Method for reducing EMI (Electro-Magnetic Interference) noise of Cuk converter by combining chaotic spread spectrum and soft switching

Abstract

The invention relates to a method for reducing EMI noise of a converter, in particular to a method for reducing EMI noise of a Cuk converter combining chaotic spread spectrum and soft switching. According to the method, the EMI noise of the Cuk converter is reduced through cooperation of the chaotic spread spectrum technology and the soft switching technology, the chaotic spread spectrum technology and the soft switching technology are combined for the EMI problem generated in the high-speed switching process of the Cuk converter, and the broadband EMI noise is comprehensively suppressed. According to the method for carrying out EMI noise suppression on the Cuk converter by combining improved chaotic spread spectrum and soft switching technologies, a non-inductive Chua's chaotic circuit is designed and built, the non-inductive Chua's chaotic circuit serves as a frequency modulation signal to generate a chaotic PWM signal, switching-on and switching-off of a driving signal of a switching tube of the Cuk converter are controlled, and zero-voltage switching-on is achieved. According to the method, the conduction noise of the Cuk converter is suppressed, the suppression effect is good, the implementation method is simple, and industrial application is facilitated.

Description

Technical Field

[0001] A method for reducing EMI noise of a converter according to the present invention specifically relates to a method for reducing EMI noise of a Cuk converter combining chaotic spread spectrum and soft switching. Background Art

[0002] In recent years, DC-DC converters have been widely used in new energy vehicle charging systems and portable electronic devices. Among them, the Cuk converter, due to its unique topological structure, can achieve step-up and step-down conversion and provide negative voltage output, and has the advantages of continuous input and output current and small ripple. However, with the continuous increase of the switching frequency, the electromagnetic interference (EMI) problem generated by the Cuk converter during the high-speed switching process has become increasingly prominent. EMI noise not only affects the normal operation of neighboring electronic devices through conduction and radiation, but may also violate the electromagnetic compatibility (EMC) standard, restricting its application in high-precision or high-reliability fields.

[0003] Due to the characteristics of non-periodicity and wide spectrum, chaotic spread spectrum technology can randomize the switching frequency by applying chaotic signals to PWM modulation, thereby dispersing EMI energy into a wider frequency band and significantly reducing the noise peak at the fundamental frequency and harmonics. On the other hand, soft switching technology can optimize the switching transient characteristics, reduce voltage / current spikes and high-frequency oscillations during the switching process, and thus effectively reduce the EMI source intensity. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for reducing EMI noise of a Cuk converter combining chaotic spread spectrum and soft switching. This method uses chaotic spread spectrum and soft switching technologies to synergistically reduce the EMI noise of the Cuk converter. Aiming at the EMI problem generated by the Cuk converter during the high-speed switching process, the chaotic spread spectrum technology and the soft switching technology are combined to comprehensively suppress the EMI noise in a wide frequency band, and the suppression effect is obvious.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] A method for reducing EMI noise of a Cuk converter combining chaotic spread spectrum and soft switching, the method includes a Cuk buck converter capable of reducing electromagnetic interference, and this converter includes a power supply part and a control part; wherein the power supply part is a soft switching Cuk converter topological structure, which is composed of inductors L1, L2, capacitors C1, C2, a freewheeling diode D, a power switch SW, an output resistor R1, a resonant inductor L r , a capacitor C r ; the control part includes a comparator, a compensation circuit and a spread spectrum circuit, and the compensation circuit is composed of capacitors C3, C4, C5, resistors R2, R3, R4, an amplifier EA, a reference voltage V reIt consists of f. The spread spectrum circuit is composed of an improved inductorless Chua's chaotic circuit, a voltage-controlled oscillator VCO, a voltage source V CC , a current source I SAW , a capacitor C SAW , a switch Q, and a reference voltage V b . Among them, the inductorless Chua's chaotic circuit uses an analog inductor module. The circuit includes an analog inductor part, a non-linear resistor part, a variable resistor R8, capacitors C7 and C8. The analog inductor is composed of two amplifiers EA1 and EA2, resistors R 15 , R5, R6, R7, and capacitor C6. The non-linear resistor is composed of two amplifiers EA3 and EA4, resistors R9, R 10 , R 11 , R 12 , R 13 , R 14 . Finally, the chaotic signal generated by this circuit is sent into the chaotic spread spectrum circuit.

[0007] In a method for reducing EMI noise of a Cuk converter by combining chaotic spread spectrum and soft switching, an inductorless Chua's chaotic circuit and a spread spectrum circuit are built. In the spread spectrum circuit, the frequency of the chaotic signal is adjusted by a voltage-controlled oscillator, and a sawtooth wave of the chaotic frequency is generated by using a sawtooth wave generator. The sawtooth wave and the feedback voltage ΔV of the Cuk converter are compared by a comparator Comp to generate chaotic PWM. By the method of expanding the spectrum clock, the EMI noise of the Cuk converter is suppressed.

[0008] In a method for reducing EMI noise of a Cuk converter by combining chaotic spread spectrum and soft switching, a soft-switching Cuk converter topology is built. During the operation of the soft-switching Cuk converter, when the power switch SW is turned off, the resonant capacitor C r starts to be linearly charged, and its voltage gradually rises to the threshold, triggering the resonant inductor L r and capacitor C r to form an oscillation loop, and the freewheeling diode D conducts. When the voltage V cr across the resonant capacitor is 0, the power switch SW realizes conduction under the zero-voltage condition, and the resonant inductor is charged to balance with the output inductor current. Finally, the switch SW is turned off again, the freewheeling diode is turned off, and the system resets to enter the next cycle. Through the coordinated action of the timing control of the resonant network and the chaotic frequency modulation PWM, not only the switching transient voltage spikes are eliminated, but also the noise is significantly reduced and the efficiency is improved.

[0009] A method for reducing EMI noise of a Cuk converter combining chaotic spread spectrum and soft switching, which sets and implements a compensation circuit part. Through the operational amplifier EA, compensation resistors and capacitors in the circuit, the signal output by the power supply part is amplified and compensated. Then, this signal is compared with the chaotic sawtooth wave by a comparator. According to the comparison result, a corresponding PWM output signal is generated to control the conduction and turn-off of the switch. When the voltage at the non-inverting input terminal of the comparator Comp is higher than that at the inverting input terminal, Comp outputs a high level to turn on the switch. On the contrary, when the voltage at the non-inverting input terminal of the comparator Comp is lower than that at the inverting input terminal, Comp outputs a low level to turn off the switch.

[0010] The advantages and economic effects of the present invention are:

[0011] The present invention applies a method for suppressing EMI noise of a Cuk converter by combining improved chaotic spread spectrum and soft switching technologies. It designs and builds an inductorless Chua's chaotic circuit, which is used as a frequency modulation signal to generate a chaotic PWM signal to control the on and off of the driving signal of the switch tube of the Cuk converter, and realizes zero-voltage turn-on. The method of the present invention suppresses the conducted noise of the Cuk converter, has a good suppression effect, and the implementation method is simple, which is beneficial to industrial applications. Description of the Drawings

[0012] Figure 1 It is the inductorless Chua's chaotic circuit diagram applied in the present invention;

[0013] Figure 2 It is the time-domain diagram and phase diagram of the Chua's chaotic circuit applied in the present invention;

[0014] Figure 3 It is the actual circuit time-domain diagram and phase diagram of the inductorless Chua's chaotic circuit;

[0015] Figure 4 It is the schematic diagram of the Cuk converter combining chaotic spread spectrum and soft switching designed by the present invention;

[0016] Figure 5 It is the working waveform diagram of the soft-switching Cuk converter designed by the present invention;

[0017] Figure 6 It is the spectrum diagram of the chaotic soft-switching PWM signal of the present invention. Detailed Embodiment

[0018] The following further describes the embodiments of the present invention with reference to the drawings, so that relevant personnel in the field can refer to and implement them accordingly. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Usually, the components of the embodiments of the present application described in the drawings can be arranged and designed by various different types of devices.

[0019] Figure 1 shows the inductorless Chua's chaotic circuit diagram applied in the design of the present invention. The circuit includes: an analog inductor part, a non-linear resistor part, a variable resistor R8, capacitors C7 and C8. The analog inductor consists of two amplifiers EA1 and EA2, resistors R 15 , R5, R6, R7, and capacitor C6. The non-linear resistor consists of two amplifiers EA3 and EA4, resistors R9, R 10 , R 11 , R 12 , R 13 , R 14 . The circuit is designed to generate chaotic signals for subsequent signal modulation. Among them, R5 = 5 kΩ, R6 = R7 = 1.2 kΩ, R8 = 2 kΩ, R9 = R 10 = 22 kΩ, R 11 = 3.3 kΩ, R 12 = R 13 = 220 Ω, R 14 = 2.2 kΩ, C6 = 1.5 nF, C7 = 100 nF, C8 = 10 nF. The models of EA1 and EA2 are TL082CP, and the models of EA3 and EA4 are LM358P.

[0020] Figure 2 shows the time-domain diagram and phase diagram generated by the Chua's chaotic circuit applied in the present invention. According to Figure 1 using Multisim software to build a model, the time-domain diagrams of nodes a and b at both ends of the variable resistor R8 in its chaotic circuit and its xy phase diagram are obtained respectively. Nodes a and b can output chaotic voltage signals, and its xy phase diagram is a clear double-vortex structure.

[0021] Figure 3 shows the time-domain diagram and phase diagram of the actually built inductorless Chua's chaotic circuit of the present invention. Its working principle is to adjust the combined behavior of capacitors and resistors to a characteristic similar to that of an inductor through the gain characteristics of operational amplifiers and feedback networks. Using a negative impedance converter (NIC) to make the input impedance of the circuit proportional to the frequency, thus simulating the voltage and current relationship of an ideal inductor. By adjusting the parameters of resistors and capacitors, the equivalent inductance value can be changed. According to Figure 1 configuring the circuit device parameters and models: R5 = 5 kΩ, R6 = R7 = 1.2 kΩ, R8 = 2 kΩ, R9 = R 10 = 22 kΩ, R 11 = 3.3 kΩ, R 12 = R 13 = 220 Ω, R 14R = 2.2 kΩ, C6 = 1.5 nF, C7 = 100 nF, C8 = 10 nF. The models of EA1 and EA2 are TL082CP, and the models of EA3 and EA4 are LM358P. The operating waveforms and the generated chaotic signals are obtained through demonstration with a DH0914S oscilloscope.

[0022] Figure 4 Figure 4 shows the schematic diagram of the Cuk converter combining chaotic spread spectrum and soft switching applied in the design of the present invention. This figure is divided into a power supply part and a control part. The power supply part is the topology of the soft-switching Cuk converter, including power supply V in , power switch SW, inductors L1, L2, capacitors C1, C2, freewheeling diode D, output resistor R1, resonant inductor L r , and resonant capacitor C r . Utilizing the principle of the unidirectional conduction of the diode and the charge and discharge principles of capacitors and inductors, the soft-switching Cuk converter realizes the zero-voltage turn-on of SW through the resonant network. During the resonant process, the voltage across SW is zero before it turns on, and no loss and noise are generated when SW turns on, thus reducing the switching EMI noise of the Cuk converter.

[0023] In the control part, the output voltage of the Cuk converter is sampled by voltage division and connected to the inverting input terminal of amplifier EA, and compared with the reference voltage V ref entering the non-inverting input terminal of amplifier EA to generate an error signal. This signal is phase-corrected and gain-amplified through a compensation circuit to form a stabilized control voltage signal, which is finally connected to the non-inverting input terminal of comparator Comp. The chaotic signal generated by the circuit in Figure 1 is used as a modulation signal and connected to the spread spectrum circuit. After frequency modulation by a voltage-controlled oscillator, it enters a sawtooth wave generator to generate a sawtooth wave signal. The sawtooth wave signal generated by the chaotic signal is input to the inverting input terminal of comparator Comp. In the comparator, the two-way signals are compared. The compensated voltage at the non-inverting terminal represents the steady-state operating point of the system, while the chaotic frequency-modulated sawtooth wave at the inverting terminal carries the spectrum expansion information. When the compensated voltage is higher than the instantaneous sawtooth wave level, the comparator outputs a high level to drive the switch tube SW to conduct; otherwise, it enters the turn-off period. The PWM pulse generated by this dynamic threshold comparison has its duty cycle and frequency double-modulated by the chaotic signal, forming a switch control sequence with pseudo-random characteristics. Thus, a chaotic PWM signal is generated to control the conduction and turn-off of switch SW, thereby achieving the suppression of the EMI noise of the Cuk converter.

[0024] Figure 5 Figure 5 shows the working waveform diagram of the soft-switching Cuk converter designed by the present invention. Assuming that t0 - t4 is a switching cycle of the converter, the converter operates in four modes. Mode 1 [t0 - t1]: At t0, switch SW is turned off, and the voltage of the resonant capacitor V crRises linearly. When it rises to the moment of t1, the voltage V of the resonant capacitor cr = V in + V C2 . This mode ends. Mode 2 [t1 - t2]: L r and C r start to resonate. At this time, the freewheeling diode D conducts. When resonating to the moment of t2, the voltage V of the resonant capacitor cr = 0. This mode ends. Mode 3 [t2 - t3]: At the moment of t2, the switch SW turns on under Z VS . At this time, the resonant inductor starts to charge. When the current value of the resonant inductor reaches the constant equilibrium value of the average output inductor current, this mode ends. Mode 4 [t3 - t4]: This mode starts from the moment of t3. When reaching the moment of t4, the freewheeling diode D turns off and the switch SW turns off again to prepare for the next switching cycle. This mode ends.

[0025] Figure 6 shows the chaotic soft - switching PWM signal spectrum diagram of the present invention. The parameters of the Cuk converter are set as: V in = 10V, L1 = 22uF, L2 = 330uF, L r = 1uF, C r = 1nF, C1 = 1uF, C2 = 470uF, R1 = 24Ω, V0 = - 12V. The PWM signal spectrum is obtained through Simplis&SIMetrix simulation. Experiments show that through the synergistic effect of the non - inductive chaotic circuit and the soft - switching resonant network, the chaotic soft - switching technology applied in this patent can make the amplitude of the PWM signal spectrum of the Cuk converter 80mV. The optimized spectrum energy is evenly distributed, and the switching transient spikes are significantly suppressed. By optimizing the spectrum characteristics of the PWM signal, the Cuk converter can effectively reduce the EMI noise generated by it.

[0026] The above - mentioned is only one of the embodiments of this application. The power supply part can be replaced with the topological structure of other converters, and at the same time, the component models and parameter values in the circuit are adjusted to reduce the noise of other buck - boost converters. The specific operation can be understood by referring to the description of the embodiments and will not be described in detail here. It should be noted that these examples only show the technical solutions of the present invention and do not constitute limitations on it. Although the above examples elaborate on each step of the present invention in detail, those skilled in the art should recognize that the technical solutions in these examples can be adjusted, or some or all of the technical features can be equivalently replaced. In addition, any modification or substitution of the present invention, as long as it does not deviate from the essence of the present invention, falls within the protection scope of the present invention.

Claims

1. A method for reducing EMI noise of a Cuk converter combining chaotic spread spectrum and soft switching, characterized in that The method includes a Cuk buck converter that can reduce electromagnetic interference. This converter includes a power supply part and a control part. Among them, the power supply part is a soft-switching Cuk converter topology, which consists of inductors L1 and L2, capacitors C1 and C2, a freewheeling diode D, a power switch SW, an output resistor R1, a resonant inductor L r and a capacitor C r . The control part includes a comparator, a compensation circuit and a spread-spectrum circuit. The compensation circuit consists of capacitors C3, C4, C5, resistors R2, R3, R4, an amplifier EA, and a reference voltage V re f. The spread-spectrum circuit consists of an improved inductorless Chua's chaotic circuit, a voltage-controlled oscillator VCO, a voltage source V CC , a current source I SAW , a capacitor C SAW , a switch Q, and a reference voltage V b . Among them, the inductorless Chua's chaotic circuit uses an analog inductor module. The circuit includes an analog inductor part, a non-linear resistor part, a variable resistor R8, capacitors C7 and C8. The analog inductor consists of two amplifiers EA1 and EA2, resistors R 15 , R5, R6, R7, and a capacitor C6. The non-linear resistor consists of two amplifiers EA3 and EA4, resistors R9, R 10 , R 11 , R 12 , R 13 , R 14 . Finally, the chaotic signal generated by this circuit is fed into the chaotic spread-spectrum circuit.

2. A method for reducing EMI noise of a Cuk converter combining chaotic spread spectrum and soft switching according to claim 1, characterized in that Build an inductorless Chua's chaotic circuit and a spread spectrum circuit. In the spread spectrum circuit, adjust the frequency of the chaotic signal through a voltage controlled oscillator, and use a sawtooth wave generator to generate a sawtooth wave of the chaotic frequency; this sawtooth wave and the feedback voltage ΔV of the Cuk converter are compared by a comparator Comp to generate chaotic PWM, and by the method of spreading spectrum clock, the EMI noise of the Cuk converter is suppressed.

3. A method for reducing EMI noise of a Cuk converter combining chaotic spread spectrum and soft switching according to claim 1, characterized in that, The soft-switching Cuk converter topology is built. During the operation of the soft-switching Cuk converter, when the power switch SW is turned off, the resonant capacitor C r begins to be linearly charged, and its voltage gradually rises to the threshold value, triggering the resonant inductor L r and the capacitor C r to form an oscillation loop, and the freewheeling diode D conducts; when the voltage V cr across the resonant capacitor is 0, the power switch SW realizes conduction under zero-voltage conditions, and the resonant inductor is charged to balance with the output inductor current; finally, the switch SW is turned off again, the freewheeling diode is turned off, and the system resets to enter the next cycle; through the coordinated action of the timing control of the resonant network and chaotic frequency modulation PWM, not only the switch transient voltage spikes are eliminated, but also the noise is significantly reduced and the efficiency is improved.

4. A method for reducing EMI noise of a Cuk converter combining chaotic spread spectrum and soft switching according to claim 1, characterized in that, Set up and implement the compensation circuit part. Through the operational amplifier EA, compensation resistors and capacitors in the circuit, amplify and compensate the signal output by the power supply part; then, this signal is compared with the chaotic sawtooth wave by a comparator; according to the comparison result, generate a corresponding PWM output signal to control the on and off of the switch; when the voltage at the non-inverting input terminal of the comparator Comp is higher than that at the inverting input terminal, Comp outputs a high level to turn on the switch; conversely, when the voltage at the non-inverting input terminal of the comparator Comp is lower than that at the inverting input terminal, Comp outputs a low level to turn off the switch.

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