Constant current source based on self-oscillating soft-switching LLC converter topology

摘要

A driver circuit (e.g., an LED driver circuit) provides power to a load (e.g. an LED light source) from a DC power rail. A self-oscillating LLC series resonant inverter is configured to connect to the DC power rail, receive DC power from the DC power rail, and provide an AC output signal. A current limiting capacitor is connected to the self-oscillating LLC series resonant inverter. The current limiting capacitor receives the AC output signal from the self-oscillating LLC series resonant inverter and provides an AC current signal. The rectifier circuit receives the AC current signal from the current limiting capacitor and provides a DC current to the load.

主权项

1. A driver circuit operable to provide power to a load from a direct current (DC) power rail, the driver circuit comprising:
a self-oscillating inductor-inductor-capacitor (LLC) series resonant inverter configured to connect to the DC power rail, receive DC power from the DC power rail, and provide an alternating current (AC) output signal; a current limiting capacitor connected to the self-oscillating LLC series resonant inverter, wherein the current limiting capacitor is configured to receive the AC output signal from the self-oscillating LLC series resonant inverter and provide an AC current signal; a rectifier circuit connected to the current limiting capacitor, wherein the rectifier circuit is configured to receive the AC current signal from the current limiting capacitor and provide a DC current to the load; and wherein the DC power rail has an associated ground, and the self-oscillating LLC series resonant inverter comprises
a first switch having a first terminal connected to the DC power rail, a second terminal, and a control terminal,a second switch having a first terminal connected to the second terminal of the first switch, a second terminal connected to the ground associated with the DC power rail, and a control terminal,a resonant capacitor having a first terminal and a second terminal, wherein the first terminal is connected to the ground associated with the DC power rail, anda transformer having a primary winding, a first secondary winding, a second secondary winding, and an output secondary winding, whereinthe primary winding of the transformer is connected between the second terminal of the first switch and the second terminal of the resonant capacitor,the first secondary winding is connected between the control terminal of the first switch and the second terminal of the first switch,the second secondary winding is connected between the control terminal of the second switch and the second terminal of the second switch, andthe output secondary winding is configured to provide the AC output signal.