Inductive power transfer transmitter and system
An inductive power transfer transmitter comprising: an inverter sub-circuit comprising at least one inverter, and a tuned circuit comprising a plurality of components including at least: a transmitting coil; a first tuning network comprising: an inductor, and a capacitor; a second tuning network comprising a first additional component wherein the plurality of components are arranged such that the tuned circuit can: vary current through the transmitting coil to compensate for variations in K coefficient, provide an output current from the inverter sub-circuit independent of a transmitting coil current.
1 . An inductive power transfer transmitter comprising:
an inverter sub-circuit comprising at least one inverter, and; and
a tuned circuit comprising a plurality of components including at least:
a transmitting coil;
a first tuning network comprising an inductor, and a capacitor; and
a second tuning network comprising a first additional component,
wherein the transmitting coil, the inductor, the capacitor, and the first additional component are each placed on separate branches of the tuned circuit, and
wherein the plurality of components are arranged such that the tuned circuit is configured to be remodeled as if the transmitting coil is series tuned so that the tuned circuit is configured to vary current through the transmitting coil to compensate for variations in K coefficient, and provide an output current from the inverter sub-circuit independent of a transmitting coil current.
2 . An inductive power transfer transmitter according to claim 1 wherein the output current from the inverter sub-circuit is less than the transmitting coil current.
3 . An inductive power transfer transmitter according to claim 1 wherein there is reduced current output from the inverter sub-circuit as a result of the two tuning networks that decouple the inverter from the transmitter coil.
4 . An inductive power transfer transmitter according to claim 1 wherein there is reduced power loss in the inverter sub-circuit.
5 . An inductive power transfer transmitter according to claim 1 wherein the tuned circuit further comprises at least one further additional component to improve power factor of power supplied from the inverter sub-circuit to the transmitting coil.
6 . An inductive power transfer transmitter according to claim 5 wherein the at least one further additional component is a variable component to vary the power factor.
7 . An inductive power transfer transmitter according to claim 6 wherein the variable component is a variable capacitor and/or a variable inductor.
8 . An inductive power transfer transmitter according to claim 1 wherein the inductor and/or capacitor and/or the first additional component and/or a second additional component are arranged in the tuned circuit to provide filtering.
9 . An inductive power transfer transmitter according to claim 8 wherein the tuned circuit can filter out harmonics in the output current from the inverter sub-circuit to improve EMI performance.
10 . An inductive power transfer transmitter according to claim 1 wherein the tuned circuit comprises a variable component that is a variable to vary the portion of current through transmitting coil.
11 . An inductive power transfer transmitter according to claim 10 wherein the variable component is a variable capacitor and/or a variable inductor.
12 . An inductive power transfer transmitter according to claim 1 , wherein the inductor is placed at the output of the inverter sub-circuit.
13 . An inductive power transfer transmitter according to claim 1 , wherein the capacitor is placed at the output of the inverter sub-circuit.
14 . An inductive power transfer transmitter according to claim 1 , wherein the branch the capacitor is located on intersects with the branch that the inductor is located on.
15 . An inductive power transfer transmitter according to claim 1 wherein the capacitor, the first additional component and the transmitting coil are connected in parallel.
16 . An inductive power transfer transmitter according to claim 1 wherein the inductor, the first additional component and the transmitting coil are connected in parallel.
17 . An inductive power transfer transmitter according to claim 1 , wherein the first and second tuning networks together are Norton and Thevenin equivalent of a series tuned circuit to vary current through a transmitting coil to compensate for variations in K coefficient, while comprising one or more components, optionally parallel to the transmitting coil, to decouple the inverter from the transmitter coil.
18 . An inductive power transfer transmitter according to claim 1 , wherein the tuned circuit can be remodeled by:
applying Norton's theorem to transform a series connection of a voltage source (provided by the voltage of the inverter sub-circuit), the inductor and the capacitor into a parallel connection of a current source, the inductor and the capacitor, for creating an appearance of the first tuning network providing a current source for the transmitting coil, and
applying Thevenin's theorem to transform a parallel connection of the current source, the first additional component, and the transmitting coil into a series connection of a voltage source, the first additional component and the transmitting coil, such that the transmitting coil appears series tuned.
19 . An inductive power transfer transmitter according to claim 18 , wherein the inductor and capacitor each have an absolute reactance such that the absolute reactance of the inductor is substantially the same as the absolute reactance of the capacitor such that the combined impedance of the inductor and capacitor creates an appearance of an open circuit component so that the first tuning network appears to provide the current source to the transmitting coil.
20 . An inductive power transfer transmitter according to claim 1 , wherein the first tuning network further comprises a second inductor, the second inductor is located at the output of the inverter sub-circuit, the second inductor located on a branch separate to the first inductor branch.
21 . An inductive power transfer transmitter according to claim 1 , wherein the first tuning network further comprises a second capacitor, the second capacitor is located at the output of the inverter sub-circuit, the second capacitor located on a branch separate to the first capacitor branch.
22 . An inductive power transfer transmitter according to claim 1 , wherein the tuned circuit further comprises a second additional component, wherein:
the second additional component is located on a branch that intersects with the branch that the capacitor is located on;
the second additional component is located on a branch that intersects with the branch that the inductor is located on; and/or
the branch the first additional component is located on intersects with the branch that the second additional component is located on.
23 . An inductive power transfer transmitter according to claim 1 ,
wherein one or more of:
the first inductor,
a second inductor,
the capacitor,
the first additional component,
a second additional component, and
a third additional component
are tunable or fixed in any combination.