CN100417017C

CN100417017C - Asynchronous bridging load of D class audio amplifier

Info

Publication number: CN100417017C
Application number: CNB200510052573XA
Authority: CN
Inventors: 陈敏雄; 钟尚书
Original assignee: Princeton Technology Corp
Current assignee: Princeton Technology Corp
Priority date: 2005-02-17
Filing date: 2005-02-17
Publication date: 2008-09-03
Anticipated expiration: 2025-02-17
Also published as: CN1822493A

Abstract

The present invention provides an asynchronous type BTL design of a D-class audio amplifier, which adopts two separate signal paths, each path comprises a PWM modulator, a preposing driver and a power MOS circuit; input signals are received by the PWM modulator of each separate signal path, and then, a loudspeaker is driven by output signals of the power MOS circuits of the separate signal paths together, wherein the two PWM modulators do not input synchronous signals, and the two power MOS circuits can respectively feed back signals before wave filtering and/or signals after wave filtering to the PWM modulators without interacting. The present invention leaves out the synchronous design of the prior art, enables two paths of push-pull signals needed by the BTL design to be respectively processed, and enables the signals of the two paths of signals not to interact; but finally, the loudspeaker is still driven by the two paths of signals together.

Description

The asynchronous bridging load of D class audio amplifier

Technical field

The present invention relates to the improvement of D class audio amplifier, especially relate to the D class audio amplifier that adopts asynchronous system BTL (Bridge Tied Load, bridging load) design.

Background technology

Referring to Fig. 1 (a) and (b), be the outgoing carrier signal OUTA and the OUTB of a push-pull type (push-pull) D class audio amplifier.The outgoing carrier signal OUTA of this push-pull type D class audio amplifier identical with the carrier phase of OUTB (shown in Fig. 1 (a)), or the carrier phase of outgoing carrier signal OUTA and OUTB differs stationary phase, as 180 degree (shown in Fig. 1 (b)).The carrier wave of output signal can filtered device or the filtering of people's ear when usually using, so input sync signal makes the design of carrier synchronization of output signal there is no need in fact the output of music signal.

Referring to Fig. 2, be a kind of circuit diagram of D class audio amplifier.Audio signal V _InTwo input a, b input operational amplifier 1 from the left side, 1 output of operational amplifier two-way audio signal is delivered to operational amplifier 2 and 3 (both is a comparator) respectively, pass through predriver (Predriver) 4 and 5 then respectively and produce output signals, drive power cmos circuit 6,7 thereafter and produce output signal OUTA and OUTB.Output signal OUTA and OUTB drive loud speaker 8 jointly, and this is a kind of push-pull type (push-pull) circuit, promptly so-called BTL (Bridge Tied Load, bridging load)

design.Resistor

9,10 is used for feedback signal, capacitor the 11, the 12nd, and a kind of compensating circuit, inductor 13,14 and capacitor 15,16 provide filter circuit for filtering.The triangular wave V of 500KHz _TriangularInput operational amplifier 2 and 3, purpose are to make the two-way carrier signal of input operational amplifier 2 and 3 synchronous, and the result makes output signal OUTA consistent with the carrier phase of OUTB, shown in Fig. 1 (a); Or the carrier phase that makes output signal OUTA and OUTB differs 180 °, shown in Fig. 1 (b).

Operational amplifier

1,2 and 3 forms the PWM modulator (Pulse WidthModulator pulse width modulator) of this kind D class audio amplifier.The PWM modulator has various designs, shown here just wherein a kind of design.

The triangular wave V of foregoing circuit _TriangularThe necessary triangular wave of design in addition generator, but the triangular wave generator is comparatively complicated and be difficult for the accurate triangular wave of generation, the triangular wave generator is inserted often occupy too many circuit space in the integrated circuit, thereby increase cost.Input sync signal makes the design of carrier synchronization of output signal there is no need in fact output signal OUTA and OUTB.

Output signal OUTA and OUTB respectively must be very accurate when

resistor

9,10 feedback signals arrive operational amplifier 1, otherwise make the two paths of signals can not balance.This makes the admissible error of IC circuit layout less, therefore increases manufacturing cost.

Summary of the invention

Therefore the object of the present invention is to provide a kind of asynchronous system BTL design of D class audio amplifier, as shown in Figure 3 two signal paths independently, each self-contained PWM modulator (Pulse Width Modulator pulse width modulator), a predriver and a MOS circuit; These two each free its PWM modulator receiving inputted signal of signal path independently, each free its MOS circuit output signal and drive a loud speaker jointly then; Wherein these two PWM modulators do not have synchronizing signal input, and these two MOS circuit respectively before feedback filterings and/or after the filtering signal do not interact to this PWM modulator.The present invention omits the Synchronization Design of prior art, and the two-way push-pull signal of BTL design is handled respectively, two paths of signals is not interacted, but still drive loud speaker jointly at last.

Description of drawings

Fig. 1 is the output signal schematic diagram of conventional D class audio amplifier.

Fig. 2 is the circuit diagram of conventional D class audio amplifier.

Fig. 3 is the circuit diagram of D class audio amplifier of the present invention.

Fig. 4 is the output signal schematic diagram of D class audio amplifier of the present invention.

Embodiment

With reference to figure 3, demonstrated the present invention the D class audio amplifier has been improved.Audio signal V _InTwo input a, the b difference input operational amplifier 21,22 from the left side, 21,22 of operational amplifiers output audio signal are separately delivered to operational amplifier 23 and 24 respectively, pass through predriver (Predriver) 25 and 26 then respectively and produce output signal, drive power cmos circuit 27,28 thereafter and produce output signal OUTC and OUTD.Output signal OUTC and OUTD drive loud speaker 29 jointly, and this is a kind of push-pull type (push-pull) circuit, promptly so-called BTL (Bridge Tied Load, bridging load) design.Resistor the 30, the 31st is used for feedback signal, and capacitor the 32, the 33rd is used to provide vibration, and inductor 34,35 and capacitor the 36, the 37th are used to provide filter circuit for filtering.Operational amplifier 21,23 and the so-called PWM modulator of operational amplifier 22,24 each self-forming.The PWM modulator has various designs, shown here just wherein a kind of design.

The characteristics of Fig. 3 circuit maximum are exactly the triangular wave V that does not have 500KHz _TriangularInput operational amplifier 23 and 24 is made synchronous usefulness, so output signal OUTC and OUTD phase place are inconsistent, as shown in Figure 4.Complicated triangular wave generator has been omitted in the sort circuit design, has saved the circuit space in IC (integrated circuit) design, thereby has reduced cost.The Synchronization Design of triangular wave there is no need in fact for operational amplifier 23 and 24, because triangular wave just makes carrier signal synchronous, but obtain to the end needing to have removed carrier signal behind output signal OUTC and the OUTD, so carrier synchronization is unimportant with filter circuit or people's ear.

Fig. 2 output signal OUTA and OUTB respectively must be very accurate when

resistor

9,10 feeds back signal to same operational amplifier 1, otherwise two paths of signals can not balance.This makes in the manufacture process admissible error of integrated circuit layout less, therefore increases manufacturing cost.But it 21,22 o'clock was feedback signal separately that the OUTC of Fig. 3 circuit of the present invention and OUTD feed back signal to operational amplifier through resistor 30,31 respectively, do not interact, so the admissible error of integrated circuit layout was bigger in the manufacture process, therefore reduced manufacturing cost.

The OUTC of Fig. 3 circuit and OUTD feed back signal to operational amplifier 21,22 through resistor 30,31 respectively, also the signal SP+ and the SP-of 29 liang of inputs of loud speaker can be fed back to operational amplifier 21,22 through resistor 30,31 respectively.

Power cmos circuit 27,28 can be used general MOS circuit instead among Fig. 3.

Spirit of the present invention and scope are not limited to the foregoing description, but depend on following claims.

Claims

1. the asynchronous bridging load of a D class audio amplifier, this D class audio amplifier comprises two independently signal paths, this signal path every each self-contained pulse width modulator, a predriver and a MOS circuit; These two each free its PWM modulator receiving inputted signal of signal path independently, each free its MOS circuit output signal and drive a loud speaker jointly then; Wherein said two PWM modulators do not have synchronizing signal input, and described two MOS circuit feed back it respectively and output signal to described two PWM modulators, do not interact.

2. the asynchronous bridging load of D class audio amplifier as claimed in claim 1, wherein said two MOS circuit back connect a filter circuit separately, the output signal of described two filter circuits then drives this loud speaker jointly, and the signal of two inputs of this loud speaker is fed back to described two PWM modulators respectively.

3. the asynchronous bridging load of D class audio amplifier as claimed in claim 1 or 2, wherein this MOS circuit is the power cmos circuit.