Non-contact electrical power transmission system having function of making load voltage constant
First Claim
1. A non-contact electrical power transmission system comprising:
- a transformer separable/detachable between a primary winding and a secondary winding;
a capacitor connected in parallel with said secondary winding of said transformer;
an output terminal on said secondary winding side;
said output terminal being connectable to a load;
a high-frequency AC voltage supplied to said primary winding induces an induction voltage to be generated on the secondary winding by the electromagnetic induction action, whereby an electrical power is supplied to a load connected to said output terminal;
said voltage supplied to said load is substantially constant either while said load current varies, or said load varies;
in a first condition, at a time of a maximum load (load current Imax), the time of the reversal of the voltage polarity of said primary winding substantially coincides with a time when an oscillating voltage of said capacitor reaches at least one of a maximum or minimum value;
in a second condition, at a time of a minimum load (load current Imin), the time of the reversal of the voltage polarity of said primary winding substantially coincides with the time when the oscillating voltage of said capacitor completes one cycle; and
a capacitance of said capacitor is set to satisfy simultaneously said first and second conditions, thereby making substantially constant the load voltage in a load current range from Imin to Imax.
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Accused Products
Abstract
A transformer separable/detachable between a primary winding and a secondary winding, has a capacitor connected parallel to the secondary winding. A high-frequency AC voltage supplied to the primary winding of the transformer generates an induced voltage in the secondary winding. The secondary winding transmits electrical power to a load in non-contact manner. Either the output voltage remains constant as the output current varies, or vice versa. Taking as a first condition a fact that at the time of a maximum load, the time of the reversal of the voltage polarity of the primary winding substantially coincides with the time when an oscillating voltage of the capacitor reaches a maximum or minimum value. Taking as a second condition a fact that at the time of a minimum load, the time of the reversal of the voltage polarity of the above-mentioned primary winding substantially coincides with the time when the oscillating voltage of the above-mentioned capacitor completes one cycle. The capacitance of the capacitor is selected to satisfy simultaneously the first and second conditions. This allows the load voltage to remain constant in a load current range from a minimum to a maximum without requiring a feedback circuit.
66 Citations
32 Claims
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1. A non-contact electrical power transmission system comprising:
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a transformer separable/detachable between a primary winding and a secondary winding;
a capacitor connected in parallel with said secondary winding of said transformer;
an output terminal on said secondary winding side;
said output terminal being connectable to a load;
a high-frequency AC voltage supplied to said primary winding induces an induction voltage to be generated on the secondary winding by the electromagnetic induction action, whereby an electrical power is supplied to a load connected to said output terminal;
said voltage supplied to said load is substantially constant either while said load current varies, or said load varies;
in a first condition, at a time of a maximum load (load current Imax), the time of the reversal of the voltage polarity of said primary winding substantially coincides with a time when an oscillating voltage of said capacitor reaches at least one of a maximum or minimum value;
in a second condition, at a time of a minimum load (load current Imin), the time of the reversal of the voltage polarity of said primary winding substantially coincides with the time when the oscillating voltage of said capacitor completes one cycle; and
a capacitance of said capacitor is set to satisfy simultaneously said first and second conditions, thereby making substantially constant the load voltage in a load current range from Imin to Imax. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
at the time of a minimum load (load current Imin), instead of the second condition described in claim 1, taking as a second condition that the time of the reversal of the voltage polarity of the primary winding substantially coincides with the time of starting oscillation of the oscillating voltage of said capacitor, and that the next time of the reversal of the voltage polarity of the primary winding substantially coincides with the time when the oscillating voltage of said capacitor completes one cycle; and
said capacitance of said capacitor simultaneously satisfying said first and second conditions.
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3. A non-contact electrical power transmission system as set forth in claim 1, wherein when expressing a leakage inductance converted to the secondary side of said transformer as L02, the capacitance of said capacitor as C2, and the frequency of said high-frequency AC voltage as f, circuit constants are set so as to satisfy the condition formula
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4. A non-contact electrical power transmission system as set forth in claim 1, wherein, in a load current range smaller than a minimum value of said load current, a dummy load for flowing a current equal to or larger than said minimum value is connected between said output terminals.
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5. A non-contact electrical power transmission system as set forth in claim 1, wherein said drive circuit for supplying said high-frequency AC voltage to said primary winding, varies a frequency of said high-frequency AC voltage automatically to maintain said load current within a range which maintains substantially constant said voltage supplied to said load.
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6. A non-contact electrical power transmission system as set forth in claim 5, wherein said drive circuit includes means for varying said frequency so that, the larger the load current, the higher the frequency of said high-frequency AC voltage automatically becomes.
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7. A non-contact electrical power transmission system as set forth in claim 5, wherein at least one of the rising time and the fall time of said high-frequency AC voltage from said drive circuit automatically varies so as to correspond to a change of the load current, whereby the frequency of said high-frequency AC voltage varies.
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8. A non-contact electrical power transmission system as set forth in claim 7, wherein:
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said drive circuit includes a resonating capacitor connected in parallel with said primary winding; and
at least one of the rising time and the falling time of said high-frequency AC voltage is determined by a resonance voltage of said resonating capacitor and a leakage inductance component.
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9. A non-contact electrical power transmission system as set forth in claim 1, wherein said drive circuit includes means for varying a waveform of said high-frequency AC voltage so that a voltage supplied to said load remains substantially constant.
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10. A non-contact electrical power transmission system as set forth in claim 9, wherein said high-frequency AC voltage varies in the voltage waveform so that an equivalent voltage amplitude of the high-frequency AC voltage increases/decreases corresponding to increases/decreases of said load current.
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11. A non-contact electrical power transmission system as set forth in claim 10, wherein said voltage waveform of said high-frequency AC voltage is a trapezoidal wave shape, and an inclination of an oblique side of said voltage waveform varies corresponding to the load current, whereby the equivalent voltage amplitude varies to maintain said load voltage substantially constant.
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12. A non-contact electrical power transmission system as set forth in claim 11, wherein:
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said drive circuit includes a resonating capacitor connected in parallel with said primary winding, in which drive circuit; and
a waveform of at least one of a rising time and a falling time of said high-frequency AC voltage is determined by utilizing a resonance voltage by said resonating capacitor and a leakage inductance component.
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13. A non-contact electrical power transmission system as set forth in claim 12, wherein said drive circuit is a resonance-type inverter.
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14. A non-contact electrical power transmission system as set forth in claim 13, wherein said drive circuit is a partial resonance-type inverter having a resonating capacitor connected in parallel with said primary winding for resonance with an inductance of said primary winding.
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15. A non-contact electrical power transmission system as set forth in claim 13, wherein said drive circuit includes a voltage resonance circuit by said primary winding and the resonating capacitor connected parallel to said primary winding, and the voltage waveform of said high-frequency AC voltage is a sinusoidal wave shape.
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16. A non-contact electrical power transmission system as set forth in claim 14, wherein in the drive circuit, the on-time of a switching element switched in said drive circuit is constant, and during a period when a partial resonance develops, in at least one of the rising time and the falling time of the voltage waveform of said high-frequency AC voltage, at least one of the time of the period and the voltage waveform in the period varies.
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17. A non-contact electrical power transmission system as set forth in claim 16, wherein said inverter is a half-bridge type inverter.
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18. A non-contact electrical power transmission system as set forth in claim 16, wherein said inverter is a push-pull type inverter.
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19. A non-contact electrical power transmission system as set forth in claim 17, wherein said inverter includes a feedback winding and an auxiliary winding each magnetically coupled to the primary winding of said transformer, a voltage-drive type switching element to which an input voltage at the control terminal is given through the feedback winding, and a charging/discharging circuit connected between both ends of the auxiliary winding for controlling said input voltage, and in that said inverter is a self-excited inverter which when a charging voltage due to the induced voltage of the auxiliary winding reaches a predetermined voltage, lowers said input voltage to cause said switching element to be turned off.
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20. A non-contact electrical power transmission system as set forth in claim 19, wherein, under light-load conditions, a resistance connected between output terminals flows a current at least as large as said minimum value.
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21. A non-contact electrical power transmission system comprising:
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an inverter circuit including a transformer having a structure in which a primary winding and a secondary winding on which a voltage is induced by said primary winding are separable and detachable;
a first capacitor connected to said secondary winding side for matching a load;
a rectifier circuit for rectifying a voltage induced in said secondary winding;
a current smoothing reactor for smoothing an output current of said rectifier circuit;
an output terminal to which a smoothed output by said reactor is supplied and a load is connected;
an inductance of said reactor has a value effective to reduce changes in a load current when the output current of said rectifier circuit is changed from a discontinuous condition to a continuous condition, thereby restraining a rise of said output voltage when said load is no-load or minute-load. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29)
a dummy load connected across an output of said system; and
said dummy load having a resistance effective to maintain at least a minimum load current load current.
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23. A non-contact electrical power transmission system as set forth in claim 21, further comprising:
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a second capacitor connected in parallel with said current smoothing reactor; and
a capacitance of said second capacitor having a value effective to produce an AC voltage component of a voltage on an input side of said current smoothing reactor having a sinusoidal shape.
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24. A non-contact electrical power transmission system as set forth in claim 23, wherein said capacitance of said second capacitor has a value effective to maintain an output terminal voltage substantially equal to an AC voltage on the input side of said current smoothing reactor.
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25. A non-contact electrical power transmission system as set forth in claim 23, wherein when a load is made increased gradually from no-load, the electrostatic capacity of said second capacitor is set so that the load current value when the zero period of the output current of said rectifier circuit being zero dissipates becomes a minimum.
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26. A non-contact electrical power transmission system as set forth in claim 23, wherein a resonance frequency determined by an inductance value of said current-smoothing reactor and a capacitance of said second capacitor is equal to twice the frequency of the voltage applied to the primary winding.
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27. A non-contact electrical power transmission system as set forth in claim 21, wherein a resonance frequency determined by the capacitance of said first capacitor and a leakage inductance value converted to the secondary side of the separable/detachable transformer is equal to twice the frequency of the voltage applied to the primary winding.
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28. A non-contact electrical power transmission system as set forth in claim 21, further comprising:
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a center tap on a secondary of said transformer;
a full-wave rectifier circuit;
said rectifier circuit including two diodes;
one terminal of each of said diodes is connected to opposed outer terminals of said transformer;
second terminals of said two diodes being connected together;
said second terminals being connected to one side of a load;
a second side of said load being connected to said center tap.
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29. A non-contact electrical power transmission system as set forth in claim 21, wherein, when making the inductance value of said current-smoothing reactor large causes the magnitude of a load to be changed, the load current value when the output current of said rectifier circuit is changed from a discontinuous condition to a continuous condition remains small, thereby restraining a rise of the output terminal voltage when the load is no-load or minute-load.
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30. A non-contact electrical power transmission system comprising:
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a source of AC power;
a transformer having a primary winding and a secondary winding, said secondary winding having a center tap;
a full-wave rectifier coupled to outer ends of said secondary winding and to said center tap; and
a tuning capacitor connected in parallel with said secondary winding, a capacitance of said tuning capacitor being selected so that an output voltage at a load is automatically stabilized without active feedback control as the load changes between maximum and minimum. - View Dependent Claims (31, 32)
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Specification