Constant current drive circuit for multi-channel LED lighting

摘要

An LED driver circuit is provided for driving a multi-channel LED string with constant and balanced current. The driver circuit includes a half-bridge inverter and a resonant tank circuit in a power stage. An isolating (first) transformer includes a primary winding coupled between a resonant tank output and circuit ground and a plurality of secondary windings, while a balancing (second) transformer includes a plurality of balancing windings. A plurality of output stages each provide an output power to a respective load, and each of the output stages further includes one of the balancing windings of the balancing transformer and one of the secondary windings of the isolating transformer coupled in series, and a rectifier circuit coupled to an output end of the series coupled windings. In an embodiment, an impedance value of the balancing transformer is further configured to be greater than three times a maximum load impedance value.

主权项

1. A driver circuit operable to provide current to a plurality of light sources from a direct current (DC) power source having a power rail and a ground, the driver circuit comprising:
a half-bridge inverter having an input and an output, wherein the input is configured to connect to the power rail and the ground of the DC power source and provide an alternating current (AC) signal at the output; a resonant tank circuit comprising a resonant inductor and a resonant capacitor coupled in series between the output of the half-bridge inverter and the ground of the DC power source; an isolating transformer comprising a primary winding coupled between an output of the resonant tank circuit and the ground of the DC power source, and a plurality of secondary windings; a balancing transformer comprising a plurality of balancing windings; and a plurality of output stages configured to provide an output power to a respective load, each of the output stages further comprising
one of the balancing windings of the balancing transformer and one of the secondary windings of the isolating transformer coupled in series, anda rectifier circuit coupled to an output end of the series coupled windings.