A Buck-Boost Converter and Its Common-Mode Voltage Suppression Method

Abstract

The present invention discloses a buck-boost converter and a common-mode voltage suppression method thereof, belonging to the field of power electronics technology. It includes a buck-boost module and a common-mode voltage suppression module, and the buck-boost module is connected to the common-mode voltage suppression module; the common-mode voltage suppression module includes a first winding, a second winding, a first capacitor, and a second capacitor. The first end of the first winding is connected to the midpoint of the power inductor of the buck-boost module through the second capacitor, the second end of the first winding is connected to the power ground, the first end of the second winding is connected to the protective ground through the first capacitor, and the second end of the second winding is connected to the power ground. The present invention can achieve common-mode voltage suppression only through passive cancellation windings and compensation capacitors, without the need for additional auxiliary power supplies and calculation circuits, which is beneficial to reducing the system volume and increasing the power density.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and particularly to a buck-boost converter and a method for suppressing its common-mode voltage. Background Art

[0002] The new generation of wide bandgap power devices has increased the switching frequency of converters day by day. While greatly improving the performance and power density of the converters, it has also brought more serious electromagnetic interference, posing more challenges to electromagnetic noise suppression technology. The buck-boost converter is widely used in application scenarios with a wide voltage input range such as distributed power systems, portable power supply systems, and new energy power generation systems because of its small volume, simple circuit, and the functions of both boosting and bucking. However, the electromagnetic noise problem it generates cannot be ignored. In addition, the user's demand for more energy-efficient, more portable, and higher-performance power supplies has driven engineers to continuously pursue power supply design solutions with higher efficiency, smaller volume, and better performance, which also brings more challenges to the electromagnetic compatibility design of the power supply. Moreover, the high-frequency operation of the converter will also bring serious electromagnetic compatibility problems.

[0003] For a buck-boost converter, a large amount of heat is generated during the operation of the switching tube. To prevent the switching tube from being damaged due to overheating, a radiator is usually externally connected to the ground. The parasitic capacitance between the switching tube and the radiator becomes a path for conducted electromagnetic interference. And, during the turn-on and turn-off processes of the semiconductor switching tube in the converter, there will be short rising and falling edges, resulting in induced electrical signals in the parasitic capacitance in the converter under high-frequency operation. These electrical signals will cause the original PWM signal to mutate, generating strong electromagnetic interference noise. Electromagnetic interference (EMI) can pollute the surrounding electromagnetic environment through the ways of line conduction and space radiation, affect the stability of the converter and the external power supply system, reduce the performance of electrical equipment, and seriously endanger human health in severe cases.

[0004] Currently, there are mainly two methods for suppressing the electromagnetic interference of buck-boost converters. One is to design an EMI filter according to the spectrum of the original noise, and the other is to adjust the control strategy to effectively attenuate the noise in the circuit. Among them, the method of using a filter is relatively cumbersome in design, and the filter usually has a large volume, reducing the power density of the system. The existing method of reducing noise by adjusting the control strategy is computationally complex and difficult to implement. Summary of the Invention

[0005] The present invention aims to provide a buck-boost converter and a method for suppressing its common-mode voltage. By adopting a passive cancellation method, an equivalent common-mode noise source is made zero by adding a passive cancellation winding and a compensation capacitor, thereby canceling the common-mode voltage. The circuit structure is simple, the operation is convenient, no complex calculation is required, and the effect of suppressing the common-mode voltage is obvious.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A buck-boost converter includes a buck-boost module and a common-mode voltage suppression module. The buck-boost module is connected to the common-mode voltage suppression module. The common-mode voltage suppression module includes a first winding, a second winding, a first capacitor, and a second capacitor. The first end of the first winding is connected to the midpoint of the power inductor of the buck-boost module through the second capacitor. The second end of the first winding is connected to the power ground. The first end of the second winding is connected to the protective ground through the first capacitor. The second end of the second winding is connected to the power ground.

[0008] Further, the positions of the same-named ends of the first winding and the second winding are opposite.

[0009] Further, the first winding and the second winding are implemented by a transformer.

[0010] Further, the capacitance value of the first capacitor C com is:

[0011] ,

[0012] where the capacitor C pA is the parasitic capacitance between the midpoint of the bridge arm of the buck-boost module and the ground.

[0013] Further, the buck-boost module is a four-switch buck-boost module.

[0014] The present invention also provides a method for suppressing the common-mode voltage of a buck-boost converter, including

[0015] Connecting the first end of the first winding to the midpoint of the power inductor of the buck-boost converter through the second capacitor, and connecting the second end of the first winding to the power ground; connecting the first end of the second winding to the protective ground through the first capacitor, and connecting the second end of the second winding to the power ground;

[0016] Extracting the parasitic capacitances between each part of the buck-boost converter and the protective ground;

[0017] Establishing a common-mode equivalent circuit after adding the first winding and the second winding, and obtaining the simplest common-mode equivalent circuit after simplifying the circuit;

[0018] Calculating the capacitance value of the first capacitor according to the established common-mode equivalent circuit and the simplest common-mode equivalent circuit to achieve the cancellation of the common-mode voltage.

[0019] Further, the positions of the same-named ends of the first winding and the second winding are opposite.

[0020] Further, the first winding and the second winding are implemented by a transformer.

[0021] Further, an impedance analyzer is used to extract the parasitic capacitance between each part of the buck-boost converter and the protective ground.

[0022] Further, according to the established common-mode equivalent circuit and the simplest common-mode equivalent circuit, calculate the capacitance value of the first capacitor, including,

[0023] Obtain the equivalent common-mode noise source V ENS after adding the passive cancellation winding according to the common-mode equivalent circuit:

[0024] ,

[0025] In the formula, C com represents the first capacitor; V Q2 and V Q4 respectively represent the noise voltage sources obtained by equivalent substitution of the noise sources Q2 and Q4 using the substitution theorem; the capacitor C sum represents the total parasitic capacitance in the simplest common-mode equivalent circuit, and its expression is as follows:

[0026] ,

[0027] Among them, the capacitor C pC is the parasitic capacitance between the input port and the ground; the capacitor C pE is the parasitic capacitance between the negative bus and the ground; the capacitor C pD is the parasitic capacitance between the output port and the ground; the capacitor C pA is the parasitic capacitance between the midpoint of the bridge arm formed by the switching tubes Q1 and Q2 and the ground; the capacitor C pB is the parasitic capacitance between the midpoint of the bridge arm formed by the switching tubes Q3 and Q4 and the ground;

[0028] Obtain the expression of the common-mode voltage V CM as follows:

[0029] ;

[0030] Substitute the expression of the equivalent common-mode noise source V ENS after adding the passive cancellation winding into the expression of the common-mode voltage V CM , and let the common-mode voltage V CM = 0, and the capacitance value of the first capacitor is obtained as:

[0031] .

[0032] Beneficial effects: For a buck-boost converter and its common-mode voltage suppression method of the present invention, a common-mode equivalent circuit considering parasitic capacitance after adding a passive cancellation winding is established. This equivalent circuit is simple to calculate and relatively easy to implement; the effect of introducing a compensation voltage source is achieved by using the passive cancellation winding to cancel the noise voltage source in the buck-boost converter, making the equivalent common-mode noise voltage zero, and having a good suppression effect on the common-mode voltage; the addition of the cancellation voltage source can be achieved by using a single transformer, and the method is simple and easy to operate; the common-mode voltage suppression can be achieved only through the passive cancellation winding and the compensation capacitor, without the need for an additional auxiliary power supply and calculation circuit, which is beneficial to reducing the system volume and increasing the power density.

[0033] To make the above features and advantages of the invention more obvious and understandable, specific embodiments are hereinafter given and described in detail in conjunction with the accompanying drawings as follows. Brief Description of the Drawings

[0034] Figure 1 It is a circuit schematic diagram of a buck-boost converter of the present invention.

[0035] Figure 2 For Figure 1 It is a schematic diagram of the common-mode equivalent circuit of the buck-boost converter in

[0036] Figure 3 For Figure 1 It is a schematic diagram of the simplest common-mode equivalent circuit of the buck-boost converter in

[0037] Figure 4 It is a flowchart of a common-mode voltage suppression method for a buck-boost converter of the present invention.

[0038] Figure 5 It is a circuit schematic diagram with a line impedance stabilization network connected between the input voltage and the buck-boost converter.

[0039] Figure 6 It is a schematic diagram of the common-mode voltage spectrum of the buck-boost converter before and after using passive cancellation. Detailed Embodiments

[0040] To make the objectives and technical solutions of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of 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 described embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0041] Figure 1 It is a circuit schematic diagram of a buck-boost converter of the present invention. As Figure 1As shown in the figure, a buck-boost converter 1 of the present invention includes a buck-boost module 11 and a common-mode voltage suppression module 12, and the buck-boost module 11 is connected to the common-mode voltage suppression module 12.

[0042] In a specific embodiment, the buck-boost module 11 is a four-switch buck-boost module (Four-Switch Buck-Boost, FSBB), which specifically includes a switching transistor Q1, a switching transistor Q2, a switching transistor Q3, a switching transistor Q4, and an inductor L f , the first end of the switching transistor Q1 is connected to the first end of the input voltage V in , the second end of the switching transistor Q1 is connected to the first end of the switching transistor Q2, the second end of the switching transistor Q2 is connected to the second end of the input voltage V in , the second end of the switching transistor Q1 is connected to the first end of the inductor L f , the second end of the inductor L f is connected to the second end of the switching transistor Q3 and the first end of the switching transistor Q4, the first end of the switching transistor Q3 and the second end of the switching transistor Q4 are connected to the output voltage V o , the second end of the switching transistor Q2 is connected to the second end of the switching transistor Q4, and the second end of the input voltage V in is connected to the power ground PG. Among them, the inductor L f is a power inductor.

[0043] Optionally, the buck-boost module 11 may further include a capacitor C in , the capacitor C in is connected in parallel between the first end of the switching transistor Q1 and the second end of the switching transistor Q2, and the capacitor C in functions as an input filter.

[0044] Optionally, the buck-boost module 11 may further include a capacitor C o , the capacitor C o is connected in parallel between the first end of the switching transistor Q3 and the second end of the switching transistor Q4, and the capacitor C o functions as an output filter.

[0045] Optionally, the buck-boost module 11 is further connected to a load R L , the load R L is connected in parallel between the first end of the switching transistor Q3 and the second end of the switching transistor Q4.

[0046] In a specific embodiment, the buck-boost module 11 adopts a two-mode control strategy. For the bridge arm formed by the switching transistor Q1 and the switching transistor Q2, there is always a potential static point and a potential moving point at the midpoint potential of the bridge arm formed by the switching transistor Q3 and the switching transistor Q4.

[0047] Further, the common-mode voltage suppression module 12 includes a first winding N1, a second winding N2, and a capacitor Ccom and capacitor C s , the first end of the first winding N1 is connected to the midpoint of the inductor L s through the capacitor C f . The second end of the first winding N1 is connected to the power ground PG. The first end of the second winding N2 is connected to the protection ground PE com through the capacitor C, and the second end of the second winding N2 is connected to the power ground PG.

[0048] Among them, the capacitor C com is a compensation capacitor; the first winding N1 and the second winding N2 form a passive cancellation winding.

[0049] Furthermore, the positions of the corresponding ends of the first winding N1 and the second winding N2 are opposite.

[0050] Furthermore, the turn ratio of the first winding N1 to the second winding N2 is 1:1.

[0051] In a specific embodiment, the first winding N1 and the second winding N2 can be implemented by a transformer. The first winding N1 is the primary winding of the transformer, and the second winding N2 is the secondary winding of the transformer; or the first winding N1 is the secondary winding of the transformer, and the second winding N2 is the primary winding of the transformer.

[0052] Furthermore, there are parasitic capacitors between each part of the buck-boost module 11 and the protection ground PE, including the capacitor C pC , that is, the parasitic capacitor between the input port and the ground; the capacitor C pE , that is, the parasitic capacitor between the negative bus and the ground; the capacitor C pD , that is, the parasitic capacitor between the output port and the ground; the capacitor C pA , that is, the parasitic capacitor between the midpoint of the bridge arm formed by the switching transistors Q1 and Q2 and the ground, that is, the parasitic capacitor between the midpoint of the left bridge arm of the buck-boost module and the ground; the capacitor C pB , that is, the parasitic capacitor between the midpoint of the bridge arm formed by the switching transistors Q3 and Q4 and the ground, that is, the parasitic capacitor between the midpoint of the right bridge arm of the buck-boost module and the ground. These parasitic capacitors provide a conduction path for the common-mode current and cause common-mode interference.

[0053] In Figure 1 , the midpoint of the bridge arm formed by the switching transistors Q1 and Q2 is point A, the midpoint of the bridge arm formed by the switching transistors Q3 and Q4 is point B, the first end of the switching transistor Q1 is point C, the first end of the switching transistor Q3 is point D, and the second end of the switching transistor Q2 is point E.

[0054] More specifically, the buck-boost converter of the present application compensates for the common-mode noise voltage by using the passive cancellation idea. Utilizing the characteristic that the potential at the midpoint of the power inductor in the buck-boost converter is synchronized with the potential jump of the noise source, the potential at the midpoint of the power inductor is led out through the passive cancellation winding formed by the first winding N1 and the second winding N2, and is connected to the safety ground through the compensation capacitor. By selecting an appropriate capacitance value of the compensation capacitor, the compensation current is equal in magnitude and opposite in direction to the common-mode current generated at nodes A and B where the voltage in the circuit jumps at high frequencies, thereby suppressing the common-mode conducted interference caused by the nodes where the voltage in the circuit jumps at high frequencies. Among them, is the current flowing through capacitor C com , is the current flowing through capacitor C PA , is the current flowing through capacitor C PB .

[0055] Furthermore, the same-name ends of the passive cancellation winding are in opposite positions to provide a compensation current in the direction opposite to the common-mode current . Then, the excitation inductance of the transformer is appropriately designed. The excitation inductance of the transformer belongs to the common-mode voltage suppression module 12, and this module does not process the main power current. Therefore, it should present a high-impedance characteristic for the main power current. Thus, the value of the excitation inductance of the transformer should be greater than the value of inductance L f .

[0056] In a specific embodiment, according to the engineering experience value, the magnitude of the excitation inductance is taken as 10 times the value of inductance L f and it can work well.

[0057] Next, the working principle of a buck-boost converter of the present invention will be continued to be introduced. According to Figure 1 the parasitic capacitances of the buck-boost converter in Figure 2 , the common-mode equivalent circuit of the buck-boost converter in can be established. The voltage source com is connected in series with capacitor C CM and then connected in parallel across the two ends of the common-mode voltage V pC is connected in parallel across the two ends of the common-mode voltage V CM , the voltage source V Q2 is connected in series with capacitor C pA and then connected in parallel across the two ends of the common-mode voltage V CM , capacitor C pE is connected in parallel across the two ends of the common-mode voltage V CM , the voltage source V Q4 is connected in series with capacitor C pB and then connected in parallel across the two ends of the common-mode voltage V CM , capacitor CpD is connected in parallel across the common-mode voltage V CM at both ends, and the second end of the common-mode voltage V CM is connected to the protective ground PE. Among them, the voltage source V Q2 and the voltage source V Q4 respectively represent the noise voltage sources obtained by equivalent substitution of the noise sources Q2 and Q4 using the substitution theorem. The voltage source represents the compensation voltage source obtained by equivalent substitution of the second winding N2 using the substitution theorem; the common-mode voltage V CM represents the common-mode voltage collected by the line impedance stabilization network. In Figure 3 the common-mode voltage V CM is expressed as the voltage across a 25Ω resistor.

[0058] Figure 3 is Figure 1 the simplest common-mode equivalent circuit of the buck-boost converter in CM . The common-mode voltage V sum , the capacitor C ENS and the equivalent common-mode noise source V CM are connected in series to form a loop. The series midpoint of the common-mode voltage V ENS and the equivalent common-mode noise source V

[0059] is connected to the protective ground PE. In a specific embodiment, the switch tubes Q1, Q2, Q3, and Q4 have the same model, and the difference between the capacitor C pA and the capacitor C pB is very small. In subsequent analysis, it can be considered that the capacitor C pA is equal to the capacitor C pB .

[0060] From Figure 2 the common-mode equivalent circuit in ENS the expression of the equivalent common-mode noise source V

[0061]

[0062] In the formula, V Q2 and V Q4 respectively represent the noise voltage sources obtained by equivalent substitution of the switch tube Q2 (i.e., the noise source) and the switch tube Q4 (i.e., the noise source) using the substitution theorem; the capacitor C sum represents the total parasitic capacitance in the simplest common-mode equivalent circuit, and its expression is as follows:

[0063] .

[0064] As described above, the function of the compensation capacitor is to make the compensation current equal in magnitude and opposite in direction to the common-mode current generated by the nodes with high-frequency jumps in the circuit, thereby suppressing the common-mode conduction interference caused by the nodes with high-frequency voltage jumps in the circuit. Therefore, the capacitance C com should be such that the common-mode voltage V CM is zero.

[0065] According to Figure 3 the simplest common-mode equivalent circuit, the expression of the common-mode voltage V CM can be obtained from the impedance voltage division formula as follows:

[0066] .

[0067] Let the common-mode voltage V CM = 0, and the expression of the common-mode voltage V CM satisfies the following equation:

[0068] ,

[0069] After simplification, we get:

[0070]

[0071] Furthermore, the capacitance value of the capacitor C com is obtained as:

[0072] .

[0073] In this embodiment, the acquisition of the compensation voltage source is related to the midpoint potential of the power inductor and can be achieved using a transformer without the need for an additional auxiliary power supply and operational circuit.

[0074] As Figure 4 shown, the present invention also provides a method for suppressing the common-mode voltage of a buck-boost converter, including steps S1 to S4.

[0075] Step S1, connect the first end of the first winding N1 to the midpoint of the power inductor of the buck-boost converter through the capacitor C s , and connect the second end of the first winding N1 to the power ground; connect the first end of the second winding N2 to the protective ground through the capacitor C com , and connect the second end of the second winding N2 to the power ground.

[0076] In a specific embodiment, the first winding N1 and the second winding N2 can be implemented by a transformer. The first winding N1 is the primary winding of the transformer, and the second winding N2 is the secondary winding of the transformer; or the first winding N1 is the secondary winding of the transformer, and the second winding N2 is the primary winding of the transformer.

[0077] Further, the positions of the corresponding ends of the first winding N1 and the second winding N2 are opposite.

[0078] Further, the turns ratio of the first winding N1 to the second winding N2 is 1:1.

[0079] Step S2: Extract the parasitic capacitances between each part of the buck-boost converter and the protective ground, including capacitor C pC , capacitor C pE , capacitor C pD , capacitor C pA , capacitor C pB .

[0080] Among them, capacitor C pC is the parasitic capacitance between the input port and the ground; capacitor C pE is the parasitic capacitance between the negative bus and the ground; capacitor C pD is the parasitic capacitance between the output port and the ground; capacitor C pA is the parasitic capacitance between the midpoint of the bridge arm formed by switch Q1 and switch Q2 and the ground; capacitor C pB is the parasitic capacitance between the midpoint of the bridge arm formed by switch Q3 and switch Q4 and the ground.

[0081] In a specific embodiment, an impedance analyzer is used to extract the parasitic capacitances between each part of the buck-boost converter and the protective ground.

[0082] Optionally, as shown in Figure 5 , a line impedance stabilization network 2 (LISN) can be connected between the input voltage V in and the buck-boost converter 1 to isolate power supply interference and provide a stable test impedance, so as to accurately extract the parasitic capacitances between each part of the buck-boost converter and the protective ground.

[0083] Step S3: Establish a common-mode equivalent circuit after adding the first winding and the second winding, and obtain the simplest common-mode equivalent circuit after circuit simplification.

[0084] Further, step S3 includes using the substitution theorem to derive the noise model, using current source I Q1 and current source I Q3 to replace switch Q1 and switch Q3 respectively, using voltage source V Q2 and voltage source V Q4 to replace switch Q2 and switch Q4 respectively, and the waveforms of these current sources and voltage sources are exactly the same as the currents or voltages borne by their respective switches; using voltage source to replace the second winding N2, and this voltage source is exactly the same as the voltage borne by the second winding N2. Using the superposition theorem to derive the contributions of each current source and voltage source to the common-mode voltage V CMThe role is obtained by the superposition theorem. When the current source acts alone, the current source is short-circuited. Therefore, only the voltage source affects the common-mode voltage V CM has an impact.

[0085] The common-mode equivalent circuit established according to step S3 is as shown in Figure 2 shown, and the simplest common-mode equivalent circuit is as shown in Figure 3 shown.

[0086] Step S4: Calculate the capacitance value of capacitor C com to cancel the common-mode voltage.

[0087] Furthermore, the specific steps of step S4 are as follows.

[0088] Step S41: According to the Figure 2 common-mode equivalent circuit, using Thevenin's theorem, the simplest common-mode equivalent circuit of Figure 3 can be derived, and the equivalent common-mode noise source V Figure 3 in ENS is obtained as follows:

[0089]

[0090] where V Q2 and V Q4 respectively represent the noise voltage sources obtained by equivalent substitution of switch tube Q2 and switch tube Q4 using the substitution theorem; capacitor C sum represents the total parasitic capacitance in the simplest common-mode equivalent circuit, and its expression is as follows:

[0091] .

[0092] Step S42: The expression of the common-mode voltage V CM is obtained according to the simplest common-mode equivalent circuit as follows:

[0093] .

[0094] Step S43: Substitute the expression of the equivalent common-mode noise source V ENS into the expression of the common-mode voltage V CM , and let the common-mode voltage V CM = 0, then the capacitance value of capacitor C com is:

[0095] .

[0096] Among them, let the common-mode voltage V CM = 0, and the expression of the common-mode voltage V CM satisfies the following equation:

[0097] ,

[0098] After simplification, we get:

[0099]

[0100] Furthermore, the capacitance value of capacitor C com is:

[0101] .

[0102] Furthermore, simulation circuits of the buck-boost converter before and after adopting passive cancellation are respectively built in Saber. As Figure 6 shown are the common-mode voltage spectra of the buck-boost converter before and after adopting passive cancellation. It can be seen that, compared with the buck-boost converter without passive cancellation, after adopting the method based on passive cancellation, the common-mode voltage of the system is reduced by more than 50 dBμV in the frequency range of 150 kHz - 30 MHz, verifying that a buck-boost converter and its common-mode voltage suppression method of this application can effectively suppress the common-mode conducted interference of the buck-boost converter.

[0103] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field to which the present invention pertains may make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to that defined by the appended patent application scope.

Claims

1. A buck-boost converter, characterized in that, It includes a buck-boost module and a common-mode voltage suppression module, and the buck-boost module is connected to the common-mode voltage suppression module; the common-mode voltage suppression module includes a first winding, a second winding, a first capacitor, and a second capacitor. The first end of the first winding is connected to the midpoint of the power inductor of the buck-boost module through the second capacitor, the second end of the first winding is connected to the power ground, the first end of the second winding is connected to the protection ground through the first capacitor, and the second end of the second winding is connected to the power ground; The capacitance value of the first capacitor is calculated according to the following method: Extract the parasitic capacitance between each part of the buck-boost converter and the protection ground; Establish a common-mode equivalent circuit after adding the first winding and the second winding, and simplify the circuit to obtain the simplest common-mode equivalent circuit; According to the established common-mode equivalent circuit and the simplest common-mode equivalent circuit, set the capacitance value of the first capacitor to achieve the cancellation of the common-mode voltage; The setting of the capacitance value of the first capacitor to achieve the cancellation of the common-mode voltage includes, According to the common-mode equivalent circuit, the expression of the equivalent common-mode noise source V after adding the passive cancellation winding is obtained: ENS : Where, C com represents the first capacitor; V Q2 and V Q4 respectively represent the noise voltage sources obtained by using the substitution theorem to perform equivalence on the switching transistors Q2 and Q4; the capacitor C sum represents the total parasitic capacitance in the simplest common-mode equivalent circuit, and its expression is as follows: ， Among them, capacitor C pC is the parasitic capacitance of the input port to the ground; capacitor C pE is the parasitic capacitance of the negative bus to the ground; capacitor C pD is the parasitic capacitance of the output port to the ground; capacitor C pA is the parasitic capacitance of the midpoint of the bridge arm formed by switch Q1 and switch Q2 to the ground; capacitor C pB is the parasitic capacitance of the midpoint of the bridge arm formed by switch Q3 and switch Q4 to the ground; The common-mode voltage V is obtained according to the simplest common-mode equivalent circuit CM and its expression is as follows: ； Substitute the expression of the equivalent common-mode noise source V ENS after adding the passive cancellation winding into the expression of the common-mode voltage V CM . Let the common-mode voltage V CM = 0, and the capacitance value of the first capacitor is obtained as: 。 2. The buck-boost converter according to claim 1, wherein The positions of the same-name ends of the first winding and the second winding are opposite.

3. The buck-boost converter according to claim 2, characterized in that, The first winding and the second winding are implemented through a transformer.

4. The buck-boost converter according to claim 1, characterized in that, The buck-boost module is a four-switch buck-boost module.

5. A method for suppressing the common-mode voltage of a buck-boost converter, characterized in that, Including, Connect the first end of the first winding to the midpoint of the power inductor of the buck-boost converter through the second capacitor, and connect the second end of the first winding to the power ground; connect the first end of the second winding to the protection ground through the first capacitor, and connect the second end of the second winding to the power ground; Extract the parasitic capacitance between each part of the buck-boost converter and the protection ground; Establish a common-mode equivalent circuit after adding the first winding and the second winding, and simplify the circuit to obtain the simplest common-mode equivalent circuit; According to the established common-mode equivalent circuit and the simplest common-mode equivalent circuit, set the capacitance value of the first capacitor to achieve the cancellation of the common-mode voltage; The setting of the capacitance value of the first capacitor to achieve the cancellation of the common-mode voltage includes, According to the common-mode equivalent circuit, the expression of the equivalent common-mode noise source V after adding the passive cancellation winding is obtained: ENS : where C com represents the first capacitor; V Q2 and V Q4 respectively represent the noise voltage sources obtained by equivalent substitution of the switching transistors Q2 and Q4 using the substitution theorem; the capacitor C sum represents the total parasitic capacitance in the simplest common-mode equivalent circuit, and its expression is as follows: ， Among them, capacitor C pC That is, the parasitic capacitance of the input port to the ground; capacitor C pE That is, the parasitic capacitance of the negative bus to the ground; capacitor C pD That is, the parasitic capacitance of the output port to the ground; capacitor C pA That is, the parasitic capacitance of the midpoint of the bridge arm formed by switch Q1 and switch Q2 to the ground; capacitor C pB That is, the parasitic capacitance of the midpoint of the bridge arm formed by switch Q3 and switch Q4 to the ground; The expression for the common-mode voltage V obtained from the simplest common-mode equivalent circuit is as follows: CM ​ ； Substitute the expression of the equivalent common-mode noise source V ENS after adding the passive cancellation winding into the expression of the common-mode voltage V CM . Let the common-mode voltage V CM = 0, and the capacitance value of the first capacitor is obtained as follows: 。 6. The common-mode voltage suppression method for a buck-boost converter according to claim 5, characterized in that, The positions of the same-name ends of the first winding and the second winding are opposite.

7. The common-mode voltage suppression method for a buck-boost converter according to claim 6, wherein The first winding and the second winding are implemented through a transformer.

8. The common-mode voltage suppression method of a buck-boost converter as claimed in claim 5, wherein Use an impedance analyzer to extract the parasitic capacitance between each part of the buck-boost converter and the protection ground.

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