LED lamp head with variable brightness

A dimming circuit configured to be electrically coupled solely to a power-supply element, a return element and at least one LED configured to emit light, a power voltage carried by the power-supply element being regulated by a control element, the circuit comprising:

• a first element coupled to the power-supply and return elements, the first element configured to generate a first reference voltage;
• a second element coupled to the first element, the power-supply element and the return element, the second element configured to determine a difference between the first reference voltage and the power voltage and generate a first signal based on the determined difference;
• a third element coupled to the second element, the third element configured to generate a second reference voltage based on the first signal;
• and
• a fourth element coupled to the third element, the fourth element configured to maintain a constant level of current flow through the at least one LED, the constant level of current flow being a function of the second reference voltage, wherein the brightness of the light emitted by the at least one LED is adjusted solely in response to adjustments made to the power voltage by the control element.

A lamp head configured to be electrically coupled solely to a power-supply element and a return element, a power voltage carried by the power-supply element being regulated by a control element, the lamp head comprising:

• at least one LED configured to emit light;
• and
• a first circuit coupled to the at least one LED and configured to adjust the brightness of the light emitted by the at least one LED solely in response to adjustments made to the power voltage by the control element, wherein the first circuit comprises:
• a second circuit coupled to the power-supply and return elements, the second circuit configured to generate a first reference voltage;
• and
• a third circuit coupled to the second circuit, the power-supply element and the return element, the third circuit configured to determine a difference between the first reference voltage and the power voltage and generate a first signal based on the determined difference,
• wherein the third circuit comprises first and second operational amplifiers,
• wherein if the first reference voltage is less than the power voltage, then the first signal causes the at least one LED to emit light at a first brightness level, and if the first reference voltage is greater than the power voltage, then the first signal causes the at least one LED to emit light at a second brightness level lower than the first brightness level.