CN1567714A

CN1567714A - Digital power amplifier with ultralow internal resistance

Info

Publication number: CN1567714A
Application number: CN 03129578
Authority: CN
Inventors: 于志伟
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-06-27
Filing date: 2003-06-27
Publication date: 2005-01-19
Also published as: WO2005002043A2

Abstract

The invention relates to a modified digital switch amplifier circuit, especially relating to a method of by a large margin reducing open-loop output inner resistance of digital switch power amplifier, increasing damping coefficient, reducing ripple voltage and increasing converting efficiency. Because of property improvement, as used in digital audio power amplifier, it obviously improves the control ability to the load because of increasing the damping coefficient by a large margin, thus by a large margin improving tone quality, layer feeling and resolution. It can be widely applied to digital controlled power output circuit, switching power supply converter and other current supply devices and dynamic power supply devices of digital circuits, analog circuits, and analog power amplifiers.

Description

Ultralow internal resistance digital power amplifier

The present invention relates to a kind of improved digital switching amplifier circuit, particularly relate to a kind of digital switch power amplifier open loop output internal resistance that significantly reduces, reduce ripple voltage, improve the method for conversion efficiency.

In the digital switch power amplifier of prior art, during switch conduction, the output internal resistance of amplifier is lower.When switch turn-offed, the inductance back-emf continued stream [Fig. 1] when by diode by backward diode D or synchronous rectifier V and power supply E, and particularly by behind the power supply E, back-emf raises, and electric current descends, and making continues flows interior internal resistance of time period and significantly rise.Simultaneously, under the open loop situations, when the output switch turn-offed, the output internal resistance reached peak.Export internal resistance this moment and pass through power supply E at the high internal resistance state of little electric current by oppositely continue stream diode or synchronous rectifier.Under this state, the back-emf of inductance must the value of boosting surpass power supply and V _D(E+V _D) voltage, it is many than short circuit [a], the decline of [b] end to keep electric current, so internal resistance is risen.Simultaneously, descended fast by initial value owing to keep electric current, cause waveform recessed fast (Fig. 3), make ripple become big, it is many that the high order harmonic component product becomes.In addition, because the unexpected rising of back-emf, higher-order wave is abundant, is equivalent to frequency and raises, and has limited the raising of former switching frequency, and switching device has all been improved requirement.Simultaneously, because the rising of back-emf, the rising of power conversion ratio all can make gross efficiency descend.

The purpose of this invention is to provide a kind of method (Fig. 2), significantly reduce switch power amplifier open loop output internal resistance, reduce ripple, improve power-efficient at [a], [b] end short circuit.

At shorting switch V _AWhen connecting desirable situation, the electric current pace of change in the inductance becomes minimum (Fig. 3), power conversion ratio minimum, and current/voltage high order composition is minimum, makes switching circuit enter soft state, and circuit conversion efficient reaches peak.The gross efficiency of this kind state of switch circuit can reach more than 90～98%, further raises the efficiency 1～10% than primary circuit.

Short circuit constantly is arranged in switching circuit and turn-offs, comprise that device rises, fall time section outside the influential time period, and make current break minimum in the inductance L, be changed to smooth transition, do not make switch conduction electric current and voltage constantly by [V in the shorting member [Fig. 2] _A] short circuit, to cause phenomenons such as decrease in efficiency, device failure.For this reason, short circuit is opened constantly with short circuit constantly, constantly should keep safe, most effective time interval Δ t[Fig. 4 with any switching device conducting].

The short circuit time also comprises all other any fundamental signals [F], [D] or [G], [H] end is zero, the moment of t ≠ 0.This point is different with supply convertor and general digital power amplifier.

The method of this kind short-circuit is applicable to half-bridge and full-bridge circuit [Fig. 5], [Fig. 6].Also be suitable for its any single switching circuit.[V in the short circuit device [Fig. 2] _A] generally adopt the controllable devices of active amplification controller spare as bipolar transistor, FET triode and other any kind of.

Fundamental signal in [Fig. 2] [F], [D] or [G], [H] terminal can be used for the negative feedback control of fundamental signal.

In all amplifiers, it is the most basic improving open-loop performance.Use short circuit method of the present invention, can make the internal resistance of switch output circuit be low to moderate 0.01m Ω～below 2000 Ω, usually, can be low to moderate 0.1m Ω～below 10 Ω.The size of internal resistance is mainly determined by conducting resistance Ron and switching speed ton, the toff of active controllable devices.For R, the internal resistance of fundamental frequency is also by the impedance of L and the impedance decision of C.When R one timing, C increases, and L descends; C reduces L and increases, and goes up the amplitude requirement of fundamental signal to keep R.But the time constant of R, L, C circuit must satisfy the requirement of fundamental frequency signal, and promptly the signal at R two ends must be identical with the circuit fundamental frequency signal.

Side circuit is with the V in [Fig. 2] _AThe short circuit device is installed in [a], [b] end of [Fig. 5], [Fig. 6].[V _A] must be two-way withstand voltage device greater than E.For example: constitute short circuit device [V in [Fig. 7] mode _A], with MOSFET (or JFET) differential concatenation of two identical raceway grooves, each MOSFET (or JFET) is withstand voltage greater than power supply E.Only shown several series-mountings among Fig. 7, principle is, all devices that diode in the body is arranged are correct method with diode reverse butt joint in the body, and the pressure drop the when forward of short circuit device is with reverse current simultaneously should be identical, forward is withstand voltage all need greater than power supply E.All gate-controlled switch devices that meets above-mentioned condition all can be used for the short circuit device.For example, thyristor, MCT pipe etc.

In addition, the device of diode D in adopting no body during as JFET, can adopt two JFET serial connections, can also be used as the short circuit device by a JFET, because of D, the S electrode of JFET can exchange use.

An embodiment is a full-bridge circuit preferably, sees [Fig. 6].

V1, V2, V3, V4 in the full-bridge circuit can double as short circuit devices.When the diagonally opposing corner conducting, as power supply power supply usefulness, when parallel conducting, as short circuit device usefulness, job order is:

1, V1, V4 conducting, 2, V1 disconnects, the V2 conducting, V4 is conducting still.

3, V4 disconnects, the V3 conducting, and V2 is conducting still

4, V2 disconnects, the V1 conducting, and V3 is conducting still

5, V3 disconnects, V4 conducting, still conducting of V1 (following periodic duty.)

N. when not having input (output) fundamental frequency signal, press on-state at that time, or V1, V3 short circuit, or V2, V4 short circuit.

Above-mentioned switch short circuit still keeps safety, Δ t time slot efficiently constantly.

Method of the present invention is applicable to all digital power amplifiers and preposition small signal amplifier and digital processing circuit.

The generation of short circuit signal is by the digital DSP circuit control of arbitrary form.In some cases, can use, help the accuracy of safe time slot Δ t to shift memory.

In addition, at output [F], [D], [G], [H] point is established level sensitive circuit, and as [F], [D] or [G], when [H] has with incoming signal level long period and big level difference value owing to any reason, short-circuit all disconnects, and the control way circuit cuts off.Short circuit device and the reciprocal lock of digital control pulsion phase.

Safe time slot [Δ t], by the ton of device, the decision of toff performance, design Δ t is 0.1ns～below the 5 μ s, be generally below 1～200ns, when guaranteeing that circuit efficiency improves simultaneously, and Δ t is hour, shows that time slot is designed to optimum value.

Circuit design should make the circuit pulse duty ratio smaller preferably, and is for example, permanent in (5～50) %.Finish by direct voltage adjustable AC/DC or DC/DC and regulate power output.Simultaneously, for the efficient that makes AC/DC and DC/DC improves, should make voltage transformating ratio not excessive.For this reason, the tap that can increase the transformer primary and secondary is regulated.Switching circuit duty ratio and supply voltage E ratio are manual or grading automatical control.

Amplifier of the present invention, when its fundamental frequency signal output amplitude and power when enough, can with simulation category-A or AB class or S class or AA class combination of circuits, in AA class and S class circuit as connecting the dynamic power supplies feeder, thereby significantly improve the power-efficient of above-mentioned AA class, S analoglike power amplifier.The output feeder ear is [F], [D] or [G], [H], is connected the electric current supply end of foregoing circuit, and the analog current supply side of promptly former AA class or S class circuit substitutes with [F], [D] or [G], [H].

Switching signal produces fundamental frequency signal at [F], [D] or [G], [H] end after L, C filtering.[F], [D] still can apply negative feedback by resistance with [G], [H] end.

Fundamental frequency is fed back to and promotes level enforcement feedforward preferably, and power stage is implemented rear feed, and transient response is better like this.

Certainly, also can implement big ring feedback or compound feedback.

Because the present invention has adopted pulse signal positive and negative " 1 " constantly safe short circuit in addition, makes the open loop output internal resistance of power amplifier reach enough low numerical value, making it has fabulous, control energy accurately to various loads.Simultaneously, the energy conversion voltage jump in the inductance L greatly reduces, and energy conversion efficiency is improved more than 1%～10%, reduces caloric value, promptly is equivalent to reduce device installation volume, weight.In addition,, reduced electromagnetic radiation, also reduced ripple voltage simultaneously, improved signal noise ratio with fundamental signal because the minimizing of voltage jump among the L reduces the higher-order wave product of switching frequency.

Fundamental frequency damping coefficient f when needs control R two ends _DThe time, can apply the current feedback of corresponding proportion, or the small resistor R that before R, connects _DCan regulate the feedback proportional of Rf1 and Rf2 respectively, to regulate output impedance and f _DThe size of value.Go up the current feedback that is fed back to of sampling from [Rf], it makes f _DDescend.Regulate [Rf1], [Rf2], can change f arbitrarily _DNumerical value.

Description of drawings:

Fig. 1, regular tap power amplifier

Fig. 2, short circuit device V _ABe connected in circuit a, b the end.

In Fig. 3, the regular tap power amplifier, the electric current I t2 that flows through among the stream diode D that continues.

Fig. 4, time slot Δ t for preventing that the short switch electric current from setting.

Fig. 5, half-bridge circuit

Fig. 6, full-bridge circuit

The constructive method of Fig. 7, some short circuit devices.

In Fig. 8, the first-harmonic feedback, feedback resistance Rf1, Rf2, current feedback sample resistance R _F, resistance R is regulated in the output internal resistance _D

Claims

1, a kind of improved digital amplifier is characterized in that: at [a], [b] end of amplifier, the time outside the positive negative pulse stuffing is with active controller spare [V _A] short circuit [a], [b] end, the short circuit time can also comprise that [F], [D] or [G], [H] fundamental frequency signal are zero time period, [F], [D] or [G], [H] terminal can apply negative feedback to fundamental frequency signal.

2, amplifier according to claim 1, it is further characterized in that: V _AThe short circuit device uses two oppositely JFET or JFET of serial connection.

3, amplifier according to claim 1, it is further characterized in that: V _AThe short circuit device uses two series connection MOSFET formations of diode reverse butt joint in the body, or with formations such as bidirectional thyristor or two-way MCT pipes, also can in full-bridge circuit, utilize V1, V2, V3, V4 double as short circuit device, can adopt any two-way blocking-up, the controllable devices that Ron is identical.

4, amplifier according to claim 1, it is further characterized in that: regulating output impedance can be with being connected in series [R _D] or add electric current sample resistance [R _F], [Rf2], [Rf1] make current feedback and Voltage Feedback ratio is regulated, or uses feedforward and rear feed, or compound feedback.

5, amplifier according to claim 1, it is further characterized in that: V _AThe Ron of short circuit device is less than 0.01m Ω～below the 2k Ω.

6, according to the described amplifier of claim 1, it is further characterized in that: short circuit device V _AShort circuit with disconnect the Δ t time, can produce and control by promoting circuit controller numeral DSP circuit, output switching pulse and [F], [D], [G], [H] signal, DSP circuit are locked mutually with the short circuit device, and output detection circuit measures signal level and output level difference than greatly the time, V _ADisconnect and the cut-out way circuit.

7, amplifier according to claim 1, it is further characterized in that: it is controllable way that adjusting AC/DC or DC/DC and transformer tapping make power output with the change supply voltage, simultaneously, the duty ratio perseverance that keeps digital power amplifier is less than below 5%～50%, and its duty ratio compares with manual control or grading automatical control with the relation of supply voltage.

8, amplifier according to claim 1, it is further characterized in that: output [F], [D] or [G], [H] are connected the electric current supply end of analogue amplifier, replace the primary current feeder.