Electromagnetic interference suppression circuit based on chaotic mapping and PFM switching power supply

Abstract

The invention relates to the technical field of electromagnetic interference suppression, and discloses an electromagnetic interference suppression circuit based on chaotic mapping and a PFM switching power supply, and the circuit comprises a chaotic generation circuit and a chaotic signal modulation circuit. The chaotic generation circuit comprises a digital signal generation circuit, a digital-to-analog conversion circuit and an analog signal processing circuit which are connected in sequence; the chaotic signal modulation circuit comprises a voltage comparison module, and a voltage modulation module, an RS trigger module and an integral module which are connected with the voltage comparison module, the RS trigger module is connected with the integral module, the RS trigger module and the voltage comparison module are both connected with the switching power supply, and the voltage modulation module is connected with the analog signal processing circuit. According to the invention, chaos and aperiodicity of the switching frequency are realized by introducing the chaos signal, the frequency spectrum energy is dispersed, the harmonic interference amplitude is obviously reduced, the frequency spectrum distribution is more uniform, the electromagnetic compatibility of the switching power supply is effectively improved, and the electromagnetic interference of the switching power supply is inhibited.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic interference suppression, and particularly to an electromagnetic interference suppression circuit and a PFM switching power supply based on chaotic mapping. Background Art

[0002] In the application of switching power supplies, the problem of electromagnetic interference has always been an important challenge in design and application. The switching power supply generates high-frequency noise by switching high-frequency switching elements between on and off. The main sources of electromagnetic interference include switching transient interference and high-frequency noise during conduction and turn-off. Especially during the switching process, the sudden changes in current and voltage will cause the generation of electromagnetic waves. When the switching frequency is relatively high, these high-frequency noises may interfere with other devices and affect the normal operation of the devices. Due to the relatively high operating frequency of the switching power supply and the limited effectiveness of traditional power filters in dealing with these high-frequency signals, the problem of electromagnetic interference is particularly prominent. Therefore, how to effectively suppress the electromagnetic interference generated by switching power supplies has become a technical problem in the current field of power electronics.

[0003] To address this problem, chaotic spread spectrum technology has gradually been introduced into switching power supplies. The core principle of chaotic spread spectrum technology is to expand the switching frequency by using chaotic signals. By utilizing the broad-spectrum property of chaotic signals, the energy of electromagnetic interference is dispersed over a wider frequency band, thereby avoiding the concentration of energy in a specific frequency band and reducing interference to surrounding devices. Chaotic signals are generated by nonlinear dynamic systems, which have characteristics similar to random noise but are deterministic. Therefore, their power spectra are widely distributed in the frequency domain, avoiding spectral concentration. This enables chaotic signals to effectively disperse the spectrum of electromagnetic interference in switching power supplies, thus achieving more effective electromagnetic interference suppression.

[0004] However, the current applications of chaotic spread spectrum technology mostly focus on PWM (pulse width modulation) switching power supplies. In PWM switching power supplies, chaotic spread spectrum technology can apply chaotic signals to the switching frequency through frequency modulation, enabling the electromagnetic interference to be distributed over a wider frequency band, thereby reducing interference to other devices. However, for PFM (pulse frequency modulation) switching power supplies, the situation is much more complex. The frequency changes greatly during the transient process of PFM switching power supplies, and the variation range of the modulation signal is very wide. Therefore, the existing chaotic spread spectrum technology cannot be directly applied to PFM switching power supplies. Currently, the frequency regulation of PFM switching power supplies usually adopts frequency hopping technology, but its modulation method lacks sufficient chaos and ergodicity, resulting in the high concentration of harmonic energy in a specific frequency band. Moreover, the existing frequency hopping circuits are relatively complex and have limited effectiveness in electromagnetic interference suppression. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides an electromagnetic interference suppression circuit and a PFM switching power supply based on chaotic mapping, so as to solve the problems of concentrated spectral energy, too high harmonic peaks, and strong electromagnetic interference in traditional modulation circuits, and achieve the effect of improving the electromagnetic compatibility of the system.

[0006] In a first aspect, the present invention provides an electromagnetic interference suppression circuit based on chaotic mapping. The electromagnetic interference suppression circuit is applied to a switching power supply and includes:

[0007] a chaotic generation circuit and a chaotic signal modulation circuit;

[0008] The chaotic generation circuit includes a digital signal generation circuit, a digital-to-analog conversion circuit, and an analog signal processing circuit connected in sequence;

[0009] The chaotic signal modulation circuit includes a voltage comparison module, a voltage modulation module, an RS trigger module, and an integration module connected to the voltage comparison module. The RS trigger module is connected to the integration module. Both the RS trigger module and the voltage comparison module are connected to the switching power supply. The voltage modulation module is connected to the analog signal processing circuit;

[0010] Among them, the digital signal generation circuit is used to generate an improved digital chaotic signal. The digital-to-analog conversion circuit is used to perform digital-to-analog conversion on the improved digital chaotic signal. The analog signal processing circuit is used to amplify and adjust the converted initial analog chaotic signal to obtain an analog chaotic signal and output it to the voltage modulation module;

[0011] The voltage comparison module is used to receive the output voltage of the switching power supply, generate a trigger pulse, and output it to the RS trigger module;

[0012] The RS trigger module is used to generate a first trigger signal and a second trigger signal according to the trigger pulse, output the first trigger signal to the switching power supply to trigger the switch tube of the switching power supply to conduct, and output the second trigger signal to the integration module;

[0013] The integration module is used to integrate the voltage signal according to the second trigger signal and output the integrated voltage to the voltage comparison module;

[0014] The voltage modulation module is used to generate a chaotic modulation voltage according to the analog chaotic signal and output it to the voltage comparison module;

[0015] The voltage comparison module is further used to generate a set signal according to the integrated voltage and the chaotic modulation voltage and output it to the RS trigger module to set the RS trigger module, realizing dynamic control of the turn-off moment of the switch tube.

[0016] Further, the digital signal generation circuit generates an improved digital chaotic signal by using the following mapping formula:

[0017]

[0018] where y n represents the chaotic sequence value of the nth iteration, a represents the range scaling parameter, and ρ represents the control parameter.

[0019] Further, the voltage comparison module includes a first comparator and a second comparator;

[0020] The first comparator is respectively connected to the switching power supply and the RS trigger module, and is used for receiving the output voltage of the switching power supply and a preset reference voltage, and outputting a trigger pulse to the RS trigger module;

[0021] The second comparator is connected to the integration module, the voltage modulation module and the RS trigger module, and is used for receiving the integration voltage and the chaotic modulation voltage, and outputting a set signal to the RS trigger module.

[0022] Further, the integration module includes a detection circuit and an integrator. The detection circuit is connected to the RS trigger module, and the integrator is respectively connected to the detection circuit and the second comparator;

[0023] The detection circuit is used for receiving the second trigger signal and outputting a voltage signal to the integrator;

[0024] The integrator is used for receiving the voltage signal and outputting an integration voltage to the second comparator.

[0025] Further, the detection circuit includes a first DC voltage source, a first detection resistor and a first auxiliary switch. After the first DC voltage source is connected to the first detection resistor through the first auxiliary switch, it is connected to the integrator;

[0026] The first auxiliary switch is connected to the RS trigger module.

[0027] Further, the voltage modulation module is used for superimposing the analog chaotic signal and the DC voltage to generate a chaotic modulation voltage.

[0028] Further, the RS trigger module is composed of two NOR gates.

[0029] Further, the analog signal processing circuit includes two-stage operational amplifiers and a resistor network;

[0030] Among them, the first operational amplifier is used to amplify the amplitude of the converted initial analog chaotic signal, and the second operational amplifier and the resistor network are used to adjust the mean value and range of the signal output by the first operational amplifier to obtain an analog chaotic signal.

[0031] In a second aspect, the present invention provides a PFM switching power supply, including a buck transformer module and the electromagnetic interference suppression circuit as described above, and the buck transformer module is connected to the electromagnetic interference suppression circuit.

[0032] Further, the switching transistor of the buck transformer module is connected to the RS trigger module through a second auxiliary switch;

[0033] The second auxiliary switch is used to receive the first trigger signal to trigger the conduction of the switching transistor, and receive the set signal to trigger the turn-off of the switching transistor.

[0034] The present invention provides an electromagnetic interference suppression circuit and a PFM switching power supply based on chaotic mapping. By introducing a chaotic signal, the present invention realizes the chaos and aperiodicity of the switching frequency, can effectively disperse the spectral energy, reduce the amplitude of harmonic interference, make the spectral distribution more uniform, thereby effectively improving the electromagnetic compatibility of the switching power supply and suppressing the electromagnetic interference of the switching power supply. Description of the Drawings

[0035] Figure 1 is a schematic structural diagram of the electromagnetic interference suppression circuit based on chaotic mapping in an embodiment of the present invention;

[0036] Figure 2 is a schematic diagram showing the distribution of state variable values of the traditional Cubic chaotic mapping;

[0037] Figure 3 is the chaotic evolution diagram of the traditional Cubic chaotic mapping;

[0038] Figure 4 is a distribution diagram showing the change of the state variable value of the improved chaotic mapping with the number of iterations in an embodiment of the present invention;

[0039] Figure 5 is the chaotic evolution diagram of the improved chaotic mapping in an embodiment of the present invention;

[0040] Figure 6 is a schematic diagram of the state variable mapping sequence of the simplified improved chaotic mapping in an embodiment of the present invention;

[0041] Figure 7 is Figure 1 the schematic structural diagram of the chaotic generation circuit in

[0042] Figure 8 is Figure 1Schematic diagram of the Cubic iteration program in the chaotic generation circuit;

[0043] Figure 9 It is another structural schematic diagram of the electromagnetic interference suppression circuit based on chaotic mapping in the embodiment of the present invention;

[0044] Figure 10 It is a schematic diagram of the simulation waveform of the chaotic modulation voltage in the simulation experiment of the embodiment of the present invention;

[0045] Figure 11 It is a schematic diagram of the PWM modulation waveform of the switching tube in the traditional PWM modulation circuit;

[0046] Figure 12 It is Figure 11 Schematic diagram of the frequency domain analysis result of the PWM signal of the switching tube in;

[0047] Figure 13 It is a schematic diagram of the frequency domain analysis result of the output voltage of the traditional PWM modulation circuit;

[0048] Figure 14 It is a schematic diagram of the modulation waveform of the switching tube of the switching power supply in the embodiment of the present invention;

[0049] Figure 15 It is Figure 14 Schematic diagram of the frequency domain analysis result of the switching tube signal in;

[0050] Figure 16 It is a schematic diagram of the frequency domain analysis result of the output voltage of the switching power supply in the embodiment of the present invention;

[0051] Figure 17 It is a schematic diagram of the structure of the PFM switching power supply in the embodiment of the present invention. Detailed implementation manners

[0052] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0053] Please refer to Figure 1, an electromagnetic interference suppression circuit based on chaotic mapping proposed in the first embodiment of the present invention includes: a chaotic generation circuit 1 and a chaotic signal modulation circuit 2. Among them, the chaotic generation circuit 1 includes a digital signal generation circuit 11, a digital-to-analog conversion circuit 12, and an analog signal processing circuit 13 connected in sequence; the chaotic signal modulation circuit 2 includes a voltage comparison module 21, a voltage modulation module 22, an RS trigger module 23, and an integration module 24 connected to the voltage comparison module 21. The RS trigger module 23 and the integration module 24 are connected, and both the RS trigger module 23 and the voltage comparison module 21 are connected to the switching power supply 3, and the voltage modulation module 22 is connected to the analog signal processing circuit 13. The structures and functions of each circuit will be described in detail below.

[0054] Cubic chaotic mapping is a non-linear sequence generation method with strong chaos and broad-spectrum characteristics, having more complex non-linear dynamic characteristics, and being able to generate a richer spectrum distribution within a certain parameter range. In a PWM switching power supply, the chaotic spread spectrum technology can apply the chaotic signal to the switching frequency through frequency modulation, so that the electromagnetic interference is distributed in a wider frequency band, thereby reducing the interference to other devices. Among them, the mathematical expression of the traditional Cubic chaotic mapping is:

[0055]

[0056] In the formula, ρ is the control parameter; x n+1 is the (n + 1)-th iteration value; x n is the n-th iteration value.

[0057] Figure 2 shows the distribution of the state variable values of the traditional Cubic chaotic mapping. The horizontal axis represents the number of iterations, from 0 to 2000, representing each iteration of generating the chaotic sequence; the vertical axis represents the corresponding state variable value, and the value range is between (0, 1). From Figure 1 it can be observed that the distribution of the state variable values of the traditional Cubic chaotic mapping is relatively uniform, but is always limited to the interval (0, 1). This indicates that during the iterative process of the traditional Cubic chaotic mapping, the generated chaotic sequence can cover the entire interval (0, 1), but its distribution range fails to expand to a wider interval range, such as (-1, 1). In addition, the state variable values have a certain degree of chaos and irregularity, which is an embodiment of the chaotic characteristics. At the same time Figure 1It also reflects that when appropriate control parameters are selected (such as ρ = 2.595), the traditional Cubic chaotic map can generate chaotic sequences with better ergodicity. However, its defect is that the values are positively biased, that is, they are always positive, resulting in the mean deviating from zero. In the electromagnetic interference (EMI) suppression of PFM switching power supplies, a symmetric distribution is required. This deviation existing in the existing chaotic signals may introduce unnecessary DC components, thus affecting the modulation performance.

[0058] Figure 3 The chaotic evolution diagram of the traditional Cubic chaotic map is shown, which is used to reflect the dynamic behavior of the system and the distribution of its state variables under different control parameter ρ values. The horizontal axis represents the variation range of the control parameter ρ, and the vertical axis represents the corresponding state variable values. Figure 3 It can be seen that when the ρ value is small (ρ < 2.2), the behavior of the Cubic chaotic map shows periodicity, that is, the state variable tends to a fixed point with iteration or cycles between finite values, and the system is still in an ordered state. As the ρ value gradually increases to the critical point (ρ ≈ 2.2), the system enters the period-doubling bifurcation stage, and the bifurcation phenomenon is obvious, indicating that the state variable gradually becomes more complex, and the system transitions from an ordered state to a chaotic state. When the control parameter ρ exceeds 2.2, the system enters the fully chaotic region, and the distribution of the state variable shows irregularity and chaos, with a wider coverage range and higher density, indicating that the chaos and ergodicity of the system are enhanced. When ρ = 2.595, the state variable values are concentrated between (0, 1) and are densely and evenly distributed, indicating that the generated chaotic sequence has good ergodicity and dynamic characteristics at this time. This parameter value is usually used as the recommended value for generating traditional Cubic chaotic sequences. When the ρ value further increases to 2.61 and above, the distribution of the state variable of the Cubic chaotic map extends to the interval (-1, 1), and at the same time, the chaos and distribution complexity of the state are further improved. This characteristic is particularly suitable for application scenarios that require a symmetric distribution (such as a mean of 0). That is to say, when ρ = 2.595, the state values of the Cubic chaotic map are between (0, 1), and when ρ = 2.61, the state values of the Cubic chaotic map are between (-1, 1).

[0059] Therefore, by adjusting the control parameter ρ, chaotic signals with different distribution characteristics and dynamic characteristics can be flexibly generated, thus providing more efficient technical support for the electromagnetic interference (EMI) suppression of PFM switching power supplies.

[0060] In this embodiment, in order to obtain a chaotic sequence that can take values within any range in the interval (-1, 1) and whose mean is close to 0, it is necessary to transform the mathematical expression of the traditional Cubic chaotic map to obtain the transformed chaotic map formula:

[0061]

[0062] where y n represents the value of the chaotic sequence at the n-th iteration, a represents the range scaling parameter, and ρ represents the control parameter.

[0063] Through the above chaotic mapping formula, an improved Cubic chaotic mapping can be obtained. Figure 4 Figure 1 shows the distribution of the state variable values of the improved Cubic chaotic mapping in the present invention with respect to the number of iterations. Among them, the horizontal axis represents the number of iterations (or dimension), and the vertical axis represents the magnitude of the state variable values, with a value range of (-0.25, 0.25). Compared with the traditional Cubic chaotic mapping, through mathematical transformation in the present invention, the distribution center of the state variable values is symmetric and evenly covers the negative and positive value regions. The improved state variable values exhibit chaos and uniformity, and at the same time, their mean value is close to 0. This characteristic makes the chaotic signal suitable for scenarios that require symmetry and chaos, such as EMI suppression in PFM switching power supplies. The state values with chaotic distribution can effectively disperse the spectral energy and reduce the concentration and sharpness of electromagnetic interference.

[0064] Figure 5 Figure 2 shows the chaotic evolution diagram of the improved Cubic chaotic mapping in the present invention, reflecting the dynamic changes of the state variable values under different control parameters (ρ). Among them, the horizontal axis represents the value range of the control parameter ρ, and the vertical axis represents the state variable values of the chaotic mapping at the corresponding ρ value. Compared with the traditional Cubic chaotic mapping, when the value of ρ increases in the improved mapping, the distribution range of the state variable values expands from the traditional (0, 1) to the symmetric interval (-0.25, 0.25). When the value of ρ is small (ρ < 2.2), the system exhibits periodic behavior, and the state variable values cycle within a limited range; as the value of ρ increases, the system enters the chaotic state, and the state variable values show complex bifurcations and chaotic distributions. When the value of ρ approaches 2.61, the bifurcation phenomenon disappears, and the system completely enters the chaotic region, where the state variable values are densely distributed, showing higher chaos and dynamic adaptability. By adjusting the control parameter and the mapping formula, the present invention not only expands the value range of the state variable but also ensures the symmetry of the state values and the characteristic that the mean value is 0. This improvement makes the generated chaotic sequence more suitable for EMI suppression, can effectively reduce the concentration effect of sharp harmonic interference, disperse the interference energy, and improve the electromagnetic compatibility of the power supply.

[0065] Figure 6It shows the state variable mapping sequence of the improved simplified Cubic chaotic mapping in the present invention, which is used to illustrate the distribution characteristics of the state values generated by the improved Cubic chaotic mapping during the iteration process. Among them, the horizontal axis represents the number of iterations (from 1 to 5000), and the vertical axis represents the value of the state variable, with the value range being (-0.25, 0.25). Compared with the traditional Cubic chaotic mapping, the improved mapping optimizes the mathematical model and adjusts the control parameters, enabling the state variable to be chaotically distributed within the symmetric interval, while the mean value is close to 0. That is to say, the distribution of the state variable has good chaos and ergodicity throughout the interval. The state value is no longer limited to the positive value range (0, 1) of the traditional mapping, but evenly covers the negative and positive value regions. This characteristic of symmetric distribution not only eliminates the possible offset problem of the traditional Cubic mapping, but also enables the state variable to have higher dynamic adaptability, which is beneficial to applications in scenarios that require chaos and a mean value of 0.

[0066] The chaotic voltage with a mean value of 0 has advantages in the electromagnetic interference (EMI) suppression of PFM switching power supplies because the chaotic voltage with a mean value of 0 can make the energy of the electromagnetic interference signal evenly distributed in the frequency spectrum, avoiding concentration in a certain specific frequency band, thereby converting the sharp interference peak into a smooth continuous distribution, greatly reducing the harmonic interference intensity, and enhancing the electromagnetic compatibility. In addition, the chaotic voltage with a mean value of 0 can eliminate the influence of the DC offset on the system operating point, avoid power supply instability caused by the offset, and thus ensure the stable operation of the circuit under different load conditions. The chaotic voltage with a mean value of 0 ensures that the modulation signal maintains symmetry within the positive and negative ranges, avoiding problems such as uneven duty cycle distribution or modulation imbalance. This symmetry optimizes the steady-state performance of the power supply and improves the accuracy of the output voltage. At the same time, the chaotic signal with a mean value of 0 is more evenly distributed in the frequency spectrum, with stronger ergodicity and chaos, making the change of the switching frequency more complex and unpredictable, thereby effectively suppressing the periodic characteristics of EMI and further enhancing the interference dispersion effect. In addition, the chaotic voltage with a mean value of 0 is more friendly to the load, avoiding the DC bias and performance degradation problems that non-zero mean signals may introduce to the load, especially in precision electronic devices, which can improve the reliability of the system. From the perspective of energy efficiency, the chaotic voltage with a mean value of 0 makes the power supply work more efficiently by reducing unnecessary energy losses caused by DC bias and distortion. At the same time, its good dynamic adaptability ensures efficient operation during the power modulation process. More importantly, the chaotic voltage with a mean value of 0 can reduce the influence of high-frequency interference on surrounding devices, meet more stringent electromagnetic compatibility (EMC) requirements, and make the system more likely to pass strict EMC tests. This characteristic is particularly crucial in application scenarios sensitive to electromagnetic interference (such as medical devices, communication systems, etc.).

[0067] Based on the above improved chaotic signal, the present invention designs a chaotic generation circuit 1 in the electromagnetic interference suppression circuit to generate an improved analog chaotic signal. Among them, the chaotic generation circuit 1 includes a digital signal generation circuit 11, a digital-to-analog conversion circuit 12, and an analog signal processing circuit 13 connected in sequence. The digital signal generation circuit 11 is used to generate an improved digital chaotic signal. The digital-to-analog conversion circuit 12 is used to perform digital-to-analog conversion on the improved digital chaotic signal to obtain an initial analog chaotic signal. The analog signal processing circuit 13 is used to amplify and adjust the converted initial analog chaotic signal, and finally obtain an analog chaotic signal that meets the dynamic range and zero-mean requirements of electromagnetic interference suppression. In this embodiment, the main difference between the chaotic generation circuit 1 and the conventional circuit for generating chaotic signals for electromagnetic interference suppression is that the chaotic mapping formula used when generating the chaotic signal is different. Through the above-converted mapping formula and taking ρ as 2.61, a chaotic signal with symmetric state distribution and a mean value of 0 is obtained.

[0068] Please refer to Figure 7 , in a preferred embodiment, the digital signal generation circuit 11 includes an AT89C51 single-chip microcomputer, a clock crystal oscillator (Y1), a first capacitor (C1), a second capacitor (C2), a third capacitor (C3), and a DC power supply (VCC); the digital-to-analog conversion circuit 12 includes a DAC0832 chip; the analog signal processing circuit 13 is composed of two-stage operational amplifiers and a resistor network.

[0069] Specifically, the positive terminal of the first capacitor (C1) is connected to the EA terminal of the AT89C51 single-chip microcomputer; the positive terminal of the first capacitor (C1) is connected to the DC power supply (VCC); the negative terminal of the first capacitor (C1) is connected to the RESET terminal of the AT89C51 single-chip microcomputer; one end of the clock crystal oscillator (Y1) is connected to the second capacitor (C2) and then grounded, and the other end of the clock crystal oscillator is connected to the third capacitor (C3) and then grounded; both ends of the clock crystal oscillator (Y1) are respectively connected to the X1 terminal and the X2 terminal of the AT89C51 single-chip microcomputer.

[0070] Both ends of the clock crystal oscillator (Y1) are grounded through the second capacitor (C2) and the third capacitor (C3) respectively, and are simultaneously connected to the X1 and X2 pins of the AT89C51 to provide a working clock for the single-chip microcomputer. The positive electrode of the first capacitor (C1) is connected to the EA pin and the DC power supply of the AT89C51, and the negative electrode is connected to the RESET pin for the initialization of the single-chip microcomputer. The P0.0 to P0.7 ports of the AT89C51 single-chip microcomputer correspond one-to-one to the D0-D7 data pins of the DAC0832 chip, and are used to send the low 8-bit digital signals of the chaotic sequence.

[0071] The digital signal generation circuit 11 burns the Cubic iteration program in the AT89C51 single-chip microcomputer. After the AT89C51 single-chip microcomputer is powered on, it can execute according to the Cubic iteration program, thereby outputting a Cubic digital chaotic signal, that is, an improved digital chaotic signal. The flow of the Cubic iteration program is as Figure 8 shown, including:

[0072] ① Program initialization and interrupt closing

[0073] The program starts from closing the interrupt. The purpose is to ensure that it will not be interfered by other interrupts during the calculation of the chaotic sequence and protect the execution integrity of the program.

[0074] ② Protect the values of registers

[0075] When performing the protection operation, the data values in the current registers will be saved to ensure that the original data will not be overwritten in subsequent operations. For an embedded system, the saving of register values is particularly important because the previous state needs to be restored after the interrupt returns.

[0076] ③ Initialize port P0.7 to 1

[0077] Port P0.7 is set to 1. This is a flag bit used to control a specific function of the system. Here it indicates the start of the calculation process of the chaotic sequence.

[0078] ④ Calculate the chaotic sequence according to the Cubic mapping formula

[0079] This is the core part of the program. According to the formula obtained in the first aspect above:

[0080]

[0081] It should be noted that y n refers to the current chaotic sequence value; y n+1 refers to the next chaotic sequence value. α is the range scaling parameter of the sequence, used to control the value range of the chaotic sequence, and takes 0.2 in this program; ρ refers to the control parameter of the chaotic sequence, and takes ρ = 2.61 in this program.

[0082] The program performs iterative calculations according to this formula, that is, inputs the current value y n , and outputs the next chaotic value y n+1 . The initial value y0 = 0.3, and the iterative values are calculated. The clock of the single-chip microcomputer is provided by a 24MHz crystal oscillator, and the stability and accuracy of the iterative operation are guaranteed by the high-precision clock signal. The lower 8 bits of the chaotic signal are output to the digital-to-analog conversion circuit 12 through port P0 to complete the transmission of the digital signal.

[0083] ⑤ Extract the lower eight bits and output them to port P0

[0084] In a microcontroller, the bit width of registers is usually limited (such as 8 bits or 16 bits). Therefore, in order to convert the chaotic value y n+1 into a controllable output value, its lower 8 bits need to be extracted and output to port P0. This process will lose the high-order information, but due to the chaotic nature of the chaotic signal, its lower 8 bits can still retain the chaotic characteristics.

[0085] ⑥ Set the timing constant

[0086] Set y n+1 as the new timing constant for subsequent D / A conversion. The timing constant can control the output frequency of the digital signal and indirectly affect the sampling rate of the chaotic signal.

[0087] ⑦ D / A conversion

[0088] Through D / A conversion, the digital chaotic sequence is converted into an analog signal. For the actual EMI suppression scenario, this analog signal is used to modulate the frequency of the switching power supply.

[0089] ⑧ Restore port P0.7

[0090] Set port P0.7 to 1, which is a flag to end this calculation process, indicating that the system has completed the update of the chaotic sequence.

[0091] ⑨ Enable the interrupt and return

[0092] Enabling the interrupt allows other system tasks to continue running, and the program returns to the main function to prepare for the next iteration calculation of the chaotic sequence.

[0093] ⑩ Final output

[0094] The final output of the AT89C51 single-chip microcomputer is the improved Cubic chaotic digital sequence.

[0095] In this embodiment, the core of the digital-to-analog conversion circuit 12 is the DAC0832 chip. Among them, the D0 terminal of the DAC0832 chip (that is, D0.0~D0.7 of the DAC0832 chip) is connected to the P0 terminal of the AT89C51 single-chip microcomputer (that is, D0.0~D0.7 of the AT89C51 single-chip microcomputer) to receive the Cubic digital chaotic signal output by the AT89C51 single-chip microcomputer; the DC power supply (VCC) is connected to the LE terminal, Vref terminal and Vcc terminal of the DAC0832 chip; the Xfsr terminal and CS terminal of the DAC0832 chip are grounded (GND); the WR1 terminal and WR2 terminal of the DAC0832 chip are connected to the WR terminal of the AT89C51 single-chip microcomputer.

[0096] Based on the above circuit structure, the DAC0832 chip receives an 8-bit Cubic chaotic digital signal from the AT89C51 through the D0-D7 data pins. The WR1 and WR2 pins are connected to the WR pin of the single-chip microcomputer to initiate data conversion. The LE and Xfsr pins are grounded respectively to ensure conversion stability. The Vref is connected to a DC power supply to set the reference voltage. The Vcc is connected to a DC power supply to provide the working voltage. Thus, a corresponding analog voltage signal is generated according to the set reference voltage Vref and working voltage Vcc.

[0097] In a preferred embodiment of the present invention, the signal processing circuit 13 is used to process the Cubic analog chaotic signal output by the DAC0832 chip, including a first operational amplifier ( Figure 7 the LM324 on the left), a second operational amplifier ( Figure 7 the LM324 on the right), a first resistor (R1), a second resistor (R2), a third resistor (R3), a fourth resistor (R4), a fifth resistor (R5), a sixth resistor (R6) and a DC power supply (VCC). It should be noted here that the DC power supplies in the digital signal generation circuit 11, the digital-to-analog conversion circuit 12 and the analog signal processing circuit 13 are the same DC power supply.

[0098] Specifically, the 3 terminals of the first operational amplifier and the second operational amplifier are connected to the DC power supply; the positive terminal and the negative terminal of the first operational amplifier are respectively connected to the Out1 terminal and the Out2 terminal of the DAC0832 chip, and the Out2 terminal and the 4 terminal of the first operational amplifier are grounded; the output terminal of the first operational amplifier is connected to the Rb terminal of the DAC0832 chip; the output terminal of the first operational amplifier is connected to the first resistor, and the first resistor is connected to the fourth resistor and grounded; the first resistor and the fourth resistor are respectively connected to the second resistor and connected to the positive terminal of the second operational amplifier; the positive terminal of the second operational amplifier is connected to the third resistor and connected to the output terminal of the second operational amplifier; the negative terminal of the second operational amplifier is respectively connected to the fifth resistor and the sixth resistor and grounded, and the 4 terminal of the second operational amplifier is grounded.

[0099] Based on the above circuit structure, the positive input terminal of the first operational amplifier is connected to the Out1 pin of the DAC0832, and the negative input terminal is connected to the Out2 pin and ground. The output of the first operational amplifier is connected to the feedback resistor Rb and transmitted to the positive input terminal of the second operational amplifier. The negative input terminal of the second operational amplifier is connected to the fifth resistor and the sixth resistor to set the gain. The output terminal of the second operational amplifier outputs the processed Cubic analog chaotic signal, and the amplitude range of the final signal is (-0.2V, 0.2V).

[0100] In this embodiment, the primary signal is amplified in amplitude by the first operational amplifier, and the signal mean value and range are adjusted by the second operational amplifier in combination with a resistor network to ensure that the output signal meets the requirements of the dynamic range and zero mean value. The output Cubic chaotic analog signal is the chaotic signal required for the switching power supply of the present invention to suppress EMI.

[0101] To achieve electromagnetic interference suppression, the present invention further modulates the chaotic signal generated by the chaotic generation circuit 1 through the chaotic signal modulation circuit 2, and dynamically adjusts the on and off times of the switching transistor of the switching power supply through the chaotic modulation signal. By means of non-periodic modulation, the spectral energy of the switching frequency is dispersed, thereby effectively reducing the concentration effect of electromagnetic interference (EMI) and improving the electromagnetic compatibility of the system.

[0102] The chaotic signal modulation circuit 2 includes a voltage comparison module 21, a voltage modulation module 22, an RS trigger module 23, and an integration module 24 connected to the voltage comparison module 21. The RS trigger module 23 and the integration module 24 are connected, and both the RS trigger module 23 and the voltage comparison module 21 are connected to the switching power supply 3, and the voltage modulation module 22 is connected to the analog signal processing circuit 13. Among them, the voltage comparison module 21 is used to receive the output voltage of the switching power supply 3, generate a trigger pulse, and output it to the RS trigger module 23; the RS trigger module 23 is used to generate a first trigger signal and a second trigger signal according to the trigger pulse, and output the first trigger signal to the switching power supply 3 to trigger the switching transistor of the switching power supply 3 to conduct, and output the second trigger signal to the integration module 24; the integration module 24 is used to integrate the voltage signal according to the second trigger signal and output the integrated voltage to the voltage comparison module 21; the voltage modulation module 22 is used to generate a chaotic modulation voltage according to the analog chaotic signal and output it to the voltage comparison module 21; the voltage comparison module 21 is further used to generate a set signal according to the integrated voltage and the chaotic modulation voltage and output it to the RS trigger module 23 to set the RS trigger module 23, realizing dynamic control of the off time of the switching transistor of the switching power supply 3.

[0103] Please refer to Figure 9 In a preferred embodiment, the voltage comparison module 21 includes a first comparator (comp1) and a second comparator (comp2). Among them, the negative input terminal of the first comparator samples the output voltage V of the switching power supply 3 o , the positive input terminal of the first comparator inputs a reference voltage V ref . When the reference voltage V ref is greater than the output voltage V o , the first comparator outputs a trigger pulse S. The positive input terminal of the second comparator is connected to the integration module 24, the negative input terminal is connected to the voltage modulation module 22, and the output terminal is connected to the RS trigger module 23.

[0104] The RS trigger module 23 is composed of two - stage NOR gates, namely the first NOR gate (nor1) and the second NOR gate (nor2). Among them, the output terminal of the first NOR gate is connected to one of the input terminals of the second NOR gate, and the output terminal of the second NOR gate is connected to one of the input terminals of the first NOR gate, forming a feedback structure. The output terminal of the first comparator is connected to one of the input terminals of the second NOR gate, and the output terminal of the second comparator is connected to one of the input terminals of the first NOR gate.

[0105] The trigger pulse S output by the first comparator is input to the second NOR gate, triggering the RS trigger module 23 to generate a first trigger signal S1 and a second trigger signal S2. The first trigger signal S1 is output to the switching power supply 3, thereby triggering the switch - tube of the switching power supply 3 to conduct. For example, an auxiliary switch is set on the switch - tube path, and the auxiliary switch is controlled by the first trigger signal S1 to achieve the control of the switch - tube conduction.

[0106] In a preferred embodiment, the integration module 24 is composed of a detection circuit and an integrator. Among them, the detection circuit is used to receive the second trigger signal and output a voltage signal to the integrator, and the integrator is used to receive the voltage signal and output an integrated voltage to the positive input terminal of the second comparator.

[0107] Specifically, the detection circuit includes a first DC voltage source (Vset), a first detection resistor (Rs1), and a first auxiliary switch. The positive terminal of the first DC voltage source is connected to one end of the first detection resistor through the first auxiliary switch, the negative terminal is grounded, and the positive terminal of the first DC voltage source is connected to the other end of the first detection resistor and the input terminal of the integrator through the first auxiliary switch, for inputting the signal passing through the first detection resistor to the integrator. The output terminal of the integrator is connected to the positive input terminal of the second comparator. The first auxiliary switch is connected to the RS trigger module 23, and the on - off of the first auxiliary switch is controlled by the second trigger signal S2.

[0108] The voltage modulation module 22 is connected to the analog signal processing circuit 13, and is used to superimpose the analog chaotic signal (Vcubic) and the DC voltage (Vd) output by the analog signal processing circuit 13 to generate a chaotic modulation voltage and input it to the negative input terminal of the second comparator.

[0109] Based on the above circuit structure, when S2 triggers the first auxiliary switch to work, the first DC voltage source provides a driving voltage for the detection circuit. The load current (or input current) is converted into a voltage signal through the first detection resistor. The voltage signal output through the first detection resistor reflects the circuit state and serves as the input of the integrator. The integrator performs time integration on the input signal and outputs an integrated voltage V f , and the principle of the integration circuit is:

[0110]

[0111] That is to say, according to the feedback resistor R in the integrator f and the feedback capacitor C f the integration time constant t can be determined.

[0112] The integrated voltage V output by the integrator f is input to the positive input terminal of the second comparator. The chaotic modulation voltage is used as the input of the negative input terminal of the second comparator. When the integration duration is reached, that is, when the integrated voltage V f reaches the threshold value, the second comparator (Comp2) outputs a set signal to set the RS trigger module 23. At this time, the first trigger signal changes, and the switching transistor of the switching power supply 3 is turned off. In this embodiment, the integration module 24 realizes the control of the conduction duration of the switching transistor through the setting of the time constant.

[0113] To further illustrate the interference suppression effect of the electromagnetic interference suppression circuit provided by the present invention, the following describes the specific control steps of the switching power supply 3. It is assumed that the switching power supply 3 adopts a buck - type Buck converter structure, including an input voltage source (Vin), a power field - effect transistor (i.e., the switching transistor SQ), a diode (VD), an inductor (L), an output capacitor (Co), an output resistor (Ro), and a second detection resistor (Rs2). Among them, the positive terminal of the input voltage source is connected to the drain of the power field - effect transistor, and the negative terminal is grounded; the source of the power field - effect transistor is connected to one end of the inductor through the cathode of the diode, and the anode of the diode is grounded; the other end of the inductor is commonly connected to one end of the output capacitor and one end of the output resistor, and the other ends of the output capacitor and the output resistor are both grounded; one end of the second detection resistor is connected to the common connection point of the output capacitor and the output resistor, and the other end is grounded. A second auxiliary switch is provided at the switching transistor SQ of the switching power supply 3, and the second auxiliary switch is controlled to conduct by the first trigger signal S1. It should be noted here that the switching power supply 3 can also adopt other circuits, and only a preferred circuit structure is given here.

[0114] Based on the above circuit structure, the output voltage of the switching power supply 3 is sampled in real time and fed into the negative input terminal of the first comparator (Comp1), where it is compared with the set reference voltage Vref. When the output voltage is lower than the reference voltage, the first comparator outputs a trigger signal S to start the operation of the RS trigger module 23. The RS trigger module 23 is composed of two-stage NOR gates (NOR1 and NOR2). After receiving the trigger signal S, it generates two output signals: S1 is used to control the conduction of the switching transistor SQ, and S2 is used to control the operation of the first auxiliary switch in the detection circuit. At this time, the switching transistor SQ conducts, and the input voltage Vin is converted into an output voltage through the inductor L and the freewheeling diode VD to provide energy for the load, thereby increasing the output voltage.

[0115] The first auxiliary switch operates, and the load current is converted into a voltage signal through the first detection resistor and used as the input signal of the integrator. The integrator performs time integration on the input signal and outputs an integrated voltage. The voltage modulation module 22 superimposes the chaotic signal generated by the Cubic chaotic map and the DC voltage to generate a chaotic modulation voltage. The chaotic modulation voltage is input to the negative input terminal of the second comparator and compared with the integrated voltage. When the integrated voltage reaches the threshold value, that is, the chaotic modulation voltage, the second comparator (Comp2) outputs a signal to set the RS trigger module 23, thereby turning off the switching transistor SQ and stopping the supply of the input voltage.

[0116] The electromagnetic interference suppression circuit provided by the present invention takes closed-loop control as the core. By real-time feedback of the difference between the output voltage and the reference voltage, it drives the working state of the switching transistor SQ, thereby stabilizing the output voltage. At the same time, due to the high chaos and ergodicity of the chaotic modulation voltage, the on and off times of the switching transistor are chaoticized, realizing the dynamic adjustment of the turn-off moment. This non-periodic modulation disperses the spectral energy of the switching frequency, effectively reducing the concentration effect of electromagnetic interference (EMI) and improving the electromagnetic compatibility of the system.

[0117] Next, simulation experiments are carried out to verify the EMI suppression effect of the electromagnetic interference suppression circuit provided by the present invention. Figure 10The simulation waveform of the chaotic modulation voltage obtained through simulation experiments. The horizontal axis represents time (in seconds), and the vertical axis represents the voltage value of the chaotic signal. The waveform exhibits obvious non-periodicity and chaos. It can be seen that the chaotic signal changes frequently within a short period of time, and the waveform shows different amplitudes and change rates in different time periods, reflecting the high irregularity of the chaotic signal. This chaos enables the chaotic signal to be widely used in non-deterministic modulation, effectively avoiding the problem of electromagnetic interference (EMI) concentration caused by fixed-frequency modulation. At the same time, the chaotic signal has high ergodicity, and the values in the waveform can be evenly distributed within the amplitude range, which helps to disperse the spectral energy in the circuit. The chaotic characteristics of the chaotic signal make it suitable as a modulation signal input into the PFM modulation circuit to dynamically adjust the on and off times of the switching transistor. This non-periodic modulation method effectively chaoticizes the frequency of the PFM waveform, avoiding the sharp harmonic peak problem caused by spectral concentration in the traditional fixed-frequency modulation method and improving the electromagnetic compatibility (EMC). In addition, by superimposing the chaotic signal, the dynamic change of the switching power supply frequency is optimized, which helps to enhance the load adaptability, improve the dynamic performance and operating efficiency of the system. The chaotic characteristics of the chaotic signal disperse the EMI spectral energy of the switching power supply, thereby reducing the interference intensity and improving the electromagnetic compatibility of the power supply.

[0118] Figure 11 is the PWM modulation waveform of the switching transistor in the traditional PWM modulation circuit. The horizontal axis represents time (in seconds), and the vertical axis represents the on state of the switching transistor. The on state switches between 0 and 1 (1 for on and 0 for off). It can be observed that the PWM waveform exhibits a fixed duty cycle and periodicity, indicating that the switching frequency is constant. The fixed-frequency PWM waveform means that the on and off times of the switching transistor operate according to a fixed modulation signal. Although this periodic waveform can stably adjust the output voltage, the fixed frequency will cause the spectral energy to concentrate at specific frequency points, thereby generating strong harmonic interference in the frequency domain.

[0119] Figure 12 is Figure 11 the frequency domain analysis result (FFT transform) of the corresponding switching transistor PWM signal. The horizontal axis represents frequency (in Hz), and the vertical axis represents the spectral amplitude of the signal. It can be seen that the spectrum of the signal forms obvious harmonic peaks at fixed frequency points (about 100 kHz), and secondary harmonics appear at the multiples of this frequency. This spectral concentration effect is a typical problem of traditional PWM modulation, indicating that the fixity of the switching frequency will cause electromagnetic interference to concentrate at a few frequency points, especially the fundamental frequency and harmonic frequencies. The concentration of harmonic frequencies makes the circuit prone to generate sharp interference peaks, thereby reducing the electromagnetic compatibility (EMC) of the system and may cause interference to surrounding devices in practical applications.

[0120] Figure 13 The result of the frequency-domain analysis of the output voltage of the traditional PWM modulation circuit. The horizontal axis is the frequency (unit: Hz), and the vertical axis is the spectral amplitude of the output voltage. It can be seen from the figure that, similar to the FFT analysis of the switching transistor, obvious harmonic peaks appear at the fixed switching frequency point (about 100 kHz) and its multiple frequencies in the spectrum of the output voltage. In addition, there is also a decay trend of the high-frequency components. Since the output voltage is directly affected by the modulation signal of the switching transistor, the sharp peaks in the frequency characteristics reflect the concentration of spectral energy. This phenomenon will lead to a relatively high harmonic content in the output voltage, affect the power supply quality, and cause interference problems in some loads.

[0121] According to Figure 11 , Figure 12 and Figure 13 it can be known that the main disadvantage of the traditional PWM modulation circuit is that due to the modulation signal with a fixed frequency, the spectral energy is highly concentrated at specific frequency points (fundamental frequency and multiple frequencies), forming sharp harmonic peaks in the frequency domain. This spectral concentration phenomenon causes strong electromagnetic interference (EMI) and reduces the electromagnetic compatibility (EMC) of the circuit. This interference may have a negative impact on other devices or signals in a complex electronic system, especially in high-power density application scenarios. Therefore, it is necessary to introduce a more chaotic modulation method (such as chaotic modulation) to disperse the spectral energy and reduce the harmonic interference peaks, thereby improving the electromagnetic compatibility performance of the system.

[0122] Figure 14 Shows the modulation waveform of the switching transistor of the switching power supply in the present invention. The horizontal axis is the time (unit: second), and the vertical axis is the state of the switching signal, whose value changes between 0 (off) and 1 (on). It can be observed from the waveform that, compared with the traditional PWM modulation circuit, the PFM waveform of the present invention exhibits obvious chaotic characteristics. Specifically, although the overall modulation frequency range remains within a certain range, the on-time and off-time are no longer fixed, but show non-periodic changes with the modulation of the chaotic signal. This chaotic modulation method avoids the problem of constant switching frequency and can effectively disperse the spectral energy of electromagnetic interference (EMI).

[0123] Figure 15 is Figure 14Frequency domain analysis of the middle switch tube signal (FFT result). The horizontal axis represents frequency (unit: Hz), and the vertical axis represents the spectral amplitude of the signal. As can be seen from the figure, compared with the traditional PWM, the harmonic peak of the switch tube spectrum of the present invention is reduced. The fundamental frequency and multiple frequency harmonics that were originally very concentrated in the traditional PWM spectrum are dispersed into a wider frequency range in the present invention, and the spectral energy distribution is more uniform. In the figure, the main harmonic amplitude near the fundamental frequency (about 100 kHz) drops to 0.37 dB, which is significantly lower than 0.56 dB of the traditional PWM. This spectral dispersion characteristic is the advantage of introducing chaotic modulation in the present invention, which can effectively weaken the sharp harmonic interference in fixed-frequency modulation.

[0124] Figure 16 This is the frequency domain analysis result of the output voltage of the switching power supply of the present invention. The horizontal axis is frequency (unit: Hz), and the vertical axis is the spectral amplitude of the output voltage. As can be seen from the figure, compared with the traditional PWM, the harmonic peaks of the output voltage spectrum of the present invention at the fixed frequency and multiple frequencies are reduced, and the overall spectral distribution shows a smoother performance. At the same time, the high-frequency components decay rapidly as the frequency increases, indicating that chaotic modulation makes the spectral energy of the output voltage more dispersed and reduces the spike interference at specific frequencies. This improvement not only improves the quality of the output voltage but also reduces the interference impact of the power supply on the outside world and enhances the electromagnetic compatibility (EMC).

[0125] According to the above simulation results, it can be known that the present invention effectively reduces the harmonic amplitudes at the fundamental frequency and multiple frequencies, and at the same time weakens the influence of high-frequency noise, making the output voltage more stable and less interfering. Compared with the traditional PWM modulation method, the present invention provides an efficient and low-interference solution for the PFM switching power supply through chaotic modulation technology. It not only improves the operation stability and output quality of the power supply system but also enhances the electromagnetic compatibility, providing strong technical support for the wide application of switching power supplies in the fields of industry, communication, and consumer electronics.

[0126] For the electromagnetic interference suppression circuit based on chaotic mapping provided in this embodiment, compared with the problems of concentrated spectral energy, too high harmonic peaks, and strong electromagnetic interference (EMI) existing in the traditional PWM modulation circuit, the present invention realizes the chaos and non-periodicity of the switching frequency by introducing chaotic signals, disperses the spectral energy, significantly reduces the harmonic interference amplitude, makes the spectral distribution more uniform, effectively improves the electromagnetic compatibility of the switching power supply, and suppresses the electromagnetic interference of the switching power supply.

[0127] Please refer to Figure 17 , based on the same inventive concept, a PFM switching power supply proposed in the second embodiment of the present invention includes: a buck transformer module 31 and the electromagnetic interference suppression circuit as described above, and the buck transformer module 31 is connected to the electromagnetic interference suppression circuit.

[0128] Further, the switching transistor of the buck transformer module 31 is connected to the RS trigger module 23 through a second auxiliary switch; the second auxiliary switch is used to receive a first trigger signal to trigger the conduction of the switching transistor and receive a set signal to trigger the turn-off of the switching transistor.

[0129] The technical features and technical effects of the PFM switching power supply proposed in the embodiment of the present invention are the same as those of the electromagnetic interference suppression circuit based on chaotic mapping proposed in the embodiment of the present invention, and will not be elaborated here.

[0130] In summary, an electromagnetic interference suppression circuit and a PFM switching power supply based on chaotic mapping proposed in the embodiment of the present invention, the electromagnetic interference suppression circuit includes a chaos generation circuit and a chaos signal modulation circuit; the chaos generation circuit includes a digital signal generation circuit, a digital-to-analog conversion circuit, and an analog signal processing circuit connected in sequence; the chaos signal modulation circuit includes a voltage comparison module, a voltage modulation module, an RS trigger module, and an integration module connected to the voltage comparison module, the RS trigger module is connected to the integration module, the RS trigger module and the voltage comparison module are both connected to the switching power supply, and the voltage modulation module is connected to the analog signal processing circuit; wherein, the digital signal generation circuit is used to generate an improved digital chaos signal, the digital-to-analog conversion circuit is used to perform digital-to-analog conversion on the improved digital chaos signal, the analog signal processing circuit is used to amplify and adjust the converted initial analog chaos signal to obtain an analog chaos signal and output it to the voltage modulation module; the voltage comparison module is used to receive the output voltage of the switching power supply, generate a trigger pulse, and output it to the RS trigger module; the RS trigger module is used to generate a first trigger signal and a second trigger signal according to the trigger pulse, output the first trigger signal to the switching power supply to trigger the conduction of the switching transistor of the switching power supply, and output the second trigger signal to the integration module; the integration module is used to integrate the voltage signal according to the second trigger signal and output an integrated voltage to the voltage comparison module; the voltage modulation module is used to generate a chaos modulation voltage according to the analog chaos signal and output it to the voltage comparison module; the voltage comparison module is further used to generate a set signal according to the integrated voltage and the chaos modulation voltage and output it to the RS trigger module to set the RS trigger module and realize the dynamic control of the turn-off moment of the switching transistor. The present invention realizes the chaos and non-periodicity of the switching frequency by introducing a chaos signal, disperses the spectrum energy, significantly reduces the harmonic interference amplitude, makes the spectrum distribution more uniform, effectively improves the electromagnetic compatibility of the switching power supply, and suppresses the electromagnetic interference of the switching power supply.

[0131] Each embodiment in this specification is described in a progressive manner. For the parts that are the same or similar in each embodiment, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple. For the relevant parts, reference can be made to the partial description of the method embodiment. It should be noted that the technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0132] The above embodiments only represent several preferred embodiments of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and substitutions can be made, and these improvements and substitutions should also be regarded as the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the protection scope of the claims.

Claims

1. An electromagnetic interference suppression circuit based on chaotic mapping, characterized in that: The electromagnetic interference suppression circuit is applied to a switching power supply, comprising: Chaos generating circuit and chaotic signal modulation circuit; The chaos generating circuit comprises a digital signal generating circuit, a digital-to-analog conversion circuit and an analog signal processing circuit connected in sequence; The chaotic signal modulation circuit includes a voltage comparison module, a voltage modulation module, an RS trigger module and an integration module connected to the voltage comparison module, the RS trigger module is connected to the integration module, the RS trigger module and the voltage comparison module are both connected to a switching power supply, and the voltage modulation module is connected to the analog signal processing circuit; The digital signal generating circuit is used to generate an improved digital chaotic signal, the digital-to-analog conversion circuit is used to perform digital-to-analog conversion on the improved digital chaotic signal, and the analog signal processing circuit is used to amplify and adjust the converted initial analog chaotic signal to obtain an analog chaotic signal, and output it to the voltage modulation module; The voltage comparison module is used to receive the output voltage of the switching power supply, generate a trigger pulse, and output it to the RS trigger module; The RS trigger module is used to generate a first trigger signal and a second trigger signal according to the trigger pulse, and output the first trigger signal to the switching power supply to trigger the switch tube of the switching power supply to turn on, and output the second trigger signal to the integration module; The integration module is used to integrate the voltage signal according to the second trigger signal, and output the integrated voltage to the voltage comparison module; The voltage modulation module is used to generate a chaotic modulation voltage according to the simulated chaotic signal, and output the chaotic modulation voltage to the voltage comparison module; The voltage comparison module is also used to generate a setting signal according to the integrated voltage and the chaotic modulation voltage, and output it to the RS trigger module to set the RS trigger module to achieve dynamic control of the turn-off moment of the switch tube.

2. The electromagnetic interference suppression circuit based on chaotic mapping according to claim 1 is characterized in that: The digital signal generating circuit uses the following mapping formula to generate an improved digital chaotic signal: In the formula, y n represents the chaotic sequence value of the nth iteration, a represents the range scaling parameter, and ρ represents the control parameter.

3. The electromagnetic interference suppression circuit based on chaotic mapping according to claim 1, characterized in that: The voltage comparison module includes a first comparator and a second comparator; The first comparator is connected to the switching power supply and the RS trigger module respectively, and is used to receive the output voltage of the switching power supply and a preset reference voltage, and output a trigger pulse to the RS trigger module; The second comparator is connected to the integration module, the voltage modulation module and the RS trigger module, and is used for receiving the integration voltage and the chaotic modulation voltage, and outputting a setting signal to the RS trigger module.

4. The electromagnetic interference suppression circuit based on chaotic mapping according to claim 3 is characterized in that: The integration module includes a detection circuit and an integrator, the detection circuit is connected to the RS trigger module, and the integrator is respectively connected to the detection circuit and the second comparator; The detection circuit is used to receive the second trigger signal and output a voltage signal to the integrator; The integrator is used to receive the voltage signal and output an integrated voltage to the second comparator.

5. The electromagnetic interference suppression circuit based on chaotic mapping according to claim 4, characterized in that: The detection circuit includes a first DC voltage source, a first detection resistor and a first auxiliary switch, wherein the first DC voltage source is connected to the first detection resistor through the first auxiliary switch and then connected to the integrator; The first auxiliary switch is connected to the RS trigger module.

6. The electromagnetic interference suppression circuit based on chaotic mapping according to claim 1, characterized in that: The voltage modulation module is used to superimpose the simulated chaotic signal and the direct current voltage to generate a chaotic modulation voltage.

7. The electromagnetic interference suppression circuit based on chaotic mapping according to claim 1, characterized in that: The RS trigger module is composed of two levels of NOR gates.

8. The electromagnetic interference suppression circuit based on chaotic mapping according to claim 1, characterized in that: The analog signal processing circuit includes a two-stage operational amplifier and a resistor network; The first operational amplifier is used to amplify the amplitude of the converted initial simulated chaotic signal, and the second operational amplifier and the resistor network are used to adjust the mean value and range of the signal output by the first operational amplifier to obtain the simulated chaotic signal.

9. A PFM switching power supply, characterized in that: It comprises a step-down transformer module and the electromagnetic interference suppression circuit according to any one of claims 1 to 8, wherein the step-down transformer module is connected to the electromagnetic interference suppression circuit.

10. The PFM switching power supply according to claim 9, characterized in that: The switch tube of the step-down transformer module is connected to the RS trigger module through a second auxiliary switch; The second auxiliary switch is used to receive the first trigger signal to trigger the switch tube to turn on, and to receive the set signal to trigger the switch tube to turn off.

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