Lighting apparatus with inductor current limiting for noise reduction

1. A lighting apparatus comprising:

a lighting circuit; and

a driver circuit having an output coupled to the lighting circuit and an input configured to be coupled to a power source that provides a varying voltage waveform, the driver circuit comprising an electromagnetic interference (EMI) filter inductor configured to be coupled in series with the power source and a bypass circuit configured to conduct a bypass current to thereby divert current from the EMI filter inductor for a first state of a voltage across the EMI filter inductor to limit a current in the EMI filter inductor and to terminate conduction of the bypass current for a second state of the voltage across the EMI filter inductor.

2. The lighting apparatus of claim 1 , wherein the bypass circuit is configured to divert current responsive to an edge of the varying voltage waveform.

3. The lighting apparatus of claim 1 , wherein the edge comprises a leading edge of a phase cut AC waveform.

4. The lighting apparatus 3 , wherein the bypass circuit is configured to limit a magnitude of the voltage across the EMI filter inductor to a value less than a saturation threshold of the EMI inductor and greater than a maximum magnitude of the voltage across the EMI filter inductor when the power source is applying a non-phase cut AC waveform to the input of the driver circuit.

5. The lighting apparatus of claim 1 , wherein the bypass circuit is configured to limit the current in the EMI filter inductor responsive to the voltage across the EMI filter inductor.

6. The lighting apparatus of claim 1 , wherein the bypass circuit comprises a diode.

7. The lighting apparatus of claim 1 , wherein the bypass circuit is coupled in parallel with the EMI filter inductor.

8. The lighting apparatus of claim 7 , wherein the bypass circuit comprises a TVS coupled in parallel with the EMI filter inductor.

9. The lighting apparatus of claim 1 , wherein the lighting circuit comprises an LED lighting circuit.

10. The lighting apparatus of claim 1 , wherein the power source comprises a phase cut dimmer.

11. A lighting apparatus comprising:

a lighting circuit; and

a driver circuit having an output coupled to the lighting circuit and an input configured to be coupled to a power source that provides a varying voltage waveform, the driver circuit comprising an electromagnetic interference (EMI) filter inductor configured to be coupled in series with the power source and a bypass circuit configured to divert current from the EMI filter inductor to limit a current in the EMI filter inductor, wherein the bypass circuit comprises a transient voltage suppressor (TVS) coupled in parallel with the EMI filter inductor.

12. The lighting apparatus of claim 11 , wherein the TVS is configured to clamp a magnitude of a voltage across the EMI filter inductor to a value less than a saturation threshold of the EMI filter inductor.

13. A lighting apparatus comprising:

a lighting circuit; and

a driver circuit having an output coupled to the lighting circuit and an input configured to be coupled to a power source that provides a varying voltage waveform, the driver circuit comprising an electromagnetic interference (EMI) filter inductor configured to be coupled in series with the power source and a bypass circuit configured to divert current from the EMI filter inductor to limit a current in the EMI filter inductor, wherein the bypass circuit comprises a series combination of a TVS and a resistor coupled in parallel with the EMI filter inductor.

14. A lighting apparatus comprising:

a lighting circuit; and

a driver circuit having an output coupled to the lighting circuit and an input configured to be coupled to a dimmer, the driver circuit comprising an inductor coupled to the input and an inductor current limiter circuit configured to initiate a diversion of current from the EMI filter inductor and thereby limit a current in the inductor responsive to a leading edge of a phase cut voltage applied to the input.

15. The lighting apparatus of claim 14 , wherein the inductor current limiter circuit comprises a bypass circuit configured to divert current from the inductor responsive to the leading edge.

16. The lighting apparatus of claim 15 , wherein the bypass circuit is configured to limit the current through the inductor responsive to a voltage across the inductor.

17. The lighting apparatus of claim 15 , wherein the bypass circuit is coupled across the inductor.

18. The lighting apparatus of claim 15 , wherein the bypass circuit comprises a transient voltage suppressor (TVS) coupled in parallel with the inductor.

19. The lighting apparatus of claim 15 , wherein the bypass circuit comprises a series combination of a TVS and a resistor coupled in parallel with the inductor.

20. The lighting circuit of claim 14 , wherein the inductor comprises an EMI filter inductor.

21. The lighting apparatus of claim 14 , wherein the inductor current limiter circuit is configured to terminate the diversion of current within a cycle of the phase cut voltage following the leading edge.

22. A driver circuit for a lighting apparatus, the driver circuit comprising:

an inductor configured to be coupled to an AC power source;

a capacitor coupled to the power source via the inductor; and

a bypass circuit configured to divert current away from the inductor responsive to an edge of a phase cut voltage produced by the AC power source.

23. The driver circuit of claim 22 , wherein the bypass circuit is coupled across the inductor.

24. The driver circuit of claim 23 , wherein the bypass circuit comprises at least one diode coupled across the inductor.

25. The driver circuit of claim 24 , wherein the at least one diode comprises a TVS.

26. The driver circuit of claim 24 , wherein the bypass circuit comprises a series combination of a TVS and a resistor.

27. The driver circuit of claim 22 , wherein the inductor comprises an EMI filter inductor.

28. The driver circuit of claim 27 , wherein the bypass circuit is configured to limit a magnitude of a voltage across the EMI filter inductor to a value less than a saturation threshold of the EMI inductor and greater than a maximum magnitude of the voltage across the EMI filter inductor when the AC power source produces a non-phase cut AC voltage.

29. The driver circuit of claim 22 , wherein the edge comprises a leading edge.