently amplify and reduce high-frequency noise in an output signal with a simple configuration. For the purpose.

  The invention according to claim 1 is a first amplifying means for amplifying the first signal of the first signal and the second signal that are out of phase with each other by a switching method; substantially the same amplification as the first amplifying means A second amplifying means for amplifying the second signal by a switching method at a rate, and constituting a BTL amplifying means together with the first amplifying means; and a third signal output from the first amplifying means, First low-pass filter means for transmitting a signal component in a defined low frequency range; second low-pass filter means for receiving the fourth signal output from the second amplification means and transmitting the signal component in the low frequency range The fifth signal output from the first low-pass filter means and the sixth signal output from the second low-pass filter means are input, and the switching signal superimposed on the sixth signal is input. First composite filter means for transmitting the low-frequency signal component in the fifth signal while extracting the signal and synthesizing it with the fifth signal; and inputting the fifth signal and the sixth signal signal And second composite filter means for extracting the switching noise superimposed on the fifth signal and synthesizing it with the sixth signal, and transmitting the low-frequency signal component in the sixth signal. Is a power amplification device characterized by

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In the present embodiment, as in the conventional examples 1 and 2, the power amplifying apparatus that amplifies the audio signal S0 output from the signal source 910 and supplies the amplified audio signal S0 to the speaker 920 as a load will be described as an example. .

[Constitution]
3 and 4 show a configuration of the power amplifying apparatus 100 according to the present embodiment. Here, FIG. 3 shows a schematic configuration of the power amplifying apparatus 100 in a block diagram. FIG. 4 shows low-pass filters (LPF) 130A and 130B and composite filters 140A and 140B described later in FIG. The part is shown in the detailed circuit diagram.

  As shown in FIG. 3, the power amplification device 100 includes a pulse width modulation (PWM) circuit 110, amplification circuits 120A and 120B, LPFs 130A and 130B, and composite filters 140A and 140B.

  The PWM circuit 110 performs the same function as the PWM circuit 710 in the conventional examples 1 and 2 described above. That is, the PWM circuit 110 receives the audio signal S0 from the signal source 910, performs pulse width modulation, and generates and outputs a normal phase PWM signal S1A and a negative phase PWM signal S1B that are opposite in phase to each other.

  The amplifier circuit 120A amplifies the positive phase PWM signal S1A by a switching method, and generates and outputs a positive phase PWM signal S2A. In addition, the amplifier circuit 120B amplifies the reverse phase PWM signal S1B by the switching method with substantially the same amplification factor as that of the amplifier circuit 120A, and generates and outputs the reverse phase PWM signal S2B.

  As illustrated in FIG. 4, the LPF 130A includes an inductor L1A and a capacitor C1A. Here, one terminal of the inductor L1A is connected to the output terminal of the amplifier circuit 120A. The other terminal of inductor L1A is connected to one terminal of capacitor C1A. The other terminal of the capacitor C1A is grounded. In the LPF 130A, one terminal of the inductor L1A is an input terminal of the LPF 130A, and one terminal of the capacitor C1A is an output terminal of the LPF 130A.

  In the LPF 130A configured as described above, integration is performed on the positive phase PWM signal S2A according to a time constant that is the reciprocal of the cutoff frequency determined by the inductance value of the inductor L1A and the capacitance value of the capacitor C1A. As a result, the high frequency component (including the positive phase switching noise) in the positive phase PWM signal S2A having a frequency higher than the cutoff frequency of the LPF 130A is efficiently attenuated, and the positive phase signal S3A is generated and output.

  As shown in FIG. 4, the LPF 130B includes an inductor L1B and a capacitor C1B, and is configured symmetrically with the above-described LPF 130A. That is, one terminal of the inductor L1B is connected to the output terminal of the amplifier circuit 120B. The other terminal of inductor L1B is connected to one terminal of capacitor C1B. The other terminal of the capacitor C1B is grounded. In this LPF 130B, one terminal of the inductor L1B is an input terminal of the LPF 130B, and one terminal of the capacitor C1B is an output terminal of the LPF 130B.

  The inductance value of the inductor L1B is substantially the same as the inductance value of the inductor L1A. Further, the capacitance value of the capacitor C1B is substantially the same as the capacitance value of the capacitor C1A.

  In the LPF 130B configured in this manner, the integration according to the time constant that is the reciprocal of the cutoff frequency determined by the inductance value of the inductor L1B and the capacitance value of the capacitor C1B is performed on the anti-phase PWM signal S2B. As a result, the high-frequency component (including anti-phase switching noise) in the anti-phase PWM signal S2B having a frequency higher than the cutoff frequency of the LPF 130B is efficiently attenuated, and the anti-phase signal S3B is generated and output.

  As shown in FIG. 4, the composite filter 140A includes an inductor L2A, a capacitor C2A, and a bandpass filter (BPF) 141A. Here, the BPF 141A includes an inductor L3A and a capacitor C3A.

  In BPF 141A, one terminal of capacitor C3A is connected to the output terminal of LPF 130B. The other terminal of capacitor C3A is connected to one terminal of inductor L3A. The other terminal of inductor L3A is connected to the other terminal of inductor L3A. In this BPF 141A, one terminal of the capacitor C3A is an input terminal of the BPF 141A, and the other terminal of the inductor L3A is an output terminal of the BPF 141A.

  In composite filter 140A, one terminal of inductor L2A is connected to the output terminal of LPF 130A. The other terminal of the inductor L2A is connected to the output terminal of the BPF 141A (the other terminal of the inductor L3A) and one terminal of the capacitor C2A. The other terminal of the capacitor C2A is grounded. In the composite filter 140A, one terminal of the inductor L2A and one terminal of the capacitor C3A are input terminals, and one terminal of the capacitor C2A is an output terminal.

  Note that the inductor value of the inductor L2A and the inductor value of the inductor L3A are set to be substantially the same. Further, the cut-off frequency determined by the inductor value of the inductor L2A and the capacitor C2A is set to be substantially the same as the cut-off frequency of the LPF 130A described above.

  Further, the inductance value of the inductor L3A and the capacitance value of the capacitor C3A are set so that the frequency of the signal passed through as the BPF 141A is around the switching frequency. Since the signal passing through the BPF 141A is a high-frequency signal having a frequency near the switching frequency attenuated by the LPF 130B, the current flowing through the inductor L3A is very small. Therefore, an inductor having a small current capacity, that is, a small inductor can be adopted as the inductor L3A.

  In composite filter 140A configured in this way, the signal through inductor L2A and high-frequency signal S4A that has passed through BPF 141A are combined, and the reciprocal of the cutoff frequency determined by the inductance value of inductor L2A and the capacitance value of capacitor C2A. Integration is performed according to the time constant. As a result, the high frequency component having a frequency higher than the cutoff frequency is attenuated, and the positive phase signal S5A is generated and output.

  As shown in FIG. 4, the composite filter 140B includes an inductor L2B, a capacitor C2B, and a BPF 141B, and is configured symmetrically with the above-described composite filter 140A. Here, the BPF 141B includes an inductor L3B and a capacitor C3B.

  In BPF 141B, one terminal of capacitor C3B is connected to the output terminal of LPF 130A. The other terminal of capacitor C3B is connected to one terminal of inductor L3B. The other terminal of inductor L3B is connected to the other terminal of inductor L2B. In the BPF 141B, one terminal of the capacitor C3B is an input terminal of the BPF 141B, and the other terminal of the inductor L3B is an output terminal of the BPF 141B.

  In composite filter 140B, one terminal of inductor L2B is connected to the output terminal of LPF 130B. The other terminal of the inductor L2B is connected to the output terminal of the BPF 141B (the other terminal of the inductor L3B) and one terminal of the capacitor C2B. The other terminal of the capacitor C2B is grounded. In this composite filter 140B, one terminal of the inductor L2B and one terminal of the capacitor C3B are input terminals, and one terminal of the capacitor C2B is an output terminal.

  Note that the inductor values of the inductors L2B and L3B are set to be approximately the same as the inductor values of the above-described inductors L2A and L3A. The capacitance values of the capacitors C2B and C3B are set to be substantially the same as the inductor values of the capacitors C2A and C3A. For this reason, the BPF 141B is set to pass a signal having a frequency around the switching frequency, like the BPF 141A. In addition, the composite filter 140B attenuates the high-frequency component, similarly to the composite filter 140A.

  In composite filter 140B configured in this manner, the signal through inductor L2B and high-frequency signal S4B that has passed through BPF 141B are combined, and the reciprocal of the cutoff frequency determined by the inductance value of inductor L2B and the capacitance value of capacitor C2B. Integration is performed according to the time constant. As a result, a high frequency component having a frequency higher than the cutoff frequency is attenuated, and a reverse phase signal S5B is generated and output.

[Operation]
Next, the amplifying operation of the audio signal S0 by the power amplifying apparatus 100 configured as described above will be described mainly with reference to FIG.

  The audio signal S0 output from the signal source 910 is received by the PWM circuit 110 in the power amplification device 100. Upon receiving the audio signal S0, the PWM circuit 110 performs pulse width modulation that modulates the pulse signal having the same height according to the signal value at the sampling time of the audio signal S0, and the waveform is illustrated in FIG. Thus, a positive phase PWM signal S1A and a negative phase PWM signal S1B having opposite phases and similar amplitudes are generated. Then, the PWM circuit 110 outputs the normal phase PWM signal S1A toward the amplifier circuit 120A and outputs the negative phase PWM signal S1B toward the amplifier circuit 120B.

  Receiving the positive phase PWM signal S1A, the amplifier circuit 120A amplifies the positive phase PWM signal S1A using a switching method to generate a positive phase PWM signal S2A. Then, the amplifier circuit 120A outputs the positive phase PWM signal S2A toward the LPF 130A.

  On the other hand, the amplifier circuit 120B that has received the reverse-phase PWM signal S1B amplifies the reverse-phase PWM signal S1B at substantially the same amplification factor as the amplifier circuit 120A using a switching method in parallel with the amplification operation by the amplifier circuit 120A. A negative phase PWM signal S2B is generated. Then, the amplification circuit 120B outputs the reverse phase PWM signal S2B toward the LPF 130B.

  Receiving the positive phase PWM signal S2A, the LPF 130A generates a positive phase signal S3A by the attenuation action of the high frequency component according to the characteristic determined by the cutoff frequency of the LPF 130A. Then, the positive phase signal S3A is output from the LPF 130A to the composite filter 140A and the composite filter 140B. In the positive phase signal S3A, switching noise having a switching frequency (positive phase switching noise) mainly remains as a noise component.

  On the other hand, the LPF 130B that has received the anti-phase PWM signal S2B, in parallel with the operation of the LPF 130A, has the anti-phase signal S3B due to the characteristic determined by the cutoff frequency of the LPF 130B, that is, the high-frequency component attenuation action according to the same characteristic as the LPF 130A. Is generated. Then, the anti-phase signal S3B is output from the LPF 130B toward the composite filter 140A and the composite filter 140B. In the negative phase signal S3B, switching noise having a switching frequency (negative phase switching noise) mainly remains as a noise component. The negative phase switching noise has a phase opposite to that of the normal phase switching noise and a similar amplitude.

  In composite filter 140A, the signal from LPF 130A is received by one terminal of inductor L2A, and the signal from LPF 130B is received by the input terminal of BPF 141A. The BPF 141A transmits a high-frequency signal having a frequency around the switching frequency including reverse-phase switching noise in the input signal, and outputs it as a high-frequency signal S4A. As a result, the signal via the inductor L2A and the high frequency signal S4A are synthesized.

  By the way, the high frequency noise having a frequency around the switching frequency in the signal via the inductor L2A (hereinafter also referred to as “switching frequency peripheral positive phase noise”) and the high frequency signal S4A are generated based on the circuit configuration described above. Therefore, they have substantially opposite phases and the same amplitude. For this reason, as a result of the synthesis of the signal via the inductor L2A and the high-frequency signal S4A, much of the positive frequency noise around the switching frequency remaining in the signal via the inductor L2A is canceled with the high-frequency signal S4A.

  In the composite filter 140A, in addition to the removal of the positive frequency noise around the switching frequency by the signal synthesis described above, the high frequency noise remaining in the signal from the LPF 130A is further removed by the LPF composed of the inductor L2A and the capacitor C2A. . As a result, the composite filter 140A removes the positive frequency noise around the switching frequency with the same removal rate as when three stages of LPFs equivalent to the LPF 130A are connected.

  The positive phase signal S5A in which the high frequency noise is reduced as described above is supplied from the composite filter 140A to the speaker 920.

  On the other hand, composite filter 140B receives a signal from LPF 130B at one terminal of inductor L2B and receives a signal from LPF 130A at an input terminal of BPF 141B. In the BPF 141B, similarly to the case of the BPF 141A described above, a high-frequency signal having a frequency around the switching frequency including reverse-phase switching noise in the input signal is transmitted and output as a high-frequency signal S4B. As a result, the signal via the inductor L2B and the high frequency signal S4B are synthesized.

  By the way, the high frequency noise having a frequency around the switching frequency in the signal via the inductor L2B (hereinafter also referred to as “switching frequency peripheral anti-phase noise”) and the high frequency signal S4B are generated based on the above-described circuit configuration. Thus, as in the case of the composite filter 140A, they have substantially opposite phases and the same amplitude. For this reason, as a result of the synthesis of the signal via the inductor L2B and the high frequency signal S4B, much of the switching frequency peripheral noise remaining in the signal via the inductor L2B is canceled out with the high frequency signal S4B.

  In the composite filter 140B, in the same manner as in the composite filter 140A, in addition to the removal of the anti-phase noise around the switching frequency by the signal synthesis described above, the high frequency noise remaining in the signal from the LPF 130B It is further removed by the LPF composed of As a result, the composite filter 140B removes the switching frequency peripheral anti-phase noise with the same removal rate as when the LPF 130B, that is, the LPF equivalent to the LPF 130A is connected in three stages.

  The anti-phase signal S5B in which the high frequency noise is reduced as described above is supplied from the composite filter 140B to the speaker 920.

  As described above, in the power amplifying apparatus 100 of the present embodiment, the amplifier circuit 120A and the amplifier circuit 120B efficiently amplify the positive phase PWM signal S1A and the negative phase PWM signal S1B by the class D operation by the switching method. The positive phase PWM signal S2A and the negative phase PWM signal S2B are generated. The positive-phase PWM signal S2A passes through the LPF 130A, thereby generating the positive-phase signal S3A in which high-frequency noise including the positive-phase switching noise remains, and the reverse-phase PWM signal S2B passes through the LPF 130B. A positive phase signal S3B in which high frequency noise including noise remains is generated. The normal phase signal S3A is combined with the switching frequency peripheral negative phase noise extracted by the BPF 141A from the negative phase signal S3B in the composite filter 140A, and the high frequency noise is reduced. The anti-phase signal S3B is combined with the switching frequency peripheral normal phase noise extracted by the BPF 141B from the normal phase signal S3A in the composite filter 140B, and the high frequency noise is reduced.

  Here, since circuit components constituting the BPF 141A and the BPF 141B can have a small current capacity, small circuit components can be employed. For this reason, the switching noise can be removed in the space in the case of the two-stage configuration of the LPF as in the case of the three-stage configuration of the LPF. Therefore, according to the power amplifying apparatus 100 of the present embodiment, efficient amplification can be performed, and reduction of high-frequency noise in the output signal can be efficiently reduced with a simple configuration.

[Modification of Embodiment]
The present invention is not limited to the above-described embodiment, and various modifications are possible.

  For example, in the above embodiment, in the BPF 141A and the BPF 141B, the capacitor is disposed on the input side, but the inductor may be disposed on the input side.

  Further, when it is desired to remove high-frequency noise, an LPF can be arranged in the front stage or the rear stage of the composite filters 140A and 140B.

  In particular, when it is desired to further remove switching noise, a composite filter configured in the same manner as the composite filters 140A and 140B can be arranged at the subsequent stage of each of the composite filters 140A and 140B.

  Further, when it is necessary to reduce the common mode noise in the two output signals S5A and S5B, a CMR similar to the CMR filter 750 for reducing the common mode noise in the subsequent stage of the power amplifying apparatus 100 of the above embodiment is used. The power amplifying apparatus 200 shown in FIG. 6 in which the filter 190 is disposed may be configured.

  In the above-described embodiment, after the signal from the signal source 910 is pulse width modulated, the modulated signal is amplified by the class D operation using the switching method. On the other hand, instead of pulse width modulation, after performing pulse train modulation that changes the number of pulses per unit time in accordance with the amplitude value of the signal from the signal source 910, the modulated signal is obtained by class D operation using a switching method. Can also be amplified.

  In the above embodiment, the sound signal S0 is amplified. However, when an analog signal other than the sound signal S0 is amplified, the power amplifying apparatus can be configured with the same configuration as the above embodiment. it can.

It is a flock figure which shows the schematic structure of the power amplifier of the prior art example 1. It is a block diagram which shows the schematic structure of the power amplifier of the prior art example 2. It is a block diagram which shows the schematic structure of the power amplifier concerning one Embodiment. It is a figure for demonstrating the circuit structure of LPF and a composite filter in the apparatus of FIG. It is a figure for demonstrating operation | movement of the apparatus of FIG. It is a block diagram for demonstrating the schematic structure of the apparatus of a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100,200 ... Power amplifier 110 ... PWM circuit (pulse width modulation means)
120A, 120B ... Amplifying circuit (first and second amplifying means)
130A, 130B... LPF (first and second low-pass filter means)
140A, 140B ... Composite filter (first and second composite filter means)
141A, 141B ... BPF (first and second band pass filter means)
190 ... CMR filter (common-mode component removing means)
L2A, L2B, L3A, L3B ... Inductors (first to fourth inductance elements)
C2A, C2B, C3A, C3B ... Capacitors (first to fourth capacitive elements)

Claims (6)

First amplification means for amplifying the first signal out of phase with each other by a switching method;
Second amplification means for amplifying the second signal by a switching method at substantially the same amplification factor as the first amplification means, and constituting a BTL amplification means together with the first amplification means;
First low-pass filter means for inputting a third signal output from the first amplifying means and transmitting a signal component in a predetermined low frequency range;
Second low-pass filter means for inputting the fourth signal output from the second amplifying means and transmitting the low-frequency signal component;
The fifth signal output from the first low-pass filter means and the sixth signal output from the second low-pass filter means are input, the switching noise superimposed on the sixth signal is extracted, and the fifth signal is extracted. First composite filter means for transmitting the low-frequency signal component of the fifth signal while combining with the signal;
The fifth signal and the sixth signal are input, the switching noise superimposed on the fifth signal is extracted and synthesized with the sixth signal, and the low frequency signal component of the sixth signal is synthesized. And a second composite filter means for transmitting the power. The first composite filter means includes
First bandpass filter means for selectively transmitting switching noise superimposed on the sixth signal;
A first inductance element having one terminal connected to the output terminal of the first low-pass filter means and the other terminal connected to the output terminal of the first band-pass filter means;
A first capacitance element having one terminal connected to the other terminal of the first inductance element and the other terminal connected to a ground level;
The second composite filter means includes
Second bandpass filter means for selectively transmitting switching noise superimposed on the fifth signal;
A second inductance element having one terminal connected to the output terminal of the second low-pass filter means and the other terminal connected to the output terminal of the second band-pass filter means;
2. The power amplification according to claim 1, further comprising: a second capacitive element having one terminal connected to the other terminal of the second inductance element and having the other terminal connected to a ground level. apparatus. The first band pass filter means includes:
A third inductance element;
One terminal of the third inductance element; and a third capacitance element connected to one terminal;
The second band pass filter means includes:
A fourth inductance element;
The power amplifying apparatus according to claim 2, further comprising: one terminal of the fourth inductance element; and a fourth capacitor element to which the one terminal is connected.   The first inductance element and the third inductance element have substantially the same inductance value, and the second inductance element and the fourth inductance element have substantially the same inductance value. 4. The power amplifying device according to 3.   5. The power amplifying apparatus according to claim 1, further comprising: a pulse width modulation unit that performs pulse width modulation on an original signal to generate the first signal and the second signal. . An in-phase component that receives the seventh signal output from the first composite filter means and the eighth signal output from the second composite filter means, and removes in-phase components in the seventh signal and the eighth signal. The power amplifying apparatus according to claim 1, further comprising a component removing unit.

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