Summary of the invention
In order to solve the problems of the technologies described above, the invention provides a kind of transformer of no Y capacitance, it has removed the Y electric capacity in the transformer, thereby can prevent the generation of leaky, can reduce electromagnetic radiation again simultaneously.
The transformer of a kind of no Y capacitance of the present invention, it comprises: magnetic core, elementary main winding, secondary winding and the auxiliary winding on this magnetic core successively, it also comprises the primary shield winding that is connected with described elementary main winding, the secondary shielding winding that is connected with described secondary winding; Described primary shield winding has the identical number of turns and same-phase with the secondary shielding winding.
Particularly, an end of described primary shield winding links to each other with the negative or positive electrode of described elementary main winding.One end of described secondary shielding winding links to each other with the negative or positive electrode of described secondary winding.The material of above-mentioned primary shield winding and secondary shielding winding is a Copper Foil; Preferably, the number of turns of above-mentioned primary shield winding and secondary shielding winding can be a circle, and its two ends separately do not link to each other.
Further, the transformer of above-mentioned no Y capacitance also comprises the second primary shield winding that is connected with elementary main winding; The one end links to each other with the negative or positive electrode of elementary main winding.
The present invention also provides a kind of preparation method of transformer of no Y capacitance, and it may further comprise the steps:
A, on magnetic core the elementary main winding of coiling;
B, at the auxiliary winding of described elementary main winding upside coiling;
C, at described auxiliary winding upside coiling primary shield winding, the one end is connected with an end of described elementary main winding;
D, coiling secondary shielding winding; Described primary shield winding has the identical number of turns and same-phase with the secondary shielding winding;
E, coiling secondary winding, the one end is connected with an end of secondary shielding winding;
Further, between steps A and B, also comprise step: the second primary shield winding that is connected with described elementary main winding in the coiling of described elementary main winding downside; The one end links to each other with the negative or positive electrode of described elementary main winding.
The present invention is not owing to adopting Y electric capacity to reduce the electromagnetic radiation of transformer, so leaky can not take place; The present invention is connected with secondary winding with elementary main winding respectively by coiling same number of turns and synchronous primary shield winding and secondary shielding winding; Make the effective capacitance of transformer reduce greatly, thereby make and to be coupled to secondary common mode disturbances electric current and to reduce greatly, thereby solve the problem of electromagnetic radiation from elementary.
Embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, the present invention is described in further detail below in conjunction with accompanying drawing.
At first, begin to set forth realization principle of the present invention from the capacitive-based present principles:
I=C×(dV/dt)
In the above formula: I represents the electric current by electric capacity; C represents the capacity by electric capacity; DV/dt represents the capacitor voltage at both ends variable gradient.
If there is way to reduce the parasitic capacitance of transformer, also just can reduces electric current, thereby solve the problem of common mode disturbances noise by electric capacity.
Primary and secondary between the direct capacitance computing formula as follows:
Cox=0.0886*Sx*ε/tx?(pF)
Wherein Sx represents the relative area (cm^2) of capacitor plate; Tx represents the distance (cm) between the electric capacity two-plate; ε represent the to insulate dielectric constant of material
If increasing apart from tx between the electric capacity two-plate will cause leakage inductance to increase, decrease in efficiency, other problems such as temperature rising, the measure method that reduces direct capacitance is very limited, but can reduce effective capacitance by the relative current potential that reduces the parasitic capacitance two ends.
Effective capacitance computing formula between transformer is first and secondary is as follows:
Cy=(Cox/3)*(Va^2+Va*Vb+Vb^2)/V^2
Wherein: Cox represents direct capacitance (pF); Va represents to be calculated the potential difference (V) of one end between the electric capacity two-plate; Vb represents to be calculated the potential difference (V) of the other end between the electric capacity two-plate; V represents to be calculated the average potential differences in electric capacity the two poles of the earth (V).
With reference to figure 3, the transformer of a kind of no Y capacitance of the present invention, it comprises: magnetic core, elementary main winding 11, secondary winding 13 and the auxiliary winding 12 on this magnetic core successively, it also comprises the primary shield winding 21 that is connected with described elementary main winding 11, the secondary shielding winding 22 that is connected with described secondary winding 13; Described primary shield winding 21 has the identical number of turns and same-phase with secondary shielding winding 22.
Particularly, an end of described primary shield winding 21 links to each other with the negative or positive electrode of described elementary main winding 11.One end of described secondary shielding winding 22 links to each other with the negative or positive electrode of described secondary winding 13.Above-mentioned primary shield winding 21 is a Copper Foil with the material of secondary shielding winding 22; Preferably, the number of turns of above-mentioned primary shield winding and secondary shielding winding can be a circle, and its two ends separately do not link to each other.
Further, the transformer of above-mentioned no Y capacitance also comprises the second primary shield winding 23 that is connected with elementary main winding 11; The one end links to each other with the negative or positive electrode of elementary main winding 11.
With reference to figure 3 and Fig. 4, the transformer device structure of no Y capacitance of the present invention, primary shield winding 21 and secondary shielding winding 22 same-phases among the figure, calculating effective capacitance in theory is zero, in fact be coupled to secondary common mode disturbances noise electric current and reduce greatly from elementary, thereby solve the problem of electromagnetic radiation.
The present invention has solved the equilibrium problem of Switching Power Supply electromagnetic radiation and electric leakage by the transformer device structure of innovation, has realized that Switching Power Supply does not need Y electric capacity to test by electromagnetic radiation easily.Be applicable to charger for mobile phone, the product that fixed station power supply etc. are quite responsive to leakage current.
With reference to figure 3 and Fig. 4, the manufacture method of the transformer of a kind of no Y capacitance of the present invention process step in one embodiment is as follows:
A, coiling screen E1: with the wide Copper Foil of skeleton on skeleton around a circle, head and the tail can not short circuit, the head end solder taul connects transformer 1 pin;
B, the elementary main winding N1:1 of coiling pin hanging wire are once around intact N1, and ending closes at 3 pin;
C, the elementary main winding N2:4 of coiling pin hanging wire be once around intact N2, and ending closes at 5 pin, can be multi-thread and around, the even full whole skeleton width spaces of row;
D, the elementary main winding E2 of coiling: with the wide Copper Foil of skeleton on skeleton around a circle, head and the tail can not short circuit, the head end solder taul connects transformer 1 pin;
E, the elementary main winding E3 of coiling: with the wide Copper Foil of skeleton on skeleton around a circle, head and the tail can not short circuit, the head end solder taul connects transformer FLY1 pin;
F, coiling secondary winding N3:FLY1 pin hanging wire be once around intact N3, and ending closes at the FLY2 pin, can be multi-thread and around, the even full whole skeleton width spaces of row.
In order to guarantee good EMI effect, end of the same name should be placed on transformer the same side.In addition, very big flexibility is arranged in the transformation manufacturing process, more than only for reference, as limiting protection scope of the present invention.
Fig. 2 is a concrete application circuit of the invention process, and Fig. 5 is the circuit after simplifying at electromagnetic radiation.
The present invention is not owing to adopting Y electric capacity to reduce the electromagnetic radiation of transformer, so leaky can not take place; The present invention is connected with secondary winding with elementary main winding respectively by coiling same number of turns and synchronous primary shield winding and secondary shielding winding; Make the effective capacitance of transformer reduce greatly, thereby make and to be coupled to secondary common mode disturbances electric current and to reduce greatly, thereby solve the problem of electromagnetic radiation from elementary.
Above disclosed is a kind of preferred embodiment of the present invention only, can not limit the present invention's interest field certainly with this, and therefore the equivalent variations of doing according to claim of the present invention still belongs to the scope that the present invention is contained.