1. A LED light source comprising:
a first input terminal and a second input terminal for connection to a supply voltage source supplying a low frequency AC supply voltage with frequency f,
a rectifier coupled to the input terminals for rectifying the low frequency AC supply voltage,
a series arrangement comprising N LED loads, a first and second end of said series arrangement being coupled to a first output terminal and a second output terminal of the rectifier,
control circuitry for subsequently and sequentially making the LED loads conduct a current, one by one, in dependency of the instantaneous value of the low frequency AC supply voltage when the instantaneous value increases and for subsequently making the LED loads stop conducting a current, one by one, in dependency of the instantaneous value of the low frequency AC supply voltage when the instantaneous value decreases,
wherein the control circuitry comprises
N control strings, each control string comprising a controllable current regulator and each controllable current regulator being between the cathode of a LED load and the second output terminal of the rectifier,
current sensing circuitry for sensing the current in the last N\u22121 control strings and for decreasing the current in the first n control strings when the (n+1)th control string is conducting current, wherein 1\u2266n\u2266N\u22121
N\u22121 voltage sensing circuits, coupled between the cathode of the (n+1)th LED load and the controllable current regulator comprised in the nth control string, for making the nth control string non-conductive when the voltage across the (n+1)th control string is higher than a reference value, wherein 1\u2266n\u2266N\u22121,
a global current control circuit coupled to the controllable current regulators for controlling the instantaneous value of the current through the control strings, wherein
each controllable current regulators comprises a series arrangement of a transistor and at least one impedance
each controllable current regulator comprises an impedance that is not comprised in any of the other controllable current regulators; and
the global current control circuit and the voltage sensing circuits are coupled to the control electrodes of the transistors comprised in the controllable current regulators.
2. A LED light source as claimed in claim 1, wherein the impedances in the control strings are comprised in a conductive path coupled between the transistor comprised in the first control string and the second output terminal of the rectifier.
3. The LED light source as claimed in claim 1, wherein the voltage sensing circuits each contain a further transistor.
4. The LED light source as claimed in claim 3, wherein the current sensing circuitry comprises N\u22121 current sensing circuits, the nth current sensing circuit being coupled to a common terminal of the transistor and the impedance comprised in the (n+1)th control string and coupled to control electrodes of the transistors in the first n control strings, and wherein 1\u2266n\u2266N\u22121.
5. The LED light source as claimed in claim 4, wherein the further transistors comprised in the voltage sensing circuits form also part of the N\u22121 current sensing circuits.
6. The LED light source as claimed in claim 1, wherein the global current control circuit comprises a modulator for modulating the current through the LED loads with a frequency 2 f such that the instantaneous value of the current is decreased when the instantaneous value of the rectified low frequency AC supply voltage increases and the instantaneous value of the current is increased when the instantaneous value of the rectified low frequency AC supply voltage decreases.
7. The LED light source as claimed in claim 1, wherein the LED light source is dimmable by adjusting the voltage at the control electrodes of the transistors in the controllable current regulators via the global current control circuit.
8. The LED light source as claimed in claim 7, wherein the LED light source comprises a series arrangement of a switch and a capacitor coupled between the output terminals of the rectifier and control circuitry for rendering the switch conductive in case the instantaneous value of the low frequency AC supply voltage drops below a reference value.
9. The LED light source as claimed in claim 7, wherein the LED light source is suitable for operation with a phase cut dimmer, wherein the global current control circuit comprises circuitry for adjusting the voltage at the control electrodes of the transistors in the controllable current regulators in dependency of the adjusted phase angle of the phase cut dimmer.
10. A method of supplying a LED light source, the method comprising the steps of:
providing a supply voltage source supplying a low frequency AC supply voltage with frequency f,
rectifying the low frequency AC supply voltage,
supplying the rectified AC supply voltage to a series arrangement of N LED loads,
subsequently making the LED loads conduct a current, one by one, in dependency of the instantaneous value of the lo frequency AC supply voltage when the instantaneous value increases and subsequently making the LED loads stop conducting a current, one by one, in dependency of the instantaneous value of the low frequency AC supply voltage when the instantaneous value decreases, by
providing N control strings, each control string comprising a controllable current regulator and coupling each controllable current regulator between the cathode of a LED load and the second output terminal of the rectifier,
sensing the voltages across the control strings, and rendering the transistor in the nth control string non-conductive when the voltage across the (n+1)th control string is higher than a reference value, wherein 1\u2266n\u2266N\u22121
sensing the current in the last N\u22121 control strings and decreasing the current in the first n control strings when the (n+1)th control string is conducting current, wherein 1\u2266n\u2266N\u22121
controlling the instantaneous value of the current through the control strings by controlling the voltages at the control electrodes of the transistors comprised in the control strings.
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 system for detecting an object in three-dimensional space comprising:
four emitters defining a rectangular detection area, the emitters being disposed around the four vertices of the rectangular detection area respectively;
two receivers being disposed at the midpoints of two edges of the rectangular detection area respectively;
an electronic controller being connected with the emitters and the receivers and configured to control the emitters to radiate light in predetermined wavelengths, to control the receivers to capture light in the predetermined wavelengths reflected by the object and thereby output a plurality of signals, and to convert the signals into coordinates of the object; and
a host system, wherein:
the electronic controller is configured to communicate with and transmit the coordinates of the object to the host system;
the emitters are light-emitting-diodes being configured to emit light in near-infrared wavelengths, the receivers are photodiodes, the electronic controller comprises analog-to-digital converters, digital logic circuits, random access memory, and non-volatile memory, and the host system comprises a display device;
the electronic controller is configured to initialize a set of system factors to be used for subsequent calculations, to convert the signals output by the receivers into digital signals, to perform calculations based on the digital signals to determine virtual coordinates of the object in 3D space, to further process the X and Y virtual coordinate values based on the resultant Z coordinate value so that the X and Y coordinate values correspond to pixel points on the host system’s display device, and to output the final X, Y, and Z coordinate values to the host system; and
the set of system factors comprises orientation information of the host system’s display device, factors to be used to set overall boundaries of the rectangular detection area, scaling factors for scaling up X and Y boundaries of the rectangular detection area, and virtual boundaries of the rectangular detection area.
2. The system of claim 1, wherein each edge of the rectangular detection area that has a receiver disposed thereon is longer than the distance between the centers of emitters disposed at the two ends of the edge, while each edge of the rectangular detection area that has no receiver disposed thereon is shorter than the distance between the centers of emitters disposed at the two ends of the edge.
3. The system of claim 1, wherein the electronic controller is configured to control one emitter to radiate light at a time.
4. The system of claim 1, wherein the rectangular detection area is set equivalent to the size of the display device of the host system.
5. The system of claim 1, wherein the signals output by the receivers are analog signals and the electronics controller is configured to filter and amplify the analog signals and then convert the analog signals to digital signals with an analog-to-digital converter.
6. The system of claim 5, wherein to calculate the virtual coordinates, the electronic controller is configured to compare the digital signals and find the maximum values at the four edges of the rectangular detection area.
7. The system of claim 5, wherein the electronic controller is configured to adjust the depth of a first-in-first-out memory buffer so as to calculate the Z coordinate of the object in 3D space.
8. The system of claim 5, wherein the electronic controller is configured to scale up the X and Y virtual coordinates by the virtual boundaries so that an effective sensing region larger than the rectangular detection area is defined.
9. The system of claim 5, wherein to further process the X and Y virtual coordinate values, the electronic controller is configured to move the origin of the X and Y coordinates to a corner of the effective sensing region.
10. The system of claim 5, wherein to further process the X and Y virtual coordinate values, the electronic controller is configured to crop the effective sensing region so that the cropped effective sensing region is equal to a region defined by the virtual boundaries.
11. The system of claim 5, wherein to further process the X and Y virtual coordinate values, the electronic controller is configured to scale down the X and Y virtual coordinate values.
12. The system of claim 1, wherein the electronic controller is configured to resemble the button-clicking action of a computer mouse based on the Z coordinate value of the object and two thresholds defined in the range of the Z coordinate value.
13. A method for detecting an object in three-dimensional space comprising:
defining a rectangular detection area with four emitters, the emitters being disposed around the four vertices of the rectangular detection area respectively;
disposing two receivers at the midpoints of two edges of the rectangular detection area respectively;
controlling the emitters to radiate light in predetermined wavelengths;
controlling the receivers to capture light in the predetermined wavelengths reflected by the object and thereby output a plurality of signals;
converting the signals into coordinates of the object; and
communicating with and transmitting the coordinates of the object to a host system, the host system comprising a display device;
wherein the step of converting the signals into coordinates of the object comprises:
initializing a set of system factors to be used for subsequent calculations, the set of system factors comprising orientation information of the display device, factors to be used to set overall boundaries of the rectangular detection area, scaling factors for scaling up X and Y boundaries of the rectangular detection area, and virtual boundaries of the rectangular detection area;
converting the signals output by the receivers into digital signals;
performing calculations based on the digital signals to determine virtual coordinates of the object in 3D space;
further processing the X and Y virtual coordinate values based on the resultant Z coordinate value so that the X and Y coordinate values correspond to pixel points on the display device; and
outputting the final X, Y, and Z coordinate values to the host system.
14. A system for detecting an object in three-dimensional space comprising:
four emitters defining a rectangular detection area, the emitters being disposed around the four vertices of the rectangular detection area respectively;
two receivers being disposed at the midpoints of two edges of the rectangular detection area respectively;
an electronic controller being connected with the emitters and the receivers and configured to control the emitters to radiate light in predetermined wavelengths, to control the receivers to capture light in the predetermined wavelengths reflected by the object and thereby output a plurality of signals, and to convert the signals into coordinates of the object; and
a host system, which comprises a display device; wherein:
each edge of the rectangular detection area that has a receiver disposed thereon is longer than the distance between the centers of emitters disposed at the two ends of the edge, while each edge of the rectangular detection area that has no receiver disposed thereon is shorter than the distance between the centers of emitters disposed at the two ends of the edge;
the electronic controller is configured to control one emitter to radiate light at a time;
the electronic controller is configured to initialize a set of system factors to be used for subsequent calculations, to convert the signals output by the receivers into digital signals, to perform calculations based on the digital signals to determine virtual coordinates of the object in 3D space, to further process the X and Y virtual coordinate values based on the resultant Z coordinate value so that the X and Y coordinate values correspond to pixel points on the display device, and to output the final X, Y, and Z coordinate values to the host system; and
the set of system factors comprises orientation information of the display device, factors to be used to set overall boundaries of the rectangular detection area, scaling factors for scaling up X and Y boundaries of the rectangular detection area, and virtual boundaries of the rectangular detection area.
15. The system of claim 14, wherein the electronic controller is configured to resemble the button-clicking action of a computer mouse based on the Z coordinate value of the object and two thresholds defined in the range of the Z coordinate value.