JP2010104159A - Power receiving terminal and contactless power transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contactless power receiving terminal and a contactless power transmission system which improve the stability of output voltage to operation frequency fluctuations and power transmission efficiency. <P>SOLUTION: A power receiving terminal 1 is provided with a floating circuit 101 and a load output circuit 102. The floating circuit 101 is provided with a power receiving coil 14 and a capacitor C<SB>0</SB>, and floats from an output line. The power receiving coil 14 is supplied with power from a feeding electric field of a transmission coil 23. The capacitor C<SB>0</SB>is connected to a closed loop including the power receiving coil 14. The load output circuit 102 is provided with a power receiving coil 15, and converts an output voltage from the power receiving coil 15 into a load output voltage to output the load output voltage from the output line. The power receiving coil 15 receives power from the feeding electric field. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power receiving terminal that is coupled to a power feeding electromagnetic field and receives power without contact, and a contactless power transmission system including a power transmission terminal and a power receiving terminal.

  In order to perform charging without connecting a power line in a handset of a fixed telephone, an electric shaver, etc., a power transmission terminal and a power reception terminal may be coupled with a coil antenna to perform power transmission without contact (for example, (See Patent Document 1).

  FIG. 1 is a schematic circuit diagram of a configuration example of a conventional contactless power transmission system.

The power transmission device 110 includes a power transmission coil 111 and a booster circuit 112, boosts a DC input by the booster circuit 112, and applies an AC output to the power transmission coil 111. The power receiving device 120 includes a power receiving coil 121 and a step-down circuit 122. The AC input excited in the power receiving coil 121 is rectified and smoothed by a rectifying / smoothing circuit, stepped down by the step-down circuit 122, and output as a DC output. In this conventional example, by increasing the power transmission voltage of the power transmission coil 111 and the power reception voltage of the power reception coil 121, the coil current is reduced and the power transmission efficiency is improved.
JP 2008-104319 A

  In general, if the power receiving voltage of the power receiving coil is high, the ripple generated in the subsequent stage of the power receiving coil tends to be large, and there is a concern that the temperature rise based on the ripple component increases. In addition, when charging a lithium ion battery, one cell, etc., a low voltage DC output is required. When obtaining a low voltage load output based on a high voltage receiving voltage, a step-down circuit element, for example, It is necessary to employ a large capacity element such as a choke coil, a smoothing capacitor, or a DC-DC converter, resulting in an increase in the size of the circuit module. These problems can be solved by lowering the receiving voltage of the receiving coil compared to the transmitting voltage of the transmitting coil by adjusting the turns ratio, etc., but in that case, the number of turns of the receiving coil is out of the proper range and the power transmission efficiency is reduced. There is a risk of significant reduction. For this reason, it is difficult to lower the received voltage without impairing the power transmission efficiency.

  In general, a contactless power transmission system employs an operating frequency of tens to hundreds of kHz, which is higher than 50-60 Hz of a commercial power source. Thus, at a relatively high operating frequency, even if the operating frequency is very small, the impedance of the circuit element may fluctuate, and the output voltage and power transmission efficiency have frequency characteristics. Therefore, if there is a difference in the operating frequency for each product due to the impedance tolerance of the circuit elements, the output voltage and power transmission efficiency of each product will have a deviation. If this deviation is large, the number of products that cannot satisfy the required performance with respect to the output voltage and power transmission efficiency increases, resulting in a problem in that the yield of non-defective products decreases.

  Therefore, the present invention can reduce the receiving voltage compared to the transmission voltage without significantly reducing the power transmission efficiency, and can easily improve the stability of the output voltage and the power transmission efficiency with respect to fluctuations in the operating frequency. The purpose is to provide terminals and contactless power transmission systems.

  The power receiving terminal of the present invention includes a floating circuit and a load output circuit. The floating circuit includes a first power receiving coil and a capacitor, and floats from the output line. The first power receiving coil is supplied with power linked to the magnetic flux from the power transmitting coil. The capacitor is connected to a closed loop including the first power receiving coil. The load output circuit includes a second power receiving coil, converts the output voltage of the second power receiving coil into a load output voltage, and outputs the load output voltage from the output line. The second power receiving coil is fed with the magnetic flux from the floating circuit.

  In this configuration, the impedance of the entire power transmission circuit consisting of the power transmission terminal and the power reception terminal can be changed without changing the impedance of other circuit elements by the capacitor provided in the floating circuit, and the frequency of the output voltage and power transmission efficiency can be changed. Can affect the characteristics. For this reason, if the impedance of the resonant capacitor is set appropriately, the stability of the output voltage and the power transmission efficiency against frequency fluctuations can be improved.

  In addition, since the load output circuit is supplied with power through the floating circuit, even if the power transmission voltage of the power transmission coil is set to a high voltage and power loss is suppressed, the second power receiving coil does not depend on the turn ratio of the second power receiving coil. The receiving voltage of the receiving coil can be lowered. For this reason, a low receiving voltage can be obtained without significantly reducing the power transmission efficiency.

  The second power receiving coil is preferably roughly coupled to the power transmitting coil and tightly coupled to the first power receiving coil. Thereby, the adjustment effect of the output voltage and electric power transmission efficiency by a capacitor | condenser can be heightened. In addition, the power transmission efficiency can be further improved.

  The load output circuit preferably includes a rectifying / smoothing circuit. The rectifying / smoothing circuit rectifies and smoothes the output of the second power receiving coil. When the output of the second power receiving coil is rectified and smoothed, a ripple may be generated. However, if the power receiving voltage is set to a low voltage, the ripple is reduced, and adverse effects due to the ripple such as a temperature rise in the subsequent stage can be suppressed.

  The load output circuit preferably includes a step-down circuit. The step-down circuit steps down the output of the rectifying / smoothing circuit. If a low-voltage DC output necessary for charging a lithium-ion battery, 1 cell, etc. is obtained by converting the low-voltage receiving voltage, it can be applied to a step-down circuit element such as a choke coil or a smoothing capacitor. Small capacity can be adopted, and the circuit module can be downsized.

  The power receiving terminal may include a rechargeable battery connected to the output end of the output line.

  The contactless power transmission system of the present invention may include the above-described power receiving terminal and power transmission terminal, or a power transmission circuit, a floating circuit, and a load output circuit.

  According to the present invention, by appropriately setting the impedance of the capacitor provided in the floating circuit at the design stage, the frequency characteristics of the output voltage and the power transmission efficiency can be made smooth near the operating frequency. Thereby, even if a circuit element having a large impedance tolerance is adopted, the stability of the output voltage and the power transmission efficiency against the frequency fluctuation can be improved. In addition, since the load output circuit is supplied with power via the floating circuit, a low power receiving voltage can be obtained without significantly reducing the power transmission efficiency.

  Hereinafter, as a specific example of the non-contact power transmission system, an embodiment of the present invention will be described assuming a non-contact charging system including a secondary side charging circuit and a primary side charging adapter used for charging a mobile phone or a mobile PC. To do.

  FIG. 2 is a cross-sectional view showing a schematic configuration example of the contactless power transmission system according to the embodiment of the present invention.

  The non-contact power transmission system includes a secondary power receiving terminal 1 and a primary power transmitting terminal 2. In a state where the power receiving terminal 1 is mounted on the power transmission terminal 2 at the time of charging, contactless power transmission is performed from the power transmission terminal 2 to the power receiving terminal 1, and the rechargeable battery 13 is charged by the power receiving terminal 1.

  The power transmission terminal 2 includes a non-magnetic casing 21, and the casing 21 includes a circuit module 22, a power transmission coil 23, and a magnetic sheet 24. The circuit module 22 is provided with a circuit pattern and circuit elements of a power transmission circuit 200 described later on a circuit board. The power transmission coil 23 is formed as an air-core coil, and is disposed above the magnetic sheet 24. The magnetic sheet 24 is disposed between the circuit module 22 and the power transmission coil 23, restricts the flux linkage of the power transmission coil 23 from leaking to the circuit module 22 side, and facilitates coupling between the power transmission coil and the power reception coil. ing.

The power receiving terminal 1 includes a non-magnetic casing 11, and the casing 11 includes a circuit module 12, a rechargeable battery 13, power receiving coils 14 and 15, and a magnetic sheet 16. The circuit module 12 is a circuit board in which circuit patterns and circuit elements (for example, a DC-DC converter 104 and a capacitor C ₀ ) of a power receiving circuit 100 and a control circuit (not shown) of the power receiving terminal 1 described later are provided on a circuit board. The power receiving coils 14 and 15 are each formed as an air-core coil so that most of the interlinkage magnetic flux of the power receiving coil 14 that is the first power receiving coil is common to the interlinkage magnetic flux of the power receiving coil 15 that is the second power receiving coil. In addition, the power receiving coil 14 is coaxially disposed below the power receiving coil 15. The magnetic sheet 16 is disposed above the power receiving coils 14 and 15 and separates the circuit module 12 and the power receiving coils 14 and 15. The magnetic sheet 16 restricts the interlinkage magnetic flux of the power receiving coils 14 and 15 from leaking to the circuit module 12 side, thereby facilitating coupling between the power receiving coil and the power transmitting coil.

  FIG. 3 is a circuit diagram showing a schematic circuit example of the non-contact power transmission system. The power receiving terminal 1 includes a power receiving circuit 100, and the power transmitting terminal 2 includes a power transmitting circuit 200.

  The power transmission circuit 200 includes a power transmission coil 23, a driver circuit 201, and a primary side signal processing unit 202. The driver circuit 201 converts an AC input supplied to the input line from a commercial power source or the like into a frequency of hundreds of tens of kHz, and boosts the power transmission voltage to 100 V or more and supplies power to the power transmission coil 23 during charging. The primary-side signal processing unit determines the mounting state of the power receiving terminal 1 based on the voltage change of the power transmission coil 23 and controls the driver circuit 201. An AC output from the driver circuit 201 is applied to the power transmission coil 23 to excite the feeding electromagnetic field.

The power receiving circuit 100 includes a floating circuit 101 and a load output circuit 102. Floating circuit 101 is an LC series resonant loop circuit composed of a power receiving coil 14 and the capacitor C ₀ connected in series. When the power receiving terminal 1 is disposed at a chargeable position of the power transmission terminal 2, the power receiving coil 14 is linked to a power supply electromagnetic field that excites the primary power transmission coil 23, and is thereby coupled to the primary power transmission coil 23. To do. Capacitor C ₀ is provided for impedance setting, it contributes to the adjustment of the frequency characteristic of the power transmission efficiency and the output voltage.

The load output circuit 102 is a circuit that converts the AC output of the power receiving coil 15 and outputs a DC output. The power receiving coil 15, the rectifier circuit 103, the smoothing capacitor C ₁ , the DC-DC converter 104, and the secondary side signal processing unit 105. And a load modulation circuit 106.

  When the power receiving terminal 1 is arranged at the chargeable position of the power transmitting terminal 2, the power receiving coil 15 is linked with most of the magnetic flux interlinked with the power receiving coil 14, thereby floating with the power transmitting coil 23 on the primary side. Coupled to the power receiving coil 14 of the circuit 101.

The rectifier circuit 103 rectifies the AC output of the power receiving coil 15. The smoothing capacitor C ₁ smoothes the output of the rectifier circuit 103. A rectifier circuit 103 and a smoothing capacitor C ₁ constitute a rectifying smoothing circuit of the present invention. For the diode D ₁ is to prevent the backflow of charge from the smoothing capacitor C _1, are connected in series between the rectifier circuit 103 and the smoothing capacitor C _1. DC-DC converter 104 is a step-down circuit of the present invention, converted by lowering the output of the smoothing capacitor C ₁ to the DC output of the load output voltage. The power receiving load _RL includes the rechargeable battery 13 and its protection circuit, and is connected to the output line of the load output circuit 102. The rechargeable battery 13 is charged by the direct current output of the DC-DC converter 104. The load modulation circuit 106 includes a load modulation resistor R ₁ and a load modulation switch Q ₁ . The resistor R ₁ has a first end connected to a connection point between the rectifier circuit 103 and the diode D ₁ . Switch Q ₁ is, is connected between the second end and the ground resistor R _1. Secondary signal processing unit 105 generates a transmission signal containing the terminal identifier, and controls the switch Q ₁ in response to the transmission signal.

The current flowing through the resistor R ₁ is modulated by turning on and off the switch Q ₁ , and the impedance of the load modulation circuit 106 is changed, whereby the load impedance on the secondary side as viewed from the power transmission coil 23 on the primary side is changed. Therefore, the primary-side signal processing unit 202 of the power transmission circuit 200 can detect a signal of load modulation communication from the voltage change of the power transmission coil 23.

  4A and 4B are diagrams illustrating an example of an operation flow of the contactless power transmission system. FIG. 4A illustrates an operation flow of the power receiving circuit 100, and FIG. 4B illustrates an operation flow of the power transmission circuit 200.

  This contactless power transmission system switches between a load modulation communication mode and a power transmission mode.

  In the power receiving circuit 100, the secondary-side signal processing unit 105 determines the mode from the output voltage of the rectifier circuit 103, and performs operation control as the load modulation communication mode if the voltage level is lower than the specified value (S11).

In load modulation communication mode, the secondary-side signal processing unit 105 controls the switch Q _1, performs load modulation communication as a transmission signal to terminal unique terminal identifier (S12). Thus switching off of the switch Q ₁ is in accordance with the transmission signal, the load impedance changes in the secondary side as viewed from the primary side of the power transmission coil 23, the voltage level of the power transmission coil 23 changes. Thereby, the primary side signal processing unit 202 switches the mode to the power transmission mode and increases the transmission voltage on the primary side.

  The secondary-side signal processing unit 105 monitors the output of the rectifier circuit 103 for a certain period of time after load modulation communication, and performs operation control as a power transmission mode if the voltage level is about 20 V, which is higher than a specified value. Operation control in the load modulation communication mode is performed again (S13).

In the power transmission mode, the output of the power receiving coil 15 is rectified and smoothed, stepped down by the DC-DC converter 104, and applied to the power receiving load _RL as a direct current output. Thereby, charge of the rechargeable battery 13 progresses (S14).

  On the other hand, in the power transmission circuit 200, in the standby state, the primary-side signal processing unit 202 performs operation control in the load modulation communication mode, and sets the power transmission voltage to a low voltage. (S21). As a result, the receiving voltage is excited at the secondary receiving coil 15 at a low voltage level, the secondary signal processing unit 105 detects a voltage level lower than 20 V, and the load modulation communication transmission operation is performed. .

  Next, the primary side signal processing unit 202 detects a transmission signal from the secondary side (S22). The primary signal processing unit 202 that has detected the transmission signal authenticates the terminal identifier (S23). If verification is possible, the transmission voltage is set to a high voltage (S24). As a result, the feeding electromagnetic field excited in the power transmission coil 23 is strengthened, the power reception voltage is excited in the secondary power reception coil 15 at a high voltage level, and the output voltage of the rectifier circuit 103 is about 20 V, which is higher than the predetermined value. The power transmission mode is set, and charging of the rechargeable battery 13 proceeds.

  Thereafter, when a certain time elapses and the periodic authentication timing comes, the primary-side signal processing unit 202 performs operation control in the load modulation communication mode again (S25).

In the above non-contact power transmission system, the impedance of the entire circuit including the power transmission circuit 200 and the power reception circuit 100 can be changed without changing the impedance of other circuit elements by setting the capacitor C ₀ provided in the floating circuit 101. . For this reason, it is possible to adjust the frequency characteristics of the output voltage and the power transmission efficiency, and to increase the stability of the output voltage and the power transmission efficiency against the frequency fluctuation.

In addition, since the load output circuit 102 is supplied with power via the floating circuit 101, it is possible to obtain a power reception voltage that is lower than the power transmission voltage without significantly reducing power transmission efficiency. As a result, the ripple generated at the output of the rectifier circuit 103 is reduced, and adverse effects due to ripples such as a temperature rise in the DC-DC converter 104 can be suppressed. The circuit elements of the step-down, can adopt a small capacity DC-DC converter 104 and a smoothing capacitor C _1, can be miniaturized circuit module.

Incidentally, the power receiving coil 15 is loosely coupled to the power transmission coil 23, when tightly coupled to the receiving coil 14, an elevated effect of adjusting the output voltage and power transmission efficiency due to the capacitor C ₀ of the floating circuit 101, further improving the power transmission efficiency it can.

  Here, with respect to the example in which the power transmission efficiency is optimized with the configuration of the power receiving circuit of the present embodiment, the result of confirming the performance difference from the comparative example in which the configuration of the floating circuit 101 is omitted and the power transmission efficiency is optimized is shown. explain.

  FIG. 5 is a diagram illustrating a circuit of a contactless power transmission system of a comparative example.

The power receiving circuit 300 of the comparative example includes a power receiving coil 35, a smoothing capacitor C _2, and a DC-DC converter 304. The power receiving coil 35 has its number of turns changed to optimize the power transmission efficiency, and the power receiving voltage is about 100V. Smoothing capacitor C ₂ is the output of the rectifier circuit 103, about 100V adopted mass product for smoothing. DC-DC converter 304 steps down the output of about 100V of the smoothing capacitor _{C 2} employs a large article to a DC output of 12V. When this power receiving circuit 300 is adopted, the power transmission efficiency at full load is about 60%, the module temperature is about 55 ° C., the transmission power fluctuation at the operating frequency ± 10 kHz is about 10%, and the size of the circuit module 12 is about 40 mm. The power receiving circuit 300 had to be configured with × 40 mm and the size of the housing 11 being about 100 mm × 100 mm × 20 mm.

  On the other hand, in the power receiving circuit 100 of this configuration example, the power receiving voltage of the second power receiving coil 15 can be suppressed to about 20 V while maintaining the power transmission efficiency at about 60%. In addition, when obtaining a DC output of 12V, the module temperature is about 50 ° C., the transmission power fluctuation is about 3% at the operating frequency ± 10 kHz, the size of the circuit module 12 is about 20 mm × 20 mm, and the size of the housing 11 is The power receiving circuit 100 was able to be configured as approximately 80 mm × 50 mm × 15 mm. The size of the power receiving coil 14 was an outer diameter of 40 mm and a thickness of 1 mm.

As described above, according to this configuration example, even when a low-voltage DC output is obtained, the received voltage can be suppressed. Therefore, the DC-DC converter 104 or the smoothing capacitor C ₁ that is a step-down circuit element is used. A small capacity can be adopted, and the circuit module can be miniaturized. In addition, the ripple is reduced and the power loss in the DC-DC converter 104 can be suppressed, and the module temperature can be suppressed. And the capacitance value of the capacitor C ₀ of the floating circuit 101 was appropriately set, and fluctuations in power transmission efficiency with respect to frequency fluctuations near the operating frequency could be suppressed.

  Next, another configuration example of the embodiment of the present invention will be described.

FIG. 6 is a cross-sectional view of another configuration example.
In the power receiving terminal 1 described above, the power receiving coil 14 and the power receiving coil 15 are arranged in separate layers in the vertical direction, but in the power receiving terminal 3 of this configuration, the first power receiving coil 34 and the second power receiving coil 35 are A para-winding structure is employed in which each layer is alternately arranged in the inner and outer directions within a single layer. Thus, even if it arrange | positions the receiving coils 34 and 35, this invention can be implemented suitably.

  In addition, a configuration in which a floating circuit is provided in the power transmission terminal instead of the power reception terminal may be employed. Also in this case, the power transmission efficiency and the frequency characteristic of the output voltage can be adjusted by the floating circuit, which is effective in improving the yield rate of manufactured products.

  The floating circuit may be separately provided with a coil for receiving power from the primary side and a coil for transmitting power to the load output circuit. Further, the capacitor of the floating circuit may be arranged so as to cause parallel resonance with the power receiving coil. Even in such a case, the power transmission efficiency and the frequency characteristic of the output voltage can be adjusted by the floating circuit, which is effective in improving the yield of non-defective products.

  Although the present invention can be implemented as shown in the above embodiments, the scope of the present invention is shown not by the above-described embodiments but by the scope of claims, and the scope of the present invention is equivalent to the scope of claims. And all changes within the scope are intended to be included.

It is a circuit diagram explaining the structural example of the conventional non-contact electric power transmission system. 1 is a schematic cross-sectional view of a contactless power transmission system according to an embodiment of the present invention. FIG. FIG. 3 is a schematic circuit diagram of the non-contact power transmission system shown in FIG. 2. It is a figure explaining the operation | movement flow of the non-contact electric power transmission system shown in FIG. It is a schematic circuit diagram of a non-contact power transmission system having a configuration as a comparative example. It is a schematic sectional drawing of the non-contact electric power transmission system which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Power receiving terminal 2 ... Power transmitting terminal 11, 21 ... Case 12, 22 ... Circuit module 13 ... Rechargeable battery 14, 15 ... Power receiving coil 23 ... Power transmitting coil 16, 24 ... Magnetic material sheet 100 ... Power receiving circuit 200 ... Power transmitting circuit 101 ... floating circuit 102 ... load output circuit 103 ... rectifier circuit 104 ... DC-DC converter 105 ... secondary signal processing unit 106 ... load modulator 201 ... driver circuit 202 ... primary signal processor C 0 _... capacitor R L _... receiving load

Claims (7)

A floating circuit that floats from an output line, comprising: a first power receiving coil interlinked with magnetic flux from the power transmitting coil; and a capacitor connected to a closed loop including the first power receiving coil;
A load output circuit that includes a second power receiving coil that receives power in linkage with the magnetic flux from the floating circuit, and converts an output voltage of the second power receiving coil into a load output voltage and outputs the load output voltage from the output line;
A power receiving terminal.   The power receiving terminal according to claim 1, wherein the second power receiving coil is roughly coupled to the power transmitting coil and is tightly coupled to the first power receiving coil.   The power receiving terminal according to claim 1, wherein the load output circuit includes a rectifying / smoothing circuit that rectifies and smoothes the output of the second power receiving coil.   The power receiving terminal according to claim 3, wherein the load output circuit includes a step-down circuit that steps down an output of the rectifying and smoothing circuit.   The power receiving terminal according to claim 4, comprising a rechargeable battery connected to an output end of the output line. The power receiving terminal according to any one of claims 1 to 5,
A contactless power transmission system comprising: a power transmission terminal including the power transmission coil. A power transmission circuit provided in a first housing, including a power transmission coil that is excited by an input from an input line;
A floating coil that floats from the input line and the output line, and includes a first power receiving coil that is fed with a magnetic flux linked to the magnetic flux from the power transmitting coil, and a capacitor connected to a closed loop including the first power receiving coil. Circuit,
A second casing that includes a second power receiving coil that is fed with the magnetic flux from the floating circuit and that converts the output voltage of the second power receiving coil into a load output voltage and outputs the load output voltage from the output line; A load output circuit built in
A contactless power transmission system.

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