Coreless printed-circuit-board (PCB) transformers and operating techniques therefor
First Claim
1. A coreless transformer, comprising first and second windings, said first winding being disposed in a first plane, said second winding being disposed in a second plane proximate and parallel to said first plane, wherein said transformer is adapted to be operated by a high-frequency carrier signal modulated by a low-frequency non-zero switching signal, and wherein said transformer is adapted to be operated only at a frequency that is less than a resonant frequency of said transformer.
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Abstract
Optimal operating techniques are disclosed for using coreless printed-circuit-board (PCB) transformers under (1) minimum input power conditions and (2) maximum energy efficiency conditions. The coreless PCB transformers should be operated at or near the ‘maximum impedance frequency’ (MIF) in order to reduce input power requirement. For maximum energy efficiency, the transformers should be at or near the “maximum efficiency frequency” (MEF) which is below the MIF. The operating principle has been confirmed by measurement and simulation. The proposed operating techniques can be applied to coreless PCB transformers in many circuits that have to meet stringent height requirements, for example to isolate the gates of power MOSFET and IGBT devices from the input power supply.
71 Citations
15 Claims
- 1. A coreless transformer, comprising first and second windings, said first winding being disposed in a first plane, said second winding being disposed in a second plane proximate and parallel to said first plane, wherein said transformer is adapted to be operated by a high-frequency carrier signal modulated by a low-frequency non-zero switching signal, and wherein said transformer is adapted to be operated only at a frequency that is less than a resonant frequency of said transformer.
- 4. A coreless transformer comprising first and second windings, said first winding being disposed in a first plane, said second winding being disposed in a second plane proximate and parallel to said first winding plane, further comprising means for adjusting a resonant frequency of the transformer, wherein said transformer is adapted to be operated only at a frequency that is less than said resonant frequency of said transformer.
- 6. A method of operating a coreless planar transformer, wherein said transformer is operated at an optimum frequency which is at or near the frequency at which the impedance of a transformer equivalent circuit is at its maximum and which is less than the resonant frequency of the transformer.
- 10. A method of driving a gate of a power MOSFET or IGBT device comprising isolating said gate from a power supply by means of a coreless planar transformer and driving said gate at an optimum frequency which is at or near the frequency at which the impedance of a transformer equivalent circuit is at its maximum and which is less than the resonant frequency of the transformer.
- 14. A coreless transformer comprising first and second windings, said first winding being disposed in a first plane, said second winding being disposed in a second plane proximate and parallel to said first plane, said coreless transformer further comprising a capacitance across said second winding to resonate with said coreless transformer in order to maximize an input impedance of the coreless transformer, wherein an operating frequency of the coreless transformer is less than a resonant frequency of the transformer.
Specification