JP2002208824A - Switching amplifier and method for driving the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching amplifier capable of avoiding the destruction of the semiconductor power amplifying element of a switching circuit, also performing the muting operation of a delta sigma modulation part, without having to perform complicated control and surely reducing the noise output and to provide a method for driving the switching amplifier. SOLUTION: The delta sigma modulating part is set in a muting state, the delta sigma modulation part is started within its muting time T and the switching circuit is subsequently started within the same muting time T. Within the muting time T, the output from the delta sigma modulation part is always, e.g. zero and is will not be undefined. Then, an output from the drive circuit of the switching circuit will not become undefined, even if the switching circuit is started within the muting time T. Thus, it is possible to normally operate a switching element driven by the drive circuit and to complete the operation of the delta sigma modulation part as a whole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitably applied to, for example, an audio signal, and can amplify a 1-bit digital signal obtained by converting an analog signal such as the audio signal or a multi-bit signal by 1 bit with high efficiency. The present invention relates to a switching amplifier using delta-sigma modulation and a driving method thereof.

[0002]

2. Description of the Related Art A 1-bit signal obtained by delta-sigma modulation can be used to increase an effective frequency band or a dynamic range by appropriately selecting coefficients of an integrator and an adder described later. It has an excellent feature that frequency characteristics can be set according to a sound source or the like. For this reason, CD (compact disk), SA
In the new standard of CD (Super Audio Compact Disc), this 1-bit signal is adopted and commercialized.

On the other hand, a 1-bit signal obtained by the delta-sigma modulation is used for recording an audio signal as described above,
It is not only used for transmission between devices. The 1-bit signal is directly input to the semiconductor power amplifier,
By simply passing the obtained high-voltage switching pulse through an LPF (low-pass filter), a power-amplified demodulated analog signal can be obtained.

FIG. 6 is a block diagram showing an electrical configuration of a conventional typical switching amplifier 51 using delta-sigma modulation. As shown in the figure, a switching amplifier 51 includes a delta-sigma (ΔΣ) modulation section 52.
, Switching circuit 53, LPF 54, power supply 55
・ 56 is provided.

As shown in FIG. 7, the switching circuit 53 includes a plurality of FETs (field effect transistors) 71 to 74, which are semiconductor power amplifiers, and an FET driver 75 for controlling gate voltages of the FETs 71 to 74. ing. The switching circuit 53 applies a large voltage (+ V, −V or 0) supplied from a power supply (not shown) to each of the FETs 7 in accordance with an output signal from the delta-sigma modulation unit 52.
Switching is performed by 1 to 74, and a pulse signal of a constant voltage corresponding to the output signal is output.

[0006] The LPF 54 converts the pulse signal from the switching circuit 53 into an analog signal.

A power supply 55 supplies a constant voltage to a delta-sigma modulation circuit 57 of the delta-sigma modulation section 52, which will be described later, to drive the delta-sigma modulation circuit 57. On the other hand, the power supply 56
Supplies a constant voltage to the switching circuit 53 to drive the switching circuit 53.

Further, the delta-sigma modulator 52 includes
A delta-sigma (ΔΣ) modulation circuit 57, an attenuator 58,
An adder 59 is provided.

The delta-sigma modulation circuit 57 includes a cascade-connected high-order integrator for sequentially integrating an input signal such as an input audio signal, and an adder for mutually adding outputs from the respective integrators. And a quantizer (not shown) for quantizing an output from the adder into a 1-bit signal.

[0010] The attenuator 58 attenuates the output (large voltage pulse signal) from the switching circuit 53. Adder 59
Subtracts the pulse signal attenuated by the attenuator 58 from the input signal. Therefore, the delta-sigma modulator 52
Then, feedback control is performed so that the one-bit signal from the quantizer corresponds to the input signal.

In the above configuration, when an input signal (input audio signal) from an input signal source (not shown) is input to the switching amplifier 51 via the input terminal 60, the input signal is converted into a delta-sigma modulated signal of the switching amplifier 51. Part 5
2 converts the signal into a 1-bit digital signal.

The 1-bit signal is supplied to the switching circuit 53
, The switching circuit 53 outputs the above 1
The predetermined constant voltage pulse signal corresponding to the bit signal is LPF
The LPF 54 outputs the pulse signal to an analog signal (analog audio signal). And
The analog signal is sounded by a speaker or the like connected to the output terminal 61.

The switching amplifier 51 thus configured does not use the linear region (unsaturated region) of the semiconductor power amplifying element used in the switching circuit 53 as in the conventional amplifier, Since the non-linear region (saturation region) of the power amplification element is used, there is an advantage that power amplification can be performed with extremely high efficiency.

[0014]

By the way, when initializing the integration / addition operation inside the delta-sigma modulation section 52, in order to suppress noise generation at the time of the initial operation, when starting up the delta-sigma modulation section 52, FIG. As shown in FIG. 6, conventionally, a reset signal (muting signal) or the like is supplied to the delta-sigma modulation circuit 57 to put the delta-sigma modulation circuit 57 in a mute state. In the related art, after the mute state of the delta-sigma modulation circuit 57 is released, a constant voltage is applied from the power supply 56 to the switching circuit 53 to start the switching circuit 53.

However, when a constant voltage is applied to the switching circuit 53 after the mute state of the delta-sigma modulation circuit 57 is released, an excessive current is applied to the semiconductor power amplifying element of the switching circuit 53 at the moment of applying the constant voltage. Flows, causing a problem that the semiconductor power amplifying element is destroyed. To explain this in more detail,
It is as follows.

In a switching amplifier that attenuates an output signal from the switching circuit 53 and negatively feeds back to the delta-sigma modulation circuit 57, a constant voltage is applied to the switching circuit 53 even if the delta-sigma modulation circuit 57 rises. Until 53 operates normally, the negative feedback to the delta-sigma modulation circuit 57 is in a state of zero, so that the operation of the delta-sigma modulation unit 52 is not completed (the delta-sigma modulation unit 52 does not operate normally).

Therefore, if the switching circuit 53 starts up after the lapse of the muting period, the delta-sigma modulation section 52 does not operate properly.
Since the constant voltage is applied to the switching circuit 53, the output from the delta-sigma modulation circuit 57 becomes indefinite at the moment of the application of the constant voltage, whereby the FET driver of the switching circuit 53 shown in FIG. 75
The output from is unstable.

In this case, usually, the FET 71 and the FET 71
74 or the combination of the FET 72 and the FET 73 turns on the gate of each FET.
1 and the FET 72, the combination of the FET 73 and the FET 74, or the gates of all the FETs are turned ON. As a result, in FIG. 7, + V → FET71D → FET7
1S → FET72D → FET72S → −V, or
+ V → FET73D → FET73S → FET74D → F
Excessive current flows in each FET along the path of ET74S → −V, and each FET is destroyed. The above D means the drain of the FET, and the above S is the FET
Means the source.

Further, for example, Japanese Patent Application Laid-Open No. 2000-19645
Japanese Patent Application Laid-Open No. 4 (Kokai) No. 4 (Kokai) No. 4 (1995) discloses a digital signal processing device having the characteristics of a noise shaper. In this device, the output is set to 0 by the muting setting, and the D / A
By stopping the bit clock corresponding to the bit of the digital data supplied to the (digital-analog) converter, noise is prevented from being output to the outside when the parameter of the processor is changed.

However, such an operation of stopping the clock causes a problem that external control performed by a microcomputer or the like becomes complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to prevent a semiconductor power amplifying element of a switching circuit from being destroyed.
An object of the present invention is to provide a switching amplifier that can perform a muting operation of a delta-sigma modulation unit without performing complicated control and that can reliably reduce a noise output, and a driving method thereof.

[0022]

A driving method of a switching amplifier according to the present invention has the following objects.
A delta-sigma modulation unit that performs delta-sigma modulation on an input signal; a switching element that switches and outputs a constant voltage; and a drive circuit that drives the switching element according to an output signal from the delta-sigma modulation unit. A driving circuit for a switching amplifier that performs a delta-sigma modulation by feeding back an output from the switching circuit to the delta-sigma modulation unit, wherein the delta-sigma modulation unit is muted, The switching circuit is activated within a period.

In the above configuration, for example, if the delta-sigma modulator has already risen within the muting period, the output from the delta-sigma modulator can be a 1-bit signal during the muting period. If it is always zero, it is not undefined. Therefore, even if the switching circuit is started during the muting period, the output from the driving circuit of the switching circuit does not become unstable. Thus, the switching element driven by the driving circuit can operate normally.
As a result, it is possible to prevent an excessive current from flowing through the switching element when the switching circuit is activated as in the related art, and to prevent the switching element from being destroyed.

Further, when the switching circuit operates normally, the delta-sigma modulation section to which the output from the switching circuit is fed back also operates normally. This stabilizes the noise shaping operation in the delta-sigma modulation unit, so that the output from the delta-sigma modulation unit does not include an excessive noise component after the elapse of the muting period.

Further, in removing the noise component from the output signal, since the clock used for controlling the operation timing of each unit is not stopped unlike the related art, the control of each unit does not become complicated.

In order to solve the above-mentioned problems, a method of driving a switching amplifier according to the present invention includes the steps of: starting up the delta-sigma modulation section during the muting period;
It is characterized in that the switching circuit is started.

According to the above configuration, the delta-sigma modulation section is started up before the switching circuit is started up within the muting period. Therefore, when the switching circuit is started up, the output of the switching circuit is fed back. , The operation of the delta-sigma modulator can be completed (the delta-sigma modulator can operate normally). As a result, the above-described effects can be reliably obtained.

In order to solve the above-mentioned problems, in the driving method of the switching amplifier according to the present invention, in the muting state of the delta-sigma modulation section, an output signal from the delta-sigma modulation section is constant. It is characterized by:

According to the above configuration, while the delta-sigma modulator is in the muting state, the output signal from the delta-sigma modulator is not indefinite. The output from the drive circuit of the circuit does not become undefined. Thereby, the switching element of the switching circuit can normally switch the constant voltage. As a result, destruction of the switching element due to excessive current can be reliably avoided.

In order to solve the above-mentioned problems, the driving method of the switching amplifier according to the present invention is characterized in that the delta-sigma modulation unit is in a reset state in a muting state of the delta-sigma modulation unit.

According to the above configuration, the output signal from the delta-sigma modulation unit is kept constant by setting the delta-sigma modulation unit in the reset state, and the output signal is not unstable. Thus, the operation of the switching element by the drive circuit can be performed normally, and the destruction of the switching element can be reliably avoided.

In order to solve the above-mentioned problems, a switching amplifier according to the present invention includes a delta-sigma modulation section for delta-sigma-modulating an input signal, a switching element for switching and outputting a constant voltage, and a delta-sigma modulation section. A switching circuit having a drive circuit for driving the switching element according to the output signal from the control circuit, and controlling the operations of the delta-sigma modulation unit and the switching circuit, and performing a muting operation of the delta-sigma modulation unit. Control means for controlling the output of the switching circuit to feed back the output from the switching circuit to the delta-sigma modulation unit to perform delta-sigma modulation, wherein the control means sets the delta-sigma modulation unit to a muting state. , Within the muting period, the above switch It is characterized by raising the grayed circuit.

In the above configuration, for example, if the delta-sigma modulation section has already risen within the muting period, the output from the delta-sigma modulation section can be said to be, for example, a 1-bit signal during the muting period. If it is always zero, it is not undefined. Therefore, even if the control means starts the switching circuit within the muting period, the output from the driving circuit of the switching circuit does not become unstable. Thus, the switching element driven by the driving circuit can operate normally. As a result, it is possible to prevent an excessive current from flowing through the switching element when the switching circuit is activated as in the related art, and to prevent the switching element from being destroyed.

When the switching circuit operates normally, the delta-sigma modulation section to which the output from the switching circuit is fed back also operates normally. This stabilizes the noise shaping operation in the delta-sigma modulation unit, so that the output from the delta-sigma modulation unit does not include an excessive noise component after the elapse of the muting period.

Further, in removing the noise component from the output signal, since the clock used for controlling the operation timing of each unit is not stopped as in the related art, the control of each unit does not become complicated.

In the switching amplifier according to the present invention, in order to solve the above-mentioned problems, the control means may start up the delta-sigma modulation section and then start up the switching circuit within the muting period. It is characterized by.

According to the above configuration, the control means activates the delta-sigma modulation section before the activation of the switching circuit within the muting period. Therefore, at the time of activation of the switching circuit, the control means outputs the output from the switching circuit. Complete the operation of the delta-sigma modulation unit by feedback (normally operate the delta-sigma modulation unit)
be able to. As a result, the above-described effects can be reliably obtained.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
The following is a description based on the drawings.

FIG. 2 is a block diagram showing an example of the electrical configuration of the switching amplifier 1 of the present invention using delta-sigma modulation. As shown in FIG. 1, a switching amplifier 1 constituting a digital switching amplifier includes a delta-sigma (ΔΣ) modulator 2, a switching circuit 3,
An LPF 4, a power source 5 (second power source), a power source 6 (first power source), and a microcomputer 7 (control means) are provided.

The delta-sigma modulator 2 performs delta-sigma modulation on an input signal (for example, an input audio signal) to generate a 1-bit digital signal (modulated signal). Switching circuit 3
Outputs a constant-voltage pulse signal by switching a constant voltage from a power supply (not shown) according to a modulation signal output from the delta-sigma modulation unit 2. The detailed configurations of the delta-sigma modulator 2 and the switching circuit 3 will be described later. The LPF 4 demodulates the output from the switching circuit 3 into an analog signal.

The power supply 5 supplies a constant voltage to a delta-sigma modulation circuit 8 described later of the delta-sigma modulation section 2 to drive the delta-sigma modulation circuit 8, and supplies a constant voltage to a logic circuit 9 described later. Thus, the power supply 5b for driving the logic circuit 9 is provided. The power supply 6 drives the switching circuit 3 by supplying a constant voltage to the switching circuit 3.

The microcomputer 7 controls the operations of the delta-sigma modulator 2 and the switching circuit 3. In particular,
The microcomputer 7 includes a delta-sigma modulation circuit 8 using a power supply 5a.
A constant voltage is applied to the logic circuit 9 by the power supply 5b, and a constant voltage is applied to the switching circuit 3 by the power supply 6.

In the present embodiment, the microcomputer 7 outputs the muting signal, which is a reset signal, to the logic circuit 9.
, The output from the delta-sigma modulator 2 can be set to 0 (muting state).

In the above configuration, when an input signal (input audio signal) from an input signal source (not shown) is input to the switching amplifier 1 via the input terminal 12, the input signal is subjected to delta-sigma modulation of the switching amplifier 1. The signal is converted into a 1-bit digital signal by the unit 2.

When the 1-bit signal is input to the switching circuit 3, a predetermined constant voltage pulse signal corresponding to the 1-bit signal is output from the switching circuit 3 to the LPF 4, and the pulse signal is converted into an analog signal by the LPF 4. The signal is demodulated into a signal (analog audio signal). Then, the analog signal is sonicated by a speaker or the like connected to the output terminal 13.

Next, the details of the delta-sigma modulator 2 and the switching circuit 3 will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 3 is a block diagram showing a detailed configuration of the delta-sigma modulation unit 2 and the switching circuit 3.

In practice, as shown in FIG. 3, a differential input / output mode is used. However, FIG. 2 shows a single input / output mode.

The delta-sigma modulator 2 includes a delta-sigma (ΔΣ) modulator 8, a logic circuit 9, and an attenuator 10.
And an adder 11.

The delta-sigma modulation circuit 8 sequentially integrates an input signal such as an input audio signal.
An integrator-adder group 15 comprising two cascaded high-order integrators (RC integrators), an adder for mutually adding outputs from the integrators, And a quantizer 16 that quantizes the output of 1 into a 1-bit signal. The quantizer 16 includes a comparator, a D flip-flop, etc., inputs an output from the adder to the comparator,
64 fs (2.8224 MHz) with flip-flops
Is quantized to a 1-bit signal by the clock of (1).

The logic circuit 9 is a circuit for digitally processing the output from the quantizer 16. For example, a logical product of a 1-bit signal from the delta-sigma modulation circuit 8 and a muting signal supplied from the microcomputer 7 is provided. And AND circuits 17 and 17 which take the form

Here, as shown in FIG. 1, the muting signal is a signal represented by a binary level of a high level (for example, 1) and a low level (for example, 0). Therefore, when the muting signal is supplied from the microcomputer 7 to the logic circuit 9, each A of the logic circuit 9
In the ND circuits 17 and 17, the logical product is obtained as described above. Therefore, when the muting signal is at the High level, the logic circuit 9 outputs the delta-sigma modulation circuit 8.
Is output, and when the muting signal is at the low level, the output from the logic circuit 9 is always at the low level (0). Therefore, when a low-level muting signal is supplied to the logic circuit 9, the delta-sigma modulator 2 enters a muting state.

The attenuator 10 attenuates the output (constant voltage pulse signal) from the switching circuit 3. Adder 11
Subtracts the pulse signal attenuated by the attenuator 10 from the input signal. Therefore, in the delta-sigma modulator 2, feedback control is performed so that the 1-bit signal from the quantizer 16 of the delta-sigma modulation circuit 8 corresponds to the input signal.

On the other hand, the switching circuit 3 has a plurality of switching elements for switching and outputting a constant voltage, and a drive circuit for driving each switching element in accordance with an output signal from the delta-sigma modulation section 2. ing. More specifically, the switching circuit 3 comprises four p-channel FETs (field effect transistors) 18 to 21 as semiconductor power amplifiers and one-bit signals output from the logic circuit 9 to switch the FETs 18 to 21. And a FET driver 22 for controlling the gate voltage of the FET.

The drains of the FETs 18 and 20 are connected to a power supply (not shown) that outputs a voltage of + V (for example, +32 V). The source of FET18 / 20 is FET1
Connected to the drains 9 and 21 respectively,
An output terminal to the LPF 4 and the attenuator 10. The sources of the FETs 19 and 21 are connected to -V (for example, -32
V) is connected to a power supply (not shown) that outputs a voltage of V) or is grounded.

The FET driver 22 is connected to the logic circuit 9.
The FET 18 and the FET 21 are simultaneously turned on in response to the output signal (1 or 0) from the
0 is simultaneously turned off or the FET 18 and the FET 21 are simultaneously turned off and the FET 19 and the FET 20 are simultaneously turned on. As a result, in the switching circuit 3, a constant voltage (+ V, -V or 0) according to the output signal from the logic circuit 9 is selected, and a constant voltage pulse signal is generated corresponding to the combination of the FETs. become.

Next, the operation timing when the switching amplifier 1 performs the muting operation will be described. FIG. 1 shows waveforms of voltages applied from power supplies 5a and 5b to delta-sigma modulation circuit 8 and logic circuit 9,
2 shows a waveform of a voltage applied from the power supply 7 to the switching circuit 3, a waveform of a 1-bit signal output from the delta-sigma modulation circuit 8, and a waveform of a muting signal. FIG. 4 is a flowchart showing the flow of the muting operation.

First, the microcomputer 7 sets the logic circuit 9 to L
In a state in which the muting signal of the ow level is supplied, that is, within the muting period T, the power supplies 5a and 5b of the delta-sigma modulation circuit 8 and the logic circuit 9 are started up,
A drive voltage is applied from the power supplies 5a and 5b to the delta-sigma modulation circuit 8 and the logic circuit 9 (S1).

Next, after a lapse of time t1 from the application of the driving voltage, the microcomputer 7 starts up the power supply 6 of the switching circuit 3 and applies the driving voltage to the switching circuit 3 from the power supply 6 (S2).

After a lapse of time t2 from the application of the driving voltage, the microcomputer 7 outputs the muting signal to Hig.
The level is set to the h level, and the muting state of the logic circuit 9 is released (S3).

Here, assuming that the muting period T is, for example, 500 msec, the power sources 5a and 5
For example, 200 msec can be considered as the time t1 from the rise of the voltage b to the rise of the voltage of the power supply 6 and the time t2 from the rise of the voltage of the power supply 6 to the end of the muting period. If at least 200 msec is secured as the time t1 and the time t2, the voltage can be sufficiently stabilized during the power-on period.

The times t1 and t2 are not limited to the time of 200 msec.
For example, it may be set in consideration of the muting period T so as to satisfy the following expression.

T1 + t2 <Tt1> 0, t2> 0, T> 0 In addition to performing the muting operation using the logic circuit 9 as described above, for example, the reset function of the delta-sigma modulation circuit 8 is used. Alternatively, the muting operation may be performed.

That is, the muting operation can be performed by the operation procedure according to the flowchart of FIG. In this case, first, in the reset state of the delta-sigma modulation circuit 8, that is, in the state of built-in mute, the microcomputer 7
Starts the delta-sigma modulation circuit 8 (S11).
That is, the microcomputer 7 starts up the power supply 5a and causes the delta-sigma modulation circuit 8 to apply a drive voltage from the power supply 5a. Next, the microcomputer 7 determines from FIG.
After the elapse of the time t1 shown in FIG.
Is started, and a drive voltage is applied from the power supply 6 to the switching circuit 3 (S12). Thereafter, the microcomputer 7 releases the reset state of the delta-sigma modulation circuit 8 at time t2 after the activation of the switching circuit 3 (S13).

When such an operation procedure is adopted, it is not necessary to provide the logic circuit 9 in the delta-sigma modulation unit 2, so that the configuration of the delta-sigma modulation unit 2 can be simplified.

As described above, according to the present invention, when the delta-sigma modulator 2 is in the muting state, the switching circuit 3 is activated within the muting period T. During the muting period T, the output from the delta-sigma modulation circuit 8 is always zero as shown in FIG. 1 and does not become indefinite. At the time of startup, the output from the FET driver 22 does not become unstable.

Therefore, the FET driver 22 can be operated normally, so that the FET driver 22
ON / OFF of each FET 18-21 driven by
Operation can be performed normally. As a result, it is possible to prevent an excessive current from flowing through each of the FETs 18 to 21 when the switching circuit 3 starts up, and to prevent the FETs 18 to 21 from being destroyed.

The 1-bit signal output from the delta-sigma modulation circuit 8 is voltage-amplified by the switching circuit 3,
The signal obtained by subtracting the signal attenuated by the attenuator 10 from the input signal by the adder 11 is further added to the delta-sigma modulation circuit 8.
Thus, a signal loop for performing delta-sigma modulation is formed, so that the noise shaping operation of the delta-sigma modulation circuit 8 is stabilized. Note that the above-described noise shaping operation refers to giving a differential characteristic (a characteristic in which a high frequency rises) to quantization noise. Thus, even after the muting operation is canceled, the output from the delta-sigma modulation circuit 8 does not include an excessive noise component. As a result, excellent audio performance can be secured.

In removing noise from the output signal, the clock supplied to the delta-sigma modulation circuit 8 and the LPF 4 does not need to be stopped, so that the microcomputer 7 controls the operation timing of the delta-sigma modulation unit 2 and the like. It doesn't get complicated.

For example, if the delta-sigma modulator 2 is started after the switching circuit 3 is started within the muting period T, the delta-sigma modulator 2 is operated without passing through the muting state. Become. In this case, an undefined output signal when the delta-sigma modulation unit 2 starts up may cause the FETs 18 to 21 to be destroyed due to an undefined operation of the FET driver 22, and excessive noise due to an unstable operation state may be output. Happens.

However, according to the present invention, within the muting period T of the delta-sigma modulator 2,
Then, the switching circuit 3 is started. Within the muting period T, the delta-sigma modulator 2
By operating the active circuits such as the integrator / adder group 15, the quantizer 16, and the logic circuit 9 in the processing loop of the above, the operation of the delta-sigma modulation unit 2 is performed when the switching circuit 3 starts up. Can be completed. Therefore, in the present invention in which the switching circuit 3 is started after the delta-sigma modulation section 2 is started within the muting period T, the above problem does not occur.

In the present embodiment, the delta-sigma modulator 2 is started up after a certain period of time has elapsed after the delta-sigma modulator 2 has been put into the muting state. 2 may be started at the same time (the muting period T may be started from the start of the operation of the active circuit). That is, t1 + t2 = T t1> 0, t2> 0, and T> 0.

The driving method of the switching amplifier described in the present embodiment can also be expressed as the following first to fourth driving methods of the switching amplifier.

The driving method of the first switching amplifier is as follows.
Delta-sigma modulation of an input signal, switching of a constant voltage from a power supply in response to the modulated signal, and analog conversion of the switching output by a low-pass filter and outputting the converted signal, thereby efficiently amplifying the input signal. In a switching amplifier using sigma modulation, a rise timing of a switching control signal generation section (delta sigma modulation circuit) is earlier than a rise timing of a switching circuit section for switching the constant voltage within a muting period. It is.

According to the above configuration, in the switching amplifier configured as described above, the noise shaping operation of the delta-sigma modulation circuit is stabilized when the operation is started, and the output of the delta-sigma modulation circuit is released even after the muting operation is canceled. This has the advantage that no excessive noise component is included in the semiconductor power amplifying element, and no excessive current flows through the semiconductor power amplifying element, and no noise is output when the muting operation is canceled.

The driving method of the second switching amplifier is as follows.
Delta-sigma modulation of an input signal, switching of a constant voltage from a power supply in response to the modulated signal, and analog conversion of the switching output by a low-pass filter and outputting the converted signal, thereby efficiently amplifying the input signal. In a switching amplifier using sigma modulation, a muting state is released after a constant voltage is applied for driving a switching control signal generation unit (delta sigma modulation circuit).

According to the above configuration, in the switching amplifier configured as described above, the noise shaping operation of the delta-sigma modulation circuit is stabilized at the time of starting operation, and the delta-sigma modulation circuit is released after the muting operation is canceled. The output does not include an excessive noise component, so that an excessive current does not flow through the semiconductor power amplifying element and no noise is output when the muting operation is canceled.

The driving method of the third switching amplifier is as follows.
In the first or second driving method, in the muting state, muting has a configuration in which a quantized output signal is in a low state.

According to the above configuration, in the switching amplifier configured as described above, since the clock of the delta-sigma modulation circuit is not stopped, the operation timing of the delta-sigma modulation circuit is not complicatedly controlled. The muting operation is performed, and even after the muting is released, the output of the delta-sigma modulation circuit does not include an excessive noise component. It has the advantage of not being output.

The driving method of the fourth switching amplifier is as follows.
In the first or second driving method, the muting state is a reset state of the switching control signal generation circuit.

According to the above configuration, in the switching amplifier configured as described above, since the clock of the delta-sigma modulation circuit is not stopped, the operation timing of the delta-sigma modulation circuit is not complicatedly controlled. The muting operation is performed, and the output of the delta-sigma modulation circuit does not contain an excessive noise component even after the muting is released, and an excessive current flows to the semiconductor power amplifier element, and noise is generated when the muting operation is released. It has the advantage of not being output.

Further, the driving method of the switching amplifier according to the present invention includes a delta-sigma modulation section for delta-sigma-modulating an input signal, a switching element for switching and outputting a constant voltage, and an output signal from the delta-sigma modulation section. A driving circuit for driving the switching element in response to the switching circuit, wherein the output from the switching circuit is fed back to the delta-sigma modulation unit to perform delta-sigma modulation. The delta-sigma modulation section is set to a muting state, and within the muting period, the delta-sigma modulation section is started, and then the switching circuit is started, and then the muting state is released. I can also say.

Further, the switching amplifier of the present invention comprises a delta-sigma modulator for delta-sigma-modulating an input signal;
A switching circuit having a switching element for switching a constant voltage in accordance with an output signal from the delta-sigma modulation unit, a driving circuit for driving the switching element, and a first circuit for supplying a driving voltage to the switching circuit. A switching amplifier comprising: a power supply; and control means for controlling a muting operation of the delta-sigma modulation unit; and a feedback amplifier for performing delta-sigma modulation by feeding back an output from the switching circuit to the delta-sigma modulation unit. It can be said that the means controls the operation of the first power supply so that a drive voltage is supplied to the switching circuit within a muting period of the delta-sigma modulation unit.

Further, the switching amplifier of the present invention includes a second power supply for supplying a drive voltage to the delta-sigma modulation section, and the control means supplies a drive voltage to the switching circuit by the first power supply. Before the operation, the operation of the second power supply is controlled so that the drive voltage is supplied to the delta-sigma modulation unit.

[0084]

As described above, the driving method of the switching amplifier according to the present invention has a structure in which the delta-sigma modulation section is set to the muting state and the switching circuit is started up within the muting period.

Therefore, the output from the delta-sigma modulation section is not undefined during the muting period. Therefore, even if the switching circuit is activated during the muting period, the output from the drive circuit of the switching circuit is undefined. Does not. Thus, the switching element driven by the driving circuit can operate normally. As a result, it is possible to prevent an excessive current from flowing through the switching element when the switching circuit is activated as in the related art, and to prevent the switching element from being destroyed.

When the switching circuit operates normally, the delta-sigma modulator to which the output from the switching circuit is fed back also operates normally. This stabilizes the noise shaping operation in the delta-sigma modulation unit, so that the output from the delta-sigma modulation unit does not include an excessive noise component after the elapse of the muting period.

In removing a noise component from an output signal, since the clock used for controlling the operation timing of each unit is not stopped unlike the related art, there is an effect that the control of each unit does not become complicated. Play together.

As described above, the driving method of the switching amplifier according to the present invention has a configuration in which the delta-sigma modulation section is started and then the switching circuit is started within the muting period.

Therefore, when the switching circuit starts up, the operation of the delta-sigma modulation section can be completed by the feedback of the output from the switching circuit. As a result, there is an effect that the above-described effect can be reliably obtained.

As described above, the driving method of the switching amplifier according to the present invention has a configuration in which the output signal from the delta-sigma modulator is constant in the muting state of the delta-sigma modulator.

Therefore, while the delta-sigma modulator is in the muting state, the output signal from the delta-sigma modulator is not indefinite, and the output from the drive circuit of the switching circuit does not become indefinite. Thereby, the switching element of the switching circuit can normally switch the constant voltage. As a result, there is an effect that the destruction of the switching element due to an excessive current can be reliably avoided.

As described above, the driving method of the switching amplifier according to the present invention has a configuration in which the delta-sigma modulation unit is in the reset state when the delta-sigma modulation unit is in the muting state.

Therefore, the output signal from the delta-sigma modulation section is in a constant state, and does not become unstable. Thus, there is an effect that the operation of the switching element by the drive circuit can be performed normally, and the destruction of the switching element can be reliably avoided.

As described above, the switching amplifier according to the present invention is configured such that the control means sets the delta-sigma modulation section in a muting state, and activates the switching circuit within the muting period.

Therefore, during the muting period, the output from the delta-sigma modulation section does not become indefinite. Therefore, even if the control means starts up the switching circuit within the muting period, the output from the driving circuit of the switching circuit is not changed. Output is not undefined. Thus, the switching element driven by the driving circuit can operate normally. As a result, it is possible to prevent an excessive current from flowing through the switching element when the switching circuit is activated as in the related art, and to prevent the switching element from being destroyed.

Further, by the normal operation of the switching circuit, the delta-sigma modulation section to which the output from the switching circuit is fed back also operates normally. This stabilizes the noise shaping operation in the delta-sigma modulation unit, so that the output from the delta-sigma modulation unit does not include an excessive noise component after the elapse of the muting period.

In removing noise components from the output signal, since the clock used for controlling the operation timing of each unit is not stopped unlike the related art, there is an effect that the control of each unit does not become complicated. Play together.

As described above, the switching amplifier according to the present invention has a configuration in which the control means starts up the delta-sigma modulation section and then starts up the switching circuit within the muting period.

Therefore, when the switching circuit starts up, the operation of the delta-sigma modulation section can be completed by feedback of the output from the switching circuit. As a result, there is an effect that the above-described effect can be reliably obtained.

[Brief description of the drawings]

FIG. 1 shows a waveform of a power supply voltage applied to a delta-sigma modulation circuit and a logic circuit of a switching amplifier according to the present invention, and a waveform of a power supply voltage applied to a switching circuit.
FIG. 4 is a waveform diagram showing an output waveform from a delta-sigma modulation circuit and a waveform of a muting signal.

FIG. 2 is a block diagram showing a schematic configuration of the switching amplifier.

FIG. 3 is a block diagram showing a detailed configuration of a delta-sigma modulator, a logic circuit, and a switching circuit of the switching amplifier.

FIG. 4 is a flowchart showing an example of a flow of a muting operation in the switching amplifier.

FIG. 5 is a flowchart showing another example of the flow of the muting operation in the switching amplifier.

FIG. 6 is a block diagram showing a schematic configuration of a conventional switching amplifier.

FIG. 7 is a block diagram showing a detailed configuration of a switching circuit in the switching amplifier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Switching amplifier 2 Delta-sigma modulation part 3 Switching circuit 7 Microcomputer (control means) 18-21 FET (switching element) 22 FET driver (drive circuit)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J064 AA01 BA03 BB02 BB07 BC03 BC11 BC19 BC25 BD03 5J091 AA02 AA26 AA66 CA48 CA57 CA92 FA00 GP02 HA09 KA00 KA23 KA26 KA31 KA33 KA42 KA48 KA53 MA11 SA05 A09 TA06 A07 TA06 A07 CA57 CA92 FA00 FR05 FR07 HA09 KA00 KA23 KA26 KA31 KA33 KA42 KA48 KA53 MA11 SA05 TA01 TA06 TA07

Claims (6)

[Claims] 1. A delta-sigma modulator for delta-sigma-modulating an input signal, a switching element for switching and outputting a constant voltage, and a driving element for driving the switching element according to an output signal from the delta-sigma modulator. And a switching circuit having a driving circuit, wherein the output from the switching circuit is fed back to the delta sigma modulation unit to perform delta sigma modulation, wherein the delta sigma modulation unit is in a muting state. And driving the switching circuit during the muting period. 2. The driving method of a switching amplifier according to claim 1, wherein said switching circuit is started after said delta-sigma modulation section is started within said muting period. 3. An output signal from the delta-sigma modulation section is constant in the muting state of the delta-sigma modulation section.
3. The method for driving a switching amplifier according to claim 1. 4. The method according to claim 1, wherein the delta-sigma modulator is in a reset state in the muting state of the delta-sigma modulator. 5. A delta-sigma modulation section for performing delta-sigma modulation on an input signal, a switching element for switching and outputting a constant voltage, and a driving element for driving the switching element in accordance with an output signal from the delta-sigma modulation section. A switching circuit having a drive circuit, and control means for controlling the operations of the delta-sigma modulation unit and the switching circuit, and controlling a muting operation of the delta-sigma modulation unit, and comprising an output from the switching circuit. A switching amplifier that performs delta-sigma modulation by feeding back to the delta-sigma modulation unit, wherein the control unit sets the delta-sigma modulation unit in a muting state, and activates the switching circuit within the muting period. A switching amplifier characterized in that: 6. The control circuit according to claim 5, wherein the control circuit starts up the switching circuit after starting up the delta-sigma modulation section within the muting period.
3. The switching amplifier according to claim 1.