CN101931372B - D type amplifier with second-order noise filtering circuit - Google Patents
D type amplifier with second-order noise filtering circuit Download PDFInfo
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- CN101931372B CN101931372B CN 200910150713 CN200910150713A CN101931372B CN 101931372 B CN101931372 B CN 101931372B CN 200910150713 CN200910150713 CN 200910150713 CN 200910150713 A CN200910150713 A CN 200910150713A CN 101931372 B CN101931372 B CN 101931372B
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Abstract
The invention relates to a D type amplifier with a second-order noise filtering circuit. Two differential output ends form a two-order feedback loop respectively with a first differential amplifier and a second differential amplifier so as to provide a higher high frequency attenuation value, therefore, the noise and other nonlinear elements of the first differential amplifier and the second amplifier are fast attenuated to improve the overall distortion noise ratio; in addition, after respectively synthesized by the first differential amplifier and the second differential amplifier, the distortion components contained in output signals of the differential output ends are amplified in the way of second-order difference, thereby effectively improving over all loop gain and forming a high-gain system. And moreover, the differential output signals of the D type amplifier can be corrected more finely after being subjected to second-order gain processing.
Description
Technical field
The present invention is about a kind of D class A amplifier A, espespecially a kind of D class A amplifier A with second-order noise filtering circuit.
Background technology
In general, the amplifying circuit of output stage generally includes the amplifiers such as category-A, category-B, AB class and D class, early stage more common be class ab ammplifier, but along with the maturation of manufacture of semiconductor, the D class A amplifier A that has than low consumpting power gradually is common.
D class A amplifier A and class ab ammplifier maximum difference namely are that the output pulse width modulating signal promotes inductive load, and are not to promote with linear signal; Wherein this pulse-width modulation signal includes voice signal and pulse-width modulation switching signal and harmonic signal.Because D class A amplifier A output pulse width modulating signal, so that each switch of output stage switch circuit switches extremely Low ESR from high impedance, and ON time is short, and the conducting resistance time shortens relatively so that On current is flowed through, and more efficient than class ab ammplifier, and consumed power is less.
See also shown in Figure 5ly, existing open the D class A amplifier A 70 in loop for a kind of, this D class A amplifier A 70 includes a gain amplifier 71, a PWM modulator 72, an internal oscillator 73 and a H type bridge switching circuit 74; Wherein these gain amplifier 71 inputs receive external analog voice signal (Vi+, Vi-), and after this external analog voice signal amplified, by the oscillator signal output pulse width modulating signal of this PWM modulator 72 according to internal oscillator 73 outputs, and export this pulse-width modulation signal to H bridge switching circuit 74, with ON time and the conducting loop of controlling these H bridge switching circuit 74 each switches.
Because above-mentioned D class A amplifier A 70 belongs to out the difference channel in loop, add that this gain amplifier 71 includes a differential amplifier 701, and this differential amplifier 701 itself includes noise floor (Noise Floor), wherein this noise floor belongs to a kind of of dynamic noise, therefore when voice signal inputs to this gain amplifier 71, this dynamic noise can be incorporated in the voice signal after the amplification, cause the voice signal distortion of inductive load reduction, relatively have relatively poor distorted signals noise ratio (SDNR).
Therefore, see also shown in Figure 7ly, be a kind of circuit block diagram that closes the D class A amplifier A 70a of feedback loop, it includes:
One gain adjustment circuit 711, it includes one group of analog input end (Vi+, Vi-), for connecting voice signal;
One first differential amplifier 712, its input are connected to respectively the analog input end (Vi+, Vi-) of this gain adjustment circuit 711, adjust the yield value of this first differential amplifier 712 by gain adjustment circuit 711;
First-order Integral circuit 75, include one second differential amplifier 751 and two groups of RC circuit, wherein two groups of RC circuit are connected to two difference output end (D0+ of D class A amplifier A, D0-) and the in-phase input end of this second differential amplifier 751 (+,-) between, the differential output signal of D class A amplifier A 70a output exported with the first differential amplifier 712 exported again after the voice emplifying signals are merged;
Two comparators 76, a wherein input of each comparator 76 is connected to the difference output end to the second differential amplifier 751 that should First-order Integral circuit 75, each another input of two comparators 76 then is connected to a triangular wave generator 77 jointly again, therefore each comparator 76 is compared output signal and the triangular signal of First-order Integral circuit 75, as shown in Figure 8, because First-order Integral circuit 75 is output as string ripple signal (Vi+, Vi-), after comparing with triangular signal S2, i.e. output pulse width modulating signal; And
One logical circuit 78, its input is connected to the output of this two comparator 76, drives signal according to two groups of two groups of pulse-width modulation signal deciding; And
One H type bridge switching circuit 74, including two half-bridge switch circuit 741 consists of, two tandem node of two half-bridge switch circuit 741 connect for an inductive load 60, and the control end of this two half-bridge switch circuit 741 is connected to the output of this logical circuit 78, opens and closes with two groups of driving signals that are subjected to these logical circuit 78 outputs.
In above-mentioned D class A amplifier A 70a framework, because the second differential amplifier 751 and two groups of RC circuit consist of the single order feedback loop, therefore inputing to the signal of comparator 76 and be the error signal (error signal) that is produced by the second differential amplifier 751 merges the first input audio signal that differential amplifier 712 amplifies and true output signal (high-voltage square-wave) and gets, and the input audio signal that the first differential amplifier 712 amplifies includes some nonlinear terms (non-linear terms), frequency limitation such as differential amplifier, amplifier noise, the reference voltage noise, gain/frequency range product limit, and the feedback loop output signal etc. that contains the non-linear value of triangular-wave generator.And those non-linear elements are eliminated by the single order feedback loop.
Therefore yet above-mentioned single order feedback loop is made differential amplification after only by the second single differential amplifier voice signal being synthesized, the whole loop gain limited of opening.
Summary of the invention
The problem of stating is in view of this arranged, and main purpose of the present invention can improve integral body and open loop gain and better noise distortion signal ratio is provided for a kind of D class A amplifier A with second-order noise filtering circuit is provided.
Wanting to reach the employed technical way of above-mentioned purpose makes this D class A amplifier A include a gain adjustment circuit, second-order integrator, two comparators, a logical circuit and a H type bridge switching circuit; Wherein this second-order integrator includes:
One first differential amplifier includes a positive input, a reverse input end, a backward difference output and a forward difference output end, and wherein this positive input is connected to this gain adjustment circuit, to adjust the gain of this first differential amplifier;
2 the one RC circuit are connected between the forward and reverse input end of D class A amplifier A difference output end and this first differential amplifier, consist of two group of first rank integrating circuit;
One second differential amplifier, include a positive input, a reverse input end, wherein this positive input is connected to the forward difference output end of this first differential amplifier, and this reverse input end then is connected to the backward difference output of this first differential amplifier; And
2 the 2nd RC circuit are connected between the forward and reverse input end of D class A amplifier A difference output end and this second differential amplifier, consist of two groups of second-order integrating circuit;
As shown in the above description, the beneficial effect of D class A amplifier A of the present invention is, two difference output ends consist of second order feedback loop with first and second differential amplifier respectively, therefore higher high frequency attenuation value is provided, effectively make the non-linear elements such as noise of first and second differential amplifier itself decay more fast, improve whole noise distortion noise ratio; Moreover, the present invention is to comprising the composition (Distortion) of distortion in the output signal of difference output end, amplify to give synthetic rear second order difference respectively with first and second differential amplifier, the gain of Effective Raise bulk loop, consist of a high gain system, and can get meticulousr correction after the D class A amplifier A differential output signal of the present invention process secondary gain process.
Moreover, (error signal-is output signal and the feedback signal (high-voltage square-wave) that merges first order amplifier to the error signal that the second differential amplifier produces, and comprise some nonlinear terms (non-linear terms) in this loop, comprise frequently product limit of amplifier frequency limitation, amplification noise, reference voltage noise, gain, and contain the non-linear component that triangular wave is given birth to device, these non-linear elements can be eliminated via negative feedback; In like manner, the present invention also also includes first order differential amplifier in the reponse system to consist of second order feedback loop, even whole D class A amplifier A full linear, and relatively obtain better total harmonic distortion plus noise than (THD+N) usefulness.
The present invention's time purpose provides a kind of D class A amplifier A that can significantly reduce electromagnetic interference, meaning is that above-mentioned H type bridge switching circuit includes two half-bridge circuits, each half-bridge circuit is formed by a plurality of high-side switch groups and a plurality of low side switch group serial connection, wherein each half-bridge circuit becomes two groups of sub-half-bridge switch circuit with the high-side switch group with the low side switch component, wherein the high/low side number of switches of the first sub-half-bridge switch group is more than the high/low side number of switches of the second sub-half-bridge switch group, make above-mentioned logical circuit export four groups of pulse-width modulation signals to H type bridge switching circuit of the present invention, wherein the logical operation formula of this logical circuit is X-=(Y-)-(Y+); X+=(Y+)-(Y-), this X-and X+ are the first sub-half-bridge switch circuit of two groups of half-bridge circuits of control, Y-and Y+ are the second sub-half-bridge switch circuit of two groups of half-bridge switch circuit of control, a logical operation formula as can be known thus, when the difference output end no-output of D class A amplifier A, the pulse-width modulation that this logical circuit exports Y-and Y+ to is transferred width ratio, and (Duty Cycle-is respectively 50%, and X-and X+ are respectively the difference of Y-and Y+, therefore exporting the pulse-width modulation of X-and X+ to transfers width ratio (Duty Cycle-is respectively 0%, therefore the first sub-half-bridge switch circuit in two half-bridge circuits need not switch when D class A amplifier A no signal is exported fully; And at the D class A amplifier A in signal when output, arranged, two group of first sub-half-bridge also only wherein one group action is arranged; Therefore, switch cost and the output switching revolution rate (output switch slew rate) of half-bridge circuit can be effectively reduced, the EMI value of whole D class A amplifier A can be reduced.
Description of drawings
Fig. 1 is the circuit block diagram of the present invention's the first preferred embodiment;
Fig. 2 is the circuit block diagram of the present invention's the second preferred embodiment;
Fig. 3 A is the oscillogram of Fig. 2 when D class A amplifier A no signal is exported;
Fig. 3 B is the oscillogram of Fig. 2 when the D class A amplifier A has signal output;
Fig. 4 is the frequency domain figure of the voice emplifying signal under second order and the single-order feedback loop;
Fig. 5 is a kind of D class A amplifier A circuit block diagram of opening the loop;
Fig. 6 is the frequency domain figure that Fig. 5 exports the voice emplifying signal;
Fig. 7 is a kind of D class A amplifier A circuit block diagram of loop circuit;
Fig. 8 is the oscillogram of Fig. 7.
Description of reference numerals:
10,10a-D class A amplifier A; The 11-gain adjustment circuit; 20-the first differential amplifier; 21-the one RC circuit; 22-the second differential amplifier; 23-the 2nd RC circuit; The 30-comparator; The 31-comparator; 40,40a-logical circuit; 50,50a-H type bridge switching circuit; The 51-half-bridge circuit; 511-the first sub-half-bridge switch circuit; 512-the second sub-half-bridge switch circuit; The 52-half-bridge circuit; 521-the first sub-half-bridge switch circuit; 522-the second sub-half-bridge switch circuit; The 60-inductive load; 70,70a-D class A amplifier A; The 701-differential amplifier; The 71-gain amplifier; The 711-gain adjustment circuit; 712-the first differential amplifier; The 72-PWM modulator; The 73-internal oscillator; 74-H type bridge switching circuit; 741-half-bridge switch circuit; 75-First-order Integral device; 751-the second differential amplifier; The 76-comparator; The 77-triangular signal; The 78-logical circuit; The 80-low pass filter.
Embodiment
See also shown in Figure 1, the circuit block diagram that has D class A amplifier A 10 1 preferred embodiments of second-order noise filtering circuit for the present invention, it includes a gain adjustment circuit 11, second-order integrator, two comparators 30,31, a logical circuit 40 and a H type bridge switching circuit 50, wherein this H type bridge switching circuit 50 includes two half- bridge circuits 51,52, each half- bridge circuit 51,52 control end is connected to respectively the output of this logical circuit, and each half- bridge circuit 51,52 tandem node are the difference output end (D0+, D0-) of D class A amplifier A 10.Wherein this second-order integrator includes:
One first differential amplifier 20 includes a positive input, a reverse input end, a backward difference output and a forward difference output end, and wherein this positive input is connected to this gain adjustment circuit 11, to adjust the gain of this first differential amplifier 20;
2 the one RC circuit 21 are connected between the forward and reverse input end of D class A amplifier A difference output end (D0+, D0-) and this first differential amplifier 20, consist of two group of first rank integrating circuit;
One second differential amplifier 22, include a positive input, a reverse input end, wherein this positive input is connected to the forward difference output end of this first differential amplifier 20, and this reverse input end then is connected to the backward difference output of this first differential amplifier 20; And
2 the 2nd RC circuit 23 are connected between the forward and reverse input end of D class A amplifier A difference output end (D0+, D0-) and this second differential amplifier 22, consist of two groups of second-order integrating circuit.
As shown in the above description, two difference output end (D0+ of D class A amplifier A 10 of the present invention, D0-) respectively with first and second differential amplifier 20,22 consist of second order feedback loop, therefore provide higher high frequency attenuation value (40dB), effectively make first and second differential amplifier 20,22 non-linear elements such as noise own decay more fast, improve whole noise distortion noise ratio; Moreover, the present invention is to comprising the composition (Distortion) of distortion in the output signal of difference output end, with first and second differential amplifier 20,22 amplify to give synthetic rear second order difference respectively, the gain of Effective Raise bulk loop, consist of a high gain system, and can get meticulousr correction after the D class A amplifier A 10 differential output signals of the present invention process secondary gain process.Moreover, the error signal (error signal) that the second differential amplifier 22 produces is for merging output signal and the feedback signal (high-voltage square-wave) of first order amplifier 20, and comprise some nonlinear terms (non-linear terms) in this loop, comprise the amplifier frequency limitation, amplify noise, the reference voltage noise, gain is product limit frequently, and the non-linear component that contains triangular-wave generator, because the second differential amplifier 22 and the 2nd RC circuit 23 and two difference output end (D0+, D0-) consist of negative feedback loop, these non-linear elements can be eliminated; In like manner, the present invention also also includes first order differential amplifier in the reponse system to consist of second order feedback loop, even whole D class A amplifier A full linear, and relatively obtain better total harmonic distortion plus noise than (THD+N) usefulness.
See also shown in Figure 2, be D class A amplifier A 10a of the present invention the second preferred embodiment, itself and the first preferred embodiment circuit structure are roughly the same, but because each half- bridge circuit 51,52 are formed by a plurality of high-side switch groups and a plurality of low side switch group serial connection, therefore the present embodiment further makes the high-side switch group of each half-bridge circuit become two groups of sub-half-bridge circuits with the low side switch component, namely include one first sub-half-bridge switch circuit 511, the 521 and second sub-half-bridge switch circuit 512,522, wherein the high/low side number of switches of this first sub-half-bridge switch circuit 511,521 is more than the high/low side number of switches (approximately 3-5 doubly) of the second sub-half-bridge switch circuit 512,522.
Please cooperate the design of the present embodiment H type bridge switching circuit, logical circuit 40a of the present invention includes four groups of pulse-width modulation signal output part X+, Y-, Y+, X-is to be connected to respectively this two half-bridge circuit 51, the first sub-half-bridge switch circuit 511,521 of 52 and the second sub-half-bridge switch circuit 512,522.Wherein the logical operation formula of this logical circuit 40a is X-=(Y-)-(Y+); X+=(Y+)-(Y-), this X-and X+ are the first sub-half-bridge switch circuit 511,512 of two groups of half- bridge circuits 51,52 of control, Y-and Y+ are control the second sub-half-bridge switch circuit 521,522.
Please cooperate and consult shown in Fig. 3 A, difference output end (D0+ as D class A amplifier A 10a, D0-) during no-output, this logical circuit 40a exports the pulse-width modulation of Y-and Y+ to and transfers width ratio (Duty Cycle) to be respectively 50%, according to above-mentioned logical operation formula, this X-and X+ are respectively the difference of Y-and Y+, transfer width ratio (Duty Cycle) to be respectively 0% therefore export the pulse-width modulation of X-and X+ to, therefore two half-bridge circuits 51, the first sub-half-bridge switch circuit 511,521 in 52 need not switch when D class A amplifier A 10a no signal is exported fully.See also again shown in Fig. 3 B, when in signal when output, arranged at D class A amplifier A 10a, two group of first sub-half-bridge 511,521 also only wherein one group action is arranged; Therefore, switch cost and the output switching revolution rate (output switch slew rate) of half-bridge circuit can be effectively reduced, the EMI value of whole D class A amplifier A 10a can be reduced.
The above description of this invention is illustrative, and nonrestrictive, and those skilled in the art is understood, and can carry out many modifications, variation or equivalence to it within spirit that claim limits and scope, but they will fall within the scope of protection of the present invention all.
Claims (3)
1. D class A amplifier A with second-order noise filtering circuit, include a gain adjustment circuit, a second-order integrator, two comparators, a logical circuit and a H type bridge switching circuit, wherein this H type bridge switching circuit includes two half-bridge circuits, the control end of each half-bridge circuit is connected to respectively the output of this logical circuit, and the tandem node of each half-bridge circuit is the difference output end of D class A amplifier A; It is characterized in that, this second-order integrator includes:
One first differential amplifier includes a positive input, a reverse input end, a backward difference output and a forward difference output end, and wherein this positive input is connected to this gain adjustment circuit, to adjust the gain of this first differential amplifier;
2 the one RC circuit are connected between the forward and reverse input end of D class A amplifier A difference output end and this first differential amplifier, consist of two group of first rank integrating circuit;
One second differential amplifier, include a positive input, a reverse input end, wherein this positive input is connected to the forward difference output end of this first differential amplifier, and this reverse input end then is connected to the backward difference output of this first differential amplifier; And
2 the 2nd RC circuit are connected between the forward and reverse input end of D class A amplifier A difference output end and this second differential amplifier, consist of two groups of second-order integrating circuit.
2. the D class A amplifier A with second-order noise filtering circuit as claimed in claim 1, it is characterized in that, described each half-bridge circuit is formed by a plurality of high-side switch groups and a plurality of low side switch group serial connection, described each half-bridge circuit further becomes the first sub-half-bridge switch circuit and the second sub-half-bridge switch circuit with described high-side switch group with described low side switch component, the high/low side number of switches of this first sub-half-bridge switch circuit is more than the high/low side number of switches of the second sub-half-bridge switch circuit;
This logical circuit includes four groups of pulse-width modulation signal output parts, and with the first sub-half-bridge switch circuit and the second sub-half-bridge switch circuit that are connected to respectively this two half-bridge circuit, wherein the logical operation formula of this logical circuit is X-=(Y-)-(Y+); X+=(Y+)-(Y-), this X-and X+ are the second sub-half-bridge switch circuit of described two half-bridge circuits of control for the first sub-half-bridge switch circuit of described two half-bridge circuits of control, Y-and Y+.
3. the D class A amplifier A with second-order noise filtering circuit as claimed in claim 2 is characterized in that, the high/low side number of switches of this first sub-half-bridge switch circuit is 3 to 5 times of high/low side number of switches of the second sub-half-bridge switch circuit.
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| Application Number | Priority Date | Filing Date | Title |
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| CN 200910150713 CN101931372B (en) | 2009-06-24 | 2009-06-24 | D type amplifier with second-order noise filtering circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN 200910150713 CN101931372B (en) | 2009-06-24 | 2009-06-24 | D type amplifier with second-order noise filtering circuit |
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| CN101931372A CN101931372A (en) | 2010-12-29 |
| CN101931372B true CN101931372B (en) | 2013-05-01 |
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Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8330541B2 (en) * | 2011-03-01 | 2012-12-11 | Maxim Integrated Products, Inc. | Multilevel class-D amplifier |
| CN103248393B (en) * | 2012-02-14 | 2015-06-17 | 英特尔移动通信有限责任公司 | Elimination of RF second-order intermodulation distortion |
| CN104065353A (en) * | 2013-03-22 | 2014-09-24 | 意法半导体研发(深圳)有限公司 | Mute-starting class-D amplifier |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1311918A (en) * | 1998-07-24 | 2001-09-05 | 托加塔技术有限公司 | Method of attenuating zero crossing distortion and noise in a amplifier, amplifier and uses of the method and amplifier |
| US6590619B1 (en) * | 1999-04-26 | 2003-07-08 | Mitsubishi Denki Kabushiki Kaisha | Broadcast sound signal processing circuit |
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2009
- 2009-06-24 CN CN 200910150713 patent/CN101931372B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1311918A (en) * | 1998-07-24 | 2001-09-05 | 托加塔技术有限公司 | Method of attenuating zero crossing distortion and noise in a amplifier, amplifier and uses of the method and amplifier |
| US6590619B1 (en) * | 1999-04-26 | 2003-07-08 | Mitsubishi Denki Kabushiki Kaisha | Broadcast sound signal processing circuit |
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