Dynamic Bleeder Current Control for LED Dimmers
AssigneeDialog Semiconductor GmbH
InventorsXiaoyan Wang, Nan Shi, Clarita Chiting Knoll, Guang Feng
Life of this patent
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Abstract
LED lamp systems as described herein include a dimmer switch and a bleeder circuit. The bleeder circuit provides a bleeder current to management voltage and to prevent the dimmer switch from turning off prematurely. The bleeder circuit may monitor the AC input voltage outputted by the dimmer switch. When the AC input voltage is less than a first threshold, the bleeder circuit provides a bleeder current. When the AC input voltage is greater than a second threshold, the bleeder circuit adjusts the bleeder current to less than a predetermined level.
Claims18
A light-emitting diode (LED) lamp, comprising:
- an LED string including one or more LEDs;
- a rectifier circuit configured to receive an AC input voltage and to generate a rectified voltage corresponding to the AC input voltage, the rectified voltage is a phase-cut AC input voltage indicating a dimming level;
- a bleeder circuit coupled to the rectifier circuit and configured to turn on to provide a bleeder current at a first current level responsive to the AC input voltage less than a first threshold voltage and to reduce the bleeder current to a second current level responsive to the AC input voltage exceeding a second threshold voltage;
- and
- an LED driver circuit configured to switch on or off a power stage switch according to a duty cycle based on the rectified voltage, to regulate a driving current through the LED string.
A method of powering a light-emitting diode (LED) string, comprising:
- receiving an AC input voltage and generating a rectified voltage corresponding to the AC input voltage, the rectified voltage being a phase-cut voltage indicating a dimming level;
- determining a level of the AC input voltage;
- providing a bleeder current at a first current level responsive to the AC input voltage being less than the first threshold voltage, and reducing the bleeder current to a second current level responsive to the AC input voltage exceeding the second threshold voltage;
- and
- regulating a driving current through the LED string by switching on or off a power stage switch according to a duty cycle based on the rectified voltage.
Dependencies are inferred from the claim text.