Power transmission device, power reception device, and wireless power supply system
A power transmission circuit is connected to a power transmission coil having a coil aperture. The power transmission circuit includes a conductive or magnetic power-transmission-coil near member opposed to the coil aperture of the power transmission coil, and a repeating coil arranged on a side opposite to a side on which the power-transmission-coil near member is arranged with respect to the power transmission coil and coupled to the power transmission coil at least via a magnetic field. When a shortest distance between the power transmission coil and the power-transmission-coil near member is expressed as (dt1) and a shortest distance between the power transmission coil and the repeating coil is expressed as (dt2), dt2≤dt1.
1. A power transmission device in a wireless power supply system in which high-frequency power is wirelessly provided from the power transmission device to a power reception device, the power transmission device including a power transmission coil, the power reception device including a power reception coil at least magnetically coupled to the power transmission coil, and the power transmission coil having a coil aperture, the power transmission device comprising:
a power transmission circuit connected to the power transmission coil;
a conductive or magnetic power-transmission-coil near member opposed to the coil aperture of the power transmission coil and having a planar or curved surface portion, an eddy current caused by a magnetic field based on an operation of the wireless power supply system being allowed to flow in the power-transmission-coil near member, the power-transmission-coil near member being a shield plate that is disposed on a lower surface of a nonmagnetic and insulating casing of the power transmission device; and
a repeating coil arranged on a side opposite to a side on which the power-transmission-coil near member is arranged with respect to the power transmission coil and coupled to the power transmission coil at least via a magnetic field,
wherein when a shortest distance between the power transmission coil and the power-transmission-coil near member is expressed as dt1 and a shortest distance between the power transmission coil and the repeating coil is expressed as dt2, dt2≤dt1, and
dt2≤dt1 causes an increase in power loss of the power transmission device to be suppressed and causes a decrease in power efficiency of the power transmission device to be suppressed.
2. A power transmission device in a wireless power supply system in which high-frequency power is wirelessly provided from the power transmission device to a power reception device, the power transmission device including a power transmission coil, the power reception device including a power reception coil at least magnetically coupled to the power transmission coil, and the power transmission coil having a coil aperture, the power transmission device comprising:
a power transmission circuit connected to the power transmission coil;
a casing housing the power transmission coil, the casing including a nonmagnetic and insulating material, and the casing having an inner surface opposed to the coil aperture of the power transmission coil, an outer surface on a back side of the inner surface, and a shield plate that is disposed on a lower surface of the casing; and
a repeating coil arranged on a side opposite to the inner surface of the casing with respect to the power transmission coil and coupled to the power transmission coil at least via a magnetic field,
wherein when a shortest distance between the power transmission coil and the shield plate is expressed as dt1′ and a shortest distance between the power transmission coil and the repeating coil is expressed as dt2, dt2≤dt1′, and
dt2≤dt1′ causes an increase in power loss of the power transmission device to be suppressed and causes a decrease in power efficiency of the power transmission device to be suppressed.
3. The power transmission device according to claim 1 , further comprising a resonance capacitor connected to the repeating coil and constituting a resonance circuit together with the repeating coil.
4. The power transmission device according to claim 3 , wherein a resonance frequency of the resonance circuit is equal to a frequency of an alternating magnetic field formed from the power transmission coil.
5. The power transmission device according to claim 2 , further comprising a resonance capacitor connected to the repeating coil and constituting a resonance circuit together with the repeating coil.
6. A wireless power supply system in which high-frequency power is wirelessly provided from a power transmission device to a power reception device, the power transmission device including a power transmission coil, the power reception device including a power reception coil at least magnetically coupled to the power transmission coil,
the power transmission coil having a coil aperture, and
the power transmission device including a power transmission circuit connected to the power transmission coil, a conductive or magnetic power-transmission-coil near member opposed to the coil aperture of the power transmission coil and having a planar or curved surface portion, an eddy current caused by a magnetic field based on an operation of the wireless power supply system being allowed to flow in the power-transmission-coil near member, and a repeating coil arranged on a side opposite to a side on which the power-transmission-coil near member is arranged with respect to the power transmission coil and coupled to the power transmission coil at least via a magnetic field, the power-transmission-coil near member being a shield plate that is disposed on a lower surface of a nonmagnetic and insulating casing of the power transmission device,
wherein when a shortest distance between the power transmission coil and the power transmission-coil near member is expressed as dt1 and a shortest distance between the power transmission coil and the repeating coil is expressed as dt2, dt2≤dt1, and
dt2≤dt1 causes an increase in power loss of the power transmission device to be suppressed and causes a decrease in power efficiency of the power transmission device to be suppressed.
7. The wireless power supply system according to claim 6 , wherein, where an ordinal number is expressed as n-th (n is an integer greater than or equal to one),
when the repeating coil includes an n-th repeating coil and an (n+1)-th repeating coil positioned farther from the power transmission coil than the n-th repeating coil, and
a distance from the n-th repeating coil to the (n+1)-th repeating coil is expressed as dt(n+2) and a distance from an (n−1)-th repeating coil positioned nearer the power transmission coil than the n-th repeating coil to the n-th repeating coil or a distance from the power transmission coil to the n-th repeating coil is expressed as dt(n+1), dt(n+2)≤dt(n+1).
8. The wireless power supply system according to claim 6 , further comprising a resonance capacitor connected to the repeating coil and constituting a resonance circuit together with the repeating coil.
9. The wireless power supply system according to claim 8 , wherein a resonance frequency of the resonance circuit is equal to a frequency of an alternating magnetic field formed from the power transmission coil.