SEPIC driver circuit with low input current ripple

Patent metadata

Field	Value
Publication number	US-9303823-B2
Application number	US-201414292001-A
Country	US
Kind code	B2
Filing date	May 30, 2014
Priority date	Apr 25, 2014
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

A SEPIC driver circuit with low input current ripple is disclosed. Embodiments of the present invention provide a driver circuit that accommodates universal input, has a wide output voltage range and good efficiency. An LED lighting system using such as circuit is also disclosed. In at least some embodiments, the circuit is configured as a single-ended primary inductor converter circuit using a magnetic element, and a floating capacitor is connected between the input winding and the output winding of the magnetic element. In some embodiments, an inductor is also included at the DC input to the circuit. An output rectifier such as a diode can also be connected to the output winding of the magnetic element, and an output capacitor can be connected across the output of the circuit. An FET, a bipolar transistor, or a plurality of FETs can be used as the switching device.

First claim

The invention claimed is:

1. A driver circuit to control current in one or more series and parallel connected LEDs, the driver circuit comprising:
a switching device;
a magnetic element comprising an input winding and an output winding;
an input inductor selected to reduce switching ripple at an input;
an output rectifier connected to the output winding of the magnetic element;
an output capacitor connected to the output rectifier; and
a floating capacitor connected to the switching element, and between the input winding and the output winding of the magnetic element.

2. The driver circuit of claim 1 wherein the switching device comprises at least one of a field-effect transistor (FET) and a bipolar transistor.

3. The driver circuit of claim 2 further comprising a control circuit connected to the switching device to cause the switching device to control the current through the input inductor and the magnetic element.

4. The driver circuit of claim 3 wherein the magnetic element further comprises a coupled inductor with a one-to-one turns ratio.

5. The driver circuit of claim 3 wherein the magnetic element further comprises a coupled inductor with an n-to-one turns ratio where n is greater than one.

6. The driver circuit of claim 1 wherein the switching device comprises two field effect transistors (FETs) in a cascode configuration.

7. The driver circuit of claim 6 further comprising a control circuit connected to at least one of the two FETs to cause the switching device to control the current through the input inductor and the magnetic element.

8. The driver circuit of claim 7 wherein the magnetic element further comprises a coupled inductor with a one-to-one turns ratio.

9. The driver circuit of claim 7 wherein the magnetic element further comprises a coupled inductor with an n-to-one turns ratio where n is greater than one.

10. A lighting system comprising:
a single-ended primary inductor converter (SEPIC) circuit comprising a switching device, a magnetic element, an inductor selected to reduce switching ripple at an input, and a floating capacitor connected between an input winding and an output winding of the magnetic element;
a control circuit connected to the switching device to cause the switching device to control current through the magnetic element to supply an output current; and
an LED connected to the single-ended primary inductor converter circuit to be operable to be energized from the output current.

11. The lighting system of claim 10 wherein the switching device comprises a field-effect transistor (FET).

12. The lighting system of claim 11 wherein the magnetic element further comprises a coupled inductor with a one-to-one turns ratio.

13. The lighting system of claim 11 wherein the magnetic element comprises a coupled inductor with an n-to-one turns ratio where n is greater than one.

14. The lighting system of claim 10 wherein the switching device comprises two field effect transistors (FETs) in a cascode configuration.

15. The lighting system of claim 14 wherein the magnetic element comprises a coupled inductor with a one-to-one turns ratio.

16. The lighting system of claim 14 wherein the magnetic element comprises a coupled inductor with an n-to-one turns ratio where n is greater than one.

17. A method of assembling a lighting system, the method comprising:
providing a single-ended primary inductor converter (SEPIC) including a magnetic element, a coupled inductor, a switching device, and a floating capacitor connected to the switching device, the floating capacitor also connected between an input winding and an output winding of the magnetic element; and
selecting a magnetic coupling for the coupled inductor to substantially reduce switching ripple at an input and control current in one or more series and parallel connected LEDs.

18. The method of claim 17 wherein the switching device comprises at least one field-effect transistor (FET).

19. The method of claim 18 wherein the SEPIC comprises an input inductor and wherein the coupled inductor has a one-to-one turns ratio.

20. The method of claim 18 wherein the coupled inductor has an n-to-one turns ratio where n is greater than one.

Assignees

• Cree Inc

Inventors

• Hu Qingcong
• Ekbote Ashish

Classifications

• F21V29/503

  of light sources (cooling arrangements structurally associated with gas-discharge or vapour-discharge lamps H01J61/52; cooling arrangements structurally associated with electric incandescent lamps H01K1/58; cooling arrangements structurally associated with light-emitting diodes H10H20/858) · CPC title

• F21V23/007

  enclosed in a casing · CPC title

• F21V23/06

  the elements being coupling devices {, e.g. connectors} · CPC title

• F21V29/773

  the planes containing the fins or blades having the direction of the light emitting axis · CPC title

• F21W2131/103

  of streets or roads · CPC title