WO2022116413A1 - Variable circuit topology capable of switching wireless power transmission coil and compensation capacitor - Google Patents

Abstract

Disclosed is variable circuit topology capable of switching a wireless power transmission coil and a compensation capacitor. The circuit comprises: a primary-side circuit, comprising a first resonant capacitor, a first primary-side coil and a first relay resonant circuit which are connected in series, wherein the first relay resonant circuit comprises a second primary-side coil and a first relay resonant switching module, and the first relay resonant switching module is used for switching the second primary-side coil to a resonant state in which the second primary-side coil is not connected to a power source; and a secondary-side circuit, comprising a third resonant capacitor, a first secondary-side coil and a second relay resonant circuit which are connected in series, wherein the second relay resonant circuit comprises a second secondary-side coil and a second relay resonant switching module, and the second relay resonant switching module is used for switching the second secondary-side coil to a resonant state in which the second secondary-side coil is not connected to a load. By means of the present invention, a rated power can be output within a relatively wide coupling range under the condition of voltage limiting and current limiting, thereby greatly improving the use range and use flexibility.

Description

A Variable Circuit Topology with Switchable Wireless Power Transfer Coils and Compensation Capacitors technical field

The invention relates to the technical field of garden tools, in particular to a variable circuit topology with a switchable wireless power transmission coil and a compensation capacitor.

Background technique

In recent years, with the continuous development of science and technology, various terminal devices emerge in an endless stream. The traditional charging method is that different terminal devices rely on the matching charging cable for charging, and this wired charging method is cumbersome and cannot meet the needs of modern life, so wireless charging technology came into being. Wireless Charging Technology (Wireless Charging Technology) is a technology derived from wireless power transfer, which uses near-field induction to transfer energy from the power supply device (charger) to the power-consuming device, and the device uses the received energy to charge the battery, and at the same time for its own operation. The application of wireless charging technology can get rid of the shackles of the charging power cord, which has the advantages of safety, reliability, convenience and flexibility, and can charge multiple electronic products at the same time, and different electronic products can be charged by the same wireless charging device. Therefore, this technology has Broad application prospects.

Figure 1 is a conventional series-to-series wireless power transfer system model in wireless charging technology. According to the two-coil formula:

(R ₁ +jX ₁ )I ₂₁ +jωM _ab I ₂₂ =V ₁ (1)

jωM _ab I ₂₁ +(R ₂ +R _L +jX ₂ )I ₂₂ =0 (2)

where R ₁ is the primary resistance, C ₁ is the primary capacitance, L _n is the primary coil; R ₂ is the secondary resistance, X ₁ is the reactance of the primary coil, X ₂ is the reactance of the secondary coil, and ω is the angle Frequency, I ₂₁ is the alternating current of the primary coil of the conventional two-coil structure, I ₂₂ is the alternating current of the secondary coil of the conventional two-coil structure, M _ab is the mutual inductance between the primary coil and the secondary coil, and R _L is the AC equivalent load resistance. In order to make the calculation more concise, it is assumed that the internal resistances are all 0, that is, R ₁ =0, R ₂ =0, and in order to maximize its efficiency, the source-side circuit and the secondary-side circuit are in a resonant state, that is, X ₁ , X ₂ is also 0, which can be calculated:

In the above formula, P _2O is the output power of the secondary side in the two-coil structure, and P _2in is the input power of the primary side in the two-coil structure.

At the same time, according to the secondary side power:

In the above formula, _VO is the AC output voltage of the secondary side, and I _O is the AC output current of the secondary side. Simultaneously (3) and (4):

Simultaneous (5)(6)(7) get:

Wherein I _O =V _O /R _L , which can be calculated according to the designed system power.

Therefore, when the mutual inductance of the two coils satisfies (8), the rated power can be guaranteed to be output under the condition that the input voltage and current are limited. However, under actual working conditions, it is difficult to output rated power under the condition of voltage and current limitation due to the limitation of voltage and current, and the coupling range is also very limited.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a variable circuit topology with switchable wireless power transmission coils and compensation capacitors. The present invention can realize the output rated power in a wider coupling range under the condition of limiting voltage and current, and greatly improves the range of use and the flexibility of use.

Technical scheme of the present invention: a variable circuit topology with switchable wireless power transmission coil and compensation capacitor, characterized in that the circuit includes:

a primary circuit, comprising a series-connected first resonant capacitor, a first primary coil and a first relay resonant circuit; the first relay resonant circuit includes a second primary coil and a first relay resonant switching module, The first relay resonance switching module is used for switching the second primary coil to a resonance state that is not connected to the power supply;

A secondary circuit includes a third resonant capacitor, a first secondary coil and a second relay resonant circuit connected in series; the second relay resonant circuit includes a second secondary coil and a second relay resonant switching module, The second relay resonance switching module is used for switching the second secondary coil to a resonance state that is not connected to the load.

In the above-mentioned variable circuit topology of the switchable wireless power transmission coil and the compensation capacitor, when the first relay resonance switching module does not function, the second primary coil is connected in series in the primary circuit; the first relay resonance switching module When active, the second primary coil is switched to a resonant state that is not connected to the power supply; when the second relay resonance switching module is inactive, the second secondary coil is connected in series in the secondary circuit; the second relay resonates When the switching module acts, the second secondary coil is switched to a resonant state that is not connected to the load.

In the aforementioned variable circuit topology of the switchable wireless power transmission coil and the compensation capacitor, the first relay resonant circuit includes a second primary coil and a second resonant capacitor connected in series in the primary circuit; Both ends of the series circuit of the coil and the second resonant capacitor are connected in parallel with a first switch; after the first switch is connected, the second primary coil is switched to a resonant state that is not connected to the power supply; the second relay The resonance circuit includes a second secondary coil and a fourth resonance capacitor connected in series in the secondary circuit; a second switch is connected in parallel at both ends of the series circuit of the second secondary coil and the fourth resonance capacitor; the second switch After the switch is connected, the second secondary coil is switched to a resonant state that is not connected to the load.

In the aforementioned variable circuit topology of the switchable wireless power transmission coil and the compensation capacitor, the first relay resonance switching module further includes a first resonance compensation element, and the first resonance compensation element is a capacitor or an inductance; the first resonance compensation One end of the element is connected with the first switch, and the other end of the first resonance compensation element is connected between the first primary coil and the second primary coil.

In the aforementioned variable circuit topology of the switchable wireless power transmission coil and the compensation capacitor, the second relay resonance switching module further includes a second resonance compensation element, and the second resonance compensation element is a capacitor or an inductance; the second resonance compensation One end of the element is connected with the second switch, and the other end of the second resonance compensation element is connected between the first secondary coil and the second secondary coil.

In the aforementioned variable circuit topology of the switchable wireless power transmission coil and the compensation capacitor, the switching method of the circuit is through the switching of the first relay resonance switching module or/and the second relay resonance switching module, so that the second primary side is switched. The coil or/and the second secondary coil are switched between a state without repeater resonance and a state with repeater resonance, so as to achieve output rated power in different coupling ranges.

In the aforementioned variable circuit topology of the switchable wireless power transmission coil and the compensation capacitor, the switching mode of the circuit specifically includes:

Mode a: When the first switch and the second switch are disconnected, the first primary coil and the second primary coil are connected in series with the external power supply terminal; the first secondary coil and the second secondary coil are connected in series with connected to the external load terminal;

Mode b: When the first switch is turned off and the second switch is connected, the first primary coil and the second primary coil are connected in series and then connected to the external power supply terminal; the second secondary coil is in a relay resonance state, and the secondary In the circuit, only the first secondary coil is connected to the external load terminal;

Mode c: When the first switch is connected and the second switch is disconnected, the second primary coil is in a relay resonance state, and only the first primary coil is connected to the external power supply in the primary circuit; the first secondary coil is connected to the external power supply terminal; It is connected in series with the second secondary coil and then connected to the external load terminal;

Mode d: When both the first switch and the second switch are connected, the second primary coil and the second secondary coil are both in the relay resonance state; in the primary circuit, only the first primary coil is connected to the external power supply terminal , in the secondary circuit, only the first secondary coil is connected to the external load terminal.

In the aforementioned variable circuit topology of the switchable wireless power transmission coil and the compensation capacitor, when the mode a and the mode b or the mode c are switched to each other, the following needs to be satisfied:

inferred:

That is, when the coil mutual inductances of the primary circuit and the secondary circuit satisfy equations (27) and (28) at the same time, when mode a and mode b or mode c are switched to each other, the output power does not drop and remains at the rated value; in the above formula P _2O is the output power in mode a; P _3O is the output power in mode b or mode c; V ₁ is the AC input voltage of the primary circuit; R _L is the AC equivalent load resistance; ω is the angular velocity; V _O is the secondary circuit The AC output voltage of the side circuit; M _ab is the mutual inductance of the first primary coil and the first secondary coil in the two-coil mode; M _βγ is the mutual inductance of the three-coil mode of the primary coil and the secondary coils, and M _βγ is the third coil mode. The mutual inductance of the second secondary coil and the first secondary coil; M _αβ is the mutual inductance of the three-coil mode of the primary coil and the secondary coil, and M _αβ is the series connection of the first primary coil and the second primary coil. Mutual inductance between the transmitter coil and the second secondary coil.

In the aforementioned variable circuit topology of the switchable wireless power transmission coil and the compensation capacitor, when the mode b and the mode c are switched to each other, the following needs to be satisfied:

inferred:

That is, when the coil mutual inductances of mode b and mode c satisfy equations (30) and (31) at the same time, when mode b and mode c are switched to each other, the output power does not drop and remains at the rated value; in the above formula, P _3O and P ′ _3O is the output power of mode b or mode c; V ₁ is the AC input voltage of the primary circuit; _RL is the AC equivalent load resistance; ω is the angular velocity; _VO is the AC output voltage of the secondary circuit; M _βγ is the The mutual inductance of the three-coil mode of the primary side of one coil and the secondary side of two coils, and M _βγ is the mutual inductance of the first secondary side coil of the second secondary side coil; M _αβ is the primary side of one coil. And M _αβ is the mutual inductance between the transmitting coil and the second secondary coil formed by the first primary coil and the second primary coil in series; M' _βγ is the mutual inductance of the two coils on the primary side and the secondary coil is a three-coil mode, and M ' _βγ is the mutual inductance of the receiving coil formed by the second primary coil, the first secondary coil and the second secondary coil in series; M' _αβ is the mutual inductance of the three-coil mode with two primary coils and one secondary coil, and M ' _αβ is the mutual inductance between the first primary coil and the second primary coil.

In the aforementioned variable circuit topology of the switchable wireless power transmission coil and the compensation capacitor, when the mode b or the mode c and the mode d are switched to each other, the following needs to be satisfied:

It can be concluded that:

That is, when the coil mutual inductances of the primary circuit and the secondary circuit satisfy the equations (33) and (34) at the same time, when the mode b or the mode c and the mode d are switched to each other, the output power does not drop and remains at the rated value; the above formula where P _4O is the output power of mode d; I ₃₁ is the AC current of the primary circuit in mode b or c; I ₄₁ is the AC current of the primary circuit in mode d; R _L is the AC equivalent load resistance; ω is the angular velocity; _M14 is the mutual inductance of the first primary coil and the first secondary coil; _M23 is the mutual inductance of the second primary coil and the second secondary coil; _M24 is the mutual inductance of the second primary coil and the first secondary coil ; M ₁₂ is the mutual inductance of the first primary side coil and the second primary side coil; M ₃₄ is the mutual _inductance of the first secondary side coil and the second secondary side coil; , and M _βγ is the mutual inductance of the second secondary coil and the first secondary coil; M _αβ is the mutual inductance of the three-coil mode of the primary coil and the secondary coil, and M _αβ is the first primary coil and the first secondary coil. The mutual inductance between the transmitting coil formed by the two primary coils in series and the second secondary coil; M' _βγ is the mutual inductance of the three-coil mode of the two primary coils and one secondary coil, and M' _βγ is the second primary coil and the second coil. Mutual inductance of the receiving coil formed by a secondary coil and a second secondary coil in series; M' _αβ is the mutual inductance of the three-coil mode with two primary coils and one secondary coil, and M' _αβ is the first primary coil and the second The mutual inductance of the primary coil.

Compared with the prior art, the present invention sets a first relay resonant circuit on the primary circuit, and the first relay resonant circuit includes a second primary coil and a first relay resonant switching module. The switching module is used to switch the second primary coil to a resonant state that is not connected to the power supply; at the same time, a second relay resonant circuit is set on the secondary circuit, and the second relay resonant circuit includes the second secondary coil and The second relay resonance switching module is used for switching the second secondary coil to a resonance state that is not connected to the load. Through the actions of the first relay resonant circuit and the second relay resonant circuit, the circuit topology can be switched to four operating modes, and the rated power can be output in a wide coupling range under the condition of voltage limiting and current limiting. , greatly improving the scope and flexibility of use. As a further preference, the applicant also specifically defines the first relay resonant circuit and the second relay resonant circuit, and the first relay resonant circuit includes a second primary coil and a second primary coil connected in series in the primary circuit. Two resonant capacitors; a first switch is connected in parallel at both ends of the series circuit of the second primary coil and the second resonant capacitor; after the first switch is connected, the second primary coil is switched to a resonance that is not connected to the power supply state; the second relay resonant circuit includes a second secondary coil and a fourth resonant capacitor connected in series in the secondary circuit; a second secondary coil and a fourth resonant capacitor are connected in parallel at both ends of the series circuit a switch; after the second switch is connected, the second secondary coil is switched to a resonant state that is not connected to the load. It can be seen from the performance results of psim simulation of this specific circuit that when the air gap is between 90mm and 215mm, the present invention can output 100% rated power under the limitation of input voltage and input current, and only slightly drop at 175mm . While the conventional two-coil circuit can output rated power in an air gap range of only 175mm to 215mm, it can be seen that the present invention can output rated power in a wider coupling range or air gap, greatly improving the use range and flexibility of use sex.

Description of drawings

Figure 1 is a circuit schematic diagram of a conventional series-series wireless power transmission system;

Fig. 2 is the circuit structure diagram of scheme a in embodiment 1;

Fig. 3 is the circuit structure diagram of scheme b in embodiment 1;

4 is a structural diagram of a conventional two-coil wireless power transmission coil;

Figure 5 is a structural diagram of a three-coil structure;

Figure 6 is a circuit schematic diagram of a three-coil structure;

Figure 7 is a structural diagram of a four-coil structure;

Figure 8 is a schematic circuit diagram of a four-coil structure;

9 is a specific circuit schematic diagram of the present invention in Embodiment 4;

Figure 10 is a comparison diagram of the coupling range of the three-coil turns ratio of 16:16;

Figure 11 is a comparison diagram of the coupling range of the three-coil turns ratio of 24:24;

Figure 12 is a comparison diagram of the coupling range of the three-coil turns ratio of 30:30;

Figure 13 is a comparison diagram of the coupling range when the turns ratio of the first primary coil and the second primary coil of four coils is 2:28;

Fig. 14 is a comparison diagram of the coupling range when the turns ratio of the first primary coil and the second primary coil of four coils is 3:27;

Figure 15 is a comparison diagram of the coupling range when the turns ratio of the first primary coil and the second primary coil of four coils is 6:24;

Figure 16 is a comparison diagram of the coupling range when the turns ratio of the first primary coil and the second primary coil of four coils is 8:22;

Fig. 17 is the system architecture diagram of mode a;

Figure 18 is a system architecture diagram of mode b;

Figure 19 is a system architecture diagram of mode c;

Figure 20 is a system architecture diagram of mode d;

FIG. 21 is a graph of the performance results obtained from the psim simulation of mode d.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but not as a basis for limiting the present invention.

Embodiment 1: A variable circuit topology of a switchable wireless power transmission coil and a compensation capacitor, the circuit comprising:

a primary circuit, comprising a series-connected first resonant capacitor, a first primary coil and a first relay resonant circuit; the first relay resonant circuit includes a second primary coil and a first relay resonant switching module, The first relay resonance switching module is used for switching the second primary coil to a resonance state that is not connected to the power supply;

A secondary circuit includes a third resonant capacitor, a first secondary coil and a second relay resonant circuit connected in series; the second relay resonant circuit includes a second secondary coil and a second relay resonant switching module, The second relay resonance switching module is used for switching the second secondary coil to a resonance state that is not connected to the load.

The specific circuit includes two variable circuit topologies. The first scheme a is shown in FIG. 2 , including a primary circuit and a secondary circuit. The primary circuit includes a series-connected first resonant capacitor C ₁ and a first primary coil L ₁ and a first relay resonant circuit, the first relay resonant circuit includes a second primary coil and a first relay resonant switching module, when the first relay resonant switching module of the first relay resonant circuit does not function , the second primary coil is connected in series in the primary circuit, that is, when the first relay resonance switching module does not work, the first primary coil and the second primary coil form a large coil for wireless transmission of electric energy; When a relay resonance switching module acts, the second primary coil is switched to a resonance state that is not connected to the power supply. The secondary circuit includes a third resonant capacitor C ₄ , a second primary coil L ₂ and a second relay resonant circuit connected in series, and the second relay resonant circuit includes a second secondary coil and a second relay resonant switch module, when the second relay resonance switching module of the second relay resonance circuit is inactive, the second secondary coil is connected in series in the secondary circuit; when the second relay resonance switching module is active, the second secondary coil is switched to a resonant state where it is not connected to the load. As a specific preference, as shown in FIG. 2 , the first relay resonant circuit of the first solution includes a second resonant capacitor C ₂ connected in series with the first resonant capacitor C ₁ and the second primary coil L ₂ ; Both ends of the series circuit of the primary coil L ₂ and the second resonant capacitor C ₂ are connected in parallel with a first switch S _a , when the first switch S _a is connected, the second primary coil L ₂ is immediately in a self-resonant state, and also That is, the _second primary coil L2 is switched to a resonance state in which it is not connected to the power source. The second relay resonant circuit includes a fourth resonant capacitor C ₃ connected in series with the _third resonant capacitor C ₄ and the second secondary coil L _{3 ;} A second switch S _b is connected in parallel with the terminal. When the second switch S _b is connected, the second secondary coil L ₃ is immediately in a self-resonant state, that is, the second secondary coil L ₃ is switched to a state that is not connected to the load. resonance state.

Another solution b of the present invention, as shown in FIG. 3 , includes a primary side circuit and a secondary side circuit, and the primary side circuit includes a series-connected first resonant capacitor C ₂ , a first primary side coil L ₂ and a first relay resonance circuit, the first relay resonance circuit includes a second primary coil L1 and _{a first} relay resonance switching module, when the _first relay resonance switching module is inactive, the second primary coil L1 is The open circuit state does not act on the primary side circuit; when the first relay resonance switching module acts, the second primary side coil is switched to a resonance state that is not connected to the power supply. The secondary circuit includes a third resonant capacitor C ₃ , a second primary coil L ₃ and a second relay resonant circuit connected in series, and the second relay resonant circuit includes a second secondary coil L ₄ and a second relay Resonance switching module, when the second relay resonance switching module of the second relay resonance circuit does not work, the second secondary coil is in an open circuit state and does not act on the secondary circuit; when the second relay resonance switching module works , the second secondary coil _L4 is switched to a resonant state that is not connected to the load. As a specific preference, as shown in FIG. 3 , the first relay resonant circuit of scheme b is connected in parallel between the first primary coil L ₂ and the power supply, and the first relay resonant circuit includes the second primary coil L ₁ connected in series , the second resonant capacitor C ₁ and the first switch S _a ; similarly, the second relay resonant circuit is connected in parallel between the first secondary side coil L ₃ and the load, and the second relay resonant circuit includes the second secondary side connected in series The coil L ₄ , the fourth resonance capacitor C ₄ and the second switch S _b . When the first switch S _a is turned off, the second primary coil L ₁ is in an open circuit state and does not act on the primary circuit; when the first switch S _a is connected, the second primary coil L ₁ is switched to not. The resonant state of the connection to the power supply. When the second switch S _b is turned off, the second secondary coil L ₄ is in an open state and does not act on the secondary circuit; when the second switch S _b is turned on, the second secondary coil L ₄ is switched to not Resonant state connected to the load.

As a further preferred solution, the first relay resonance switching module further includes a first resonance compensation element, and the first resonance compensation element is a capacitor or an inductor; one end of the first resonance compensation element is connected to the first switch, and another end of the first resonance compensation element is connected to the first switch. One end is connected between the first primary coil and the second primary coil. The second relay resonance switching module further includes a second resonance compensation element, which is a capacitor or an inductor; one end of the second resonance compensation element is connected to the second switch, and the other end of the second resonance compensation element is connected to the second switch. between the first secondary coil and the second secondary coil. The first resonance compensating element and the second resonance compensating element are used for auxiliary resonance compensation, which can be determined as an inductance or a capacitance according to the calculated value.

Embodiment 2: The switching method of the circuit is to switch between the first relay resonance switching module or/and the second relay resonance switching module, so that the second primary coil or/and the second secondary coil are resonated without a relay. The state and the repeater resonance state are switched, so as to realize the output rated power in different coupling ranges.

The switching mode of the circuit specifically includes:

Mode a: When the first switch and the second switch are disconnected, the first primary coil and the second primary coil are connected in series with the external power supply terminal; the first secondary coil and the second secondary coil are connected in series with connected to the external load terminal;

Mode b: When the first switch is turned off and the second switch is connected, the first primary coil and the second primary coil are connected in series and then connected to the external power supply terminal; the second secondary coil is in a relay resonance state, and the secondary In the circuit, only the first secondary coil is connected to the external load terminal;

Mode c: When the first switch is connected and the second switch is disconnected, the second primary coil is in a relay resonance state, and only the first primary coil is connected to the external power supply in the primary circuit; the first secondary coil is connected to the external power supply terminal; It is connected in series with the second secondary coil and then connected to the external load terminal;

Mode d: When both the first switch and the second switch are connected, the second primary coil and the second secondary coil are both in the relay resonance state; in the primary circuit, only the first primary coil is connected to the external power supply terminal , in the secondary circuit, only the first secondary coil is connected to the external load terminal.

The four working modes are shown in Table 1:

Table 1: Circuit structure table of four working modes (0 in Table 1 means the switch is off, 1 means the switch is on)

It can be seen that through the actions of the first relay resonance switching module and the second relay resonance switching module, the circuit topology can be switched into four working modes, which can be realized in a wider range under the condition of voltage and current limiting. The rated power is output within the coupling range, which greatly improves the use range and flexibility.

Example 3:

1. Conventional series-series compensation inductive wireless power transmission system

1. Coil structure

The conventional wireless power transmission coil structure is shown in Figure 1. It is divided into two coils, the primary side and the secondary side. Each coil contains the same three-layer structure, which are coil winding, magnetic core, and aluminum shielding layer. The primary and secondary coils use the same structure.

2. Circuit model

According to the two-coil formula:

(R ₁ +jX ₁ )I ₂₁ +jωM _ab I ₂₂ =V ₁ (1)

jωM _ab I ₂₁ +(R ₂ +R _L +jX ₂ )I ₂₂ =0 (2)

where R ₁ is the primary resistance, C ₁ is the primary capacitance, L _n is the primary coil; R ₂ is the secondary resistance, X ₁ is the reactance of the primary coil, X ₂ is the reactance of the secondary coil, and ω is the angle Frequency, I ₂₁ is the alternating current of the primary coil of the conventional two-coil structure, I ₂₂ is the alternating current of the secondary coil of the conventional two-coil structure, M _ab is the mutual inductance between the primary coil and the secondary coil, and R _L is the AC equivalent load resistance. In order to make the calculation more concise, it is assumed that the internal resistances are all 0, that is, R ₁ =0, R ₂ =0, and in order to maximize its efficiency, the source-side circuit and the secondary-side circuit are in a resonant state, that is, X ₁ , X ₂ is also 0, which can be calculated:

In the above formula, P _2O is the output power of the secondary side in the two-coil structure, and P _2in is the input power of the primary side in the two-coil structure.

At the same time, according to the secondary side power:

In the above formula, _VO is the AC output voltage of the secondary side, and I _O is the AC output current of the secondary side. Simultaneously (3) and (4):

Simultaneous (5)(6)(7) get:

Wherein I _o =V _o /R _L , which can be calculated according to the designed system power.

Under actual working conditions, it is often limited by voltage and current conditions, so if the rated power can be output under the condition of voltage and current limiting, the coupling range is very limited. Therefore, when the mutual inductance of the two coils satisfies (8), it can ensure that the rated power can be output under the condition that the input voltage and current are limited.

Two, three coil wireless power transmission system

1. Coil structure

The winding of the primary coil in FIG. 2 is divided into two windings, which are coil 1 and coil 2 respectively, and the secondary coil is coil 3, as shown in FIG. 5 .

2. Circuit model

The circuit model is shown in Figure 6. In Figure 6, coil 1 is L _α , coil 2 is L _β , and coil 3 is L _γ

According to the three-coil formula:

(R ₁ +jX ₁ )I ₃₁ +jωM _αβ I ₃₂ +jωM _αγ I ₃₃ =V ₁ (9)

jωM _αβ I ₃₁ +(R ₂ +jX ₂ )I ₃₂ +jωM _βγ I ₃₃ =0 (10)

jωM _αγ I ₃₁ +jωM _βγ I ₃₂ +(R ₃ +R _L +jX ₃ )I ₃₃ =0 (11)

In order to make the input voltage and current in the same phase, ignore the internal resistance at the same time, that is, R1, R2, R3 = 0, and at the same time, the relay coil and the secondary side fully resonate, that is, X2, X3 = 0, which can be calculated.

At the same time, according to the secondary side power:

Lian Li (12), (13):

Lian Li (14), (15), (16):

Wherein I _o =V _o /R _L , which can be calculated according to the designed system power. Therefore, when the mutual inductance of the three coils satisfies (17), it can ensure that the rated power can be output under the condition that the input voltage and current are limited.

Three, four coil wireless power transmission system

1. Coil structure

The four-coil coil structure is shown in FIG. 7 .

2. Circuit model

The circuit model is shown in FIG. 8 . In FIG. 8 , coil 1 is L ₁ , coil 2 is L ₂ , coil 3 is L ₃ , and coil 4 is L ₄ .

According to the four-coil formula:

(R ₁ +jX ₁ )I ₄₁ +jωM ₁₂ I ₄₂ +jωM ₁₃ I ₄₃ +jωM ₁₄ I ₄₄ =V ₁ (18)

jωM ₁₂ I ₄₁ +(R ₂ +jX ₂ )I ₄₂ +jωM ₂₃ I ₄₃ +jωM ₂₄ I ₄₄ =0 (19)

jωM ₁₃ I ₄₁ +jωM ₂₃ I ₄₂ +(R ₃ +jX ₃ )I ₄₃ +jωM ₃₄ I ₄₄ =0 (20)

jωM ₁₄ I ₄₁ +jωM ₂₄ I ₄₂ +jωM ₃₄ I ₄₃ +(R ₄ +R _L +jX ₄ )I ₄₄ =0 (21)

In order to make the input voltage and current in the same phase, the internal resistances of R1, R2, R3 and R4=0 are ignored at the same time, while the relay coil and the secondary side are fully resonated, that is, X2, X3 and X4=0. Similarly, the input voltage and current of the four coils can be calculated. expression:

Combine the formulas (22), (23) and (24):

Wherein I _o =V _o /R _L , which can be calculated according to the designed system power. Therefore, when the mutual inductance of the four coils satisfies (25), it can ensure that the rated power can be output under the condition that the input voltage and current are limited.

Embodiment 4: Combining Embodiment 1 and Embodiment 2, the circuit topology of the preferred example system of the present invention is obtained. As shown in FIG. 9 , it includes a primary circuit, and the primary circuit includes a first resonance capacitor C connected in series _{1. A} first primary coil L ₁ , a second primary coil L ₂ and a second resonant capacitor C ₂ , a first switch is connected in parallel at both ends of the series circuit of the second primary coil L ₂ and the second resonant capacitor C ₂ The switch S _a and the first resonant compensation element _La ; the primary circuit is also connected with a conversion circuit inverter and a power supply DC; the secondary circuit includes a series-connected third resonant capacitor C ₄ , a first secondary coil L ₄ , and a second secondary The side coil L ₃ and the fourth resonance capacitor C ₃ are connected in parallel with a second switch S _b and a second resonance compensation element L _b at both ends of the series circuit of the second secondary side coil L ₃ and the fourth resonance capacitor C ₃ ; A rectifier circuit Rectifier and a load Load are connected to the side circuit.

This topology design combines the structure of two, three and four coils. Different coils work through the switching of the first switch S _a and the second switch S _b . In each mode, there is a coupling range to ensure that the voltage is limited. The rated power is output under the condition of current limitation, and the appropriate turns ratio can be selected according to formulas (8), (17) and (25), which can connect the coupling ranges in different modes.

(a) If two coils are switched to three coils, it must satisfy:

It can be concluded that:

That is, when the coil mutual inductances of the primary circuit and the secondary circuit satisfy equations (27) and (28) at the same time, when mode a and mode b or mode c are switched to each other, the output power does not drop and remains at the rated value; in the above formula P _2O is the output power in mode a; P _3O is the output power in mode b or mode c; V ₁ is the AC input voltage of the primary circuit; R _L is the AC equivalent load resistance; ω is the angular velocity; V _O is the secondary circuit The AC output voltage of the side circuit; M _ab is the mutual _inductance of the two-coil mode coil a and the coil b; The mutual inductance of the first secondary coil); M _αβ is the three-coil mode (one coil on the primary side and two coils on the secondary side). secondary coil) mutual inductance.

(b) If the triple coil (1-2) is switched to the triple coil (2-1), it must satisfy:

It can be concluded that:

That is, when the coil mutual inductances of mode b and mode c satisfy equations (30) and (31) at the same time, when mode b and mode c are switched to each other, the output power does not drop and remains at the rated value; in the above formula, P _3O and P ′ _3O is the output power of mode b or mode c; V ₁ is the AC input voltage of the primary circuit; _RL is the AC equivalent load resistance; ω is the angular velocity; _VO is the AC output voltage of the secondary circuit; M _βγ is the The mutual inductance of the three-coil mode of the primary side of one coil and the secondary side of two coils, and M _βγ is the mutual inductance of the first secondary side coil of the second secondary side coil; M _αβ is the primary side of one coil. And M _αβ is the mutual inductance between the transmitting coil and the second secondary coil formed by the first primary coil and the second primary coil in series; M' _βγ is the mutual inductance of the two coils on the primary side and the secondary coil is a three-coil mode, and M ' _βγ is the mutual inductance of the receiving coil formed by the second primary coil, the first secondary coil and the second secondary coil in series; M' _αβ is the mutual inductance of the three-coil mode with two primary coils and one secondary coil, and M ' _αβ is the mutual inductance between the first primary coil and the second primary coil.

(c) If three coils are switched to four coils, it must satisfy:

It can be concluded that:

That is, when the mutual inductances of the three coils and the four coils satisfy the equations (33) and (34) at the same time, the three-coil mode and the four-coil mode can be connected, and both can output rated power (I _o , I ₃₁ , I ₄₁ , R _L can be calculated according to the constraints). In the above formula, P _4O is the output power of mode d; I ₃₁ is the AC current of the primary circuit in mode b or c; I ₄₁ is the AC current of the primary circuit in mode d; R _L is the AC equivalent load resistance; ω is Angular velocity; _M14 is the mutual inductance of the first primary coil and the first secondary coil; _M23 is the mutual inductance of the second primary coil and the second secondary coil; _M24 is the second primary coil and the first secondary coil M ₁₂ is the mutual inductance of the first primary coil and the second primary coil; M ₃₄ is the mutual inductance of the first secondary coil and the second secondary coil; M _βγ is the three Mutual inductance of the coil mode, and M _βγ is the mutual inductance of the second secondary coil and the first secondary coil; M _αβ is the mutual inductance of the three-coil mode of the primary coil and the secondary coil, and M _αβ is the first primary coil. Mutual inductance between the transmitting coil and the second secondary coil formed in series with the second primary coil; M' _βγ is the mutual inductance of the three-coil mode with two primary coils and one secondary coil, and M' _βγ is the second primary coil Mutual inductance of the receiving coil formed in series with the first secondary coil and the second secondary coil; M' _αβ is the mutual inductance of the three-coil mode with two primary coils and one secondary coil, and M' _αβ is the first primary coil The mutual inductance of the second primary coil.

Thus, the entire system can output the rated power required by the system within a wide coupling range.

The four operating modes and parameter calculation methods of this specific circuit are as follows:

When the turns ratio is different, the switching sequence of the working mode, that is, the corresponding coupling range is also different. The full range of turns ratio analysis is done for the total turns of 16, 24, and 30 as follows:

Figures 10 to 12 are comparison diagrams of the full-range turns ratio coupling range of three coils.

The length of the line segment on the left of Figure 10 represents the air gap distance that can transmit the rated power under the N1:N2 turns ratio. At this time, the two coils on the secondary side are connected in series and combined into one large coil. Similarly, the right side of Figure 10 The length of the line segment in the figure represents the air gap distance that can transmit rated power under the turns ratio of N4:N3. At this time, the two coils on the primary side are combined in series to form a large coil; the middle line segment in Figure 10 represents the two coils on the primary side in series. Combined into a large coil, the two secondary coils are combined in series into a large coil, at this time, the air gap distance that can transmit rated power in the traditional two-coil working mode under the condition of voltage limiting and current limiting.

Through the comparison of the three figures, it can be found that when the total number of turns is more, that is, the ratio of the turns ratio changes less, and the change rate of the coupling range corresponding to different turns ratio is also smaller. The range is better connected. The following analysis selects the total number of turns as 30 turns. The following table lists the parameters of the 30-turn coil.

Table 2: Coil Parameters Table

The coil parameters when the total number of turns is 30 turns are shown in Table 2. It can be seen from Figure 10-Figure 12 that when the turns ratio is different, there can be a variety of different combinations that can correspond to different coupling ranges. There are many types of turns ratio in the full range of the coil, and it is affected by the turns ratio of the three coils. Therefore, the turns ratio in the three-coil mode is selected first, and then to analyze whether four coils can be introduced, you can first determine the relationship between the two coils and one of the coils. The position sequence of the three coils is compared, and then the full-range turns ratio coupling range of the four coils is compared, as shown in Figure 13-16.

The turn ratios that can be connected are as follows (the following results are theoretical analysis):

N1:N2:N3:N4＝3:27:27:3, the corresponding coupling range is 175mm----320mm

N1:N2:N3:N4＝8:22:21:9, the corresponding coupling range is 100mm----215mm

N1:N2:N3:N4＝6:24:17:13, the corresponding coupling range is 95mm----215mm

N1:N2:N3:N4＝8:22:26:4, the corresponding coupling range is 110mm----260mm

N1:N2:N3:N4＝6:24:27:3, the corresponding coupling range is 140mm----290mm

N1:N2:N3:N4＝2:28:21:9, the corresponding coupling range is 145mm----280mm

Different turn ratios can be selected according to different applications, so that the rated power can be transmitted within a wide coupling range. However, in the actual situation, the four coils will have a large harmonic influence, and the coupling range may deviate from the above theoretical value, so it needs to be comprehensively analyzed by circuit model simulation.

The following parameter calculation takes N1:N2:N3:N4=8:22:21:9 as an example:

Mode a in Embodiment 2: (S _a , S _b )=(0,0), coil 1 (ie, the first primary coil) and coil 2 (ie, the second primary coil) work in series, and coil 3 (ie, the first primary coil) works in series. The two secondary coils) work in series with the coil 4 (ie, the first secondary coil), which is equivalent to the conventional two-coil series compensation system. The system architecture diagram of mode a is shown in FIG. 17 . The air gap for this mode to work properly ranges from 175mm to 215mm. In this working mode, the total inductive reactance of the primary coil is compensated, and the total inductive reactance of the secondary side is compensated. Among them, L ₁ , L ₂ , L ₃ , and L ₄ take the inductance value of the weakest coupling position in this mode, that is, the inductance value at 215mm. sense value

Mode b in Embodiment 2: (S _a , S _b )=(0,1) Coil 1 and coil 2 work in series, and coil 3 is in a self-resonant state. The system architecture of mode b is shown in Figure 18, and the air gap range for this mode to work normally is 145mm to 175mm.

C ₃ and L _b are calculated through the strongest coupling position that can output rated power under the condition of voltage and current limiting. At this time, the compensated equivalent capacitance C _e = 11.3nF, and the self-inductance and mutual inductance values select the strongest coupling position That is, the value at 145mm:

Mode c in Embodiment 2: (S _a , S _b )=(1,0) Coil 3 and coil 4 work in series, and coil 2 is in a self-resonant state. The system architecture diagram of mode c is shown in FIG. 19 .

The circuit for this mode can be described by the following system of equations:

(R ₁ +jX ₁ )I ₁ +jωM ₁₂ I ₂ +jωM _1b I _b =V ₁ (39)

jωM ₁₂ I ₁ +(R ₂ +jX ₂ )I ₂ +jωM _2b I _b =0 (40)

jωM _1b I ₁ +jωM _2b I _b +(R ₃ +R ₄ +R _L +jX _b )I _b =0 (41)

where M _1b =M ₁₃ +M ₁₄ , and M _2b =M ₂₃ +M ₂₄ .

From the above equations, the input impedance of the system can be solved, which is set as Z _in . Setting Z _in to zero, the value of C ₁ required to achieve the input voltage and the input current in phase can be solved. R ₁ , R ₂ , R ₃ , and R ₄ can be calculated according to the existing finite element auxiliary calculation method, but they have little effect on the input impedance, and can be set to zero when calculating C ₁ . At the same time, C ₂ and L _a can be calculated by the following formulas, where L ₂ takes the inductance value of the weakest coupling position in this mode, that is, the inductance value at 145mm:

Mode d in Embodiment 2: (S _a , S _b )=(1,1) The coil 2 and the coil 3 are in a self-resonant state. The system architecture diagram of mode d is shown in FIG. 20 . The air gap range for this mode to work properly is 90mm to 115mm.

Simultaneously (35), (36), (37), (38), (42) can be solved to obtain the component parameter values under this combination as shown in Table 3:

parameter	Calculation results
C 1	187.2nF
C 2	7.52nF
C3	8.8nF
C 4	40.55nF
La	183.6μH
L b	88.2μH

Table 3 Component parameters

Circuit simulation verification:

Each working mode can be simulated and verified by circuit simulation software. Figure 21 shows the simulation circuit diagram of mode 4. The simulation diagrams of other modes are not listed one by one. The simulation results verify the above theoretical calculation results one by one.

The applicant has also simulated the mode. After using a two-switch variable circuit to select and switch modes in different distance ranges, the ratio of the maximum output power to the rated power, the input voltage, and the input current of the system are shown in Figure 21. , this is the performance result obtained by psim simulation. Due to the influence of harmonics, the coupling range of the four coils has been changed. The four coils can still output rated power under the condition of voltage and current limiting at 90mm. It can be seen that when the air gap is between 90mm and 215mm, the system can output 100% rated power under the limit of input voltage and input current, and only slightly drop at 175mm. For conventional systems, that is, Mode 1, the air gap range for rated power output is only 175mm to 215mm.

Claims (10)

1. A variable circuit topology for switchable wireless power transmission coils and compensation capacitors, characterized in that the circuit includes:

   a primary circuit, comprising a series-connected first resonant capacitor, a first primary coil and a first relay resonant circuit; the first relay resonant circuit includes a second primary coil and a first relay resonant switching module, The first relay resonance switching module is used for switching the second primary coil to a resonance state that is not connected to the power supply;

   A secondary circuit includes a third resonant capacitor, a first secondary coil and a second relay resonant circuit connected in series; the second relay resonant circuit includes a second secondary coil and a second relay resonant switching module, The second relay resonance switching module is used for switching the second secondary coil to a resonance state that is not connected to the load.
2. The variable circuit topology of switchable wireless power transmission coil and compensation capacitor according to claim 1, characterized in that: when the first relay resonance switching module is inactive, the second primary coil is connected in series in the primary circuit ; When the first relay resonance switching module works, the second primary coil is switched to a resonant state that is not connected to the power supply; when the second relay resonance switching module does not work, the second secondary coil is connected in series with the secondary side In the circuit; when the second relay resonance switching module acts, the second secondary coil is switched to a resonance state that is not connected to the load.
3. The variable circuit topology of the switchable wireless power transmission coil and the compensation capacitor according to claim 1 or 2, wherein the first relay resonant circuit comprises a second primary coil connected in series in the primary circuit and a a second resonant capacitor; a first switch is connected in parallel at both ends of the series circuit of the second primary coil and the second resonant capacitor; after the first switch is connected, the second primary coil is switched to the one that is not connected to the power supply Resonance state; the second relay resonant circuit includes a second secondary coil and a fourth resonance capacitor connected in series in the secondary circuit; a second secondary coil and a fourth resonance capacitor are connected in parallel at both ends of the series circuit Two switching switches; after the second switching switch is connected, the second secondary coil is switched to a resonant state that is not connected to the load.
4. The variable circuit topology of the switchable wireless power transmission coil and the compensation capacitor according to claim 3, wherein the first relay resonance switching module further comprises a first resonance compensation element, and the first resonance compensation element is Capacitance or inductance; one end of the first resonance compensation element is connected to the first switch, and the other end of the first resonance compensation element is connected between the first primary coil and the second primary coil.
5. The variable circuit topology of the switchable wireless power transmission coil and the compensation capacitor according to claim 3, wherein the second relay resonance switching module further comprises a second resonance compensation element, and the second resonance compensation element is Capacitance or inductance; one end of the second resonance compensation element is connected with the second switch, and the other end of the second resonance compensation element is connected between the first secondary coil and the second secondary coil.
6. The variable circuit topology of switchable wireless power transmission coil and compensation capacitor according to any one of claims 1 to 5, characterized in that: the switching method of the circuit is through the first relay resonance switching module or/and the second The switching of the relay resonance switching module enables the second primary coil or/and the second secondary coil to be switched between a state without repeater resonance and a state with repeater resonance, thereby achieving rated power output in different coupling ranges.
7. The variable circuit topology of the switchable wireless power transmission coil and the compensation capacitor according to claim 6, wherein the switching mode of the circuit specifically includes:

   Mode a: When the first switch and the second switch are disconnected, the first primary coil and the second primary coil are connected in series with the external power supply terminal; the first secondary coil and the second secondary coil are connected in series with connected to the external load terminal;

   Mode b: When the first switch is turned off and the second switch is connected, the first primary coil and the second primary coil are connected in series and then connected to the external power supply terminal; the second secondary coil is in a relay resonance state, and the secondary In the circuit, only the first secondary coil is connected to the external load terminal;

   Mode c: When the first switch is connected and the second switch is disconnected, the second primary coil is in a relay resonance state, and only the first primary coil is connected to the external power supply in the primary circuit; the first secondary coil is connected to the external power supply terminal; It is connected in series with the second secondary coil and then connected to the external load terminal;

   Mode d: When both the first switch and the second switch are connected, the second primary coil and the second secondary coil are both in the relay resonance state; in the primary circuit, only the first primary coil is connected to the external power supply terminal , in the secondary circuit, only the first secondary coil is connected to the external load terminal.
8. The variable circuit topology of the switchable wireless power transmission coil and the compensation capacitor according to claim 7, characterized in that, when the mode a and the mode b or the mode c are switched with each other, the following needs to be satisfied:

   

   inferred:

   

   

   That is, when the coil mutual inductances of the primary circuit and the secondary circuit satisfy equations (27) and (28) at the same time, when mode a and mode b or mode c are switched to each other, the output power does not drop and remains at the rated value; in the above formula P _2O is the output power in mode a; P _3O is the output power in mode b or mode c; V ₁ is the AC input voltage of the primary circuit; R _L is the AC equivalent load resistance; ω is the angular velocity; V _O is the secondary circuit The AC output voltage of the side circuit; M _ab is the mutual inductance of the first primary coil and the first secondary coil in the two-coil mode; M _βγ is the mutual inductance of the three-coil mode of the primary coil and the secondary coils, and M _βγ is the third coil mode. The mutual inductance of the second secondary coil and the first secondary coil; M _αβ is the mutual inductance of the three-coil mode of the primary coil and the secondary coil, and M _αβ is the series connection of the first primary coil and the second primary coil. Mutual inductance between the transmitter coil and the second secondary coil.
9. The variable circuit topology of the switchable wireless power transmission coil and the compensation capacitor according to claim 7, characterized in that, when the mode b and the mode c are switched with each other, the following needs to be satisfied:

   

   inferred:

   

   

   That is, when the coil mutual inductances of mode b and mode c satisfy equations (30) and (31) at the same time, when mode b and mode c are switched to each other, the output power does not drop and remains at the rated value; in the above formula, P _3O and P ′ _3O is the output power of mode b or mode c; V ₁ is the AC input voltage of the primary circuit; _RL is the AC equivalent load resistance; ω is the angular velocity; _VO is the AC output voltage of the secondary circuit; M _βγ is the The mutual inductance of the three-coil mode of the primary side of one coil and the secondary side of two coils, and M _βγ is the mutual inductance of the first secondary side coil of the second secondary side coil; M _αβ is the primary side of one coil. And M _αβ is the mutual inductance between the transmitting coil and the second secondary coil formed by the first primary coil and the second primary coil in series; M' _βγ is the mutual inductance of the two coils on the primary side and the secondary coil is a three-coil mode, and M ' _βγ is the mutual inductance of the receiving coil formed by the second primary coil, the first secondary coil and the second secondary coil in series; M' _αβ is the mutual inductance of the three-coil mode with two primary coils and one secondary coil, and M ' _αβ is the mutual inductance between the first primary coil and the second primary coil.
10. The variable circuit topology of the switchable wireless power transmission coil and the compensation capacitor according to claim 7, characterized in that, when the mode b or the mode c and the mode d are switched to each other, the following needs to be satisfied:

    

    It can be concluded that:

    

    

    That is, when the coil mutual inductances of the primary circuit and the secondary circuit satisfy the equations (33) and (34) at the same time, when the mode b or the mode c and the mode d are switched to each other, the output power does not drop and remains at the rated value; the above formula where P _4O is the output power of mode d; I ₃₁ is the AC current of the primary circuit in mode b or c; I ₄₁ is the AC current of the primary circuit in mode d; R _L is the AC equivalent load resistance; ω is the angular velocity; _M14 is the mutual inductance of the first primary coil and the first secondary coil; _M23 is the mutual inductance of the second primary coil and the second secondary coil; _M24 is the mutual inductance of the second primary coil and the first secondary coil ; M ₁₂ is the mutual inductance of the first primary side coil and the second primary side coil; M ₃₄ is the mutual _inductance of the first secondary side coil and the second secondary side coil; , and M _βγ is the mutual inductance of the second secondary coil and the first secondary coil; M _αβ is the mutual inductance of the three-coil mode of the primary coil and the secondary coil, and M _αβ is the first primary coil and the first secondary coil. The mutual inductance between the transmitting coil formed by the two primary coils in series and the second secondary coil; M' _βγ is the mutual inductance of the three-coil mode of the two primary coils and one secondary coil, and M' _βγ is the second primary coil and the second coil. Mutual inductance of the receiving coil formed by a secondary coil and a second secondary coil in series; M' _αβ is the mutual inductance of the three-coil mode with two primary coils and one secondary coil, and M' _αβ is the first primary coil and the second The mutual inductance of the primary coil.

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