LED lamp with half wave dimming

1. An LED lamp assembly, the assembly comprising:

a power supply configured to receive an input power signal and provide a DC lamp current;

a dimming controller coupled to the power supply and configured to adjust the DC lamp current; and

an LED lamp coupled to the DC lamp current,

wherein the dimming controller is configured to determine if full brightness or dimmed brightness is required based at least in part on the input power signal, and to maintain the DC lamp current at a first amount when full brightness is required and to maintain the DC lamp current at a second amount when dimmed brightness is required by:

determining whether the input power signal contains a half-wave signal;

measuring a zero-level duration of the input power signal; and

maintaining the LED lamp current at the first amount when the zero-level duration is not greater than a predetermined threshold time or the input power signal does not contain a half-wave signal; or

maintaining the LED lamp current at the second amount when the zero-level duration is greater than the predetermined threshold time and the input power signal contains a half-wave signal.

2. The LED lamp assembly according to claim 1 , comprising an inrush limiter coupled between the input power signal and the power supply, wherein the inrush limiter is configured to prevent an inrush current from exceeding a predetermined amount.

3. The LED lamp assembly according to claim 2 , wherein the inrush limiter is further configured to filter and clean the input power signal.

4. The LED lamp assembly according to claim 1 , wherein the LED lamp comprises one or more LED elements.

5. The LED lamp assembly according to claim 1 , wherein the LED lamp assembly is configured to be physically and electrically compatible with current incandescent signal lamps.

6. The LED lamp assembly according to claim 1 , wherein determining whether the input power signal contains a half-wave signal comprises:

generating a series of zero level-triggers from the input power signal;

measuring a period between each pair of zero-level trigger in the series of zero-level triggers; and

determining that the input power signal contains a half-wave signal when the period is greater than a threshold time.

7. The LED lamp assembly according to claim 1 , wherein the dimming controller comprises an analog-to-digital converter, a processor and a memory, and is further configured to:

provide a digitized power signal from the input power signal by sampling the input power signal with an analog-to-digital converter;

measure a zero-level duration of the digitized power signal;

maintain the LED lamp current at the first amount if the zero-level duration is not greater than a predetermined threshold time or the input power signal does not contain a half-wave signal; and

maintain the LED lamp current at the second amount if the zero-level duration is greater than the predetermined threshold time and the input power signal contains a half-wave signal.

8. The LED lamp assembly according to claim 7 , wherein determining whether the input power signal contains a half-wave signal comprises:

generating a series of zero level-triggers from the digitized power signal;

measuring a period between each pair of zero-level triggers in the series of zero-level triggers; and

determining that the input power signal contains a half-wave signal when the period is greater than a threshold time.

9. A method of controlling the brightness of an LED lamp, the method comprising:

sampling an input power signal;

determining whether the input power signal contains a half-wave signal;

measuring a zero-level duration of the input power signal;

comparing the zero-level duration to a predetermined threshold duration value; and

maintaining the LED lamp at a full brightness if the zero-level duration is not greater than the threshold duration time or the input power signal does not contain a half-wave signal.

10. The method according to claim 9 , further comprising maintaining the LED lamp at a dimmed brightness if the zero level duration is greater than the threshold duration time and the input power signal contains a half-wave signal.

11. The method according to claim 10 , wherein determining whether the input signal contains a half-wave signal comprises:

generating a series of zero level-triggers from the input power signal;

measuring a period between each pair of zero-level triggers in the series of zero-level triggers; and

determining that the input power signal contains a half-wave signal when the period is greater than a threshold time.

12. The method according to claim 10 , wherein the input power signal is a digital signal and sampling an input power signal comprises:

receiving an analog power signal;

converting the analog power signal to a digital input power signal using an analog-to-digital converter; and

sampling the digital input power signal to create the input power signal.

13. A method of retrofitting traffic control signals that contain incandescent signal lamps with dimmable energy saving LED signal lamps, the method comprising:

providing a dimmable LED lamp assembly wherein the dimmable LED lamp assembly is configured to produce a full brightness when a full-wave power signal is applied and to produce a dimmed brightness when a half-wave rectified power signal is applied;

packaging the dimmable LED lamp assembly such that it is physically and electrically compatible with the incandescent signal lamps; and

replacing each incandescent signal lamp with the packaged dimmable LED lamp assembly.

14. The method of claim 13 , wherein the dimmable LED lamp assembly comprises:

a power supply configured to receive an input power signal and provide a DC lamp current;

a dimming controller coupled to the power supply and configured to adjust the DC lamp current; and

an LED lamp coupled to the DC lamp current,

wherein the dimming controller is configured to determine if full brightness or dimmed brightness is required based at least in part on the input power signal, and to maintain the DC lamp current at a first amount when full brightness is required and to maintain the DC lamp current at a second amount when dimmed brightness is required.