A high-power digital power amplifier and a modulation method thereof

Abstract

The application discloses a kind of high-power digital power amplifiers and modulation method thereof, belong to power amplifier field.It includes: the power supply, AC-AC module, transformer, cascaded switching power module, inverter circuit connected in turn;The transformer is multiple secondary winding transformer, the cascaded switching power module includes multiple series connection switching power module, further include control module, each secondary edge of the transformer is respectively corresponding with each switching power module one-to-one connection, the output of the cascaded switching power module is connected with the input of the inverter circuit, control each power module work in SM or PWM modulation mode, by superimposing PWM modulation on SM modulation, form half cycle expected waveform, after inverting by inverter circuit, the output of target ac voltage signal can be realized, the power amplifier of the application has the advantages of wide output power range and can reach megawatt level, wide frequency band, low harmonic content, good output waveform quality, simple structure and high efficiency.

Description

Technical Field

[0001] This invention belongs to the field of power amplifier technology, and more specifically, relates to a high-power digital power amplifier and its modulation method. Background Technology

[0002] With the continuous development of power electronics technology and the increasing demands on power amplifier performance in high-power applications, the improvement of high-power amplifier performance has gained significant attention. This has led to the continuous development of high-power amplifiers towards higher frequencies, higher performance, modularity, and miniaturization. High-power amplifiers often require output capabilities of hundreds or even megawatts. Furthermore, in sonar systems, for example, due to the complex marine environment in shallow seas, sonar systems must overcome the effects of reverberation while achieving effective detection range. This requires high-power amplifiers in sonar systems to output high power while also possessing a wide frequency bandwidth.

[0003] However, due to limitations in topology and operating principles, the output power of existing high-power amplifiers is generally limited to less than kilowatts, with narrow output frequency bandwidth and a single output waveform. This makes it impossible to meet the demands of certain high-power applications (such as underwater sonar drive, high-power motor drive, plasma discharge, sewage treatment, flue gas desulfurization, and high-power laser technologies) for high-power, wide-bandwidth, diverse waveforms, and low harmonic voltage output. Summary of the Invention

[0004] In response to the shortcomings and improvement needs of existing technologies, this invention provides a high-power digital power amplifier and its modulation method, aiming to simultaneously improve the existing problems of low output power, narrow bandwidth, high harmonics, and monotonous waveform.

[0005] To achieve the above objectives, according to one aspect of the present invention, a high-power digital power amplifier is provided, comprising: a power supply, an AC-AC module, a transformer, a cascaded switching power module, and an inverter circuit connected in sequence;

[0006] The transformer is a multi-side winding transformer, and the cascaded switching power module includes multiple switching power modules connected in series; it also includes a control module, which includes a controller;

[0007] Each secondary side of the transformer is connected to each cascaded switching power module in a corresponding manner, and the output of the cascaded switching power module is connected to the input of the inverter circuit.

[0008] The controller is used to control the switching signals of the cascaded switching power modules and the on / off state of each switching transistor in the inverter circuit, so that N switching power modules are in stepped modulation (SM) mode and M switching power modules are in pulse width modulation (PWM) mode under the control of the controller, where N≥0 and M≥0; the sum of the voltages output by the N switching power modules and the sum of the voltages output by the M switching power modules are equal to the instantaneous target voltage at the current moment.

[0009] Furthermore, each switching power module includes: a first switching transistor and a reverse-connected diode connected in series.

[0010] Furthermore, each switching power module also includes: a second switching transistor, a three-phase full-wave rectifier circuit structure, a soft-start resistor, an RCD buffer circuit structure, and two bus capacitors;

[0011] The second switching transistor and the first switching transistor form an IGBT half-bridge structure;

[0012] The input terminal of the three-phase full-wave rectifier circuit is connected to one secondary winding of the transformer, and the output terminal forms a series circuit with the soft-start resistor, the second switch, and the two bus capacitors. The IGBT half-bridge structure is connected in parallel with the RCD buffer circuit structure. The first switch is connected in series with the reverse diode and then connected in parallel across the two bus capacitors.

[0013] Furthermore, a fuse and a mechanical switch are connected in series between the three-phase full-wave rectifier circuit structure and the transformer. The fuse is also connected to a secondary winding of the transformer, and the mechanical switch is also connected to the input terminal of the three-phase full-wave rectifier circuit structure.

[0014] Two bus resistors are connected in parallel across each of the two bus capacitors.

[0015] Furthermore, the multiple series-connected switching power modules have the same structure.

[0016] Furthermore, it also includes a filtering and matching module, which is used to filter out high-frequency harmonic components in the target AC voltage signal output by the inverter circuit and match it with the load impedance.

[0017] Furthermore, the control module also includes a detection and protection unit for detecting circuit faults in the amplifier and protecting the components in the circuit from damage when a fault occurs.

[0018] Furthermore, the inverter circuit structure is an H-bridge structure.

[0019] According to a second aspect of the present invention, a modulation method for a high-power digital power amplifier as described in any one of the first aspects is provided, comprising:

[0020] At the current moment, based on the instantaneous target voltage U L N switching power modules are controlled to be in stepped modulation (SM) mode and M switching power modules are in pulse width modulation (PWM) mode, where N≥0 and M≥0;

[0021] The sum of the voltages output by the N switching power modules and the sum of the voltages output by the M switching power modules are controlled to sum with the instantaneous target voltage U. L equal.

[0022] Furthermore, if one switching power module is controlled in pulse width modulation (PWM) mode, then the number N of switching power modules in stepped modulation (SM) mode and the duty cycle D of the switching power module in PWM mode are respectively:

[0023]

[0024]

[0025] Among them, U d U represents the maximum output voltage across each switching power module. L This represents the instantaneous target voltage at the current moment, and [.] represents the floor operator.

[0026] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0027] (1) The power amplifier topology and modulation method of the present invention are designed with cascaded switching power modules. The switching of each power module is achieved by controlling its modulation state and turn-on timing according to requirements. Each power module can operate in SM modulation mode or PWM modulation mode. By superimposing PWM modulation on SM modulation to form a half-cycle expected waveform, the overall waveform is then inverted by an inverter circuit to achieve the output of the target AC voltage signal. Compared with existing cascaded inverter structures, this method has fewer switching devices and a simpler circuit structure. It can improve the output accuracy of the digital power amplifier without changing the circuit structure of each power module or the overall topology, achieving a wide-range continuously adjustable AC voltage output. The target output voltage is obtained by superimposing multiple switching power modules, resulting in high output power.

[0028] In multiple switching power modules, the power module in SM modulation mode operates at a low frequency, while the power module in PWM modulation mode operates at an ultra-high frequency. Due to the large difference in switching frequency between SM and PWM modulation modes, a low harmonic waveform with a wide frequency range of 0-2000Hz can be output at a limited sub-module switching frequency. Furthermore, within this wide frequency range, the difference in switching frequency between the two modes is significant at any frequency. A low-pass filter can be used to filter out the harmonics generated by the switching power module in PWM modulation mode. Compared to the existing modulation methods where the output target voltage has a wide distribution of low-frequency and high-frequency harmonics, the amplifier structure and modulation method of this invention can obtain a low-harmonic output voltage.

[0029] (2) The cascaded switching power module designed in this invention uses a three-phase full-wave rectifier circuit structure to rectify the rated input voltage provided by the transformer to each switching power module and output it to two DC bus capacitors to charge the bus capacitors. The IGBT half-bridge structure controls the charging and discharging of the DC bus capacitors. The RCD buffer circuit structure is used to absorb the turn-off overvoltage caused by the leakage inductance of the transformer, as well as the stray inductance introduced by the transmission lines, electrical connections and devices in the circuit. Ultimately, this makes the voltage ripple output by each switching power module small and has the functions of small overshoot and rapid fault response, providing a high-quality unit DC source for the overall topology of the power amplifier.

[0030] (3) By controlling the timing of the turn-on of multiple identical power modules, desired waveforms of any shape can be generated, such as square waves, pulse waves, triangular waves, sine waves, linear frequency modulated waves (LFM), continuous waves (CW), etc., which can meet the load's demand for diverse waveforms.

[0031] In summary, the power amplifier topology and modulation method of the present invention have the advantages of high output power, low harmonic content, good output waveform quality, simple structure and high efficiency. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a high-power digital power amplifier topology provided in one embodiment of the present invention.

[0033] Figure 2 This is a schematic diagram of a cascaded switching power module and inverter circuit in a topology provided in an embodiment of the present invention.

[0034] Figure 3 This is a schematic diagram of the structure of each switching power module provided in one embodiment of the present invention.

[0035] Figure 4 This is the modulation strategy process for the sine wave in the embodiments of the present invention.

[0036] Figure 5This is the modulation strategy process of the linear frequency modulated wave (LFM) in the embodiment of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0038] In this invention, the terms "first," "second," etc., used in the invention and accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0039] like Figure 1 The high-power digital power amplifier provided by the present invention mainly includes:

[0040] Power supply, AC-AC module, transformer, cascaded switching power module, inverter circuit, control module and filter matching module;

[0041] The input of the AC-AC module is connected to the power supply, and the output is connected to the transformer. Each secondary side of the transformer is connected to each cascaded switching power module. The output of the cascaded switching power modules is connected to the input of the inverter circuit. The output of the inverter circuit is connected to the input of the filter matching module. The output of the filter matching module is connected to the load. The controller in the control module is connected to the drive terminals of the cascaded switching power modules and the switching transistors in the inverter circuit.

[0042] Specifically, the power supply is connected to the AC-AC module, which is used to rectify and invert the output voltage of the power supply to provide the required rated input voltage for the cascaded switching power modules. In this embodiment, the required rated input voltage for the cascaded switching power modules is 560V.

[0043] The transformer is a multi-secondary winding transformer, with each secondary winding connected to each cascaded switching power module in a corresponding manner. This is used to apply the voltage after rectification and inversion by the AC-AC module to each cascaded switching power module.

[0044] The cascaded switching power module includes multiple switching power modules with the same structure, which are connected in series. Each switching power module can operate in stepped modulation (SM) mode or pulse width modulation (PWM) mode according to the modulation strategy, and finally outputs a continuously adjustable target DC voltage signal.

[0045] Inverter circuits are used to convert target DC voltage signals into target AC voltage signals;

[0046] The filtering and matching module includes a filtering circuit and an impedance matching circuit. The filtering circuit is used to filter out high-frequency harmonic components in the target AC voltage signal. The impedance matching circuit is used to match the power supply impedance with the load impedance based on the filtered target AC voltage signal, so that the power supply impedance and the load impedance are approximately equal to obtain high power output.

[0047] The control module includes a controller and a detection and protection unit. The controller controls the switching signals of the cascaded switching power modules and the on / off state of each switching transistor in the inverter circuit. The switching signals indicate the turn-on timing of each switching power module, including the operating mode, operating frequency, output voltage value, and turn-on time of each module. The detection and protection unit detects circuit faults and protects the components in the circuit from damage when faults occur. It mainly functions in the event of overvoltage, overcurrent, overtemperature, switching power module faults, and inverter circuit faults.

[0048] Specifically, in this embodiment, the power supply voltage is 220V or 380V.

[0049] The AC-AC module includes: a rectifier circuit, a power factor correction boost converter circuit, and a DC-AC inverter connected in series.

[0050] Specifically, in the cascaded switching power modules, each switching power module includes: a first switching transistor and a reverse-connected diode, wherein the first switching transistor and the reverse-connected diode are connected in series, such as... Figure 2 As shown in the figure, switch S i Represents the first switching transistor in the i-th switching power module, where i = 1, 2, ..., or n.

[0051] As a preferred option, such as Figure 3 As shown, to stabilize the output voltage of each power module and improve the waveform quality of the output voltage, each switching power module also includes: a fuse, a mechanical switch, a three-phase full-wave rectifier circuit structure, a soft-start resistor, an RCD buffer circuit structure, two bus capacitors, two bus resistors, and a second switching transistor S; wherein, the second switching transistor S and the first switching transistor S i An IGBT half-bridge structure is formed. One end of the fuse is connected to a secondary winding of the transformer, and the other end is connected to one end of a mechanical switch. The other end of the mechanical switch is connected to the input terminal of the three-phase full-wave rectifier circuit. The output terminal of the three-phase full-wave rectifier circuit forms a series circuit with the soft-start resistor, the second switch in the IGBT half-bridge structure, and the two bus capacitors. The IGBT half-bridge structure is connected in parallel with the RCD buffer circuit. The first switch in the IGBT half-bridge structure is connected in series with the reverse diode and then in parallel across the two bus capacitors. One bus resistor is connected in parallel with one bus capacitor.

[0052] In this design, fuses and series-connected mechanical switches provide fault protection. The three-phase full-wave rectifier circuit rectifies the rated input voltage provided by the transformer to each switching power module and outputs it to the two DC bus capacitors to charge them. Soft-start resistors limit the inrush current of the transformer and the charging current of the bus capacitors. The IGBT half-bridge structure controls the charging and discharging of the DC bus capacitors. Specifically, controlling the switching on and off of the second switch in the IGBT half-bridge structure charges the DC bus capacitors, and controlling the switching on and off of the first switch discharges them. The RCD buffer circuit absorbs the turn-off overvoltage caused by transformer leakage inductance, as well as stray inductance introduced by transmission lines, electrical connections, and devices in the circuit. The bus resistors connected in parallel across each bus capacitor provide voltage equalization and protection. Through this design, the voltage ripple output by each switching power module is small, and it features low overshoot and rapid fault response, providing a high-quality unified DC source for the overall power amplifier topology.

[0053] In this embodiment, the switching device in the cascaded switching power module is an insulated gate bipolar transistor (IGBT).

[0054] The inverter circuit is an H-bridge structure composed of four switching transistors: a first upper left switch, a second lower left switch, a third upper right switch, and a fourth lower right switch. In this embodiment, the switching transistors in the inverter circuit are IGBTs.

[0055] Based on the above-mentioned high-power digital power amplifier, the present invention also provides a hierarchical hybrid modulation method for the power amplifier, mainly comprising:

[0056] At the current moment, the modulated wave signal provided by the controller is compared with the magnitude, frequency and shape of the target voltage signal on the load to generate the switching signals of each switching power module and the turn-on signals of each switching transistor in the inverter circuit, thereby controlling the target voltage waveform, frequency and amplitude.

[0057] Specifically, this hierarchical hybrid modulation method includes pre-stage modulation and post-stage modulation, wherein the pre-stage modulation includes:

[0058] At the current moment, based on the instantaneous target voltage U L N switching power modules in each switching power module are controlled to be in stepped modulation (SM) mode, and M switching power modules are controlled to be in pulse width modulation (PWM) mode, where N≥0 and M≥0;

[0059] Control the sum of the voltages output by N switching power modules and the sum of the voltages output by M switching power modules, and the instantaneous target voltage U. L equal;

[0060] Post-modulation includes:

[0061] The control module sends a turn-on signal to trigger the switching transistors in the inverter circuit at a frequency consistent with the target voltage signal. The expected half-cycle waveform of the pre-amplifier output is flipped by the H-bridge structure, completing the inversion. Figure 4 , Figure 5 As shown, Figure 5 In this context, Um represents the maximum amplitude of the linear frequency modulated (LFM) wave. Preferably, in the cascaded switching power modules, N switching power modules are in SM modulation mode and 1 switching power module is in PWM modulation mode; then the instantaneous target voltage U... L for:

[0062] U L =DU d +NU d

[0063] In the cascaded switching power modules, the number N of switching power modules in SM modulation mode and the duty cycle D of the switching power modules in PWM modulation mode are respectively:

[0064]

[0065]

[0066] Among them, U d This represents the maximum output voltage across each switching power module. The output voltage of each switching power module in SM modulation mode is U. d The output voltage of the switching power module in PWM modulation mode is adjusted by the duty cycle, and the output voltage range is 0-DU. d The numbers vary between [.], where [.] represents the floor operator. In this embodiment, N = 9.

[0067] In addition, under normal circumstances, in order to balance the lifespan of each module, PWM mode is cyclically enabled in N+1 modules to balance the switching losses of each module, thereby balancing the lifespan of each module.

[0068] Specifically, such as Figure 2 As shown in the diagram, in the cascaded switching power module and inverter structure, the variables are defined as follows:

[0069] D1, D2, ..., D n These are reverse-connected diodes in each power module, which function when the power module is disconnected. In this embodiment, n = N + 1.

[0070] S1, S2, ..., S n S represents the operating state of the first switching transistor in each switching power module.i When S = 0, the first switch in the i-th switching power module is turned off, i.e., the power module is disconnected. i When = 1, the first switch is closed, meaning the power module is put into use;

[0071] S 11 S 12 S 13 S 14 This indicates the operating state of the four switching devices in the H-bridge circuit, i.e., closed or open. The left and right bridge arms cannot be turned on simultaneously. In this embodiment, the first upper left switch and the fourth lower right switch are in the same on state, and the second lower left switch and the third upper right switch are in the same on state.

[0072] The target AC voltage signal u output by the H-bridge H The expression is:

[0073]

[0074] Amplifier output voltage U out for:

[0075]

[0076] Where i = 1, 2, ..., n.

[0077] The power amplifier topology and modulation method of this invention combine the advantages of SM and PWM modulation strategies. Compared with the existing cascaded inverter structure, this invention switches power modules according to demand by controlling the modulation state and turn-on timing of each power module. Each single power module can work in SM mode or PWM mode. By superimposing PWM pulse width modulation on SM step modulation to form a half-cycle expected waveform, the target AC voltage signal can be achieved by performing overall inversion through the subsequent H-bridge. It has fewer switching devices and a simple circuit structure. That is, it can improve the output accuracy of digital power amplifier without changing the circuit structure of each power module and the overall topology without being bulky, and can achieve a wide range of continuously adjustable AC voltage output. The target output voltage is obtained by superimposing multiple switching power modules, which features high output power. Among the multiple switching power modules, the power module in SM modulation mode operates at a low frequency, while the power module in PWM modulation mode operates at an ultra-high frequency. Due to the large difference in switching frequency between SM and PWM modulation modes, a low-harmonic waveform with a wide frequency range of 0-2000Hz can be output within a limited sub-module switching frequency. Furthermore, within this wide frequency range, the difference in switching frequency between the two modes is significant at any frequency. A low-pass filter can effectively filter out the harmonics generated by the switching power module in PWM modulation mode. Compared to existing modulation methods where the output target voltage has a wide distribution of low- and high-frequency harmonics, the amplifier structure and modulation method of this invention can achieve a low-harmonic output voltage. By controlling the timing of the turn-on of multiple identical power modules, desired waveforms of any shape can be generated, such as square waves, pulse waves, triangular waves, and sine waves, meeting the diverse waveform requirements of the load. In other words, the power amplifier topology and modulation method of this invention have advantages such as high output power, low harmonic content, good output waveform quality, simple structure, and high efficiency.

[0078] Furthermore, the cascaded switching power modules designed in this invention rectify the rated input voltage provided by the transformer to each switching power module through a three-phase full-wave rectifier circuit structure to charge the two DC bus capacitors. The IGBT half-bridge structure controls the charging and discharging of the DC bus capacitors, and the RCD buffer circuit structure is used to absorb the turn-off overvoltage caused by the transformer leakage inductance, as well as the stray inductance introduced by transmission lines, electrical connections and devices in the circuit. Ultimately, this results in small voltage ripple output by each switching power module, and has the functions of small overshoot and rapid fault response, providing a high-quality unit DC source for the overall power amplifier topology.

[0079] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-power digital power amplifier, characterized in that, include: The power supply, AC-AC module, transformer, cascaded switching power module and inverter circuit are connected in sequence. The transformer is a multi-side winding transformer, and the cascaded switching power module includes multiple switching power modules connected in series; it also includes a control module, which includes a controller; Each secondary side of the transformer is connected to each cascaded switching power module in a corresponding manner, and the output of the cascaded switching power module is connected to the input of the inverter circuit. The controller is used to control the switching signals of the cascaded switching power modules and the on / off state of each switching transistor in the inverter circuit, so that N switching power modules are in stepped modulation (SM) mode and M switching power modules are in pulse width modulation (PWM) mode under the control of the controller, where N≥0 and M≥0; the sum of the voltages output by the N switching power modules and the sum of the voltages output by the M switching power modules are equal to the instantaneous target voltage at the current moment. Each switching power module includes: a first switching transistor and a reverse-connected diode connected in series; Each switching power module also includes: a second switching transistor, a three-phase full-wave rectifier circuit structure, a soft-start resistor, an RCD buffer circuit structure, and two bus capacitors. The second switching transistor and the first switching transistor form an IGBT half-bridge structure; The input terminal of the three-phase full-wave rectifier circuit is connected to one secondary winding of the transformer, and the output terminal forms a series circuit with the soft-start resistor, the second switch, and the two bus capacitors. The IGBT half-bridge structure is connected in parallel with the RCD buffer circuit structure. The first switch is connected in series with the reverse diode and then connected in parallel across the two bus capacitors.

2. The high-power digital power amplifier according to claim 1, characterized in that, Between the three-phase full-wave rectifier circuit structure and the transformer, a fuse and a mechanical switch are connected in series. The fuse is also connected to a secondary winding of the transformer, and the mechanical switch is also connected to the input terminal of the three-phase full-wave rectifier circuit structure. Two bus resistors are connected in parallel across each of the two bus capacitors.

3. The high-power digital power amplifier according to claim 1, characterized in that, The multiple series-connected switching power modules have the same structure.

4. The high-power digital power amplifier according to claim 1, characterized in that, It also includes a filtering and matching module, which is used to filter out high-frequency harmonic components in the target AC voltage signal output by the inverter circuit and match it with the load impedance.

5. The high-power digital power amplifier according to claim 1, characterized in that, The control module also includes a detection and protection unit for detecting circuit faults in the amplifier and protecting the components in the circuit from damage when a fault occurs.

6. The high-power digital power amplifier according to claim 1, characterized in that, The inverter circuit structure is an H-bridge structure.

7. A modulation method for a high-power digital power amplifier as described in any one of claims 1-6, characterized in that, include: At the current moment, based on the instantaneous target voltage U L N switching power modules are controlled to be in stepped modulation (SM) mode and M switching power modules are in pulse width modulation (PWM) mode, where N≥0 and M≥0; The sum of the voltages output by the N switching power modules and the sum of the voltages output by the M switching power modules are controlled to sum with the instantaneous target voltage U. L equal.

8. The modulation method according to claim 7, characterized in that, If one switching power module is controlled in pulse width modulation (PWM) mode, then the number N of switching power modules in stepped modulation (SM) mode and the duty cycle of the switching power module in PWM mode are... They are respectively: in, U represents the maximum output voltage across each switching power module. L This represents the instantaneous target voltage at the current moment. This represents the floor operator.

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