Summary of the invention
In order to overcome the deficiencies of the prior art, the present invention is directed to propose the LC matching system of piezoelectric ultrasonic transducer.For this purpose, this
Invention the technical solution adopted is that, the LC of piezoelectric ultrasonic transducer matches modeling method, and steps are as follows:
1) model preparation:Specify the original design intention of LC match circuit, the i.e. purpose of Match circuits, it is desirable to the function of realization
The effect that can and reach;
2) model hypothesis:Circuit model after establishing matching, and simplify, determine the constant, variable and ginseng to be determined of model
Number carries out symbol definition;
3) model is constituted:It determines the constraint relationship between each constant, variable, and simplifies, according to original design intention, select mould
Type input quantity, output quantity derive the functional relation between input quantity, output quantity according to the constraint relationship;
4) model solution:The functional relation of above-mentioned establishment is solved, using the zero of function, pole as characteristic point, weight
Point analysis chooses the best value of parameter to be determined, obtains a kind of matching way of optimization according to original design intention;
5) model analysis:The matching way of above-mentioned optimization is substituted into system model, analyzes influence of its dependent variable to model,
The advantage and disadvantage for analyzing the matching way of above-mentioned optimization further determine that the reasonability of above-mentioned value;
6) model testing:The match circuit of ultrasonic transducer is built by the matching way of above-mentioned optimization, is surpassed after detection matching
The frequency and load response characteristic of sonic transducer;
7) model application:According to above-mentioned analysis, the application field of the matching way of above-mentioned optimization is analyzed, and is provided corresponding
Suggestion and strategy when device selection, frequency-tracking.
Specific steps further refine as follows:
Step 1:Model preparation:The original intention for determining LC matched design is the following aspects:
Original intention 1) power factor:It is tuned in Several Typical Load resistance value, makes system at purely resistive, power factor 1;
Original intention 2) power is larger:In the work of series resonance point, system output power, that is, active power is maximum or larger;
Original intention 3) power stability:System is set more to adapt to load resistance R1Variation, in R1Effective power fluctuation is small when fluctuation,
And maintain higher level;
Original intention 4) protection circuit:In extreme circumstances:Unloaded or load R1It is smaller, so that system power is unlikely to excessive,
To protect circuit;
Step 2:Model hypothesis:Circuit model after establishing matching, and simplify, determine the constant of model, variable and to true
Determine parameter, carries out symbol definition;
Converter circuitry model after LC matching, L is matching inductance, C2For matching capacitance, C0Transducer static capacitor, R1
For energy converter load resistance, C1Energy converter dynamic capacity, L1For energy converter dynamic inductance, VinFor driving voltage, Vo is energy converter
The voltage at both ends, wherein C0For constant, driving voltage VinCorresponding angular frequencys2Frequency fs2, R1、C1、L1It is with load and ring
The variable of border variation, energy converter correspond to angular frequencysSeries resonance frequency fsBy C1、L1It determines,Work as fs2
=fsWhen, C1、L1Resonance is ignored, L, C2For parameter to be determined, then enable C=C1+C2, C C1And C2The sum of, dependent variable has
Power factor η, apparent energy S, active-power P, then system model is defined as:
(η, S, P)=f (Vin,L,C,R1,fs)
(y1,y2,y3...)=f (x1,x2,x3...) indicate by x1,x2,x3... arrive y1,y2,y3... mapping relations;
Step 3:Model is constituted:It determines the constraint relationship between each constant, variable, and simplifies, according to original design intention, choosing
Mode input amount, output quantity are selected, according to the constraint relationship, derives the functional relation between input quantity, output quantity;
System complex impedance Z (w at this times) be:
Circuit to be made is pure configuration, i.e. imaginary part is equal to 0, in driving angular frequencys2=ωs, R1=R0Shi Jinhang matching, then
The relationship of matching inductance L and C is:
In addition, matching inductance L, matching capacitance C2Addition, new resonance frequency f is added to system0, i.e. L and C's is humorous
Vibration frequency f0:
L, C value is worked as f by formula (2), formula (3) constraint0When determining, L, C are uniquely determined, and are enabled:
Then ρ and R0When determining, the value of L, C are also uniquely determined, and system model is at this time:
(η, S, P)=f (Vin,ρ,R0, R1,fs)
It is obtained by formula (3), formula (4):
Substitution formula (2) obtains:
By the nodal method of analysis:It obtains:
The then active power that energy converter obtainsAnd R1Functional relation be:
Step 4:Model solution:The functional relation of above-mentioned establishment is solved, using the zero of function, pole etc. as feature
Point, selective analysis choose the best value of parameter to be determined, obtain a kind of matching way of optimization according to original design intention;
The functional relation established by formula (7), in R1>In the range of 0, function has and only one pole, is maximum
Point, is easy to get and works asWhen, active powerObtain maximum value
According to original design intention 1), original intention 2) when output power is very big, power factor should be 1, therefore, enables R1max=R0,
I.e.It solves:
TakeBest value as ρ;Formula (8) substitution formula (6) is obtained:
Formula (9) is the preliminary optimization value of undetermined parameter;
Step 5:Model analysis:The matching way that step 4 is optimized substitutes into system model, analyzes its dependent variable to model
It influences, analyzes the advantage and disadvantage of the matching way of above-mentioned optimization, further determine that the reasonability of above-mentioned value;
Step 6:Model testing:The match circuit of ultrasonic transducer, detection matching are built by the matching way of above-mentioned optimization
The frequency of ultrasonic transducer and load response characteristic afterwards;Above-mentioned emulation sufficiently simulates actual state, demonstrates above-mentioned excellent
The feasibility and good characteristic of the matching way of change;
Step 7:Model application:According to above-mentioned analysis, the application field of the matching way of above-mentioned optimization is analyzed, and provides phase
Answer device selection, frequency-tracking when suggestion and strategy.
Step 5 specifically, driving frequency fs2Equal to energy converter series resonance frequency fs, as load resistance R1Fluctuation, R1For allusion quotation
Offset R0When, the active power of system is very big, and power factor be 1, meet original design intention 1) and original design intention 2), below it is right
System performance at this time is further analyzed:
Formula (9) are substituted into formula (1), are obtained:
The then impedance of system | Z (jws) | it is:
It is obtained by formula (11), as load resistance R1When variation, the impedance of system | Z (jws) | it remains unchanged, perseverance is
Then the apparent energy S of system is:
It is obtained by formula (12), the apparent energy S (ω of the system after optimizing values) remain unchanged, it is a constant;
Further, if R1Fluctuation, by formula (10), the power factor η for obtaining system is:
The active power of systemFor:
IfIt is fluctuated in the range of [0.63,1.6], substitutes into formula (13), formula (14) obtains, power factor η and wattful power
RateFluctuation range be [0.9,1];
In conclusion when takingOptimization value as LC match circuit;
Consider fs1、fs2Influence, enableIt is same to enable
Firstly, enabling ρ2=1, i.e. analysis ρ1Influence to system, system model at this time are:
(η, S, P)=f (Vin,R0,ρ1,ρ3)
By formula (9), actual match parameter is:
At this point, the complex impedance of system is:
If Vin=200V, R0=200 Ω draw active power and ρ according to formula (13), formula (14), formula (15)1、ρ3Between
Function curve P=f (ρ1、ρ3) and power factor η and ρ1、ρ3Between function curve η=f (ρ1、ρ3);
Further, ρ is enabled1=1, analyze frequency tracking error ρ2Influence to system, frequency tracking error ρ2To system
Influence direct and energy converter quality factor qmIt is related, it is necessary to take into account, QmBigger bandwidth is smaller, gets over to frequency tracking error
It is sensitive.System model at this time is:
(η, S, P)=f (Vin,R0,ρ2,ρ3, Qm)
Energy converter quality factor qmFor:
The series resonance angular frequency of energy converter is:
Joint type (17), formula (16):
Complex impedance Z (jw at this times2) be:
If Vin=200V, R0=200 Ω, Qm=50, according to formula (13), formula (14), formula (18) draws active power and ρ2、
ρ3Between function curve P=f (ρ2、ρ3) and power factor and ρ2、ρ3Between function curve n=f (ρ2、ρ3)。
Should be a little higher than series resonance frequency of driving frequency in frequency-tracking, if carry out frequency sweep, need from high frequency to
Low frequency carries out, to avoid high-power point.
The features of the present invention and beneficial effect are:
1) present invention establishes the ultrasound transducer system mathematical model after LC matching, quantifies to each parameter in system
Analysis, realizes comprehensive, the accurate analysis and assessment to the matched transducer system of LC.
2) one embodiment of the present of invention, the angle new from one, with matching inductance L2, matching capacitance C2The resonance of introducing
Frequency f0With energy converter series resonance frequency fsThe ratio between ρ analyzed as input quantity, simplify system model, can it is more succinct,
Intuitively obtain influence of the different LC values to system.
3) one embodiment of the present of invention proposes a kind of LC matching way of optimization, has the following advantages that:A) phase is used
To simple LC matching network, do not increase adjustable element, reduces system cost, volume and design difficulty;B) it is typically bearing
Under load, the output power of energy converter is very big, and power factor is 1, when being supported on the fluctuation of biggish range (0.6~1.5 times),
It is still able to maintain biggish output power (more than 0.9 times of rated power), and power factor is improved in higher range (0.9 or more)
The stability and robustness of ultrasonic system;C) the LC matching way of a kind of optimization, when the load, total view of system is in function
Rate remains unchanged, even if in load resistance R1Under minimum extreme case, still ensure that the apparent energy of system is constant, thus
It solves ultrasonic technique field " system is burnt in zero load " this technical problem, improves the safety of system.
4) present invention has done further analysis of uncertainty to the circuit after above-mentioned optimization LC matching, proposes corresponding
Suggestion and strategy when device selection, frequency-tracking, can further improve system performance;
Specific embodiment
To achieve the goals above, the technical solution adopted by the present invention is that, a kind of LC matching of piezoelectric ultrasonic transducer is built
Mould method and a kind of matching way of optimization, include the following steps:
1) model preparation:Specify the original design intention of LC match circuit, the i.e. purpose of Match circuits, it is desirable to the function of realization
The effect that can and reach;
2) model hypothesis:Circuit model after establishing matching, and simplify, determine the constant, variable and ginseng to be determined of model
Number carries out symbol definition;
3) model is constituted:It determines the constraint relationship between each constant, variable, and simplifies, according to original design intention, select mould
Type input quantity, output quantity derive the functional relation between input quantity, output quantity according to the constraint relationship;
4) model solution:The functional relation of above-mentioned establishment is solved, using the zero of function, pole etc. as characteristic point,
Selective analysis chooses the best value of parameter to be determined, obtains a kind of matching way of optimization according to original design intention;
5) model analysis:The matching way of above-mentioned optimization is substituted into system model, analyzes influence of its dependent variable to model,
The advantage and disadvantage for analyzing the matching way of above-mentioned optimization further determine that the reasonability of above-mentioned value;
6) model testing:The match circuit of ultrasonic transducer is built by the matching way of above-mentioned optimization, is surpassed after detection matching
The frequency and load response characteristic of sonic transducer;
7) model application:According to above-mentioned analysis, the application field of the matching way of above-mentioned optimization is analyzed, and is provided corresponding
Suggestion and strategy when device selection, frequency-tracking;
Specific implementation process is as follows:
Step 1:Model preparation:Specify the original design intention of LC match circuit, the i.e. purpose of Match circuits, it is desirable to realize
Function and the effect that reaches;The matched main purpose of LC is tuning, while original design intention should include the stability of realization system
And safety, comprehensively consider, determines that the original intention of LC matched design is the following aspects:
Original intention 1) power factor:It is tuned in Several Typical Load resistance value, makes system at purely resistive, power factor 1;
Original intention 2) power is larger:In the work of series resonance point, system output power, that is, active power is maximum or larger;
Original intention 3) power stability:System is set more to adapt to load resistance R1Variation, in R1Effective power fluctuation is small when fluctuation,
And maintain higher level;
Original intention 4) protection circuit:(unloaded or load R in extreme circumstances1It is smaller), so that system power is unlikely to excessive,
To protect circuit;
Step 2:Model hypothesis:Circuit model after establishing matching, and simplify, determine the constant of model, variable and to true
Determine parameter, carries out symbol definition;
Converter circuitry model after LC matching is as shown in Figure 2 a, and L is matching inductance, C2For matching capacitance, C0Energy converter is quiet
State capacitor, R1For energy converter load resistance, C1Energy converter dynamic capacity, L1For energy converter dynamic inductance, VinFor driving voltage, Vo
For the voltage at energy converter both ends.Wherein C0For constant, driving voltage VinFrequency fs2(corresponding angular frequencys2), R1、C1、L1It is
With the variable of load and environmental change, the series resonance frequency f of energy converters(corresponding angular frequencys) by C1、L1It determines,Work as fs2=fsWhen, C1、L1Resonance can be ignored, and circuit model is as shown in Figure 2 b at this time, L, C2For
Parameter to be determined, then enable C=C1+C2, simplified circuit model is as shown in Figure 2 c, C C1And C2The sum of.System because become
Power factor η, apparent energy S, active-power P etc. are measured, then system model can be defined as:
(η, S, P)=f (Vin,L,C,R1,fs)
(y1,y2,y3...)=f (x1,x2,x3...) indicate by x1,x2,x3... arrive y1,y2,y3... mapping relations.
Step 3:Model is constituted:It determines the constraint relationship between each constant, variable, and simplifies, according to original design intention, choosing
Mode input amount, output quantity are selected, according to the constraint relationship, derives the functional relation between input quantity, output quantity;
In figure 2 c, system complex impedance Z (w at this times) be:
Circuit to be made is pure configuration, i.e. imaginary part is equal to 0, in driving angular frequencys2=ωs, R1=R0Shi Jinhang matching, then
The relationship of matching inductance L and C is:
In addition, matching inductance L, matching capacitance C2Addition, new resonance frequency f is added to system0, i.e. L and C's is humorous
Vibration frequency f0:
L, C value is worked as f by formula (2), formula (3) constraint0When determining, L, C are uniquely determined, and are enabled:
Then ρ and R0When determining, the value of L, C are also uniquely determined, and system model is at this time:
(η, S, P)=f (Vin,ρ,R0, R1,fs)
It is obtained by formula (3), formula (4):
Substitution formula (2) obtains:
By the nodal method of analysis:It obtains:
The then active power that energy converter obtainsAnd R1Functional relation be:
Step 4:Model solution:The functional relation of above-mentioned establishment is solved, using the zero of function, pole etc. as feature
Point, selective analysis choose the best value of parameter to be determined, obtain a kind of matching way of optimization according to original design intention;
The functional relation established by formula (7), in R1>In the range of 0, function has and only one pole, is maximum
Point, is easy to get and works asWhen, active powerObtain maximum value
According to original design intention 1), original intention 2) when output power is very big, power factor should be 1, therefore, enables R1max=R0,
I.e.It solves:
TakeBest value as ρ.
Formula (8) substitution formula (6) is obtained:
Formula (9) is the preliminary optimization value of undetermined parameter.
Step 5:Model analysis:The matching way of above-mentioned optimization is substituted into system model, analyzes its dependent variable to model
It influences, analyzes the advantage and disadvantage of the matching way of above-mentioned optimization, further determine that the reasonability of above-mentioned value;
If driving frequency fs2Equal to energy converter series resonance frequency fs, as load resistance R1Fluctuation, R1For representative value R0When,
The active power of system is very big, and power factor be 1, meet original design intention 1) and original design intention 2), below at this time be
System performance is further analyzed.
Formula (9) are substituted into formula (1), are obtained:
The then impedance of system | Z (jws) | it is:
It is obtained by formula (11), as load resistance R1When variation, the impedance of system | Z (jws) | it remains unchanged, perseverance is
Then the apparent energy S of system is:
It is obtained by formula (12), the apparent energy S (ω of the system after optimizing values) remain unchanged, it is a constant, explanation
In load resistance R1When variation, the size of current of major loop is remained unchanged, even if under the extreme cases such as zero load, it will not be because of mistake
It flows and burns circuit, to ensure that the safety of system, realize original intention 4).
Further, if R1Fluctuation, by formula (10), the power factor η for obtaining system is:
The active power of systemFor:
IfIt is fluctuated in the range of [0.63,1.6], substitutes into formula (13), formula (14) obtains, power factor η and wattful power
RateFluctuation range be [0.9,1], i.e. load resistance R1In larger range variation, system active power and power because
Number fluctuation is smaller, and keeps higher level, realizes original design intention 3.
In conclusion when takingOptimization value as LC match circuit
When, system can satisfy every original design intention in step 1.
As described above, working asSystem after matching has every excellent performance, but this premise is:1) selected when matching
Frequency fs1The as series resonance frequency f of energy converters;2) the driving frequency f of energy converters2Equal to the series resonance frequency of energy converter
fs.But in fact, above-mentioned two premise cannot achieve, because of the series resonance frequency f of rate energy convertersIt can change at any time,
And the frequency-tracking of energy converter certainly exists certain error.
Consider fs1、fs2Influence, enableIt is same to enable
Firstly, enabling ρ2=1, i.e. analysis ρ1Influence to system, system model at this time are:
(η, S, P)=f (Vin,R0,ρ1,ρ3)
By formula (9), actual match parameter is:
At this point, the complex impedance of system is:
If Vin=200V, R0=200 Ω draw active power and ρ according to formula (13), formula (14), formula (15)1、ρ3Between
Function curve P=f (ρ1、ρ3) and power factor η and ρ1、ρ3Between function curve η=f (ρ1、ρ3), respectively such as Fig. 3 a and
Shown in Fig. 3 b.By Fig. 3 a and Fig. 3 b as it can be seen that when the error of matching frequency presence ± 5%, i.e. ρ1∈ [0.95,1.05], in ρ1∈
When [0.7,1.5], the power factor of system is maintained at 0.9 or more, is in higher level, it is seen then that (the ρ when frequency-tracking is accurate2
=1), the error (ρ of matching frequency1) smaller to systematic influence, system still keeps preferable stability.
Further, ρ is enabled1=1, analyze frequency tracking error (ρ2) influence to system, frequency tracking error (ρ2) to being
System influences direct and energy converter quality factor qmIt is related, it is necessary to take into account, QmBigger bandwidth is smaller, misses to frequency-tracking
Difference is more sensitive.System model at this time is:
(η, S, P)=f (Vin,R0,ρ2,ρ3, Qm)
The tracking of energy converter series resonance frequency is always the hot and difficult issue of ultrasound field, and numerous scholars propose locking phase
The frequency-trackings modes such as method, maximum current method, be continuously improved ultrasonic transducer frequency-tracking precision, but due to energy converter quality because
Number QmIt is larger, there are precipitous mechanical admittance curves, tremendous influence can be caused to system lesser frequency departure, therefore divide
Analyse frequency tracking error (ρ2) influence to system is very necessary.Energy converter quality factor qmFor:
The series resonance angular frequency of energy converter is:
Joint type (17), formula (16):
Complex impedance Z (jw at this times2) be:
If Vin=200V, R0=200 Ω, Qm=50, according to formula (13), formula (14), formula (18) draws active power and ρ2、
ρ3Between function curve P=f (ρ2、ρ3) and power factor and ρ2、ρ3Between function curve n=f (ρ2、ρ3), respectively such as
Shown in Fig. 4 a and Fig. 4 b.Ideally, at series resonance frequency, obtain maximum power is energy converterBy scheming
4a is as it can be seen that when frequency-tracking is there are when error, and energy converter obtains active power, and there are larger fluctuations, in ρ3=0.5, ρ2=0.98
Place, or even there is the active power of up to 1400w, it is extremely dangerous.Under comparing, in ρ3>1 and ρ2>In the range of 1, power
Variation is steady, and no high-power point of crossing occurs.From fig. 4b, it can be seen that working as Qm=50, in load resistance R1When fluctuation, to keep 0.9 with
On power factor, frequency tracking error will be within ± 0.5%, within even ± 0.3%, and the energy converter of corresponding 40k allows
Frequency tracking error be ± 120hz, the frequency tracking error that the energy converter of higher quality factor allows can be smaller.
Step 6:Model testing:The match circuit of ultrasonic transducer, detection matching are built by the matching way of above-mentioned optimization
The frequency of ultrasonic transducer and load response characteristic afterwards;Above-mentioned emulation sufficiently simulates actual state, demonstrates above-mentioned excellent
The feasibility and good characteristic of the matching way of change;
Step 7:Model application:According to above-mentioned analysis, the application field of the matching way of above-mentioned optimization is analyzed, and provides phase
Answer device selection, frequency-tracking when suggestion and strategy;The LC matching way of energy converter optimization proposed in this paper, circuit letter
Clean, calculation method is simple, does not increase adjustable element, while improving system output power, avoids because of dynamic electric resistor R1Variation
Bring is detuning and power flash-up, has many advantages, such as high security, high power stability, High Power Factor, is widely used in surpassing
The fields such as sound processing, ultrasonic cleaning, ultrasonic welding.Fig. 4 shows that the precision of frequency-tracking directly influences the performance of system, and
Due to various reasons, frequency-tracking precision can not further increase, therefore should select the lesser ultrasound of broader bandwidth, quality factor
Energy converter, to reduce influence of the frequency tracking error to system.In addition, Fig. 4 is shown, driving frequency is larger and smaller than practical series connection
When resonance frequency, the influence to system is different, works as ρ2<When 1, power swing is larger, or even occurs being up to the power of 1400w, right
System causes larger threat, and in ρ2>In the range of 1, changed power is steady, it is no cross high-power point occur, therefore frequency with
It should be a little higher than series resonance frequency of driving frequency when track, if carrying out frequency sweep, need to carry out from high frequency to low frequency, to avoid
High-power point.
The present invention is described in detail with reference to the accompanying drawings and detailed description.
A kind of LC matching modeling method flow chart of piezoelectric ultrasonic transducer as shown in Figure 1, modeling analysis process according to this
Flow chart executes, and one embodiment of the present of invention process is as follows:
Step 1:Model preparation:Specify the original design intention of LC match circuit, the i.e. purpose of Match circuits, it is desirable to realize
Function and the effect that reaches;The matched main purpose of LC is tuning, while original design intention should include the stability of realization system
And safety, comprehensively consider, determines that the original intention of LC matched design is the following aspects:
Original intention 1) power factor:It is tuned in Several Typical Load resistance value, makes system at purely resistive, power factor 1;
Original intention 2) power is larger:In the work of series resonance point, system output power, that is, active power is maximum or larger;
Original intention 3) power stability:System is set more to adapt to load resistance R1Variation, in R1Effective power fluctuation is small when fluctuation,
And maintain higher level;
Original intention 4) protection circuit:(unloaded or load R in extreme circumstances1It is smaller), so that system power is unlikely to excessive,
To protect circuit;
Step 2:Model hypothesis:Circuit model after establishing matching, and simplify, determine the constant of model, variable and to true
Determine parameter, carries out symbol definition;
Converter circuitry model after LC matching is as shown in Figure 2 a, and L is matching inductance, C2For matching capacitance, C0Energy converter is quiet
State capacitor, R1For energy converter load resistance, C1Energy converter dynamic capacity, L1For energy converter dynamic inductance, VinFor driving voltage, Vo
For the voltage at energy converter both ends.Wherein C0For constant, driving voltage VinFrequency fs2(corresponding angular frequencys2), R1、C1、L1It is
With the variable of load and environmental change, the series resonance frequency f of energy converters(corresponding angular frequencys) by C1、L1It determines,Work as fs2=fsWhen, C1、L1Resonance can be ignored, and circuit model is as shown in Figure 2 b at this time, L, C2For to
Determining parameter, then enable C=C1+C2, simplified circuit model is as shown in Figure 2 c, C C1And C2The sum of.The dependent variable of system
Power factor η, apparent energy S, active-power P etc., then system model can be defined as:
(η, S, P)=f (Vin,L,C,R1,fs)
(y1,y2,y3...)=f (x1,x2,x3...) indicate by x1,x2,x3... arrive y1,y2,y3... mapping relations.
Step 3:Model is constituted:It determines the constraint relationship between each constant, variable, and simplifies, according to original design intention, choosing
Mode input amount, output quantity are selected, according to the constraint relationship, derives the functional relation between input quantity, output quantity;
In figure 2 c, system complex impedance Z (w at this times) be:
Circuit to be made is pure configuration, i.e. imaginary part is equal to 0, in driving angular frequencys2=ωs, R1=R0Shi Jinhang matching, then
The relationship of matching inductance L and C is:
In addition, matching inductance L, matching capacitance C2Addition, new resonance frequency f is added to system0, i.e. L and C's is humorous
Vibration frequency f0:
L, C value is worked as f by formula (2), formula (3) constraint0When determining, L, C are uniquely determined, and are enabled:
Then ρ and R0When determining, the value of L, C are also uniquely determined, and system model is at this time:
(η, S, P)=f (Vin,ρ,R0, R1,fs)
It is obtained by formula (3), formula (4):
Substitution formula (2) obtains:
By the nodal method of analysis:It obtains:
The then active power that energy converter obtainsAnd R1Functional relation be:
Step 4:Model solution:The functional relation of above-mentioned establishment is solved, using the zero of function, pole etc. as feature
Point, selective analysis choose the best value of parameter to be determined, obtain a kind of matching way of optimization according to original design intention;
The functional relation established by formula (7), in R1>In the range of 0, function has and only one pole, is maximum
Point, is easy to get and works asWhen, active powerObtain maximum value
According to original design intention 1), original intention 2) when output power is very big, power factor should be 1, therefore, enables R1max=R0,
I.e.It solves:
TakeBest value as ρ.
Formula (8) substitution formula (6) is obtained:
Formula (9) is the preliminary optimization value of undetermined parameter.
Step 5:Model analysis:The matching way of above-mentioned optimization is substituted into system model, analyzes its dependent variable to model
It influences, analyzes the advantage and disadvantage of the matching way of above-mentioned optimization, further determine that the reasonability of above-mentioned value;
If driving frequency fs2Equal to energy converter series resonance frequency fs, as load resistance R1Fluctuation, R1For representative value R0When,
The active power of system is very big, and power factor be 1, meet original design intention 1) and original design intention 2), below at this time be
System performance is further analyzed.
Formula (9) are substituted into formula (1), are obtained:
The then impedance of system | Z (jws) | it is:
It is obtained by formula (11), as load resistance R1When variation, the impedance of system | Z (jws) | it remains unchanged, perseverance is
Then the apparent energy S of system is:
It is obtained by formula (12), the apparent energy S (ω of the system after optimizing values) remain unchanged, it is a constant, explanation
In load resistance R1When variation, the size of current of major loop is remained unchanged, even if under the extreme cases such as zero load, it will not be because of mistake
It flows and burns circuit, to ensure that the safety of system, realize original intention 4).
Further, if R1Fluctuation, by formula (10), the power factor η for obtaining system is:
The active power of systemFor:
IfIt is fluctuated in the range of [0.63,1.6], substitutes into formula (13), formula (14) obtains, power factor η and wattful power
RateFluctuation range be [0.9,1], i.e. load resistance R1In larger range variation, system active power and power because
Number fluctuation is smaller, and keeps higher level, realizes original design intention 3.
In conclusion when takingOptimization value as LC match circuit
When, system can satisfy every original design intention in step 1.
As described above, working asSystem after matching has every excellent performance, but this premise is:1) selected when matching
Frequency fs1The as series resonance frequency f of energy converters;2) the driving frequency f of energy converters2Equal to the series resonance frequency of energy converter
fs.But in fact, above-mentioned two premise cannot achieve, because of the series resonance frequency f of rate energy convertersIt can change at any time,
And the frequency-tracking of energy converter certainly exists certain error.
Consider fs1、fs2Influence, enableIt is same to enable
Firstly, enabling ρ2=1, i.e. analysis ρ1Influence to system, system model at this time are:
(η, S, P)=f (Vin,R0,ρ1,ρ3)
By formula (9), actual match parameter is:
At this point, the complex impedance of system is:
If Vin=200V, R0=200 Ω draw active power and ρ according to formula (13), formula (14), formula (15)1、ρ3Between
Function curve P=f (ρ1、ρ3) and power factor η and ρ1、ρ3Between function curve η=f (ρ1、ρ3), respectively such as Fig. 3 a and
Shown in Fig. 3 b.By Fig. 3 a and Fig. 3 b as it can be seen that when the error of matching frequency presence ± 5%, i.e. ρ1∈ [0.95,1.05], in ρ1∈
When [0.7,1.5], the power factor of system is maintained at 0.9 or more, is in higher level, it is seen then that (the ρ when frequency-tracking is accurate2
=1), the error (ρ of matching frequency1) smaller to systematic influence, system still keeps preferable stability.
Further, ρ is enabled1=1, analyze frequency tracking error (ρ2) influence to system, frequency tracking error (ρ2) to being
System influences direct and energy converter quality factor qmIt is related, it is necessary to take into account, QmBigger bandwidth is smaller, misses to frequency-tracking
Difference is more sensitive.System model at this time is:
(η, S, P)=f (Vin,R0,ρ2,ρ3, Qm)
The tracking of energy converter series resonance frequency is always the hot and difficult issue of ultrasound field, and numerous scholars propose locking phase
The frequency-trackings modes such as method, maximum current method, be continuously improved ultrasonic transducer frequency-tracking precision, but due to energy converter quality because
Number QmIt is larger, there are precipitous mechanical admittance curves, tremendous influence can be caused to system lesser frequency departure, therefore divide
Analyse frequency tracking error (ρ2) influence to system is very necessary.Energy converter quality factor qmFor:
The series resonance angular frequency of energy converter is:
Joint type (17), formula (16):
Complex impedance Z (jw at this times2) be:
If Vin=200V, R0=200 Ω, Qm=50, according to formula (13), formula (14), formula (18) draws active power and ρ2、
ρ3Between function curve P=f (ρ2、ρ3) and power factor and ρ2、ρ3Between function curve n=f (ρ2、ρ3), respectively such as
Shown in Fig. 4 a and Fig. 4 b.Ideally, at series resonance frequency, obtain maximum power is energy converterBy scheming
4a is as it can be seen that when frequency-tracking is there are when error, and energy converter obtains active power, and there are larger fluctuations, in ρ3=0.5, ρ2=0.98
Place, or even there is the active power of up to 1400w, it is extremely dangerous.Under comparing, in ρ3>1 and ρ2>In the range of 1, power
Variation is steady, and no high-power point of crossing occurs.From fig. 4b, it can be seen that working as Qm=50, in load resistance R1When fluctuation, to keep 0.9 with
On power factor, frequency tracking error will be within ± 0.5%, within even ± 0.3%, and the energy converter of corresponding 40k allows
Frequency tracking error be ± 120hz, the frequency tracking error that the energy converter of higher quality factor allows can be smaller.
Step 6:Model testing:The match circuit of ultrasonic transducer, detection matching are built by the matching way of above-mentioned optimization
The frequency of ultrasonic transducer and load response characteristic afterwards;Above-mentioned emulation sufficiently simulates actual state, demonstrates above-mentioned excellent
The feasibility and good characteristic of the matching way of change;
Step 7:Model application:According to above-mentioned analysis, the application field of the matching way of above-mentioned optimization is analyzed, and provides phase
Answer device selection, frequency-tracking when suggestion and strategy;The LC matching way of energy converter optimization proposed in this paper, circuit letter
Clean, calculation method is simple, does not increase adjustable element, while improving system output power, avoids because of dynamic electric resistor R1Variation
Bring is detuning and power flash-up, has many advantages, such as high security, high power stability, High Power Factor, is widely used in surpassing
The fields such as sound processing, ultrasonic cleaning, ultrasonic welding.Fig. 4 shows that the precision of frequency-tracking directly influences the performance of system, and
Due to various reasons, frequency-tracking precision can not further increase, therefore should select the lesser ultrasound of broader bandwidth, quality factor
Energy converter, to reduce influence of the frequency tracking error to system.In addition, Fig. 4 is shown, driving frequency is larger and smaller than practical series connection
When resonance frequency, the influence to system is different, works as ρ2<When 1, power swing is larger, or even occurs being up to the power of 1400w, right
System causes larger threat, and in ρ2>In the range of 1, changed power is steady, it is no cross high-power point occur, therefore frequency with
It should be a little higher than series resonance frequency of driving frequency when track, if carrying out frequency sweep, need to carry out from high frequency to low frequency, to avoid
High-power point.