CN102859868A - Digital amplifier - Google Patents
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- CN102859868A CN102859868A CN2011800102156A CN201180010215A CN102859868A CN 102859868 A CN102859868 A CN 102859868A CN 2011800102156 A CN2011800102156 A CN 2011800102156A CN 201180010215 A CN201180010215 A CN 201180010215A CN 102859868 A CN102859868 A CN 102859868A
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/52—Circuit arrangements for protecting such amplifiers
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
- H03F3/21—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only
- H03F3/217—Class D power amplifiers; Switching amplifiers
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F2200/00—Indexing scheme relating to amplifiers
- H03F2200/03—Indexing scheme relating to amplifiers the amplifier being designed for audio applications
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F2200/00—Indexing scheme relating to amplifiers
- H03F2200/351—Pulse width modulation being used in an amplifying circuit
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F2200/00—Indexing scheme relating to amplifiers
- H03F2200/426—Indexing scheme relating to amplifiers the amplifier comprising circuitry for protection against overload
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Abstract
The disclosed amplifier can reduce both overcurrent in output-current and resonance current detection time, minimises output suspension, and is capable of more appropriate current control operations. A digital amplifier has: in the output portion of switch elements (Q1, Q2), an overcurrent detection circuit (19) for detecting overcurrent, which is equal to or exceeds a specified value, in the output current; a phase advance circuit (22) which advances the phase of an overcurrent detection signal; and a resonance current detection circuit (21) which detects resonance current equal to or exceeding a specified value relating to the output current when resonance is generated at an output filter (15). When an abnormal state is detected in the output current on the basis of the overcurrent detection signal or a resonance current detection signal, a drive circuit (12) carries out current limiting operations by turning a drive signal to OFF and stopping the switching operation of the switching elements (Q1, Q2).
Description
Technical field
The present invention relates to digital amplifier, make the switch element of output stage carry out switch motion, input signal is carried out the D class amplify.
Background technology
Digital amplifier is by PWM(Pulse Width Modulation: pulse width modulation) conversion is transformed to digital pulse signal with the input signal of simulation, utilize this digital pulse signal to make the active elements such as FET (switch element) carry out switch motion, carry out thus power amplification (amplification of D class).And, make the low pass filter of digital pulse signal by lc circuit after the power amplification, obtain thus source signal is carried out the output signal of the simulation after the power amplification.
When having produced in load-side in the situations such as overcurrent, resonance, this digital amplifier has the function of the amplifying circuits such as switch element of protection output stage.For example, when becoming overcurrent condition owing to load short circuits etc., utilize in cut-out such as relay of amplifier efferent setting and export the protection switch element.And, when the loud speaker that is connected with digital amplifier is less etc. during underload (during high impedance), producing resonance at the low pass filter of amplifier efferent, amplifying circuit might damage owing to this resonance phenomena.In order to prevent the damage based on the digital amplifier of this resonance phenomena; known have such technology (for example with reference to patent documentation 1); resonance current when detecting underload makes input signal quiet in the situation that excessive resonance current flows through, and protects thus amplifying circuit.
The prior art document
Patent documentation
Patent documentation 1: TOHKEMY 2007-258903 communique
Summary of the invention
The problem that invention will solve
In the structure such as above-mentioned patent documentation 1, there is such problem, if the resonance current when namely detecting underload just makes input signal quiet at once, in the situation that revert to regular event next time, because the initialization of the action in the pwm circuit, the starting of digital amplifier needs the time.In this case, will cause output (sound etc.) owing to the quiet of input signal stops.
In addition, in order to protect the circuit of digital amplifier, also can consider to assemble the structure of the demand limiter that adopts analog circuit, the output current of this analogue circuit constraints amplifying circuit.In this structure, exist the control of demand limiter to produce phase delay and have little time to carry out the situation that current limit moves.And, carry out current limit control if suppose this control lag, then time of playing a role of demand limiter so that the frequency increases, produces and easily causes exporting the problem of cut-out too early.
The present invention In view of the foregoing proposes, and its purpose is to provide a kind of digital amplifier, can shorten the unusual time of detecting output current, does not stop as much as possible output, can protect amplifying circuit when unusual.
Be used for solving the means of problem
The invention provides and a kind of input signal is carried out the digital amplifier that the D class is amplified, this digital amplifier has: switch element, carry out switch motion according to the driving signal based on the digital pulse signal of described input signal; Drive circuit is supplied with described driving signal to described switch element; Output filter comprises the low pass filter that is connected with the efferent of described switch element; And abnormal state detection section, be located at the efferent of described switch element, detection is from the abnormality of the output current of described switch element, and output abnormality state detection signal, described abnormal state detection section have the phase place that makes described abnormal state detection signal leading advance the phase function, in the situation of the abnormality that arrives output current according to described abnormal state detection input, described drive circuit stops described driving signal, and the switch motion of described switch element is stopped.
According to said structure, the driving signal from drive circuit is stopped, the switch motion of switch element is stopped, can carrying out thus the current limit action, and need not stop the actions such as input signal, cut-out output signal.And, according to abnormal state detection section advance the phase function, can eliminate or reduce the phase delay of abnormal state detection signal.Therefore, can shorten the unusual time of detecting output current, not stop as much as possible output, when unusual, can protect amplifying circuit.
And, in above-mentioned digital amplifier of the present invention, described abnormal state detection section comprises: overcurrent sensing circuit, detect from the overcurrent more than the predetermined value in the output current of described switch element, and the output over-current detection signal is as described abnormal state detection signal; And advance circuitry phase, make the phase place of described over-current detection signal leading.
According to said structure, as the abnormality of output current, in situation about detecting from the overcurrent more than the predetermined value in the output current of switch element, stop to drive signal, the switch motion of switch element is stopped, can carrying out current limit.In this case, when overcurrent occurs, can carry out fast the current limit action, not stop as much as possible output, can protect the amplifying circuit that comprises switch element.
And, in above-mentioned digital amplifier of the present invention, described abnormal state detection section comprises resonance electric current detection circuit, detect the resonance current more than the predetermined value relevant with output current when the described output filter generation resonance, and the export resonance current detection signal is as described abnormal state detection signal.
According to said structure, as the abnormality of output current, in the situation that detects the resonance current more than the relevant predetermined value of output current with at output filter generation resonance the time, stop to drive signal, the switch motion of switch element is stopped, can carrying out current limit.In this case, when at efferent generation resonance, can carry out fast the current limit action, make impact not feed through to the interior output of the range of audibility, can protect the amplifying circuit that comprises switch element.
And in above-mentioned digital amplifier of the present invention, described digital amplifier has: temperature detecting part, detect described switch element or the temperature around it; The output cutting portion is cut off the output of described switch element; The quiet section of input signal makes described input signal become predetermined level following tone-off state or small state; And interlock control part, make quiet linkage action of described output cutting portion and described input signal, detected by described temperature detecting part in the situation of the condition of high temperature more than the predetermined value, described interlock control part makes described output cutting portion and quiet linkage action of described input signal.
According to said structure; become in the situation of the condition of high temperature more than the predetermined value at switch element or the temperature around it; by making output cutting portion and quiet linkage action of input signal, input and output both sides that can the shutdown switch element come the protection switch element.In this case, if cut off the output of switch element, become no-load condition, and become the state that resonance easily occurs in output filter, yet by carrying out the quiet of input signal, can prevent the resonance at output filter.
And, in above-mentioned digital amplifier of the present invention, described drive circuit carries out the current limit action of described switch element by repeatedly carrying out following control, described being controlled to be: according to described abnormal state detection signal, in the situation that described output current is to stop described driving signal more than the predetermined value, the switch motion of described switch element is stopped, in the situation that described output current is exported described driving signal repeatedly less than predetermined value, make the switch motion that again begins described switch element.
According to said structure, stop/again beginning carrying out current limit action by what repeatedly carry out switch motion, can protect the amplifying circuit that comprises switch element, and make the action of switch element continue as much as possible to carry out and not stop output.
And, in above-mentioned digital amplifier of the present invention, described drive circuit is in current limit when action of carrying out described switch element, exports/stop described driving signal at 1 cycle unit or the arbitrary timing in the 1 cycle unit of the benchmark frequency of oscillation of described digital pulse signal.
According to said structure; when the abnormalities such as generation of the generation that detects overcurrent or resonance current; can carry out fast real-time current limit action according to the benchmark frequency of oscillation of the digital pulse signal of input signal; do not stop as much as possible output, can protect the amplifying circuit that comprises switch element.
And, in above-mentioned digital amplifier of the present invention, described digital amplifier has control part, this control part judges that the resonance current detection signal of described resonance electric current detection circuit is continued export scheduled time, and in the situation that continues the signal of this situation of output expression of the described scheduled time of output.
According to said structure, can detect the system oscillation of sound reinforcement system, and notify the user of sound reinforcement system that system oscillation has occured, thereby can prevent the fault of frequency mixer, digital amplifier or loud speaker etc.
The invention effect
Can provide a kind of digital amplifier according to the present invention, can shorten the unusual time of detecting output current, not stop as much as possible output, when unusual, can protect amplifying circuit.
Description of drawings
Fig. 1 is the circuit diagram of structure of the digital amplifier of expression an embodiment of the invention.
Fig. 2 is the circuit diagram of concrete structure example of the digital amplifier of expression present embodiment.
Fig. 3 is the output characteristics figure of comparison of the thermal design benchmark of representative digit amplifier and analogue amplifier.
The movement oscillogram of the waveform when Fig. 4 is expression based on the amplifier action of the current limit circuit of present embodiment.
Fig. 5 (A), (B) are that the current limit circuit of present embodiment has or not into the comparison diagram of the output current wave of circuitry phase.
Fig. 6 is the circuit diagram of the basic structure of representative digit amplifier.
Fig. 7 is the gain-frequency characteristic figure of the amplifying circuit when in the low pass filter of amplifier efferent resonance occuring.
Fig. 8 is the flow chart of the expression first action example relevant with the circuit protection function of the digital amplifier of present embodiment.
Fig. 9 is the state transition diagram of the expression second action example relevant with the circuit protection function of the digital amplifier of present embodiment.
Figure 10 is the figure of sound reinforcement system that the digital amplifier of present embodiment has been used in expression.
Figure 11 is the circuit diagram of structure of the digital amplifier of expression another embodiment of the invention.
Embodiment
In the execution mode below, show such topology example as an example of digital amplifier of the present invention, namely the switch element of the output stage of digital amplifier adopts FET, and load is connected with loud speaker, and this digital amplifier carries out the amplification of voice signal.
Fig. 1 is the circuit diagram of structure of the digital amplifier of expression an embodiment of the invention.The digital amplifier of present embodiment constitute have pwm circuit 11, drive circuit 12, switch element Q1, Q2.Switch element Q1, Q2 utilize the formations such as MOSFET of N raceway groove, mutually are connected in series between the drain electrode-source electrode, thereby consist of the pair of switches element.This switch element Q1, Q2 be according to alternately carrying out switch motion for the input of the driving signal of grid, and carry out the power amplification of input signal.At this moment, the drain electrode of switch element Q1 is applied in voltage+VB, and the source electrode of switch element Q2 is applied in voltage-VB, and switch element Q1, Q2 are according to grid voltage and conduction and cut-off.In addition, switch element is not limited to FET, also can be other element that bipolar transistor etc. can carry out switch motion.
The efferent of switch element Q1, Q2 is connected with output filter 15, and output filter 15 comprises the low pass filter that is made of coil 13 and capacitor 14.The output of this output filter 15 is connected with the relay 16 that be used for to open and close output signal path as an example of output cutting portion, and passes through relay 16 and be connected with loud speaker 17 as load.In addition, the output cutting portion often adopts relay, but also can be other switch element.
The input signal of the voice signal of simulation is transformed to digital pulse signal via pwm circuit 11, and input driving circuit 12.According to this digital pulse signal, the grid input drive signal from drive circuit 12 to switch element Q 1, Q2, switch element Q 1, Q2 carry out switch motion according to driving signal.Digital pulse signal after being exaggerated from the power of the efferent of switch element Q1, Q2 output is transformed to analog signal via output filter 15, and the voice signal of the simulation after being exaggerated as power is exported, and offers loud speaker 17.Loud speaker 17 drives according to this output signal, and plays out sound.
And, be connected in series with at the coil 13 of the output filter 15 of amplifier efferent and detect resistor 18, be provided with overcurrent sensing circuit 19, detect the electric current that flows to coil 13 according to the both end voltage that detects resistor 18, and detect the overcurrent that flows to load.In addition, capacitor 14 is connected in series with and detects resistor 20, is provided with resonance electric current detection circuit 21, detects the electric current that flows to capacitor 14 according to the both end voltage that detects resistor 20, and detects the resonance current that produces at output filter 15.
The leading circuitry phase 22 that advances of the output of overcurrent sensing circuit 19 and the phase place that makes over-current detection signal is connected, and advances circuitry phase 22 by this and be connected with drive circuit 12.The output of resonance electric current detection circuit 21 also is connected with drive circuit 12.In the situation that the overcurrent detected value is more than the predetermined value, the over-current detection signal of overcurrent sensing circuit 19 output high level is as the abnormal state detection signal.In the situation that the resonance current detected value is more than the predetermined value, the resonance current detection signal of resonance electric current detection circuit 21 output high level is as the abnormal state detection signal.In addition, overcurrent sensing circuit 19 and advance circuitry phase 22 and can certainly utilize same circuit unit to consist of, but not different circuit.In this case, utilize not shown operational amplifier to detect the voltage at the two ends of resistor 18, after the phase place that makes this detection waveform is leading, compared by not shown comparator and predetermined value, thus detection of excessive current.And the circuit structure of resonance electric current detection circuit 21 except advancing circuitry phase can utilize the circuit structure identical with above-mentioned overcurrent sensing circuit 19 to realize.
Input side at pwm circuit 11 is provided with quiet 23 of input signal.Quiet 23 of input signal have mute circuit 24, bypass resistance 25, to the switch 26,27 that they switch, make mute circuit 24 or bypass resistance 25 and input signal Path Connection according to the control signal from the outside.It is below the predetermined level that mute circuit 24 is used for making attenuated input signal, has the function that makes input signal become tone-off state or small state.
And, near switch element Q1, Q2, be provided with the temperature detecting part 28 of the temperature around sense switch element Q1, Q2 or its.The output of temperature detecting part 28 is connected with interlock control part 29, the control that links of link 29 pairs of relays 16 of control part and quiet 23 of input signal.Under the temperature detection value of temperature detecting part 28 was situation more than the predetermined value, interlock control part 29 was to relay 16 and quiet 23 output of input signal control signal, made their linkage actions and carried out that relay disconnects and input signal is quiet.Thus, the input and output for switch element Q1, Q2 stop.
Fig. 2 is the circuit diagram of concrete structure example of the digital amplifier of expression present embodiment.Fig. 2 represents drive circuit and advances an example of the concrete structure of circuitry phase.Drive circuit 31 constitute have circuit for reversing 32, optical coupler 33,34, driver 35,36, switch element 37 and NOR circuit 38.The LED of an optical coupler 33 directly is connected with the output of pwm circuit 11, and the LED of another optical coupler 34 is by circuit for reversing 32 and the output that is connected pwm circuit 11. Optical coupler 33,34 photistor are connected with driver 35,36 respectively.According to this structure, root conducting according to the digital pulse signal of exporting from pwm circuit 11 in the optical coupler 33,34, the opposing party's cut-off, driver 35,36 is by the signal of alternative supply high level thus. Driver 35,36 is alternately supplied with to switch element Q1, Q2 and is driven signal according to from optical coupler 33,34 input signal, makes thus switch element Q1, Q2 carry out switch motion and conduction and cut-off alternately.In addition, show the topology example that adopts optical coupler and switch element etc. at this, utilize other switch element to export/stop the structure that drives signal but also can adopt.
And the other end of optical coupler 33,34 LED is grounded by switch element 37.From via the over-current detection signal of the overcurrent sensing circuit 19 that advances circuitry phase 41 or from the resonance current detection signal of resonance electric current detection circuit 21, supply to the control input end of switch element 37 by NOR circuit 38.Conducting and connecting when switch element 37 is transfused to high level in the control input end, cut-off and disconnecting when being transfused to low level.In this case, when over-current detection signal and resonance current detection signal at least one party become high level, switch element 37 cut-offs, optical coupler 33,34 both sides' LED cut-off.Therefore, when being detected overcurrent more than the predetermined value or resonance current by overcurrent sensing circuit 19 and resonance electric current detection circuit 21, the action of drive circuit 31 is stopped, the switch motion of switch element Q1, Q2 is stopped.
At this, the thermal design benchmark of digital amplifier is described.Fig. 3 is the output characteristics figure of comparison of the thermal design benchmark of representative digit amplifier and analogue amplifier.In the curve chart of Fig. 3, transverse axis represents output, and the longitudinal axis represents loss.Digital amplifier is compared in whole output area loss with analogue amplifier less, but basically is linear with respect to the loss of output, along with output increases (output current increases), and the loss increase.That is, the loss of digital amplifier be (when usually using)＜＜(unusual time).Relative therewith, the loss of analogue amplifier is (when usually using) ≈ (unusual time), even the loss when unusual increases, compares also during with common use and can not produce larger difference.The thermal design benchmark of amplifier normally loss when usually using is set, and determines heat sink size etc. according to this thermal design benchmark.In analogue amplifier, if when usually using, carry out thermal design, can not have problems when unusual even then do not consider yet.But, in digital amplifier, if when insufficient consideration is unusual and carry out thermal design, then sometimes produce the problems such as fault that cause amplifying circuit.
But, consider can make when unusual radiator to become large-scale, this does not expect in the design of digital amplifier, thereby adopts the situation of the structure of the current limit control when current limit circuit being set overcurrent occuring in this hypothesis.Have in the present embodiment following structure, make drive circuit stop to carry out current limit control according to overcurrent detection and resonance current detection, also in overcurrent sensing circuit, append the phase delay that compensates over-current detection signal into circuitry phase.Thus, when producing overcurrent or resonance current in the load at digital amplifier, can shorten the time of the abnormality detection of output current, not stop as much as possible output, and limit the current limit control of the output current when unusual.
Below, the current limit action during to the generation overcurrent is elaborated.The movement oscillogram of the waveform when Fig. 4 is expression based on the amplifier action of the current limit circuit of present embodiment.In Fig. 4, current limit value refers to use based on the current limit of the predetermined value that detects abnormality in overcurrent sensing circuit 19 current value of threshold value.Reach in this situation more than current limit value in the unusual grade of output current value owing to load, the action of drive circuit 12 stops, and no longer flows through the above output current of this current limit value.At this, in the situation that output current value reaches more than the predetermined value, drive circuit 12 stops to drive signal, and the switch motion of switch element Q1, Q2 is stopped.Wherein, under output current value reached state more than the predetermined value, drive circuit 12 continued to stop action.Then, in the situation that output current value is less than predetermined value, drive circuit 12 output drive signals begin the switch motion of switch element Q1, Q2 again.
Therefore, when detecting abnormality and carry out the current limit action, as the current limit control based on current limit circuit, benchmark frequency of oscillation (the benchmark frequency of oscillation of digital pulse signal, the switching frequency of switch element with digital amplifier ... 400kHz for example) 1 cycle unit, drive circuit 12 drives the output of signal/stop control in real time.Thus, the repeatedly beginning of switch motion of switch element Q1, Q2 (side's conducting)/stop (both sides' cut-off).At this moment, shown in the enlarged drawing among Fig. 4, output current is with 1 cycle unit (for example every cycle T) the indentation change of benchmark frequency of oscillation, and current value is restricted to less than predetermined value.Therefore, need not stop the output from switch element Q1, Q2, as much as possible persistent switch action, and protection comprises the amplifying circuit of switch element.In addition, the output of driving signal/stop to control also and can export/stop control according to the arbitrary timing in 1 cycle, but not 1 cycle unit.
Fig. 5 (A), (B) are that the current limit circuit of present embodiment has or not into the comparison diagram of the output current wave of circuitry phase, the action waveforms when (A) expression does not arrange into circuitry phase, the action waveforms when (B) expression setting is advanced circuitry phase.Not arranging in the situation of circuitry phase shown in Fig. 5 (A), the beginning that will cause current limit action is owing to the phase delay of over-current detection signal postpones.Switch element Q1, Q2 carry out switch motion according to benchmark frequency of oscillation when 400kHz (for example be every 2.5 μ sec), thereby at once shutdown switch action when having the phase delay of over-current detection signal, can not carry out real-time current limit.In this case, as utilize symbol α illustrates, overcurrent occurs after than short-term between in, output current surpasses current limit value, if thereby abnormality continue, then will cause the fault of amplifying circuit etc.Reduce current limit value if consider this phase delay, then produce output and early stop, frequently carrying out the problems such as current limit action.Relative therewith, advance in the setting shown in Fig. 5 (B) in the situation of circuitry phase (present embodiment), can shorten overcurrent detection time, prevent that the beginning of current limit action from postponing with respect to switch motion, realize real-time current limit.In this case, as utilize symbol beta illustrates, output current can not reach more than the current limit value from initial generation overcurrent, can implement reliably current limit.
Below, the current limit action during to the generation resonance current is elaborated.Fig. 6 is the circuit diagram of the basic structure of representative digit amplifier.Fig. 7 is the gain-frequency characteristic figure of the amplifying circuit when in the low pass filter of amplifier efferent resonance occuring.The basic structure of digital amplifier is to have input signal source 51, amplifying circuit 52, low pass filter 53, loud speaker even load 54.For underload or when not having load (load resistance RL hour), the LC resonant circuit that is made of coil L and the capacitor C of low pass filter 53 carries out resonance in load 54, and amplifying circuit 52 vibrates.Usually, the resonance frequency fR that this resonance occurs reaches than the high frequency of 20kHz that surpasses the range of audibility according to the constant of low pass filter 53.In the present embodiment, if the output current value when resonance current occurs reaches more than the predetermined value, then stop the action of drive circuit, and suppress resonance current.In this case, overcurrent for the frequency of the range of audibility, the demand limiter that detects based on overcurrent moves, carry out thus current limit, resonance current for the frequency that surpasses the range of audibility, the demand limiter that detects based on resonance current moves, and carries out thus resonance current and suppresses.
Current limit action when the current limit action when wherein, resonance current occuring and above-mentioned generation overcurrent is to carry out in real time current limit equally.Therefore, its impact can not feed through to the output of the range of audibility, can suppress resonance current.Therefore, even owing to the unusual of load produces in the situation of resonance, also can not stop as much as possible output, and suppress resonance current.
Fig. 8 is the flow chart of the expression first action example relevant with the circuit protection function of the digital amplifier of present embodiment.In the first action example, when digital amplifier moves, carry out the overcurrent detection of output stage and the resonance current detection (S11) of being carried out output stage by resonance electric current detection circuit 21 by overcurrent sensing circuit 19.At this, whether reach more than the predetermined value according to overcurrent detected value or resonance current detected value, when switch occuring, overcurrent/resonance current has or not the circuit protection action (S12) of digital amplifier.Do not have unusually, do not detect at output current in the situation of overcurrent more than the predetermined value or resonance current, the repeatedly action of S11～S12.
Reach more than the predetermined value and detect in the situation of abnormality of output current at overcurrent detected value or resonance current detected value, over-current detection signal or resonance current detection signal are high level, the action of drive circuit 12 stops, and switch element Q1, Q2 all end (S13).Whether then, reach more than the predetermined value according to overcurrent detected value or resonance current detected value, the action of switch driving circuit 12 has or not again and begins (S14).At this, in the situation that overcurrent detected value or resonance current detected value reach more than the predetermined value, drive circuit 12 continues to stop action.In the situation that overcurrent detected value and resonance current detected value be less than predetermined value, over-current detection signal and resonance current detection signal are low level, and the action of drive circuit 12 begins again, and the switch motion of switch element Q1, Q2 begins (S15) again.
And, when digital amplifier moves, whether reach more than the predetermined value according to the temperature detection value of temperature detecting part 28 couples of switch element Q1, Q2, the digital amplifier when switching abnormal high temperature have or not circuit protection action (S16).The temperature detection value of switch element Q1, Q2 less than predetermined value, be not in the situation of abnormal high temperature state, the repeatedly action of S11～S16.
Continue grade, switch element Q1, Q2 excessive heating and become abnormal high temperature state, temperature detection value and reach in the situation more than the predetermined value in the abnormality of output current, control by interlock control part 29, quiet 23 linkage actions of relay 16 and input signal are carried out relay and are disconnected and input signal quiet (S17).
When relay 16 disconnected and cut off output signal path, load was cut off and is become no-load condition, thereby resonance more easily occurs.In the present embodiment, drive circuit 12 and switch element Q1, Q2 also move off and on when resonance occurs, and carry out current limit, if thereby resonance condition continue, then switch element Q1, Q2 might reach abnormal high temperature and damage.Therefore, to the control that links of relay 16 and quiet 23 of input signal, make and carry out simultaneously that relay disconnects and input signal is quiet, the input and output both sides are stopped, can preventing resonance.
In addition, in the flow chart of Fig. 8, with last in flow process of the temperature detection (S16) of switch element design, but also can design after just starting.This is more effective for following situation, namely at switch element Q1, the Q2 adstante febre because device is bad etc. in the early stage, and rapidly halt circuit action, and need not carry out the abnormal current detection.
Fig. 9 is the state transition diagram of the expression second action example relevant with the circuit protection function of the digital amplifier of present embodiment.In the second action example, when digital amplifier moved, the overcurrent of being carried out output stage by overcurrent sensing circuit 19 detected, carries out the resonance current detection (S21) of output stage and the temperature detection (S22) of being carried out switch element Q1, Q2 by temperature detecting part 28 by resonance electric current detection circuit 21.In the situation that overcurrent detected value and resonance current detected value are normal and less than predetermined value, the overcurrent of S21 detects and the resonance current detection repeatedly.In the situation that temperature detection value is normal and less than predetermined value, the temperature detection of S22 repeatedly.
In the situation that overcurrent detected value or resonance current detected value reach more than the predetermined value, over-current detection signal or resonance current detection signal are high level, and the action of drive circuit 12 stops, and switch element Q1, Q2 end (S23).And, proceed overcurrent detection and resonance current and detect (S24).At this, in the situation that overcurrent detected value or resonance current detected value reach more than the predetermined value, the overcurrent of S24 detects and the resonance current detection repeatedly, and the action halted state of drive circuit 12 continues.In the situation that overcurrent detected value and resonance current detected value are normal and less than predetermined value, over-current detection signal and resonance current detection signal are low level, the action of drive circuit 12 begins (S25) again.Then, the overcurrent that turns back to S21 detects and the resonance current detection, repeatedly carries out identical action.
In the situation that temperature detection value reaches more than the predetermined value, by the control of interlock control part 29, quiet 23 linkage actions of relay 16 and input signal are carried out relay and are disconnected and input signal quiet (S26).And, proceed temperature detection (S27).At this, in the situation that temperature detection value reaches more than the predetermined value, the temperature detection of S27 repeatedly, relay disconnects and the quiet state continuance of input signal.In the situation that temperature detection value is normal and less than predetermined value, by the control of interlock control part 29, the linkage action that releasing relay 16 and input signal are quiet 23 is carried out relay and connected and quiet releasing (S28).Then, turn back to the temperature detection of S22, repeatedly carry out identical action.In addition, also can move as follows, namely after beginning again, the action of the drive circuit 12 of S25 enters into the temperature detection of S22, in the situation that temperature detection value reaches more than the predetermined value, the relay that is in S26 disconnects and the input signal mute state, the S21 overcurrent detects and resonance current detects in the situation that temperature detection value less than predetermined value, enters into.
Below, use Figure 10 and Figure 11 explanation the digital amplifier of present embodiment to be applied to the situation of sound reinforcement system.Figure 10 is the figure of sound reinforcement system that the digital amplifier of present embodiment has been used in expression.Sound reinforcement system will be by the voice signal of microphone 70 collection sounds by cable transmission to frequency mixer 71, be transferred to digital amplifier 72 from frequency mixer 71 again, be transferred to loud speaker 73 from digital amplifier 72 again, thus from loud speaker 73 with the voice signal public address to the public address space of wanting public address.
And Figure 11 represents the structure of the digital amplifier that this sound reinforcement system is used.In structure shown in Figure 11, be to have control part 80 and LED81 with the difference of Fig. 2, so that the output of resonance electric current detection circuit 21 also is input to control part 80,, can show at LED81 in the situation that continued the scheduled time in the control part 80 when the Output rusults of resonance electric current detection circuit 21.
In this sound reinforcement system, digital amplifier 72 of the present invention can detect the less resonance current that occurs when being so-called underload etc. at the number of connection of loud speaker 73, but the frequency that detects also can be the above non-range of audibility frequency band of 20kHz as shown in Figure 7.
In addition, known in the sound reinforcement system that comprises microphone 70 and loud speaker 73: the public address sound from loud speaker 73 is collected sound via microphone 70 again, and the frequency of oscillation that occurs in range of audibility frequency band thus becomes singing.Relative therewith, mutually along each other and during wiring etc., input and output are carried out electric/magnetic coupling and are implemented positive feedback, cause vibration at the cable of as shown in figure 10 microphone 70 and loud speaker 73.This vibration is called as system oscillation, can be heard by people's ear unlike singing, thereby be delayed and detect, and often become the reason of the fault that causes frequency mixer 71, digital amplifier 72 and loud speaker 73 etc.
But, according to the resonance electric current detection circuit 21 of digital amplifier of the present invention, also can detect in the lump the frequency band of generation systems vibration, thereby when producing this resonance current consistently, can be judged as system oscillation has occured.Therefore, the output that detects resonance electric current detection circuit 21 continues the scheduled time in control part 80 or not shown microprocessor etc., in the situation that continued the scheduled time LED81 is lighted, can notify thus the user of sound reinforcement system that system oscillation has occured.In addition, control part 80 also can constitute in inside has integrating circuit, if this integrated value reaches LED81 is lighted.
Thus, the user can learn the generation of system oscillation, and takes suitable countermeasure before frequency mixer 71, digital amplifier 72 and loud speaker 73 etc. break down.
In addition, as control part 80, as long as can judge that detecting the output that detects resonance electric current detection circuit 21 continues the scheduled time, thereby also can adopt timer etc.And, LED81 also can be located in the digital amplifier, also can be located at for example frequency mixer 71 of the user easily sees in the sound reinforcement system position, perhaps the luminous element of the monomers such as LED or emergency warning lamp or the demonstration body of the monomers such as liquid crystal or organic EL can also be set at ceiling, wall etc.In addition, in will the situation from the voice signal public address of various audio frequency sources of sound, also can detection system vibrate to replace the voice signal from microphone 70.
As described above, in the present embodiment, the circuitry phase that advances of detection signal is set for the circuit of the abnormality of the output current that carries out current limit control in detection, response in the time of can accelerating abnormal state detection thus, shorten detection time, carry out fast and reliably the current limit action.In this case, do not need to have supposed the current limit control of phase delay, thereby when the abnormalities such as generation overcurrent, can when carrying out current limit, continue to export, and do not need to cut off output current at once.Thus, can before breaking down fully, amplifying circuit continue to move and lasting output sound in the situation of public affair Play System, emergency playing system, sound reinforcement system etc. such as being applicable at the digital amplifier with present embodiment.
And, resonance electric current detection circuit is set, the resonance phenomena of the output filter of the amplifier efferent that occurs when the underload according to the current detecting of the capacitor that flows to output filter detects by this resonance current and can carry out current limit.Therefore, to also can carrying out appropriate current limit action based on the overcurrent of the resonance phenomena of efferent, and the protection amplifying circuit.That is, in the present embodiment, when overcurrent occuring in the time of can tackling the load short circuits as abnormality etc. and load both sides' when resonance occuring when disconnecting or during underload etc. load abnormal.
In the current limit control of present embodiment, only when detecting abnormality, stop the output of drive circuit, the pwm circuit of its prime etc. normally moves, thereby again begins when reverting to normal condition between action when not required.Therefore, when abnormality is disengaged, can start rapidly digital amplifier make begin output.
And, the temperature detection that the interlock control part carries out the switch element of output stage is set, in the situation that temperature detection value reaches more than the predetermined value, make the relay of efferent disconnect and make the interlock control that the quiet output of input signal stops.Thus, when being in the abnormal high temperature state, stop the input and output both sides, can prevent that switch element from damaging.For example, under the state that carries out the current limit action according to abnormal state detection, when having produced overcurrent at load change etc., can stop output according to temperature detection, and the protection amplifying circuit.
Like this, according to present embodiment, can shorten overcurrent that the switch element that causes output stage damages and the detection time of resonance current, and will export stop to be controlled at Min., can implement more appropriate current limit and move.
In addition; about the present invention, under the prerequisite that does not break away from aim of the present invention and scope, those skilled in the art carry out various changes, application according to record and the known technology of specification; all are items that can predict of the present invention, and are included within the claimed scope.And, also can in the scope that does not break away from aim of the present invention, each inscape to above-mentioned execution mode carry out combination in any.
The present invention is dependent on the Japanese patent application (Japanese Patent Application 2010-033362) of filing an application on February 8th, 2010, and its content is contained in this by reference.
Utilizability on the industry
The present invention has the time of the abnormality detection that can shorten output current, does not stop as much as possible output, and the effect of protection amplifying circuit when unusual is such as can be as the digital amplifier of the amplification of carrying out the voice signal etc. in the public affair broadcast etc. etc.
Label declaration
11 pwm circuits
12,31 drive circuits
13 coils
14 capacitors
15 output filters
16 relays
17 loud speakers
18,20 detect resistance
19 overcurrent sensing circuits
21 resonance electric current detection circuit
22,41 advance circuitry phase
The quiet section of 23 input signals
24 mute circuits
25 bypass resistances
26,27 switches
28 temperature detecting parts
29 interlock control parts
32 circuit for reversing
33,34 optical couplers
35,36 drivers
37 switch elements
38 NOR circuit
42 capacitors
43,44 resistors
51 input signal sources
52 amplifying circuits
53 low pass filters
54 loads
Q1, Q2 switch element
Claims (7)
1. a digital amplifier carries out the D class to input signal and amplifies, and it is characterized in that having:
Switch element carries out switch motion according to the driving signal based on the digital pulse signal of described input signal;
Drive circuit is supplied with described driving signal to described switch element;
Output filter comprises the low pass filter that is connected with the efferent of described switch element; And
Abnormal state detection section is located at the efferent of described switch element, detects the abnormality from the output current of described switch element, and the output abnormality state detection signal,
Described abnormal state detection section have the phase place that makes described abnormal state detection signal leading advance the phase function,
In the situation of the abnormality that arrives output current according to described abnormal state detection input, described drive circuit stops described driving signal, and the switch motion of described switch element is stopped.
2. digital amplifier according to claim 1, described abnormal state detection section has: overcurrent sensing circuit, detection is from the overcurrent more than the predetermined value in the output current of described switch element, and the output over-current detection signal is as described abnormal state detection signal; And advance circuitry phase, make the phase place of described over-current detection signal leading.
3. digital amplifier according to claim 1, described abnormal state detection section has resonance electric current detection circuit, detect the resonance current more than the predetermined value relevant with output current when the described output filter generation resonance, and the export resonance current detection signal is as described abnormal state detection signal.
4. digital amplifier according to claim 1, described digital amplifier has:
Temperature detecting part detects described switch element or the temperature around it;
The output cutting portion is cut off the output of described switch element;
The quiet section of input signal makes described input signal become predetermined level following tone-off state or small state; And
The interlock control part makes quiet linkage action of described output cutting portion and described input signal,
Detected by described temperature detecting part in the situation of the condition of high temperature more than the predetermined value, described interlock control part makes described output cutting portion and quiet linkage action of described input signal.
5. digital amplifier according to claim 1, described drive circuit carries out the current limit action of described switch element by repeatedly carrying out following control, described being controlled to be: according to described abnormal state detection signal, in the situation that described output current is to stop described driving signal more than the predetermined value, the switch motion of described switch element is stopped, and in the situation that described output current makes the switch motion that again begins described switch element less than the described driving signal of predetermined value output.
6. digital amplifier according to claim 5, described drive circuit is in current limit when action of carrying out described switch element, exports/stop described driving signal at 1 cycle unit or the arbitrary timing in the 1 cycle unit of the benchmark frequency of oscillation of described digital pulse signal.
7. digital amplifier according to claim 3, described digital amplifier has control part, this control part judges that the resonance current detection signal of described resonance electric current detection circuit is continued export scheduled time, and in the situation that continues the signal of this situation of output expression of the described scheduled time of output.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2010033362A JP5430438B2 (en) | 2010-02-18 | 2010-02-18 | Digital amplifier |
| JP2010-033362 | 2010-02-18 | ||
| PCT/JP2011/000648 WO2011102092A1 (en) | 2010-02-18 | 2011-02-04 | Digital amplifier |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN102859868A true CN102859868A (en) | 2013-01-02 |
| CN102859868B CN102859868B (en) | 2015-05-20 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201180010215.6A Expired - Fee Related CN102859868B (en) | 2010-02-18 | 2011-02-04 | Digital amplifier |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JP5430438B2 (en) |
| CN (1) | CN102859868B (en) |
| WO (1) | WO2011102092A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110896516A (en) * | 2018-09-12 | 2020-03-20 | 拉碧斯半导体株式会社 | Semiconductor device and audio output device |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103296982B (en) * | 2012-02-27 | 2016-10-05 | 无锡华润矽科微电子有限公司 | D class audio frequency power amplification circuit realizes the circuit structure of adaptation function |
| JP5638597B2 (en) * | 2012-12-27 | 2014-12-10 | 株式会社東芝 | Digital amplitude modulation apparatus and digital amplitude modulation control method |
| GB2510396A (en) * | 2013-02-01 | 2014-08-06 | Nujira Ltd | Controlling resonance in an envelope tracking power supply |
| US9647612B2 (en) | 2014-09-30 | 2017-05-09 | JVC Kenwood Corporation | Power amplifying apparatus and power amplifying method |
| KR102081971B1 (en) * | 2018-11-13 | 2020-02-26 | 한국항공우주연구원 | Device and method of protecting source for acoustic testing |
| KR101992293B1 (en) * | 2019-01-02 | 2019-06-26 | (주)하이텍영상 | Digital Amplifier Device with real-time detection and Automatic Switching Broadcasting System using it |
| KR102214729B1 (en) * | 2019-01-11 | 2021-02-10 | 박창길 | Emergency broadcasting control system |
| TWI724980B (en) | 2020-10-14 | 2021-04-11 | 立積電子股份有限公司 | Amplification circuit |
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| JP2003037452A (en) * | 2001-07-26 | 2003-02-07 | Denon Ltd | Protective circuit for amplifier |
| JP2004254021A (en) * | 2003-02-19 | 2004-09-09 | Rohm Co Ltd | Method for protecting amplifier, and semiconductor device provided with amplifier |
| JP2005203968A (en) * | 2004-01-14 | 2005-07-28 | Denon Ltd | Protective device for digital amplifier |
| JP2007258903A (en) * | 2006-03-22 | 2007-10-04 | Toa Corp | Resonance current detection device and protection device for digital amplifier |
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| JPH07146722A (en) * | 1993-10-01 | 1995-06-06 | Fuji Electric Co Ltd | Overcurrent protective device for transistor |
| JP4929208B2 (en) * | 2008-02-29 | 2012-05-09 | 三菱重工業株式会社 | Magnetic bearing device |
| JP2009260834A (en) * | 2008-04-18 | 2009-11-05 | Sony Corp | Overcurrent protection circuit and class-d amplifier |
-
2010
- 2010-02-18 JP JP2010033362A patent/JP5430438B2/en active Active
-
2011
- 2011-02-04 CN CN201180010215.6A patent/CN102859868B/en not_active Expired - Fee Related
- 2011-02-04 WO PCT/JP2011/000648 patent/WO2011102092A1/en active Application Filing
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003037452A (en) * | 2001-07-26 | 2003-02-07 | Denon Ltd | Protective circuit for amplifier |
| JP2004254021A (en) * | 2003-02-19 | 2004-09-09 | Rohm Co Ltd | Method for protecting amplifier, and semiconductor device provided with amplifier |
| JP2005203968A (en) * | 2004-01-14 | 2005-07-28 | Denon Ltd | Protective device for digital amplifier |
| JP2007258903A (en) * | 2006-03-22 | 2007-10-04 | Toa Corp | Resonance current detection device and protection device for digital amplifier |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110896516A (en) * | 2018-09-12 | 2020-03-20 | 拉碧斯半导体株式会社 | Semiconductor device and audio output device |
| CN110896516B (en) * | 2018-09-12 | 2023-10-31 | 拉碧斯半导体株式会社 | Semiconductor device and sound output device |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2011102092A1 (en) | 2011-08-25 |
| JP2011171967A (en) | 2011-09-01 |
| JP5430438B2 (en) | 2014-02-26 |
| CN102859868B (en) | 2015-05-20 |
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Effective date of registration: 20150915 Address after: Osaka Patentee after: PANASONIC INTELLECTUAL PROPERTY MANAGEMENT Co.,Ltd. Address before: Osaka Patentee before: Matsushita Electric Industrial Co.,Ltd. |
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