CN101320961A - Power amplification circuit - Google Patents
Power amplification circuit Download PDFInfo
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- CN101320961A CN101320961A CNA2008101104623A CN200810110462A CN101320961A CN 101320961 A CN101320961 A CN 101320961A CN A2008101104623 A CNA2008101104623 A CN A2008101104623A CN 200810110462 A CN200810110462 A CN 200810110462A CN 101320961 A CN101320961 A CN 101320961A
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Abstract
The present invention relates to a power amplification circuit driving capacitive load, which can reduce the power consumption. The power amplification comprising: a forestage amplification circuit(110) and a connecting amplification circuit(140)which amplify input signals (Vin, Vip) to form output signals, thereby driving a piezoelectric loudspeaker(120) used as the capacitive load; a control part(130) which is corresponding to the testing result of an electric current part(131)and output signals of a comparator(132), and controls a supply voltage supplied to the BTL connecting amplification circuit(140).
Description
Technical field
The present invention relates to a kind of power amplification circuit, particularly a kind of technology that can when driving capacitive load, reduce power consumption.
The present invention is based on Japan's patent application 2007-149201 number of application on June 5th, 2007 and Japan's patent application of application on June 5th, 2007 and require priority for 2007-149202 number, quote its content here.
Background technology
As the driven object of power amplification circuit, use capacity load sometimes.For example open an example that discloses existing power amplification circuit in the clear 51-132746 communique the spy.Figure 15 is that the circuit diagram of piezoelectric speaker as an example of the power amplification circuit under the situation of capacity load used in expression.BTL (Bridged Transless) mode as shown in the drawing, that power amplification circuit 240 adopts amplifying device 241a and anti-phase amplifying device 241b bridge joint is to obtain bigger output.
The supply voltage of power amplification circuit 240 is produced by power supplys such as lithium ion battery 250, but piezoelectric speaker 220 needs 12V usually
Pp～15V
PpSuch higher drive.Therefore, under the situation of the lithium ion battery that uses 3.7V, use charge pump 260 grades boost to required voltage and supply with as the supply voltage of power amplification circuit 240.
Figure 16 A illustrates the frequency-impedance operator of piezoelectric speaker 220, and Figure 16 B illustrates the frequency-output sound pressure characteristic of piezoelectric speaker 220.Because piezoelectric speaker 220 has capacitive character, so if shown in Figure 16 A frequency gets higher, then impedance gradually becomes very low.In addition, if also have frequencies go lower shown in Figure 16 B then export the characteristic that acoustic pressure reduces gradually.
Summary of the invention
If because piezoelectric speaker 220 frequency gets higher, then impedance gradually becomes very low, also increase gradually so in high-frequency region, flow through the electric current of power amplification circuit 240.Because the driving voltage of piezoelectric speaker 220 is also higher, so, then exist the loss of power amplification circuit 240 to increase the problem that caloric value also increases if be in high-frequency region.
If, the delivery efficiency of power amplification circuit 240 is worsened in order to prevent that the electric current in the high-frequency region from increasing and the value of increase protective resistance R10.In addition,, then need bigger voltage transitions if adopt the D class to amplify for the loss that reduces power amplification circuit 240, need be at the countermeasure of unnecessary radiation.
The present invention proposes in view of above-mentioned condition, and its purpose is, the power amplification circuit of driving capacitive load is reduced the wastage.
In order to solve above-mentioned problem, power amplification circuit involved in the present invention has: amplifying unit, and it generates output signal with the input signal amplification and comes driving capacitive load; Current detecting unit, it detects the current sinking of amplifying unit; And power control unit, its testing result with current detecting unit is corresponding, and control is supplied to the supply voltage of amplifying unit.
According to the present invention,,, the loss of power amplification circuit is reduced so supply voltage is reduced owing to the corresponding supply voltage that is supplied to amplifying unit of controlling with the testing result of current detecting unit.That is,, also can reduce the consumption electric power that reduces power amplification circuit by making supply voltage even descend and electric current is increased at the high-frequency region middle impedance.
More particularly, power control unit can be optionally with one in high voltage and the low-voltage as power supply voltage supplying to amplifying unit, under the situation of detected current value less than the 1st current value, high voltage is supplied to amplifying unit by current detecting unit.Thus, can under the situation of current value, obtain enough output less than the 1st current value.
In addition, also can make power control unit have comparing unit, its voltage and reference voltage with above-mentioned input signal compares, by the detected current value of above-mentioned current detecting unit more than or equal to the 1st current value under the situation less than the 2nd current value, comparative result based on above-mentioned comparing unit, the voltage of above-mentioned input signal more than or equal to the said reference voltage condition under, above-mentioned high voltage is supplied to above-mentioned amplifying unit, the voltage of above-mentioned input signal less than the said reference voltage condition under, above-mentioned low-voltage is supplied to above-mentioned amplifying unit.Thus, at current value more than or equal to the 1st current value under the situation less than the 2nd current value, Switching power voltage dynamically, so under the less situation of input signal, loss is reduced, under the bigger situation of input signal, can obtain enough output simultaneously.
In addition, preferred above-mentioned power control unit by the detected current value of above-mentioned current detecting unit more than or equal to the 2nd current value under the situation less than the 3rd current value, comparative result based on above-mentioned comparing unit, the voltage of above-mentioned input signal more than or equal to the said reference voltage condition under, above-mentioned high voltage is supplied to above-mentioned amplifying unit, the voltage of above-mentioned input signal less than the said reference voltage condition under, above-mentioned low-voltage is supplied to above-mentioned amplifying unit, if begin through the stipulated time more than or equal to said reference voltage from the voltage of above-mentioned input signal, then, all above-mentioned low-voltage is supplied to above-mentioned amplifying unit regardless of the voltage of above-mentioned input signal.Become big if detect the size of electric current, then the loss of amplifying unit increases, but according to the present invention, since at current value more than or equal to the 2nd current value under the situation less than the 3rd current value, if begin to have passed through the stipulated time more than or equal to reference voltage from the voltage of input signal, then forcibly low-voltage is supplied to amplifying unit,, reduces consuming electric power simultaneously so can suppress the excessive heating of amplifying unit.
In addition, power control unit can be optionally with one in high voltage and the low-voltage as power supply voltage supplying to amplifying unit, under the situation of detected current value more than or equal to the 3rd current value, low-voltage is supplied to amplifying unit by current detecting unit.Thus, even under the situation of current value more than or equal to the 3rd current value, also can be by reducing the consumption electric power that supply voltage reduces power amplification circuit.
In order to solve above-mentioned problem, power amplification circuit involved in the present invention has: amplifying unit, and it generates output signal with the input signal amplification and comes driving capacitive load; Frequency detecting unit, it detects input signal or output signal frequency; And power control unit, its testing result with frequency detecting unit is corresponding, and control is supplied to the supply voltage of amplifying unit.
According to the present invention, owing to the corresponding supply voltage that is supplied to amplifying unit of controlling with the testing result of frequency detecting unit, thus supply voltage is reduced, thus the loss of power amplification circuit reduced.That is,, also can reduce the consumption electric power that reduces power amplification circuit by making supply voltage even increase because of high-frequency region makes impedance decline, electric current.
More particularly, power control unit can be optionally with one in high voltage and the low-voltage as power supply voltage supplying to amplifying unit, under the situation of detected frequency less than the 1st frequency, high voltage is supplied to amplifying unit by frequency detecting unit.Thus, can under the situation of frequency, obtain enough output less than the 1st frequency.
In addition, can make power control unit have comparing unit, its voltage and reference voltage with above-mentioned input signal compares, by the detected frequency of said frequencies detecting unit more than or equal to the 1st frequency under the situation less than the 2nd frequency, comparative result based on above-mentioned comparing unit, the voltage of above-mentioned input signal more than or equal to the said reference voltage condition under, above-mentioned high voltage is supplied to above-mentioned amplifying unit, the voltage of above-mentioned input signal less than the said reference voltage condition under, above-mentioned low-voltage is supplied to above-mentioned amplifying unit.Thus, more than or equal to the 1st frequency under the situation less than the 2nd frequency, dynamically Switching power voltage so under the less situation of input signal, loss is reduced, under the bigger situation of input signal, can obtain enough output simultaneously in frequency.
In addition, preferably by the detected frequency of said frequencies detecting unit more than or equal to the 2nd frequency under the situation less than the 3rd frequency, comparative result based on above-mentioned comparing unit, the voltage of above-mentioned input signal more than or equal to the said reference voltage condition under, above-mentioned high voltage is supplied to above-mentioned amplifying unit, the voltage of above-mentioned input signal less than the said reference voltage condition under, above-mentioned low-voltage is supplied to above-mentioned amplifying unit, if begin through the stipulated time more than or equal to said reference voltage from the voltage of above-mentioned input signal, then, all above-mentioned low-voltage is supplied to above-mentioned amplifying unit regardless of the voltage of above-mentioned input signal.Because if frequency gets higher then load impedance reduce, so the loss of amplifying unit increases, but according to the present invention, since in frequency more than or equal to the 2nd frequency under the situation less than the 3rd frequency, if begin to have passed through the stipulated time more than or equal to reference voltage from the voltage of input signal, then forcibly low-voltage is supplied to amplifying unit,, reduces consuming electric power simultaneously so can suppress the excessive heating of amplifying unit.
In addition, power control unit can be optionally with one in high voltage and the low-voltage as power supply voltage supplying to amplifying unit, under the situation of detected frequency more than or equal to the 3rd frequency, low-voltage is supplied to amplifying unit by frequency detecting unit.Thus, even under the situation of frequency more than or equal to the 3rd frequency, load impedance reduces and electric current is increased, also can be by reducing the consumption electric power that supply voltage reduces power amplification circuit.
Description of drawings
Fig. 1 is the block diagram of the basic comprising example of the power amplification circuit in the expression embodiments of the present invention 1.
Fig. 2 is the expression supply voltage configuration part judgment standard that makes switch and switch, the i.e. block diagram of a regular example.
Fig. 3 is that expression is used the present invention and the block diagram of an example of the structure of the piezoelectric speaker drive unit that constitutes.
Fig. 4 A is the figure of the particular circuit configurations of expression comparator.
Fig. 4 B is that expression constitutes the figure of particular circuit configurations that BTL connects the amplifying device of amplifying circuit.
Fig. 5 is the block diagram of the functional structure of expression control part.
Fig. 6 is the flow chart of the processing of explanation control part.
Fig. 7 A is the figure of the relation of expression output signal of amplifying device and supply voltage.
Fig. 7 B is the figure of other relations of expression output signal of amplifying device and supply voltage.
Fig. 8 is the block diagram of the basic comprising example of the power amplification circuit in the expression embodiments of the present invention 2.
Fig. 9 is the expression supply voltage configuration part judgment standard that makes switch and switch, the i.e. figure of a regular example.
Figure 10 is that expression is used the present invention and the block diagram of an example of the structure of the piezoelectric speaker drive unit that constitutes.
Figure 11 A is the figure of the particular circuit configurations of expression comparator.
Figure 11 B is that expression constitutes the figure of particular circuit configurations that BTL connects the amplifying device of amplifying circuit.
Figure 12 is the block diagram of the functional structure of expression control part.
Figure 13 is the flow chart of the processing of explanation control part.
Figure 14 A is the figure of the relation of expression output signal of amplifying device and supply voltage.
Figure 14 B is the figure of other relations of expression output signal of amplifying device and supply voltage.
Figure 15 is illustrated in to use the circuit diagram of piezoelectric speaker as an example of the power amplification circuit under the situation of capacity load.
Figure 16 A is the figure of the frequency-impedance operator of expression piezoelectric speaker.
Figure 16 B is the figure of the frequency-output sound pressure characteristic of expression piezoelectric speaker.
Embodiment
(execution mode 1)
With reference to description of drawings embodiments of the present invention 1.At first, summary of the present invention is described.Fig. 1 is the block diagram of expression basic comprising example of the present invention.In the figure, 10 drivings of illustration power amplification circuit are as the situation of the piezoelectric speaker 20 of capacity load.
For simplicity, power amplification circuit 10 uses common anti-phase negative feedback amplifier circuit, and this anti-phase negative feedback amplifier circuit uses operational amplifier OpAmp and resistance R 1, R2 to constitute.Certainly this power amplification circuit also can be made of the positive negative feedback amplifier circuit.Here, anti-phase negative feedback amplifier circuit or positive negative feedback amplifier circuit work as amplifying unit, are used for amplification input signal and generate output signal and driving capacitive load.And, constitute and make the supply voltage ± Vd that is supplied to operational amplifier OpAmp, control by the control part 30 that works as power control unit.
Fig. 2 is expression supply voltage configuration part 33 judgment standard that makes switch 37 and switch, the i.e. figure of regular example, and Fig. 2 (a) represents the 1st example, and Fig. 2 (b) represents other examples.In this example, the combination that voltage division by input signal Vi and the current value of electric current I d are divided is judged which of high voltage 35 and low-voltage 36 is used as supply voltage.That is, be supplied to the supply voltage of power amplification circuit 10 according to this combination adjustment of electric current of crossing based on sound size and the actual flow of input signal Vi.
Here, the voltage division of input signal Vi is divided into more than or equal to the situation of the magnitude of voltage of regulation with less than these 2 kinds of the magnitudes of voltage of regulation, current value divide be divided into little electric current, medium and small electric current, in big electric current, big these 4 zones of electric current.Usually, if output signal frequency uprises, then the impedance of piezoelectric speaker 20 reduces, so current value sharply becomes greatly.In addition, voltage division can directly be used applied signal voltage Vi, also can extract the value corresponding with amplitude and carries out.In addition, division numbers separately is not limited to this example.
As shown in the drawing, control part 30 is supplied to power amplification circuit 10 with high voltage 35 all the time in little galvanic areas.This is because in little galvanic areas, even input voltage uprises, the loss of power amplification circuit 10 can not become problem basically yet.In addition, by supplying with high voltage 35 all the time, can realize driving fully piezoelectric speaker 20.
In medium and small galvanic areas,, thereby carry out the switching of high voltage 35 and low-voltage 36 and be supplied to power amplification circuit 10 by control switch 37 with the big or small corresponding of input voltage.That is, input voltage less during, be low-voltage 36 by making supply voltage, reduce the loss of power amplification circuit 10.In addition, preferably make the value of low-voltage 36 be set at the degree that under the less situation of input signal, can make power amplification circuit 10 carry out the regulation amplification.On the other hand, input voltage bigger during, be high voltage 35 by making supply voltage, can carry out enough amplifications to bigger input signal.
In in the big galvanic areas, shown in Fig. 2 (b), preestablish binding hours, in binding hours, by control switch 37, thereby carry out the switching of high voltage 35 and low-voltage 36 and be supplied to power amplification circuit 10 with the big or small corresponding of input voltage, passed through binding hours after, regardless of input voltage, all low-voltage 36 is supplied to power amplification circuit 10.Because the continuous input signal of big galvanic areas seldom can switch in the too much time owing to output is continuously risen the temperature of power amplification circuit 10 so can be limited to not in considering.This is for preferential loss reduction and the circuit protection of guaranteeing.
In big galvanic areas, all the time low-voltage 36 is supplied to power amplification circuit 10.This is for when big electric current flows through, and reduces the loss that reduces power amplification circuit 10 by the supply voltage that makes power amplification circuit 10.
Below, be that example further specifies the present invention with the side circuit.Fig. 3 is that expression is used the present invention and the block diagram of an example of the structure of the piezoelectric speaker drive unit that constitutes.In the example of this figure, connect amplifying circuit 140 by output stage use BTL, thereby improve output to piezoelectric speaker 120 in power amplification.Prime in power amplification is provided with preamplifying circuit 110, and it constitutes the resistance R 1～R4 that has driver element D and be used for the regulation magnification ratio, and this driver element D carries out the output of positive and anti-phase with the differential amplification of input signal (Vin, Vip).Driver element D is supplied with V
BIAS: 1.5V is as bias voltage, and the mid point of regulation working point.
Utilize comparator 132 that the output signal and the assigned voltage of preamplifying circuit 110 are compared, export its result to control part 130.In addition, comparator 132 is parts that 2 input signals are compared with reference voltage respectively, for example can be realized by the circuit shown in Fig. 4 A.That is, can constitute by comparator 132a, the comparator 132b of common 2 inputs and according to the logic OR circuit 132c that the two output result moves.Its result, if any one of 2 input signals greater than reference voltage, comparator 132 output high level then.
It is circuit that amplifying device 141a and amplifying device 141b bridge joint are constituted that the BTL that drives piezoelectric speaker 120 connects amplifying circuit 140.Constitute the amplifying device 141 that BTL connects amplifying circuit 140, the circuit that can be made of for example these two transistors of use TrN shown in Fig. 4 B and TrP is realized.If the impedance of piezoelectric speaker 120 reduces and flows through bigger electric current, then consume more electric power by resistance R n.In addition, in this circuit, owing to do not need protective resistance in series to be set, so the output that can be efficiently connects amplifying circuit 140 with BTL drives piezoelectric speaker 120 with piezoelectric speaker 120.
The supply voltage that BTL connects amplifying circuit 140 is produced by power supplys such as lithium ion battery 150.When low-voltage, the output voltage of power supply 150 is directly supplied with via diode D1, when high voltage, the output voltage of power supply 150 is supplied with via charge pump 160 back of boosting.In addition, also can replace charge pump 160, use increasing apparatus such as Switching Power Supply.The electric current that flows through BTL connection amplifying circuit 140 is measured by current measurement portion 131, exports measurement result to control part 130.
In the example of this figure, when switch 137 disconnects when low-voltage, will from the 3.7V of power supply 150, deduct the voltage drop V of diode D 1
FAfter voltage supply with as the supply voltage that BTL connects amplifying circuit 140, when switch 137 is closed when high voltage, be that voltage behind the 7.4V is supplied with as the supply voltage that BTL connects amplifying circuit 140 with utilizing charge pump 160 to boost to 2 times.In addition, if the voltage drop V of diode D 1
FBe 0.3V, then the reference voltage of comparator 132 is 3.7V-0.3V=3.4V.
Describe control part 130 in detail.Fig. 5 is the block diagram of the functional structure of expression control part 130.As shown in the drawing, control part 130 has: galvanic areas detection unit 136, and its measurement result based on current measurement portion 131 is judged galvanic areas; And switch judgement part 133, its based on the comparison the output result of device 132 and galvanic areas detection unit 136 result of determination and switch 137 is switched.These function portions can realize by software, also can realize by hardware.
In this example, galvanic areas detection unit 136 is under the situation of measurement result less than IaA of current measurement portion 131, be judged to be little electric current, under the situation less than IbA more than or equal to IaA, be judged to be medium and small electric current, under the situation less than IcA more than or equal to IbA, big electric current in being judged to be, under situation, be judged to be big electric current more than or equal to IcA.Wherein, make Ia＜Ib＜Ic.The result of determination of galvanic areas detection unit 136 exports switch judgement part 133 to.
The 2nd timer be the 1st timer expiration back in the big galvanic areas comparator 132 continue to measure the timer of duration under the situation of output high level.That is, after considering that the 1st timer expiration switches to low-voltage, if passed through the stipulated time then the temperature that rises also reduces, so the 2nd timer is set in order to switch to high-tension control once more.Therefore, the time expiration of the 2nd timer considers that the temperature of BTL connection amplifying circuit 140 reduces ability and stipulates.But also can omit the 2nd timer.In addition, be transferred under other regional situations the value of the 1st timer and the 2nd timer of resetting in the therefrom big galvanic areas of size that detects electric current.
Fig. 6 is the flow chart of the processing of explanation control part 130.In in the big galvanic areas, use the rule shown in Fig. 2 (b).Control part 130 is obtained the result of determination (S101) of galvanic areas detection unit 136.Its result under the situation that is little electric current, makes switch 137 closures, high voltage is supplied to BTL connects amplifying circuit 140 (S201).
Fig. 7 A is the figure that is illustrated in to the relation of the output waveform of amplifying device 141a under the situation of little electric current and amplifying device 141b and supply voltage.As shown in the drawing, it is 7.4V that supply voltage (thick line among the figure) is supplied with high voltage all the time.Even among amplifying device 141a and the amplifying device 141b is saturated in the GND side, also can amplitude be increased by another compensate for amplitude, can obtain desired undistorted output waveform in piezoelectric speaker 120 sides.In addition, the oblique line among the figure partly is a voltage between the collector emitter relevant with the loss of transistor Tr N, the TrP of amplifying device 141.
Result of determination at galvanic areas detection unit 136 is under the situation of big electric current, and switch 137 is disconnected, and low-voltage is supplied to BTL connects amplifying circuit 140 (S501).
Under the situation that is medium and small electric current, corresponding with the output of comparator 132 and control (S301).That is (S301: not), switch 137 is disconnected, low-voltage is supplied to BTL connects amplifying circuit 140 under the situation of, comparator 132 output low levels less, at input voltage.On the other hand, under the situation big at input voltage, that comparator 132 is exported high level (S301: be), make switch 137 closures, high voltage is supplied to BTL connects amplifying circuit 140 (S303).
Fig. 7 B is the figure that is illustrated in the relation of the output waveform of amplifying device 141a and amplifying device 141b under the situation of medium and small electric current and supply voltage.As shown in the drawing, supply voltage (thick line among the figure) is supplied with high voltage 7.4V under the input voltage condition with higher, supplies with low-voltage 3.4V under the lower situation of input voltage.That is, at the input waveform when being little amplitude, the voltage of the transistor Tr N by making amplifying device 141 reduces and reduces power consumption, becomes output waveform shown in dotted line.On the other hand, owing to when importing waveform, can export required voltage amplitude for large amplitude, so become the output waveform shown in solid line.In addition, the oblique line among the figure partly is a voltage between the collector emitter relevant with the loss of transistor Tr N, the TrP of amplifying device 141.
In the result of determination of galvanic areas detection unit 136 is under the situation of big electric current, whether the output of at first judging comparator 132 is high level (S401), be output as (S401: not) under the low level situation, switch 137 is disconnected, low-voltage is supplied to BTL connects amplifying circuit 140 (S402).
On the other hand, be output as (S401: be) under the situation of high level, judging whether the 1st timer is (S403) in starting.Since the 1st timer for the situation in starting under (S403: be), do not carry out the switching of high voltage low-voltage as yet under the big electric current in being illustrated in, so judge the 1st timer whether expire (S404).(S404: not), switch 137 is remained closed, continue the timing (S405) of the 1st timer under the still unexpired situation of the 1st timer.Under the situation that the 1st timer has expired (S404: be),, switch 137 is disconnected owing to need be transferred to low-voltage.In addition, for to be transferred to low-voltage during measure, start the 2nd timer and reset the 1st timer (S406).
Whether at the 1st timer is that judged result in starting is (S403: not), judge whether the 2nd timer is (S407) in starting under the 1st timer situation about not starting.Under the situation that the 2nd timer does not start (S407: not), begin to supply with high voltage under the big electric current in being illustrated in, shown in make switch 137 closures, high voltage is supplied to BTL connects amplifying circuit 140, make the 1st timer pick up counting (S408) simultaneously.
On the other hand, the 2nd timer for the situation in starting under (S407: be), represent that the 1st timer has expired and is transferred to low-voltage forcibly, so judge the 2nd timer whether expire (S409).Its result, under the situation that the 2nd timer has expired (S409: be), even also can not go wrong owing to being transferred to high voltage, institute is so that switch 137 closures are supplied to BTL connection amplifying circuit 140 with high voltage.(S409: not), make switch 137 keep disconnecting, continue the timing (S411) of the 2nd timer under the still unexpired situation of the 2nd timer.
By repeating above-mentioned processing, control part 130 can suitably be controlled and be supplied to the supply voltage that BTL connects amplifying circuit 140.In addition, in above-mentioned example, the voltage and the reference voltage of input signal compared, but also the voltage and the reference voltage of output signal can be compared.
In addition, in the above-described embodiment, BTL is connected amplifying circuit 140 be illustrated as an example of amplifying circuit, but the present invention is not limited to this, its form also can be single-ended amplifying circuit certainly.
In addition, with the size of electric current be divided into little electric current, medium and small electric current, in these 4 kinds in big electric current and big electric current, carry out and divide corresponding supply voltage with each and control, but can certainly these divisions of combination in any and carry out the control of supply voltage.
(execution mode 2)
With reference to the description of drawings embodiments of the present invention.At first, summary of the present invention is described.Fig. 8 is the block diagram of expression basic comprising example of the present invention.In the figure, situation about driving as the piezoelectric speaker 20 of capacity load with power amplification circuit 10 is an example.
For convenience of explanation, power amplification circuit 10 uses common anti-phase negative feedback amplifier circuit, and this anti-phase negative feedback amplifier circuit uses operational amplifier OpAmp and resistance R 1, R2 and constitutes.Certainly this power amplification circuit 10 also can be made of the positive negative feedback amplifier circuit.Here, anti-phase negative feedback amplifier circuit or positive negative feedback amplifier circuit work as amplifying unit, are used for amplification input signal and generate output signal and driving capacitive load.And, constitute and make the supply voltage ± Vd that is supplied to operational amplifier OpAmp, control by the control part 30 that works as power control unit.
Fig. 9 is expression supply voltage configuration part 33 judgment standard that makes switch 37 and switch, the i.e. figure of regular example, and Fig. 9 (a) represents the 1st example, and Fig. 9 (b) represents other examples.In this example, the combination of voltage division by input signal Vi and the frequency partition of output signal Vo is judged which of high voltage 35 and low-voltage 36 is used as supply voltage.That is the supply voltage that is supplied to power amplification circuit 10 according to sound height and big or small combination adjustment, based on input signal Vi.
Here, the voltage division of input signal Vi is divided into more than or equal to the situation of the magnitude of voltage of regulation with less than these 2 kinds of the magnitudes of voltage of stipulating, frequency partition is divided into low frequency, medium and low frequency, medium-high frequency, these 4 zones of high frequency.In addition, signal output Vo can be directly used in the judgement of frequency partition, also can extract to represent frequency, for example fundamental frequency and carry out.In addition, voltage division can directly be used applied signal voltage Vi, also can extract the value corresponding with amplitude and carries out.Division numbers separately is not limited to this example.
As shown in the drawing, control part 30 is supplied to power amplification circuit 10 with high voltage 35 all the time in low frequency region.This is because in low frequency region, and the impedance of piezoelectric speaker 20 is higher, even therefore input voltage uprises also and can not flow through big electric current, the loss of power amplification circuit 10 does not become problem basically yet.In addition, by supplying with high voltage 35 all the time, even, also can realize sufficient driving at the lower low frequency region of the output sound pressure characteristic of piezoelectric speaker 20.
In the medium and low frequency zone,, thereby carry out the switching of high voltage 35 and low-voltage 36 and be supplied to power amplification circuit 10 by control switch 37 with the big or small corresponding of input signal.That is, input voltage less during, be low-voltage 36 by making supply voltage, thereby reduce the loss of power amplification circuit 10.In addition, the value of preferred low-voltage 36 is set at and can makes power amplification circuit 10 carry out the degree that regulation is amplified under the less situation of input signal.On the other hand, input voltage bigger during, be high voltage 35 by making supply voltage, can carry out enough amplifications to bigger input signal.
In the medium-high frequency zone, shown in Fig. 9 (b), preestablish binding hours, in binding hours, by control switch 37, thereby carry out the switching of high voltage 35 and low-voltage 36 and be supplied to power amplification circuit 10 with the big or small corresponding of input voltage, passed through binding hours after, regardless of input voltage, all low-voltage 36 is supplied to power amplification circuit 10.Owing to consider the continuous input signal in medium-high frequency zone seldom, can switch in the too much time owing to output is continuously risen the temperature of power amplification circuit 10 so can be limited to not.This is for preferential loss reduction and the circuit protection of guaranteeing.
In high-frequency region, all the time low-voltage 36 is supplied to power amplification circuit 10.Its reason is, because in high-frequency region, the impedance step-down of piezoelectric speaker 20 flows through bigger electric current, so reduce the loss that reduces power amplification circuit 10 by the supply voltage that makes power amplification circuit 10.
Below, be example explanation the present invention with the side circuit.Figure 10 is that expression is used the present invention and the block diagram of an example of the structure of the piezoelectric speaker drive unit that constitutes.In the example of this figure, connect amplifying circuit 140 by output stage use BTL, thereby improve output to piezoelectric speaker 120 in power amplification.Prime in power amplification is provided with preamplifying circuit 110, and it constitutes the resistance R 1～R4 that has drive unit D and be used for the regulation magnification ratio, and this drive unit D carries out the output of positive and anti-phase with the differential amplification of input signal (Vin, Vip).Drive unit D is supplied with V
BIAS: 1.5V is as bias voltage, and the mid point of regulation working point.
Utilize comparator 132 that the output signal and the assigned voltage of preamplifying circuit 110 are compared, export its result to control part 130.In addition, comparator 132 is parts that 2 input signals are compared with reference voltage respectively, for example can be realized by the circuit shown in Figure 11 A.That is, can constitute by comparator 132a, the comparator 132b of common 2 inputs and according to the logic OR circuit 132c that the two output result moves.Its result, if any one of 2 input signals greater than reference voltage, comparator 132 output high level then.
It is circuit that amplifying device 141a and amplifying device 141b bridge joint are constituted that the BTL that drives piezoelectric speaker 120 connects amplifying circuit 140.Constitute the amplifying device 141 that BTL connects amplifying circuit 140, the circuit that can be made of for example these two transistors of use TrN shown in Figure 11 B and TrP is realized.If the impedance of piezoelectric speaker 120 reduces and flows through bigger electric current, then consume more electric power by resistance R n.In addition, in this circuit, owing to do not need protective resistance in series to be set, so the output that can be efficiently connects amplifying circuit 140 with BTL drives piezoelectric speaker 120 with piezoelectric speaker 120.
The supply voltage that BTL connects amplifying circuit 140 is produced by power supplys such as lithium ion battery 150.When low-voltage, the output voltage of power supply 150 is directly supplied with via diode D1, when high voltage, the output voltage of power supply 150 is supplied with via charge pump 160 back of boosting.In addition, also can replace charge pump 160, use increasing apparatus such as Switching Power Supply.
In the example of this figure, when switch 137 disconnects when low-voltage, will from the 3.7V of power supply 150, deduct the voltage drop V of diode D1
FAfter voltage supply with as the supply voltage that BTL connects amplifying circuit 140, when switch 137 is closed when high voltage, be that voltage behind the 7.4V is supplied with as the supply voltage that BTL connects amplifying circuit 140 with utilizing charge pump 160 to boost to 2 times.In addition, if the voltage drop V of diode D1
FBe 0.3V, then the reference voltage of comparator 132 is 3.7V-0.3V=3.4V.
Describe control part 130 in detail.Figure 12 is the block diagram of the functional structure of expression control part 130.As shown in the drawing, control part 130 has: frequency field detection unit 131, and it judges the output signal frequency zone of preamplifying circuit 110; And switch judgement part 133, its based on the comparison the output result of device 132 and frequency field detection unit 131 result of determination and switch 137 is switched.These function portions can realize by software, also can realize by hardware.
In this example, frequency field detection unit 131 is under the situation of output signal frequency less than 500Hz of preamplifying circuit 110, be judged to be low frequency, under the situation less than 5KHz more than or equal to 500Hz, be judged to be medium and low frequency, under the situation less than 10KHz, be judged to be medium-high frequency more than or equal to 5KHz, under situation, be judged to be high frequency more than or equal to 10KHz.The result of determination of frequency field detection unit 131 exports switch judgement part 133 to.
The 2nd timer is to continue to measure the timer of duration under the situation of output high level at the 1st timer expiration back comparator 132 in the medium-high frequency zone.That is, after considering that the 1st timer expiration switches to low-voltage, if passed through the stipulated time then the temperature that rises also reduces, so the 2nd timer is set in order to switch to high-tension control once more.Therefore, the time expiration of the 2nd timer considers that the temperature of BTL connection amplifying circuit 140 reduces ability and stipulates.But also can omit the 2nd timer.In addition, detect frequency therefrom high-frequency region be transferred under other regional situations the value of the 1st timer and the 2nd timer of resetting.
Figure 13 is the flow chart of the processing of explanation control part 130.In the medium-high frequency zone, use the rule shown in Fig. 9 (a).Control part 130 is obtained the result of determination (S 101) of frequency field detection unit 131.Its result under the situation that is low frequency, makes switch 137 closures, high voltage is supplied to BTL connects amplifying circuit 140 (S201).
Figure 14 A is the figure that is illustrated in to the relation of the output waveform of amplifying device 141a under the situation of low frequency and amplifying device 141b and supply voltage.As shown in the drawing, it is 7.4V that supply voltage (thick line among the figure) is supplied with high voltage all the time.Even among amplifying device 141a and the amplifying device 141b is saturated in the GND side, also can amplitude be increased by another compensate for amplitude, can obtain desired undistorted output waveform in piezoelectric speaker 120 sides.In addition, the oblique line among the figure partly is a voltage between the collector emitter relevant with the loss of transistor Tr N, the TrP of amplifying device 141.
Result of determination at frequency field detection unit 131 is under the situation of high frequency, and switch 137 is disconnected, and low-voltage is supplied to BTL connects amplifying circuit 140 (S501).
Under the situation that is medium and low frequency, corresponding with the output of comparator 132 and control (S301).That is (S301: not), switch 137 is disconnected, low-voltage is supplied to BTL connects amplifying circuit 140 under the situation of, comparator 132 output low levels less, at input voltage.On the other hand, under the situation big at input voltage, that comparator 132 is exported high level (S301: be), make switch 137 closures, high voltage is supplied to BTL connects amplifying circuit 140 (S303).
Figure 14 B is the figure that is illustrated in the relation of the output waveform of amplifying device 141a and amplifying device 141b under the situation of medium and low frequency and supply voltage.As shown in the drawing, supply voltage (thick line among the figure) is supplied with high voltage 7.4V under the input voltage condition with higher, supplies with low-voltage 3.4V under the lower situation of input voltage.That is, at the input waveform when being little amplitude, the voltage of the transistor Tr N by making amplifying device 141 reduces and reduces power consumption, becomes output waveform shown in dotted line.On the other hand, owing to when importing waveform, can export required voltage amplitude for large amplitude, so become the output waveform shown in solid line.In addition, the oblique line among the figure partly is a voltage between the collector emitter relevant with the loss of transistor Tr N, the TrP of amplifying device 141.
Result of determination at frequency field detection unit 131 is under the situation of medium-high frequency, whether the output of at first judging comparator 132 is high level (S401), be output as (S401: not), switch 137 is disconnected, low-voltage is supplied to BTL connects amplifying circuit 140 (S402) under the low level situation.
On the other hand, be output as (S401: be) under the situation of high level, judging whether the 1st timer is (S403) in starting.Since the 1st timer for the situation in starting under (S403: be), be illustrated in the switching of not carrying out the high voltage low-voltage under the medium-high frequency as yet, so judge the 1st timer whether expire (S404).(S404: not), switch 137 is remained closed, continue the timing (S405) of the 1st timer under the still unexpired situation of the 1st timer.Under the situation that the 1st timer has expired (S404: be),, switch 137 is disconnected owing to need be transferred to low-voltage.In addition, for to be transferred to low-voltage during measure, start the 2nd timer and reset the 1st timer (S406).
Whether at the 1st timer is that judged result in starting is (S403: not), judge whether the 2nd timer is (S407) in starting under the 1st timer situation about not starting.Under the situation that the 2nd timer does not start (S407: not), be illustrated in and begin to supply with high voltage under the medium-high frequency, shown in make switch 137 closures, high voltage is supplied to BTL connects amplifying circuit 140, make the 1st timer pick up counting (S408) simultaneously.
On the other hand, the 2nd timer for the situation in starting under (S407: be), represent that the 1st timer has expired and is transferred to low-voltage forcibly, so judge the 2nd timer whether expire (S409).Its result, under the situation that the 2nd timer has expired (S409: be), even also can not go wrong owing to being transferred to high voltage, institute is so that switch 137 closures are supplied to BTL connection amplifying circuit 140 with high voltage.(S409: not), make switch 137 keep disconnecting, continue the timing (S411) of the 2nd timer under the still unexpired situation of the 2nd timer.
By repeating above-mentioned processing, control part 130 can suitably be controlled and be supplied to the supply voltage that BTL connects amplifying circuit 140.In addition, in above-mentioned example, detect output signal frequency, but also can detect the frequency of input signal.In addition, the voltage and the reference voltage of input signal compared, but also the voltage and the reference voltage of output signal can be compared.
In addition, in the above-described embodiment, BTL is connected amplifying circuit 140 be illustrated as an example of amplifying circuit, but the present invention is not limited to this, its formation also can be single-ended amplifying circuit certainly.
In addition, be these 4 kinds of low frequency, medium and low frequency, medium-high frequency and high frequencies with frequency partition, carry out the control of the supply voltage corresponding with each division, but can certainly these divisions of combination in any and carry out the control of supply voltage.
More than, illustrate at preferred implementation of the present invention, but these must not be defined in this only for the illustration of invention, can append, delete, replace in the scope that does not break away from purport of the present invention and other changes.That is, the present invention is not limited to above-mentioned execution mode, is limited by aforementioned claims.
Claims (14)
1. power amplification circuit has:
Amplifying unit, it generates output signal with the input signal amplification and comes driving capacitive load;
Current detecting unit, it detects the current sinking of above-mentioned amplifying unit; And
Power control unit, its testing result with above-mentioned current detecting unit is corresponding, and control is supplied to the supply voltage of above-mentioned amplifying unit.
2. power amplification circuit according to claim 1,
Above-mentioned power control unit
Optionally with one in high voltage and the low-voltage as above-mentioned power supply voltage supplying to above-mentioned amplifying unit,
Under by the situation of the detected current value of above-mentioned current detecting unit, above-mentioned high voltage is supplied to above-mentioned amplifying unit less than the 1st current value.
3. power amplification circuit according to claim 1,
Above-mentioned power control unit
Have comparing unit, its voltage and reference voltage with above-mentioned input signal compares,
By the detected current value of above-mentioned current detecting unit more than or equal to the 1st current value under the situation less than the 2nd current value,
Comparative result based on above-mentioned comparing unit, the voltage of above-mentioned input signal more than or equal to the said reference voltage condition under, above-mentioned high voltage is supplied to above-mentioned amplifying unit, on the other hand, the voltage of above-mentioned input signal less than the said reference voltage condition under, above-mentioned low-voltage is supplied to above-mentioned amplifying unit.
4. power amplification circuit according to claim 2,
Above-mentioned power control unit
Have comparing unit, its voltage and reference voltage with above-mentioned input signal compares,
By the detected current value of above-mentioned current detecting unit more than or equal to the 1st current value under the situation less than the 2nd current value,
Comparative result based on above-mentioned comparing unit, the voltage of above-mentioned input signal more than or equal to the said reference voltage condition under, above-mentioned high voltage is supplied to above-mentioned amplifying unit, on the other hand, the voltage of above-mentioned input signal less than the said reference voltage condition under, above-mentioned low-voltage is supplied to above-mentioned amplifying unit.
5. power amplification circuit according to claim 3,
Above-mentioned power control unit
By the detected current value of above-mentioned current detecting unit more than or equal to the 2nd current value under the situation less than the 3rd current value,
Comparative result based on above-mentioned comparing unit, the voltage of above-mentioned input signal more than or equal to the said reference voltage condition under, above-mentioned high voltage is supplied to above-mentioned amplifying unit, the voltage of above-mentioned input signal less than the said reference voltage condition under, above-mentioned low-voltage is supplied to above-mentioned amplifying unit
If begin then, all above-mentioned low-voltage to be supplied to above-mentioned amplifying unit more than or equal to said reference voltage regardless of the voltage of above-mentioned input signal through the stipulated time from the voltage of above-mentioned input signal.
6. power amplification circuit according to claim 4,
Above-mentioned power control unit
By the detected current value of above-mentioned current detecting unit more than or equal to the 2nd current value under the situation less than the 3rd current value,
Comparative result based on above-mentioned comparing unit, the voltage of above-mentioned input signal more than or equal to the said reference voltage condition under, above-mentioned high voltage is supplied to above-mentioned amplifying unit, the voltage of above-mentioned input signal less than the said reference voltage condition under, above-mentioned low-voltage is supplied to above-mentioned amplifying unit
If begin then, all above-mentioned low-voltage to be supplied to above-mentioned amplifying unit more than or equal to said reference voltage regardless of the voltage of above-mentioned input signal through the stipulated time from the voltage of above-mentioned input signal.
7. according to any described power amplification circuit in the claim 1 to 6,
Above-mentioned power control unit
Optionally with one in high voltage and the low-voltage as above-mentioned power supply voltage supplying to above-mentioned amplifying unit,
Under by the situation of the detected current value of above-mentioned current detecting unit, above-mentioned low-voltage is supplied to above-mentioned amplifying unit more than or equal to the 3rd current value.
8. power amplification circuit has:
Amplifying unit, it generates output signal with the input signal amplification and comes driving capacitive load;
Frequency detecting unit, it detects above-mentioned input signal or above-mentioned output signal frequency; And
Power control unit, its testing result with the said frequencies detecting unit is corresponding, and control is supplied to the supply voltage of above-mentioned amplifying unit.
9. power amplification circuit according to claim 8,
Above-mentioned power control unit
Optionally with one in high voltage and the low-voltage as above-mentioned power supply voltage supplying to above-mentioned amplifying unit,
Under by the situation of the detected frequency of said frequencies detecting unit, above-mentioned high voltage is supplied to above-mentioned amplifying unit less than the 1st frequency.
10. power amplification circuit according to claim 8,
Above-mentioned power control unit
Have comparing unit, its voltage and reference voltage with above-mentioned input signal compares,
By the detected frequency of said frequencies detecting unit more than or equal to the 1st frequency under the situation less than the 2nd frequency,
Comparative result based on above-mentioned comparing unit, the voltage of above-mentioned input signal more than or equal to the said reference voltage condition under, above-mentioned high voltage is supplied to above-mentioned amplifying unit, the voltage of above-mentioned input signal less than the said reference voltage condition under, above-mentioned low-voltage is supplied to above-mentioned amplifying unit.
11. power amplification circuit according to claim 9,
Above-mentioned power control unit
Have comparing unit, its voltage and reference voltage with above-mentioned input signal compares,
By the detected frequency of said frequencies detecting unit more than or equal to the 1st frequency under the situation less than the 2nd frequency,
Comparative result based on above-mentioned comparing unit, the voltage of above-mentioned input signal more than or equal to the said reference voltage condition under, above-mentioned high voltage is supplied to above-mentioned amplifying unit, the voltage of above-mentioned input signal less than the said reference voltage condition under, above-mentioned low-voltage is supplied to above-mentioned amplifying unit.
12. power amplification circuit according to claim 10,
Above-mentioned power control unit
By the detected frequency of said frequencies detecting unit more than or equal to the 2nd frequency under the situation less than the 3rd frequency,
Comparative result based on above-mentioned comparing unit, the voltage of above-mentioned input signal more than or equal to the said reference voltage condition under, above-mentioned high voltage is supplied to above-mentioned amplifying unit, the voltage of above-mentioned input signal less than the said reference voltage condition under, above-mentioned low-voltage is supplied to above-mentioned amplifying unit
If begin then, all above-mentioned low-voltage to be supplied to above-mentioned amplifying unit more than or equal to said reference voltage regardless of the voltage of above-mentioned input signal through the stipulated time from the voltage of above-mentioned input signal.
13. power amplification circuit according to claim 11,
Above-mentioned power control unit
By the detected frequency of said frequencies detecting unit more than or equal to the 2nd frequency under the situation less than the 3rd frequency,
Comparative result based on above-mentioned comparing unit, the voltage of above-mentioned input signal more than or equal to the said reference voltage condition under, above-mentioned high voltage is supplied to above-mentioned amplifying unit, the voltage of above-mentioned input signal less than the said reference voltage condition under, above-mentioned low-voltage is supplied to above-mentioned amplifying unit
If begin then, all above-mentioned low-voltage to be supplied to above-mentioned amplifying unit more than or equal to said reference voltage regardless of the voltage of above-mentioned input signal through the stipulated time from the voltage of above-mentioned input signal.
14. any described power amplification circuit in 13 according to Claim 8,
Above-mentioned power control unit
Optionally with one in high voltage and the low-voltage as above-mentioned power supply voltage supplying to above-mentioned amplifying unit,
Under by the situation of the detected frequency of said frequencies detecting unit, above-mentioned low-voltage is supplied to above-mentioned amplifying unit more than or equal to the 3rd frequency.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2007149202 | 2007-06-05 | ||
| JP2007-149202 | 2007-06-05 | ||
| JP2007-149201 | 2007-06-05 | ||
| JP2007149201A JP2008306269A (en) | 2007-06-05 | 2007-06-05 | Power amplifying circuit |
| JP2007149201 | 2007-06-05 | ||
| JP2007149202A JP4983412B2 (en) | 2007-06-05 | 2007-06-05 | Power amplifier circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN101320961A true CN101320961A (en) | 2008-12-10 |
| CN101320961B CN101320961B (en) | 2012-07-04 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2008101104623A Expired - Fee Related CN101320961B (en) | 2007-06-05 | 2008-06-03 | Power amplification circuit |
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| JP (1) | JP2008306269A (en) |
| CN (1) | CN101320961B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103546105A (en) * | 2012-07-17 | 2014-01-29 | 美国亚德诺半导体公司 | Apparatus and methods for amplifier power supply control |
| WO2014169861A1 (en) | 2013-09-18 | 2014-10-23 | 中兴通讯股份有限公司 | Piezoelectric loudspeaker driving device |
| CN104581525A (en) * | 2013-10-16 | 2015-04-29 | 现代摩比斯株式会社 | Audio amplifier for vehicle |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8823343B2 (en) | 2009-12-22 | 2014-09-02 | Yamaha Corporation | Power amplifying circuit, DC-DC converter, peak holding circuit, and output voltage control circuit including the peak holding circuit |
| JP5711041B2 (en) * | 2011-05-09 | 2015-04-30 | 新日本無線株式会社 | Capacitive speaker drive circuit |
| CN105263084B (en) * | 2015-09-18 | 2019-04-12 | 浙江胜必得汽车配件科技有限公司 | Self-insurance's electronic horn and automobile comprising self-insurance's electronic horn |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4320350A (en) * | 1979-11-29 | 1982-03-16 | Rockwell International Corporation | Sliding power supply for RF power amplifier |
| JPS5766494A (en) * | 1980-10-14 | 1982-04-22 | Suwa Seikosha Kk | Device for driving piezoelectric element sound producing unit for portable small size information device |
| JPS59146296A (en) * | 1983-02-08 | 1984-08-22 | Murata Mfg Co Ltd | Driving method of piezoelectric speaker |
| JPS62133496U (en) * | 1986-02-18 | 1987-08-22 | ||
| JPH07240636A (en) * | 1994-03-01 | 1995-09-12 | Kenwood Corp | Power amplifier |
| JP3512654B2 (en) * | 1998-11-09 | 2004-03-31 | ローム株式会社 | Amplifier driving piezoelectric speaker |
| AU7551600A (en) * | 2000-03-10 | 2001-09-17 | Paragon Communications Ltd. | Method and apparatus for improving the efficiency of power amplifiers, operatingunder a large peak-to-average ratio |
| JP2003052095A (en) * | 2001-08-07 | 2003-02-21 | Denon Ltd | Audio amplifying circuit |
| JP2005109665A (en) * | 2003-09-29 | 2005-04-21 | Matsushita Electric Ind Co Ltd | Load driver |
| JP4261316B2 (en) * | 2003-11-06 | 2009-04-30 | フォスター電機株式会社 | Audio circuit |
-
2007
- 2007-06-05 JP JP2007149201A patent/JP2008306269A/en active Pending
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2008
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103546105A (en) * | 2012-07-17 | 2014-01-29 | 美国亚德诺半导体公司 | Apparatus and methods for amplifier power supply control |
| CN103546105B (en) * | 2012-07-17 | 2016-08-24 | 美国亚德诺半导体公司 | The equipment controlled for APS amplifier power supply and method |
| WO2014169861A1 (en) | 2013-09-18 | 2014-10-23 | 中兴通讯股份有限公司 | Piezoelectric loudspeaker driving device |
| CN104581525A (en) * | 2013-10-16 | 2015-04-29 | 现代摩比斯株式会社 | Audio amplifier for vehicle |
| CN104581525B (en) * | 2013-10-16 | 2018-02-23 | 现代摩比斯株式会社 | Vehicle audio amplifying device and its method |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2008306269A (en) | 2008-12-18 |
| CN101320961B (en) | 2012-07-04 |
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