System and method for selectively dimming an LED
AssigneePermlight Products, Inc.
InventorChris Peng
Life of this patent
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Abstract
Embodiments of the present disclosure include an LED ballast circuit for dimming one or more LEDs using a phase controlled dimmer switch. The LED ballast circuit has a power conditioning unit which includes a substantially fixed duty cycle clock for outputting a clock cycle and a transformer configured to store energy and discharge a substantial portion of the stored energy once per clock cycle in order to power one or more LEDs. The LED ballast circuit and load collectively behave like a resistor.
Claims30
A lighting fixture adapted to be dimmable by a thyristor-based dimmer, the fixture comprising:
- a power conditioning unit adapted to accept an AC electrical input and having an output, the power conditioning unit comprising;
- a switching MOSFET;
- a control circuit adapted to output a switching clock cycle and duty cycle that are generally fixed during normal operation of the power conditioning unit, the duty cycle and clock cycle adapted to gate the switching MOSFET;
- and
- a transformer having a primary winding configured to store electrical energy when the MOSFET is gated on, a secondary winding of the transformer receiving electrical energy from the primary winding and delivering it to the outlet;
- an impedance matching unit connected in series between a thyristor-based dimmer and the rest of the power conditioning unit, wherein the impedance matching resistor is chosen to prevent a false trigger by the thyristor-based dimmer;
- a lighting unit connected to the power conditioning unit output and adapted to receive electric power therefrom, the lighting unit comprising one or more light emitting diodes (LEDs);
- wherein the duty cycle, clock and transformer are chosen so that the primary winding discharges substantially all of the energy stored therein at least once per a predetermined number of clock cycles.
A method of dimming an LED using a thyristor-based dimmer, comprising:
- providing an LED;
- providing an LED driver comprising a substantially fixed operating frequency clock and a transformer;
- providing a thyristor-based dimmer adapted to supply a power to the LED driver;
- providing an impedance matching unit connected in series between a thyristor-based dimmer and the rest of the power conditioning unit, wherein the impedance matching resistor is chosen to prevent a false trigger by the thyristor-based dimmer;
- supplying power to the transformer as a function of the duty cycle so as to charge the transformer;
- wherein the transformer is adapted to substantially fully discharge at least once per a predetermined number of clock cycles;
- and
- directing at least a portion of the energy discharged from the transformer to the LED.
A light emitting diode dimming circuit for use with a thyristor-based dimmer switch, the light emitting diode dimmer circuit comprising:
- a switching MOSFET;
- a control circuit configured to provide a clock frequency and a duty cycle gate drive signal for controlling the MOSFET, the frequency and duty cycle being generally fixed during normal operation;
- a transformer configured to store energy and discharge substantially all of the stored energy at least once per a predetermined number of clock cycles;
- an impedance matching unit connected in series between a thyristor-based dimmer and the rest of the power conditioning unit, wherein the impedance matching resistor is chosen to prevent a false trigger by the thyristor-based dimmer;
- and
- one or more light emitting diodes configured to receive at least a portion of energy discharged by the transformer.
Dependencies are inferred from the claim text.