JPH0823242A - Output circuit - Google Patents

Abstract

PURPOSE:To reduce a higher harmonic wave component contained in an output waveform to be ouputted to a load by rectifying a signal from the secondary side terminal of a transformer while alternately repeating the forward and backward phase signals by turning on/off a switching element, and adding it later. CONSTITUTION:Corresponding to the driving signal of a driver part 2, a voltage resonance switch part 8 alternately performs ON and OFF switching operations and converts ON and OFF voltages to resonant waveforms. The outputs of switching elements Q1 and Q2 in a switch part 8 are respectively connected to the primary side terminal of a transformer 6 and according to the push/pull operations of the elements Q1 and Q2, the transformer 6 transmits those signals to a secondary coil. Then, the output signals of the transformer 6 are connected from the secondary side terminal to a rectifying/synthesizing part 7 so that they can be mutually added with opposite phases. Therefore, since the signals from the transformer 6 are rectified/added by the rectifying/adding part 7 after the forward and backward phase signals are mutually repeated according to the ON/OFF of the elements Q1 and Q2 at the switch part 8, the higher harmonic wave component contained in the output waveform to a load 5 can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse modulation amplifier for pulse-modulating an analog input signal into a rectangular wave, and more particularly to an output circuit for reducing switching noise.

[0002]

2. Description of the Related Art Generally, as a method for efficiently power-amplifying an input signal such as an audio signal, an analog input signal such as an audio signal is pulse-width modulated, and a driving pulse from a pulse conversion unit causes a switching operation to output the load. A so-called pulse width modulation amplifier that supplies the power and amplifies the power has been considered. Furthermore, an output circuit as shown in FIG. 9 is conceivable as a method of supplying a signal of high output to a load.

An output circuit in a conventional pulse width modulation amplifier will be described below. FIG. 9 shows a block diagram of this conventional output circuit. In FIG. 9, as components, 1 is a pulse converter for pulse-width modulating an analog input signal such as an audio signal, 2 is a driver unit for alternately operating switching elements according to the drive pulse from the pulse converter 1, and 3 is a driver unit. Switching element Q according to the pulse width modulation signal sequentially output from 2
1, a switch unit for turning on / off Q2, 14 is a transformer for electrically insulating output signals of the switching elements Q1 and Q2 of the switch unit 3 and transmitting energy, and 4 is included in the output signal of the transformer 14. A low-pass filter 5 for removing high-frequency components is a load resistor.

The operation of the output circuit composed of the above components will be described below. First, the pulse conversion unit 1 performs pulse width modulation on analog input signals that are sequentially input, and sequentially outputs the resulting pulse width modulation signals to the driver unit 2. Next, the driver unit 2 converts the input pulse width modulation signals into gate input signals having mutually opposite phases, and sequentially outputs the respective gate input signals to the gates of the switching elements Q1 and Q2 of the switch unit 3. The switching elements Q1 and Q2 alternately perform on and off operations according to the gate input signals that are sequentially input. As a result, the switching elements Q1 and Q2 repeat the push-pull operation and supply a voltage to the primary side terminal of the transformer 14 to drive the transformer 14. In this way transformer 14
The signal that is amplified by and is sequentially extracted from the secondary side terminal is output through the low-pass filter 4 and the output waveform is changed to the load resistance 5.
Supply to.

[0005]

However, in the above output circuit, since the signal switched by the switch section 3 has a rectangular waveform, it contains a lot of harmonic components, and unwanted radiation from the pattern or wiring on the substrate. There is a drawback in that noise is radiated, which interferes with reception of a tuner or the like. Further, in the above output circuit, the switch unit 3
When the switching elements Q1 and Q2 are operated for switching, residual energy remains in the transformer 14,
The circuit described above does not have a means for processing residual energy, and there is a problem in that the pulse-modulated signal has a DC level shift, which causes distortion in the output waveform. further,
The lowest frequency of audio signals that are sequentially input is 50 to 6
In the case of 0 Hz, the frequency component is used as it is in the transformer 14
However, the transformer 14 is heavy and large in size because it is passed through.

The present invention solves the above-mentioned problems of the prior art by eliminating the generation of harmonic components contained in a pulse-modulated signal that is switched, processing residual energy in the transformer, and providing a DC level to the pulse-modulated signal. An object of the present invention is to provide an output circuit capable of suppressing an occurrence of shift and obtaining an output waveform without distortion.

[0007]

In order to achieve this object, the output circuit of the first invention is a pulse converter for pulse-modulating an analog input signal such as an audio signal, and a pulse output from the pulse converter. A driver section that outputs a drive signal based on a signal; a voltage resonance switch section that alternately performs on or off switching operations according to the drive signal and converts on and off voltages into resonance waveforms; and the voltage resonance switch. The output signal of the transformer is used as an input, an external power source is connected to the center tap of the primary winding, and the secondary winding has a transformer composed of windings for extracting outputs of opposite phases, and the output signal of the transformer. It is composed of a synthetic rectifying unit that rectifies and synthesizes.

The output circuit of the second invention is a pulse converter for pulse-modulating an analog input signal such as an audio signal, and a driver unit for outputting a drive signal based on the pulse signal output from the pulse converter. And a switch section that alternately performs on or off switching operation according to the drive signal and an output signal of the switch section as an input, and an external power source is connected to the intermediate tap of the primary winding, and the secondary winding is A transformer composed of windings for extracting outputs of opposite phases, a current resonance unit for converting an output signal of the transformer into a resonance waveform, and a synthetic rectification unit for synthesizing after rectifying the output signals of the current resonance unit. It is composed by.

The output circuit of the third invention is a pulse converter for pulse-modulating an analog input signal such as an audio signal, and a driver unit for outputting a drive signal based on the pulse signal output from the pulse converter. And a voltage resonance switch section for alternately performing on or off switching operations according to the drive signal and converting on and off voltages into a resonance waveform, and an output signal of the voltage resonance switch section as an input for a primary winding. An external power supply is connected to the intermediate tap, and a secondary winding has a first winding for taking out outputs of opposite phases, and a second winding for taking out outputs of opposite phases to the two windings. A transformer configured by two windings and an output signal of the first winding are rectified and then combined to output a positive phase signal, and an output signal of the second winding is output. It is constituted by a rectifying synthesizing unit for outputting a negative-phase signal by synthesizing after rectification.

The output circuit according to the fourth aspect of the invention comprises a pulse converter for pulse-modulating an analog input signal such as an audio signal, and a driver unit for outputting a drive signal based on the pulse signal output from the pulse converter. And a switch section that alternately performs on or off switching operation according to the drive signal and an output signal of the switch section as an input, and an external power source is connected to the intermediate tap of the primary winding, and the secondary winding is A transformer including a first winding for extracting outputs of opposite phases to each other, and a second winding for extracting outputs of opposite phases to the two windings, and the first winding. A current resonance unit for converting an output signal output from a wire and an output signal output from the second winding into a resonance waveform, and a current obtained from the output signal of the first winding. A rectifying and synthesizing unit for rectifying and synthesizing the swing signal to output a positive phase signal, and rectifying and synthesizing the current resonance signal obtained from the output signal of the second winding for outputting a negative phase signal. It is configured.

[0011]

In the output circuit of the first invention described above, the driver section outputs the drive signal based on the pulse signals sequentially output from the pulse conversion section. The outputs of the switching elements Q1 and Q2 of the voltage resonance switch unit, which alternately perform ON or OFF switching operation according to the drive signal and convert ON and OFF voltages into resonance waveforms, are connected to the primary side terminals of the transformer, respectively. The transformer transmits a signal to the secondary winding according to the push-pull operation of the switching elements Q1 and Q2 in the section. The output signals of the transformers are connected from the secondary side terminals through the rectifying / combining unit so that they are combined in opposite phases. As a result, the signal output from the secondary side terminal of the transformer is alternately a positive-phase signal or a negative-phase signal according to ON or OFF of the switching elements Q1 and Q2 of the switch unit, and these signals are output by the rectifying / synthesizing unit. Since they are rectified and then synthesized,
It is possible to reduce the harmonic component included in the output waveform output to the load.

In the output circuit of the second invention, the driver section outputs the drive signal based on the pulse signals sequentially output from the pulse conversion section. The outputs of the switching elements Q1 and Q2 of the switch section, which alternately perform ON or OFF switching operation according to the drive signal, are connected to the primary side terminals of the transformer, respectively, and follow the push-pull operation of the switching elements Q1 and Q2 of the switch section. The transformer transfers the signal to the secondary winding. The output signals of the transformer are connected from the secondary side terminals through the rectifying / combining section so that they are combined in opposite phases, and the signal output from the secondary side terminals of the transformer is converted into a resonance waveform by the current resonance section. To be converted. As a result, the signal output from the current resonance unit is the switching elements Q1 and Q of the switch unit.
The positive-phase or negative-phase signals according to ON or OFF of 2 are alternately repeated, and these signals are combined after being rectified by the rectifying / combining unit, so that the harmonics included in the output waveform output to the load The components can be reduced.

In the output circuit of the third invention, the driver section outputs a drive signal based on the pulse signals sequentially output from the pulse conversion section. The outputs of the switching elements Q1 and Q2 of the voltage resonance switch unit, which alternately perform ON or OFF switching operation according to the drive signal and convert ON and OFF voltages into resonance waveforms, are connected to the primary side terminals of the transformer, The transformer transmits a signal to the secondary winding according to the push-pull operation of the switching elements Q1 and Q2 of the switch section. The secondary winding has a first winding for outputting a positive phase signal, and a second winding for taking out a signal having a phase opposite to that of the first winding.
, And the output signals of the first and second windings are connected via a rectifying / combining unit so as to be combined in opposite phases. As a result, the pulse signals according to the ON or OFF state of the switching elements Q1 and Q2 of the switch section are alternately repeated, and the positive phase output signal and the second phase output signal output from the first winding after being rectified by the rectifying and combining section. Since the output waveform is obtained by adding the output signal of the opposite phase output from the winding wire, the harmonic component included in the output waveform output to the load can be reduced.

In the output circuit of the fourth aspect of the invention, the driver section outputs a drive signal based on the pulse signals sequentially output from the pulse conversion section. The outputs of the switching elements Q1 and Q2 of the switch section, which alternately perform ON or OFF switching operation according to the drive signal, are connected to the primary side terminals of the transformer, respectively, and follow the push-pull operation of the switching elements Q1 and Q2 of the switch section. The transformer transfers the signal to the secondary winding. The secondary winding is composed of a first winding for outputting a positive phase signal and a second winding for extracting a signal having a phase opposite to that of the first winding. The output signals output from the windings are converted into resonance waveforms by the current resonance unit. Further, the current resonance signals obtained from the output signals of the first and second windings are connected via the rectifying / synthesizing unit so that they are synthesized in opposite phases. As a result, the pulse signals according to the ON or OFF state of the switching elements Q1 and Q2 of the switch section are alternately repeated, and the positive phase output signal and the second phase output signal output from the first winding after being rectified by the rectifying and combining section. Since the output waveform is obtained by adding the output signal of the opposite phase output from the winding wire, the harmonic component included in the output waveform output to the load can be reduced.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the first invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of an output circuit in an embodiment of the first invention. In FIG. 1, a characteristic component 6 is a transformer that electrically insulates the output signals of the switching elements Q1 and Q2 of the voltage resonance switch section 8 and transmits energy.
The voltage resonance switch unit 8 performs a switching operation in accordance with an on or off timing alternately output from the driver unit 2, and then voltage resonance of the output signals of the switching elements Q1 and Q2 is obtained. The signal is output to the transformer 6. Reference numeral 7 is a rectifying / synthesizing unit. Others are the same as the conventional configuration.

The operation of the output circuit of this embodiment will be described below. First, in the pulse converter 1, the analog input signal is, for example, a pulse width modulation signal having a constant repetition frequency and a varying pulse width. The pulse width modulation signals are made into signals having mutually opposite phases by the driver unit 2 and are input to the gates of the switching elements Q1 and Q2 of the voltage resonance switch unit 8 to switch the switching elements Q1 and Q2. The switching elements Q1 and Q2 used in the voltage resonance switch unit 8
For this reason, it is preferable to use an FET in order to increase the switching frequency. Further, the switching element Q1,
Capacitors C1 and C are placed between the drain and source terminals of Q2.
2 are connected to each other and resonate in parallel at a frequency determined by the time constant of the inductance of the transformer 6 and the capacitances of the capacitors C1 and C2. Therefore, the output waveforms output from the switching elements Q1 and Q2 are harmonic components. Results in a reduced voltage resonance waveform. Here, when the switching element Q1 of the voltage resonance switch section 8 is turned on, the transformer 6
A current flows through the primary winding L11 toward the switching element Q1 and a positive current flows through the secondary winding L21 through the diode D1 of the rectifying / combining unit 7. At this time, the positive current flowing through the diode D1 also tries to flow into the secondary winding L22 of the transformer 6 through the diode D2. However, the secondary winding L22 is the secondary winding L2.
1 is a reverse phase output, and is blocked by the current flowing toward the diode D2, so that the voltage resonance waveform as shown by the solid line in FIG. 5A is output. Next, when the switching element Q1 is turned off, a flyback output as shown by the broken line in FIG. 5A is generated in the secondary winding L21 of the transformer 6, but the diode D1 has a polarity opposite to that of the flyback output. No current flows because it is connected. Further, when the switching element Q2 of the voltage resonance switch unit 8 is turned on, a current flows through the primary winding L11 of the transformer 6 toward the switching element Q2, and the secondary winding L22 of the diode D2 of the rectifying / synthesizing unit 7 is connected.
Negative current flows through. At this time, transformer 6
A current tries to flow from the secondary winding L21 toward the ground point, but the current does not flow because the diode D1 is connected in the opposite polarity, and the output voltage waveform as shown by the solid line in FIG. can get. Next, when the switching element Q2 is turned off, a flyback output as shown by a broken line in FIG. 5B is generated in the secondary winding L22 of the transformer 6, but the diode D2 has a polarity opposite to that of the flyback output. No current flows because it is connected.

By repeating the above operation, the switching elements Q1 and Q2 of the voltage resonance switch section 8 perform push-pull operation to drive the transformer 6. Therefore, the signal amplified and taken out by the transformer 6 is
After being synthesized by the rectifying / synthesizing unit 7, the output waveform as shown in FIG. 5C is supplied to the load resistor 5 through the low-pass filter 4.

The load resistor 5 may be a speaker. In this case, the amplitude of the output waveform may fluctuate due to resonance between the inductance and reactance components of the low pass filter 4 and the inductance component of the speaker itself. There is a nature. As a countermeasure, a method of connecting a resistor and a capacitor in parallel with the load resistor 5 and performing damping can be considered. Further, in this embodiment, the pulse width modulation method is used as the pulse modulation method, but there is no restriction on the modulation method, and it goes without saying that other modulation methods such as pulse density modulation have the same effect.

As described above, according to the embodiment of the first aspect of the present invention, the two switching elements and the load resistance are transformer-coupled to each other, and a means for converting the output voltage of the switch section into a resonance waveform is provided. By providing a means for processing the residual energy inside the transformer in the output stage, the harmonic components contained in the pulse width modulation signal are reduced, and the DC level shift is suppressed to obtain an output waveform without distortion. It will be.

Next, FIG. 2 shows a block diagram of an output circuit of an embodiment of the second invention. In FIG. 2, as a characteristic component, 6 is a transformer that electrically insulates the output signals of the switching elements Q1 and Q2 of the switch unit 3 and transmits energy, and 9 is a pulse width modulation that is sequentially output from the transformer 6. A current resonance conversion unit for series-resonating a signal and converting it into a current resonance signal, and 7 is a rectifying / combining unit, and the other components are the same as in the conventional configuration.

The operation of the output circuit of this embodiment will be described below. First, in the pulse converter 1, the analog input signal is, for example, a pulse width modulation signal having a constant repetition frequency and a varying pulse width. The driver unit 2 sequentially inputs the gate input signals obtained by converting the pulse width modulated signals into signals of opposite phases to the gates of the switching elements Q1 and Q2 of the switch unit 3, respectively. The switching elements Q1 and Q2 perform a switching operation according to the gate input signals sequentially input. When the switching element Q1 of the switch unit 3 is turned on, a current flows through the primary winding L11 of the transformer 6 toward the switching element Q1 and the secondary winding L2.
A current is input from 1 to the current resonance converter 9. The current resonance conversion unit 9 performs series resonance at a frequency according to the time constant of the coil L1 and the capacitor C3, and sequentially outputs current resonance signals having waveforms with reduced harmonics to the rectification synthesis unit 7. The current input to the diode D1 of the rectifying / synthesizing unit 7 has a waveform as shown in FIG. Next, the rectifying / combining unit 7 rectifies the current resonance signals sequentially input through the diode D1 and outputs a positive current. At this time, the positive current flowing through the diode D1 also tries to flow through the secondary winding L22 of the transformer 6 through the diode D2, but the secondary winding L22 has an opposite phase output to the secondary winding L21 and the diode D2. The voltage waveform output from the rectifying / synthesizing unit 7 has a waveform as shown by the solid line in FIG. Next, when the switching element Q1 is turned off, a flyback output as shown by a broken line in FIG. 6A is generated in the secondary winding L21 of the transformer 6, but the diode D1 has a polarity opposite to that of the flyback output. No current flows because it is connected.
Further, when the switching element Q2 of the switch unit 3 is turned on, a current flows through the primary winding L11 of the transformer 6 toward the switching element Q2 and the secondary winding L11.
Negative currents sequentially output from the diode D2 of the rectifying / combining unit 7 are input to the line 22 through the current resonance converting unit 9. The current resonance converter 9 includes a coil L2 and a capacitor C4.
The series resonance is performed at a frequency according to the time constants of and, and the current resonance signal obtained after resonating the current sequentially input from the diode D2 is sequentially output to the secondary winding L22. The current input to the secondary winding L22 has a waveform as shown in FIG. 6 (d). At this time, current tries to flow from the secondary winding L21 of the transformer 6 toward the ground point,
Since the diode D1 is connected in reverse polarity, no current flows, and the output voltage waveform as shown by the solid line in FIG. 5C is obtained. Next, when the switching element Q2 is turned off, a flyback output as shown by a broken line in FIG. 5B is generated in the secondary winding L22 of the transformer 6, but the diode D2 has a polarity opposite to that of the flyback output. No current flows because it is connected.

By repeating the above operation, the switching elements Q1 and Q2 of the switch section 3 perform the push-pull operation to drive the transformer 6. Therefore, the signals amplified and taken out by the transformer 6 are combined by the rectifying / combining unit 7, and then passed through the low-pass filter 4 to generate an output voltage waveform as shown in FIG.
An output current waveform as shown in (f) is supplied to the load resistor 5.

In this embodiment, the pulse width modulation method is used as the pulse modulation method, but there is no restriction on the modulation method, and it goes without saying that other modulation methods such as pulse density modulation have the same effect. Yes.

As described above, according to the embodiment of the second aspect of the present invention, the two switching elements and the load resistance are transformer-coupled to each other, and means for converting the output current of the transformer into a resonance waveform is provided. By providing a means for processing the residual energy inside the transformer in the stage, it is possible to reduce harmonic components contained in the pulse width modulation signal, suppress DC level shift, and obtain an output waveform without distortion. Become.

Next, FIG. 3 is a block diagram of an output circuit according to an embodiment of the third invention. In FIG. 3, a characteristic component 8 is a switching element Q1 and a switching element Q2 after performing a switching operation according to an on or off timing alternately output from the driver unit 2.
Voltage resonance switch unit for outputting to the transformer 6 voltage resonance signals obtained by respectively resonating the output signals of
Is a transformer, 11 is a rectifying / synthesizing unit that synthesizes after rectifying the output signal of the transformer 10, and 12 is a low-pass filter that removes high-frequency components of the output signal output from the rectifying / synthesizing unit 11 and extracts audio signal components. Others are the same as the conventional configuration.

The operation of the output circuit of this embodiment having the above components will be described below. First, the pulse conversion unit 1 converts the signal into a pulse width modulation signal whose pulse width changes, for example, based on the amplitude value of the sequentially input analog input signal, and then sequentially outputs the signal to the driver unit 2. Next, after the driver unit 2 converts the signals into phases opposite to each other,
The switching elements Q1 and Q2 of the voltage resonance switch unit 8 are input to the gates of the switching elements Q1 and Q2, respectively.
Are sequentially switched. Further, a capacitor C is provided between the drain and source terminals of the switching elements Q1 and Q2.
1 and C2 are connected to each other, and parallel resonance occurs at a frequency determined by the time constant of the inductance of the transformer 10 and the capacitances of the capacitors C1 and C2. Therefore, the output waveforms sequentially output from the switching elements Q1 and Q2, respectively. Is a voltage resonance waveform with reduced harmonic components. When the switching element Q1 of the voltage resonance switch section 8 is turned on, a current flows through the primary winding L11 of the transformer 10 toward the switching element Q1 and the secondary winding L21 passes through the diode D1 of the rectifying / combining section 11 to be positive. An electric current flows. At this time, the positive current flowing through the diode D1 also tries to flow through the secondary winding L22 of the transformer 10 through the diode D2, but the secondary winding L22 has an opposite phase output to that of the secondary winding L21 and is supplied to the diode D2. It is blocked by the current flowing toward it, and an output voltage waveform as shown by the solid line in FIG. 7A is obtained. Next, when Q1 of the voltage resonance switch unit 8 is turned off, the secondary winding L21 of the transformer 10 is connected to the secondary winding L21 of FIG.
A flyback output as indicated by the broken line is generated, but no current flows because the diode D1 is connected in the opposite polarity to this flyback output.

On the other hand, when the switching element Q1 of the voltage resonance switch section 8 is turned on, the secondary winding L of the transformer 10 is turned on.
Negative current flows through the diode D3 of the rectifying / combining unit 11 through 23. At this time, the negative current flowing through the diode D3 also tries to flow through the secondary winding L24 of the transformer 10 through the diode D4, but no current flows because the diode D4 is connected in the opposite polarity.
An output voltage waveform like the solid line shown in FIG. 7B is obtained. Next, the switching element Q of the voltage resonance switch section 8
When 1 is turned off, a flyback output as shown by the broken line in FIG. 7B is generated in the secondary winding L23 of the transformer 10, but the diode D has a polarity opposite to that of the flyback output.
No current flows because 3 is connected.

Further, when the switching element Q2 of the voltage resonance switch section 8 is turned on, a current flows through the primary winding L11 of the transformer 10 toward the switching element Q2, and the diode of the rectifying / synthesizing section 11 is connected to the secondary winding L22. Negative current flows through D2. At this time,
A current tries to flow from the secondary winding L21 of the transformer 10 toward the grounding point, but since the diode D1 is connected in reverse polarity, no current flows, and the output shown by the solid line in FIG. 7C is output. A voltage waveform is obtained. Next, when the switching element Q2 of the voltage resonance switch unit 8 is turned off, a flyback output as shown by a broken line in FIG. 7C is generated in the secondary winding L22 of the transformer 10. What is this flyback output? No current flows because the diode D2 is connected to the opposite polarity.

On the other hand, when the switching element Q2 of the voltage resonance switch section 8 is turned on, the secondary winding L of the transformer 10 is turned on.
A positive current flows in the diode 24 through the diode D4 of the rectifying / combining unit 11. At this time, the positive current flowing through the diode D4 passes through the diode D3 and the transformer 10
Of the secondary winding L23, the secondary winding L23 has an output opposite in phase to the secondary winding L24 and is blocked by the current flowing toward the diode D3. An output voltage waveform like the solid line shown in d) is obtained. Next, when the switching element Q2 of the voltage resonance switch unit 8 is turned off, the secondary winding L24 of the transformer 10 is turned on.
A flyback output as shown by the broken line in FIG. 7 (d) is generated, but no current flows because the diode D4 is connected in the opposite polarity to this flyback output.

By repeating the above operation, the switching elements Q1 and Q2 of the voltage resonance switch section 8 perform the push-pull operation to drive the transformer 10. Therefore,
The positive-phase and negative-phase signals amplified and taken out by the transformer 10 are combined by the rectifying / combining unit 11,
Output waveforms as shown in FIG. 7E are supplied to the load resistor 5 through the respective low-pass filters 12. This output waveform is a positive-phase signal and a negative-phase signal, and since the load resistor 5 is connected in balance, an output voltage waveform with double the amplitude is obtained from the load resistor 5.

In this embodiment, the pulse width modulation method is used as the pulse modulation method, but there is no restriction on the modulation method, and it goes without saying that other modulation methods such as pulse density modulation have the same effect. Yes.

As described above, according to the embodiment of the third aspect of the present invention, the two switching elements and the load resistance are transformer-coupled to each other, and means for converting the output voltage of the switch section into a resonance waveform is provided. By providing a means for processing the residual energy inside the transformer in the output stage, the harmonic components contained in the pulse width modulation signal are reduced, and the DC level shift is suppressed to obtain an output waveform without distortion. It will be.

Next, FIG. 4 is a block diagram of an output circuit according to the fourth embodiment of the invention. In FIG. 4, 10 is a transformer and 11 is a transformer 10 as characteristic components.
A rectifying / synthesizing unit for rectifying and then synthesizing the output signal of 12;
Reference numeral 13 is a current resonance conversion unit for converting the pulse width modulation signals sequentially output from the transformer 10 into series resonance and converting them into a current resonance signal. Others are the same as the conventional configuration.

The operation of the output circuit of the embodiment having the above components will be described below. First, the pulse conversion unit 1 converts the signal into a pulse width modulation signal with a varying pulse width, for example, based on the amplitude values of the analog signals that are sequentially input, and then sequentially outputs the pulse width modulation signal to the driver unit 2. Next, the driver unit 2 converts the sequentially input pulse width modulation signals into signals having mutually opposite phases, and then inputs the signals to the gates of the switching elements Q1 and Q2 of the switch unit 3 to switch the switching elements Q1 and Q2. . When the switching element Q1 of the switch unit 3 is turned on, a current flows through the primary winding L11 of the transformer 10 toward the switching element Q1 and a current is input from the secondary winding L21 to the current resonance conversion unit 13. . The current resonance conversion unit 13 performs series resonance at a frequency according to the time constant of the coil L1 and the capacitor C3, and sequentially outputs current resonance signals obtained after resonating sequentially input currents to the rectification / synthesis unit 11. The current input to the diode D1 of the rectifying / synthesizing unit 11 has a waveform with reduced harmonic components as shown in FIG. 8 (b). Next, the rectifying / combining unit 11 operates the diode D1.
The current resonance signal sequentially input through is rectified and a positive current is output. At this time, the positive current flowing through the diode D1 passes through the diode D2 and the transformer 10
Of the secondary winding L22, the secondary winding L22 has an output opposite in phase to the secondary winding L21 and is blocked by the current flowing toward the diode D2. An output voltage waveform like the solid line shown in a) is obtained. Next, when the switching element Q1 of the switch part 3 is turned off, the secondary winding L21 of the transformer 10 is connected to the secondary winding L21 of FIG.
A flyback output as shown by the broken line in (a) is generated, but the diode D1 has a polarity opposite to that of the flyback output.
No current flows because is connected.

On the other hand, the switching element Q of the switch unit 3
When 1 is turned on, the negative current sequentially output from the diode D3 of the rectifying / combining unit 11 is input to the secondary winding L23 of the transformer 10 via the current resonance converting unit 13.
The current resonance conversion unit 13 performs series resonance at a frequency according to the time constant of the coil L3 and the capacitor C5, and the diode D
The current resonance signals obtained after resonating the currents sequentially input from 3 are sequentially output to the secondary winding L23. The current input to the secondary winding L23 has a current waveform in which the polarity of FIG. 8B is reversed. At this time, the negative current flowing through the diode D3 also tries to flow through the secondary winding L24 of the transformer 10 through the diode D4.
Since the diode D4 is connected to the opposite polarity, no current flows, and an output voltage waveform obtained by inverting the polarity of the solid line shown in FIG. 8A is obtained. Next, when the switching element Q1 of the switch unit 3 is turned off, the secondary winding L2 of the transformer 10 is turned on.
A flyback output in which the polarity of the broken line shown in FIG. 8A is inverted is generated in FIG. 3, but no current flows because the diode D3 is connected in the opposite polarity to this flyback output.

When the switching element Q2 of the switch section 3 is turned on, a current flows through the primary winding L11 of the transformer 10 toward the switching element Q2, and the secondary winding L22 of the diode D2 of the rectifying / synthesizing section 11 is supplied. Negative currents sequentially output from are input via the current resonance converter 13. The current resonance conversion unit 13 performs series resonance at a frequency according to the time constant of the coil L2 and the capacitor C4, and resonates the current sequentially input from the diode D2 to obtain a current resonance signal and obtain a current resonance signal from the secondary winding L22.
Sequentially output to. The current input to the secondary winding L22 has a waveform with reduced harmonic components as shown in FIG. 8 (d). At this time, a current tries to flow from the secondary winding L21 of the transformer 10 toward the ground point, but no current flows because the diode D1 is connected in the opposite polarity, and the solid line shown in FIG. Such an output voltage waveform is obtained.
Next, when the switching element Q2 of the switch unit 3 is turned off, a flyback output as shown by a broken line in FIG. 8C is generated in the secondary winding L22 of the transformer 10, but the polarity is opposite to that of the flyback output. No current flows because the diode D2 is connected to.

On the other hand, the switching element Q of the switch section 3
When 2 is turned on, the pulse width modulation signal sequentially output from the secondary winding L24 of the transformer 10 is the current resonance conversion unit 13
A positive current is sequentially output from the diode D4 of the rectifying / combining unit 11 via the. At this time, the positive current flowing through the diode D4 also tries to flow through the secondary winding L23 of the transformer 10 through the diode D3, but the secondary winding L23 has an opposite phase output to that of the secondary winding L24, and thus is supplied to the diode D3. An output voltage waveform is obtained, which is blocked by the current that tends to flow toward and the polarity of the solid line shown in FIG. 8C is inverted. Next, when the switching element Q2 of the switch unit 3 is turned off, the secondary winding L2 of the transformer 10 is turned on.
A flyback output in which the polarity of the broken line shown in FIG. 8 (c) is inverted is generated in No. 4, but no current flows because the diode D4 is connected in the opposite polarity to this flyback output.

By repeating the above operation, the switching elements Q1 and Q2 of the switch section 3 perform push-pull operation to drive the transformer 10. Therefore, the positive-phase and negative-phase signals amplified and taken out by the transformer 10 are combined by the rectifying / combining unit 11 and then passed through the low-pass filter 12, respectively, and output voltage waveforms and diagrams as shown in FIG. An output current waveform as shown in 8 (f) is supplied to the load resistor 5. This output voltage is a positive-phase signal and a negative-phase signal, and since the load resistor 5 is connected in balance, an output voltage waveform with double the amplitude is obtained from the load resistor 5. In this embodiment, the pulse width modulation method is used as the pulse modulation method, but there is no restriction on the modulation method, and it goes without saying that other modulation methods such as pulse density modulation have the same effect.

As described above, according to the embodiment of the fourth aspect of the present invention, the two switching elements and the load resistance are transformer-coupled with each other, and means for converting the output current of the transformer into a resonance waveform is provided. By providing a means for processing the residual energy inside the transformer in the stage, it is possible to reduce harmonic components contained in the pulse width modulation signal, suppress DC level shift, and obtain an output waveform without distortion. Becomes

[0040]

As is apparent from the above description of the embodiment, the first invention drives the transformer by turning on / off the switch section according to the pulse width modulation signal sequentially output from the pulse converting section. The switch section causes the output signal of the switching element to resonate in parallel according to the reactance of the transformer and the resonance frequency of the capacitor connected to the output terminal of the switching element, and sequentially inputs the obtained voltage resonance signal to the primary side terminal of the transformer. An external voltage is supplied to the middle point of the primary winding of the transformer, turning on the switch.
Turns off to transfer energy to the secondary side of the transformer. Furthermore, the junction point of the secondary winding of the transformer is grounded, and the output signals of the transformer are rectified by the rectifying / synthesizing unit and then combined so that they have opposite phases, and then unnecessary high-frequency components are removed by a low-pass filter. Since it is input to the load resistance, harmonic components included in the voltage waveform of the pulse width modulation signal transmitted to the transformer can be reduced, and reception interference such as a tuner can be avoided. Since the frequency components in the audio band can be taken out without passing the low frequency components through the transformer, the power can be amplified without increasing the weight and size of the transformer.

According to the second aspect of the present invention, the transformer is driven by turning on / off the switch section according to the pulse width modulation signal sequentially output from the pulse converting section. An external voltage is supplied to the middle point of the primary winding of the transformer, and energy is transmitted to the secondary side of the transformer by turning on / off the switch section. A current resonance conversion unit including a coil and a capacitor is connected to the secondary side terminal of the transformer, and the current resonance conversion unit causes series resonance according to the resonance frequency of the inductor and the capacitance of the capacitor and sequentially outputs the obtained current resonance signal. . Furthermore, the junction point of the secondary winding of the transformer is grounded, and the output signals of the transformer are rectified by the rectifying / synthesizing unit and then combined so that they are in opposite phases, and then the unnecessary high-frequency components are filtered by the low-pass filter. Since it is input to the load resistance by removing the, harmonic components included in the current waveform of the pulse width modulated signal transmitted to the transformer can be reduced, and reception interference such as tuners can be avoided. In addition, since the frequency components in the audio band can be extracted without passing the low frequency components through the transformer, the power can be amplified without increasing the weight and size of the transformer. According to a third aspect of the invention, the switch section is turned on / off according to the pulse width modulation signal sequentially output from the pulse conversion section to drive the transformer. The switch section causes the output signal of the switching element to resonate in parallel according to the reactance of the transformer and the resonance frequency of the capacitor connected to the output terminal of the switching element, and sequentially inputs the obtained voltage resonance signal to the primary side terminal of the transformer. An external voltage is supplied to the middle point of the primary winding of the transformer, and energy is transmitted to the secondary side of the transformer by turning on / off the switch section. The junction of the secondary windings of the transformer is grounded, and the output signals output from the first secondary windings are rectified by the rectifying / combining unit and then combined so as to have opposite phases. Further, the output signal output from the second secondary winding has a phase opposite to that of the output signal output from the first secondary winding, and after being rectified by the rectifying / combining unit, they have phases opposite to each other. To be synthesized. Further, the output signal of the first secondary winding and the output signal of the second secondary winding are so-called balanced connection input to the load resistance after unnecessary high-frequency components are removed by the low-pass filter. As a result, harmonic components included in the voltage waveform of the pulse width modulation signal transmitted to the transformer can be reduced, reception interference such as tuners can be avoided, and the output voltage input to the load resistor is Since it is possible to obtain double the amplitude and to extract the frequency component in the audio band without passing the low frequency component through the transformer, it is possible to amplify the power without increasing the weight and size of the transformer. .

According to the fourth aspect of the invention, the transformer is driven by turning on / off the switch section according to the pulse width modulation signal sequentially output from the pulse converting section. A current resonance conversion unit including a coil and a capacitor is connected to the secondary side terminal of the transformer, and the current resonance conversion unit causes series resonance according to the resonance frequency of the inductor and the capacitance of the capacitor and sequentially outputs the obtained current resonance signal. . An external voltage is supplied to the middle point of the primary winding of the transformer, and energy is transmitted to the secondary side of the transformer by turning on / off the switch section. The junction of the secondary windings of the transformer is grounded, and the output signals output from the first secondary windings are rectified by the rectifying / combining unit and then combined so as to have opposite phases. Further, the output signal output from the second secondary winding has a phase opposite to that of the output signal output from the first secondary winding, and the phases are opposite to each other after being rectified by the rectification combining unit. Is synthesized. Further, the output signal of the first secondary winding and the output signal of the second secondary winding are so-called balanced connection input to the load resistance after unnecessary high-frequency components are removed by the low-pass filter. Therefore, it is possible to reduce harmonic components included in the current waveform of the pulse width modulation signal transmitted to the transformer, avoid reception interference such as a tuner, and output voltage input to the load resistance. Since it is possible to obtain double the amplitude and to extract the frequency component of the audio band without passing the low frequency component through the transformer, it is possible to amplify the power without increasing the weight and size of the transformer.

[Brief description of drawings]

FIG. 1 is a block diagram of an output circuit according to an embodiment of the first invention.

FIG. 2 is a block diagram of an output circuit according to an embodiment of the second invention.

FIG. 3 is a block diagram of an output circuit according to an embodiment of the third invention.

FIG. 4 is a block diagram of an output circuit according to an embodiment of the fourth invention.

FIG. 5 is a diagram showing operating voltage waveforms of respective parts in the output circuit of the embodiment of the first invention.

FIG. 6 is a diagram showing operating voltage waveforms of respective parts in the output circuit of the embodiment of the second invention.

FIG. 7 is a diagram showing operating voltage waveforms of various parts in the output circuit of the third embodiment of the invention.

FIG. 8 is a diagram showing operating voltage waveforms of various parts in the output circuit of the fourth embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of a conventional output circuit.

[Explanation of symbols]

 1 pulse conversion unit 2 driver unit 4 low-pass filter 5 load resistance 6 transformer 7 rectification / synthesis unit 8 voltage resonance switch unit

Claims (4)

[Claims] 1. A pulse converter for pulse-modulating an analog input signal such as an audio signal, a driver unit for outputting a drive signal based on the pulse signal output from the pulse converter, and an ON or OFF circuit according to the drive signal. A voltage resonance switch unit that alternately performs an OFF switching operation and converts ON and OFF voltages into a resonance waveform,
An external power source is connected to the intermediate tap of the primary winding with the output signal of the voltage resonance switch unit as an input, and the secondary winding is a transformer configured to take out output signals of opposite phases, and An output circuit having a rectifying / synthesizing unit that rectifies and then synthesizes the output signal of the transformer. 2. A pulse converter that pulse-modulates an analog input signal such as an audio signal, a driver unit that outputs a drive signal based on the pulse signal output from the pulse converter, and an ON or OFF signal according to the drive signal. In order to connect the external power supply to the intermediate tap of the primary winding, which receives the output signal of the switching section and the switch section that alternately performs the OFF switching operation as input, and the secondary winding outputs the output signals of opposite phases to each other. An output circuit comprising: a transformer configured by the windings, a current resonance unit that converts an output signal of the transformer into a resonance waveform, and a rectification synthesis unit that rectifies and synthesizes the output signal of the current resonance unit. 3. A pulse conversion unit for pulse-modulating an analog input signal such as an audio signal, a driver unit for outputting a drive signal based on the pulse signal output from the pulse conversion unit, and an ON or OFF circuit according to the drive signal. A voltage resonance switch unit that alternately performs an OFF switching operation and converts ON and OFF voltages into a resonance waveform,
An external power source is connected to the intermediate tap of the primary winding with the output signal of the voltage resonance switch unit as an input, and the secondary winding has a first winding for extracting outputs of opposite phases, and further the first winding. A transformer having a second winding for extracting an output signal having a phase opposite to that of the first winding; and rectifying and synthesizing the output signal of the first winding to output a positive phase signal, And an output circuit having a rectifying / combining unit for rectifying the output signal of the second winding and then synthesizing the output signal to output a reverse-phase signal. 4. A pulse conversion unit for pulse-modulating an analog input signal such as an audio signal, a driver unit for outputting a drive signal based on the pulse signal output from the pulse conversion unit, and an ON or OFF circuit according to the drive signal. An external power supply is connected to the intermediate tap of the primary winding, which receives the output signal of the switch portion and the switch portion that alternately performs the OFF switching operation as an input, and the secondary winding is for extracting the outputs of opposite phases to each other. A transformer including a first winding and a second winding for extracting an output signal having a phase opposite to that of the first winding; an output signal output from the first winding; A current resonance unit that converts an output signal output from the second winding into a resonance waveform;
The current resonance signal obtained from the output signal of the first winding is rectified and then combined to output a positive phase signal, and the second resonance signal is output.
And a rectifying / combining unit that rectifies the current resonance signal obtained from the output signal of the winding and synthesizes the current resonance signal to output a reverse-phase signal.