JPH11346121A - High efficiency power amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high efficiency power amplifier which realizes constitution, minimizing an expensive passive filter required for the high efficiency power amplifier and totally reduces cost and lowers high frequency noise, as compared with an existing high efficiency power amplifier. SOLUTION: High frequency noise is suppressed effectively, while the constitution of a passive filter 3 is minimized by equivalently realizing an active filter by using a linear power amplifier 6 synchronously driven in parallel with a D-grade power amplifier 2. In addition, the phase of an audio signal inputted from a signal input terminal 21 is corrected by a phase correcting circuit 7 for correcting the delay of a signal generated by the passive filter 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high efficiency power amplifier having a class D power amplifier, and more particularly to a low noise high efficiency power amplifier suitable for audio signal amplification.

[0002]

BACKGROUND OF THE INVENTION According to prior art high efficiency power amplifiers used in connection with loudspeakers, class D power amplifiers have heretofore been used in various forms as power efficient power amplifiers for audio. I have.

Hereinafter, a conventional example of a high-efficiency power amplifier of the class D power amplifier described above will be described with reference to the drawings. In FIG. 19, 301 is a signal input terminal, 302 is a class D power amplifier, 303 is a speaker input terminal, and 304 is a D input terminal.
Output terminal of the class D power amplifier 302, 305 is a positive power supply terminal of the class D power amplifier 302, 306 is a negative power supply terminal of the class D power amplifier 302, 307 is a passive low-pass filter, 31
Reference numerals 0A, 310B, and 310C denote coils that form the passive filter 307, 311A, 311B, and 311C denote capacitors that form the passive filter 307, and 326 denotes a speaker.

[0004] The operation of the conventional high-efficiency power amplifier configured as described above will be described below. First, an audio signal input to the signal input terminal 301 is power-amplified by a class D power amplifier 302 while performing a switching operation by a PWM (pulse width modulation) method. Therefore, a modulated carrier signal having a large PWM is output from the output terminal 304 of the class D power amplifier 302. In order to remove this modulated carrier signal, the passive low-pass filter 307
It operates as a 6th-order Butterworth-type steep filter composed of stage coils and capacitors.

FIG. 20 shows a typical filter characteristic. As can be seen from FIG. 20, in order to transmit the audio signal to the speaker without attenuating, the cutoff frequency (fc) of the filter is usually set to a region of 20 kHz or more, which is the upper limit of the audio signal. Further, if the PWM modulation carrier frequency is, for example, 200 kHz, the attenuation determined by the characteristics of the passive low-pass filter indicates a certain finite value (for example, -60 dB). Therefore, the PWM modulation carrier frequency component is input to the speaker 326 as residual noise at the speaker input terminal 303.

[0006]

However, in the configuration of the conventional high-efficiency power amplifying apparatus as described above, no matter how steep the filter characteristics of the passive low-pass filter 307, a finite PWM modulation carrier frequency component is required. The residual noise of the value is superimposed on the audio signal, and this component is radiated through the speaker code, which may adversely affect all devices as so-called high-frequency noise. Alternatively, it is necessary to use expensive coils and capacitors in order to form a high-order passive low-pass filter, and there has been a problem that a high cost is generally spent on a noise suppression filter.

The present invention has been made in view of the above-mentioned conventional problems, and realizes a configuration for minimizing an expensive passive filter, and is generally less expensive than a conventional high-efficiency power amplifying apparatus and has less high-frequency noise. It is intended to provide an efficient power amplifier.

[0008]

SUMMARY OF THE INVENTION A first aspect of the present invention is as follows.
In a high-efficiency power amplifying device for amplifying an input signal input to a signal input terminal, a PWM power amplifier for amplifying an input signal from the signal input terminal by pulse width modulation and outputting the amplified signal, and an output from the PWM power amplifier A passive low-pass filter that demodulates and outputs the pulse width modulated signal, a positive floating voltage source that supplies a positive current by shifting the demodulated signal output from the passive low-pass filter by a predetermined voltage + DV, For a negative floating voltage source that supplies a negative current by shifting the demodulated signal output from the low-pass filter by a predetermined voltage −DV, and for an input signal input from a signal input terminal,
A phase correction circuit that corrects the phase of the signal output from the passive low-pass filter;
a linear voltage amplifier composed of a linear circuit, which is shifted by dV and -dV, respectively, and output; and a voltage amplification signal shifted by + dV is current amplified by a positive current to generate a positive current amplification signal, A voltage-amplified signal shifted by −dV is current-amplified with a negative-direction current to generate a negative-direction current-amplified signal. And an output device for generating and outputting the power.

A second aspect of the present invention is to provide a high-efficiency power amplifier for amplifying the power of an input signal input to a signal input terminal, by applying a positive bias voltage to an input signal from the signal input terminal. A first bias power supply, a first PWM power amplifier that outputs a first pulse width modulated signal generated by power-amplifying the positively biased input signal by pulse width modulation, and the first pulse A first passive low-pass filter for outputting a first demodulated signal generated by demodulating the width-modulated signal, a second bias power supply for applying a negative bias voltage to an input signal from a signal input end, A second PWM power amplifier that outputs a second pulse width modulated signal generated by power-amplifying the input signal biased in the negative direction by pulse width modulation, and demodulates and generates the second pulse width modulated signal. A second passive low-pass filter that outputs the second demodulated signal, a phase correction circuit that performs a phase correction on a signal output from the passive low-pass filter with respect to an input signal input from the signal input terminal, A linear voltage amplifier composed of a linear circuit, which amplifies the phase-corrected signal by the phase correction circuit and shifts and outputs the signals by predetermined voltages + dV and -dV, respectively, and a voltage-amplified signal shifted by + dV The current is amplified by the first demodulation signal to generate a positive current amplification signal, and the voltage amplification signal shifted by -dV is current amplified by the second demodulation signal to generate a negative current amplification signal. An output device for generating and outputting a power amplification signal by adding the direction current amplification signal and the negative direction current amplification signal in a push-pull form. It is the rate power amplifier.

A third aspect of the present invention is the high-efficiency power amplifier according to the first or second aspect, wherein the output unit is constituted by a push-pull circuit formed by a complementary circuit. A high-efficiency power amplifying device characterized in that:

A fourth aspect of the present invention is the high efficiency power amplifier according to any one of the first to third aspects, wherein the linear voltage amplifier and the output unit form a class B power amplifier. Is a high-efficiency power amplifier.

A fifth aspect of the present invention is the high-efficiency power amplifier according to any one of the first to third aspects, wherein the linear voltage amplifier and the output unit form a class AB power amplifier. Is a high-efficiency power amplifier.

A sixth aspect of the present invention is the high-efficiency power amplifier according to any one of the first to third aspects, wherein the linear voltage amplifier and the output unit form a class A power amplifier. Is a high-efficiency power amplifier.

According to a seventh aspect of the present invention, there is provided a high-efficiency power amplifier according to any one of the first and second aspects, wherein the passive low-pass filter comprises a spiral electrode formed on a substrate. And a high efficiency power amplifying device.

An eighth aspect of the present invention is the high-efficiency power amplifier according to the seventh aspect, wherein the spiral electrode comprises:
This is a high-efficiency power amplifying device formed of a copper foil pattern and forming a coil.

A ninth aspect of the present invention is the high-efficiency power amplifier according to any one of the first and second aspects, wherein the phase correction circuit is formed by a passive filter having the same number of poles as a passive low-pass filter. And a high efficiency power amplifying device.

A tenth aspect of the present invention is the high-efficiency power amplifier according to any one of the first and second aspects, wherein the phase correction circuit is formed by an active filter having the same number of poles as a passive low-pass filter. And a high efficiency power amplifying device.

An eleventh aspect of the present invention is the high-efficiency power amplifier according to any one of the first and second aspects, wherein the phase correction circuit is formed in a linear voltage amplifier. This is a high-efficiency power amplification device.

A twelfth aspect of the present invention is the high-efficiency power amplifier according to the eleventh aspect, wherein the linear voltage amplifier includes an operational amplifier for amplifying a voltage of a signal input to a signal input terminal; An input circuit for adjusting the input impedance of the operational amplifier, and a feedback circuit in the operational amplifier are provided. Each of the input circuit and the feedback circuit has a capacitor and performs a predetermined phase correction on an input signal from a signal input terminal. A high efficiency power amplifying device characterized by being formed with predetermined circuit constants as described above.

A thirteenth aspect of the present invention is the high-efficiency power amplifier according to the twelfth aspect, wherein the input circuit and the feedback circuit are formed so as to have the same number of poles as the number of poles of the passive low-pass filter. This is a high-efficiency power amplifying device characterized in that:

The PWM power amplifier connected to the signal input terminal is a class D power amplifier, and the linear voltage amplifier and the output device are linear power amplifiers. The output device is a complementary output device and is equivalent to an active filter.

According to the present invention, from the viewpoint of power efficiency, the present invention is the sum of the power loss of the class D power amplifier and the power loss of the linear power amplifier. Minimizing the power loss of a linear power amplifier if the positive and negative floating voltage sources driving the complementary output of the linear power amplifier can be set to the lowest acceptable voltage Therefore, the original high efficiency of the class D power amplifier is not lost. In addition, the passive filter is made up of a pair of coil, capacitor and resistor to minimize the configuration, and the limit of the passive filter characteristic is reduced by using the complementary output of the linear power amplifier as an equivalent active filter. Since an extremely large attenuation characteristic can be provided for overcoming and removing the PWM modulation carrier frequency component, an audio signal having almost no high frequency noise can be reproduced on the output terminal of the high efficiency power amplifier.

On the other hand, the signal input from the signal input terminal is
By performing voltage amplification with a linear voltage amplifier after performing phase correction with a phase correction circuit, or with a linear voltage amplifier, specifically, performing phase correction with an input circuit and a feedback circuit of an operational amplifier in a linear voltage amplifier, Phase correction can be performed for the signal delay caused by the passive low-pass filter.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail based on an embodiment shown in the drawings. (First Embodiment) FIG. 1 is a schematic block diagram showing a basic configuration of a high-efficiency power amplifier according to a first embodiment of the present invention.

In FIG. 1, a high efficiency power amplifying device 1
A class D power amplifier 2 for amplifying the power of an audio signal;
A passive filter 3 serving as a low-pass filter for removing unnecessary modulated carrier signals output from the class D power amplifier 2, a positive floating voltage source 4, a negative floating voltage source 5, and power amplification of an audio signal And a phase correction circuit 7 having a phase characteristic similar to that of the passive filter 3 and correcting the phase of an audio signal input to the linear power amplifier 6.

The passive filter 3 includes a capacitor 13 and a terminating resistor 14 in a series circuit of a resistor 11 and a coil 12.
Are connected and formed. Further, the linear power amplifier 6 is formed of a linear voltage amplifier 15 formed of a linear circuit and a complementary output device 16 formed of a complementary circuit forming a push-pull circuit. A current is supplied to a speaker (not shown) according to the amplified audio signal. Phase correction circuit 7
Are formed by an active filter forming a low-pass filter.

The signal input terminal 21 of the high efficiency power amplifier 1
Is the input terminal 2a of the class D power amplifier 2 and the phase correction circuit 7
Are connected respectively to the input terminals 7a. The class D power amplifier 2 further includes a positive power supply terminal 2b, a negative power supply terminal 2c, a control input terminal 2d to which an external control signal is input, and an output terminal 2e. Is connected to the input terminal 3a. The output terminal 3b of the passive filter 3 and the positive power supply terminal 16 of the complementary output device 16
a between the output terminal 3 b of the passive filter 3 and the complementary output device 16.
The negative floating voltage source 5 is connected to the negative power supply terminal 16b.

On the other hand, the output terminal 7b of the phase correction circuit 7 is connected to the input terminal 15a of the linear voltage amplifier 15. The linear voltage amplifier 15 further includes a positive power supply terminal 15b, a negative power supply terminal 15c, and two output terminals. The output terminals 15e and 15f have complementary ends 16e and 15f.
Are connected corresponding to the input terminals 16c and 16d.
A speaker is connected to the output terminal 16e of the complementary output device 16.

FIG. 2 is a diagram showing a circuit example of the class D power amplifier 2 shown in FIG. The class D power amplifier 2 according to the first embodiment of the present invention is a PWM power amplifier that performs power amplification by pulse width modulation (PWM), and its basic configuration will be described.

In FIG. 2, 41 is an operational amplifier, and 42 and 43 are resistors for determining the voltage gain of the class D power amplifier 2. An integrator 38 includes capacitors 45 and 46 and a resistor 47.
, And the integrator 38 and the operational amplifier 41 form an integrating circuit. The pnp transistors 48 and 51, the diodes 49 and 50, and the resistors 52, 53 and 54 form a comparator 39. The NAND gates 55 and 56 form a phase inverter 40 for generating a phase inversion pulse, and 2d is a control input terminal for controlling the stop of the PWM carrier switching of the class D power amplifier 2. Although not shown in FIG. 2, the control input terminal 2d is pulled up in the class D power amplifier 2 using a pull-up resistor or the like.

Npn transistors 58 and 65, pnp transistors 60 and 66, resistors 59, 61, 62, 64,
The zener diode 63, the capacitor 67, and the diode 68 form a positive driver 80 that turns on and off an N-channel power MOS transistor 69 that functions as a positive power switch.

Npn transistors 70, 77, pnp transistors 72, 78, resistors 71, 73, 74, 76,
And Zener diode 75 are N-channel power MOS transistor 7 functioning as a negative power switch.
A negative-side driver 81 for turning ON / OFF 9 is formed.

The audio signal input from the signal input terminal 21 is converted into a sawtooth wave by an integrator 38 and an integrating circuit of an operational amplifier 41, and the sawtooth wave is converted into a rectangular wave by a comparator 39. When the control input terminal 2d is pulled down, the NAND gates 55 and 56 of the phase inverter 40 are turned off.
Are both at the high level, and the output of the signal from the output terminal 2e stops.

FIG. 3 shows the linear power amplifier 6 shown in FIG.
FIG. 3 is a diagram showing an example of a basic configuration circuit of FIG. In FIG.
The linear voltage amplifier 15 includes resistors 91 and 92, a capacitor 93, and an operational amplifier 94. The operational amplifier 94 includes a first voltage amplification stage 95 and a second voltage amplification stage 96. The resistors 91 and 92 are connected to the linear power amplifier 6
And the capacitor 93 is a phase compensation capacitor.

The first voltage amplifying stage 95 includes pnp transistors 101 and 102 and npn transistors 103 and 104.
The pnp transistors 101 and 102 form a differential amplifier circuit, and the npn transistors 103 and 104 form a current mirror circuit. The base of the pnp transistor 101 forms the inverted input of the operational amplifier 94, and the base of the pnp transistor 102 forms the non-inverted input of the operational amplifier 94 and is grounded.

The second voltage amplifying stage 96 includes an npn transistor 110, a constant current source 111, a capacitor 112, and diodes 113 and 114. Capacitor 1
Reference numeral 12 denotes a phase compensation capacitor which forms a dominant pole of the linear voltage amplifier 15, and the diodes 113 and 114 form a constant voltage bias diode group 115 which determines a bias current of the complementary output device 16.

The complementary output unit 16 includes a push-pull circuit 131 formed of a complementary circuit,
A resistor 132 and a capacitor 133 for ensuring the load stability of the complementary output device 16, a coil 134 and a dump resistor 13 for ensuring the stability of the speaker load
5. The push-pull circuit 131
p power transistor 141, the power transistor 1
Npn transistor 142, npn driving
Power transistor 143, power transistor 14
3 is composed of a pnp transistor 144 for driving the driving circuit 3 and resistors 145 to 148.

The power transistors 141 and 143 are
The transistors 142 and 144 have complementary characteristics with each other, and similarly, the transistors 142 and 144 have complementary characteristics with each other. The resistance 145 is the collector resistance of the npn transistor 142, and the resistance 146 is the pnp transistor 14
4 collector resistance. The resistor 147 serves as a collector resistor of the power transistor 141 and has npn
The resistor 148 forms the emitter resistance of the transistor 142,
Is the collector resistance of the power transistor 143 and the emitter resistance of the pnp transistor 144.

On the other hand, the transformer 150, the diode bridge circuit 151, and the smoothing capacitors 152 and 153 form a floating voltage source. Capacitor 15
2 and its associated transformer 150 and bridge circuit 151 correspond to the positive floating voltage source 4 of FIG.
The reference numeral 50 and the bridge circuit 151 correspond to the negative floating voltage source 5 in FIG.

From the connection point J1 of the bridge circuit 151,
A positive current flowing from the emitter to the collector of the power transistor 141 and flowing to the output terminal 131 a of the push-pull circuit 131 is supplied. At the same time, from the connection point J2 of the bridge circuit 151, a negative current flowing from the output terminal 131a of the push-pull circuit 131 to the collector of the power transistor 143, and further from the collector of the power transistor 143 to the connection point J2 via the emitter. Supplied. The currents flowing through the power transistors 141 and 143 are in a push-pull relationship.

FIG. 4 is a diagram showing a circuit example of the phase correction circuit 7 shown in FIG. In FIG. 4, the phase correction circuit 7
Is composed of an operational amplifier 121, capacitors 122 and 123, and resistors 124 and 125.
1 is an active low-pass filter. Since the passive filter 3 in FIG. 1 forms a two-pole filter, the active filter forming the phase correction circuit 7 also forms a two-pole filter. Thus, the active filter forming the phase correction circuit 7 is formed of a filter having the same number of poles as the number of poles of the passive filter 3.

An example of the operation of the high-efficiency power amplifier 1 configured as described above will be described. Signal input terminal 21
Are input to the class D power amplifier 2 and the phase correction circuit 7 at the same time. Class D power amplifier 2
Is a half-bridge type high-speed switching power M
By using OS transistors 69 and 79,
It operates as a high-speed and high-efficiency PWM (pulse width modulation) switching amplifier.

A waveform S21 in FIG. 5A shows an audio signal (a sine wave is exemplified) input to the signal input terminal 21, and a waveform S2e is power-amplified by the class D power amplifier 2 and PWM-modulated. The output waveform is shown. The waveform S3b in FIG.
3 shows an output waveform from an output terminal 3b of the passive filter 3. In the passive filter 3, a signal obtained by demodulating the PWM modulation signal and returning to the original audio signal is output.
As shown in FIG. 5 (b), a sine wave as an original audio signal is output with fine high frequency noise added.

On the other hand, the audio signal input to the phase correction circuit 7 is first subjected to phase correction by the phase correction circuit 7 shown in FIG. 4 and then to the linear voltage amplifier 15 shown in FIG.
Then, the voltage is amplified. The voltage-amplified signal is further applied with a bias voltage of + dV and -dV (for example, +5 V and -5 V) by a constant voltage bias diode group 115 including diodes 113 and 114, and is output from an output terminal 15e. The upper voltage amplified signal S15e,
Lower voltage amplified signal S15f output from output terminal 15f
Are generated, and the respective output waveforms are shown in FIG. The upper voltage amplified signal S15e and the lower voltage amplified signal S15f are vertically
The signals are shifted by the potential difference of dV, and all have the same waveform as the input signal S21. The signal S15e is input to the input terminal 16c of the complementary output device 16, and the signal S15f is input to the input terminal 16d of the complementary output device 16.

The complementary output unit 16 further receives the signal S3b from the output terminal 3b of the passive filter 3, which is shifted in the positive and negative directions, and is input to the power supply terminals 16a and 16b, respectively. That is, the signal S3b
Are + DV and -DV by the capacitors 152 and 153.
(For example, + 10V and -10V), and then applied to the power supply terminals 16a and 16b, respectively. Waveform S16 of FIG.
a and S16b are voltage waveforms at the power supply terminals 16a and 16b,
It has the same waveform. As is apparent from FIG. 6, preferably, the waveforms S16a and S16b sandwich the waveforms S15e and S15f as close as possible from both upper and lower sides, and the waveforms S16a and S16b do not overlap with the waveforms S15e and S15f. To

Of the audio signals voltage-amplified by the linear voltage amplifier 15, the audio signal indicated by the waveform S15e is current-amplified by the power transistor 141. This current is supplied from the connection point J1 of the diode bridge circuit 151, flows from the emitter to the collector of the power transistor 141, and is output from the output terminal 131 of the push-pull circuit 131.
a is a positive current flowing through a. Similarly, of the audio signal voltage-amplified by the linear voltage amplifier 15, the waveform S15f
Are amplified by the power transistor 143. This current is supplied from the connection point J2 of the diode bridge circuit 151, and the push-pull circuit 1
31 is a negative current flowing from the output terminal 131a of the power transistor 143 to the collector of the power transistor 143 and from the collector to the emitter of the power transistor 143.

That is, the power transistor 141
The current amplification of the upper voltage amplified signal S15e is performed by the positive current from the connection point J1 to generate a positive current amplified signal.
The power transistor 143 is connected to the lower voltage amplified signal S15.
f is amplified by a negative current from the connection point J2 to generate a negative current amplified signal. Then, the positive current amplified signal and the negative current amplified signal are added in a push-pull form, and the power amplified signal is output from the output terminal 131a.

Since the power transistors 141 and 143 are configured as a push-pull, the current flowing through the power transistor 141 and the current flowing through the power transistor 143 are added and averaged, and the resulting current is added to the push-pull circuit. 131 is output from the output terminal 131a. Therefore, the signal waveform of the voltage from the output terminal 131a becomes the waveform S131a in FIG. 6, which is an intermediate point between the waveforms S15e and S15f.

Thus, the power of the audio signal S21 can be faithfully amplified. In addition, since the current source for power amplification is limited between the waveforms S16a and S16b, the current of the supply source is set to a low supply power when the current is small, and to a high supply power when a large current is required. Can be controlled. Therefore, the efficiency of current supply can be increased.

Here, the signal output from the passive filter 3 shown in FIG. 5B has a waveform obtained by delaying the original audio signal input from the signal input terminal 21 by the delay time τ by the passive filter 3. It has become. Therefore, when the audio signal input from the signal input terminal 21 is directly input to the input terminal 15a of the linear voltage amplifier 15, the waveforms S16a and S16b become the waveform S16 as shown in FIG.
Both waveforms are delayed with respect to 131a by the delay time τ.

Accordingly, the phase correction circuit 7 converts the audio signal input from the signal input terminal 21 into the delay time τ
The signal is output to the input terminal 15a of the linear voltage amplifier 15 after being delayed by only Thus, the output terminal 2e of the class D power amplifier 2
An active filter similar to the phase characteristic of the passive filter 3 connected to the
By connecting to a, it is possible to accurately track up to a high band frequency in the audio signal, for example, a frequency of 10 KHz or more, and it is possible to prevent distortion and interference noise caused by a phase shift.

Hereinafter, more specific examples will be described.
It is possible to set the PWM switching carrier frequency of no signal around 500 KHz, which is much higher than the upper limit of the audio frequency of 20 KHz. Moreover, the power efficiency can be developed with a target of, for example, 90%. The voltage gain of this self-excited class D power amplifier 2 is
It is determined by the ratio of the resistance 42 and the resistance 43. If the resistance value of the resistor 42 is R42 and the resistance value of the resistor 43 is R43,
The voltage gain of the class D power amplifier 2 = R43 / R42.

On the other hand, the audio signal input to the linear power amplifier 6 is voltage-amplified by the linear voltage amplifier 15. The linear voltage amplifier 15 is supplied with a voltage from a fixed power supply to the positive power supply terminal 15b and the negative power supply terminal 15c of the linear voltage amplifier. It can be expected to function as a voltage amplifying unit for a simple audio signal.

Next, a pure audio output signal without high-frequency noise is input to the complementary output device 16 through the first output terminal 15e of the linear voltage amplifier 15 and the second output terminal 15f of the linear voltage amplifier 15, and The output signal is power-converted through the complementary output device 16 and the output terminal 1 serving as the output terminal of the high-efficiency power amplifier 1 is output.
6e.

The voltage gain of the linear power amplifier 6 is determined by the ratio between the resistors 91 and 92. Here, assuming that the resistance value of the resistor 91 is R91 and the resistance value of the resistor 92 is R92, the voltage gain of the linear power amplifier 6 = R92 / R91.

The PWM signal at the output terminal 2 e of the class D power amplifier 2 is demodulated by the secondary passive low-pass filter 3. Even if the PWM switching carrier frequency component can be attenuated by about 40 dB, for example, the PWM switching pulse Assuming that the amplitude is ± 50 V, a PW of about 1 V
The M switching carrier frequency component is generated at the output terminal 3b of the secondary passive filter 3. Therefore, an audio output signal having the same PWM switching carrier frequency component is input to the positive power supply terminal 16a and the negative power supply terminal 16b of the complementary output device 16 through the positive floating voltage source 4 and the negative floating voltage source 5. Can be considered.

Here, the voltage gain of the class D power amplifier 2 = R
43 / R42 and the voltage gain of the linear power amplifier 6 = R92 / R91
Are set to have substantially the same voltage gain, the audio output signal operates while maintaining a voltage value substantially intermediate between the positive floating voltage source 4 and the negative floating voltage source 5. In order to minimize the power loss, the voltage value of the positive floating voltage source 4 and the voltage value of the negative floating voltage source 5 may be minimized. For example, if the operation can be performed at ± 5 V, a linear power amplifier of ± 50 V may be used. By comparison, the power loss will be reduced to about 1/10.

Referring to FIGS. 8 and 9, the principle of suppressing the high frequency noise of the complementary output unit 16 will be described. FIG. 8 is an equivalent circuit diagram for explaining the principle of suppressing the high-frequency noise of the complementary output device 16. In FIG. 8, 1
Reference numeral 60A denotes a high-frequency noise source that transmits from the positive floating voltage source 4 to the output terminal 16e of the high-efficiency power amplifier 1 through the positive power supply terminal 16a of the complementary output device 16. 160B is a high-frequency noise source that transmits from the negative floating voltage source 5 to the output terminal 16e of the high-efficiency power amplifier 1 through the negative power supply terminal 16b of the complementary output device 16. 161 is the positive equivalent output resistance of the complementary output unit 16, 162 is the positive equivalent output capacitance of the complementary output unit 16, and 163 is the complementary output unit 1
Reference numeral 6 denotes a negative equivalent output resistance, 164 denotes a negative equivalent output capacitance of the complementary output unit 16, and 165 denotes a speaker end load resistance.

Next, the operation of the equivalent circuit of FIG. 8 will be described. 2
With the next output terminal 3b of the passive filter 3 as a virtual ground, the high-frequency noise source 160A and the high-frequency noise source 160B can be regarded as mutually opposite-phase components. Therefore, if the positive equivalent output resistance 161 and the positive equivalent output capacitance 162 of the complementary output device 16 and the negative equivalent output resistance 163 and the negative equivalent output capacitance 164 of the complementary output device 16 have very well matched values, respectively. In addition, a large amount of attenuation can be provided from a low frequency region to a high frequency region. Therefore, as a circuit configuration of the complementary output device 16 that effectively suppresses high-frequency noise, a feedback type device having a large equivalent output resistance as in the present embodiment is excellent. In addition, since the collector electrode corresponds to the back surface of silicon due to the physical structure of the silicon power transistor, the stray capacitance between the ground and the ground is larger than that of the emitter electrode. From this point as well, it can be said that when the emitter electrode is in the high-frequency noise source, the stray capacitance between the ground and the ground is small, so that it is superior.

When calculated using actual numerical values, for example, the positive equivalent output resistance 161 is 10 KΩ, the negative equivalent output resistance 163 is 9 KΩ, and the speaker load resistance 165 is 10 Ω.
, The suppression ratio of high-frequency noise is 80 dB, and assuming that the noise source has an amplitude of 1 V,
/ 10000 to 100 μV.

FIG. 9 shows the frequency characteristic of the amount of attenuation of the complementary output device 16. As can be seen from FIG. 9, the positive equivalent output capacitance 162 and the negative equivalent output capacitance 164
Is completely matched, a certain amount of attenuation can be expected up to an infinite frequency.

Here, the push-pull circuit 131 of FIG. 3 may be configured as a three-stage feedback type emitter follower so as to perform a complementary operation.
In this case, the push-pull circuit 131
FIG. 6 is a circuit diagram showing another example of the embodiment. In FIG. 10, FIG.
The difference is that the power transistor 141 is driven by a pnp transistor 171 and the pnp transistor 1
71 is driven by an npn transistor 172, and the power transistor 143 is driven by an npn transistor 173.
3 is driven by a pnp transistor 174.

The transistors 171 and 173 have complementary characteristics with each other.
72 and 174 have complementary characteristics to each other. The resistor 175 forms the emitter resistance of the pnp transistor 171, and the resistor 176 forms the collector resistance of the npn transistor 172. The resistor 177 represents the emitter resistance of the npn transistor 173, and the resistor 178 represents the pn transistor.
It forms the collector resistance of the p-transistor 174. In this way, by performing a complementary operation as a feedback-type emitter follower having a three-stage configuration, a complementary output device 16 having a larger equivalent output resistance can be realized.

In the push-pull circuit 131 shown in FIGS. 3 and 10, a case where a complementary operation is performed as a feedback type emitter follower has been described as an example. However, a complementary operation may be performed as an emitter follower. In this case, 2
A circuit example of a push-pull circuit 131 having a staged emitter follower is shown as a push-pull circuit 131a in FIG.
FIG. 12 shows an example of a push-pull circuit 131 having a three-stage emitter follower as a push-pull circuit 131b.

In FIG. 11, a push-pull circuit 131
a includes an npn power transistor 141a, an npn transistor 142a that drives the power transistor 141a, an npn power transistor 143a, an npn transistor 144a that drives the power transistor 143a, and resistors 145a to 148a.

Power transistors 141a and 143a
Have complementary characteristics to each other, and similarly, the transistors 142a and 144a have complementary characteristics to each other. The resistor 145a forms the emitter resistance of the npn transistor 142a, the resistor 146a forms the collector resistance of the npn transistor 144a and the base resistance of the power transistor 143a, and the resistance 147a
Represents the emitter resistance of the power transistor 141a, and the resistor 148a represents the collector resistance of the npn transistor 143a.

In FIG. 12, a push-pull circuit 131
b denotes a pnp power transistor 141b, an npn transistor 171b driving the power transistor 141b, an npn transistor 172b driving the npn transistor 171b, a pnp power transistor 143b, a pnp transistor 173b driving the power transistor 143b, and the pnp transistor 173b. Drive transistor 174
b, and resistors 147b, 148b, 181, and 182.

Power transistors 141b and 143
b, transistors 171b and 173b, and transistors 172b and 174b have complementary characteristics with each other. The resistor 147b is an emitter resistor of the power transistor 141b, and the resistor 148b is a pnp
It forms the emitter resistance of the transistor 143b. The resistor 181 serves as an emitter resistor of each of the transistors 171b and 173b, and the resistor 182 serves as an emitter resistor of each of the transistors 172b and 174b.

As described above, in the push-pull circuit shown in FIGS. 11 and 12, the equivalent output resistance is not larger than that of the feedback type emitter follower. An output device can be realized. As shown in FIGS. 11 and 12, by changing the bias value by changing the number of diodes of the constant voltage bias diode group 115 of the linear voltage amplifier 6 that determines the idling current of the push-pull circuit, a so-called class A is achieved. , AB, and B biases can be set.

FIG. 13 is a diagram showing an example of mounting the passive filter 3 of FIG. In FIG.
Denotes a metal substrate, and 191 denotes a copper foil pattern formed on the metal substrate 190 by insulation. That is, 192 forms an input end of the secondary passive filter, and 193 forms a coil with a spiral copper foil pattern having a predetermined width. 1
94 is an aluminum wire bonded by wire bonding, 195
Is a bonding pad, 196 is a chip capacitor, 1
Reference numeral 97 denotes a chip resistor, 198 denotes an output terminal of the secondary passive filter, and 199 denotes a ground terminal of the secondary passive filter. FIG. 14 shows a circuit diagram of the passive filter of FIG. 13, and the same reference numerals are used for corresponding portions in the circuit configuration.

FIGS. 13 and 14 show a basic configuration for mounting the secondary passive filter 3 on a metal substrate.
If the sheet resistance value of the copper foil is used, it is possible to form a coil having a predetermined equivalent series resistance value by controlling the width of the copper foil, which indicates that a high power chip and low resistance are not required. . Therefore, the secondary passive filter 3 including the chip capacitor can realize an extremely inexpensive and highly reliable filter.

In the present embodiment, the case where the passive filter 3 is formed by a two-pole filter has been described as an example. However, the present invention is not limited to this. Is a natural number) pole filter, and the phase correction circuit 7 is formed by a filter having the same number of poles as the passive filter 3. FIG.
Although the case where the phase correction circuit 7 is formed by an active filter has been described as an example, the phase correction circuit 7 may be formed by a passive low-pass filter as shown in FIG.
Also in FIG. 15, the passive filter forming the phase correction circuit 7 is formed of a filter having the same number of poles as the number of poles of the passive filter 3, and the passive filter 3 of FIG.
Is formed by a two-pole filter,
A pole filter is formed.

(Second Embodiment) In the first embodiment, the phase correction circuit 7 is provided. However, the phase correction may be performed by a linear voltage amplifier. A second embodiment is assumed. FIG. 16 is a schematic block diagram showing a basic configuration of a high-efficiency power amplifier according to the second embodiment of the present invention. In FIG. 16,
The same components as those in FIG. 1 are denoted by the same reference numerals, and a description thereof will be omitted, and only different points from FIG. 1 will be described.

FIG. 16 differs from FIG. 1 in that the phase correction circuit 7 in FIG. 1 is eliminated and the linear voltage amplifier 15 in FIG.
1 is changed to a linear voltage amplifier 212, and the linear power amplifier 6 of FIG. 1 is changed to a linear power amplifier 211. The high efficiency power amplifier 1 of FIG.

In FIG. 16, the high efficiency power amplifier 21
Numeral 0 includes a class D power amplifier 2, a passive filter 3, a positive floating voltage source 4, a negative floating voltage source 5, and a linear power amplifier 211 for amplifying power of an audio signal. Linear power amplifier 21
1 is a linear voltage amplifier 212 formed by a linear circuit.
The linear voltage amplifier 212 performs the same operation as the linear voltage amplifier 15 in FIG. 1 except that the linear voltage amplifier 212 corrects the phase of the audio signal input from the signal input terminal 21.

FIG. 17 is a diagram showing a circuit example of the linear voltage amplifier 212 shown in FIG. In FIG. 17, the same components as those shown in FIG. 3 are denoted by the same reference numerals, and the description thereof will be omitted, and only the differences from the linear voltage amplifier 15 of FIG. 3 will be described. 17 differs from FIG. 3 in that a capacitor 215 is added. In FIG. 17, a capacitor 215 is connected to a resistor 9
1 is connected between the inverting input terminal side of the operational amplifier 94 and the ground.

The resistor 91 and the capacitor 215 form an input circuit 217 of the operational amplifier 94, and the resistor 92 and the capacitor 93 form a feedback circuit 218 of the operational amplifier 94. The input circuit 217 corresponds to one pole of the filter and the feedback circuit 218 corresponds to one pole of the filter. By adjusting the values of the resistors and the capacitors of the input circuit 217 and the feedback circuit 218, the signal input terminal 2 is adjusted.
The phase correction of the audio signal input from 1 can be performed.

As described above, the phase correction of the audio signal input from the signal input terminal 21 can be performed by the linear voltage amplifier, and the cost can be reduced since there is no need to separately provide a phase correction circuit. In the present embodiment, the case where the passive filter 3 is formed of a two-pole filter has been described as an example. However, the present invention is not limited to this, and the passive filter 3 is formed of n (n is a natural number). ) The linear voltage amplifier 21 is formed by a pole filter and has the same number of poles as the passive filter 3.
2 form an input circuit 217 and a feedback circuit 218.

(Third Embodiment) In the first and second embodiments, when forming the positive floating voltage source 4 and the negative floating voltage source 5, the transformer 150, the diode bridge circuit 151 and the smoothing Capacitor 152,
Since components such as 153 were required, further integration was difficult, and the cost could not be further reduced. Therefore, in the third embodiment, a description is given of a high-efficiency power amplifying device that can obtain the same effects as those of the first and second embodiments without using components that are difficult to integrate. In the present embodiment, the circuit configuration of the first embodiment will be described as an example. However, the same applies to the case of the second embodiment, and a description thereof will be omitted.

FIG. 18 is a schematic block diagram showing a basic configuration of a high-efficiency power amplifier according to the third embodiment of the present invention. In FIG. 18, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted, and only the differences from FIG. 1 will be described. FIG. 1 in FIG.
The difference between the first and second class D power amplifiers 2A and 2B is that the positive floating voltage source 4 and the negative floating voltage source 5 shown in FIG.
In addition, two passive filters 3A and 3B are provided, and a first bias power supply 221 and a second bias power supply 222 are provided on the signal input terminal 21 side. For these reasons, the high-efficiency power amplifier 1 of FIG.

In FIG. 18, the output terminal 3Ab of one passive filter 3A is connected to the positive power supply terminal 16a of the complementary output device 16, and the input terminal 2Aa of the class D power amplifier 2A connected to the passive filter 3A is connected to the output terminal 3Ab. A first bias power supply 221 is connected between the input terminal 7a of the phase correction circuit 7 and the input terminal 7a. The output terminal 3Bb of the other passive filter 3B is connected to the negative power supply terminal 16b of the complementary output device 16, and the passive filter 3B
The second bias power supply 222 is connected between the input terminal 2Ba of the class D power amplifier 2B and the input terminal 7a of the phase correction circuit 7.

The high efficiency power amplifier 220 shown in FIG.
, The linear power amplifier 6 and the phase correction circuit 7
It is the same as that shown in FIG. 1 and FIG. Further, both the class D power amplifiers 2A and 2B have substantially the same circuit configuration as the class D power amplifier 2 shown in FIGS. 1 and 2, and the passive filters 3A and 3B are both shown in FIG. It has substantially the same circuit configuration as the passive filter 3 shown. However, as compared with the high-efficiency power amplifier 1 shown in FIG. 1, a larger amount of current flows through each class D power amplifier and each passive filter. As described above, in the present embodiment, the transformer 150, the diode bridge circuit 151, and the smoothing capacitors 152 and 153 shown in FIG. 3 are not required, and the circuit configuration can be further reduced and the cost can be reduced.

[0083]

As described above, according to the present invention, by inserting an equivalent active filter in the demodulation part of a class D power amplifier, a high-efficiency power device with extremely low high-frequency noise without sacrificing high efficiency. It is expected to have a wide range of applications not only in audio applications but also in the entire power control field where high efficiency is required.

The signal input from the signal input terminal is
By performing voltage amplification with a linear voltage amplifier after performing phase correction with a phase correction circuit, or with a linear voltage amplifier, specifically, performing phase correction with an input circuit and a feedback circuit of an operational amplifier in a linear voltage amplifier, Phase correction can be performed for the signal delay caused by the passive low-pass filter. In particular, when used for audio applications, a high frequency band in an audio signal, for example, 10 KHz
It is possible to accurately track up to the above frequencies, and to prevent distortion and interference noise caused by a phase shift.

From the above description of the present invention, it will be apparent that the invention is capable of various modifications. These modifications should not be deemed to depart from the scope of the invention, and all such modifications that would be apparent to a person skilled in the art are included in the claims of the invention. It is said.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing a basic configuration of a high-efficiency power amplifier according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a circuit example of the class D power amplifier 2 shown in FIG.

FIG. 3 is a diagram showing an example of a basic configuration circuit of the linear power amplifier 6 shown in FIG.

FIG. 4 is a diagram showing a circuit example of the phase correction circuit 7 shown in FIG.

FIG. 5 is a diagram showing signal waveforms at main points in FIG. 1;

FIG. 6 is a diagram showing signal waveforms at main points in FIG. 1;

FIG. 7 is a diagram showing an example of a signal waveform for explaining the operation of the phase correction circuit 7 of FIG. 1;

FIG. 8 is an equivalent circuit diagram for explaining the principle of suppressing the high-frequency noise of the complementary output device 16;

FIG. 9 is a diagram illustrating a frequency characteristic of an attenuation amount of the complementary output device 16;

FIG. 10 is a circuit diagram showing another example of the push-pull circuit 131.

FIG. 11 is a circuit diagram showing another example of the push-pull circuit 131.

FIG. 12 is a circuit diagram showing another example of the push-pull circuit 131.

FIG. 13 is a diagram showing a mounting example of the passive filter 3 of FIG. 1;

FIG. 14 is a circuit diagram of the passive filter shown in FIG.

FIG. 15 is a circuit diagram showing another example of the phase correction circuit 7.

FIG. 16 is a schematic block diagram showing a basic configuration of a high-efficiency power amplifier according to a second embodiment of the present invention.

17 is a diagram illustrating a circuit example of the linear voltage amplifier 212 illustrated in FIG.

FIG. 18 is a schematic block diagram showing a basic configuration of a high efficiency power amplifier according to a third embodiment of the present invention.

FIG. 19 is a diagram showing a basic configuration of a conventional high-efficiency power amplifier.

FIG. 20 is a diagram showing characteristics of a conventional passive filter.

[Explanation of symbols]

 1,210,220 High-efficiency power amplifier 2,2A, 2B Class D power amplifier 3,3A, 3B Passive low-pass filter 4 Positive floating voltage source 5 Negative floating voltage source 6,211 Linear power amplifier 15,212 Linear voltage Amplifier 16 Complementary output device 21 Signal input terminal 131, 131a, 131b Push-pull circuit 190 Metal substrate 191 Copper foil pattern 217 Input circuit 218 Feedback circuit 221 First bias power supply 222 Second bias power supply

Claims (13)

[Claims] 1. A high-efficiency power amplifier for amplifying power of an input signal input to a signal input terminal, comprising: a PWM power amplifier for power-amplifying an input signal from a signal input terminal by pulse width modulation and outputting the amplified signal; A passive low-pass filter that demodulates and outputs a pulse width modulation signal output from the PWM power amplifier; and a positive floating circuit that shifts the demodulated signal output from the passive low-pass filter by a predetermined voltage + DV and supplies a positive current. A voltage source, a negative floating voltage source that shifts the demodulated signal output from the passive low-pass filter by a predetermined voltage −DV and supplies a negative current, and an input signal input from the signal input terminal. A phase correction circuit for performing phase correction on a signal output from the passive low-pass filter, A linear voltage amplifier composed of a linear circuit, which amplifies the signal whose phase has been corrected by the circuit and shifts the signal by a predetermined voltage + dV and -dV, respectively, and outputs the amplified voltage. A current amplification is performed by the direction current to generate a positive direction current amplification signal, and the voltage amplification signal shifted by −dV is current amplified by the negative direction current to generate a negative direction current amplification signal. A high-efficiency power amplifier, comprising: an output unit that generates and outputs a power amplified signal by adding the amplified signal and the negative current amplified signal in a push-pull form. 2. A high-efficiency power amplifier for amplifying an input signal input to a signal input terminal, comprising: a first bias power supply for applying a positive bias voltage to an input signal from the signal input terminal; A first PWM power amplifier for outputting a first pulse width modulation signal generated by power-amplifying the positively biased input signal by pulse width modulation; and demodulating the first pulse width modulation signal. A first passive low-pass filter for outputting the generated first demodulated signal, a second bias power supply for applying a negative bias voltage to an input signal from a signal input terminal, and the negatively biased input A second PWM power amplifier that outputs a second pulse width modulation signal generated by power-amplifying the signal by pulse width modulation, and a second demodulation generated by demodulating the second pulse width modulation signal A second passive low-pass filter that outputs a signal, a phase correction circuit that performs a phase correction on a signal output from the passive low-pass filter with respect to an input signal input from the signal input terminal, A linear voltage amplifier configured by a linear circuit, which amplifies the phase-corrected signal and outputs the signal by shifting the signal by a predetermined voltage + dV and -dV, respectively; The current is amplified by the demodulation signal to generate a positive current amplification signal, and the voltage amplification signal shifted by -dV is current amplified by the second demodulation signal to generate a negative current amplification signal. An output unit for generating and outputting a power amplification signal by adding the direction current amplification signal and the negative direction current amplification signal in a push-pull form. And a high efficiency power amplifier. 3. The high-efficiency power amplifying device according to claim 1, wherein said output device is constituted by a push-pull circuit formed by a complementary circuit. 4. The linear voltage amplifier and the output device include a B
The high-efficiency power amplifier according to any one of claims 1 to 3, wherein the high-efficiency power amplifier comprises a class power amplifier. 5. The linear voltage amplifier and the output device include: A
The high-efficiency power amplifier according to any one of claims 1 to 3, wherein the device comprises a class B power amplifier. 6. The linear voltage amplifier and the output device include: A
The high-efficiency power amplifier according to any one of claims 1 to 3, wherein the high-efficiency power amplifier comprises a class power amplifier. 7. The high-efficiency power amplifying device according to claim 1, wherein said passive low-pass filter comprises a spiral electrode formed on a substrate. 8. The coil according to claim 7, wherein the spiral electrode is formed of a copper foil pattern to form a coil.
2. The high-efficiency power amplifier according to 1. 9. The high-efficiency power amplifier according to claim 1, wherein the phase correction circuit is formed of a passive filter having the same number of poles as the passive low-pass filter. 10. The high-efficiency power amplifier according to claim 1, wherein the phase correction circuit is formed by an active filter having the same number of poles as the passive low-pass filter. 11. The high efficiency power amplifier according to claim 1, wherein the phase correction circuit is formed in a linear voltage amplifier. 12. An operational amplifier for amplifying a voltage of a signal input to a signal input terminal, an input circuit for adjusting an input impedance of the operational amplifier, a feedback circuit in the operational amplifier, The input circuit and the feedback circuit each have a capacitor, and are formed with predetermined circuit constants so that predetermined phase correction is performed on an input signal from a signal input terminal. 12. The high-efficiency power amplifier according to 11. 13. The high-efficiency power amplifier according to claim 12, wherein the input circuit and the feedback circuit are formed to have the same number of poles as the number of poles of the passive low-pass filter.