1. Microwave tube (3) for generation of an electromagnetic wave with frequency F, characterised in that it comprises mechanical means for varying the frequency F composed of a set of rings (A, B, C, D) defining a periodic structure inside the tube and mechanical means (4, 5, 2, G; 7, 8, 9, 10) for displacing the rings with respect to each other while maintaining a periodicity for the periodic structure during displacement of the rings.
2. Microwave tube (3) according to claim 1, characterised in that the mechanical means for displacing the rings comprise a set of electrical contacts (2) between rings, at least one lead screw (4), a set of nuts (5) installed on the lead screw, a set of rods (6), each rod firmly connecting a nut to a ring, the tube (3) being provided with at least one slit (G) enabling rods (6) to pass in the wall of the tube, the lead screw (4) comprising several sectors with different pitches capable of keeping intervals between the rings during rotation of the lead screw.
3. A microwave tube (3) according to claim 1, characterised in that the mechanical means for displacing the rings comprises a set of electrical contacts (2) between the rings, one set of pins (7), each pin being firmly connected to a ring, the tube (3) being provided with at least one longitudinal slit (9) through which pins (7) can pass in the wall of the tube, a ring (8) external to the tube comprising a set of slits (10), each slit (10) in the outer ring (8) allowing the passage of a pin (7), the slits in the set of slits having a different inclination for each ring so as to maintain a periodicity for the different rings during displacement of the rings.
4. A microwave tube according to claim 1, characterised in that it is a PWT, a BWO type tube, a klystron, a magnetron, a carcinotron, or a maser.
5. A microwave tube according to claim 1, characterised in that the periodic structure of the microwave is made of corrugated plate.
6. A microwave tube according to claim 1, characterised in that it comprises an insert with an adjustable length.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A switching circuit for a ballast, comprising:
a resonant circuit, formed by a capacitor and a transformer connected in series to operate a lamp, wherein said transformer has a first winding connected in series with said lamp, and a second winding and a third winding of said transformer respectively generate a first control signal and a second control signal in response to a switching current of said resonant circuit;
a first switch, coupled to said resonant circuit to supply a first voltage to said resonant circuit, wherein said first switch is controlled by a first switching signal;
a second switch, coupled to said resonant circuit to supply a second voltage to said resonant circuit, wherein said second switch is controlled by a second switching signal;
a first control circuit, coupled to generate said first switching signal in response to said first control signal; and
a second control circuit, coupled to generate said second switching signal in response to said second control signal.
2. The switching circuit as claimed in claim 1, wherein said first switching signal is enabled once said first control signal is higher than a first threshold, and after a quarter resonant period of said resonant circuit, said first switching signal is disabled once said first control signal is lower than a second threshold.
3. The switching circuit as claimed in claim 1, wherein said second switching signal is enabled once said second control signal is higher than a first threshold, and after a quarter resonant period of said resonant circuit, said second switching signal is disabled once said second control signal is lower than a second threshold.
4. The switching circuit as claimed in claim 1, wherein said first control circuit comprises:
a first input resistor and a second input resistor, coupled to said transformer;
a first current source and a second current source, coupled to said first input resistor and said second input resistor respectively;
a third current source, coupled to said second input resistor via a control switch;
a first comparator, having an input coupled to said first input resistor, another input of said first comparator being connected to said first input resistor via a delay circuit, and an output of said first comparator being coupled to turn onoff said control switch; and
a second comparator, having an input coupled to said first input resistor, another input of said second comparator being connected said second input resistor, wherein said first switching signal is enabled in response to an output of said second comparator.
5. The switching circuit as claimed in claim 4, wherein said first control circuit further comprises a debounce circuit coupled to generate said first switching signal.
6. The switching circuit as claimed in claim 1, wherein said second control circuit comprises:
a first input resistor and a second input resistor, coupled to said transformer;
a first current source and a second current source, coupled to said first input resistor and said second input resistor respectively;
a third current source, coupled to said second input resistor via a control switch;
a first comparator, having an input coupled to said first input resistor, another input of said first comparator being connected to said first input resistor via a delay circuit, and an output of said first comparator being coupled to turn onoff said control switch; and
a second comparator, having an input coupled to said first input resistor, another input of said second comparator being connected to said second input resistor, wherein said second switching signal is enabled in response to an output of said second comparator.
7. The switching circuit as claimed in claim 6, wherein said second control circuit further comprises a debounce circuit coupled to generate said second switching signal.
8. A ballast circuit, comprising:
a resonant circuit, having a transformer connected in series with a lamp to operate said lamp, wherein said transformer has a first winding connected in series with said lamp, and a second winding and a third winding of said transformer generate a first control signal and a second control signal respectively in response to a switching current of said resonant circuit;
a first switch, coupled to said resonant circuit to supply a first voltage to said resonant circuit, wherein said first switch is controlled by a first switching signal;
a second switch, coupled to said resonant circuit to supply a second voltage to said resonant circuit, wherein said second switch is controlled by a second switching signal;
a first control circuit, coupled to generate said first switching signal in response to said first control signal; and
a second control circuit, coupled to generate said second switching signal in response to said second control signal.
9. The ballast circuit as claimed in claim 8, wherein said first switching signal is enabled once said first control signal is higher than a first threshold, and after a quarter resonant period of said resonant circuit, said first switching signal is disabled once said first control signal is lower than a second threshold; said second switching signal being enabled once said second control signal being higher than said first threshold, and after the quarter resonant period of said resonant circuit, said second switching signal being disabled once said second control signal being lower than a second threshold.
10. The ballast circuit as claimed in claim 8, wherein said first control circuit comprises:
a first input resistor and a second input resistor, coupled to said transformer;
a first current source and a second current source, coupled to said first input resistor and said second input resistor, respectively;
a third current source, coupled to said second input resistor via a control switch;
a first comparator, having an input coupled to said first input resistor, and another input of said first comparator being connected to said first input resistor via a delay circuit, wherein an output of said first comparator is coupled to turn onoff said control switch; and
a second comparator, having an input coupled to said first input resistor, and another input of said second comparator being connected to said second input resistor, wherein said first switching signal is enabled in response to an output of said second comparator.
11. The ballast circuit as claimed in claim 10, wherein said first control circuit further comprises a debounce circuit coupled to generate said first switching signal.
12. The ballast circuit as claimed in claim 8, wherein said second control circuit comprises:
a first input resistor and a second input resistor, coupled to said transformer;
a first current source and a second current source, coupled to said first input resistor and said second input resistor, respectively;
a third current source, coupled to said second input resistor via a control switch;
a first comparator, having an input coupled to said first input resistor, and another input of said first comparator being connected to said first input resistor via a delay circuit, wherein an output of said first comparator is coupled to turn onoff said control switch; and
a second comparator, having an input coupled to said first input resistor, and another input of said second comparator being connected to said second input resistor, wherein said second switching signal is enabled in response to an output of said second comparator.
13. The ballast circuit as claimed in claim 12, wherein said first control circuit further comprises a debounce circuit coupled to generate said second switching signal.