Reduced flicker driver circuit for LED systems
View Patent ↗LED systems and circuits for generating a driver output for powering one or more LED devices are provided. A dimmable driver circuit can include a controller configured to reduce output ripple current to reduce flicker over the dimming range of the LED system. The dimmable driver circuit can receive a dimming control signal (e.g. a 0V to 10V dimming control signal) over an isolated dimming interface to reduce leakage current at the dimming interface. In addition, a dual-switch flyback converter circuit can be employed to increase efficiency of the driver circuit as well as to reduce electromagnetic interference (EMI) with the LED devices, such as EMI resulting from differential mode noise.
1. A driver circuit for providing a driver output to one or more light emitting diode (LED) devices, the driver circuit comprising:
an input configured to receive an input power signal;
a converter circuit configured to adjust the input power signal to an adjusted power signal;
a dual-switch flyback converter circuit, the dual-switch flyback converter circuit comprising a first switching element and a second switching element, the dual-switch flyback converter circuit configured to convert the adjusted power signal to a driver output; and
a controller configured to generate a flyback drive signal for switching the first switching element and the second switching element of the dual-switch flyback converter circuit, the controller configured to control the converter circuit to reduce low frequency AC components in the adjusted power signal so that low frequency ripple in the driver output is reduced;
wherein the dual-switch flyback converter circuit comprises an output transformer, the controller configured to generate the flyback drive signal based at least in part on a flyback voltage sense signal received from the output transformer.
2. The driver circuit of claim 1 , wherein the driver circuit comprises a dimming circuit configured to receive a dimming control signal, the controller configured to generate the flyback drive signal based at least in part on the dimming control signal.
3. The driver circuit of claim 2 , wherein the dimming circuit comprises an isolating transformer.
4. The driver circuit of claim 2 , wherein the dimming control signal is a 0V to 10V dimming control signal.
5. The driver circuit of claim 1 , wherein the converter circuit comprises a power switching element, the controller configured to generate a converter drive signal to control the power switching element to convert the input power signal to the adjusted power signal.
6. The driver circuit of claim 5 , wherein the converter circuit comprises a rectifier circuit, the rectifier signal configured to provide the input power signal as an AC rectified input signal.
7. The driver circuit of claim 1 , wherein the controller is configured to control the power switching element based on at least one of a converter current feedback signal or a converter voltage feedback signal.
8. The driver circuit of claim 1 , wherein the driver circuit comprises an L-shaped heat sink in thermal communication with the power switching element.
9. The driver circuit of claim 1 , wherein the dual-switch flyback converter circuit comprises an input transformer configured to split the flyback drive signal into a first drive signal for driving the first switching element and a second drive signal for driving the second switching element.
10. The driver circuit of claim 1 , wherein the controller is configured to generate the flyback drive signal based at least in part on a flyback current feedback signal received from the output transformer.
11. A light emitting diode (LED) lighting system, comprising:
one or more LED devices;
a converter circuit comprising a rectifier and a power switching element, the rectifier configured to convert an AC input power into an AC rectified input signal, the converter circuit configured to convert the AC rectified input signal to an adjusted power signal;
a dual-switch flyback converter circuit configured to receive the adjusted power signal and to convert the adjusted power signal to a driver output, the dual-switch flyback converter comprising an input transformer, an output transformer, a first switching element and a second switching element;
a dimming circuit configured to receive a dimming control signal; and
a controller configured to generate a flyback drive signal for switching the first switching element and the second switching element of the dual-switch flyback converter circuit based at least in part on the dimming signal;
wherein the controller is configured to control the power switching element to reduce low frequency AC components in the adjusted power signal, the controller further configured to generate the flyback drive signal based at least in part on a flyback voltage sense signal and a flyback current sense signal associated with the output transformer.
12. The LED system of claim 11 , wherein the dimming circuit comprises an isolating transformer.
13. The LED system of claim 11 , wherein the dimming control signal is a 0V to 10V dimming control signal.
14. The LED system of claim 11 , wherein the power switching element is a bipolar junction transistor.
15. The LED system of claim 14 , further comprising an L-shaped heat sink in communication with the bipolar junction transistor.
16. The LED system of claim 11 , wherein the controller is configured to control the power switching element based on at least one of a converter current sense feedback signal or a converter voltage sense feedback signal.
17. A light emitting diode (LED) unit, the LED unit comprising:
one or more LED devices,
a converter circuit comprising a power switching element, the converter circuit configured to convert an input power signal to an adjusted power signal;
a dual-switch flyback converter circuit configured to receive the adjusted power signal and to convert the adjusted power signal to a driver output, the dual-switch flyback converter comprising a first switching element and a second switching element; and
means for reducing a ripple current of the driver output so as to reduce flicker in the one or more LED devices;
wherein the means comprises a controller configured to generate a flyback drive signal based at least in part on a flyback voltage feedback signal associated with an auxiliary winding of an output transformer of the dual-switch flyback converter circuit.
18. The LED unit of claim 17 , wherein LED unit further comprises means for dissipating heat generated by the power switching element.