A demodulation method and system for the load side of an LLC resonant converter

Abstract

The application relates to the field of power electronics, and discloses a demodulation method and system for a load side of an LLC resonant converter, which comprises the following steps: a load receives electric energy transmitted from the LLC converter, and then out-of-band noise is filtered through a band-pass filter; S2, an analog-to-digital converter converts the carrier signal filtered through the band-pass filter into a discrete sampling sequence; a low-pass filtering process after signal multiplication in coherent demodulation is replaced by an integral process; since the to-be-measured signal is converted into a discrete sequence through sampling, a sine signal multiplied in the integral process is converted into a sine sequence obtained by the same sampling frequency, and the integral process is converted into an accumulation process; the amplitude and the phase of the discrete signal are obtained; and digital information is obtained in advance from the output voltage of the LLC converter by analyzing the frequency, the amplitude and the phase of the signals.

Description

Technical Field

[0001] This invention relates to the field of electronic communication technology, and in particular to a demodulation method and system for the load side of an LLC resonant converter. Background Technology

[0002] Traditional power electronics is described as an interdisciplinary field comprised of electronics, electrical engineering, and control theory. In various power systems, communication networks are typically required to achieve power regulation and ensure stable system operation, with strict requirements on parameters such as communication rate and communication delay.

[0003] Traditional power electronics is fully capable of handling the demands of DC power generation (directly generating DC power or converting it to DC power through rectification, as DC systems do not have issues with reactive power compensation, power quality, and frequency synchronization, greatly reducing system control complexity and significantly improving system reliability. Therefore, they are widely used in electric vehicles, consumer electronics, and energy storage systems). However, it cannot handle the information functions of power supply systems. Most existing research attempts to achieve informationization by directly applying existing communication technologies, such as Ethernet, fieldbus, and radio frequency communication, to power electronic devices.

[0004] As research into power electronics deepens, it has become increasingly clear that power electronic systems themselves possess information-based characteristics. In other words, power electronic systems can not only transmit electrical power but also modulate information into electrical energy for transmission, and simultaneously demodulate information from electrical energy.

[0005] Some scholars believe that power electronic conversion and communication processes share inherent similarities, both involving modulation, transmission, and demodulation of the target signal, differing only significantly in their actual signal frequency bands. Therefore, power electronic conversion encounters fewer obstacles in information modulation and offers multiple implementation schemes. Existing LLC converters typically rely on independent low-voltage communication interfaces (such as CAN and RS485) for data exchange with external devices. This approach not only requires complex strong-weak current isolation designs but is also susceptible to electromagnetic interference generated by the main power circuit, leading to high error rates and poor stability. Furthermore, the multiple low-voltage auxiliary power supplies required for the communication module and control circuit further increase the complexity of the system design, impacting overall integration and reliability. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art. The present invention proposes a demodulation method and system for the load side of an LLC resonant converter. The method utilizes the LLC converter to demodulate the digital information modulated into the small fluctuations of the output voltage or current while transmitting power, and completes the demodulation of the information at the load end.

[0007] The technical solution of the present invention is as follows: On one hand, the present invention discloses a demodulation method for the load side of an LLC resonant converter, the method comprising the following steps:

[0008] S1. The load receives the voltage transmitted from the LLC resonant converter, and then the out-of-band noise is filtered out by the bandpass filter.

[0009] S2. The analog-to-digital converter converts the bandpass-filtered carrier signal into a discrete sampling sequence, setting the signal to be measured. The expression for the sampling sequence is:

[0010]

[0011] in, Let A be the signal to be measured, ω be the amplitude, and ω be the angular frequency. It is a non-zero natural number. The sampling angular frequency of the analog-to-digital converter. The Nyquist sampling theorem must be satisfied: ;

[0012] S3, the signal to be measured With a set of amplitudes and phases known, and with the signal to be measured When multiplying sine waves of the same frequency but 90° out of phase, the integration process of the following formula can be used to replace the low-pass filtering process after signal multiplication in coherent demodulation:

[0013]

[0014] in, For the integration period, The value is an integer multiple of the period of the signal under test, that is:

[0015]

[0016] in, For the modulo operation, ω is the angular frequency;

[0017] S4. Since the signal under test is converted into a discrete sequence after sampling, the sinusoidal signal multiplied by it during integration should also be converted into a sinusoidal sequence obtained from the same sampling frequency. The integration process can be transformed into an accumulation process using the following formula:

[0018]

[0019] in, The integral period is ω, and the angular frequency is ω. , , where is the component of the signal to be measured;

[0020] S5. Use the following formula to obtain the amplitude of the discrete signal. and phase ,Right now:

[0021]

[0022] in, The target signal amplitude, The phase of the target signal;

[0023] S6. By analyzing the frequency and amplitude of the target signal With phase The amplitude, phase angle and frequency change sequence are obtained, and the corresponding symbol information is output, thereby demodulating digital information from the output voltage of the LLC converter.

[0024] As described above, the signal first passes through a bandpass filter to remove noise. The resulting signal is then multiplied by a set of sine waves with known amplitude and phase, exhibiting the same frequency as the signal under test but with a 90° phase difference. The signals are then low-pass filtered, retaining only the DC component. The amplitude and phase angle of the remaining signal are then calculated. Information extraction is performed based on the digital signals corresponding to the amplitude, phase angle, and frequency. The load receives electrical energy from the LLC converter and demodulates the digital information embedded in the small fluctuations of the output voltage. By analyzing the frequency, amplitude, and phase of these components and obtaining their variation sequence, the information can be extracted. Thus, digital information is extracted from the output voltage of the LLC converter, enabling demodulation on the load side of the charging system.

[0025] In S2, the signal under test in coherent demodulation The expression is:

[0026]

[0027] in, The signal to be measured, The amplitude of the signal to be measured. The phase of the signal to be measured. ω is the angular frequency of the signal to be measured.

[0028] In S3, the signal under test in coherent demodulation The low-pass filtering process after multiplying a sine wave with the same frequency as the signal under test but with a 90° phase difference is as follows:

[0029]

[0030] in, , The component of a sine wave with the same frequency as the signal under test but with a 90° phase difference.

[0031] The bandpass filter is an FIR bandpass filter.

[0032] In S1, the voltage transmitted from the LLC resonant converter contains small-amplitude high-frequency fluctuations and carries digital information.

[0033] On the other hand, the present invention discloses a demodulation system for implementing a load-side demodulation method such as that of an LLC resonant converter. The demodulation system includes an ADC sampling module, an orthogonal decomposition and integration module, an amplitude and phase decision module, and a data criterion module disposed in a microprocessor. The ADC sampling module is used to sample the output voltage. The orthogonal decomposition and integration module is used to decompose the target signal into orthogonal components and to perform integration and accumulation. The amplitude and phase decision module is used to calculate the amplitude and phase. The data criterion module is used to parse digital information based on the changes in amplitude and phase.

[0034] The microprocessor is a TMS320F28035 microcontroller. Attached Figure Description

[0035] Figure 1 This is a control block diagram of the present invention;

[0036] Figure 2 This is a schematic diagram of a traditional split-phase code waveform;

[0037] Figure 3 This is a schematic diagram of a frequency-symmetric split-term code;

[0038] Figure 4 This is a block diagram of a two-stage charging system with power-data multiplexing modulation;

[0039] Figure 5 This is the main topology diagram of the LLC converter;

[0040] Figure 6 This is a schematic diagram of information modulation on the LLC converter side;

[0041] Figure 7 This is a schematic diagram of load-side information demodulation;

[0042] Figure 8 This is a schematic diagram of the power control loop;

[0043] Figure 9 This is a waveform test diagram when the load side receives random digital signals. Detailed Implementation

[0044] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0045] like Figures 1 to 9As shown, a two-stage charging system with power-data multiplexing modulation (PFC+LLC) can be represented as follows: Figure 4 This invention relates to the transmission of electrical energy and information between an LLC converter and a load. Both power and data are unidirectional, transmitted only from the LLC converter to the load. Therefore, the LLC converter is equipped with modulation functionality; in the solution provided by this invention, the load needs to be equipped with demodulation functionality.

[0046] The load receives electrical energy from the LLC converter and demodulates the digital information contained within the small fluctuations in the output voltage. To illustrate this demodulation process simply, we can first introduce coherent demodulation.

[0047] The signal is first passed through a bandpass filter to remove noise. Assuming the signal under test after passing through the bandpass filter (BPF) is a single-frequency signal, its expression is:

[0048]

[0049] Then, by multiplying the signal with a set of sine waves whose amplitude and phase are known, and which have the same frequency as the signal under test but are 90° out of phase, we can obtain:

[0050]

[0051] Next, by performing low-pass filtering on the signals in the above formula and retaining only the DC component, we can obtain:

[0052]

[0053] The signal is input to the amplitude and phase angle calculation module, and the amplitude and phase angle of the signal can be obtained by the following formula.

[0054]

[0055] After the amplitude and phase angle calculation module outputs the calculation results to the digital signal decision module, the digital signal corresponding to the amplitude, phase angle and frequency can be determined, and the information extraction can be completed.

[0056] In order to achieve the digitization process, or in other words, in order to perform the above-mentioned calculation process using a microprocessor such as a DSP, it is necessary to use the relevant steps of this invention to perform discretized coherent demodulation.

[0057] This invention provides a demodulation method for the load side of an LLC resonant converter, comprising the following steps:

[0058] S1. The load receives the voltage transmitted from the LLC resonant converter, and then the out-of-band noise is filtered out by the bandpass filter.

[0059] S2. The analog-to-digital converter converts the bandpass-filtered carrier signal into a discrete sampling sequence, setting the signal to be measured. The expression for the sampling sequence is:

[0060]

[0061] in, Let A be the signal to be measured, ω be the amplitude, and ω be the angular frequency. It is a non-zero natural number. The sampling angular frequency of the analog-to-digital converter. The Nyquist sampling theorem must be satisfied: ;

[0062] S3, the signal to be measured With a set of amplitudes and phases known, and with the signal to be measured When multiplying sine waves of the same frequency but 90° out of phase, the integration process of the following formula can be used to replace the low-pass filtering process after signal multiplication in coherent demodulation:

[0063]

[0064] in, For the integration period, The value is an integer multiple of the period of the signal under test, that is:

[0065]

[0066] in, For the modulo operation, ω is the angular frequency;

[0067] S4. Since the signal under test is converted into a discrete sequence after sampling, the sinusoidal signal multiplied by it during integration is converted into a sinusoidal sequence obtained from the same sampling frequency. The integration process can be transformed into an accumulation process using the following formula:

[0068]

[0069] in, The integral period is ω, and the angular frequency is ω. , , where is the component of the signal to be measured;

[0070] S5. Use the following formula to obtain the amplitude of the discrete signal. and phase ,Right now:

[0071]

[0072] in, The target signal amplitude, The phase of the target signal;

[0073] S6. By analyzing the frequency and amplitude of the target signal With phase The amplitude, phase angle and frequency change sequence are obtained, and the corresponding symbol information is output, thereby demodulating digital information from the output voltage of the LLC converter.

[0074] As described above, the signal first passes through a bandpass filter to remove noise. The resulting signal is then multiplied by a set of sine waves with known amplitude and phase, exhibiting the same frequency as the signal under test but with a 90° phase difference. The signals are then low-pass filtered, retaining only the DC component. The amplitude and phase angle of the remaining signal are then calculated. Information extraction is performed based on the digital signals corresponding to the amplitude, phase angle, and frequency. The load receives electrical energy from the LLC converter and demodulates the digital information embedded in the small fluctuations of the output voltage. By analyzing the frequency, amplitude, and phase of these components and obtaining their variation sequence, the information can be extracted. Thus, digital information is extracted from the output voltage of the LLC converter, enabling demodulation on the load side of the charging system.

[0075] The bandpass filter is an FIR bandpass filter.

[0076] In S1, the voltage transmitted from the LLC resonant converter contains small-amplitude high-frequency fluctuations and carries digital information.

[0077] On the other hand, the present invention discloses a demodulation system for implementing a load-side demodulation method such as that of an LLC resonant converter. The demodulation system includes an ADC sampling module, an orthogonal decomposition and integration module, an amplitude and phase decision module, and a data criterion module disposed in a microprocessor. The ADC sampling module is used to sample the output voltage. The orthogonal decomposition and integration module is used to decompose the target signal into orthogonal components and to perform integration and accumulation. The amplitude and phase decision module is used to calculate the amplitude and phase. The data criterion module is used to parse digital information based on the changes in amplitude and phase.

[0078] The microprocessor is a TMS320F28035 microcontroller.

[0079] In this embodiment, the switching network of the front-end LLC converter uses a frequency-symmetric split-phase code for encoding. However, its output level is still DC. This frequency-symmetric variation information becomes a small-amplitude fluctuation component in the output voltage due to the frequency-gain characteristic of the LLC resonant converter. Therefore, by analyzing the frequency, amplitude, and phase of these components and obtaining their variation sequence, information can be extracted. This allows for the extraction of digital information from the LLC converter's output voltage, achieving demodulation.

[0080] On the other hand, the present invention also includes a demodulation system for a load-side demodulation method applied to an LLC resonant converter. The system includes an ADC sampling module, an orthogonal decomposition and integration module, an amplitude and phase decision module, and a data criterion module. The ADC sampling module includes a microprocessor and an LLC converter. The microprocessor is a TMS320F28035. In this embodiment, the present invention obtains the frequency, amplitude, and phase of the signal under test through discretized coherent demodulation, thereby extracting information. Figure 3 As shown, the data criterion module is used to identify code A and code B in the encoded information from the LCC resonant converter side. The LCC resonant converter side encoding is a frequency-symmetric split-phase code. This frequency-symmetric split-phase code expresses different code elements, namely code A and code B, through frequency jumps, expressed in different frequency difference orders. The two code elements are at the target frequency. Based on different methods of change And so it is constructed. Here, symbol A is first constructed with a frequency of [frequency value missing] in the first half of the cycle. The frequency in the second half of the cycle is Symbol B has a frequency of [missing value] in the first half of the cycle. The frequency in the second half of the cycle is This encoding method is a symmetrical frequency hopping method that incorporates phase shift delay. It has both frequency and phase shift parameters, so it is essentially a quaternion encoding method, but it only represents a single binary number.

[0081] In this embodiment, the converter load-side demodulation process of the present invention is as follows:

[0082] The code for the ADC sampling module is as follows:

[0083] #include "DSP28x_Project.h"

[0084] #define SAMPLE_BUFFER_SIZE 256

[0085] Uint16 adcBuffer[SAMPLE_BUFFER_SIZE];

[0086] Uint16 bufferIndex = 0;

[0087] Uint16 flag_adc_buffer_full = 0;

[0088] / / ADC interrupt service routine

[0089] interrupt void adc_isr(void) {

[0090] adcBuffer[bufferIndex++] = AdcResult.ADCRESULT0; / / Assuming channel 0 is used

[0091] if (bufferIndex>= SAMPLE_BUFFER_SIZE) {

[0092] bufferIndex = 0;

[0093] flag_adc_buffer_full = 1; / / Buffer full flag

[0094] }

[0095] AdcRegs.ADCTRL2.bit.SOC_SEQ1 = 1; / / Continue to the next sampling

[0096] }

[0097] Design an FIR bandpass filter with a center frequency of f0 and a bandwidth of BW:

[0098] #define BPF_TAP_NUM 32

[0099] float bpf_coeff[BPF_TAP_NUM]; / / Pre-designed filter coefficients

[0100] float bpf_buffer[BPF_TAP_NUM];

[0101] void initBPF(float f0, float fs, int num_taps);

[0102] float applyBPF(float input);

[0103] / / Example usage (in the main loop)

[0104] if (flag_adc_buffer_full) {

[0105] for (int i = 0; i <SAMPLE_BUFFER_SIZE; i++) {

[0106] float filtered = applyBPF((float)adcBuffer[i]);

[0107] / / Follow-up processing

[0108] }

[0109] }

[0110] The code for the orthogonal decomposition and integration module is as follows:

[0111] #include<math.h>

[0112] #define INTEGRATION_SAMPLES 64 / / Integration window length

[0113] float s_cos_d = 0.0;

[0114] float s_sin_d = 0.0;

[0115] float local_oscillator_freq = 50000.0; / / Local oscillator frequency

[0116] float sample_rate = 100000.0; / / Sampling rate

[0117] void integrateOrthogonal(float *input, int size) {

[0118] s_cos_d = 0.0;

[0119] s_sin_d = 0.0;

[0120] for (int i = 0; i <size&&i<INTEGRATION_SAMPLES; i++) {

[0121] float t = i / sample_rate;

[0122] float cos_val = cosf(2 * M_PI * local_oscillator_freq * t);

[0123] float sin_val = sinf(2 * M_PI * local_oscillator_freq * t);

[0124] s_cos_d += input[i] * sin_val;

[0125] s_sin_d += input[i] * cos_val;

[0126] }

[0127] }

[0128] The code for the amplitude and phase decision module is as follows:

[0129] float amplitude;

[0130] float phase;

[0131] void computeAmplitudeAndPhase() {

[0132] amplitude = 2.0 * sqrtf(s_cos_d * s_cos_d + s_sin_d * s_sin_d);

[0133] phase = atan2f(s_sin_d, s_cos_d);

[0134] }

[0135] The code for the data criterion module used to identify code elements A / B is as follows:

[0136] typedef enum {

[0137] CODE_A,

[0138] CODE_B,

[0139] CODE_UNKNOWN

[0140] CodeType;

[0141] CodeType decodeSymbol(float current_phase, float previous_phase) {

[0142] float delta_phase = current_phase - previous_phase;

[0143] if (delta_phase>0) {

[0144] return CODE_A; / / High frequency first, then low frequency

[0145] } else if (delta_phase<0) {

[0146] return CODE_B; / / Low frequencies first, then high frequencies

[0147] } else {

[0148] return CODE_UNKNOWN;

[0149] }

[0150] }

[0151] uint16 decodeBit(CodeType code) {

[0152] switch (code) {

[0153] case CODE_A:

[0154] return 0;

[0155] case CODE_B:

[0156] return 1;

[0157] default:

[0158] return 0xFF; / / Error code

[0159] }

[0160] }

[0161] The configuration diagram of the Simulink simulation environment is as follows: Figures 5-8 As shown. Figure 5 As shown, the main topology diagram of the LLC converter is the upper-level schematic diagram of an embodiment of the present invention. The device parameters, resonant cavity parameters, and operating conditions can be modified here. For example... Figure 6 As shown, this simulation model represents the PWM modulation section of an LLC converter. It illustrates the process of PFM (Pulse Frequency Modulation) combining the count value and the number of cycles. The modulated signal, after processing the count value and the number of cycles, is used to modulate the digital signal into the LLC resonant converter. Figure 7 As shown, the sampled analog-to-digital converter (ADC) is used to set the power loop through the digitization process of demand voltage and current. The digitization process of demand current and voltage involves the sampled ADC acquiring analog quantities from each node and converting them into digital quantities. The sampled ADC is then used to demodulate load-side information, such as... Figure 8 The power control loop module shown adopts a classic inner and outer loop structure. In this power control loop module, the outer loop is used for voltage control, while the inner loop is used for current control.

[0162] like Figure 9As shown, CH1 is the gate signal, CH2 is the output voltage ripple, CH3 is the transmitted digital signal, CH4 is the received digital signal, and CH5 is the spectrum of the output voltage ripple. It can be seen that all digital signals are correctly transmitted and received.

[0163] This invention innovatively combines information modulation with power conversion, demodulating information on the load side during power transmission to obtain data information embedded in the main power path.

[0164] Figure 4 This is a block diagram of a two-stage charging system with PFC+LLC featuring power-data multiplexing modulation. It mainly includes information modulation on the LLC converter module side and demodulation on the load side. This invention is applied to the transmission of power and information between the LLC converter and the load. In this power system, both power and data are unidirectional, only transmitted from the LLC converter to the load. Therefore, the LLC converter is equipped with modulation functionality. However, the main solution of this invention is to integrate demodulation functionality on the load, thereby achieving synchronous transmission of information and power between the LLC converter and the load.

[0165] This invention utilizes the output voltage or current waveform changes during the power transmission process of an LLC converter to embed the required data information, achieving synchronous energy transmission and data communication within the same physical channel. This eliminates the need for separate communication links and related hardware modules, effectively simplifying the system structure and improving overall integration. By directly modulating the power waveform, this invention embeds information interaction entirely within the main power path, eliminating the need for any physical connections between high and low voltage circuits. This fundamentally avoids reliance on isolation devices, improving system safety and long-term operational stability. By modulating information onto the main power waveform for transmission, this invention eliminates the need for additional communication lines, effectively avoiding external electromagnetic interference and significantly improving communication stability. Finally, this invention achieves information transmission through controllable small-amplitude modulation of the output voltage or current. The modulation depth can be precisely controlled, without disrupting the original soft-switching characteristics of the LLC converter or affecting its power conversion efficiency.

[0166] Finally, it should be emphasized that the above description is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A demodulation method for the load side of an LLC resonant converter, characterized in that, The method includes the following steps: S1. The load receives the voltage transmitted from the LLC resonant converter, and then the out-of-band noise is filtered out by the bandpass filter. S2. The analog-to-digital converter converts the carrier signal after bandpass filtering into a discrete sampling sequence, setting the signal to be measured. The expression for the sampling sequence is: ， in, Let A be the signal to be measured, ω be the amplitude, and ω be the angular frequency. It is a non-zero natural number. The sampling angular frequency of the analog-to-digital converter. The Nyquist sampling theorem must be satisfied: ; S3, the signal to be measured With a set of amplitudes and phases known, and with the signal to be measured When multiplying sine waves of the same frequency but 90° out of phase, the integration process of the following formula can be used to replace the low-pass filtering process after signal multiplication in coherent demodulation: ， in, For the integration period, The value is an integer multiple of the period of the signal under test, that is: ， in, For the modulo operation, ω is the angular frequency; S4. Since the signal under test is converted into a discrete sequence after sampling, the sinusoidal signal multiplied by it during integration is converted into a sinusoidal sequence obtained from the same sampling frequency. The integration process can be transformed into an accumulation process using the following formula: ， in, Let ω be the integral period and ω be the angular frequency. , , where is the component of the signal to be measured; S5. Use the following formula to find the amplitude of the discrete signal. and phase ,Right now: ， in, The target signal amplitude, The phase of the target signal; S6. By analyzing the frequency and amplitude of the target signal With phase The amplitude, phase angle and frequency change sequence are obtained, and the corresponding symbol information is output, thereby demodulating digital information from the output voltage of the LLC converter.

2. The demodulation method for the load side of an LLC resonant converter according to claim 1, characterized in that: In S2, the signal under test in coherent demodulation The expression is: ， in, The signal to be measured, The amplitude of the signal to be measured. The phase of the signal to be measured. ω is the angular frequency of the signal to be measured.

3. The demodulation method for the load side of an LLC resonant converter according to claim 1, characterized in that: In S3, the signal under test in coherent demodulation The low-pass filtering process after multiplying a sine wave with the same frequency as the signal under test but with a 90° phase difference is as follows: ， in, , The component of a sine wave with the same frequency as the signal under test but with a 90° phase difference.

4. The demodulation method for the load side of an LLC resonant converter according to claim 1, characterized in that: The bandpass filter is an FIR bandpass filter.

5. The demodulation method for the load side of an LLC resonant converter according to claim 1, characterized in that: In S1, the voltage transmitted from the LLC resonant converter contains small-amplitude high-frequency fluctuations and carries digital information.

6. A demodulation system implementing the demodulation method for the load side of an LLC resonant converter as described in claim 1, characterized in that: The demodulation system includes an ADC sampling module, an orthogonal decomposition and integration module, an amplitude and phase decision module, and a data criterion module, all housed within a microprocessor. The ADC sampling module is used to sample the output voltage. The orthogonal decomposition and integration module is used to decompose the target signal into orthogonal components and to perform integration and accumulation. The amplitude and phase decision module is used to calculate the amplitude and phase. The data criterion module is used to analyze digital information based on changes in amplitude and phase.

7. The demodulation system according to claim 6, characterized in that: The microprocessor is a TMS320F28035 microcontroller.

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