Enhanced active preload for high performance LED driver with extended dimming
First Claim
1. An active preload circuit configured to be coupled to an output of a light-emitting diode (LED) driver converter having a phase-angle control dimmer circuit, the active preload circuit comprising:
- a biasing circuit coupled to receive a control signal representative of a conduction angle of the phase-angle control dimmer circuit, wherein the biasing circuit is configured to output a biasing signal; and
a preload switching device coupled to receive the biasing signal, wherein the preload switching device is configured to operate in a linear mode as a current source to draw a variable sinking current, and wherein a value of the sinking current is based on the biasing signal.
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Abstract
Enhanced active preload circuits for an LED driver implementing phase-angle dimming are disclosed. The enhanced active preload circuits may be used with any type of phase-angle control dimmer that either controls the leading edge or trailing edge of the line voltage cycle. In one example, the enhanced active preload circuitry may be used with an isolated or non-isolated LED driver converter having a Triac leading edge phase-angle control dimmer by directly sensing (e.g., by sensing the dimming level using an output/load voltage signal or output/load current signal) or indirectly sensing (e.g., by sensing a signal of output or bias winding) the Triac conduction angle. The enhanced active preload circuitry may advantageously improve performance of the LED driver by extending the dimming ratio at deep dimming and by adjusting the preload sinking current in response to a preload control signal.
62 Citations
20 Claims
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1. An active preload circuit configured to be coupled to an output of a light-emitting diode (LED) driver converter having a phase-angle control dimmer circuit, the active preload circuit comprising:
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a biasing circuit coupled to receive a control signal representative of a conduction angle of the phase-angle control dimmer circuit, wherein the biasing circuit is configured to output a biasing signal; and a preload switching device coupled to receive the biasing signal, wherein the preload switching device is configured to operate in a linear mode as a current source to draw a variable sinking current, and wherein a value of the sinking current is based on the biasing signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A light-emitting diode (led) driver comprising:
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a phase-angle control dimmer circuit coupled to receive an input voltage and output a phase-adjusted voltage; a rectifier circuit coupled to receive the phase-adjusted voltage and output a rectified voltage; a converter coupled to receive the rectified voltage and output an output voltage; an active preload circuit coupled to an output of the converter, wherein the active preload circuit comprises; a biasing circuit coupled to receive a control signal representative of a conduction angle of the phase-angle control dimmer circuit, wherein the biasing circuit is configured to output a biasing signal; and a preload switching device coupled to receive the biasing signal, wherein the preload switching device is configured to operate in a linear mode as a current source to draw a variable sinking current, and wherein a value of the sinking current is based on the biasing signal. - View Dependent Claims (17, 18, 19, 20)
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Specification