Soft switching control method of asynchronous Buck converter

Abstract

The embodiment of the invention discloses a soft switching control method for an asynchronous Buck converter, and the method comprises the steps: obtaining the input voltage, the output voltage, the output current and the natural frequency of the asynchronous Buck converter, and then determining the turn-on time, the natural commutation time, the turn-on time and the forced commutation time according to the input voltage, the output voltage, the output current and the natural frequency, the method comprises the following steps: switching on time, natural commutation time, conduction time and forced commutation time, determining a switching period and a duty ratio according to the switching on time, the natural commutation time, the conduction time and the forced commutation time, and finally inputting the duty ratio and the switching period into a PWM module to generate a switching control signal which is used for controlling the switching action of the asynchronous Buck converter. The invention provides a novel control method which does not depend on zero crossing point detection of inductive current, so that the dependence on a high-frequency current sensor can be thoroughly eliminated, and the interference of switching noise on a control system is effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a soft switching control method for an asynchronous Buck converter. Background Art

[0002] The asynchronous Buck converter is a simple and widely used step-down converter. Its core circuit consists of a switch tube, a diode, and an LC filter network. In traditional application scenarios, the converter mostly operates in continuous conduction mode, in which the switch tube operates in hard switching mode. However, this operating mode brings significant switching losses, which not only limits the increase in the switching frequency of the converter, but also leads to an increase in the volume and weight of passive components such as inductors and capacitors, making it difficult to achieve the design goal of high power density.

[0003] In order to reduce switching losses and improve the operating efficiency of the converter at high switching frequencies, the industry has begun to explore operating the asynchronous Buck converter in the boundary conduction mode (BCM). In this mode, the switch tube can achieve soft switching operation, thereby effectively reducing switching losses.

[0004] However, the existing BCM control method relies on complex hardware circuits to accurately detect the zero-crossing point of the inductor current. As the switching frequency continues to increase, the existing current sensors can no longer meet the demand for accurate measurement of the inductor current, and the zero-crossing detection circuit is easily interfered by switching noise, which may cause false triggering of the switch and thus affect the stability of the control system. Summary of the invention

[0005] Based on this, it is necessary to propose a soft switching control method for an asynchronous Buck converter to address the above problems. Since it does not rely on the zero-crossing point detection of the inductor current, it can completely eliminate the dependence on high-frequency current sensors and effectively avoid the interference of switching noise on the control system.

[0006] To achieve the above object, the present invention provides a soft switching control method for an asynchronous Buck converter in a first aspect, the method comprising:

[0007] Get the input voltage, output voltage, output current and natural frequency of the asynchronous Buck converter;

[0008] Determine a turn-on time, a natural commutation time, a conduction time and a forced commutation time according to the input voltage, the output voltage, the output current and the natural frequency;

[0009] Determine a switching period and a duty cycle according to the turn-on time, the natural commutation time, the conduction time and the forced commutation time;

[0010] The duty cycle and the switching period are input into a PWM module to generate a switching control signal, and the switching control signal is used to control the switching action of the asynchronous Buck converter.

[0011] Optionally, determining the turn-on time, the natural commutation time, the conduction time and the forced commutation time according to the input voltage, the output voltage, the output current and the natural frequency includes:

[0012] Obtaining the inductance value of the asynchronous Buck converter and the equivalent capacitance of the switch node to ground;

[0013] Determining a normalized base resistance value according to the inductance value and an equivalent capacitance of the switch node to ground;

[0014] Determining a normalized base current according to the normalized base resistance value and the output voltage;

[0015] determining a normalized output current according to the normalized base current and the output current;

[0016] determining a voltage conversion ratio according to the input voltage and the output voltage;

[0017] The turn-on time, the natural commutation time, the conduction time and the forced commutation time are determined according to the voltage conversion ratio, the normalized output current and the natural frequency by using a preset set of equations.

[0018] Optionally, the preset equation group is:

[0019]

[0020] Wherein, J1 is the normalized inductor current corresponding to the end time t1 of the on-time, J0 is the normalized inductor current corresponding to the initial time t0 of the on-time, J0=J4, J4 is the normalized inductor current corresponding to the end time t4 of the forced commutation time, m is the voltage conversion ratio, ω0 is the natural frequency, t s is the opening time, t s =t1-t0, J2 is the normalized inductor current corresponding to the end time t2 of the natural commutation time, cos() is the cosine function, t n is the natural commutation time, t n =t2-t1, sin() is a sine function, J3 is the normalized inductor current corresponding to the end time t3 of the conduction time, J3=0, t d is the on-time, t d =t3-t2, t f is the forced commutation time, t f=t4-t3, J avg is the normalized output current.

[0021] Optionally, the method further comprises:

[0022] Obtaining a normalized inductor current expression corresponding to the turn-on time, a normalized inductor current expression and a normalized switch node voltage expression corresponding to the natural commutation time, a normalized inductor current expression corresponding to the turn-on time, a normalized inductor current expression and a normalized switch node voltage expression corresponding to the forced commutation time, and an expression of the normalized output current;

[0023] Determine the expression of the normalized inductor current corresponding to the end moment of the on-time according to the normalized inductor current expression corresponding to the on-time;

[0024] Determining an expression of normalized inductor current and an expression of normalized switch node voltage corresponding to the end moment of the natural commutation time according to the normalized inductor current expression and the normalized switch node voltage expression corresponding to the natural commutation time;

[0025] Determine an expression of the normalized inductor current corresponding to the end moment of the conduction time according to the normalized inductor current expression corresponding to the conduction time;

[0026] Determining the expression of the normalized inductor current and the expression of the normalized switch node voltage corresponding to the end moment of the forced commutation time according to the normalized inductor current expression and the normalized switch node voltage expression corresponding to the forced commutation time;

[0027] The preset equation group is constructed according to the expression of the normalized inductor current corresponding to the end moment of the turn-on time, the expression of the normalized inductor current and the expression of the normalized switch node voltage corresponding to the end moment of the natural commutation time, the expression of the normalized inductor current corresponding to the end moment of the conduction time, the expression of the normalized inductor current and the expression of the normalized switch node voltage corresponding to the end moment of the forced commutation time, the expression of the normalized inductor current corresponding to the turn-on time, the expression of the normalized inductor current corresponding to the natural commutation time, the expression of the normalized inductor current corresponding to the conduction time, the expression of the normalized inductor current corresponding to the forced commutation time, and the expression of the normalized output current.

[0028] Optionally, the normalized inductor current expression corresponding to the turn-on time is:

[0029] J L (t) = J0 + (m-1)ω0 (t-t0);

[0030] The normalized inductor current expression and the normalized switch node voltage expression corresponding to the natural commutation time are:

[0031]

[0032] The normalized inductor current expression corresponding to the on-time is:

[0033] J L (t) = J2-ω0(t-t2);

[0034] The normalized inductor current expression and the normalized switch node voltage expression corresponding to the forced commutation time are:

[0035]

[0036] Among them, J0 is the normalized inductor current corresponding to the initial moment t0 of the turn-on time, J0=J4, J4 is the normalized inductor current corresponding to the end moment t4 of the forced commutation time, m is the voltage conversion ratio, ω0 is the natural frequency, J1 is the normalized inductor current corresponding to the end moment t1 of the turn-on time, cos() is the cosine function, sin() is the sine function, J2 is the normalized inductor current corresponding to the end moment t2 of the natural commutation time, J3 is the normalized inductor current corresponding to the end moment t3 of the turn-on time, and J3=0.

[0037] Optionally, the expression of the normalized inductor current corresponding to the end moment of the turn-on time is:

[0038] J L (t1) = J1 = J0 + (m-1) ω0t s ;

[0039] The expression of the normalized inductor current and the expression of the normalized switch node voltage corresponding to the end time of the natural commutation time are:

[0040]

[0041] The expression of the normalized inductor current corresponding to the end time of the on-time is:

[0042] J L (t3) = J3 = J2 - ω0t d ;

[0043] The expression of the normalized inductor current and the expression of the normalized switch node voltage corresponding to the end time of the forced commutation time are:

[0044]

[0045] Wherein, J1 is the normalized inductor current corresponding to the end time t1 of the on-time, J0 is the normalized inductor current corresponding to the initial time t0 of the on-time, J0=J4, J4 is the normalized inductor current corresponding to the end time t4 of the forced commutation time, m is the voltage conversion ratio, ω0 is the natural frequency, t s is the opening time, t s =t1-t0, J2 is the normalized inductor current corresponding to the end time t2 of the natural commutation time, cos() is the cosine function, t n is the natural commutation time, t n =t2-t1, sin() is the sine function, v N2 is the normalized switch node voltage corresponding to the end time t2 of the natural commutation time, J3 is the normalized inductor current corresponding to the end time t3 of the conduction time, J3=0, t d is the on-time, t d =t3-t2, t f is the forced commutation time, t f =t4-t3,v N4 is the normalized switch node voltage corresponding to the end time t4 of the forced commutation time.

[0046] Optionally, the expression of the normalized output current is:

[0047]

[0048] Among them, J avg is the normalized output current, t s is the opening time, t n is the natural commutation time, t d is the on-time, t f is the forced commutation time, t4 is the end time of the forced commutation time, t0 is the initial time of the opening time, J L (t) is the normalized inductor current expression.

[0049] Optionally, obtain the natural frequency, including:

[0050] Obtaining the inductance value of the asynchronous Buck converter and the equivalent capacitance of the switch node to ground;

[0051] The natural frequency is determined according to the inductance value and the equivalent capacitance of the switch node to ground.

[0052] Optionally, determining a switching period and a duty cycle according to the turn-on time, the natural commutation time, the conduction time and the forced commutation time includes:

[0053] The sum of the on-time, the natural commutation time, the on-time and the forced commutation time is taken as the switching period;

[0054] The duty cycle is determined according to the switching period, the turn-on time and the forced commutation time.

[0055] Optionally, determining the duty cycle according to the switching period, the turn-on time and the forced commutation time includes:

[0056] The ratio between the target sum value and the switching period is used as the duty cycle, wherein the target sum value is the sum of the turn-on time and the forced commutation time.

[0057] To achieve the above object, the present invention provides a soft switch control device for an asynchronous Buck converter in a second aspect, the device comprising:

[0058] An acquisition module is used to obtain the input voltage, output voltage, output current and natural frequency of the asynchronous Buck converter;

[0059] A first determination module, configured to determine a turn-on time, a natural commutation time, a conduction time, and a forced commutation time according to the input voltage, the output voltage, the output current, and the natural frequency;

[0060] A second determination module, configured to determine a switching period and a duty cycle according to the turn-on time, the natural commutation time, the conduction time and the forced commutation time;

[0061] A generation control module is used to input the duty cycle and the switching period into a PWM module to generate a switch control signal, wherein the switch control signal is used to control the switching action of the asynchronous Buck converter.

[0062] To achieve the above-mentioned object, the present invention provides in a third aspect a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a controller, the controller executes the method as described in any one of the first aspects.

[0063] To achieve the above-mentioned purpose, the present invention provides a computer device in a fourth aspect, comprising a memory and a controller, wherein the memory stores a computer program, and when the computer program is executed by the controller, the controller executes the method as described in any one of the first aspects.

[0064] The embodiment of the present invention has the following beneficial effects: the above method obtains the input voltage, output voltage, output current and natural frequency of the asynchronous Buck converter, and then determines the turn-on time, natural commutation time, conduction time and forced commutation time according to the input voltage, output voltage, output current and natural frequency, and then determines the switching period and duty cycle according to the turn-on time, natural commutation time, conduction time and forced commutation time, and finally inputs the duty cycle and switching period into the PWM module to generate a switch control signal, which is used to control the switching action of the asynchronous Buck converter; that is, a new control method is proposed, by real-time acquisition of key parameters such as the input voltage, output voltage, output current and natural frequency of the asynchronous Buck converter, using these parameters to online calculate the switching frequency (the inverse of the switching period) and duty cycle required for realizing soft switching, so as to generate a switch control signal for switching action control, and since the method does not rely on the zero-crossing point detection of the inductor current, it can completely eliminate the dependence on the high-frequency current sensor and effectively avoid the interference of the switching noise on the control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0066] in:

[0067] Figure 1 This is a schematic diagram of an asynchronous Buck converter in an embodiment of the present application;

[0068] Figure 2 A schematic diagram of a soft switching control method for an asynchronous Buck converter in an embodiment of the present application;

[0069] Figure 3 Schematic diagram of simulation waveforms of a switch control signal, a normalized inductor current, and a normalized switch node voltage in an embodiment of the present application;

[0070] Figure 4 A schematic diagram of a soft switch control device for an asynchronous Buck converter in an embodiment of the present application;

[0071] Figure 5 1 is a diagram of the internal structure of a computer device in some embodiments. DETAILED DESCRIPTION

[0072] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0073] The asynchronous Buck converter is a simple and widely used step-down converter. Its core circuit consists of a switch tube, a diode, and an LC filter network. In traditional application scenarios, the converter mostly operates in continuous conduction mode, in which the switch tube operates in hard switching mode. However, this operating mode brings significant switching losses, which not only limits the increase in the switching frequency of the converter, but also leads to an increase in the volume and weight of passive components such as inductors and capacitors, making it difficult to achieve the design goal of high power density.

[0074] In order to reduce switching losses and improve the operating efficiency of the converter at high switching frequencies, the industry has begun to explore operating the asynchronous Buck converter in the boundary conduction mode (BCM). In this mode, the switch tube can achieve soft switching operation, thereby effectively reducing switching losses.

[0075] However, the existing BCM control method relies on complex hardware circuits to accurately detect the zero-crossing point of the inductor current. As the switching frequency continues to increase, the existing current sensors can no longer meet the demand for accurate measurement of the inductor current, and the zero-crossing detection circuit is easily interfered by switching noise, which may cause false triggering of the switch and thus affect the stability of the control system.

[0076] In response to the above problems, the present application proposes a soft switching control method for an asynchronous Buck converter. Since it does not rely on the zero-crossing detection of the inductor current, it can completely eliminate the dependence on high-frequency current sensors and effectively avoid the interference of switching noise on the control system. The specific implementation principle will be described in detail in the following embodiments.

[0077] In order to better explain the following embodiments, the present application first provides a circuit topology diagram of an asynchronous Buck converter and briefly describes it. Figure 1 , is a schematic diagram of an asynchronous Buck converter in an embodiment of the present application, wherein the asynchronous Buck converter shown in the schematic diagram includes a DC power supply, an input filter capacitor C1, a switch tube S, a diode D, an inductor L, an output filter capacitor C2 and a load resistor R L .

[0078] Among them, one end of the DC power supply is connected to one end of the input filter capacitor C1 and the drain end of the switch tube S respectively, and the other end of the DC power supply is connected to the other end of the input filter capacitor C1, the anode end of the diode D, one end of the output filter capacitor C2, and the load resistor R L One end of the output filter capacitor C2 is connected to the load resistor R L The other end of each is connected to one end of the inductor L, and the other end of the inductor L is connected to the source end of the switch tube S and the cathode end of the diode D respectively.

[0079] In some embodiments, the asynchronous Buck converter can be operated by inputting a switch control signal into the gate terminal of the switch tube S.

[0080] in, Figure 1 The V g is the input voltage of the asynchronous Buck converter, i L is the inductor current of the inductor L, I O is the output current of the asynchronous Buck converter, v sw is the switch node voltage of the asynchronous Buck converter, V O is the output voltage of the asynchronous Buck converter, and c is the switch control signal.

[0081] In a first aspect, the present application provides a soft switching control method for an asynchronous Buck converter.

[0082] See also Figure 2 , is a schematic diagram of a soft switching control method of an asynchronous Buck converter in an embodiment of the present application, the method comprising:

[0083] Step 210: Obtain the input voltage, output voltage, output current and natural frequency of the asynchronous Buck converter.

[0084] The natural frequency refers to the oscillation frequency of the asynchronous Buck converter determined by the parameters of the circuit itself (such as inductance, capacitance, etc.) when there is no external control.

[0085] In some embodiments, the natural frequency may be determined based on parameters such as the inductance and capacitance of the asynchronous Buck converter.

[0086] In some embodiments, the asynchronous Buck converter may be sampled to obtain input voltage, output voltage, and output current.

[0087] Step 220: Determine the turn-on time, natural commutation time, conduction time and forced commutation time according to the input voltage, the output voltage, the output current and the natural frequency.

[0088] Among them, the turn-on time refers to the turn-on time of the switch tube of the asynchronous Buck converter; the natural commutation time refers to the commutation time of the current switching from the switch tube of the asynchronous Buck converter to the diode; the conduction time refers to the conduction time of the diode of the asynchronous Buck converter; the forced commutation time refers to the commutation time of the current switching from the diode of the asynchronous Buck converter to the switch tube.

[0089] Step 230: Determine the switching period and duty cycle according to the turn-on time, the natural commutation time, the conduction time and the forced commutation time.

[0090] The switching period refers to the period in the switching control signal of the asynchronous Buck converter, and the duty cycle refers to the duty cycle in the switching control signal of the asynchronous Buck converter.

[0091] In some embodiments, the sum of the turn-on time, the natural commutation time, the conduction time and the forced commutation time may be taken as the switching period, and the duty cycle may be determined based on the switching period.

[0092] Step 240: Input the duty cycle and the switching period into the PWM module to generate a switch control signal, which is used to control the switching action of the asynchronous Buck converter.

[0093] Among them, the PWM module is a pulse width modulation module.

[0094] In some embodiments, the duty cycle and switching period can be input into the PWM module to generate a switching control signal. The generated switching control signal is then amplified by the driving circuit and input into the gate end of the switching tube of the asynchronous Buck converter to control the switching action of the asynchronous Buck converter.

[0095] It should be noted that since the switching period and the switching frequency are inversely related, in other embodiments, the switching frequency can be obtained according to the switching period, and then the duty cycle and the switching frequency are input into the PWM module to generate a switching control signal. The generated switching control signal is then amplified by the driving circuit and input into the gate end of the switching tube of the asynchronous Buck converter to control the switching action of the asynchronous Buck converter.

[0096] In an embodiment of the present application, a new control method is proposed. By acquiring key parameters such as the input voltage, output voltage, output current and natural frequency of the asynchronous Buck converter in real time, these parameters are used to online calculate the switching frequency (the inverse of the switching period) and duty cycle required to achieve soft switching, so as to generate a switching control signal for switching action control. Since this method does not rely on the zero-crossing point detection of the inductor current, it can completely eliminate the dependence on high-frequency current sensors and effectively avoid the interference of switching noise on the control system.

[0097] In addition, this method of the present application also has the following advantages: by implementing the soft switching control method proposed in the present application, the asynchronous Buck converter can achieve stable soft switching operation, which not only significantly reduces switching losses and electromagnetic interference, but also improves the operating efficiency and power density of the converter, and enhances the stability and reliability of the control system, laying a solid foundation for the widespread application of asynchronous Buck converters in high-performance, high-reliability application scenarios.

[0098] In a feasible implementation, step 220 in the above embodiment determines the turn-on time, natural commutation time, conduction time and forced commutation time according to the input voltage, output voltage, output current and natural frequency, including: obtaining the inductance value and the equivalent capacitance of the switch node to ground of the asynchronous Buck converter; determining the normalized base resistance value according to the inductance value and the equivalent capacitance of the switch node to ground; determining the normalized base current according to the normalized base resistance value and the output voltage; determining the normalized output current according to the normalized base current and the output current; determining the voltage conversion ratio according to the input voltage and the output voltage; and using a preset set of equations to determine the turn-on time, natural commutation time, conduction time and forced commutation time according to the voltage conversion ratio, the normalized output current and the natural frequency.

[0099] Among them, the preset equation group can be obtained and pre-set by the operator based on a large amount of experience, experiments or statistics; the inductance value refers to the inductance value of the inductor of the asynchronous Buck converter; the equivalent capacitance of the switch node to the ground refers to the equivalent capacitance formed between the source of the switch tube of the asynchronous Buck converter and the ground.

[0100] Regarding the determination method of the normalized base resistance value, in some embodiments, the formula Determine the normalized base resistance value; where R b is the normalized base resistance value, L is the inductance value, and C is the equivalent capacitance of the switch node to ground.

[0101] Regarding the determination method of the normalized base current, in some embodiments, the output voltage may be used as the normalized base voltage, and the ratio between the normalized base voltage and the normalized base resistance value may be used as the normalized base current.

[0102] Regarding the determination method of the normalized output current, in some embodiments, the ratio between the output current and the normalized base current may be used as the normalized output current.

[0103] Regarding the determination method of the voltage conversion ratio, in some embodiments, the ratio between the input voltage and the output voltage may be used as the voltage conversion ratio.

[0104] In the embodiment of the present application, by introducing intermediate variables such as the normalized base resistance value, the normalized base current and the normalized output current, the subsequent calculation process can be simplified and the calculation accuracy can be improved.

[0105] Furthermore, by using a preset set of equations to determine key parameters such as the turn-on time, the characteristic changes of the asynchronous Buck converter under different operating conditions can be fully considered. Since the preset set of equations is obtained based on a large amount of experience, experiments or statistics, it can adapt to a variety of different application scenarios and load conditions, thereby enhancing the adaptability and robustness of the control system.

[0106] In addition, using a preset set of equations to determine key parameters such as the turn-on time can improve calculation efficiency and ensure the accuracy of the calculated turn-on time, natural commutation time, conduction time and forced commutation time.

[0107] In a feasible implementation, the preset equation group in the above embodiment is:

[0108]

[0109] Wherein, J1 is the normalized inductor current corresponding to the end time t1 of the on-time, J0 is the normalized inductor current corresponding to the initial time t0 of the on-time, J0=J4, J4 is the normalized inductor current corresponding to the end time t4 of the forced commutation time, m is the voltage conversion ratio, ω0 is the natural frequency, t s is the opening time, t s =t1-t0, J2 is the normalized inductor current corresponding to the end time t2 of the natural commutation time, cos() is the cosine function, t n is the natural commutation time, t n =t2-t1, sin() is a sine function, J3 is the normalized inductor current corresponding to the end time t3 of the conduction time, J3=0, t d is the on-time, t d =t3-t2, t f is the forced commutation time, t f =t4-t3, J avg is the normalized output current.

[0110] It should be noted that in the above preset equations, since J3 = 0, J0 = J4, there are still 7 unknowns in the preset equations, namely J1, J2, J4, t s ,t n ,t d and t f , and the preset equation group contains 7 equations, so the preset equation group can be solved to obtain t s ,t n ,td and t f .

[0111] It should be further noted that J0, J1, J2, J3 and J4 in the present application are all normalized inductor currents, and are not inductor currents that can be obtained by directly sampling the asynchronous Buck converter.

[0112] In the embodiments of the present application, a rigorous set of preset equations is provided from a mathematical perspective. The accuracy of the calculated turn-on time, natural commutation time, conduction time and forced commutation time can be ensured from the rigor of mathematical logic, and the above-mentioned set of preset equations is preferably shown to provide reference, understanding and calculation for technical personnel.

[0113] In addition, by adopting the preset equation group preferably provided in the above-mentioned present application to calculate the turn-on time, natural commutation time, conduction time and forced commutation time, the calculation complexity can be effectively reduced and the calculation efficiency can be improved, and the accuracy of the calculated turn-on time, natural commutation time, conduction time and forced commutation time can be ensured.

[0114] In a feasible implementation, the method in the above embodiment further includes: obtaining a normalized inductor current expression corresponding to the turn-on time, a normalized inductor current expression and a normalized switch node voltage expression corresponding to the natural commutation time, a normalized inductor current expression corresponding to the conduction time, a normalized inductor current expression and a normalized switch node voltage expression corresponding to the forced commutation time, and an expression of the normalized output current; determining an expression of the normalized inductor current corresponding to the end time of the turn-on time according to the normalized inductor current expression corresponding to the turn-on time; determining an expression of the normalized inductor current and an expression of the normalized switch node voltage corresponding to the end time of the natural commutation time according to the normalized inductor current expression corresponding to the natural commutation time; determining an expression of the normalized inductor current corresponding to the end time of the conduction time according to the normalized inductor current expression corresponding to the conduction time; Expression; determining the expression of the normalized inductor current and the expression of the normalized switch node voltage corresponding to the end time of the forced commutation time according to the normalized inductor current expression and the normalized switch node voltage expression corresponding to the forced commutation time; constructing a preset equation group according to the expression of the normalized inductor current corresponding to the end time of the turn-on time, the expression of the normalized inductor current and the expression of the normalized switch node voltage corresponding to the end time of the natural commutation time, the expression of the normalized inductor current corresponding to the end time of the conduction time, the expression of the normalized inductor current and the expression of the normalized switch node voltage corresponding to the end time of the forced commutation time, the normalized inductor current expression corresponding to the turn-on time, the normalized inductor current expression corresponding to the natural commutation time, the normalized inductor current expression corresponding to the conduction time, the normalized inductor current expression corresponding to the forced commutation time, and the expression of the normalized output current.

[0115] It should be noted that, from the above embodiments, it can be known that there is a corresponding relationship between the output current and the normalized output current, that is, the normalized output current can be calculated based on the output current. Therefore, in some embodiments, the expression of the output current of the asynchronous Buck converter can be obtained first, and then the expression of the normalized output current can be determined based on the expression of the output current.

[0116] In an embodiment of the present application, the construction process of the preset set of equations is derived in detail through the normalized inductor current expression and the normalized switch node voltage expression of the asynchronous Buck converter, and combined with the expression of the normalized output current, to ensure the accuracy of the preset set of equations from the perspective of mathematical logic.

[0117] In a feasible implementation, the normalized inductor current expression corresponding to the turn-on time in the above embodiment is:

[0118] J L(t) = J0 + (m-1)ω0 (t-t0);

[0119] The normalized inductor current expression and the normalized switch node voltage expression corresponding to the natural commutation time in the above embodiment are:

[0120]

[0121] The normalized inductor current expression corresponding to the on-time in the above embodiment is:

[0122] J L (t) = J2-ω0(t-t2);

[0123] The normalized inductor current expression and the normalized switch node voltage expression corresponding to the forced commutation time in the above embodiment are:

[0124]

[0125] Among them, J0 is the normalized inductor current corresponding to the initial moment t0 of the turn-on time, J0=J4, J4 is the normalized inductor current corresponding to the end moment t4 of the forced commutation time, m is the voltage conversion ratio, ω0 is the natural frequency, J1 is the normalized inductor current corresponding to the end moment t1 of the turn-on time, cos() is the cosine function, sin() is the sine function, J2 is the normalized inductor current corresponding to the end moment t2 of the natural commutation time, J3 is the normalized inductor current corresponding to the end moment t3 of the conduction time, and J3=0.

[0126] In other embodiments, a normalized switch node voltage expression corresponding to the turn-on time and a normalized switch node voltage expression corresponding to the conduction time may be established according to actual needs; wherein the normalized switch node voltage expression corresponding to the turn-on time is: v N (t) = m; the normalized switch node voltage expression corresponding to the on-time is: v N (t)=0.

[0127] In the embodiments of the present application, rigorous normalized inductor current expressions and normalized switch node voltage expressions corresponding to the turn-on time, natural commutation time, conduction time and forced commutation time are provided from a mathematical perspective. The accuracy of the constructed preset equation group can be ensured from the rigor of mathematical logic, and the above-mentioned normalized inductor current expressions and normalized switch node voltage expressions are preferably shown to provide reference, understanding and calculation for technical personnel.

[0128] In addition, by adopting the normalized inductor current expression and the normalized switch node voltage expression preferably provided in the above-mentioned present application, the accuracy of the preset equation group can be ensured from the source.

[0129] In a feasible implementation, the expression of the normalized inductor current corresponding to the end time of the turn-on time in the above embodiment is:

[0130] J L (t1) = J1 = J0 + (m-1) ω0t s ;

[0131] The expression of the normalized inductor current and the expression of the normalized switch node voltage corresponding to the end time of the natural commutation time in the above embodiment are:

[0132]

[0133] The expression of the normalized inductor current corresponding to the end time of the conduction time in the above embodiment is:

[0134] J L (t3) = J3 = J2 - ω0t d ;

[0135] The expression of the normalized inductor current and the expression of the normalized switch node voltage corresponding to the end time of the forced commutation time in the above embodiment are:

[0136]

[0137] Wherein, J1 is the normalized inductor current corresponding to the end time t1 of the on-time, J0 is the normalized inductor current corresponding to the initial time t0 of the on-time, J0=J4, J4 is the normalized inductor current corresponding to the end time t4 of the forced commutation time, m is the voltage conversion ratio, ω0 is the natural frequency, t s is the opening time, t s =t1-t0, J2 is the normalized inductor current corresponding to the end time t2 of the natural commutation time, cos() is the cosine function, t n is the natural commutation time, t n =t2-t1, sin() is the sine function, v N2 is the normalized switch node voltage corresponding to the end time t2 of the natural commutation time, J3 is the normalized inductor current corresponding to the end time t3 of the conduction time, J3=0, t d is the on-time, t d =t3-t2, t f is the forced commutation time, t f =t4-t3,v N4 is the normalized switch node voltage corresponding to the end time t4 of the forced commutation time.

[0138] In other embodiments, an expression of a normalized switch node voltage corresponding to the end time of the on-time and an expression of a normalized switch node voltage corresponding to the end time of the on-time may be established according to actual needs; wherein the expression of the normalized switch node voltage corresponding to the end time of the on-time is: v N (t1) = v N1 =m,v N1 is the normalized switch node voltage corresponding to the end time t1 of the on-time; the expression of the normalized switch node voltage corresponding to the end time of the on-time is: v N (t3) = v N3 =0, v N3 is the normalized switch node voltage corresponding to the end time t3 of the on-time.

[0139] It should be noted that the v N1 、v N2 、v N3 and v N4 They are all normalized switch node voltages, and are similar to the explanations for J0, J1, J2, J3 and J4 in the above embodiments, which will not be repeated here.

[0140] In some embodiments, the asynchronous Buck converter can be sampled to obtain the switch node voltages corresponding to the turn-on time, natural commutation time, conduction time and forced commutation time, respectively, and then the output voltage is used as the normalized base voltage, and the ratio between the switch node voltage corresponding to the turn-on time and the normalized base voltage is used as the normalized switch node voltage corresponding to the end time t1 of the turn-on time, the ratio between the switch node voltage corresponding to the natural commutation time and the normalized base voltage is used as the normalized switch node voltage corresponding to the end time t2 of the natural commutation time, the ratio between the switch node voltage corresponding to the conduction time and the normalized base voltage is used as the normalized switch node voltage corresponding to the end time t3 of the conduction time, and the ratio between the switch node voltage corresponding to the forced commutation time and the normalized base voltage is used as the normalized switch node voltage corresponding to the end time t4 of the forced commutation time.

[0141] In the embodiment of the present application, rigorous expressions of the normalized inductor current and the normalized switch node voltage corresponding to the turn-on time, natural commutation time, conduction time and end time of the forced commutation time are provided from a mathematical perspective. The accuracy of the constructed preset equation group can be ensured from the rigor of mathematical logic, and the above-mentioned expressions of the normalized inductor current and the normalized switch node voltage are preferably shown to provide reference, understanding and calculation for technical personnel.

[0142] In addition, by adopting the expression of the normalized inductor current and the expression of the normalized switch node voltage preferably provided in the above-mentioned present application, the accuracy of the preset equation group can be ensured from the source.

[0143] In a feasible implementation, the expression of the normalized output current in the above embodiment is:

[0144]

[0145] Among them, J avg is the normalized output current, t s is the opening time, t n is the natural commutation time, t d is the on-time, t f is the forced commutation time, t4 is the end time of the forced commutation time, t0 is the initial time of the opening time, J L (t) is the normalized inductor current expression.

[0146] In some embodiments, the expression of the output current may be first obtained, and then the expression of the normalized output current may be determined according to the expression of the output current using the relationship between the output current and the normalized output current.

[0147] Among them, the expression of output current is: I0 is the output current, I b is the normalized base current. For the normalized base current, reference may be made to the explanation of the above embodiment, which will not be described in detail here.

[0148] In the embodiments of the present application, a rigorous expression of the normalized output current is provided from a mathematical perspective. The accuracy of the constructed preset equation group can be ensured from the rigor of mathematical logic, and the expression of the normalized output current is preferably shown to provide reference, understanding and calculation for technical personnel.

[0149] In addition, by adopting the expression of the normalized output current preferably provided in the above-mentioned present application, the accuracy of the preset equation group can be ensured from the source.

[0150] In a feasible implementation, step 210 in the above embodiment, obtaining the natural frequency, includes: obtaining the inductance value of the asynchronous Buck converter and the equivalent capacitance of the switch node to ground; and determining the natural frequency according to the inductance value and the equivalent capacitance of the switch node to ground.

[0151] Regarding the determination method of the natural frequency, in some embodiments, the formula is used Determine the natural frequency; where ω0 is the natural frequency, L is the inductance value, and C is the equivalent capacitance of the switch node to ground.

[0152] In the embodiment of the present application, by directly obtaining the inductance value of the asynchronous Buck converter and the equivalent capacitance of the switch node to the ground, and determining the natural frequency based on these two key parameters, the oscillation characteristics of the circuit itself can be reflected more directly and accurately. Compared with other complex calculation or measurement methods, it not only simplifies the operation process, but also improves the accuracy of determining the natural frequency. The accurate natural frequency value is an important basis for the subsequent calculation of the turn-on time, natural commutation time, conduction time and forced commutation time, thereby ensuring the accuracy and reliability of the entire soft switching control method.

[0153] In a feasible implementation, step 230 in the above embodiment determines the switching period and the duty cycle according to the turn-on time, the natural commutation time, the conduction time and the forced commutation time, including: taking the sum of the turn-on time, the natural commutation time, the conduction time and the forced commutation time as the switching period; determining the duty cycle according to the switching period, the turn-on time and the forced commutation time.

[0154] In the embodiment of the present application, by directly taking the sum of the turn-on time, the natural commutation time, the conduction time and the forced commutation time as the switching period, the total time of the asynchronous Buck converter in a complete working cycle can be accurately reflected, thereby ensuring the accuracy of the switching period and providing a reliable basis for the subsequent determination of the duty cycle.

[0155] Furthermore, by determining the duty cycle based on the switching cycle, turn-on time and forced commutation time, the commutation process of the switch tube and the diode, as well as the impact on the switching cycle, can be fully considered to ensure that the switch tube is turned on and off at the appropriate time point, thereby achieving soft switching operation and reducing switching losses.

[0156] In a feasible implementation, the duty cycle is determined according to the switching period, the turn-on time and the forced commutation time in the above embodiment, including: taking the ratio between the target sum value and the switching period as the duty cycle, wherein the target sum value is the sum of the turn-on time and the forced commutation time.

[0157] In the embodiment of the present application, the duty cycle is accurately calculated by directly calculating the sum of the turn-on time and the forced commutation time as the target sum value, and taking its ratio to the switching period as the duty cycle. This calculation method not only simplifies the duty cycle determination process, but also fully considers the influence of the commutation process of the switch tube and the diode on the switching period, thereby ensuring the accuracy and reliability of the duty cycle.

[0158] In order to verify the effectiveness and feasibility of this application, this application also conducted detailed simulation experiments.

[0159] In the simulation, the present application sets the following main parameters: input voltage is 270V, output voltage is 200V, input filter capacitor is 200μF, output filter capacitor is 80μF, inductor value is 12μF, and equivalent capacitance of switch node to ground is 400pF.

[0160] This application is particularly verified under various output current conditions. Through simulation, this application has obtained Figure 3 The waveform shown in the figure, Figure 3 : is a schematic diagram of simulation waveforms of the switch control signal, the normalized inductor current and the normalized switch node voltage in the embodiment of the present application, wherein c is the switch control signal, t s is the opening time, t n is the natural commutation time, t d is the on-time, t f is the forced commutation time, v N is the normalized switch node voltage expression at each time, j L is the normalized inductor current expression at each moment, J0 is the normalized inductor current corresponding to the initial moment t0 of the turn-on time, J0=J4, J4 is the normalized inductor current corresponding to the end moment t4 of the forced commutation time, J1 is the normalized inductor current corresponding to the end moment t1 of the turn-on time, J2 is the normalized inductor current corresponding to the end moment t2 of the natural commutation time, J3 is the normalized inductor current corresponding to the end moment t3 of the turn-on time, J3=0.

[0161] It can be clearly seen from the simulation waveform diagram that before the rising edge of the switch control signal of the switch tube arrives, the normalized switch node voltage has smoothly increased from 0 to the normalized input voltage, that is, the switch node voltage has smoothly increased from 0 to the input voltage. This phenomenon fully proves that the switch tube of the asynchronous Buck converter realizes soft switching operation, thereby verifying the effectiveness and feasibility of the soft switching control method proposed in this application.

[0162] In a second aspect, the present application provides a soft switching control device for an asynchronous Buck converter.

[0163] See also Figure 4 , is a schematic diagram of a soft switch control device for an asynchronous Buck converter in an embodiment of the present application, the device 410 includes:

[0164] An acquisition module 411 is used to acquire an input voltage, an output voltage, an output current and a natural frequency of an asynchronous Buck converter;

[0165] A first determination module 412, for determining a turn-on time, a natural commutation time, a conduction time and a forced commutation time according to an input voltage, an output voltage, an output current and a natural frequency;

[0166] A second determination module 413, configured to determine a switching period and a duty cycle according to the turn-on time, the natural commutation time, the conduction time and the forced commutation time;

[0167] The generation control module 414 is used to input the duty cycle and the switching period into the PWM module to generate a switch control signal, and the switch control signal is used to control the switching action of the asynchronous Buck converter.

[0168] In the embodiment of the present application, the related contents of the acquisition module 411, the first determination module 412, the second determination module 413 and the generation control module 414 can be referred to in Figure 2 The contents in the illustrated embodiment will not be described in detail here.

[0169] It should be noted that the device 410 of the present application also includes some other modules. It can be understood that the method of the present application and the device 410 have a one-to-one correspondence. Therefore, some other modules of the device 410 of the present application are the contents corresponding to the method of the present application in the above-mentioned embodiment.

[0170] In an embodiment of the present application, a new control device is proposed. By acquiring key parameters such as the input voltage, output voltage, output current and natural frequency of the asynchronous Buck converter in real time, these parameters are used to online calculate the switching frequency (the inverse of the switching period) and duty cycle required to achieve soft switching, so as to generate a switching control signal to control the switching action. Since the device does not rely on the zero-crossing point detection of the inductor current, it can completely eliminate the dependence on high-frequency current sensors and effectively avoid the interference of switching noise on the control system.

[0171] In addition, this method of the present application also has the following advantages: by implementing the soft switching control device proposed in the present application, the asynchronous Buck converter can achieve stable soft switching operation, which not only significantly reduces switching losses and electromagnetic interference, but also improves the operating efficiency and power density of the converter, and enhances the stability and reliability of the control system, laying a solid foundation for the widespread application of asynchronous Buck converters in high-performance, high-reliability application scenarios.

[0172] In a third aspect, the present application further provides a computer-readable storage medium storing a computer program. When the computer program is executed by a controller, the controller executes a soft switching control method for an asynchronous Buck converter in the above method embodiment.

[0173] In a fourth aspect, the present application further provides a computer device, including a memory and a controller, wherein the memory stores a computer program, and when the computer program is executed by the controller, the controller executes a soft switching control method for an asynchronous Buck converter in the above method embodiment.

[0174] Figure 5 The internal structure diagram of a computer device in some embodiments is shown. The computer device may be a terminal, a server, or a gateway. Figure 5 As shown, the computer device includes a controller, a memory and a network interface connected through a system bus.

[0175] The memory includes a non-volatile storage medium and an internal memory. The non-volatile storage medium of the computer device stores an operating system and may also store a computer program. When the computer program is executed by the controller, the controller can implement each step in the above method embodiment. The internal memory may also store a computer program. When the computer program is executed by the controller, the controller can implement each step in the above method embodiment. Those skilled in the art can understand that Figure 5 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0176] A person skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing related hardware through a computer program. The program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods.

[0177] Among them, any reference to memory, storage, database or other media used in the embodiments provided in the present application may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0178] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, 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, they should be considered to be within the scope of this specification.

[0179] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A soft switching control method for an asynchronous Buck converter, characterized in that: The method comprises: Get the input voltage, output voltage, output current and natural frequency of the asynchronous Buck converter; Determine a turn-on time, a natural commutation time, a conduction time and a forced commutation time according to the input voltage, the output voltage, the output current and the natural frequency; Determine a switching period and a duty cycle according to the turn-on time, the natural commutation time, the conduction time and the forced commutation time; The duty cycle and the switching period are input into a PWM module to generate a switching control signal, and the switching control signal is used to control the switching action of the asynchronous Buck converter.

2. The method according to claim 1, characterized in that The determining of the turn-on time, the natural commutation time, the conduction time and the forced commutation time according to the input voltage, the output voltage, the output current and the natural frequency comprises: Obtaining the inductance value of the asynchronous Buck converter and the equivalent capacitance of the switch node to ground; Determining a normalized base resistance value according to the inductance value and an equivalent capacitance of the switch node to ground; Determining a normalized base current according to the normalized base resistance value and the output voltage; determining a normalized output current according to the normalized base current and the output current; determining a voltage conversion ratio according to the input voltage and the output voltage; The turn-on time, the natural commutation time, the conduction time and the forced commutation time are determined according to the voltage conversion ratio, the normalized output current and the natural frequency by using a preset set of equations.

3. The method according to claim 2, characterized in that The preset equation group is: Wherein, J1 is the normalized inductor current corresponding to the end time t1 of the on-time, J0 is the normalized inductor current corresponding to the initial time t0 of the on-time, J0=J4, J4 is the normalized inductor current corresponding to the end time t4 of the forced commutation time, m is the voltage conversion ratio, ω0 is the natural frequency, t s is the opening time, t s =t1-t0, J2 is the normalized inductor current corresponding to the end time t2 of the natural commutation time, cos() is the cosine function, t n is the natural commutation time, t n =t2-t1, sin() is a sine function, J3 is the normalized inductor current corresponding to the end time t3 of the conduction time, J3=0, t d is the on-time, t d =t3-t2, t f is the forced commutation time, t f =t4-t3, J avg is the normalized output current.

4. The method according to claim 3, characterized in that The method further comprises: Obtaining a normalized inductor current expression corresponding to the turn-on time, a normalized inductor current expression and a normalized switch node voltage expression corresponding to the natural commutation time, a normalized inductor current expression corresponding to the turn-on time, a normalized inductor current expression and a normalized switch node voltage expression corresponding to the forced commutation time, and an expression of the normalized output current; Determine the expression of the normalized inductor current corresponding to the end moment of the on-time according to the normalized inductor current expression corresponding to the on-time; Determining an expression of normalized inductor current and an expression of normalized switch node voltage corresponding to the end moment of the natural commutation time according to the normalized inductor current expression and the normalized switch node voltage expression corresponding to the natural commutation time; Determine an expression of the normalized inductor current corresponding to the end moment of the conduction time according to the normalized inductor current expression corresponding to the conduction time; Determining the expression of the normalized inductor current and the expression of the normalized switch node voltage corresponding to the end moment of the forced commutation time according to the normalized inductor current expression and the normalized switch node voltage expression corresponding to the forced commutation time; The preset equation group is constructed according to the expression of the normalized inductor current corresponding to the end moment of the turn-on time, the expression of the normalized inductor current and the expression of the normalized switch node voltage corresponding to the end moment of the natural commutation time, the expression of the normalized inductor current corresponding to the end moment of the conduction time, the expression of the normalized inductor current and the expression of the normalized switch node voltage corresponding to the end moment of the forced commutation time, the expression of the normalized inductor current corresponding to the turn-on time, the expression of the normalized inductor current corresponding to the natural commutation time, the expression of the normalized inductor current corresponding to the conduction time, the expression of the normalized inductor current corresponding to the forced commutation time, and the expression of the normalized output current.

5. The method according to claim 4, characterized in that The normalized inductor current expression corresponding to the turn-on time is: J L (t)=J0+(m-1)ω0(t-t0); The normalized inductor current expression and the normalized switch node voltage expression corresponding to the natural commutation time are: The normalized inductor current expression corresponding to the on-time is: J L (t)=J2-ω0(t-t2); The normalized inductor current expression and the normalized switch node voltage expression corresponding to the forced commutation time are: Among them, J0 is the normalized inductor current corresponding to the initial moment t0 of the turn-on time, J0=J4, J4 is the normalized inductor current corresponding to the end moment t4 of the forced commutation time, m is the voltage conversion ratio, ω0 is the natural frequency, J1 is the normalized inductor current corresponding to the end moment t1 of the turn-on time, cos() is the cosine function, sin() is the sine function, J2 is the normalized inductor current corresponding to the end moment t2 of the natural commutation time, J3 is the normalized inductor current corresponding to the end moment t3 of the turn-on time, and J3=0.

6. The method according to claim 4, characterized in that The expression of the normalized inductor current corresponding to the end time of the on-time is: J L (t1)=J1=J0+(m-1)ω0t s ; The expression of the normalized inductor current and the expression of the normalized switch node voltage corresponding to the end time of the natural commutation time are: The expression of the normalized inductor current corresponding to the end time of the on-time is: <h2 style=";text-align:left;direction:ltr">J<h2 style=";text-align:left;direction:ltr"> L <h2 style=";text-align:left;direction:ltr"> (t3) = J3 = J2 - ω0t<h2 style=";text-align:left;direction:ltr"> d <h2 style=";text-align:left;direction:ltr"> ; The expression of the normalized inductor current and the expression of the normalized switch node voltage corresponding to the end time of the forced commutation time are: Wherein, J1 is the normalized inductor current corresponding to the end time t1 of the on-time, J0 is the normalized inductor current corresponding to the initial time t0 of the on-time, J0=J4, J4 is the normalized inductor current corresponding to the end time t4 of the forced commutation time, m is the voltage conversion ratio, ω0 is the natural frequency, t s is the opening time, t s =t1-t0, J2 is the normalized inductor current corresponding to the end time t2 of the natural commutation time, cos() is the cosine function, t n is the natural commutation time, t n =t2-t1, sin() is the sine function, v N2 is the normalized switch node voltage corresponding to the end time t2 of the natural commutation time, J3 is the normalized inductor current corresponding to the end time t3 of the conduction time, J3=0, t d is the on-time, t d =t3-t2, t f is the forced commutation time, t f =t4-t3,v N4 is the normalized switch node voltage corresponding to the end time t4 of the forced commutation time.

7. The method according to claim 4, characterized in that The expression of the normalized output current is: Among them, J avg is the normalized output current, t s is the opening time, t n is the natural commutation time, t d is the on-time, t f is the forced commutation time, t4 is the end time of the forced commutation time, t0 is the initial time of the opening time, J L (t) is the normalized inductor current expression.

8. The method according to claim 1, characterized in that Get natural frequencies, including: Obtaining the inductance value of the asynchronous Buck converter and the equivalent capacitance of the switch node to ground; The natural frequency is determined according to the inductance value and the equivalent capacitance of the switch node to ground.

9. The method according to claim 1, characterized in that: Determining the switching period and the duty cycle according to the turn-on time, the natural commutation time, the conduction time and the forced commutation time includes: The sum of the on-time, the natural commutation time, the on-time and the forced commutation time is taken as the switching period; The duty cycle is determined according to the switching period, the turn-on time and the forced commutation time.

10. The method according to claim 9, characterized in that Determining the duty cycle according to the switching period, the turn-on time and the forced commutation time includes: The ratio between the target sum value and the switching period is used as the duty cycle, wherein the target sum value is the sum of the turn-on time and the forced commutation time.

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