Electronic circuit for dc conversion of fluorescent lighting ballast

Abstract

Embodiments of an illumination device including LEDs for connection to an existing fluorescent lamp fixture including a conventional ballast described. One illumination device includes protection circuitry configured to protect the illumination device from the ballast current signal, a full-wave rectifier, a smoothing filter electrically coupled to the full wave rectifier, and a current regulator power circuit electrically coupled to the smoothing filter and the LEDS. The current regulator power circuit can include a first switching element configured to operate in response to a first (PWM) ON/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; and 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.

What is claimed is: 
     
         1 . 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 protection circuitry 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; and 
 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. 
   
     
     
         2 . The illumination device of  claim 1 , wherein the protection circuitry comprises:
 an inrush protection circuit configured to limit inrush current from the ballast.   
     
     
         3 . The illumination device of  claim 1 , wherein the protection circuitry comprises:
 a surge suppressor configured to suppress ballast voltage from the ballast.   
     
     
         4 . The illumination device of  claim 1 , wherein the smoothing filter comprises:
 at least one capacitor;   at least one discharge resistor electrically coupled in parallel to the at least one capacitor.   
     
     
         5 . The illumination device of  claim 1 , wherein the current regulator power circuit further comprises:
 at least one inductor in series with the LEDs.   
     
     
         6 . The illumination device of  claim 5 , wherein the current regulator power circuit further comprises:
 a recirculation diode electrically coupled in parallel with the at least one inductor and the LEDs.   
     
     
         7 . A method of supplying power to an illumination device including LEDs and connected to an existing fluorescent lamp fixture including a conventional ballast, the method comprising:
 receiving a current signal from the conventional ballast;   protecting the illumination device from the received current signal;   rectifying the received current signal to produce a rectified voltage output;   sensing current through the LEDs;   generating a pulse width modulated (PWM) control signal from a current control circuit based on the sensed current; and   supplying current to the LEDs in response to the PWM control signal so that the LED current reaches an average LED current.   
     
     
         8 . The method of  claim 7 , wherein the average LED current is determined based on the rectified voltage output and an output voltage of the LEDs. 
     
     
         9 . The method of  claim 7 , wherein the PWM control signal is supplied to a switching element. 
     
     
         10 . The method of  claim 7 , wherein protecting the illumination device further comprises:
 limiting the current received from the conventional ballast.   
     
     
         11 . The method of  claim 7 , wherein protecting the illumination device further comprises:
 suppressing ballast voltage from the conventional ballast.   
     
     
         12 . The method of  claim 7 , further comprising:
 filtering the rectified current signal.   
     
     
         13 . An illumination device including LEDs for connection to an existing fluorescent lamp fixture including a conventional ballast, the illumination device comprising:
 means for receiving a current signal from the conventional ballast;   means for protecting the illumination device from the received current signal;   means for rectifying the received current signal to produce a rectified voltage output;   means for sensing the current through the LEDs;   means for generating a pulse width modulated (PWM) control signal from a current control circuit based on the sensed current;   means for supplying current to the LEDs in response to the PWM control signal so that the LED current reaches an average LED current.   
     
     
         14 . The illumination device of  claim 13 , further comprising:
 means for filtering the rectified current signal.   
     
     
         15 . The illumination device of  claim 13 , wherein the means for protecting the illumination device comprises:
 an inrush protection circuit configured to limit inrush current from the ballast.   
     
     
         16 . The illumination device of  claim 13 , wherein the means for protecting the illumination device comprises:
 a surge suppressor configured to suppress ballast voltage from the ballast.