Isolated capacitive power transfer
First Claim
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1. An electronic device to provide isolated capacitive power transfer to a low-power load, the electronic device comprising:
- an inductor connected to a first terminal of a first capacitor to form a series resonance circuit that provides an alternating current (AC) voltage to a low-power load across the first capacitor;
a switching circuit connected to provide a switched voltage to the series resonance circuit at a sub-harmonic of the resonant frequency of the series resonance circuit;
a rectifier connected to a second terminal of the first capacitor, the rectifier providing a rectified voltage to the low-power load;
a feedback circuit connected to change the sub-harmonic at which the switching circuit operates in response to a change in the low-power load; and
a buck converter connected to provide an input voltage to the switching circuit;
wherein the feedback circuit receives voltage information across a feedback capacitor that has a smaller capacitance than the first capacitor;
wherein the feedback circuit is further connected to fine tune the frequency of the switched voltage;
wherein the feedback circuit is further connected to adjust the input voltage provided by the buck converter;
wherein the first capacitor is printed on top of a silicon chip containing the electronic device;
wherein the inductor is an external inductor;
wherein the electronic device provides power in the range of 15-25 mW at sixty percent efficiency across a functional isolated barrier of 0.5-1 kV.
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Abstract
A method and device for providing isolated power transfer to a low-power load across a capacitor of a series resonance circuit are shown. The method includes comparing an output voltage received via a feedback loop with a desired output voltage. Responsive to determining that the output voltage is not equal to the desired output voltage, the method determines a sub-harmonic order of the resonant frequency of the series resonance circuit to use as a switching frequency and switches the series resonance circuit at substantially the determined subharmonic order of the resonant frequency.
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Citations
10 Claims
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1. An electronic device to provide isolated capacitive power transfer to a low-power load, the electronic device comprising:
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an inductor connected to a first terminal of a first capacitor to form a series resonance circuit that provides an alternating current (AC) voltage to a low-power load across the first capacitor; a switching circuit connected to provide a switched voltage to the series resonance circuit at a sub-harmonic of the resonant frequency of the series resonance circuit; a rectifier connected to a second terminal of the first capacitor, the rectifier providing a rectified voltage to the low-power load; a feedback circuit connected to change the sub-harmonic at which the switching circuit operates in response to a change in the low-power load; and a buck converter connected to provide an input voltage to the switching circuit; wherein the feedback circuit receives voltage information across a feedback capacitor that has a smaller capacitance than the first capacitor; wherein the feedback circuit is further connected to fine tune the frequency of the switched voltage; wherein the feedback circuit is further connected to adjust the input voltage provided by the buck converter; wherein the first capacitor is printed on top of a silicon chip containing the electronic device; wherein the inductor is an external inductor; wherein the electronic device provides power in the range of 15-25 mW at sixty percent efficiency across a functional isolated barrier of 0.5-1 kV.
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2. An electronic device to provide isolated capacitive power transfer to a low-power load, the electronic device comprising:
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an inductor connected to a first terminal of a first capacitor to form a series resonance circuit that provides an alternating current (AC) voltage to a low-power load across the first capacitor; a switching circuit connected to provide a switched voltage to the series resonance circuit at a sub-harmonic of the resonant frequency of the series resonance circuit; a rectifier connected to a second terminal of the first capacitor, the rectifier providing a rectified voltage to the low-power load; a feedback circuit connected to change the sub-harmonic at which the switching circuit operates in response to a change in the low-power load; and a buck converter connected to provide an input voltage to the switching circuit; wherein the feedback circuit receives voltage information across a feedback capacitor that has a smaller capacitance than the first capacitor; wherein the feedback circuit is further connected to fine tune the frequency of the switched voltage; wherein the feedback circuit is further connected to adjust the input voltage provided by the buck converter; wherein the first capacitor is printed on top of a silicon chip containing the electronic device; wherein the inductor is an external inductor; wherein the electronic device has a form factor less than or equal to about 3 mm by 2.5 mm.
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3. A method of providing isolated power transfer to a low-power load across a capacitor of a series resonance circuit, the method comprising:
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determining whether an output voltage received via a feedback loop is equal to a desired output voltage; responsive to determining that the output voltage is not equal to the desired output voltage, determining a sub-harmonic order of the resonant frequency of the series resonance circuit to use as a switching frequency; and switching the series resonance circuit at substantially the determined subharmonic order of the resonant frequency. - View Dependent Claims (4, 5, 6, 7, 8)
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9. A method of providing isolated power transfer to a low-power load across a capacitor of a series resonance circuit, the method comprising:
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determining whether an output voltage received via a feedback loop is equal to a desired output voltage; responsive to determining that the output voltage is not equal to the desired output voltage, determining a combination of an input voltage and a sub-harmonic order of the resonant frequency of the series resonance circuit that when used as a switching frequency will provide the desired output voltage at the greatest efficiency; and responsive to the determining, setting the input voltage to the determined value and setting the switching frequency to the determined subharmonic order of the resonant frequency. - View Dependent Claims (10)
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Specification