CN86101540A - High-efficiency class-a audio power amplifier - Google Patents
High-efficiency class-a audio power amplifier Download PDFInfo
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- CN86101540A CN86101540A CN86101540.1A CN86101540A CN86101540A CN 86101540 A CN86101540 A CN 86101540A CN 86101540 A CN86101540 A CN 86101540A CN 86101540 A CN86101540 A CN 86101540A
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- power supply
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Abstract
The present invention is a kind of supply voltage of output stage and the efficient category-A audio-frequency power amplifier that bias supply is exaggerated signal controlling, is made of power amplifier, voltage controlled source and controlled bias circuit.In arbitrary moment, the supply voltage and the bias current value of efficient category-A audio power output stage are the desired supply voltage of traditional category-A power amplifier output-stage and the bias current value of taking peak power output with the power output in this moment as.Therefore, the invention solves the major defect of traditional category-A power amplifier.
The present invention is applicable to high-fidelity audio power amplifier.
Description
The present invention is a kind of supply voltage of output stage and the audio-frequency power amplifier that biasing is exaggerated the efficient class-A of signal controlling, belongs to the improvement technology that improves the semiconductor amplifier delivery efficiency.
In recent years, the non-band of the development of high fidelity amplifier is active, and some producers in Japan, the U.S. and West Europe have all developed many new products in succession and put on market, and domestic also have some products to come out.Usually, these amplifiers work in first (A) class or second (B) class (comprising the AB class) state.The power amplifier that is operated in the category-A state can not produce intermodulation distortion and switch distortion, and tonequality is better than being operated in the power amplifier of category-B state, but its efficient is far below the power amplifier that is operated in the category-B state.For obtaining graceful tonequality, higher efficient is arranged again simultaneously, some power amplifiers have adopted " not having by biasing circuit ", as " dynamic bias circuit ", " no switch motion amplifier ", " super Class A amplifying circuit ", " the new Class A amplifying circuit " of PANASONIC (Technics) company of JVC (JVC) company of Japan vanguard (pioneer) company of U.S. Shi Lixiaoerde company, " biasing circuit in real time " of Japanese Columbia Co., Ltd or the like.These do not have by the design of amplifying circuit all more ingenious.Wherein " biasing circuit in real time " of the Denon board POA3000 type power amplifier of Japanese Columbia Co., Ltd is more novel, and it is started with from output stage biased electric current aspect, and part has solved the low efficiency problem of traditional category-A power amplifier.Yet, analysis circuit can be seen, its whole biasing circuits are arranged in the signal path of output stage, bias circuit construction is very numerous and diverse, in addition, because the supply voltage of its output stage immobilizes, so this " biasing circuit in real time " efficient when the amplifier small-power is exported is still lower.German patent DE 3013186 " high efficiency power amplifier " has been narrated the efficient that improves power amplifier in the mode that changes supply voltage.But the supply voltage that puts on amplifier output stage is significantly, and step changes, and consequent pulsive noise may have influence on the output of amplifier by power supply, and is even more serious when the variation jump voltage of supply voltage is big.Secondly, use this mode to improve the efficient of power amplifier, the variation that must make supply voltage is the output voltage of follower amplifier more critically, forces down unnecessary supply voltage as far as possible, can obviously improve the efficient of amplifier, thereby just require to increase greatly the variation progression of supply voltage.If, the independent current source group that doubles mains voltage variations progression will be set, therefore by German patent DE 3013186 described schemes; When the change in voltage progression of this requirement more for a long time, can become difficult to achieve in actual applications.Special when amplifier will have high fan-out capability, all the more so, thereby, the described scheme of above-mentioned patent, the improvement of pair amplifier efficient is " coarse ", limited.The present invention combines these basic thoughts that improves efficiency of amplitude, improves the efficient category-A audio-frequency power amplifier that has designed a kind of brand new.
The objective of the invention is, with efficient and irrelevant voltage controlled source and the simple controlled bias circuit of output voltage, put on the category-A power amplifier, thereby under the prerequisite of the graceful tonequality that guarantees the category-A power amplifier, reduce unwanted losses and heating, improve the efficient of amplifier.
The efficient category-A audio-frequency power amplifier of the present invention is made up of category-A power amplifier, analog power, quantification power supply and simple controlled bias circuit.The input stage of power amplifier and promotion level are by the power supply Vc of fixed voltage
1Power supply, output stage is then by voltage controlled source Vc
2Power supply.The voltage controlled source is made up of the two large divisions: analog power and quantification power supply, the voltage of analog power output is the output voltage V c of voltage controlled source just
2Wherein analog power is made up of absolute value circuit, peak holding circuit, drive circuit and follower; Quantizing power supply is made up of testing circuit, code converter, triggering drive circuit, electronic switch, continued flow tube, unit power supply, base beginning power supply and storage capacitor C.Because the output voltage of analog power is controlled by the output voltage of power amplifier, so the output voltage of power amplifier is higher, the output voltage V c of voltage controlled source
2Value also higher, this variable supply voltage can guarantee the arbitrary moment of amplifier before not reaching maximum output, output signal voltage is not cut the top, simultaneously, can save unnecessary supply voltage again; Otherwise, when the output voltage of power amplifier hangs down, Vc
2Value also can decrease.But Vc
2A minimum retention value is arranged, be called initial voltage, it can overcome the saturation voltage drop of output-stage power pipe on the one hand, and the buffering capacity of a compensate for variable power-supply system response time delay also is provided simultaneously.Quantize power supply can both provide at any time one a little more than or equal the output voltage V c of analog power
2Quantification voltage with follower operating voltage sum of the two.
Tradition category-A power amplifier output-stage bias current is set constant by the following formula requirement usually:
Bias current I
Q=(the voltage peak V during peak power output
Omax)/(load impedance R
L) * 1/2
So,, also to flow through sizable bias current even under the small-power output state.Efficient category-A power amplifier of the present invention has a simple controlled bias circuit in the output stage design, and the bias current of output stage is controlled by output signal, and its value is the function of instant output voltage peak value:
Bias current I
Q=(the voltage peak V of instant power output
O)/(load impedance R
L) * 1/2
That is, take to be the desired bias current of category-A power amplifier output-stage of peak power output as with the instant power output of amplifier.Bias current and base resistance R because of output stage
bThe bias voltage V at two ends
BRelevant, therefore, can derive the bias voltage V of output stage
BWith output voltage peak value V
oThe relational expression of the two:
V
B＝R
e/R
LV
o+2N V
be
In the formula, R
eBe output-stage power pipe emitter feedback resistance, R
LBe load resistance, N is the progression of output stage by Darlington connection, V
BeBe transistorized base-emitter-base bandgap grading pressure drop, V
oBe the output voltage peak value.In view of the above, two biasing resistors of the present invention have satisfied bias voltage V
BDynamic change require (Re/RI V
o) and promote the initial voltage of the bias current of level and voltage controlled source at base resistance R with cascode
bOn acting in conjunction, the static state that satisfies VB requires (2N V
Be).Be each output stage with a resistance pressure-dividing network (for example, can hinder), connect between voltage controlled source output and the output stage biased current controling end and realize controlled bias by three resistance.After the output stage controlled bias, class-a amplifier just can save unnecessary bias current, thereby further improve the efficient of amplifier before reach maximum output.
Because the present invention has saved unnecessary supply voltage and the bias current of class-a amplifier output stage simultaneously, so output stage always works in the maximum output state of category-A power amplifier, has reduced unwanted losses and heating significantly; Because amplifier is operated under the pure category-A state in the present invention, so its amplifying signal verily.Efficient its theoretical efficiency of category-A power amplifier of the present invention can reach 50%, and does not reduce with the minimizing of relative power output.Shown in Figure 8 as the back, the shadow region is improved efficiency of the present invention district.
Because the music signal peak is a very big value, thereby requirement is used for the peak power output of the power amplifier of hi-fi reproduction and on average uses more than ten times of power often.In this regard, the present invention is used for HD Audio and resets, and has special meaning, and actual improved efficiency degree is bigger.So the present invention is a kind of high-fidelity, high output and high efficiency good quality audio power amplifier have vast potential for future development.
Description of drawings:
Fig. 1 is a theory diagram of the present invention.Wherein (1) is the power amplifier of BTL, and (2) are that voltage controlled source, (3) are that analog power, (4) are that quantification power supply, (5) are load R
L, (6) be absolute value circuit, (7) be peak holding circuit, (8) be drive circuit, (9) be follower, (10) be testing circuit, (11) be code converter, (12) be trigger drive circuit, (13) are that electronic switch, (14) they are that unit power supply, (15) they are that continued flow tube, (16) they are that base beginning power supply, (17) they are base resistance R
b, (18) be power tube emitter-base bandgap grading feedback resistance R
e, (19) be that biasing resistor, (20) they are energy storage capacitors.
Fig. 2 is the simplest absolute value circuit (6).
Fig. 3 is the simplest peak holding circuit (7).
Fig. 4 is drive circuit (8).
Fig. 5 is testing circuit (10).
Code converter when Fig. 6 is 16 grades for quantizing voltage progression.
Fig. 7 is for to control the quantification power supply with " window comparator " mode.
Fig. 8 is the chart that concerns of power output and efficient.
Below in conjunction with the description of drawings embodiments of the invention.
The input stage of power amplifier (1) and promotion level are by the power supply of fixed voltage
Power supply, output stage is by voltage controlled source (2)
Power supply.Voltage controlled source (2) is made up of analog power (3) and quantification power supply (4).In analog power, the output voltage that picks up from load (5) two ends, be transformed into unipolarity voltage through absolute value circuit (6), input peak holding circuit (7), the realization peak value keeps, the time constant of peak holding circuit can be selected between second at 0-0.1, retention time is longer, improvement degree to efficient is littler, but the response of voltage controlled source system time-delay is littler to the influence that high-frequency signal amplifies, and therefore, this parameter depends primarily on the response device speed of voltage controlled source, secondly, depend on requirement to fidelity.Drive circuit (8) has two functions: (1) is before the output signal that does not obtain peak holding circuit (7), produce an initial voltage, to overcome the saturation voltage drop of output-stage power pipe, also can provide the buffer voltagc amount of a compensation usefulness to the delay on the voltage controlled source tracking time; (2) after the output voltage of peak holding circuit (7) comes across the input of drive circuit (8), drive circuit (8) is superimposed upon the output voltage of peak holding circuit (7) on the initial voltage, drive follower (9), therefore, the output voltage of voltage controlled source
Be absolute value or its peak value retention value sum of initial voltage and amplifier (1) output voltage.Follower (9) can be the transistor of one group of Darlington connection, also can be a three terminal regulator.This analog power (3) also prevents to quantize the side effect that voltage jump causes, and can reduce the internal resistance of source.
Quantizing power supply (4) is made up of testing circuit (10), code converter (11), triggering drive circuit (12), electronic switch (13), unit power supply (14), continued flow tube (15), base beginning power supply (16) and storage capacitor (20).Testing circuit (10) and code converter (11) are formed an A/D converter, it can detect comparison to the height of voltage controlled source output voltage, and by corresponding relation output binary code control signal given in advance, control electronic switch (13) in each unit power supply (14) loop by triggering drive circuit (12) then, make it to disconnect or closed.The magnitude of voltage difference of each unit power supply (14), the relation between them is relevant with control mode, controls when respectively organizing unit power supply (14) in the binary code mode, becomes two multiplying powers to concern recursion approximately between the magnitude of voltage of each unit power supply (14), promptly
V
K＝2V
K-1，K＝1，2，3，4……。
K is the group number of unit power supply (14) in the formula, V
KBe the magnitude of voltage of K group unit power supply (14).
In the present embodiment, get V
1=5V, then V
2=10V, V
3=20, V
4=40V.
Like this, under the binary code control mode, open and close each road electronic switch (13), just can have 2 at synthetic one of the input of analog power (3)
KThe quantification voltage of kind of magnitude of voltage quantizes voltage after analog power (3) is in addition simulated, puts on the output stage of efficient category-A power amplifier.Adopt this coded system to synthesize materialization voltage, available a spot of unit power supply (14) combination obtains more quantification change in voltage progression.For example come to synthesize the highest quantification voltage that is output as 80 volts at interval, only need four groups of unit power supplys (14) and the base more than 5 volts power supply (16) that begins with 5 volts quantification voltage jump.The magnitude of voltage of each unit power supply (14) is respectively V
1=5V, V
2=10V, V
3=20V, V
4=40V.See table one for details.
Because voltage controlled source (2) also will be for amplifier (1) provides a minimum sustaining voltage, other establishes the base beginning power supply of often opening (16).The effect that quantizes the continued flow tube (15) in the power supply (4) is, after the unit of corresponding levels power supply (14) loop is disconnected by electronic switch (13), a current path can be provided, make the synthetic quantification voltage of other unit power supply (14) still can put on the input of analog power (3), and when the electronic switch (13) of the corresponding levels is connected, then continued flow tube (15) is partially anti-, the effect that quantizes the storage capacitor (20) in the power supply (4) is to guarantee to quantize voltage can not change instantaneous interruption, and can eliminate contingent impulse disturbances, because its capacity is less, so, can not influence the output voltage climbing speed of whole voltage controlled source (2).
Therefore, quantize the setting of power supply (4), make the input and output voltage difference of analog power (3) begin eventually to be limited in certain scope, the scope of its fluctuation is one and quantizes the voltage steps difference, so, the loss of power unit can not change because of the reduction of output voltage, and can only be the output voltage of voltage controlled source (2)
Lower, the group number that quantizes the unit power supply (14) that power supply (4) turn-offs the more or magnitude of voltage higher, thereby the power of asking for to electrical network is also fewer.
Controlled source biasing among the present invention is implemented as follows: the output voltage V in the load (5)
oMake the output voltage of voltage controlled source (2)
An increment △ Vc is arranged
2=V
o, this voltage increment also produces an increment △ V by biasing resistor (19) on base resistance Rb (17)
BThereby, make the bias current of output stage rise to category-A and amplify desired numerical value, promptly by biasing resistor (19) and base resistance R
b(17) potential-divider network of Zu Chenging has satisfied the biasing requirement that efficient category-A amplifies.Also must insert temperature-sensitive element in case of necessity, carry out thermal compensation with power tube to output stage.
Voltage controlled source of the present invention (2) and controlled current flow biasing can be used for the OCL power amplifier, also can be used for the BTL power amplifier.When being used for OCL, requiring has two groups of power supplys, and two groups of analog powers (3) and two groups of quantification power supplys (4) promptly are set, and detects control circuit control by one group.When being used for the BTL power amplifier, its balanced capacity is stronger, and output stage only needs one group of unipolar supply voltage.Under the identical condition of peak power output, the supply voltage absolute value that the BTL power amplifier requires is 1/2nd of an OCL power amplifier.Thereby, in the BTL power amplifier, implement the present invention and can design the jump that quantizes voltage littler, make the fluctuation range of input and output voltage difference of analog power (3) littler, thereby, the fluctuation range of minimizing unwanted losses.The group number that maybe can reduce unit power supply (14) also can achieve the goal.In addition, when on these two kinds of circuit, realizing controlled bias, because of OTL is one group of output stage, thus need a cover resistor network, and BTL wants two groups.
As mentioned above, in the present embodiment, quantize the suitable jump voltage of voltage and be taken between the 1V-10V, under the constant situation of the highest resultant voltage value that quantizes power supply (4), jump voltage is suitably got littler, and is favourable to raising the efficiency, but the group number of unit power supply (14) increases; Otherwise jump voltage is got greatly, and the group number of unit power supply (14) can reduce, but unfavorable to raising the efficiency.Therefore, should suitably select.
The present invention also can be implemented by alternate manner. For example, analog power (3) The A/D conversion portion can be replaced by a window comparator (21) and a counter (22), and the input and output voltage that detects analog power is poor. Be below or above predefined scope, just respectively output " adding " pulse or " subtracting " pulse changes the output state of forward-backward counter, thereby controls the combination that quantizes voltage. Such as Fig. 7, other parts are the same.
In addition, when enforcement is of the present invention, also can save analog power (3), directly control the output voltage height that quantizes power supply (4) by the output voltage in the load (5), other parts are the same.
Perhaps the output voltage of analog power (3) directly is controlled by the input signal of amplifier by an additional voltage amplifier.
Certainly, the present invention also can partly implement by following form, and namely the output stage biased power settings utilizes voltage controlled source (2) to improve the efficient of amplifier at the required value of class-a amplifier; Or fixedly the supply voltage of output stage utilizes a low power voltage controlled source (can quantize power supply) in the required value of traditional class-a amplifier, by biasing resistor (19) and base resistance (17), realizes the controlled bias electric current. Improved efficiency degree when these two kinds of ways are exported for the power amplifier small-power is identical, can both make the efficient of amplifier be higher than traditional category-A power amplifier, but be lower than 50%.
The efficient category-A power amplifier of the present invention is worked in pure category-A mode, so tonequality is splendid. In addition, owing to be provided with voltage controlled source (2) and controlled bias electric current, so at any one time, the supply voltage of amplifier output stage and bias current value all are the desired supply voltage of category-A power amplifier and the bias current values of taking peak power output with the power output of this moment amplifier as. Therefore, solved the major defect of traditional category-A power amplifier.
" 1 " expression is led in the notes table, and " 0 " expression is broken.
Claims (8)
1, a kind of efficient category-A audio-frequency power amplifier that comprises amplifying circuit, load, follower, it is characterized in that by be exaggerated signal controlling by analog power and quantize voltage controlled source that power supply forms and the controlled bias circuit that is exaggerated signal controlling.
2, efficient category-A audio-frequency power amplifier according to claim 1, it is characterized in that quantizing power supply by testing circuit, code converter, triggering drive circuit, base beginning power supply, organize magnitude of voltage more and become unit power supply, energy storage capacitor, electronic switch and the continued flow tube of two multiplying powers relation to constitute approximately.
3, efficient category-A audio-frequency power amplifier according to claim 1 is characterized in that analog power is made of absolute value circuit, peak holding circuit, drive circuit and follower.
4, efficient category-A audio-frequency power amplifier according to claim 1 is characterized in that the controlled bias circuit is the potential-divider network that is connected between voltage controlled source output and the output stage biased current controling end, and basic structure is three pieces of resistance.
5, efficient category-A audio-frequency power amplifier according to claim 3 is characterized in that said follower is that controlled the following of reference voltage managed or three terminal regulator.
6, efficient category-A audio-frequency power amplifier according to claim 2 is characterized in that said electronic switch is a binary code formula switch.
7, efficient category-A audio-frequency power amplifier according to claim 1 is characterized in that quantizing power supply and includes one " window voltage comparator " and one " forward-backward counter ".
8, efficient category-A audio-frequency power amplifier according to claim 1 is characterized in that the output stage of power amplifier also can only directly be powered by quantizing power supply; Or voltage controlled source or controlled bias circuit can only be set.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 86101540 CN1009044B (en) | 1986-08-18 | 1986-08-18 | High-efficiency class-a audio power amplifier |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 86101540 CN1009044B (en) | 1986-08-18 | 1986-08-18 | High-efficiency class-a audio power amplifier |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN86101540A true CN86101540A (en) | 1988-04-13 |
| CN1009044B CN1009044B (en) | 1990-08-01 |
Family
ID=4801437
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 86101540 Expired CN1009044B (en) | 1986-08-18 | 1986-08-18 | High-efficiency class-a audio power amplifier |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN1009044B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104660190A (en) * | 2013-11-18 | 2015-05-27 | 伍锦程 | Photocoupling dynamic class A biasing circuit |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1059767C (en) * | 1995-07-07 | 2000-12-20 | 沙占起 | Power amplifier circuit |
| JP4330549B2 (en) * | 2005-04-19 | 2009-09-16 | パナソニック株式会社 | High frequency power amplifier |
-
1986
- 1986-08-18 CN CN 86101540 patent/CN1009044B/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104660190A (en) * | 2013-11-18 | 2015-05-27 | 伍锦程 | Photocoupling dynamic class A biasing circuit |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1009044B (en) | 1990-08-01 |
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