Patent ID: 8330381

Claim:
An illumination device including LEDs for connection to an existing fluorescent lamp fixture including a conventional ballast, the ballast configured to provide a current signal, the illumination device comprising: protection circuitry configured to protect the illumination device from the ballast current signal; a full-wave rectifier electrically coupled to the circuit protection means and configured to produce a rectified voltage output; a smoothing filter electrically coupled to the full wave rectifier and configured to produce a smoothed rectified voltage output; and a current regulator power circuit electrically coupled to the smoothing filter and the LEDS, the current regulator power circuit including: a first switching element configured to operate in response to a first pulse width modulated (PWM) ON/OFF control signal, the first switching element delivering current to the LEDs in response to the ON control signal and the first switching element not delivering current to the LEDs in response to the OFF control signal; a current controller electrically coupled to a gate of the first switching element, the current controller configured to generate the first PWM control signal; a current sense resistor electrically coupled to the first switching element and configured to sense the current through the LEDS, wherein the sensed current is fed back to the current controller; a load resistor; and a shunt voltage regulator circuit electrically coupled to the current regulator power circuit and the load resistor and configured to dissipate power through the load resistor when the rectified output voltage is greater than a maximum voltage.