Medium-wave multi-phase modulation amplifier based on silicon carbide MOS (Metal Oxide Semiconductor) tube

Abstract

The invention relates to a medium-wave multi-phase modulation amplifier based on a silicon carbide MOS (Metal Oxide Semiconductor) tube, which comprises a multi-phase modulator circuit and a power amplifier circuit which are arranged in sequence, and is characterized in that the multi-phase modulator circuit is used for receiving multiple paths of independent pulse width modulation signals, processing the signals and then transmitting the signals to the power amplifier circuit; the power amplifier circuit comprises an H-bridge circuit composed of a plurality of silicon carbide MOS tubes, and the H-bridge circuit generates a radio frequency output signal by alternately conducting diagonal switches. The high-performance silicon carbide MOS tubes are adopted, under cooperation of a multi-phase modulation framework, the efficiency bottleneck of a traditional scheme is broken through, the conduction loss of the medium wave modulation amplifier is reduced, the system efficiency is improved, the power consumption is reduced, and the increasingly high requirement standard at the present stage is met.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of medium waves, in particular to a medium wave multi-phase modulation amplifier based on a silicon carbide MOS tube. BACKGROUND

[0002] As the core equipment of the amplitude modulation broadcast transmission system, the medium wave transmitter undertakes the key function of converting audio signals into electromagnetic waves. The technical trend of the medium wave transmitter is constantly evolving with the changes in the demand of the broadcasting industry and the development of emerging technologies, mainly focusing on multi-phase, high-efficiency energy saving, digitization, intelligentization, modularization and the like. Among them, the modulation amplifier of the medium wave transmitter as the core component, its technical development directly affects the transmission efficiency, reliability and multi-frequency adaptability of the medium wave transmitter.

[0003] At present, the modulation amplifiers used by the medium wave transmitter still have relatively high conduction loss, and high conduction loss will lead to low system efficiency and high power consumption of the final system. The final system efficiency and power consumption of the medium wave transmitter at the present stage have gradually failed to meet the increasingly high standard requirements.

[0004] In view of this, how to overcome the defects existing in the prior art and solve the problem of low system efficiency and high power consumption caused by high conduction loss of the medium wave modulation amplifier in the prior art is a difficult problem to be solved in the technical field. SUMMARY

[0005] In view of the above defects or improvement requirements of the prior art, in order to solve the problem of low system efficiency and high power consumption caused by high conduction loss of the medium wave modulation amplifier in the prior art, the application provides a medium wave multi-phase modulation amplifier based on a silicon carbide MOS tube, which adopts a high-performance silicon carbide MOS tube. Under the cooperation of the multi-phase modulation architecture, the efficiency bottleneck of the traditional scheme is broken through, the conduction loss of the medium wave modulation amplifier is reduced, the system efficiency is improved, the power consumption is reduced, and the increasingly high demand standard at the present stage is met.

[0006] The embodiment of the application adopts the following technical scheme: The application provides a medium wave multi-phase modulation amplifier based on a silicon carbide MOS tube, which comprises a multi-phase modulator circuit and a power amplifier circuit arranged in sequence, wherein: The multi-phase modulator circuit is used for receiving multiple independent pulse width modulation signals and transmitting the signals to the power amplifier circuit after processing the signals. The power amplifier circuit comprises an H-bridge circuit composed of multiple silicon carbide MOS tubes, and the H-bridge circuit generates a radio frequency output signal by alternately conducting diagonal switches.

[0007] By adopting the technical scheme, the polyphase modulator circuit receives and processes multiple independent pulse width modulation signals, and the H-bridge circuit of the power amplifier circuit alternately conducts the diagonal switches to generate a radio frequency output signal, and the H-bridge circuit is composed of multiple silicon carbide MOS tubes, the silicon carbide MOS tube has the characteristics of high voltage resistance, low on-resistance, high working temperature, high switching frequency, low switching loss and high thermal conductivity, the efficiency bottleneck of the traditional scheme is broken, the conduction loss of the medium wave modulation amplifier is reduced, the system efficiency is improved, the power consumption is reduced, and the increasingly high demand standard at the present stage is met.

[0008] In some embodiments, the polyphase modulator circuit includes a power switch array composed of multiple silicon carbide MOS tubes, wherein each silicon carbide MOS tube is connected to a pulse width modulation signal, and each silicon carbide MOS tube is synchronously triggered to turn on or turn off according to the corresponding pulse width modulation signal.

[0009] By adopting the technical scheme, the polyphase modulator circuit sets a power switch array composed of multiple silicon carbide MOS tubes, each silicon carbide MOS tube is connected to a pulse width modulation signal and is synchronously triggered to turn on or turn off according to the signal, the processing of multiple independent pulse width modulation signals can be realized, and suitable signals are provided for the subsequent power amplifier circuit; in addition, the above design can offset the interference of the fundamental wave switching frequency, and the silicon carbide MOS tube further reduces the conduction loss, improves the system efficiency, and reduces the power consumption.

[0010] In some embodiments, the drain of each silicon carbide MOS tube of the power switch array is connected to an independent filter inductor and a freewheeling diode, and the filter inductor adopts a two-stage LC low-pass filter structure.

[0011] By adopting the technical scheme, the drain of each silicon carbide MOS tube is connected to an independent filter inductor and a freewheeling diode, the drain current can be offset by the phase difference design, the freewheeling diode provides a continuous path for the inductor current when the MOS tube is turned off and clamps the drain voltage to prevent voltage spikes, and the filter inductor with a two-stage LC low-pass filter structure can better filter out the PDM fundamental frequency and its harmonics.

[0012] In some embodiments, the gate of each silicon carbide MOS tube of the H-bridge circuit is connected to a direct current recovery circuit, the direct current recovery circuit includes an energy storage capacitor, a rectifier diode, a zener diode and a load resistor, the energy storage capacitor and the load resistor are both provided with two, the first load resistor is arranged between the two energy storage capacitors, the second load resistor, the zener diode and the rectifier diode are arranged on the side of the energy storage capacitor close to the silicon carbide MOS tube, and the zener diode and the rectifier diode are connected in series and connected in parallel with the second load resistor.

[0013] By adopting the technical scheme, the gate connection direct current recovery circuit of each silicon carbide MOS tube of the H-bridge circuit is composed of an energy storage capacitor, a rectifier diode, a Zener diode and a load resistor, which can ensure reliable opening and complete closing of the silicon carbide MOS tube.

[0014] In some embodiments, the output voltage of the direct current recovery circuit switches between -4V and 18V.

[0015] By adopting the technical scheme, the direct current recovery circuit switches between -4V and 18V, so that the MOS tube driver output can be regarded as a square wave signal switching between 0V and 22V, thereby ensuring reliable opening and complete closing of the silicon carbide MOS tube.

[0016] In some embodiments, the control signal of the power amplifier circuit is generated by a delay chip combined with two logic chips, one of which is an AND gate and the other is an NOR gate, for generating two-phase opposite TTL signals with a fixed delay time.

[0017] By adopting the technical scheme, the control signal is generated by a delay chip combined with two logic chips, namely an AND gate and an NOR gate, to generate two-phase opposite TTL signals with a fixed delay time, which ensures that the upper and lower MOS tubes of the H-bridge cannot be turned on at the same time, guarantees the switching reliability, and further ensures the stable operation of the power amplifier circuit.

[0018] In some embodiments, the fixed delay time is 60ns.

[0019] By adopting the technical scheme, the two-phase opposite TTL signals generated have a fixed delay time of 60ns, which ensures that the upper and lower MOS tubes of the H-bridge cannot be turned on at the same time, guaranteeing the switching reliability.

[0020] In some embodiments, the power amplifier circuit is connected with a protection monitoring circuit, which continuously monitors the voltage, current, modulation level, radio frequency drive level and power amplifier temperature of the power amplifier circuit through a microprocessor, and sends an alarm signal to the outside through a communication interface when the monitoring value exceeds the preset threshold.

[0021] By adopting the technical scheme, the protection monitoring circuit can continuously monitor the voltage, current, modulation level, radio frequency drive level and power amplifier temperature of the power amplifier circuit, and send an alarm signal to the outside when the monitoring value exceeds the preset threshold, which can timely find the abnormal situation of the power amplifier circuit and guarantee the stable operation of the amplifier.

[0022] In some embodiments, the working frequency range of the silicon carbide MOS tube-based medium wave multi-phase modulation amplifier is 530kHz to 1602kHz.

[0023] By adopting the above technical solution, the medium-wave multiphase modulation amplifier based on silicon carbide MOS transistors can cover the AM broadcast frequency band and is suitable for medium-wave broadcasting, communication and industrial applications.

[0024] In some embodiments, the fundamental frequency of the pulse width modulation signal is 150 kHz, and the range of the audio signal is 50 Hz to 4.5 kHz.

[0025] By adopting the above technical solution, the fundamental frequency and audio signal range of the pulse width modulation signal are clarified, which is conducive to designing a suitable low-pass filter to filter out the PDM fundamental frequency and its harmonics, and ensure the accuracy and stability of the signal during modulation and amplification.

[0026] Compared with the prior art, the beneficial effects of this application include, but are not limited to, the following: 1. The multiphase modulator circuit receives and processes multiple independent pulse width modulation signals. Combined with the H-bridge circuit of the power amplifier circuit, it alternately conducts diagonal switches to generate RF output signals. The H-bridge circuit is composed of multiple silicon carbide MOSFETs. By utilizing the high voltage withstand, low on-resistance, high operating temperature, high switching frequency, low switching loss, and high thermal conductivity of silicon carbide MOSFETs, it breaks through the efficiency bottleneck of traditional solutions, reduces the conduction loss of the medium wave modulator amplifier, improves system efficiency, reduces power consumption, and meets the increasingly higher standards required at present.

[0027] 2. The multiphase modulator circuit is equipped with a power switch array composed of multiple silicon carbide MOSFETs. Each silicon carbide MOSFET is connected to a pulse width modulation signal and is synchronously triggered to turn on or off according to the signal. This enables the processing of multiple independent pulse width modulation signals and provides suitable signals for subsequent power amplifier circuits. In addition, the above design can also cancel the interference of the fundamental switching frequency, and further reduce conduction losses through silicon carbide MOSFETs, thereby improving system efficiency and reducing power consumption.

[0028] 3. By using a delay chip and two logic chips, namely AND gates and NOR gates, control signals can be generated. Two TTL signals with opposite phases and fixed delay times can be generated to ensure that the two MOSFETs of the H-bridge will not be turned on at the same time, thus ensuring the reliability of the switch and ensuring the stable operation of the power amplifier circuit. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 A whole principle block diagram of a medium wave polyphase modulation amplifier based on silicon carbide MOS tube is provided for the present application; Figure 2 A polyphase modulator circuit topology is provided for the present application; Figure 3 A generation schematic diagram of a single-phase PDM signal is provided for the present application; Figure 4 A polyphase PDM signal waveform schematic diagram is provided for the present application; Figure 5 A comparison result schematic diagram of polyphase and single-phase PDM waveforms is provided for the present application; Figure 6 A frequency response schematic diagram of a low-pass filter structure is provided for the present application; Figure 7 A power amplifier circuit topology is provided for the present application; Figure 8 A circuit simulation model schematic diagram is provided for the present application; Figure 9 A simulation result schematic diagram is provided for the present application; Figure 10 A DC recovery circuit schematic diagram is provided for the present application; Figure 11 A power amplifier H-bridge circuit schematic diagram is provided for the present application; Figure 12 A class-D power amplifier output waveform schematic diagram is provided for the present application; Figure 13 A protection monitoring circuit topology schematic diagram is provided for the present application. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0032] In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as there is no conflict.

[0033] Silicon carbide MOS (Metal-Oxide-Semiconductor Field-Effect Transistor) is a kind of wide band gap semiconductor device, compared with traditional silicon-based MOS and IGBT (Insulated Gate Bipolar Transistor), it has higher withstand voltage and lower on-resistance, higher working temperature, higher switching frequency, lower switching loss, higher thermal conductivity, and is particularly suitable for scenes with strict requirements on efficiency, power or temperature, and is one of the key technologies of the next generation of power electronic systems. The high-temperature, high-frequency and high-power silicon carbide MOS made of wide band gap semiconductor can significantly improve the performance of the medium wave transmitter system. How to use wide band gap semiconductor silicon carbide MOS power device to develop and apply high-power wideband solid-state amplifier in medium wave frequency band has become a key technology that needs to be solved urgently in current engineering application, and the solution proposed in the present application is also aimed at this demand.

[0034] The present application will be described in detail below in combination with the drawings and examples.

[0035] Example 1 As Figure 1 shown, the present application embodiment 1 provides a medium wave multi-phase modulation amplifier based on silicon carbide MOS, which includes a multi-phase modulator circuit and a power amplifier circuit arranged in sequence. The multi-phase modulator circuit can be a three-phase modulator circuit, and correspondingly connects three PDM (Pulse Width Modulation signal), such as Figure 1 PDM A, PDM B, PDM C; a filter circuit is also arranged between the multi-phase modulator circuit and the power amplifier circuit, which can also be integrated in the multi-phase modulator circuit. The input end of the power amplifier circuit is also connected with a radio frequency driving signal, and the output end is connected with a radio frequency output through a transformer. The power amplifier circuit is also connected with a protection monitoring circuit, which is connected with an upper computer to monitor and alarm various parameters. The multi-phase modulator circuit is used for receiving multiple independent pulse width modulation signals, processing the signals and transmitting them to the power amplifier circuit; the power amplifier circuit includes an H-bridge circuit composed of multiple silicon carbide MOS, and the H-bridge circuit generates a radio frequency output signal by alternately conducting diagonal switches. Through the above technical solution, the multi-phase modulator circuit receives multiple independent pulse width modulation signals and processes and transmits them, and the H-bridge circuit of the power amplifier circuit alternately conducts diagonal switches to generate a radio frequency output signal. The H-bridge circuit is composed of multiple silicon carbide MOS, which takes advantage of the characteristics of silicon carbide MOS such as high withstand voltage, low on-resistance, high working temperature, high switching frequency, low switching loss and high thermal conductivity, breaks through the efficiency bottleneck of traditional solutions, reduces the conduction loss of the medium wave modulation amplifier, improves the system efficiency, reduces the power consumption, and meets the increasingly high demand standards at present.

[0036] In some embodiments, the working frequency range of the silicon carbide MOS tube-based medium wave multi-phase modulation amplifier is 530 kHz to 1602 kHz. Through the above technical solutions, the silicon carbide MOS tube-based medium wave multi-phase modulation amplifier can cover the AM broadcast (amplitude modulation broadcast) frequency band, and is suitable for medium wave broadcasting, communication and industrial applications. Specifically, the amplifier covers the AM broadcast frequency band of 530 kHz-1602 kHz, is powered by 400V and 22V direct current power supply, has a carrier output power of 2500 watts, and a peak power of up to 13.25 kilowatts; it internally integrates a three-phase modulator unit (i.e. a multi-phase modulator circuit) to directly drive a high-efficiency class-D radio frequency amplifier (i.e. a power amplifier circuit); all circuits are integrated on a single printed circuit board, eliminating the need for inter-stage interconnection wiring, and significantly simplifying the troubleshooting and maintenance process of the entire power link.

[0037] Reference Figure 2 As shown in some embodiments, the multi-phase modulator circuit includes a power switch array composed of a plurality of silicon carbide MOS tubes, such as the three silicon carbide MOS tubes Q1, Q2, and Q3 arranged side by side in the figure; wherein each silicon carbide MOS tube is connected to a pulse width modulation signal, such as PDM A connected to Q1 through a driver, PDM B connected to Q2 through a driver, and PDM C connected to Q3 through a driver; each silicon carbide MOS tube is synchronously triggered to turn on or turn off according to the corresponding pulse width modulation signal. Further, the drain of each silicon carbide MOS tube in the power switch array is connected to an independent filter inductor and a freewheeling diode, and the filter inductor adopts a two-stage LC low-pass filter structure; for example, Q1 is connected to filter inductor L1 and freewheeling diode D1, Q2 is connected to filter inductor L2 and freewheeling diode D2, Q3 is connected to filter inductor L3 and freewheeling diode D3, L1, L2, and L3 form a first-stage LC filter structure with capacitor C4, and a second-stage LC filter structure formed by filter inductor L4 and capacitor C5 is further connected. Through the above technical solutions, the multi-phase modulator circuit sets up a power switch array composed of a plurality of silicon carbide MOS tubes, each silicon carbide MOS tube is connected to a pulse width modulation signal and synchronously triggered to turn on or turn off according to the signal, and can process multiple independent pulse width modulation signals to provide appropriate signals for the subsequent power amplifier circuit; in addition, the above design can also offset the interference of the fundamental switching frequency, and further reduce the conduction loss through the silicon carbide MOS tube to improve the system efficiency and reduce the power consumption. In addition, the drain of each silicon carbide MOS tube is connected to an independent filter inductor and a freewheeling diode, which can make the drain current pass through the phase difference design to realize mutual offset of the PDM fundamental frequency, the freewheeling diode provides a continuous path for the inductor current when the MOS tube is turned off and clamps the drain voltage to prevent voltage spikes, and the filter inductor with a two-stage LC low-pass filter structure can better filter out the PDM fundamental frequency and its harmonics.

[0038] Specifically, the poly-phase modulator circuit is a voltage regulating stage between 400V DC voltage and RF amplifier. Its output will change with the variation of PDM (pulse width modulation) duty cycle, which is determined by the carrier level and envelope information together. The generation of PDM signal is generally realized by the method of comparing sine wave and triangle wave. When the amplitude of sine wave signal is greater than the amplitude of triangle wave, the comparator output is high level; when the amplitude of sine wave signal is less than the amplitude of triangle wave, the comparator output is low level, as shown in FIG. 2, that is, single-phase PDM signal. When it is at the envelope peak value (maximum duty cycle), the modulator output is close to 400V voltage; when it is at the envelope valley value (minimum duty cycle), the output tends to zero. The modulator receives three independent PDM signals, which are 120° apart in phase but have the same duty cycle, as shown in FIG. 3, that is, poly-phase PDM signal. This design can offset the interference of fundamental switching frequency, as shown in FIG. 4. Figure 3 Figure 4 Figure 5

[0039] The driver chip has high-speed switching capability and can absorb / output large current. These devices drive the gate of the modulator power MOS tube on / off through fast switching. The power MOS tube switching circuit Q1, Q2 and Q3 form a power switching array with ground reference, which has the following characteristics: (1) synchronous triggering: turned on in the positive duty cycle of PDM signal; (2) phase configuration: three tubes work based on the same PDM duty cycle, but the phase difference is 120°; (3) voltage switching: the drain of each MOS tube switches between 400V voltage and ground; when turned on: the drain voltage drops to 0V, forming a current path; when turned off: the drain voltage rises to 400V level. The modulator output voltage is determined by the on-duty cycle of the MOS tube.

[0040] ​​​The drain of each power MOSFET is connected to an independent filter inductor L1, L2, L3 and freewheeling diode D1, D2, D3, respectively, and the working characteristics are as follows: the three-way inductors converge the drain current at the common node of the modulator filter structure, and the mutual cancellation of the PDM fundamental frequency is achieved through phase difference design. When the MOSFET is turned off, the freewheeling diode provides a continuous path for the inductor current, clamps the drain voltage at 400V level, and prevents voltage spikes. The output voltage of the modulator filter structure exists across the capacitor (non-ground reference), and the voltage applied to the power amplifier circuit is superimposed by the direct current component (carrier level) and the alternating current component (modulation signal). When the duty cycle is constant, a pure DC level is output, and when the duty cycle changes, a DC + AC composite signal is output. The modulator filter structure is used to filter out the PDM fundamental frequency and its harmonics. The PDM fundamental frequency is 150kHz, and the audio signal ranges from 50Hz to 4.5kHz. Therefore, a low-pass filter structure is designed with a cutoff frequency of 10kHz. In order to better suppress the fundamental frequency, a two-stage LC low-pass filter structure is adopted. The first-stage LC filter structure is composed of capacitor C4 and parallel inductors L1, L2, L3; the second-stage LC filter is composed of inductor L4 and parallel RF decoupling capacitor C5. According to the formula , it is calculated that L1, L2, L3 are 155uH, C4 capacitor is 150nF, L4 is 12.25uH, and C5 capacitor is 54nF. The frequency response of the modulator low-pass filter structure is shown in Figure 6 .

[0041] Reference Figure 7As shown, in some embodiments, the gate of each silicon carbide MOS tube of the H-bridge circuit is connected with a DC recovery circuit, the DC recovery circuit comprises an energy storage capacitor, a rectifier diode, a Zener diode and a load resistor, the energy storage capacitor and the load resistor are both provided with two, the first load resistor is arranged between the two energy storage capacitors, the second load resistor, the Zener diode and the rectifier diode are arranged on the side of the energy storage capacitor close to the silicon carbide MOS tube, and the Zener diode and the rectifier diode are connected in series and form a parallel connection with the second load resistor; through the above technical solution, the reliable opening and complete shutdown of the silicon carbide MOS tube can be ensured. Further, the output voltage of the DC recovery circuit is switched between -4V and 18V; through the above technical solution, the MOS tube driver output can be regarded as a square wave signal switched between 0V and 22V, thereby ensuring the reliable opening and complete shutdown of the silicon carbide MOS tube. Further, the control signal of the power amplifier circuit is generated by a delay chip combined with two logic chips, one of which is an AND gate and the other is a NOR gate, for generating two-phase opposite TTL signals with a fixed delay time; through the above technical solution, the control signal is generated by using a delay chip combined with two logic chips, i.e. an AND gate and a NOR gate, to generate two-phase opposite TTL signals with a fixed delay time, so as to ensure that the upper and lower MOS tubes of the H-bridge will not be turned on at the same time, guarantee the switching reliability, and further ensure the stable operation of the power amplifier circuit.

[0042] Specifically, the power amplifier circuit adopts a class-D switching amplifier design, uses silicon carbide (SIC) switching MOS tubes with extremely low on-resistance, significantly reduces conduction loss, and has a working frequency range of 530kHz-1602kHz; each MOS tube is equipped with an independent gate drive circuit and supports asymmetric drive signals; by adjusting the drive signal, a controllable dead time can be inserted between each switching period of the class-D amplifier to ensure switching reliability.

[0043] The radio frequency drive signal is input into the power amplifier circuit, one way through the delay chip U1 and the other way directly input into two logic chips U2 and U3, U2 is an AND gate and U3 is a NOR gate, generating two-phase opposite TTL signals to control the conduction or shutdown of the MOS tubes at opposite angles of the H-bridge circuit, and there is a fixed delay time of 60ns between the two signals to ensure that the upper and lower MOS tubes of the H-bridge will not be turned on at the same time. The simulation circuit is built as shown in Figure 8 V1 is a pulse signal, the high level is 3.3V, the low level is 0V, the period is 2us, and the pulse width is 1us. Referring to (a) and (b) shown in Figure 9 (a) is the pulse signal at probe 1 in Figure 8 (b) is the pulse signal at probe 2 in Figure 8The pulse signals at the middle probe 2 and the probe 3, as can be seen from the figure, after being delayed and passing through a logic gate, two reverse signals are generated (the thick line is the waveform at the probe 2, and the thin line is the waveform at the probe 3), and there is a fixed interval of 60 ns between the two signals.

[0044] The driving circuit of the silicon carbide MOS tube is realized in the form of an isolated pulse transformer. The gate of each radio frequency power MOS tube is provided with a direct current recovery circuit, which can provide the MOS tube with optimal conduction and shutdown voltage. The direct current recovery circuit is composed of an energy storage capacitor, a rectifier diode, a Zener diode and a direct current load resistor. The energy storage capacitors C6 and C7 are 1uF, the voltage stabilizing value VZ of the Zener diode D4 is 3.3V, the forward voltage drop VFD2 of the rectifier diode D5 is 0.7V, R4 is a gate driving resistor with a resistance of 5Ω and a withstand power of 5W, and R5 is a gate-to-ground resistor with a resistance of 1kΩ. Figure 10

[0045] Since the turn-on voltage of the used silicon carbide MOS tube is 18V and the turn-off voltage is -4V, the driving voltage of the MOS tube should be switched between -4V and 18V. As shown in Figure 10 , the MOS tube driver output can be regarded as a square wave signal switched between 0V and 22V. In the initial state, the gate signal will be switched between 0V and 22V until a direct current voltage is established across the capacitor C7. The voltage on C7 is determined by the combined clamping voltage of the Zener diode D4 and the rectifier diode D5, and the specific value is VC7=(Vcc / 2)-(VZ+VFD2), where Vcc is the supply voltage, for example 22V, and VC7=11-(3.3+0.7)=7V DC. The actual gate drive signal voltage is switched between -4V and +18V, thereby ensuring reliable turn-on and complete turn-off of the silicon carbide MOS tube.

[0046] The class-D power amplifier is composed of four switching devices and adopts an H-bridge topology structure, as shown in Figure 11 , for generating an unfiltered modulated radio frequency output signal. The control circuit makes the diagonal switches of each pair conduct simultaneously, while the other pair remains off. This alternating switching action generates two opposite direction power pulses on the load connected at the center of the H-bridge. The amplifier switches at the target carrier frequency to generate a radio frequency signal with an amplitude varying between ±E voltage, as shown in Figure 12 . The DC blocking capacitor is connected to one side of the H-bridge to ensure that no DC current flows into the RF transformer connected to the module.

[0047] According to the Fourier transform formula, a square wave signal is composed of an infinite number of sine signals, that is: ​where ω is the angular frequency of the sinusoidal wave, calculated from the period T: ω = 2π / T / T The coefficients in the above formula represent the amplitude of each sinusoidal signal. Obviously, as the frequency of the sinusoidal wave increases, its amplitude gradually decreases, so only the first few terms are needed to approximate the square wave signal, and the peak voltage can be approximated as: 4E / π ≈ 1.27E; When the duty cycle of the PDM is 42.5%, the voltage applied to the class-D power amplifier is 400V x 42.5% = 170V, i.e. E = 170V. According to the formula: When the output power is 2500W, the output impedance R of the power amplifier is about 9.3Ω.

[0048] Reference Figure 13 As shown in the figure, in some embodiments, the power amplifier circuit is connected with a protection monitoring circuit, which is responsible for performing all necessary control, monitoring and protection functions through a microprocessor. The microprocessor continuously monitors the analog signal sampling and alarm state, and feeds back information to the rack main controller through a serial data bus. The microprocessor mainly monitors the voltage, current, modulation level, RF drive level and power amplifier temperature of the power amplifier circuit, and compares them with the set threshold value. When the monitoring value exceeds the preset threshold value, an alarm signal is sent to the upper layer main controller through RS485 communication. Through the above technical solution, abnormal conditions of the power amplifier circuit can be found in time, and stable operation of the amplifier is ensured.

[0049] In summary, the application uses high-performance silicon carbide MOS tubes, breaking through the efficiency bottleneck of traditional solutions, and under the coordination of multiphase modulation architecture, the system efficiency is improved by 15%, the power consumption is reduced by 20%, and at the same time, more compact size and longer life are supported. This innovation provides a more energy-efficient and reliable transmitter solution for medium wave broadcasting, communication and industrial applications.

[0050] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A silicon carbide MOSFET-based medium wave polyphase modulated amplifier, characterized by, The application relates to a silicon carbide MOS (Metal-Oxide-Semiconductor) based medium wave multi-phase modulation amplifier. The multi-phase modulator circuit is used for receiving multiple independent pulse width modulation signals, processing the signals and transmitting the signals to the power amplifier circuit. The power amplifier circuit comprises an H-bridge circuit composed of multiple silicon carbide MOS tubes.

2. The silicon carbide MOSFET-based medium wave polyphase modulation amplifier of claim 1, wherein, The multi-phase modulator circuit comprises a power switch array composed of multiple silicon carbide MOS tubes.

3. The silicon carbide MOSFET-based medium wave polyphase modulation amplifier of claim 2, wherein, The drain of each silicon carbide MOS tube of the power switch array is connected with an independent filter inductor and freewheeling diode.

4. The silicon carbide MOSFET-based medium wave polyphase modulation amplifier of claim 1, wherein, The gate of each silicon carbide MOS tube of the H-bridge circuit is connected with a direct current recovery circuit.

5. The silicon carbide MOSFET-based medium wave polyphase modulation amplifier of claim 4, wherein, The output voltage of the direct current recovery circuit is switched between -4V and 18V.

6. The silicon carbide MOSFET-based medium wave polyphase modulation amplifier of claim 1, wherein, The control signal of the power amplifier circuit is generated by combining a delay chip and two logic chips.

7. The silicon carbide MOSFET-based medium wave polyphase modulation amplifier of claim 6, wherein, The fixed delay time is 60ns.

8. The silicon carbide MOSFET-based medium wave polyphase modulation amplifier of claim 1, wherein, The power amplifier circuit is connected with a protection monitoring circuit.

9. The silicon carbide MOSFET-based medium wave polyphase modulation amplifier of any of claims 1-8, wherein, The working frequency range of the silicon carbide MOS based medium wave multi-phase modulation amplifier is 530kHz-1602kHz.

10. The silicon carbide MOSFET-based medium wave polyphase modulation amplifier of any one of claims 1-8, wherein, The base frequency of the pulse width modulation signal is 150kHz, and the range of the audio signal is 50Hz-4.5kHz.

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