JP4529390B2 - Switching amplifier and its correction control circuit and method - Google Patents

Description

  The present invention relates to a switching amplifier such as a so-called class D amplifier, PWM amplifier, or 1-bit ΔΣ amplifier, and a correction control circuit and method thereof.

  As a signal amplifier, a switching amplifier such as a so-called class D amplifier, a PWM amplifier, or a 1-bit ΔΣ amplifier has been proposed. Switching amplifiers are widely studied to be applied as audio amplifiers because the maximum level of an output signal can be increased to a power supply voltage without distortion and has high power efficiency.

  However, the switching amplifier has a problem that its ability to eliminate the influence of the fluctuation of the power supply voltage called the power supply rejection ratio (PSRR) is very small. That is, the switching amplifier has a problem that the fluctuation of the power supply voltage directly affects the output voltage.

  In order to solve such a problem, there has been proposed a power supply voltage fluctuation suppression circuit for a PWM amplifier that increases or decreases an input signal according to the fluctuation amount of the power supply voltage and corrects the fluctuation of the power supply voltage with positive feedback (for example, a patent) Reference 1 and Patent Document 2). If the power supply voltage fluctuation suppression circuit proposed in Patent Document 1 and Patent Document 2 is used, the power supply rejection ratio of the switching amplifier can be improved.

JP 9-33374 A

JP-A-61-39708

Such a switching amplifier is supplied with a power supply voltage (V _cc ) from an external power supply device in order to supply a bias voltage.

  However, the output impedance of the power supply device fluctuates due to changes over time, temperature changes, AC power supply status changes, and the like, and the power supply fluctuation detection circuit (for example, patent) of the power supply voltage fluctuation suppression circuit shown in Patent Document 1 and Patent Document 2 This affects the detection output of the voltage dividing circuit of Document 1 and the level adjustment circuit of Patent Document 2. If the detection output of the power supply fluctuation fluctuates due to the output impedance of the power supply device, the positive feedback amount given to the input signal fluctuates and the output signal becomes unstable. Specifically, when the output impedance of the power supply becomes large, a positive feedback amount larger than the originally assumed positive feedback amount is given to the input signal, the amplifier oscillates, and the output signal becomes the power supply voltage. It sticks. On the other hand, when the output impedance of the power supply becomes small, a positive feedback amount smaller than the originally assumed positive feedback amount is given to the input signal, and the effect of removing the power supply fluctuation is reduced.

  In order to solve the conventional problems as described above, the present invention suppresses fluctuations in the output signal due to fluctuations in the power supply, and stably suppresses output fluctuations even if there are fluctuations in the output impedance of the power supply. It is an object of the present invention to provide a switching amplifier and its correction control circuit and method.

A switching amplifier according to the present invention is connected in series between a power supply input terminal connected to a power supply and a ground, and includes a first voltage dividing resistor and a second voltage dividing voltage for dividing the power supply voltage of the power supply. A connection point between the first voltage dividing resistor and the second voltage dividing resistor of the power supply voltage of the power source divided by the resistor, the first voltage dividing resistor, and the second voltage dividing resistor. Generates a correction signal for correcting the input signal input from the signal input terminal by attenuating the partial pressure value based on the attenuation ratio for attenuating the partial pressure value, and outputs the generated correction signal An attenuating means that subtracts the correction signal output from the attenuating means from the input signal input from the signal input terminal, and outputs a corrected input signal obtained by subtraction, and the correcting means Output corrected input Switching the power supply voltage of the power supply according to the signal, amplifying the corrected input signal, and outputting the amplified corrected input signal to the outside from the signal output terminal; and the power input terminal When the on / off switch is connected and connected between the power input terminal and the on / off switch, and the on / off switch is switched to the on state, the maximum current consumption is output from the power source. The on / off switch is turned on at the start of operation when the signal amplifying means starts operating or when the amplifying operation of the signal amplifying means is stopped. Switch to the ON state, output the maximum current consumption from the power supply to the load resistor, and detect the power supply voltage when the maximum current consumption is output from the power supply to the load resistor. A power supply voltage detecting means; a power supply voltage when the maximum current consumption detected by the power supply voltage detecting means is output; a power supply voltage when the on / off switch is switched off; Output impedance calculation means for calculating the output impedance of the power source based on the set resistance value of the load resistance, and attenuation ratio calculation for calculating the attenuation ratio based on the output impedance calculated by the output impedance calculation means And an attenuation ratio output means for outputting the attenuation ratio calculated by the attenuation ratio calculation means to the attenuation means .

The correction control circuit for a switching amplifier according to the present invention is a switching amplifier that outputs a signal obtained by amplifying the input signal by switching the power supply voltage output from the power supply in accordance with the input signal input from the signal input terminal. On the other hand, in a correction control circuit for performing correction control, a first voltage dividing resistor and a first voltage divider connected in series between a power input terminal connected to a power source and a ground, and for dividing the power source voltage of the power source. The voltage dividing value at the connection point between the first voltage dividing resistor and the second voltage dividing resistor, divided by the voltage dividing resistor of 2, is based on the attenuation ratio for attenuating the voltage dividing value. Attenuating means for generating a correction signal for correcting the input signal input from the signal input terminal by attenuating, and outputting the generated correction signal; and input from the signal input terminal A correction means that subtracts the correction signal output from the attenuation means from the input signal and outputs a corrected input signal obtained by subtraction, and at the start of operation when the switching amplifier starts operation, or When the amplification operation of the switching amplifier is stopped, when the operation is stopped, the on / off switch connected to the power input terminal for inputting current from the power supply is turned on so that the power input terminal and the on / off switch are turned on. Connected to an off switch, and when the on / off switch is switched to the on state, the maximum current consumption is output from the power source to the load resistor whose resistance value is set so that the maximum current consumption is output from the power source. A power supply voltage detecting means for detecting a power supply voltage when outputting a current and outputting a maximum current consumption from the power supply to the load resistor; and the power supply voltage detecting means Based on the power supply voltage when the maximum current consumption is output, the power supply voltage when the on / off switch is turned off, and the resistance value of the preset load resistance The output impedance calculating means for calculating the output impedance of the power source, the attenuation ratio calculating means for calculating the attenuation ratio based on the output impedance calculated by the output impedance calculating means, and the attenuation ratio calculating means Attenuation ratio output means for outputting the attenuation ratio to the attenuation means .

The switching amplifier correction control method according to the present invention switches a power supply voltage output from a power supply in accordance with an input signal input from a signal input terminal, and outputs a signal obtained by amplifying the input signal. In contrast, in a correction control method for performing correction control, a first voltage dividing resistor and a first voltage divider connected in series between a power supply input terminal connected to a power supply and a ground, and for dividing the power supply voltage of the power supply. The voltage dividing value at the connection point between the first voltage dividing resistor and the second voltage dividing resistor, divided by the voltage dividing resistor of 2, is based on the attenuation ratio for attenuating the voltage dividing value. An attenuation step for generating a correction signal for correcting the input signal input from the signal input terminal by attenuation, and the input signal input from the signal input terminal A correction step for subtracting the correction signal generated in the decay step to obtain a corrected input signal, and an operation at the start of operation when the operation of the switching amplifier is started, or an operation where the amplification operation of the switching amplifier is stopped At the time of stop, the on / off switch connected to the power input terminal for inputting current from the power source is switched to the on state, and the on / off switch is connected between the power input terminal and the on / off switch. When the off switch is switched to the on state, the maximum current consumption is output from the power source to the load resistance whose resistance value is set so that the maximum current consumption is output from the power source. A power supply voltage detection step for detecting the power supply voltage when the maximum current consumption is output, and the maximum current consumption detected in the power supply voltage detection step are output. The output impedance of the power supply is calculated based on the power supply voltage when the on / off switch is switched off and the resistance value of the preset load resistance. Based on the output impedance calculation step, the output impedance calculated in the output impedance calculation step, the attenuation ratio calculation step for calculating the attenuation ratio, and the attenuation ratio calculated in the attenuation ratio calculation step are executed in the attenuation step. An attenuation rate setting step for setting an attenuation rate for attenuating the partial pressure value .

  In the switching amplifier and its correction control circuit and method according to the present invention described above, a correction signal whose level changes in accordance with fluctuations in the power supply voltage is generated, the input signal of the amplifier is corrected in accordance with the correction signal, and the power supply The gain of the correction signal is adjusted according to the output impedance.

  In the switching amplifier and the correction control circuit and method according to the present invention, a correction signal whose level changes in accordance with fluctuations in the power supply voltage is generated, the input signal of the amplifier is corrected in accordance with the correction signal, and the output of the power supply The gain of the correction signal is adjusted according to the impedance.

  For this reason, in the present invention, fluctuations in the output signal accompanying fluctuations in the power supply can be suppressed by positive feedback. Furthermore, in the present invention, even if there is a fluctuation in the output impedance of the power supply, the positive feedback amount is optimally adjusted according to the fluctuation, so that the output signal does not oscillate or the effect of the output fluctuation is lost. Output fluctuation suppression can be performed stably.

  Hereinafter, a switching amplifier to which the present invention is applied will be described as an embodiment of the present invention.

FIG. 1 shows a circuit configuration diagram of a switching amplifier 10 according to an embodiment of the present invention. Switching amplifier 10, the input signal V _in is input, the signal level of the input signal V _in is amplified to A times, a circuit for outputting an output signal V _out obtained by amplification. In addition, A which shows an amplification factor is an integer.

  As shown in FIG. 1, the switching amplifier 10 includes a signal input terminal 11, a signal output terminal 12, and a power input terminal 13.

The signal input terminal 11 is input the input signal _{V in} is, from the signal output terminal 12 an output signal _{V out} is output. Further, a stabilized DC power supply voltage _Vcc is supplied to the power input terminal 13 from the external power supply device 1. The power supply voltage _Vcc is supplied as a power supply voltage for each circuit in the switching amplifier 10.

The switching amplifier 10 includes a first and second voltage dividing resistors 14 and 15 divide the power supply voltage _{V cc,} the power supply voltage _{V cc} of the attenuator 16 for attenuating the voltage dividing value _{V r} attenuation ratio a , a correction circuit 17 which subtracts the correction signal aV _r from the input signal _{V in} input from the input terminal 11, D-class amplification corrected input signal a _(V in -av _r) amplified to a times by the correction circuit 17 And a circuit 18.

The first voltage dividing resistor 14 and the second voltage dividing resistor 15 are connected in series between the power input terminal 13 and the ground. From a connection point between the first voltage dividing resistor 14 and the second voltage dividing resistor 15, a divided value V _{r obtained by} dividing the power supply voltage V _cc with a predetermined voltage dividing ratio is detected. Note that the resistance value of the first voltage dividing resistor 14 is R ₁ , the resistance value R _{2 of the second} voltage dividing resistor 15, and the first voltage dividing resistor 14 is connected to the power source side, Assuming that the voltage dividing resistor 15 is connected to the ground side, the divided value V _r is V _r = V _cc × R ₂ / (R ₁ + R ₂ ).

Attenuator 16 attenuates the voltage dividing value V _r attenuation ratio a. The signal output from the attenuator 16 is supplied to the correction circuit 17 as a correction signal aV _r. Note that the attenuation rate a here is a coefficient to be multiplied by the divided voltage value V _r, is typically a value between 0 and 1. However, depending on the division ratio of the partial pressure value V _r, its value may be made with one or more. That is, the attenuation ratio a is equivalent to the gain to be multiplied to the partial pressure value V _r. Further, the attenuation ratio a of the attenuator 16 can be changed, and the value is controlled by the controller 26 described later. Details of the control of the attenuation ratio a will be described later.

Correction circuit 17, an input signal _{V in} input from the input terminal 11, and a correction signal aV _r is input. Correction circuit 17 subtracts the correction signal aV _r from the input signal _{V in,} to produce a subtraction signal _(V in _{-aV r).} The subtraction signal (V _in −aV _r ) is supplied to the class D amplifier circuit 18.

  The class D amplifier circuit 18 is a switching type amplifier circuit that amplifies an input signal by A times. Specifically, FIG. 2 shows a circuit configuration example of the class D amplifier circuit 18.

Class D amplifier circuit 18, as shown in FIG. 2, a modulation circuit 21 for modulating an input signal, a switching circuit 22 for switching the power supply voltage V _cc in response to the modulated signal outputted from the modulation circuit 21, a switching circuit And a low-pass filter 23 that performs low-pass filtering on the switched power supply voltage signal output from 22.

  The modulation circuit 21 modulates the input signal by a modulation method in which the ON time of the 1-bit signal is adjusted according to the input level X. Specifically, the input signal is modulated such that its integrated output corresponds to the signal level X of the input signal, such as PWM (Pulse Width Modulation) or ΔΣ modulation. Here, the signal level X of the input signal is an analog value, but a serial or parallel digital value may be input as the signal level X of the input signal.

The switching circuit 22 by turning on / off the power supply voltage V _cc in synchronization with the modulation signal of 1 bit outputted from the modulation circuit 21 switches the power supply voltage V _cc. The switching circuit 22 outputs the switching-controlled power supply voltage _Vcc to the outside.

The low-pass filter 23 performs a low-pass filtering process on the switched power supply voltage V _cc output from the switching circuit 22. The cut-off frequency of the low-pass filter 23 is set to a value sufficiently lower than the switching frequency of the power supply voltage _Vcc (that is, the frequency of the 1-bit modulation signal). Therefore, the level of the signal output from the low-pass filter 23 has a level obtained by multiplying the time-averaged duty ratio in a direction to the supply voltage V _cc.

Thus, the class D amplifier circuit 18 is an amplifier whose amplification factor is determined by the modulation of the modulation circuit 21 and the level of the power supply voltage _Vcc . In the class D amplifier circuit 18 of this example, the modulation formula of the modulation circuit 21 is set to an amplification factor A, assuming that the power supply voltage _Vcc is constant at a predetermined rated value.

In the switching amplifier 10 embodiment of the present invention as described above, the subtraction signal obtained by subtracting the correction signal aV _r from the input signal _{V in (V in -aV r)} is input to the class D amplifier circuit 18. The class D amplifier circuit 18 amplifies the subtraction signal (V _in −aV _r ) A times. The correction signal aV _r is divide the power supply voltage V _cc min, the attenuated signal at the partial pressure value V _r attenuation ratio a.

Therefore, if the power supply voltage V _cc is changed, the correction signal aV _r the fluctuation component is reflected in the control amount corresponding to the fluctuation component is amplified is removed from the input signal V _in. Therefore, in the switching amplifier 10 according to the embodiment of the present invention, even if the power supply voltage V _cc fluctuates, the amplification factor A of the switching amplifier 10 is not affected, and fluctuations in the output signal due to power fluctuations are suppressed. The

  Next, a control mechanism of the attenuation ratio a of the attenuator 16 will be described.

  In order to control the attenuation ratio a of the attenuator 16, the switching amplifier 10 further includes a load resistor 24 and an on / off switch 25 for detecting the output impedance of the power supply device 1, and a controller. 26.

The load resistor 24 and the on / off switch 25 are connected in series and provided between the power input terminal 13 and the ground. When the load resistor 24 is connected to the power supply device 1 as a load, a resistance value _RL is set such that a maximum current on the specifications of the power supply device 1 flows. The on / off switch 25 is normally turned off (for example, when the signal is amplified or when the power is turned off), and is turned on in accordance with control from the controller 26.

For example, when the operation of the switching amplifier 10 is started or when the amplification operation is stopped, the controller 26 temporarily turns on the on / off switch 25 and outputs the maximum current consumption from the power supply device 1. . The controller 26 has a voltage detection function for detecting the voltage value of the power input terminal 13, and detects the power supply voltage β when the maximum current consumption is output from the power supply device 1 by the voltage detection function. Then, the controller 26 calculates the output impedance of the power supply device 1 based on the power supply voltage β when the maximum current consumption is output, the power supply voltage V _cc when the current consumption is 0, and the resistance value _RL of the load resistor 24. To do.

  The controller 26 calculates the attenuation ratio a based on the calculated output impedance. The calculation method of the attenuation ratio a is performed by, for example, a method of referring to an internal table in which a correspondence relationship between the output impedance and the attenuation ratio a is described, or a method using a function indicating the relationship between the output impedance and the attenuation ratio a. . Then, the controller 26 sets the calculated attenuation ratio a in the attenuator 16.

Attenuation ratio a is, the correction signal aV _r is not Shimawa stuck to become large excessively with class D amplifier circuit 18 oscillates and outputs a signal supply voltage, and removal of the correction signal aV _r becomes too small power fluctuation An optimal value is set according to each output impedance value of the power supply device 1 so as not to reduce the effect. Specifically, the attenuation ratio a to the output impedance of the power supply unit 1, the correction signal aV _r becomes large when the output impedance is large, the correction signal aV _r becomes small when the output impedance is reduced Is given by a simple increase function.

As described above, in the switching amplifier 10 of the embodiment of the present invention, the level generates a correction signal aV _r that varies depending on the variation of the power supply voltage V _cc, the corrected input signal of the class D amplifier circuit 18 It is corrected in response to the signal aV _r, and adjust the level of the correction signal aV _r in accordance with the output impedance of the power supply device 1.

For this reason, in the switching amplifier 10 according to the embodiment of the present invention, fluctuations in the output signal _Vout accompanying fluctuations in the power supply voltage _Vcc can be suppressed. That is, the amplification factor can be kept constant even if the power supply voltage _Vcc of the power supply device 1 varies. Furthermore, in the switching amplifier 10 according to the embodiment of the present invention, even if the output impedance of the power supply device 1 varies, the control amount is optimally adjusted according to the variation, so that the output signal _Vout oscillates, The effect of suppressing fluctuations in power supply voltage is no longer lost.

Since the correction signal aV _r reflects how much the power supply voltage V _cc varies from a predetermined voltage value, or simply reflects the differential amount of the power supply voltage V _cc , The generation method is not limited to a signal generated by dividing the power supply voltage _Vcc as in this example.

  Further, the circuit for detecting the output impedance of the power supply device 1 is not limited to the load resistor 24 and the on / off switch 25 connected in series between the power supply and the ground.

For example, a circuit for detecting the output impedance of the power supply device 1 includes a detection resistor 31 having a very low resistance value _RD provided on the power supply line and a voltage drop across the detection resistor 31 as shown in FIG. A circuit provided with a drop voltage detector 32 for detection may be used. In this case, the controller 32 calculates the current amount I output from the power supply apparatus 1 based on the voltage drop amount by the drop voltage detector 32 and the resistance value _RD of the detection resistor 31, and calculates the calculated current amount I. And the output voltage of the power supply device 1 are calculated based on the detected voltage β of the power input terminal 13. As described above, when the current amount I output from the power supply device 1 is directly detected from the power supply line, the attenuation ratio a of the attenuator 16 can be controlled during the signal amplification process. For this reason, it is possible to perform fine control according to the constantly changing situation.

It is a block block diagram of the switching type amplifier of embodiment of this invention. It is a block block diagram of the class D amplifier circuit in the said switching type amplifier. It is a block block diagram which shows the modification of the switching type amplifier of embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Power supply device, 10 Switching type amplifier, 11 Signal input terminal, 12 Signal output terminal, 13 Power supply input terminal, 14 1st voltage dividing resistor, 15 2nd voltage dividing resistor, 16 Attenuator, 17 Correction circuit, 18 D Class amplifier circuit, 24 load resistance, 25 on / off switch, 26 controller

Claims (3)

A first voltage dividing resistor and a second voltage dividing resistor connected in series between a power input terminal connected to the power source and the ground, and for dividing the power source voltage of the power source;
A divided voltage value at a connection point between the first voltage dividing resistor and the second voltage dividing resistor of the power supply voltage of the power source divided by the first voltage dividing resistor and the second voltage dividing resistor. Attenuating means for generating a correction signal for correcting the input signal input from the signal input terminal by attenuating the signal based on the attenuation ratio for attenuating the partial pressure value, and outputting the generated correction signal When,
Correction means for subtracting the correction signal output from the attenuation means from the input signal input from the signal input terminal, and outputting a corrected input signal obtained by subtraction;
The power supply voltage of the power supply is switched according to the corrected input signal output from the correction means, thereby amplifying the corrected input signal and outputting the amplified corrected input signal to the outside from the signal output terminal. Signal amplification means;
An on / off switch connected to the power input terminal;
Connected between the power input terminal and the on / off switch, and when the on / off switch is turned on, the resistance value is set so that the maximum current consumption is output from the power source. Load resistance,
At the start of operation when the signal amplifying means starts operating or when the amplification operation of the signal amplifying means is stopped, the on / off switch is turned on to switch the power source to the load resistance. A power supply voltage detecting means for detecting a power supply voltage when outputting the maximum current consumption and outputting the maximum current consumption from the power supply to the load resistor;
The power supply voltage when the maximum current consumption detected by the power supply voltage detection means is output, the power supply voltage when the on / off switch is switched off, and the preset load resistance. Output impedance calculating means for calculating the output impedance of the power source based on the resistance value;
Attenuation rate calculating means for calculating the attenuation rate based on the output impedance calculated by the output impedance calculating means,
Attenuation ratio output means for outputting the attenuation ratio calculated by the attenuation ratio calculation means to the attenuation means;
A switching amplifier . In a correction control circuit that performs correction control on a switching amplifier that outputs a signal obtained by amplifying the input signal by switching the power supply voltage output from the power supply according to the input signal input from the signal input terminal .
The first input is connected in series between a power supply input terminal connected to the power supply and the ground, and is divided by a first voltage dividing resistor and a second voltage dividing resistor for dividing the power supply voltage of the power supply. Input from the signal input terminal by attenuating the divided voltage value at the connection point of the first divided voltage resistor and the second divided voltage resistor based on the attenuation ratio for attenuating the divided voltage value Attenuating means for generating a correction signal for correcting the input signal and outputting the generated correction signal;
Correction means for subtracting the correction signal output from the attenuation means from the input signal input from the signal input terminal, and outputting a corrected input signal obtained by subtraction;
An on / off switch connected to a power supply input terminal for inputting current from the power supply when the switching amplifier starts operation or when the amplification operation of the switching amplifier is stopped Is turned on and connected between the power supply input terminal and the on / off switch, and when the on / off switch is turned on, the maximum current consumption is output from the power supply. A power supply voltage detection means for detecting a power supply voltage when a maximum resistance current is output from the power supply to a load resistance having a resistance value set to the power supply, and a maximum current consumption is output from the power supply to the load resistance;
The power supply voltage when the maximum current consumption detected by the power supply voltage detection means is output, the power supply voltage when the on / off switch is switched off, and the preset load resistance. Output impedance calculating means for calculating the output impedance of the power source based on the resistance value;
Attenuation rate calculating means for calculating the attenuation rate based on the output impedance calculated by the output impedance calculating means,
Attenuation ratio output means for outputting the attenuation ratio calculated by the attenuation ratio calculation means to the attenuation means;
A correction control circuit for a switching amplifier comprising: In a correction control method for performing correction control on a switching amplifier that outputs a signal obtained by amplifying the input signal by switching the power supply voltage output from the power supply according to the input signal input from the signal input terminal .
The first input is connected in series between a power supply input terminal connected to the power supply and the ground, and is divided by a first voltage dividing resistor and a second voltage dividing resistor for dividing the power supply voltage of the power supply. Input from the signal input terminal by attenuating the divided voltage value at the connection point of the first divided voltage resistor and the second divided voltage resistor based on the attenuation ratio for attenuating the divided voltage value An attenuation step for generating a correction signal for correcting the input signal;
A correction step for obtaining a corrected input signal by subtracting the correction signal generated in the attenuation step from the input signal input from the signal input terminal;
On / off connected to a power supply input terminal for inputting current from the power supply when the operation of the switching amplifier is started or when the amplification operation of the switching amplifier is stopped The switch is turned on and connected between the power input terminal and the on / off switch. When the on / off switch is turned on, the maximum current consumption is output from the power supply. A power supply voltage detection step for detecting a power supply voltage when a maximum resistance current is output from the power supply to the load resistance having a resistance value set as described above, and a maximum current consumption is output from the power supply to the load resistance;
The power supply voltage when the maximum current consumption detected in the power supply voltage detection step is output, the power supply voltage when the on / off switch is turned off, and the preset load resistance. An output impedance calculating step for calculating the output impedance of the power source based on the resistance value;
An attenuation ratio calculating step for calculating the attenuation ratio based on the output impedance calculated in the output impedance calculating step;
An attenuation ratio setting step for setting the attenuation ratio calculated in the attenuation ratio calculation step as an attenuation ratio for attenuating the partial pressure value executed in the attenuation step;
A correction control method for a switching amplifier including:

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