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.
2. The transformer as claimed in claim 1, wherein said carrier signal is at an optimum frequency, said optimum frequency being a frequency at which an input impedance of said transformer is a maximum.
3. The transformer as claimed in claim 1, wherein said high frequency carrier signal is in a range of from 300 kHz to 20 MHz and said low frequency non-zero switching signal is in a range of from above DC to 300 kHz.
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.
5. The transformer as claimed in claim 4, wherein said adjusting means comprises a capacitance connected directly across the second winding.
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.
7. A method as claimed in claim 6 wherein the transformer is operated at a frequency of between 100 kHz and 20 Mhz.
8. A method as claimed in claim 6 wherein said transformer is operated by a high-frequency carrier signal modulated by a low frequency non-zero switching signal, said carrier signal being at said optimum frequency.
9. A method as claimed in claim 8 wherein said switching signal is at a frequency of less than 300 kHz.
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.
11. A method as claimed in claim 10 wherein said gate is driven at a frequency in the range of from about 100 kHz to 20 MHz.
12. A method as claimed in claim 10 wherein a low frequency non-zero switching signal is used to modulate a high-frequency carrier signal input to said transformer, and wherein said carrier signal is demodulated after said transformer to drive said gate at said low switching frequency, said carrier signal being at said optimum frequency.
13. A method as claimed in claim 12 wherein said switching signal is at a frequency of less than 300 kHz.
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.
15. The coreless transformer of claim 14, wherein said operating frequency is between 300 kHz and 20 MHz.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A seat belt spooling device comprising:
a frame including a pair of sidewalls;
a reel disposed between the pair of sidewalls, for spooling a seat belt;
a resilient member for urging the reel in the spooling direction;
a pretensioner for driving the reel to rotate in the spooling direction in an emergency; and
a locking structure for locking the reel in the emergency,
wherein the pretensioner comprises:
a driven shaft connected to the reel;
balls disposed along one of the sidewalls and around the periphery of the driven shaft;
a gas generator for applying pressure of gas to the balls so as to move around the periphery of the driven shaft; and
a ball-receiving member for receiving the balls which move into the ball-receiving member,
wherein the ball-receiving member extends from said one of the sidewalls to the other one of the sidewalls, and an opening is formed toward an end in the extending direction of the ball-receiving member, the opening opposing said other one of the sidewalls.
2. A seat belt spooling device according to claim 1, further comprising a guide surface integrally formed with the ball-receiving member for guiding the balls which move into the ball-receiving member.
3. A seat belt spooling device according to claim 1, wherein a case disposed around the periphery of the driven shaft, for supporting the balls, is formed integrally with the ball-receiving member.
4. A seat belt spooling device according to claim 3, wherein the case and the ball-receiving member are formed by casting.
5. A seat belt spooling device comprising:
a pretensioner having a plurality of balls;
a ball receiving member positioned to receive the balls following operation of the pretensioner;
wherein the ball receiving member includes a passage for retaining the balls and an inclined surface for guiding the balls into the passage;
wherein the inclined surface is integrally attached to a wall of the passage.
6. The device of claim 5, wherein the passage includes a first opening at a first end of the passage and a second opening at a second end of the passage.
7. The device of claim 6, wherein second opening is blocked by a frame supporting a drive shaft for a spool.