A circuit structure and parameter design method for current balancing between strands of a double-stranded wireless power transmission coil

Abstract

The present invention is a circuit structure and parameter design method for current balancing between strands of a double-strand parallel-wound wireless power transmission coil. The present invention relates to the field of magnetically coupled wireless power transmission technology, and the circuit includes a double-strand parallel-wound coil, a compensation capacitor array, and a controlled voltage source array; the double-strand parallel-wound coil includes a first coil and a second coil, the compensation capacitor array includes a first compensation capacitor and a second compensation capacitor, and the controlled voltage source array includes a first controlled voltage source and a second controlled voltage source. Compared with the existing centralized series compensation scheme, the scheme proposed by the present invention can achieve that the currents in the two strands of the double-strand parallel-wound coil are basically consistent, eliminating the current imbalance problem existing in the traditional compensation method, thereby giving full play to the current carrying capacity of the double-strand parallel-wound coil and improving the practicality of the double-strand parallel-wound coil in practical applications.

Description

Technical Field

[0001] The invention relates to the technical field of magnetically coupled wireless power transmission, and is a circuit structure and parameter design method for current balancing between strands of a wireless power transmission coil wound in parallel with two strands. Background Art

[0002] In wireless power transmission systems, in order to improve the current carrying capacity of the coil without significantly changing the shape of the coupling coil, researchers have proposed a solution of winding multiple strands in parallel. Each strand of the coil can be regarded as an independent coil, and there is strong coupling between the multiple coils. Since it is impossible to achieve completely consistent coil parameters for each strand in actual winding, in actual applications, there is a problem of unbalanced current in each strand of the multi-strand coil, resulting in the inability to fully utilize the advantage of the increased current carrying capacity of the multi-strand coil. Summary of the invention

[0003] The present invention realizes current balancing in each strand of a double-strand parallel-wound coil. The present invention is based on the idea of ​​independent compensation of the two strands. By analyzing the influence of the compensation capacitor on the current balancing, the compensation capacitor is optimized and designed to achieve approximate balance of the current in the two strands. The present invention provides a circuit structure and parameter design method for current balancing between strands of a double-strand parallel-wound wireless power transmission coil. The present invention provides the following technical solutions:

[0004] A circuit for balancing the current between strands of a two-strand parallel-wound wireless power transmission coil, the circuit comprising a two-strand parallel-wound coil, a compensation capacitor array and a controlled voltage source array;

[0005] The bifilar parallel-wound coil includes a first coil and a second coil, the compensation capacitor array includes a first compensation capacitor and a second compensation capacitor, and the controlled voltage source array includes a first controlled voltage source and a second controlled voltage source;

[0006] One end of the first coil is connected to one end of the first compensation capacitor, and the other end of the first compensation capacitor is connected to one end of the first controlled voltage source; one end of the second coil is connected to one end of the second compensation capacitor, and the other end of the second compensation capacitor is connected to one end of the second controlled voltage source.

[0007] Preferably, the other ends of the first coil and the second coil are connected to one end of a load resistor or a voltage source, and the other ends of the first controlled voltage source and the second controlled voltage source are connected to the other end of the load resistor or the voltage source.

[0008] A parameter design method for a circuit for current balancing between strands of a wireless power transmission coil with two strands wound in parallel, comprising the following steps:

[0009] Step 1: Measure the self-inductance of the first coil and the second coil, and L1 and L2 represent the self-inductance of the first coil and the second coil respectively;

[0010] Step 2: Measure the mutual inductance between the two coils in the bifilar coil, using M 12 represents the mutual inductance between the first coil and the second coil;

[0011] Step 3: The compensation capacitors in the compensation capacitor array are respectively arranged on the two coils of the bifilar parallel-wound coil. When the operating frequency is ω, the capacitances of the first compensation capacitor and the second compensation capacitor are determined by the following formula:

[0012] C1=1 / (ω^2*(L1+M 12 ))

[0013] C2=1 / (ω^2*(L2+M 12 ))

[0014] Wherein, C1 and C2 are the capacitances of the first compensation capacitor and the second compensation capacitor respectively.

[0015] The present invention has the following beneficial effects:

[0016] Compared with the existing centralized series compensation scheme, the scheme proposed in the present invention can achieve that the currents in the two wires in the double-strand parallel-wound coil are basically consistent, eliminating the current imbalance problem existing in the traditional compensation method, thereby giving full play to the current carrying capacity of the double-strand parallel-wound coil and improving the practicability of the double-strand parallel-wound coil in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A circuit diagram for realizing current balancing between strands of a wireless power transmission coil with two strands wound in parallel by using independent series compensation;

[0018] Figure 2 This is a circuit diagram of a double-strand parallel-wound coil compensation circuit for traditional centralized series compensation;

[0019] Figure 3 It is a schematic diagram of a square double-strand parallel-wound coil;

[0020] Figure 4 It is a receiving end equivalent circuit using a double-strand parallel-wound receiving coil and an independent series compensation structure;

[0021] Figure 5 It is an equivalent circuit of the transmitting end using a double-strand parallel-wound transmitting coil and an independent series compensation structure. DETAILED DESCRIPTION

[0022] The present invention is described in detail below in conjunction with specific embodiments. Specific embodiment one:

[0024] according to Figures 1 to 5 As shown, the present invention provides a circuit structure and parameter design method for current balancing between strands of a wireless power transmission coil wound in parallel with two strands, specifically:

[0025] A circuit for balancing the current between strands of a two-strand parallel-wound wireless power transmission coil, the circuit comprising a two-strand parallel-wound coil 1, a compensation capacitor array and a controlled voltage source array;

[0026] The bifilar parallel-wound coil 1 includes a first coil 11 and a second coil 12, the compensation capacitor array includes a first compensation capacitor 21 and a second compensation capacitor 22, and the controlled voltage source array includes a first controlled voltage source and a second controlled voltage source;

[0027] One end of the first coil 11 is connected to one end of the first compensation capacitor 21, and the other end of the first compensation capacitor 21 is connected to one end of the first controlled voltage source; one end of the second coil 12 is connected to one end of the second compensation capacitor 22, and the other end of the second compensation capacitor 22 is connected to one end of the second controlled voltage source.

[0028] The other ends of the first coil 11 and the second coil 12 are connected to one end of a load resistor or a voltage source, and the other ends of the first controlled voltage source and the second controlled voltage source are connected to the other end of the load resistor or the voltage source.

[0029] A parameter design method for a circuit for current balancing between strands of a wireless power transmission coil with two strands wound in parallel, comprising the following steps:

[0030] Step 1: Measure the self-inductance of the first coil and the second coil, and L1 and L2 represent the self-inductance of the first coil and the second coil respectively;

[0031] Step 2: Measure the mutual inductance between the two coils in the bifilar coil, using M 12 represents the mutual inductance between the first coil and the second coil;

[0032] Step 3: The compensation capacitors in the compensation capacitor array are respectively arranged on the two coils of the bifilar parallel-wound coil. When the operating frequency is ω, the capacitances of the first compensation capacitor and the second compensation capacitor are determined by the following formula:

[0033] C1=1 / (ω^2*(L1+M 12 ))

[0034] C2=1 / (ω^2*(L2+M 12 ))

[0035] Wherein, C1 and C2 are the capacitances of the first compensation capacitor and the second compensation capacitor respectively.

[0036] It can be achieved that the currents of the coils corresponding to the strands are approximately equal, and the system works in a resonant state.

[0037] When the two-strand parallel-wound coil is used for a wireless power receiving end, assuming that the resistance rating of the AC equivalent load 4 is Rs, and the induced voltages of the two single-strand coils are Us1 and Us2 respectively, then under the actual application conditions that ωLi / Rs (i=1,2) is significantly greater than 1 and the difference between Us1 and Us2 is not too large, it can be calculated that the current of each coil is approximately equal to (Us1+Us2) / 4Rs.

[0038] When the two-strand parallel-wound coil is used for a wireless power transmitter, the analysis process is similar to that of the receiver. Assuming that the resistance rating of the input equivalent load is Rp, and the reverse induced voltages of the receiving coil on the upper two single-strand transmitting coils are Up1 and Up2 respectively, then under the actual application condition that ωLi / Rp(i=1,2) is significantly greater than 1 and the difference between Up1 and Up2 is not too large, it can be calculated that the current of each coil is approximately equal to (Us1+Us2) / 4Rs.

[0039] Compared with the existing centralized series compensation scheme (such as Figure 2 The proposed scheme can achieve that the currents in the two wires of the double-strand parallel-wound coil are basically the same, thus eliminating the current imbalance problem existing in the traditional compensation method.

[0040] Figure 3 It is a typical square double-strand parallel-wound coil structure. The double-strand parallel winding method is used for coil winding, which can achieve a coil with a large current-carrying capacity using a wire with a small current-carrying capacity. At the same time, compared with the cross-winding method of Litz wire, which improves current balance, it is more conducive to the flattening design of the coil, but introduces the problem of current imbalance.

[0041] Figure 4 The figure shows the equivalent circuit of the receiving end using a double-strand parallel-wound receiving coil and an independent series compensation structure. When C1=1 / (ω^2*(L1+M 12 ))、C2=1 / (ω^2*(L2+M 12 )), assuming that the resistance of the AC equivalent load 4 is rated as R s The induced voltages of the two single-strand coils are U s1 and U s2 , according to Kirchhoff's voltage law, U s1 =jωM 12 (I2-I1)+(I1+I2)Rs,U s2 =jωM 12 (I1-I2)+(I1+I2)Rs, then the current of the first coil 11 can be calculated as

[0042]

[0043] The current of the second coil 12 is

[0044]

[0045] Since the coils corresponding to the two parallel-wound wires are tightly coupled, the mutual inductance M12 is of the same order of magnitude as the self-inductance of the single-wire coil, so M 12 ω / R s is significantly greater than 1; and although the induced voltages of the two single-strand coils are different, the difference is not too large, so The same can be said Therefore, I1≈I2, and current balance can be achieved.

[0046] Figure 5 The figure shows the equivalent circuit of the transmitting end of a double-stranded transmitting coil. The voltage source 5 can be regarded as a negative resistor with the same Figure 5 The same characteristics are used at the receiving end. When C1=1 / (ω^2*(L1+M 12 ))、C2=1 / (ω^2*(L2+M 12 )), assuming the input equivalent load has a resistance rating of R p The induced voltages of the two single-strand coils are U p1 , U p2 , then the current of the first coil 11 can be calculated as

[0047]

[0048] The current of the second coil 12 is

[0049]

[0050] The current of the first coil 11 is Since the coils corresponding to the two parallel-wound wires are closely coupled, the mutual inductance M12 and the self-inductance of the single-wire coil are of the same order of magnitude, so M 12 ω / R p is significantly greater than 1; and although the reverse induced voltage of the receiving coil on the two single-strand transmitting coils is different, the difference is not too large, so the imaginary part in the current expression is approximately 0, that is, The same can be said Therefore, I1≈I2, and current balance can be achieved.

[0051] The analysis process of the above example can be further extended to realize current balancing analysis of n-strand parallel-wound coils in wireless power transmitting or receiving applications.

[0052] The above is only a preferred implementation of a circuit structure and parameter design method for current balance between strands of a wireless power transmission coil with two strands wound in parallel. The protection scope of a circuit structure and parameter design method for current balance between strands of a wireless power transmission coil with two strands wound in parallel is not limited to the above embodiment. All technical solutions under this idea belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, several improvements and changes without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A parameter design method for a circuit for current balancing between strands of a two-strand parallel-wound wireless power transmission coil, the method is based on a circuit for current balancing between strands of a two-strand parallel-wound wireless power transmission coil, the circuit comprising a two-strand parallel-wound coil, a compensation capacitor array and a controlled voltage source array; The bifilar parallel-wound coil includes a first coil and a second coil, the compensation capacitor array includes a first compensation capacitor and a second compensation capacitor, and the controlled voltage source array includes a first controlled voltage source and a second controlled voltage source; One end of the first coil is connected to one end of a first compensation capacitor, and the other end of the first compensation capacitor is connected to one end of a first controlled voltage source; One end of the second coil is connected to one end of a second compensation capacitor, and the other end of the second compensation capacitor is connected to one end of a second controlled voltage source; The other ends of the first coil and the second coil are connected to one end of the load resistor or the voltage source, and the other ends of the first controlled voltage source and the second controlled voltage source are connected to the other end of the load resistor or the voltage source; the method is characterized in that it includes the following steps: Step 1: Measure the self-inductance of the first coil and the second coil, and L1 and L2 represent the self-inductance of the first coil and the second coil respectively; Step 2: Measure the mutual inductance between the two coils in the bifilar coil, using M 12 represents the mutual inductance between the first coil and the second coil; Step 3: The compensation capacitors in the compensation capacitor array are respectively arranged on the two coils of the bifilar parallel-wound coil. When the operating frequency is ω, the capacitances of the first compensation capacitor and the second compensation capacitor are determined by the following formula: C1=1 / (ω^2*(L1+M 12 )) C2=1 / (ω^2*(L2+M 12 )) Wherein, C1 and C2 are the capacitances of the first compensation capacitor and the second compensation capacitor respectively.

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