CN100481715C - Electric level detector for protection control power amplifier and power amplifier thereof - Google Patents

Abstract

This invented potential detector detects the potential of a stand-by end of an audio power amplifier at the boost period, a detector is self-activated and the fault state of an output module can be tested, such as, short circuit of an output end to the earth. In said detectors, a second earth short circuit detector tests the potential of stand-by end and that of the output end when the voltage boosts, the detector activates a cut-off signal generation module according to the potential reaching to the first threshold value level. A resume module makes the cut-off signal generation module fail according to the detection. It reaches the potential of the second threshold value level greater then the first. Since the cut-off signal module sends the cut-off signal as the request for cutting off the activated protection switch it can protect the switch module and stop sending the failed cut off signals.

Description

Be used to protect the electric potential detector and the power amplifier thereof of control power amplifiers

Technical field

The present invention relates to power amplifier, particularly protect at the power amplifier of malfunction.

Background technology

In power amplifier system, preferably to avoid in the fault mode operation, such operation may cause the nonvolatil damage of system's (particularly power transistor).With designed protective circuit, malfunction can be repaired by system, and reenters normal running and the influence that is not subject to any damage.Design routinely, following any malfunction does not appear in protective circuit protection power amplifier: output over the ground, to power supply or to the short circuit of other outputs; The power output overloading; Supply voltage overload or supply voltage are low; It is overheated to encapsulate.U.S. Patent No. 4053996 discloses an example of this protective circuit.

Fig. 9 shows the block diagram that is used for conventional audio-frequency power amplifier protection.Power amplifier comprises: output module 2, output 3, biasing module 4, stand-by end 5 and protection module 70.

Output module 2 is included in two power transistors of connecting between power supply and the ground that voltage is Vcc.Output 3 is connected between two power transistors.Biasing module 4 provides bias current for other circuit module, and therefore other circuit modules are setovered and be in state of activation, specifically are to make two power transistor conductings.Then, a large amount of electric currents flows through power transistor and output 3, therefore, gives the external loading power supply such as loudspeaker (not having to show).

Protection module 70 comprises: protection switch module 71, ASO (safety operation area) detection module 72 and shorted to earth detect piece 73.ON/OFF (conducting/disconnection) state of the protection switch module 71 protection switch 7As of control between output module 2 and biasing module 4, and allow (perhaps stoping) bias current to flow into (or flowing out respectively).ASO detection module 72 is designed to detect the work of power transistor of their ASO outside.Here, the operation of ASO outside is meant the malfunction that above-mentioned power transistor occurred, for example: " over the ground, to power supply or to other the short circuit of output " and " overload " etc.ASO detection module 72 is by the work of electric current, voltage and the temperature detection output module 2 of power transistor.When electric current and voltage surpassed the limit of temperature variant ASO, ASO detection module 72 sent a signal to protection switch module 71 (for fear of faulty operation, usually at predetermined time-delay T _DSignal is carried in the back).Then, protection switch module 71 disconnects protection switch 7A, so, disconnect the bias current that is used for output module 2.Therefore, power transistor is not considered the type of these two faults and all is limited at the OFF state.Simultaneously, protection switch module 71 connects shorted to earth detection piece 73 to biasing module 4.Then, shorted to earth detects piece 73 and is activated, and detects the above earth potential of output 3.In the incident of output 3 shorted to earths, shorted to earth detects piece 73 and sends a signal to protection switch module 71 continuously.Thus, protection switch module 71 makes protection switch 7A keep the OFF state.Therefore, protection module 70 prevents because overcurrent makes the power transistor permanent damages.When not detected or having eliminated short circuit over the ground, shorted to earth detects piece 73 termination signals and carries.Then, protection switch module 71 conducting protection switch 7A.Thus, allow bias current to flow to output module 2.Therefore power transistor work, the power amplifier enabling.

The above-mentioned protection that is used for power transistor in the course of normal operation of power amplifier is effective; because the electric current of output module 2 and voltage are so big, to such an extent as to ASO detection module 72 can be easily and detected the operation of the power transistor of ASO outside quickly.But in following voltage elevation process (power-up), for example, output 3 just can go wrong during the malfunction of shorted to earth.

Figure 10 demonstrates the voltage V of protection switch 7A, protection switch module 71, ASO detection module 72, shorted to earth detection piece 73 and stand-by end 5 _STBThe working timing figure (see figure 9) of level.Among Figure 10, high (or low) level represents each circuit module in state of activation (or unactivated state).Here, give stand-by end 5 making alive V with the external device (ED) of for example microcontroller _STB, in the process that voltage raises by predetermined ratio its level that raises.The voltage V that biasing module 4 detects in the voltage elevation process _STBLevel, when stand-by end 5 is fully activated, that is to say voltage V _STBLevel reach predetermined level V _ON, supply with bias current just for protection module 70.Thus, protection module 70 is avoided the misoperation that raises and cause owing to surge current and mutation voltage.Specifically, audio-frequency power amplifier prevents that when voltage raises loudspeaker from playing and does not wish the noise (known " the emergent noise that pipes ") that occurs.The configuration of stand-by end 5 is common components of existing power amplifier (specifically being audio-frequency power amplifier).

When voltage began to raise, T0 back protection module 70 constantly kept unactivated state, up to moment T _ONThe current potential V of stand-by end 5 _STBReach predetermined level V _ONTill.Therefore, from T0 the time, be carved into T _ON ASO detection module 72 can not detect the work of the power transistor of ASO outside in period constantly.Therefore, in a period PON, protection switch 7A keeps the ON state, and described period PON is constantly to constantly postponing T again from TON from T0 _DThe time that finishes.For example, in the short circuit event over the ground of output 3, in period PON, excessive electric current flow through power transistor when voltage raise, and consumed a large amount of power in power transistor.Unless in the extremely short period, eliminate this short circuit event, otherwise this power consumption can cause the permanent damages of power transistor and even power amplifier.Because protection module 70 can not respond the generation of fault fast during voltage raises, therefore, be difficult to reduce harm to the permanent damage of power transistor.

In order to activate protection module 70, particularly the ASO detection module 72, require ASO detection module 72 its detection ranges of expansion and improve its accuracy of detection in the stage early that voltage raises, and guarantee its reliability during voltage raises thus.Yet, because output module 2 is usually designed to enough big size,, therefore want to make its chip size minimum so that enough power to be provided, need the strict ASO that limits power transistor.Therefore, be the operate as normal of power amplifier, the accuracy of detection that ASO detection module 72 requires is high.In addition, when Designing power amplifier becomes monolithic integrated circuit IC, strict the qualification to carry out ASO detection module 72 available areas own.On the other hand, because the parameter error of chip manufacture has limited the design accuracy of ASO detection module 72.Design routinely, the detection range of ASO detection module 72 is defined as the working range that can cover the power transistor in the course of normal operation, guarantees the high accuracy that detects thus.Therefore ASO detection module 72 is difficult to reach and has the bigger detection range of high measurement accuracy, and this higher accuracy of detection is to be applicable to the reliably protecting that is used for output module 2 during voltage raises.

Summary of the invention

The purpose of this invention is to provide a kind of power amplifier, it comprises that the output module of power transistor is avoided because the damage that malfunction causes with protection during voltage raises, and original performance of power amplifier not.

By the present invention, power amplifier comprises the electric potential detector that is used to protect control.Here, power amplifier preferably includes:

Output module comprises power transistor and the output that is connected to load;

Biasing module comprises that stand-by end and other pieces that are used to the bias power amplifier are in state of activation, specifically is power transistor conducting when stand-by end keeps state of activation;

The ASO detection module, be used to detect it ASO (area of safety operaton) outside power transistor operation and send cut-off signal;

The first fault detect piece is used for the malfunction of detection power transistor and output and sends cut-off signal; With

The protection switch module is used for disconnecting output module from biasing module, and is connected the first fault detect piece arrives biasing module during receiving cut-off signal.

Preferably include by electric potential detector of the present invention:

The second fault detect piece is used for detecting during voltage raises at the current potential of stand-by end with according to the testing result of the current potential that reaches threshold level, the malfunction of detection power transistor and output; With

Cut-off signal generation module when the malfunction of one of the second fault detect piece detection power transistor and output, sends cut-off signal.

Be activated up to stand-by end during power amplifier voltage raises, the biasing module ASO detection module of can not setovering is in state of activation.Electric potential detector itself detects the current potential of stand-by end, and therefore, it is starting more Zao stage startup than ASO detection module, so, can be at the stage detection failure state more Zao than the detection of ASO detection module.In the incident of nonserviceabling, for example, under output short-circuit condition over the ground, during voltage raise, electric potential detector can activate the protection switch module with cut-off signal, then, disconnected power transistor in the stage morning that voltage raises from biasing module.Therefore, power amplifier can protect output module to avoid because the permanent damages that the malfunction during the voltage rising causes.

Also comprise by electric potential detector of the present invention:

Recover module, be used for detecting the current potential of stand-by end and, making cut-off signal generation module stop cut-off signal and send according to the testing result of the current potential that reaches second threshold level at the voltage elevation process.

In the voltage elevation process, when electric potential detector detection failure state and activation protection switch module, the protection switch module connects the first fault detect piece to biasing module, activates the first fault detect piece then.Under the certain situation that takes place and continue of the malfunction that detects, the first fault detect piece is the detection failure state reliably, makes the protection switch module keep output module to disconnect from biasing module.On the other hand, the malfunction that electric potential detector detects is not a virtual condition, and when perhaps having eliminated, the first fault detect piece is the detection failure state not.And, when the current potential of stand-by end reaches second threshold level, electric potential detector release guard switch module, and no matter whether break down.Therefore, power amplifier recovers operate as normal apace.Therefore, electric potential detector has avoided influencing original performance of power amplifier.

New feature of the present invention is specifically limited by appending claims, by below in conjunction with the detailed description of accompanying drawing to formation of the present invention and content, and other purposes and the feature that the present invention may be better understood.

Description of drawings

Fig. 1 be by the demonstration of the embodiment of the invention block diagram of the BTL of power amplifier 10 (BalancedTransformer Less, Balanced Transformer-Less) structure;

Fig. 2 is the structured flowchart that has shown power amplifier 10, and this power amplifier is at the protection that is used for output module 2;

Fig. 3 is collector current Ic and the collector emitter voltage V that has shown power transistor typical case ASO _CEBetween graph of relation;

Fig. 4 is the circuit diagram of preferred embodiment that has shown the electric potential detector 8 of power amplifier 10;

Fig. 5 is the flow chart that has shown the protection that is used for power amplifier 10 in operate as normal;

Fig. 6 is the flow chart that has shown the first of the protection that is used for power amplifier 10 in the voltage elevation process;

Fig. 7 is the flow chart of second portion that has shown the protection of voltage elevation process intermediate power amplifier 10;

Fig. 8 is the sequential chart in the voltage elevation process; shown the protection switch 7A in the power amplifier 10; protection switch module 71; ASO detection module 72; detect the work of piece 73 and two cut-off signal Sc1 that detect that piece 73 and electric potential detector 8 send by first shorted to earth respectively and Sc2 with first shorted to earth and at the current potential V of stand-by end 5 _STBThe variation current potential;

Fig. 9 is the block diagram that has shown the protection that is used for conventional audio-frequency power amplifier;

Figure 10 is the sequential chart in the voltage elevation process, has shown that protection switch 7A in conventional audio-frequency power amplifier shown in Figure 9, protection switch module 71, ASO detection module 72 and shorted to earth detect piece 73 and at the current potential V of stand-by end 5 _STBOperating potential.

In some or all accompanying drawings, use graphic mode and describe, not it may be noted that actual relative dimensions or device position.

Embodiment

Below describe most preferred embodiment of the present invention in detail referring to accompanying drawing.

Fig. 1 has shown the Balanced Transformer-Less BTL structure by the power amplifier 10 of the embodiment of the invention.Power amplifier 10 is preferably the audio-frequency power amplifier that is used to drive loudspeaker Sp.Power amplifier 10 comprises: input 1, output module 2, the first output 3A and the second output 3B, biasing module 4, stand-by end 5, noise elimination end 6 and protection module 7.

Input 1 is from the external device (ED) received audio signal V of for example microcontroller _INOutput module 2 comprises first and second operational amplifier 2A and the 2B, buffer 21A and inverter 21B.Audio signal V _INBy buffer 21A and inverter 21B and anti-phase respectively first and second operational amplifier 2A and the 2B that enter.The first and second operational amplifier 2A and 2B are the push-pull type operational amplifiers, that is to say, each operational amplifier in them is included in voltage power transistor that to be the power supply of Vcc be connected with pair of series between the ground.The first and second output 3A and 3B in the middle of every pair of power transistor are connected across on the loudspeaker Sp.The first and second operational amplifier 2A and 2B are with audio signal V _INConvert respectively opposite polarity a pair of output voltage V at the first and second output 3A and 3B _OUTWith-V _OUTThen, two output voltage V _OUTBe added on the loudspeaker Sp.

Biasing module 4 provides bias current for other circuit module, and other the circuit module of setovering thus is in state of activation, specifically is to make the power transistor conducting.Biasing module 4 detects the state of stand-by end 5 and noise elimination end 6, and beginning (or termination) activates biasing at stand-by end (or respectively at noise elimination end 6).Here, be controlled at the current potential V of stand-by end 5 and noise elimination end 6 respectively with for example external device (ED) of microcontroller _STBAnd V _MTFor example, at the current potential V of stand-by end 5 _STBBe arranged on 0V and+5V by operation and ready mode respectively.Especially, in the voltage elevation process, at the current potential V of stand-by end 5 _STBPressing estimated rate raises.Reach predetermined level V according to detection _ONCurrent potential V _STB, biasing module 4 is supplied with bias current to protection module 7.Therefore protection module 7 has been avoided producing malfunction owing to the rising of surge current and mutation voltage, has prevented that especially loudspeaker Sp plays " the unexpected noise that pipes " when voltage raises.

Protection module 7 detects the malfunction of output module 2.Malfunction for example comprises: one of output 3A and 3B over the ground, to power supply or to the short circuit of other outputs; The power output overloading; The overvoltage of power supply or low-voltage; It is overheated to encapsulate.According to the detection of malfunction, protection module 7 disconnects protection switch 7A, disconnects output module 2 from biasing module 4 thus.Therefore, prevent that output module 2 from keeping conducting state under nonserviceabling, and prevents because malfunction causes permanent damage.Opposite with prior art, to illustrate that as following protection module 7 itself detects the states of stand-by end 5, thus protection output module 2 in the voltage elevation process of power amplifier 10.

Fig. 2 demonstrates the structure at the power amplifier 10 of protection output module 2.Protection module 7 comprises that protection switch module 71, ASO detection module 72, first shorted to earth detect piece 73 and electric potential detector 8.

The ON/OFF state of the protection switch 7A of protection switch module 71 control setting between output module 2 and biasing module 4, and allow (or forbidding) bias current to flow into (or flowing back to respectively).Especially, be the cut-off signal Sc that sends by other circuit modules in the protection module 7 according to receiving, protection switch module 71 disconnects protection switch 7A and sends enabling signal Ss and detects piece 73 to first shorted to earth.And, when suspending cut-off signal Sc, protection switch module 71 conducting protection switch 7A.

ASO detects the work of the power transistor of its ASO outside of piece 72 detections.Because output module 2 is designed to work in the ASO that determines, so, the existence of the malfunction of the work indicated horsepower amplifier of ASO outside.Fig. 3 has shown collector current Ic and the collector emitter voltage V of power transistor typical case ASO _CEBetween graph of relation (if MOSFET is respectively leakage current and drain source voltage).Curve C is represented the limit of ASO, and for example, it is by the upper limit, the collector emitter voltage V of collector current Ic _CEAnd the temperature rise that suppresses the node place in the power transistor power consumption that can allow is definite.The transistorized electric current of ASO detection module 72 detection power, voltage and temperature.When electric current and voltage surpass the limit of ASO (it depends on temperature), usually at predetermined delay T _DAfterwards, ASO detection module 72 send cut-off signal Sc to protection switch module 71 to avoid misoperation.

According to receiving the commencing signal Ss that is sent by protection switch module 71, first over the ground the short-circuit detecting piece 73 is connected to biasing module 4.Then, first over the ground the short-circuit detecting piece 73 is activated and detects output 3 current potential relatively.If at output 3 situation of shorted to earths takes place, first over the ground the short-circuit detecting piece 73 sends cut-off signal Sc continuously to protection switch module 71.When not detected or having eliminated short circuit over the ground, first over the ground the short-circuit detecting piece 73 stops the transmission of cut-off signal Sc.

The generation of the transistorized malfunction of detecting operation indicated horsepower of ASO outside.But, the type of ASO detection module 72 indeterminate fault states.First over the ground the short-circuit detecting piece 73 is directed to and prevents in the short circuit over the ground of output 3 and reliable protection is provided.The malfunction two that is directed to other types provides other fault detect pieces of reliably protecting can be included in the protection module 7.Other fault detect piece can activate with ASO detection module 72, and utilizes protection switch module 71 to carry out each protection with first over the ground the similar mode of mode of short-circuit detecting piece 73 of foregoing description.

Electric potential detector 8 comprise second over the ground short-circuit detecting piece 81, recover module 82 and cut-off signal generation module 83.In the voltage elevation process of power amplifier 10, second over the ground the short-circuit detecting piece 81 detects the current potential V of stand-by end 5 _STBCurrent potential Vout with output 3.Reach first threshold level V according to what detect _Th1Current potential V _STBWith the short circuit over the ground at output 3, what second over the ground the short-circuit detecting piece 81 activated it outputs to cut-off signal generation module 83.In power amplifier 10 voltage elevation process, recover the current potential V that module 82 detects stand-by end 5 _STBAccording to reaching of detecting above first threshold level V _Th1The second threshold level V _Th2(V _Th2V _Th1) current potential V _STB, that recovers that module 82 activates it outputs to cut-off signal generation module 83.Based on from second over the ground the activation of short-circuit detecting piece 81 input, cut-off signal generation module 83 sends cut-off signal Sc, on the other hand, based on from recovering the activation of module 82 inputs, stops the transmission of cut-off signal.

By the transmission of cut-off signal Sc, the reaction time that electric potential detector 8 activates protection switch modules 71 is mainly by the current potential V of stand-by end 5 _STBBe elevated to first threshold level V from 0V _Th1The needed time is determined.Opposite with prior art, first threshold level V is set _Th1Be lower than the level V of ASO detection module 72 beginnings _ON, can be in the fast detecting of the stage realization morning of power amplifier 10 voltage elevation process shorted to earth.

By stopping the transmission of cut-off signal Sc, the reaction time of electric potential detector 8 release guard switch modules 71 is mainly by the current potential V of stand-by end 5 _STBFrom first threshold level V _Th1Be elevated to the second threshold level V _Th2The needed time is determined.In the reaction time, protection switch module 71 activation first short-circuit detecting piece 73 over the ground.Optimize the second threshold level V _Th2, so that instant-free protection switch module 71 and by first over the ground the detection high reliability of short-circuit detecting piece 73.Thus, power amplifier 10 fast quick-recovery operate as normal.Therefore, electric potential detector 8 has avoided influencing original performance of power amplifier 10.

Fig. 4 demonstrates a preference of the circuit of electric potential detector 8.

Second over the ground the short-circuit detecting piece 81 comprises: two PNP transistor Q1 and Q2, two NPN transistor Q3 and Q4, two resistor R 1 and R2, and ESD (static discharge) resistor R _ESDThe emitter of two PNP transistor Q1 and Q2 is connected to power supply.The base stage of two PNP transistor Q1 and Q2 interconnects.The collector electrode of the one PNP transistor Q1 is through first resistor R, 1 ground connection.Base stage and the collector electrode of the 2nd PNP transistor Q2 interconnect.Therefore, the emitter current of two PNP transistor Q1 and Q2 is each other in mirror image.The ratio of two emitter currents is substantially equal to the ratio of the size of two PNP transistor Q1 and Q2.The collector electrode of the first NPN transistor Q3, base stage and emitter are connected respectively to collector electrode, the stand-by end 5 of the 2nd PNP transistor Q2 and are connected to the base stage of the second NPN transistor Q4 through second resistor R 2.Base stage and the emitter of the second NPN transistor Q4 interconnect.The collector electrode of the second NPN transistor Q4 is through ESD (static discharge) resistor R _ESDBe connected to output 3.ESD (static discharge) resistor R _ESDBe illustrated in the resistance of the protective device that prevents ESD (static discharge) of output 3, therefore, resistor R _ESDResistance value should be less than the resistance value of other resistor R 1 and R2.

In the process that common voltage raises, the current potential V of output 3 _OUTThe level and smooth rising, therefore, at the current potential V of stand-by end 5 _STBThe current potential V of specific output end 3 _OUTSlightly high or lower slightly.Then, two NPN transistor Q3 and Q4 keep the OFF state, the current potential V of the node J between a PNP transistor Q1 and first resistor R 1 _JBe substantially equal to 0V.Current potential V at stand-by end 5 _STBCurrent potential V usually above output 3 _OUTThe time, positive voltage is added on the second NPN transistor Q4, and enough big then base current flows through the first NPN transistor Q3.Therefore, two NPN transistor Q3 and all conductings of Q4, then, the current potential V of the node J between a PNP transistor Q1 and first resistor R 1 _JRaise the voltage V between stand-by end 5 and the output 3 _STB-V _OUTProvide with following equation (1):

$V_{\mathrm{STB}}-V_{\mathrm{OUT}}=V_{\mathrm{BE}3}+{\mathrm{<figure-callout\; id="4"\; label="V\; BC"\; filenames="C200410031163E00251.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\mathrm{BC}}+\frac{A_2}{A_1}\frac{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="C200410031163E00221.png"\; state="\{\{state\}\}">R</figure-callout>}2+R_{\mathrm{ESD}}}{R1}{V}_J,---\left(1\right)$

In the formula, V _BE3Be the base-emitter voltage of the first NPN transistor Q3 in the ON state, V _BC4Be the base stage-collector voltage of the second NPN transistor Q4 in the ON state, A ₁/ A ₂It is the size ratio of two PNP transistor Q1 and Q2.(3 resistor R 1, R2 and R _ESDResistance value with the indication of identical reference symbol.)

Recovering module 82 comprises: two NPN transistor Q5 and Q6 and two resistor R 3 and R4.The collector electrode of the 3rd NPN transistor Q5, base stage and emitter are connected respectively to power supply, stand-by end 5 and through two resistors in series R3 and R4 ground connection.The collector electrode of the 4th NPN transistor Q6, base stage and emitter are connected respectively to node and the ground connection between node J between a PNP transistor Q1 and first resistor R 1, two resistor R 3 and the R4.

In the voltage elevation process, the current potential V of stand-by end 5 _STBRaise with the base current of the 3rd NPN transistor Q5.The 3rd NPN transistor Q5 is owing to there is enough big base current during conducting, and the 4th NPN transistor Q6 is also because obviously increase and conducting of base current.Then, the current potential V at the node J place between a PNP transistor Q1 and first resistor R 1 _JDrop to 0V.At this moment, the current potential V of stand-by end 5 _STBProvide with following equation (2):

$V_{\mathrm{STB}}=V_{\mathrm{<figure-callout\; id="5"\; label="BE"\; filenames="C200410031163E00181.png,C200410031163E00251.png"\; state="\{\{state\}\}">BE</figure-callout>}5}+\frac{R3+R4}{R4}{V}_{\mathrm{BE}6}---\left(2\right)$

In the formula, V _BE5And V _BE6Be respectively two NPN transistor Q5 in the ON state and the base-emitter voltage of Q6.(indicating the resistance value of two resistor R 3 and R4 with identical reference symbol)

Cut-off signal generation module 83 comprises the 5th NPN transistor Q7.The collector electrode of the 5th NPN transistor Q7, base stage and emitter are connected respectively to protection switch module 71 (see figure 2)s, node J between a PNP transistor Q1 and first resistor R 1 and ground.And the collector electrode of the 5th NPN transistor Q7 draws high predetermined positive potential (not showing).Current potential V as node J _JDuring rising, the 5th NPN transistor Q7 is owing to its base current obviously increases and conducting.Then, the collector emitter voltage of the 5th NPN transistor Q7 descends.Protection switch module 71 detects because the voltage drop of the activation of cut-off signal Sc.Current potential V as node J _JDuring decline, the 5th NPN transistor Q7 disconnects.The current potential of the 5th NPN transistor Q7 collector electrode draws high original high level then.Protection switch module 71 detects because the current potential of the removal of cut-off signal Sc draws high.

In the voltage elevation process, if there are output 3 shorted to earths that the current potential V of output 3 takes place _OUTRemain on the low level that is substantially equal to 0V, and the current potential of stand-by end 5 raises.In this case, cut-off signal Sc activates, that is, and and the current potential V that the conducting of the 5th NPN transistor Q7 requires at stand-by end 5 _STBSurpass first threshold level V _Th1, it is provided by following equation (3) according to equation (1):

$V_{\mathrm{STB}}\&GreaterEqual;{\mathrm{<figure-callout\; id="1"\; label="V\; th"\; filenames="C200410031163E00181.png,C200410031163E00211.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\mathrm{th}}=V_{\mathrm{BE}3}+V_{\mathrm{BC}4}+\frac{A_2}{A_1}\frac{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="C200410031163E00221.png"\; state="\{\{state\}\}">R</figure-callout>}2+R_{\mathrm{ESD}}}{R1}{V}_{\mathrm{BE}7},---\left(3\right)$

V in the formula _BE7Be the base-emitter voltage of the 5th NPN transistor Q7 of ON state.As what clearly seen, can activate the response time of the electric potential detector 8 of protection switch module 71 than the ratio optimization of the resistance value between A1/A2 and two resistor R 1 and the R2 with the size between two PNP transistor Q1 and the Q2 from equation (3).The ESD resistor R _ESDIts existence has so little resistance value, so that can not impact to the response time of electric potential detector 8.

Cut-off signal Sc lost efficacy, that is, the disconnection of the 5th NPN transistor Q7 requires the current potential V of stand-by end 5 _STBSurpass the second threshold level V _Th2, it provides by the equation (2) of foregoing description:

$V_{\mathrm{STB}}\&GreaterEqual;{\mathrm{<figure-callout\; id="2"\; label="V\; th"\; filenames="C200410031163E00221.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\mathrm{th}}=V_{\mathrm{BE}5}+\frac{R3+R4}{R4}{V}_{\mathrm{BE}6}>V_{\mathrm{th}1}---\left(4\right)$

Understand easily from equation (4), optimize the response time of electric potential detector 8 release guard switch modules 71 with the specific energy of the resistance value between two resistor R 3 and the R4.

In the operate as normal that does not break down, the 5th NPN transistor Q7 can not activate protection switch module 71.And, the current potential V of node J _JRest on 0V, therefore, two NPN transistor Q3 and Q4 have high impedance at output 3.Like this, electric potential detector 8 has been avoided original performance of the power amplifier 10 in operate as normal.

7 pairs of power amplifiers of protection module 10 with said structure are carried out following protection.

Fig. 5 demonstrates the flow chart of protection power amplifier in operate as normal.

Step S1

In the operate as normal, stand-by end 5 keeps activating, and then, is biased in the transistorized electric current of ASO detection module 72 detection power, voltage and the temperature of state of activation.

Step S2

ASO detection module 72 is determined the ASO limit according to detected temperature.Detected curtage surpasses under the situation of the ASO limit, and handle and enter into next step S3, otherwise repeating step S1.

Step S3 and S4

The latency delays time T _DAfter, ASO detection module 72 sends cut-off signal Sc to protection switch module 71, activates protection switch module 71 thus, and can not cause misoperation owing to the sudden change of electric current and voltage.

Step S5

Protection switch module 71 disconnects protection switch 7A, disconnects from biasing module 4 to output module 2 bias current thus.Then, a plurality of power transistors all are limited in the off-state.

Step S6

Protection switch module 71 sends commencing signal Ss, is thus connected first over the ground the short-circuit detecting piece 73 to biasing module 4.Then, start first over the ground short-circuit detecting piece 73 and detect the current potential of output 3 with respect to ground.(the same) with other fault detect pieces in the protection module 7.

Step S7

If output 3 short circuit over the ground takes place, first over the ground the short-circuit detecting piece 73 sends cut-off signal Sc continuously to protection switch module 71.(the same) with other fault detect pieces in the protection module 7.Protection switch module 71 keeps protection switch 7A in off-state thus.Therefore, power amplifier 10 stops operate as normal, and power transistor has avoided because the permanent damages that overcurrent causes.When not detected or having eliminated short circuit over the ground, handle entering step S8.

Step S8 and S9

First over the ground the short-circuit detecting piece 73 stops the transmission of cut-off signal Sc.(the same) with other fault detect pieces in the protection module 7.Protection switch module 71 lost efficacy protection switch 7A conducting then.Allow bias current to flow to output module 2 thus.Therefore, power transistor discharges, and power amplifier 10 recovers operate as normal.

Fig. 6 and Fig. 7 demonstrate the flow chart of protection power amplifier 10 in the voltage elevation process.Fig. 8 demonstrates the work schedule of protection switch 7A in the voltage elevation process, protection switch module 71, ASO detection module 72 and first short-circuit detecting piece 73 over the ground.Fig. 8 also demonstrates respectively by first over the ground short-circuit detecting piece 73 and two cut-off signal Sc1 sending of electric potential detector 8 and the Sc2 and at the current potential V of stand-by end 5 _STBThe sequential current potential.Among Fig. 8, high (or low) level is represented activation (or the non-activation) state of each module.(noticing that the cut-off signal Sc2 that above-mentioned example and the electric potential detector among Fig. 48 send is more sluggish (active-low)).

As shown in Figure 8, when voltage raises beginning, since moment T0, the current potential V of stand-by end 5 _STBRaise by predetermined ratio from 0V.The current potential V that biasing module 4 detects in the voltage elevation process _STB, be activated just up to stand-by end 5 and supply with bias currents for ASO detection module 72, that is, and current potential V _STBReach level V _ONTherefore, current potential is up to moment T _ON, ASO detection module 72 could be worked, and just at this constantly, current potential V _STBReach level V _ONOn the other hand, electric potential detector 8 is worked when voltage raises, and therefore, in the voltage elevation process, output module 7 is carried out following protection.

Step S11 and S12

The current potential V that current potential electric potential detector 8 detects at stand-by end 5 _STBCurrent potential V with output 3 _OUT, up to moment T1, and just at this constantly, current potential V _STBReach first threshold level V _Th1The time.Here protection switch 7A remains on the ON state.

Step S13

At moment T1, current potential V _STBReach first threshold level V _Th1At moment T1, the short circuit over the ground that the short-circuit detecting piece 81 over the ground of second in the electric potential detector 8 detects at output 3 is handled and is entered step S14, otherwise enters into step S18.

Step S14

Electric potential detector 8 sends cut-off signal Sc2 to protection switch module 71,, activates cut-off signal Sc that is, activates protection switch module 71 thus.Here, transmission cut-off signal Sc2 is used to avoid because the misoperation that the sudden change of electric current and voltage causes after a time of delay.

Step S15

Protection switch module 71 disconnects protection switch 7A, disconnects from biasing module 4 to output module 2 bias current thus.Then, a plurality of power transistors all are limited to the OFF state.

Step S16

Protection switch module 71 sends commencing signal Ss, is thus connected first over the ground the short-circuit detecting piece 73 to biasing module 4.Then, first over the ground the short-circuit detecting piece 73 is activated behind moment T1 immediately, then, detects output 3 current potential relatively.

Step S17 and S18

If there is output 3 short circuit over the ground to take place, first over the ground the short-circuit detecting piece 73 sends cut-off signal Sc1 continuously to protection switch module 71 (seeing the solid line among Fig. 8).Thus, protection switch module 71 keeps protection switch 7A at the OFF state.When not detected or having eliminated short circuit over the ground, first over the ground the short-circuit detecting piece 73 stops the transmission (seeing the dotted line among Fig. 8) of cut-off signal Sc1

Step S19 and S20

The current potential V that current potential electric potential detector 8 also detects at stand-by end 5 _STB, up to moment T2, and just at this constantly, current potential V _STBReach the second threshold level V _Th2As the indication of the solid line of Fig. 8, if detect output 3 short circuit over the ground at second over the ground the short-circuit detecting piece 81 at step S13, here, behind moment T1, electric potential detector 8 sends cut-off signal Sc2 continuously, keeps protection switch 7A in the OFF state.Otherwise electric potential detector 8 stops the transmission of cut-off signal Sc2, and then, protection switch 7A remains on the OFF state, indicates as the length dotted line among Fig. 8.

Step S21

At moment T2, current potential V _STBReach the second threshold level V _Th2Then, the recovery module 82 in the electric potential detector 8 stops the transmission of cut-off signal Sc2, and the release guard switch module 71 thus, and no matter whether break down.

At step S16, if first over the ground the short-circuit detecting piece 73 is activated and at step S17, detect in output 3 short circuit over the ground, first over the ground the short-circuit detecting piece 73 sends cut-off signal Sc1 continuously, as the indication of the solid line among Fig. 8.Therefore, behind the T2, protection switch module 71 keeps activating constantly, and protection switch 7A remains on the OFF state.Therefore, in the voltage elevation process, take place if having in output 3 short circuit over the ground, electric potential detector 8 can activate protection switch module 71, and then, the stage early that raises at voltage disconnects power transistor from biasing module 4.Especially, the ON time PON that follows the protection switch 7A behind moment T0 closely reduces greatly, and therefore, output module 2 can prevent in the voltage elevation process permanent damage that the shorted to earth at output 3 causes.

At step S16, if there is first over the ground the short-circuit detecting piece 73 to be activated, still,, do not detect generation in the short circuit over the ground of output 3 at step S17, first over the ground the short-circuit detecting piece 73 does not send the cut-off signal Sc1 as the indication of the dotted line among Fig. 8.Therefore, at moment T2, protection switch module 71 lost efficacy protection switch 7A conducting.Therefore, the operation of the normal voltage rising of power amplifier 10 fast quick-recoveries.Therefore, electric potential detector 8 has avoided influencing power amplifier 10 original performances.

Above-mentioned presses in the embodiments of the invention, and electric potential detector 8 comprises: second over the ground the short-circuit detecting piece 81 that is directed to the shorted to earth protection of output 3.Other fault detect pieces of protection that are directed to the other types of malfunction in the voltage elevation process also can be included in the electric potential detector 8.By the current potential V that detects at stand-by end 5 _STB, other fault detect pieces can initiate self, and the protection switch module 71 of utilizing the commitment that raises at voltage is to carry out various protections with above-mentioned second over the ground the similar mode of mode of short-circuit detecting piece 81.

More than use by the disclosed the present invention of the preferred embodiments of the present invention and do not limit the present invention.The technical staff of the industry finds that the present invention also has various changes and modifications after having read disclosed content.Thus can inference, these changes and improvements all fall in the spirit and scope of the invention.And, should be appreciated that appending claims covers these changes and improvements.

Claims (4)

1, a kind of electric potential detector is used for the protection control of power amplifier, comprising:

One output module comprises that a power transistor and is connected to the output of load;

Biasing module comprises a stand-by end, and other circuit modules that can be used for the bias power amplifier are in state of activation, specifically is when stand-by end keeps state of activation, the power transistor conducting;

One safety operation area detection module, be used to detect it the outside, safety operation area power transistor work and send cut-off signal;

The first fault detect piece is used for the malfunction of detection power transistor and output and sends cut-off signal; With

One protection switch module is used for disconnecting output module from biasing module during receiving cut-off signal, and is connected the first fault detect piece to biasing module;

Described electric potential detector comprises:

The second fault detect piece is used for detecting at the current potential of the stand-by end of voltage elevation process with according to detection and reaches the current potential of a threshold level, the malfunction of detection power transistor and output; With

Cut-off signal generation module is used for sending cut-off signal when one of them malfunction of the second fault detect piece detection power transistor and output.

2, according to the electric potential detector of claim 1, comprising:

One recovers module, is used for detecting the current potential of the stand-by end of voltage elevation process and reaches the current potential of second threshold level according to detection, makes cut-off signal generation module stop the transmission of cut-off signal.

3, a kind of power amplifier comprises:

One output module comprises that power transistor and is connected to the output of load;

One biasing module, other circuit modules that comprise a stand-by end and can be used for the bias power amplifier are in state of activation, specifically are power transistor conductings when stand-by end keeps state of activation;

One safety operation area detection module, be used to detect it the outside, safety operation area power transistor work and send cut-off signal;

The first fault detect piece is used for the malfunction of detection power transistor and output and sends cut-off signal; With

One protection switch module is used for disconnecting output module from biasing module during receiving cut-off signal, and is connected the first fault detect piece to biasing module;

One electric potential detector comprises:

The second fault detect piece is used for detecting at the current potential of the stand-by end of voltage elevation process with according to detection and reaches the current potential of a threshold level, the malfunction of detection power transistor and output; With

One cut-off signal generation module is used for sending cut-off signal when one of them malfunction of the second fault detect piece detection power transistor and output.

4, according to the power amplifier of claim 3, it is characterized in that electric potential detector comprises that one recovers module, is used for detecting the current potential of the stand-by end of voltage elevation process, with the current potential that reaches second threshold level according to detection, make cut-off signal generation module stop the transmission of cut-off signal.

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