CN102332869A

CN102332869A - High-integration BTL (bridge-tied load) audio power amplifier

Info

Publication number: CN102332869A
Application number: CN201110155195A
Authority: CN
Inventors: 王海兵; 易法友; 朱慧
Original assignee: WUXI YOUDA ELECTRONICS CO Ltd
Current assignee: WUXI YOUDA ELECTRONICS CO Ltd
Priority date: 2011-06-10
Filing date: 2011-06-10
Publication date: 2012-01-25
Anticipated expiration: 2031-06-10
Also published as: CN102332869B

Abstract

The invention discloses a high-integration BTL (bridge-tied load) audio power amplifier which integrates necessary structures of BTL application without peripheral debugging components. The high-integration BTL audio power amplifier comprises four AMPs (Amplifiers) and two transconductance amplifiers, wherein the amplifiers A and B are main amplifiers and provide a main access; the amplifiers C, D and E form an output common mode imbalance compensation module, and the amplifiers C and D are an upper drive unit and a lower drive unit of an audio power amplifier; the transconductance amplifier E is in charge of detecting direct-current common mode imbalance at two ends of a BTL and feeding back to a current control end for finely regulating current to further reduce imbalance, and can also be used for finely regulating gains when outputting clip waves so that the gains at two output ends are completely same, the output power reaches the maximum, and the efficiency is highest; and the transconductance amplifier F is in charge of providing frequency compensation of a system except for Miller compensation, has an equivalent capacity of 100nF, and provides enough phase margin for the system.

Description

High integration BTL audio-frequency power amplifier

Technical field

The present invention relates to a kind of audio power amplifying circuit, particularly BTL uses offset compensation in the audio frequency power amplifier, gain compensation, and phase compensation.

Background technology

Under same voltage,, all can adopt the BTL mode to use in order to obtain higher sound output; As shown in Figure 1 is a kind of popular usage, and this usage has been saved output coupling capacitor, also reduces outside dividing potential drop consumption; But this usage has two shortcomings: there is not the offset compensation circuit, and output outside need building-out capacitor, the offset voltage that BTL uses circuit output end requires high especially; If imbalance is dealt with improperly, can influence quiescent dissipation on the contrary, also can produce very big current sound; When large-signal output slicing,, can influence whole delivery efficiency if the two ends gain has difference; Circuit was used than monophony and is made circuit unstable more when BTL used in addition, and phase margin diminishes, and general settling mode is the electric capacity of external 100nF, but the present invention improves internal structure, need not outside any building-out capacitor.

Summary of the invention

Technical problem: the present invention mainly solves the BTL imbalance and the inconsistent problem that gains, and the circuit stability problem.

Technical scheme:

The present invention includes 4 AMP, 2 trsanscondutance amplifiers, amplifier A, B are main amplifier, and primary path is provided; Amplifier C, D, E form output offset compensation module, and wherein C, D still are the driver element up and down of audio frequency power amplifier, and trsanscondutance amplifier E is responsible for detecting the direct current common mode imbalance of BTL two ends; Feed back to current controling end inching electric current, and then reduce imbalance, also when the output slicing; E can also finely tune gain, makes the gain of output two ends identical, makes power output reach maximum; Most effective, the reference current module, being responsible for output provides and exports mid point comparatively accurately; The F trsanscondutance amplifier is responsible for providing the frequency compensation of the system except that miller-compensated, and its equivalent capacity is 100nF, for system provides enough phase margins.

Beneficial effect: owing to adopted the offset compensation network, circuit is with the fluctuation of technology, and imbalance obviously reduces; Dispersion degree also reduces greatly, does not have the circuit of this compensating network, on delivery efficiency, also improves; Because integrated 104 necessary electric capacity of BTL; Make peripheral the simplification, use simplyr, system is more stable.

Description of drawings

The general BTL functional block diagram of Fig. 1.Comprise among the figure: the first amplifier A, the second amplifier B.

Fig. 2 is band offset compensation and frequency compensated block diagram.Comprise among the figure: the first amplifier A, the second amplifier B.

The 3rd amplifier C, four high guaily unit D, the 5th trsanscondutance amplifier E, the 6th trsanscondutance amplifier F.

Fig. 3 is the impedance isoboles.

Embodiment

Utilized six amplifiers among the present invention, wherein A, B confirm the gain of primary path, the closed loop gain of BTL

GV={1+R2/ (R1+R3) }+R4/ (R1+R3) }+Σ GV (correction); ,, must be arranged to wherein R2=R4, R1=R3 in order to remedy the fluctuation of technology; If gain when inconsistent in two amplifiers, the common mode imbalance will appear, depart from mid point, compensating circuit can start, adjustment gain compensation electric current, the amplifier of suitable reduction elder generation slicing makes the two-way gain in full accord.

The common mode imbalance; Circuit itself is provided with a reference current i0=(VCC-2Vref)/R2; Suppose fully symmetry, under the prerequisite of the electric current that not have to compensate, reference current is divided equally by amplifier A, B; The resistance R of in amplifier A, flowing through 2 electric currents equal to flow through among the amplifier B electric current of resistance R 4, so A amplifier output mid point is:

VA=i0*R2/2+Vref=Vref+VCC/2-Vref=VCC/2

The purpose that Vref is set is in order to improve the maximum input level that input bears.

VB=VCC/2 in like manner.

There are the common mode imbalance in amplifier A, B in the reality, and amplifier C, D are responsible for detecting imbalance, and when output gain did not match, vo voltage deviation mid point started gain compensation circuit, and output offset current, and then adjustment gain passage bigger than normal make the gain of two-way output suitable; When technological fluctuation caused the output common mode imbalance, the common-mode voltage testing circuit started, the output corrective current, and adjustment output mid point reaches the effect of correcting static imbalance.C, D are that a simple closed loop is used amplifier, and gain is set to 3; Owing to be arranged on output driving part, also play the THD that reduces to export, and then reduce the whole distortion factor.

Because what adopt is that BTL uses, two system A that work independently, B combine; Needed frequency compensation is complicated more, and the present invention selects compensation point at the G point, from whole system; Suppose an input section ground connection, G point is the interchange ground of system, if system is powering on or other interference makes A, B output exist high frequency to lack of proper care; There is disturbing pulse in the G point so, owing to be that BTL uses, this disturbs the feedback through A, B to be sustained; Form concussion, this concussion will be sustained, and form self-excitation.This phenomenon is general phase compensation theory,

Because the frequency compensation of A, B self is no problem, it is highly stable to work independently, and uses but be combined into BTL, for stablizing of system, needs extra again setting compensation network.The present invention is provided with one to earth capacitance at the G point, as high-frequency ac ground, makes the high frequency waves of A, B output after feeding back, directly arrive ground through building-out capacitor, and the primary path of not flowing through can not form positive feedback.Prevent high-frequency self-excitation.Derive below and how to realize 100nF electric capacity.

Suppose that the electric current that flows into is i, port voltage is v, and the resistance voltage is VR, is c to earth capacitance, and equiva lent impedance is rin; The equivalence equivalent capacity is cin; The mutual conductance of gm trsanscondutance amplifier is A; Then satisfy following relational expression:

i=VR*A+VR/R（1）

v=VR/jωc*R?+VR(2)

Can draw rin=ri+cin=1/A*R+1/ j ω c*R*A (3) by (1), (2), isoboles is as shown in Figure 3.

Ri=1/A*R wherein; Cin=1/j ω c*R*A; Ri ≈ 0, equivalent capacity cin=(A*R) 1/j ω c is so equivalent capacity has been amplified (A*R) doubly; Suppose that mutual conductance is A=10, R=10K, so inner integrated capacitance c=1pF is cin=(10*10k*1p) F=100nF; Utilize smaller capacitive, realized the function of big electric capacity, eliminated high-frequency self-excitation.

Claims

1. a high integration BTL audio-frequency power amplifier is characterized in that comprising 4 AMP, 2 trsanscondutance amplifiers; Amplifier A (1), B (2) are main amplifier, and primary path is provided, and amplifier C (3), D (4), E (5) form output offset compensation module; Wherein C, D still are the driver element up and down of audio frequency power amplifier, and trsanscondutance amplifier E is responsible for detecting the direct current common mode imbalance of BTL two ends; Feed back to current controling end inching electric current, and then reduce imbalance, also when the output slicing; E can also finely tune gain, makes the gain of output two ends identical, makes power output reach maximum; Most effective, the reference current module is responsible for output and provides and export mid point comparatively accurately, and F (6) trsanscondutance amplifier is responsible for providing the frequency compensation of the system except that miller-compensated; Its equivalent capacity is 100nF, for system provides enough phase margins.

2. high integration BTL audio-frequency power amplifier according to claim 1 is characterized in that amplifier C (3), D (4), E (5), direct current common mode imbalance adjustment, ac gain adjustment, the compensation of F (6) BTL high frequency network.