JPH0898437A - Noncontact power supply - Google Patents

Abstract

PURPOSE: To obtain a noncontact power supply for supplying a desired power efficiently to a load without increasing the size or the price. CONSTITUTION: A pickup coil 7 to be coupled magnetically with a feeder line 2 is divided into a resonance coil and a power supply coil. The resonance coil 73 is connected with a capacitor 8 while the power supply coil 72 is connected with a load 6 so that a desired power can be fed efficiently to the load 6 by determining the capacitance of the capacitor 8 arbitrarily. Alternatively, only one coil is employed and the capacitor is divided so that the inductance or the capacitance can be selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact type power feeding device comprising a line for passing a high-frequency alternating current and a pickup section (hereinafter also referred to as a pickup coil) magnetically coupled to the line.

[0002]

2. Description of the Related Art Conventionally, as an apparatus of this type, for example, FIG.
Those shown in are known. In the figure, 1 is a high frequency AC power supply, 2 is a power supply line, 3 is a pickup coil, 4 is a resonance capacitor, 5 is a diode bridge, and 6 is a load circuit. The power supply line 2 is an inductive line in which one conductive wire having an insulating coating is folded back and arranged in parallel at a constant interval, and both ends thereof are connected to a high frequency AC power supply 1 for flowing an AC current having a predetermined amplitude and frequency. Has been done.

As shown in FIG. 7, the pickup coil 3 is magnetically coupled to the power supply line 2, and is formed by winding a conducting wire (coil) 32 around a ferrite core 31, for example. Then, the resonance capacitor 4 that resonates at the frequency of the current flowing through the pickup coil 3 and the power supply line 2 and the diode bridge 5 are connected in parallel to the pickup coil 3 (see FIG. 6).

In the load circuit 6, as shown in FIG. 6, for example, a VVVF inverter 66 is connected to a stabilized power supply 61 which controls the output to a predetermined DC voltage, and the VVVF inverter 66 drives an alternating current (AC) motor 67 and the like. It is configured as. Examples of the stabilizing power supply 61 include a DC reactor 62, an output adjusting switch 63, and a diode 6 as disclosed in Japanese Patent Laid-Open No. 5-207603.
4 and the voltage smoothing capacitor 65 are used.

In the above-described structure, the pickup coil 3 and the capacitor 4 resonate, so that the magnetic flux density inside the ferrite core 31 increases and a predetermined power can be supplied to the stabilized power supply 61. Become. The relationship between the constants and the voltage and current of the contactless power feeder will be described with reference to FIG. FIG. 8 is a rewrite of FIGS. 6 and 7 for the description thereof.

That is, the number of turns of the pickup coil 3 is N _P , the self-inductance is L _P , and the mutual inductance between the feeder line 2 and the pickup coil 3 is M.
Further, the capacitance of the capacitor 4 is C _P. The current flowing through the power supply line 2 is a sine wave, its effective value is I ₁ , and its frequency is f
Let s.

Here, if the resonance frequencies of C _P and L _P and fr are given, fr is given by the following equation (1). fr = 1 / 2π√ (L _P C _P ) ... (1) C _P is set so that fr = fs. At this time,
Formula (2) is established. C _P = 1 / ω ² L _P (2) where ω = 2πfs, π: Pi

The input current of the diode bridge 5 is i _E ,
The output current is i _L, and the voltage across the capacitor 4 is v _C. Further, the effective value of the resonance current circulating in the pickup coil 3 and the capacitor 4 is Ir. Now, when the reactance of the DC reactor 62 is sufficiently large, i _L can be regarded as a DC current in a steady state. Therefore, i _E has the amplitude i _L and the voltage v across the capacitor
It becomes a rectangular wave with the same phase as _C. The above currents i ₁ , i _L , i
Schematic waveforms of _E and voltage v _C are shown in FIG.

Here, the effective value of the fundamental wave component of i _E is I _E , the effective value when v _C is approximated to a sine wave is V _C , and the load power is P _L. Then, when the relation of the equation (2) is established, the following relational equation is established between the circuit constant and the voltage and current. I ₁ = L _{P IE} / M∝N _{P IE} (3) P _L = V _C I _E (4) Ir = ωC _P V _C = V _C / ωL _P (5)

From the above formula (4), it can be seen that in order to increase the load power P _L , it is sufficient to increase V _C or I _E , but V _C is limited by the withstand voltage of the semiconductor element used. , I _E need to be increased.
From equation (3), it can be seen that I ₁ may be increased or N _P may be decreased to increase I _E.

[0011]

However, when the number of turns N _P of the pickup coil 3 is reduced, the inductance L _P is reduced. Therefore, according to the above equation (2), the capacitor 4
The capacity of will increase. At this time, it is necessary to use a film capacitor having good high-frequency characteristics as the resonance capacitor 4, and since this film capacitor has only a relatively small capacity, a plurality of film capacitors must be used to increase the capacity. There is a problem that not only the size becomes large by connecting the two in parallel, but also the cost increases remarkably.

Further, by decreasing the number of turns N _P of the pickup coil 3 to reduce its inductance L _P ,
From the relationship of the above equation (5), the resonance current Ir becomes large, and the iron loss and copper loss in the coil increase. As a result, the overall efficiency of the device is reduced.

On the other hand, if I ₁ is increased without decreasing N _P in order to prevent the capacity of the capacitor 4 from increasing, there is a problem that heat generation and loss in the power supply line 2 increase. Therefore, the efficiency of the device is lowered, and it is necessary to increase the diameter of the power supply line 2 and the rating of the high frequency power supply 1, resulting in an increase in cost. Particularly, when a large output is required, there is a problem that when I ₁ becomes large, electromagnetic waves are radiated from the power supply line 2 and electromagnetic interference is caused in the surroundings. Therefore, an object of the present invention is to increase the size of the device without increasing the cost.
It is intended to allow a desired electric power to be efficiently supplied to a load, or to prevent an increase in power supply line current and suppress electromagnetic interference.

[0014]

In order to solve such a problem, in the first invention, a contactless power supply comprising a line for passing a high-frequency alternating current and a pickup coil magnetically coupled to this line. In the device, the pickup coil is divided into a power supply coil and a resonance coil,
A load is connected to the power supply coil, and a capacitor is connected to the resonance coil.

According to a second aspect of the present invention, in a contactless power feeding device comprising a line for flowing a high-frequency alternating current and a pickup coil magnetically coupled to this line, two capacitors are connected in series to the pickup coil. To form a closed loop, and the inductance of the pickup coil and the capacitances of the two capacitors are selected so that the closed loop resonates with the alternating current, and a load is connected across one of the two capacitors. It is characterized by that.

[0016]

The pickup coil is divided into one for power supply and one for resonance, and the number of turns of the resonance coil is adjusted so that the capacity of the resonance capacitor can be arbitrarily determined, and the increase in size and cost are avoided. Further, the number of turns of the power supply coil can be determined independently of the capacity of the resonance capacitor, so that desired power can be efficiently supplied to the load. Further, the capacitor is divided into two, these capacitors and the pickup coil are connected in series to form a closed loop, and each of the two capacitors and the pickup coil is arranged so that this closed loop resonates with the alternating current flowing through the feeder line. By selecting a capacity and connecting a load to both ends of one of the two capacitors, the current of the power supply line is reduced, the conduction loss of the power supply line is reduced, and the efficiency of the device is improved. By reducing the current of the power supply line, the current rating of the device is lowered to reduce the cost, and the electromagnetic waves emitted from the power supply line are reduced to suppress electromagnetic interference.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an overall configuration diagram showing a first embodiment of the present invention, and FIG. 2 is a configuration diagram showing the configuration of a pickup coil. In these figures, the same parts as those in FIGS. 6 to 8 are designated by the same reference numerals. As is clear from FIGS. 1 and 2, the pickup coil 7 here is configured by providing a core 71 with a power supply coil 72 and a resonance coil 73. These two coils may be arranged in any manner as long as they share a magnetic path. Further, the resonance coil 73 is connected in parallel with the capacitor 8 that resonates at the frequency of the current flowing through the power supply line 2.

The operation will be described. First, the high frequency AC power supply 1 supplies a current having a predetermined frequency and amplitude to the power supply line 2. As a result, a magnetic flux is generated in the power supply line 2, and this magnetic flux links the pickup coil 7. As a result, the resonance coil 73 includes the resonance coil 7
Resonance between the capacitor 3 and the capacitor 8 causes a resonance current to flow.
This resonance current increases the magnetic flux density of the core 71 in the pickup coil 7 and allows a desired current to flow through the power supply coil 72.

The operation of the above configuration will be described with reference to FIG. Note that FIG. 3 is a rewriting of FIGS. 1 and 2 for the purpose of explanation. Further, the number of turns of the power supply coil 72 is N _P , the inductance is L _P , the number of turns of the resonance coil 73 is Nr, the inductance is Lr, and the capacity of the capacitor 8 is Cr. Power supply coil 72
Is an effective value of the output voltage of V _L , an effective value of a voltage across the resonance capacitor is V _C , and an effective value of a resonance current circulating through the resonance coil 73 and the capacitor 8 is Ir.

Here, if the frequency of the current flowing through the feeder line 2 is fs, the capacity of the capacitor 8 for matching the resonance frequency of Cr and Lr with fs is ω at the angular frequency of the feeder line current I _1. , Is given by the following equation (6). Cr = 1 / ω ² Lr (6) Further, if the above equation (6) is established, the following relational expression is established between the circuit constant and the voltage and current.

Lr = (Nr / N _P ) ² L _P (7) V _C = (Nr / N _P ) V _L (8) Ir = ωCrV _C = V _C / ωLr (9) The above (2) ) And the above formulas (6) and (7), the following formula is established. Cr = 1 / ω ² Lr = (1 / ω ² L _P ) (N _P / Nr) ² = C _P (N _P / Nr) ² (10)

From the above equation (10), it can be seen that the capacitance Cr of the capacitor 8 can be reduced by setting Nr> N _P. Further, the following equation is established from the equations (8) and (9). Ir = (1 / ωL _P ) (N _P / Nr) ² · (Nr / N _P ) _VL = (1 / ωL _P ) (N _P / Nr) V _L (11)

From the equation (11), it can be seen that the resonance current Ir can be reduced by setting Nr> N _P.
Although the case where the pickup is movable has been described above, it is needless to say that the present invention can be applied to the case where the pickup is fixed in the same manner as described above.

FIG. 4 is a block diagram showing a second embodiment of the present invention. In the figure, 41 and 42 are capacitors for resonance, and those having good high frequency characteristics such as film capacitors are used. And capacitor 4
A diode bridge 5 is connected to both ends of 2. The relationship between the constants shown in FIG. 4 and the current and voltage will be described with reference to FIG. Note that FIG. 5 is rewritten for explaining FIG. 4 and is similar to FIG.

Assuming that the capacitance of the capacitor 41 is C _S and the capacitance of the capacitor 41 is C _O , the combined capacitance Ca
Can be expressed as Ca = C _S C _O / (C _S + C _O ) ... (12). Here, assuming that the frequency of the current of the power supply line 2 is fs, the condition for making the resonance frequencies of Ca and L _P coincide with fs is: Ca = 1 / ω ² L _P … (13)

When the above equation (13) is established, the following equation holds among the circuit constants and the voltage and current. I ₁ = L _P CaI _E / MC _O (14) P _L = V _{C IE} (15) Since Ca <C _O , this formula (14) becomes smaller than the above formula (3), Therefore, it can be seen that the power supply line current I ₁ can be reduced in this embodiment as compared with the conventional one. Moreover, the value of I ₁ can be set to a desired value by selecting the ratio of Ca and C _O.

[0027]

According to the first aspect of the present invention, the pickup coil is provided separately as the power supply coil and the resonance coil, so that the current of the power supply coil and the value of the resonance capacitor are independent. Can be set,
Even if a large output current is required, the capacitance of the resonance capacitor can be small, so that the device can be downsized and the cost can be reduced. Further, even when a large load power is required, only the number of turns of the power supply coil needs to be reduced, and the resonance current in the resonance coil and the resonance capacitor can be suppressed to a small value.
The generated loss can be reduced. From this, there is an advantage that an efficient power supply can be achieved.

According to the second aspect of the present invention, the inductance of the coil and the capacitance of the capacitor are selected so that the pickup coil and the two capacitors resonate with the current of the feeder line, and a load is placed across both ends of one capacitor. Since it is connected, it is possible to reduce the current of the power supply line,
It is possible to reduce the conduction loss in the power supply line to improve the efficiency of the device and reduce the current rating of the high frequency alternating current to reduce the cost. Also, by reducing the current of the power supply line, the electromagnetic waves radiated from the power supply line are reduced,
Electromagnetic interference can be suppressed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a pickup coil in FIG.

FIG. 3 is an operation explanatory diagram of FIG. 1.

FIG. 4 is a configuration diagram showing another embodiment of the present invention.

5 is an operation explanatory diagram of FIG. 4;

FIG. 6 is a configuration diagram showing a conventional example of a contactless power supply device.

7 is a configuration diagram showing a pickup coil in FIG.

8 is an example of an operation explanatory diagram of FIG. 6. FIG.

FIG. 9 is a waveform diagram showing voltages and currents at respective portions shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... High-frequency AC power supply, 2 ... Feeding wire, 3, 7 ... Pickup coil, 4, 41, 42, 8 ... Capacitor, 5 ... Diode bridge, 6 ... Load, 31, 71 ... Core, 32,
72, 73 ... Coil, 61 ... Stabilized power supply, 62 ... DC reactor, 63 ... Semiconductor switch, 64 ... Diode,
65 ... Smoothing capacitor, 66 ... VVVF inverter, 6
7 ... Alternating current (AC) motor.

Claims (2)

[Claims] 1. A contactless power supply device comprising a line for passing a high-frequency alternating current and a pickup coil magnetically coupled to the line, wherein the pickup coil is divided into a power supply coil and a resonance coil. A contactless power supply device characterized in that a load is connected to the power supply coil and a capacitor is connected to the resonance coil. 2. A contactless power supply device comprising a line for flowing a high-frequency alternating current and a pickup coil magnetically coupled to the line, wherein two capacitors are connected in series to the pickup coil to form a closed loop. In addition, the inductance of the pickup coil and the capacitances of the two capacitors are selected so that the closed loop resonates with the alternating current, and a load is connected to both ends of one of the two capacitors. Contactless power supply device.