An autonomous coreless transformer and its fine design method

Abstract

The present invention discloses an autonomous coreless transformer and a refined design method thereof. The transformer comprises an autonomous voltage source, a circular winding bobbin, a primary winding, a secondary winding, a primary series compensation capacitor, a secondary series compensation capacitor, an uncontrolled rectifier module, an output filter capacitor, and a load resistor. The secondary winding is wound around the center of the circular winding bobbin, and the primary winding is evenly distributed on both sides of the secondary winding. Adjusting the number of turns and gap between the primary and secondary windings can control the transformer parameters. The present invention achieves refined design of the autonomous coreless transformer parameters by combining winding structure design with voltage deviation compensation.

Description

Technical Field

[0001] The present invention relates to the technical field of coreless transformers, and in particular to an autonomous coreless transformer and a fine design method thereof. Background Art

[0002] Compared with traditional ferrite core transformers, coreless transformers use air as the magnetic permeability medium, which avoids the influence of magnetic material properties on the transformer, such as magnetic saturation, hysteresis loss, eddy current loss, flux imbalance, and the influence of magnetic permeability on temperature. At the same time, there are no core materials and skeleton size constraints, so the weight is lighter, it is easy to customize the design, and the weight power density is further improved. In addition, the coupling coefficient is lower, and the leakage inductance is used instead of the resonant inductance, making magnetic integration easier to achieve and lowering the cost.

[0003] Autonomous coreless transformers exhibit the same magnetic potential balance characteristics as ideal transformers when parity-time symmetry conditions are met, achieving constant voltage and current ratios independent of the load. The parity-time symmetry conditions require that the natural resonant frequencies of the primary and secondary circuits be equal, and that the coreless transformer operates at a unit power factor under the action of an autonomous voltage source. The key is to maintain the natural resonant frequencies of the primary and secondary circuits equal to achieve the target resonant parameters. Coreless transformers are easy to customize, eliminating the constraints of core material and bobbin size, while the AP design method used for traditional ferrite transformers is no longer applicable. In summary, achieving refined resonant parameter design is crucial for the application of autonomous coreless transformers. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art, and propose an autonomous coreless transformer and a fine design method thereof, which realizes the fine design of the parameters of the autonomous coreless transformer through the combination of winding structure design and voltage deviation compensation.

[0005] To achieve the above-mentioned objectives, the technical solution provided by the present invention is as follows: an autonomous coreless transformer, comprising an autonomous voltage source, a circular winding frame, a primary winding, a secondary winding, a primary series compensation capacitor, a secondary series compensation capacitor, an uncontrolled rectifier module, an output filter capacitor and a load resistor; one end of the primary winding is connected to one end of the primary series compensation capacitor, the other end of the primary series compensation capacitor is connected to the negative electrode of the autonomous voltage source, and the positive electrode of the autonomous voltage source is connected to the other end of the primary winding; one end of the secondary winding is connected to one end of the uncontrolled rectifier module, the other end of the uncontrolled rectifier module is connected to one end of the secondary series compensation capacitor, and the other end of the secondary series compensation capacitor is connected to the other end of the secondary winding; the output of the uncontrolled rectifier module is respectively connected to the output filter capacitor and the load resistor; the secondary winding is wound in the middle of the circular winding frame, and the primary winding is evenly distributed on both sides of the secondary winding. Adjusting the number of turns and gaps of the primary and secondary windings can control the transformer parameters.

[0006] The present invention also provides a method for fine design of the autonomous coreless transformer, comprising the following steps:

[0007] Step 1: Design the autonomous coreless transformer. The parameters are input, including: V i 、V o 、P o 、ω o , Q h , k; where V i is the input voltage of the autonomous voltage source, V o is the output capacitor voltage, P o is the transformer rated power, ω o is the resonant angular frequency of the primary and secondary circuits, Q h is the quality factor at the bifurcation point, k is the coupling coefficient of the transformer;

[0008] Step 2: Calculate the turns ratio n t =V i / V o , the actual input value n is less than n t ;

[0009] Step 3: Calculate the following parameters: Primary winding self-inductance Capacitance of the primary series compensation capacitor Secondary winding self-inductance L s =L p / n 2 , the capacitance of the secondary series compensation capacitor C s =n 2 C p , transformer mutual inductance M ps =kL p / n;

[0010] Step 4: Enter the number of column layers N of the transformer primary winding. cp 、N number of column layers of the primary winding cs , radius of circular winding frame b, primary winding diameter d p , secondary winding diameter d s ; Secondary winding self-inductance L s The expression is:

[0011] L s The expression of is about N s Implicit function, solving this implicit function can calculate the number of turns N of the secondary winding s ; Among them, vacuum permeability μ0=4π×10 -7 μH / m, coefficient Secondary winding transverse layers Secondary winding x s row, yth s The elements of the column (x s ,y s ) Distance r from the central axis s =b+d s (2x s -1) / 2, the secondary winding x s 'Row, y s 'The elements of the column (x s ',y s ') Distance from the central axis r s '=b+d s (2x s '-1) / 2; define variable z s 2 =4r s r s ' / [(r s +r s ') 2 +d s 2 (y s -y s ') 2 ],K(z s ) and F(z s ) are complete elliptic integrals of the first and second kinds respectively; N can be determined in step 4 s , and then get the height l of the secondary winding s =m s d s ;

[0012] Step 5: Number of turns N of the primary winding p The primary winding is equivalent to two coaxial series windings with equal inductance, which are represented by N p1and N p2 , N p1 With N p2 The mutual inductance between them is M 12 The height of the primary winding is The air gap distance between the primary and secondary windings is c; considering l s Much larger than c, ignoring the effect of c on M 12 Calculate N according to step 4 s N can be calculated by p To achieve the target value L p , thus determining N p The value of

[0013] Step 6: Just calculate N p1 With N s Mutual induction between:

[0014] The mutual inductance M of the primary and secondary windings can be obtained ps =2M p1_s , c can be calculated to achieve the target value M ps ; Among them, the coefficient ), the number of layers of the primary winding Primary winding x p row, yth p The elements of the column (x p ,y p ) Distance r from the central axis p =b+d p (2x p -1) / 2;z ps 2 =4r s r p / {(r s +r p ) 2 +[d s (2y s -1) / 2+d p (m p -y p +1 / 2)+c] 2},K(z ps ) and F(z ps ) are complete elliptic integrals of the first and second kinds respectively; the value of the air gap spacing c can be obtained in step 6;

[0015] Step 7: From steps 4 and 5, we can get N p and N s , we can know the minimum height a of the transformer skeleton min Need to meet In order to facilitate adjustment during winding, the actual selected value of the transformer skeleton a must be greater than a min ;

[0016] Step 8: Wind the transformer and measure the stray resistance R of the primary winding p and the secondary winding stray resistance R s , and the voltage loss is calculated as ΔV=R p ×(P o / V i )+R s ×(P o / V o )+V d +V s ; where V d is the diode conduction voltage drop of the uncontrolled rectifier module, V s is the conduction voltage drop of the switching device in the autonomous voltage source; if the conditions are met: nV i / (V o +ΔV)<1%, the design is completed; if not, return to step 2, further reduce the value of n, and repeat steps 2 to 8 until the conditions are met.

[0017] Furthermore, the autonomous voltage source operating frequency ω of the autonomous coreless transformer satisfies:

[0018]

[0019] Where Q is the quality factor of the primary and secondary circuits, Q>Q h .

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] 1. The fine parameter design of the autonomous coreless transformer is realized, making the application of high efficiency and high power density of the coreless transformer feasible.

[0022] 2. The deviation correction of the voltage ratio of the coreless transformer is realized, avoiding the voltage loss caused by parasitic resistance and semiconductor devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the circuit schematic diagram of the autonomous coreless transformer.

[0024] Figure 2 The circuit diagram of the autonomous voltage source;

[0025] Figure 3 This is a schematic diagram of the structure of the winding designed using a segmented arrangement. DETAILED DESCRIPTION

[0026] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0027] like Figure 1 As shown, this embodiment discloses an autonomous coreless transformer, including an autonomous voltage source, a circular winding frame, a primary winding, a secondary winding, a primary series compensation capacitor, a secondary series compensation capacitor, an uncontrolled rectifier module, an output filter capacitor and a load resistor; one end of the primary winding is connected to one end of the primary series compensation capacitor, the other end of the primary series compensation capacitor is connected to the negative pole of the autonomous voltage source, and the positive pole of the autonomous voltage source is connected to the other end of the primary winding; one end of the secondary winding is connected to one end of the uncontrolled rectifier module, the other end of the uncontrolled rectifier module is connected to one end of the secondary series compensation capacitor, and the other end of the secondary series compensation capacitor is connected to the other end of the secondary winding; the output of the uncontrolled rectifier module is respectively connected to the output filter capacitor and the load resistor.

[0028] like Figure 2 As shown, the autonomous voltage source in this embodiment is a full-bridge inverter circuit composed of switch tubes S1, S2, S3 and S4, and the input voltage is DC V i , specifically, DC V i The positive electrode is connected to the switch tube S1 and the switch tube S2, and the DC V i The negative electrode is connected to the switch tube S3 and the switch tube S4, the switch tube S1 is connected to the switch tube S3, and the switch tube S2 is connected to the switch tube S4. The autonomous voltage source is not limited to the above structure.

[0029] like Figure 3 As shown, the secondary winding is wound in the middle of the circular winding frame, and the primary winding is evenly distributed on both sides of the secondary winding. The transformer parameters can be controlled by adjusting the number of turns and gaps of the primary and secondary windings.

[0030] The following is a detailed design method for the autonomous coreless transformer according to this embodiment, which is characterized by comprising the following steps:

[0031] Step 1: Design the autonomous coreless transformer. The parameters are input, including: V i 、V o 、P o 、ω o , Q h , k; where V i is the input voltage of the autonomous voltage source, V o is the output capacitor voltage, P o is the transformer rated power, ω o is the resonant angular frequency of the primary and secondary circuits, Q h is the quality factor at the bifurcation point, k is the coupling coefficient of the transformer;

[0032] Step 2: Calculate the turns ratio n t =V i / V o , the actual input value n is slightly smaller than n t ;

[0033] Step 3: Calculate the following parameters: Primary winding self-inductance L p =(16n 2 V o 2 Q h ) / (π 2 ω o P o ), the capacitance of the primary series compensation capacitor Secondary winding self-inductance L s =L p / n 2 , the capacitance of the secondary series compensation capacitor C s =n 2 C p , transformer mutual inductance M ps =kL p / n;

[0034] Step 4: Enter the number of column layers N of the transformer primary winding. cp 、N number of column layers of the primary winding cs , radius of circular winding frame b, primary winding diameter d p , secondary winding diameter d s ; Secondary winding self-inductance L s The expression is:

[0035] L s The expression of is about N s Implicit function, solving this implicit function can calculate the number of turns N of the secondary winding s ; Among them, vacuum permeability μ0=4π×10 -7 μH / m, coefficient Secondary winding transverse layers Secondary winding x s row, yth s The elements of the column (x s ,y s ) Distance r from the central axis s =b+d s (2x s -1) / 2, the secondary winding x s 'Row, y s 'The elements of the column (x s ',y s ') Distance from the central axis rs '=b+d s (2x s '-1) / 2; define variable z s 2 =4r s r s ' / [(r s +r s ') 2 +d s 2 (y s -y s ') 2 ],K(z s ) and F(z s ) are complete elliptic integrals of the first and second kinds respectively; N can be determined in step 4 s , and then get the height l of the secondary winding s =m s d s ;

[0036] Step 5: Number of turns N of the primary winding p The primary winding is equivalent to two coaxial series windings with equal inductance, which are represented by N p1 and N p2 , N p1 With N p2 The mutual inductance between them is M 12 The height of the primary winding is The air gap distance between the primary and secondary windings is c; considering l s Much larger than c, the effect of c on M can be ignored 12 Calculate N according to step 4 s N can be calculated by p To achieve the target value L p , thus determining N p The value of

[0037] Step 6: Just calculate N p1 With N s Mutual induction between:

[0038] The mutual inductance M of the primary and secondary windings can be obtained ps =2M p1_s , c can be calculated to achieve the target value M ps ; Among them, the coefficient Number of primary winding layers Primary winding x p row, yth p The elements of the column (x p ,y p ) Distance r from the central axisp =b+d p (2x p -1) / 2;z ps 2 =4r s r p / {(r s +r p ) 2 +[d s (2y s -1) / 2+d p (m p -y p +1 / 2)+c] 2},K(z ps ) and F(z ps ) are complete elliptic integrals of the first and second kinds respectively; the value of the air gap spacing c can be obtained in step 6;

[0039] Step 7: From steps 4 and 5, we can get N p and N s , we can know the minimum height a of the transformer skeleton min Need to meet In order to facilitate adjustment during winding, the actual selected value of the transformer skeleton a needs to be slightly larger than a min ;

[0040] Step 8: Wind the transformer and measure the stray resistance R of the primary winding p and the secondary winding stray resistance R s , and the voltage loss is calculated as ΔV=R p ×(P o / V i )+R s ×(P o / V o )+V d +V s ; where V d is the diode conduction voltage drop of the uncontrolled rectifier module, V s is the conduction voltage drop of the switching device in the autonomous voltage source; if the conditions are met: nV i / (V o +ΔV)<1%, the design is completed; if not, return to step 2, further reduce the value of n, and repeat steps 2 to 8 until the conditions are met.

[0041] The operating frequency ω of the autonomous voltage source of the autonomous coreless transformer satisfies:

[0042]

[0043] Where Q is the quality factor of the primary and secondary circuits, Q>Q h.

[0044] In order to further illustrate the usefulness and feasibility of the present invention, an example is designed for illustration, and its input parameters are: input voltage V i =110V, output voltage V o =48V, rated power P o =620W, resonant angular frequency ω o =100kHz, Q h =2.0, k=0.52, radius of circular winding frame b=20mm, primary winding diameter d p =1.83mm, secondary winding diameter d s =2.75mm. According to step 3 of the above design method, the resonance parameters can be obtained as follows: n = 2.27, L p =101.37uH、L s =19.56uH、C p =25.0nF, C s =129.5nF, M ps =23.3uH. According to the above design method, steps 4, 5, 6, 7 and 8, the winding parameters of the autonomous coreless transformer can be obtained as follows: the number of turns of the primary winding N p =60, the number of columns of the primary winding N cp =4, the number of transverse layers of the primary winding m p =16, the height of the primary winding l p =29.3mm, the number of turns of the secondary winding is N s =21, the number of column-direction layers of the secondary winding N cs =3, the number of transverse layers of the secondary winding m s =8, height of secondary winding l s =22mm, transformer skeleton height a=48mm, air gap spacing c=1mm; the designed parameters meet the deviation correction of voltage transformation ratio.

[0045] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. An autonomous coreless transformer, characterized in that: It includes an autonomous voltage source, a circular winding skeleton, a primary winding, a secondary winding, a primary series compensation capacitor, a secondary series compensation capacitor, an uncontrolled rectifier module, an output filter capacitor and a load resistor; one end of the primary winding is connected to one end of the primary series compensation capacitor, the other end of the primary series compensation capacitor is connected to the negative electrode of the autonomous voltage source, and the positive electrode of the autonomous voltage source is connected to the other end of the primary winding; one end of the secondary winding is connected to one end of the uncontrolled rectifier module, the other end of the uncontrolled rectifier module is connected to one end of the secondary series compensation capacitor, and the other end of the secondary series compensation capacitor is connected to the other end of the secondary winding; the output of the uncontrolled rectifier module is respectively connected to the output filter capacitor and the load resistor; the secondary winding is wound in the middle of the circular winding skeleton, and the primary winding is evenly distributed on both sides of the secondary winding. Adjusting the number of turns and gaps of the primary and secondary windings can control the transformer parameters; Among them, the parameters of the autonomous coreless transformer include: V i 、V o 、P o 、ω o , Q h , k; where V i is the input voltage of the autonomous voltage source, V o is the output capacitor voltage, P o is the transformer rated power, ω o is the resonant angular frequency of the primary and secondary circuits, Q h is the quality factor at the bifurcation point, k is the coupling coefficient of the transformer; The autonomous voltage source operating frequency ω of the autonomous coreless transformer satisfies: ； Where Q is the quality factor of the primary and secondary circuits, Q>Q h .

2. A fine design method for the autonomous coreless transformer according to claim 1, characterized in that: The following steps are involved: Step 1: Design the parameters of the autonomous coreless transformer; Step 2: Calculate the turns ratio n t =V i / V o , the actual input value n is less than n t ; Step 3: Calculate the following parameters: Primary winding self-inductance , the capacitance of the primary series compensation capacitor , secondary winding self-inductance , the capacitance of the secondary series compensation capacitor , transformer mutual inductance ; Step 4: Enter the number of column layers N of the transformer primary winding. cp 、N number of column layers of the primary winding cs , radius of circular winding frame b, primary winding diameter d p , secondary winding diameter d s ; Secondary winding self-inductance L s The expression is: , L s The expression is about N s The implicit function of the secondary winding can be calculated by solving the implicit function. s ; Among them, the vacuum permeability μ0=4π×10 -7 μH / m, coefficient =N s / (N cs ×⌈N s / N cs ⌉), the number of transverse layers of the secondary winding m s =⌈N s / N cs ⌉, secondary winding x s row, yth s The elements of the column (x s ,y s ) Distance r from the central axis s =b+d s (2x s -1) / 2, the secondary winding x s 'Row, y s 'The elements of the column (x s ',y s ') Distance from the central axis r s '=b+d s (2x s '-1) / 2; define variable z s 2 =4r s r s ' / [(r s +r s ') 2 +d s 2 (y s -y s ') 2 ],K(z s ) and F(z s ) are complete elliptic integrals of the first and second kinds respectively; N can be determined in step 4 s , and then get the height l of the secondary winding s =m s d s ; Step 5: Number of turns N of the primary winding p The primary winding is equivalent to two coaxial series windings with equal inductance, which are represented by N p1 and N p2 , N p1 With N p2 The mutual inductance between them is M 12 , the height of the primary winding is l p / 2=d p ⌈N p / N cp ⌉ / 2; the air gap between the primary and secondary windings is c; considering l s Much larger than c, ignoring the effect of c on M 12 Calculate N according to step 4 s N can be calculated by p To achieve the target value L p , thus determining N p The value of Step 6: Just calculate N p1 With N s Mutual induction between: , we can get the mutual inductance M of the primary and secondary windings ps =2M p1_s , c can be calculated to achieve the target value M ps ; Among them, the coefficient ζ ps =(N p N s ) / (N cp N cs ×⌈N s / N cs ⌉×⌈N p / N cp ⌉), the number of layers of the primary winding in row direction m p =⌈N p / N cp ⌉; Primary winding x p row, yth p The elements of the column (x p ,y p ) Distance r from the central axis p =b+d p (2x p -1) / 2;z ps 2 =4r s r p / {(r s +r p ) 2 +[d s (2y s -1) / 2+d p (m p -y p +1 / 2)+c] 2 },K(z ps ) and F(z ps ) are complete elliptic integrals of the first and second kinds respectively; the value of the air gap spacing c can be obtained in step 6; Step 7: From steps 4 and 5, we can get N p and N s , we can know the minimum height a of the transformer skeleton min Need to meet ; To facilitate adjustment during winding, the actual selected value of the transformer skeleton a must be greater than a min ; Step 8: Wind the transformer and measure the stray resistance R of the primary winding p and the secondary winding stray resistance R s , and the voltage loss is calculated as ∆V=R p ×(P o / V i )+R s ×(P o / V o )+V d +V s ; where V d is the diode conduction voltage drop of the uncontrolled rectifier module, V s is the conduction voltage drop of the switching device in the autonomous voltage source; if the conditions are met: nV i / (V o +∆V)<1%, the design is completed; if not, return to step 2, further reduce the value of n, and repeat steps 2 to 8 until the conditions are met.

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