CN101989836B - Efficient audio amplifier and related method thereof - Google Patents

Efficient audio amplifier and related method thereof Download PDF

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CN101989836B
CN101989836B CN2009101624266A CN200910162426A CN101989836B CN 101989836 B CN101989836 B CN 101989836B CN 2009101624266 A CN2009101624266 A CN 2009101624266A CN 200910162426 A CN200910162426 A CN 200910162426A CN 101989836 B CN101989836 B CN 101989836B
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signal
frequency
reference voltage
input
input audio
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CN101989836A (en
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陈以尚
许君豪
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Wistron Corp
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Wistron Corp
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Abstract

The invention relates to an efficient audio amplifier and a related method thereof. The efficient audio amplifier comprises an input end, a signal generator, a waveform converter, a pre-drive circuit, an output stage and a filter, wherein the input end is used for receiving an input audio signal; the signal generator is coupled with the input end and used for determining the frequency of an oscillating signal according to the distribution condition of the input audio signal and a reference voltage and generating the oscillating signal of the corresponding frequency; the waveform converter is coupled with the input end and the signal generator and used for comparing the input audio signal with the oscillating signal to generate an impulse modulation signal; the pre-drive circuit is used for generating a pre-drive signal according to the impulse modulation signal; the output stage is coupled with the pre-drive circuit and used for generating an output signal according to the pre-drive signal; and the filter is used for filtering the output signal to generate an output audio signal to an output end. The audio amplifier can effectively improve the condition of poor amplification efficiency in low output power.

Description

Audio Frequency Amplifer and correlation technique thereof
Technical field
The present invention relates to a kind of Audio Frequency Amplifer and correlation technique thereof, relate in particular to a kind of audio frequency amplifier and correlation technique thereof that promotes efficient by the adjustment frequency of oscillation.
Background technology
Power amplifier mainly is used for the power of amplifying signal, in general, can be divided into A, B, AB, C and D class according to employed output stage.Wherein, Use the D genus audio power amplifier (class-D audio power amplifier) of switch output stage because volume is little, efficient is high and advantage such as power saving; Therefore extensively applied in the various consumption electronic products, for example notebook computer, LCD screen, mobile phone, multimedia playing apparatus etc.
Please refer to Figure 1A, Figure 1A is the sketch map of a known D class audio amplifier 10.D class audio amplifier 10 includes an input 102, a reference signal end 104, a comparator 106, a grid drive circuit 108, an output stage 110, a filter 112 and a loud speaker 114.Input 102 is used for receiving an audio input signal S IN Reference signal end 104 is used for receiving a triangular wave reference signal S TComparator 106 is used for audio input signal S INTriangular wave reference signal S with fixed frequency TDo comparison operation, to produce a pulse width modulating signal S P, and with pulse width modulating signal S PBe sent to grid drive circuit 108.Grid drive circuit 108 is according to pulse width modulating signal S P, produce a grid drive signal S G,, and then make output stage 110 export signal S with the switch of driving output stage 110 APAgain via 112 pairs of output of filter signal S APProduce an audio output signal S after the filtering O, and it is sent to loud speaker 114 output.
Yet, on practice, please refer to Figure 1B, Figure 1B is the operating efficiency sketch map of D class audio amplifier 10.D class audio amplifier 10 is compared to the audio frequency amplifier of other types, when higher output power, amplifies efficient and can reach more than 90%, has goodish amplification efficient performance.But under the situation of low power output, D class audio amplifier 10 but can't effectively obtain preferable efficient performance.Therefore, during to low power output, how to promote the amplification efficient performance of audio frequency amplifier, real in problem to be solved is arranged.
Summary of the invention
Therefore, main purpose of the present invention promptly is to provide a kind of Audio Frequency Amplifer and correlation technique thereof.
The present invention discloses a kind of Audio Frequency Amplifer, includes: an input is used for receiving an input audio signal; One output is used for exporting an output audio signal; One signal generator is coupled to this input, is used for a distribution situation and a reference voltage according to this input audio signal, determines the frequency of an oscillator signal, and produces this oscillator signal of corresponding frequency according to this; One waver is coupled to this input and this signal generator, is used for relatively this input audio signal and this oscillator signal, to produce a pulse-modulated signal (PWM signal); One predrive circuit is coupled to this waver, is used for producing a pre-drive signal according to this pulse-modulated signal; One output stage is coupled to this predrive circuit, is used for according to this pre-drive signal, produces an output signal; And a filter, be coupled to this output stage, be used for this output signal is carried out filtering, to produce this output audio signal to this output.
The present invention also discloses a kind of method of lifting one audio frequency amplifier efficient, includes a distribution situation and a reference voltage according to an input audio signal, determines the frequency of an oscillator signal, and produces this oscillator signal of corresponding frequency according to this; Relatively this input audio signal and this oscillator signal are to produce a pulse-modulated signal; According to this pulse-modulated signal, produce a pre-drive signal; According to this pre-drive signal, produce an output signal; And this output signal carried out filtering, to produce this output audio signal.
The present invention is the characteristics of signals according to input audio signal, flexibly adjusts the frequency of oscillator signal, with the loss power of minimizing audio frequency amplifier, and then the amplification efficient of lifting audio frequency amplifier.Thus, the audio frequency amplifier of the embodiment of the invention can effectively improve and when hanging down power output, amplify the not good situation of efficient.
Description of drawings
Figure 1A is the sketch map of a known D class audio amplifier.
Figure 1B is the operating efficiency sketch map of a known D class audio amplifier.
Fig. 2 is the sketch map of an audio frequency amplifier of the embodiment of the invention.
Fig. 3 is the sketch map of signal generator among Fig. 2.
Fig. 4 is the sketch map of an audio frequency amplifier of the tool dual track output of the embodiment of the invention.
Fig. 5 is the sketch map of the embodiment of the invention one flow process.
The primary clustering symbol description:
The 10D class audio amplifier
102,202,402 inputs
104 reference signal ends
106 comparators
108 grid drive circuits
110,210,414,416 output stages
112,212,418,420 filters
114,216,424 loud speakers
20,40 audio frequency amplifiers
204,404 signal generators
206,406,408 wavers
208,410,412 predrive circuits
214,422 outputs
302,426 decision circuitry
304,428 waveform generators
306,430 testing circuits
308,432 select circuit
434 first comparators
436 second comparators
438 or the door
50 flow processs
500、502、504、506、
508,510,512 steps
L 1, L 2Inductance
C 1, C 2Electric capacity
S AP, S AP1, S AP2The output signal
S G, S G1, S G2The grid drive signal
S INAudio input signal
S O, S O1, S O2Output audio signal
S P, S P1, S P2Pulse width modulating signal/pulse-modulated signal
S ROscillator signal
S TThe triangular wave reference signal
V RefReference voltage
S CControl signal
S DDetection signal
Embodiment
Please refer to Fig. 2, Fig. 2 is the sketch map of an audio frequency amplifier 20 of the embodiment of the invention.Audio frequency amplifier 20 comprises an input 202, a signal generator 204, a waver 206, a predrive circuit 208, an output stage 210, a filter 212, an output 214 and a loud speaker 216.Input 202 is used for receiving an input audio signal S INSignal generator 204 is coupled to input 202, is used for according to input audio signal S INA distribution situation and a reference voltage V Ref, determine an oscillator signal S RFrequency, and produce the oscillator signal S of corresponding frequency according to this RWaver 206 is coupled to input 202 and signal generator 204, is used for comparison input audio signal S INWith oscillator signal S R, to produce a pulse-modulated signal S PPredrive circuit 208 is coupled to waver 206, is used for according to pulse-modulated signal S P, produce a pre-drive signal S GOutput stage 201 is coupled to predrive circuit 208, is used for according to pre-drive signal S G, produce an output signal S APFilter 212 is coupled to output stage 210, is used for to output signal S APCarry out filtering, to produce an output audio signal S O, and pass through output 214 with output audio signal S OBe sent to loud speaker 216 outputs.In other words, signal generator 204 can be according to input audio signal S INSize, adjustment oscillator signal S RFrequency, and then promote the amplification efficient performance of audio frequency amplifier 20.
In general, performance of the efficient of amplifier and loss power P LossBe inversely proportional to loss power P LossUsually comprise 3 parts, be respectively the transistorized switch cost P in the amplifier Sw, transistorized conducting loss P CondAnd the loss P of parasitic capacitance Gd, loss power P wherein LossFor:
P loss = P sw + P cond + P gd
= ( C oss * V BUS 2 * f pwm + I D * t f * f pwm ) P sw + ( R DS R L * P o ) P cond + ( 2 * Q g * V gs * f pwm ) p gd - - - ( 1 )
C wherein OssBe transistorized output capacitance value, V BUSBe transistorized supply voltage, I DBe conducting electric current, t fBe the rise and fall time of pulse signal, f PwmBe pulse-modulated signal S PThe pulse modulation frequency, R LLoad impedance, R DSBe transistorized conduction impedance, P OBe power output, Q gBe transistorized grid capacitance amount, Vgs is transistorized conducting voltage.By formula (1), when practice, above-mentioned parameter is all fixed value, in the case, and can be by changing the pulse modulation frequency f PwmChange the loss power of amplifier.Moreover, the pulse modulation frequency f PwmMainly be according to oscillator signal S RFrequency and become.Therefore, in audio frequency amplifier 20, through adjustment oscillator signal S RFrequency (and then change the pulse modulation frequency f Pwm), can change audio frequency amplifier 20 loss power P Loss, and then the performance of the efficient of control audio amplifier 20.For instance, when hanging down power output, can be by reducing oscillator signal S RFrequency, reduce loss power P Loss, thus, can promote the amplification efficient performance of audio frequency amplifier 20.
On the other hand, the audio signal of D class audio amplifier input is proportional to the audio signal of output usually, and therefore, in order to solve amplification efficient not good when hanging down power output, embodiments of the invention are according to input audio signal S INSignal strength signal intensity, adjust oscillator signal S RFrequency.Please continue with reference to figure 3.Fig. 3 is the sketch map of signal generator 204 among Fig. 2.Signal generator 204 includes a decision circuitry 302 and a waveform generator 304.Decision circuitry 302 is coupled to input 202, is used for according to input audio signal S INDistribution situation and reference voltage V Ref, decision oscillator signal S RFrequency.As input audio signal S INLittle (greatly) is in reference voltage V RefThe time, decision circuitry 302 can downgrade the frequency of (raising) oscillator signal, and produces control signal S according to this CFor instance, as the input audio signal S of the continuous string waveshape of tool INSignal strength signal intensity surpass reference voltage V RefTime scale little (greatly) when one first preset value, decision circuitry 302 can downgrade (heightening) oscillator signal S RFrequency.In addition, decision circuitry 302 also can be at input audio signal S INMean size little (greatly) in reference voltage V RefThe time, downgrade (heightening) oscillator signal S RFrequency, but not as limit.In brief, the embodiment of the invention is according to input audio signal S INCharacteristics of signals adjust the frequency of oscillator signal, and then amplify the not good situation of efficient when improving low power output.
Further specify decision circuitry 302, please continue with reference to figure 3.Decision circuitry 302 includes a testing circuit 306 and and selects circuit 308.Testing circuit 306 is coupled to input 202, mainly is used for according to input audio signal S INWith reference voltage V Ref, judge input audio signal S INDistribution situation, to produce a detection signal S D Select circuit 308 to be coupled to testing circuit 306 and waveform generator 304, be used for according to detection signal S D, select oscillator signal S RFrequency, and produce control signal S according to this CFor example, select circuit 308 to realize by a MUX, when receiving detection signal S DAfter, just according to detection signal S D, select control signal S by switching in a plurality of candidate's control signals of the different oscillation signal frequencies of expression C, to provide to waveform generator 304.Therefore, waveform generator 304 is just according to control signal S C, produce oscillator signal S with corresponding frequency R
Be noted that audio frequency amplifier 20 is merely of the present invention one explanation for example, those of ordinary skills should make various modifications according to this, and are not limited thereto.For instance, please refer to Fig. 4, Fig. 4 is the sketch map of an audio frequency amplifier 40 of the tool dual track output of the embodiment of the invention.It should be noted that; Have similar working method and function owing to have the assembly of same names in the audio frequency amplifier 20 of Fig. 2 and the audio frequency amplifier 40 of Fig. 4; Therefore for asking description for purpose of brevity; Specify just and omit at this, the connection relationship of these assemblies is as shown in Figure 4, repeats no more at this.Audio frequency amplifier 40 comprises an input 402, a signal generator 404, waver 406,408, predrive circuit 410,412, output stage 414,416, filter 418,420, output 422 and a loud speaker 424.Wherein signal generator 404 includes a decision circuitry 426 and a waveform generator 428.And decision circuitry 426 includes a testing circuit 430 and a selection circuit 432.Testing circuit 430 utilizes first comparator 434 and second comparator 436 to produce one first comparative result and one second comparative results respectively, again by one door 438 is carried out or logical operation after, generation detection signal S DTo waveform generator 428.As shown in Figure 4, the positive and negative input of first comparator 434 receives reference voltage V respectively RefAnd input audio signal S IN, with by output output reference voltage V RefAnd input audio signal S IN(first) comparative result.The positive and negative input of second comparator 436 receives input audio signal S respectively INAnd reference voltage V Ref, to export input audio signal S by output INAnd reference voltage V Ref(second) comparative result.In other words, testing circuit 430 can be estimated input audio signal S INThe order of magnitude of signal strength signal intensity whether exceed reference voltage V RefLevel, with as selecting oscillator signal S RThe benchmark of frequency.Certainly, testing circuit 430 can be in every way or circuit realize that those of ordinary skills should make various modifications according to this.In addition, in Fig. 4, select circuit 432 to realize by a MUX.The totem pillar output of output stage 414,416 for forming by two metal oxide semiconductor transistor serial connections.Filter 418,420 is for respectively by inductance L 1With capacitor C 1, inductance L 2With capacitor C 2The low pass filter of being formed.
In addition, preferably, assemblies such as the predrive circuit in the audio frequency amplifier 20, output stage or filter can be with the utilization situation of audio frequency amplifier, and does the various modifications design.Reference voltage V RefCan be a direct current voltage.Oscillator signal S RThen, can be a triangular signal, a sawtooth signal or other forms of oscillator signal according to the difference of system design.In addition, in audio frequency amplifier 20, according to the difference of the channel number of system, those of ordinary skills should do corresponding modification according to this.
Working method about audio frequency amplifier 20 please refer to Fig. 5, and Fig. 5 is the sketch map of the embodiment of the invention one flow process 50.Flow process 50 comprises the following step:
Step 500: beginning.
Step 502: signal generator 204 is according to input audio signal S INDistribution situation and reference voltage V Ref, decision oscillator signal S RFrequency, and produce the oscillator signal S of corresponding frequency according to this R
Step 504: waver 206 is input audio signal S relatively INWith oscillator signal S R, to produce pulse-modulated signal S P
Step 506: predrive circuit 208 is according to pulse-modulated signal S P, produce pre-drive signal S G
Step 508: output stage 201 is according to pre-drive signal S G, produce output signal S AP
Step 510: 212 pairs of output of filter signal S APCarry out filtering, to produce output audio signal S O
Step 512: finish.
Flow process 50 is in order to the working method of explanation audio frequency amplifier 20, and detailed description and associated change can not given unnecessary details at this with reference to above stated specification.
In sum, the present invention is the characteristics of signals according to input audio signal, flexibly adjusts the frequency of oscillator signal, with the loss power of minimizing audio frequency amplifier, and then the amplification efficient of lifting audio frequency amplifier.Thus, the audio frequency amplifier of the embodiment of the invention can effectively improve and when hanging down power output, amplify the not good situation of efficient.
The above is merely preferred embodiment of the present invention, and every equivalent variations and modification of being done according to claims scope of the present invention all should belong to covering scope of the present invention.

Claims (31)

1. Audio Frequency Amplifer comprises:
One input is used for receiving an input audio signal;
One output is used for exporting an output audio signal;
One signal generator is coupled to said input, is used for a distribution situation and a reference voltage according to said input audio signal, determines the frequency of an oscillator signal, and produces the said oscillator signal of corresponding frequency according to this;
One waver is coupled to said input and said signal generator, is used for more said input audio signal and said oscillator signal, to produce a pulse-modulated signal;
One predrive circuit is coupled to said waver, is used for producing a pre-drive signal according to said pulse-modulated signal;
One output stage is coupled to said predrive circuit, is used for according to said pre-drive signal, produces an output signal; And
One filter is coupled to said output stage, is used for said output signal is carried out filtering, to produce said output audio signal to said output.
2. audio frequency amplifier as claimed in claim 1, wherein said signal generator comprises:
One decision circuitry is coupled to said input, is used for distribution situation and said reference voltage according to said input audio signal, determines the frequency of said oscillator signal, and produces a control signal according to this; And
One waveform generator is coupled to said decision circuitry and said waver, is used for producing said oscillator signal according to said control signal.
3. audio frequency amplifier as claimed in claim 2, wherein said decision circuitry are, to heighten the frequency of said oscillator signal, and produce said control signal according to this during greater than said reference voltage at said input audio signal.
4. audio frequency amplifier as claimed in claim 3, wherein said decision circuitry are the time scales during greater than one first preset value that surpasses said reference voltage at said input audio signal, heighten the frequency of said oscillator signal, and produce said control signal according to this.
5. audio frequency amplifier as claimed in claim 3, wherein said decision circuitry are mean sizes at said input audio signal during greater than said reference voltage, heighten the frequency of said oscillator signal, and produce said control signal according to this.
6. audio frequency amplifier as claimed in claim 2, wherein said decision circuitry are, to downgrade the frequency of said oscillator signal, and produce said control signal according to this during less than said reference voltage at said input audio signal.
7. audio frequency amplifier as claimed in claim 6, wherein said decision circuitry are the time scales during greater than one second preset value that is lower than said reference voltage at said input audio signal, downgrade the frequency of said oscillator signal, and produce said control signal according to this.
8. audio frequency amplifier as claimed in claim 6, wherein said decision circuitry are mean sizes at said input audio signal during less than said reference voltage, downgrade the frequency of said oscillator signal, and produce said control signal according to this.
9. audio frequency amplifier as claimed in claim 2, wherein said decision circuitry comprises:
One testing circuit is coupled to said input, is used for judging the distribution situation of said input audio signal, to produce a detection signal according to said input audio signal and said reference voltage; And
One selects circuit, is coupled to said testing circuit and said waveform generator, is used for selecting the frequency of said oscillator signal according to said detection signal, and produces said control signal according to this.
10. audio frequency amplifier as claimed in claim 9, wherein said testing circuit comprises:
One first comparator comprises a positive input terminal, is used for receiving said reference voltage; One negative input end is coupled to said input, is used for receiving said input audio signal; Reach an output, be used for exporting one first comparative result of said positive input terminal and said negative input end;
One second comparator comprises a positive input terminal, is coupled to said input; Be used for receiving said input audio signal, a negative input end is used for receiving said reference voltage; Reach an output, be used for exporting one second comparative result of said positive input terminal and said negative input end; And
One or door, be coupled to the said output and the said selection circuit of the said output of said first comparator, said second comparator, be used for said first comparative result and said second comparative result are carried out the logic OR computing, to produce said detection signal.
11. audio frequency amplifier as claimed in claim 9, wherein said selection circuit comprises:
One MUX is coupled to said testing circuit and said waveform generator, is used for according to said detection signal, selects said control signal by switching in a plurality of candidate's control signals of the different oscillation signal frequencies of expression, to provide to said waveform generator.
12. audio frequency amplifier as claimed in claim 1, wherein said output stage comprises:
One the first transistor comprises one first end, is coupled to said predrive circuit; Be used for receiving said pre-drive signal, one second end, and one the 3rd end; Be coupled to a power end, be used for according to the conducting state between said second end of the signal controlling of said first end to said the 3rd end; And
One transistor seconds comprises one first end, is coupled to said predrive circuit; Be used for receiving said pre-drive signal; One second end is connected to earth terminal, and one the 3rd end; Be coupled to second end of said the first transistor, be used for according to the conducting state between said second end of the signal controlling of said first end to said the 3rd end;
Wherein said filter is coupled to said second end of said the first transistor and said the 3rd end of said transistor seconds, to export said output signal.
13. audio frequency amplifier as claimed in claim 12, wherein said the first transistor are a NMOS transistor, said first end is a grid, and said second end is a source electrode, and said the 3rd end is drain electrode.
14. audio frequency amplifier as claimed in claim 12, wherein said transistor seconds are a NMOS transistor, said first end is a grid, and said second end is a source electrode, and said the 3rd end is drain electrode.
15. audio frequency amplifier as claimed in claim 1, wherein said filter are a low pass filter.
16. audio frequency amplifier as claimed in claim 1, wherein said reference voltage are a direct current voltage.
17. audio frequency amplifier as claimed in claim 1, wherein said oscillator signal are a triangular signal or a sawtooth signal.
18. audio frequency amplifier as claimed in claim 1 also comprises a loud speaker, is coupled to said output, is used for playing said output audio signal.
19. a method that promotes an audio frequency amplifier efficient comprises:
A distribution situation and a reference voltage according to an input audio signal determine the frequency of an oscillator signal, and produce the said oscillator signal of corresponding frequency according to this;
More said input audio signal and said oscillator signal are to produce a pulse-modulated signal;
According to said pulse-modulated signal, produce a pre-drive signal;
According to said pre-drive signal, produce an output signal; And
Said output signal is carried out filtering, to produce said output audio signal.
20. like the method for claim 19, wherein, determine the frequency of said oscillator signal, and the step that produces the said oscillator signal of corresponding frequency according to this comprises according to the distribution situation and the said reference voltage of said input audio signal:
Distribution situation and said reference voltage according to said input audio signal determine the frequency of said oscillator signal, and produce a control signal according to this; And
According to said control signal, produce said oscillator signal.
21. like the method for claim 20, wherein, determine the frequency of said oscillator signal, and the step that produces said control signal according to this comprises according to the distribution situation and the said reference voltage of said input audio signal:
, heighten the frequency of said oscillator signal, and produce said control signal according to this during at said input audio signal greater than said reference voltage.
22. like the method for claim 21, wherein, determine the frequency of said oscillator signal, and the step that produces said control signal according to this comprises according to the distribution situation and the said reference voltage of said input audio signal:
The time scale that surpasses said reference voltage at said input audio signal is heightened the frequency of said oscillator signal, and is produced said control signal according to this during greater than one first preset value.
23. like the method for claim 21, wherein, determine the frequency of said oscillator signal, and the step that produces said control signal according to this comprises according to the distribution situation and the said reference voltage of said input audio signal:
, heighten the frequency of said oscillator signal, and produce said control signal according to this during at the mean size of said input audio signal greater than said reference voltage.
24. like the method for claim 20, wherein, determine the frequency of said oscillator signal, and the step that produces said control signal according to this comprises according to the distribution situation and the said reference voltage of said input audio signal:
, downgrade the frequency of said oscillator signal, and produce said control signal according to this during at said input audio signal less than said reference voltage.
25. like the method for claim 24, wherein, determine the frequency of said oscillator signal, and the step that produces said control signal according to this comprises according to the distribution situation and the said reference voltage of said input audio signal:
The time scale that surpasses said reference voltage at said input audio signal downgrades the frequency of said oscillator signal, and produces said control signal according to this during less than one first preset value.
26. like the method for claim 24, wherein, determine the frequency of said oscillator signal, and the step that produces said control signal according to this comprises according to the distribution situation and the said reference voltage of said input audio signal:
, downgrade the frequency of said oscillator signal, and produce said control signal according to this during at the mean size of said input audio signal less than said reference voltage.
27. like the method for claim 20, wherein, determine the frequency of said oscillator signal, and the step that produces said control signal according to this comprises according to the distribution situation and the said reference voltage of said input audio signal:
According to said input audio signal and said reference voltage, judge the distribution situation of said input audio signal, to produce a detection signal; And
According to said detection signal, select the frequency of said oscillator signal, and produce said control signal according to this.
28. like the method for claim 27,, judge the distribution situation of said input audio signal, comprise with the step that produces said detection signal according to said input audio signal and said reference voltage:
Whether the amplitude of the positive edge of more said input audio signal and negative edge is greater than said reference voltage, to produce one first comparative result and one second comparative result respectively; And
The comparative result that said first comparative result and said second comparator are exported carries out the logic OR computing, to produce said detection signal.
29. like the method for claim 19,, select the frequency of said oscillator signal, and the step that produces said control signal according to this comprises wherein according to said detection signal:
According to said detection signal, select said control signal by switching in a plurality of candidate's control signals of the different oscillation signal frequencies of expression.
30. like the method for claim 19, wherein said reference voltage is a direct current voltage.
31. like the method for claim 19, wherein said oscillator signal is a triangular signal or a sawtooth signal.
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