Generating a voltage feedback signal in non-isolated led drivers

A light-emitting diode (LED) lamp, comprising:

• one or more LEDs;
• a transformer comprising a primary winding, the primary winding coupled to an input voltage source and the one or more LEDs;
• a switch coupled to the primary winding, current in the primary winding being generated responsive to the switch being turned on and not generated responsive to the switch being turned off;
• a first current detector coupled between the input voltage source and a ground node of the LED lamp, the first current detector detecting a current that is proportional to a bulk voltage across the input voltage source;
• a second current detector coupled between the primary winding and the ground node, the second current detector detecting a current that is proportional to a drain voltage across the switch;
• a current-to-voltage converter configured to:
• convert a difference between the current detected by the first current detector and the current detected by the second current detector to a voltage signal using a resistance of the first current detector and a resistance of the second current detector, and
• generate a feedback signal proportional to a regulated output voltage from the LED lamp based on the voltage signal;
• and
• a switch controller receiving the feedback signal and controlling switching of the switch based on the feedback signal to regulate an output current through the one or more LEDs.

A method for driving an LED lamp comprising one or more LEDs, an inductor coupled to an input voltage source and the one or more LEDs, a switch coupled to the inductor, a first current detector coupled between the input voltage source and a ground node of the LED lamp, and a second current detector coupled between the inductor and the ground node, wherein current in the inductor is generated responsive to the switch being turned on and not being generated responsive to the switch being turned off, current detected by the first current detector is proportional to a bulk voltage across the input voltage source, and current detected by the second current detector is proportional to a drain voltage across the switch, the method comprising:

• receiving the current detected by the first current detector and the current detected by the second current detector;
• converting a difference between the current detected by the first current detector and the current detected by the second current detector to a voltage signal using a resistance of the first current detector and a resistance of the second current detector;
• generating a feedback signal proportional to a regulated output voltage from the LED lamp based on the voltage signal;
• and
• controlling switching of the switch based on the feedback signal to regulate an output current through the one or more LEDs.