Damping resonance in a converter including a coupling capacitor

1. A converter circuit, comprising:

an input filter including an input capacitor and having an associated filter inductance;

a second capacitor;

a damping circuit coupled in parallel with the second capacitor and configured to damp a resonant frequency associated with the second capacitor, the input capacitor and the filter inductance;

an output capacitor;

a first inductor coupled to the input capacitor; and

a switch coupled to the first inductor and configured to control a level of current flowing in the first inductor;

wherein the second capacitor comprises a coupling capacitor connected to the first inductor.

2. The converter circuit of claim 1 , further comprising

a second inductor coupled to the Output capacitor, wherein the second inductor and the first inductor are wound on a common core.

3. The converter circuit of claim 2 , further comprising an output rectifier coupled between the second inductor and the output capacitor.

4. The converter circuit of claim 1 , wherein the damping circuit comprises a damping resistor and a damping capacitor in series.

5. The converter circuit of claim 4 , wherein a capacitance of the damping capacitor is based on a capacitance of the input capacitor and the coupling capacitor.

6. The converter circuit of claim 5 , wherein the input filter comprises a filter inductor, and wherein a resistance of the damping resistor is given by:

R

f

=

R

0

⁢

f

⁢

(

2

+

n

)

·

(

4

+

3

·

n

)

2

·

n

2

·

(

4

+

n

)

where R is the resistance of the damping resistor, and R 0f is given as:

R

0

⁢

f

=

L

f

C

f

where L f is the inductance of the filter inductor and C f is equal to the sum of the capacitances of the coupling capacitor and the input capacitor; and where n is given by

n

=

C

b

C

f

where C b is the capacitance of the damping capacitor.

7. The converter circuit of claim 1 , further comprising:

a control circuit configured to control a state of the switch.

8. The converter circuit of claim 1 , wherein the converter circuit further comprises a single ended primary inductor converter circuit.

9. A single ended primary inductor converter circuit, comprising:

an input filter coupled to an input voltage and configured to filter electromagnetic interference from the input voltage;

a first inductor coupled to the input filter;

an output rectifier;

a second inductor coupled to the output rectifier;

a coupling capacitor connected between the first inductor and the second inductor; and

a damping circuit coupled in parallel with the coupling capacitor and configured to damp a resonant frequency of the converter circuit.

10. The single ended primary inductor converter circuit of claim 9 , wherein the second inductor and the first inductor are wound on a common core.

11. The single ended primary inductor converter circuit of claim 9 , wherein the damping circuit comprises a damping resistor and a damping capacitor in series.

12. The single ended primary inductor converter circuit of claim 11 , wherein the input filter comprises a filter capacitor, and wherein a capacitance of the damping capacitor is based on a capacitance of the filter capacitor and the coupling capacitor.

13. The single ended primary inductor converter circuit of claim 12 , wherein the input filter comprises a filter inductor, and wherein a resistance of the damping resistor is given by:

R

f

=

R

0

⁢

f

⁢

(

2

+

n

)

·

(

4

+

3

·

n

)

2

·

n

2

·

(

4

+

n

)

where R f is the resistance of the damping resistor, R 0f is given as

R

0

⁢

f

=

L

f

C

f

where L 1 is the inductance of the filter inductor and C f is equal to the sum of the capacitances of the coupling capacitor and the filter capacitor; and where n is given by

n

=

C

b

C

f

where Cb is the capacitance of the damping capacitor.

14. A solid state lighting apparatus, comprising:

a rectification and filtering circuit configured to rectify and filter an input ac voltage signal;

a single ended primary inductor converter circuit configured to convert a level of a rectified voltage output by the filter, the single ended primary inductor converter circuit comprising a coupling capacitor and a damping circuit coupled in parallel with the coupling capacitor, wherein the damping circuit is configured to damp a resonant frequency associated with the coupling capacitor and the rectification and filtering circuit; and

a light emitting diode coupled to an output of the single ended primary inductor converter circuit.

15. The solid state lighting apparatus of claim 14 , wherein the single ended primary inductor converter circuit comprises:

a first inductor coupled to the filter and to the coupling capacitor;

a second inductor coupled to the coupling capacitor;

an output rectifier coupled to the second inductor;

an output capacitor coupled to the output rectifier;

a switch coupled to the first inductor; and

a control circuit coupled to the switch.

16. The solid state lighting apparatus of claim 15 , wherein the damping circuit comprises a damping resistor and a damping capacitor in series.

17. The solid state lighting apparatus of claim 16 , wherein the single ended primary inductor converter circuit comprises an input capacitor and wherein a capacitance of the damping capacitor is based on a capacitance of the input capacitor and the coupling capacitor.

18. The solid state lighting apparatus of claim 17 , wherein the rectification and filtering circuit comprises a filter inductor, and wherein a resistance of the damping resistor is given by:

R

f

=

R

0

⁢

f

⁢

(

2

+

n

)

·

(

4

+

3

·

n

)

2

·

n

2

·

(

4

+

n

)

where R f is the resistance of the damping resistor, and R 0t , is given as:

R

0

⁢

f

=

L

f

C

f

where L f is the inductance of the filter inductor and C f is equal to the sum of the capacitances of the coupling, capacitor and the input capacitor; and where n is given by

n

=

C

b

C

f

where C b is the capacitance of the damping capacitor.