US Patent No. 10,925,138

FLICKER-FREE LINEAR LED DRIVE CIRCUIT


Patent No. 10,925,138
Issue Date February 16, 2021
Title Flicker-free Linear Led Drive Circuit
Inventorship Chih-Hsien Wu, New Taipei (TW)
Kai-Cheng Chuang, New Taipei (TW)
Chun-Chieh Kuo, New Taipei (TW)
Yu-Hsien He, New Taipei (TW)
Assignee UNITY OPTO TECHNOLOGY CO., LTD., New Taipei (TW)

Claim of US Patent No. 10,925,138

1. A flicker-free linear LED drive circuit, electrically coupled to an external power supply which is an alternating current power supply, and converting an input voltage of the external power supply into an output current to be supplied to at least one LED; the flicker-free linear LED drive circuit comprising a measuring module, a regulating module and a rectifier module, and the regulating module being electrically coupled to the rectifier module and the measuring module, and the rectifier module being electrically coupled to the external power supply, characterized in that the measuring module is provided for measuring a phase angle of the input voltage to generate and send a measurement signal to the regulating module, wherein the regulating module sets a conduction angle range having a fixed power for driving of the at least one LED, and adjusts the measurement signal according to a phase angle of the measurement signal, and the measurement signal forms a plurality of voltage signals during a half-wave period of the input voltage according to the conduction angle range and adjusts the plurality of voltage signals to form the output current, and the output current is a direct current signal provided for the at least one LED to emit light; wherein the plurality of voltage signals has a same maximum current value, and a duty cycle of the plurality of voltage signals is smaller than the half-wave period of the input voltage to reduce flickering of the at least one LED formed by the output current;wherein the measuring module further comprises a measuring RC circuit and a measurement amplifier; the measurement amplifier has an input terminal electrically coupled to the measuring RC circuit and a reference voltage device for adjusting and generating the phase of the input voltage according to a measured resistance of the measuring RC circuit, and the measurement amplifier has an output terminal electrically coupled to the regulating module for forming and coupling the measurement signal to the regulating module;
wherein the measuring RC circuit further comprises a first filter capacitor electrically coupled to the rectifier module and the measurement amplifier, so that the input voltage forms a ripple signal and couples the ripple signal to the measurement amplifier;
wherein the regulating module further comprises a regulation comparator and a regulating RC circuit; the regulating RC circuit is provided for coupling the measurement signal to the regulation comparator, so that the regulation comparator can receive and adjust the measurement signal to generate the plurality of voltage signals, and the regulating RC circuit adjusts the plurality of voltage signals to form the output current and couples the output current to the at least one LED; wherein the regulation comparator adjusts the duty cycle of the plurality of voltage signals according to a compensation capacitance and a compensation resistance of the regulating RC circuit;
wherein the regulating RC circuit further comprises a regulation switch electrically coupled to the regulation comparator for conducting or switching off the plurality of voltage signals to form the output current to be supplied to the at least one LED.