Method and apparatus for scaling the average current supply to light-emitting elements
View Patent ↗The present invention provides a method and apparatus for scaling the average drive current supplied to a light-emitting element or string thereof by coupling a scaling signal to an original control signal thereby generating an effective control signal for control of the light-emitting element(s). The scaling signal can be a modulated signal, for example a Pulse Width Modulation (PWM) signal, Pulse Code Modulation (PCM) signal, or other signal and modifies the original control signal to produce an effective control signal. The effective control signal is subsequently used to control the supply of power to the light-emitting element(s) from a power source via a switching device. The effective control signal essentially modifies the ON time of the light-emitting element(s), thereby modifying the average drive current passing through the light-emitting element(s). The scaling signal is coupled to the original control signal by a coupling mechanism, thereby enabling the modification of the original control signal by the scaling signal forming the effective control signal.
1. A light-emitting element driving apparatus for driving two or more strings of one or more light-emitting elements, said apparatus comprising:
a) one or more control signal generators for generating two or more original control signals;
b) one or more scaling signal generators for generating one or more scaling signals;
c) one or more coupling means, a particular coupling means receiving one of the original control signals and a particular scaling signal, each coupling means generating an effective control signal for control of a particular string by coupling the received scaling signal to the received original control signal; and
d) switching means associated with each string, the switching means adapted for connection to a power source, and each switching means responsive to a particular control signal for controlling power supplied to a particular string, wherein the particular control signal is either one of the two or more original control signals or the effective control signal generated by one of the one or more coupling means;
thereby driving said two or more strings of one or more light-emitting elements.
2. The light-emitting element driving apparatus according to claim 1 , wherein one or more coupling means is an AND logic gate or an inverted NAND logic gate.
3. The light-emitting element driving apparatus according to claim 1 , wherein one or more coupling means is a control switch operatively responsive to the scaling signal, the control switch controlling transmission of the original control signal to one of the one or more stings.
4. The light-emitting element driving apparatus according to claim 1 , wherein one or more scaling signal generators is a free running square wave oscillator.
5. The light-emitting element driving apparatus according to claim 1 , wherein one or more scaling signal generators is a timer circuit.
6. The light-emitting element driving apparatus according to claim 5 , wherein the timer circuit generates one or more scaling signals having a fixed duty cycle.
7. The light-emitting element driving apparatus according to claim 5 , wherein the timer circuit generates one or more scaling signals having an adjustable duty cycle.
8. The light-emitting element driving apparatus according to claim 1 , wherein one or more scaling signal generators is an operational amplifier circuit configured with an AND result.
9. The light-emitting element driving apparatus according to claim 1 , wherein one or more scaling signal generators is a Field Programmable Gate Array with a microcontroller core.
10. The light-emitting element driving apparatus according to claim 1 , wherein the one or more scaling signal generators autonomously generate one or more scaling signals.
11. The light-emitting element driving apparatus according to claim 1 , wherein the one or more scaling signal generators generate one or more scaling signals in response to one or more input signals received thereby.
12. The light-emitting element driving apparatus according to claim 1 , wherein one of the one or more scaling signal generators generates scaling signals for two or more strings.
13. The light-emitting element driving apparatus according to claim 1 , wherein each of the one or more scaling signals is a pulsed digital signal selected from the group comprising pulse width modulation signal, pulse code modulation signal and frequency modulation signal.
14. The light-emitting element driving apparatus according to claim 1 , wherein each of the one or more original control signals is a signal selected from the group comprising pulse width modulation signal, pulse code modulation signal, frequency modulated signal, constant signal, linearly increasing signal, linearly decreasing signal, non-linear increasing signal and non-linear decreasing signal.
15. The light-emitting element driving apparatus according to claim 1 , wherein the switching means is a transistor switch.
16. The light-emitting element driving apparatus according to claim 15 , wherein the transistor switch is selected from the group comprising a FET switch, BJT switch and relay.
17. The light-emitting element driving apparatus according to claim 1 , wherein the scaling signal has a first frequency and a respective original control signal has a second frequency, wherein the first frequency is greater than the second frequency.
18. The light-emitting element driving apparatus according to claim 1 , wherein the one or more scaling signals and the one or more original control signals are generated by a microprocessor.
19. A method for driving two or more strings of one or more light-emitting elements, said method comprising the steps of:
a) generating two or more original control signals;
b) generating one or more scaling signals;
c) independently coupling each scaling signal with one of the two or more original control signals, thereby generating one or more effective control signals;
d) transmitting a particular control signal to each string of one or more light-emitting elements for controlling power supplied to each string, wherein the particular control signal is either one of the two or more original control signals or one of the one or more effective control signals;
thereby driving said two or more strings of one or more light-emitting elements.