CN117674749A - Power amplifier with matching network and matching network parameter design method thereof - Google Patents
Power amplifier with matching network and matching network parameter design method thereof Download PDFInfo
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- CN117674749A CN117674749A CN202311511277.6A CN202311511277A CN117674749A CN 117674749 A CN117674749 A CN 117674749A CN 202311511277 A CN202311511277 A CN 202311511277A CN 117674749 A CN117674749 A CN 117674749A
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Abstract
The invention discloses a power amplifier with a matching network and a matching network parameter design method thereof, wherein the power amplifier comprises the following components: a direct current bus power supply for supplying power to the power amplifier main circuit; the auxiliary power supply is used for supplying power to the control circuit and the chips in the driving circuit; the control circuit modulates the switching frequency triangular wave with the frequency exceeding a first preset threshold value into a pulse width modulation signal; the driving circuit outputs a corresponding driving signal according to the pulse width modulation signal to drive a switching tube in the power amplifier main circuit; the power amplifier main circuit drives the switching tube to be turned on and off based on the driving signal, and outputs square wave voltage waveforms with the amplitude of direct current bus voltage, the frequency of switching frequency and the duty ratio of change; a filter circuit outputting a voltage waveform of a required bandwidth; a transformer outputting a voltage of a voltage class required by a load; and the matching network is used for carrying out impedance matching with the load, so that the load has pure resistance to the power amplifier in the whole working frequency band.
Description
Technical Field
The invention relates to the technical field of power amplifiers, in particular to a power amplifier with a matching network and a matching network parameter design method thereof.
Background
The piezoelectric transducer is an underwater acoustic load which can generate sound by vibrating the ceramic plate through high voltage, and has wide application in detection and other aspects. Because the transducer is a capacitive load to the power amplifier and its voltage emission response and impedance characteristics vary with frequency, in a high-power acoustic radiation system, there is often a problem that the output voltage of the power amplifier is insufficient due to the load impedance characteristics, resulting in insufficient sound source level or difficult control of the output spectrum type of the overall acoustic radiation system. For this problem, a method of impedance matching a load by connecting an inductance in series or in parallel between a power amplifier and the load is generally employed. By introducing the matching inductance, the load can be made to be purely resistive to the power amplifier at the resonance frequency point of the inductance, so that the voltage of the power amplifier at the resonance frequency point is improved. However, the method is effective only in the resonance frequency point and the nearby narrow bandwidth, and in the application scene with wider working frequency band, the impedance characteristic of the load changes more widely, and the method has difficulty in ensuring better matching effect in the whole broadband.
Disclosure of Invention
In view of the above, the invention provides a power amplifier with a matching network and a matching network parameter design method thereof, which can solve the technical problem of matching of capacitive loads in a high-power acoustic radiation system.
The present invention is so implemented as to solve the above-mentioned technical problems.
A power amplifier including a matching network, the power amplifier comprising:
the direct current bus power supply is used for rectifying and converting alternating current commercial power, outputting direct current bus voltage and supplying power for the power amplifier main circuit;
the auxiliary power supply is used for converting alternating current commercial power into various voltages and supplying power for chips in the control circuit and the driving circuit;
the control circuit is used for modulating a switching frequency triangular wave with the frequency exceeding a first preset threshold value into a pulse width modulation signal compared with the frequency range of the control signal after filtering the control signal input from the outside;
the driving circuit is used for outputting corresponding driving signals according to the pulse width modulation signals and driving switching tubes in the power amplifier main circuit;
the power amplifier main circuit drives the switching tube to be turned on and off based on the driving signal, and outputs square wave voltage waveforms with the amplitude of direct current bus voltage, the frequency of switching frequency and the duty ratio of change;
the filter circuit is used for filtering harmonic waves of the switching frequency based on LC low-pass filtering and outputting voltage waveforms with required bandwidth;
the transformer boosts the output voltage of the power amplifier main circuit after being filtered by the filter circuit and outputs the voltage of the voltage class required by the load;
and the matching network is used for matching the impedance with the load through an LC series-parallel circuit according to the voltage emission response and the impedance characteristic of the load, so that the load has pure resistance to the power amplifier in the whole working frequency band.
Preferably, the control circuit has working condition acquisition and protection functions, can acquire busbar voltage and busbar current output by a direct current busbar power supply in real time, and uploads acquired data to an upper computer through a communication interface; and when the bus voltage and the bus current exceed rated values, the control circuit triggers protection to close the output of the bus voltage and the bus current.
Preferably, the direct current bus power supply is connected with the input terminal of the power amplifier main circuit through the output terminal.
Preferably, the auxiliary power supply is connected with the control circuit and the power input terminal of the driving circuit through the contact pin, the control circuit is connected with the input terminal of the driving circuit through the output terminal, the output contact pin of the driving circuit is connected with the driving signal contact pin of the power amplifier main circuit, the output terminal of the power amplifier main circuit is connected with the input terminal of the filter circuit, the output terminal of the filter circuit is connected with the primary side input terminal of the transformer, the secondary side output terminal of the transformer is connected with the input terminal of the matching network, and the output terminal of the matching network is connected with the load terminal.
Preferably, the voltage of the auxiliary power supply conversion includes + -15V, 12V, + -5V voltages.
The invention provides a matching network parameter design method of a power amplifier with a matching network, which is based on the power amplifier with the matching network, and comprises the following steps:
step S21: determining the number N of resonant frequency points of the matching network based on the working bandwidth and the size of the power amplifier;
step S22: based on the number N of resonant frequency points, determining a circuit structure of an LC series-parallel circuit capable of performing impedance matching with a load;
step S23: determining a position of a resonance frequency point for each of the N resonance frequency points based on a voltage emission response and an impedance characteristic of the load;
step S24: based on the number and the positions of the resonance frequency points, in the LC series-parallel circuit, the number of the capacitors is determined according to the number of the resonance frequency points, and the inductance is determined by taking the maximum difference of the capacitance values of the capacitors as the constraintWherein Ln is the matching inductance corresponding to the Nth resonance frequency point, cn is the matching capacitance corresponding to the Nth resonance frequency point, and fn is the Nth resonance frequency point.
Preferably, the number N of resonant frequency points is determined by combining the matching effect of the matching network and the overall volume weight of the power amplifier.
Preferably, the step S22 is configured to determine a circuit configuration of the LC series-parallel circuit capable of impedance matching with the load based on the number N of resonant frequency points, and includes: the number N of resonant frequency points corresponds to N stages of LC resonant circuits, and each stage is composed of a resonant inductor L n And a resonance capacitor C n Each stage of staggered series-parallel connection is formed, namely, the inductance of one stage is connected in series with the capacitance of the other stage in parallel, and the inductance of the next stage is connected in series with the inductance of the other stage in parallel; wherein, the load is a first-stage capacitor when the load is capacitive, and is a first-stage inductor when the load is inductive.
The invention has the beneficial technical effects that:
(1) Compared with the prior art, the invention can be applied to wider working frequency band and application scenes with larger impedance change range.
(2) The invention can have better matching effect in the whole working frequency band.
(3) For wider working frequency bands, the invention can design more resonance frequency points by introducing more inductance and capacitance to realize better matching effect.
Drawings
FIG. 1 is a schematic diagram of a power amplifier according to the present invention;
FIG. 2 is a schematic diagram of a matching network structure;
FIG. 3 is a schematic diagram of the equivalent structure of a high frequency end matching network;
fig. 4 is a schematic diagram of an equivalent structure of a low-frequency end matching network.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and examples.
As shown in fig. 1, the present invention proposes a power amplifier including a matching network, the power amplifier including: the power amplifier comprises a direct current bus power supply, an auxiliary power supply, a control circuit, a driving circuit, a power amplifier main circuit, a filter circuit, a transformer and a matching network.
The direct current bus power supply is used for rectifying and converting alternating current commercial power, outputting direct current bus voltage and supplying power to the power amplifier main circuit.
The auxiliary power supply is used for converting alternating current commercial power into various voltages and supplying power for chips in the control circuit and the driving circuit.
After the control circuit carries out filtering processing on a control signal input from the outside, the switching frequency triangular wave with the frequency exceeding a first preset threshold value is modulated into a pulse width modulation signal compared with the frequency range of the control signal.
The driving circuit is used for outputting corresponding driving signals according to the pulse width modulation signals and driving switching tubes in the power amplifier main circuit.
The power amplifier main circuit drives the switching tube to be turned on and off based on the driving signal, and outputs square wave voltage waveforms with the amplitude of direct current bus voltage, the frequency of switching frequency and the duty ratio of change.
The filter circuit filters harmonics of the switching frequency based on LC low pass filtering and outputs a voltage waveform of a required bandwidth.
The transformer boosts the output voltage of the power amplifier main circuit after being filtered by the filter circuit and outputs the voltage of the voltage class required by the load.
The matching network performs impedance matching with the load through the LC series-parallel circuit according to the voltage emission response and the impedance characteristic of the load, so that the load has pure resistance to the power amplifier in the whole working frequency band.
Further, the voltages of the auxiliary power supply conversion include + -15V, 12V, + -5V voltages.
Further, the control circuit has the working condition acquisition and protection functions, can acquire busbar voltage and busbar current output by a direct current busbar power supply in real time, and uploads acquired data to an upper computer through a communication interface; and when the bus voltage and the bus current exceed rated values, the control circuit triggers protection to close the output of the bus voltage and the bus current.
The connection relation among the components is as follows: the DC bus power supply is connected with the power amplifier main circuit input terminal through the output terminal, the auxiliary power supply is connected with the control circuit and the power input terminal of the driving circuit through the contact pin, the control circuit is connected with the driving circuit input terminal through the output terminal, the driving circuit output contact pin is connected with the power amplifier main circuit driving signal contact pin, the power amplifier main circuit output terminal is connected with the filter circuit input terminal, the filter circuit output terminal is connected with the primary side input terminal of the transformer, the secondary side output terminal of the transformer is connected with the matching network input terminal, and the matching network output terminal is connected with the load terminal.
The invention provides a specific embodiment of a power amplifier with a matching network.
A power amplifier comprising a matching network, comprising:
the power supply comprises a direct current bus power supply (1), an auxiliary power supply (2), a control circuit (3), a driving circuit (4), a power amplifier main circuit (5), a filter circuit (6), a transformer (7) and a matching network (8).
The direct current bus power supply (1) is used for rectifying and converting alternating current 220V/50Hz mains supply, outputting stable direct current bus voltage and supplying power to the power amplifier main circuit.
(2) The auxiliary power supply is used for converting alternating current 220V/50Hz commercial power into voltages of +/-15V, 12V, +/-5V and the like and supplying power to chips in the control circuit and the driving circuit.
(3) And the control circuit is used for filtering the control signal input from the outside and outputting a pulse width modulation signal through triangular wave modulation of a switching frequency with the frequency far higher than the frequency range of the signal.
(4) The driving circuit is used for outputting corresponding driving signals according to the pulse width modulation signals output by the control signals and driving the switching tube in the power amplifier main circuit.
(5) The power amplifier main circuit is used for driving the on-off of the switching tube through a driving signal and outputting square wave voltage waveforms with the amplitude of direct current bus voltage, the frequency of switching frequency and the change of duty ratio.
(6) And the filter circuit is used for filtering harmonic waves of the switching frequency through LC low-pass filtering and outputting voltage waveforms with required bandwidth.
(7) And the transformer is used for boosting the output voltage of the power amplifier main circuit after being filtered by the filter circuit and outputting the voltage of the voltage class required by the load.
(8) And the matching network is used for matching the impedance of the load through a reasonable LC series-parallel circuit according to the voltage emission response and the impedance characteristic of the load, so that the load has pure resistance to the power amplifier as much as possible in the whole working frequency band.
The specific working process of the power amplifier is as follows:
after 220V/50Hz alternating current is electrified, the direct current bus power supply converts the alternating current into stable direct current bus voltage output, and the auxiliary power supply converts the direct current bus voltage output into +/-15V, 12V, +/-5V and other voltage output to supply power for chips in the control circuit and the driving circuit. Before receiving an external control signal, the control circuit outputs a square wave control signal with the switching frequency and the duty ratio of 50%, the driving circuit drives a switching tube in the power amplifier main circuit to be switched on and off, and the power amplifier main circuit outputs the square wave voltage with the output amplitude of direct current bus voltage, the frequency of the square wave voltage being the switching frequency and the duty ratio of 50% after filtering by the filter circuit, and the output is basically zero. After the control circuit receives the control signal, the control circuit filters and modulates the signal and outputs a pulse width modulation signal with a variable duty ratio, a switching tube in the power amplification main circuit is driven to be switched on and off by the driving circuit, and the power amplification main circuit outputs square wave voltage with the amplitude of direct current bus voltage, the frequency of the square wave voltage being the switching frequency and the variable duty ratio. After the switching frequency is filtered by the filter circuit, the output waveform is the same as the control signal, the amplitude is the voltage waveform of the DC bus voltage, and the voltage waveform is output to the load after being boosted by the transformer and matched by the matching network.
As shown in fig. 2-4, the present invention provides a matching network parameter design method for a power amplifier including a matching network, the method is based on the power amplifier including the matching network as described above, and the matching network parameter design method includes:
step S21: determining the number N of resonant frequency points of the matching network based on the working bandwidth and the size of the power amplifier;
step S22: based on the number N of resonant frequency points, determining a circuit structure of an LC series-parallel circuit capable of performing impedance matching with a load;
step S23: determining a position of a resonance frequency point for each of the N resonance frequency points based on a voltage emission response and an impedance characteristic of the load;
step S24: based on the number and the positions of the resonance frequency points, in the LC series-parallel circuit, the number of the capacitors is determined according to the number of the resonance frequency points, and the inductance is determined by taking the maximum difference of the capacitance values of the capacitors as the constraintWherein L is n C is the matching inductance corresponding to the Nth resonance frequency point n Is the matching capacitance corresponding to the Nth resonance frequency point, f n Is the nth resonance frequency point.
Further, the number N of resonant frequency points is determined by combining the matching effect of the matching network and the overall volume weight of the power amplifier. The mode of determining the position of the resonance frequency point is as follows: selecting a point at which the load voltage emission response is below a first preset threshold; selecting a point at which the load impedance characteristic reactance is greater than a second preset threshold; the individual resonance frequency points are distributed evenly. The number of resonant frequency points is small, so that the matching effect is poor, and the number of resonant frequency points is large, so that the whole volume of the power amplifier with the required capacitance and inductance is large.
Further, the step S22 of determining a circuit structure of the LC series-parallel circuit capable of impedance matching with the load based on the number N of resonant frequency points includes: the number N of resonant frequency points corresponds to N stages of LC resonant circuits, and each stage is composed of a resonant inductor L n And a resonance capacitor C n Each stage of staggered series-parallel connection is formed, namely, the inductance of one stage is connected in series with the capacitance of the other stage in parallel, and the inductance of the next stage is connected in series with the inductance of the other stage in parallel; wherein, the load is a first-stage capacitor when the load is capacitive, and is a first-stage inductor when the load is inductive.
The invention provides a specific embodiment of a matching network parameter design method of a power amplifier with a matching network.
Taking a matching network of two resonance frequency points as an example, the structure diagram is shown in fig. 2. Wherein Cp and R0 are load parallel equivalent impedance, ls is series inductance, lp is parallel inductance, cs is series capacitance
Firstly, according to the voltage emission response and impedance characteristics of a load, two resonance frequency points f are selected 1 、f 2 (f 1 ＞f 2 ) The principle of selecting the frequency points includes: the impedance of the load in a frequency band near the frequency point is relatively stable; the load has a low voltage emission response at this frequency point; both frequency points are within the operating band and as far apart as possible.
At f 1 At the frequency point, the Lp reactance is large for the entire matching network, which can be considered an open circuit, and the Cs reactance is small for the entire matching network, which can be considered a short circuit. The matching network can be equivalent to that shown in fig. 3.
Wherein:
the series inductance Ls is calculated as follows:
at f 2 At the frequency point, the Ls reactance is small for the entire matching network, which can be considered a short circuit, and the Cp reactance is large for the entire matching network, which can be considered an open circuit. The matching network can be equivalent to that shown in fig. 4.
Wherein:
because the equivalent treatment is adopted in the method, ls is far smaller than Lp, and Cs is far larger than Cp so as to ensure the equivalent effect. The proper value of the parallel inductance Lp and the serial capacitance Cs are selected comprehensively.
The above specific embodiments merely describe the design principle of the present invention, and the shapes of the components in the description may be different, and the names are not limited. Therefore, the technical scheme described in the foregoing embodiments can be modified or replaced equivalently by those skilled in the art; such modifications and substitutions do not depart from the spirit and technical scope of the invention, and all of them should be considered to fall within the scope of the invention.
Claims (8)
1. A power amplifier including a matching network, comprising:
the direct current bus power supply is used for rectifying and converting alternating current commercial power, outputting direct current bus voltage and supplying power for the power amplifier main circuit;
the auxiliary power supply is used for converting alternating current commercial power into various voltages and supplying power for chips in the control circuit and the driving circuit;
the control circuit is used for modulating a switching frequency triangular wave with the frequency exceeding a first preset threshold value into a pulse width modulation signal compared with the frequency range of the control signal after filtering the control signal input from the outside;
the driving circuit is used for outputting corresponding driving signals according to the pulse width modulation signals and driving switching tubes in the power amplifier main circuit;
the power amplifier main circuit drives the switching tube to be turned on and off based on the driving signal, and outputs square wave voltage waveforms with the amplitude of direct current bus voltage, the frequency of switching frequency and the duty ratio of change;
the filter circuit is used for filtering harmonic waves of the switching frequency based on LC low-pass filtering and outputting voltage waveforms with required bandwidth;
the transformer boosts the output voltage of the power amplifier main circuit after being filtered by the filter circuit and outputs the voltage of the voltage class required by the load;
and the matching network is used for matching the impedance with the load through an LC series-parallel circuit according to the voltage emission response and the impedance characteristic of the load, so that the load has pure resistance to the power amplifier in the whole working frequency band.
2. The power amplifier of claim 1, wherein the control circuit has the functions of working condition collection and protection, can collect bus voltage and bus current output by a direct current bus power supply in real time, and uploads collected data to an upper computer through a communication interface; and when the bus voltage and the bus current exceed rated values, the control circuit triggers protection to close the output of the bus voltage and the bus current.
3. The power amplifier of claim 1, wherein the dc bus power supply is connected to the power amplifier main circuit input terminal through an output terminal.
4. The power amplifier of claim 1, wherein the auxiliary power supply is connected to the control circuit and the power input terminal of the driving circuit through pins, the control circuit is connected to the driving circuit input terminal through output terminals, the driving circuit output pins are connected to the driving signal pins of the power amplifier main circuit, the power amplifier main circuit output terminal is connected to the filter circuit input terminal, the filter circuit output terminal is connected to the primary side input terminal of the transformer, the secondary side output terminal of the transformer is connected to the matching network input terminal, and the matching network output terminal is connected to the load terminal.
5. The power amplifier of any of claims 1-4, wherein the auxiliary power supply converted voltage comprises a +15v, a 12V, a +5v voltage.
6. A matching network parameter design method for a power amplifier comprising a matching network, the method being implemented based on the power amplifier comprising a matching network according to any one of claims 1-5, the matching network parameter design method comprising:
step S21: determining the number N of resonant frequency points of the matching network based on the working bandwidth and the size of the power amplifier;
step S22: based on the number N of resonant frequency points, determining a circuit structure of an LC series-parallel circuit capable of performing impedance matching with a load;
step S23: determining a position of a resonance frequency point for each of the N resonance frequency points based on a voltage emission response and an impedance characteristic of the load;
step S24: based on the number and the positions of the resonance frequency points, in the LC series-parallel circuit, the number of the capacitors is determined according to the number of the resonance frequency points, and the inductance is determined by taking the maximum difference of the capacitance values of the capacitors as the constraintWherein L is n C is the matching inductance corresponding to the Nth resonance frequency point n Is the matching capacitance corresponding to the Nth resonance frequency point, f n Is the nth resonance frequency point.
7. The method of claim 6, wherein the number of resonant frequency points N is determined by integrating the matching network matching effect with the overall volumetric weight of the power amplifier.
8. The method of claim 6, wherein the step S22 of determining the circuit structure of the LC series-parallel circuit capable of impedance matching with the load based on the number N of resonant frequency points includes: the number N of resonant frequency points corresponds to N stages of LC resonant circuits, and each stage is composed of a resonant inductor L n And a resonance capacitor C n Each stage of staggered series-parallel connection is formed, namely, the inductance of one stage is connected in series with the capacitance of the other stage in parallel, and the inductance of the next stage is connected in series with the inductance of the other stage in parallel; wherein, the load is a first-stage capacitor when the load is capacitive, and is a first-stage inductor when the load is inductive.
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