CN1206956A

CN1206956A - Amplifier whose final biased current being synchronously controlled by singal change rate

Info

Publication number: CN1206956A
Application number: CN 98113661
Authority: CN
Inventors: 李文华
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-08-07
Filing date: 1998-08-07
Publication date: 1999-02-03

Abstract

The amplifier capable of synchro-controlling final bias current by using signalling rate includes the voltage amplifier circuit, current amplifier circuit and sliding bias circuit. It is characterized by that the bias current or bias voltage of the described sliding bias circuit is controlled by signalling changing rate converter, and the input control signal of said signalling changing rate converter can be input signal,process signal of input signal, output signal and sampling signal of output signal. Said invention completely improves the dynamic characteristics of A and B type power amplifiers, greatly reduces the dynamic internal resistance when the signal is passed zero, raises the temporal response and reduces the switch distortion.

Description

Amplifier by signal rate of change Synchronization Control final bias current

The present invention relates to the transistor high-fidelity power amplifier, especially a kind of amplifier by signal rate of change Synchronization Control final stage power tube bias current.

The transistor high-fidelity power amplifier is to be used for driving load---the equipment of audio amplifier sounding.Because form the vibrating membrane and the interlocking system of the loud speaker of audio amplifier certain mass and inertia are always arranged, be the mass inertia body of a complexity, unavoidably be subjected to support system, the influence of external factors such as audio amplifier and magnetic circuit, therefore it is a dynamic load, and does not have constant damping.

In the pushing course of power amplifier, if the dynamic internal resistance of power amplifier is excessive to audio amplifier---underdamping, can be to the oscillating action deficiency of audio amplifier.Then the state of vibrating diaphragm is mainly by the domination of audio amplifier its own inertial, in case promptly it moves, even coil current is zero, vibrating diaphragm also vibrates under action of inertia, falls up to damped factor complete attenuation.This unnecessary vibration is that we are needs.It causes the response back along distortion.Therefore, high-fidelity power amplifier must have the dynamic internal resistance of enough little output.

The bias current of final stage electric current amplifying power pipe has determined the dynamic internal resistance of output of amplifier.Static state for the degenerative power amplifier of no giant single is consistent with dynamic internal resistance, is inversely proportional to static no-load current.Have greatly improved though be added with the static internal resistance of the degenerative power amplifier of giant single, because very limited to the adaptability to changes of the transient change of dynamic load.Therefore, from certain situation, the dynamic internal resistance of amplifier is approximately the static internal resistance of its open loop.

The basic circuit of conventional power amplifier such as Fig. 1

Voltage amplifier part 1 is amplified to enough voltage with input signal VI, guarantees to have full power output.Electric current amplifier section 3 provides enough current drives loads, and the general direct voltage supply circuit that is called ＂ biasing circuit 2 ＂ that inserts between these two parts is adjusted the situation of current flowing in the level circuit not by it, determines that it exports internal resistance.

Audio-frequency power amplifier can be divided into two kinds of citation forms usually by the transistor state.Be Class A and Class B.

The more employing of present power amplifier is operated in class AB (AB class) between the two.Its no-load current is between Class A and Class B, and small-signal is the Class A, and large-signal is a Class B.Purpose is to make the positive-negative half-cycle waveform level and smooth.Super class a audio power amplifier has also appearred in recent years.Its bias current changes with the size of input signal, and can not end.

If the qualitatively analyze power amplifier can be found Class B to the driving process of audio amplifier, class AB, there is very big shortcoming in super class a audio power amplifier.

1, in the forward position of signal, when coil excitation signals is come, because inertia, the rate of change of vibrating diaphragm does not catch up with signal, less than pumping signal, the equiva lent impedance of mass inertia system is very little by the induced electromotive force of the rate of change of vibrating diaphragm decision, and power amplifier will provide bigger exciting current.

2, on the back edge of signal, coil and vibrating diaphragm system make the damped oscillation cutting magnetic line, and produce corresponding induced electromotive force, and the speed of its size and vibrating diaphragm is directly proportional.This electromotive force is kept the motion of vibrating diaphragm, if amplifier can provide the path of releasing for this electromotive force, perhaps offsets this electromotive force, and the vibration reverberation of coil can effectively be suppressed.

Certainly, the suitable complexity of action and reaction meeting between this power conversion, closely related with current excitation and magnetic circuit intensity or the like, but a bit can determine---the instant speed of coil is big more, be that the pumping signal rate of change is big more, induced electromotive force is big more, and power amplifier is big more to the restraint that the vibrating diaphragm system need provide.

Because the rate of change maximum of audio signal is minimum at peak point often at zero crossing.Therefore can reach a conclusion: no matter zero crossing, the power amplifier on the forward position of signal and edge, back need littler dynamic internal resistance to satisfy the demand of dynamic load, promptly bias current should be maximum; At signal peak, because rate of change is zero, it is static relatively that the dynamic characteristic of load shows, and little static internal resistance is enough to servo load, does not need little dynamic internal resistance, i.e. the bias current minimum.Yet traditional Class B, class AB and super Class A are when signal zero crossing, and Class B, class AB final stage electric current are constant, super Class A final stage electric current minimum, low dynamic internal resistance, the maximum bias opposite current of they and zero crossing response institute palpus, so this class power amplifier servo limited in one's ability to dynamic load.The acoustics that can not get.Though and there is low dynamic internal resistance the Class A at zero crossing, exist power consumption big, the heating serious problems.

The present invention seeks in order to solve the deficiency that the above-mentioned background technology exists, it is big to propose a kind of power consumption, can the boster dynamic characteristic, be reduced in the amplifier by signal rate of change Synchronization Control final bias current of the dynamic internal resistance of zero crossing.

Purpose of the present invention is realized by following scheme.A kind of amplifier by signal rate of change Synchronization Control final bias current, comprise voltage amplifier circuit, current amplification circuit and slip biasing circuit, its special character is that the bias current or the bias voltage of described slip biasing circuit controlled by signal rate of change converter, the input control signal of this signal rate of change converter is following several

A, input signal

The process signal of b, input signal

C, output signal

The sampled signal of d, output signal

In such scheme, described signal rate of change converter is made up of differential circuit and rectification circuit.

The maximum difference of the present invention and background technology is in the processing of current biasing circuit.Traditional biasing circuit is roughly a voltage stabilizing circuit such as Fig. 1, and the voltage U AB that it is recommended final stage between the control end (the twin-stage type is a ground level, and field effect transistor is a grid base) of two power tubes is adjusted to fixing value, a final stage electric current constant like this.And biasing circuit employing of the present invention is the slip biasing circuit, as Fig. 2, the voltage of its circuit bias is also non-constant, it is constant and a positive side-play amount sum of a static state, the size of side-play amount is in the absolute value of bias current input control signal time differential, i.e. its rate of change.With the input sine wave signal is example, and with input signal as the bias current control signal.Its differential result is the input signal cosine wave, and its absolute value is asked in shaping to cosine wave then, i.e. the rate of change of signal.With the amount of bias of this value control biasing circuit, the i.e. recruitment of final stage electric current.Relation such as Fig. 3 between VI and the bias voltage UAB.UABO is static constant.When signal zero crossing, its final bias current maximum; When signal was expired the width of cloth, final bias current stream was minimum.As not having input signal, final bias current is also minimum, is initial value.Like this, when not having input, the power consumption minimum of amplifier is opposite with pure Class A.

With regard to technical scheme of the present invention, it has improved the dynamic characteristic of class AB power amplifier completely under the prerequisite of the power consumption more much lower than pure Class A, dynamic internal resistance when greatly reducing signal zero crossing, improved transient response, reduced switch distortion, the parsing power of sound system is improved a lot, more valuable is, the present invention forms quite simple, and cost is low, roughly on the traditional circuit basis, only increased several elements, (Fig. 4 takes way of full-wave rectification.With the mode of halfwave rectifier, circuit is more succinct) and the increase of these several elements makes circuit characteristic that the leap of value arranged.The present invention is applicable to that the back level of high-fidelity music center or preposition amplification drive, and also are applicable to the control of the complex load that sound system is outer.

Describe principle of the present invention and embodiment in detail below in conjunction with accompanying drawing.

Fig. 1 is traditional amplifier and circuit theory diagrams.

Fig. 2 is circuit theory diagrams of the present invention.

Fig. 3 is the graph of a relation between input signal among Fig. 2 (with the sine wave is example, and wherein the bias current input control signal is an input signal) and the bias voltage UAB.

Fig. 4 is one embodiment of the present of invention circuit diagrams.

With reference to figure 2, the present invention is made up of voltage amplifier circuit, signal rate of change transducer 2, slip biasing circuit 3 and current amplification circuit 4.Wherein input signal VI is after voltage amplifier circuit 1 amplifies, be input in the slip biasing circuit 3, this figure signal rate of change transducer 2 is made of differential circuit and rectification circuit, its input bias current control signal V can be connected on input signal VI end, obtain the signal rate of change after this transducer 2 pairs of bias current control signals differential and the rectification, and this signal rate of change is input in the slip biasing circuit, be superimposed upon on the quiescent biasing voltage, reach with the rate of change of signal control or servo current amplify in the current offset of driving tube.Make final bias current and signal rate of change synchronous.

Fig. 4 is seen in preferably enforcement of the present invention.

Fig. 4 is the push-pull type structure, wherein the also available corresponding field effect transistor of bipolar transistor.

T1, T2 are power tube, and R11, R12 are the Current Negative Three-Point Capacitance resistance of T1, T2, the bias current of T1, T2 is risen set and stabilization.T9, T10 are for promoting pipe, and R10 is that the bias current of T9, T10 is set resistance.TN, TP, R5, R6, R7, R8, D1-D4, C1, C2, C3 finish the differential of input signal VI, promptly try to achieve its rate of change.TN, TP are advisable with firm conducting.R7, R8 are sample resistance, and C2, C3 are anti-self-excitation capacitances.TN, TP, T7, T8, R13, R14 are as rectifying device.Two voltage-stabiliser tube D5, D6 and R9 provide the constant voltage biasing for T7, T8.In order to prevent T5, T6 pipe overcurrent, R5, R6 resistance are not less than 100 ohm.The resonance frequency of R5, R6 and C1 is preferably in more than the 20K.The electric current that flows through T3, R3 and T4, R4 is the mirror image that flows through R7, the last electric current of R8.R3, R4, T3, R1, T4, R2, D1, D2 constitute the slip biasing circuit, and R1, R2 are biasing resistor, when the electric current of T3, T4 is subjected to the control of signal rate of change and when changing, the bias voltage size changes, the biasing of promptly sliding thereupon.

Circuit theory:

The electric current that input signal VI increases---the C1 pressure drop can not suddenly change---T5, R5 increases; T6 increases by the pressure drop of-R7; R13, T7 electric current reduce---and the electric current of T3, R3 increases; The T4 electric current is constant, and the R2 electric current increases---and the pressure drop of R1 and R2 increases.The pressure drop of R11, R12---T1, T2 bias current increase.

Otherwise, in like manner.

Claims

1, a kind of amplifier by signal rate of change Synchronization Control final bias current, comprise voltage amplifier circuit, current amplification circuit and slip biasing circuit, the bias current or the bias voltage that it is characterized in that described slip biasing circuit are controlled by signal pace of change converter, the input control signal of this signal rate of change converter is following several

A, input signal

The process signal of b, input signal

C, output signal

The sampled signal of d, output signal.

2,, it is characterized in that described signal rate of change converter is made up of differential circuit and rectification circuit according to the described amplifier of claim 1 by signal rate of change Synchronization Control final bias current.