KR20170055595A - Method for transmitting high power of wireless power transmission system - Google Patents

Abstract

The present invention relates to a high-efficiency power transmission method of a wireless power transmission system, comprising: a step of, when wireless power transmission is performed, determining if it is needed to increase the transmission efficiency; a step of, when it is needed to increase the transmission efficiency, estimating a transmission-side load quality coefficient, a reception-side load quality coefficient, and a combination coefficient; a step of, based on the estimated transmission-side load quality coefficient, reception-side load quality coefficient, and combination coefficient, calculating a target free resonant frequency of a primary resonator and a target free resonant frequency of a secondary resonator; and a step of adjusting the power supply-side resonant capacitor and load-side resonant capacitor; and synchronizing the free resonant frequency of the primary resonator with the target free resonant frequency of the primary resonator, and synchronizing the free resonant frequency of the secondary resonator with the target free resonant frequency of the secondary resonator. The present invention is to provide a high-efficiency power transmission method of a wireless power transmission system, which is capable of improving the wireless power transmission efficiency without changing the frequency of power transmission.

Description

TECHNICAL FIELD [0001] The present invention relates to a high-efficiency power transmission method for a wireless power transmission system,

The present invention relates to a wireless power transmission technique, and more particularly, to a high efficiency transmission method of a wireless power transmission system capable of improving a wireless power transmission efficiency without changing a frequency of a transmission power.

Most of the wireless power transmission (or wireless charging) products currently available are being released to the Wireless Power Consortium (WPC) standard.

The WPC standard proposes to change the operating frequency of the transmission power from 110 to 205 kHz in order to improve the power transmission efficiency.

This WPC standard is unsuitable for applications where the allowable frequency for wireless power transmission is narrow (in the case of narrow bandwidth), since a wide frequency range is only applicable when allowed for wireless power transmission.

For example, in the case of A4WP (Alliance for Wireless Power) standard, the frequency used for wireless power transmission is 6.765 ~ 6.795kHz among the ISM (Industry Science Medical) band and the bandwidth is very narrow, 30kHz. The ISM band of 13.553 ~ 13.567MHz, which is a candidate for another radio power transmission frequency, is narrower with a bandwidth of 14 kHz.

As described above, when the wireless power is transmitted using a standard that provides a narrow bandwidth for the bandwidth of the wireless power transmission as in the A4WP standard, it is difficult to expect the increase of the power transmission efficiency due to the variable transmission frequency.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the conventional art as described above, and it is an object of the present invention to provide a high-efficiency power transmission system of a wireless power transmission system capable of improving wireless power transmission efficiency without changing the transmission power frequency And a transmission method.

According to an aspect of the present invention, there is provided a method for transmitting high-efficiency power in a wireless power transmission system, the method comprising: determining whether an increase in transmission efficiency is required when wireless power transmission is performed; Estimating a transmission side load quality coefficient, a reception side load quality coefficient, and a coupling coefficient when an increase in transmission efficiency is required; Calculating a target free resonance frequency of the first resonator and a target free resonance frequency of the second resonator based on the estimated transmission side load quality coefficient, the reception side load quality coefficient, and the coupling coefficient; And the power-side resonance capacitor and the load-side resonance capacitor are tuned so that the free resonance frequency of the first resonator is tuned to the target free resonance frequency of the first resonator and the free resonance frequency of the second resonator is tuned to the target free resonance frequency of the second resonator .

According to an aspect of the present invention, there is provided a high-efficiency power transmission method of a wireless power transmission system, comprising: determining whether an increase in transmission efficiency is required when wireless power transmission is performed; Estimating a load factor and a coupling coefficient on the transmission side when the transmission efficiency needs to be increased; Calculating optimal power resistance and load resistance based on the estimated transmission side load quality factor, the reception side load quality factor and the coupling factor; And adjusting the input matching circuit on the power transmitting side and the output matching circuit on the power receiving side so that the power source resistance and the load resistance become the optimum power source resistance and load resistance.

According to an aspect of the present invention, there is provided a high-efficiency power transmission method of a wireless power transmission system, comprising: determining whether an increase in transmission efficiency is required when wireless power transmission is performed; Estimating a transmission side load quality coefficient, a reception side load quality coefficient, and a coupling coefficient when an increase in transmission efficiency is required; Calculating a target power resistance or a target load resistance such that a coupling coefficient is a critical coupling coefficient based on the estimated transmission side load quality coefficient, the reception side load quality coefficient, and the coupling coefficient; And adjusting the power source resistance to be the target power source resistance or the load resistance to be the target load resistance so that the coupling coefficient is the critical coupling coefficient.

According to the present invention as described above, it is possible to improve the wireless power transmission efficiency without changing the frequency of the transmission power.

Accordingly, when wireless power is transmitted using a standard that provides a narrow bandwidth for the bandwidth of the wireless power transmission, the wireless power transmission efficiency of the present invention can be improved by applying the wireless power transmission method of the present invention.

Further, when the load resistance changes, the transfer efficiency can be increased by only changing the power source resistance.

1 is a block diagram illustrating an example of a wireless power transmission system to which the high efficiency power transmission method of the present invention is applied.
2 is a block diagram showing a detailed configuration of a transmission driver of the power transmission unit of FIG.
3 is a block diagram showing a detailed configuration of a reception driver of the power receiver shown in FIG.
4 is a diagram showing an equivalent circuit model of the wireless power transmission system of FIG.
Fig. 5 is a diagram showing a case where a matching circuit is applied to the equivalent circuit model of Fig.
6 is a diagram illustrating an example of a wireless power transmission system implemented by an L-section matching circuit using a capacitor as a lumped element.
7 is a diagram illustrating an example of a wireless power transmission system implemented with an air-core transformer matching circuit.
FIG. 8 is a flow chart showing a procedure according to an efficiency enhancement algorithm through a change of a free resonance frequency.
FIG. 9 is a graph showing a change in output power before and after the application of the algorithm of FIG.
FIG. 10 is a flowchart showing a procedure according to an efficiency enhancement algorithm through modification of a matching circuit.
11 is a graph showing an example of a result of applying the algorithm of FIG.
12 is a flow chart showing a procedure according to an efficiency enhancement algorithm by varying the power resistance or the load resistance.
13 is a graph showing an example of a result of applying the algorithm of FIG.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like numbers refer to like elements throughout.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions in the embodiments of the present invention, which may vary depending on the intention of the user, the intention or the custom of the operator. Therefore, the definition should be based on the contents throughout this specification.

Hereinafter, a high-efficiency power transmission method in a wireless power transmission system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating an example of a wireless power transmission system to which the high efficiency power transmission method of the present invention is applied.

Referring to FIG. 1, the wireless power transmission system includes a power transmitter 100 for transmitting power wirelessly, and a power receiver 300 for receiving wireless power transmitted from the power transmitter 100 and supplying power to a battery or a load .

The power transmitter 100 may include a primary coil 110, a transmission driver 120, and a power source 130.

Referring to the operation of the power transmitter 100, the transmission driver 120, which receives power from the power source 130, converts the power into an AC power having a desired operating frequency and a desired power, Is transmitted to the power receiving unit 300 through the primary coil 110. [

The power receiving unit 300 may include a secondary coil 310, a receiving driving unit 320, and a battery (or a load) 330.

When receiving AC power wirelessly transmitted from the power transmitter 100 through the secondary coil (receiving coil 310), the receiving driver 320 rectifies the received AC power To the battery / load (330), and the power receiving unit (300) may be one or more.

2 is a block diagram showing a detailed configuration of a transmission driver of the power transmission unit of FIG.

2, the impedance matching circuit 121 receives the impedance of the tuning unit 122 from the tuning unit 122 through the tuning unit 127, as viewed from the impedance matching circuit 121, to a desired impedance The tuning unit 122 tunes the primary coil 110 to resonance at a desired frequency and can be included in the impedance matching circuit 121 to perform a role .

The AC switching unit 124 receives the external power 130 and outputs a signal having a desired operating frequency and a desired level of power To an alternating current (AC) power.

The in-band communication unit 125a may include an in-band communication unit 125a or an out-band communication unit 125b. And the outband communication unit 125b is used when a resonator for wireless power and an antenna 126 for wireless communication are used.

The control unit 127 is connected to the configurations in the transmission driver 120 and senses the output of the AC switching unit 124 to obtain frequency and power level information and controls the AC switching Thereby adjusting the portion 124.

The control unit 127 determines the switching timing of the switching unit 123 and transmits and receives a message necessary for operating the system through communication with the communication unit 125.

Further, the adjusting unit 127 senses the impedance value when viewed from the input portion of the impedance matching circuit 121, and adjusts the impedance matching circuit 121 to have a desired impedance value.

The tuning unit 127 senses the capacitor value of the tuning unit 122 and adjusts the capacitor value of the tuning unit 122 to a desired capacitor value so that the first-order resonator resonates at a desired frequency.

3 is a block diagram showing a detailed configuration of a reception driver of the power receiver shown in FIG.

3, the reception driver 320 is similar to the transmission driver 120, and the transmission driver 120 includes an AC switching unit 124, , But the receiving driver 320 includes a rectifying unit 324 and a DC / DC converter 325.

The impedance matching circuit 321, the tuning unit 322, the switching unit 323, the communication unit 326 and the adjusting unit 328 of the reception driving unit 320 shown in FIG. 3 correspond to the transmission driving unit 120 The tuning unit 122, the switching unit 123, the communication unit 125, and the control unit 127, detailed description thereof will be omitted.

The DC / DC converter 325 of the reception driver 320 converts the AC power supplied from the rectifier 324 to the AC power supplied from the rectifier 324 through the switching unit 323, And converts the transmitted DC power into a DC power of a desired level.

FIG. 4 illustrates an equivalent circuit model of the wireless power transmission system of FIG. 1, and FIG. 5 illustrates a wireless power transmission system represented by the equivalent circuit model of FIG. 4 by applying a matching circuit.

In FIG. 4, Vs is an AC power supply in which the power source 130 and the AC switching unit 120 are expressed together, and may be implemented by a function generator, a DC-to-AC inverter, a power amplifier, or the like. Rs is the resistance of the AC power supply (Vs), which means power supply resistance.

R _L denotes a load resistance and includes all of the switching unit 323, the rectifying unit 324, the DC / DC converter 325, and the battery / load 330. C ₁ and C ₂ are capacitors (resonance capacitors) for resonance between the primary coil 110 and the secondary coil 310 and are connected to the tuning unit 122 and the power receiving unit 300 of the power transmitting unit 100, And means a tuning unit 322.

L ₁ and L ₂ are the primary coil 110 and the secondary coil 310 and M is the mutual inductance between the primary coil 110 and the secondary coil 310. R _1P and R _2P denote the parasitic resistance of the primary coil 110 and the secondary coil 310.

The Q-factor is used to represent the performance of the coil and the loaded Q-factor is expressed as Q ₁ = ω ₀ L ₁ / R ₁ for the transmitter, In this case, Q ₂ = ω ₀ L ₂ / R ₂ . Here,? ₀ is the power supply frequency.

On the other hand, the unloaded Q-factor is expressed as Q _1u = ω ₀ L ₁ / R _1P for the transmitter side and Q _2u = ω ₀ L ₂ / R _2P for the receiver side.

Therefore, the total resistance R ₁ of the power transmission unit is R _1P + R _S , the total resistance R ₂ of the power receiving unit is R _2P + R _L , and the coupling coefficient k is

Lt; / RTI >

Such a wireless power transmission system can be represented as shown in FIG. 5 using an input matching circuit and an output matching circuit. Here, C ₁ and C ₂ in FIG. 4 are included in the matching circuit and are not shown in FIG. Thus, as C ₁ and C ₂ are included in the matching circuit, the number of elements used in the entire system can be minimized.

5, the matching circuit is used to convert the power source resistance R _S and the load resistance R _L to the optimum power source resistance Z _{S , opt} and the load resistance Z _{L , opt} . The matching circuit may be implemented as an L-section, a π-section, a T-section or the like, which is composed of a lumped element, and may be implemented as an air-core transformer composed of a transformer.

FIG. 6 shows an example of a wireless power transmission system implemented by an L-section matching circuit using a capacitor, which is a lumped element, and FIG. 7 shows an example of a wireless power transmission system implemented by an air- have.

6, the input matching circuit is composed of a power source side capacitor C _1S connected in series to the power source Vs and a power source side parasitic capacitor C _1P connected in parallel to the power source Vs, source consists of a load resistance of the load capacitor connected in series (R _L) (C _2S), and a load resistance (R _L) load the parasitic capacitor (C _2P) connected in parallel to the.

7, the input matching circuit is composed of a primary side comprising a source parasitic resistance (R _PS ), a source coil (L _S ) and a source capacitor (C _S ) and a secondary side comprising a power source side resonance capacitor (C ₁ ) .

At this time, the source parasitic resistance R _PS , the source coil L _S and the source capacitor C _S are connected in series to the power source Vs and the power source side resonant capacitor C ₁ is connected to the primary coil L ₁ And M _S denotes the mutual inductance between the source coil L _S and the primary coil L ₁ .

On the other hand, the output matching circuit is composed of a primary side composed of a load parasitic resistance (R _PL ), a load coil (L _L ) and a load capacitor (C _L ) and a secondary side composed of a load side resonant capacitor (C ₂ ).

At this time, the load parasitic resistance R _PL , the load coil L _L and the load capacitor C _L are connected in series to the load resistance Z _L , and the load side resonant capacitor C ₂ is connected to the secondary coil L ₂ And M _L denotes the mutual inductance between the load coil L _L and the secondary coil L ₂ .

In the case of a wireless power transmission system having the configuration as described above, a method of increasing a wireless power transmission efficiency by changing a power frequency of a power supply unit is mainly used as a load resistance or a transmission environment is changed. This power frequency change has a problem that it is impossible to apply to a wireless power transmission system using a narrow frequency band.

Hereinafter, a wireless power transmission method capable of improving the wireless power transmission efficiency without changing the power frequency of the transmission power will be described.

8 is a flowchart illustrating a procedure according to a wireless power transmission efficiency enhancement algorithm through a free resonance frequency change. At this time, the algorithm of FIG. 8 can be applied to a wireless power transmission system represented by an equivalent circuit model as shown in FIG.

8, when the wireless power transmission is performed (S800), the adjusting units 127 and 328 of the power transmitting and receiving units 100 and 300 increase the transmission efficiency (output power) according to the change of the load resistance or the transmission environment (Step S810).

As a result of the determination in step S810, if it is determined that the increase in transmission efficiency is not necessary (No in step S810), wireless power transmission is performed at the current transmission efficiency (S800).

On the other hand, if it is determined in step S810 that the increase in transmission efficiency is required (S810-Yes), an operation for increasing the transmission efficiency is performed.

First, the free self-resonant frequencies (ω ₁ , ω ₂ ) of the first resonator and the second resonator in FIG. 1 can be expressed by Equation 1 as follows.

[Equation 1]

Normally, the free resonance angular frequencies (? ₁ ,? ₂ ) of the primary and secondary resonators are tuned to be equal to? ₀ , the power supply frequency.

However, when the load resistance changes or the environment between the wireless power transmitting and receiving sections changes, that is, when the transmission efficiency needs to be increased (S810-Yes), the adjusting sections 127 and 328 of the power transmitting and receiving sections 100 and 300 The first and second target free resonance angular frequencies (? _{1, goal} ,? _{2, goal} ) are calculated as follows by estimating k, Q ₁ and Q ₂ in the changed state (S820) (S830).

[Equation 2]

Here, k is a coupling coefficient between the primary coil L1 and the secondary coil L2, and has a relationship such as mutual inductance M and [Equation 3].

[Equation 3]

Then, Q ₁ and Q ₂ can be estimated from Q ₁ = ω ₀ L ₁ / R ₁ and Q ₂ = ω ₀ L ₂ / R ₂ , respectively.

If the first and second target free resonance angular frequencies (ω _{1, goal} , ω _{2, goal} ) are calculated in accordance with step S 830, the controllers 127 and 328 control the capacitors C ₁ ) And the capacitor C ₂ for resonance of the secondary coil (S840), and the free resonance angular frequency of the first and second resonators is adjusted to the first and second target free resonance angular frequencies calculated according to Equation (2) (S850).

Accordingly, the adjusting units 127 and 328 adjust the resonance capacitor C _{1 on the} power source side and the resonance capacitor C _{2 on the} load side (S840). Then, the free resonance angular frequencies of the first and second resonators It is determined whether the tuning has been performed with the target free resonance angular frequency (S850).

If it is determined in step S850 that the free resonance angular frequencies of the first and second resonators are tuned to the first and second target free resonance angular frequencies (S850-Yes), the wireless power transmission efficiency increase algorithm ends , A wireless power transmission is performed.

On the other hand, if it is determined in step S850 that the free resonance angular frequencies of the first and second resonators are not tuned to the first and second target free resonance angular frequencies (S850-No), the adjusters 127 and 328 Side resonance capacitor C ₁ and the load side resonance capacitor C ₂ so that the free resonance angular frequencies of the first and second resonators are tuned to the first and second target free resonance angular frequencies at operation S840.

FIG. 9 is a graph showing a change in output power before and after the application of the algorithm of FIG.

9, the output power before and after applying the algorithm of the present invention is approximately equal to 0.12 before the coupling coefficient k is approximately 0.12. However, in the interval T, the output powers after the application of the algorithm of the present invention (graphs B and D) Is larger than the output power before the algorithm application (graphs A and C), it can be seen that the wireless power transmission efficiency is increased.

FIG. 10 is a flowchart showing a procedure according to an efficiency enhancement algorithm through modification of a matching circuit.

The algorithm shown in FIG. 10 can be applied to a wireless power transmission system to which a matching circuit as shown in FIG. 5 is applied, and is an algorithm for increasing a wireless power transmission efficiency through a variable of a matching circuit.

In addition, the matching circuit to which the algorithm of FIG. 10 is applied may be implemented as shown in FIG. 6 and may be implemented as shown in FIG.

10, when the wireless power transmission is performed (S1000), the adjusting units 127 and 328 of the power transmitting and receiving units 100 and 300 increase the transmission efficiency (output power) according to the change of the load resistance or the transmission environment (S1010).

As a result of the determination in step S1010, if it is determined that the increase in transmission efficiency is not necessary (S1010-No), the controllers 127 and 328 perform wireless power transmission at the current transmission efficiency (S1010).

On the other hand, if it is determined as a result of the determination in step S1010 that the transmission efficiency should be increased (1010-Yes), the controller 127 or 328 performs an operation for increasing the transmission efficiency.

First, when the coupling coefficient k between the primary coil L ₁ and the secondary coil L ₂ is determined by the operating environment of the wireless power transmission system as shown in FIG. 5, The power resistance (Z _{s , opt} ) and the load resistance (Z _{L , opt} ) can be calculated as [Equation 4] or [Equation 5]. Therefore, the optimal power resistance (Z _{s , opt} ) and the load resistances (Z _{L , opt} ) can be calculated by [Equation 4] and can be calculated by [Equation 5].

[Equation 4]

[Equation 5]

In Equations (4) and (5), R ₁ is the transmission-side total resistance, and R _1P + R _S , R ₂ is the receiving total resistance, and R _2P + R _L , where R _1P is the parasitic resistance of the primary coil, R _S is the power supply resistance, R _2P is the parasitic resistance of the secondary coil, and R _L is the load resistance.

Q _1u is the no-load quality factor of the transmitter, expressed as ω ₀ L ₁ / R _1p , and Q _2u is the receive-side no-load quality factor, expressed as ω ₀ L ₂ / R _2p .

The determination result of the step S1010, when it is determined to be required an increase in the transmission efficiency (S1010-Yes), control unit (127, 328) is (S1020) to estimate a k, Q _1, Q ₂ of the change in circumstances, [ Optimal power resistance (Z _{s , opt} ) and load resistances (Z _{L , opt} ) are calculated based on Equation (4) or Equation (5) (S1030).

Thereafter, the adjusting units 127 and 328 adjust the input / output matching circuit (S1040) so that the power source resistance R _s becomes the optimum power source resistance Z _{s , opt} and the load resistance R _L becomes So that the optimum load resistance Z _{L , opt} is obtained (S1050).

In this case, when the wireless power transmission system is implemented as an L-section matching circuit using a capacitor as shown in FIG. 6, the adjusting unit 127 adjusts C _1s and C _{1p so} that the power resistance (R _s ) and in that the power resistors (Z _{s, opt),} the control section 328 controls the C _2s and _2p C and the load resistance (R _L) is such that the optimum load resistance (Z _{L, opt).}

7, when the adjustment unit 127 adjusts M _{s so} that the power source resistance R _s is the optimum power source resistance Z _{s , opt} ), and the control unit 328 adjusts M _{L so} that the load resistance R _L becomes the optimum load resistance Z _{L , opt} .

In this case, to adjust M _s and M _L , the distance between coils and the alignment state can be changed, and the permittivity or permeability of the medium between the coils can be changed.

Here, M _S means the mutual inductance between the source coil L _S and the primary coil L ₁ and M _L means the mutual inductance between the load coil L _L and the secondary coil L ₂ do.

On the other hand, in order for the power source resistance R _s and the load resistance R _L to be the optimum power source resistance Z _{s , opt} and the optimum load resistance Z _{L, opt} , After adjusting the input / output matching circuit (S1040), it is determined whether or not the power source resistance R _s and the load resistance R _L are the optimum power source resistance Z _{s , opt} and the optimum load resistance Z _{L , opt} (S1050).

If it is determined in step S1050 that the power source resistance R _s and the load resistance R _L are the optimum power source resistance Z _{s , opt} and the optimum load resistance Z _{L , opt} , Yes), the wireless power transmission efficiency enhancement algorithm is terminated and wireless power transmission is performed.

On the other hand, if it is determined that the power source resistance R _s and the load resistance R _L do not reach the optimum power source resistance Z _{s , opt} and the optimum load resistance Z _{L , opt} (S1050) S1050-No), the adjusting sections 127 and 328 adjust the power source resistance R _s and the load resistance R _{L such} that the power source resistance Z _{s , opt} and the optimum load resistance Z _{L , opt} The input / output matching circuit is adjusted (S1040).

11 is a graph showing an example of a result of applying the algorithm of FIG. 10, wherein the graph shown in FIG. 11 shows that the wireless power transmission system having the maximum efficiency at a co- And the coupling coefficient k is deteriorated to 0.005.

At this time, when the coupling coefficient k is changed from 0.013 to 0.005, the wireless power transmission system can not transmit the wireless power with the optimal transmission efficiency when the wireless power transmission is performed while maintaining the same characteristic as the graph E.

However, in the wireless power transmission system to which the algorithm of FIG. 10 is applied, when the coupling coefficient k is changed, the input / output matching circuit is varied to have the maximum efficiency in the new environment, Respectively.

Therefore, as shown in Graph F, the wireless power transmission system transmits the wireless power according to the characteristic having the maximum efficiency at the coupling coefficient (k) of 0.005. Therefore, even if the environment changes, the wireless power can be transmitted with the optimum efficiency have.

The wireless power transmission system includes a rectifier, a DC-DC converter, a secondary battery, and the like for charging the secondary battery. Generally, the value of Z _L expressed by the load resistance changes according to the charged amount of the secondary battery. Further, the wireless power transmission system may include a device other than a secondary battery as a load, depending on the state of the device, the load resistance is always changed.

As the load resistance changes, the efficiency of a wireless power transmission system with a specific load resistance and a coupling coefficient designed for optimum efficiency becomes low.

The efficiency enhancement algorithm described above with reference to FIGS. 8 and 10 is a method of changing the resonance frequency and the matching circuit on both the primary coil side and the secondary coil side. However, the efficiency enhancement algorithm, It is a method to achieve maximum efficiency by changing only the resistance.

In addition, by using the efficiency enhancement algorithm to be described, not only the maximum efficiency can be achieved by changing only the load resistance when the power source resistance changes, but also in the case where k is changed due to the power transmission environment change, The maximum efficiency can be achieved only by changing the resistance.

The wireless power transmission system shown in FIG. 4 has the maximum efficiency in a critical coupling state. The critical coupling coefficient (k _critical ) of the system is determined from the following equation (6).

[Equation 6]

4, by changing R _S or R _L so that the coupling coefficient k between the primary coil L ₁ and the secondary coil L ₂ has a value of k _critical in Equation 6, The efficiency can be increased.

For example, when the load resistance R _L can not be changed and only the power source resistance R _S can be changed, the power source resistance R _S is adjusted according to the following Equation 7 or Equation 8, (R _{s , critical} ) value or the optimum power resistance (R _{S , opt} ). Here, the critical power resistance (R _{s , critical} ) or the optimum power source resistance (R _{S , opt} ) is the target power source resistance.

That is, the power is adjusted to the resistance (R _S) is [Formula 7] or [formula 8] target power resistance (power threshold resistance (R _{s, critical)} R or _{S, opt} (optimum power resistor)) according to the.

[Equation 7]

[Equation 8]

Similarly, when the power source resistance R _S can not be changed and only the load resistance R _L can be changed, the load resistance R _L is adjusted according to the following equation (9) or (10) Critical load resistance (R _{L , critical} ) value or optimum load resistance (R _{L , opt} ) value. Here, the critical load resistance R _{L , critical} or the optimum load resistance R _{L , opt} becomes the target load resistance.

That is, the negative resistance R _L is adjusted to the target load resistance (critical load resistance (R _{L , critical} ) or optimum load resistance (R _{L , opt} )) according to [Expression 9] or [Expression 10].

[Equation 9]

[Equation 10]

Further, as shown in FIG. 5, when the system is expressed using a matching circuit, R _S and R _L Instead of The same effect can be obtained by changing Z _S and Z _L.

If the efficiency of the power transmission efficiency decreases due to the increase of the load resistance during the wireless power transmission, it is possible to increase the efficiency by reducing the power resistance.

At this time, as a method of changing the power source resistance, there is a method of changing the resistance Z ' _s viewed by the input matching circuit of FIG. 5, or a method of switching a small resistance to a power source by connecting them in parallel.

12 is a flow chart showing a procedure according to an efficiency enhancement algorithm by varying the power resistance or the load resistance. In this case, the algorithm of FIG. 12 can be applied to a wireless power transmission system represented by an equivalent circuit model as shown in FIG. 4, and the wireless power transmission system of FIG. 4 can be applied to a wireless power transmission system .

12, when the wireless power transmission is performed 1200, the controllers 127 and 328 of the power transmission and reception units 100 and 300 increase the transmission efficiency (output power) according to the change of the load resistance or the transmission environment (S1210).

If it is determined in step S1210 that the increase in transmission efficiency is not required (No in step S1210), the controllers 127 and 328 perform wireless power transmission at the current transmission efficiency (step S1210).

On the other hand, if it is determined in step S1210 that the transmission efficiency should be increased (S1010-Yes), the controller 127 or 328 performs an operation for increasing the transmission efficiency.

First, if it is determined in step 1210 that an increase in transmission efficiency is required (S1210-Yes), the adjusting units 127 and 328 estimate the coupling coefficient k and the load quality factors Q1 and Q2 in the changed state (S1220), calculates the coefficient (k) is the target power threshold coefficient resistance so as to have the value of (k _{critical) (R'S)} and the target load resistance _(R'L) calculated from equation 6 (S1230 ).

Then, the control unit (127, 328) is a power resistance (R _S) R (a target power resistor _(R'S) such that the power resistors so that the resistance or load (R _L), the target load resistance _(R'L) is _S Or the load resistance R _{L in step} S1240 so that the coupling coefficient k has a critical coupling coefficient k _{critical in step} S1250.

At this time, in order to to the coupling coefficient (k) is the value of the critical coupling coefficient (k _critical), control unit (127, 328) is such that the power or the load is a resistance (R _S), the target power resistor _(R'S) resistance (R _L) power resistor (R _S), or the load resistance is critical coupling coefficient (R _L) was adjusted to (S1240), the coupling coefficient (k) so that the target load resistance _(R'L) (k _critical) (S1250). ≪ / RTI >

If it is determined in step S1250 that the coupling coefficient k has become the value of the _critical coupling coefficient k _critical (S1250-Yes), the wireless power transmission efficiency increase algorithm is terminated and wireless power transmission is performed.

On the other hand, if it is determined in step S1250 that the coupling coefficient k is not the critical coupling coefficient k _critical (S1250-No), the controller 127 or 328 determines that the power source resistance R _S is less than the target power source resistance _R'S) to control the power resistor (R _S), or the load resistance (R _L) such that this or that load resistor (R _L) the target load resistance _(R'L) (S1240).

FIG. 13 is a graph showing an example of a result of applying the algorithm of FIG. 12, and shows the result when efficiency is increased by adjusting the power resistance for a fixed load resistance.

Referring to FIG. 12, as in the case of the graph G, the efficiency decreases when the coupling coefficient k becomes equal to or larger than the predetermined value. However, when the algorithm of FIG. 12 is applied as in the case of the graph H, It can be confirmed that the maximum efficiency is maintained almost constant even if it exceeds the predetermined value.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. And various alternatives, modifications, and alterations can be made within a range.

Therefore, the embodiments described in the present invention and the accompanying drawings are intended to illustrate rather than limit the technical spirit of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments and accompanying drawings . The scope of protection of the present invention should be construed according to the claims, and all technical ideas within the scope of equivalents should be interpreted as being included in the scope of the present invention.

100: power transmission unit 110: primary coil
120: Transmitting driver 121: Impedance matching circuit
122: Tuning unit 123:
124: AC switching section 125:
125a: an in-band communication unit
125b: an out-band communication unit
126: antenna 127:
130: Power source 300: Power receiving unit
310: secondary coil 320: receiving driver
321: Impedance matching circuit 322:
323: Switching unit 324:
325: DC / DC converter 326:
326a: In-band communication unit 326b: Out-band communication unit
327: antenna 328:
330: Battery / Load

Claims (22)

A high efficiency power transmission method of a wireless power transmission system,
If wireless power transmission is performed, determining whether an increase in transmission efficiency is required;
Estimating a transmission side load quality coefficient, a reception side load quality coefficient, and a coupling coefficient when an increase in transmission efficiency is required;
Calculating a target free resonance frequency of the first resonator and a target free resonance frequency of the second resonator based on the estimated transmission side load quality coefficient, the reception side load quality coefficient, and the coupling coefficient; And
The free side resonance frequency of the first resonator is tuned to the target free resonance frequency of the first resonator by adjusting the power side resonance capacitor and the load side resonance capacitor so that the free resonance frequency of the second resonator is tuned to the target free resonance frequency of the second resonator step
Wherein the high-efficiency power transmission method comprises the steps of:
The method according to claim 1,
As a result of the determination in the step of determining whether the increase of the transmission efficiency is required, if it is determined that the increase of the transmission efficiency is not necessary, the wireless power transmission is performed at the current transmission efficiency
A method of high efficiency power transmission in a wireless power transmission system.
The method according to claim 1,
The target free resonance frequency of the first resonator and the target free resonance frequency of the second resonator are

And

Calculated from
A method of high efficiency power transmission in a wireless power transmission system. (Where, ω _{1, goal} is the target free resonance frequency of the first resonator, ω _{2, goal} is the target free resonance frequency of the second resonator, and ω _o is the power frequency)
The method according to claim 1,
The transmitting side load quality factor is estimated from the equation Q ₁ = ω _o L ₁ / R ₁ , and the receiving side load quality factor is estimated from the formula Q ₂ = ω _o L ₂ / R ₂ ,

Estimated from
A method of high efficiency power transmission in a wireless power transmission system.
Herein, the Q1 is the transmitting-side load quality factor, Q ₂ is a receiving-side load quality coefficient, k is the coupling coefficient, L1 is the primary coil, L ₂ is a secondary coil, R ₁ is a transmitting-side total resistance, R ₂ is received Side total resistance, M is the mutual inductance of L and L (note that R ₁ is R _1P + R _S , R ₂ is R _2P + R _L , where R _1P is the parasitic resistance of the primary coil, R _S is the power supply resistance, R _2P is the parasitic resistance of the secondary coil, and R _L is the load resistance.
A high efficiency power transmission method of a wireless power transmission system,
If wireless power transmission is performed, determining whether an increase in transmission efficiency is required;
Estimating a transmission side load quality coefficient, a reception side load quality coefficient, and a coupling coefficient when an increase in transmission efficiency is required;
Calculating optimal power resistance and load resistance based on the estimated transmission side load quality factor, the reception side load quality factor and the coupling factor; And
Adjusting the input matching circuit on the power transmitting side and the output matching circuit on the power receiving side so that the power source resistance and the load resistance become optimum power source resistances and load resistances
Wherein the high-efficiency power transmission method comprises the steps of:
6. The method of claim 5,
When the input matching circuit and the output matching circuit are L-section matching circuits using capacitors,
Wherein the input matching circuit comprises a power source side capacitor connected in series to a power source and a power source side parasitic capacitor connected in parallel to the power source,
Wherein the output matching circuit comprises a load side source capacitor connected in series to the load resistor and a load side parasitic capacitor connected in parallel to the load resistor
A method of high efficiency power transmission in a wireless power transmission system.
6. The method of claim 5,
The optimal power resistance

And the optimum load resistance is calculated by

Calculated by
A method of high efficiency power transmission in a wireless power transmission system.
Where, Z _{s, opt} is the optimum power resistor, Z _{L, opt} is the optimal load resistance, R ₁ is a transmitting-side total resistance, R ₂ is a receiving-side total resistance, Q _1u is the no-load quality factor on the transmission side, Q _2u (Where Q _1u is ω _o L ₁ / R _1p and Q _2u is ω _o L ₂ / R _2p ).
6. The method of claim 5,
The optimal power resistance

, And the optimal load resistance is calculated by

Calculated by
A method of high efficiency power transmission in a wireless power transmission system.
Where, Z _{s, opt} is the optimum power resistor, Z _{L, opt} is the optimal load resistance, R ₁ is a transmitting-side total resistance, R ₂ is a receiving-side total resistance, Q _1u is the no-load quality factor on the transmission side, Q _2u (Where Q _1u is ω _o L ₁ / R _1p and Q _2u is ω _o L ₂ / R _2p ).
6. The method of claim 5,
The transmission side load quality factor is estimated from the equation Q ₁ = L ₁ / R ₁ , and the reception side load quality factor is estimated from the equation Q ₂ = L ₂ / R ₂ ,

Estimated from
A method of high efficiency power transmission in a wireless power transmission system.
Where Q ₁ is the transmission side load quality factor, Q ₂ is the reception side load quality factor, k is the coupling coefficient, L ₁ is the primary coil, L ₂ is the secondary coil, R ₁ is the transmission side total resistance, R ₂ Is the receiving total resistance (where R ₁ is R _1P + R _S , R ₂ is R _2P + R _L , where R _1P is the parasitic resistance of the primary coil, R _S is the power supply resistance, R _2P is the parasitic resistance of the secondary coil, and R _L is the load resistance.
10. The method of claim 9,
The step of causing the power source resistance and the load resistance to be optimal power source resistance and load resistance,
The power source side source capacitor and the power source side parasitic capacitor are adjusted so that the power source resistance becomes the optimum power source resistance,
Adjusting the load-side source capacitor and the load-side parasitic capacitor so that the load resistance becomes the optimum load resistance
A method of high efficiency power transmission in a wireless power transmission system.
6. The method of claim 5,
If the input matching circuit and the output matching circuit are air-core transformer matching circuits,
The input matching circuit is connected in series to the power supply (V _s) source parasitic resistance (R _PS) are connected respectively in series to the source coil (L _S), a source capacitor (C _S), and a primary coil (L ₁₎ Side resonance capacitor C ₁ ,
The output matching circuit includes a load parasitic resistor R _pL , a load coil L _L and a load capacitor C _L connected in series to the load resistance Z _L and a load capacitor C _L in series with the secondary coil L ₂ . And a load-side resonance capacitor (C ₂ ) connected thereto
A method of high efficiency power transmission in a wireless power transmission system.
12. The method of claim 11,
The step of causing the power source resistance and the load resistance to be optimal power source resistance and load resistance,
Adjust the M _{s so} that the power resistance is the optimal power resistance and adjust the M _L so that the load resistance (Z _L ) is the optimal load resistance
A method of high efficiency power transmission in a wireless power transmission system. (Where M _S denotes the mutual inductance between the source coil L _S and the primary coil L ₁ and M _L denotes the mutual inductance between the load coil L _L and the secondary coil L ₂ it means.)
13. The method of claim 12,
Adjustment of the Ms is the dielectric constant of the medium between the source coil (L _S) and the primary coil (L ₁₎ to change the distance and the alignment, or between the source coil (L _S) and the primary coil (L ₁₎ Or by changing the investment rate
A method of high efficiency power transmission in a wireless power transmission system.
13. The method of claim 12,
The adjustment of M _L may be performed by changing the distance or the alignment state between the load coil L _L and the secondary coil L ₂ or by changing the dielectric constant between the load coil L _L and the secondary coil L ₂ What is achieved by changing the permeability
A method of high efficiency power transmission in a wireless power transmission system.
A high efficiency power transmission method of a wireless power transmission system,
If wireless power transmission is performed, determining whether an increase in transmission efficiency is required;
Estimating a transmission side load quality coefficient, a reception side load quality coefficient, and a coupling coefficient when an increase in transmission efficiency is required;
Calculating a target power resistance or a target load resistance such that a coupling coefficient is a critical coupling coefficient based on the estimated transmission side load quality coefficient, the reception side load quality coefficient, and the coupling coefficient; And
Adjusting the power source resistance to be the target power source resistance or the load resistance to be the target load resistance so that the coupling coefficient is the critical coupling coefficient
Wherein the method comprises the steps of:
16. The method of claim 15,
The change of the power source resistance may be achieved by connecting a resistance to the power source resistance in parallel or by changing the resistance of the input matching circuit when the wireless power transmission system is represented by a matching circuit
A method of high efficiency power transmission in a wireless power transmission system.
16. The method of claim 15,
The coupling coefficient being the critical coupling coefficient includes adjusting the load resistance to be the target load resistance when the power source resistance is changed
A method of high efficiency power transmission in a wireless power transmission system.
16. The method of claim 15,
And adjusting the coupling coefficient to be the critical coupling coefficient so that the power source resistance becomes the target power source resistance when the load resistance is changed
A method of high efficiency power transmission in a wireless power transmission system.
16. The method of claim 15,
The transmission side load quality factor is estimated from the equation Q ₁ = L ₁ / R ₁ , and the reception side load quality factor is estimated from the equation Q ₂ = L ₂ / R ₂ ,

Estimated from
A method of high efficiency power transmission in a wireless power transmission system.
Here, Q ₁ is a transmission side load quality coefficient, Q ₂ is a reception side load quality coefficient, k is a coupling coefficient, L ₁ is a primary coil, L ₂ is a secondary coil, R ₁ is a transmission side total resistance, R ₂ And M is the mutual inductance of L and L (where R ₁ is R _1P + R _S , R ₂ is R _2P + R _L , where R _1P is the parasitic resistance of the primary coil, R _S is the power supply resistance, R _2P is the parasitic resistance of the secondary coil, and R _L is the load resistance.
16. The method of claim 15,
The critical coupling coefficient (k _critical )

Calculated by
A method of high efficiency power transmission in a wireless power transmission system.
Here, the Q ₁ is a transmitting-side load quality factor, Q ₂ is a receiving-side load quality coefficient, k is the coupling coefficient, the primary coil, L ₂ is a secondary coil, R _1P has the primary parasitic resistance, R _S is R _2P is the parasitic resistance of the secondary coil, R _L is the load resistance, and ω is the free resonance frequency.
16. The method of claim 15,
The target power-

or

Calculated by
A method of high efficiency power transmission in a wireless power transmission system.
Q _1u is the transmit side no-load quality factor, and Q ₂ is the transmit power of the receiving side _, where Z _{s , opt} is the optimal power resistance, Z _{s , critical} is the critical power resistance, R _1p is the parasitic resistance of the primary coil, a load quality coefficient (where, Q _1u is _{ω o L 1 / R 1p,} Q 2 is _{ω o L 2 / R 2 =} ω o L 2 / (R 2p + R L), L 1 is the primary winding, L ₂ is the secondary coil, R ₂ is the receiving total resistance, R _L is the load resistance).
16. The method of claim 15,
The target load resistance

or

Calculated by
A method of high efficiency power transmission in a wireless power transmission system.
Where, Z _{L, opt} is the optimal load resistance, Z _{L, critical} is the critical load resistance, R _2p is a secondary winding parasitic resistance, k is the coupling coefficient, Q ₁ is a transmitting-side load quality factor, Q _2u is the receiving end a no-load quality factor (where, Q ₁ is _{ω o L 1 / R 1 =} ω o L 1 / (R 1p + R s), Q 2u is _{ω o L 2 / R 2p,} L 1 is the primary, R ₁ is the transmitting total resistance, R _S is the power resistance).

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